All-solid state secondary battery

Abstract

Disclosed is an all-solid state secondary battery comprising: a positive electrode layer; a negative electrode layer; and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, wherein: the positive electrode layer includes a positive electrode current collector and a positive electrode active material layer disposed on one surface or both surfaces of the positive electrode current collector; the positive electrode active material contains an M2S-containing composite; M is Li or Na; the solid electrolyte layer includes a first solid electrolyte layer containing a solid electrolyte represented by chemical formula 1 and a second solid electrolyte layer containing a solid electrolyte represented by chemical formula 2; the first solid electrolyte layer is disposed directly on at least one of the positive electrode active material layer and a first negative electrode active material layer; and the negative electrode layer includes a negative electrode current collector and the first negative electrode active material layer disposed on one surface of the negative electrode current collector. Chemical formulas 1 and 2 are as defined in the detailed description.

Description

All-solid-state secondary batteries

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

[0002] Recently, there has been active development of batteries that offer increased energy density and safety. Lithium batteries are used in information technology, communication devices, and automobiles. Because automobiles are life-threatening, safety is paramount.

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

[0004] Solid electrolytes offer reduced risk of overheating and fire during short circuits compared to liquid electrolytes. Lithium batteries containing solid electrolytes can offer improved safety compared to those containing liquid electrolytes.

[0005] Secondary batteries use sulfur-based materials (e.g., S) as cathode active materials to increase capacity. Since lithium is not included in the cathode during the manufacturing of secondary batteries containing sulfur-based materials, lithium metal is used for the anode. During the initial discharge process of the secondary battery, lithium metal migrates to the cathode containing the sulfur-based material, and then, during the subsequent charging process, lithium metal is deposited again between the anode current collector and the electrolyte layer. During the lithium deposition process, irregular lithium deposition can easily form lithium dendrites and / or isolated lithium. The formation of such lithium dendrites and / or isolated lithium can reduce the reversibility of the electrode reaction. A method for suppressing the uneven deposition of lithium from the anode is required.

[0006] In secondary batteries containing lithium metal, a short circuit between the lithium metal and the cathode may occur due to the growth of lithium dendrites and / or the dissolution of molten lithium during the charge / discharge process. A secondary battery capable of effectively preventing the growth of lithium dendrites and / or the short circuit between the lithium metal and the cathode during the charge / discharge process is required.

[0007] In the above secondary batteries, LiPSCl, a sulfide-based solid electrolyte, is mainly used as a solid electrolyte. However, this solid electrolyte has low ionic conductivity, resulting in poor high-rate characteristics, and thus, improvement is required.

[0008] One aspect is to provide an all-solid-state secondary battery with improved rate characteristics and life characteristics by using a solid electrolyte layer with improved ionic conductivity.

[0009] According to one embodiment, an all-solid-state secondary battery comprising a positive electrode layer; a negative electrode layer; and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer,

[0010] The above positive electrode layer comprises a positive electrode current collector; and a positive electrode active material layer disposed on one or both sides of the positive electrode current collector,

[0011] The above cathode active material contains a M2S-containing complex, wherein M is an alkali metal, and the alkali metal is Li or Na,

[0012] The solid electrolyte layer includes a first solid electrolyte layer containing a solid electrolyte represented by the following chemical formula 1 and a second solid electrolyte layer containing a solid electrolyte represented by the following chemical formula 2, wherein the first solid electrolyte layer is directly disposed on at least one of the positive electrode active material layer and the first negative electrode active material layer.

[0013] 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 disposed on one surface of the negative electrode current collector.

[0014] <Chemical Formula 1>

[0015] (Li1-b M b ) 7-z PS 6-z M3 z

[0016] In chemical formula 1, M is Na, K, Fe, Mg, Ca, Ag, Cu, Zr, Zn or a combination thereof, M3 is an element selected from group 17 of the periodic table, and 0≤b≤0.05, 0≤z≤2,

[0017] <Chemical Formula 2>

[0018] Li a M1 x M2 w PS y M3 z

[0019] In chemical formula 2, M1 is an element selected from groups 2 and 11 of the periodic table, M2 is a metal element other than Li selected from group 1 of the periodic table, and M3 is an element selected from group 17 of the periodic table, and 4≤a≤8, 0≤x≤0.5, 0≤w≤0.5, 3≤y≤7, 0≤z≤2.

[0020] According to one aspect, an all-solid-state secondary battery with improved energy density and high-rate characteristics can be provided through an improved sulfide-based solid electrolyte.

[0021] Figure 1 is a cross-sectional view of an all-solid-state secondary battery according to an embodiment.

[0022] Figure 2 is a cross-sectional view of an all-solid-state secondary battery according to another embodiment.

[0023] Figures 3 to 6 are cross-sectional views of an all-solid-state secondary battery according to another embodiment.

[0024] <Explanation of symbols for major parts of the drawing>

[0025] 1 All-solid-state secondary battery 10 Cathode layer

[0026] 11. Cathode current collector 12. Cathode active material layer

[0027] 20 Cathode layer 21 Cathode current collector

[0028] 22 Lithium host layer 30 Solid electrolyte layer

[0029] 40 Inert elements

[0030] Various embodiments are illustrated in the accompanying drawings. However, the present invention may be embodied in many different forms and should not be construed as limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. Like reference numerals in the drawings indicate like elements.

[0031] 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.

[0032] Although the terms "first," "second," "third," etc. may be used herein to describe various components, elements, regions, layers, and / or zones, these components, elements, regions, layers, and / or zones should not be limited by these terms. These terms are used only 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 specification.

[0033] 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.

[0034] For example, "at least one of a, b, or c," "at least one of a, b, c," "at least one of a through c," etc. can mean a alone, b alone, c alone, both a and b (e.g., simultaneously), both a and c, both b and c (e.g., simultaneously), all a, b, and c, or variations thereof. As used herein, " / " can be interpreted as "and" or "or," depending on the context.

[0035] Spatially relative terms such as "below," "under," "bottom," "above," "above," and "top" 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.

[0036] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. Furthermore, it will be understood that terms defined in commonly used dictionaries should be interpreted to have a meaning consistent with their meaning within the context of the relevant art and the present disclosure, and not in an idealized or overly formal sense.

[0037] Exemplary embodiments are described herein 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 herein should not be construed as limited to the specific shapes of regions as depicted herein, 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.

[0038] "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.

[0039] As used herein, "particle diameter" or "particle size" refers to the average diameter / size of particles (e.g., crystallites or crystallite particles) when the particles are spherical, or the average major axis length when the particles are non-spherical. Particle diameter can be measured using a particle size analyzer (PSA). "Particle diameter" is, for example, the average particle diameter. "Average particle diameter" is, for example, the median particle diameter, D50.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] In this disclosure, “metal” includes both metals and metalloids such as silicon and germanium, in their elemental or ionic states.

[0044] In this disclosure, “alloy” means a mixture of two or more metals.

[0045] In the present disclosure, “electrode active material” means an electrode material capable of undergoing lithiation and delithiation.

[0046] In the present disclosure, “positive electrode material” means a positive electrode material capable of undergoing lithiation and delithiation.

[0047] In the present disclosure, “negative electrode active material” means a negative electrode material capable of undergoing lithiation and delithiation.

[0048] In the present disclosure, “lithiation” and “lithiating” mean a process of adding lithium to an electrode active material.

[0049] In the present disclosure, “delithiation” and “delithiate” mean a process of removing lithium from an electrode active material.

[0050] In this disclosure, “charging” and “charging” mean a process of providing electrochemical energy to a battery.

[0051] In this disclosure, “discharging” and “discharging” mean the process of removing electrochemical energy from a battery.

[0052] In the present disclosure, “positive electrode” and “cathode” mean an electrode at which electrochemical reduction and lithiation occur during a discharge process.

[0053] In the present disclosure, “cathode” and “anode” mean electrodes where electrochemical oxidation and delithiation occur during a discharge process.

[0054] In this disclosure, “length,” “thickness,” and “width” represent, for example, average length, average thickness, and average width, respectively. The length, thickness, and width can be measured using software utilizing a scanning electron microscope.

[0055] In the present disclosure, the aspect ratio represents the ratio (L1 / L2) of the major axis length L1 (e.g., length) and the minor axis length L2 (e.g., diameter). Here, the aspect ratio, major axis length, minor axis length, length, and diameter represent the average aspect ratio, average major axis length, average minor axis length, average length, and average diameter. The aspect ratio can be evaluated using a scanning electron microscope.

[0056] 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.

[0057] Hereinafter, an all-solid-state secondary battery according to exemplary implementation examples will be described in more detail.

[0058] An all-solid-state secondary battery according to one embodiment includes a positive electrode layer; a negative electrode layer; and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, wherein the positive electrode layer includes a positive electrode current collector; and a positive electrode active material layer disposed on one or both surfaces of the positive electrode current collector, wherein the positive electrode active material contains a M2S-containing complex, wherein M is an alkali metal, and the alkali metal is Li or Na. In addition, the solid electrolyte layer includes a first solid electrolyte layer containing a solid electrolyte represented by the following chemical formula 1 and a second solid electrolyte layer containing a solid electrolyte represented by the following chemical formula 2, wherein the first solid electrolyte layer is directly disposed on at least one of the positive electrode active material layer and the first negative electrode active material layer, and the negative electrode layer includes a negative electrode current collector and a first negative electrode active material layer disposed on one surface of the negative electrode current collector.

[0059] <Chemical Formula 1>

[0060] (Li 1-b M b ) 7-z PS 6-z M3 z

[0061] In chemical formula 1, M is Na, K, Fe, Mg, Ca, Ag, Cu, Zr, Zn or a combination thereof, M3 is an element selected from group 17 of the periodic table, and 0≤b≤0.05, 0≤z≤2,

[0062] <Chemical Formula 2>

[0063] Li a M1 x M2 w PS y M3 z

[0064] In chemical formula 2, M1 is an element selected from groups 2 and 11 of the periodic table,

[0065] M2 is a metallic element other than Li selected from group 1 of the periodic table,

[0066] M3 is an element selected from group 17 of the periodic table, where 4≤a≤8, 0≤x≤0.5, 0≤w≤0.5, 3≤y≤7, and 0≤z≤2.

[0067] The first solid electrolyte layer of the above solid electrolyte layer is arranged adjacent to the positive electrode layer.

[0068] The first solid electrolyte layer includes a solid electrolyte represented by chemical formula 1, and this solid electrolyte has excellent lithium ion conductivity, oxidation stability, and atmospheric stability, and thus, by including the solid electrolyte, an all-solid-state secondary battery with improved stability and cycle characteristics can be provided.

[0069] Lithium-sulfur solid-state batteries using the existing sulfide-based electrolyte, LiPSCl, exhibit poor high-rate performance due to low ionic conductivity. Ionic conductivity can be improved by using a sulfide-based electrolyte with some lithium cations substituted.

[0070] The solid electrolyte represented by Chemical Formula 1 can improve the ionic conductivity of lithium ions and reduce the activation energy in the compound by including Na, K, Fe, Mg, Ca, Ag, Cu, Zr, Zn or a combination thereof in some of the lithium sites in the crystal. Ionic conductivity is a very important factor in the lifespan and high-rate characteristics of an all-solid-state secondary battery, and by using the above-described solid electrolyte layer, not only can the ionic conductivity of lithium sulfide, which is insufficient in the positive electrode, be improved, but also the lithium sulfide content can be increased, thereby manufacturing an all-solid-state secondary battery with improved energy density.

[0071] The solid electrolyte represented by the above chemical formula 1 is represented by the following chemical formula 1-1.

[0072] It is a solid electrolyte.

[0073] <Chemical Formula 1-1>

[0074] (Li 1-b Cu b ) 7-z PS 6-z M3 z

[0075] In chemical formula 1-1, M3 is F, Cl, Br, or I, and 0≤b≤0.05, 0≤z≤2.

[0076] In the above chemical formulas 1, 2 and 1-1, M3 is F, Cl, Br, or I, in chemical formula 2, M1 is Mg, Ag, Cu, Hf, In, Ti, Pb, Sb, Fe, Zr, Zn, Cr, B, Sn, Ge, Si, Zr, Ta, Nb, V, Ga, Al, As, or a combination thereof, and M2 is Na, K, or a combination thereof.

[0077] The solid electrolytes of the above Chemical Formula 1 and Chemical Formula 1-1 can improve the ionic conductivity of lithium ions and reduce the activation energy in the compound by including copper that substitutes for some of the lithium sites in the crystal, thereby manufacturing an all-solid-state secondary battery with improved rate characteristics and initial capacity. By using the solid electrolyte with improved ionic conductivity as a positive electrode electrolyte, the ionic conductivity characteristics of a positive electrode containing a lithium sulfide-containing complex can be improved, and the energy density can be increased by increasing the relative content of lithium sulfide by reducing the content of the positive electrode electrolyte.

[0078] The thickness of the first solid electrolyte layer and the second solid electrolyte are each 10 to 200 μm, and the thickness ratio of the first solid electrolyte layer and the second solid electrolyte is 1:1 to 6:4. When the thickness and thickness ratio of the first solid electrolyte layer and the second solid electrolyte are within the above-described range, an all-solid-state secondary battery with improved energy density and high-rate characteristics can be provided.

[0079] The above solid electrolyte layer may further contain a third solid electrolyte layer containing a third sulfide-based solid electrolyte different from the first sulfide-based solid electrolyte.

[0080] The third sulfide-based solid electrolyte is represented by the following chemical formula 3, and the third solid electrolyte layer can be arranged on top of the second solid electrolyte layer. As a result, the solid electrolyte layer has a three-layer structure.

[0081] <Chemical Formula 3>

[0082] (Li 1-b M b ) 7-z PS 6-z M4 z

[0083] In chemical formula 3, M is Na, K, Fe, Mg, Ca, Ag, Cu, Zr, Zn or a combination thereof,

[0084] M4 is an element selected from group 17 of the periodic table, 0≤b≤0.05, 0≤z≤2.

[0085] The solid electrolyte represented by chemical formula 3 is, for example, a solid electrolyte represented by chemical formula 3-1 below.

[0086] <Chemical Formula 3-1>

[0087] (Li 1-b Cu b ) 7-z PS 6-z M4 z

[0088] In chemical formula 3-1, M4 is F, Cl, Br, or I, and 0≤b≤0.05, 0≤z≤2.

[0089] The first sulfide-based solid electrolyte and the second sulfide-based solid electrolyte include a large-particle-size solid electrolyte having an average particle size of 3 to 10 μm and a small-particle-size solid electrolyte having an average particle size of 1 to 3 μm, respectively, and the mixing weight ratio of the large-particle-size solid electrolyte and the small-particle-size solid electrolyte is 10:90 to 90:10. The first sulfide-based solid electrolyte and the second sulfide-based solid electrolyte, in which the large-particle-size solid electrolyte and the small-particle-size solid electrolyte are mixed in this way, can suppress the formation of defects such as cracks in the solid electrolyte layer by filling pinholes, etc. existing in the solid electrolyte. The cycle characteristics of the all-solid-state secondary battery can be further improved. For example, the high-rate characteristics, life characteristics, etc. of the all-solid-state secondary battery can be improved.

[0090] Referring to FIGS. 1 and 2, an all-solid-state secondary battery (1) includes a positive electrode layer (10); a negative electrode layer (10); and a solid electrolyte layer (30) disposed between the positive electrode layer (10) and the negative electrode layer (10).

[0091] The above solid electrolyte layer (30) includes a first solid electrolyte layer (30a) and a second solid electrolyte layer (30b), as shown in FIG. 1.

[0092] The positive electrode layer (10) includes a positive electrode current collector (11) and a positive electrode active material layer (12) disposed on one or both surfaces of the positive electrode current collector (11), and the positive electrode active material layer (12) includes a Li2S-containing complex. The negative electrode layer (20) includes a negative electrode current collector (21) and a first negative electrode active material layer (22) disposed on one surface of the negative electrode current collector (21).

[0093] The solid electrolyte layer (30) includes a first solid electrolyte layer (30a), a second solid electrolyte layer (30b), and a third solid electrolyte layer (30c), as shown in FIG. 2.

[0094] The total thickness of the solid electrolyte layer (30) is 10 to 200 um, and the thickness of the first solid electrolyte layer (30a) and the thickness of the second solid electrolyte layer (30b) are each 50 to 80 um. In addition, the thickness ratio of the first solid electrolyte layer (30a) and the thickness ratio of the second solid electrolyte layer (30b) are each 10:90 to 90:10, for example, 60:40 to 40:60.

[0095] The above positive electrode layer may include a solid electrolyte represented by the following chemical formula 1.

[0096] <Chemical Formula 1>

[0097] (Li 1-b M b ) 7-z PS 6-z M3 z

[0098] In chemical formula 1, M is Na, K, Fe, Mg, Ca, Ag, Cu, Zr, Zn or a combination thereof, M3 is an element selected from group 17 of the periodic table, and 0≤b≤0.05, 0≤z≤2.

[0099] The solid electrolyte represented by the above chemical formula 1 is, for example, a solid electrolyte represented by the following chemical formula 1-1.

[0100] <Chemical Formula 1-1>

[0101] (Li 1-b Cu b ) 7-z PS 6-z M3 z

[0102] In chemical formula 1-1, M3 is an element selected from group 17 of the periodic table, and 0≤b≤0.05, 0≤z≤2.

[0103] The solid electrolyte represented by the above chemical formula 1 and the solid electrolyte represented by the chemical formula 2 provide improved lithium ion conductivity. The electrolyte represented by the chemical formula 1 provides an ion conductivity of 1.0 mS / cm or more, 1.5 mS / cm or more, 2.0 mS / cm or more, 2.5 mS / cm or more, 3.0 mS / cm or more, 3.5 mS / cm or more, 4.0 mS / cm or more, or 5.0 mS / cm or more at room temperature, for example, at about 25°C. The solid electrolyte represented by Chemical Formula 1 provides an ionic conductivity of 1.0 to 500 mS / cm, 1.5 to 400 mS / cm, 2.0 to 300 mS / cm, 2.5 to 200 mS / cm, 3.0 to 150 mS / cm, 3.5 to 100 mS / cm, 4.0 to 100 mS / cm, or 5.0 to 100 mS / cm at room temperature, for example, at about 25°C. Therefore, in an all-solid-state secondary battery including a positive electrode; a negative electrode; and an electrolyte represented by Chemical Formula 1 disposed between the positive electrode and the negative electrode, ion transfer between the positive electrode and the negative electrode can be effectively performed, thereby reducing internal resistance between the positive electrode and the negative electrode. The ionic conductivity can be measured using a DC polarization method. Alternatively, ionic conductivity can be measured using complex impedance.

[0104] [Solid electrolyte layer: solid electrolyte]

[0105] 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.

[0106] The solid electrolyte is, for example, a sulfide-based solid electrolyte. The sulfide-based solid electrolyte is, 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.

[0107] The sulfide-based solid electrolyte may include, for example, an argyrodite type solid electrolyte represented by the following chemical formula 4:

[0108] <Chemical Formula 4>

[0109] Li + 12-n-x A n+ X 2- 6-x Y - x

[0110] In chemical formula 4, 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.

[0111] 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.

[0112] Oxide-based solid electrolytes include, for example, Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (0 <x<2, 0≤y<3), BaTiO3, Pb(Zr,Ti)O3(PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT)(0≤x<1, 0≤y<1), PB(Mg3Nb 2 / 3 )O3-PbTiO3(PMN-PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, Li3PO4, Li x Ti y (PO4)3(0 <x<2, 0<y<3), Li x Al y Ti z (PO4)3(0 <x<2, 0<y<1, 0<z<3), Li1+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.

[0113] 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.

[0114] A polymer solid electrolyte is an electrolyte that includes, for example, a mixture of a lithium salt and a polymer, or a polymer having an ion-conducting functional group. A polymer solid electrolyte is, for example, a polymer electrolyte that does not include a liquid electrolyte.Polymers included in the polymer solid electrolyte include, for example, polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene (PVDF-HFP), poly(styrene-b-ethylene oxide) block copolymer (PS-PEO), poly(styrene-butadiene), poly(styrene-isoprene-styrene), poly(styrene-b-divinylbenzene) block copolymer, poly(styrene-ethylene oxide-styrene) block copolymer, polystyrene sulfonate (PSS), polyvinyl fluoride (PVF), polymethyl methacrylate (PMMA), poly(methylmethacrylate), polyethylene glycol (PEG), polyacrylonitrile (PAN), polytetrafluoroethylene (PTFE), polyethylenedioxythiophene (PEDOT), polypyrrole (PPY), polyaniline, polyacetylene, Nafion, Aquivion, Flemion, Gore, Aciplex, Morgane ADP, sulfonated poly(ether ether ketone) (SPEEK), sulfonated poly(arylene ether ketone ketone sulfone) (SPAEKKS), sulfonated poly(aryl ether ketone) (SPAEK), poly[bis(benzimidazobenzisoquinolinones)] (SPBIBI), poly(styrene sulfonate) (PSS), lithium 9,10-diphenylatlacene-2-sulfonate 9,10-diphenylanthracene-2-sulfonate, DPASLi. +) or a combination thereof, but is not limited thereto, and any polymer electrolyte used in the art may be used. The lithium salt may be any lithium salt that can be used in the art. The lithium salt may be, 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.

[0115] A gel electrolyte is, for example, a gel polymer electrolyte. A gel polymer electrolyte is, for example, an electrolyte that includes a liquid electrolyte and a polymer, or an organic solvent and a polymer having an ion-conducting functional group. The liquid electrolyte can be, for example, an ionic liquid, a mixture of a lithium salt and an organic solvent, a mixture of an ionic liquid and an organic solvent, or a mixture of a lithium salt, an ionic liquid, and an organic solvent. The polymer can be selected from the polymers used in solid polymer electrolytes. The organic solvent can be selected from the organic solvents used in liquid electrolytes. The lithium salt can be selected from the lithium salts used in solid polymer electrolytes. An ionic liquid refers to a salt that is liquid at room temperature or a room-temperature molten salt that has a melting point below room temperature and is composed only of ions. Ionic liquids include, for example, a) one or more cations selected from ammonium, pyrrolidinium, pyridinium, pyrimidinium, imidazolium, piperidinium, pyrazolium, oxazolium, pyridazinium, phosphonium, sulfonium, triazolium and mixtures thereof, and b) BF4-, PF6-, AsF6-, SbF6-, AlCl4-, HSO4-, ClO4-, CH3SO3-, CF3CO2-, Cl-, Br-, I-, SO4 2-, CF3SO3-, (FSO2)2N-, (C2F5SO2)2N-, (C2F5SO2)(CF3SO2)N-, and (CF3SO2)2N- may include at least one selected from compounds containing at least one anion selected from among the following. The polymer solid electrolyte may form a gel polymer electrolyte by being impregnated into an electrolyte solution in a lithium battery. The gel electrolyte may further include inorganic particles.

[0116] [Solid electrolyte layer: binder]

[0117] 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.

[0118] 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).

[0119] [Anode layer]

[0120] [Anode layer: cathode active material]

[0121] Referring to FIGS. 1 to 6, 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 an M2S-containing composite as the positive electrode active material.

[0122] The M2S-containing composite includes a composite of M2S and a carbon-based material, a composite of M2S and a carbon-based material and a solid electrolyte, a composite of M2S and a solid electrolyte, a composite of M2S and a carbon-based material and an alkali metal salt, a composite of M2S and an alkali metal salt, a composite of M2S and a metal carbide, a composite of M2S and a carbon-based material and a metal carbide, a composite of M2S and a metal nitride, a composite of M2S and a carbon-based material and a metal nitride, or a combination thereof.

[0123] A composite cathode active material according to an embodiment of the present invention contains M2S; and an alkali metal salt, wherein M is an alkali metal, and the alkali metal is Li or Na.

[0124] The above M2S-containing complex is a Li2S-containing complex, and the Li2S-containing complex includes a complex of Li2S and a carbon-based material, a complex of Li2S and a carbon-based material and a solid electrolyte, a complex of Li2S and a solid electrolyte, a complex of Li2S and a carbon-based material and a lithium salt, a complex of Li2S and a lithium salt, a complex of Li2S and a metal carbide, a complex of Li2S and a carbon-based material and a metal carbide, a complex of Li2S and a metal nitride, a complex of Li2S and a carbon-based material and a metal nitride, or a combination thereof.

[0125] According to one embodiment, a composite cathode active material includes a composite of M2S, an alkali metal salt, and a carbon-based material. M is an alkali metal. The alkali metal is Li or Na. M2S is, for example, Li2S or Na2S. The size of M2S crystallites obtained from an XRD spectrum of the composite is less than 9.9 nm. The size of M2S crystallites obtained from an XRD spectrum of the composite is, for example, 9.85 nm or less, 9.83 nm or less, 9.8 nm or less, 9.5 nm or less, 9.0 nm or less, or 8.5 nm or less. The composite includes a solid solution of M2S and an alkali metal salt. The size of the M2S crystallites obtained from the XRD spectrum of the complex is, for example, 1 nm or more and less than 9.9 nm, 1 to 9.8 nm, 2 to 9.8 nm, 2 to 9.5 nm, 2 to 9.0 nm, 2 to 8.5 nm or 3 to 8.5 nm. The complex comprises a solid solution of M2S and an alkali metal salt.

[0126] By forming a composite of M2S with an alkali metal salt and a carbon-based material, the ionic conductivity and electronic conductivity of M2S can be simultaneously improved. Since the composite includes an alkali metal salt, the ionic conductivity of the composite cathode active material can be improved, and the internal resistance of the cathode and lithium battery including the composite cathode active material can be reduced. Since the composite includes a carbon-based material, the electronic conductivity of the composite cathode active material can be improved, and the internal resistance of the cathode and lithium battery including the composite cathode active material can be reduced.

[0127] The composite includes M2S crystallites, and as the size of the M2S crystallites is reduced to 21 nm or less, the volume change of the M2S crystallites during charge and discharge can be alleviated. For example, as the size of the M2S crystallites is reduced, the volume change due to a single M2S crystallite is reduced, so the overall volume change of the composite during charge and discharge can be alleviated. For example, as the size of the M2S crystallites is reduced, the grain boundaries between a plurality of M2S crystallites can more easily accommodate the volume change of the M2S crystallites during charge and discharge, so the volume change of the composite during charge and discharge can be alleviated. The possibility of defects such as cracks occurring due to the volume change of the composite during charge and discharge can be reduced. When the composite cathode active material includes such a composite, the cycle characteristics of a secondary battery including the composite cathode active material can be improved. For example, the cycle characteristics of a lithium battery including such a composite cathode active material are improved.

[0128] The composite includes M2S crystallites, and as the size of the M2S crystallites is reduced to 21 nm or less, the contact area between the M2S crystallites and the alkali metal salt and / or the carbon-based material can be further increased. As the contact area between the M2S crystallites and the alkali metal salt and / or the carbon-based material increases, the ionic conductivity and / or battery conductivity of the composite can be further improved. As the composite cathode active material includes such a composite, the reversibility of the electrode reaction can be improved in a secondary battery including the composite cathode active material. As a result, the specific capacity of the composite cathode active material can be increased.

[0129] The ionic conductivity of the composite may increase when the composite includes a solid solution of M2S and an alkali metal salt. For example, since the solid solution of M2S and an alkali metal salt includes alkali metal ions arranged within the M2S crystallites, the ionic conductivity of the solid solution of M2S and an alkali metal salt may be improved compared to the ionic conductivity of M2S. Consequently, the ionic conductivity of the composite may be improved and the internal resistance of the composite may be reduced. When the composite cathode active material includes such a composite, the cycle characteristics of a secondary battery including the composite cathode active material may be improved. For example, the high-rate characteristics of a secondary battery including such a composite cathode active material may be improved.

[0130] Li2S-alkali metal salt-carbon material composites are distinguished from simple mixtures of Li2S, alkali metal salts, and carbon-based materials. Simple mixtures of Li2S, alkali metal salts, and carbon-based materials fail to maintain a dense interface between the Li2S, alkali metal salt, and carbon-based materials, resulting in high interfacial resistance and consequently degrading the lifespan characteristics of secondary batteries.

[0131] The composite includes M2S. Since M2S has a high theoretical capacity, an all-solid-state secondary battery having a high energy density can be provided. However, since M2S has low ionic conductivity and / or electronic conductivity, a composite is formed with an alkali metal salt and a carbon-based material to overcome this drawback. The content of M2S in the composite may be, for example, 10 to 80 wt%, 20 to 70 wt%, 30 to 60 wt%, or 40 to 60 wt% of the total weight of the composite. If the content of M2S is excessively increased, it may not be easy to improve the ionic conductivity and / or electronic conductivity of M2S. If the content of M2S is excessively low, the energy density of the secondary battery may be reduced.

[0132] The complex comprises an alkali metal salt. An alkali metal salt is, for example, a compound that does not contain sulfur (S). The alkali metal salt may be, for example, a binary compound or a ternary compound. The alkali metal salt may be, for example, a binary compound composed of an alkali metal and one element selected from Groups 13 to 17 of the Periodic Table of the Elements. The alkali metal salt may be, for example, a ternary compound composed of an alkali metal and two elements selected from Groups 13 to 17 of the Periodic Table of the Elements.

[0133] The alkali metal salt may be, for example, a lithium salt. The lithium salt binary compound may include, for example, LiI, LiBr, LiCl, LiF, LiH, Li2O, Li2Se, Li2Te, Li3N, Li3P, Li3As, Li3Sb, Li3Al2, LiB3, or a combination thereof. The lithium salt ternary compound may include, for example, Li3OCl, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiNO3, Li2CO3, LiBH4, Li2SO4, Li3BO3, Li3PO4, Li4NCl, Li5NCl2, Li3BN2, or a combination thereof. The ionic conductivity of the complex may be further improved by including such a lithium salt in the complex. Such a lithium salt may more easily form a solid solution with Li2S, for example, in the complex.

[0134] The alkali metal salt may be, for example, a sodium salt. The sodium salt binary compound may include, for example, NaI, NaBr, NaCl, NaF, Na2O, Na2Se, Na3N, Na3P, Na3As, Na3Sb, Na3Al2, NaB3, or a combination thereof. The sodium salt ternary compound may include, for example, Na3OCl, NaBF4, NaPF6, NaAsF6, NaClO4, NaNO3, NaAlO2, NaAlCl4, NaNO3, Na2CO3, NaBH4, Na2SO4, Na3BO3, Na3PO4, Na4NCl, Na5NCl2, Na3BN2, or a combination thereof. The ionic conductivity of the complex may be further improved by including such sodium salts in the complex. Such sodium salts may more readily form a solid solution with Na2S, for example, in the complex.

[0135] The content of the alkali metal salt in the composite may be 1 to 40 wt%, 5 to 35 wt%, 10 to 35 wt%, 15 to 35 wt%, 20 to 35 wt%, or 25 to 35 wt% of the total weight of the composite. If the content of the alkali metal salt is excessively increased, the energy density of the secondary battery may decrease. If the content of the alkali metal salt is excessively low, the ionic conductivity of the composite may decrease, which may increase the internal resistance of the composite cathode active material. As a result, the cycle characteristics of the secondary battery may deteriorate.

[0136] The molar ratio of M2S and the alkali metal salt in the composite may be, for example, 50:50 to 95:5, 60:40 to 95:5, 60:40 to 90:10, 65:35 to 90:10, 65:35 to 85:15, or 70:30 to 85:15. The molar ratio of M2S and the alkali metal salt in the composite may be, for example, 50:50 to 95:5, 50:50 to 90:10, 50:50 to 85:15, 50:50 to 80:20, 50:50 to 75:25, or 50:50 to 70:30. When M2S and the alkali metal salt have a molar ratio in this range, the cycle characteristics of a secondary battery including the composite positive electrode active material can be further improved. If the molar ratio of M2S is excessively high, the ionic conductivity enhancement effect of the alkali metal salt may be minimal. If the molar ratio of M2S is excessively high, the energy density of the secondary battery containing the composite cathode active material may be reduced.

[0137] The molar ratio of Li2S and lithium salt in the composite may be, for example, 50:50 to 95:5, 60:40 to 95:5, 60:40 to 90:10, 65:35 to 90:10, 65:35 to 85:15, or 70:30 to 85:15. The molar ratio of Li2S and lithium salt in the composite may be, for example, 50:50 to 95:5, 50:50 to 90:10, 50:50 to 85:15, 50:50 to 80:20, 50:50 to 75:25, or 50:50 to 70:30. By having Li2S and lithium salt in this range of molar ratio, the cycle characteristics of a lithium battery including the composite cathode active material can be further improved. If the molar ratio of Li2S is excessively high, the ionic conductivity enhancement effect of lithium salt may be minimal. If the molar ratio of Li2S is excessively high, the energy density of lithium batteries containing composite cathode active materials may decrease.

[0138] The molar ratio of Na2S and sodium salt in the composite may be, for example, 50:50 to 95:5, 60:40 to 95:5, 60:40 to 90:10, 65:35 to 90:10, 65:35 to 85:15, or 70:30 to 85:15. The molar ratio of Na2S and sodium salt in the composite may be, for example, 50:50 to 95:5, 50:50 to 90:10, 50:50 to 85:15, 50:50 to 80:20, 50:50 to 75:25, or 50:50 to 70:30. By having the molar ratio of Na2S and sodium salt in this range, the cycle characteristics of a sodium battery including the composite cathode active material may be further improved. If the molar ratio of Na2S is excessively high, the effect of sodium salt on improving ionic conductivity may be minimal. If the molar ratio of Na2S is excessively high, the energy density of a sodium battery containing a composite cathode active material may decrease.

[0139] The composite includes a carbon-based material. The carbon-based material can be, for example, any material containing carbon atoms that is used as a conductive material in the art. The carbon-based material can be, for example, crystalline carbon, amorphous carbon, or a combination thereof. The carbon-based material can be, for example, a sintered product of a carbon precursor. The carbon-based material can be, for example, a carbon nanostructure. The carbon nanostructure can 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 can be, for example, a carbon nanotube, a carbon nanofiber, a carbon nanobelt, a carbon nanorod, graphene, or a combination thereof. The carbon-based material can be, for example, a porous carbon-based material or a non-porous carbon-based material. The porous carbon-based material can include, for example, periodic and regular two-dimensional or three-dimensional pores. The porous carbon-based material may be, for example, carbon black such as Ketjen Black, acetylene black, Denka Black, thermal black, channel black, etc.; graphite, activated carbon, or a combination thereof. The form of the carbon-based material may be, but is not limited to, particle form, sheet form, flake form, etc., and any form used as a carbon-based material in the relevant technical field may be used.

[0140] The content of the carbon-based material included in the composite may be, for example, 1 to 20 wt%, 5 to 20 wt%, or 10 to 20 wt% of the total weight of the composite. If the content of the carbon-based material increases excessively, the energy density of the secondary battery may decrease. If the content of the carbon-based material decreases excessively, the electronic conductivity of the composite may decrease, which may increase the internal resistance of the composite cathode active material. As a result, the cycle characteristics of the secondary battery may deteriorate.

[0141] In the XRD spectrum of the composite, for example, a first peak appearing at a diffraction angle 2θ = 27° ± 2.0° corresponding to the (111) crystal plane of M2S has a first diffraction angle, and in the XRD spectrum of M2S used in the preparation of the composite, a second peak appearing at a diffraction angle 2θ = 27° ± 2.0° corresponding to the (111) crystal plane of M2S has a second diffraction angle, and the first diffraction angle may be smaller than the second diffraction angle. For example, the position of the first peak may shift to a low angle compared to the position of the second peak. Therefore, the M2S-alkali metal salt-carbon-based material composite may have a reduced crystallite size compared to M2S used in the preparation of the composite. Since the M2S-alkali metal salt-carbon material composite has a reduced crystallite size, the volume change of the crystallites during charge and discharge is reduced, so the volume change of the composite containing multiple crystallites during charge and discharge can be alleviated. The occurrence of defects such as cracks during charge and discharge of the composite cathode active material containing such a composite can be suppressed. Consequently, the cycle characteristics of the secondary battery containing the composite cathode active material can be improved.

[0142] In the XRD spectrum of the composite, for example, a first peak appearing at a diffraction angle 2θ = 27° ± 2.0° corresponding to the (111) crystal plane of M2S has a first full width at half maximum (FWHM1), and in the XRD spectrum of M2S used in the production of the composite, a second peak appearing at a diffraction angle 2θ = 27° ± 2.0° corresponding to the (111) crystal plane of M2S has a second full width at half maximum (FWHM2), and the first full width at half maximum may be larger than the second full width. Accordingly, the M2S-alkali metal salt-carbon-based material composite may have an increased lattice strain compared to the M2S used in the production of the composite. For example, the M2S-alkali metal salt-carbon-based material composite may have an increased lattice strain when M2S and an alkali metal salt form a solid solution. Since the M2S-alkali metal salt-carbon material composite has an increased full width at half maximum (FWHM) compared to the M2S used in the composite manufacturing, the ionic conductivity of a composite cathode active material including the composite can be further improved. The internal resistance of a secondary battery including the composite cathode active material can be reduced and the cycle characteristics can be improved.

[0143] The first half-width (FWHM1) may be, for example, 1° or more, 1.05° or more, 1.10° or more, or 1.15° or more. When the composite has a first half-width (FWHM1) in this range, the ionic conductivity of the composite cathode active material including the composite can be further improved. The internal resistance of the secondary battery including the composite cathode active material can be reduced and the cycle characteristics can be improved.

[0144] The Mohs hardness of the alkali metal salt and carbon-based material may be greater than that of the M2S. The Mohs hardness of M2S is, for example, 0.6 or less. The Mohs hardness of Li2S is, for example, 0.6.

[0145] The Mohs hardness of the alkali metal salt may be 0.7 or more, 0.8 or more, 0.9 or more, 1.0 or more, 1.5 or more, or 2.0 or more. When the alkali metal salt has a Mohs hardness within this range, the pulverization of M2S can be performed more easily during the milling process, and a solid solution of M2S and the alkali metal salt can be formed more easily. The Mohs hardness of LiI is, for example, 2.0. The Mohs hardness of NaI is, for example, 2.1.

[0146] The Mohs hardness of the carbon-based material may be 0.7 or more, 0.8 or more, 0.9 or more, 1.0 or more, 1.2 or more, or 1.5 or more, respectively. Since the carbon-based material has a Mohs hardness within this range, the pulverization of M2S can be performed more easily during the milling process, and the M2S-alkali metal salt-carbon-based material composite can be easily formed. The modal hardness of carbon nanofibers (CNF) is, for example, 1.5.

[0147] The particle size of the composite cathode active material, i.e., the size of the composite particles, may be, for example, 2 ㎛ or less, 1.5 ㎛ or less, or 1 ㎛ or less. The size of the composite particles may be, for example, 0.1 to 2 ㎛, 0.1 to 1.5 ㎛, or 0.1 to 1 ㎛ or less. Since the composite particles have a size in this range, the volume change during charge and discharge is suppressed, and thus the deterioration of the composite cathode active material including the composite during charge and discharge can be suppressed. If the size of the composite particles increases excessively, the volume change of the composite during charge and discharge may increase, and thus the deterioration of the composite cathode active material including the composite may be accelerated. As a result, the cycle characteristics of a secondary battery including such a composite cathode active material may deteriorate.

[0148] Therefore, the cycle characteristics, such as life characteristics, of a secondary battery including a composite cathode active material can be improved. The size of the composite particles can be measured, for example, using laser diffraction, scanning electron microscopy, etc. The particle size of the composite particle is, for example, the arithmetic mean of the particle sizes of multiple particles measured using software from a scanning electron microscopy image.

[0149] The composite includes a carbon-based material, and the carbon-based material may include, for example, a fibrous carbon-based material. The inclusion of the fibrous carbon-based material in the composite can further enhance the electronic conductivity of the composite. The inclusion of the fibrous carbon-based material in the composite can facilitate electron conduction from the surface to the interior of the composite. The internal resistance of a composite cathode active material including the composite can be reduced, and the cycle characteristics of a secondary battery including the composite cathode active material can be further improved.

[0150] The aspect ratio of the fibrous carbon-based material can be, for example, 2 or more, 3 or more, 4 or more, 5 or more, 10 or more, or 20 or more. The aspect ratio of the fibrous carbon-based material can be, for example, 2 to 30, 3 to 30, 4 to 30, 5 to 30, 10 to 30, or 20 to 30. The aspect ratio of the fibrous carbon-based material can be, for example, 2 to 30, 2 to 20, 2 to 10, 2 to 8, 2 to 5, or 2 to 4. By having the fibrous carbon-based material having 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.

[0151] The fibrous carbon-based material may include, for example, carbon nanostructures. The carbon nanostructures may include, for example, carbon nanofibers (CNFs), carbon nanotubes (CNTs), carbon nanobelts, carbon nanorods, or combinations thereof.

[0152] The carbon nanostructure can form a primary carbon nanostructure composed of a single carbon nanostructure and a secondary carbon nanostructure composed of a plurality of carbon nanostructures aggregated together.

[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] The composite may contain, for example, 10 to 80 parts by weight of M2S, 1 to 40 parts by weight of an alkali metal salt, and 1 to 20 parts by weight of a carbon-based material, relative to 100 parts by weight of the composite. The M2S content contained in the composite may be, for example, 10 to 80 parts by weight, 20 to 70 parts by weight, 30 to 60 parts by weight, or 40 to 60 parts by weight of M2S, relative to 100 parts by weight of the composite. The alkali metal salt content contained in the composite may be, for example, 10 to 40 parts by weight, 15 to 40 parts by weight, 20 to 40 parts by weight, or 25 to 35 parts by weight of the alkali metal salt, relative to 100 parts by weight of the composite. The carbon-based material content contained in the composite may be, for example, 1 to 20 parts by weight, 5 to 20 parts by weight, or 5 to 15 parts by weight of the carbon-based material, relative to 100 parts by weight of the composite. Since the composite has a composition of M2S, alkali metal salt, and carbon-based material in this range, a composite cathode active material including the composite can provide excellent ionic conductivity and / or electronic conductivity.

[0156] The above M2S-containing composite is a Li2S-containing composite, and the Li2S-containing composite includes a composite of Li2S, a lithium salt, and a carbon-based material, and includes 10 to 80 parts by weight of Li2S, 1 to 40 parts by weight of a lithium salt, and 1 to 20 parts by weight of a carbon-based material, based on 100 parts by weight of the composite.

[0157] The ionic conductivity of the complex is, for example, 1×10 at 25°C. -5 S / cm or more, 2×10 -5 S / cm or more, 4×10 -5 S / cm or more, 6×10 -5 S / cm or more, 8×10 -5 S / cm or more or 1×10 -4It can be S / cm or more. The ionic conductivity can be measured using, for example, electrochemical impedance spectroscopy, DC polarization method, etc. Since the composite has an ionic conductivity in this range, the internal resistance of the composite cathode active material including the composite can be reduced. The cycle characteristics of the secondary battery including the composite cathode active material can be improved. The electronic conductivity of the composite can be, for example, 1×10 at 25°C. -5 S / cm or more, 2×10 -5 S / cm or more, 4×10 -5 S / cm or more, 6×10 -5 S / cm or more, 8×10 -5 S / cm or more or 1×10 -4 It can be S / cm or more. The electronic conductivity can be measured using, for example, electrochemical impedance spectroscopy, DC polarization method, etc. Since the composite has an electronic conductivity in this range, the internal resistance of the composite cathode active material including the composite can be reduced. The cycle characteristics of the secondary battery including the composite cathode active material can be improved.

[0158] [anode]

[0159] [Cathode: Cathode active material]

[0160] According to one embodiment, a positive electrode includes a positive electrode current collector; and a positive electrode active material layer disposed on one or both surfaces of the positive electrode current collector. The positive electrode active material layer includes the composite positive electrode active material described above and a solid electrolyte. By including the composite positive electrode active material and the solid electrolyte, the positive electrode can have further reduced internal resistance. Accordingly, the cycle characteristics of a secondary battery including the positive electrode can be further improved.

[0161] Referring to FIGS. 3 to 6, 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 the composite positive electrode active material and solid electrolyte described above.

[0162] The composite cathode active material may be included in an amount of 40 to 90 parts by weight, 40 to 80 parts by weight, 50 to 80 parts by weight, or 50 to 70 parts by weight, based on 100 parts by weight of the cathode active material layer (12). If the content of the composite cathode active material is excessively reduced, the energy density of the secondary battery is reduced. If the content of the composite cathode active material is excessively increased, the deterioration of the cathode may be accelerated due to the change in the volume of the cathode during charge and discharge. As a result, the cycle characteristics of the secondary battery (1) may be reduced.

[0163] The cathode active material layer (12) may additionally include other cathode active materials in addition to the composite cathode active material described above.

[0164] Other cathode active materials may include, for example, a Li2S-containing composite. The Li2S composite includes, for example, a composite of Li2S and a carbon-based material, a composite of Li2S and a carbon-based material and a solid electrolyte, a composite of Li2S and a solid electrolyte, a composite of Li2S and a lithium salt, a composite of Li2S and a metal carbide, a composite of Li2S and a carbon-based material and a metal carbide, a composite of Li2S and a metal nitride, a composite of Li2S and a carbon-based material and a metal nitride, or a combination thereof.

[0165] The composite of Li2S and a carbon-based material includes a carbon-based material. The carbon-based material refers to the carbon-based material of the composite cathode active material described above. The method for producing the composite of Li2S and a carbon-based material may be a dry method, a wet method, or a combination thereof, but is not limited thereto, and any method used in the art may be used. The method for producing the composite of Li2S and a carbon-based material includes, but is not limited to, milling, heat treatment, deposition, etc., and any method used in the art may be used.

[0166] A composite of Li2S, a carbon-based material, and a solid electrolyte includes a carbon-based material and a solid electrolyte. The carbon-based material refers to the composite of Li2S and a carbon-based material described above. The solid electrolyte can be, for example, any material used as an ion-conducting material in the relevant technical field. 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 includes, for example, Li, S, and P, and may optionally further include a halogen element. The sulfide-based solid electrolyte can be selected from among the sulfide-based solid electrolytes used in the electrolyte layer. The sulfide-based solid electrolyte has, for example, a molecular weight of 1×10 at room temperature. -5 It can have an ionic conductivity of S / cm or more. The oxide-based solid electrolyte contains, for example, Li, O, and transition metal elements, and may optionally contain other elements. The oxide-based solid electrolyte has an ionic conductivity of, for example, 1×10 at room temperature. -5 It may be a solid electrolyte having an ionic conductivity of S / cm or more. The oxide-based solid electrolyte may be selected from among oxide-based solid electrolytes used in the electrolyte layer.

[0167] The composite of Li2S and a solid electrolyte includes a solid electrolyte. The solid electrolyte refers to the composite of Li2S, a carbon-based material, and a solid electrolyte described above.

[0168] The composite of Li2S and a lithium salt comprises Li2S and a lithium salt. The lithium salt refers to the lithium salt of the composite cathode active material described above. The lithium salt is particularly one or more lithium halide compounds selected from LiF, LiCl, LiBr, and LiI. The composite of Li2S and a lithium salt may be, for example, a composite of Li2S and a lithium halide. The composite of Li2 and a lithium salt may provide improved ionic conductivity by including a lithium halide compound. The composite of Li2S and a lithium salt is distinguished from a simple mixture of Li2S, a carbon-based material, and a lithium salt. A simple mixture of Li2S and a lithium salt may provide high interfacial resistance by failing to maintain a dense interface between Li2S and a lithium salt, which may result in reduced cycle life characteristics of an all-solid-state secondary battery.

[0169] 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, 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 xor a combination thereof. The surface of the two-dimensional metal carbide is terminated with O, OH and / or F.

[0170] A composite of Li2S, a carbon-based material, and a metal carbide includes Li2S, a carbon-based material, and a metal carbide. The carbon-based material refers to the composite of Li2S and a carbon-based material described above. The metal carbide refers to the composite of Li2S and a metal carbide described above.

[0171] The complex of Li2S and metal nitride contains Li2S and metal nitride. The metal nitride is, for example, a two-dimensional metal nitride. The two-dimensional metal nitride is, for example, M n+1 N n T x (M is a transition metal, T is a terminal group, T is O, OH and / or F, n=1, 2, or 3, and x is the number of terminal groups) is expressed as The surface of the two-dimensional metal nitride is terminated with O, OH and / or F.

[0172] A composite of Li2S, a carbon-based material, and a metal nitride includes Li2S, a carbon-based material, and a metal nitride. The carbon-based material refers to the composite of Li2S and a carbon-based material described above. The metal carbide refers to the composite of Li2S and a metal nitride described above.

[0173] The cathode active material layer (12) may additionally include, for example, a sulfide-based compound that is distinct from the cathode active material described above. The sulfide-based compound may be, for example, a compound containing a metal element other than Li and the element sulfur. The sulfide-based compound may be, for example, a compound containing a metal element belonging to Groups 1 to 14 of the Periodic Table of Elements having an atomic weight of 10 or more and the element sulfur. The sulfide-based compound may be, for example, FeS2, VS2, NaS, MnS, FeS, NiS, CuS, or a combination thereof. By the cathode active material layer additionally including a sulfide-based compound, the cycle characteristics of the all-solid-state secondary battery may be further improved. The content of the sulfide-based compound included in the cathode active material layer (12) may be 10 wt% or less, 5 wt% or less, 3 wt% or less, or 1 wt% or less of the total weight of the cathode active material layer (12).

[0174] [Anode: Solid electrolyte]

[0175] The cathode active material layer (12) may further include, for example, a solid electrolyte (e.g., in particle form). The solid electrolyte may be, for example, a sulfide-based solid electrolyte. The solid electrolyte included in the cathode (10) may be the same as or different from the solid electrolyte included in the electrolyte layer (30). For more details on the solid electrolyte, refer to the electrolyte layer (30) section.

[0176] The solid electrolyte included in the positive electrode active material layer (12) may have a smaller average D50 particle diameter than the solid electrolyte included in the electrolyte layer (30). For example, the average D50 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 average D50 particle diameter of the solid electrolyte included in the electrolyte layer (30). The average D50 particle diameter is, for example, a median particle diameter (D50). The median particle diameter (D50) is the size of particles corresponding to 50% of the cumulative volume, calculated from the side of particles having a small particle size in a size distribution of particles measured by, for example, a laser diffraction method.

[0177] The solid electrolyte may be included in an amount of 10 to 60 parts by weight, 10 to 50 parts by weight, 20 to 50 parts by weight, or 30 to 50 parts by weight, based on 100 parts by weight of the positive electrode active material layer (12). If the content of the solid electrolyte is excessively reduced, the internal resistance of the positive electrode may increase, thereby deteriorating the cycle characteristics of the secondary battery. If the content of the sulfide-based solid electrolyte is excessively increased, the energy density of the all-solid-state secondary battery (1) may be reduced.

[0178] [Polar: Challenger]

[0179] The cathode active material layer (12) may further include a conductive material. The conductive material may be, for example, a carbon-based conductive material, a metal-based conductive material, or a combination thereof. The carbon-based conductive material may be, for example, graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or a combination thereof, but is not limited thereto, and any material used as a carbon-based conductive material in the art may be used. The metal-based conductive material may be, for example, metal powder, metal fiber, or a combination thereof, but is not limited thereto, and any material used as a metal-based conductive material in the art may be used. The content of the conductive material included in the cathode active material layer (12) may be, for example, 1 wt% to 30 wt%, 1 wt% to 20 wt%, or 1 wt% to 10 wt% of the total weight of the cathode active material layer (12).

[0180] The cathode active material layer (12) includes a carbon-based material, and the carbon-based material may be disposed only in the composite cathode active material. The cathode active material layer (12) may not additionally include a separate carbon-based material other than the composite cathode active material including the carbon-based material. Since the cathode active material layer does not include a separate carbon-based material, the energy density of the cathode and the secondary battery (1) can be improved and the manufacturing process can be simplified.

[0181] [Positive: Binder]

[0182] The positive electrode active material layer (12) may further include a binder. The binder may be, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc., but is not limited thereto, and any binder used in the relevant technical field may be used. The binder content included in the positive electrode active material layer (12) may be, for example, 1 wt% to 10 wt% of the total weight of the positive electrode active material layer (12). The binder may be omitted.

[0183] [Positive: Other additives]

[0184] The cathode active material layer (12) may further include additives such as fillers, coating agents, dispersants, and ion conductive aids in addition to the cathode active material, solid electrolyte, binder, and conductive agent described above.

[0185] As fillers, coating agents, dispersants, ion conductivity aids, etc. that the positive electrode active material layer (12) may include, known materials generally used in electrodes of all-solid-state secondary batteries may be used.

[0186] [Anode: Anode current collector]

[0187] 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.

[0188] 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. When the thickness of the metal layer is reduced, the limit current and / or the maximum current of the positive electrode current collector (11) decrease, so that the stability of the all-solid-state secondary battery in case of a short circuit can be improved. 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 make the welding of the metal layer and the lead tab more solid, a metal chip can be added between the metal layer and the lead tab.The metal piece may be a thin piece of the same material as the metal of the metal layer. The metal piece may be, for example, a metal foil, a metal mesh, etc. The metal piece may be, for example, aluminum foil, copper foil, SUS foil, etc. After the metal piece is placed on the metal layer, the lead tab may be welded to the metal piece / metal layer laminate or the metal piece / metal layer / base film laminate. During welding, the base film, the metal layer, and / or the metal piece may melt, so that the metal layer or the metal layer / metal piece laminate may be electrically connected to the lead tab. A metal chip and / or a lead tab may be added to a portion of the metal layer. The base film may have a thickness of, for example, 1 to 50 μm, 1.5 to 50 μm, 1.5 to 40 μm, or 1 to 30 μm. When the base film has a thickness in this range, the weight of the electrode assembly can be more effectively reduced. The melting point of the base film may be, for example, 100 to 300°C, 100 to 250°C or less, or 100 to 200°C. Since the base film has a melting point within this range, the base film can be melted and easily bonded to the lead tab during the welding process of the lead tab. To improve the adhesion between the base film and the metal layer, a surface treatment such as corona treatment may be performed on the base film. The thickness of the metal layer may be, for example, 0.01 to 3 μm, 0.1 to 3 μm, 0.1 to 2 μm, or 0.1 to μm. Since the metal layer has a thickness within this range, conductivity can be maintained while ensuring the stability of the electrode assembly. The thickness of the metal piece may be, for example, 2 to 10 μm, 2 to 7 μm, or 4 to 6 μm. Since the metal piece has a thickness within this range, the connection between the metal layer and the lead tab can be performed more easily. By having this structure, the positive electrode collector (11) can reduce the weight of the positive electrode and consequently improve the energy density of the positive electrode and lithium battery.

[0189] [Anode: Inert member]

[0190] Referring to FIGS. 5 and 6, 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. 5, 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. 6, 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.

[0191] By including an inert member (40), cracking of the electrolyte layer (30) is prevented during the manufacture and / or charging / discharging of the all-solid-state secondary battery (1), and as a result, the cycle characteristics of the all-solid-state secondary battery (2) are improved. In an all-solid-state secondary battery (1) that does not include an inert member (40), when the manufacture and / or charging / discharging of the all-solid-state secondary battery (1) is performed, uneven pressure is applied to the electrolyte layer (30) in contact with the positive electrode (10), which increases the possibility of cracking in the electrolyte layer (30), and thus, a short circuit may occur due to the growth of lithium metal through the crack.

[0192] 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.

[0193] 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.

[0194] Referring to FIGS. 5 and 6, 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).

[0195] Referring to FIGS. 5 and 6, 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.

[0196] 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.

[0197] 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).

[0198] 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.

[0199] 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).

[0200] The area (S1) of the positive electrode (10) is smaller than the area (S4) of the negative electrode current collector (21). The area (S1) of the positive electrode (10) is, for example, less than 100%, 99% or less, 98% or less, 97% or less, 96% or less, or 95% or less of the area (S4) of the negative electrode current collector (21). The area (S1) of the positive electrode (10) is, for example, 50% to less than 100%, 50% to 99%, 55% to 98%, 60% to 97%, 70% to 96%, 80% to 95%, or 85% to 95% of the area (S4) of the negative electrode current collector (21). The area (S4) of the negative electrode current collector (21) is, for example, the same as the area of ​​the negative electrode (20). The area (S4) of the negative electrode current collector (21) is, for example, the same as the area of ​​the first negative electrode active material layer (22).

[0201] 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%.

[0202] 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).

[0203] 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.

[0204] 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.

[0205] 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).

[0206] 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.

[0207] 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).

[0208] 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.

[0209] 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).

[0210] 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).

[0211] 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.

[0212] [All-solid-state secondary battery]

[0213] An all-solid-state secondary battery according to one embodiment includes the above-described positive electrode; a negative electrode; and a solid electrolyte layer disposed between the positive electrode and the negative electrode. The negative electrode includes a negative electrode current collector and a first negative electrode active material layer disposed on one surface of the negative electrode current collector.

[0214] Referring to FIGS. 1 to 6, an all-solid-state secondary battery (1) includes a positive electrode (10); a negative electrode (20); and a solid electrolyte layer (30) disposed between the positive electrode (10) and the negative electrode (20). The negative electrode (20) includes a negative electrode current collector (21) and a first negative electrode active material layer (22) disposed on one surface of the negative electrode current collector.

[0215] [anode]

[0216] See the above mentioned polarities.

[0217] [cathode]

[0218] [Cathode: Cathode active material]

[0219] Referring to FIGS. 1 to 6, 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.

[0220] 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.

[0221] 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.

[0222] The negative electrode active material included in the first negative electrode active material layer (22) includes, for example, at least one selected from among a carbon-based negative electrode active material and a metal or semi-metal negative electrode active material.

[0223] Carbon-based negative electrode materials include, for example, amorphous carbon, crystalline carbon, porous carbon, or a combination thereof.

[0224] 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 graphitic carbon.

[0225] The carbon-based negative electrode active material may be, for example, porous carbon. The porous carbon has a pore volume of, for example, 0.1 cc / g to 10.0 cc / g, 0.5 cc / g to 5 cc / g, or 0.1 cc / g to 1 cc / g. The porous carbon has an average pore diameter of, for example, 1 nm to 50 nm, 1 nm to 30 nm, or 1 nm to 10 nm. The porous carbon has a BET surface area of, for example, 100 m 2 / g to 3000 m 2 / g is.

[0226] 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.

[0227] 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 limited to these ranges 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.

[0228] 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.

[0229] 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.

[0230] 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.

[0231] The carbonaceous support is, for example, amorphous carbon. Amorphous carbon includes, but is not limited to, carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), graphene, activated carbon, carbon nanofibers (CNF), carbon nanotubes (CNT), etc., and any material classified as amorphous carbon in the relevant technical field is possible. Amorphous carbon is carbon that has no crystallinity or very low crystallinity, and is distinguished from crystalline carbon or graphitic carbon. Carbonaceous materials are, for example, carbonaceous negative electrode active materials.

[0232] 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.

[0233] [Cathode: Binder]

[0234] The binder included in the first negative electrode active material layer (22) is, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, etc., but is not 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.

[0235] 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 detached from the negative electrode current collector (21), the possibility of a short circuit occurring increases at the exposed portion of the negative electrode current collector (21) due to the negative electrode current collector (21) coming into contact with the solid electrolyte layer (30). 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).

[0236] [Cathode: Other additives]

[0237] 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.

[0238] [Cathode: Solid electrolyte]

[0239] 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 solid 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), as a space where the formed lithium metal is stored, or as a path for transferring lithium ions. The solid electrolyte may be omitted.

[0240] 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 solid 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 solid electrolyte layer (30) to an area adjacent to the negative electrode current collector (21).

[0241] [Cathode: First negative electrode active material layer]

[0242] The ratio (B / A) of the initial charge capacity (B) of the first negative electrode active material layer (22) and the initial charge capacity (A) of the positive electrode active material layer is 0.005 to 0.45. The initial charge capacity of the positive electrode active material layer (12) is the first open circuit voltage (1 st Li / Li from open circuit voltage) + The initial charge capacity of the first negative electrode active material layer (22) is determined at the maximum charging voltage. The initial charge capacity of the first negative electrode active material layer (22) is determined at the second open circuit voltage (2 nd Li / Li from open circuit voltage) + It is determined at 0.01 V.

[0243] The maximum charging voltage is determined by the type of cathode active material. The maximum charging voltage can be, for example, 1.5 V, 2.0 V, 2.5 V, 3.0 V, 3.5 V, 4.0 V, 4.2 V, or 4.3 V. For example, the maximum charging voltage of Li2S or Li2S composite is Li / Li + can be 2.5 V for Li2S or Li2S complex. For example, the maximum charging voltage of Li / Li + It can be 3.0 V for. The ratio (B / A) of the initial charge capacity (B) of the first negative electrode active material layer (22) and the initial charge capacity (A) of the positive electrode active material layer is, for example, 0.01 to 0.3, 0.01 to 0.2, or 0.05 to 0.1. The initial charge capacity (mAh) of the positive electrode active material layer (12) is obtained by multiplying the charge capacity density (charge specific capacity) (mAh / g) of the positive electrode active material by the mass (g) of the positive electrode active material in the positive electrode active material layer (12). When several types of positive electrode active materials are used, the charge capacity density × mass value is calculated for each positive electrode active material, and the sum of these values ​​is the initial charge capacity of the positive electrode active material layer (12). The initial charge capacity of the first negative electrode active material layer (22) is also calculated in the same way. The initial charge capacity of the first negative electrode active material layer (22) is obtained by multiplying the charge capacity density (mAh / g) of the negative electrode active material by the mass of the negative electrode active material in the first negative electrode active material layer (22). When several types of negative electrode active materials are used, the charge capacity density Х mass value is calculated for each negative electrode active material, and the sum of these values ​​is the initial charge capacity of the first negative electrode active material layer (22). The charge capacity density of each of the positive electrode active material and the negative electrode active material can be measured using an all-solid-state half-cell using lithium metal as a counter electrode. The initial charge capacity of each of the positive electrode active material layer (12) and the first negative electrode active material layer (22) is obtained by multiplying the charge capacity density (mAh / g) of the negative electrode active material by the mass value of the negative electrode active material in the first negative electrode active material layer (22). 2can be directly measured using 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 for an operating voltage of up to 0.01 V for the cathode, for example, lithium metal, from the second open circuit voltage (OCV). For example, an all-solid-state half-cell having a cathode active material layer can exhibit a current of 0.1 mA / cm from the first open circuit voltage to 3.0 V. 2 The all-solid-state half-cell having the first negative active material layer is charged with a constant current of 0.1 mA / cm from the second open circuit voltage to 0.01 V. 2 It can be charged with a constant current. The current density during constant current charging is, for example, 0.2 mA / cm 2 , or 0.5 mA / cm 2 The all-solid-state half-cell having the positive electrode active material layer can be charged from the first open circuit voltage to, for example, 2.5 V, 2.0 V, 3.5 V, or 4.0 V. The maximum charge voltage of the positive electrode active material layer can be determined by the maximum voltage of the battery that satisfies the safety conditions according to JISC8712:2015 of the Japanese Standards Association.

[0244] 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).

[0245] 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.

[0246] [Cathode: Second negative electrode active material layer]

[0247] 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).

[0248] 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.

[0249] 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).

[0250] 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 disposed 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).

[0251] [Cathode: Negative current collector]

[0252] The negative electrode current collector (21) is composed of, for example, a material that does not react with lithium, i.e., does not form an alloy or a compound. The material constituting the negative electrode current collector (21) is, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni), but is not limited thereto, and any material that can be used as an electrode current collector in the relevant technical field is possible. 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.

[0253] 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.

[0254] 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.

[0255] 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 on 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 the all-solid-state secondary battery (91).

[0256] [Solid electrolyte layer]

[0257] [Solid electrolyte layer: solid electrolyte]

[0258] Referring to FIGS. 1 to 6, the solid electrolyte layer (30) includes a solid electrolyte disposed between the positive electrode (10) and the negative electrode (20). The solid electrolyte refers to the solid electrolyte of the solid electrolyte layer described above.

[0259] 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.

[0260] (Manufacturing of composite cathode active materials)

[0261] Manufacturing Example 1: Li2S-LiI-CNF, 2 steps, 10 hr, 600 rpm, 28G

[0262] (Stage 1)

[0263] Li2S and LiI were mixed in a weight ratio of 30:20. The mixture was mechanically milled using a ball mill to prepare a Li2S-LiI composite. The milling conditions were 25°C, 600 rpm for 10 h. The milling energy applied to the sample during milling was 28 G.

[0264] (Stage 2)

[0265] Li2S-LiI composite and carbon nanofiber (CNF) were mixed at a weight ratio of 50:10. The mixture was mechanically milled using a ball mill to prepare a Li2S-LiI-CNF composite. The milling conditions were 25°C, 600 rpm, and 10 h. The milling energy applied to the sample during milling was 28 G. The Li2S-LiI-CNF composite was used as a composite cathode active material.

[0266] The Mohs hardness of Li2S was 0.6, the Mohs hardness of LiI was 2.0, and the Mohs hardness of carbon nanofiber (CNF) was 1.5.

[0267] Manufacturing Example 2: Li2S-LiI-CNF, 2 steps, 8 hr, 600 rpm, 28G

[0268] A Li2S-LiI-CNF composite was manufactured in the same manner as in Manufacturing Example 1, except that the milling time in the first and second steps was changed to 8 hours.

[0269] (Manufacturing of solid electrolyte layer)

[0270] Manufacturing Example 3: Solid electrolyte (Li 5.72 Cu 0.03 )PS 4.75 Cl 1.25 (D 50=3.0 um, crystalline)

[0271] Li2S, a lithium precursor, P2S5, a phosphorus (P) precursor, LiCl, a chlorine precursor, and Cu2S, a copper precursor, were prepared individually.

[0272] The above-mentioned precursors were individually prepared by wet grinding. 10 g of the precursor, 30 ml of xylene solvent, and 100 g of zirconia balls (ZrO2 balls) were placed in an 80 ml container and wet ball milled at 800 rpm for 2 hours. The xylene solvent was removed by vacuum drying at 120°C for 36 hours, and the ground precursors were stored in an inert atmosphere. Agglomeration of the ground particles was prevented by wet grinding.

[0273] Li, the composition of which is the target, individually prepared precursor particles 5.72 Cu 0.03 PS 4.75 Cl 1.25 A precursor mixture was prepared by mixing in a stoichiometric ratio so that .

[0274] Mixing of precursor particles was performed using a dry mixer. Using a dry mixer prevented agglomeration and mechanochemical reactions of the precursor particles. The dry mixer process involved mixing individual precursors (10 g of the target composition) and high-speed mixing at 25,000 rpm for 5 minutes (repeated cycles of 10 seconds of rotation and 10 seconds of pause).

[0275] The prepared precursor mixture powder was placed in a carbon crucible, and the carbon crucible was sealed in an argon atmosphere using a quartz glass tube. The argon-sealed precursor mixture was heated from room temperature to 450°C at 1.0°C / min using an electric furnace, heat-treated at 450°C for 18 hours, and then cooled to room temperature at 1.0°C / min to prepare a solid electrolyte. The composition of the prepared solid electrolyte was Li 5.72 Cu 0.03 PS 4.75 Cl 1.25 It was.

[0276] Manufacturing Example 4: Small particle solid electrolyte (Li 5.72 Cu 0.03 )PS 4.75 Cl 1.25 (D 50 =1.0 um, crystalline)

[0277] In a glove box with an Ar atmosphere, lithium precursor Li2S, phosphorus precursor P2S5, chlorine precursor LiCl and copper precursor Cu2S are used as the target or appropriate composition (Li 5.72 Cu 0.03 )PS 4.75 Cl 1.25 A precursor mixture was obtained by combining the precursors in a stoichiometric ratio so that .

[0278] The obtained mixture was pressed with uniaxial pressure to prepare pellets with a thickness of about 10 mm and a diameter of about 13 mm. The prepared pellets were covered with gold foil and placed in a carbon crucible, and the carbon crucible was vacuum-sealed using a quartz glass tube. The vacuum-sealed pellets were subjected to a first heat treatment using an electric furnace at 300°C for 12 hours at 1.0°C / min, and a second heat treatment was performed at 500°C for 12 hours at 1.0°C / min. Thereafter, the pellets were cooled to room temperature at 1.0°C / min to obtain a small-particle sulfide-based solid electrolyte (Li) having an average particle size of about 1.0 μm. 5.72 Cu 0.03 )PS 4.75 Cl1.25 was manufactured.

[0279] Manufacturing Example 5: Solid electrolyte (Li 5.72 Cu 0.03 )PS 4.75 Cl 1.25 (D 50 =5.0 um, crystalline)

[0280] In a glove box with an Ar atmosphere, lithium precursor Li2S, phosphorus precursor P2S5, chlorine precursor LiCl, and copper precursor Cu2S were mixed to form a target composition (Li 5.72 Cu 0.03 )PS 4.75 Cl 1.25 After combining in a stoichiometric ratio to obtain a precursor mixture, the precursor mixture was ground and mixed at 100 rpm for 1 hour in a planetary ball mill in an Ar atmosphere containing zirconia (YSZ) balls, and then ground and mixed at 800 rpm for 30 minutes to obtain a finely divided precursor mixture. The average particle diameter of the finely divided precursor mixture was D50=6 um.

[0281] The obtained mixture was pressed under uniaxial pressure to prepare pellets with a thickness of approximately 10 mm and a diameter of approximately 13 mm. The prepared pellets were covered with gold foil and placed in a carbon crucible, which was then vacuum-sealed using a quartz glass tube. The vacuum-sealed pellets were heat-treated using an electric furnace at 420°C for 12 hours and then cooled to room temperature at 1.0°C / min to obtain a sulfide-based solid electrolyte.

[0282] (Manufacturing of positive and all-solid-state secondary batteries)

[0283] Example 1: Li2S containing cathode (containing only Cu SE) / (Li 1-b Cu b ) 7-z PS 6-z M3 zSE (hereinafter, Cu SE) (first SE) / LiPSCl SE (second SE) / Ag-C cathode (SE layer: two-layer structure)

[0284] (Manufacturing of composite cathode active materials)

[0285] Li2S and LiI were mixed at a weight ratio of 30:20. The mixture was mechanically milled using a ball mill to prepare a Li2S-LiI composite. The milling conditions were 25°C, 600 rpm for 10 h. The milling energy applied to the sample during milling was 20 G. Subsequently, the Li2S-LiI composite and carbon nanofibers (CNF) were mixed at a weight ratio of 50:10. The mixture was mechanically milled using a ball mill to prepare a Li2S-LiI-CNF composite. The milling conditions were 25°C, 600 rpm for 10 h. The milling energy applied to the sample during milling was 20 G. The Li2S-LiI-CNF composite was used as a composite cathode active material.

[0286] (bipolar layer)

[0287] The Li2S-LiI-CNF composite described above was prepared as a cathode active material. As a solid electrolyte, the solid electrolyte (Li) obtained according to Manufacturing Example 4 5.72 Cu 0.03 )PS 4.75 Cl 1.25 (hereinafter, Cu SE) (D50=3.0um, crystalline), and PTFE as a binder were prepared. These materials were mixed in a weight ratio of composite cathode active material: solid electrolyte: binder = 60:40:1.2 to prepare a cathode mixture. The cathode mixture was dry-mixed using a Thinky Mixer to produce a dry cathode.

[0288] The positive electrode was manufactured by placing the positive electrode active material mixture 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 thickness of the positive electrode was approximately 120 μm. The thickness of the positive electrode active material layer was approximately 100 μm, and the thickness of the carbon-coated aluminum foil was approximately 20 μm. The areas of the positive electrode active material layer and the positive electrode current collector were the same.

[0289] (Cathode manufacturing)

[0290] A 10 ㎛ thick SUS foil was prepared as a negative electrode current collector. Carbon black (CB) with a primary particle diameter of approximately 30 nm and silver (Ag) particles with an average particle diameter of approximately 60 nm were prepared as negative electrode active materials.

[0291] A mixed powder of 4 g of carbon black (CB) and silver (Ag) particles in a weight ratio of 3:1 was placed in a container, and 4 g of NMP (N-methylpyrrolidone) solution containing 7 wt% of PVDF binder (Kureha #9300) was added thereto to prepare a mixed solution. A slurry was prepared by stirring the mixed solution while adding NMP little by little to the prepared mixed solution. The prepared slurry was applied to a SUS sheet using a bar coater, dried in air at 80°C for 10 minutes, and then vacuum-dried at 40°C for 10 hours to prepare a laminate. The prepared laminate was cold roll pressed to flatten the surface, thereby preparing a negative electrode having a first negative electrode active material layer / negative electrode current collector structure. The thickness of the first negative electrode active material layer was approximately 15 μm. The areas of the first negative electrode active material layer and the negative electrode current collector were the same.

[0292] (Manufacturing of solid electrolyte layer)

[0293] Solid electrolyte (Li) obtained according to Manufacturing Example 3 5.72 Cu 0.03 )PS 4.75 Cl 1.25(hereinafter, Cu SE), a mixture was prepared by adding 1.5 parts by weight of an acrylic binder to 98.5 parts by weight of the solid electrolyte. Octyl acetate was added to the prepared mixture and stirred to prepare a slurry. The prepared slurry was applied onto a 15 μm thick nonwoven fabric placed on a 75 μm thick 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 first solid electrolyte layer with a thickness of 60 μm.

[0294] Solid electrolyte (Li) obtained according to Manufacturing Example 3 5.72 Cu 0.03 )PS 4.75 Cl 1.25 Instead, a solid electrolyte of Li6PS5Cl in the form of argyrodite crystals (D 50 =3.0 um, crystalline) was used, the second solid electrolyte layer was manufactured in the same manner as the first solid electrolyte layer manufacturing method. The second solid electrolyte layer was manufactured to a thickness of 40 um.

[0295] (inert absence)

[0296] A flame-retardant inert member was manufactured by forming a slurry containing pulp fibers, glass fibers, aluminum hydroxide (Al(OH)3), an acrylic binder, and a solvent into a gasket shape and then removing the solvent.

[0297] The weight ratio of cellulose fiber, glass fiber, aluminum hydroxide (Al(OH)3) and acrylic binder as pulp fibers was 20:8:70:2. The thickness of the inert material was 120 ㎛.

[0298] Before placing the manufactured flame-retardant inert material on the solid electrolyte layer, moisture, etc. of the flame-retardant inert material was removed by vacuum heat treatment at 80°C for 5 hours.

[0299] (Manufacturing of all-solid-state secondary batteries)

[0300] A solid electrolyte layer was formed by placing a first negative electrode active material layer on the negative electrode so as to be in contact with the first solid electrolyte layer and a second solid electrolyte layer on top of the first solid electrolyte layer, and a positive electrode was placed on the solid electrolyte layer. A laminate was prepared by placing a gasket surrounding the positive electrode and in contact with the solid electrolyte layer. The thickness of the gasket was approximately 120 ㎛. The above-described flame-retardant inert material was used as the gasket. The gasket was placed so as to be in contact with the side surface of the positive electrode and the solid electrolyte layer. The positive electrode was placed at the center of the solid electrolyte layer, and the gasket was placed so as to surround the positive electrode and extend to the end of the solid electrolyte layer. The area of ​​the positive electrode was approximately 90% of the area of ​​the solid electrolyte layer, and the gasket was placed over the entire remaining 10% of the area of ​​the solid electrolyte layer where the positive electrode was not placed.

[0301] 85 prepared laminates o The solid electrolyte layer was plate-pressed at 500 MPa for 30 min at C. This pressurization process sintered the solid electrolyte layer, thereby improving battery characteristics. The thickness of the sintered solid electrolyte layer was approximately 45 ㎛. The density of the Li6PS5Cl solid electrolyte, which was an argyrodite-type crystal contained in the sintered solid electrolyte layer, was 1.6 g / cc. The area of ​​the solid electrolyte layer was the same as that of the negative electrode.

[0302] 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.

[0303] Example 2: Li2S-containing cathode (containing only Cu SE) / Li5.72 Cu 0.03 PS 4.75 Cl 1.25 (1st SE) / LiPSCl (2nd SE) / Li 5.72 Cu 0.03 PS 4.75 Cl 1.25 (3rd SE) / Ag-C cathode (SE layer: 3-layer structure)

[0304] An all-solid-state secondary battery was manufactured in the same manner as Example 1, except that a solid electrolyte layer having a three-layer structure was used instead of a two-layer solid electrolyte layer as the solid electrolyte layer.

[0305] (Manufacturing of solid electrolyte layer)

[0306] A solid electrolyte layer having a three-layer structure was manufactured by laminating a third solid electrolyte layer on top of the second solid electrolyte layer of a two-layer structure having a first solid electrolyte layer / second solid electrolyte layer.

[0307] The third solid electrolyte layer was manufactured in the same manner as the first solid electrolyte layer of Example 1. The thickness of the third solid electrolyte layer was 60 μm.

[0308] Example 3: Li2S containing cathode (containing only Cu SE) / (Li 1-b Cu b ) 7-z PS 6-z M3 z SE (hereinafter, CuSE) (1st SE) (containing small particles and large particles in a weight ratio of 3:7 / LiPSCl SE (2nd SE) / Ag-C cathode (SE layer: 2-layer structure)

[0309] When manufacturing the first solid electrolyte layer, the solid electrolyte (Li) obtained according to Manufacturing Example 3 5.72 Cu 0.03 )PS 4.75 Cl 1.25 Instead, a 3:7 mixed weight ratio Manufacturing Example 4 Small particle 1SE(D 50 =1.0 um,) and the second SE (D) of manufacturing example 5 50An all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that the first solid electrolyte layer was manufactured using (=5.0 um).

[0310] Example 4: Li2S containing cathode (LiPSCl containing SE alone) / (Li 1-b Cu b ) 7-z PS 6-z M3 z SE (hereinafter, CuSE) (first SE) / LiPSCl SE (second SE) / Ag-C cathode (SE layer: two-layer structure)

[0311] An all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that Li6PS5Cl (D50=3.0um, crystalline), an argyrodite-type crystal, was prepared instead of CuSE alone as the positive electrode solid electrolyte.

[0312] Example 5: Li2S containing cathode (containing only Cu SE) / (Li 1-b Cu b ) 7-z PS 6-z M3 z SE (hereinafter, CuSE) (1st SE) (containing small particles and large particles in a weight ratio of 4:6 / LiPSCl SE (2nd SE) / Ag-C cathode (SE layer: 2-layer structure)

[0313] Solid electrolyte (Li) obtained according to Manufacturing Example 3 5.72 Cu 0.03 )PS 4.75 Cl 1.25 Instead, a 4:6 mixed weight ratio Manufacturing Example 4 Small particle 1SE(D 50 =1.0 um) and the second SE (D) of manufacturing example 5 50 An all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that the first solid electrolyte layer was manufactured using (=5.0 um).

[0314] Example 6: Cathode layer: Using Ag-supported carbon

[0315] An all-solid-state secondary battery was manufactured in the same manner as Example 1, except that the silver particle-supported carbon black described below was used instead of the mixture of carbon black and silver particles as the negative electrode active material.

[0316] (Manufacture of carbon black loaded with silver particles)

[0317] Carbon black was dispersed in a 1.0 M sulfuric acid solution, stirred for 2 hours, filtered, and dried to prepare acid-treated carbon black.

[0318] 10 g of acid-treated carbon black was added to a mixed solvent of 1500 g of distilled water, 1500 g of ethanol, and 30 g of glycerol, and stirred, followed by adding 2 g of AgNO3 and stirring to prepare a mixed solution. The particle size of the carbon black was 80 nm. A reducing agent was added to the mixed solution to reduce and support silver ions on the carbon black. The carbon black supported with silver-containing particles was filtered, washed, and dried to prepare a composite negative electrode active material. Scanning electron microscope and XPS measurements confirmed that multiple silver-containing particles were supported on the carbon black particles. The silver-containing particles were silver particles, silver oxide (Ag2O) particles, and composite particles of silver (Ag) and silver oxide (Ag2O). The content of silver-containing particles included in the composite negative electrode active material was 5 wt%. The average particle size of the silver particles was 10 nm.

[0319] Comparative Example 1: Li2S and LiPSCl SE containing positive electrode / LiPSCl SE (second SE) / Ag-C negative electrode (SE layer:

[0320] 1st floor structure)

[0321] An all-solid-state secondary battery was manufactured in the same manner as Example 1, except that only the second solid electrolyte layer was used as the solid electrolyte layer and Li6PS5Cl (D50=3.0um, crystalline) (LiPSCl SE), an argyrodite-type crystal, was used as the positive electrolyte.

[0322] Comparative Example 2: Li2S and LiPSCl SE-containing anode / Cu SE (first SE) / Ag-C cathode (SE layer: 1-layer structure)

[0323] An all-solid-state secondary battery was manufactured in the same manner as Example 1, except that only the first solid electrolyte layer was used as the solid electrolyte layer.

[0324] Comparative Example 3: Li2S and LiPSCl SE containing cathode / LiPSCl SE (second SE) / Ag-C cathode (SE layer: 1-layer structure)

[0325] An all-solid-state secondary battery was manufactured in the same manner as Example 1, except that only the second solid electrolyte layer was used as the solid electrolyte layer and Li6PS5Cl (D50=3.0um, crystalline) (LiPSCl SE), an argyrodite-type crystal, was used as the positive solid electrolyte.

[0326] Comparative Example 4: Li2S and Cu SE containing anode / Cu SE (first SE) / Ag-C cathode (SE layer: 1-layer structure)

[0327] An all-solid-state secondary battery was manufactured in the same manner as Example 1, except that only the first solid electrolyte layer was used as the solid electrolyte layer.

[0328] Comparative Example 5: Li2S-containing cathode (containing only Cu SE) / LiPSCl (second SE) / Li 5.72 Cu 0.03 PS 4.75 Cl 1.25 (1st SE) / LiPSCl (3rd SE) / Ag-C cathode (SE layer: 3-layer structure)

[0329] The solid electrolyte layer placed between the positive and negative electrodes is LiPSCl(2SE) / Li 5.72 Cu 0.03 PS 4.75 Cl 1.25 An all-solid-state secondary battery was manufactured in the same manner as Example 2, except that (1st SE) / LiPSCl (3rd SE) were stacked in that order.

[0330] Reference Example 1: Lithium metal cathode

[0331] An all-solid-state secondary battery was manufactured in the same manner as Example 1, except that a lithium metal foil having a thickness of 20 μm was used instead of the first negative electrode active material layer containing carbon black (CB) and silver (Ag) particles as the negative electrode active material layer.

[0332] Reference Example 2: First inert member not used (free)

[0333] An all-solid-state secondary battery was manufactured in the same manner as Example 1, except that a flame-retardant inert material (i.e., a gasket) was not used during the manufacture of the all-solid-state secondary battery.

[0334] Evaluation Example 1: Moisture barrier properties

[0335] The composite cathode active materials manufactured in Examples 1-6, Comparative Examples 1-5, and Reference Examples 1-2 were evaluated for moisture barrier properties using XRD spectra with Cu Kα radiation. The moisture barrier properties were calculated by calculating the LiOH peak area size generated after 3 days of exposure in a dry room, and Example 2, which had the smallest area, was selected as 100%. The moisture barrier properties were evaluated by examining the ratio of the LiOH peak area size generated after 3 days of exposure in a dry room of the composite cathode active material of Example 2 to the LiOH peak area size generated after 3 days of exposure in a dry room of the cathode active materials of Examples 1, 3-6, Comparative Examples 1-5, and Reference Examples 1-2. The results of the moisture barrier property evaluation are shown in Table 1 below.

[0336] Example 1: Li2S containing cathode (containing only Cu SE) / (Li 1-b Cu b ) 7-z PS 6-z M3 z SE (hereinafter, Cu SE) (first SE) / LiPSCl SE (second SE) / Ag-C cathode (SE layer: two-layer structure) 88 Example 2: Li2S-containing cathode (containing only Cu SE) / Li 5.72Cu 0.03 PS 4.75 Cl 1.25 (1st SE) / LiPSCl (2nd SE) / Li 5.72 Cu 0.03 PS 4.75 Cl 1.25 (3rd SE) / Ag-C cathode (SE layer: 3-layer structure) 100 Example 3: Li2S containing cathode (containing only Cu SE) / (Li 1-b Cu b ) 7-z PS 6-z M3 z SE (hereinafter, Cu SE) (1st SE) (containing small particles and large particles in a weight ratio of 3:7 / LiPSCl SE (2nd SE) / Ag-C negative electrode (SE layer: two-layer structure) 93 Example 4: Containing only LiPSCl SE as a positive electrode solid electrolyte) / (Li 1-b Cu b ) 7-z PS 6-z M3 z SE (hereinafter, Cu SE) (first SE) / LiPSCl SE (second SE) / Ag-C cathode (SE layer: two-layer structure) 83 Example 5: Li2S-containing cathode (containing only Cu SE) / (Li 1-b Cu b ) 7-z PS 6-z M3 zSE (hereinafter, Cu SE) (1st SE) (small particles and large particles 4:6 weight ratio containing / LiPSCl SE (2nd SE) / Ag-C negative electrode (SE layer: 2-layer structure) 85 Example 6: Li2S containing positive electrode (containing only Cu SE) / (Cu SE) (1st SE) / LiPSCl SE (2nd SE) / Ag-C negative electrode (using Ag-supported carbon) (SE layer: 2-layer structure) 91 Comparative Example 1: Li2S and LiPSCl SE containing positive electrode / LiPSCl SE (2nd SE) / Ag-C negative electrode (SE layer: 1-layer structure) 51 Comparative Example 2 Li2S and LiPSCl SE containing positive electrode / Cu SE (1st SE) / Ag-C negative electrode (SE layer: 1-layer structure) 58 Comparative Example 3 Li2S and LiPSCl SE containing positive electrode / LiPSCl SE (2nd SE) / Ag-C negative electrode (SE layer: 1-layer structure) Structure) 59 Comparative Example 4 Li2S and Cu SE containing anode / Cu SE (1st SE) / Ag-C cathode (SE layer: 1-layer structure) 67 Comparative Example 5: Li2S containing anode (containing only Cu SE) / LiPSCl (2nd SE) / Li 5.72 Cu 0.03 PS 4.75 Cl 1.25 (1st SE) / LiPSCl (3rd S E) / Ag-C negative electrode (SE layer: 3-layer structure) 57 Reference Example 1 Lithium metal negative electrode 34 Reference Example 2 First inert material not used (free) 48

[0337] As shown in Table 1, it was found that the all-solid-state secondary batteries of Examples 1 to 6 had improved moisture barrier properties compared to the all-solid-state secondary batteries of Comparative Examples 1-5 and Reference Examples 1-2.

[0338] The all-solid-state secondary battery of Comparative Example 5 above had a position where the first SE was not arranged adjacent to at least one of the positive or negative electrodes, and thus the moisture blocking characteristics were lowered compared to those of Examples 1-6. From this, Li 5.72 Cu 0.03 PS 4.75 Cl 1.25 It was confirmed that improved moisture barrier properties can be achieved only when (1SE) is in direct contact with the positive and negative electrodes.

[0339] Evaluation Example 2: Life Characteristics Test

[0340] The charge / discharge characteristics of the all-solid-state secondary batteries manufactured in Examples 1 to 6 and Comparative Examples 1-3 and 5, and Reference Examples 1 and 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.

[0341] Charge and discharge tests were performed by placing the all-solid-state secondary battery in a constant temperature chamber at 45°C.

[0342] The first cycle involved charging for 12.5 hours at a constant current of 0.1 C until the battery voltage reached 2.5 V 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.

[0343] The discharge capacity of the first cycle was taken as the standard capacity. The standard capacity is expressed as the specific capacity of Li2S in Table 3 below.

[0344] After the first cycle, charging and discharging were performed up to 150 cycles under the same conditions as the first cycle. The measurement results are shown in Table 2 below. The initial efficiency is expressed by Equation 1 below.

[0345] <Formula 1>

[0346] Initial efficiency [%] = [1st cycle discharge capacity / 1st cycle charge capacity] × 100

[0347] The cycle count is the number of cycles required for the discharge capacity to decrease to 80% of the standard capacity after the second cycle. A higher cycle count is considered to indicate better life characteristics.

[0348] Initial efficiency [%] Cycle count [times] Example 1: Li2S containing cathode (containing Cu SE only) / (Li 1-b Cu b ) 7-z PS 6-zM3 z SE (hereinafter, Cu SE) (first SE) / LiPSCl SE (second SE) / Ag-C cathode (SE layer: two-layer structure) 82180 Example 2: Li2S-containing cathode (containing only Cu SE) / Li 5.72 Cu 0.03 PS 4.75 Cl 1.25 (1st SE) / LiPSCl (2nd SE) / Li 5.72 Cu 0.03 PS 4.75 Cl 1.25 (3rd SE) / Ag-C cathode (SE layer: 3-layer structure) 84250 Example 3: Li2S containing cathode (containing only Cu SE) / (Li 1-b Cu b ) 7-z PS 6-z M3 z SE (hereinafter, CuSE) (1st SE) (containing small particles and large particles in a weight ratio of 3:7) / LiPSCl SE (2nd SE) / Ag-C negative electrode (SE layer: two-layer structure 85240 Example 4: Containing only LiPSCl SE as a positive electrode solid electrolyte) / (Li 1-b Cu b ) 7-z PS 6-z M3 z SE (hereinafter, Cu SE) (first SE) / LiPSCl SE (second SE) / Ag-C cathode (SE layer: two-layer structure) 78130 Example 5: Li2S-containing cathode (containing only Cu SE) / (Li 1-b Cu b ) 7-z PS 6-z M3 zSE (hereinafter, Cu SE) (1st SE) (small particles and large particles 4:6 weight ratio containing / LiPSCl SE (2nd SE) / Ag-C negative electrode (SE layer: 2-layer structure) 75100 Example 6: Li2S containing positive electrode (containing only Cu SE) / (Cu SE) (1st SE) / LiPSCl SE (2nd SE) / Ag-C negative electrode (using Ag-supported carbon) (SE layer: 2-layer structure) 85220 Comparative Example 1: Li2S and LiPSCl SE containing positive electrode / LiPSCl SE (2nd SE) / Ag-C negative electrode (SE layer: 1-layer structure) 7560 Comparative Example 2 Li2S and LiPSCl SE containing positive electrode / Cu SE (1st SE) / Ag-C negative electrode (SE layer: 1-layer structure) 7780 Comparative Example 3 Li2S and LiPSCl SE containing positive electrode / LiPSCl SE (2nd SE) / Ag-C cathode (SE layer: 1-layer structure) 7670 Comparative example 5: Li2S-containing cathode (containing only Cu SE) / LiPSCl (2nd SE) / Li 5.72 Cu 0.03 PS 4.75 Cl 1.25 (1st SE) / LiPSCl (3rd SE) / Ag-C negative electrode (SE layer: 3-layer structure) 7565 Reference example 1 Lithium metal negative electrode 8350 Reference example 2 1st inert material not used (free) 7130

[0349] As shown in Table 2, the all-solid-state secondary batteries of Examples 1 to 6 showed improved discharge capacity, initial efficiency, and lifespan characteristics compared to the all-solid-state secondary batteries of Reference Example 2 and Comparative Examples 2 and 3. The all-solid-state secondary batteries of Comparative Examples 1 and 5 showed the same initial efficiency as that of Example 5, but showed deteriorated lifespan characteristics. In addition, the all-solid-state secondary battery of Reference Example 1 showed excellent initial efficiency but very deteriorated lifespan characteristics, as shown in Table 2.

[0350] Evaluation Example 3: High-rate characteristics

[0351] The high-rate characteristics of the all-solid-state secondary batteries manufactured in Examples 1 to 6, Reference Examples 1 and 2, and Comparative Examples 1 to 5 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.

[0352] The all-solid-state secondary batteries manufactured in Examples 1 to 8, Reference Examples 1-2, and Comparative Examples 1 to 5 were 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 was achieved at a current of 0.05 C rate while maintaining 2.5 V in constant voltage mode. Subsequently, the batteries were discharged at a constant current of 0.1 C rate until the voltage reached 0.3 V (vs. Li) during discharge (formation cycle).

[0353] 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).

[0354] 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 2.5 V (vs. Li). Subsequently, it was discharged at a constant current of 0.33 C rate until the voltage reached 0.3 V (vs. Li) (second cycle).

[0355] 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).

[0356] 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).

[0357] 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 2 below. The high-rate characteristics are defined by Equation 2 below.

[0358] <Formula 2>

[0359] High-rate characteristic [%] = [Discharge capacity in the 4th cycle / Discharge capacity in the 1st cycle] × 100

[0360] Discharge rate characteristics (1C / 0.2C) [%] Example 1: Li2S containing cathode (containing only Cu SE) / (Li 1-b Cu b ) 7-z PS 6-z M3 z SE (hereinafter, Cu SE) (first SE) / LiPSCl SE (second SE) / Ag-C cathode (SE layer: two-layer structure) 84 Example 2: Li2S-containing cathode (containing only Cu SE) / Li 5.72 Cu 0.03 PS 4.75 Cl 1.25 (1st SE) / LiPSCl (2nd SE) / Li 5.72 Cu 0.03 PS 4.75 Cl 1.25 (3rd SE) / Ag-C cathode (SE layer: 3-layer structure) 89 Example 3: Li2S-containing cathode (containing only Cu SE) / (Cu SE)(1st SE) (containing small particles and large particles) / LiPSCl SE (2nd SE) / Ag-C cathode (SE layer: 2-layer structure) 91 Example 4: Anode solid electrolyte containing only LiPSCl SE) / (Li 1-b Cu b ) 7-z PS 6-z M3 zSE (hereinafter, Cu SE) (first SE) / LiPSCl SE (second SE) / Ag-C negative electrode (SE layer: two-layer structure) 78 Example 5: Anode solid electrolyte containing Cu SE + LiPSCl SE) / Cu SE (first SE) / LiPSCl SE (second SE) / Ag-C negative electrode (SE layer: two-layer structure) 82 Example 6: Li2S-containing positive electrode (containing only Cu SE) / (CuSE) (first SE) / LiPSCl SE (second SE) / Ag-C negative electrode (using Ag-supported carbon) (SE layer: two-layer structure) 86 Comparative Example 1: Li2S and LiPSCl SE-containing positive electrode / LiPSCl SE (second SE) / Ag-C negative electrode (SE layer: one-layer structure) 68 Comparative Example 2 Li2S and LiPSCl SE-containing positive electrode / Cu SE (first SE) / Ag-C negative electrode (SE layer: one-layer structure) Structure) 71 Comparative Example 3 Li2S and LiPSCl SE containing anode / LiPSCl SE (second SE) / Ag-C cathode (SE layer: 1-layer structure) 67 Comparative Example 4 Li2S and Cu SE containing anode / Cu SE (first SE) / Ag-C cathode (SE layer: 1-layer structure) 75 Comparative Example 5: Li2S containing anode (containing Cu SE only) / LiPSCl (second SE) / Li 5.72 Cu 0.03 PS 4.75 Cl 1.25 (1st SE) / LiPSCl (3rd SE) / Ag-C negative electrode (SE layer: 3-layer structure) 69 Reference Example 1 Lithium metal negative electrode 62 Reference Example 2 First inert material not used (free) 48

[0361] As shown in Table 3, the all-solid-state secondary batteries of Examples 1 to 6 had improved high-rate characteristics compared to the all-solid-state secondary batteries of Comparative Examples 1 to 5 and Reference Examples 1-2.

[0362] While exemplary embodiments have been described in detail with reference to the attached drawings, the present invention is not limited to these examples. It is self-evident that those skilled in the art to which the present invention pertains can devise various modifications or variations within the scope of the technical concepts described in the patent claims, and these also naturally fall within the technical scope of the present invention.

Claims

1. An all-solid-state secondary battery comprising a positive electrode layer; a negative electrode layer; and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer. The above positive electrode layer comprises a positive electrode current collector; and a positive electrode active material layer disposed on one or both sides of the positive electrode current collector, The above cathode active material contains a M2S-containing complex, wherein M is an alkali metal, and the alkali metal is Li or Na, The solid electrolyte layer includes a first solid electrolyte layer containing a solid electrolyte represented by the following chemical formula 1 and a second solid electrolyte layer containing a solid electrolyte represented by the following chemical formula 2, wherein the first solid electrolyte layer is directly disposed on at least one of the positive electrode active material layer and the first negative electrode active material layer. 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 disposed on one surface of the negative electrode current collector: <Chemical Formula 1> (Li 1-b M b ) 7-z PS 6-z M3 z In chemical formula 1, M is Na, K, Fe, Mg, Ca, Ag, Cu, Zr, Zn or a combination thereof, M3 is an element selected from group 17 of the periodic table, and 0≤b≤0.05, 0≤z≤2, <Chemical Formula 2> Li a M1 x M2 w PS y M3 z In chemical formula 2, M1 is an element selected from groups 2 and 11 of the periodic table, M2 is a metallic element other than Li selected from group 1 of the periodic table, M3 is an element selected from group 17 of the periodic table, where 4≤a≤8, 0≤x≤0.5, 0≤w≤0.5, 3≤y≤7, and 0≤z≤2.

2. An all-solid-state secondary battery in the first paragraph, wherein the first solid electrolyte layer of the solid electrolyte layer is arranged adjacent to the positive electrode layer.

3. In the first paragraph, the solid electrolyte represented by the chemical formula 1 is an all-solid-state secondary battery represented by the following chemical formula 1-1: <Chemical Formula 1-1> (Li 1-b Cu b ) 7-z PS 6-z M3 z In Chemical Formula 1-1, M3 is F, Cl, Br, or I, and 0≤b≤0.05, 0≤z≤2.

4. In the first paragraph, an all-solid-state secondary battery in which M1 in the chemical formula 2 is Mg, Ag, Cu, Hf, In, Ti, Pb, Sb, Fe, Zr, Zn, Cr, B, Sn, Ge, Si, Zr, Ta, Nb, V, Ga, Al, As, or a combination thereof, M2 is Na, K, or a combination thereof, and M3 is F, Cl, Br, or I.

5. In the first paragraph, the solid electrolyte layer contains a third solid electrolyte layer containing a third solid electrolyte, The above third solid electrolyte is represented by the following chemical formula 3: The above third solid electrolyte layer is disposed on top of the second solid electrolyte layer, an all-solid-state secondary battery: <Chemical Formula 3> (Li 1-b With b ) 7-z PS 6-z M4 z In chemical formula 3, M4 is an element selected from group 17 of the periodic table, and 0≤b≤0.05, 0≤z≤2.

6. In the first paragraph, the first solid electrolyte and the second solid electrolyte each include a large-particle-diameter solid electrolyte having an average particle diameter of 3 to 10 ㎛ and a small-particle-diameter solid electrolyte having an average particle diameter of 1 to 3 ㎛, An all-solid-state secondary battery, wherein the mixing weight ratio of the large-particle-diameter solid electrolyte and the small-particle-diameter solid electrolyte is 10:90 to 90:

10.

7. In the first paragraph, the positive electrode layer is an all-solid-state secondary battery including at least one selected from a solid electrolyte represented by Chemical Formula 1 and a solid electrolyte represented by Chemical Formula 2 below: <Chemical Formula 1> (Li 1-b M b ) 7-z PS 6-z M3 z In chemical formula 1, M is Na, K, Fe, Mg, Ca, Ag, Cu, Zr, Zn or a combination thereof, M3 is an element selected from group 17 of the periodic table, and 0≤b≤0.05, 0≤z≤2, <Chemical Formula 2> Li a M1 x M2 w PS y M3 z In chemical formula 2, M1 is an element selected from groups 2 and 11 of the periodic table, M2 is a metallic element other than Li selected from group 1 of the periodic table, M3 is an element selected from group 17 of the periodic table, where 0≤a≤8, 0≤x≤0.5, 0≤w≤0.5, 3≤y≤7, and 0≤z≤2.

8. In the first paragraph, the thickness of the first solid electrolyte layer and the second solid electrolyte are each 10 um to 200 um, An all-solid-state secondary battery in which the thickness ratio of the first solid electrolyte layer and the second solid electrolyte layer is 1:1 to 6:

4.

9. An all-solid-state secondary battery according to claim 1, wherein the M2S-containing complex comprises a complex of M2S and a carbon-based material, a complex of M2S and a carbon-based material and a solid electrolyte, a complex of M2S and a solid electrolyte, a complex of M2S and a carbon-based material and an alkali metal salt, a complex of M2S and an alkali metal salt, a complex of M2S and a metal carbide, a complex of M2S and a carbon-based material and a metal carbide, a complex of M2S and a metal nitride, a complex of M2S and a carbon-based material and a metal nitride, or a combination thereof.

10. In paragraph 9, the alkali metal salt is a lithium salt or a sodium salt, The above alkali metal salt is a binary compound or a ternary compound, The above binary compound comprises LiI, LiBr, LiCl, LiF, LiH, Li2O, Li2Se, Li2Te, Li3N, Li3P, Li3As, Li3Sb, Li3Al2, LiB3 or a combination thereof, or comprises NaI, NaBr, NaCl, NaF, Na2O, Na2Se, Na3N, Na3P, Na3As, Na3Sb, Na3Al2, NaB3 or a combination thereof, A solid secondary battery, wherein the ternary compound comprises Li3OCl, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiNO3, Li2CO3, LiBH4, Li2SO4, Li3BO3, Li3PO4, Li4NCl, Li5NCl2, Li3BN2 or a combination thereof, or comprises Na3OCl, NaBF4, NaPF6, NaAsF6, NaClO4, NaNO3, NaAlO2, NaAlCl4, NaNO3, Na2CO3, NaBH4, Na2SO4, Na3BO3, Na3PO4, Na4NCl, Na5NCl2, Na3BN2 or a combination thereof.

11. In paragraph 9, the carbon-based material includes a fibrous carbon-based material, The above fibrous carbon material includes a carbon nanostructure, An all-solid-state secondary battery, wherein the carbon nanostructure comprises carbon nanofibers, carbon nanotubes, carbon nanobelts, carbon nanorods, or a combination thereof.

12. An all-solid-state secondary battery in claim 10, wherein the M2S-containing composite is a Li2S-containing composite.

13. In the 12th paragraph, the Li2S-containing composite includes a composite of Li2S, a lithium salt, and a carbon-based material, An all-solid-state secondary battery comprising 10 to 80 parts by weight of Li2S, 1 to 40 parts by weight of a lithium salt, and 1 to 20 parts by weight of a carbon-based material relative to 100 parts by weight of the above complex.

14. 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.

15. In the first 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.

16. In the 14th paragraph, the negative electrode active material comprises a carbon-based support; and a metal-based negative electrode active material supported on the carbon-based support, The above metal-based negative electrode active material includes a metal, a metal oxide, a complex of a metal and a metal oxide, or a combination thereof, The above metal-based negative electrode active material has a particle form, and the particle size of the metal-based negative electrode active material is 1 nm to 200 nm, An all-solid-state secondary battery, wherein the carbon-based support has a particle shape and the particle size of the carbonaceous material is 10 nm to 2 ㎛.

17. In the first paragraph, at least one of the positive electrode current collector and the negative electrode current collector includes a base film and a metal layer disposed on one or both sides of the base film, The above base film comprises a polymer, and the polymer comprises polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI) or a combination thereof, An all-solid-state secondary battery, wherein the metal layer comprises indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof.

18. An all-solid-state secondary battery according to claim 1, further comprising a first inert member disposed on one side of the positive electrode, wherein the first inert member comprises a flame-retardant inert member.

19. In the first paragraph, the solid electrolyte layer includes a solid electrolyte, a gel electrolyte, or a combination thereof, 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 paragraph 1, 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.

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