All-solid-state secondary batteries

Abstract

The all-solid-state secondary battery includes a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, the positive electrode layer includes a positive electrode current collector and a positive electrode active material layer disposed on one or more surfaces of the positive electrode current collector, at least one of the positive electrode active material layer and the solid electrolyte layer includes a first fibrous sulfide-based solid electrolyte, and the negative electrode layer includes a negative electrode current collector and a first negative electrode active material layer disposed on one surface of the negative electrode current collector, and an initial charge capacity (B) of the first negative electrode active material layer is less than approximately 50% of an initial charge capacity (A) of the positive electrode active material layer.

Description

[Technical Field]

[0001] The present invention relates to an all-solid-state secondary battery. [Background technology]

[0002] Recently, there has been active development of batteries that offer increased energy density and stability. Lithium batteries are used in information devices, communication devices, automobiles, etc. Since automobiles are a matter of life and death, stability is important.

[0003] Lithium batteries containing liquid electrolytes contain flammable organic solvents, which pose a high risk of overheating and fire in the event of a short circuit.

[0004] Solid electrolytes have a reduced likelihood of overheating and fire during a short circuit compared to liquid electrolytes, and lithium batteries containing solid electrolytes may offer improved stability compared to lithium batteries containing liquid electrolytes. Summary of the Invention [Problem to be solved by the invention]

[0005] The lithium battery includes a positive electrode active material layer, which may include a conductive material to improve charge / discharge characteristics. The conductive material may be, for example, a carbon-based conductive material. Carbon-based conductive materials have high electronic conductivity but low ionic conductivity. A solid electrolyte may be used to improve the ionic conductivity of the positive electrode active material layer. Conventional solid electrolytes have, for example, a particle shape with an aspect ratio of less than 2. Conventional solid electrolyte particles with an aspect ratio of less than 2 have difficulty forming long-distance ion conduction paths. Lithium batteries including conventional solid electrolyte particles with an aspect ratio of less than 2 are more likely to experience ion conduction path interruption during charging and discharging. Lithium batteries include, for example, a sulfide-based positive electrode active material, which may undergo significant volume change during charging and discharging. Conventional solid electrolyte particles with an aspect ratio of less than 2 have difficulty suppressing ion conduction path interruption and increased internal resistance due to volume change of the sulfide-based positive electrode active material during charging and discharging of the lithium battery. Therefore, there is a need for a method that can suppress the disconnection of the ion conduction path in the positive electrode active material layer due to the volume change of the positive electrode active material during charging and discharging of the lithium battery, thereby suppressing the increase in the internal resistance of the lithium battery.

[0006] Lithium batteries containing solid electrolytes may have relatively increased interfacial resistance and decreased ionic conductivity compared to lithium batteries containing liquid electrolytes. Therefore, lithium batteries containing solid electrolytes have relatively inferior high-rate characteristics and power characteristics compared to lithium batteries containing liquid electrolytes. Therefore, a method is needed to improve the high-rate characteristics and power characteristics of lithium batteries containing solid electrolytes by reducing the interfacial resistance and increasing the ionic conductivity in lithium batteries containing solid electrolytes.

[0007] One aspect is to provide a new all-solid-state secondary battery. [Means for solving the problem]

[0008] According to one embodiment, a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer; the positive electrode layer includes a positive electrode current collector and a positive electrode active material layer disposed on one or more surfaces (e.g., one surface or both surfaces) of the positive electrode current collector, At least one of the positive electrode active material layer and the solid electrolyte layer includes a first fibrous sulfide-based solid electrolyte; the negative electrode layer includes a negative electrode current collector and a first negative electrode active material layer disposed on one surface of the negative electrode current collector, An all-solid-state secondary battery is provided, wherein the initial charge capacity (B) of the first negative electrode active material layer is less than 50% of the initial charge capacity (A) of the positive electrode active material layer.

[0009] According to another embodiment, a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer; the positive electrode layer includes a positive electrode current collector and a positive electrode active material layer disposed on one or more surfaces (e.g., one surface or both surfaces) of the positive electrode current collector, At least one of the positive electrode active material layer and the solid electrolyte layer includes a first fibrous sulfide-based solid electrolyte; An all-solid-state secondary battery is provided, in which the negative electrode layer includes a negative electrode current collector and a first negative electrode active material layer disposed on one or more surfaces (eg, one surface or both surfaces) of the negative electrode current collector. According to another embodiment, a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer; the positive electrode layer includes a positive electrode current collector and a positive electrode active material layer disposed on one or both surfaces of the positive electrode current collector, An all-solid-state secondary battery is provided, in which at least one of the positive electrode active material layer and the solid electrolyte layer includes a first fibrous sulfide-based solid electrolyte. [Effects of the Invention]

[0010] According to one aspect, an all-solid-state secondary battery having a new structure can provide an all-solid-state secondary battery with improved cycle characteristics. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram of a fibrous sulfide-based solid electrolyte according to an exemplary embodiment. [Figure 2] FIG. 1 is a schematic diagram of a core / shell structured fibrous sulfide-based solid electrolyte according to an exemplary embodiment. [Figure 3] FIG. 1 is a schematic diagram of a core / shell structured fibrous sulfide-based solid electrolyte according to an exemplary embodiment. [Figure 4] FIG. 1 is a cross-sectional view of a core / shell structured fibrous sulfide-based solid electrolyte according to an exemplary embodiment. [Figure 5] FIG. 1 is a schematic diagram of a core / interlayer / shell structured fibrous sulfide-based solid electrolyte according to an exemplary embodiment. [Figure 6A] FIG. 2 is a cross-sectional view of a cathode active material layer including a fibrous sulfide-based solid electrolyte according to an exemplary embodiment. [Figure 6B] FIG. 2 is a cross-sectional view of a cathode active material layer including a fibrous sulfide-based solid electrolyte according to an exemplary embodiment. [Figure 6C] FIG. 2 is a cross-sectional view of a cathode active material layer including a fibrous sulfide-based solid electrolyte according to an exemplary embodiment. [Figure 7] FIG. 1 is a cross-sectional view of an all-solid-state secondary battery according to an exemplary embodiment. [Figure 8] FIG. 1 is a cross-sectional view of a bi-cell all-solid-state secondary battery according to an exemplary embodiment. [Figure 9] FIG. 1 is a cross-sectional view of an all-solid-state secondary battery according to an exemplary embodiment. [Figure 10] FIG. 1 is a cross-sectional view of an all-solid-state secondary battery according to an exemplary embodiment. [Figure 11] FIG. 1 is a cross-sectional view of a bi-cell all-solid-state secondary battery according to an exemplary embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Various embodiments are illustrated in the accompanying drawings. However, the present invention may be embodied in various other forms and should not be construed as limited to the embodiments set forth herein. Rather, these examples are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. Like reference numerals refer to like elements throughout.

[0013] It will be understood that when an element is referred to as being "on" another element, it may be directly on top of the other element, or there may be other intervening elements. In contrast, when an element is referred to as being "directly on" another element, there are no intervening elements.

[0014] Terms such as "first," "second," and "third" may be used herein to describe various components, components, regions, layers, and / or sections, but these components, components, regions, layers, and / or sections should not be limited by these terms. These terms are used only to distinguish one component, component, region, layer, or section from other components, components, regions, layers, or sections. Thus, a first component, component, region, layer, or section described below may also be referred to as a second component, component, region, layer, or section without departing from the teachings of this specification.

[0015] The terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the invention. As used herein, the singular forms "a," "an," "the ...

[0016] Spatially relative terms such as "below," "lower," "bottom," "top," "upper," and "top" may be used to easily describe the relationship of one component or feature to another. It will be understood that the spatially relative terms are intended to encompass different orientations of the device when in use or operation relative to the orientation depicted in the figures. For example, if the device in the figures were inverted, a component described as "below" or "below" another component or feature would be oriented "above" that other component or feature. Thus, the exemplary term "below" can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or rotated in another direction), and the spatially relative terms used herein interpreted accordingly.

[0017] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by a person of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms as defined in commonly used dictionaries should be interpreted to have a meaning consistent with the context of the relevant art and the content of this disclosure, and should not be interpreted as an idealized or overly formal meaning.

[0018] Exemplary embodiments are described herein with reference to cross-section illustrations that are schematic illustrations of idealized embodiments. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and / or tolerances, are to be expected. Therefore, the examples described herein should not be construed as limited to the specific shapes of regions as illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, a region illustrated or described as flat may typically have rough and / or non-linear characteristics. Additionally, corners illustrated as sharp may also be rounded. Accordingly, regions illustrated in the figures are schematic in nature, and their shapes are not intended to illustrate the precise shapes of the regions and are not intended to limit the scope of the claims.

[0019] "Group" means a group in the Periodic Table of the Elements according to the International Union of Pure and Applied Chemistry (IUPAC) Groups 1-18 classification system.

[0020] As used herein, "aspect ratio" can be measured, for example, from scanning electron microscope (SEM), transmission electron microscope (TEM) or atomic force microscope (AFM) images.

[0021] The "length," "diameter," and / or "thickness" of the fibrous sulfide-based solid electrolyte herein may be measured, for example, from a scanning electron microscope (SEM), transmission electron microscope (TEM), or atomic force microscope (AFM) image.

[0022] The "thickness" and / or "diameter" of the core and shell of the fibrous sulfide-based solid electrolyte herein may be measured, for example, from scanning electron microscope (SEM), transmission electron microscope (TEM) or atomic force microscope (AFM) images.

[0023] As used herein, "particle size" refers to the average diameter when the particles are spherical, and refers to the average major axis length when the particles are non-spherical. Particle size can be measured using a particle size analyzer (PSA). "Particle size" refers to, for example, the average particle size. "Average particle size" refers to, for example, D50, which is the median particle size.

[0024] D50 is the particle size corresponding to 50% cumulative volume calculated from the particle side having a small particle size in the particle size distribution measured by laser diffraction method.

[0025] D90 is the particle size corresponding to 90% cumulative volume calculated from the particle side having a small particle size in the particle size distribution measured by laser diffraction method.

[0026] D10 is the particle size corresponding to 10% cumulative volume calculated from the particle side having a small particle size in the particle size distribution measured by laser diffraction method.

[0027] In the present invention, "metal" includes both metals and metalloids such as silicon and germanium, in the elemental or ionic state.

[0028] In the present invention, "alloy" means a mixture of two or more metals.

[0029] In the present invention, the term "electrode active material" refers to an electrode material that can be lithiated and delithiated.

[0030] In the present invention, the term "positive electrode active material" refers to a positive electrode material that can be lithiated and delithiated.

[0031] In the present invention, the term "negative electrode active material" refers to a negative electrode material that can be lithiated and delithiated.

[0032] In the present invention, "lithiation" and "lithiating" refer to the process of adding lithium to an electrode active material.

[0033] In the present invention, "delithiation" and "delithiating" refer to the process of removing lithium from an electrode active material.

[0034] As used herein, "charge" and "charging" refer to the process of providing electrochemical energy to a battery.

[0035] As used herein, "discharge" and "discharging" refer to the process of removing electrochemical energy from a battery.

[0036] For purposes of this invention, "positive electrode" and "cathode" refer to the electrodes where electrochemical reduction and lithiation occurs during the discharge process.

[0037] In the present invention, "negative electrode" and "anode" refer to electrodes where electrochemical oxidation and delithiation occur during the discharge process.

[0038] While particular embodiments have been described, presently unforeseen or unanticipated alternatives, modifications, variations, improvements, and substantial equivalents may occur to applicant or those skilled in the art, and it is accordingly intended that the application and the claims, as amended, include all such alternatives, modifications, variations, improvements, and substantial equivalents.

[0039] All-solid-state secondary batteries according to exemplary embodiments will be described in further detail below.

[0040] [All-solid-state secondary battery] An all-solid-state secondary battery according to one embodiment includes a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, wherein the positive electrode layer includes a positive electrode current collector and a positive electrode active material layer disposed on one or both sides of the positive electrode current collector, at least one of the positive electrode active material layer and the solid electrolyte layer includes a first fibrous sulfide-based solid electrolyte, and the negative electrode layer includes a negative electrode current collector and a first negative electrode active material layer disposed on one side of the negative electrode current collector, and an initial charge capacity (B) of the first negative electrode active material layer is less than 50% of an initial charge capacity (A) of the positive electrode active material layer.

[0041] The all-solid-state secondary battery includes a positive electrode active material layer, and the positive electrode active material layer includes a first fibrous sulfide-based solid electrolyte, which can ensure an extended ion conduction path in the positive electrode active material layer. Therefore, the disconnection of the ion conduction path due to volume change of the positive electrode active material in the positive electrode active material layer during charging and discharging of the all-solid-state secondary battery can be more effectively prevented. As a result, the initial efficiency, discharge capacity, high-rate characteristics, and / or life characteristics of the all-solid-state secondary battery can be improved.

[0042] The all-solid-state secondary battery includes a positive electrode active material layer, and the positive electrode active material layer includes a first fibrous sulfide-based solid electrolyte, which can improve the uniformity of ion conduction paths within the positive electrode active material layer. Therefore, the pressure required during the manufacture of the all-solid-state secondary battery can be reduced. That is, an all-solid-state secondary battery having excellent ion conduction paths can be realized even with reduced pressure. Furthermore, the formation of local overvoltage within the positive electrode active material layer during the charge / discharge process of the all-solid-state secondary battery can be effectively prevented.

[0043] The all-solid-state secondary battery includes a cathode active material layer, and the cathode active material layer includes a first fibrous sulfide-based solid electrolyte having a reduced specific surface area, which increases water stability, reduces side reactions between the cathode active material and the sulfide-based solid electrolyte, reduces interfacial resistance of the cathode active material layer, and suppresses a decrease in ionic conductivity, thereby improving the high-rate and power characteristics of the all-solid-state secondary battery.

[0044] The all-solid-state secondary battery includes a cathode active material layer, and the cathode active material layer includes a first fibrous sulfide-based solid electrolyte, which can more effectively accommodate volume changes of the cathode active material during charge and discharge. A fibrous sulfide-based solid electrolyte can be disposed around the cathode active material in the cathode active material layer. The fibrous sulfide-based solid electrolyte can accommodate volume changes of the cathode active material during charge and discharge by distributing the volume changes throughout its length, and therefore can more effectively accommodate volume changes of the cathode active material than, for example, spherical particulate sulfide-based solid electrolytes. As a result, separation between the cathode active material and the solid electrolyte due to volume changes of the cathode active material in the cathode active material layer is suppressed, thereby improving the uniformity of the components within the cathode active material layer. As a result, the cycle characteristics of the all-solid-state secondary battery can be improved.

[0045] 1 to 11, the all-solid-state secondary battery 1 includes a positive electrode layer 10, a negative electrode layer 20, and a solid electrolyte layer 30 disposed between the positive electrode layer 10 and the negative electrode layer 20. The positive electrode layer 10 includes a positive electrode current collector 11 and a positive electrode active material layer 12 disposed on one or both sides of the positive electrode current collector. The positive electrode active material layer 12, the solid electrolyte layer 30, or a combination thereof includes a first fibrous sulfide-based solid electrolyte 100. The negative electrode layer 20 includes a negative electrode current collector 21 and a first negative electrode active material layer 22 disposed on one side of the negative electrode current collector. The initial charge capacity (B) of the first negative electrode active material layer 22 is less than 50% of the initial charge capacity (A) of the positive electrode active material layer 12.

[0046] [Positive electrode layer] [Positive electrode layer: solid electrolyte] The positive electrode active material layer 12 includes a first fibrous sulfide-based solid electrolyte.

[0047] 1 to 5, the first fibrous sulfide-based solid electrolyte 100 is defined by a length L and a diameter D. The length L of the first fibrous sulfide-based solid electrolyte 100 is the distance between both ends of the first fibrous sulfide-based solid electrolyte 100 in the longitudinal direction (z direction). The diameter D of the first fibrous sulfide-based solid electrolyte 100 is the maximum distance between both ends of the first fibrous sulfide-based solid electrolyte 100 in a direction perpendicular to the longitudinal direction (z direction) of the first fibrous sulfide-based solid electrolyte 100. In another embodiment, the first fibrous sulfide-based solid electrolyte 100 includes a first side surface SS1, a second side surface SS2 opposing the first side surface SS1, and the first and second side surfaces SS1 and SS2, and is defined by the area of ​​the first or second side surface SS1 and the distance between the first and second side surfaces SS1. The area of ​​the first side surface SS1 or the second side surface SS2 is, for example, double the maximum and minimum values ​​of the distance between both ends of the perimeter of the first side surface SS1 or the second side surface SS2. The distance between the first side surface SS1 and the second side surface SS1 is the maximum value of the length from the first side surface SS1 to the second side surface SS1. In another embodiment, the area of ​​the first side surface SS1 or the second side surface SS2 is the integral value of the area read from a scanning electron microscope plane view image of the first fibrous sulfide-based solid electrolyte 100 viewed in the longitudinal direction (z direction). The distance between the first side surface SS1 and the second side surface SS1 is the maximum value of the length read from a scanning electron microscope image of the first fibrous sulfide-based solid electrolyte 100 viewed in a direction perpendicular to the longitudinal direction (x direction or y direction).

[0048] The aspect ratio of the length L to the diameter D of the first fibrous sulfide-based solid electrolyte 100 is, for example, 5 or more, 10 or more, 15 or more, 20 or more, or 30 or more. The aspect ratio of the length L to the diameter D of the first fibrous sulfide-based solid electrolyte 100 is, for example, 5 to 1000, 5 to 600, 5 to 400, 5 to 200, or 10 to 200. When the aspect ratio of the first fibrous sulfide-based solid electrolyte 100 is within this range, the ion conduction path in a lithium battery including the first fibrous sulfide-based solid electrolyte 100 is extended, more effectively accommodating volumetric changes in the positive electrode active material during charging and discharging of the lithium battery, and maintaining the ion conduction path in the lithium battery despite volumetric changes in the positive electrode active material. As a result, deterioration of the lithium battery is suppressed, and the cycle characteristics of the lithium battery can be improved.

[0049] The length L of the first fibrous sulfide-based solid electrolyte 100 is, for example, 0.1 to 100 μm, 0.5 to 100 μm, 1 to 100 μm, 1 to 50 μm, 1 to 30 μm, 1 to 20 μm, or 1 to 10 μm. The diameter D of the first fibrous sulfide-based solid electrolyte 100 is, for example, 10 nm to 10 μm, 10 nm to 5 μm, 50 nm to 5 μm, 100 nm to 5 μm, 100 nm to 3 μm, 100 nm to 2 μm, 200 nm to 2 μm, 200 nm to 1.5 μm, or 200 nm to 1 μm. The diameter D of the first fibrous sulfide-based solid electrolyte 100 can be, for example, 10 nm to 10 μm, 10 nm to 5 μm, 10 nm to 1 μm, 10 nm to 800 nm, 10 nm to 500 nm, 10 nm to 300 nm, 10 nm to 200 nm, or 10 nm to 100 nm. When the length and / or diameter of the first fibrous sulfide-based solid electrolyte 100 are within these ranges, the ion conduction path in a lithium battery containing the first fibrous sulfide-based solid electrolyte 100 can be extended, more effectively accommodating volumetric changes in the positive electrode active material during charging and discharging of the lithium battery, and maintaining the ion conduction path in the lithium battery despite volumetric changes in the positive electrode active material. As a result, deterioration of the lithium battery can be suppressed, and the cycle characteristics of the lithium battery can be improved.

[0050] The first fibrous sulfide-based solid electrolyte 100 may have, for example, a rod structure, a tube structure, a needle structure, a wire structure, or a combination thereof. However, it is not necessarily limited to these shapes and any fibrous structure commonly used in the art may be used. The rod structure, tube structure, needle structure, wire structure, or the like of the first fibrous sulfide-based solid electrolyte 100 extends the ion conduction path within a lithium battery including the first fibrous sulfide-based solid electrolyte 100, thereby more effectively accommodating volumetric changes in the positive electrode active material during charging and discharging of the lithium battery. This allows the ion conduction path within the lithium battery to be maintained despite volumetric changes in the positive electrode active material. As a result, deterioration of the lithium battery may be suppressed, and the cycle characteristics of the lithium battery may be improved.

[0051] A cross section perpendicular to the longitudinal direction of the first fibrous sulfide-based solid electrolyte 100, i.e., the side surfaces SS1 and SS2 of the first fibrous sulfide-based solid electrolyte 100, may have, for example, an irregular, circular, or polygonal shape. The shape of the side surfaces SS1 and SS2 of the first fibrous sulfide-based solid electrolyte 100 is determined, for example, by a plan view of the first fibrous sulfide-based solid electrolyte 100 as seen from the longitudinal direction (z direction). Polygonal shapes include, but are not limited to, triangles, squares, pentagons, hexagons, heptagons, octagons, nonagons, and decagons. Any polygonal shape used in the art may be used. Circular shapes may be, for example, perfect circles, ellipses, etc., but are not limited to these shapes. Any shape that is circular overall may be used. The sphericity of the cross section perpendicular to the longitudinal direction of the first fibrous sulfide-based solid electrolyte 100, i.e., the circularity of the side surfaces SS1 and SS2 of the first fibrous sulfide-based solid electrolyte 100, is, for example, 0.6 or more, 0.7 or more, 8 or more, or 0.9 or more. 2where A is the area of ​​the sides SS1, SS2 or cross section of the first fibrous sulfide-based solid electrolyte 100, and P is the perimeter of the sides SS1, SS2 or cross section.

[0052] 2 to 5, the first fibrous sulfide-based solid electrolyte 100 may have, for example, a core 110 / shell 120 structure including a core 110 and a shell 120 disposed on the core 110. Because the first fibrous sulfide-based solid electrolyte 100 has a core 110 / shell 120 structure, the ion conduction path within a lithium battery including the first fibrous sulfide-based solid electrolyte 100 may be further extended, more effectively accommodating volumetric changes in the positive electrode active material during charging and discharging of the lithium battery, and maintaining the ion conduction path within the lithium battery despite volumetric changes in the positive electrode active material. As a result, deterioration of the lithium battery may be suppressed, and the cycle characteristics of the lithium battery may be improved. In contrast, a simple mixture of the core 110 and the shell 120 is prone to aggregation of the core 110 and / or the shell 120, and therefore is unable to provide an extended ion conduction path within the lithium battery. This effectively accommodates volume changes in the positive electrode active material during charging and discharging of the lithium battery, and the volume changes in the positive electrode active material may interrupt the ion conduction path within the lithium battery. As a result, deterioration of the lithium battery may increase, and the cycle characteristics of the lithium battery may deteriorate. Therefore, the first fibrous sulfide-based solid electrolyte 100 having a core 110 / shell 120 structure is distinguished from a simple mixture of the core 110 material and the shell 120 material, as it is a composite in which the core 110 is coated with the shell 120.

[0053] The core 110 may include, for example, a carbon-based material, a polymeric material, a metal-containing inorganic material, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or a combination thereof. Any material capable of forming a fibrous structure can be used for the core 110.

[0054] Examples of carbon-based materials include, but are not limited to, artificial graphite, natural graphite, carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), graphene, graphene oxide, reduced graphene oxide, carbon nanobelts, and carbon nanosheets. Any carbon-based material having a fibrous structure that is used in the art may be used.

[0055] Examples of polymeric materials include poly-2-vinylpyridine, polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, polychlorotrifluoroethylene, perfluoroalkoxy copolymer, fluorinated cyclic ethers, polyethylene oxide diacrylate, polyethylene oxide dimethacrylate, polypropylene oxide diacrylate, polypropylene oxide dimethacrylate, polymethylene oxide diacrylate, polymethylene oxide dimethacrylate, polyalkyldiol diacrylate, polyalkyldiol dimethacrylate, polydivinylbenzene, polyether, polycarbonate, polyamide, polyester, polyvinyl chloride, polyimide, polycarboxylic acid, polysulfonic acid, polyvinyl alcohol, polysulfone, polystyrene, polyethylene, polypropylene, poly(p-phenylene), polyacetylene, poly(p-phenylene vinylene), polyaniline, polypyrrole, polythiophene, poly(2,5-ethylene vinylene), polyacene, and poly(naphthalene-2,6-diyl), polyethylene oxide, polypropylene oxide, polyvinylidene fluoride, copolymer of vinylidene fluoride and hexafluoropropylene, poly(vinyl acetate), poly(vinyl butyral-co-vinyl alcohol-co-vinyl acetate), poly(methyl methacrylate-co-ethyl acrylate), polyacrylonitrile, polyvinyl chloride-co-vinyl acetate, poly(1-vinylpyrrolidone-co-vinyl acetate), polyvinylpyrrolidone, polyacrylate, polymethacrylate, polyurethane, polyvinyl ether, acrylonitrile-butadiene rubber, styrene-butadiene rubber, acrylonitrile-butadiene-styrene The polymer may be one or more selected from the group consisting of ethylene rubber, sulfonated styrene / ethylene-butylene triblock copolymer, ethoxylated neopentyl glycol diacrylate, ethoxylated bisphenol A diacrylate, ethoxylated aliphatic urethane acrylate, ethoxylated alkylphenol acrylate, and alkyl acrylate, polyvinyl alcohol, polyimide, epoxy resin, and acrylic resin, or a combination thereof, but is not limited thereto. Any polymer capable of forming a fibrous structure in the art may be used. The polymer material may further contain a lithium salt.

[0056] Examples of metal-containing inorganic materials include, but are not limited to, SiO2, TiO2, Al2O3, AlN, SiC, BaTiO3, MOF (Metal Organic Framework), POSS (Polyhedral Oligomeric Silsesquioxanes), Li2CO3, Li3PO4, Li3N, Li3S4, Li2O, montmorillonite, or combinations thereof, and any metal-containing inorganic material known in the art that can form a fibrous structure can be used. The metal-containing inorganic material may have a fibrous structure.

[0057] Examples of sulfide-based solid electrolytes include Li2S-P2S5, Li2S-P2S5-LiX, where X is a halogen element, 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, and Li2S-P2S5-Z. m S n , m and n are positive numbers, Z is one of Ge, Zn or Ga, Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q , p, q are positive numbers, M is one of P, Si, Ge, B, Al, Ga, In, Li 7-x PS 6-x Cl x , 0≦x≦2, Li 7-x PS 6-x Br x , 0≦x≦2, and Li 7-x PS 6-x I x , and 0≦x≦2. The sulfide-based solid electrolyte is prepared by processing starting materials such as Li2S and P2S5 by a melt quenching method or a mechanical milling method. After such processing, a heat treatment may be performed. The sulfide-based solid electrolyte may be amorphous, crystalline, or a mixture thereof. The sulfide-based solid electrolyte may contain, for example, sulfur (S), phosphorus (P), and lithium (Li) as constituent elements of the sulfide-based solid electrolyte material. For example, the sulfide-based solid electrolyte may be a material containing Li2S-P2S5. When the sulfide-based solid electrolyte material contains Li2S-P2S5, the molar ratio of Li2S to P2S5 is, for example, in the range of about Li2S:P2S5=50:50 to 90:10. The sulfide-based solid electrolyte may contain, for example, Li 7-x PS 6-x Cl x , 0≦x≦2, Li 7-x PS 6-x Br x , 0≦x≦2, and Li 7-xPS 6-x I x The sulfide-based solid electrolyte may be an argyrodite-type compound containing one or more selected from the group consisting of 0≦x≦2. The sulfide-based solid electrolyte may contain one or more selected from the group consisting of Li6PS5Cl, Li6PS5Br, and Li6PS5I. The sulfide-based solid electrolyte may have a fibrous structure.

[0058] The oxide-based solid electrolyte is, for example, 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, Li3PO4, Li x Ti y (PO4)3(0 <x<2、0<y<3)、Li x Al y Ti z (PO4)3(0 <x<2、0<y<1、0<z<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), Li x La y TiO3(0 <x<2、0<y<3)、Li2O、LiOH、Li2CO3、LiAlO2、Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2、Li 3+x La3M2O 12(M = Te, Nb, or Zr, 0 ≦ x ≦ 10), or a combination thereof. The oxide-based solid electrolyte is produced, for example, by a sintering method or the like. The oxide-based solid electrolyte is, for example, Li7La3Zr2O 12 (LLZO) and Li 3+x La3Zr 2-a M a O 12 (M doped LLZO, M = Ga, W, Nb, Ta, or Al, 0 < a < 2, 0 ≦ x ≦ 10) is a garnet-type solid electrolyte selected therefrom. The oxide-based solid electrolyte may have a fibrous structure.

[0059] The carbon-based material, polymer, metal-containing inorganic material, or a combination thereof may further contain P, S, or a combination thereof. The carbon-based material, polymer, metal-containing inorganic material, or a combination thereof may be doped, for example, with P, S, or a combination thereof. The carbon-based material, polymer, metal-containing inorganic material, or a combination thereof may be mixed, for example, with a compound containing P, S, or a combination thereof.

[0060] The core 110 can be used as a template for the first fibrous sulfide-based solid electrolyte 100. The core 110 may have a high elastic modulus. The elastic modulus of the core 110 is, for example, 1 MPa or more, 10 MPa or more, or 100 MPa or more. The elastic modulus of the core 110 is also, for example, 1 MPa to 1 GPa, 10 MPa to 1 GPa, or 100 MPa to 1 GPa. By the core 110 having an elastic modulus within such a range, the mechanical properties of the first fibrous sulfide-based solid electrolyte 100 can be further improved.

[0061] The shell 120 may include, for example, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, and a coating material. The coating material can be disposed on a part or all of the core 110. The coating material can impart, for example, water resistance and adhesion to the core 110.

[0062] The sulfide-based solid electrolyte and the oxide-based solid electrolyte may be selected from the solid electrolytes contained in the core 110 .

[0063] The coating material is not particularly limited, and any material that provides the first fibrous sulfide-based solid electrolyte 100 with the properties required for lithium batteries, such as water resistance and binding strength, can be used. The coating material can also be, for example, a sulfide-based solid electrolyte that is substantially free of bridging sulfur and Li2S. The coating material can also be, for example, a composition containing only Li2S and a compound containing an element from Groups 14 to 15 of the Periodic Table, such as P, Si, or Ge. In a composition containing only Li2S and P2S5, the Li2S content is 70% to 85%. In a composition containing only Li2S and P2S5, the Li2S content is 50% to 80%. In a composition containing only Li2S and GeS2, the Li2S content is also 50% to 80%. In the above-mentioned compositions, no bridging sulfur peak is observed in the Raman spectrum, and no Li2S peak is observed in the XRD spectrum. By having the above-mentioned molar fractions in the sulfide-based solid electrolyte, the amount of hydrogen sulfide generated can be reduced. The sulfide-based solid electrolyte does not contain bridging sulfur and does not contain Li2S, which can reduce the amount of hydrogen sulfide generated. The sulfide-based solid electrolyte is also a sulfide glass.

[0064] The coating material is also a sulfide-based solid electrolyte containing, for example, crystallized glass having a composition of yLi2S-(100-x-y)P2S5.xP2O5 (0 < x < 25 and 67 < y < 80). Such crystallized glass has improved stability against water due to having an ortho composition, and the amount of hydrogen sulfide generated can be reduced. Ortho generally refers to the oxo acid obtained by hydrating the same oxide with the highest degree of hydration. In the Li2S-P2S5-based sulfide-based solid electrolyte, the crystal composition with the most Li2S added to P2S5, that is, Li3PS4, corresponds to the ortho composition. Since the molar fraction of Li2S is 75% in 75Li2S-25 P2S5, it has an ortho composition and substantially does not contain cross-linked sulfur. Cross-linked sulfur is, for example, the sulfur that cross-links two phosphorus atoms in S3P-S-PS3 formed by the reaction of Li2S and P2S5. Such cross-linked sulfur easily reacts with water and easily generates hydrogen sulfide. The fact that the sulfide-based solid electrolyte substantially does not contain cross-linked sulfur can be confirmed, for example, by measuring the Raman spectrum. In the Raman spectrum, the peak of S3P-S-PS3 is usually at 402 cm -1 as shown. In the Raman spectrum of the sulfide-based solid electrolyte, the peak at 402 cm -1 is not detected at all. In the Raman spectrum of the sulfide-based solid electrolyte, a peak (417 cm 3- ) indicating PS4 -1 can be confirmed.

[0065] The coating material may include, for example, a binder, such as, but not limited to, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), styrene-butadiene rubber, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer, polychlorotrifluoroethylene, vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymer, ethylene-acrylic acid copolymer, or a combination thereof.

[0066] At least one of the core 110 and the shell 120 may include a sulfide-based solid electrolyte. By including at least one of the core 110 and the shell 120 in a compound-based solid electrolyte, excellent ionic conductivity and mechanical properties may be simultaneously provided.

[0067] The core 110 may include, for example, a fibrous nanostructure, i.e., a two-dimensional nanostructure. When the core 110 includes a two-dimensional nanostructure, the shell 120 disposed on the core 110 can easily have a two-dimensional structure.

[0068] The two-dimensional nanostructure may include, for example, carbon nanofibers, carbon nanorods, carbon nanotubes, carbon nanoneedles, carbon nanowires, SiO2, TiO2, Al2O3, AlN, SiC, BaTiO3, or combinations thereof, but is not necessarily limited thereto, and any two-dimensional nanostructure used in the art may be used.

[0069] By including such a two-dimensional nanostructure as the core 110 in the first fibrous sulfide-based solid electrolyte 100, the ion conduction path is extended within a lithium battery including the first fibrous sulfide-based solid electrolyte 100, and the volume change of the positive electrode active material during charging and discharging of the lithium battery can be more effectively accommodated, maintaining the ion conduction path within the lithium battery despite the volume change of the positive electrode active material. As a result, deterioration of the lithium battery can be further suppressed, and the cycle characteristics of the lithium battery can be further improved.

[0070] 2 to 5, the ratio of the first diameter D1 of the core 110 to the first thickness T1 of the shell 120 may be, for example, 1:0.01 to 1:1000, 1:0.1 to 1:1000, 1:0.1 to 1:100, 1:0.1 to 1:10, 1:0.5 to 1:5, 1:1 to 1:4, 1:1 to 1:3, or 1:1 to 1:2. The ratio of the first length L1 of the core 110 to the second length L2 of the shell 120 may be 1:1 to 1:10, 1:1.01:1:5, 1.01:1:2, 1:1.03 to 1:1.5, 1:1.05 to 1:1.3, or 1:1.05 to 1:1.1.

[0071] When the core 110 and shell 120 of the first fibrous sulfide-based solid electrolyte 100 have a thickness ratio and / or length ratio within such ranges, the ion conduction path is extended within a lithium battery including the first fibrous sulfide-based solid electrolyte 100, more effectively accommodating volume changes in the positive electrode active material during charging and discharging of the lithium battery, and maintaining the ion conduction path within the lithium battery despite volume changes in the positive electrode active material. As a result, deterioration of the lithium battery is further suppressed, and the cycle characteristics of the lithium battery are further improved.

[0072] Although not shown in the drawings, the core 110 may have a multi-layer structure. The multi-layer structure of the core 110 allows for more flexible adjustment of the shape, physical properties, etc. of the core 110. The core 110 may have, for example, a two-layer structure, a three-layer structure, or a four-layer structure. The layers of the core 110 having a multi-layer structure may contain the same or different materials.

[0073] Although not shown in the drawings, the shell 120 may have a multi-layer structure. The multi-layer structure of the shell 120 allows for more flexible adjustment of the shape, physical properties, etc. of the shell 120. The shell 120 may have, for example, a two-layer structure, a three-layer structure, or a four-layer structure. The layers of the shell 120 having a multi-layer structure may contain the same or different materials.

[0074] 5, an interlayer 130 may be further included between the core 110 and the shell 120. When the first fibrous sulfide-based solid electrolyte 100 further includes the interlayer 130, the bonding strength between the core 110 and the shell 120 may be improved, and the structural stability of the core 110 and the shell 120 may be improved. The interlayer 130 is optional.

[0075] The mid layer 130 may have a second thickness T2 and a third length L3. The third length L3 of the mid layer 130 may be, for example, greater than the first length L1 of the core 110 and less than the second length L2 of the shell 120. The third length L3 of the mid layer 130 may be, for example, 101% to 150%, 101% to 120%, or 101% to 110% of the first length L1 of the core 110. The second thickness T2 of the mid layer 130 may be, for example, 1% to 50%, 1% to 20%, or 1% to 10% of the first diameter (D1) of the core 110. The material of the mid layer 130 may be selected from the materials used for the core 110 and the shell 120. The material of the mid layer may be, for example, a polymer.

[0076] 6A and 7 to 11, the cathode layer 10 includes a cathode current collector 11 and a cathode active material layer 12. The cathode active material layer 12 includes a first region 12A adjacent to the cathode current collector 11 and a second region 12B adjacent to the solid electrolyte layer 30. For example, a first fibrous sulfide-based solid electrolyte 100 is disposed in the first region 12A, and the first fibrous sulfide-based solid electrolyte 100 is free in the second region 12B. The thickness of the first region 12A is 50% or less, 40% or less, 30% or less, or 20% or less of the total thickness of the cathode active material layer 12. The first fibrous sulfide-based solid electrolyte 100 may be uniformly distributed within the first region 12A. In another embodiment, the first fibrous sulfide-based solid electrolyte 100 may have a concentration gradient that decreases within the first region 12A, for example, in the direction from the positive electrode current collector 11 to the solid electrolyte layer 30. Because the first fibrous sulfide-based solid electrolyte 100 is disposed in the first region 12A and absent in the second region 12B, a long-distance ion conduction path is more easily formed in the first region 12A, which has an increased separation distance from the positive electrode layer, and lithium ions may be more easily conducted within the positive electrode active material layer 12. Therefore, an increase in internal resistance during charge and discharge of the lithium battery may be suppressed, and the cycle characteristics of the lithium battery may be further improved.

[0077] 6B and 7 to 11, the cathode layer 10 includes a cathode current collector 11 and a cathode active material layer 12. The cathode active material layer 12 includes a first region 12A adjacent to the cathode current collector 11 and a second region 12B adjacent to the solid electrolyte layer 30. For example, a first fibrous sulfide-based solid electrolyte 100 is disposed in the second region 12B, and the first fibrous sulfide-based solid electrolyte 100 is free in the first region 12A. The thickness of the second region 12B is 50% or less, 40% or less, 30% or less, or 20% or less of the total thickness of the cathode active material layer 12. The first fibrous sulfide-based solid electrolyte 100 may be uniformly distributed within the second region 12B, for example. In another embodiment, the first fibrous sulfide-based solid electrolyte 100 may have a concentration gradient that decreases within the second region 12B, for example, in the direction from the solid electrolyte layer 30 to the positive electrode current collector 11. By disposing the first fibrous sulfide-based solid electrolyte 100 in the second region 12B adjacent to the solid electrolyte layer 30, the interfacial resistance between the electrolyte layer 30 and the positive electrode active material layer 12 may be more effectively reduced, and lithium ions may be more easily conducted from the solid electrolyte layer 30 into the positive electrode active material layer 12. Therefore, an increase in internal resistance during charge and discharge of the lithium battery may be suppressed, and the cycle characteristics of the lithium battery may be further improved.

[0078] 6C and 7 to 11, the cathode layer 10 includes a cathode current collector 11 and a cathode active material layer 12. The cathode active material layer 12 includes a first region 12A adjacent to the cathode current collector and a second region 12B adjacent to the solid electrolyte layer 30. For example, the first fibrous sulfide-based solid electrolyte 100 may be disposed in the first region 12A and the second region 12B. By disposing the first fibrous sulfide-based solid electrolyte 100 simultaneously in the first region 12A and the second region 12B, the ionic conductivity of the cathode active material layer 12 may be improved overall. The first fibrous sulfide-based solid electrolyte 100 may be disposed uniformly throughout the first region 12A and the second region 12B. For example, the first fibrous sulfide-based solid electrolyte 100 may have a concentration gradient that decreases overall from the cathode current collector 11 toward the solid electrolyte layer 30 in the first region 12A and the second region 12B. The first fibrous sulfide-based solid electrolyte 100 may have, for example, a concentration gradient that decreases in the direction from the solid electrolyte layer 30 toward the positive electrode current collector 11 in the first region 12A and the second region 12B.

[0079] 6A to 6C and 7 to 11, the content of the first fibrous sulfide-based solid electrolyte 100 may be, for example, 1 to 50 wt%, 1 to 40 wt%, 5 to 40 wt%, 10 to 40 wt%, 15 to 40 wt%, 20 to 40 wt%, or 25 to 40 wt% of the total weight of the positive electrode active material layer 12. The content of the first fibrous sulfide-based solid electrolyte 100 may be, for example, 1 to 30 wt%, 1 to 25 wt%, 1 to 20 wt%, 1 to 10 wt%, or 1 to 5 wt% of the total weight of the positive electrode active material layer 12. When the cathode active material layer 12 has a first fibrous sulfide-based solid electrolyte 100 content within this range, the ion conduction paths within the cathode active material layer 12 containing the first fibrous sulfide-based solid electrolyte 100 are extended, more effectively accommodating volumetric changes in the cathode active material during charging and discharging of the lithium battery, and maintaining the ion conduction paths within the lithium battery despite volumetric changes in the cathode active material. As a result, deterioration of the lithium battery is further suppressed, and the cycle characteristics of the lithium battery are further improved. If the content of the first fibrous sulfide-based solid electrolyte 100 is excessively high, the filling between the first fibrous sulfide-based solid electrolyte 100 particles within the cathode active material layer 12 may be incomplete, resulting in increased interfacial resistance.

[0080] The positive electrode active material layer 12 may further include an irregular-shaped sulfide-based solid electrolyte that is distinct from the first fibrous sulfide-based solid electrolyte 100. The aspect ratio of the irregular sulfide-based solid electrolyte is less than 2, 1.5 or less, or 1.3 or less. The particle size of the irregular sulfide-based solid electrolyte may be, for example, 0.1 to 50 μm, 0.1 to 50 μm, 0.1 to 30 μm, 0.1 to 20 μm, 0.1 to 10 μm, 0.1 to 5 μm, or 0.1 to 3 μm. The weight ratio of the first fibrous sulfide-based solid electrolyte 100 to the amorphous sulfide-based solid electrolyte may be, for example, 1:99 to 99:1, 5:95 to 95:5, 10:90 to 90:10, 20:80 to 80:20, or 30:70 to 70:30. The weight ratio of the first fibrous sulfide-based solid electrolyte 100 to the amorphous sulfide-based solid electrolyte may be, for example, 1:99 to 50:50, 3:97 to 40:60, 5:95 to 30:70, 5:95 to 25:75, or 5:95 to 20:80. When the weight ratio of the first fibrous sulfide-based solid electrolyte 100 to the amorphous sulfide-based solid electrolyte falls within such a range, deterioration of the lithium battery may be further suppressed, and the cycle characteristics of the lithium battery may be further improved.

[0081] The size of the solid electrolyte contained in the positive electrode active material layer 12 is smaller than the size of the solid electrolyte contained in the solid electrolyte layer 30. For example, the D50 average particle size of the solid electrolyte contained in the positive electrode active material layer 12 is 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, or 20% or less of the D50 average particle size of the solid electrolyte contained in the solid electrolyte layer 30. The D50 average particle size is, for example, the median particle size (D50). The median particle size (D50) is the particle size corresponding to a 50% cumulative volume calculated from the particle side having a small particle size in a particle size distribution measured by, for example, a laser diffraction method. The particle size of the sulfide-based solid electrolyte can be measured, for example, using a measuring device using a laser diffraction method or a dynamic light scattering method. The particle size is measured, for example, using a laser scattering particle size distribution analyzer (e.g., HORIBA LA-920) and is the median particle size (D50) value when 50% of the particles are accumulated from the smallest particle side in volume conversion. In another embodiment, the particle size of the sulfide-based solid electrolyte can be measured from a scanning electron microscope (SEM) image or an optical microscope.

[0082] [Cathode layer: Cathode active material] 7 to 11, the positive electrode active material layer 12 includes, for example, a positive electrode active material.

[0083] The positive electrode active material contained in the positive electrode active material layer 12 is a positive electrode active material that can reversibly absorb and desorb lithium ions. The positive electrode active material includes, for example, an oxide-based positive electrode active material, a sulfide-based positive electrode active material, or a combination thereof.

[0084] The oxide-based positive electrode active material may include, for example, a lithium transition metal oxide, a metal oxide, or a combination thereof. Examples of the lithium transition metal oxide include, for example, lithium cobalt oxide, lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese oxide, lithium manganate, lithium iron phosphate, or a combination thereof. Examples of the lithium oxide include, for example, iron oxide, vanadium oxide, or a combination thereof.

[0085] Sulfide-based positive electrode active materials include, for example, nickel sulfide, copper sulfide, Li2S, Li2S-containing composites, or combinations thereof.

[0086] The oxide-based positive electrode active material can be, for example, one or more composite oxides of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof. a A 1-b B' b D2 (wherein 0.90≦a≦1, and 0≦b≦0.5), Li a E 1-b B' b O 2-c D c (wherein, 0.90≦a≦1, 0≦b≦0.5, 0≦c≦0.05), LiE 2-b B' b O 4-c D c (wherein 0≦b≦0.5 and 0≦c≦0.05), Lia Ni 1-b-c Co b B' c D α (wherein, 0.90≦a≦1, 0≦b≦0.5, 0≦c≦0.05, 0<α≦2), Li a Ni 1-b-c Co b B' c O 2-α F' α (wherein, 0.90≦a≦1, 0≦b≦0.5, 0≦c≦0.05, 0<α<2), Li a Ni 1-b-c Co b B' c O2 (wherein 0.90≦a≦1, 0≦b≦0.5, and 0≦c≦0.05), Li a Ni 1-b-c Mn b B' c D α (wherein, 0.90≦a≦1, 0≦b≦0.5, 0≦c≦0.05, 0<α≦2), Li a Ni 1-b-c Mn b B' c O 2-α F' α (wherein, 0.90≦a≦1, 0≦b≦0.5, 0≦c≦0.05, 0<α<2), Li a Ni 1-b-c Mn b B' c O2 (wherein 0.90≦a≦1, 0≦b ≦0.5, 0≦c≦0.05), Li a Ni b E c G d O2 (wherein 0.90≦a≦1, 0≦b≦0.9, 0≦c≦0.5, 0.001≦d≦0.1), Li a Ni b Co c Mn d G e O2 (wherein 0.90≦a≦1, 0≦b≦0.9, 0≦c≦0.5, 0≦d ≦0.5, 0.001≦e≦0.1), Li a NiG bO2 (wherein 0.90≦a≦1, 0.001≦b≦0.1), Li a CoG b O2 (wherein 0.90≦a≦1, 0.001≦b≦0.1), Li a MnG b O2 (wherein 0.90≦a≦1, 0.001≦b≦0.1), Li a Mn2G b O4 (wherein 0.90≦a≦1, 0.001≦b≦0.1), LiV2O5, LiI'O2, LiNiVO4, Li (3-f) J2(PO4)3(0≦f≦2), Li (3-f) It may contain a compound represented by any one of the chemical formulas Fe2(PO4)3(0≦f≦2) and LiFePO4.

[0087] In the chemical formula representing the above-mentioned compound, A is Ni, Co, Mn, or a combination thereof; B' 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; E is Co, Mn, or a combination thereof; F' is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; I' is Cr, V, Fe, Sc, Y, or a combination thereof; and J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof. Compounds with a coating layer added to the surface of the above-mentioned compound can also be used, or a mixture of the above-mentioned compound and a compound with a coating layer added can also be used. The coating layer applied to the surface of the aforementioned compound includes a coating element compound such as an oxide, hydroxide, oxyhydroxide, oxycarbonate, or hydroxycarbonate of the coating element. The compound forming the coating layer may be amorphous or crystalline. The coating element contained in the coating layer may be Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof. The coating layer formation method is selected within a range that does not adversely affect the physical properties of the positive electrode active material. Examples of the coating method include spray coating and dipping. Specific coating methods are well known to those skilled in the art, so a detailed description will be omitted.

[0088] The oxide-based positive electrode active material may include, for example, lithium transition metal oxides represented by the following Chemical Formulas 1 to 8:

[0089] <C1> Li a Ni x Co y M z O 2-b A b

[0090] In the chemical formula 1, 1.0 ≤ a ≤ 1.2, 0 ≤ b ≤ 0.2, 0.8 ≤ x < 1, 0 ≤ y ≤ 0.3, 0 < z ≤ 0.3, and x + y + z = 1, M is manganese (Mn), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B) or a combination thereof, A is F, S, Cl, Br or a combination thereof,

[0091] <Chemical formula 2> LiNi x Co y Mn z O2

[0092] <Chemical formula 3> LiNi x Co y Al z O2

[0093] In the chemical formulas 2 and 3, 0.8 ≤ x ≤ 0.95, 0 ≤ y ≤ 0.2, 0 < z ≤ 0.2 and x + y + z =​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​ 1.0 ≤ a ≤ 1.2, 0 ≤ b ≤ 0.2, 0.9 ≤ x ≤ 1, 0 ≤ y ≤ 0.1, and x + y = 1, M is manganese (Mn), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B) or a combination thereof, A is F, S, Cl, Br or a combination thereof,

[0098] <Chemical Formula 6> Li a Ni x Mn y M’ z O 2-b A b

[0099] In Chemical Formula 6 above, 1.0 ≤ a ≤ 1.2, 0 ≤ b ≤ 0.2, 0 < x ≤ 0.3, 0.5 ≤ y < 1, 0 < z ≤ 0.3, and x + y + z = 1, M’ is cobalt (Co), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B) or a combination thereof, A is F, S, Cl, Br or a combination thereof,

[0100] <Chemical Formula 7> Li a M1 x M2 y PO 4-b X b

[0101] In Chemical Formula 7 above, 0.90 ≤ a ≤ 1.1, 0 ≤ x ≤ 0.9, 0 ≤ y ≤ 0.5, 0.9 < x + y < 1.1, 0 ≤ b ≤ 2, M1 is chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr), or a combination thereof; M2 is magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), titanium (Ti), zinc (Zn), boron (B), niobium (Nb), gallium (Ga), indium (In), molybdenum (Mo), tungsten (W), aluminum (Al), silicon (Si), chromium (Cr), vanadium (V), scandium (Sc), yttrium (Y), or a combination thereof; and X is O, F, S, P, or a combination thereof.

[0102] <8> Li a M3 z PO4

[0103] In the above Chemical Formula 8, 0.90≦a≦1.1 and 0.9≦z≦1.1; M3 is chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr), or a combination thereof.

[0104] The oxide-based positive electrode active material is also covered with a coating layer. Any known coating layer for a positive electrode active material in an all-solid-state secondary battery can be used. For example, the coating layer is Li2O-ZrO2 (LZO).

[0105] The size of the oxide-based positive electrode active material is, for example, 0.1 to 30 μm, 0.5 to 20 μm, or 1 to 15 μm. The oxide-based positive electrode active material is, for example, single crystal particles or polycrystalline particles.

[0106] The sulfide-based positive electrode active material may include, for example, a LiS-containing composite, such as a composite of LiS and carbon, a composite of LiS, carbon, and a solid electrolyte, a composite of LiS and a solid electrolyte, a composite of LiS and a lithium salt, a composite of LiS, a lithium salt, and carbon, a composite of LiS and a metal carbide, a composite of LiS, carbon, and a metal carbide, a composite of LiS and a metal nitride, a composite of LiS, carbon, and a metal nitride, or a combination thereof.

[0107] The Li2S and carbon composite includes carbon. Carbon can be, for example, any material containing carbon atoms that is used as a conductive material in the art. Carbon can be, for example, crystalline carbon, amorphous carbon, or a combination thereof. Carbon can be, for example, a calcined product of a carbon precursor. Carbon can be, for example, a carbon nanostructure. Carbon nanostructures can be, for example, one-dimensional carbon nanostructures, two-dimensional carbon nanostructures, three-dimensional carbon nanostructures, or a combination thereof. Carbon nanostructures can be, for example, carbon nanotubes, carbon nanofibers, carbon nanobelts, carbon nanorods, graphene, graphene oxide (GO), reduced graphene oxide (rGO), graphene balls (GB), or a combination thereof. Carbon can be, for example, porous carbon or non-porous carbon. Porous carbon can include, for example, periodic and regular two-dimensional or three-dimensional pores. Porous carbon can be, for example, carbon black such as Ketjen black, acetylene black, Denka black, thermal black, or channel black, graphite, activated carbon, or a combination thereof. The carbon can be in the form of, for example, particles, sheets, or fibers, but is not limited thereto, and any method commonly used in the art can be used. The LiS / carbon composite can be produced by, for example, a dry method, a wet method, or a combination thereof, but is not limited thereto. Examples of methods commonly used in the art for producing LiS / carbon composites include, but are not limited to, milling, heat treatment, and vapor deposition. Any method commonly used in the art can be used.

[0108] The composite of Li2S, carbon, and a solid electrolyte includes carbon and a solid electrolyte. Carbon refers to the composite of Li2S and carbon described above. The solid electrolyte is, for example, an amorphous solid electrolyte, and any solid electrolyte used as an ion-conducting material in the art can be used. The solid electrolyte is, for example, an inorganic solid electrolyte. The solid electrolyte is, for example, a crystalline solid electrolyte, an amorphous solid electrolyte, or a combination thereof. The solid electrolyte is, for example, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or a combination thereof. The sulfide-based solid electrolyte contains, for example, Li, S, and P, and may optionally further contain a halogen element. The sulfide-based solid electrolyte can be selected from sulfide-based solid electrolytes used in the solid electrolyte layer. The sulfide-based solid electrolyte has a specific surface area of, for example, 1×10 at room temperature. -5 Examples of sulfide-based solid electrolytes include Li3PO4-Li2SO4, Li2S-P2S5, Li2S-P2S5-LiX, where X is a halogen element, 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, and Li2S-P2S5-Z. m S n , m and n are positive numbers, Z is one of Ge, Zn or Ga, Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q , p, q are positive numbers, M is one of P, Si, Ge, B, Al, Ga, In, Li 7-x PS 6-x Cl x , 0≦x≦2, Li 7-x PS 6-x Br x , 0≦x≦2, and Li 7-x PS 6-x I x , 0≦x≦2. The oxide-based solid electrolyte may include, for example, Li, O, and a transition metal element, and may further include other elements selectively. The oxide-based solid electrolyte may have a specific surface area of ​​1×10-5 The solid electrolyte may also be a solid electrolyte having an ionic conductivity of 500 S / cm or more. The oxide-based solid electrolyte may be selected from oxide-based solid electrolytes used in the solid electrolyte layer. The solid electrolyte may also be, for example, a mixture of a sulfide-based solid electrolyte and a lithium salt. For example, the solid electrolyte may be a mixture of Li3PO4-Li2SO4 and a binary lithium salt, or a mixture of Li3PO4-Li2SO4 and a ternary lithium salt.

[0109] The composite of Li2S and a solid electrolyte includes a solid electrolyte, which refers to the composite of Li2S, carbon, and a solid electrolyte described above.

[0110] The complex of Li2S and a lithium salt includes a lithium salt compound. The lithium salt compound does not contain, for example, a sulfur (S) atom. The lithium salt compound can also be, for example, a binary compound consisting of lithium and one element selected from Groups 13 to 17 of the periodic table. The binary compound can include, for example, one or more elements selected from LiF, LiCl, LiBr, LiI, LiH, Li2S, Li2O, Li2Se, Li2Te, Li3N, Li3P, Li3As, Li3Sb, LiI3, and LiB3. The lithium salt compound can also be, for example, a ternary compound consisting of lithium and two elements selected from Groups 13 to 17 of the periodic table. The ternary compound may include, for example, one or more selected from Li3OCl, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiNO3, Li2CO3, LiBH4, Li2SO4, Li3BO3, Li3PO4, Li4NCl, Li5NCl2, and Li3BN2. The lithium salt compound may be, in particular, one or more lithium halide compounds selected from LiF, LiCl, LiBr, and LiI. The composite of Li2S and a solid electrolyte includes a solid electrolyte. The solid electrolyte refers to the solid electrolyte used in the composite of Li2S, carbon, and a solid electrolyte described above. The composite of Li2S and a solid electrolyte includes, for example, a composite of Li2S and one or more lithium salts selected from LiF, LiCl, LiBr, LiI, LiH, Li2S, Li2O, Li2Se, Li2Te, Li3N, Li3P, Li3As, Li3Sb, LiI3, and LiB3.

[0111] The composite of Li2S, a lithium salt, and carbon includes a lithium salt compound and carbon. The carbon refers to the composite of Li2S and carbon described above.

[0112] The composite of Li2S and metal carbide includes a metal carbide. The metal carbide is, for example, a two-dimensional metal carbide. The two-dimensional metal carbide is, for example, MXene. The two-dimensional metal carbide is, for example, M n+1 C n T x(M is a transition metal, T is an end group, T is O, OH and / or F, n=1, 2 or 3, x is the number of end groups). Two-dimensional metal carbides are, for example, Ti2CT x , (Ti 0.5 , Nb 0.5 )2CT x , Nb2CT x , V2CT x , Ti3C2T x , (V 0.5 , Cr 0.5 )3C2T x , Ti3CNT x , Ta4C3T x , Nb4C3T x or a combination thereof. The surface of the two-dimensional metal carbide is terminated with O, OH and / or F.

[0113] The composite of Li2S, carbon, and metal carbide includes carbon and metal carbide. Carbon refers to the composite of Li2S and carbon described above. Metal carbide refers to the composite of Li2S and metal carbide described above.

[0114] The composite of Li2S and metal nitride includes a metal nitride. The metal nitride is, for example, a two-dimensional metal nitride. The two-dimensional metal nitride is, for example, M n+1 N n T x (M is a transition metal, T is a terminal group, T is O, OH and / or F, n=1, 2 or 3, x is the number of terminal groups). The surface of the two-dimensional metal nitride is terminated with O, OH and / or F.

[0115] The composite of Li2S, carbon, and metal nitride includes carbon and metal nitride. Carbon refers to the composite of Li2S and carbon described above. Metal carbide refers to the composite of Li2S and metal nitride described above.

[0116] The LiS-containing composite may further include, for example, a second fibrous sulfide-based solid electrolyte (not shown). The LiS-containing composite may be a composite of LiS and the second fibrous sulfide-based solid electrolyte, or a composite of LiS and the second fibrous sulfide-based solid electrolyte with the aforementioned carbon, solid electrolyte, lithium salt, metal carbide, or metal nitride.

[0117] When the Li2S-containing composite further contains a second fibrous sulfide-based solid electrolyte, deterioration of the lithium battery can be further suppressed, and the cycle characteristics of the lithium battery can be further improved. The size of the second fibrous sulfide-based solid electrolyte is smaller than that of the first fibrous sulfide-based solid electrolyte 100. The length and / or thickness of the second fibrous sulfide-based solid electrolyte are 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less of the length and / or thickness of the first fibrous sulfide-based solid electrolyte 100. The length and / or thickness of the second fibrous sulfide-based solid electrolyte are 0.1 to 50%, 0.5 to 40%, 1 to 30%, 1 to 20%, or 1 to 10% of the length and / or thickness of the first fibrous sulfide-based solid electrolyte 100. The second fibrous sulfide-based solid electrolyte can have the same shape as the first fibrous sulfide-based solid electrolyte 100, but be smaller in size. The second fibrous sulfide-based solid electrolyte having such a reduced length and / or thickness can be easily distributed within the LiS-containing composite, and the second fibrous sulfide-based solid electrolyte having such a reduced length and / or thickness can further suppress deterioration of the lithium battery and further improve the cycle characteristics of the lithium battery.

[0118] The size of the sulfide-based positive electrode active material is, for example, 0.1 to 50 μm, 0.5 to 30 μm, 0.5 to 20 μm, or 1 to 10 μm. The size of Li2S is, for example, 1 nm to 10 μm, 10 nm to 5 μm, 10 nm to 3 μm, or 10 nm to 1 μm. The size of the Li2S-containing composite is, for example, 0.1 to 50 μm, 0.5 to 30 μm, 0.5 to 20 μm, or 1 to 10 μm.

[0119] The positive electrode active material may also be a composite positive electrode active material including, for example, a core that absorbs / desorbs lithium and a shell disposed on the core.

[0120] The composite positive electrode active material includes, for example, a core that absorbs / desorbs lithium and a shell disposed along the surface of the core, and the shell is represented by the chemical formula M a O bOne or more first metal oxides represented by (0 < a ≤ 3, 0 < b < 4, and if a is 1, 2, or 3, b is not an integer), and graphene, wherein the first metal oxide is disposed within a graphene matrix, and M is one or more metals selected from Groups 2 to 13, Group 15, and Group 16 of the periodic table. The core for lithium intercalation / deintercalation includes, for example, the aforementioned Li₂S-containing composite. The Li₂S-containing composite includes, for example, a composite of Li₂S and carbon, a composite of Li₂S, carbon, and a solid electrolyte, a composite of Li₂S and a solid electrolyte, a composite of Li₂S and a lithium salt, a composite of Li₂S, a lithium salt, and carbon, a composite of Li₂S and a metal carbide, a composite of Li₂S, carbon, and a metal carbide, a composite of Li₂S and a metal nitride, a composite of Li₂S, carbon, and a metal nitride, or a combination thereof. The core for lithium intercalation / deintercalation may include, for example, lithium transition metal oxides represented by Chemical Formulas 1 to 8. The core for lithium intercalation / deintercalation may include, for example, a lithium transition metal oxide having a Ni content of 80 mol% or more. On the core for lithium intercalation / deintercalation, a shell containing, for example, the first metal oxide and graphene is disposed. Conventional graphene aggregates, making it difficult to form a uniform coating on the core. In contrast, the composite cathode active material uses a composite containing a plurality of first metal oxides disposed in a graphene matrix, thereby preventing the aggregation of graphene and disposing a uniform shell on the core. Therefore, by effectively blocking the contact between the core and the electrolyte, side reactions due to the contact between the core and the electrolyte are prevented. The shell containing graphene has flexibility, so during charge and discharge, by easily accommodating the volume change of the composite cathode active material, the generation of cracks inside the composite cathode active material is suppressed. Graphene has high conductivity, so the interfacial resistance between the composite cathode active material and the electrolyte is reduced. Therefore, even though a shell containing graphene is introduced, the internal resistance of the lithium battery is maintained or decreased. Also, since the first metal oxide has voltage resistance, it can prevent the deterioration of the Li₂S-containing composite or the lithium transition metal oxide contained in the core during charge and discharge at high voltage.As a result, the cycle characteristics and high-temperature stability of the lithium battery containing the composite cathode active material are improved. The shell may include, for example, one type of first metal oxide or two or more different first metal oxides. The metal contained in the first metal oxide is, for example, one or more selected from Al, Nb, Mg, Sc, Ti, Zr, V, W, Mn, Fe, Co, Pd, Cu, Ag, Zn, Sb, and Se. The first metal oxide is, for example, Al2O. z (0 < z < 3), NbO x (0 < x < 2.5), MgO x (0 < x < 1), Sc2O z (0 < z < 3), TiO y (0 < y < 2), ZrO y (0 < y < 2), V2O z (0 < z < 3), WO y (0 < y < 2), MnO y (0 < y < 2), Fe2O z (0 < z < 3), Co3O w (0 < w < 4), PdO x (0 < x < 1), CuO x (0 < x < 1), AgO x (0 < x < 1), ZnO x (0 < x < 1), Sb2O z (0 < z < 3), and SeO y (0 < y < 2) and is one or more selected therefrom. By arranging such a first metal oxide in the graphene matrix, the uniformity of the shell disposed on the core is improved, and the voltage resistance of the composite cathode active material is further improved. For example, the shell contains Al2Ox (0 < x < 3) as the first metal oxide. The shell has the chemical formula M a O cIt may further contain one or more second metal oxides represented by (0 < a ≤ 3, 0 < c ≤ 4, and if a is 1, 2, or 3, c is an integer). The M is one or more metals selected from Groups 2 to 13, Group 15, and Group 16 of the periodic table. For example, the second metal oxide contains the same metal as the first metal oxide, and c / a, which is the ratio of c to a of the second metal oxide, has a value greater than b / a, which is the ratio of b to a of the first metal oxide. For example, c / a > b / a. The second metal oxide is selected from, for example, Al2O3, NbO, NbO2, Nb2O5, MgO, Sc2O3, TiO2, ZrO2, V2O3, WO2, MnO2, Fe2O3, Co3O4, PdO, CuO, AgO, ZnO, Sb2O3, and SeO2. The first metal oxide is a reduction product of the second metal oxide. The first metal oxide is obtained by reducing part or all of the second metal oxide. Therefore, the first metal oxide has a lower oxygen content and a higher metal oxidation number than the second metal oxide. For example, the shell is the first metal oxide Al2O xIt contains (0 < x < 3) and Al2O3 which is the second metal oxide. The thickness of the shell is, for example, 1 nm to 5 μm, 1 nm to 1 μm, 1 nm to 500 nm, 1 nm to 200 nm, 1 nm to 100 nm, 1 nm to 90 nm, 1 nm to 80 nm, 1 nm to 70 nm, 1 nm to 60 nm, 1 nm to 50 nm, 1 nm to 40 nm, 1 nm to 30 nm, 1 nm to 20 nm, or 1 nm to 10 nm. By having the shell with such a range of thickness, an increase in the internal resistance of the lithium battery containing the composite cathode active material is suppressed. The average particle size of one or more selected from the first metal oxide and the second metal oxide contained in the composite is 1 nm to 1 μm, 1 nm to 500 nm, 1 nm to 200 nm, 1 nm to 100 nm, 1 nm to 70 nm, 1 nm to 50 nm, 1 nm to 30 nm, 3 nm to 30 nm, 3 nm to 25 nm, 5 nm to 25 nm, 5 nm to 20 nm, or 7 nm to 20 nm. By having the first metal oxide and / or the second metal oxide with such a nano-scale particle size, it can be more uniformly distributed within the graphene matrix of the composite. Therefore, such a composite can be uniformly coated on the core without aggregation to form a shell. Also, by having the first metal oxide and / or the second metal oxide with such a range of particle sizes, it can be more uniformly arranged on the core. Therefore, by uniformly arranging the first metal oxide and / or the second metal oxide on the core, the withstand voltage characteristics can be more effectively exhibited. The average particle size of the first metal oxide and the second metal oxide can be measured, for example, using a measuring device of a laser diffraction method or a dynamic light scattering method. In other embodiments, the particle sizes of the first metal oxide and the second metal oxide can be measured from a scanning electron microscope and a transmission electron microscope.

[0121] The shape of the positive electrode active material is, for example, particulate, such as a perfect sphere or an oval sphere. The particle size of the positive electrode active material is not particularly limited and is within a range applicable to positive electrode active materials in conventional all-solid-state secondary batteries. The content of the positive electrode active material in the positive electrode layer 10 is also not particularly limited and is within a range applicable to positive electrode layers in conventional all-solid-state secondary batteries. The content of the positive electrode active material in the positive electrode active material layer 12 is, for example, 10 wt% to 99 wt%, 10 wt% to 90 wt%, 10 wt% to 80 wt%, 10 wt% to 70 wt%, or 10 wt% to 50 wt% of the total weight of the positive electrode active material layer 12.

[0122] [Positive electrode layer: conductive material] The positive electrode active material layer 12 may further include a conductive material. The conductive material may be, for example, a carbon-based conductive material, a metal-based conductive material, or a combination thereof. The carbon-based conductive material may be, for example, graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or a combination thereof, but is not limited thereto, and any material used as a carbon-based conductive material in the art may be used. The metal-based conductive material may be, for example, metal powder, metal fiber, or a combination thereof, but is not limited thereto, and any material used as a metal-based conductive material in the art may be used. The content of the conductive material in the positive electrode active material layer 12 may be, for example, 1 wt% to 30 wt%, 1 wt% to 20 wt%, or 1 wt% to 10 wt% of the total weight of the positive electrode active material layer 12.

[0123] [Positive electrode layer: binder] The positive electrode active material layer 12 may further include a binder. Examples of the binder include, but are not limited to, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, and polyethylene. Any binder usable in the art may be used. The content of the binder in the positive electrode active material layer 12 is, for example, 1 wt % to 10 wt % of the total weight of the positive electrode active material layer 12. The binder may be omitted.

[0124] [Positive electrode layer: Other additives] The positive electrode active material layer 12 may further include additives such as a filler, a coating agent, a dispersant, and an ion-conductive auxiliary agent in addition to the above-described positive electrode active material, solid electrolyte, binder, and conductive material.

[0125] As the filler, coating agent, dispersant, ion-conducting auxiliary agent, etc. that may be contained in the positive electrode active material layer 12, known materials that are generally used in electrodes of all-solid-state secondary batteries may be used.

[0126] [Positive electrode layer: Positive electrode current collector] The positive electrode current collector 11 is, for example, a plate or foil made of indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof. The positive electrode current collector 11 can be omitted. The thickness of the positive electrode current collector 11 is, for example, 1 μm to 100 μm, 1 μm to 50 μm, 5 μm to 25 μm, or 10 μm to 20 μm.

[0127] The positive electrode current collector 11 may include, for example, a base film and a metal layer disposed on one or both sides of the base film. The base film may include, for example, a polymer. The polymer may also include, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof. The base film may also be an insulator. When the base film includes an insulating thermoplastic polymer, the base film softens or liquefies in the event of a short circuit, thereby shutting down the battery operation and suppressing a sudden increase in current. The metal layer may include, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), or an alloy thereof. The metal layer acts as an electrochemical fuse and breaks in the event of an overcurrent, thereby preventing a short circuit. The limiting current and maximum current can be adjusted by adjusting the thickness of the metal layer. The metal layer is electrodeposited or vapor-deposited on the base film. A thinner metal layer reduces the limiting current and / or maximum current of the positive electrode current collector 11, thereby improving the stability of the lithium battery during a short circuit. A lead tab can be added to the metal layer for external connection. The lead tab can be welded to the metal layer or the metal layer / base film laminate by ultrasonic welding, laser welding, spot welding, etc. During welding, the base film and / or metal layer melts, electrically connecting the metal layer to the lead tab. To further strengthen the weld between the metal layer and the lead tab, a metal chip can be added between the metal layer and the lead tab. The metal chip can be a thin piece of the same material as the metal of the metal layer. The metal chip can be, for example, a metal foil or a metal mesh. The metal chip can be, for example, an aluminum foil, a copper foil, or a stainless steel foil.After disposing a metal piece on the metal layer, the lead tab can be welded to the metal piece / metal layer laminate or the metal piece / metal layer / base film laminate. During welding, the base film, metal layer, and / or metal piece melt, electrically connecting the metal layer or the metal layer / metal piece laminate to the lead tab. A metal piece and / or lead tab can be added to a portion of the metal layer. The thickness of the base film can be, for example, 1 to 50 μm, 1.5 to 50 μm, 1.5 to 40 μm, or 1 to 30 μm. The weight of the electrode assembly can be further effectively reduced by using a base film having a thickness within this range. The melting point of the base film can be, for example, 100 to 300°C, 100 to 250°C, or 100 to 200°C. By using a base film having a melting point within this range, the base film can be melted during the process of welding the lead tab and easily bonded to the lead tab. To improve the adhesion between the base film and the metal layer, a surface treatment such as a corona treatment may be performed on the base film. The thickness of the metal layer may be, for example, 0.01 to 3 μm, 0.1 to 3 μm, 0.1 to 2 μm, or 0.1 to μm. When the metal layer has a thickness within this range, the stability of the electrode assembly may be ensured while maintaining conductivity. The thickness of the metal piece may be, for example, 2 to 10 μm, 2 to 7 μm, or 4 to 6 μm. When the metal piece has a thickness within this range, the connection between the metal layer and the lead tab may be more easily achieved. When the positive electrode current collector 11 has such a structure, the weight of the positive electrode may be reduced, thereby improving the energy density of the positive electrode and the lithium battery.

[0128] [Positive electrode layer: inactive material] 9 to 11, the positive electrode 10 includes a positive electrode current collector 11, a positive electrode active material layer 12 disposed on one side of the positive electrode current collector, and further includes inactive members 40, 40a, and 40b disposed on one side of the positive electrode layer 10.

[0129] The inclusion of the inactive member 40 prevents cracks in the solid electrolyte layer 30 during manufacture and / or charge / discharge of the all solid state secondary battery 1, resulting in improved cycle characteristics of the all solid state secondary battery 2. In an all solid state secondary battery 1 that does not include the inactive member 40, cracks occur in the solid electrolyte layer 30 due to uneven pressure being applied to the solid electrolyte layer 30 that contacts the positive electrode 10 during manufacture and / or charge / discharge of the all solid state secondary battery 1, and this causes growth of lithium metal, increasing the possibility of short circuit occurrence.

[0130] The inactive member 40 is disposed along the side surface of the positive electrode layer 10, surrounding the positive electrode layer. For example, the inactive member 40 surrounds part or all of the side surface of the positive electrode 10 and contacts the solid electrolyte layer 30. By surrounding the side surface of the positive electrode 10 and contacting the solid electrolyte layer 30, the inactive member 40 can effectively prevent cracks in the solid electrolyte layer 30, which may occur due to a pressure difference during a pressing process from the solid electrolyte layer 30 that is not in contact with the positive electrode 20. The inactive member 40 surrounds the side surface of the positive electrode 10 and separates it from the anode 20, more specifically, the first anode active material layer 22. The inactive member 40 surrounds the side surface of the positive electrode 10, contacts the solid electrolyte layer 30, and separates it from the anode 20. Therefore, the possibility of a short circuit occurring due to physical contact between the positive electrode 10 and the first anode active material layer 22 or due to lithium overcharge is reduced. 3, an inactive member 40 is disposed on one side of the positive electrode active material layer 12 and also on one side of the positive electrode current collector 11, thereby more effectively preventing the occurrence of a short circuit due to contact between the positive electrode current collector 11 and the negative electrode 20. In another embodiment, referring to FIG. 4, an inactive member 40 is disposed on one side of the positive electrode active material layer 12 and is disposed between the solid electrolyte layer 40 and the positive electrode current collector 11 facing the solid electrolyte layer 40. The inactive member 40 is not disposed on one side of the positive electrode current collector 11. The inactive member 40 is disposed between the positive electrode current collector 11 and the solid electrolyte layer 30, thereby effectively preventing a short circuit due to contact between the positive electrode current collector 11 and the negative electrode 20.

[0131] Although not shown in the drawings, some or all of the inactive members 40, 40a, 40b may be disposed spaced apart from the side surfaces of the positive electrode layer 10. By disposing some or all of the inactive members 40, 40a, 40b spaced apart from the side surfaces of the positive electrode layer 10, the manufacturing process of the all-solid-state secondary battery 1 may be further facilitated and the manufacturing speed of the all-solid-state secondary battery 1 may be increased. By disposing some or all of the inactive members 40, 40a, 40b spaced apart from the side surfaces of the positive electrode layer 10, volume changes in the lateral direction of the positive electrode layer 10 during charge and discharge may be more effectively accommodated, thereby further improving the life characteristics of the all-solid-state secondary battery 1. The distances between the inactive members 40, 40a, 40b and the side surfaces of the positive electrode layer 10 are, independently of one another, for example, 0.1 μm to 10 mm, 1 μm to 1 mm, 1 μm to 500 μm, 1 μm to 100 μm, 1 μm to 50 μm, or 1 μm to 10 μm.

[0132] The inactive member 40 may further include a positioning portion (not shown) configured to determine the position of the inactive member 40 on the solid electrolyte layer 30. When the inactive member 40 includes the positioning portion, it may be easier to determine the position at which to place the inactive member 40 on the solid electrolyte layer 30. As a result, the manufacturing speed of the all-solid-state secondary battery 1 may increase, and manufacturability may be improved.

[0133] 9 and 10 , the inactive member 40 extends from one side surface of the positive electrode 30 to an end portion of the solid electrolyte layer 30. The inactive member 40 extends to the end portion of the solid electrolyte layer 30, thereby suppressing cracks from occurring at the end portion of the solid electrolyte layer 30. The end portion of the solid electrolyte layer 30 is the outermost portion that contacts the side surface of the solid electrolyte layer 30. The inactive member 40 extends to the outermost portion that contacts the side surface of the solid electrolyte layer 30. The inactive member 40 is separated from the anode layer 20, more specifically, the first anode active material layer 22. The inactive member 40 extends to the end portion of the solid electrolyte layer 30 but does not contact the anode layer 20. The inactive member 40 fills a space extending from one side surface of the positive electrode layer 30 to the end portion of the solid electrolyte layer 30, for example.

[0134] The inert member 40 is, for example, a gasket. By using a gasket as the inert member 40, cracks in the solid electrolyte layer 30 caused by a pressure difference during the pressing process can be effectively prevented.

[0135] The inactive member 40 has, for example, a single-layer structure. In other embodiments, although not shown, the inactive member 40 may have a multi-layer structure. In the inactive member 40 having a multi-layer structure, each layer may have a different composition. The inactive member having a multi-layer structure may have, for example, a two-layer structure, a three-layer structure, a four-layer structure, or a five-layer structure. The inactive member 40 having a multi-layer structure may include, for example, one or more adhesive layers and one or more support layers. The adhesive layer effectively prevents separation between the positive electrode layer 10 and the solid electrolyte layer 30 due to volumetric changes in the positive electrode layer 10 that occur during the charge / discharge process of the all-solid-state secondary battery 10, and improves the film strength of the inactive member 40 by providing bonding strength between the support layer and other layers. The support layer provides support to the inactive member 40 and prevents uneven pressure from being applied to the solid electrolyte layer 30 during the pressurization process or charge / discharge process, thereby preventing deformation of the manufactured all-solid-state secondary battery 1.

[0136] 11 , the all-solid-state secondary battery 1 includes a positive electrode 10, a negative electrode 20, and solid electrolyte layers 30, 30a, and 30b disposed therebetween. The positive electrode layer 10 includes a positive electrode current collector 11 and a first positive electrode active material layer 12a and a second positive electrode active material layer 12b disposed on both surfaces of the positive electrode current collector 11, respectively. The solid electrolyte layer 30 includes a first solid electrolyte layer 30a in contact with the first positive electrode active material layer 12a and a second solid electrolyte layer 30b in contact with the second positive electrode active material layer 12b, respectively. The negative electrode layer 20 includes a first negative electrode layer 20a in contact with the first solid electrolyte layer 30a and a second negative electrode layer 20b in contact with the second solid electrolyte layer 30b, respectively. An inactive member 40 is disposed between the opposing first solid electrolyte layer 30a and second solid electrolyte layer 30b to surround the side of the positive electrode layer 10. The inactive member 40 includes, for example, a first inactive member 50a in contact with the first solid electrolyte layer 30a and a second inactive member 40b in contact with the second solid electrolyte layer 30b. Therefore, the all-solid-state secondary battery 1 has a bi-cell structure. The all-solid-state secondary battery 1 has such a bi-cell structure, where the solid electrolyte layer 30 and the anode layer 20 are symmetrically arranged facing each other with the cathode layer 10 at the center. This effectively suppresses structural deformation due to pressure applied during the manufacturing process of the all-solid-state secondary battery 1. Therefore, cracks in the solid electrolyte layer 30 during the manufacturing process of the all-solid-state secondary battery 1 and / or during charging and discharging are suppressed, thereby preventing short circuits in the all-solid-state secondary battery 1. As a result, the cycle characteristics of the all-solid-state secondary battery 1 are further improved. Furthermore, since only one cathode current collector 11 is used for multiple cathode active material layers 12a and 12b, the energy density of the all-solid-state secondary battery 1 is increased.

[0137] 9 to 11, the inactive member 40 is, for example, a flame-retardant inactive member. The flame-retardant inactive member provides flame retardancy, thereby preventing the possibility of thermal runaway and ignition of the all-solid-state secondary battery 1. As a result, the stability of the all-solid-state secondary battery 1 is further improved. The flame-retardant inactive member absorbs residual moisture in the all-solid-state secondary battery 1, thereby preventing deterioration of the all-solid-state secondary battery 1 and improving the life characteristics of the all-solid-state secondary battery 1.

[0138] The flame-retardant inert member includes, for example, a matrix and a filler. The matrix includes, for example, a base material and a reinforcing material. The matrix includes, for example, a fibrous base material and a fibrous reinforcing material. When the matrix includes the base material, the matrix can have elasticity. Therefore, the matrix can be arranged in various positions while effectively accommodating volume changes during charging and discharging of the all-solid-state secondary battery 1. The base material included in the matrix includes, for example, a first fibrous material. When the base material includes the first fibrous material, the matrix can effectively accommodate volume changes in the positive electrode layer 30 that occur during charging and discharging of the all-solid-state secondary battery 1, thereby effectively suppressing deformation of the first inert member 40 due to volume changes in the positive electrode layer 30. The first fibrous material is, for example, a material with an aspect ratio of 5 or more, 20 or more, or 50 or more. The first fibrous material is, for example, a material with an aspect ratio of 5 to 1000, 20 to 1000, or 50 to 1000. The first fibrous material is, for example, an insulating material. The insulating first fibrous material can effectively prevent short circuits between the positive electrode layer 30 and the negative electrode layer 20 due to lithium dendrites or the like that occur during the charge and discharge process of the all-solid-state secondary battery 1. The first fibrous material includes, for example, one or more selected from pulp fiber, insulating polymer fiber, and ion-conductive polymer fiber. The matrix includes a reinforcing material, which improves the strength of the matrix. Therefore, the matrix can prevent excessive volume change during charge and discharge of the all-solid-state secondary battery 1, thereby preventing deformation of the all-solid-state secondary battery. The reinforcing material included in the matrix includes, for example, a second fibrous material. The reinforcing material includes the second fibrous material, which can more uniformly increase the strength of the matrix. The second fibrous material is, for example, a material with an aspect ratio of 3 or more, 5 or more, or 10 or more. The first fibrous material is, for example, a material with an aspect ratio of 3 to 100, 5 to 100, or 10 to 100. The second fibrous material is, for example, a flame-retardant material, which can effectively prevent ignition due to thermal runaway that occurs during the charge / discharge process or upon external impact of the all-solid-state secondary battery 1. The second fibrous material is, for example, glass fiber, metal oxide fiber, ceramic fiber, etc.

[0139] The flame-retardant inert member includes a filler in addition to the matrix. The filler may be disposed inside the matrix, on the surface of the matrix, or both inside and on the surface. The filler may be, for example, an inorganic material. The filler contained in the flame-retardant inert member may be, for example, a moisture getter, a flame retardant, or a lithium immobilizer. The moisture adsorbent adsorbs moisture at temperatures below 100°C, for example, to remove moisture remaining in the all-solid-state secondary battery 1 and prevent deterioration of the all-solid-state secondary battery 1. Furthermore, if the temperature of the all-solid-state secondary battery 1 increases to 150°C or higher due to thermal runaway occurring during the charge / discharge process or due to external impact, the moisture adsorbent releases the adsorbed moisture, thereby effectively suppressing ignition of the all-solid-state secondary battery 1. The moisture adsorbent may be, for example, a metal hydroxide having moisture adsorption properties. The metal hydroxide contained in the filler is, for example, Mg(OH)2, Fe(OH)3, Sb(OH)3, Sn(OH)4, Ti(OH)3, Zr(OH)4, Al(OH)3, or a combination thereof. The flame retardant is, for example, one or more selected from zinc borate, calcium molybdate zinc complex, MoO3, (NH4)2Mo2O7, Sb2O3, and Sb3O5. The lithium immobilizing agent is, for example, a compound that reacts with liquid lithium at or above 180°C, the melting temperature of lithium, to immobilize lithium. The lithium immobilizing agent can, for example, react with liquid lithium to convert lithium into another insoluble compound. The lithium immobilizing agent is, for example, a metal oxide that is reactive with liquid lithium. The metal oxide contained in the filler is, for example, TiO2, ZrO2, HfO2, ThO2, or a combination thereof. For example, the metal oxide reacts with liquid lithium to produce Li2O and a metal. The reaction formula is, for example, 4Li + MO2 → M + 2Li2O. The liquid lithium reacts with the metal oxide to produce lithium oxide, thereby immobilizing the liquid lithium. This can prevent liquid lithium melted at high temperatures from leaking into the positive electrode. This can improve the stability of the all-solid-state secondary battery.

[0140] The content of the filler contained in the flame-retardant inert material is, for example, 1 to 80 parts by weight, 5 to 80 parts by weight, 10 to 80 parts by weight, 20 to 80 parts by weight, 30 to 80 parts by weight, 40 to 80 parts by weight, 50 to 80 parts by weight, 60 to 80 parts by weight, or 65 to 80 parts by weight per 100 parts by weight of the flame-retardant inert material 4.

[0141] The flame-retardant inert member may further include, for example, a binder. The binder may include, for example, a curable polymer or a non-curable polymer. The curable polymer is a polymer that is cured by heat and / or pressure. The curable polymer is, for example, solid at room temperature. The flame-retardant inert member may include, for example, a heat-pressure-curable film and / or its cured product. An example of a heat-pressure-curable polymer is TSA-66 from Toray Industries.

[0142] The flame-retardant inert member may further include other materials in addition to the substrate, reinforcing material, filler, and binder described above. The flame-retardant inert member may further include at least one material selected from the group consisting of paper, insulating polymers, ion-conducting polymers, insulating inorganic materials, oxide-based solid electrolytes, and sulfide-based solid electrolytes. The insulating polymer may be, for example, an olefin-based polymer such as polypropylene (PP) or polyethylene (PE).

[0143] The density of the substrate or reinforcing material contained in the flame-retardant inert member is, for example, 10% to 300%, 10% to 150%, 10% to 140%, 10% to 130%, or 10% to 120% of the density of the positive electrode active material contained in the lithium host layer 22.

[0144] The inactive component 40 is a component that does not contain a material having electrochemical activity, such as an electrode active material. An electrode active material is a material that absorbs / desorbs lithium. The inactive component 40 is a component made of a material used in the art as a material other than an electrode active material.

[0145] [Solid electrolyte layer] [Solid electrolyte layer: solid electrolyte] 7 to 11, the solid electrolyte layer 30 includes a solid electrolyte disposed between the positive electrode layer 10 and the negative electrode layer 20.

[0146] The solid electrolyte layer 30 may include a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a polymer solid electrolyte, or a combination thereof. The solid electrolyte layer 30 does not include the first fibrous sulfide-based solid electrolyte 100.

[0147] The sulfide-based solid electrolyte can be selected from the sulfide-based solid electrolytes used in the positive electrode active material layer 12.

[0148] The sulfide-based solid electrolyte may further include, for example, a first fibrous sulfide-based solid electrolyte 100. The content of the first fibrous sulfide-based solid electrolyte 100 may be, for example, 50 wt% or more, 60 wt% or more, 70 wt% or more, 80 wt% or more, 90 wt% or more, or 95 wt% or more of the total weight of the solid electrolyte layer 30. The content of the first fibrous sulfide-based solid electrolyte 100 may be, for example, 50 to 100 wt%, 60 to 100 wt%, 70 to 100 wt%, 80 to 100 wt%, 90 to 99.99 wt%, or 95 to 99 wt% of the total weight of the solid electrolyte layer 30. When the solid electrolyte layer 30 includes the first fibrous sulfide-based solid electrolyte 100, the life characteristics of the all-solid-state secondary battery may be further improved.

[0149] The oxide-based solid electrolyte can be selected from the oxide-based solid electrolytes used in the positive electrode active material layer 12 .

[0150] The polymer solid electrolyte is, for example, an electrolyte containing a mixture of a lithium salt and a polymer, or a polymer having an ion-conducting functional group. The polymer solid electrolyte is, for example, a polymer electrolyte that does not contain a liquid electrolyte. Examples of the polymer contained in the polymer solid electrolyte include polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyethylene oxide (PEO), poly(styrene-b-ethylene oxide) block copolymer (PS-PEO), poly(styrene-butadiene), poly(styrene-isoprene-styrene), poly(styrene-b-divinylbenzene) block copolymer, poly(styrene-ethylene oxide-styrene) block copolymer, polystyrene sulfonate (PSS), polyvinyl fluoride (PVF, Polyvinyl Fluoride), polymethyl methacrylate (PMMA, poly(methylmethacrylate), polyethylene glycol (PEG), polyacrylonitrile (PAN), polytetrafluoroethylene (PTFE), polyethylenedioxythiophene (PEDOT), polypyrrole (PPY), polyacrylonitrile (PAN), polyaniline, polyacetylene, Nafion, Aquivion, Flemion, Gore, Aciplex, Morgane ADP, sulfonated poly(ether ether ketone) (SPEEK), sulfonated poly(arylene ether ketone ketone) (SPAEKKS), sulfonated poly(aryl ether ketone) (sulfonated poly(aryl ether ketone) ketone, SPAEK), poly[bis(benzimidazobenzisoquinolinones)] (SPBIBI), poly(styrene sulfonate) (PSS), lithium 9,10-diphenylanthracene-2-sulfonate (lithium 9,The lithium salt may be, but is not limited to, any lithium salt used in the art as a polymer electrolyte, such as, for example, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(C, x F 2x+1 SO2)(C y F 2y+1 SO2) (x and y are each 1 to 20), LiCl, LiI, or a mixture thereof.

[0151] The gel electrolyte is, for example, a gel polymer electrolyte. The gel polymer electrolyte is, for example, an electrolyte including a liquid electrolyte and a polymer, or including an organic solvent and a polymer having an ion-conducting functional group. The liquid electrolyte can be, for example, an ionic liquid, a mixture of a lithium salt and an organic solvent, a mixture of an ionic liquid and an organic solvent, or a mixture of a lithium salt, an ionic liquid, and an organic solvent. The polymer can be selected from the polymers used in solid polymer electrolytes. The organic solvent can be selected from the organic solvents used in liquid electrolytes. The lithium salt can be selected from the lithium salts used in solid polymer electrolytes. An ionic liquid has a melting point below room temperature and refers to a salt that is liquid at room temperature or a room-temperature molten salt composed only of ions. The ionic liquid may include, for example, one or more compounds containing: a) one or more cations selected from ammonium, pyrrolidinium, pyridinium, pyrimidinium, imidazolium, piperidinium, pyrazolium, oxazolium, pyridazinium, phosphonium, sulfonium, triazolium, and mixtures thereof; and b) one or more anions selected from 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-. A gel polymer electrolyte can be formed by impregnating the polymer solid electrolyte with an electrolyte solution in a lithium battery. The gel electrolyte may further include inorganic particles.

[0152] The solid electrolyte layer 30 is also impermeable to lithium polysulfide. Therefore, it can block a side reaction between the lithium polysulfide generated during charging and discharging of the sulfide-based positive electrode active material and the negative electrode layer. Therefore, the cycle characteristics of the all-solid-state secondary battery 1 including the solid electrolyte layer 30 can be improved.

[0153] [Solid electrolyte layer: binder] The solid electrolyte layer 30 may include, for example, a binder. Examples of the binder included in the solid electrolyte layer 30 include, but are not limited to, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, and polyethylene. Any binder available in the art may be used. The binder of the solid electrolyte layer 30 may be the same as or different from the binder included in the positive electrode active material layer 12 and the negative electrode active material layer 22. The binder may be omitted.

[0154] The binder content of the solid electrolyte layer 30 is 0.1 to 10 wt%, 0.1 to 5 wt%, 0.1 to 3 wt%, 0.1 to 1 wt%, 0 to 0.5 wt%, or 0 to 0.1 wt% based on the total weight of the solid electrolyte layer 30.

[0155] [Negative electrode layer] [Negative electrode layer: negative electrode active material] 7 to 11, the negative electrode layer 20 includes a first negative electrode active material layer 22. The first negative electrode active material layer 22 includes, for example, a negative electrode active material and a binder.

[0156] The negative electrode active material contained in first negative electrode active material layer 22 is, for example, a negative electrode material that can form an alloy or compound with lithium.

[0157] The negative electrode active material contained in the first negative electrode active material layer 22 is, for example, particulate. The average particle size of the particulate negative electrode active material is, for example, 4 μm or less, 3 μm or less, 2 μm or less, 1 μm or less, 500 nm or less, 300 nm or less, or 100 nm or less. The average particle size of the particulate negative electrode active material is, for example, 10 nm to 4 μm, 10 nm to 3 μm, 10 nm to 2 μm, 10 nm to 1 μm, 10 nm to 500 nm, 10 nm to 300 nm, or 10 nm to 100 nm. When the negative electrode active material has an average particle size within such a range, reversible absorbing and / or desorbing of lithium during charging and discharging is further facilitated. The average particle size of the negative electrode active material is, for example, the median diameter (D50) measured using a laser particle size distribution analyzer.

[0158] The negative electrode active material contained in the first negative electrode active material layer 22 includes, for example, one or more selected from a carbon-based negative electrode active material and a metal or semi-metal negative electrode active material.

[0159] The carbon-based negative electrode active material includes, for example, amorphous carbon, crystalline carbon, porous carbon, or a combination thereof.

[0160] The carbon-based negative electrode active material is particularly amorphous carbon. Examples of amorphous carbon include, but are not limited to, carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), and graphene. Any amorphous carbon classified as amorphous carbon in the art can be used. Amorphous carbon is carbon that has no crystallinity or very low crystallinity and is distinguished from crystalline carbon or graphite-based carbon.

[0161] The carbon-based negative electrode active material may be, for example, porous carbon. The pore volume of the porous carbon is, for example, 0.1 cc / g to 10.0 cc / g, 0.5 cc / g to 5 cc / g, or 0.1 cc / g to 1 cc / g. The average pore diameter of the porous carbon is, for example, 1 nm to 50 nm, 1 nm to 30 nm, or 1 nm to 10 nm. The BET specific surface area of ​​the porous carbon is, for example, 100 m 2 / g~3000m 2 / g.

[0162] The metal or semimetal negative electrode active material may include, but is not limited to, one or more selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). Any metal or semimetal negative electrode active material known in the art that forms an alloy or compound with lithium may be used. For example, nickel (Ni) is not a metal negative electrode active material because it does not form an alloy with lithium.

[0163] The first negative electrode active material layer 22 may include one of these negative electrode active materials or a mixture of multiple different negative electrode active materials. For example, the first negative electrode active material layer 22 may include only amorphous carbon, or may include one or more selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). In another embodiment, the first negative electrode active material layer 22 includes a mixture of amorphous carbon and one or more selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). The mixing ratio of the mixture of amorphous carbon and gold or the like is, for example, 99:1 to 1:99, 10:1 to 1:2, 5:1 to 1:1, or 4:1 to 2:1 by weight, but is not necessarily limited to such ranges and is selected depending on the required characteristics of the all-solid-state secondary battery 1. When the negative electrode active material has such a composition, the cycle characteristics of the all-solid-state secondary battery 1 are further improved.

[0164] The negative electrode active material contained in the first negative electrode active material layer 22 includes, for example, a mixture of first particles made of amorphous carbon and second particles made of a metal or a metalloid. Examples of the metal or metalloid include gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). In other embodiments, the metalloid is a semiconductor. The content of the second particles is 1 to 99 wt %, 1 to 60 wt %, 8 to 60 wt %, 10 to 50 wt %, 15 to 40 wt %, or 20 to 30 wt %, based on the total weight of the mixture. When the content of the second particles is within such a range, for example, the cycle characteristics of the all-solid-state secondary battery 1 are further improved.

[0165] In another embodiment, the first anode active material layer 22 includes a composite anode active material. The composite anode active material may include, for example, a carbon-based support and a metal-based anode active material supported on the carbon-based support. The composite anode active material has such a structure, which prevents uneven distribution of the metal-based anode active material within the first anode active material layer and achieves a uniform distribution. As a result, the cycle characteristics of the all-solid-state secondary battery 1 including the first anode active material layer 22 are further improved.

[0166] Metal-based negative electrode active materials supported on carbon-based supports include, for example, metals, metal oxides, composites of metals and metal oxides, or combinations thereof. Metals include, for example, gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). Metal oxides include, for example, gold (Au) oxide, platinum (Pt) oxide, palladium (Pd) oxide, silicon (Si) oxide, silver (Ag) oxide, aluminum (Al) oxide, bismuth (Bi) oxide, tin (Sn) oxide, and zinc (Zn) oxide. Metal oxides include, for example, Au x O y (0 <x≦2、0<y≦3)、Pt x O y (0 <x≦1、0<y≦2)、Pd x O y(0 < x ≤ 1, 0 < y ≤ 1), Si x O y (0 < x ≤ 1, 0 < y ≤ 2), Ag x O y (0 < x ≤ 2, 0 < y ≤ 1), Al x O y (0 < x ≤ 2, 0 < y ≤ 3), Bi x O y (0 < x ≤ 2, 0 < y ≤ 3), Sn x O y (0 < x ≤ 1, 0 < y ≤ 2), Zn x O y (0 < x ≤ 1, 0 < y ≤ 1), or combinations thereof may be included. The composite of metal and metal oxide is, for example, a composite of Au and Au x O y (0 < x ≤ 2, 0 < y ≤ 3), a composite of Pt and Pt x O y (0 < x ≤ 1, 0 < y ≤ 2), a composite of Pd and Pd x O y (0 < x ≤ 1, 0 < y ≤ 1), a composite of Si and Si x O y (0 < x ≤ 1, 0 < y ≤ 2), a composite of Ag and Ag x O y (0 < x ≤ 2, 0 < y ≤ 1), a composite of Al and Al x O y (0 < x ≤ 2, 0 < y ≤ 3), a composite of Bi and Bi x O y (0 < x ≤ 2, 0 < y ≤ 3), a composite of Sn and Sn x O y (0 < x ≤ 1, 0 < y ≤ 2), a composite of Zn and Zn x O y (0 < x ≤ 1, 0 < y ≤ 1), or combinations thereof may be included.

[0167] The carbon-based support may be, for example, amorphous carbon. Examples of amorphous carbon include, but are not limited to, carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), graphene, activated carbon, carbon nanofibers (CNF), and carbon nanotubes (CNT). Any amorphous carbon classified as amorphous carbon in the art may be used. Amorphous carbon is carbon with no or very low crystallinity, and is distinguished from crystalline carbon or graphite-based carbon. Carbon paper is, for example, a carbon-based negative electrode active material.

[0168] The composite negative electrode active material may be, for example, particulate. The particle size of the particulate composite negative electrode active material may be, for example, 10 nm to 4 μm, 10 nm to 1 μm, 10 nm to 500 nm, 10 nm to 200 nm, or 10 nm to 100 nm. When the composite negative electrode active material has a particle size within such a range, reversible absorbing and / or desorbing of lithium during charging and discharging is facilitated. The metal-based negative electrode active material supported on the support may be, for example, particulate. The particle size of the metal-based negative electrode active material may be, for example, 1 nm to 200 nm, 1 nm to 150 nm, 5 nm to 100 nm, or 10 nm to 50 nm. The carbon-based support may be, for example, particulate. The particle size of the carbon-based support may be, for example, 10 nm to 2 μm, 10 nm to 1 μm, 10 nm to 500 nm, 10 nm to 200 nm, or 10 nm to 100 nm. By having the carbon-based support have a particle size within such a range, it may be more uniformly distributed within the first negative electrode active material layer. The carbon-based support may also be, for example, nanoparticles having a particle size of 500 nm or less. The particle sizes of the composite negative electrode active material, the metal-based negative electrode active material, and the carbon-based support are, for example, average particle sizes. The average particle size is, for example, the median diameter (D50) measured using a laser particle size analyzer. In other embodiments, the average particle size may be determined automatically using software from, for example, an electron microscope image, or may be determined passively manually.

[0169] [Negative electrode layer: binder] Examples of the binder contained in the first negative electrode active material layer 22 include, but are not limited to, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, etc. Any binder known in the art may be used. The binder may be a single binder or a combination of multiple different binders.

[0170] The inclusion of a binder in the first negative electrode active material layer 22 stabilizes the first negative electrode active material layer 22 on the negative electrode current collector 21. Furthermore, cracking of the first negative electrode active material layer 22 is suppressed despite volume changes and / or relative position changes of the first negative electrode active material layer 22 during charge and discharge. For example, if the first negative electrode active material layer 22 does not include a binder, the first negative electrode active material layer 22 can be easily separated from the negative electrode current collector 21. When the first negative electrode active material layer 22 is detached from the negative electrode current collector 21, the negative electrode current collector 21 comes into contact with the solid electrolyte layer 30 at the exposed portion, increasing the possibility of a short circuit. The first negative electrode active material layer 22 is prepared, for example, by applying a slurry in which materials constituting the first negative electrode active material layer 22 are dispersed onto the negative electrode current collector 21 and drying the slurry. The negative electrode active material can be stably dispersed in the slurry by including a binder in the first negative electrode active material layer 22. For example, when the slurry is applied onto the negative electrode current collector 21 by a screen printing method, clogging of the screen (for example, clogging due to agglomerates of the negative electrode active material) can be suppressed.

[0171] [Negative electrode layer: Other additives] The first negative electrode active material layer 22 may further include additives used in conventional all-solid-state secondary batteries 1, such as fillers, coating agents, dispersants, and ion-conducting auxiliary agents.

[0172] [Negative electrode layer: solid electrolyte] The first anode active material layer 22 may further include a solid electrolyte. The solid electrolyte may be, for example, a material selected from the solid electrolytes included in the solid electrolyte layer 30. The solid electrolyte included in the first anode active material layer 22 may act as a reaction site where lithium metal formation begins within the first anode active material layer 22, as a space where the formed lithium metal is stored, or as a path for transporting lithium ions. The solid electrolyte is optional.

[0173] In the first negative electrode active material layer 22, the content of the solid electrolyte may be high in a region adjacent to the solid electrolyte layer 30 and low in a region adjacent to the negative electrode current collector 21. In the first negative electrode active material layer 22, the solid electrolyte may have a concentration gradient, for example, where the concentration decreases from the region adjacent to the solid electrolyte layer 30 to the region adjacent to the negative electrode current collector 21.

[0174] [Negative electrode layer: first negative electrode active material layer] The initial charge capacity (B) of the first negative electrode active material layer is, for example, less than 50%, 45% or less, 40% or less, 30% or less, 20% or less, or 10% or less of the initial charge capacity (A) of the positive electrode active material layer. The ratio (B / A) of the initial charge capacity (B) of the first negative electrode active material layer 22 to the initial charge capacity (A) of the positive electrode active material layer is, for example, 0.005 to 0.45. The initial charge capacity of the positive electrode active material layer 12 is determined by the first open circuit voltage (1 st open circuit voltage) to Li / Li + The initial charge capacity of the first negative electrode active material layer 22 is determined at a maximum charging voltage (2 nd open circuit voltage) to Li / Li + Determined at 0.01 V vs.

[0175] The maximum charging voltage is determined by the type of positive electrode active material. The maximum charging voltage may be, for example, 1.5 V, 2.0 V, 2.5 V, 3.0 V, 3.5 V, 4.0 V, 4.2 V, or 4.3 V. For example, the maximum charging voltage of Li2S or a Li2S composite is Li / Li + For example, the maximum charging voltage of Li2S or Li2S composite is 2.5V for Li / Li + The ratio (B / A) of the initial charge capacity (B) of the first negative electrode active material layer 22 to the initial charge capacity (A) of the positive electrode active material layer is, for example, 0.01 to 0.3, 0.01 to 0.2, or 0.05 to 0.1.

[0176] The initial charge capacity (mAh) of the positive electrode active material layer 12 is obtained by multiplying the charge specific capacity (mAh / g) of the positive electrode active material by the mass (g) of the positive electrode active material in the positive electrode active material layer 12. When various positive electrode active materials are used, the charge capacity density x mass value is calculated for each positive electrode active material, and the sum of these values ​​is the initial charge capacity of the positive electrode active material layer 12. The initial charge capacity of the first negative electrode active material layer 22 is calculated in a similar manner. The initial charge capacity of the first negative electrode active material layer 22 is obtained by multiplying the charge capacity density (mAh / g) of the negative electrode active material by the mass of the negative electrode active material in the first negative electrode active material layer 22. When various negative electrode active materials are used, the charge capacity density x mass value is calculated for each negative electrode active material, and the sum of these values ​​is the initial charge capacity of the first negative electrode active material layer 22. The charge capacity densities of the positive electrode active material and the negative electrode active material can be measured using an all-solid-state half-cell using lithium metal as a counter electrode. The initial charge capacity of each of the positive electrode active material layer 12 and the first negative electrode active material layer 22 is determined by a constant current density, for example, 0.1 mA / cm 2 For the positive electrode, the measurement can be performed by measuring the voltage from the first open circuit voltage (OCV) to the maximum charging voltage, e.g., 3.0 V (vs. Li / Li + For the negative electrode, the measurements can be performed for an operating voltage from the second open circuit voltage (OCV) to 0.01 V relative to the negative electrode, e.g., lithium metal. For example, an all-solid-state half-cell with a positive electrode active material layer can have a current of 0.1 mA / cm from the first open circuit voltage to 3.0 V. 2 The all-solid-state half-cell having the first negative electrode active material layer was charged at a constant current of 0.1 mA / cm from the second open circuit voltage to 0.01 V. 2 The current density during constant current charging is, for example, 0.2 mA / cm 2 , or 0.5mA / cm 2An all-solid-state half-cell having a positive electrode active material layer can be charged from the first open circuit voltage to, for example, 2.5 V, 2.0 V, 2.5 V, 2.8 V, 3.0 V, 3.5 V, or 4.0 V. The maximum charging voltage of the positive electrode active material layer can be determined by the maximum voltage of a battery that satisfies the safety conditions defined in JIS C8712:2015 of the Japanese Standards Association.

[0177] If the initial charge capacity of the first anode active material layer 22 is excessively small, the thickness of the first anode active material layer 22 becomes very thin, and thus lithium dendrites formed between the first anode active material layer 22 and the anode current collector 21 during repeated charge and discharge processes collapse the first anode active material layer 22, making it difficult to improve the cycle characteristics of the all-solid-state secondary battery 1. If the charge capacity of the first anode active material layer 22 increases excessively, the energy density of the all-solid-state secondary battery 1 decreases and the internal resistance of the all-solid-state secondary battery 1 due to the first anode active material layer 22 increases, making it difficult to improve the cycle characteristics of the all-solid-state secondary battery 1.

[0178] The thickness of the first negative electrode active material layer 22 is, for example, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 5% or less of the thickness of the positive electrode active material layer 12. The thickness of the first negative electrode active material layer 22 is, for example, 1 to 50%, 1 to 40%, 1 to 30%, 1 to 20%, 1 to 10%, or 1 to 5% of the thickness of the positive electrode active material layer 12. The thickness of the first negative electrode active material layer 22 is, for example, 1 μm to 20 μm, 2 μm to 15 μm, or 3 μm to 10 μm. If the thickness of the first negative electrode active material layer 22 is excessively thin, lithium dendrites formed between the first negative electrode active material layer 22 and the negative electrode current collector 21 will collapse the first negative electrode active material layer 22, making it difficult to improve the cycle characteristics of the all-solid-state secondary battery 1. If the thickness of the first negative electrode active material layer 22 increases excessively, the energy density of the all solid state secondary battery 1 decreases, and the internal resistance of the all solid state secondary battery 1 due to the first negative electrode active material layer 22 increases, making it difficult to improve the cycle characteristics of the all solid state secondary battery 1. If the thickness of the first negative electrode active material layer 22 decreases, for example, the initial charge capacity of the first negative electrode active material layer 22 also decreases.

[0179] [Negative electrode layer: second negative electrode active material layer] Although not shown in the drawings, the all-solid-state secondary battery 1 further includes, for example, a second negative electrode active material layer disposed between the negative electrode current collector 21 and the first negative electrode active material layer 22 after charging. The second negative electrode active material layer is a metal layer containing lithium or a lithium alloy. The metal layer contains lithium or a lithium alloy. Therefore, since the second negative electrode active material layer is a metal layer containing lithium, it functions, for example, as a lithium reservoir. Examples of lithium alloys include, but are not limited to, Li-Al alloys, Li-Sn alloys, Li-In alloys, Li-Ag alloys, Li-Au alloys, Li-Zn alloys, Li-Ge alloys, and Li-Si alloys. Any lithium alloy commonly used in the art can be used. The second negative electrode active material layer can be composed of one of these alloys or lithium, or various types of alloys. The second negative electrode active material layer can be, for example, a plated layer. The second negative electrode active material layer is deposited between the first negative electrode active material layer 22 and the negative electrode current collector 21 during the charging process of the all solid state secondary battery 1, for example.

[0180] The thickness of the second negative electrode active material layer is not particularly limited, and may be, for example, 1 μm to 500 μm, 1 μm to 200 μm, 1 μm to 150 μm, 1 μm to 100 μm, or 1 μm to 50 μm. If the thickness of the second negative electrode active material layer is too thin, it may be difficult for the second negative electrode active material layer to function as a lithium reservoir. If the thickness of the second negative electrode active material layer is too thick, the mass and volume of the all-solid-state secondary battery 1 may increase, and the cycle characteristics of the all-solid-state secondary battery 1 may actually deteriorate.

[0181] In another embodiment, the second negative electrode active material layer in the all solid state secondary battery 1 may be disposed between the negative electrode current collector 21 and the first negative electrode active material layer 22, for example, before assembling the all solid state secondary battery 1. When the second negative electrode active material layer 23 is disposed between the negative electrode current collector 21 and the first negative electrode active material layer 22 before assembling the all solid state secondary battery 1, the second negative electrode active material layer is a metal layer containing lithium and therefore acts as a lithium reservoir. For example, a lithium foil may be disposed between the negative electrode current collector 21 and the first negative electrode active material layer 22 before assembling the all solid state secondary battery 1.

[0182] When the second anode active material layer is deposited by charging after the all-solid-state secondary battery 1 is assembled, the energy density of the all-solid-state secondary battery 1 increases because the all-solid-state secondary battery 1 does not include a second anode active material layer during assembly. When the all-solid-state secondary battery 1 is charged, it is charged beyond the charge capacity of the first anode active material layer 22. That is, the first anode active material layer 22 is overcharged. At the initial stage of charging, lithium is absorbed into the first anode active material layer 22. The anode active material contained in the first anode active material layer 22 forms an alloy or compound with lithium ions transferred from the positive electrode layer 10. When the first anode active material layer 22 is charged beyond its capacity, lithium is deposited on the back surface of the first anode active material layer 22, i.e., between the anode current collector 21 and the first anode active material layer 22, and the deposited lithium forms a metal layer corresponding to the second anode active material layer. The second anode active material layer is a metal layer mainly composed of lithium (i.e., metallic lithium). Such results can be achieved, for example, by the negative electrode active material contained in the first negative electrode active material layer 22 containing a material that forms an alloy or compound with lithium. During discharge, lithium in the first negative electrode active material layer 22 and the second negative electrode active material layer, i.e., the metal layer, is ionized and migrates toward the positive electrode layer 10. This allows lithium to be used as the negative electrode active material in the all-solid-state secondary battery 1. Furthermore, since the first negative electrode active material layer 22 covers the second negative electrode active material layer, it serves as a protective layer for the second negative electrode active material layer, i.e., the metal layer, and also serves to suppress the precipitation and growth of lithium dendrites. This prevents short circuits and capacity reduction in the all-solid-state secondary battery 1, thereby improving the cycle characteristics of the all-solid-state secondary battery 1. Furthermore, when the second negative electrode active material layer is disposed by charging after the all solid state secondary battery 1 is assembled, the negative electrode layer 20, i.e., the negative electrode current collector 21, the first negative electrode active material layer 22, and the region therebetween are Li-free regions that do not contain lithium (Li) in the initial state of the all solid state secondary battery 1 or in the state after full discharge.

[0183] [Negative electrode layer: negative electrode current collector] The negative electrode current collector 21 is made of, for example, a material that does not react with lithium, i.e., does not form any alloy or compound. Materials constituting the negative electrode current collector 21 include, but are not limited to, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni), and any material used as an electrode current collector in the art can be used. The negative electrode current collector 21 may be made of one of the above-mentioned metals, or an alloy or coating material of two or more metals. The negative electrode current collector 21 is, for example, in the form of a plate or foil.

[0184] Although not shown in the drawings, the all-solid-state secondary battery 1 may further include a thin film containing an element that forms an alloy with lithium on one surface of the negative electrode current collector 21. The thin film is disposed between the negative electrode current collector 21 and the first negative electrode active material layer 22. The thin film contains, for example, an element that forms an alloy with lithium. Examples of elements that form an alloy with lithium include, but are not limited to, gold, silver, zinc, tin, indium, silicon, aluminum, and bismuth. Any element known in the art that can form an alloy with lithium can be used. The thin film may be composed of one of these metals or an alloy of various metals. By disposing the thin film on one surface of the negative electrode current collector 21, for example, the deposition morphology of the second negative electrode active material layer deposited between the thin film 24 and the first negative electrode active material layer 22 may be further flattened, thereby further improving the cycle characteristics of the all-solid-state secondary battery 1.

[0185] The thickness of the thin film is, for example, 1 nm to 800 nm, 10 nm to 700 nm, 50 nm to 600 nm, or 100 nm to 500 nm. If the thickness of the thin film is less than 1 nm, it is difficult for the thin film to exhibit its function. If the thin film is excessively thick, the thin film itself may occlude lithium, reducing the amount of lithium deposited at the negative electrode, thereby reducing the energy density of the all-solid-state battery and the cycle characteristics of the all-solid-state secondary battery 1. The thin film can be disposed on the negative electrode current collector 21 by, for example, vacuum deposition, sputtering, plating, or the like, but is not necessarily limited to such methods, and any method capable of forming a thin film in the relevant technical field can be used.

[0186] Although not shown in the drawings, the negative electrode current collector 21 may include, for example, a base film and a metal layer disposed on one or both sides of the base film. The base film may include, for example, a polymer. The polymer may also be, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof. The polymer may also be an insulating polymer. When the base film includes an insulating thermoplastic polymer, the base film softens or liquefies in the event of a short circuit, thereby shutting down battery operation and suppressing a sudden increase in current. The metal layer may include, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), or an alloy thereof. The negative electrode current collector 21 may further include a metal piece and / or a lead tab. For more specific details regarding the base film, metal layer, metal chip, and lead tab of the negative electrode current collector 21, please refer to the above-described positive electrode current collector 11. The negative electrode current collector 21 having such a structure can reduce the weight of the negative electrode, thereby improving the energy density of the negative electrode and the lithium battery.

[0187] The present invention will be described in more detail through the following examples and comparative examples, but the examples are intended to illustrate the present invention and are not intended to limit the scope of the present invention.

[0188] (fibrous sulfide-based solid electrolyte) Production Example 1: First fibrous sulfide-based solid electrolyte (core / shell structure)

[0189] Polyacrylonitrile (PAN, Mw 150,000 Daltons, Sigma-Aldrich) was dissolved in DMF (dimethylformamide) solvent to prepare a 10 wt% solution. The prepared solution was injected into a syringe and electrospinned to prepare polymer fibers. The applied voltage was 17.5 kV and the extraction rate was 15 μL / min. The prepared polymer fibers were carbonized by heat treatment at 700°C for 5 hours in an argon atmosphere to produce carbon nanofibers (CNF).

[0190] Carbon nanofiber (CNF) powder and argyrodite-type crystal Li6PS5Cl powder were mixed in a 2:1 weight ratio to prepare a mixture. An equal volume of ethanol was added and stirred at 90°C for 20 hours to prepare a mixture containing dissolved Li6PS5Cl. The mixture was then dried and heat-treated at 300°C for 8 hours in a nitrogen atmosphere to prepare a CNF-Li6PS5Cl composite. The CNF-Li6PS5Cl composite is a first fibrous sulfide-based solid electrolyte consisting of a CNF core coated with a Li6PS5Cl shell. The CNF-Li6PS5Cl composite had a thickness of approximately 500 nm, a length of approximately 5 μm, and a rod-like shape with an aspect ratio of 10. The cross section of the CNF-Li6PS5Cl composite was circular. The thickness and length of the CNF-Li6PS5Cl composite were average values ​​calculated from multiple composite particles captured from scanning electron microscope images.

[0191] (All-solid-state secondary battery) Example 1: Mono-cell all-solid-state secondary battery, sulfide-based positive electrode active material (LiS-C-LiI composite), fibrous solid electrolyte:particulate solid electrolyte=10:40 weight ratio (including first fibrous solid electrolyte)

[0192] (Manufacturing of negative electrode layer) A 10 μm thick SUS foil was prepared as the negative electrode current collector, and carbon black (CB) particles with a primary particle size of approximately 30 nm and silver (Ag) particles with an average particle size of approximately 60 nm were prepared as the negative electrode active material.

[0193] A mixed solution was prepared by adding 4 g of a 3:1 weight ratio mixed powder of carbon black (CB) and silver (Ag) particles to a container and adding 4 g of an NMP solution containing 7 wt% PVDF binder (Kureha #9300). NMP (N-methyl-2-pyrrolidone) was gradually added to the mixed solution while stirring to prepare a slurry. The slurry was applied to a SUS sheet using a bar coater and dried in air at 80°C for 10 minutes to prepare a laminate. The prepared laminate was vacuum-dried at 40°C for 10 hours. The dried laminate was cold roll-pressed to flatten the surface of the first negative electrode active material layer of the laminate, thereby preparing the negative electrode layer. The thickness of the first negative electrode active material layer was approximately 15 μm. The area of ​​the first negative electrode active material layer and the negative electrode current collector were the same. The initial charge capacity of the negative electrode layer (ie, the first negative electrode active material layer) was measured using the above-described half-cell.

[0194] (Production of positive electrode layer) A Li2S-C-LiI composite was prepared as a positive electrode active material. The Li2S-C-LiI composite was prepared by the method disclosed in Nano Lett. 2016, 16, 7, 4521-4527, except that Li6PS5Cl was replaced with LiI. The CNF-Li6PS5Cl composite prepared in Preparation Example 1 was prepared as a first fibrous solid electrolyte. Li6PS5Cl (D50 = 3.0 μm, crystalline), an argyrodite-type crystal, was prepared as an irregular-shaped particulate solid electrolyte. Ketjen black was prepared as a conductive agent. The aspect ratio of the irregular particulate solid electrolyte was less than 2.

[0195] These materials were mixed in a weight ratio of 40:10:40:10 (positive electrode active material, first fibrous solid electrolyte, amorphous particulate solid electrolyte, and conductive agent) to prepare a positive electrode mixture. The positive electrode mixture was obtained by dry mixing using a ball mill. The positive electrode mixture obtained by ball milling formed an ionically conductive and electrically conductive network.

[0196] The positive electrode mixture was placed on one side of a carbon-coated aluminum foil positive electrode current collector and plate-pressed at a pressure of 200 MPa for 10 minutes to prepare a positive electrode layer. The thickness of the positive electrode layer was approximately 120 μm. The thickness of the positive electrode active material layer was approximately 100 μm, and the thickness of the carbon-coated aluminum foil was approximately 20 μm. The areas of the positive electrode active material layer and the positive electrode current collector were the same. The initial charge capacity of the positive electrode layer (i.e., the positive electrode active material layer) was measured using the half-cell described above. The ratio (B / A) of the initial charge capacity of the first negative electrode active material layer (B) to the initial charge capacity of the positive electrode active material layer (A) was less than 0.5. The initial charge capacity of the positive electrode active material layer was measured using the first open-circuit voltage (1 st open circuit voltage) to 2.8 V vs. Li / Li + The initial charge capacity of the first negative electrode active material layer was determined by charging up to the second open circuit voltage (2 nd open circuit voltage) to 0.01 V vs. Li / Li + In Examples 2 to 9, the ratio (B / A) was less than 0.5.

[0197] (Manufacturing of solid electrolyte layer) A mixture was prepared by adding 1.5 parts by weight of an acrylic binder to 98.5 parts by weight of Li6PS5Cl solid electrolyte (D50 = 3.0 μm, crystalline), an argyrodite-type crystal. Octyl acetate was added to the mixture and stirred to prepare a slurry. The prepared slurry was applied using a bar coater to a 15 μm-thick nonwoven fabric placed on a 75 μm-thick PET substrate and dried in air at 80°C for 10 minutes to obtain a laminate. The obtained laminate was then vacuum-dried at 80°C for 2 hours. A solid electrolyte layer was manufactured using the above process.

[0198] (Flame-retardant inert material) A slurry made by mixing pulp fiber, glass fiber, aluminum hydroxide (Al(OH)3), acrylic binder, and solvent was formed into a gasket shape, and then the solvent was removed to produce a flame-retardant inert member.

[0199] The weight ratio of cellulose fiber, glass fiber, aluminum hydroxide (Al(OH)3), and acrylic binder was 20:8:70:2. The thickness of the inert member was 120 μm.

[0200] The flame-retardant inert member thus prepared was subjected to a vacuum heat treatment at 80° C. for 5 hours before being placed on the solid electrolyte layer to remove moisture and the like from the flame-retardant inert member.

[0201] (Manufacturing of all-solid-state secondary batteries) 6, a solid electrolyte layer was disposed on the negative electrode layer such that the first negative electrode active material layer was in contact with the solid electrolyte layer, and a flame-retardant inert member was disposed on the solid electrolyte layer under heat and pressure to prepare a negative electrode layer / solid electrolyte layer / inert member laminate.

[0202] The inert member was placed on one side of the positive electrode layer, facing the positive electrode active material layer, to prepare an anode layer / solid electrolyte layer / positive electrode layer electrode assembly. The inert member was placed around the positive electrode layer, surrounding the side of the positive electrode layer and in contact with the solid electrolyte layer. The inert member was used as a gasket. The positive electrode layer was placed on the center of the solid electrolyte layer, and the gasket surrounded the positive electrode layer and extended to the edge of the solid electrolyte layer. The area of ​​the positive electrode layer was approximately 90% of the area of ​​the solid electrolyte layer, and a gasket was placed over the entire remaining 10% area of ​​the solid electrolyte layer where the positive electrode layer was not placed.

[0203] The prepared anode / solid electrolyte / cathode electrode assembly was subjected to plate pressing. This pressing process sintered the solid electrolyte layer, improving battery performance. The thickness of the sintered solid electrolyte layer was approximately 45 μm. The sintered electrode assembly was placed in a pouch and sealed to prepare a sealed electrode assembly. Portions of the cathode current collector and anode current collector protruded from the sealed electrode assembly to serve as cathode and anode terminals.

[0204] The electrode assembly was placed between two pressure plates (not shown), and the two pressure plates were screwed together to apply a certain pressure to both sides of the electrode assembly, thereby manufacturing an all-solid-state secondary battery.

[0205] Example 2: Mono-cell all-solid-state secondary battery, sulfide-based positive electrode active material (LiS-C-LiI composite), fibrous solid electrolyte:particulate solid electrolyte=5:45 weight ratio (including first fibrous solid electrolyte)

[0206] An all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that the weight ratio of the fibrous solid electrolyte to the particulate solid electrolyte was changed to 5:45.

[0207] Example 3: Mono-cell all-solid-state secondary battery, sulfide-based positive electrode active material (LiS-C-LiI composite), fibrous solid electrolyte:particulate solid electrolyte=20:20 weight ratio (including first fibrous solid electrolyte)

[0208] An all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that the weight ratio of the fibrous solid electrolyte to the particulate solid electrolyte was changed to 20:20.

[0209] Example 4: Mono-cell all-solid-state secondary battery, sulfide-based positive electrode active material (LiS-C-LiI composite), fibrous solid electrolyte:particulate solid electrolyte=30:20 weight ratio (including first fibrous solid electrolyte)

[0210] An all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that the weight ratio of the fibrous solid electrolyte to the particulate solid electrolyte was changed to 30:20.

[0211] Example 5: Mono-cell all-solid-state secondary battery, sulfide-based positive electrode active material (LiS-C-LiI composite), fibrous solid electrolyte:particulate solid electrolyte=40:10 weight ratio (including first fibrous solid electrolyte)

[0212] An all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that the weight ratio of the fibrous solid electrolyte to the particulate solid electrolyte was changed to 40:10.

[0213] Example 6: Mono-cell all-solid-state secondary battery, sulfide-based positive electrode active material (LiS-C-LiI-fibrous solid electrolyte composite), fibrous solid electrolyte:particulate solid electrolyte = 10:40 weight ratio (including first and second fibrous solid electrolytes)

[0214] An all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that a Li2S-C-LiI-fibrous solid electrolyte composite was used instead of the Li2S-CNF composite as the positive electrode active material.

[0215] The Li2S-CNF-fibrous solid electrolyte composite was prepared by the following method.

[0216] A Li2S-CNF composite was prepared in the same manner as in Example 1. A 4:1 weight ratio mixture of the Li2S-C-LiI composite and the CNF-Li6PS5Cl composite prepared in Preparation Example 1 was mixed at low speed using a mixer, and then milled again using the mixer at a rotation speed of about 100 to 2000 rpm for about 0.1 to 20 hours to prepare a Li2S-C-LiI-fibrous solid electrolyte composite.

[0217] Example 7: Mono-cell all-solid-state secondary battery, sulfide-based positive electrode active material (LiS-C-LiI-fibrous solid electrolyte composite), fibrous solid electrolyte:particulate solid electrolyte = 0:50 weight ratio (particulate solid electrolyte included)

[0218] An all-solid-state secondary battery was fabricated in the same manner as in Example 1, except that the LiS-C-LiI-fibrous solid electrolyte composite used in Example 6 was used as the positive electrode active material instead of the LiS-CNF composite, and the weight ratio of the fibrous solid electrolyte to the particulate solid electrolyte in the positive electrode mixture was changed to 0:50, omitting the use of the fibrous solid electrolyte.

[0219] Example 8: Mono-cell all-solid-state secondary battery, sulfide-based positive electrode active material (LiS-C-LiI composite), fibrous solid electrolyte:particulate solid electrolyte = 10:40 weight ratio, two-layer positive electrode active material layer (arranged on top of fibrous solid electrolyte)

[0220] A first positive electrode mixture was prepared in the same manner as in Example 1.

[0221] A second positive electrode mixture was prepared in the same manner as in Example 1, except that the weight ratio of the fibrous solid electrolyte to the particulate solid electrolyte was changed to 0:50, and the fibrous solid electrolyte was not used.

[0222] An all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that the first positive electrode mixture (containing a fibrous solid electrolyte) and the second positive electrode mixture (a fibrous solid electrolyte member) were sequentially arranged on the positive electrode current collector to manufacture the positive electrode layer.

[0223] The positive electrode active material layer included a first positive electrode active material layer derived from the first positive electrode mixture and a second positive electrode active material layer derived from the second positive electrode mixture, each having a thickness of 50 μm.

[0224] The first positive electrode active material layer adjacent to the positive electrode current collector contained a fibrous solid electrolyte, and the second positive electrode active material layer adjacent to the solid electrolyte layer was free of fibrous solid electrolyte.

[0225] Example 9: Mono-cell all-solid-state secondary battery, sulfide-based positive electrode active material (LiS-C-LiI composite), fibrous solid electrolyte:particulate solid electrolyte = 10:40 weight ratio, two-layer positive electrode active material layer (fibrous solid electrolyte arranged at bottom)

[0226] An all-solid-state secondary battery was fabricated in the same manner as in Example 8, except that the positions of the first and second positive electrode active material layers were reversed, with the second positive electrode active material layer disposed adjacent to the positive electrode current collector and the first positive electrode active material layer disposed adjacent to the solid electrolyte layer. The second positive electrode active material layer adjacent to the positive electrode current collector contained a fibrous solid electrolyte, and the first positive electrode active material layer adjacent to the solid electrolyte layer was free of fibrous solid electrolyte.

[0227] Example 10: Mono-cell all-solid-state secondary battery, oxide-based positive electrode active material (NCA), fibrous solid electrolyte:particulate solid electrolyte = 10:40 weight ratio (fibrous solid electrolyte disposed at the entire upper and lower ends)

[0228] (Production of positive electrode layer) Li2O-ZrO2 (LZO) coated LiNi as the positive electrode active material 0.8 Co 0.15 Mn 0.05O2 (NCM) was prepared. The LZO-coated cathode active material was prepared according to the method disclosed in Korean Patent Publication No. 10-2016-0064942. The CNF-Li6PS5Cl composite prepared in Preparation Example 1 was prepared as the first fibrous solid electrolyte. Argyrodite-type crystals, Li6PS5Cl (D50 = 0.5 μm, crystalline), were prepared as the irregular-shaped particulate solid electrolyte. Polytetrafluoroethylene (PTFE) was prepared as the binder. Carbon nanofibers (CNF) were prepared as the conductive agent. These materials were mixed with xylene solvent in a weight ratio of 84:2:9.5:3:1.5 (cathode active material: first fibrous solid electrolyte: irregular particulate solid electrolyte: conductive agent: binder). The slurry was formed into a sheet and then vacuum-dried at 40°C for 8 hours to prepare a cathode sheet. The prepared positive electrode sheet was placed on the carbon layer of a positive electrode current collector made of aluminum foil coated with a carbon layer on one side, and then heated at 85°C to prepare a positive electrode layer. The total thickness of the positive electrode layer was approximately 120 μm. The thicknesses of the positive electrode active material layers were approximately 95 μm, and the thickness of the carbon-coated aluminum foil was approximately 25 μm. The initial charge capacity of the positive electrode layer (i.e., the positive electrode active material layer) was measured using the half-cell described above. The ratio (B / A) of the initial charge capacity (B) of the first negative electrode active material layer to the initial charge capacity (A) of the positive electrode active material layer was less than 0.5. The initial charge capacity of the positive electrode active material layer was measured using the first open circuit voltage (1 st open circuit voltage) to 4.25 V vs. Li / Li + The initial charge capacity of the first negative electrode active material layer was determined by charging up to the second open circuit voltage (2 nd open circuit voltage) to 0.01 V vs. Li / Li + determined by the charge to

[0229] (All-solid-state secondary battery manufacturing) An all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that the above-described positive electrode layer was used.

[0230] Comparative example 1: Mono-cell all-solid-state secondary battery, sulfide-based positive electrode active material (Li2S-C-LiI composite), fibrous solid electrolyte: particulate solid electrolyte = 0:50 weight ratio

[0231] An all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that the weight ratio of the fibrous solid electrolyte to the particulate solid electrolyte was changed to 0:50, and the fibrous solid electrolyte was not used.

[0232] Comparative Example 2: Mono-cell all-solid-state secondary battery, oxide-based positive electrode active material (NCA), fibrous solid electrolyte:particulate solid electrolyte=0:50 weight ratio

[0233] An all-solid-state secondary battery was manufactured in the same manner as in Example 10, except that the weight ratio of the fibrous solid electrolyte to the particulate solid electrolyte was changed to 0:50, and the fibrous solid electrolyte was not used.

[0234] Comparative Example 3: Mono-cell all-solid-state secondary battery, sulfide-based positive electrode active material (Li2S-C-LiI composite), fibrous solid electrolyte (composite of CNF and Li6PS5Cl) instead of a simple mixture of CNF and Li6PS5Cl

[0235] An all-solid-state secondary battery was prepared in the same manner as in Example 1, except that a 2:1 weight ratio mixture of CNF and Li6PS5Cl was used instead of the fibrous solid electrolyte (a composite of CNF and Li6PS5Cl).

[0236] Comparative Example 4: Mono-cell all-solid-state secondary battery, oxide-based cathode active material (NCA), fibrous solid electrolyte (composite of CNF and Li6PS5Cl) instead of a simple mixture of CNF and Li6PS5Cl

[0237] An all-solid-state secondary battery was prepared in the same manner as in Example 10, except that a 2:1 weight ratio mixture of CNF and Li6PS5Cl was used instead of the fibrous solid electrolyte (a composite of CNF and Li6PS5Cl).

[0238] Reference example 1: Sulfide-based positive electrode active material, no inert materials used (free)

[0239] An all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that no flame-retardant inactive member (ie, gasket) was used during the manufacture of the all-solid-state secondary battery.

[0240] Reference example 2: Oxide-based positive electrode active material, no inert materials used (free)

[0241] An all-solid-state secondary battery was manufactured in the same manner as in Example 10, except that no flame-retardant inert member (ie, gasket) was used during the manufacture of the all-solid-state secondary battery.

[0242] Example 11: One bi-cell all-solid-state secondary battery, sulfide-based positive electrode active material (LiS-C-LiI composite), fibrous solid electrolyte:particulate solid electrolyte=10:40 weight ratio, first two-dimensional solid electrolyte

[0243] (Manufacturing bi-cell all-solid-state secondary batteries) The positive electrode layer was prepared in the same manner as in Example 1, except that the positive electrode active material layers were arranged on both sides of the positive electrode current collector.

[0244] The total thickness of the positive electrode layer was about 220 μm, the thickness of each positive electrode active material layer was about 100 μm, and the thickness of the carbon-coated aluminum foil was about 20 μm.

[0245] Two negative electrode layers, two solid electrolyte layers, and two flame-retardant inert members were prepared in the same manner as in Example 1.

[0246] Referring to FIG. 10, a solid electrolyte layer was disposed on the negative electrode layer so that the first negative electrode active material layer was in contact with the solid electrolyte layer, and a positive electrode layer was disposed on the solid electrolyte layer. The positive electrode layer had a structure in which a positive electrode active material layer was disposed on each side of a positive electrode current collector. A gasket was disposed around the positive electrode layer, surrounding the positive electrode layer and in contact with the solid electrolyte layer. The gasket had a thickness of approximately 220 μm. The gasket was, for example, a structure in which two 110 μm-thick gaskets were stacked, or a single 220 μm-thick gasket. The flame-retardant inert material was used as the gasket.

[0247] The gasket was placed so as to contact the side of the positive electrode layer and the solid electrolyte layer. The positive electrode layer was placed at the center of the solid electrolyte layer, and the gasket surrounded the positive electrode layer and extended to the end of the solid electrolyte layer. The area of ​​the positive electrode layer was approximately 90% of the area of ​​the solid electrolyte layer, and the gasket was placed over the remaining 10% of the area of ​​the solid electrolyte layer where the positive electrode layer was not placed. A stack was prepared by placing the solid electrolyte layer on the positive electrode layer and the gasket, and then placing the negative electrode layer on the solid electrolyte layer.

[0248] The prepared stack was plate-pressed at 85°C. This pressurization sintered the solid electrolyte layer, improving battery performance. The thickness of one sintered solid electrolyte layer was approximately 45 μm. The area of ​​the solid electrolyte layer was the same as that of the anode layer. The pressed stack was placed in a pouch and vacuum-sealed to fabricate an all-solid-state secondary battery. Portions of the positive and negative electrode current collectors were extended to the outside of the sealed battery to serve as the positive and negative electrode terminals.

[0249] Evaluation example 1: High temperature life characteristic test

[0250] The charge-discharge characteristics of the all-solid-state secondary batteries prepared in Examples 1 to 9, Example 11, Comparative Example 1, Comparative Example 3, and Reference Example 1 were evaluated by the following charge-discharge test. The charge-discharge test was carried out by placing the all-solid-state secondary batteries in a thermostatic chamber at 45°C.

[0251] The first cycle is 0.6mA / cm until the battery voltage reaches 2.5V to 2.8V.2 The battery was charged at a constant current of 0.6 mA / cm for 12.5 hours until the battery voltage reached 0.5 V. 2 The battery was discharged at a constant current of 1000 kJ / s for 12.5 hours.

[0252] The charge-discharge characteristics of the all-solid-state secondary batteries prepared in Example 10, Comparative Example 2, Comparative Example 4, and Reference Example 2 were evaluated by the following charge-discharge test. The charge-discharge test was carried out by placing the all-solid-state secondary batteries in a thermostatic chamber at 45°C.

[0253] The first cycle was 0.6 mA / cm until the battery voltage reached 3.9 V to 4.25 V. 2 The battery was charged at a constant current of 0.6 mA / cm for 12.5 hours until the battery voltage reached 2.5 V. 2 The battery was discharged at a constant current of 1000 kJ / s for 12.5 hours.

[0254] The discharge capacity of the first cycle was taken as the standard capacity. After the second cycle, charging and discharging were repeated up to 150 cycles under the same conditions as the first cycle. The measurement results are shown in Table 2 below.

[0255] The more cycles required for the discharge capacity to decrease to 95% of the standard capacity after the second cycle, the better the lifespan characteristics were considered to be.

[0256] In the all-solid-state secondary batteries of Reference Examples 1 and 2, a short circuit occurred before the completion of the first cycle, making it impossible to measure the life characteristics.

[0257] [Table 1]

[0258] As shown in Table 1, the all-solid-state secondary batteries including the sulfide-based positive electrode active materials of Examples 1 to 9 and Example 12 had improved life characteristics compared to the all-solid-state secondary batteries of Comparative Examples 1 and 3.

[0259] It was determined that the lithium batteries of Examples 1 to 9 had increased ion conduction paths due to the inclusion of the fibrous solid electrolyte, and thus more effectively accommodated the volume change of the positive electrode active material during charge and discharge, thereby improving the life characteristics.

[0260] In the all-solid-state secondary batteries of Examples 1 to 5, the life characteristics changed depending on the weight ratio of the fibrous solid electrolyte to the particulate solid electrolyte.

[0261] The all-solid-state secondary battery containing the fibrous solid electrolyte of Example 1 had improved life characteristics compared to the all-solid-state secondary battery of Comparative Example 3 containing a simple mixture of graphene and a solid electrolyte. It was determined that the simple mixture of graphene and a solid electrolyte increases side reactions due to non-uniform mixing, thereby deteriorating the performance of the all-solid-state secondary battery.

[0262] The all-solid-state secondary battery containing the oxide-based positive electrode active material of Example 10 had improved life characteristics compared to the all-solid-state secondary batteries of Comparative Examples 2 and 4.

[0263] The all-solid-state secondary battery of Example 10 was determined to have improved life characteristics by having an increased ion conduction path due to the fibrous electrolyte disposed in the positive electrode active material layer and more effectively accommodating the volume change of the positive electrode active material during charge and discharge.

[0264] The all-solid-state secondary battery containing the fibrous solid electrolyte of Example 10 had improved life characteristics compared to the all-solid-state secondary battery of Comparative Example 4 containing a simple mixture of graphene and a solid electrolyte. It was determined that the simple mixture of graphene and a solid electrolyte increases side reactions due to non-uniform mixing, thereby deteriorating the performance of the all-solid-state secondary battery.

[0265] The all-solid-state secondary battery of Example 11 has a bi-cell structure in which components are symmetrically arranged, and is therefore judged to have improved life characteristics by effectively mitigating volume changes during charge and discharge compared to the all-solid-state secondary batteries of Examples 1 to 5, which have a mono-cell structure.

[0266] After the first cycle charging was completed for the all-solid-state secondary batteries of Examples 1 to 11, SEM images of the cross sections of the batteries were measured, and it was confirmed that a lithium metal deposition layer corresponding to the second negative electrode active material layer was formed between the solid electrolyte layer and the negative electrode current collector.

[0267] As described above, the all-solid-state secondary battery according to this embodiment can be applied to various portable devices, vehicles, and the like.

[0268] Although an exemplary embodiment has been described in detail above with reference to the accompanying drawings, the present invention is not limited to such an example. It is obvious to those skilled in the art that various modifications and alterations can be made within the scope of the technical idea described in the claims, and it goes without saying that these modifications and alterations also fall within the technical scope of the present invention.

[0269] According to one aspect, an all-solid-state secondary battery having a new structure can provide an all-solid-state secondary battery with improved cycle characteristics. [Explanation of symbols]

[0270] 1 All-solid-state secondary battery 10 Positive electrode layer 11 Positive electrode current collector 12 Cathode active material layer 12A 1st area 12B 2nd area 20 negative electrode layer 21 Negative electrode current collector 22 First negative electrode active material layer 30 Solid electrolyte layer 40 Inert Materials 100 First fibrous sulfide-based solid electrolyte 110 cores 120 shells 130 Middle Class

Claims

1. a positive electrode layer, a negative electrode layer, and a solid electrolyte layer between the positive electrode layer and the negative electrode layer; the positive electrode layer includes a positive electrode current collector and a positive electrode active material layer on one or more surfaces of the positive electrode current collector, At least one of the positive electrode active material layer and the solid electrolyte layer includes a first fibrous sulfide-based solid electrolyte; the negative electrode layer includes a negative electrode current collector and a first negative electrode active material layer on one surface of the negative electrode current collector, an initial charge capacity (B) of the first negative electrode active material layer is less than about 50% of an initial charge capacity (A) of the positive electrode active material layer.

2. the first fibrous sulfide-based solid electrolyte is defined by a length and a diameter, and the aspect ratio of the length to the diameter is about 5 or more; The first fibrous sulfide-based solid electrolyte has a length of about 1 to 50 μm and a diameter of about 10 nm to 10 μm, 2. The all-solid-state secondary battery according to claim 1, wherein the first fibrous sulfide-based solid electrolyte comprises a rod structure, a tube structure, a needle structure, a wire structure, or a combination thereof.

3. The first fibrous sulfide-based solid electrolyte has an irregular, circular, or polygonal cross section perpendicular to the longitudinal direction thereof, The polygonal shape includes a triangle, a square, a pentagon, a hexagon, a heptagon, an octagon, a nonagon, or a decagon; The all-solid-state secondary battery according to claim 1 , wherein the cross-sectional circularity of the first fibrous sulfide-based solid electrolyte 100 is, for example, 0.6 or more.

4. the first fibrous sulfide-based solid electrolyte comprises a core and a shell on the core, the core comprises a carbon-based material, a polymer, a metal-containing inorganic material, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or a combination thereof; the carbon-based material, polymer, metal-containing inorganic material, or combination thereof further comprises P, S, or combination thereof; the shell comprises a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a coating material, or a combination thereof; At least one of the core and the shell contains a sulfide-based solid electrolyte, The core comprises a one-dimensional nanostructure, and the one-dimensional nanostructure is a carbon nanofiber, a carbon nanorod, a carbon nanotube, a carbon nanoneedle, a carbon nanowire, or SiO ２ , TiO ２ , Al ２ O ３ , AlN, SiC, BaTiO ３ or a combination thereof.

5. a ratio of the first diameter of the core to the first thickness of the shell is 1:0.01 to 1:100; 5. The all-solid-state secondary battery according to claim 4, wherein a ratio of the first length of the core to the second length of the shell is 1:1 to 1:

10.

6. the positive electrode active material layer includes a first region adjacent to the positive electrode current collector and a second region adjacent to the solid electrolyte layer, A first fibrous sulfide-based solid electrolyte is present in the first region, and the first fibrous sulfide-based solid electrolyte is free in the second region; The fibrous sulfide-based solid electrolyte is free, or The all-solid-state secondary battery according to claim 1 , wherein the first fibrous sulfide-based solid electrolyte is present in the first region and the second region.

7. the first fibrous sulfide-based solid electrolyte is homogeneous in the first region or has a concentration gradient in which the first fibrous sulfide-based solid electrolyte decreases in a direction from the positive electrode current collector to the solid electrolyte layer, the first fibrous sulfide-based solid electrolyte is homogeneous in the second region or has a concentration gradient in which the first fibrous sulfide-based solid electrolyte decreases in a direction from the solid electrolyte layer toward the positive electrode current collector, 7. The all-solid-state secondary battery according to claim 6, wherein the first fibrous sulfide-based solid electrolyte is homogeneous in the first region and the second region, or has a concentration gradient in which the first fibrous sulfide-based solid electrolyte decreases in the first region and the second region from the positive electrode current collector toward the solid electrolyte layer, or has a concentration gradient in which the first fibrous sulfide-based solid electrolyte decreases in the first region and the second region from the solid electrolyte layer toward the positive electrode current collector.

8. 2. The all-solid-state secondary battery of claim 1, wherein the content of the first fibrous sulfide-based solid electrolyte is about 1 to 50 wt % of the total weight of the positive electrode active material layer.

9. The positive electrode active material layer further includes an irregular-shaped sulfide-based solid electrolyte that is distinct from the first fibrous sulfide-based solid electrolyte, 2. The all-solid-state secondary battery according to claim 1, wherein the weight ratio of the first fibrous sulfide-based solid electrolyte to the amorphous sulfide-based solid electrolyte is 1:99 to 99:

1.

10. the positive electrode active material layer contains a positive electrode active material, the positive electrode active material comprises an oxide-based positive electrode active material, a sulfide-based positive electrode active material, or a combination thereof; the oxide-based positive electrode active material includes a lithium transition metal oxide, a metal oxide, or a combination thereof, the lithium transition metal oxide includes lithium cobalt oxide, lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese oxide, lithium manganate, lithium iron phosphate, or a combination thereof, and the lithium oxide includes iron oxide, vanadium oxide, or a combination thereof; The sulfide-based positive electrode active material is nickel sulfide, copper sulfide, Li ２ S., Li. ２ 10. The all-solid-state secondary battery of claim 1, comprising an S-containing composite or a combination thereof.

11. The Li ２ The S-containing complex is Li ２ S and carbon complex, Li ２ S, carbon, and solid electrolyte composite, Li ２ S and solid electrolyte composite, Li ２ S and lithium salt complex, Li ２ S, lithium salt and carbon complex, Li ２ S and metal carbide complex, Li ２ S, carbon and metal carbide composite, Li ２ S and metal nitride complex, Li ２ The all-solid-state secondary battery according to claim 10 , comprising a composite of S, carbon, and a metal nitride, or a combination thereof.

12. The Li ２ the S-containing composite further comprises a second fibrous sulfide-based solid electrolyte; The second fibrous sulfide-based solid electrolyte contains Li ２ 0.1 to 50 wt % of the total weight of the S-containing composite; The all-solid-state secondary battery according to claim 10 , wherein the second fibrous sulfide-based solid electrolyte is smaller in size than the first fibrous sulfide-based solid electrolyte.

13. The positive electrode active material layer further includes at least one selected from a conductive material and a binder, The all-solid-state secondary battery according to claim 1 , wherein the conductive material comprises a carbon-based conductive material.

14. Further comprising an inactive member on one side of the positive electrode layer, the inactive member surrounds the positive electrode layer along a side surface of the positive electrode layer, The all-solid-state secondary battery according to claim 1 , wherein the inactive member includes a positioning portion configured to determine a position of the inactive member on the solid electrolyte layer.

15. the first negative electrode active material layer includes a negative electrode active material and a binder, 2. The all-solid-state secondary battery according to claim 1, wherein the negative electrode active material is in a particulate form, and the average particle size of the negative electrode active material is about 4 μm or less.

16. the negative electrode active material includes at least one selected from a carbon-based negative electrode active material and a metal-based negative electrode active material, The carbon-based negative electrode active material includes amorphous carbon, crystalline carbon, porous carbon, or a combination thereof; 16. The all-solid-state secondary battery according to claim 15, wherein the metal-based negative electrode active material comprises gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), zinc (Zn), or a combination thereof.

17. the negative electrode active material comprises a mixture of first particles including amorphous carbon and second particles including a metal, The all-solid-state secondary battery of claim 15, wherein the content of the second particles is about 8 to 60 wt% based on the total weight of the mixture.

18. the negative electrode active material includes a carbon-based support and a metal-based negative electrode active material supported on the carbon-based support, the metal-based negative electrode active material comprises a metal, a metal oxide, a composite of a metal and a metal oxide, or a combination thereof; the metal-based negative electrode active material is particulate, and the particle size of the metal-based negative electrode active material is about 1 nm to 200 nm; The all-solid-state secondary battery according to claim 15, wherein the carbon-based support has a particulate shape and the particle size of the carbon-based support is about 10 nm to 2 μm.

19. a second negative electrode active material layer between the solid electrolyte layer and the negative electrode current collector, the second negative electrode active material layer is at least one of between the first negative electrode active material layer and the first protective layer and between the first negative electrode active material layer and the solid electrolyte layer; The all-solid-state secondary battery according to claim 1 , wherein the second negative electrode active material layer is a metal layer containing lithium metal or a lithium alloy.

20. At least one of the positive electrode current collector and the negative electrode current collector includes a base film and a metal layer disposed on at least one surface of the base film, the base film comprises a polymer, the polymer comprising polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof; 2. The all-solid-state secondary battery according to claim 1, wherein the metal layer contains indium (In), copper (Cu), magnesium (Mg), titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof.

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