All-solid-state secondary battery

Abstract

An all-solid-state secondary battery is presented, comprising: a positive electrode layer; a negative electrode layer; and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, wherein the negative electrode layer includes a negative electrode current collector and a first negative electrode active material layer on one surface of the negative electrode current collector, and the positive electrode layer includes a positive electrode current collector and a positive electrode active material layer on one surface or opposite surfaces of the positive electrode current collector, wherein the positive electrode active material layer includes a sulfide-based positive electrode active material, and an interlayer containing lithium nitrate (LiNO3) particles is disposed between the negative electrode current collector and the first negative electrode active material layer.

Description

All-solid-state secondary batteries

[0001] It's about all-solid-state secondary batteries.

[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 electrolytes. All-solid-state secondary batteries can offer improved safety.

[0005] One aspect is to provide an all-solid-state secondary battery with improved charge-discharge characteristics by having a new solid electrolyte layer.

[0006] Depending on one aspect

[0007] It comprises an anode layer; a cathode layer; and a solid electrolyte layer disposed between the anode layer and the cathode layer;

[0008] The above negative electrode layer includes a negative electrode current collector and a first negative electrode active material layer on one surface of the negative electrode current collector,

[0009] The above positive electrode layer comprises a positive electrode current collector; and a positive electrode active material layer on one or both sides of the positive electrode current collector,

[0010] The above cathode active material layer includes a sulfide-based cathode active material,

[0011] An all-solid-state secondary battery is provided, in which an interlayer including lithium nitrate (LiNO3) particles is disposed between the negative electrode current collector and the first negative electrode active material layer.

[0012] According to one aspect, an all-solid-state secondary battery is provided with improved lifespan and charge-discharge characteristics by increasing lithium deposition density and uniformity on a negative electrode current collector and reducing dendrite formation.

[0013] Figures 1a and 1b are cross-sectional views showing the structure of a negative electrode of an all-solid-state secondary battery according to one embodiment.

[0014] Figures 2 to 5 are cross-sectional views of an all-solid-state secondary battery according to an embodiment.

[0015] <Brief explanation of the main symbols in the drawing>

[0016] 1 All-solid-state secondary battery 10 Cathode

[0017] 11. Cathode current collector 12. Cathode active material layer

[0018] 13 Middle layer 20 Cathode

[0019] 21 Negative current collector 22 First negative electrode active material layer

[0020] 40 Intermediate layer 23 Second negative electrode active material layer

[0021] 30 electrolyte layer 50 inert member

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] Although terms such as "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.

[0027] 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.

[0028] Spatially relative terms such as "below," "under," "lower," "above," "upper," and the like may be used herein to readily describe the relationship of one component or feature to another. 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 may be arranged in other orientations (rotated 90 degrees or otherwise rotated), and the spatially relative terms used herein may be interpreted accordingly.

[0029] "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.

[0030] In the present disclosure, “particle diameter” or size refers to the average diameter when the particle is spherical, and refers to the average major axis length when the particle is non-spherical. The particle diameter or size can be measured using a particle size analyzer (PSA) or a scanning electron microscope. The “particle diameter” refers to the average particle diameter, for example. The “average particle diameter” refers to the median particle diameter, D50, for example.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] In this disclosure, "metal" includes both metals and metalloids such as silicon and germanium, in their elemental or ionic states. And in this disclosure, "alloy" means a mixture of two or more metals.

[0035] In this disclosure, "electrode active material" means an electrode material capable of undergoing lithiation and delithiation. In this disclosure, "positive electrode active material" means a positive electrode material capable of undergoing lithiation and delithiation, and "negative electrode active material" means a negative electrode material capable of undergoing lithiation and delithiation.

[0036] In the present disclosure, “lithiation” and “lithiating” mean a process of adding lithium to an electrode active material, and “delithiation” and “delithiating” mean a process of removing lithium from an electrode active material.

[0037] In the present disclosure, “charge” and “charge” mean a process of providing electrochemical energy to a battery, “discharge” and “discharge” mean a process of removing electrochemical energy from a battery, and “positive electrode” and “cathode” mean an electrode where electrochemical reduction and lithiation occur during the discharge process.

[0038] “Cathode” and “anode” refer to the electrodes where electrochemical oxidation and delithiation occur during the discharge process.

[0039] In the present disclosure, “thickness” means average thickness, and “length” means average length.

[0040] In this disclosure, “aspect ratio” means the ratio (L / D) of the length of the long axis (e.g., length L) to the length of the short axis (e.g., diameter D).

[0041] 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.

[0042] 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.

[0043] Hereinafter, an all-solid-state secondary battery according to exemplary implementation examples will be described in more detail.

[0044] [All-solid-state secondary battery]

[0045] An all-solid-state secondary battery according to one embodiment includes a cathode layer; a cathode layer; and a solid electrolyte layer disposed between the cathode layer and the cathode layer, wherein the cathode layer includes a cathode current collector and a first cathode active material layer on one surface of the cathode current collector, and wherein the cathode layer includes a cathode current collector; and a cathode active material layer on one or both surfaces of the cathode current collector, wherein the cathode active material layer includes a sulfide-based cathode active material, and an interlayer including lithium nitrate (LiNO3) particles is disposed between the cathode current collector and the first cathode active material layer.

[0046] In an all-solid-state secondary battery, when a first negative electrode active material layer containing silver and carbon-based materials is used, as charge and discharge progress, silver (Ag) moves to the current collector and exists in solid solution with lithium metal, and many silver particles remain in the area near the current collector during discharge. An example of the first negative electrode active material layer is a Ag / C layer. This may increase cell resistance by increasing the overvoltage due to the insufficient silver (Ag) content at the interface between the solid electrolyte layer and the Ag / C layer. In addition, as repeated charge and discharge progresses, non-uniform dendrites may grow, causing a short circuit and deteriorating the life characteristics.

[0047] Accordingly, the present disclosure provides an all-solid-state secondary battery that forms an intermediate layer containing LiNO3 particles between a negative electrode current collector and a first negative electrode active material layer to induce uniform Li deposition on the negative electrode, thereby suppressing dendrite formation.

[0048] The LiNO3-containing intermediate layer can be directly disposed on the negative electrode current collector.

[0049] [Cathode layer]

[0050] [middle class]

[0051] The intermediate layer according to one embodiment may contain an electrolyte in addition to LiNO3 particles.

[0052] According to another embodiment, the intermediate layer may contain LiNO3, an electrolyte, a reduced decomposition product thereof, or a combination thereof. The presence of such an intermediate layer can improve the ionic conductivity of the negative electrode layer and induce uniform Li deposition on the negative electrode layer, thereby suppressing dendrite formation. As a result, in a non-anode all-solid-state battery system, the density and uniformity of Li deposition can be increased, thereby reducing dendrite formation, thereby realizing a long-life / high-rate all-solid-state secondary battery.

[0053] The electrolyte of the intermediate layer includes a liquid electrolyte, a solid electrolyte, a gel electrolyte, or a combination thereof, and the gel electrolyte may include a polymer gel electrolyte. By applying the intermediate layer containing the electrolyte, the Li electrodeposition density and uniformity are increased, thereby reducing dendrite formation, thereby manufacturing an all-solid-state secondary battery with improved lifespan and rate characteristics.

[0054] The electrolyte may contain, for example, an organic solvent and a lithium salt.

[0055] According to one embodiment, the lithium salt is, for example, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, Li(FSO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(C x F 2x+1SO2)(C y F 2y+1 SO2)(x and y are each 1 to 20), LiCl, LiI or mixtures thereof.

[0056] In another embodiment, the lithium salt may be, for example, a fluorine-containing borate lithium salt.

[0057] Fluorine-containing borate lithium salts have improved high-temperature stability compared to phosphorous lithium salts and can suppress the production of hydrofluoric acid (HF). By including a fluorine-containing borate lithium salt in the lithium salt, the composition of the SEI layer formed during charge and discharge of an all-solid-state secondary battery can be more effectively modified. For example, by increasing the fluorine (F) content of the SEI layer, the structural stability of the SEI layer can be increased, side reactions with organic solvents can be effectively suppressed, and high-temperature cycle characteristics can be improved.

[0058] Fluorine-containing borate lithium salts may include, for example, LiBF4, LiBF3(C2F5), compounds represented by chemical formulae 1-1 to 1-12, or combinations thereof.

[0059] <Chemical Formula 1-1> <Chemical Formula 1-2>

[0060]

[0061] <Chemical Formula 1-3> <Chemical Formula 1-4>

[0062]

[0063] <Chemical Formula 1-5> <Chemical Formula 1-6>

[0064]

[0065] <Chemical Formula 1-7> <Chemical Formula 1-8>

[0066]

[0067] <Chemical Formula 1-9> <Chemical Formula 1-10>

[0068]

[0069] <Chemical Formula 1-11> <Chemical Formula 1-12>

[0070]

[0071] A second negative electrode active material layer is further included between the intermediate layer and the first negative electrode active material layer, and the second negative electrode active material layer is a metal layer, and the metal layer may include lithium or a lithium alloy. Here, the metal layer may include lithium nitrate. In the metal layer, lithium nitrate may be contained by migration of the added lithium nitrate during charging and discharging. In this way, when the metal layer includes lithium nitrate, the ionic conductivity of the negative electrode may be further increased.

[0072] The first negative electrode active material layer may further contain lithium nitrate. When the first negative electrode active material layer contains lithium nitrate, the ionic conductivity of the negative electrode is further increased, thereby enabling the manufacture of an all-solid-state secondary battery with improved high-rate and life-cycle characteristics.

[0073] When the first negative electrode active material layer contains lithium nitrate, the content of lithium nitrate in the intermediate layer is largely controlled compared to the content of lithium nitrate in the first negative electrode active material layer. In this case, the density and uniformity of Li electrodeposition in the metal layer between the first negative electrode active material layer and the intermediate layer are further increased. The content of lithium nitrate in the intermediate layer is 1 to 10 wt%, 1 to 8 wt%, 1 to 7 wt%, 1 to 6 wt%, 1 to 5 wt%, 1 to 4 wt%, or 1.5 to 3 wt% based on the total weight of the intermediate layer, and the content of lithium nitrate in the first negative electrode active material layer is 1 to 5 wt%, 1 to 3 wt%, or 1 to 2 wt% based on the total weight of the first negative electrode active material layer.

[0074] The content of lithium nitrate in the intermediate layer may be arranged so that the content of lithium nitrate has a concentration gradient and decreases from a region close to the negative current collector to a region close to the first negative electrode active material layer. In this way, the content of lithium nitrate in the region close to the negative current collector in the intermediate layer is 1 to 10 wt%, 1 to 9 wt%, 1 to 8 wt%, 1 to 7 wt%, 1 to 6 wt%, 1 to 5 wt%, 1 to 4 wt%, 1 to 3 wt%, or 2 to 3 wt%, and the content of lithium nitrate in the region close to the first negative electrode active material layer in the intermediate layer is 1 to 5 wt%, 1 to 4 wt%, 1 to 3 wt%, or 1 to 2 wt%.

[0075] The thickness of the intermediate layer may be, for example, 1 μm or less, 1 nm to 1000 nm, 10 to 950 nm, 30 to 900 nm, 50 to 850 nm, 80 to 820 nm, 100 to 800 nm, 150 to 750 nm, 200 to 700 nm, 300 to 600 nm, or 300 to 500 nm. When the thickness of the intermediate layer is within the above range, the lithium electrodeposition density and uniformity on the negative electrode increase, thereby enabling the production of an all-solid-state secondary battery with a long life. The thickness of the intermediate layer may be measured, for example, from a scanning electron microscope (SEM) image of a cross-section of the intermediate layer.

[0076] As the organic solvent of the electrolyte, for example, an aprotic organic solvent such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyl tetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxy methane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl pyrropionate, ethyl propionate, etc. can be used. Carbonate solvents such as propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, and diethyl carbonate can be used.

[0077] The organic solvent may be at least one selected from a carbonate compound, an ester compound, an ether compound, a nitrile compound, and a ketone compound.

[0078] As carbonate compounds, ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), etc. can be used.

[0079] As ester compounds, methyl propionate, ethyl propionate, ethyl butyrate, methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, gamma butyrolactone, decanolide, gamma valerolactone, mevalonolactone, caprolactone, etc. can be used; as ether compounds, dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, etc. can be used; as ketone compounds, cyclohexanone, etc. can be used; and as nitrile compounds, acetonitrile (AN), succinonitrile (SN), adiponitrile, butyronitrile, etc. can be used.

[0080] Examples of ether compounds that can be used include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxolane, and other dioxolanes. In addition, examples of ketone compounds that can be used include cyclohexanone. Examples of alcohol solvents that can be used include ethyl alcohol, isopropyl alcohol, and the like. Other solvents that can be used include nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double bond, an aromatic ring, or an ether group); amides such as dimethylformamide; and phosphates such as ethylmethoxyethyl sulfolane, ethylmethyl sulfolane, sulfolane, and trimethyl phosphate.

[0081] The above non-aqueous organic solvents can be used alone or in combination of two or more.

[0082] In addition, when using a carbonate compound, a cyclic carbonate and a chain carbonate can be mixed and used, and the cyclic carbonate and the chain carbonate can be mixed in a volume ratio of 1:1 to 1:9.

[0083] Other solvents that can be used in the electrolyte include, but are not limited to, dimethyl sulfoxide, dimethyl formamide, dimethyl acetamide, tetrahydrofuran, etc. Any organic solvent that can be used in the relevant technical field may be used. For example, the organic solvent may include a mixed solvent of 50 to 95 vol% of a chain carbonate and 5 to 50 vol% of a cyclic carbonate, for example, a mixed solvent of 70 to 95 vol% of a chain carbonate and 5 to 30 vol% of a cyclic carbonate. For example, the organic solvent may be a mixed solvent of three or more organic solvents.

[0084] According to another embodiment, when using a carbonate compound, a cyclic carbonate and a chain carbonate may be mixed and used, and the cyclic carbonate and the chain carbonate may be mixed in a volume ratio of 1:1 to 1:9. And according to one embodiment, the organic solvent includes a carbonate compound, and the carbonate compound includes fluoroethylene carbonate (FEC) and diethyl carbonate (DEC), and the mixing weight ratio of the FEC and DEC is 1:10 to 1:1, 1:8 to 1:1, 1:5 to 1:1, or 1:3 to 1:1. By using such an organic solvent, a gel polymer electrolyte with improved ionic conductivity can be manufactured. Therefore, an all-solid-state secondary battery with improved initial capacity and lifespan characteristics can be manufactured.

[0085] According to one embodiment, the electrolyte includes a nitrile compound, a lithium salt, and a carbonate compound, and the lithium salt may include lithium difluorodioxalatoborate (LiDFOB) and lithium tetrafluoroborate (LiBF4).

[0086] The nitrile compound is, for example, butyronitrile, valeronitrile, propionitrile, acetonitrile, or a combination thereof. The content of the nitrile compound is 3 wt% to 45 wt%, 5 wt% to 40 wt%, or 5 wt% to 35 wt% based on 100 wt% of the total weight of the gel polymer electrolyte.

[0087] The intermediate layer (13) may include, for example, a binder. By additionally including a binder in the intermediate layer (13), the bonding strength between the positive electrode current collector (11) and the positive electrode active material layer (12) may be further improved. The binder included in the intermediate layer (13) may be, for example, a conductive binder or a non-conductive binder. The conductive binder may be, for example, an ion-conductive binder and / or an electron-conductive binder. A binder having both ion-conductive and electron-conductive properties may belong to both an ion-conductive binder and an electron-conductive binder.

[0088] The binder included in the intermediate layer may be selected from binders used in the positive electrode active material layer or the negative electrode active material layer. The intermediate layer may include the same binder as the binder used in the positive electrode active material layer or the negative electrode active material layer. The binder included in the intermediate layer is, for example, a fluorinated binder. The fluorinated binder included in the intermediate layer is, for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), or a combination thereof. The intermediate layer may be, for example, a binding layer including a binder. The intermediate layer may be, for example, a conductive layer including a binder and a carbon-based conductive material.

[0089] In the intermediate layer, lithium nitrate exists in the form of particles in the intermediate layer-forming composition containing lithium nitrate and an electrolyte, which induces a uniform lithium nucleation process, suppresses lithium dendrite growth on the negative electrode, and uniformly forms lithium electrodeposition. Therefore, lithium mobility on the negative electrode increases. In order for lithium nitrate to exist in the form of particles in the composition, more lithium nitrate is added than is dissolved in the solvent constituting the composition. The average size of the lithium nitrate particles is 1 nm to 2 um, 10 nm to 1.8 um, 20 nm to 1.8 um, 30 nm to 1.6 um, 50 nm to 1.5 um, 70 nm to 1.3 um, or 100 nm to 1 um. By using the intermediate layer containing lithium nitrate having such an average size, a high lithium electrodeposition density and uniform lithium deposition can be achieved. In this specification, the average particle size refers to the average particle diameter when the particles are spherical, and refers to the average major axis length when the particles are non-spherical.

[0090] The intermediate layer can be disposed on the negative electrode current collector (21), for example, in a dry or wet manner. The intermediate layer (40) can be disposed on the negative electrode current collector (21) in a wet manner, for example, by spin coating, dip coating, or the like. The intermediate layer (40) may not include a binder. The intermediate layer (13) can be disposed on the negative electrode current collector (21), for example, by coating a composition including LiNO3, an electrolyte, a binder, and a solvent on the surface of the electrode current collector and drying it. The intermediate layer (40) can have a single-layer structure or a multi-layer structure including a plurality of layers. The multi-layer structure can be a two-layer structure, a three-layer structure, a four-layer structure, or the like.

[0091] Referring to FIG. 1a and FIG. 1b, the structure of the negative electrode of an all-solid-state secondary battery according to one embodiment is shown.

[0092] Referring to Fig. 1a, the negative electrode has an intermediate layer (40) containing lithium nitrate disposed on a negative electrode current collector (21), and a first negative electrode active material layer (22) is formed thereon. The first negative electrode active material layer (22) contains, for example, a negative electrode active material and a binder (22b). As the negative electrode active material, a carbon-based material (22a) carrying silver can be used.

[0093] After charging, a metal layer, which is a second negative electrode active material layer (23), can be formed between the intermediate layer (40) and the first negative electrode active material layer (22). Here, the metal layer is a lithium precipitation layer.

[0094] The cathode according to the present invention exhibits improved lithium deposition density and uniformity compared to a cathode without the aforementioned intermediate layer. Therefore, using this cathode, an all-solid-state secondary battery with a long lifespan can be manufactured.

[0095] Referring to FIGS. 2 to 5, an all-solid-state secondary battery (1) includes a positive electrode layer (10); a negative electrode layer (20); and a solid electrolyte layer (30) between the positive electrode layer (10) and the negative electrode layer (20). The positive electrode layer (10) includes a positive electrode current collector (11) and a positive electrode active material layer (12) disposed on one or both surfaces of the positive electrode current collector (11). The positive electrode active material layer (12) includes a positive electrode active material and a first solid electrolyte. The solid electrolyte layer (30) may include a sulfide-based solid electrolyte.

[0096] The negative electrode layer (20) includes a negative electrode current collector (21) and a first negative electrode active material layer (22) on one surface of the negative electrode current collector (21).

[0097] [First negative electrode active material layer: negative electrode active material]

[0098] Referring to FIGS. 2 to 5, the negative electrode (20) includes a first negative electrode active material layer (22). The first negative electrode active material layer (22) includes, for example, a negative electrode active material and a binder.

[0099] An intermediate layer (40) may be placed between the first negative electrode active material layer (22) and the negative electrode current collector (21).

[0100] 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.

[0101] 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.

[0102] 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 metalloid negative electrode active material.

[0103] Carbon-based negative electrode materials include, for example, amorphous carbon, crystalline carbon, porous carbon, or a combination thereof.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] 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 The y (0 <x≤1, 0<y≤1) 또는 이들의 조합을 포함할 수 있다. 금속과 금속산화물의 복합체는 예를 들어 Au와 Au x The y (0 <x≤2, 0<y≤3)의 복합체, Pt와 Pt x The y (0 <x≤1, 0<y≤2)의 복합체, Pd와 Pd x The y (0 <x≤1, 0<y≤1)의 복합체, Si와 Si x The y (0 <x≤1, 0<y≤2)의 복합체, Ag 와 Ag x The y (0 <x≤2, 0<y≤1)의 복합체, Al과 Al x The y (0 <x≤2, 0<y≤3)의 복합체, Bi와 Bi x The y (0 <x≤2, 0<y≤3)의 복합체, Sn과 Sn x The y (0 <x≤1, 0<y≤2)의 복합체, Te과 Te x The y (0 <x≤1, 0<y≤3), Zn과 Zn x The y (0 <x≤1, 0<y≤1)의 복합체, 또는 이들의 조합을 포함할 수 있다.

[0111] 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.

[0112] 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. The carbon-based support having a particle size in this range 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.

[0113] [First negative electrode active material layer: binder]

[0114] The first negative electrode active material layer (22) includes a binder. The binder may be, 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.

[0115] 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).

[0116] [First negative electrode active material layer: other additives]

[0117] The first negative electrode active material layer (22) may further include additives used in a conventional all-solid-state secondary battery (1), such as fillers, coating agents, dispersants, and ion conductive aids.

[0118] [First negative electrode active material layer: solid electrolyte]

[0119] 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.

[0120] 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).

[0121] [First negative electrode active material layer: charging capacity]

[0122] 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.

[0123] The maximum charging voltage is determined by the type of cathode active material. The maximum charging 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 charging voltage of Li2S or Li2S composite is Li / Li + can be 2.5 V for Li2S or Li2S complex. 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 an all-solid-state half-cell using lithium metal as a counter electrode.

[0124] The initial charge capacity of each of the positive electrode active material layer (12) and the first negative electrode active material layer (22) is a constant current density, for example, 0.1 mA / cm 2can be directly measured using an all-solid-state half-cell. For the positive electrode, the measurement is made from the first open circuit voltage (OCV) to the maximum charge voltage, for example, 3.0 V (vs. Li / Li + ) can be performed by charging to an operating voltage of up to 0.01 V for the negative electrode, for example, lithium metal, from a second open circuit voltage (OCV). For example, an all-solid-state half-cell having a positive electrode active material layer can be charged to an operating voltage of up to 0.1 mA / cm from a first open circuit voltage (OCV) to 3.0 V. 2 The all-solid-state 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 The all-solid-state half-cell having the positive electrode active material layer can be charged from the 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.

[0125] 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).

[0126] 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.

[0127] [Second negative electrode active material layer]

[0128] Referring to FIG. 3, the all-solid-state secondary battery (1) may further include, after being charged, a second negative electrode active material layer (23) disposed, for example, between the intermediate layer (40) and the first negative electrode active material layer (22). The second negative electrode active material layer (23) 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 (23) 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 (23) 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 (23) is deposited between the intermediate layer (40) and the first negative electrode active material layer (22), for example, during the charging process of an all-solid-state secondary battery (1).

[0129] The thickness of the second negative electrode active material layer (23) is not particularly 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 (23) to perform the role of a lithium reservoir. If the thickness of the second negative electrode active material layer (23) 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.

[0130] Alternatively, in the all-solid-state secondary battery (1), the second negative electrode active material layer (23) may be disposed between the intermediate layer (40) and the first negative electrode active material layer (22), for example, before assembling the all-solid-state secondary battery (1). When the second negative electrode active material layer (23) is disposed between the intermediate layer (40) 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 (23) acts as a lithium reservoir because it is a metal layer containing lithium. For example, a lithium foil may be disposed between the intermediate layer (40) and the first negative electrode active material layer (22) before assembling the all-solid-state secondary battery (1).

[0131] 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 (23) 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 beginning 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 (23) 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 (23), 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 (23), it functions as a protective layer for the second negative electrode active material layer (23), 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 (23) is placed by charging after assembling the all-solid-state secondary battery (1), the negative electrode (20), i.e., the intermediate layer (40) 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).

[0132] [Cathode current collector]

[0133] The negative electrode layer (20) includes a negative electrode current collector (21). 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), nickel (Ni), etc., but is not necessarily limited thereto, and any material that is used as an electrode current collector in the relevant technical field may 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.

[0134] The all-solid-state secondary battery (1) may further include a thin film (not shown) containing an element capable of forming an alloy with lithium on one surface of the negative electrode current collector (21). The thin film is disposed between the negative electrode current collector (21) and the first negative electrode active material layer (22). The thin film contains, for example, an element 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 may be composed of one of these metals or an alloy of several types of metals. By placing the thin film on one surface of the negative electrode current collector (21), for example, the deposition shape of the second negative electrode active material layer (23) deposited between the thin film 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.

[0135] The thickness of the thin film is, for example, 1 nm to 800 nm, 10 nm to 700 nm, 50 nm to 600 nm, or 100 nm to 500 nm. If the thickness of the thin film (23) is less than 1 nm, it may be difficult for the function of the thin film to be exerted. If the thickness of the thin film is excessively thick, the thin film itself may absorb lithium, which may reduce the amount of lithium precipitated from the negative electrode, thereby lowering the energy density of the all-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 a thin film in the relevant technical field may be used.

[0136] 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 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 negative electrode current collector (21) may additionally include a metal piece and / or a lead tab. The metal layer may act as an electrochemical fuse and be cut in the event of an overcurrent to prevent a short circuit. The limit current and the maximum current may be controlled by adjusting the thickness of the metal layer. The metal layer may 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 negative electrode current collector (21) decreases, thereby improving the stability of the all-solid-state secondary battery in the event of a short circuit. A lead tab may be added on the metal layer for connection to the outside. The lead tab may be welded to the metal layer or the metal layer / base film laminate by ultrasonic welding, laser welding, spot welding, or the like. When the base film and / or the metal layer are melted during welding, the metal layer may be electrically connected to the lead tab.In order to strengthen the welding between the metal layer and the lead tab, a metal chip may be added between the metal layer and the lead tab. The metal chip may be a thin piece of the same material as the metal of the metal layer. The metal chip may be, for example, a metal foil, a metal mesh, etc. The metal chip may be, for example, aluminum foil, copper foil, SUS foil, etc. By placing the metal chip on the metal layer and then welding it with the lead tab, the lead tab may be welded to the metal chip / metal layer laminate or the metal chip / metal layer / base film laminate. During welding, the base film, the metal layer, and / or the metal chip may melt, so that the metal layer or the metal layer / metal chip laminate may be electrically connected to the lead tab. The metal chip and / or the lead tab may be added to a portion of the metal layer. The thickness of the base film may be, for example, 1 to 50 ㎛, 1.5 to 50 ㎛, 1.5 to 40 ㎛, or 1 to 30 ㎛. By having a thickness of the base film in this range, the weight of the electrode assembly can be more effectively reduced. The melting point of the base film can be, for example, 100 to 300°C, 100 to 250°C or less, or 100 to 200°C. By having a melting point in this range, the base film can be melted and easily bonded to the lead tab during the process of welding the lead tab. A surface treatment, such as corona treatment, can be performed on the base film to improve the adhesion between the base film and the metal layer. The thickness of the metal layer can be, for example, 0.01 to 3 μm, 0.1 to 3 μm, 0.1 to 2 μm, or 0.1 to μm. By having a thickness of the metal layer in this range, the stability of the electrode assembly can be secured while maintaining conductivity. The thickness of the metal piece can be, for example, 2 to 10 μm, 2 to 7 μm, or 4 to 6 μm. By having the metal piece in this range of thickness, the connection between the metal layer and the lead tab can be performed more easily.By having this structure, the negative electrode current collector (21) can reduce the weight of the negative electrode and consequently improve the energy density of the negative electrode and the all-solid-state secondary battery.

[0137] [Anode layer]

[0138] Referring to FIGS. 2 to 5, the positive electrode (10) includes a positive electrode current collector (11); and a positive electrode active material layer (12) disposed on one or both sides of the positive electrode current collector (11). The positive electrode active material layer (12) includes a positive electrode active material and a first solid electrolyte.

[0139] [Cathode active material layer: Cathode active material]

[0140] The content of the positive electrode active material included in the positive electrode active material layer (12) may be, for example, 10 wt% to 99 wt%, 50 wt% to 99 wt%, 70 wt% to 95 wt%, or 80 wt% to 95 wt% of the total weight of the positive electrode active material layer (12). If the content of the positive electrode active material is excessively reduced, the energy density of the all-solid-state secondary battery (1) is lowered. If the content of the positive electrode active material is excessively increased, the deterioration of the all-solid-state secondary battery (1) may be accelerated due to a change in the volume of the positive electrode during charge and discharge.

[0141] The cathode active material included in the cathode active material layer (12) is a cathode active material that can reversibly absorb and desorb lithium ions.

[0142] The cathode active material includes, for example, an oxide-based cathode active material, a sulfide-based cathode active material, or a combination thereof.

[0143] The oxide-based cathode active material includes, for example, a lithium transition metal oxide, a metal oxide, or a combination thereof. The lithium transition metal oxide includes, for example, lithium cobalt oxide, lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide, lithium nickel cobalt mangense oxide, lithium manganate, lithium iron phosphate, or a combination thereof. The lithium oxide includes, for example, iron oxide, vanadium oxide, or a combination thereof.

[0144] Sulfide-based cathode active materials include, for example, nickel sulfide, copper sulfide, Li2S, Li2S-containing complexes, or combinations thereof.

[0145] The oxide-based cathode active material may be, for example, one or more composite oxides of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof. The lithium-containing oxide-based cathode active material may be, for example, Li. a A 1-b B' b D2 (in the above formula, 0.90 ≤ a ≤ 1, and 0 ≤ b ≤ 0.5); Li a E 1-b B' b O 2-c D c (In the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); LiE 2-b B' b O 4-c D c (In the above formula, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Lia Ni 1-b-c Co b B' c D α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Co b B' c O 2-α F' α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Co b B' c O 2-α F' α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b B' c D α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Mn b B' c O 2-α F' α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b B' c O 2-α F' α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni b E c G dO2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1); Li a Ni b Co c Mn d G e O2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0.001 ≤ e ≤ 0.1); Li a NiG b O2 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a CoG b O2 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a MnG b O2 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a Mn2G b O4 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); LiV2O5; LiI'O2; LiNiVO4; Li (3-f) J2(PO4)3(0 ≤ f ≤ 2); Li (3-f) Fe2(PO4)3(0 ≤ f ≤ 2); may include a compound represented by any one of the chemical formulas of LiFePO4.

[0146] In the chemical formula representing the above-described compound, A is Ni, Co, Mn, or a combination thereof; B' is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F' is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; I' is Cr, V, Fe, Sc, Y, or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof. It is also possible to use a compound having a coating layer added to the surface of the above-described compound, or it is also possible to use a mixture of the above-described compound and the compound having a coating layer added. The coating layer added to the surface of the above-mentioned compound includes a coating element compound of, for example, an oxide, a hydroxide, an oxyhydroxide of the coating element, an oxycarbonate of the coating element, or a hydroxycarbonate of the coating element of the coating element. The compound forming the coating layer is amorphous or crystalline. The coating elements included in the coating layer are Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof. The method for forming the coating layer is selected within a range that does not adversely affect the physical properties of the positive electrode active material. The coating method includes, for example, spray coating and dipping. Since the specific coating method is well understood by those working in the relevant field, a detailed description thereof will be omitted.

[0147] The oxide-based cathode active material may include, for example, a lithium transition metal oxide represented by the following chemical formulas 2 to 9:

[0148] <Chemical Formula 2>

[0149] Li a Ni x Co y M z O2-b A b

[0150] In the above chemical formula 2, 1.0≤a≤1.2, 0≤b≤0.2, 0.8≤x<1, 0≤y≤0.3, 0 <z≤0.3, 및 x+y+z=1이고,

[0151] M is manganese (Mn), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B), or a combination thereof,

[0152] A is F, S, Cl, Br or a combination thereof,

[0153] <Chemical Formula 3>

[0154] LiNi x Co y Mn z O2

[0155] <Chemical Formula 4>

[0156] LiNi x Co y Al z O2

[0157] In the above chemical formulas 3 and 4, 0.8≤x≤0.95, 0≤y≤0.2, 0 <z≤0.2 및 x+y+z=1이며,

[0158] <Chemical Formula 5>

[0159] LiNi x Co y Mn z Al w O2

[0160] In the above chemical formula 5, 0.8≤x≤0.95, 0≤y≤0.2, 0 <z≤0.2, 0<w≤0.2, 및 x+y+z+w=1이며,

[0161] <Chemical Formula 6>

[0162] Li a Co x M y O 2-b A b

[0163] In the above chemical formula 6, 1.0≤a≤1.2, 0≤b≤0.2, 0.9≤x≤1, 0≤y≤0.1, and x+y=1,

[0164] M is manganese (Mn), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B), or a combination thereof,

[0165] A is F, S, Cl, Br or a combination thereof,

[0166] <Chemical Formula 7>

[0167] Li a Ni x Mn y M' z O 2-b A b

[0168] In the above chemical formula 7, 1.0≤a≤1.2, 0≤b≤0.2, 0 <x≤0.3, 0.5≤y<1, 0<z≤0.3, 및 x+y+z=1이고,

[0169] M' is cobalt (Co), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B) or a combination thereof,

[0170] A is F, S, Cl, Br or a combination thereof,

[0171] <Chemical Formula 8>

[0172] Li a M1 x M2 y PO 4-b X b

[0173] In the above chemical formula 8, 0.90≤a≤1.1, 0≤x≤0.9, 0≤y≤0.5, 0.9 <x+y<1.1, 0≤b≤2이며,

[0174] M1 is chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr) or a combination thereof,

[0175] M2 is magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), titanium (Ti), zinc (Zn), boron (B), niobium (Nb), gallium (Ga), indium (In), molybdenum (Mo), tungsten (W), aluminum (Al), silicon (Si), chromium (Cr), vanadium (V), scandium (Sc), yttrium (Y) or a combination thereof, and X is O, F, S, P or a combination thereof.

[0176] <Chemical Formula 9>

[0177] Li a M3 z PO4

[0178] In the above chemical formula 9, 0.90≤a≤1.1, 0.9≤z≤1.1,

[0179] M3 is chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr), or a combination thereof.

[0180] The oxide-based cathode active material may be covered by a covering layer. The covering layer may be any material known as a covering layer for cathode active materials of all-solid-state secondary batteries. Examples of the covering layer include Li2O-ZrO2 (LZO).

[0181] The size of the oxide-based cathode active material may be, for example, 0.1 to 30 μm, 0.5 to 20 μm, or 1 to 15 μm. The oxide-based cathode active material may be, for example, a single-crystal particle or a polycrystalline particle.

[0182] The sulfide-based cathode active material may include, for example, a Li2S-containing complex. The Li2S-containing complex includes, for example, a complex of Li2S and carbon, a complex of Li2S, carbon, and a solid electrolyte, a complex of Li2S and a solid electrolyte, a complex of Li2S and a lithium salt, a complex of Li2S, a lithium salt, and carbon, a complex of Li2S and a metal carbide, a complex of Li2S, carbon, and a metal carbide, a complex of Li2S and a metal nitride, a complex of Li2S, carbon, and a metal nitride, or a combination thereof.

[0183] 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, fiber form, etc., but is not limited thereto, and any method used as carbon in the relevant technical field 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 relevant technical field may be, for example, milling, heat treatment, deposition, etc., but is not necessarily limited thereto, and any method used in the relevant technical field may be used.

[0184] A 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, such as 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 a halogen element. 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 and the oxide-based solid electrolyte refer to the sulfide-based solid electrolyte and the oxide-based solid electrolyte of the solid electrolyte layer described above.

[0185] The composite of Li2S and a solid electrolyte includes a solid electrolyte. The solid electrolyte refers to the composite of Li2S, carbon, and a solid electrolyte described above.

[0186] The complex of Li2S and a lithium salt comprises a lithium salt compound. 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, LiI3, 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. The complex of Li2S and a solid electrolyte includes a solid electrolyte. The solid electrolyte refers to the solid electrolyte used in the complex of Li2S, carbon, and a solid electrolyte described above. The complex of Li2S and the solid electrolyte includes, for example, a complex of Li2S and one or more lithium salts selected from LiF, LiCl, LiBr, LiI, LiH, Li2S, Li2O, Li2Se, Li2Te, Li3N, Li3P, Li3As, Li3Sb, LiI3 and LiB3.

[0187] The complex of Li2S and a lithium salt and carbon includes a lithium salt compound and carbon. Carbon refers to the complex of Li2S and carbon described above.

[0188] 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 , V2CT x , Ti3C2T x , (V 0.5 , Cr 0.5 )3C2T x , Ti3CNT x , Ta4C3T x , Nb4C3T x or a combination thereof. The surface of the two-dimensional metal carbide is terminated with O, OH and / or F.

[0189] The complex of Li2S, carbon, and metal carbide includes 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.

[0190] The complex of Li2S and metal nitride includes a metal nitride. The metal nitride is, for example, a two-dimensional metal nitride. The two-dimensional metal nitride is, for example, M n+1 N n T x (M is a transition metal, T is a terminal group, T is O, OH and / or F, n=1, 2, or 3, 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.

[0191] A complex of Li2S, carbon, and a metal nitride includes carbon and a metal nitride. Carbon refers to the complex of Li2S and carbon described above. Metal carbide refers to the complex of Li2S and a metal nitride described above.

[0192] The Li2S-containing composite may further include, for example, a second fibrous sulfide-based solid electrolyte (not shown). The Li2S-containing composite may be a composite of Li2S and the second fibrous sulfide-based solid electrolyte, or a composite of Li2S and the second fibrous sulfide-based solid electrolyte and the above-described carbon, solid electrolyte, lithium salt, metal carbide, or metal nitride.

[0193] By further including a second fibrous sulfide-based solid electrolyte in the Li2S-containing composite, the deterioration of the all-solid-state secondary battery can be further suppressed and the cycle characteristics of the all-solid-state secondary battery can be further improved. The size of the second fibrous sulfide-based solid electrolyte can be smaller than the size of the first fibrous sulfide-based solid electrolyte (100). The length and / or thickness of the second fibrous sulfide-based solid electrolyte can be 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less of the length and / or thickness of the first fibrous sulfide-based solid electrolyte (100), respectively. The length and / or thickness of the second fibrous sulfide-based solid electrolyte may be 0.1 to 50%, 0.5 to 40%, 1 to 30%, 1 to 20%, or 1 to 10% of the length and / or thickness of the first fibrous sulfide-based solid electrolyte (100), respectively. The second fibrous sulfide-based solid electrolyte may have, for example, the same shape as the first fibrous sulfide-based solid electrolyte (100) but a smaller size. The second fibrous sulfide-based solid electrolyte may be easily distributed in the Li2S-containing composite due to the reduced length and / or thickness. The second fibrous sulfide-based solid electrolyte may further suppress deterioration of the all-solid-state secondary battery and further improve cycle characteristics of the all-solid-state secondary battery due to the reduced length and / or thickness.

[0194] The size of the sulfide-based 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.

[0195] The shape of the cathode active material is, for example, a spherical particle shape, an elliptical particle shape, etc. The particle size of the cathode active material is not particularly limited and is within the range applicable to cathode active materials of conventional all-solid-state secondary batteries.

[0196] The cathode active material may include, for example, a composite cathode active material. The composite cathode active material may include, for example, a core including a lithium transition metal oxide; and a shell disposed along a surface of the core.

[0197] The above positive electrode active material layer includes a lithium sulfide-based positive electrode active material.

[0198] [Cathode active material layer: first solid electrolyte]

[0199] Referring to FIGS. 1 to 5, the positive electrode active material layer (12) includes a first solid electrolyte. The first solid electrolyte included in the positive electrode active material layer (12) may be the same as or different from the solid electrolyte included in the solid electrolyte layer (30).

[0200] The first solid electrolyte included in the positive electrode active material layer (12) may have a smaller average D50 particle diameter than the solid electrolyte included in the solid electrolyte layer (30). For example, the average D50 particle diameter of the first solid electrolyte included in the positive electrode active material layer (12) 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 diameter of the solid electrolyte included in the solid electrolyte layer (30). The average D50 particle diameter is, for example, a median particle diameter (D50). The median particle diameter (D50) is, for example, the size of particles corresponding to 50% of the cumulative volume, calculated from the side of particles having a small particle size in a size distribution of particles measured by laser diffraction.

[0201] The content of the first solid electrolyte included in the positive electrode active material layer (12) may be, for example, 1 wt% to 40 wt%, 1 wt% to 30 wt%, 1 wt% to 20 wt%, or 1 wt% to 10 wt% of the total weight of the positive electrode active material layer (12).

[0202] The first solid electrolyte may be, for example, a sulfide-based solid electrolyte. The sulfide-based solid electrolyte may be, for example, Li2S-P2S5, Li2S-P2S5-LiX, where X is a halogen element, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, 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 sulfide-based solid electrolyte is manufactured by treating starting materials such as Li2S and P2S5 by a melting rapid cooling method or a mechanical milling method. In addition, heat treatment may be performed after the treatment. The solid electrolyte may be amorphous, crystalline, or a mixture thereof. In addition, the solid electrolyte may be, for example, one containing sulfur (S), phosphorus (P), and lithium (Li) as at least constituent elements among the above-described sulfide-based solid electrolyte materials. For example, the solid electrolyte may be a material containing Li2S-P2S5. When using a sulfide-based solid electrolyte material containing Li2S-P2S5 to form a solid electrolyte, the mixing molar ratio of Li2S and P2S5 is, for example, in the range of Li2S:P2S5=20:80 to 90:10, 25:75 to 90:10, 30:70 to 70:30, 40:60 to 60:40.

[0203] The sulfide-based solid electrolyte may include, for example, an argyrodite type solid electrolyte represented by the following chemical formula 10:

[0204] <Chemical Formula 10>

[0205] Li + 12-n-x A n+ X 2- 6-x Y - x

[0206] In chemical formula 10, A is P, As, Ge, Ga, Sb, Si, Sn, Al, In, Ti, V, Nb or Ta, X is S, Se or Te, Y is Cl, Br, I, F, CN, OCN, SCN or N3, and 1≤n≤5, 0≤x≤2. The sulfide-based solid electrolyte is, for example, Li 7-x PS 6-x Cl x , 0≤x≤2, Li7-x PS 6-x Br x , 0<x<2, and Li 7-x PS 6-x I x , may be an argyrodite-type compound including at least one selected from 0<x<2. The sulfide-based solid electrolyte may be, for example, an argyrodite-type compound including at least one selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0207] The density of the argyrodite-type solid electrolyte may be 1.5 to 2.0 g / cc. Since the argyrodite-type solid electrolyte has a density of 1.5 g / cc or more, the internal resistance of the all-solid-state secondary battery is reduced, and penetration of the solid electrolyte layer by Li can be effectively suppressed.

[0208] [Cathode active material layer: conductive material]

[0209] The cathode active material layer (12) may further include a conductive material. The conductive material may be, for example, a carbon-based material, a metal-based material, or a combination thereof.

[0210] The conductive material content included in the positive electrode active material layer (12) may be, for example, 1 wt% to 30 wt%, 1 wt% to 20 wt%, or 1 wt% to 10 wt% of the total weight of the positive electrode active material layer (12).

[0211] The metal-based material may be, but is not limited to, metal powder, metal fiber, or a combination thereof, and any metal-based material used as a conductive material in the relevant technical field may be used.

[0212] The carbon-based material may include, for example, amorphous carbon. By including amorphous carbon in the carbon-based material, side reactions between the carbon-based material and the first solid electrolyte can be suppressed. Accordingly, the cycle characteristics of the all-solid-state secondary battery (1) including the carbon-based material can be further improved.

[0213] 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, or the like; graphite, activated carbon, or a combination thereof. The form of the carbon-based material is not limited to, but may include, for example, particle form, sheet form, flake form, etc., and any form that can be used as a carbon-based material in the relevant technical field is possible.

[0214] The carbon-based material may include, for example, a fibrous carbon-based material. By including the fibrous carbon-based material in the composite, the electronic conductivity of the composite may be further improved. By including the fibrous carbon-based material in the composite, electronic conduction may be more easily performed from the surface to the interior of the composite. The internal resistance of the composite cathode active material including the composite may be reduced, and the cycle characteristics of a secondary battery including the composite cathode active material may be further improved. The aspect ratio of the fibrous carbon-based material may 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 may 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 may 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 is improved, and the imbalance of local electronic conductivity within the composite can be further alleviated. The fibrous carbon-based material may include, for example, a carbon nanostructure. The carbon nanostructure may include, for example, a carbon nanofiber (CNF), a carbon nanotube (CNT), a carbon nanobelt, a carbon nanorod, or a combination thereof. The carbon nanostructure may form a primary carbon nanostructure composed of a single carbon nanostructure, and a secondary carbon nanostructure in which a plurality of carbon nanostructures are aggregated.

[0215] 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.

[0216] Secondary carbon nanostructures are, for example, structures formed by assembling primary carbon nanostructures in whole or in part to form bundles or bundle-type structures. The secondary carbon nanostructures may include, for example, bundle-type carbon nanostructures, rope-type carbon nanostructures, or combinations 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 the primary carbon nanostructure by, for example, dispersing it in a solvent or the like and then used in the preparation of a composite.

[0217] [Cathode active material layer: binder]

[0218] 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, 0.1 wt% to 10 wt%, 0.5 to 5 wt%, or 0.5 to 2 wt% of the total weight of the positive electrode active material layer (12). The binder may be omitted.

[0219] [Cathode active material layer: other additives]

[0220] 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.

[0221] As fillers, coating agents, dispersants, ion conductivity aids, etc. that can be included in the positive electrode active material layer (12), known materials generally used in electrodes of all-solid-state secondary batteries can be used.

[0222] [Cathode collector]

[0223] Referring to FIGS. 2 to 5, the positive electrode layer (10) includes a positive electrode current collector (11).

[0224] 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.

[0225] 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. For more specific details regarding the base film, metal layer, metal chip, and lead tab of the positive electrode current collector (11), refer to the negative electrode current collector (21) described above. By having this structure, the positive electrode current collector (11) can reduce the weight of the negative electrode, and consequently, improve the energy density of the positive electrode and the all-solid-state secondary battery.

[0226] [Inert Absence]

[0227] Referring to FIGS. 4 and 5, the positive electrode (10) includes a positive electrode current collector (11), a positive electrode active material layer (12) disposed on one side of the positive electrode current collector, and an inactive member (40) disposed on one side of the positive electrode (10). In 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 electrolyte layer (30) and the positive electrode current collector (11) facing the electrolyte layer (30). The inactive member (40) is not disposed on one side of the positive electrode current collector (11). The electrolyte layer (30) may be, for example, a solid electrolyte layer.

[0228] 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.

[0229] 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.

[0230] 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.

[0231] 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).

[0232] 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.

[0233] The area of ​​the anode (10) is smaller than the area of ​​the electrolyte layer (30) 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.

[0234] 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).

[0235] 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.

[0236] 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).

[0237] The area of ​​the positive electrode (10) is smaller than the area of ​​the negative electrode current collector (21). The area 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 of ​​the negative electrode current collector (21). The area 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 of ​​the negative electrode current collector (21). The area of ​​the negative electrode current collector (21) is, for example, the same as the area of ​​the negative electrode (20). The area of ​​the negative electrode current collector (21) is, for example, the same as the area of ​​the first negative electrode active material layer (22).

[0238] 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%.

[0239] 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).

[0240] 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.

[0241] 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.

[0242] The inert member (40) is, for example, a flame-retardant inert member. The flame-retardant inert member can prevent 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). The flame-retardant inert member may include a matrix and an additive.

[0243] 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.

[0244] [Solid electrolyte layer: solid electrolyte]

[0245] Referring to FIGS. 2 to 5, an all-solid-state secondary battery (1) is disposed between a positive electrode layer (10) and a negative electrode layer (20), and includes a solid electrolyte layer (30) containing a sulfide-based solid electrolyte. The solid electrolyte layer (30) may further include, for example, a solid electrolyte, or a combination of a solid electrolyte and a gel electrolyte.

[0246] The solid electrolyte may include, for example, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a polymer solid electrolyte, or a combination thereof.

[0247] The solid electrolyte is, for example, a sulfide-based solid electrolyte. A sulfide-based solid electrolyte has a higher density than a sulfide-based solid electrolyte, for example, 1×10 at room temperature. -5It 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 element, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, 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, 및 Li 7-x PS 6-x I x , 0 <x<2 중에서 선택된 하나 이상을 포함할 수 있다. 산화물계 고체전해질은 예를 들어 Li, O 및 전이금속 원소를 포함하며, 다른 원소를 선택적으로 더 포함할 수 있다. 산화물계 고체전해질은 예를 들어 상온에서 1×10 -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 among oxide-based solid electrolytes used in the solid electrolyte layer.

[0248] 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.

[0249] Oxide solid electrolytes include, for example, Li 1+x+yAl 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.

[0250] 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.

[0251] 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, polymethyl methacrylate (PMMA, poly(methylmethacrylate), polyethylene glycol (PEG), polyacrylonitrile (PAN), polytetrafluoroethene (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-diphenylatlacene-2-sulfonate 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, Li(FSO2)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.

[0252] A gel electrolyte is, for example, a polymer gel electrolyte. A gel electrolyte can have a gel state without containing a polymer, for example.

[0253] The 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, for example, without containing a liquid. 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; a mixture of an ionic liquid and an organic solvent; or a mixture of a lithium salt, an ionic liquid, and an organic solvent. The polymer used in the polymer gel electrolyte may be selected from among the polymers used in the solid polymer electrolyte. The organic solvent may be selected from among the organic solvents used in the liquid electrolyte. The organic solvent may be the same as the organic solvent of the electrolyte described above. The lithium salt may be selected from among the lithium salts used in the solid polymer electrolyte. Ionic liquids are salts that have a melting point below room temperature, are composed only of ions, and are liquid at room temperature or molten at room temperature. The ionic liquid may include, for example, one or more cations selected from among a) ammonium compounds, pyrrolidinium compounds, pyridinium compounds, pyrimidinium compounds, imidazolium compounds, piperidinium compounds, pyrazolium compounds, oxazolium compounds, pyridazinium compounds, phosphonium compounds, sulfonium compounds, triazolium compounds, and mixtures thereof, and b) one or more anions selected from among BF4-, PF6-, AsF6-, SbF6-, AlCl4-, HSO4-, ClO4-, CH3SO3-, CF3CO2-, Cl-, Br-, I-, SO4-, CF3SO3-, (FSO2)2N-, (C2F5SO2)2N-, (C2F5SO2)(CF3SO2)N-, and (CF3SO2)2N-. A polymer solid electrolyte can 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, for example, a compound containing 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.

[0254] [Solid electrolyte layer: binder]

[0255] The solid electrolyte layer (30) may include, for example, a binder. The binder included in the solid electrolyte layer (30) 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 of the solid electrolyte layer (30) may be the same as or different from the binder included in the positive electrode active material layer (12) and the negative electrode active material layer (22). The binder may be omitted.

[0256] The binder content included in the solid electrolyte layer (30) is 0.1 to 10 wt%, 0.1 to 5 wt%, 0.1 to 3 wt%, 0.1 to 1 wt%, 0 to 0.5 wt%, or 0 to 0.1 wt% with respect to the total weight of the solid electrolyte layer (30).

[0257] A solid electrolyte layer according to an embodiment of the present invention is prepared by mixing a sulfide-based solid electrolyte and a binder to prepare a composition for forming a solid electrolyte layer. The composition for forming a solid electrolyte layer can be provided on a substrate and heat-treated to form a solid electrolyte layer.

[0258] The above heat treatment can be performed at 50 to 200°C, 100 to 180°C, or 110 to 150°C. By performing this heat treatment step, voids in the solid electrolyte layer can be removed.

[0259] After the step of placing a solid electrolyte layer between the positive electrode layer and the negative electrode layer, a step of obtaining a battery assembly and pressurizing it may be performed.

[0260] Pressurization is not limited to a roll press, a flat press, etc., but any pressurization method used in the relevant technical field may be used. The pressurization step may be omitted.

[0261] Pressurization is performed at a temperature of, for example, room temperature (20°C to 25°C) to 90°C. Alternatively, pressurization is performed at a high temperature of 100°C or higher. The pressurization time is, for example, 30 minutes or less, 20 minutes or less, 15 minutes or less, or 10 minutes or less. The pressurization time is 1 ms to 30 minutes, 1 ms to 20 minutes, 1 ms to 15 minutes, or 1 ms to 10 minutes. The pressurization method is, for example, isotactic press, roll press, flat press, etc., but is not necessarily limited to these methods and any pressurization used in the art can be used. The pressure applied during pressurization is, for example, 500 MPa or less, for example, 400 MPa or less, 300 MPa or less, 200 MPa or less, 100 MPa or less, or 50 MPa. The pressure applied during pressurization is, for example, 1 to 50 MPa, 1 to 30 MPa, 1 to 20 MPa, or 1 to 10 MPa. By this pressurization, for example, the solid electrolyte powder is sintered to form a single solid electrolyte.

[0262] The pressurizing step is for example 40 to 100°C, for example 85 oPlate press treatment is performed at a pressure of 500 MPa for 30 min at C. This pressurization treatment sinteres the solid electrolyte layer, thereby improving battery characteristics.

[0263] According to an embodiment, the negative electrode layer can be formed on the negative electrode current collector by coating a composition for forming an intermediate layer on the negative electrode current collector and heat treating the composition. The heat treatment is performed at 80 to 150°C, 90 to 145°C, 100 to 140°C, or 110 to 130°C.

[0264] The composition for forming an intermediate layer may contain lithium nitrate, an organic solvent, and a lithium salt. The content of lithium nitrate in the composition for forming an intermediate layer is 1 to 10 wt%, 1 to 8 wt%, 1 to 6 wt%, 1 to 5 wt%, or 1.5 to 3 wt% based on the total weight of the composition for forming an intermediate layer. When the content of lithium nitrate is within the above range, the lithium electrodeposition density and uniformity on the negative electrode increase, thereby enabling the manufacture of an all-solid-state secondary battery with a long lifespan.

[0265] Any organic solvent capable of dissolving or dispersing lithium nitrate may be used, and may be used with reference to the organic solvent of the electrolyte. The lithium salt may be used with reference to the lithium salt of the electrolyte.

[0266] 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.

[0267] (Manufacturing of sulfide-based composite cathode active materials)

[0268] Manufacturing Example 1: Li2S-LiI-CNF, 2 steps, 10 hr + 6 hr, 600 rpm, 28G

[0269] (Stage 1)

[0270] Li2S and LiI were mixed in 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. The milling energy applied to the sample during milling was 28 G.

[0271] (Stage 2)

[0272] Li2S-LiI composite and carbon nanofiber (CNF) were mixed at a weight ratio of 50:10. 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 6 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.

[0273] The Mohs hardness of Li2S was 0.6, that of LiI was 2.0, and that of carbon nanofiber (CNF) was 1.5.

[0274] Manufacturing Example 2: Manufacturing of carbon black loaded with silver particles

[0275] Carbon black was dispersed in a 1.0 M sulfuric acid solution, stirred for 2 hours, filtered, and dried to prepare acid-treated carbon black.

[0276] 10 g of acid-treated carbon black was added to a mixed solvent of 1500 g of distilled water, 1500 g of ethanol, and 30 g of glycerol, and stirred, followed by adding 2 g of AgNO3 and stirring to prepare a mixed solution. The particle size of the carbon black was 80 nm. A reducing agent was added to the mixed solution to reduce and support silver ions on the carbon black. The carbon black supported with silver-containing particles was filtered, washed, and dried to prepare a composite negative electrode active material. Scanning electron microscope and XPS measurements confirmed that multiple silver-containing particles were supported on the carbon black particles. The silver-containing particles were silver particles, silver oxide (Ag2O) particles, and composite particles of silver (Ag) and silver oxide (Ag2O). The content of silver-containing particles included in the composite negative electrode active material was 20 wt%. The average particle diameter of the silver particles was 10 nm.

[0277] Comparative Manufacturing Example 1: Simple mixture of Li2S and CNF

[0278] Li2S and carbon nanofibers (CNF) were mixed at a weight ratio of 30:30. The mixture was used as a cathode active material.

[0279] Comparative Manufacturing Example 2: Li2S-LiI-CNF, 1 step, 2 hr, 600 rpm, 28 G

[0280] 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 28 G. The Li2S-LiI-CNF composite was used as a composite cathode active material.

[0281] (Manufacturing of all-solid-state secondary batteries)

[0282] Example 1: Al cathode current collector / Li6PS5Cl(40) and Li2S-LiI-CNF cathode active material layer / Li6PS5Cl solid electrolyte layer / Ag-C cathode layer (Ag-supported carbon black) / 3 wt% LiNO3-containing intermediate layer / Cu cathode current collector

[0283] (Anode layer manufacturing)

[0284] The Li2S-LiI-CNF composite manufactured in Manufacturing Example 1 was prepared as a cathode active material. Li6PS5Cl, an argyrodite-type crystal (D50=3.0 ㎛, crystalline), was prepared as a solid electrolyte. PTFE was prepared as a binder. These materials were mixed in a weight ratio of composite cathode active material: solid electrolyte: binder = 60:40:1.2 to prepare a cathode mixture. The cathode mixture was obtained by mixing using a ball mill.

[0285] The positive electrode was manufactured by placing the positive electrode mixture on one side of a positive electrode current collector made of aluminum foil on one side and plate pressing at a pressure of 200 MPa for 10 minutes. The total thickness of the positive electrode layer was approximately 113.8 μm. The thickness of the positive electrode active material layer was approximately 93.8 μm, and the thickness of the carbon-coated aluminum foil was approximately 20 μm.

[0286] (Cathode manufacturing)

[0287] A copper foil with a thickness of 10 μm was prepared as a negative electrode collector.

[0288] LiNO3 content was carried out on the top of copper foil according to the following method The intermediate layer was formed with a thickness of approximately 800 nm.

[0289] LiNO3 was dispersed in 10 mL of 1 M lithium bis(trifluoromethanesulfonyl) imide (LiTFSI), dissolved in 1,3-dioxolane (DOL) and 1,2-dimethoxyethane (DME) at a volume ratio of 1:1, and mixed for 30 minutes to obtain a composition for forming an intermediate layer. The content of lithium nitrate in the composition for forming an intermediate layer was 3 wt%. Here, the composition for forming an intermediate layer contained lithium nitrate particles, LiTFSI, DOL, and DME, and had the form of a dispersion containing lithium nitrate particles.

[0290] The composition for forming the intermediate layer was provided on copper foil, and the intermediate layer containing LiNO3 was formed on the copper foil by heat-treating the intermediate layer at 120°C. The intermediate layer contained lithium nitrate particles, and the lithium nitrate particles were uniformly distributed on the surface of the copper foil. The content of the lithium nitrate particles in the intermediate layer was 3 wt% based on the total weight of the intermediate layer.

[0291] A first negative electrode active material layer was formed on top of the LiNO3 coating layer according to the following process.

[0292] As the first negative electrode active material, the carbon black supported on silver particles manufactured in Manufacturing Example 2 was prepared. 4 g of the carbon black powder supported on silver particles was placed in a container, and 4 g of an NMP solution containing 7 wt% PVDF binder (Kureha #9300) was added thereto to prepare a mixed solution. Subsequently, NMP was added little by little to this mixed solution while stirring the mixed solution to prepare a slurry for forming the first negative electrode active material layer. The prepared slurry was applied to the upper part of the intermediate layer using a bar coater and dried in the air at 80°C for 10 minutes. The laminate thus obtained was vacuum dried at 40°C for 10 hours. The dried laminate was dried at 5 ton·f / cm 2The surface of the first negative electrode active material layer of the laminate was flattened by cold roll pressing at a pressure of 5 m / sec. The negative electrode layer was manufactured by the above process. The thickness of the first negative electrode active material layer included in the negative electrode layer was approximately 15 μm. The areas of the first negative electrode active material layer and the negative electrode current collector were the same.

[0293] The ratio (B / A) of the initial charge capacity (B) of the first negative electrode active material layer and the initial charge capacity (A) of the positive electrode active material layer was less than 1. The initial charge capacity of the positive electrode active material layer was less than 1 at the first open circuit voltage (1 st 4.25 V vs. Li / Li from open circuit voltage) + was determined from the charge up to . The initial charge capacity of the first negative electrode active material layer was determined from the second open circuit voltage (2 nd 0.01 V vs. Li / Li from open circuit voltage) + It was decided from the charging up to .

[0294] (Manufacturing of solid electrolyte layer)

[0295] Li6PS5Cl solid electrolyte in the form of argyrodite crystals (D 50 =3.0 mm, crystalline), and an acrylic binder were added to prepare a mixture. The content of Li6PS5Cl in the mixture was 98.5 wt%, and the content of the acrylic binder was 1.5 wt%.

[0296] Octyl acetate was added to the above mixture and stirred to prepare a slurry. The prepared slurry was applied onto a PET substrate using a bar coater and dried in air at 80°C for 10 minutes to prepare a laminate. The prepared laminate was vacuum-dried at 80°C for 2 hours to prepare a solid electrolyte layer.

[0297] (Manufacturing of all-solid-state secondary batteries)

[0298] A solid electrolyte layer was placed on the cathode so that the first cathode active material layer was in contact with the solid electrolyte layer, and an anode was placed on the solid electrolyte layer so that the cathode active material layer was in contact with the solid electrolyte layer, thereby preparing a laminate.

[0299] 85 prepared laminates o The solid electrolyte layer was plate-pressed at 500 MPa for 30 min in C. This pressurization process sintered the solid electrolyte layer, thereby improving battery characteristics. The thickness of the sintered solid electrolyte layer was approximately 20 μm. The pressed laminate was placed in a pouch and vacuum-sealed to manufacture an all-solid-state secondary battery. Part of the positive and negative current collectors were extended outside the sealed battery to be used as positive and negative terminals.

[0300] Example 2: Al cathode current collector / Li6PS5Cl(40) and Li2S-LiI-CNF cathode active material layer / Li6PS5Cl solid electrolyte layer / Ag-C cathode layer (Ag-supported carbon black) / 5 wt% LiNO3-containing intermediate layer / Cu cathode current collector

[0301] An all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that the content of lithium nitrate in the composition for forming the intermediate layer was changed to 5 wt% so that the content of lithium nitrate particles in the intermediate layer was changed to 5 wt%.

[0302] Example 3: Example 1: Al positive electrode current collector / Li6PS5Cl(40) and Li2S-LiI-CNF positive electrode active material layer / Li6PS5Cl solid electrolyte layer / Ag-C negative electrode layer (Ag-supported carbon black) / 1 wt% LiNO3-containing intermediate layer / Cu negative electrode current collector

[0303] An all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that the content of lithium nitrate in the composition for forming the intermediate layer was changed to 1 wt% so that the content of lithium nitrate particles in the intermediate layer was changed to 1 wt%.

[0304] Example 4: Al cathode current collector / Li6PS5Cl(40) and Li2S-LiI-CNF cathode active material layer / Li6PS5Cl solid electrolyte layer / 1 wt% LiNO3 containing Ag-C cathode layer / Ag-C cathode layer (Ag-supported carbon black) / 3 wt% LiNO3 containing intermediate layer / Cu cathode current collector

[0305] An all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that when manufacturing a slurry for forming a first negative electrode active material layer, LiNO3 was further added and the content of LiNO3 was 1 wt% based on the total weight of the slurry for forming a first negative electrode active material layer.

[0306] Example 5: Al cathode current collector / Li6PS5Cl(40) and Li2S-LiI-CNF cathode active material layer / Li6PS5Cl solid electrolyte layer / Ag-C cathode layer (using Ag-C mixture) / 3 wt% LiNO3 containing intermediate layer / Cu cathode current collector

[0307] An all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that a 3:1 weight ratio mixture of carbon black (CB) having a primary particle diameter of approximately 30 nm and silver (Ag) particles having an average particle diameter of approximately 60 nm was used instead of the silver particle-supported carbon black manufactured in Manufacturing Example 2 as the first negative electrode active material.

[0308] Reference Example 1: Al positive electrode current collector / Li6PS5Cl(40) and Li2S-LiI-CNF positive electrode active material layer / Li6PS5Cl solid electrolyte layer / Ag-C negative electrode layer (Ag-supported carbon black) / Cu negative electrode current collector

[0309] An all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that the LiNO3-containing intermediate layer was not formed on the copper foil.

[0310] Reference Example 2: Al positive electrode current collector / Li6PS5Cl(40) and Li2S-LiI-CNF positive electrode active material layer / Li6PS5Cl solid electrolyte layer / Ag-C negative electrode layer (Ag-supported carbon black + LiNO3) / Cu negative electrode current collector

[0311] An all-solid-state secondary battery was manufactured in the same manner as in Reference Example 1, except that lithium nitrate was added when forming the Ag-C negative electrode layer, the content of LiNO3 was 1 wt% based on the total weight of the slurry, and the content of lithium nitrate in the Ag-C negative electrode layer was 1 wt%.

[0312] Comparative Example 1: Bare Al positive electrode current collector / Li6PS5Cl(40) and Li2S-LiI-CNF positive electrode active material layer / Li6PS5Cl solid electrolyte layer / Ag-C negative electrode layer (using Ag-C mixture) / Cu negative electrode current collector

[0313] An all-solid-state secondary battery was manufactured in the same manner as Example 5, except that an intermediate layer was not formed on the Ag-C cathode layer.

[0314] Comparative Example 2: bare Al / Li6PS5Cl(40) and Li2S-LiI-CNF / Li6PS5Cl / (Ag-C+LiNO3) cathode layers

[0315] An all-solid-state secondary battery was manufactured in the same manner as in Comparative Example 1, except that LiNO3 was added when manufacturing a slurry for manufacturing a first negative electrode active material layer, the content of LiNO3 was 1 wt% based on the total weight of the slurry, and the content of lithium nitrate in the Ag-C negative electrode layer was 1 wt%.

[0316] Evaluation Example 1: Charge / Discharge Test

[0317] The charge / discharge characteristics of the all-solid-state secondary batteries manufactured in Example 1-5, Reference Example 1-2, and Comparative Example 1-2 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.

[0318] The first cycle involved charging for 12.5 hours at a constant current of 0.1 C until the battery voltage reached 2.5 to 2.8 V. Subsequently, discharging was performed for 12.5 hours at a constant current of 0.1 C until the battery voltage reached 0.3 V.

[0319] The discharge capacity of the first cycle was taken as the standard capacity. The standard capacity is expressed as the specific capacity of Li2S-LiI-CNF in Table 1 below.

[0320] After the second cycle, charging and discharging were performed up to 500 cycles under the same conditions as the first cycle. The measurement results are shown in Table 2 below.

[0321] The cycle count is the number of cycles required for the discharge capacity to decrease to 80% of the standard capacity after the second cycle. A higher cycle count is considered to indicate better life characteristics.

[0322] Evaluation Example 2: High-Rate Characteristic Evaluation

[0323] The high-rate characteristics of the all-solid-state secondary batteries of Examples 1 to 5, Reference Example 1-2, and Comparative Example 1-2 were evaluated by the following charge-discharge test. The charge-discharge test was performed by placing the solid-state secondary batteries in a constant-temperature bath at 45°C.

[0324] The all-solid-state secondary battery was charged at a constant current of 0.1 C rate at 45°C until the voltage reached 2.5 V (vs. Li), and then cut-off at a current of 0.05 C rate while maintaining 2.5 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 0.1 C rate until the voltage reached 0.3 V (vs. Li) (formation cycle).

[0325] The solid-state secondary battery, which had undergone a Mars cycle, was charged at a constant current of 0.2 C rate at 45°C until the voltage reached 2.5 V (vs. Li). Subsequently, it was discharged at a constant current of 0.2 C rate until the voltage reached 0.3 V (vs. Li) (first cycle).

[0326] The solid-state secondary battery that had undergone the first cycle was charged at a constant current of 0.2 C rate at 45°C until the voltage reached 4.3 V (vs. Li). Subsequently, it was discharged at a constant current of 0.33 C rate until the voltage reached 2.5 V (vs. Li) (second cycle).

[0327] The solid-state secondary battery that had undergone the second cycle was charged at a constant current of 0.2 C rate at 45°C until the voltage reached 2.5 V (vs. Li). Subsequently, it was discharged at a constant current of 0.5 C rate until the voltage reached 0.3 V (vs. Li) (third cycle).

[0328] The solid-state secondary battery that had undergone the third cycle was charged at a constant current of 0.2 C rate at 45°C until the voltage reached 2.5 V (vs. Li). Subsequently, it was discharged at a constant current of 1.0 C rate until the voltage reached 0.3 V (vs. Li) (4th cycle).

[0329] 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 1 below. The high-rate characteristics are defined by the following mathematical equation (1).

[0330] <Mathematical Formula 1>

[0331] High-rate characteristic [%] = [4th cycle discharge capacity (1.0 C) / Mars cycle discharge capacity (0.1 C)] × 100

[0332] Example 1 Al positive electrode current collector / Li6PS5Cl(40) and Li2S-LiI-CNF positive electrode active material layer / Li6PS5Cl solid electrolyte layer / Ag-C negative electrode layer (Ag-supported carbon black) / 3 wt% LiNO3 containing intermediate layer / Cu negative electrode current collector 96039895.2 Example 2 Al positive electrode current collector / Li6PS5Cl(40) and Li2S-LiI-CNF positive electrode active material layer / Li6PS5Cl solid electrolyte layer / Ag-C negative electrode layer (Ag-supported carbon black) / 5 wt% LiNO3 containing intermediate layer / Cu negative electrode current collector 92535293.8 Example 3 Example 1: Al positive electrode current collector / Li6PS5Cl(40) and Li2S-LiI-CNF positive electrode active material layer / Li6PS5Cl solid electrolyte layer / Ag-C negative electrode layer (Ag-supported carbon black) / 1 wt% LiNO3-containing intermediate layer / Cu negative electrode current collector 91033092.8 Example 4 Al positive electrode current collector / Li6PS5Cl(40) and Li2S-LiI-CNF positive electrode active material layer / Li6PS5Cl solid electrolyte layer / 1 wt% LiNO3-containing Ag-C negative electrode layer Ag-C negative electrode layer (Ag-supported carbon black) / 3 wt% LiNO3-containing intermediate layer / Cu negative electrode current collector 101048096.6 Example 5 Al positive electrode current collector / Li6PS5Cl(40) and Li2S-LiI-CNF positive electrode active material layer / Li6PS5Cl solid electrolyte layer / Ag-C negative electrode layer (using Ag-C mixture) / 3 wt% LiNO3-containing intermediate layer / Cu negative electrode current collector 89031891.2 Reference example 1 Al positive electrode current collector / Li6PS5Cl(40) and Li2S-LiI-CNF positive electrode active material layer / Li6PS5Cl solid electrolyte layer / Ag-C negative electrode layer (Ag-supported carbon black) / Cu negative electrode current collector 69012084.1 Reference Example 2 Al positive electrode current collector / Li6PS5Cl(40) and Li2S-LiI-CNF positive electrode active material layer / Li6PS5Cl solid electrolyte layer / Ag-C negative electrode layer (Ag-supported carbon black + LiNO3) / Cu negative electrode current collector 74815086.5Comparative Example 1Bare Al positive electrode collector / Li6PS5Cl(40) and Li2S-LiI-CNF / Li6PS5Cl / Ag-C negative electrode layer (using Ag-C mixture) / Cu negative electrode collector4802874.3Comparative Example 2Bare Al / Li6PS5Cl(40) and Li2S-LiI-CNF / Li6PS5Cl / (Ag-C+LiNO3) negative electrode layer5408581.2.

[0333] As shown in Table 1, the all-solid-state secondary batteries of Examples 1 to 5 had an intermediate layer containing lithium nitrate particles, thereby inducing uniform lithium deposition on the negative electrode, thereby exhibiting improved charge-discharge characteristics compared to the all-solid-state secondary batteries of Reference Examples 1-2 and Comparative Examples 1-2. Among them, the all-solid-state secondary battery of Example 4 had excellent charge-discharge characteristics by using a first negative electrode active material layer containing Ag-supported carbon in which both the intermediate layer and the first negative electrode active material layer contained lithium nitrate, and it was found that the charge-discharge characteristics were further improved compared to Examples 1 to 3 in which only the intermediate layer contained lithium nitrate. The all-solid-state secondary battery of Example 1 having a first negative electrode active material layer containing Ag-supported carbon exhibited further improved charge-discharge characteristics compared to the all-solid-state secondary battery of Example 5 using a first negative electrode active material layer containing Ag-C-containing negative electrode active material. By using a first negative electrode active material layer containing Ag-supported carbon, the migration of Ag toward the negative electrode current collector during charge and discharge can be suppressed. As charging progresses, silver (Ag) migrates to the current collector and exists in solid solution with lithium metal, and many particles can be observed to remain in the area near the current collector during discharge. This can increase cell resistance due to an increase in overvoltage due to insufficient silver (Ag) content at the interface between the solid electrolyte layer and the intermediate layer. By resolving this problem, high-rate and low-temperature operation performance can be improved.

[0334] In contrast, the all-solid-state secondary battery of Reference Example 1 did not include an intermediate layer, so the negative electrode dendrites grew unevenly, resulting in reduced charge / discharge characteristics.

[0335] It was found that the all-solid-state secondary battery of Reference Example 2 contained lithium nitrate in the first negative electrode active material layer, and that the effect of uniformly depositing lithium on the negative electrode current collector was reduced compared to the all-solid-state secondary battery of Example 4, which had an intermediate layer containing lithium nitrate. As a result, the charge-discharge characteristics of the all-solid-state secondary battery of Reference Example 2 were reduced compared to the all-solid-state secondary battery of Example 4.

[0336] The all-solid-state secondary battery of Comparative Example 1 did not contain an intermediate layer containing lithium nitrate particles, and thus dendrites grew unevenly on the negative electrode, resulting in lower charge-discharge characteristics compared to the all-solid-state secondary battery of Example 5. In addition, the all-solid-state secondary battery of Comparative Example 2 contained lithium nitrate in the first negative electrode active material layer, and thus, although it had superior charge-discharge characteristics compared to Comparative Example 1, it showed lower charge-discharge characteristics compared to Example 5.

[0337] 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 initial charging in the all-solid-state secondary batteries of Examples 1 to 5.

[0338] The formation of the lithium metal layer was confirmed through cross-sectional scanning electron microscope images of the all-solid-state secondary battery.

[0339] Evaluation Example 3: XRD Analysis and Scanning Electron Microscopy Analysis

[0340] XRD spectra were measured using Cu Kα radiation for the composite positive electrode active materials manufactured in Manufacturing Example 1 and Comparative Manufacturing Examples 1 and 2.

[0341] Some of the Li2S crystallite sizes calculated from the first peak for the (111) crystal plane appearing at a diffraction angle 2θ = 27° ± 2.0° in the measured XRD spectrum are shown in Table 2 below. The crystallite sizes were calculated using the Sherrer Equation.

[0342] For each composite cathode active material, the Li2S particle size of the composite cathode active material was measured using a scanning electron microscope. The Li2S particle size of the composite cathode active material is the arithmetic mean of the particle sizes of multiple Li2S particles measured using software from scanning electron microscope images. Some of the measurement results are shown in Table 2 below.

[0343] Classification 1st stage milling 2nd stage milling Solid solution formation Li2S crystallite size [nm] Li2S particle size [㎛] Manufacturing example 1 (28 G, 6 hr) (Li2S-LiI-CNF complex) 600 rpm, 28 G, 10 hr 600 rpm, 28 G, 6 hr ○8.91 Less than Comparative manufacturing example 1 (28 G, 2 hr) (Li2S-CNF complex) 600 rpm, 28 G, 2 hr - Х24.073 Comparative manufacturing example 2 (28 G, 2 hr) (Li2S-LiI-CNF complex) 600 rpm, 28 G, 2 hr - ○223

[0344] As shown in Table 2, the Li2S-LiI-CNF composite of Preparation Example 1 contained a Li2S-LiI solid solution, the size of the Li2S crystallites was 9.5 nm or less, and the Li2S particle size of the composite was 2 μm or less.

[0345] The Li2S-CNF composite of Comparative Manufacturing Example 1 did not form a solid solution. In addition, the Li2S-LiI-CNF composite of Comparative Manufacturing Example 2 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.

Claims

1. It comprises a positive electrode layer; a negative electrode layer; and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer; The above negative electrode layer includes a negative electrode current collector and a first negative electrode active material layer on one surface of the negative electrode current collector, The above positive electrode layer comprises a positive electrode current collector; and a positive electrode active material layer on one or both sides of the positive electrode current collector, The above cathode active material layer includes a sulfide-based cathode active material, An all-solid-state secondary battery, wherein an interlayer containing lithium nitrate (LiNO3) particles is disposed between the negative electrode current collector and the first negative electrode active material layer.

2. In paragraph 1, the intermediate layer includes an electrolyte, The electrolyte includes a liquid electrolyte, a solid electrolyte, a gel electrolyte, or a combination thereof, An all-solid-state secondary battery, wherein the gel electrolyte comprises a polymer gel electrolyte.

3. In the first paragraph, a second negative electrode active material layer is further included between the intermediate layer and the first negative electrode active material 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.

4. In the third paragraph, the metal layer is an all-solid-state secondary battery containing lithium nitrate.

5. An all-solid-state secondary battery according to claim 1, wherein the first negative electrode active material layer further comprises lithium nitrate.

6. In the fifth paragraph, the content of lithium nitrate in the intermediate layer is greater than the content of lithium nitrate in the first negative electrode active material layer, The content of lithium nitrate in the intermediate layer is 1 to 10 wt% based on the total weight of the intermediate layer, An all-solid-state secondary battery in which the content of lithium nitrate in the first negative electrode active material layer is 1 to 5 wt% based on the total weight of the first negative electrode active material layer.

7. In the first paragraph, the content of lithium nitrate in the intermediate layer has a concentration gradient from an area close to the negative electrode current collector to an area close to the first negative electrode active material layer. An all-solid-state secondary battery, wherein the content of lithium nitrate in the intermediate layer decreases from a region close to the negative electrode current collector to a region close to the first negative electrode active material layer.

8. In the 7th paragraph, the content of lithium nitrate in the region close to the negative electrode current collector in the intermediate layer is 1 to 10 wt%, and the content of lithium nitrate in the region close to the first negative electrode active material layer is 1 to 5 wt%, an all-solid-state secondary battery.

9. An all-solid-state secondary battery according to claim 1, wherein the thickness of the intermediate layer is 1 μm or less.

10. In the first paragraph, the negative electrode active material comprises a carbon-based support; and a metal-based negative electrode active material supported on the carbon-based support. The above metal-based negative electrode active material includes a metal, a metal oxide, a complex of a metal and a metal oxide, or a combination thereof, The above metal-based negative electrode active material has a particle form, and the particle size of the metal-based negative electrode active material is 1 nm to 200 nm, The above carbon-based support has a particle shape, and the particle size of the carbon-based support is 10 nm to 2 ㎛, An all-solid-state secondary battery further comprising a second negative electrode active material layer disposed between the negative electrode current collector and the first negative electrode active material layer after the above-mentioned all-solid-state secondary battery is charged, wherein the second negative electrode active material layer is a metal layer, and the metal layer includes lithium or a lithium alloy.

11. An all-solid-state secondary battery according to claim 1, wherein the sulfide-based cathode active material comprises nickel sulfide, copper sulfide, Li2S, a Li2S-containing complex, or a combination thereof.

12. In claim 11, the Li2S-containing composite is a composite of Li2S and a lithium salt, a composite of Li2S and a carbon-based material, a composite of Li2S, a carbon-based material, and a solid electrolyte, a composite of Li2S and a solid electrolyte, a composite of Li2S, a carbon-based material, and a lithium salt, a composite of Li2S and a lithium salt, a composite of Li2S and a metal carbide, a composite of Li2S, a carbon-based material, and a metal carbide, a composite of Li2S and a metal nitride, a composite of Li2S, a carbon-based material, and a metal nitride, or a combination thereof, an all-solid-state secondary battery.

13. In the 11th paragraph, the Li2S-containing complex includes a solid solution of Li2S and a lithium salt, The above Li2S-containing complex includes a complex of Li2S, LiI, and a carbon-based material, An all-solid-state secondary battery wherein the size of the complex is 1 to 10 μm, and the complex includes a solid solution of Li2S and LiI.

14. In the first paragraph, the solid electrolyte layer contains a sulfide-based solid electrolyte, The above sulfide-based solid electrolyte is Li2S-P2S5, Li2S-P2S5-LiX, X is a halogen element, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, 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, An all-solid-state secondary battery, wherein the density of the above argyrodite-type solid electrolyte is 1.5 to 2.0 g / cc.

15. In the first paragraph, the positive electrode active material layer further includes at least one selected from a conductive material and a binder, The above challenge material includes a carbon-based material, The above carbon material is amorphous, The above carbon-based material includes a fibrous carbon-based material, The above fibrous carbon material includes fibrous carbon nanostructures, An all-solid-state secondary battery, wherein the fibrous carbon nanostructure comprises carbon nanofibers, carbon nanotubes, carbon nanobelts, carbon nanorods, or a combination thereof.

16. In the first paragraph, the first negative electrode active material layer includes a negative electrode active material and a binder, The above negative electrode active material has a particle form, and the average particle diameter of the negative electrode active material is 4 ㎛ or less, The above 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. An all-solid-state secondary battery, wherein the metal or metalloid negative electrode active material comprises gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), zinc (Zn), or a combination thereof.

17. In the 16th paragraph, the negative electrode active material comprises a mixture of first particles made of amorphous carbon and second particles made of a metal or 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. An all-solid-state secondary battery according to claim 1, wherein the solid electrolyte layer includes a binder.

19. In the first paragraph, 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.

20. In the first paragraph, a first inactive member is further included that is arranged on at least one of the other surface of the positive electrode collector and the other surface of the negative electrode collector. An all-solid-state secondary battery, wherein the first inert member is an elastic member.

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