Positive electrode for all-solid secondary battery and all-solid secondary battery comprising same

Abstract

Disclosed are: a positive electrode for an all-solid secondary battery, the positive electrode comprising a positive electrode current collector, an adhesion polymer-containing adhesion binder layer on the positive electrode current collector, and a positive electrode active material layer on the adhesion binder layer and containing composite positive electrode active material and a cohesion binder, the composite positive electrode active material comprising a Li2S-containing composite; and an all-solid secondary battery comprising said positive electrode, a negative electrode, and a solid electrolyte layer between the positive and negative electrodes.

Description

Cathode for all-solid-state secondary battery and all-solid-state secondary battery containing the same

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

[0002] Recent industrial demands have led to the active development of batteries with high energy density and safety. For example, lithium batteries are used in a variety of applications, including information technology, communications devices, and automobiles. Because automobiles are life-threatening, safety is also crucial.

[0003] Lithium batteries using liquid electrolytes may have an increased risk of fire and / or explosion in the event of a short circuit. All-solid-state secondary batteries using solid electrolytes instead of liquid electrolytes are being proposed. Solid electrolytes are less likely to catch fire than liquid electrolytes.

[0004] All-solid-state secondary batteries can reduce the risk of fire or explosion by using solid electrolytes instead of liquid ones. Solid-state batteries can also offer improved safety.

[0005] One aspect is to provide a positive electrode for an all-solid-state secondary battery with improved interlayer adhesion.

[0006] Another aspect is to provide an all-solid-state secondary battery with improved performance, including the above-mentioned positive electrode.

[0007] According to the implementation example

[0008] positive current collector;

[0009] A positive electrode for an all-solid-state secondary battery is provided, comprising: an adhesion binder layer positioned on a positive electrode current collector and containing an adhesive polymer; a positive electrode active material layer positioned on the adhesive binder layer and containing a composite positive electrode active material and a cohesion binder, wherein the composite positive electrode active material includes a Li2S-containing complex.

[0010] According to another embodiment, an all-solid-state secondary battery is provided, which includes the above-described positive electrode; a negative electrode; and a solid electrolyte layer disposed between the positive electrode and the negative electrode.

[0011] According to one aspect, it is possible to provide an all-solid-state secondary battery with improved discharge capacity and rate characteristics due to improved adhesion between the substrate and the electrode, and improved life characteristics due to stable contact without stable detachment even when repeated shrinkage and expansion during a cycle.

[0012] Figure 1 is a cross-sectional view of an all-solid-state secondary battery according to an exemplary embodiment.

[0013] Figure 2 is a cross-sectional view of an all-solid-state secondary battery according to an exemplary embodiment.

[0014] Figure 3 is a cross-sectional view of an all-solid-state secondary battery according to an exemplary embodiment.

[0015] Fig. 4 is a cross-sectional view of an all-solid-state secondary battery according to an exemplary embodiment.

[0016] Fig. 5 is a cross-sectional view of an all-solid-state secondary battery according to an exemplary embodiment.

[0017] <Explanation of key symbols in the drawing>

[0018] 1 All-solid-state secondary battery 10 Cathode

[0019] 11. Cathode current collector 12. Cathode active material layer

[0020] 20 Cathode 21 Cathode current collector

[0021] 22 First negative electrode active material layer 23 Thin film

[0022] 24 Second negative electrode active material layer 30 Electrolyte layer

[0023] 40 Inert Absences

[0024] Unless otherwise defined, all terms (including technical and scientific terms) used in this disclosure have the same meaning as commonly understood by those of ordinary skill in the art to which this disclosure pertains. Furthermore, terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning within the context of the relevant technology and this disclosure, and should not be interpreted in an idealized or overly formal sense.

[0025] Exemplary embodiments are described in this disclosure with reference to cross-sectional drawings that are schematic representations of idealized embodiments. As such, variations from the shapes depicted are to be expected, for example, as a result of manufacturing techniques and / or tolerances. Therefore, the embodiments described in this disclosure should not be construed as limited to the specific shapes of regions as depicted in this disclosure, but should encompass variations in shapes resulting from, for example, manufacturing. For example, regions depicted or described as flat may typically have rough and / or non-linear features. Moreover, angles depicted as sharp may be rounded. Therefore, the regions depicted in the drawings are schematic in nature, and their shapes are not intended to depict the precise shapes of the regions, nor are they intended to limit the scope of the claims.

[0026] This creative idea may be embodied in many different forms and should not be construed as limited to the embodiments described in this disclosure. These embodiments are provided so that this disclosure will be thorough and complete, and so that it will fully convey the scope of the creative idea to those skilled in the art. Like reference numerals in the drawings indicate like elements.

[0027] When a component is referred to as being "on" another component, it can be understood that it is either directly on top of the other component or that other components may be intervening between them. Conversely, when a component is referred to as being "directly on" another component, no intervening components are present.

[0028] Although the terms "first," "second," "third," etc. may be used herein to describe various components, elements, regions, layers, and / or zones, these components, elements, regions, layers, and / or zones should not be limited by these terms. These terms are only used to distinguish one component, element, region, layer, or zone from another component, element, region, layer, or zone. Thus, a first component, element, region, layer, or zone described below may be referred to as a second component, element, region, layer, or zone without departing from the teachings of this disclosure.

[0029] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms including "at least one," unless the content clearly dictates otherwise. "At least one" should not be construed as limiting to the singular. As used herein, the term "and / or" includes any and all combinations of one or more of the listed items. The terms "comprises" and / or "comprising" as used in the detailed description specify the presence of stated features, regions, integers, steps, operations, components, and / or ingredients, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, components, ingredients, and / or groups thereof.

[0030] Spatially relative terms such as "below," "under," "bottom," "above," "above," "top," and the like may be used herein to readily describe the relationship of one component or feature to another component or feature. It will be understood that spatially relative terms are intended to encompass different orientations of the device when in use or operation in addition to the orientations depicted in the drawings. For example, if the device in the drawings were turned over, a component described as "below" or "below" another component or feature would then be oriented "above" the other component or feature. Thus, the exemplary term "below" can encompass both the above and below orientations. The device can be arranged in other orientations (rotated 90 degrees or otherwise rotated), and the spatially relative terms used herein can be interpreted accordingly.

[0031] "Group" means a group in the periodic table of elements according to the International Union of Pure and Applied Chemistry ("IUPAC") Group 1-18 classification system.

[0032] In the present disclosure, "particle size" or "particle diameter" refers to the average diameter when the particles are spherical, and refers to the average major axis length when the particles are non-spherical. The particle diameter can be measured using a particle size analyzer (PSA). The "particle size" or "particle diameter" refers to, for example, the average particle diameter. The "average particle diameter" refers to, for example, the median particle diameter, D50.

[0033] D50 is the size of the particle corresponding to 50% of the cumulative volume, calculated from the particle side with a smaller particle size in the particle size distribution measured by laser diffraction.

[0034] D90 is the size of the particle corresponding to 90% of the cumulative volume, calculated from the particle side with a smaller particle size in the particle size distribution measured by laser diffraction.

[0035] D10 is the size of the particle corresponding to 10% of the cumulative volume, calculated from the particle side with a small particle size in the particle size distribution measured by laser diffraction.

[0036] In this disclosure, “metal” includes both metals and metalloids such as silicon and germanium, in their elemental or ionic states.

[0037] In this disclosure, “alloy” means a mixture of two or more metals.

[0038] In the present disclosure, “electrode active material” means an electrode material capable of undergoing lithiation and delithiation.

[0039] In the present disclosure, “positive electrode material” means a positive electrode material capable of undergoing lithiation and delithiation.

[0040] In the present disclosure, “negative electrode active material” means a negative electrode material capable of undergoing lithiation and delithiation.

[0041] In the present disclosure, “lithiation” and “lithiating” mean a process of adding lithium to an electrode active material.

[0042] In the present disclosure, “delithiation” and “delithiate” mean a process of removing lithium from an electrode active material.

[0043] In this disclosure, “charging” and “charging” mean a process of providing electrochemical energy to a battery.

[0044] In this disclosure, “discharging” and “discharging” mean the process of removing electrochemical energy from a battery.

[0045] In the present disclosure, “positive electrode” and “cathode” mean an electrode at which electrochemical reduction and lithiation occur during a discharge process.

[0046] In the present disclosure, “cathode” and “anode” mean electrodes where electrochemical oxidation and delithiation occur during a discharge process.

[0047] In the present disclosure, length, thickness and width represent average length, average thickness and average width, respectively, and these can be evaluated using a scanning electron microscope.

[0048] In the present disclosure, the aspect ratio represents the ratio (L1 / L2) of the major axis length L1 (e.g., length) and the minor axis length L2 (e.g., diameter). Here, the aspect ratio, major axis length, minor axis length, length, and diameter represent the average aspect ratio, average major axis length, average minor axis length, average length, and average diameter. The aspect ratio can be evaluated using a scanning electron microscope.

[0049] In this specification, a solid solution is different from a mixture of two or more chemical species and refers to a homogeneous crystal phase containing two or more chemical species.

[0050] As used herein, a "two-dimensional carbon nanostructure" is a carbon nanostructure in which two dimensions are significantly larger than one of the other dimensions. In other words, it is a carbon nanostructure in which the area defined by the two dimensions is significantly larger than the thickness.

[0051] In the present disclosure, the weight average molecular weight can be evaluated by gel permeation chromatography (GPC).

[0052] While specific implementations have been described, alternatives, modifications, variations, improvements, and substantial equivalents that are not currently anticipated or unforeseen may occur to the applicant or those skilled in the art. Accordingly, the appended claims, as filed and as amended, are intended to encompass all such alternatives, modifications, variations, improvements, and substantial equivalents.

[0053]

[0054] Hereinafter, a positive electrode for an all-solid-state secondary battery, an all-solid-state secondary battery including the same, and a manufacturing method thereof according to exemplary embodiments are described in more detail.

[0055] [anode]

[0056] An all-solid-state secondary battery cathode according to an embodiment includes: a cathode current collector; an adhesion binder layer positioned on the cathode current collector and containing an adhesive polymer; and a cathode active material layer positioned on the adhesion binder layer and containing a composite cathode active material and a cohesion binder, wherein the composite cathode active material includes a Li2S-containing complex.

[0057] In order to prevent detachment from the substrate due to shrinkage and expansion during charge and discharge and to improve electronic conductivity of the positive electrode for an all-solid-state secondary battery using lithium sulfide as the positive electrode active material, it is necessary to strengthen the adhesion between the substrate and the lithium sulfide active material electrode and the substrate.

[0058] Accordingly, in the present disclosure, an adhesive binder layer is formed between a positive electrode active material layer and a substrate to improve the adhesive strength between the positive electrode active material layer containing a Li2S-containing complex and the substrate while reducing the interfacial resistance, and a positive electrode showing excellent electrochemical properties without surface detachment from the substrate even when repeated shrinkage and expansion due to charge and discharge are performed by using a positive electrode active material layer containing an adhesive binder.

[0059] The above composite cathode active material is a Li2S-containing composite, which includes a composite of Li2S and a lithium salt; and a sulfide-based solid electrolyte.

[0060] The complex of the above Li2S and lithium salt is Li2S-Li a X b (1≤a≤5, 1≤b≤5), and X is I, Br, Cl, F, H, O, Se, Te, N, P, As, Sb, Al, B, OCl, PF6, BF4, SbF6, AsF6, ClO4, AlO2, AlCl4, NO3, CO3, BH4, SO4, BO3, PO4, NCl, NCl2, BN2, or a combination thereof.

[0061] In all-solid-state secondary batteries using lithium sulfide as the cathode active material, lithium sulfide is an insulator with virtually no electrical or ionic conductivity. Therefore, composites with materials with high electrical and ionic conductivity are required. Furthermore, during charge and discharge, shrinkage and expansion of lithium sulfide-containing materials can cause the cathode active material to detach from the cathode current collector, degrading electronic conductivity. Therefore, improvements are needed.

[0062] Accordingly, the positive electrode of the present disclosure uses a Li2S-containing composite as a positive electrode active material, forms an adhesive binder layer containing an adhesive polymer between a positive electrode current collector and a positive electrode active material layer, and uses the adhesive binder in the positive electrode active material layer to further reduce the interfacial resistance between the positive electrode active material layer and the positive electrode current collector, and can effectively suppress the problem of deterioration of a sulfide-based solid electrolyte contained in the positive electrode active material layer during battery operation.

[0063] By forming the adhesive binder layer, deterioration of the sulfide-based solid electrolyte of the positive electrode active material layer can be effectively prevented, the adhesive strength of the positive electrode can be improved, and the interface resistance between the positive electrode current collector and the positive electrode active material layer can be reduced.

[0064] The thickness of the adhesive binder layer according to an embodiment may be 5 nm to 1 um, 5 nm to 800 nm, 5 nm to 500 nm, 5 nm to 400 nm, 5 nm to 300 nm, 10 nm to 300 nm, 10 nm to 100 nm, or 10 nm to 50 nm.

[0065] According to another embodiment, the thickness of the adhesive binder layer is 20 nm to 1 um, 20 nm to 800 nm, 20 nm to 500 nm, 20 nm to 300 nm, or 20 nm to 100 nm. By forming it in this thickness range, the interface resistance can be reduced while effectively protecting the sulfide-based solid electrolyte contained in the positive electrode active material layer.

[0066] The adhesive polymer constituting the adhesive binder layer is, for example, at least one selected from polydopamine, cationically substituted polycarboxylic acid and copolymers thereof, poly(norepinephrin), poly(meth)acrylamide, polyvinylalcohol, poly(2-hydroxymethyl(meth)acrylate), methyl(meth)acrylate-co-(meth)acrylic acid, polymethyl(meth)acrylate, poly((meth)acrylic acid), and styrene-co-(meth)acrylic acid.

[0067] The above cation-substituted polycarboxylic acid and its copolymer have one cation selected from lithium ion (Li+), sodium ion (Na+), potassium ion (K+), and ammonium ion (NH4+). Polycarboxylic acid means a polymer formed by polymerization of various types of monomers including one or more monomers having one or more carboxyl groups (-COOH), and has a weight average molecular weight of 1,000 to 1,000,000. Examples of such polycarboxylic acids include polyacrylic acid, polymethacrylic acid, and polymaleic acid. The cation-substituted polycarboxylic acid is a substance in which hydrogen of such polycarboxylic acid is replaced with a cation, and includes, for example, one or more selected from lithium polyacrylate (LiPAA) and lithium polymethacrylate.

[0068] A cation-substituted polycarboxylic acid copolymer is a copolymer containing a monomer repeating unit corresponding to a cation-substituted polycarboxylic acid, and examples of such copolymers include poly(acrylic acid-co-maleic acid) lithium salt, poly(methylvinyl ether-alt-maleic acid) lithium salt, or poly(butadiene-co-maleic acid) lithium salt.

[0069] At least one selected from among cation-substituted polycarboxylic acids and copolymers thereof has a glass transition temperature of 50°C or higher, for example, 50 to 200°C, specifically, 50 to 150°C. And at least one selected from among cation-substituted polycarboxylic acids and copolymers thereof has a melting point of 100°C or higher, for example, 100 to 300°C, specifically, 100 to 200°C. When an intermediate layer (e.g., an adhesive binder layer) is formed using a cation-substituted polycarboxylic acid and copolymer thereof having such a glass transition temperature and melting point, the intermediate layer can maintain its shape at a battery operating temperature (e.g., 0 to 90°C). At least one selected from the above cation-substituted polycarboxylic acid and copolymers thereof has a weight average molecular weight of 1,000 to 1,000,000 and a degree of polymerization of 10 to 1500, for example, 14 to 1400.

[0070] Examples of cation-substituted polycarboxylic acids include lithium polyacrylate.

[0071] According to one embodiment, the cohesion binder is polytetrafluoroethylene, polyvinylidene fluoride (PVdF) resin, styrene-butadiene rubber (SBR), polytetrafluoroethylene (PTFE), polyethylene glycol (PEG), polypropylene glycol (PPG), toluene diisocyanate (TDI), polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, poly(ethylene-co-vinyl acetate) copolymer, polyethylene oxide, cellulose acetate, cellulose Acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxyl methyl cellulose, acrylonitrile-styrene-butadiene copolymer, and polyimide, or a combination thereof. And the content of the adhesive binder is 0.5 to 10 parts by weight, 0.5 to 8 parts by weight, 0.5 to 5 parts by weight, 0.6 to 3 parts by weight, 0.7 to 2 parts by weight, or 0.8 to 1.5 parts by weight, and the content of the adhesive binder is 100 to 1000 parts by weight, 150 to 950 parts by weight, 200 to 900 parts by weight, 250 to 850 parts by weight, 300 to 800 parts by weight, 350 to 750 parts by weight, 400 to 700 parts by weight, or 450 to 650 parts by weight based on 100 parts by weight of the adhesive polymer of the adhesive binder layer. If the content of the adhesive binder is more than the above range, the content of the lithium sulfide complex in the positive electrode active material layer may be relatively reduced, thereby reducing the capacity characteristics, and if the content of the adhesive binder is less than the above range, the adhesive strength of the positive electrode active material layer may be reduced.

[0072] The above-described positive electrode has an adhesive binder layer, which not only improves the adhesive strength between the current collector and the positive electrode active material layer, but also enhances stability and reliability against mechanical deformation such as bending, thereby improving battery performance. Therefore, in an all-solid-state secondary battery using a positive electrode containing lithium sulfide as a positive electrode active material, the phenomenon of the positive electrode active material being detached from the surface of the current collector due to changes in the volume of the positive electrode active material is prevented, and by forming an adhesive binder layer, it is possible to implement a high-capacity all-solid-state secondary battery in which battery performance is deteriorated due to an increase in the interfacial resistance between the current collector and the positive electrode active material layer.

[0073] Li2S-containing complexes include, for example, complexes of Li2S and lithium salts.

[0074] The ductility of the Li2S and lithium salt composite distinguishes it from brittle conventional oxide-based solid electrolytes, such as garnet-structured oxide-based solid electrolytes. The Li2S and lithium salt composite exhibits lithium ion conductivity, distinguishing it from conventional lithium-free metal oxides, such as alumina, which do not exhibit lithium ion conductivity. The Li2S and lithium salt composite is, for example, the result of mechanical milling of Li2S and lithium salt. The Li2S and lithium salt composite is, for example, the result of a mechanochemical reaction between Li2S and lithium salt, distinguishing it from a simple mixture of Li2S and lithium salt. The simple mixture of Li2S and lithium salt can provide high interfacial resistance by failing to maintain a dense interface between Li2S and lithium salt, which can consequently increase the internal resistance of the solid electrolyte separator.

[0075] The complex of Li2S and lithium salt is Li2S-Li a X b(1≤a≤5, 1≤b≤5). Wherein X is I, Br, Cl, F, H, O, Se, Te, N, P, As, Sb, Al, B, OCl, PF6, BF4, SbF6, AsF6, ClO4, AlO2, AlCl4, NO3, CO3, BH4, SO4, BO3, PO4, NCl, NCl2, BN2 or a combination thereof. a is, for example, 1, 2, 3, 4 or 5. b is, for example, 1, 2, 3, 4 or 5. The lithium salt is, for example, a compound that does not contain sulfur (S). The lithium salt may be, for example, a binary compound or a ternary compound. The lithium salt may be, for example, a binary compound composed of lithium and one element selected from Groups 13 to 17 of the Periodic Table of Elements. The lithium salt may be, for example, a ternary compound composed of lithium and two elements selected from groups 13 to 17 of the periodic table. The binary compound may include, for example, LiI, LiBr, LiCl, LiF, LiH, Li2O, Li2Se, Li2Te, Li3N, Li3P, Li3As, Li3Sb, Li3Al2, LiB3, or a combination thereof. By including such a binary compound in the composite, the ionic conductivity of the composite may be further improved. By including such a complex in the solid electrolyte separator, the internal resistance of the positive electrode may be further reduced. As a result, the cycle characteristics of an all-solid-state secondary battery including such a positive electrode may be further improved. The ternary compound may include, for example, Li3OCl, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiNO3, Li2CO3, LiBH4, Li2SO4, Li3BO3, Li3PO4, Li4NCl, Li5NCl2, Li3BN2, or a combination thereof. The ionic conductivity of the complex may be further improved by including such ternary compounds.By including these complexes in the positive electrode, the internal resistance of the positive electrode can be further reduced. Consequently, the cycle characteristics of an all-solid-state secondary battery including such a solid electrolyte separator can be further improved.

[0076] The above complex may further include a carbon-based material. The complex is a complex of Li2S, a lithium salt, and a carbon-based material.

[0077] The carbon-based material may be any material containing carbon atoms that is used as a conductive material in the relevant technical field. The carbon-based material may be, for example, crystalline carbon, amorphous carbon, or a combination thereof. The carbon-based material may be, for example, a sintered product of a carbon precursor. The carbon-based material may be, for example, a carbon nanostructure. The carbon nanostructure may be, for example, a one-dimensional carbon nanostructure, a two-dimensional carbon nanostructure, a three-dimensional carbon nanostructure, or a combination thereof. The carbon nanostructure may be, for example, a carbon nanotube, a carbon nanofiber, a carbon nanobelt, a carbon nanorod, graphene, or a combination thereof. The carbon-based material may be, for example, a porous carbon-based material or a non-porous carbon-based material. The porous carbon-based material may include, for example, periodic and regular two-dimensional or three-dimensional pores. The porous carbon-based material may be, for example, carbon black such as Ketjen Black, acetylene black, Denka Black, thermal black, channel black, etc.; It can be graphite, activated carbon, or a combination thereof. The form of the carbon-based material is not limited to, for example, particle form, sheet form, flake form, etc., and any carbon-based material used in the relevant technical field can be used. The content of the carbon-based material included in the composite of Li2S, lithium salt, and carbon-based material can be, for example, 1 to 20 wt%, 5 to 20 wt%, or 10 to 20 wt% of the total weight of the composite. If the content of the carbon-based material increases excessively, the energy density of the dry positive electrode film and the all-solid-state secondary battery may decrease. If the content of the carbon-based material decreases excessively, the electronic conductivity of the composite of Li2S, lithium salt, and carbon-based material may decrease, which may increase the internal resistance of the dry positive electrode film. As a result, the cycle characteristics of the all-solid-state secondary battery may deteriorate.

[0078] The Mohs hardness of the lithium salt and the carbon-based material may be greater than that of Li2S. The Mohs hardness of Li2S is, for example, 0.6 or less. The Mohs hardness of the lithium salt may be 0.7 or more, 0.8 or more, 0.9 or more, 1.0 or more, 1.5 or more, or 2.0 or more. When the lithium salt has a Mohs hardness in this range, the pulverization of Li2S can be performed more easily during the milling process, and a solid solution of Li2S and the lithium salt can be formed more easily. The Mohs hardness of LiI is, for example, 2.0. The Mohs hardness of the carbon-based material may be 0.7 or more, 0.8 or more, 0.9 or more, 1.0 or more, 1.2 or more, or 1.5 or more, respectively. Since the carbon-based material has a Mohs hardness within this range, the grinding of Li2S can be performed more easily during the milling process, and a composite of Li2S, a lithium salt, and a carbon-based material can be formed more easily. The Mohs hardness of carbon nanofibers (CNF) is, for example, 1.5.

[0079] The carbon-based material may include, for example, a fibrous carbon-based material. By including the fibrous carbon-based material in the composite of Li2S, a lithium salt, and a carbon-based material, the electronic conductivity of the composite of Li2S, a lithium salt, and a carbon-based material can be further improved. By including the fibrous carbon-based material in the composite of Li2S, a lithium salt, and a carbon-based material, electronic conduction can be more easily performed from the surface to the inside of the composite of Li2S, a lithium salt, and a carbon-based material. The internal resistance of a dry cathode film including a composite of Li2S, a lithium salt, and a carbon-based material can be reduced, and the cycle characteristics of an all-solid-state secondary battery including the dry cathode film can be further improved.

[0080] The aspect ratio of the fibrous carbon-based material can be, for example, 2 or more, 3 or more, 4 or more, 5 or more, 10 or more, or 20 or more. The aspect ratio of the fibrous carbon-based material can be, for example, 2 to 30, 3 to 30, 4 to 30, 5 to 30, 10 to 30, or 20 to 30. The aspect ratio of the fibrous carbon-based material can be, for example, 2 to 30, 2 to 20, 2 to 10, 2 to 8, 2 to 5, or 2 to 4. When the fibrous carbon-based material has an aspect ratio in this range, the overall electronic conductivity of the composite of Li2S, a lithium salt, and a carbon-based material is improved, and the imbalance of local electronic conductivity within the composite of Li2S, a lithium salt, and a carbon-based material can be further alleviated.

[0081] The fibrous carbon-based material may include, for example, carbon nanostructures. The carbon nanostructures may include, for example, carbon nanofibers (CNFs), carbon nanotubes (CNTs), carbon nanobelts, carbon nanorods, or combinations thereof.

[0082] The carbon nanostructure can form a primary carbon nanostructure (e.g., primary particle or structure) composed of a single carbon nanostructure and a secondary carbon nanostructure (e.g., secondary particle or structure) composed of a plurality of primary carbon nanostructures aggregated together.

[0083] The diameter of the primary carbon nanostructure can be, for example, 1 nm to 200 nm, 1 nm to 150 nm, 1 nm to 100 nm, 1 nm to 50 nm, 1 nm to 30 nm, or 1 nm to 20 nm. The length of the primary carbon nanostructure can be, for example, 10 nm to 2 μm, 10 nm to 1.5 μm, 10 nm to 1 μm, 10 nm to 500 nm, 10 nm to 400 nm, 10 nm to 300 nm, 10 nm to 200 nm, or 10 nm to 100 nm. The diameter and length of the primary carbon nanostructure can be measured from scanning electron microscope (SEM) or transmission electron microscope (TEM) images. Alternatively, the diameter and / or length of the primary carbon nanostructure can be measured by laser diffraction.

[0084] Secondary carbon nanostructures are also structures formed by, for example, assembling primary carbon nanostructures (e.g., primary particles or structures) to form a bundle or a bundle-type structure in whole or in part. The secondary carbon nanostructures may include, for example, bundle-type carbon nanostructures, rope-type carbon nanostructures, or a combination thereof. The diameter of the secondary carbon nanostructures may be, for example, 2 nm to 200 nm, 3 nm to 150 nm, 5 nm to 100 nm, 5 nm to 50 nm, 5 nm to 30 nm, or 5 nm to 20 nm. The length of the secondary carbon nanotube structure can be, for example, 20 nm to 2 ㎛, 30 nm to 1.5 ㎛, 50 nm to 1 ㎛, 50 nm to 500 nm, 50 nm to 400 nm, 50 nm to 300 nm, 50 nm to 200 nm, or 50 nm to 100 nm or more. The diameter and length of the secondary carbon nanostructure can be measured from a scanning electron microscope (SEM) image or an optical microscope. Alternatively, the diameter and / or length of the secondary carbon nanostructure can be measured by laser diffraction. The secondary carbon nanostructure can be converted into a primary carbon nanostructure, for example, by dispersing it in a solvent or the like, and then used to prepare a composite of Li2S, a lithium salt, and a carbon-based material.

[0085] A composite of Li2S and a lithium salt or a composite of Li2S, a lithium salt, and a carbon-based material may include, for example, a solid solution of Li2S and a lithium salt. The ionic conductivity of the composite may increase by including the solid solution of Li2S and a lithium salt. For example, since the solid solution of Li2S and a lithium salt includes lithium ions arranged within Li2S crystallites, the ionic conductivity of the solid solution of Li2S and a lithium salt may be improved compared to the ionic conductivity of Li2S. Consequently, the ionic conductivity of the composite may be improved and the internal resistance of the composite may be reduced. By including such a composite in the positive electrode, the internal resistance of the positive electrode may be further reduced. Consequently, the cycle characteristics of an all-solid-state secondary battery including such a positive electrode may be further improved.

[0086] The size of Li2S crystallites obtained from the XRD spectrum of a complex of Li2S and a lithium salt or a complex of Li2S, a lithium salt, and a carbon-based material may be, for example, 20 nm or less, 15 nm or less, or 10 nm or less. The size of Li2S crystallites obtained from the XRD spectrum of the complex may be, for example, 1 to 20 nm, 1 to 15 nm, or 3 to 10 nm. As the size of Li2S crystallites decreases, the contact area between Li2S and a lithium salt may further increase. As the contact area between Li2S and a lithium salt further increases, the ionic conductivity of the complex of Li2S and a lithium salt may further increase. The internal resistance of the positive electrode may further decrease when the positive electrode includes such a complex. As a result, the cycle characteristics of an all-solid-state secondary battery including such a positive electrode may further improve.

[0087] Since Li2S has low ionic conductivity, a complex with a lithium salt is formed to overcome this drawback. A complex of Li2S and a lithium salt or a composite of Li2S and a lithium salt and a carbon-based material can provide improved ionic conductivity compared to Li2S alone. The content of Li2S in the complex may be 50 to 95 wt%, 50 to 90 wt%, 50 to 80 wt%, or 50 to 70 wt% of the total weight of the complex of Li2S and a lithium salt. By having the complex with a Li2S content in this range, a cathode with improved ionic conductivity and durability can be manufactured. The content of the lithium salt in the complex of Li2S and a lithium salt may be 5 to 50 wt%, 10 to 50 wt%, 20 to 50 wt%, or 30 to 50 wt% of the total weight of the complex of Li2S and a lithium salt.

[0088] The molar ratio of Li2S and lithium salt in the composite may be, for example, 50:50 to 95:5, 60:40 to 95:5, 60:40 to 90:10, 65:35 to 90:10, 65:35 to 85:15, or 70:30 to 85:15. The molar ratio of Li2S and lithium salt in the composite may be, for example, 50:50 to 95:5, 50:50 to 90:10, 50:50 to 85:15, 50:50 to 80:20, 50:50 to 75:25, or 50:50 to 70:30. By having Li2S and lithium salt in this range of molar ratio, the cycle characteristics of an all-solid-state secondary battery including a composite cathode active material may be further improved. If the molar ratio of Li2S is excessively high, the improvement in ionic conductivity by lithium salts may be minimal. If the molar ratio of Li2S is excessively high, the energy density of lithium batteries containing composite cathode active materials may decrease.

[0089] The Mohs hardness of the lithium salt and the carbon-based material may be greater than that of Li2S. The Mohs hardness of Li2S is, for example, 0.6 or less. The Mohs hardness of the lithium salt may be 0.7 or more, 0.8 or more, 0.9 or more, 1.0 or more, 1.5 or more, or 2.0 or more. When the lithium salt has a Mohs hardness in this range, the pulverization of Li2S can be performed more easily during the milling process, and a solid solution of Li2S and the lithium salt can be formed more easily. The Mohs hardness of LiI is, for example, 2.0. The Mohs hardness of the carbon-based material may be 0.7 or more, 0.8 or more, 0.9 or more, 1.0 or more, 1.2 or more, or 1.5 or more, respectively. Since the carbon-based material has a Mohs hardness in this range, the grinding of Li2S can be performed more easily during the milling process, and a composite of Li2S, a lithium salt, and a carbon-based material can be formed more easily. The modal hardness of carbon nanofibers (CNF) is, for example, 1.5.

[0090] In the composite of Li2S, a lithium salt, and a carbon-based material, the content of the lithium salt may be, for example, 1 to 40 wt%, 5 to 35 wt%, 10 to 35 wt%, 15 to 35 wt%, 20 to 35 wt%, or 25 to 35 wt% of the total weight of the composite of Li2S, a lithium salt, and a carbon-based material. If the content of the lithium salt is excessively increased, the energy density of the all-solid-state secondary battery may decrease. If the content of the lithium salt is excessively low, the ionic conductivity of the composite of Li2S, a lithium salt, and a carbon-based material may decrease, which may increase the internal resistance of the dry positive electrode film. As a result, the cycle characteristics of the all-solid-state secondary battery including the dry positive electrode film may deteriorate.

[0091] In the composite of Li2S, a lithium salt, and a carbon-based material, the molar ratio of Li2S and a lithium salt may be, for example, 50:50 to 95:5, 60:40 to 95:5, 60:40 to 90:10, 65:35 to 90:10, 65:35 to 85:15, or 70:30 to 85:15. In the composite of Li2S, a lithium salt, and a carbon-based material, the molar ratio of Li2S and a lithium salt may be, for example, 50:50 to 95:5, 50:50 to 90:10, 50:50 to 85:15, 50:50 to 80:20, 50:50 to 75:25, or 50:50 to 70:30. By maintaining the molar ratio of Li2S and lithium salt within this range, the cycle characteristics of an all-solid-state secondary battery including a dry cathode film can be further improved. If the molar ratio of Li2S is excessively high, the ionic conductivity enhancement effect of the lithium salt may be minimal. If the molar ratio of Li2S is excessively high, the energy density of an all-solid-state secondary battery including a composite cathode active material may be reduced.

[0092] The ionic conductivity of a complex of Li2S and a lithium salt or a complex of Li2S, a lithium salt and a carbon-based material is, for example, 1×10 at 25°C. -5 S / cm or more, 2×10 -5 S / cm or more, 4×10 -5 S / cm or more, 6×10 -5 S / cm or more, 8×10 -5 S / cm or more or 1×10 -4 It can be S / cm or more. The ionic conductivity can be measured using, for example, electrochemical impedance spectroscopy, direct current polarization method, etc. Since the complex of Li2S and lithium salt has an ionic conductivity in this range, the internal resistance of the positive electrode including the complex of Li2S and lithium salt can be further reduced. The cycle characteristics of an all-solid-state secondary battery including the positive electrode can be improved.

[0093] The Li2S-containing composite may further comprise a solid electrolyte. The solid electrolyte may further comprise a sulfide-based solid electrolyte.

[0094] The content of the complex of Li2S and a lithium salt may be, for example, 0.1 to 20 wt%, 0.5 to 20 wt%, 0.5 to 15 wt%, 0.5 to 10 wt% or 1 to 5 wt% of the total weight of the complex of Li2S and a lithium salt and the sulfide-based solid electrolyte. The content of the complex of Li2S and a lithium salt may be, for example, 0.1 to 20 wt%, 0.5 to 20 wt%, 0.5 to 15 wt%, 0.5 to 10 wt% or 1 to 5 wt% of the total weight of the positive electrode. When the positive electrode has the content of the complex of Li2S and a lithium salt in this range, the durability of the positive electrode can be further improved and the internal resistance can be further reduced. If the content of the complex of Li2S and a lithium salt is too low, the effect may be minimal. If the content of the complex of Li2S and lithium salt increases excessively, the internal resistance of the positive electrode may increase.

[0095] The cathode active material layer may include, for example, composite particles of Li2S and a lithium salt and sulfide-based solid electrolyte particles. The size of the composite particles of Li2S and a lithium salt may be smaller than, for example, the size of the sulfide-based solid electrolyte particles. The size of the composite particles of Li2S and a lithium salt may be, for example, 90% or less, 80% or less, 60% or less, 40% or less, 20% or less, or 10% or less of the size of the sulfide-based solid electrolyte particles. The composite particles of Li2S and a lithium salt may be arranged in pores between a plurality of sulfide-based solid electrolytes, for example. By arranging the composite particles of Li2S and a lithium salt in the pores between a plurality of sulfide-based solid electrolytes, pinhole formation within the cathode can be suppressed, and the internal resistance of the cathode can be reduced. As a result, the durability of the cathode can be improved.

[0096] The size of the sulfide-based solid electrolyte particles may be, for example, 1 to 10 μm, 1 to 8 μm, 1 to 6 μm, 1 to 5 μm, or 1 to 3 μm. When the sulfide-based solid electrolyte particles have a size in this range, the durability of the positive electrode can be further improved. The size of the sulfide-based solid electrolyte particles can be measured, for example, using laser diffraction, scanning electron microscopy, etc. The size of the sulfide-based solid electrolyte particles is, for example, an arithmetic mean value of particle sizes of a plurality of particles measured using software from a scanning electron microscope image. The size of the Li2S-containing composite particles, which are composite positive electrode active materials, may be, for example, 10 μm or less, 8 μm or less, 5 μm or less, 2 μm or less, 1.5 μm or less, or 1 μm or less. The size of the composite particles may be, for example, 1 to 10 μm, 2 to 10 μm, 2 to 8 μm, or 3 to 8 μm. The size of the composite particles may be, for example, 0.1 to 10 μm, 0.1 to 8 μm, 0.1 to 5 μm, 0.1 to 2 μm, 0.1 to 1.5 μm, or 0.1 to 1 μm or less. Since the composite particles have a size in this range, the volume change during charge and discharge is suppressed, and thus the deterioration of the composite cathode active material including the composite during charge and discharge can be suppressed. If the size of the composite particles increases excessively, the volume change of the composite during charge and discharge may increase, and thus the deterioration of the composite cathode active material including the composite may be accelerated. As a result, the cycle characteristics of an all-solid-state secondary battery including such a composite cathode active material may deteriorate.

[0097] The size of the Li2S particles included in the composite cathode active material, i.e., the size of the Li2S particles included in the composite, may be, for example, 2 μm or less, 1.5 μm or less, or 1 μm or less. The size of the Li2S particles may be, for example, 0.1 to 2 μm, 0.1 to 1.5 μm, or 0.1 to 1 μm or less. When the composite particles have a size in this range, they can be more easily arranged in the gaps between the plurality of sulfide-based solid electrolytes, pinhole formation within the cathode can be suppressed, and the internal resistance of the cathode can be reduced. As a result, the durability of the cathode can be improved.

[0098] The size of the Li2S-containing composite particles can be measured using, for example, laser diffraction, scanning electron microscopy, etc. The size of the Li2S-containing composite is, for example, the arithmetic mean of the particle sizes of multiple particles measured using software from scanning electron microscopy images.

[0099] The ratio of the size of the sulfide-based solid electrolyte particles to the size of the Li2S-containing composite particles may be, for example, 2:1 to 200:1, 2:1 to 100:1, or 2:1 to 50:1. When the ratio of the size of the sulfide-based solid electrolyte particles to the size of the Li2S-containing composite particles is within this range, defect formation in the positive electrode is suppressed, thereby further improving the durability of the positive electrode. If the ratio of the size of the sulfide-based solid electrolyte particles to the size of the Li2S-containing composite particles is excessively small, the porosity of the positive electrode may excessively increase, thereby reducing the durability of the positive electrode. If the ratio of the size of the sulfide-based solid electrolyte particles to the size of the Li2S-containing composite particles is excessively large, uniform dispersion of the Li2-containing composite particles within the positive electrode may be difficult.

[0100] By using a positive electrode containing the above-described composite, a lithium metal negative electrode can be eliminated, enabling the use of an all-solid-state secondary battery without an anode, thereby providing an all-solid-state secondary battery with improved energy density. Furthermore, by including such a composite positive electrode active material in the positive electrode, the cycle characteristics of the all-solid-state secondary battery containing the composite positive electrode active material can be improved. For example, the rate characteristics of the secondary battery containing such a composite positive electrode active material can be improved.

[0101] In the positive electrode active material layer, the solid electrolyte may be, for example, a sulfide-based solid electrolyte. The solid electrolyte included in the positive electrode may be the same as or different from the solid electrolyte included in the electrolyte layer. The solid electrolyte included in the positive electrode active material layer may have a smaller average D50 particle size than the solid electrolyte included in the electrolyte layer. For example, the average D50 particle size of the solid electrolyte included in the positive electrode active material layer may be 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 average D50 particle size of the solid electrolyte included in the electrolyte layer. The average D50 particle size is, for example, the median particle diameter (D50). The median particle diameter (D50) is the size of particles corresponding to 50% of the cumulative volume, calculated from the side of particles having a smaller particle size in a size distribution of particles measured, for example, by laser diffraction.

[0102] The solid electrolyte may be included in an amount of 10 to 60 parts by weight, 10 to 50 parts by weight, 20 to 50 parts by weight, or 30 to 50 parts by weight, per 100 parts by weight of the cathode active material layer.

[0103] [All-solid-state secondary battery]

[0104] An all-solid-state secondary battery according to an embodiment includes a positive electrode; a negative electrode; and a solid electrolyte layer disposed between the positive electrode and the negative electrode, wherein the positive electrode includes the positive electrode described above.

[0105] Referring to FIGS. 1 to 5, an all-solid-state secondary battery (1) includes a positive electrode (10); a negative electrode (20); and a solid electrolyte layer (30) disposed between the positive electrode (10) and the negative electrode (20). The positive electrode (10) includes a positive electrode according to one embodiment.

[0106] [anode]

[0107] [Cathode: Cathode active material]

[0108] Referring to FIGS. 1 to 5, the positive electrode (10) includes a positive electrode current collector (11); an adhesive binder layer (13) disposed on one or both sides of the positive electrode current collector (11), and a positive electrode active material layer (12) positioned thereon. The positive electrode active material layer (12) includes a Li2S-containing composite as a positive electrode active material.

[0109] The cathode active material layer (12) may additionally include other cathode active materials in addition to the composite cathode active material described above.

[0110] Other cathode active materials may include, for example, a Li2S-containing composite. The Li2S-containing composite includes, for example, a composite of Li2S and carbon, a composite of Li2S and carbon and a solid electrolyte, a composite of Li2S and a solid electrolyte, a composite of Li2S and a lithium salt and carbon, a composite of Li2S and a metal carbide, a composite of Li2S and carbon and a metal carbide, a composite of Li2S and a metal nitride, a composite of Li2S and carbon and a metal nitride, or a combination thereof.

[0111] The Li2S and carbon complex comprises carbon. The carbon may be any material containing carbon atoms that is used as a conductive material in the art. The carbon may be, for example, crystalline carbon, amorphous carbon, or a combination thereof. The carbon may be, for example, a sintered product of a carbon precursor. The carbon may be, for example, a carbon nanostructure. The carbon nanostructure may be, for example, a one-dimensional carbon nanostructure, a two-dimensional carbon nanostructure, a three-dimensional carbon nanostructure, or a combination thereof. The carbon nanostructure may be, for example, a carbon nanotube, a carbon nanofiber, a carbon nanobelt, a carbon nanorod, graphene, graphene oxide (GO), reduced graphene oxide (rGO), graphene balls (GB), or a combination thereof. The carbon may be, for example, porous carbon or non-porous carbon. The porous carbon may include, for example, periodic and regular two-dimensional or three-dimensional pores. The porous carbon may be, for example, carbon black such as Ketjen black, acetylene black, Denka black, thermal black, channel black, etc.; graphite, activated carbon, or a combination thereof. The form of the carbon may be, for example, particle form, sheet form, flake form, etc., but is not limited thereto, and any method used as carbon in the art may be used. The method for preparing the composite of Li2S and carbon may be, for example, a dry method, a wet method, or a combination thereof, but is not limited thereto, and the method for preparing the composite of Li2S and carbon in the art may be, for example, milling, heat treatment, deposition, etc., but is not necessarily limited thereto, and any method used in the art may be used.

[0112] The composite of Li2S, carbon, and a solid electrolyte comprises carbon and a solid electrolyte. Carbon refers to the composite of Li2S and carbon described above. The solid electrolyte may be any ion-conducting material used in the art, for example, an amorphous solid electrolyte. The solid electrolyte may be, for example, an inorganic solid electrolyte. The solid electrolyte may be, for example, a crystalline solid electrolyte, an amorphous solid electrolyte, or a combination thereof. The solid electrolyte may be, for example, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or a combination thereof. The sulfide-based solid electrolyte may comprise, for example, Li, S, and P, and may optionally further comprise halogens. The sulfide-based solid electrolyte may be selected from among the sulfide-based solid electrolytes used in the solid electrolyte layer. The sulfide-based solid electrolyte may have a density of, for example, 1×10 -5 It can have an ionic conductivity of S / cm or more. Sulfide-based solid electrolytes include, for example, Li3PO4-Li2SO4, Li2S-P2S5, Li2S-P2S5-LiX, where X is a halogen, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n , m, n are 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, may include one or more selected from 0≤x≤2. The oxide-based solid electrolyte includes, for example, Li, O, and a transition metal element, and may optionally further include other elements. The oxide-based solid electrolyte may include, for example, 1×10 at room temperature. -5 It may be a solid electrolyte having an ionic conductivity of 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 be, for example, a mixture of a sulfide-based solid electrolyte and a lithium salt. For example, it may be a mixture of Li3PO4-Li2SO4 and a binary lithium salt, or a mixture of Li3PO4-Li2SO4 and a ternary lithium salt.

[0113] The composite of Li2S and a solid electrolyte includes Li2S and a solid electrolyte. The solid electrolyte refers to the composite of Li2S, carbon, and a solid electrolyte described above.

[0114] A complex of Li2S, a lithium salt, and carbon comprises Li2S, a lithium salt compound, and carbon. The lithium salt compound does not contain, for example, a sulfur (S) atom. The lithium salt compound can be, for example, a binary compound composed of lithium and one element selected from Groups 13 to 17 of the Periodic Table of Elements. The binary compound can include, for example, one or more selected from LiF, LiCl, LiBr, LiI, LiH, Li2S, Li2O, Li2Se, Li2Te, Li3N, Li3P, Li3As, Li3Sb, Li3Al2, and LiB3. The lithium salt compound can be, for example, a ternary compound composed of lithium and two elements selected from Groups 13 to 17 of the Periodic Table of Elements. The ternary compound includes, 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 is particularly one or more lithium halide compounds selected from LiF, LiCl, LiBr, and LiI. Carbon refers to the complex of Li2S and carbon described above.

[0115] The composite of Li2S and metal carbide includes 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 a terminal group, T is O, OH and / or F, n=1, 2, or 3, and x is the number of terminal groups) is expressed as 2D metal carbides, for example, Ti2CT x , (Ti 0.5 , Nb 0.5 )2CT x , Nb2CT x , V2CTx , 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.

[0116] A complex of Li2S, carbon, and metal carbide includes Li2S, carbon, and metal carbide. Carbon refers to the complex of Li2S and carbon described above. Metal carbide refers to the complex of Li2S and metal carbide described above.

[0117] The complex of Li2S and metal nitride includes Li2S and 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, and x is the number of terminal groups) is expressed as The surface of the two-dimensional metal nitride is terminated with O, OH and / or F.

[0118] A complex of Li2S, carbon, and a metal nitride includes Li2S, carbon, and a metal nitride. Carbon refers to the complex of Li2S and carbon described above. Metal nitride refers to the complex of Li2S and a metal nitride described above.

[0119] The size of the cathode active material can be, 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 can be, 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 can be, for example, 0.1 to 50 μm, 0.5 to 30 μm, 0.5 to 20 μm, or 1 to 10 μm.

[0120] The cathode active material layer (12) may additionally include, for example, a sulfide-based compound that is distinct from the cathode active material described above. The sulfide-based compound may be, for example, a compound containing a metal element other than Li and the element sulfur. The sulfide-based compound may be, for example, a compound containing a metal element belonging to Groups 1 to 14 of the Periodic Table of Elements having an atomic weight of 10 or more and the element sulfur. The sulfide-based compound may be, for example, FeS2, VS2, NaS, MnS, FeS, NiS, CuS, or a combination thereof. By the cathode active material layer additionally including a sulfide-based compound, the cycle characteristics of the all-solid-state secondary battery may be further improved. The content of the sulfide-based compound included in the cathode active material layer (12) may be 10 wt% or less, 5 wt% or less, 3 wt% or less, or 1 wt% or less of the total weight of the cathode active material layer (12).

[0121] The shape of the positive electrode active material is, for example, a particle shape such as a sphere, an ellipse, or a sphere. The particle size of the positive electrode active material is not limited and is within a range applicable to positive electrode active materials of a conventional all-solid-state secondary battery. The content of the positive electrode active material of the positive electrode layer (10) is also not particularly limited and is within a range applicable to positive electrode layers of a conventional all-solid-state secondary battery. The content of the positive electrode active material included in the positive electrode active material layer (12) may be, for example, 30 wt% to 99 wt%, 30 wt% to 90 wt%, 30 wt% to 80 wt%, 30 wt% to 70 wt%, or 30 wt% to 50 wt% based on 100 wt% of the total weight of the positive electrode active material layer (12).

[0122] [Polar: Challenger]

[0123] The cathode 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 included in the cathode active material layer (12) may be, for example, 1 wt% to 30 wt%, 1 wt% to 20 wt%, or 1 wt% to 10 wt%, based on 100 wt% of the total weight of the cathode active material layer (12).

[0124] [Positive: Binder]

[0125] The positive electrode active material layer (12) may further include a binder. The binder may be, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc., but is not limited thereto, and any binder used in the relevant technical field may be used. The binder content included in the positive electrode active material layer (12) may be, for example, 1 wt% to 10 wt% of the total weight of the positive electrode active material layer (12). The binder may be omitted.

[0126] [Positive: Other additives]

[0127] The cathode active material layer (12) may further include additives such as fillers, coating agents, dispersants, and ion conductive aids in addition to the cathode active material, solid electrolyte, binder, and conductive agent described above.

[0128] As fillers, coating agents, dispersants, ion conductivity aids, etc. that the positive electrode active material layer (12) may include, known materials generally used in electrodes of all-solid-state secondary batteries may be used.

[0129] [Anode: Anode current collector]

[0130] The positive electrode collector (11) uses a plate or foil made of, for example, 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 collector (11) may be omitted. The thickness of the positive electrode 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.

[0131] The cathode 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 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 base film may be, for example, an insulator. Since the base film includes an insulating thermoplastic polymer, when a short circuit occurs, the base film softens or liquefies, thereby blocking battery operation and suppressing a rapid 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 can act as an electrochemical fuse and be cut off in case of overcurrent to prevent a short circuit. The limit current and the maximum current can be controlled by adjusting the thickness of the metal layer. The metal layer can be plated or deposited on the base film. As the thickness of the metal layer decreases, the limit current and / or the maximum current of the positive electrode current collector (11) decreases, thereby improving the stability of the lithium battery in case of a short circuit. A lead tab can be added on the metal layer for connection to the outside. 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 the metal layer melt, so that the metal layer can be electrically connected to the lead tab. In order to strengthen the welding of the metal layer and the lead tab, a metal chip can be added between the metal layer and the lead tab.The metal piece may be a thin piece of the same material as the metal of the metal layer. The metal piece may be, for example, a metal foil, a metal mesh, etc. The metal piece may be, for example, aluminum foil, copper foil, SUS foil, etc. After the metal piece is placed on the metal layer, the lead tab may be welded to the metal piece / metal layer laminate or the metal piece / metal layer / base film laminate. During welding, the base film, the metal layer, and / or the metal piece may melt, so that the metal layer or the metal layer / metal piece laminate may be electrically connected to the lead tab. A metal chip and / or a lead tab may be added to a portion of the metal layer. The base film may have a thickness of, for example, 1 to 50 μm, 1.5 to 50 μm, 1.5 to 40 μm, or 1 to 30 μm. When the base film has a thickness in this range, the weight of the electrode assembly can be more effectively reduced. The melting point of the base film may be, for example, 100 to 300°C, 100 to 250°C or less, or 100 to 200°C. Since the base film has a melting point within this range, the base film can be melted and easily bonded to the lead tab during the welding process of the lead tab. To improve the adhesion between the base film and the metal layer, a surface treatment such as 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. Since the metal layer has a thickness within this range, conductivity can be maintained while ensuring the stability of the electrode assembly. The thickness of the metal piece may be, for example, 2 to 10 μm, 2 to 7 μm, or 4 to 6 μm. Since the metal piece has a thickness within this range, the connection between the metal layer and the lead tab can be performed more easily. By having this structure, the positive electrode collector (11) can reduce the weight of the positive electrode and consequently improve the energy density of the positive electrode and lithium battery.

[0132] [Anode: Inert member]

[0133] Referring to FIGS. 4 and 5, the positive electrode (10) includes a positive electrode current collector (11) and a positive electrode active material layer (12) disposed on one side of the positive electrode current collector. An inactive member (40) is disposed on one side of the positive electrode (10). Referring to FIG. 4, the inactive member (40) is disposed on one side of the positive electrode active material layer (12) and the positive electrode current collector (11). Referring to FIG. 5, the inactive member (40) is disposed on one side of the positive electrode active material layer (12) and between the solid electrolyte layer (30) and the positive electrode current collector (11) facing the solid electrolyte layer (30). The inactive member (40) is not disposed on one side of the positive electrode current collector (11).

[0134] By including an inert member (40), cracking of the electrolyte layer (30) is prevented during the manufacture and / or charging / discharging of the all-solid-state secondary battery (1), and as a result, the cycle characteristics of the all-solid-state secondary battery (2) are improved. In an all-solid-state secondary battery (1) that does not include an inert member (40), when the manufacture and / or charging / discharging of the all-solid-state secondary battery (1) is performed, uneven pressure is applied to the electrolyte layer (30) in contact with the positive electrode (10), which increases the possibility of cracking in the electrolyte layer (30), and thus, a short circuit may occur due to the growth of lithium metal through the crack.

[0135] In the all-solid-state secondary battery (1), the thickness of the inert member (40) is greater than or equal to the thickness of the positive electrode active material layer (12). Alternatively, in the all-solid-state secondary battery (1), the thickness of the inert member (40) is substantially equal to the thickness of the positive electrode (10). Since the thickness of the inert member (40) is equal to the thickness of the positive electrode (10), a uniform pressure is applied between the positive electrode (10) and the electrolyte layer (30), and the positive electrode (10) and the electrolyte layer (30) are sufficiently adhered to each other, so that the interfacial resistance between the positive electrode (10) and the electrolyte layer (30) can be reduced. In addition, since the electrolyte layer (30) is sufficiently sintered during the pressurized manufacturing process of the all-solid-state secondary battery (1), the internal resistance of the electrolyte layer (30) and the all-solid-state secondary battery (1) including the same is reduced.

[0136] The inert member (40) surrounds the side surface of the positive electrode (10) and is in contact with the electrolyte layer (30). By the inert member (40) surrounding the side surface of the positive electrode (10) and being in contact with the electrolyte layer (30), cracks in the electrolyte layer (30) that occur due to a pressure difference during the pressing process in the electrolyte layer (30) that does not come into contact with the positive electrode (20) can be effectively suppressed. The inert member (40) surrounds the side surface of the positive electrode (10) and is separated from the negative electrode (20), more specifically, the first negative electrode active material layer (22). The inert member (40) surrounds the side surface of the positive electrode (10), is in contact with the electrolyte layer (30), and is separated from the negative electrode (20). Therefore, the possibility of a short circuit occurring due to physical contact between the positive electrode (10) and the first negative electrode active material layer (22) or a short circuit occurring due to overcharging of lithium, etc., is suppressed. For example, by placing an inert member (40) on one side of the positive electrode active material layer (12) and simultaneously on one side of the positive electrode current collector (11), the possibility of a short circuit occurring due to contact between the positive electrode current collector (11) and the negative electrode (20) is more effectively suppressed.

[0137] Referring to FIGS. 4 and 5, the inert member (40) extends from one side of the positive electrode (30) to the end of the electrolyte layer (30). By extending the inert member (40) to the end of the electrolyte layer (30), cracks occurring at the end of the electrolyte layer (30) can be suppressed. The end of the electrolyte layer (30) is the outermost part that is in contact with the side of the electrolyte layer (30). The inert member (40) extends to the outermost part that is in contact with the side of the electrolyte layer (30). The inert member (40) is separated from the negative electrode (20), more specifically, from the first negative electrode active material layer (22). The inert member (40) extends to the end of the electrolyte layer (30), but does not contact the negative electrode (20). The inert member (40) fills a space extending from, for example, one side of the anode (30) to the end of the electrolyte layer (30).

[0138] Referring to FIGS. 4 and 5, the width of the inert member (40) extending from one side of the positive electrode (10) to the end of the electrolyte layer (30) is, for example, 1 to 30%, 1 to 25%, 1 to 20%, 1 to 15%, 1 to 10%, or 1 to 5% of the width between one side of the positive electrode (10) and the other side opposite to the one side. If the width of the inert member (40) is excessively large, the energy density of the all-solid-state secondary battery (1) is reduced. If the width of the inert member (40) is excessively small, the effect of arranging the inert member (40) is minimal.

[0139] The area of ​​the anode (10) (e.g., the surface area of ​​the surface in contact with the electrolyte layer (30)) is smaller than the area of ​​the electrolyte layer (30) in contact with the anode (10) (e.g., the surface area of ​​the surface in contact with the anode (10)). An inert member (40) is arranged to surround the side of the anode (10) to compensate for the area difference between the anode (10) and the electrolyte layer (30). By compensating for the difference between the area of ​​the anode (10) and the area of ​​the electrolyte layer (30), cracks in the electrolyte layer (30) caused by the pressure difference during the pressing process are effectively suppressed. For example, the sum of the area of ​​the anode (10) and the area of ​​the inert member (40) is equal to the area of ​​the electrolyte layer (30). The electrolyte layer (30) may be, for example, a solid electrolyte layer.

[0140] The area of ​​the anode (10) is, for example, less than 100%, 99% or less, 98% or less, 97% or less, 96% or less, or 95% or less of the area of ​​the electrolyte layer (30). The area of ​​the anode (10) is, for example, 50% to less than 100%, 50% to 99%, 55% to 98%, 60% to 97%, 70% to 96%, 80% to 95%, or 85% to 95% of the area of ​​the electrolyte layer (30).

[0141] If the area of ​​the positive electrode (10) is equal to or larger than the area of ​​the electrolyte layer (30), the possibility of a short circuit occurring due to physical contact between the positive electrode (10) and the first negative electrode active material layer (22) or overcharging of lithium increases. The area of ​​the positive electrode (10) is, for example, equal to the area of ​​the positive electrode active material layer (12). The area of ​​the positive electrode (10) is, for example, equal to the area (11) of the positive electrode current collector.

[0142] The area of ​​the inert member (40) is, for example, 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less of the area of ​​the anode (10). The area of ​​the inert member (40) is, for example, 1% to 50%, 5% to 40%, 5% to 30%, 5% to 20%, or 5% to 15% of the area of ​​the anode (10).

[0143] The area (S1) of the positive electrode (10) is smaller than the area (S4) of the negative electrode current collector (21). The area (S1) of the positive electrode (10) is, for example, less than 100%, 99% or less, 98% or less, 97% or less, 96% or less, or 95% or less of the area (S4) of the negative electrode current collector (21). The area (S1) of the positive electrode (10) is, for example, 50% to less than 100%, 50% to 99%, 55% to 98%, 60% to 97%, 70% to 96%, 80% to 95%, or 85% to 95% of the area (S4) of the negative electrode current collector (21). The area (S4) of the negative electrode current collector (21) is, for example, the same as the area of ​​the negative electrode (20). The area (S4) of the negative electrode current collector (21) is, for example, the same as the area of ​​the first negative electrode active material layer (22).

[0144] As used herein, “same” area, length, width, thickness, and / or shape includes all instances of having “substantially the same” area, length, width, thickness, and / or shape, except where the area, length, width, thickness, and / or shape are intentionally different from each other. “Same” area, length, width, and / or thickness includes a range where the unintentional difference in the area, length, width, and / or thickness of the compared objects is, for example, less than 3%, less than 2%, less than 1%, less than 0.5%, or less than 0.1%.

[0145] The thickness of the inert member (40) is, for example, greater than the thickness of the first negative electrode active material layer (22). 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, or 10% or less of the thickness of the inert member (40). 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%, or 1% to 10% of the thickness of the inert member (40).

[0146] The inert member (40) may be a gasket. By using a gasket as the inert member (40), cracks in the electrolyte layer (30) caused by a pressure difference during the pressing process can be effectively suppressed.

[0147] The inert member (40) has, for example, a single-layer structure. Alternatively, although not shown in the drawing, the inert member (40) may have a multi-layer structure. In the inert member (40) having a multi-layer structure, each layer may have a different composition. The inert 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 inert 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, for example, a separation between the positive electrode (10) and the electrolyte layer (30) due to a change in the volume of the positive electrode (10) that occurs during the charge / discharge process of the all-solid-state secondary battery (10), and improves the film strength of the inert member (40) by providing a bonding force between the support layer and other layers. The support layer provides support to the inert member (40), prevents unevenness of pressure applied to the electrolyte layer (30) during the pressurization process or the charge / discharge process, and prevents deformation of the all-solid-state secondary battery (1) being manufactured.

[0148] The inert member (40) is, for example, a flame-retardant inert member. The flame-retardant inert member prevents thermal runaway and ignition of the all-solid-state secondary battery (1) by providing flame retardancy. Consequently, the safety of the all-solid-state secondary battery (1) is further improved. The flame-retardant inert member prevents deterioration of the all-solid-state secondary battery (1) by absorbing residual moisture within the all-solid-state secondary battery (1), thereby improving the lifespan characteristics of the all-solid-state secondary battery (1).

[0149] The flame-retardant inert member includes, for example, a methacrylic and a filler. The methacrylic includes, for example, a substrate and a reinforcing material. The methacrylic includes, for example, a fibrous substrate and a fibrous reinforcing material. Since the methacrylic includes the substrate, the methacrylic can have elasticity. Therefore, the methacrylic can effectively accommodate volume changes during charge and discharge of the all-solid-state secondary battery (1) and can be arranged at various positions. The substrate included in the methacrylic includes, for example, a first fibrous material. Since the substrate includes the first fibrous material, the volume changes of the positive electrode (30) occurring during charge and discharge of the all-solid-state secondary battery (1) can be effectively accommodated and deformation of the inert member (40) caused by the volume changes of the positive electrode (30) can be effectively suppressed. The first fibrous material is, for example, a material having an aspect ratio of 5 or more, 20 or more, or 50 or more. The first fibrous material is, for example, a material having an aspect ratio of 5 to 1000, 20 to 1000, or 50 to 1000. The first fibrous material is, for example, an insulating material. Since the first fibrous material is an insulating material, a short circuit between the positive electrode (30) and the negative electrode (20) caused by lithium dendrites, etc., generated during the charge and discharge process of the all-solid-state secondary battery (1) can be effectively prevented. The first fibrous material includes, for example, at least one selected from pulp fibers, insulating polymer fibers, and ion-conductive polymer fibers. The strength of the methacrylic is improved by the inclusion of a reinforcing material in the methacrylic. Therefore, the methacrylic can prevent excessive volume change during charge and discharge of the all-solid-state secondary battery (1) and deformation of the all-solid-state secondary battery. The reinforcing material included in the methacrylic includes, for example, a second fibrous material. Since the reinforcing material includes the second fibrous material, the strength of the methacrylic can be increased more uniformly. The second fibrous material is, for example, a material having an aspect ratio of 3 or more, 5 or more, or 10 or more.The first fibrous material is, for example, a material having 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. Since the second fibrous material is a flame-retardant material, ignition due to thermal runaway occurring during the charge / discharge process of the all-solid-state secondary battery (1) or due to external impact can be effectively suppressed. The second fibrous material is, for example, glass fiber, metal oxide fiber, ceramic fiber, etc.

[0150] The flame-retardant inert member includes a filler in addition to the metatrix. The filler may be disposed within the metatrix, on the surface of the metatrix, or on both the interior and the surface. The filler is, for example, an inorganic material. The filler included in the flame-retardant inert member is, for example, a moisture getter. The filler removes moisture remaining in the all-solid-state secondary battery (1) by adsorbing moisture, for example, at a temperature below 100°C, thereby preventing deterioration of the all-solid-state secondary battery (1). In addition, when 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 of the all-solid-state secondary battery (1) or an external impact, the filler releases the adsorbed moisture, thereby effectively suppressing ignition of the all-solid-state secondary battery (1). That is, the filler is, for example, a flame retardant. The filler is, 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 content of the filler contained in the flame-retardant inert member is, for example, 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, based on 100 parts by weight of the flame-retardant inert member (4).

[0151] The flame-retardant inert member may further comprise, for example, a binder. The binder may comprise, for example, a curable polymer or a non-curable polymer. A curable polymer is a polymer that cures by heat and / or pressure. A curable polymer is, for example, a solid at room temperature. The flame-retardant inert member (40) comprises, for example, a heat-pressure curable film and / or a cured product thereof. The heat-pressure curable polymer is, for example, TSA-66 from Toray.

[0152] The flame-retardant inert member may additionally include other materials in addition to the above-described substrate, reinforcing material, filler, and binder. The flame-retardant inert member may further include one or more selected from among paper, an insulating polymer, an ion-conducting polymer, an insulating inorganic material, an oxide-based solid electrolyte, and a sulfide-based solid electrolyte. The insulating polymer may be, for example, an olefin-based polymer such as polypropylene (PP) or polyethylene (PE).

[0153] The density of the substrate or the density of the reinforcing material included in the flame-retardant inert member may be, 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 included in the positive electrode active material layer (12).

[0154] The inert member (40) is a member that does not contain an electrochemically active material, for example, an electrode active material. The electrode active material is a material that absorbs / releases lithium. The inert member (40) is a member made of a material other than the electrode active material and used in the relevant technical field.

[0155] [cathode]

[0156] [Cathode: Cathode active material]

[0157] Referring to FIGS. 1 to 5, the negative electrode (20) includes a negative electrode current collector (21) and a first negative electrode active material layer (22) disposed on one surface of the negative electrode current collector (21).

[0158] The first negative electrode active material layer (22) is, for example, a metal layer, and the metal layer may include lithium or a lithium alloy.

[0159] Alternatively, the first negative electrode active material layer (22) may include, for example, a negative electrode active material and a binder.

[0160] The negative electrode active material included in the first negative electrode active material layer (22) is, for example, a negative electrode material that can form an alloy or compound with lithium.

[0161] The negative electrode active material included in the first negative electrode active material layer (22) has, for example, a particle form. The average particle diameter of the negative electrode active material having a particle form is, for example, 4 ㎛ or less, 3 ㎛ or less, 2 ㎛ or less, 1 ㎛ or less, 500 nm or less, 300 nm or less, or 100 nm or less. The average particle diameter of the negative electrode active material having a particle form is, for example, 10 nm to 4 ㎛, 10 nm to 3 ㎛, 10 nm to 2 ㎛, 10 nm to 1 ㎛, 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 diameter in this range, reversible absorption and / or desorption of lithium can be facilitated during charge and discharge. The average particle size of the negative electrode active material is, for example, the median diameter (D50) measured using a laser particle size distribution meter.

[0162] The negative electrode active material included in the first negative electrode active material layer (22) includes, for example, at least one selected from among a carbon-based negative electrode active material and a metal or semi-metal negative electrode active material.

[0163] Carbon-based negative electrode materials include, for example, amorphous carbon, crystalline carbon, porous carbon, or a combination thereof.

[0164] The carbon-based negative electrode material is, in particular, amorphous carbon. Amorphous carbon includes, but is not limited to, carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), and graphene, and any material classified as amorphous carbon in the relevant technical field is acceptable. Amorphous carbon is carbon that has no crystallinity or very low crystallinity, and is distinguished from crystalline carbon or graphite-based carbon.

[0165] The carbon-based negative electrode active material may be, for example, porous carbon. The porous carbon has a pore volume of, 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 porous carbon has an average pore diameter of, for example, 1 nm to 50 nm, 1 nm to 30 nm, or 1 nm to 10 nm. The porous carbon has a BET surface area of, for example, 100 m 2 / g to 3000 m 2 / g is.

[0166] Brunauer-Emmett-Teller (BET) surface area analysis is a multi-point measurement of the specific surface area (m2 / g) of an analyte through gas adsorption analysis in which an inert gas such as nitrogen is continuously flowed over a solid sample, or the solid sample is suspended in a defined volume of gas.

[0167] The metal or metalloid negative electrode active material includes, 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), and any metal or metalloid negative electrode active material that forms an alloy or compound with lithium in the relevant technical field may be used. For example, nickel (Ni) does not form an alloy with lithium and therefore is not a metal negative electrode active material.

[0168] The first negative electrode active material layer (22) includes a type of negative electrode active material among these negative electrode active materials, or includes a mixture of a plurality of different negative electrode active materials. For example, the first negative electrode active material layer (22) includes only amorphous carbon, or includes at least one 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). Alternatively, the first negative electrode active material layer (22) includes a mixture of amorphous carbon and at least one 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, etc., is a weight ratio, for example, 99:1 to 1:99, 10:1 to 1:2, 5:1 to 1:1, or 4:1 to 2:1, but is not necessarily limited to this range and is selected according to the required characteristics of the all-solid-state secondary battery (1). When the negative electrode active material has this composition, the cycle characteristics of the all-solid-state secondary battery (1) are further improved.

[0169] The negative electrode active material included 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. The metal or metalloid includes, for example, gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). Alternatively, 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 second particles have a content in this range, the cycle characteristics of, for example, an all-solid-state secondary battery (1) are further improved.

[0170] Alternatively, the first negative electrode active material layer (22) includes a composite negative electrode active material. The composite negative electrode active material may include, for example, a carbon-based support and a metal-based negative electrode active material supported on the carbon-based support. Since the composite negative electrode active material has such a structure, the metal-based negative electrode active material can be prevented from being localized within the first negative electrode active material layer and a uniform distribution can be achieved. As a result, the cycle characteristics of the all-solid-state secondary battery (1) including the first negative electrode active material layer (22) are further improved.

[0171] The metal-based negative electrode active material supported on the carbon-based support includes, for example, a metal, a metal oxide, a composite of a metal and a metal oxide, or a combination thereof. The metal includes, for example, gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), tellurium (Te), and zinc (Zn). The metal oxide includes, 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, tellurium (Te) oxide, and zinc (Zn) oxide. The metal oxide includes, 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), Te x O y (0 <x≤1, 0<y≤3), Zn x O y (0 <x≤1, 0<y≤1) 또는 이들의 조합을 포함할 수 있다. 금속과 금속산화물의 복합체는 예를 들어 Au와 Au x O y (0 <x≤2, 0<y≤3)의 복합체, Pt와 Pt x O y (0 <x≤1, 0<y≤2)의 복합체, Pd와 Pd x O y (0 <x≤1, 0<y≤1)의 복합체, Si와 Six O y (0 <x≤1, 0<y≤2)의 복합체, Ag 와 Ag x O y (0 <x≤1, 0<y≤2)의 복합체, Al과 Al x O y (0 <x≤2, 0<y≤3)의 복합체, Bi와 Bi x O y (0 <x≤2, 0<y≤3)의 복합체, Sn과 Sn x O y (0 <x≤1, 0<y≤2)의 복합체, Te과 Te x O y (0 <x≤1, 0<y≤3), Zn과 Zn x O y (0 <x≤1, 0<y≤1)의 복합체, 또는 이들의 조합을 포함할 수 있다.

[0172] The carbonaceous support is, for example, amorphous carbon. Amorphous carbon includes, but is not limited to, carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), graphene, activated carbon, carbon nanofibers (CNF), carbon nanotubes (CNT), etc., and any material classified as amorphous carbon in the relevant technical field is possible. Amorphous carbon is carbon that has no crystallinity or very low crystallinity, and is distinguished from crystalline carbon or graphite carbon. Carbonaceous materials are, for example, carbonaceous negative electrode active materials.

[0173] The composite negative electrode active material may have, for example, a particle form. The particle size of the composite negative electrode active material having a particle form is, for example, 10 nm to 4 ㎛, 10 nm to 1 ㎛, 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 in this range, reversible absorption and / or desorption of lithium may be facilitated during charge and discharge. The metal-based negative electrode active material supported on the support may have, for example, a particle form. 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 have, for example, a particle form. The particle size of the carbon-based support may be, for example, 10 nm to 2 ㎛, 10 nm to 1 ㎛, 10 nm to 500 nm, 10 nm to 200 nm, or 10 nm to 100 nm. By having a particle size in this range, the carbon-based support can be more uniformly arranged within the first negative electrode active material layer. The carbon-based support may be, for example, nanoparticles having a particle size of 500 nm or less. The particle sizes of the composite negative electrode active material, the particle sizes of the metal-based negative electrode active material, and the particle sizes of 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 distribution analyzer. Alternatively, the average particle size may be determined automatically using software, for example, from an electron microscope image, or manually by a manual method.

[0174] [Cathode: Binder]

[0175] The binder included in the first negative electrode active material layer (22) is, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, etc., but is not necessarily limited thereto and any binder used in the relevant technical field may be used. The binder may be composed of a single binder or a plurality of different binders.

[0176] Since the first negative electrode active material layer (22) includes a binder, the first negative electrode active material layer (22) is stabilized on the negative electrode current collector (21). In addition, cracking of the first negative electrode active material layer (22) is suppressed despite changes in the volume and / or relative position of the first negative electrode active material layer (22) during the charge and discharge process. 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). As the first negative electrode active material layer (22) is separated from the negative electrode current collector (21), the possibility of a short circuit occurring increases as the negative electrode current collector (21) comes into contact with the electrolyte layer (30) at the exposed portion of the negative electrode current collector (21). The first negative electrode active material layer (22) is manufactured by, for example, applying a slurry in which the material constituting the first negative electrode active material layer (22) is dispersed onto the negative electrode current collector (21) and drying the slurry. By including a binder in the first negative electrode active material layer (22), stable dispersion of the negative electrode active material in the slurry is possible. For example, when applying the slurry onto the negative electrode current collector (21) by screen printing, it is possible to suppress clogging of the screen (for example, clogging by aggregates of the negative electrode active material).

[0177] [Cathode: Other additives]

[0178] The first negative electrode active material layer (22) may further include additives used in the all-solid-state secondary battery (1), such as fillers, coating agents, dispersants, and ion conductive aids.

[0179] [Cathode: Solid electrolyte]

[0180] The first negative electrode active material layer (22) may further include a solid electrolyte. The solid electrolyte may be, for example, a material selected from among the solid electrolytes included in the electrolyte layer (30). The solid electrolyte included in the first negative electrode active material layer (22) may act as a reaction site where lithium metal formation begins within the first negative electrode active material layer (22), a space where the formed lithium metal is stored, or a path for transferring lithium ions. The solid electrolyte may be omitted.

[0181] In the first negative electrode active material layer (22), the content of the solid electrolyte may be high, for example, in an area adjacent to the electrolyte layer (30), and low, for example, in an area 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 in which the concentration decreases, for example, from an area adjacent to the electrolyte layer (30) to an area adjacent to the negative electrode current collector (21).

[0182] [Cathode: First negative electrode active material layer]

[0183] The ratio (B / A) of the initial charge capacity (B) of the first negative electrode active material layer (22) and the initial charge capacity (A) of the positive electrode active material layer is 0.005 to 0.45. The initial charge capacity of the positive electrode active material layer (12) is the first open circuit voltage (1 st Li / Li from open circuit voltage) + The initial charge capacity of the first negative electrode active material layer (22) is determined at the maximum charging voltage. The initial charge capacity of the first negative electrode active material layer (22) is determined at the second open circuit voltage (2 nd Li / Li from open circuit voltage) + It is determined at 0.01 V.

[0184] The maximum charge voltage is determined by the type of cathode active material. The maximum charge voltage can 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 charge voltage of Li2S or Li2S-containing composite is Li / Li + can be 2.5 V for Li2S or Li2S containing composites. For example, the maximum charging voltage of Li / Li + It can be 3.0 V for. The ratio (B / A) of the initial charge capacity (B) of the first negative electrode active material layer (22) and 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. The initial charge capacity (mAh) of the positive electrode active material layer (12) is obtained by multiplying the charge capacity density (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 several types of positive electrode active materials are used, the charge capacity density × 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 also calculated in the same way. 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 several types of negative electrode active materials are used, the charge capacity density Х 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 density of each of the positive electrode active material and the negative electrode active material can be measured using a solid 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 obtained by multiplying the charge capacity density (mAh / g) of the negative electrode active material by the mass value of the negative electrode active material in the first negative electrode active material layer (22). 2can be directly measured using a solid-state half-cell. For the positive electrode, the measurement is made from the first open circuit voltage (OCV) to the maximum charge voltage, e.g., 3.0 V (vs. Li / Li + ) can be performed for an operating voltage of up to 0.01 V for the cathode, for example, lithium metal, from the second open circuit voltage (OCV). For example, a solid-state half-cell having a cathode active material layer can measure a current of 0.1 mA / cm from the first open circuit voltage to 3.0 V. 2 The solid half-cell having the first negative active material layer is charged with a constant current of 0.1 mA / cm from the second open circuit voltage to 0.01 V. 2 It can be charged with a constant current. The current density during constant current charging is, for example, 0.2 mA / cm 2 , or 0.5 mA / cm 2 A solid-state battery having a positive electrode active material layer can be charged from a first open circuit voltage to, for example, 2.5 V, 2.0 V, 3.5 V, or 4.0 V. The maximum charge voltage of the positive electrode active material layer can be determined by the maximum voltage of the battery that satisfies the safety conditions according to JISC8712:2015 of the Japanese Standards Association.

[0185] If the initial charge capacity of the first negative electrode active material layer (22) is too small, the thickness of the first negative electrode active material layer (22) becomes very thin, so that lithium dendrites formed between the first negative electrode active material layer (22) and the negative electrode current collector (21) during repeated charge and discharge processes 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 charge capacity 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).

[0186] 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 too thin, lithium dendrites formed between the first negative electrode active material layer (22) and the negative electrode current collector (21) 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.

[0187] [Cathode: Second negative electrode active material layer]

[0188] Referring to FIG. 3, the all-solid-state secondary battery (1) further includes, after being charged, a second negative electrode active material layer (24) disposed, for example, between the negative electrode current collector (21) and the first negative electrode active material layer (22). The second negative electrode active material layer (24) 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 (24) is a metal layer containing lithium, it functions as, for example, a lithium reservoir. The lithium alloy is, for example, a Li-Al alloy, a Li-Sn alloy, a Li-In alloy, a Li-Ag alloy, a Li-Au alloy, a Li-Zn alloy, a Li-Ge alloy, a Li-Si alloy, etc., but is not limited thereto, and any lithium alloy used in the art may be used. The second negative electrode active material layer (24) may be made of one of these alloys or lithium, or may be made of several types of alloys. The second negative electrode active material layer (24) is, for example, a plated layer. The second negative electrode active material layer (24) is deposited between the first negative electrode active material layer (22) and the negative electrode current collector (21), for example, during the charging process of an all-solid-state secondary battery (1).

[0189] The thickness of the second negative electrode active material layer (24) is not limited, but is, for example, 1 ㎛ to 500 ㎛, 1 ㎛ to 200 ㎛, 1 ㎛ to 150 ㎛, 1 ㎛ to 100 ㎛, or 1 ㎛ to 50 ㎛. If the thickness of the second negative electrode active material layer (24) is too thin, it is difficult for the second negative electrode active material layer (24) to perform the role of a lithium reservoir. If the thickness of the second negative electrode active material layer (24) 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 rather deteriorate.

[0190] Alternatively, in the all-solid-state secondary battery (1), the second negative electrode active material layer (24) 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 (24) 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 (24) acts as a lithium reservoir because it is a metal layer containing lithium. 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).

[0191] When the second negative electrode active material layer (24) is precipitated by charging after assembling the all-solid-state secondary battery (1), the energy density of the all-solid-state secondary battery (1) increases because the second negative electrode active material layer (24) is not included when assembling the all-solid-state secondary battery (1). When charging the all-solid-state secondary battery (1), the charging is performed in excess of the charging capacity of the first negative electrode active material layer (22). That is, the first negative electrode active material layer (22) is overcharged. At the initial stage of charging, lithium is absorbed into the first negative electrode active material layer (22). The negative electrode active material included in the first negative electrode active material layer (22) forms an alloy or compound with the lithium ions that have moved from the positive electrode (10). When charging exceeds the capacity of the first negative electrode active material layer (22), for example, lithium is deposited on the back surface of the first negative electrode active material layer (22), that is, between the negative electrode current collector (21) and the first negative electrode active material layer (22), and a metal layer corresponding to the second negative electrode active material layer (24) is formed by the deposited lithium. The second negative electrode active material layer (24) is a metal layer mainly composed of lithium (i.e., metallic lithium). This result is obtained, for example, by the negative electrode active material included in the first negative electrode active material layer (22) including 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 (24), that is, the metal layer, is ionized and moves toward the positive electrode (10). Therefore, it is possible to use lithium as the negative electrode active material in an all-solid-state secondary battery (1). In addition, since the first negative electrode active material layer (22) covers the second negative electrode active material layer (24), it acts as a protective layer for the second negative electrode active material layer (24), i.e., the metal layer, and at the same time, it suppresses the precipitation and growth of lithium dendrites. Accordingly, it suppresses short circuits and capacity reduction of the all-solid-state secondary battery (1), and consequently improves the cycle characteristics of the all-solid-state secondary battery (1).In addition, when the second negative electrode active material layer (24) is placed by charging after assembling the all-solid-state secondary battery (1), the negative electrode (20), i.e., the negative electrode current collector (21) and the first negative electrode active material layer (22) and the region between them are Li-free regions that do not contain lithium (Li) in the initial state or the state after complete discharge of the all-solid-state secondary battery (1).

[0192] [Cathode: Negative current collector]

[0193] The negative electrode current collector (21) is composed of, for example, a material that does not react with lithium, i.e., does not form an alloy or a compound. The material constituting the negative electrode current collector (21) is, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni), but is not necessarily limited thereto, and any material that can be used as an electrode current collector in the relevant technical field can be used. The negative electrode current collector (21) may be composed of one type of the above-described metal, or may be composed of an alloy or a coating material of two or more types of metals. The negative electrode current collector (21) is, for example, in the form of a plate or foil.

[0194] Referring to FIG. 2, the all-solid-state secondary battery (1) may further include a thin film (23) containing an element capable of forming an alloy with lithium on one surface of the negative electrode collector (21). The thin film (23) is disposed between the negative electrode collector (21) and the first negative electrode active material layer (22). The thin film (23) contains, for example, an element capable of forming an alloy with lithium. The element capable of forming an alloy with lithium includes, but is not limited to, gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, etc., and any element capable of forming an alloy with lithium in the art may be used. The thin film (23) is composed of one of these metals or an alloy of several types of metals. By placing the thin film (23) on one surface of the negative electrode current collector (21), for example, the deposition shape of the second negative electrode active material layer (24) deposited between the thin film (23) and the first negative electrode active material layer (22) becomes flatter, and the cycle characteristics of the all-solid-state secondary battery (1) can be further improved.

[0195] The thickness of the thin film (23) 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 (23) is less than 1 nm, it may be difficult for the function of the thin film (23) to be exerted. If the thickness of the thin film (23) is excessively thick, the thin film (23) itself absorbs lithium, which reduces the amount of lithium precipitated from the negative electrode, thereby lowering the energy density of the solid-state battery and deteriorating the cycle characteristics of the all-solid-state secondary battery (1). The thin film (23) may be disposed on the negative electrode current collector (21) by, for example, a vacuum deposition method, a sputtering method, a plating method, or the like, but is not necessarily limited to these methods, and any method capable of forming the thin film (23) in the relevant technical field may be used.

[0196] Although not shown in the drawing, 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 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 be an insulating polymer. Since the base film includes an insulating thermoplastic polymer, when a short circuit occurs, the base film may soften or liquefy, thereby blocking battery operation and suppressing a rapid 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 additionally 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 collector (21), refer to the positive electrode collector (11) described above. By having this structure, the negative electrode collector (21) can reduce the weight of the negative electrode, and consequently, improve the energy density of the negative electrode and lithium battery.

[0197] [Solid electrolyte layer]

[0198] [Solid electrolyte layer: electrolyte]

[0199] Referring to FIGS. 1 to 5, a solid electrolyte layer (30) is disposed between the positive electrode (10) and the negative electrode (20) and includes a solid electrolyte separator. The solid electrolyte layer (30) may further include, for example, a solid electrolyte, a gel electrolyte, or a combination thereof.

[0200] The solid electrolyte additionally included in the solid electrolyte layer (30) may include, for example, an oxide-based solid electrolyte, a polymer solid electrolyte, or a combination thereof.

[0201] Oxide solid electrolytes include, 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 manufactured, for example, by a sintering method.

[0202] Oxide-based solid electrolytes include, 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) 중에서 선택된 가넷계(Garnet-type) 고체전해질이다.

[0203] The polymer solid electrolyte may, for example, comprise a mixture of a lithium salt and a polymer, or a polymer having ion-conducting functional groups. The polymer solid electrolyte may be, for example, a polymer electrolyte that is solid at 25°C and 1 atm. The polymer solid electrolyte may not, for example, comprise a liquid.The polymer solid electrolyte comprises a polymer, and the polymer is, for example, polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene (PVDF-HFP), 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), 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 sulfone) (SPAEKKS), sulfonated poly(aryl ether ketone) (SPAEK), poly[bis(benzimidazobenzisoquinolinones)] (SPBIBI), poly(styrene sulfonate) (PSS), lithium 9,10-Diphenylanthracene-2-sulfonate (lithium 9,10-diphenylanthracene-2-sulfonate, DPASLi. +) or a combination thereof, but is not limited thereto, and any lithium salt that can be used in polymer electrolytes in the relevant technical field is possible. The lithium salt can be any lithium salt that can be used in the relevant technical field. The lithium salt is, 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, etc. The polymer included in the polymer solid electrolyte may be, for example, a compound including 10 or more, 20 or more, 50 or more or 100 or more repeating units. The weight average molecular weight of the polymer included in the polymer solid electrolyte may be, for example, 1000 Dalton or more, 10,000 Dalton or more, 100,000 Dalton or more or 1,000,000 Dalton or more.

[0204] A gel electrolyte is, for example, a polymer gel electrolyte. A gel electrolyte can have a gel state without containing a polymer, for example.

[0205] A polymer gel electrolyte may include, for example, a liquid electrolyte and a polymer, or an organic solvent and a polymer having an ion-conducting functional group. The polymer gel electrolyte may be, for example, a polymer electrolyte that is in a gel state at 25°C and 1 atm. The polymer gel electrolyte may have a gel state without containing a liquid, for example. The liquid electrolyte used in the polymer gel electrolyte may be, for example, an ionic liquid, a mixture of a lithium salt and an organic solvent; a mixture of a lithium salt and an organic solvent; or a mixture of an ionic liquid and an organic solvent. The polymer used in the polymer gel electrolyte may be selected from among the polymers used in solid polymer electrolytes. The organic solvent may be selected from among the organic solvents used in liquid electrolytes. The lithium salt may be selected from among the lithium salts used in solid polymer electrolytes. An ionic liquid refers to a salt that has a melting point below room temperature, is composed solely of ions, and is liquid at room temperature or a molten salt at room temperature. Ionic liquids include, for example, a) one or more cations selected from ammonium, pyrrolidinium, pyridinium, pyrimidinium, imidazolium, piperidinium, pyrazolium, oxazolium, pyridazinium, phosphonium, sulfonium, triazolium, and mixtures thereof, and b) BF4-, PF6-, AsF6-, SbF6-, AlCl4-, HSO4-, ClO4-, CH3SO3-, CF3CO2-, Cl-, Br-, I-, SO4 2-, CF3SO3-, (FSO2)2N-, (C2F5SO2)2N-, (C2F5SO2)(CF3SO2)N-, and (CF3SO2)2N- may include at least one selected from compounds containing at least one anion selected from among. The polymer solid electrolyte may form a polymer gel electrolyte, for example, by being impregnated into a liquid electrolyte in a secondary battery. The polymer gel electrolyte may further include inorganic particles. The polymer included in the polymer gel electrolyte may be a compound including, for example, 10 or more, 20 or more, 50 or more, or 100 or more repeating units. The weight average molecular weight of the polymer included in the polymer gel electrolyte may be, for example, 500 Dalton or more, 1000 Dalton or more, 10,000 Dalton or more, 100,000 Dalton or more, or 1,000,000 Dalton or more.

[0206] [Cathode manufacturing method]

[0207] A method for manufacturing a positive electrode according to an embodiment includes the steps of: providing an adhesive binder layer on a positive electrode current collector; providing a Li2S-containing complex; providing a sulfide-based solid electrolyte; preparing a mixture by mixing the Li2S-containing complex and the sulfide-based solid electrolyte; and preparing a positive electrode by adding an adhesive binder to the mixture, mixing the mixture, and providing the mixture on top of the adhesive binder layer to form a positive electrode active material layer.

[0208] A Li2S-containing complex, such as a complex of Li2S and a lithium salt, can be prepared, for example, by mechanically milling Li2S and a lithium salt. The milling conditions are not limited, and any conditions that can form the above complex can be used. The complex of Li2S and a lithium salt can be prepared by placing Li2S particles and a lithium salt in a ball mill and stirring at a speed of 100 to 1000 rpm for 1 to 20 hours. The stirring can be performed more than once.

[0209] As lithium salts, for example, LiI, LiBr, LiCl, LiF, LiH, Li2O, Li2Se, Li2Te, Li3N, Li3P, Li3As, Li3Sb, Li3Al2, LiB3, Li3OCl, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiNO3, Li2CO3, LiBH4, Li2SO4, Li3BO3, Li3PO4, Li4NCl, Li5NCl2, Li3BN2 or combinations thereof can be used.

[0210] A composite of Li2S, a lithium salt, and a carbon-based material, which is a Li2S-containing complex, can be manufactured, for example, through a step of mechanically milling Li2S and a lithium salt; and a step of adding a carbon-based material to the milling product and milling it.

[0211] A sulfide-based solid electrolyte is provided. The sulfide-based solid electrolyte refers to the solid electrolyte separator section described above.

[0212] A mixture is prepared by mixing a Li2S-containing complex and the sulfide-based solid electrolyte. The mixing ratio of the Li2S-containing complex and the sulfide-based solid electrolyte may be, for example, a weight ratio of 50:50 to 95:5, 50:50 to 90:10, 50:50 to 80:20, or 50:50 to 70:30.

[0213] The mixture may additionally include a process solvent. By additionally including a process solvent, the mixture may take the form of a slurry. The solvent may be, for example, octyl acetate, but is not limited thereto, and any solvent used in the art may be used. Alternatively, the mixture may be prepared dry without including a process solvent.

[0214] Prepare a solid electrolyte.

[0215] The above adhesive binder layer is formed using a composition for forming an adhesive binder layer containing an adhesive binder.

[0216] The method for forming an adhesive binder layer using polydopamine as an example of the adhesive binder is as follows.

[0217] According to an embodiment, a composition for forming a polydopamine layer containing dopamine, a solvent, and a buffer solution is prepared.

[0218] The above dopamine becomes polydopamine through self-polymerization reaction at a pH range of about 8 to 8.8, for example, about 8.5.

[0219] The pH of the composition for forming the above polydopamine layer is 8.0 to 8.8, for example, about 8.5.

[0220] A buffer solution is a solution with a pH of about 8 to 8.8, for example, a solution containing tris(hydroxymethyl)aminomethane hydrochloride (Tris-HCl) and water.

[0221] Buffer solutions containing (HCl and H2O in a volume ratio of 3:1), Tris borate ethylene diamine tetra-acetic acid (TBE), Tris-buffered saline (TBS), phosphate-buffered saline (PBS), or a combination thereof can be used.

[0222] The solvent used herein is a substance that does not affect the pH of the composition, such as an alcohol-based compound. Examples of alcohol-based compounds include ethanol, methanol, butanol, and isopropanol. The solvent content is, for example, in the range of 100 to 3,000 parts by weight based on 100 parts by weight of dopamine.

[0223] The above drying is carried out, for example, in the range of 20 to 25°C.

[0224] The above coating may be applied by dipping, spray coating, bar coating, die casting, comma coating, screen printing, etc. In addition, it is also possible to form an adhesive binder layer on a separate substrate and then bond it to the anode by pressing or lamination. The coating according to one embodiment refers to the spray coating method.

[0225] In another embodiment, a dopamine monomer, a polydopamine precursor, is dissolved in an acid such as HCl to prepare an adhesive binder-containing composition. A positive electrode current collector is immersed in the composition. The resulting composition-coated electrode is then washed and dried to form an adhesive binder layer.

[0226] According to another embodiment, a polydopamine coating layer composition is prepared in which polydopamine is dispersed in a distilled water buffer solution. This is coated on the positive electrode current collector and dried to form a polydopamine coating layer, thereby forming an intermediate layer on the surface of the positive electrode current collector. The coating may be performed by dipping, spray coating, bar coating, die casting, comma coating, screen printing, or the like.

[0227] The above drying is carried out at, for example, 30 to 90°C, for example, 80°C.

[0228] The present invention is explained in more detail through the following examples and comparative examples. However, the examples are intended to illustrate the present invention and are not intended to limit the scope of the present invention.

[0229] (Manufacture of a complex of Li2S and lithium salt)

[0230] Manufacturing Example 1: Li2S-LiI complex

[0231] Li2S and LiI were mixed at a weight ratio of 30:20. The mixture was mechanically milled using a ball mill to prepare a Li2S-LiI composite. The milling conditions were 25°C, 600 rpm, and 10 h.

[0232] The size of the Li2S-LiI complex was less than 1 μm. The size of the Li2S-LiI complex was calculated by software from scanning electron microscope images of the Li2S-LiI complex powder. The size of the Li2S-LiI complex is the average particle diameter of D50.

[0233] The Mohs hardness of Li2S was 0.6, and that of LiI was 2.0. The Mohs hardness of the Li2S-LiI composite was less than 2.

[0234] Manufacturing Example 2: Li2S-LiBr complex

[0235] A Li2S-LiBr complex was prepared in the same manner as in Preparation Example 1, except that LiBr was used instead of LiI.

[0236] Manufacturing Example 3: Li2S-LiCl complex

[0237] A Li2S-LiCl complex was prepared in the same manner as in Preparation Example 1, except that LiCl was used instead of LiI.

[0238] Comparative Manufacturing Example 1: Simple mixture of Li2S and LiI-

[0239] A mixture of Li2S and LiI with a weight ratio of 30:20 was used as is.

[0240]

[0241] (Manufacture of Li2S-LiI-CNF cathode active material)

[0242] Manufacturing Example 4: Li2S-LiI-CNF (50:30:20), 2-step, 10 hr, 600 rpm, 28G

[0243] (Stage 1)

[0244] Li2S and LiI were mixed at a weight ratio of 50:30. The mixture was mechanically milled using a ball mill to prepare a Li2S-LiI composite. The milling conditions were 25°C, 600 rpm for 10 h. The milling energy applied to the sample during milling was 28 G.

[0245] (Stage 2)

[0246] Li2S-LiI composite and carbon nanofiber (CNF) were mixed at a weight ratio of 80:20. The mixture was mechanically milled using a ball mill to prepare a Li2S-LiI-CNF composite. The milling conditions were 25°C, 600 rpm, and 10 h. The milling energy applied to the sample during milling was 28 G. The Li2S-LiI-CNF composite was used as a composite cathode active material.

[0247] Manufacturing Example 5: Li2S-LiI-CNF, 2 steps, 8 hr, 600 rpm, 28G

[0248] A Li2S-LiI-CNF composite was manufactured in the same manner as in Manufacturing Example 4, except that the milling time in the first and second steps was changed to 8 hours.

[0249] Manufacturing Example 6: Li2S-LiI-CNF, 2 steps, 6 hr, 600 rpm, 28G

[0250] A Li2S-LiI-CNF composite was manufactured in the same manner as in Manufacturing Example 4, except that the milling time in the first and second steps was changed to 6 hours.

[0251] Manufacturing Example 7: Li2S-LiI-CNF, 2 steps, 4 hr, 600 rpm, 28G

[0252] A Li2S-LiI-CNF composite was manufactured in the same manner as in Manufacturing Example 4, except that the milling time in the first and second steps was changed to 4 hours.

[0253] Comparative Manufacturing Example 2: Simple mixture of Li2S, LiI, and CNF

[0254] A mixture of Li2S, LiI, and CNF in a weight ratio of 50:30:20 was used as is.

[0255] Comparative Manufacturing Example 3: Li2S-LiI-CNF, 2 steps, 1 hr, 600 rpm, 28G

[0256] A Li2S-LiI-CNF composite was manufactured in the same manner as in Manufacturing Example 4, except that the milling time in the first and second steps was changed to 1 hour.

[0257] Comparative Manufacturing Example 4: Li2S-LiI-CNF, 2 steps, 20 hr, 600 rpm, 28G

[0258] A Li2S-LiI-CNF composite was manufactured in the same manner as in Manufacturing Example 4, except that the milling time in the first and second steps was changed to 20 hours.

[0259] Comparative Manufacturing Example 5: Li2S-LiI-CNF, 510 rpm, 10 hr, 2 stages, 20G (KR 2017-0068448 (Tatsumi Sago) (1st stage)

[0260] A first mixture was prepared by mixing Li2S and LiI in a weight ratio of 30:20. The first mixture was mechanically milled using a ball mill to prepare a Li2S-LiI complex.

[0261] Milling conditions were 25°C, 510 rpm for 10 hours. The milling energy applied to the sample during milling was 20 G.

[0262] (Stage 2)

[0263] A second mixture was prepared by mixing the Li2S-LiI complex and carbon nanofibers (CNF) at a weight ratio of 50:10. The second mixture was mechanically milled using a ball mill to produce a Li2S-LiI-CNF complex.

[0264] The milling conditions were 25°C, 510 rpm for 10 h. The milling energy applied to the sample during milling was 20 G. The Li2S-LiI-CNF composite was used as the composite cathode active material.

[0265] Comparative Manufacturing Example 6: Li2S-LiI-CNF, 10 hr, 2 steps, 10 G

[0266] A Li2S-LiI-CNF composite was manufactured in the same manner as in Manufacturing Example 4, except that the rotation speed was reduced in the first and second steps and the milling energy was changed to 10 G.

[0267] Comparative Manufacturing Example 7: Li2S-LiI-CNF, 10 hr, 2 steps, 30 G

[0268] A Li2S-LiI-CNF composite was manufactured in the same manner as in Manufacturing Example 4, except that the rotation speed was increased in the first and second steps and the milling energy was changed to 30 G.

[0269] Comparative Manufacturing Example 8: Simple mixture of Li2S and CNF

[0270] Li2S and carbon nanofibers (CNF) were mixed at a weight ratio of 30:30. The mixture was used as a cathode active material.

[0271] Comparative Manufacturing Example 9: Li2S-CNF, 600 rpm, 2 hr, 1 step, 20 G

[0272] Li2S and carbon nanofibers (CNF) were mixed at a weight ratio of 30:30. The mixture was mechanically milled using a ball mill to prepare a Li2S-CNF composite. The milling conditions were 25°C, 600 rpm for 2 h. The milling energy applied to the sample during milling was 20 G. The Li2S-CNF composite was used as a composite cathode active material.

[0273] Comparative Manufacturing Example 10: Li2S-CNF, 600 rpm, 10 hr, 1 step, 20 G

[0274] A Li2S-CNF composite was manufactured using the same method as in Comparative Manufacturing Example 9, except that the milling time was changed to 10 hours.

[0275] Comparative Example 11: Li2S-CNF-LiI, 600 rpm, 10 hr, 2 stages, 20G

[0276] (Stage 1)

[0277] Li2S and carbon nanofibers (CNF) were mixed at a weight ratio of 30:10. The mixture was mechanically milled using a ball mill to prepare a Li2S-CNF composite. The milling conditions were 25°C, 600 rpm, and 10 h. The milling energy applied to the sample during milling was 20 G.

[0278] (Stage 2)

[0279] Li2S-CNF composite and LiI were mixed at a weight ratio of 40:20. The mixture was mechanically milled using a ball mill to prepare a Li2S-CNF-LiI composite. The milling conditions were 25°C, 600 rpm, and 10 h. The milling energy applied to the sample during milling was 20 G. The Li2S-CNF-LiI composite was used as a composite cathode active material.

[0280] Comparative Example 12: Li2S-SE-CNF, 600 rpm, 10 hr, 2 steps, 20G

[0281] (Stage 1)

[0282] Li2S and Li6PS5Cl solid electrolyte (SE) were mixed at a weight ratio of 30:20. The mixture was mechanically milled using a ball mill to prepare a Li2S-SE composite. The milling conditions were 25°C, 600 rpm, and 10 h. The milling energy applied to the sample during milling was 20 G.

[0283] (Stage 2)

[0284] Li2S-SE composite and CNF were mixed at a weight ratio of 50:10. The mixture was mechanically milled using a ball mill to prepare a Li2S-SE-CNF composite. The milling conditions were 25°C, 600 rpm, and 10 h. The milling energy applied to the sample during milling was 20 G. The Li2S-SE-CNF composite was used as a composite cathode active material.

[0285] Comparative Example 13: Li2S-LiI-CNF, 600 rpm, 2 hr, 1 step, 20 G

[0286] Li2S, LiI, and carbon nanofibers (CNF) were mixed in a weight ratio of 30:20:10. The mixture was mechanically milled using a ball mill to prepare a Li2S-LiI-CNF composite. The milling conditions were 25°C, 600 rpm, and 2 h. The milling energy applied to the sample during milling was 20 G. The Li2S-LiI-CNF composite was used as a composite cathode active material.

[0287]

[0288] (Manufacturing of positive electrode)

[0289] Example 1: Al current collector / adhesive binder layer (polydopamine binder layer) / Li2S-LiI-CNF, PTFE-containing dry cathode

[0290] A composition for forming a polydopamine layer was prepared by mixing 0.1 g of dopamine with 50 ml of a buffer solution having a pH of 8.5, and diluting the mixture with ethanol to improve viscosity and drying characteristics without affecting the pH during the process. The composition was spray-coated on the upper part of aluminum foil, which is a positive electrode current collector, through a nozzle, and dried at about 25°C to form a polydopamine layer (i.e., a polydopamine binder layer) with a thickness of about 10 nm on the upper part of the positive electrode current collector.

[0291] The Li2S-LiI-CNF composite manufactured in Manufacturing Example 4 was prepared as a cathode active material. Li6PS5Cl, an argyrodite-type crystal (D50=3.0 μm, crystalline), was prepared as a solid electrolyte. PTFE was prepared as a binder.

[0292] The Li2S-LiI-CNF composite and the sulfide-based solid electrolyte were placed in a mixer and mixed for 2 minutes.

[0293] PTFE was added to the above mixed result, mixed with a mixer for 20 seconds, and the obtained positive electrode mixture powder was kneaded and rolled out with a roller to a thickness of 100 to 150 μm to manufacture a positive electrode.

[0294] The above composite cathode active material: solid electrolyte: adhesive binder (PTFE) was mixed in a weight ratio of 60:39:1.0 to prepare a cathode mixture. The cathode mixture was obtained by dry mixing using a ball mill. The content of PTFE, which is an adhesive binder, is 500 parts by weight based on 100 parts by weight of polydopamine in the adhesive binder layer.

[0295] A positive electrode was prepared by placing the positive electrode active material mixture on an aluminum foil having an adhesive binder layer and plate pressing at a pressure of 200 MPa for 10 minutes to produce a dry positive electrode. The thickness of the positive electrode was approximately 120 μm. The thickness of the positive electrode active material layer was approximately 100 μm, and the thickness of the aluminum foil was approximately 20 μm. The areas of the positive electrode active material layer and the positive electrode current collector were the same.

[0296] Example 2: Al current collector / adhesive binder layer (PAA binder layer) / Li2S-LiI-CNF, PTFE-containing dry cathode

[0297] A positive electrode was manufactured in the same manner as in Example 1, except that an adhesive binder layer using lithium polyacrylate (Li-PAA) was formed as follows.

[0298] First, the polyacrylic acid lithium salt aqueous solution was prepared by mixing 5 g of polyacrylic acid and 3.03 g of LiOH in 127.5 g of deionized water, and stirring at room temperature (25°C) for 24 hours to obtain 4 wt% of polyacrylic acid lithium salt (weight average molecular weight: 450×10 3 ) was obtained.

[0299] A polyacrylic acid lithium salt aqueous solution was applied onto aluminum foil and dried at 100°C to form an adhesive binder layer with a thickness of approximately 1 μm.

[0300] Example 3: (Al current collector / adhesive binder layer (polydopamine layer) / Li2S-LiI-CNF, PVDF-containing dry cathode)

[0301] An anode was manufactured in the same manner as in Example 1, except that PVDF was used instead of PTFE as an adhesive binder when preparing the anode mixture.

[0302] Example 4: (Al current collector / adhesive binder layer (PAA binder layer) / Li2S-LiI-CNF, PVDF-containing dry cathode)

[0303] An anode was manufactured in the same manner as in Example 2, except that PVDF was used instead of PTFE as an adhesive binder when preparing the anode mixture.

[0304] Example 5: (Al current collector / adhesive binder layer (polydopamine binder layer) / Li2S-LiI-CNF, PTFE-containing dry cathode)

[0305] A positive electrode was manufactured in the same manner as in Example 1, except that the weight ratio of composite positive electrode active material: solid electrolyte: adhesive binder (PTFE) was changed to 60:37:3.0 when preparing the positive electrode mixture.

[0306] Comparative Example 1: Dry cathode containing Al current collector / Li2S-LiI-CNF composite

[0307] An anode was manufactured in the same manner as in Example 1, except that aluminum foil was used instead of the aluminum foil on which the adhesive binder layer was placed.

[0308] Comparative Example 2: Dry cathode containing a simple mixture of Al current collector / Li2S and LiI and CNF

[0309] A positive electrode was manufactured in the same manner as in Example 1, except that a simple mixture of Li2S, LiI, and CNF prepared in Comparative Manufacturing Example 2 was used instead of the Li2S-LiI-CNF composite manufactured in Manufacturing Example 4.

[0310] Comparative Example 3: Al current collector / polydopamine binder layer / carbon coating layer / Li2S-LiI-C containing cathode

[0311] A positive electrode was manufactured in the same manner as in Example 1, except that a carbon coating layer was formed on top of the polydopamine layer according to the following process.

[0312] A carbon coating layer composition was prepared by dispersing multilayer carbon nanotubes in an N-methyl-2-pyrrolidone (NMP) solution containing 10 wt% polyvinylidene fluoride binder. In the carbon coating layer composition, the content of the multilayer carbon nanotubes was 10 parts by weight, the content of the NMP was 80 parts by weight, and the content of the binder was 10 parts by weight. This was applied to the surface of the polydopamine layer and dried at a temperature of 120°C for 4 hours, thereby forming a carbon coating layer having a thickness of about 100 nm on the polydopamine layer.

[0313] Reference Example 1: Positive electrode current collector / polydopamine binder layer / positive electrode active material layer

[0314] A positive electrode was manufactured in the same manner as in Example 1, except that an adhesive binder layer was formed on top of aluminum foil as follows and a positive electrode active material layer using a positive electrode mixture was formed on top of the adhesive binder layer.

[0315] A composition for forming a polydopamine layer was prepared by mixing 50 mL of a buffer solution of pH 8.5 per 0.1 g of dopamine, and diluted with ethanol to improve viscosity and drying characteristics without affecting the pH during the process. The composition was spray-coated on the upper surface of aluminum foil through a nozzle, and dried at about 25°C to form a polydopamine coating layer with a thickness of about 10 nm, thereby forming a structure in which a positive electrode collector / polydopamine layer / positive electrode active material layer are laminated.

[0316]

[0317] (Manufacturing of all-solid-state secondary batteries)

[0318] Example 6: Al current collector / Carbon / Li2S-LiI-C containing dry cathode / sulfide-based solid electrolyte (SE) / Ag-C coated SUS

[0319] (Polar electrode manufacturing)

[0320] The positive electrode of Example 1 was used.

[0321] (Cathode manufacturing)

[0322] A 10 ㎛ thick SUS foil was prepared as a negative electrode current collector. Carbon black (CB) with a primary particle diameter of approximately 30 nm and silver (Ag) particles with an average particle diameter of approximately 60 nm were prepared as negative electrode active materials.

[0323] A mixed powder of 4 g of carbon black (CB) and silver (Ag) particles in a weight ratio of 3:1 was placed in a container, and 4 g of an NMP solution containing 7 wt% of PVDF binder (Kureha #9300) was added thereto to prepare a mixed solution. A slurry was prepared by stirring the mixed solution while adding NMP little by little to the prepared mixed solution. The prepared slurry was applied to a SUS sheet using a bar coater, dried in air at 80°C for 10 minutes, and then vacuum-dried at 40°C for 10 hours to prepare a laminate. The prepared laminate was cold roll pressed to flatten the surface, thereby preparing a negative electrode having a first negative electrode active material layer / negative electrode current collector structure. The thickness of the first negative electrode active material layer was approximately 15 μm. The areas of the first negative electrode active material layer and the negative electrode current collector were the same.

[0324] (Manufacturing of solid electrolyte layer)

[0325] Li6PS5Cl solid electrolyte in the form of argyrodite crystals (D 50=3.0 (m, crystalline), a mixture was prepared by adding 1.5 parts by weight of an acrylic binder to 98.5 parts by weight of a solid electrolyte. Octyl acetate was added to the prepared mixture and stirred to prepare a slurry. The prepared slurry was applied using a bar coater onto 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 prepare a laminate. The prepared laminate was vacuum-dried at 80°C for 2 hours to prepare a solid electrolyte layer.

[0326] (inert absence)

[0327] A flame-retardant inert member was manufactured by forming a slurry containing pulp fiber (cellulose fiber), glass fiber, aluminum hydroxide (Al(OH)3), an acrylic binder, and a solvent into a gasket shape and then removing the solvent.

[0328] The weight ratio of pulp fiber (cellulose fiber), glass fiber, aluminum hydroxide (Al(OH)3), and acrylic binder was 20:8:70:2. The thickness of the inert material was 120 ㎛.

[0329] Before placing the manufactured flame-retardant inert material on the solid electrolyte layer, moisture, etc. of the flame-retardant inert material was removed by vacuum heat treatment at 80°C for 5 hours.

[0330] (Manufacturing of all-solid-state secondary batteries)

[0331] Referring to Fig. 4, a solid electrolyte layer was placed on the negative electrode such that the first negative electrode active material layer was in contact with the solid electrolyte layer, and a positive electrode was placed on the solid electrolyte layer. A laminate was prepared by placing a gasket surrounding the positive electrode and in contact with the solid electrolyte layer. The thickness of the gasket was approximately 120 ㎛. The above-described flame-retardant inert material was used as the gasket. The gasket was placed so as to be in contact with the side surface of the positive electrode and the solid electrolyte layer. The positive electrode was placed at the center of the solid electrolyte layer, and the gasket was placed so as to surround the positive electrode and extend to the end of the solid electrolyte layer. The area of ​​the positive electrode was approximately 90% of the area of ​​the solid electrolyte layer, and the gasket was placed over the entire remaining 10% of the area of ​​the solid electrolyte layer where the positive electrode was not placed.

[0332] 85 prepared laminates o The solid electrolyte layer was plate-pressed at 500 MPa for 30 min at C. This pressurization process sintered the solid electrolyte layer, thereby improving battery characteristics. The thickness of the sintered solid electrolyte layer was approximately 45 ㎛. The density of the Li6PS5Cl solid electrolyte, which was an argyrodite-type crystal contained in the sintered solid electrolyte layer, was 1.6 g / cc. The area of ​​the solid electrolyte layer was the same as that of the negative electrode.

[0333] The pressurized laminate was placed in a pouch and vacuum-sealed to manufacture an all-solid-state secondary battery. Portions of the positive and negative current collectors were extended outside the sealed battery to serve as positive and negative terminals.

[0334] Examples 7 to 10

[0335] An all-solid-state secondary battery was manufactured in the same manner as in Example 6, except that the positive electrodes manufactured in Examples 2 to 5 were used.

[0336] Comparative examples 4 to 6

[0337] An all-solid-state secondary battery was manufactured in the same manner as Example 6, except that the positive electrodes manufactured in Comparative Examples 1 to 3 were used.

[0338] Reference Example 2

[0339] An all-solid-state secondary battery was manufactured in the same manner as in Example 6, except that the positive electrode manufactured in Reference Example 1 was used instead of the positive electrode of Example 1.

[0340]

[0341] Evaluation Example 1: XRD Analysis and Scanning Electron Microscopy Analysis

[0342] XRD spectra were measured using Cu Kα radiation for the raw material (bare) Li2S used in Manufacturing Example 1, the pulverized Li2S, and the Li2S-LiI-CNF composite manufactured in Manufacturing Example 4. The measurement results are shown in Table 1 below.

[0343] The Li2S crystallite size and lattice constant were derived from the first peak for the (111) crystal plane appearing at a diffraction angle of 2θ = 27° ± 2.0° in the XRD spectrum.

[0344] The crushed Li2S was prepared by milling under the same conditions as in Manufacturing Example 4, except that the mixture of Li2S and LiI was changed to Li2S in the first step of Manufacturing Example 4. The second step of Manufacturing Example 4 was not performed. The particle size (i.e., D50 particle size) of the raw material (bare) Li2S used in Manufacturing Example 1, the crushed Li2S, and the Li2S-LiI-CNF composite prepared in Manufacturing Example 4 was measured using a laser-assisted particle size analyzer (PSA), and the Li2S particle size of the composite was measured using a scanning electron microscope. The measurement results are shown in Table 1 below.

[0345] Classification Li2S crystallite size [nm] Li2S particle size [㎛] bare Li2S 6 5 8 crushed Li2S 15 -Li2S -LiI -CNF composite less than 10 less than 1

[0346] As shown in Table 1, the particle size and crystallite size of the Li2S-LiI-CNF composite were significantly reduced compared to Li2S. The Li2S-LiI-CNF composite contained a Li2S-LiI solid solution, the size of the Li2S crystallites was less than 9.9 nm, and the Li2S particle size of the composite was less than 2 μm.

[0347] Although not shown in Table 1, the lattice constant of the Li2S-LiI-CNF composite of Preparation Example 1 was larger than that of bare Li2S. The increase in the lattice constant of the Li2S-LiI-CNF composite compared to that of bare Li2S was thought to be due to the dissolution of LiI within the Li2S crystal. Therefore, it was confirmed that the Li2S-LiI-CNF composite formed a solid solution.

[0348] Although not shown in Table 1, the particle size of the Li2S-LiI-CNF composite of Manufacturing Example 4 was approximately 5 μm.

[0349] Evaluation Example 2: XRD Analysis and Scanning Electron Microscopy Analysis

[0350] XRD spectra were measured using Cu Kα radiation for the composite cathode active materials (i.e., composites) manufactured in Manufacturing Examples 4 to 7 and Comparative Manufacturing Examples 3 to 13. The Li2S crystallite sizes calculated from the first peak for the (111) crystal plane appearing at a diffraction angle of 2θ = 27° ± 2.0° in the measured XRD spectra are shown in Table 2 below. The crystallite sizes were calculated using the Sherrer Equation.

[0351] The Li2S particle sizes of the composite cathode active materials manufactured in Manufacturing Examples 4 to 7 and Comparative Manufacturing Examples 3 to 13 were measured using a scanning electron microscope. The Li2S particle sizes of the composite cathode active materials are the arithmetic mean of the particle sizes of multiple Li2S particles measured using software from scanning electron microscope images. The measurement results are shown in Table 2 below. In Table 2 below, the size represents D50.

[0352] ClassificationStep 1 MillingStep 2 MillingSolution formationLi2S crystallite size [nm]Li2S particle size [㎛] Manufacturing example 4 (28 G, 10 hr)(Li2S-LiI-CNF complex)600 rpm, 28 G, 10 hr600 rpm, 28 G, 10 hr○Less than 9.81 Manufacturing example 5 (28 G, 8 hr)(Li2S-LiI-CNF complex)600 rpm, 28 G, 8 hr600 rpm, 28 G, 8 hr○Less than 7.21 Manufacturing example 6 (28 G, 6 hr)(Li2S-LiI-CNF complex)600 rpm, 28 G, 6 hr600 rpm, 28 G, 6 hr○Less than 8.21 Manufacturing example 7 (28 G, 4 hr)(Li2S-LiI-CNF Comparative Manufacturing Example 3 (28 G, 1 hr) (Li2S-LiI-CNF complex) 600 rpm, 28 G, 4 hr 600 rpm, 28 G, 4 hr ○9.51 Less Comparative Manufacturing Example 3 (28 G, 1 hr) (Li2S-LiI-CNF complex) 600 rpm, 28 G, 1 hr 600 rpm, 28 G, 1 hr ○20.11 Less Comparative Manufacturing Example 4 (28 G, 20 hr) (Li2S-LiI-CNF complex) 600 rpm, 28 G, 20 hr 600 rpm, 28 G, 20 hr △11.81 Less Comparative Manufacturing Example 5 (Li2S-LiI-CNF complex) 510 rpm, 20 G, 10 hr 510 rpm, 20 G, 10 hr ○9.91 Less Comparative Manufacturing Example 6 (10 G, 10 hr)(Li2S-LiI-CNF complex)300 rpm, 10 G, 10 hr300 rpm, 10 G, 10 hr×27.23Comparative Manufacturing Example 7(30 G, 10 hr)(Li2S-LiI-CNF complex)700 rpm, 30 G, 10 hr700 rpm, 30 G, 10 hr△15.62Comparative Manufacturing Example 8(0 G)(Li2S+ CNF simple mixture)--×66.678Comparative Manufacturing Example 9(20 G, 2 hr)(Li2S-CNF complex)600 rpm, 20 G, 2 hr-×24.073Comparative Manufacturing Example 10(20 G, 10 hr)(Li2S-CNF complex)600 rpm, 20 G, 10 hr-×9.Less than 891 Comparative Manufacturing Example 11 (20 G, 10 hr) (Li2S-CNF-LiI complex) 600 rpm, 20 G, 10 hr 600 rpm, 20 G, 10 hr × 15.22 Comparative Manufacturing Example 12 (20 G, 10 hr) (Li2S-SE-CNF complex) 600 rpm, 20 G, 10 hr 600 rpm, 20 G, 10 hr × 8.91 Less than Comparative Manufacturing Example 13 (20 G, 2 hr) (Li2S-LiI-CNF complex) 600 rpm, 20 G, 2 hr - ○223.

[0353] As shown in Table 2, the Li2S-LiI-CNF composites of Preparation Examples 4 to 7 included a Li2S-LiI solid solution, the size of the Li2S crystallites was less than 20.1 nm, and the Li2S particle size of the composite was 2 μm or less.

[0354] In the Li2S-LiI-CNF composite of Comparative Manufacturing Example 3, the size of the Li2S crystallites was 9.9 nm or more due to the reduced milling time during manufacturing.

[0355] In the Li2S-LiI-CNF composite of Comparative Manufacturing Example 4, as the milling time increased during manufacturing, LiI was phase separated into a separate phase, a solid solution was not formed, and the size of the Li2S crystallites also increased.

[0356] The Li2S-LiI-CNF composite of Comparative Manufacturing Example 6 failed to form a Li2S-LiI solid solution because the milling energy was excessively reduced during manufacturing.

[0357] In the Li2S-LiI-CNF composite of Comparative Manufacturing Example 7, a Li2S-LiI solid solution was not properly formed due to heat generation caused by increased milling energy during manufacturing.

[0358] The Li2S-LiI-CNF composite of Comparative Manufacturing Example 13 was manufactured in the first step, so it included a Li2S-LiI solid solution, but the Li2S crystallite size increased, and the Li2S particle size of the composite exceeded 2 μm.

[0359] The simple mixture of Li2S and CNF of Comparative Manufacturing Example 8 and the complexes of Comparative Manufacturing Examples 9, 10, and 12 did not form a solid solution.

[0360] In the Li2S-CNF-LiI complex of Comparative Manufacturing Example 11, a Li2S-LiI solid solution was not properly formed because the Li2S-CNF complex was manufactured in the first step and then the Li2S-CNF-LiI complex was manufactured in the second step.

[0361] Evaluation Example 3: Charge / Discharge Test

[0362] The charge / discharge characteristics of the all-solid-state secondary batteries manufactured in Example 6-10, Comparative Examples 4-6, and Reference Example 2 were evaluated by the following charge / discharge test.

[0363] Charge and discharge tests were performed by placing the solid secondary battery in a constant temperature bath at 45°C.

[0364] The first cycle involved charging for 20 hours at a constant current of 0.05 C until the battery voltage reached 2.8 V. Subsequently, discharging was performed for 20 hours at a constant current of 0.05 C until the battery voltage reached 1.0 V.

[0365] The second cycle was charged and discharged under the same conditions as the first cycle.

[0366] The second cycle discharge capacity was set to the standard capacity.

[0367] The third cycle was performed by charging for 10 hours at a constant current of 0.1 C until the battery voltage reached 2.8 V. Subsequently, discharging was performed for 10 hours at a constant current of 0.1 C until the battery voltage reached 1.0 V.

[0368] After the third cycle, charge and discharge were performed for up to 50 cycles under the same conditions as the third cycle. The measurement results are shown in Table 3 below.

[0369] The initial efficiency is expressed by Equation 1 below, and the capacity retention rate is expressed by Equation 2 below.

[0370] <Formula 1>

[0371] Initial efficiency [%] = [1st cycle discharge capacity / 1st cycle charge capacity] × 100

[0372] <Formula 2>

[0373] Capacity retention rate (%) = [23rd cycle discharge capacity / 3rd cycle discharge capacity] × 100

[0374] Classification 0.05C discharge capacity (mAh / g) Initial efficiency (%) Capacity retention rate (%) (20 times) Example 6 (Al current collector / Adhesive binder layer (polydopamine binder layer) / Li2S-LiI-CNF, PTFE containing dry cathode) 91178.890.5 Example 7 (Al current collector / Adhesive binder layer (PAA binder layer) / Li2S-LiI-CF & PTFE containing dry cathode) 92279.291.9 Example 8 (Al current collector / Adhesive binder layer (polydopamine binder layer) / Li2S-LiI-CNF & PVDF containing dry cathode) 91881.189.2 Example 9 (Al current collector / Adhesive binder layer (PAA binder layer) / Li2S-LiI-CNF & PVDF Dry positive electrode containing Al current collector / adhesive binder layer (polydopamine binder layer) / Li2S-LiI-CNF & PTFE) 92783.691.7 Example 10 (Dry positive electrode containing Al current collector / adhesive binder layer (polydopamine binder layer) / Li2S-LiI-CNF & PTFE) 88385.294.7 Comparative example 4 (Dry positive electrode containing Al current collector / Li2S-LiI-CNF composite) 70972.659.1 Comparative example 5 (Dry positive electrode containing Al current collector / simple mixture of Li2S, LiI and CNF) 32256.479.2 Comparative example 6 (Dry positive electrode containing Al current collector / polydopamine binder layer / carbon coating layer / Li2S-LiI-CNF) 86880.281.2 Reference example 2 (Cathode current collector / polydopamine binder layer / Cathode active material layer) 57673.270.2

[0375] As shown in Table 3, the all-solid-state secondary batteries of Examples 6 to 10 employing the positive electrodes of Examples 1 to 5 showed improved life characteristics compared to the all-solid-state secondary batteries of Comparative Examples 4 to 6 employing the positive electrodes of Comparative Examples 1 to 3 and the all-solid-state secondary battery of Reference Example 2. The all-solid-state secondary batteries of Examples 8 and 10 having a polydopamine layer or Example 9 containing LiPAA showed improved discharge capacity due to improved adhesion between the positive electrode current collector and the positive electrode active material layer, and even when charge and discharge were repeated during the cycle, the contact between the positive electrode current collector and the positive electrode active material layer was stably achieved without delamination of the positive electrode active material, thereby improving the capacity retention rate.

[0376] Although not shown in the drawing, it was confirmed that a lithium metal layer, which is a second negative electrode active material layer, was formed between the first negative electrode active material layer and the negative electrode current collector after the initial charge in the all-solid-state secondary batteries of Examples 6 to 10. This was confirmed through a cross-sectional scanning electron microscope image of the all-solid-state secondary battery. In addition, it was confirmed in the scanning electron microscope image of the cross-sections of the solid electrolyte layer and the positive electrode active material layer that a Li2S-LiI-CNF complex was arranged in the gaps between a plurality of sulfide-based solid electrolyte particles.

[0377] Evaluation Example 4: Rate-limiting characteristic evaluation

[0378] The rate characteristics of the all-solid-state secondary batteries of Examples 6 to 10 and Comparative Examples 4 to 6 were evaluated by the following charge-discharge test. The charge-discharge test was performed by placing the all-solid-state secondary batteries in a constant temperature bath at 45°C.

[0379] The first cycle involved charging for 20 hours at a constant current of 0.05 C until the battery voltage reached 2.8 V. Subsequently, discharging was performed for 20 hours at a constant current of 0.05 C until the battery voltage reached 1.0 V.

[0380] The second cycle was charged and discharged under the same conditions as the first cycle.

[0381] The third cycle was performed by charging for 10 hours at a constant current of 0.1 C until the battery voltage reached 2.8 V. Subsequently, discharging was performed for 10 hours at a constant current of 0.1 C until the battery voltage reached 1.0 V. The fourth cycle was performed by charging and discharging under the same conditions as the third cycle.

[0382] In all charge / discharge cycles, a 10-minute pause was provided after each charge / discharge cycle. Some of the results of the room-temperature charge / discharge experiments are shown in Table 4 below. The rate characteristics are defined by Equation 3 below.

[0383] <Formula 3>

[0384] Rate characteristic [%] = [Discharge capacity in the 4th cycle / Discharge capacity in the 2nd cycle] Х 100

[0385] Classification Rate Characteristics (0.1C / 0.05C) Example 6 (Al current collector / Adhesive binder layer (polydopamine binder layer) / Li2S-LiI-CNF, PTFE-containing dry cathode) 96.2 Example 7 (Al current collector / Adhesive binder layer (PAA binder layer) / Li2S-LiI-CNF, PTFE-containing dry cathode) 95.8 Example 8 (Al current collector / Adhesive binder layer (polydopamine binder layer) / Li2S-LiI-CNF, PVDF-containing dry cathode) 94.8 Example 9 (Al current collector / Adhesive binder layer (PAA binder layer) / Li2S-LiI-CNF, PVDF-containing dry cathode) 94.2 Example 10 (Al current collector / Adhesive binder layer (polydopamine Binder layer) / Li2S-LiI-CNF, PTFE-containing dry cathode) 93.6 Comparative Example 4 (Al current collector / Li2S-LiI-CNF composite-containing dry cathode) 80.5 Comparative Example 5 (Al current collector / Li2S, LiI, and CNF simple mixture-containing dry cathode) 56.3 Comparative Example 6 (Al current collector / polydopamine binder layer / carbon coating layer / Li2S-LiI-CNF-containing cathode) 93.2 Reference Example 2 (cathode current collector / polydopamine binder layer / cathode active material layer) 84.2

[0386] As shown in Table 4, the all-solid-state secondary batteries of Examples 6 to 10 had improved rate characteristics compared to the all-solid-state secondary batteries manufactured in Comparative Examples 4 to 6 and Reference Example 2.

Claims

1. Bipolar collector; An adhesion binder layer located on the positive electrode collector and containing an adhesive polymer; A positive electrode active material layer positioned on the adhesive binder layer and containing a composite positive electrode active material and a cohesion binder, The above composite cathode active material is a cathode for an all-solid-state secondary battery, comprising a Li2S-containing composite.

2. In the first paragraph, the adhesive polymer is at least one selected from polydopamine, a cation-substituted polycarboxylic acid, a cation-substituted polycarboxylic acid copolymer, poly(norepinephrine), poly(meth)acrylamide, polyvinyl alcohol), polyhydroxyethyl(meth)acrylate, a methyl(meth)acrylate-co-(meth)acrylic acid copolymer, polymethyl(meth)acrylate, poly(meth)acrylic acid, and a styrene-(meth)acrylic acid copolymer.

3. A positive electrode for an all-solid-state secondary battery according to claim 1, wherein the thickness of the adhesive binder layer is 5 nm to 1 um.

4. In the first paragraph, the adhesive binder is polytetrafluoroethylene, polyvinylidene fluoride (PVdF) resin, styrene-butadiene rubber (SBR), polytetrafluoroethylene (PTFE), polyethylene glycol (PEG), polypropylene glycol (PPG), toluene diisocyanate (TDI), polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, poly(ethylene-co-vinyl acetate) copolymer, polyethylene oxide, cellulose acetate, cellulose acetate A cathode for an all-solid-state secondary battery, comprising cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxyl methyl cellulose, acrylonitrile-styrene-butadiene copolymer, and polyimide, or a combination thereof.

5. In the first paragraph, the Li2S-containing complex includes a composite of Li2S and a lithium salt; The above complex of Li2S and lithium salt is Li2S-Li a X b It is expressed as (1≤a≤5, 1≤b≤5), The above X is I, Br, Cl, F, H, O, Se, Te, N, P, As, Sb, Al, B, OCl, PF6, BF4, SbF6, AsF6, ClO4, AlO2, AlCl4, NO3, CO3, BH4, SO4, BO3, PO4, NCl, NCl2, BN2 or a combination thereof, a cathode for an all-solid-state secondary battery.

6. In the fifth paragraph, the Li2S-containing composite further includes a carbon-based material, The above carbon-based material includes a fibrous carbon-based material, The above fibrous carbon material includes a carbon nanostructure, and the carbon nanostructure includes carbon nanofibers, carbon nanotubes, carbon nanobelts, carbon nanorods, or a combination thereof. A positive electrode for an all-solid-state secondary battery, wherein the content of the carbon-based material is 1 to 20 wt% of the total weight of the composite.

7. In paragraph 5, the lithium salt is a binary compound or a ternary compound, The above binary compound comprises LiI, LiBr, LiCl, LiF, LiH, Li2O, Li2Se, Li2Te, Li3N, Li3P, Li3As, Li3Sb, Li3Al2, LiB3 or a combination thereof, A cathode for an all-solid-state secondary battery, wherein the ternary compound comprises Li3OCl, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiNO3, Li2CO3, LiBH4, Li2SO4, Li3BO3, Li3PO4, Li4NCl, Li5NCl2, Li3BN2 or a combination thereof.

8. In the first paragraph, the Li2S-containing complex includes a solid solution of Li2S and a lithium salt, The size of the above Li2S-containing composite particles is 10 μm or less, An all-solid-state secondary battery positive electrode, wherein the size of Li2S crystallites obtained from the X-ray diffraction (XRD) spectrum of the above complex is 20 nm or less.

9. In the first paragraph, the content of the adhesive binder in the positive electrode active material layer is 1 to 10 parts by weight based on 100 parts by weight of the total weight of the positive electrode active material layer, and the content of the adhesive binder is 100 to 1000 parts by weight based on 100 parts by weight of the adhesive polymer of the adhesive binder layer, a positive electrode for an all-solid-state secondary battery.

10. A positive electrode for an all-solid-state secondary battery, wherein the content of Li2S in the complex is higher than the content of lithium salt, and the molar ratio of Li2S and lithium salt in the complex is 51:49 to 95:

5.

11. A positive electrode for an all-solid-state secondary battery, wherein the content of the complex in the first paragraph is 60 to 80 wt% based on 100 wt% of the total weight of the positive electrode active material layer.

12. In the first paragraph, the positive electrode active material layer further includes a solid electrolyte, The above solid electrolyte is an all-solid-state secondary battery positive electrode including a sulfide-based solid electrolyte.

13. In the 9th paragraph, the sulfide-based solid electrolyte is Li2S-P2S5, Li2S-P2S5-LiX, X is Halogens, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n , m, n are 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 , at least one selected from 0≤x≤2, The above sulfide-based solid electrolyte includes an argyrodite-type solid electrolyte, The above argyrodite-type solid electrolyte comprises at least one selected from Li6PS5Cl, Li6PS5Br and Li6PS5I, A positive electrode for an all-solid-state secondary battery, wherein the density of the argyrodite-type solid electrolyte is 1.5 to 2.0 g / cc, the sulfide-based solid electrolyte is in the form of particles, and the average particle diameter (D50) of the particles is 0.1 ㎛ to 1.9 ㎛.

14. A positive electrode; a negative electrode; and a solid electrolyte layer disposed between the positive electrode and the negative electrode, An all-solid-state secondary battery, wherein the positive electrode comprises a positive electrode according to any one of claims 1 to 13.

15. An all-solid-state secondary battery according to claim 14, wherein the negative electrode comprises a negative electrode current collector and a first negative electrode active material layer disposed on one surface of the negative electrode current collector.

16. In the 15th paragraph, the first negative electrode active material layer is a metal layer, and the metal layer contains lithium or a lithium alloy, or An all-solid-state secondary battery, wherein the first negative electrode active material layer includes a negative electrode active material and a binder, the negative electrode active material has a particle form, and the average particle diameter of the negative electrode active material is 4 ㎛ or less.

17. In paragraph 16, the negative electrode active material includes at least one selected from a carbon-based negative electrode active material and a metal or metalloid negative electrode active material, The above carbon-based negative electrode active material includes amorphous carbon, crystalline carbon, porous carbon, or a combination thereof. The above metal or metalloid negative electrode active material includes gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), zinc (Zn) or a combination thereof, The above negative active material comprises a mixture of first particles made of amorphous carbon and second particles made of a metal or a metalloid, An all-solid-state secondary battery, wherein the content of the second particles is 1 to 60 wt% based on the total weight of the mixture.

18. In the 15th paragraph, a second negative electrode active material layer is further included, which is disposed between the negative electrode current collector and the first negative electrode active material layer and between the negative electrode current collector and the solid electrolyte layer. An all-solid-state secondary battery, wherein the second negative electrode active material layer is a metal layer, and the metal layer includes lithium or a lithium alloy.

19. In the 14th paragraph, the solid electrolyte layer further includes a solid electrolyte, a gel electrolyte, or a combination thereof, The above solid electrolyte includes an oxide-based solid electrolyte, a polymer solid electrolyte, or a combination thereof, An all-solid-state secondary battery, wherein the gel electrolyte comprises a polymer gel electrolyte.

20. In the 14th paragraph, the positive electrode includes a positive electrode collector, and the negative electrode includes a negative electrode collector. 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 one or both sides of the base film, The above base film comprises a polymer, and the polymer comprises polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI) or a combination thereof, An all-solid-state secondary battery, wherein the metal layer comprises 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.

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