All-solid-state secondary battery

Abstract

This all-solid-state secondary battery comprises a positive electrode layer, a negative electrode layer, and a solid electrolyte layer between the positive electrode layer and the negative electrode layer. The positive electrode layer includes a positive electrode current collector and a positive electrode active material layer on one surface or both surfaces of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material and a mixed ionic and electronic conductor. The mixed ionic and electronic conductor contains a metal oxide represented by MxNbyOz-δ (0≤x≤100; 0<y≤100; 0<z≤100; 0≤δ<z, x<y, and M is an element selected from Groups 3 to 15 of the Periodic Table of Elements). 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.

Description

All-solid-state secondary batteries

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

[0002] Recently, with the rapid proliferation of battery-powered electronic devices such as mobile phones, laptops, and electric vehicles, the demand for high-energy density and high-capacity secondary batteries is rapidly increasing. Accordingly, active research and development is underway to improve the performance of lithium secondary batteries. Lithium secondary batteries are batteries comprising a cathode and anode containing active materials capable of lithium ion intercalation and deintercalation, as well as an electrolyte. Lithium secondary batteries generate electrical energy through oxidation and reduction reactions that occur when lithium ions intercalate and deintercalate at the cathode and anode.

[0003] Recent industrial demands have led to the active development of batteries with high energy density and safety. Lithium batteries, for example, are used in a variety of applications, including information technology, communications devices, and automobiles. Because automobiles are life-threatening, safety is also crucial.

[0004] 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.

[0005] 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.

[0006] One aspect is to provide an all-solid-state secondary battery having improved cycle characteristics by including a mixed conductor in the cathode active material layer.

[0007] According to the implementation example

[0008] It comprises an anode layer; a cathode layer; and a solid electrolyte layer between the anode layer and the cathode layer,

[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 cathode active material and a mixed ionic and electronic conductor,

[0011] The above mixed conductor is M x Nb y O z-δ (0≤x≤100; 0 <y≤100; 0<z≤100; 0≤δ<z, x<y, M은 원소주기율표 3족 내지 15족에서 선택되는 원소)로 표시되는 금속산화물(metal oxide)을 포함하며,

[0012] An all-solid-state secondary battery is provided, 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.

[0013] According to one aspect, it is possible to provide an all-solid-state secondary battery having improved cycle characteristics by including a mixed conductor in the positive electrode active material layer.

[0014] Figure 1 is a cross-sectional view of an all-solid-state secondary battery according to an exemplary embodiment.

[0015] Figure 2 is a cross-sectional view of an all-solid-state secondary battery according to an exemplary embodiment.

[0016] Figure 3 is a cross-sectional view of an all-solid-state secondary battery according to an exemplary embodiment.

[0017] Fig. 4 is a cross-sectional view of an all-solid-state secondary battery according to an exemplary embodiment.

[0018] Fig. 5 is a cross-sectional view of an all-solid-state secondary battery according to an exemplary embodiment.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] "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.

[0027] Unless otherwise defined herein, the particle size may be the average particle size. In addition, the particle size refers to the average particle size (D50), which means the diameter of particles with a cumulative volume of 50% by volume in a particle size distribution. The average particle size (D50) can be measured by a method well known to those skilled in the art, for example, by measuring with a particle size analyzer, or by measuring with a transmission electron microscope (TEM) photograph or a scanning electron microscope (SEM) photograph. Alternatively, the average particle size (D50) value can be obtained by measuring with a measuring device that utilizes dynamic light-scattering, performing data analysis to count the number of particles for each particle size range, and calculating from the counted number. Alternatively, the average particle size (D50) value can be obtained by measuring with a laser diffraction method. When measuring by laser diffraction, more specifically, after the particles to be measured are dispersed in a dispersion medium, they are introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000) and irradiated with ultrasonic waves of approximately 28 kHz at an output of 60 W, and the average particle size (D50) based on 50% of the particle size distribution in the measuring device can be calculated.

[0028] In this disclosure, "particle diameter" 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 can be measured using a particle size analyzer (PSA). The "particle diameter" is, for example, the average particle diameter. The "average particle diameter" is, for example, D50, the median particle diameter.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] In the present disclosure, the “weight average molecular weight” of a polymer can be measured, for example, using gel permeation chromatography (GPC), and is a relative value to a polystyrene standard sample.

[0033] In this disclosure, “metal” includes both metals and metalloids such as silicon and germanium, in their elemental or ionic states.

[0034] In this disclosure, “alloy” means a mixture of two or more metals.

[0035] In the present disclosure, “electrode active material” means an electrode material capable of undergoing lithiation and delithiation.

[0036] In the present disclosure, “positive electrode material” means a positive electrode material capable of undergoing lithiation and delithiation.

[0037] In the present disclosure, “negative electrode active material” means a negative electrode material capable of undergoing lithiation and delithiation.

[0038] In the present disclosure, “lithiation” and “lithiating” mean a process of adding lithium to an electrode active material.

[0039] In the present disclosure, “delithiation” and “delithiate” mean a process of removing lithium from an electrode active material.

[0040] In this disclosure, “charging” and “charging” mean a process of providing electrochemical energy to a battery.

[0041] In this disclosure, “discharging” and “discharging” mean the process of removing electrochemical energy from a battery.

[0042] In the present disclosure, “positive electrode” and “cathode” mean an electrode at which electrochemical reduction and lithiation occur during a discharge process.

[0043] In the present disclosure, “cathode” and “anode” mean electrodes where electrochemical oxidation and delithiation occur during a discharge process.

[0044] 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.

[0045] Hereinafter, an all-solid-state secondary battery according to exemplary implementation examples will be described in more detail.

[0046] [All-solid-state secondary battery]

[0047] An all-solid-state secondary battery according to one embodiment includes a cathode layer; a cathode layer; and a solid electrolyte layer between the cathode layer and the cathode layer, wherein the cathode layer includes a cathode current collector; and a cathode active material layer on one or both sides of the cathode current collector, wherein the cathode active material layer includes a cathode active material and a mixed ionic and electronic conductor, and the mixed conductor is M x Nb y O z-δ (0≤x≤100; 0 <y≤100; 0<z≤100; 0≤δ<z, x<y, M은 원소주기율표 3족 내지 15족에서 선택되는 원소)로 표시되는 금속산화물(metal oxide)을 포함하며, 상기 음극층이 음극집전체 및 상기 음극집전체의 일면 상의 제1 음극활물질층을 포함한다.

[0048] The mixed conductor can exhibit ionic conductivity. This ionic conductivity suppresses the increase in internal resistance caused by the interruption of the ionic conduction path of the positive electrode active material layer during charge and discharge, thereby suppressing the increase in internal resistance of the all-solid-state secondary battery. Consequently, the cycle characteristics of the all-solid-state secondary battery can be improved.

[0049] The mixed conductor can exhibit electronic conductivity. This electronic conductivity suppresses the increase in internal resistance caused by the interruption of the electron conduction path in the positive electrode active material layer during charge / discharge, thereby suppressing the increase in internal resistance of the all-solid-state secondary battery. Consequently, the cycle characteristics of the all-solid-state secondary battery can be improved.

[0050] Since the mixed conductor simultaneously provides ionic and electronic conductivity, the disconnection of ionic conduction paths and / or electronic conduction paths due to volume changes in the positive electrode active material layer during charge and discharge of an all-solid-state secondary battery can be more effectively suppressed. Consequently, the life characteristics of the all-solid-state secondary battery can be improved.

[0051] The uniformity of electrode reactions within the cathode active material layer can be improved by the mixed conductor simultaneously providing ionic and electronic conductivity. Consequently, overvoltage can be more effectively suppressed during the charge / discharge process of all-solid-state secondary batteries. Consequently, deterioration caused by high voltage during the charge / discharge process of all-solid-state secondary batteries can be more effectively prevented.

[0052] By providing both ionic and electronic conductivity, the mixed conductor can more effectively suppress the increase in internal resistance of all-solid-state secondary batteries even at low temperatures. Consequently, capacity degradation of all-solid-state secondary batteries at low temperatures can be more effectively prevented.

[0053] By simultaneously providing ionic and electronic conductivity, the mixed conductor can provide long-distance ionic and electronic conduction paths in the cathode active material layer. Therefore, by increasing the length of the ionic / electronic conduction paths in the all-solid-state secondary battery, the high-rate characteristics of the all-solid-state secondary battery can be improved. Consequently, the output characteristics of the all-solid-state secondary battery can be enhanced.

[0054] Referring to FIGS. 1 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) 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 mixed conductor (Mixed Ionic and Electronic Conductor). The mixed conductor is M x Nb y O z-δ (0≤x≤100; 0 <y≤100; 0<z≤100; 0≤δ<z, x<y, M은 원소주기율표 3족 내지 15족에서 선택되는 원소)로 표시되는 금속산화물(metal oxide)을 포함한다. 음극층(20)이 음극집전체(21) 및 음극집전체(21)의 일면 상의 제1 음극활물질층(22)을 포함한다.

[0055] [Anode layer]

[0056] Referring to FIGS. 1 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 mixed conductor (Mixed Ionic and Electronic Conductor). The mixed conductor is M x Nb y O z-δ(0≤x≤100; 0 <y≤100; 0<z≤100; 0≤δ<z, x<y, M은 원소주기율표 3족 내지 15족에서 선택되는 원소)로 표시되는 금속산화물(metal oxide)을 포함한다. 양극활물질층(12)이 혼합도체를 동시에 포함함에 의하여 양극활물질층의 충방전 과정에서의 열화가 억제되고 양극활물질층의 내부 저항의 증가가 억제될 수 있다. 양극활물질층(12)의 충방전 과정에서의 부피 변화에도 불구하고 양극활물질층에서 이온 전도 경로 및 / 또는 전자 전도 경로의 단절을 보다 효과적으로 억제할 수 있다. 결과적으로, 전고체 이차전지의 사이클 특성이 향상될 수 있다.

[0057] [Cathode active material layer: mixed conductor]

[0058] Referring to FIGS. 1 to 5, the positive electrode active material layer (12) includes a mixed conductor. The mixed conductor is M x Nb y O z-δ (0≤x≤100; 0 <y≤100; 0<z≤100; 0≤δ<z, x<y, M은 원소주기율표 3족 내지 15족에서 선택되는 원소)로 표시되는 금속산화물(metal oxide)을 포함한다. M x Nb y O z-δ In M, for example, P, Ti, W, Cr, Fe, Mn, V, Cu, Mo, Al, Ga, Zr, Zn or a combination thereof. M x Nb y O z-δ For example, 0≤x≤100, 0≤x≤50, 0≤x≤20, 0≤x≤10, 0≤x≤5, 0≤x≤3, 0≤x≤2 or 0x≤1. M x Nb y O z For example, 0 in <y≤100, 0<y≤50, 0<y≤20, 0<y≤10, 0<y≤5, 0<y≤3 또는 0<y≤2 이다. M x Nb y O z-δFor example, 0 in <z≤100, 0<z≤80, 0<z≤50, 0<z≤30, 0<z≤20, 0<z≤10 또는 0<z≤5 이다.

[0059] Mixed conductors are for example Nb b O c (0 <b≤5; 0<c≤10; a<b), P a Nb b O c (0 <a30; 0<b≤50; 0<c≤100; a<b), Ti a Nb b O c (0 <a30; 0<b≤50; 0<c≤100; a<b), Mo d Ti a Nb b O c (0 <a≤30; 0<b≤50; 0<c≤100; 0<d≤30; a<b), W d Ti a Nb b O c (0 <a≤30; 0<b≤50; 0<c≤100; 0<d≤30; a<b), W a Nb b O c (0 <a≤30; 0<b≤50; 0<c≤100; a<b), Cr a Nb b O c (0 <a≤30; 0<b≤50; 0<c≤100; a<b), Fe a Nb b O c (0 <a≤30; 0<b≤50; 0<c≤100; a<b), Cr d Fe a Nb b O c (0 <a≤30; 0<b≤50; 0<d≤30; 0<c≤100; a<b), Mn a Nb b O c (0 <a≤30; 0<b≤50; 0<c≤100; a<b), V a Nb b O c (0 <a≤30; 0<b≤50; 0<c≤100; a<b), Cu a Nbb Oh c (0 <a≤30; 0<b≤50; 0<c≤100; a<b), Mo a No. b Oh c (0 <a≤30; 0<b≤50; 0<c≤100; a<b), Al a No. b Oh c (0 <a≤30; 0<b≤50; 0<c≤100; a<b), Ge a No. b Oh c (0 <a≤30; 0<b≤50; 0<c≤100; a<b), Zr a No. b Oh c (0 <a≤30; 0<b≤50; 0<c≤100; a<b), Zn a No. b Oh c (0 <a≤30; 0<b≤50; 0<c≤100; a<b) 또는 W a No. b Oh c (0 <a≤30; 0<b≤50; 0<c≤100; a<b)로 표시되는 금속산화물을 포함할 수 있다.

[0060] Compounds such as H-Nb2O5, T-Nb2O5, TT-Nb2O5, M-Nb2O5, Nb 12 WO 33 , Nb 16 W5O 55 , Nb 14 W3O 44 , Nb 18 W8O 69 , PNb9O 25 , TiNb2O7, Mo 0.125 Tea 0.875 Nb2O 7.125 , I 0.25 Tea 0.75 Nb2O 7.25 , I 0.5 Tea 0.5 Nb2O 7.5 , Nb 18 W 16 Oh 93 , Nb9W2Ti6O 40.5 , Nb9W4Ti4O42.5 , Cr 0.2 Fe 0.8 Nb 11 O 29 , Fe 0.8 Mn 0.2 Nb 11 O 29 , Fe 0.8 V 0.2 Nb 11 O 29 , Cu 0.02 Ti 0.94 Nb 2.04 O7, TiNb 24 O 62 , FeNb 11 O 29 , TiCr 0.5 Nb 10.5 O 29 , Nb 14 W3O 44 , Ti2Nb 10 O 29 , Ti2Nb 10 O 29-x (0 <x<29), Nb 12 O 29 , CrNb 11 O 29 , MoNb 12 O 33 , Nb 14 W3O 44 , AlNb 11 O 29 , TiNb 24 O 62 , Nb 12 WO 33 , FeNb 11 O 29 , Ti2Nb 10 O 29 , CrNb 49 O 124 , GaNb 11 O 29 , VNb9O 25 , ZrNb 14 O 37 , Zn2Nb 34 O 87 or combinations thereof.

[0061] The mixed conductor comprises a metal oxide, which may comprise, for example, a crystalline metal oxide. The metal oxide may comprise, for example, a Wadsly-Roth phase. The Wadsly-Roth phase has a structure derived from, for example, a ReO3 structure and has reorganized ReO3-type blocks (MO6 octahedral). The reorganized ReO3-type blocks may be connected by, for example, edge sharing or may be formed by a combination of edge sharing and corner sharing. Alternatively, the reorganized ReO3-type blocks may be formed by a combination of edge sharing and corner sharing via tetrahedral coordinated metal atoms. The introduction of such edge sharing and / or corner sharing into the metal oxide may cause the metal oxide to have a crystallographic shear structure and may result in a more dense packing of atoms within the metal oxide. As a result, the structural stability of the metal oxide can be improved during lithium ion conduction. The Wesley-Ross phase can be confirmed, for example, from an XRD spectrum. The metal oxide can include a framework formed, for example, by a plurality of MO6 octahedra, a plurality of NbO6 octahedra, or a combination thereof. The framework is formed by edge sharing and / or corner sharing of the plurality of MO6 octahedra, and pores can be arranged between the plurality of MO6 octahedra. That is, pores or channels can be included in the framework. The size of the pores can be, for example, less than 3 Å, less than 2.9 Å, or less than 2.8 Å. The size of the pores can be, for example, 2.5 Å to less than 3 Å, 2.5 Å to 2.9 Å or less, or 2.5 Å to 2.8 Å.Since the pores have a size within this range, for example, moisture (H2O) cannot be introduced into the pores. Therefore, lithium ions can easily conduct through the pores of the metal oxide. If the pore size is excessively large, impurities such as moisture can be introduced, interfering with the lithium ion conduction path, and if the pore size is excessively small, lithium ion conduction is difficult. The pore size can be confirmed using, for example, high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM).

[0062] The mixed conductor contains a metal oxide, and the lithium diffusion coefficient (D) of the metal oxide Li ) is, for example, 1.0×10 at 25 ℃ and 1 atm. -15 cm 2 / s or more, 1.0×10 -13 cm 2 / s or more, 1.0×10 -12 cm 2 / s or more, or 1.0×10 -11 cm 2 / s may be higher than the lithium diffusion coefficient of the metal oxide (D Li ) is, for example, 1.0×10 at 25 ℃ and 1 atm. -15 cm 2 / s to 1.0×10 -12 cm 2 / s, 1.0×10 -14 cm 2 / s to 1.0×10 -11 cm 2 / s or 1.0×10 -13 cm 2 / s to 1.0×10 -10 cm 2 / s may be. Since the metal oxide has a lithium diffusion coefficient in this range, the metal oxide can provide improved lithium ion conductivity. Therefore, the disconnection of the ion conduction path within the positive electrode active material layer during charge and discharge can be more effectively prevented. Consequently, the cycle characteristics of the all-solid-state secondary battery are improved. The lithium diffusion coefficient can be measured, for example, using the galvanostatic intermittent titration technique (GITT).

[0063] The mixed conductor contains a metal oxide, and the electronic conductivity of the metal oxide is, for example, 1.0×10 at 25°C and 1 atm. -9 S / cm or more, 5.0×10 -9 S / cm or more or 1.0×10 -8 S / cm or more. The electronic conductivity of metal oxides is, for example, 1.0×10 at 25°C and 1 atm. -9 S / cm to 1.0×10 -6 S / cm, 5.0×10 -9 S / cm to 1.0×10 -6 S / cm or 1.0×10 -8 S / cm to 1.0×10 -6 It can be S / cm. Since the metal oxide has an electronic conductivity in this range, it can provide an increased electron conduction path within the cathode active material layer. Furthermore, it can more effectively prevent the disconnection of the electron conduction path within the cathode active material layer during charge and discharge. Consequently, the cycle characteristics of the all-solid-state secondary battery are improved. Electronic conductivity can be measured, for example, by the direct current method or impedance spectroscopy.

[0064] The mixed conductor includes a metal oxide, and the metal oxide may further include a dopant. By further including a dopant in the metal oxide, an additional change in the crystal structure may be brought about, and as a result, the ionic conductivity and / or electronic conductivity of the metal oxide may be further improved. The dopant may include, for example, a metal belonging to Groups 3 to 15 of the Periodic Table of Elements, N, P, S, or a combination thereof. The dopant may include, for example, N, P, S, Ti, W, Cr, Fe, Mn, V, Cu, Mo, Al, Ga, Zr, Zn, or a combination thereof. The doping amount of the dopant may be, for example, 0.05 mol or less, 0.03 mol or less, or 0.01 mol or less, per 1 mol of the metal oxide. The content of the dopant may be measured, for example, by EDX, XPS, or the like.

[0065] The mixed conductor may include, for example, a fibrous mixed conductor, a particulate mixed conductor, or a combination thereof. The morphology of the mixed conductor may be measured, for example, using a scanning electron microscope, a transmission electron microscope, or an optical microscope.

[0066] By including a fibrous mixed conductor, the mixed conductor can more easily provide a long-distance electronic conduction path and / or a long-distance ionic conduction path within the positive electrode active material layer. The fibrous mixed conductor may include, for example, a fibrous microstructure, a fibrous nanostructure, or a combination thereof. The fibrous microstructure is a fibrous structure having a diameter of 1 μm or more, 3 μm or more, or 1 μm or more. The fibrous microstructure may include a microtube, a microfiber, a microrod, a microwire, or a combination thereof. The fibrous nanostructure is a fibrous structure having a diameter of less than 1 μm, 500 nm or less, 300 nm or less, or 100 nm or less. The fibrous nanostructure may include, for example, a nanotube, a nanofiber, a nanorod, a nanowire, or a combination thereof. The aspect ratio of the fibrous mixed conductor may be, for example, 5 or more, 10 or more, 20 or more, 50 or more, or 100 or more. The cross-sectional shape of the fibrous composite conductor may be, for example, circular, elliptical or polygonal. The polygonal shape may be, for example, triangular, square, pentagonal, hexagonal, heptagonal or octagonal.

[0067] Since the mixed conductor includes a particulate mixed conductor, the space between a plurality of positive electrode active material particles in the positive electrode active material layer can be more easily filled, thereby more easily suppressing the disconnection of the electronic conduction path and / or the ionic conduction path of the positive electrode active material layer. The particulate mixed conductor may include a particulate microstructure, a particulate nanostructure, or a combination thereof. The particulate microstructure is a particulate structure having a diameter of 1 μm or more, 3 μm or more, or 1 μm or more. The particulate microstructure may include a microsphere or a microparticle. The particulate nanostructure is a particulate structure having a diameter of less than 1 μm, 500 nm or less, 300 nm or less, or 100 nm or less. The particulate nanostructure may include, for example, a nanosphere or a nanoparticle. The aspect ratio of the particulate mixed conductor may be 3 or less, 2 or less, or 1.5 or less.

[0068] Mixed conductors include, for example, TiNb2O7 nanowires, Nb 14 W3O 44 Microparticles, Ti2Nb 10 O 29 Mesoporous microspheres, Ti2Nb 10 O 29 Porous nanospheres, H-Nb2O5 microspheres, Nb 12 O 29 Microspheres, TiNb2O7 mesoporous microspheres, TiO2 / Nb2O5 / TiNb2O7 microspheres, Nb2O5 / TiNb2O7 porous spheres, TiNb2O7 porous nanospheres, N-doped Ti2Nb 10 O 29-δ (0<δ<29), Ti2Nb 10 O 29-δ (0<δ<29) mesoporous microspheres, TiNb2O7 nanoparticles, CrNb 11 O 29 Nanorods, porous MoNb 12 O 33 Microspheres, Nb 14 W3O 44Nanowire, AlNb 11 O 29 Nanowire, TiNb 24 O 62 nanowire, Nb 12 WO 33 Nanowire, Ti2Nb 10 O 29 Nanoparticles, TiNb2O7 hollow nanofibers, FeNb 11 O 29 Nanotubes, TiNb2O7 nanotubes, Ti2Nb 10 O 29 Hollow nanofiber, CrNb 49 O 124 Nanotubes, GaNb 11 O 29 Nanoweb, Nb9O 25 Nanowire, ZrNb 14 O 37 Nanowire, Zn2Nb 34 O 87 nanofibers, or a combination thereof.

[0069] The mixed conductor may include, for example, a composite of the metal oxide described above and a carbon-based material. By including a composite of the metal oxide and the carbon-based material, the electronic conductivity of the mixed conductor may be further improved. The carbon-based material may include, for example, a carbon-based nanostructure. The carbon-based nanostructure may be, for example, a one-dimensional carbon-based nanostructure, a two-dimensional carbon-based nanostructure, a three-dimensional carbon-based nanostructure, or a combination thereof. The one-dimensional carbon-based nanostructure may be, for example, a carbon nanofiber, a carbon nanotube, a carbon nanowire, a carbon nanorod, a carbon nanobelt, or a combination thereof. The two-dimensional carbon-based nanostructure may include, for example, graphene, a carbon web, 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 morphology of carbon nanostructures can be measured, for example, by scanning electron microscopy or transmission electron microscopy. Mixed conductors include, for example, TiNb2O7-CNT composites, TiCr 0.5 Nb 10.5 O 29 -CNT composite, TiNb2O7-carbon composite, Ti2Nb 10 O 29 -may contain carbon nanofibers or a combination thereof.

[0070] The size of the mixed conductor may be, for example, 1 to 20 μm, 2 to 18 μm, 3 to 17 μm, or 5 to 15 μm. By having a size within this range, the mixed conductor can provide an improved ion conduction path and / or electron conduction path within the positive electrode active material layer. As a result, the cycle characteristics of the all-solid-state secondary battery can be further improved.

[0071] The content of the mixed conductor may be, for example, 20 wt% or less, 15 wt% or less, 10 wt% or less, or 5 wt% or less of the total weight of the positive electrode active material layer. The content of the mixed conductor may be, for example, 0.1 to 20 wt%, 1 to 15 wt%, 1 to 10 wt%, or 1 to 5 wt% of the total weight of the positive electrode active material layer. When the mixed conductor has a content within this range, the disconnection of the ion conduction path and / or the disconnection of the electron conduction path due to the volume change of the positive electrode active material layer during charge and discharge can be more effectively suppressed. As a result, the deterioration of the all-solid-state secondary battery can be more effectively suppressed.

[0072] [Cathode active material layer: Cathode active material]

[0073] Referring to FIGS. 1 to 5, the positive electrode active material layer (12) includes a positive electrode active material.

[0074] 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.

[0075] 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.

[0076] The cathode active material includes, for example, an oxide-based cathode active material, a sulfide-based cathode active material, or a combination thereof.

[0077] 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.

[0078] Sulfide-based cathode active materials include, for example, nickel sulfide, copper sulfide, Li2S, Li2S-containing complexes, or combinations thereof.

[0079] 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 O2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); 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 O2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni b E c G d O2 (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 Ge 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.

[0080] 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.

[0081] The oxide-based cathode active material may include, for example, a lithium transition metal oxide represented by the following chemical formulas 1 to 8:

[0082] <Chemical Formula 1>

[0083] Li a Ni x Co y M z O2-b A b

[0084] In the above chemical formula 1,

[0085] 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,

[0086] 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,

[0087] A is F, S, Cl, Br or a combination thereof,

[0088] <Chemical Formula 2>

[0089] LiNi x Co y Mn z O2

[0090] <Chemical Formula 3>

[0091] LiNi x Co y Al z O2

[0092] In the above chemical formulas 2 and 3, 0.8≤x≤0.95, 0≤y≤0.2, 0 <z≤0.2 및 x+y+z=1이며,

[0093] <Chemical Formula 4>

[0094] LiNi x Co y Mn z Al w O2

[0095] In the above chemical formula 4, 0.8≤x≤0.95, 0≤y≤0.2, 0 <z≤0.2, 0<w≤0.2, 및 x+y+z+w=1이며,

[0096] <Chemical Formula 5>

[0097] Li a Co x M y O 2-b Ab

[0098] In the above chemical formula 5,

[0099] 1.0≤a≤1.2, 0≤b≤0.2, 0.9≤x≤1, 0≤y≤0.1, and x+y=1,

[0100] 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,

[0101] A is F, S, Cl, Br or a combination thereof,

[0102] <Chemical Formula 6>

[0103] Li a Ni x Mn y M' z O 2-b A b

[0104] In the above chemical formula 6,

[0105] 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,

[0106] 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,

[0107] A is F, S, Cl, Br or a combination thereof,

[0108] <Chemical Formula 7>

[0109] Li a M1 x M2 y PO 4-b X b

[0110] In the above chemical formula 7, 0.90≤a≤1.1, 0≤x≤0.9, 0≤y≤0.5, 0.9 <x+y<1.1, 0≤b≤2 이며,

[0111] M1 is chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr) or a combination thereof,

[0112] 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.

[0113] <Chemical Formula 8>

[0114] Li a M3 z PO4

[0115] In the above chemical formula 8, 0.90≤a≤1.1, 0.9≤z≤1.1,

[0116] M3 is chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr), or a combination thereof.

[0117] 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).

[0118] The size of the oxide-based cathode active material may be, for example, 0.1 to 30 μm, 0.5 to 20 μm, 1 to 15 μm, or 1 to 10 μm. The oxide-based cathode active material may be, for example, a single crystal particle or a polycrystalline particle.

[0119] The sulfide-based cathode active material may include, for example, a Li2S-containing composite. The Li2S-containing composite includes, for example, a composite of Li2S and carbon, a composite of Li2S, carbon, and a solid electrolyte, a composite of Li2S and a solid electrolyte, a composite of Li2S and a lithium salt, a composite of Li2S, a lithium salt, and carbon, a composite of Li2S and a metal carbide, a composite of Li2S, carbon, and a metal carbide, a composite of Li2S and a metal nitride, a composite of Li2S, carbon, and a metal nitride, or a combination thereof.

[0120] 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.

[0121] The composite of Li2S, carbon, and a solid electrolyte comprises carbon and a solid electrolyte. Carbon refers to the composite of Li2S and carbon described above. The solid electrolyte may be any solid electrolyte that is used as an ion-conducting material in the relevant technical field, for example, an amorphous solid electrolyte. The solid electrolyte is, for example, an inorganic solid electrolyte. The solid electrolyte is, for example, a crystalline solid electrolyte, an amorphous solid electrolyte, or a combination thereof. The solid electrolyte is, for example, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or a combination thereof. The sulfide-based solid electrolyte comprises, 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 may have a density of, for example, 1×10 -5 It can have an ionic conductivity of S / cm or more. Sulfide-based solid electrolytes include, for example, Li3PO4-Li2SO4, Li2S-P2S5, Li2S-P2S5-LiX, where X is a halogen 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, may include one or more selected from 0≤x≤2. The oxide-based solid electrolyte includes, for example, Li, O and a transition metal element, and may optionally further include other elements. The oxide-based solid electrolyte may have a molar mass of, for example, 1Х10 at room temperature. -5 It may be a solid electrolyte having an ionic conductivity of S / cm or more. The oxide-based solid electrolyte may be selected from oxide-based solid electrolytes used in the solid electrolyte layer. The solid electrolyte may be, for example, a mixture of a sulfide-based solid electrolyte and a lithium salt. For example, it may be a mixture of Li3PO4-Li2SO4 and a binary lithium salt, or a mixture of Li3PO4-Li2SO4 and a ternary lithium salt.

[0122] 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.

[0123] 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.

[0124] 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.

[0125] 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.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] 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 a second fibrous sulfide-based solid electrolyte, or a composite of Li2S and a second fibrous sulfide-based solid electrolyte and the above-described carbon, solid electrolyte, lithium salt, metal carbide, or metal nitride. The cathode active material layer may further include, for example, a first fibrous sulfide-based solid electrolyte (not shown).

[0130] When the Li2S-containing composite further includes a second fibrous sulfide-based solid electrolyte, deterioration of the lithium battery can be further suppressed and cycle characteristics of the lithium 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. 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, respectively. The length and / or thickness of the second fibrous sulfide-based solid electrolyte can 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, respectively. The second fibrous sulfide-based solid electrolyte may have, for example, the same shape as the first fibrous sulfide-based solid electrolyte but may have a smaller size. The second fibrous sulfide-based solid electrolyte may be easily distributed within the Li2S-containing composite due to its reduced length and / or thickness. The second fibrous sulfide-based solid electrolyte may further suppress deterioration of the lithium battery and further improve cycle characteristics of the lithium battery due to its reduced length and / or thickness.

[0131] 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.

[0132] 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.

[0133] 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. The shell may include an inorganic filler. The inorganic filler may include Li a Al b M c O d Cl e (0 <a≤3; 0<b≤3; 0≤c<2; 0<d≤4; 0<e≤2; d<e, M은 원소주기율표 3족 내지 15족에서 선택되는 금속) 표시되는 리튬금속옥시할라이드(lithium metal oxyhalide)를 포함한다.

[0134] In the composite cathode active material, a shell containing an inorganic filler may be coated on part or all of the core. In the composite cathode active material, by disposing the inorganic filler on part or all of the lithium transition metal oxide core, an increase in the interfacial resistance between the composite cathode active material and the first solid electrolyte can be suppressed. Consequently, the internal resistance of the all-solid-state secondary battery (1) can be reduced, thereby improving the cycle characteristics of the all-solid-state secondary battery (1).

[0135] In the composite cathode active material, the inorganic filler content may be 0.1 to 20 parts by weight, 0.1 to 10 parts by weight, or 0.1 to 5 parts by weight based on 100 parts by weight of the core. When the composite cathode active material has an inorganic filler content within this range, part or all of the surface of the core may be coated with the inorganic filler. If the content of the inorganic filler coated on the core is too low, the coating effect may be minimal. If the content of the inorganic filler coated on the core is too high, the energy density of the cathode active material layer (12) may be reduced.

[0136] [Cathode active material layer: solid electrolyte]

[0137] Referring to FIGS. 1 to 5, the positive electrode active material layer (12) includes a solid electrolyte. The 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).

[0138] The solid electrolyte included in the positive electrode active material layer (12) may have a smaller D50 average particle diameter than the solid electrolyte included in the solid electrolyte layer (30). For example, the D50 average particle diameter of the 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 D50 average particle diameter of the solid electrolyte included in the solid electrolyte layer (30). The D50 average 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% cumulative volume, calculated from the side of particles having a small particle size in a size distribution of particles measured by laser diffraction. The average D50 particle size of the solid electrolyte may be, for example, 0.1 to 10 μm, 0.5 to 8 μm, 0.5 to 5 μm or 1 to 3 μm.

[0139] The solid electrolyte content 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).

[0140] The 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.

[0141] The sulfide-based solid electrolyte may include, for example, an argyrodite type solid electrolyte represented by the following chemical formula 9:

[0142] <Chemical Formula 9>

[0143] Li + 12-n-x A n+ X 2- 6-x Y - x

[0144] In the above formula, 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, Li 7-xPS 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.

[0145] 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.

[0146] [Cathode active material layer: conductive material]

[0147] 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.

[0148] 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).

[0149] 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.

[0150] 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.

[0151] 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.

[0152] 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 a 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 can be, for example, 2 to 30, 2 to 20, 2 to 10, 2 to 8, 2 to 5, or 2 to 4. When the fibrous carbon-based material has an aspect ratio in this range, the overall electronic conductivity of the composite is improved, and local electronic conductivity imbalances within the composite can be further alleviated. The fibrous carbon-based material can include, for example, carbon nanostructures. The carbon nanostructures can include, for example, carbon nanofibers (CNFs), carbon nanotubes (CNTs), carbon nanobelts, carbon nanorods, or combinations thereof. The carbon nanostructures can 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. The aspect ratio of the fibrous carbon-based material can be measured, for example, from scanning electron microscope (SEM) or transmission electron microscope (TEM) images.

[0153] 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.

[0154] 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.

[0155] [Cathode active material layer: binder]

[0156] 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.

[0157] [Cathode active material layer: other additives]

[0158] The cathode active material layer (12) may further include additives such as fillers, coating agents, dispersants, and ion-conducting aids in addition to the above-described cathode active material, solid electrolyte, binder, and conductive agent. As the fillers, coating agents, dispersants, and ion-conducting aids that the cathode active material layer (12) may include, known materials generally used in electrodes of all-solid-state secondary batteries may be used.

[0159] [Cathode collector]

[0160] Referring to FIGS. 1 to 5, the positive electrode layer (10) includes a positive electrode current collector (11).

[0161] 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.

[0162] The cathode current collector (11) may include, for example, a base film and a metal layer disposed on one or both sides of the base film. The base film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof. The base film may be, for example, an insulator. Since the base film includes an insulating thermoplastic polymer, when a short circuit occurs, the base film softens or liquefies, thereby blocking battery operation and suppressing a rapid increase in current. The metal layer may include, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), or an alloy thereof. The metal layer can act as an electrochemical fuse and be cut off in case of overcurrent to prevent a short circuit. The limit current and the maximum current can be controlled by adjusting the thickness of the metal layer. The metal layer can be plated or deposited on the base film. As the thickness of the metal layer decreases, the limit current and / or the maximum current of the positive electrode current collector (11) decreases, thereby improving the stability of the lithium battery in case of a short circuit. A lead tab can be added on the metal layer for connection to the outside. The lead tab can be welded to the metal layer or the metal layer / base film laminate by ultrasonic welding, laser welding, spot welding, etc. During welding, the base film and / or the metal layer melt, so that the metal layer can be electrically connected to the lead tab. In order to strengthen the welding of the metal layer and the lead tab, a metal chip can be added between the metal layer and the lead tab.The metal piece may be a thin piece of the same material as the metal of the metal layer. The metal piece may be, for example, a metal foil, a metal mesh, etc. The metal piece may be, for example, aluminum foil, copper foil, SUS foil, etc. After the metal piece is placed on the metal layer, the lead tab may be welded to the metal piece / metal layer laminate or the metal piece / metal layer / base film laminate. During welding, the base film, the metal layer, and / or the metal piece may melt, so that the metal layer or the metal layer / metal piece laminate may be electrically connected to the lead tab. A metal chip and / or a lead tab may be added to a portion of the metal layer. The base film may have a thickness of, for example, 1 to 50 μm, 1.5 to 50 μm, 1.5 to 40 μm, or 1 to 30 μm. When the base film has a thickness in this range, the weight of the electrode assembly can be more effectively reduced. The melting point of the base film may be, for example, 100 to 300°C, 100 to 250°C or less, or 100 to 200°C. Since the base film has a melting point within this range, the base film can be melted and easily bonded to the lead tab during the welding process of the lead tab. To improve the adhesion between the base film and the metal layer, a surface treatment such as corona treatment may be performed on the base film. The thickness of the metal layer may be, for example, 0.01 to 3 μm, 0.1 to 3 μm, 0.1 to 2 μm, or 0.1 to μm. Since the metal layer has a thickness within this range, conductivity can be maintained while ensuring the stability of the electrode assembly. The thickness of the metal piece may be, for example, 2 to 10 μm, 2 to 7 μm, or 4 to 6 μm. Since the metal piece has a thickness within this range, the connection between the metal layer and the lead tab can be performed more easily. By having this structure, the positive electrode current collector (11) can reduce the weight of the positive electrode and consequently improve the energy density of the positive electrode and the all-solid-state secondary battery.

[0163] [Inert Absence]

[0164] Referring to FIGS. 4 and 5, the positive electrode (10) includes a positive electrode current collector (11) and a positive electrode active material layer (12) disposed on one side of the positive electrode current collector. An inactive member (40) is disposed on one side of the positive electrode (10). Referring to FIG. 4, the inactive member (40) is disposed on one side of the positive electrode active material layer (12) and the positive electrode current collector (11). Referring to FIG. 5, the inactive member (40) is disposed on one side of the positive electrode active material layer (12) and between the 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.

[0165] 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 (1) 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 cracks.

[0166] 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.

[0167] 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.

[0168] 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).

[0169] 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.

[0170] 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.

[0171] 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).

[0172] 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.

[0173] 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).

[0174] 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).

[0175] 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%.

[0176] 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).

[0177] 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.

[0178] 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.

[0179] The inert member (40) is, for example, a flame-retardant inert member. The flame-retardant inert member prevents thermal runaway and ignition of the all-solid-state secondary battery (1) by providing flame retardancy. Consequently, the safety of the all-solid-state secondary battery (1) is further improved. The flame-retardant inert member prevents deterioration of the all-solid-state secondary battery (1) by absorbing residual moisture within the all-solid-state secondary battery (1), thereby improving the lifespan characteristics of the all-solid-state secondary battery (1).

[0180] The flame-retardant inert member includes, for example, a matrix and a filler. The matrix includes, for example, a substrate and a reinforcing material. The matrix includes, for example, a fibrous substrate and a fibrous reinforcing material. Since the matrix includes the substrate, the matrix can have elasticity. Therefore, the matrix can effectively accommodate volume changes during charge and discharge of the all-solid-state secondary battery (1) and can be arranged at various positions. The substrate included in the matrix includes, for example, a first fibrous material. Since the substrate includes the first fibrous material, the volume changes of the positive electrode (30) occurring during charge and discharge of the all-solid-state secondary battery (1) can be effectively accommodated and deformation of the inert member (40) due to the volume changes of the positive electrode (30) can be effectively suppressed. The first fibrous material is, for example, a material having an aspect ratio of 5 or more, 20 or more, or 50 or more. The first fibrous material is, for example, a material having an aspect ratio of 5 to 1000, 20 to 1000, or 50 to 1000. The first fibrous material is, for example, an insulating material. Since the first fibrous material is an insulating material, a short circuit between the positive electrode (30) and the negative electrode (20) caused by lithium dendrites, etc., generated during the charge and discharge process of the all-solid-state secondary battery (1) can be effectively prevented. The first fibrous material includes, for example, at least one selected from pulp fibers, insulating polymer fibers, and ion-conductive polymer fibers. The strength of the matrix is ​​improved by the inclusion of a reinforcing material in the matrix. Therefore, the matrix can prevent excessive volume change during charge and discharge of the all-solid-state secondary battery (1) and deformation of the all-solid-state secondary battery. The reinforcing material included in the matrix includes, for example, a second fibrous material. Since the reinforcing material includes the second fibrous material, the strength of the matrix can be increased more uniformly. The second fibrous material is, for example, a material having an aspect ratio of 3 or more, 5 or more, or 10 or more.The first fibrous material is, for example, a material having an aspect ratio of 3 to 100, 5 to 100, or 10 to 100. The second fibrous material is, for example, a flame-retardant material. Since the second fibrous material is a flame-retardant material, ignition due to thermal runaway occurring during the charge / discharge process of the all-solid-state secondary battery (1) or due to external impact can be effectively suppressed. The second fibrous material is, for example, glass fiber, metal oxide fiber, ceramic fiber, etc.

[0181] The flame-retardant inert member includes a filler in addition to a matrix. The filler may be disposed within the matrix, on the surface of the matrix, or on both the interior and the surface. The filler is, for example, an inorganic material. The filler included in the flame-retardant inert member is, for example, a moisture getter. The filler removes moisture remaining in the all-solid-state secondary battery (1) by adsorbing moisture, for example, at a temperature below 100°C, thereby preventing deterioration of the all-solid-state secondary battery (1). In addition, when the temperature of the all-solid-state secondary battery (1) increases to 150°C or higher due to thermal runaway occurring during the charge / discharge process of the all-solid-state secondary battery (1) or an external impact, the filler releases the adsorbed moisture, thereby effectively suppressing ignition of the all-solid-state secondary battery (1). That is, the filler is, for example, a flame retardant. The filler is, for example, a metal hydroxide having moisture adsorption properties. The metal hydroxide contained in the filler is, for example, Mg(OH)2, Fe(OH)3, Sb(OH)3, Sn(OH)4, TI(OH)3, Zr(OH)4, Al(OH)3, or a combination thereof. The content of the filler contained in the flame-retardant inert member is, for example, 10 to 80 parts by weight, 20 to 80 parts by weight, 30 to 80 parts by weight, 40 to 80 parts by weight, 50 to 80 parts by weight, 60 to 80 parts by weight, or 65 to 80 parts by weight, based on 100 parts by weight of the flame-retardant inert member (4).

[0182] The flame-retardant inert member may further comprise, for example, a binder. The binder may comprise, for example, a curable polymer or a non-curable polymer. A curable polymer is a polymer that cures by heat and / or pressure. A curable polymer is, for example, a solid at room temperature. The flame-retardant inert member (40) comprises, for example, a heat-pressure curable film and / or a cured product thereof. The heat-pressure curable polymer is, for example, TSA-66 from Toray.

[0183] The flame-retardant inert member may additionally include other materials in addition to the above-described substrate, reinforcing material, filler, and binder. The flame-retardant inert member may further include one or more selected from among paper, an insulating polymer, an ion-conducting polymer, an insulating inorganic material, an oxide-based solid electrolyte, and a sulfide-based solid electrolyte. The insulating polymer may be, for example, an olefin-based polymer such as polypropylene (PP) or polyethylene (PE).

[0184] The density of the substrate or the density of the reinforcing material included in the flame-retardant inert member may be, for example, 10% to 300%, 10% to 150%, 10% to 140%, 10% to 130%, or 10% to 120% of the density of the positive electrode active material included in the positive electrode active material layer (12).

[0185] 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.

[0186] [Cathode layer]

[0187] [First negative electrode active material layer: negative electrode active material]

[0188] Referring to FIGS. 1 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.

[0189] 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.

[0190] 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.

[0191] 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.

[0192] Carbon-based negative electrode materials include, for example, amorphous carbon, crystalline carbon, porous carbon, or a combination thereof.

[0193] 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.

[0194] 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. Pore volume, average pore diameter and BET specific surface area can be measured, for example, by nitrogen gas adsorption.

[0195] 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.

[0196] 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.

[0197] 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.

[0198] 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.

[0199] 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.

[0200] 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), Denka black, 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.

[0201] The composite negative electrode active material may have, for example, a particle form. The particle size of the composite negative electrode active material having a particle form is, for example, 10 nm to 4 ㎛, 10 nm to 1 ㎛, 10 nm to 500 nm, 10 nm to 200 nm, or 10 nm to 100 nm. When the composite negative electrode active material has a particle size in this range, reversible absorption and / or desorption of lithium may be facilitated during charge and discharge. The metal-based negative electrode active material supported on the support may have, for example, a particle form. The particle size of the metal-based negative electrode active material may be, for example, 1 nm to 200 nm, 1 nm to 150 nm, 5 nm to 100 nm, or 10 nm to 50 nm. The carbon-based support may have, for example, a particle form. The particle size of the carbon-based support may be, for example, 10 nm to 2 ㎛, 10 nm to 1 ㎛, 10 nm to 500 nm, 10 nm to 200 nm, or 10 nm to 100 nm. By having a particle size in this range, the carbon-based support can be more uniformly arranged within the first negative electrode active material layer. The carbon-based support may be, for example, nanoparticles having a particle size of 500 nm or less. The particle sizes of the composite negative electrode active material, the particle sizes of the metal-based negative electrode active material, and the particle sizes of the carbon-based support are, for example, average particle sizes. The average particle size is, for example, the median diameter (D50) measured using a laser particle size distribution analyzer. Alternatively, the average particle size may be determined automatically using software, for example, from an electron microscope image, or manually by a manual method.

[0202] [First negative electrode active material layer: binder]

[0203] 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.

[0204] 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).

[0205] [First negative electrode active material layer: other additives]

[0206] 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.

[0207] [First negative electrode active material layer: solid electrolyte]

[0208] 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.

[0209] 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).

[0210] [First negative electrode active material layer: charging capacity]

[0211] 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 0.5. 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) + It is determined by charging up to the maximum charging voltage. The initial charging capacity of the first negative electrode active material layer (22) is determined by the second open circuit voltage (2 nd Li / Li from open circuit voltage) +It is determined by charging up to 0.01 V.

[0212] 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) to the initial charge capacity (A) of the positive electrode active material layer is, for example, 0.01 to 0.5, 0.01 to 0.45, 0.01 to 0.4, 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 Х 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.

[0213] 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 2 can 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, 4.0 V or 4.3 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.

[0214] 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).

[0215] 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.

[0216] [Second negative electrode active material layer]

[0217] Referring to FIG. 3, the all-solid-state secondary battery (1) further includes, after being charged, a second negative electrode active material layer (24) disposed, for example, between the negative electrode current collector (21) and the first negative electrode active material layer (22). The second negative electrode active material layer (24) is a metal layer containing lithium or a lithium alloy. The metal layer contains lithium or a lithium alloy. Therefore, since the second negative electrode active material layer (24) is a metal layer containing lithium, it functions as, for example, a lithium reservoir. The lithium alloy is, for example, a Li-Al alloy, a Li-Sn alloy, a Li-In alloy, a Li-Ag alloy, a Li-Au alloy, a Li-Zn alloy, a Li-Ge alloy, a Li-Si alloy, etc., but is not limited thereto, and any lithium alloy used in the art may be used. The second negative electrode active material layer (24) may be made of one of these alloys or lithium, or may be made of several types of alloys. The second negative electrode active material layer (24) is, for example, a plated layer. The second negative electrode active material layer (24) is deposited between the first negative electrode active material layer (22) and the negative electrode current collector (21), for example, during the charging process of an all-solid-state secondary battery (1).

[0218] The thickness of the second negative electrode active material layer (24) 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 (24) to perform the role of a lithium reservoir. If the thickness of the second negative electrode active material layer (24) is too thick, the mass and volume of the all-solid-state secondary battery (1) may increase, and the cycle characteristics of the all-solid-state secondary battery (1) may rather deteriorate.

[0219] Alternatively, in the all-solid-state secondary battery (1), the second negative electrode active material layer (24) may be disposed between the negative electrode current collector (21) and the first negative electrode active material layer (22), for example, before assembling the all-solid-state secondary battery (1). When the second negative electrode active material layer (24) is disposed between the negative electrode current collector (21) and the first negative electrode active material layer (22) before assembling the all-solid-state secondary battery (1), the second negative electrode active material layer (24) acts as a lithium reservoir because it is a metal layer containing lithium. For example, a lithium foil may be disposed between the negative electrode current collector (21) and the first negative electrode active material layer (22) before assembling the all-solid-state secondary battery (1).

[0220] When the second negative electrode active material layer (24) is precipitated by charging after assembling the all-solid-state secondary battery (1), the energy density of the all-solid-state secondary battery (1) increases because the second negative electrode active material layer (24) is not included when assembling the all-solid-state secondary battery (1). When charging the all-solid-state secondary battery (1), the charging is performed in excess of the charging capacity of the first negative electrode active material layer (22). That is, the first negative electrode active material layer (22) is overcharged. At the initial stage of charging, lithium is absorbed into the first negative electrode active material layer (22). The negative electrode active material included in the first negative electrode active material layer (22) forms an alloy or compound with the lithium ions that have moved from the positive electrode (10). When charging exceeds the capacity of the first negative electrode active material layer (22), for example, lithium is deposited on the back surface of the first negative electrode active material layer (22), that is, between the negative electrode current collector (21) and the first negative electrode active material layer (22), and a metal layer corresponding to the second negative electrode active material layer (24) is formed by the deposited lithium. The second negative electrode active material layer (24) is a metal layer mainly composed of lithium (i.e., metallic lithium). This result is obtained, for example, by the negative electrode active material included in the first negative electrode active material layer (22) including a material that forms an alloy or compound with lithium. During discharge, lithium in the first negative electrode active material layer (22) and the second negative electrode active material layer (24), that is, the metal layer, is ionized and moves toward the positive electrode (10). Therefore, it is possible to use lithium as the negative electrode active material in an all-solid-state secondary battery (1). In addition, since the first negative electrode active material layer (22) covers the second negative electrode active material layer (24), it acts as a protective layer for the second negative electrode active material layer (24), i.e., the metal layer, and at the same time, it suppresses the precipitation and growth of lithium dendrites. Accordingly, it suppresses short circuits and capacity reduction of the all-solid-state secondary battery (1), and consequently improves the cycle characteristics of the all-solid-state secondary battery (1).In addition, when the second negative electrode active material layer (24) is placed by charging after assembling the all-solid-state secondary battery (1), the negative electrode (20), i.e., the negative electrode current collector (21) and the first negative electrode active material layer (22) and the region between them are Li-free regions that do not contain lithium (Li) in the initial state or the state after complete discharge of the all-solid-state secondary battery (1).

[0221] [Cathode current collector]

[0222] 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.

[0223] Referring to FIG. 2, the all-solid-state secondary battery (1) may further include a thin film (23) containing an element capable of forming an alloy with lithium on one surface of the negative electrode collector (21). The thin film (23) is disposed between the negative electrode collector (21) and the first negative electrode active material layer (22). The thin film (23) contains, for example, an element capable of forming an alloy with lithium. The element capable of forming an alloy with lithium includes, but is not limited to, gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, etc., and any element capable of forming an alloy with lithium in the art may be used. The thin film (23) is composed of one of these metals or an alloy of several types of metals. By placing the thin film (23) on one surface of the negative electrode current collector (21), for example, the deposition shape of the second negative electrode active material layer (24) deposited between the thin film (23) and the first negative electrode active material layer (22) becomes flatter, and the cycle characteristics of the all-solid-state secondary battery (1) can be further improved.

[0224] The thickness of the thin film (23) is, for example, 1 nm to 800 nm, 10 nm to 700 nm, 50 nm to 600 nm, or 100 nm to 500 nm. If the thickness of the thin film (23) is less than 1 nm, it may be difficult for the function of the thin film (23) to be exerted. If the thickness of the thin film (23) is excessively thick, the thin film (23) itself absorbs lithium, which reduces the amount of lithium precipitated from the negative electrode, thereby lowering the energy density of the 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 the thin film (23) in the relevant technical field may be used.

[0225] Although not shown in the drawing, the negative electrode current collector (21) may include, for example, a base film and a metal layer disposed on one or both sides of the base film. The base film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof. The polymer may be an insulating polymer. Since the base film includes an insulating thermoplastic polymer, when a short circuit occurs, the base film may soften or liquefy, thereby blocking battery operation and suppressing a rapid increase in current. The metal layer may include, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), or an alloy thereof. The negative electrode current collector (21) may additionally include a metal piece and / or a lead tab. For more specific details regarding the base film, metal layer, metal chip, and lead tab of the negative electrode collector (21), refer to the positive electrode collector (11) described above. By having this structure, the negative electrode collector (21) can reduce the weight of the negative electrode, and consequently, improve the energy density of the negative electrode and lithium battery.

[0226] [Solid electrolyte layer]

[0227] [Solid electrolyte layer: solid electrolyte]

[0228] Referring to FIGS. 1 to 5, the all-solid-state secondary battery (1) includes a solid electrolyte layer (30) disposed between a positive electrode layer (10) and a negative electrode layer (20). The solid electrolyte layer (30) includes, for example, a solid electrolyte or a combination of a solid electrolyte and a gel electrolyte.

[0229] 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.

[0230] The solid electrolyte is, for example, a sulfide-based solid electrolyte. For more specific information on the sulfide-based solid electrolyte, refer to the above-described positive electrode active material layer (12). The sulfide-based solid electrolyte of the solid electrolyte layer (20) may be selected from among the sulfide-based solid electrolytes used in the above-described positive electrode active material layer (12).

[0231] Oxide solid electrolytes include, for example, Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (0 <x<2, 0혏<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.

[0232] 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.

[0233] 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, for example, be a polymer electrolyte that is solid at 25°C and 1 atm. The polymer solid electrolyte may, for example, not 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), polyethylene oxide (PEO), poly(styrene-b-ethylene oxide) block copolymer (PS-PEO), poly(styrene-butadiene), poly(styrene-isoprene-styrene), poly(styrene-b-divinylbenzene) block copolymer, poly(styrene-ethylene oxide-styrene) block copolymer, polystyrene sulfonate (PSS), polyvinyl fluoride (PVF), polymethyl methacrylate (PMMA, poly(methylmethacrylate), polyethylene glycol (PEG), polyacrylonitrile (PAN), polytetrafluoroethylene (PTFE), polyethylenedioxythiophene (PEDOT), polypyrrole (PPY), polyacrylonitrile (PAN), Polyaniline, polyacetylene, Nafion, Aquivion, Flemion, Gore, Aciplex, Morgane ADP, sulfonated poly(ether ether ketone) (SPEEK), sulfonated poly(arylene ether ketone ketone sulfone) (SPAEKKS), sulfonated poly(aryl ether ketone) (SPAEK), poly[bis(benzimidazobenzisoquinolinones)] (SPBIBI), poly(styrene sulfonate) (PSS), lithium 9,10-Diphenylanthracene-2-sulfonate (lithium 9,10-diphenylanthracene-2-sulfonate, DPASLi. +) or a combination thereof, but is not limited thereto, and any lithium salt that can be used in polymer electrolytes in the relevant technical field is possible. The lithium salt can be any lithium salt that can be used in the relevant technical field. The lithium salt is, for example, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2) (x and y are each 1 to 20), LiCl, LiI or a mixture thereof, etc. The polymer included in the polymer solid electrolyte may be, for example, a compound including 10 or more, 20 or more, 50 or more or 100 or more repeating units. The weight average molecular weight of the polymer included in the polymer solid electrolyte may be, for example, 1000 Dalton or more, 10,000 Dalton or more, 100,000 Dalton or more or 1,000,000 Dalton or more.

[0234] A gel electrolyte is, for example, a polymer gel electrolyte. A gel electrolyte can have a gel state without containing a polymer, for example.

[0235] The polymer gel electrolyte may include, for example, a liquid electrolyte and a polymer, or may include 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 ionic liquid; a mixture of a lithium salt and an organic solvent; a mixture of an ionic liquid and an organic solvent; or a mixture of a lithium salt, an ionic liquid, and an organic solvent. The polymer used in the polymer gel electrolyte may be selected from among the polymers used in solid polymer electrolytes. The organic solvent may be selected from among the organic solvents used in liquid electrolytes. The organic solvent is, for example, propylene carbonate, ethylene carbonate, fluoroethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, dibutyl carbonate, benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, dioxolane, 4-methyldioxolane, N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, diethylene glycol, dimethyl ether, or a mixture thereof. The lithium salt may be selected from lithium salts used in polymer solid electrolytes. Ionic liquids are salts that have a melting point below room temperature and are composed only of ions and are liquid at room temperature or molten salts at room temperature. Ionic liquids include, for example, a) one or more cations selected from ammonium, pyrrolidinium, pyridinium, pyrimidinium, imidazolium, piperidinium, pyrazolium, oxazolium, pyridazinium, phosphonium, sulfonium, triazolium, and mixtures thereof, and b) BF4. - , PF6 - , AsF6 - , SbF6- , AlCl4 - , HSO4 - , ClO4 - , CH3SO3 - , CF3CO2 - , Cl - , Br - , I - , BF4 - , SO4 - , CF3SO3 - , (FSO2)2N - , (C2F5SO2)2N - , (C2F5SO2)(CF3SO2)N - , and (CF3SO2)2N - It may include at least one selected from compounds containing at least one anion selected from. The polymer solid electrolyte may form a polymer gel electrolyte by being impregnated in a liquid electrolyte, for example, 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.

[0236] [Solid electrolyte layer: binder]

[0237] The solid electrolyte layer (30) may include, for example, a binder. The binder included in the solid electrolyte layer (30) is not limited to, but may include, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc., 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.

[0238] 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).

[0239] 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.

[0240] (Manufacture of mixed conductors)

[0241] Manufacturing Example 1: Manufacturing of H-Nb2O5 (fibrous mixed conductor)

[0242] H-Nb2O5 (High temperature permeable modification-Nb2O5) was prepared by heat-treating Nb2O5 (purity 99.9%) at 1150 ℃ for 6 hours.

[0243] The H-Nb2O5 particles were fibrous microparticles with an aspect ratio of 5 or more. The size of the H-Nb2O5 particles was approximately 10 μm. The size of the H-Nb2O5 particles was measured from a scanning electron microscope image. The H-Nb2O5 particles were secondary particles formed by agglomeration of multiple primary particles. The primary and secondary particles were each fibrous particles with an aspect ratio of 5 or more.

[0244] Manufacturing Example 2: H-Nb2O 5- Manufacturing of M (particulate mixed conductor)

[0245] Nb2O5 (purity 99.9%) was cold pressed at a pressure of 50 MPa to form pellets and heat-treated at 1200°C for 3 hours.

[0246] The resulting product was pulverized, mixed with ethanol, and milled using a ball mill at 400 rpm for 7 hours. After milling, the slurry was dried in an oven at 70°C for 6 hours and filtered through a 500 mesh to produce pulverized H-Nb2O5-M.

[0247] H-Nb2O 5- M particles were particle-like microparticles with an aspect ratio of less than 2. H-Nb2O 5- M The particle size was approximately 10 μm. H-Nb2O 5- M The particle size was measured from scanning electron microscope images. H-Nb2O5-M The particles were secondary particles formed by agglomeration of multiple primary particles. The primary and secondary particles were each particulate particles with an aspect ratio of 2 or less.

[0248] Evaluation Example 1: Crystal Structure Measurement

[0249] The crystal structure of H-Nb2O5 was confirmed by synchrotron high energy XRD and pair distribution function (PDF) measurements, XRD spectra, transmission electron microscopy (TEM), and scanning electron microscopy (SEM).

[0250] It was confirmed that H-Nb2O5 contains the Wadsley-Roth phase with a crystallographic shear structure.

[0251] Through Rietveld refinement, it was confirmed that H-Nb2O5 has a monoclinic crystal structure and belongs to the C2 / c space group.

[0252] It was confirmed that H-Nb2O5 has a skeleton composed of NbO6 octahedra, and the size of the pores formed by multiple NbO6 octahedra is greater than 2.5 Å and less than 2.8 Å.

[0253] Evaluation Example 2: Electronic Conductivity Measurement

[0254] The electronic conductivity of the mixed conductor was measured using the direct current method.

[0255] A stainless steel blocking electrode was prepared, a mixed conductor was placed between two stainless steel electrodes, and a symmetrical cell was prepared by applying a pressure of 20 MPa.

[0256] After applying a DC voltage of 50 mV to the symmetric cell, the steady-state current was measured when the current change per minute decreased to less than 1 μA / g after 1 hour. The electronic conductivity was measured by measuring the shape of the mixed conductor. The electronic conductivity was 1×10 at 25°C and 1 atm. -8 It was S / cm.

[0257] Evaluation Example 3: Lithium diffusion coefficient measurement

[0258] (Preparation of lithiated H-Nb2O5)

[0259] A working electrode was prepared by cold pressing the powder of H-Nb2O5 at room temperature under a pressure of 20 MPa. Lithium metal was prepared as the counter electrode and reference electrode.

[0260] The electrolyte was prepared by dissolving 1.0 M LiPF6 in a 1:1:1 volume ratio mixture of EC:DMC:EMC.

[0261] The cell was prepared by placing the working electrode, counter electrode, and reference electrode in the electrolyte, and a voltage of 1.8 V was applied, and then a constant current of 50 mA / g was discharged to obtain Li 0.2 Nb2O5 was prepared.

[0262] After disassembling the cell, it was washed with DMC solvent and dried to obtain Li 0.2 Nb2O5 was isolated.

[0263] (Measurement of lithium diffusion coefficient)

[0264] Li 0.2 Nb2O5, a conductive agent, and a binder were mixed in a weight ratio of 85:9:6, added to water, and stirred to prepare a slurry. The binder used was a 1:1 weight ratio mixture of CMC (carboxymethyl cellulose) and SBR (styrene butadiene rubber). Carbon black was used as the conductive agent. The slurry was coated on an aluminum current collector and dried to prepare a cathode.

[0265] Lithium metal was used as the cathode. The electrolyte was prepared by dissolving 1.0 M LiPF6 in a 1:1:1 volume ratio mixture of EC:DMC:EMC. A polypropylene microporous membrane was used as the separator. Coin cells were prepared by placing the separator between the cathode and anode and injecting the electrolyte.

[0266] The lithium diffusion coefficient was measured by Galvanostatic Intermittent Titration Technique (GITT) in the voltage range of 1.0 to 2.5 V (vs. Li / Li+) for coin cells. The GITT titration time was 50 min, and the GITT relaxation time was 900 min. The lithium diffusion coefficient (D) measured at 25 °C and 1 atm Li ) is about 5×10 -13 m 2 / s was.

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

[0268] Manufacturing Example 3: Li2S-LiI-CNF composite cathode active material

[0269] Li2S and LiI were mixed at a weight ratio of 30:20. The mixture was mechanically milled using a ball mill to prepare a Li2S-LiI composite. The milling conditions were 25°C, 510 rpm, and 10 h.

[0270] 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, 510 rpm, and 10 h. The Li2S-LiI-CNF composite was used as a composite cathode active material.

[0271] (Manufacturing of all-solid-state secondary batteries)

[0272] Example 1: Li6PS5Cl:H-Nb2O5 (fibrous) (14:1) and NCA cathode active material layer / Li6PS5Cl solid electrolyte layer / Ag-C cathode layer

[0273] (Anode layer manufacturing)

[0274] LiNi coated with Li2O-ZrO2 (LZO) as a cathode active material 0.8 Co 0.15 Al 0.05O2(NCA) was prepared. LZO-coated NCA was prepared according to the method disclosed in Korean Patent Publication No. 10-2016-0064942. Li6PS5Cl, an argyrodite-type crystal (D50 = 0.5 μm, crystalline), was prepared as a solid electrolyte. The fibrous H-Nb2O5 prepared in Manufacturing Example 1 was prepared as a mixed conductor. A polytetrafluoroethylene (PTFE) binder was prepared as a binder. Amorphous carbon nanotubes (CNTs) were prepared as a conductive material. These materials were mixed with a xylene solvent in a weight ratio of positive electrode active material: solid electrolyte: mixed conductor: conductive material: binder = 85: 14: 1: 3: 2, and the slurry was molded into a sheet shape, and then vacuum-dried at 40°C for 8 hours to prepare a positive electrode sheet. The manufactured positive electrode sheet is placed on the carbon layer of the positive electrode current collector made of aluminum foil coated with a carbon layer on one side, and 85 o The anode layer was manufactured by heated roll pressing of C. The total thickness of the anode layer was approximately 112 μm. The thickness of the carbon-coated aluminum foil was approximately 20 μm.

[0275] (Cathode manufacturing)

[0276] A 10 ㎛ thick SUS foil was prepared as a negative electrode current collector. As a negative electrode active material, a 3:1 weight ratio mixture of carbon black (CB) with a primary particle diameter of approximately 30 nm and silver (Ag) particles with an average particle diameter of approximately 60 nm was prepared.

[0277] 3 g of negative electrode active material powder and 1 g of a mixture of carbon black (CB) and silver (Ag) were placed in a container, and 4 g of an NMP solution containing 7 wt% of PVDF binder (Kureha #9300) was added thereto to prepare a mixed solution. A slurry was prepared by stirring the mixed solution while adding NMP little by little to the prepared mixed solution. The prepared slurry was applied to a SUS substrate using a bar coater, dried in air at 80°C for 10 minutes, and then vacuum-dried at 40°C for 10 hours to prepare a laminate. The prepared laminate was cold roll pressed to flatten the surface, thereby preparing a negative electrode having a first negative electrode active material layer / negative electrode current collector structure. The thickness of the first negative electrode active material layer was approximately 27 μm.

[0278] 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 0.5. The initial charge capacity of the positive electrode active material layer was less than 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) + The initial charge capacity of the negative electrode (e.g., the first negative electrode active material layer) was measured by the half-cell described above. The initial charge capacity of the positive electrode (e.g., the positive electrode active material layer) was measured by the half-cell described above.

[0279] (Manufacturing of solid electrolyte layer)

[0280] Li6PS5Cl solid electrolyte in the form of argyrodite crystals (D 50=3.0 ㎛, crystalline), and 1.5 parts by weight of an acrylic binder was added to 98.5 parts by weight of the solid electrolyte to prepare a mixture. Octyl acetate was added to the prepared mixture and stirred to prepare a slurry. The prepared slurry was applied onto a nonwoven fabric placed on 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.

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

[0282] 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.

[0283] 75 prepared laminates o The solid electrolyte layer was plate-pressed at 500 MPa for 30 min at C. This pressurization process sintered the solid electrolyte layer, thereby improving battery characteristics. The thickness of the sintered solid electrolyte layer was approximately 20 μm. The density of the Li6PS5Cl solid electrolyte, which is an argyrodite-type crystal, contained in the sintered solid electrolyte layer was 1.6 g / cc.

[0284] The pressurized laminate was placed in a pouch and vacuum-sealed to manufacture an all-solid-state secondary battery. Portions of the positive and negative current collectors were extended outside the sealed battery to serve as positive and negative terminals.

[0285] Example 2: Li6PS5Cl: H-Nb2O5-M (particle phase) (14:1) and NCA cathode active material layer / Li6PS5Cl solid electrolyte layer / Ag-C cathode layer

[0286] An all-solid-state secondary battery was manufactured in the same manner as Example 1, except that the particle-shaped mixed conductor manufactured in Manufacturing Example 2 was used instead of the fibrous mixed conductor manufactured in Manufacturing Example 1.

[0287] Example 3: Li6PS5Cl: H-Nb2O5 (fiber): H-Nb2O5-M (particle) (14:0.5:0.5) and NCA cathode active material layer / Li6PS5Cl solid electrolyte layer / Ag-C cathode layer

[0288] An all-solid-state secondary battery was manufactured in the same manner as Example 1, except that a 1:1 weight ratio mixture of the fibrous mixed conductor manufactured in Manufacturing Example 1 and the particulate mixed conductor manufactured in Manufacturing Example 2 was used instead of the fibrous mixed conductor manufactured in Manufacturing Example 1.

[0289] Comparative Example 1: Li6PS5Cl(15:0) and NCA cathode active material layer / Li6PS5Cl solid electrolyte layer / Ag-C cathode layer

[0290] An all-solid-state secondary battery was manufactured in the same manner as Example 1, except that the content ratio of the sulfide-based solid electrolyte and the mixed conductor was changed from 14:1 to 15:0 (sulfide-based solid electrolyte only).

[0291] Example 4: Li6PS5Cl:H-Nb2O5 (fibrous) (37:3) and Li2S-LiI-CNF cathode active material layer / Li6PS5Cl solid electrolyte layer / Ag-C cathode layer

[0292] An all-solid-state secondary battery was manufactured in the same manner as Example 1, except that the positive electrode containing a sulfide-based positive electrode active material was used.

[0293] (Polar electrode manufacturing)

[0294] As a cathode active material, the Li2S-LiI-CNF composite manufactured in Manufacturing Example 3 was prepared. As a solid electrolyte, Li6PS5Cl (D50=3.0 ㎛, crystalline) in the form of an argyrodite crystal was prepared. As a mixed conductor, the fibrous H-Nb2O5 manufactured in Manufacturing Example 1 was prepared. PTFE was prepared as a binder. These materials were mixed in a weight ratio of composite cathode active material: solid electrolyte: mixed conductor: binder = 60:37:3:1.2 to prepare a cathode mixture. The cathode mixture was obtained by mixing using a ball mill.

[0295] The positive electrode was manufactured by placing the positive electrode active material on one side of a positive electrode current collector made of aluminum foil coated 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.

[0296] Example 5: Li6PS5Cl: H-Nb2O5-M (particle phase) (37:3) and Li2S-LiI-CNF cathode active material layer / Li6PS5Cl solid electrolyte layer / Ag-C cathode layer

[0297] An all-solid-state secondary battery was manufactured in the same manner as Example 1, except that the particle-shaped mixed conductor manufactured in Manufacturing Example 2 was used instead of the fibrous mixed conductor manufactured in Manufacturing Example 1.

[0298] Example 6: Li6PS5Cl: H-Nb2O5 (fiber): H-Nb2O5-M (particle) (37:1.5:1.5) and Li2S-LiI-CNF cathode active material layer / Li6PS5Cl solid electrolyte layer / Ag-C cathode layer

[0299] An all-solid-state secondary battery was manufactured in the same manner as Example 1, except that a 1:1 weight ratio mixture of the fibrous mixed conductor manufactured in Manufacturing Example 1 and the particulate mixed conductor manufactured in Manufacturing Example 2 was used instead of the fibrous mixed conductor manufactured in Manufacturing Example 1.

[0300] Comparative Example 2: Li6PS5Cl(40) and Li2S-LiI-CNF cathode active material layer / Li6PS5Cl solid electrolyte layer / Ag-C cathode layer

[0301] An all-solid-state secondary battery was manufactured in the same manner as Example 1, except that the content ratio of the sulfide-based solid electrolyte and the mixed conductor was changed from 14:1 to 15:0 (sulfide-based solid electrolyte only).

[0302] Evaluation Example 4: Charge / Discharge Test

[0303] The charge / discharge characteristics of the all-solid-state secondary batteries manufactured in Examples 1 to 3 and Comparative Example 1 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.

[0304] The first cycle involved charging for 12.5 hours at a constant current of 0.1 C until the battery voltage reached 4.3 V. Subsequently, discharging was performed for 12.5 hours at a constant current of 0.1 C until the battery voltage reached 2.5 V.

[0305] The discharge capacity of the first cycle was taken as the standard capacity. The standard capacity is shown as the specific capacity of NCA in Table 1 below.

[0306] 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 1 below.

[0307] 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. As the cycle count increases, it is considered that the battery has better life characteristics.

[0308] Evaluation Example 5: High-Rate Characteristic Evaluation

[0309] The high-rate characteristics of the all-solid-state secondary batteries of Examples 1 to 3 and Comparative Example 1 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.

[0310] The all-solid-state secondary battery was charged at a constant current of 0.1 C rate at 45°C until the voltage reached 4.3 V (vs. Li), and then cut-off at a current of 0.05 C rate while maintaining 4.3 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 0.1 C rate until the voltage reached 2.5 V (vs. Li) during discharge (formation cycle).

[0311] The solid-state secondary battery that had undergone the Mars 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 0.2 C rate until the voltage reached 2.5 V (vs. Li) (first cycle).

[0312] 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).

[0313] 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 4.3 V (vs. Li). Subsequently, it was discharged at a constant current of 0.5 C rate until the voltage reached 2.5 V (vs. Li) (third cycle).

[0314] 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 4.3 V (vs. Li). Subsequently, it was discharged at a constant current of 1.0 C rate until the voltage reached 2.5 V (vs. Li) (4th cycle).

[0315] 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).

[0316] <Mathematical Formula 1>

[0317] High-rate characteristic [%] = [4th cycle discharge capacity (1.0 C) / Mars cycle discharge capacity (0.1 C)] × 100

[0318] Specific capacity [mAh / g] Cycle count [times] High rate characteristics [%] Example 1: Li6PS5Cl:H-Nb2O5 (fibrous) (14:1) and NCA / Li6PS5Cl / Ag-C cathode layer 21850098 Example 2: Li6PS5Cl:H-Nb2O5-M (particle) (14:1) and NCA / Li6PS5Cl / Ag-C cathode layer 21031092 Example 3: Li6PS5Cl:H-Nb2O5 (fibrous):H-Nb2O5-M (particle) (14:0.5:0.5) and NCA / Li6PS5Cl solid electrolyte layer / Ag-C cathode layer 21532095 Comparative example 1: Li6PS5Cl (15) and NCA / Li6PS5Cl / Ag-C cathode layer 20826591

[0319] As shown in Table 1, the all-solid-state secondary batteries of Examples 1 to 3 exhibited improved charge / discharge characteristics compared to the all-solid-state secondary battery of Comparative Example 1.

[0320] The all-solid-state secondary batteries of Examples 1 to 3 had improved charge-discharge characteristics compared to the all-solid-state secondary battery of Comparative Example 1 by including a mixed conductor in the positive electrode active material layer.

[0321] The all-solid-state secondary battery of Example 1 has relatively improved charge-discharge characteristics compared to the all-solid-state secondary batteries of Examples 2 and 3 by easily providing a long-distance ion conduction path and / or an electron conduction path by including a fibrous mixed conductor.

[0322] The all-solid-state secondary battery of Example 3 had relatively poor charge-discharge characteristics compared to the all-solid-state secondary batteries of Examples 1 and 2, as it did not easily provide a long-distance ion conduction path and / or an electron conduction path due to the inclusion of a particulate mixed conductor.

[0323] 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 3.

[0324] The formation of the lithium metal layer was confirmed through cross-sectional scanning electron microscope images of the all-solid-state secondary battery.

[0325] Evaluation Example 6: Charge / Discharge Test

[0326] The charge / discharge characteristics of the all-solid-state secondary batteries manufactured in Examples 4 to 6 and Comparative Example 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.

[0327] 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.

[0328] 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.

[0329] 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.

[0330] 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. As the cycle count increases, it is considered that the battery has better life characteristics.

[0331] Evaluation Example 7: High-Rate Characteristic Evaluation

[0332] The high-rate characteristics of the all-solid-state secondary batteries of Examples 4 to 6 and Comparative Example 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.

[0333] 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).

[0334] 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).

[0335] 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).

[0336] 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).

[0337] 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).

[0338] 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 (2).

[0339] <Mathematical Formula 1>

[0340] High-rate characteristic [%] = [4th cycle discharge capacity (1.0 C) / Mars cycle discharge capacity (0.1 C)] × 100

[0341] Specific capacity [mAh / g] Cycle count [times] High rate characteristics [%] Example 4: Li6PS5Cl:H-Nb2O5 (fibrous) (14:1) and Li2S-LiI-CNF / Li6PS5Cl / Ag-C cathode layer 95035097 Example 5: Li6PS5Cl:H-Nb2O5-M (particle) (14:1) and Li2S-LiI-CNF / Li6PS5Cl / Ag-C cathode layer 88018088 Example 6: Li6PS5Cl:H-Nb2O5 (fibrous):H-Nb2O5-M (particle) (14:0.5:0.5) and Li2S-LiI-CNF / Li6PS5Cl solid electrolyte layer / Ag-C cathode layer 90828093 Comparative example 2: Li6PS5Cl (15) and Li2S-LiI-CNF / Li6PS5Cl / Ag-C cathode layer85015084

[0342] As shown in Table 2, the all-solid-state secondary batteries of Examples 4 to 6 exhibited improved charge / discharge characteristics compared to the all-solid-state secondary battery of Comparative Example 2.

[0343] The all-solid-state secondary batteries of Examples 4 to 6 had improved charge-discharge characteristics compared to the all-solid-state secondary battery of Comparative Example 2 by including a mixed conductor in the positive electrode active material layer.

[0344] The all-solid-state secondary battery of Example 4 has relatively improved charge-discharge characteristics compared to the all-solid-state secondary batteries of Examples 5 and 6 by easily providing a long-distance ion conduction path and / or an electron conduction path by including a fibrous mixed conductor.

[0345] The all-solid-state secondary battery of Example 6 had relatively poor charge / discharge characteristics compared to the all-solid-state secondary batteries of Examples 4 to 6, as it did not easily provide a long-distance ion conduction path and / or an electron conduction path due to the inclusion of a particulate mixed conductor.

[0346] 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 4 to 6.

[0347] The formation of the lithium metal layer was confirmed through cross-sectional scanning electron microscope images of the all-solid-state secondary battery.

[0348] [Explanation of symbols]

[0349] 1 All-solid-state secondary battery 10 Cathode

[0350] 11. Cathode current collector 12. Cathode active material layer

[0351] 20 Cathode 21 Cathode current collector

[0352] 22 First negative electrode active material layer 23 Thin film

[0353] 24 Second negative electrode active material layer 30 Electrolyte layer

[0354] 40 Inert Absences

[0355] According to one aspect, it is possible to provide an all-solid-state secondary battery having improved cycle characteristics by including a mixed conductor in the positive electrode active material layer.

Claims

1. It comprises an anode layer; a cathode layer; and a solid electrolyte layer between the anode layer and the cathode layer, 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 cathode active material and a mixed ionic and electronic conductor, The above mixed conductor is M x Nb y O z-δ (0≤x≤100; 0 <y≤100; 0<z≤100; 0≤δ<z, x<y, M은 원소주기율표 3족 내지 15족에서 선택되는 원소)로 표시되는 금속산화물(metal oxide)을 포함하며, An all-solid-state secondary battery, 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.

2. An all-solid-state secondary battery in the first paragraph, wherein M in the mixed conductor includes P, Ti, W, Cr, Fe, Mn, V, Cu, Mo, Al, Ga, Zr, Zn or a combination thereof.

3. In the first paragraph, the mixed conductor is Nb b O c (0 <b≤5; 0<c≤10; a<b)를 포함하는, 전고체 이차전지.

4. An all-solid-state secondary battery in the first paragraph, wherein the mixed conductor comprises H-Nb2O5, T-Nb2O5, TT-Nb2O5, M-Nb2O5 or a combination thereof.

5. In the first paragraph, the metal oxide includes a crystalline metal oxide, The above metal oxide comprises a Wadsly-Roth phase, The above metal oxide has a crystallographic shear structure, The above metal oxide comprises a framework formed by a plurality of MO6 octahedra, a plurality of NbO6 octahedra, or a combination thereof, An all-solid-state secondary battery, wherein the above-mentioned skeleton includes pores, and the size of the pores is less than 3 Å.

6. In the fifth paragraph, the lithium diffusion coefficient (D) of the metal oxide Li ) is 1.0×10 at 25 ℃ and 1 atm -15 cm 2 / s or more, The electronic conductivity of the above metal oxide is 1.0×10 at 25 ℃ and 1 atm. -9 All-solid-state secondary battery with S / cm or more.

7. In the fifth paragraph, the metal oxide further includes a dopant, An all-solid-state secondary battery, wherein the dopant comprises a metal belonging to group 3 to group 15 of the periodic table, N, P, S, or a combination thereof.

8. In the first paragraph, the mixed conductor includes a fibrous mixed conductor, a particulate mixed conductor, or a combination thereof, The above fibrous mixed conductor includes fibrous microstructures, fibrous nanostructures or a combination thereof, The above fibrous microstructure comprises a microtube, a microfiber, a microrod, a microwire or a combination thereof, The above fibrous nanostructure comprises a nanotube, a nanofiber, a nanorod, a nanowire or a combination thereof, The aspect ratio of the above fibrous mixed conductor is 5 or more, The cross-sectional shape of the above fibrous mixed conductor is circular, elliptical or polygonal, The above particulate mixed conductor includes particulate microstructures, particulate nanostructures or a combination thereof, The above particle-like microstructure includes microspheres and microparticles, The above particle-like nanostructure includes nanospheres and nanoparticles, An all-solid-state secondary battery, wherein the aspect ratio of the above particle-phase mixed conductor is 3 or less.

9. An all-solid-state secondary battery in accordance with claim 1, wherein the mixed conductor comprises a composite of the metal oxide and a carbon-based material.

10. In the 9th paragraph, the carbon-based material includes a carbon-based nanostructure, The above carbon nanostructure includes a one-dimensional carbon nanostructure, a two-dimensional carbon nanostructure, or a combination thereof, The above one-dimensional carbon nanostructure includes carbon nanofibers, carbon nanotubes, carbon nanowires, carbon nanorods, carbon nanobelts, or a combination thereof, An all-solid-state secondary battery, wherein the two-dimensional carbon nanostructure comprises graphene, a carbon web, or a combination thereof.

11. In the first paragraph, the size of the mixed conductor is 1 to 20 ㎛, An all-solid-state secondary battery, wherein the content of the mixed conductor is 20 wt% or less of the total weight of the positive electrode active material layer.

12. In the first paragraph, the positive electrode active material layer further includes a solid electrolyte, The above solid electrolyte includes 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.

13. In the first paragraph, the cathode active material includes an oxide-based cathode active material, a sulfide-based cathode active material, or a combination thereof, The above oxide-based cathode active material includes a lithium transition metal oxide, a metal oxide, or a combination thereof, and the lithium transition metal oxide includes 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, and the lithium oxide includes iron oxide, vanadium oxide, or a combination thereof. An all-solid-state secondary battery, wherein the sulfide-based cathode active material comprises nickel sulfide, copper sulfide, Li2S, a Li2S-containing complex, or a combination thereof.

14. In the first paragraph, the positive electrode active material includes a composite positive electrode active material, The composite cathode active material comprises a core including a lithium transition metal oxide; and a shell disposed along the surface of the core, The above shell contains an inorganic filler, An all-solid-state secondary battery, wherein the content of the inorganic filler is 0.1 to 20 parts by weight based on 100 parts by weight of the core.

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, An all-solid-state secondary battery, wherein the negative electrode active material has a particle form and the average particle diameter of the negative electrode active material is 4 ㎛ or less.

17. In the 16th paragraph, the negative electrode active material includes at least one selected from a carbon-based negative electrode active material and a metal or metalloid negative electrode active material, The above carbon-based negative electrode active material includes amorphous carbon, crystalline carbon, porous carbon, or a combination thereof. 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.

18. 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 a metalloid, The content of the second particles is 1 to 60 wt% based on the total weight of the mixture, Further comprising a second negative electrode active material layer disposed between the negative electrode current collector and the first negative electrode active material layer and between the negative electrode current collector and the electrolyte layer, An all-solid-state secondary battery, wherein the second negative electrode active material layer is a metal layer, and the metal layer includes lithium or a lithium alloy.

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

20. In the 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, The above 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, An all-solid-state secondary battery further comprising an inert member disposed on one side of the positive electrode.

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