Solid-state secondary batteries

Abstract

A solid-state secondary battery is presented, comprising a positive electrode layer; a negative electrode layer; a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer; and a first organic electrolyte disposed between the positive electrode layer and the solid electrolyte layer, a second organic electrolyte disposed between the negative electrode layer and the solid electrolyte layer, a third organic electrolyte disposed within the solid electrolyte layer, or a combination thereof, wherein the first organic electrolyte, the second organic electrolyte, and the third organic electrolyte independently comprise a polymer electrolyte, a liquid electrolyte, or a combination thereof, the viscosity of the liquid electrolyte being 10 cps or more at 25°C and 1 atm, the positive electrode layer comprising 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 positive electrode active material layer comprising a Li2S-containing composite, and the negative electrode layer comprising a negative electrode current collector and a first negative electrode active material layer disposed on one side of the negative electrode current collector.

Description

[Technical Field]

[0001] This invention relates to a solid-state rechargeable battery. [Background technology]

[0002] Recently, industrial demands have led to active development of batteries with high energy density and safety. For example, lithium batteries are used in a variety of applications, including information equipment, communication equipment, and automobiles. In the case of automobiles, safety is paramount because it involves human lives.

[0003] Lithium batteries using liquid electrolytes may have an increased risk of fire and / or explosion in the event of a short circuit. Secondary batteries using solid electrolytes instead of liquid electrolytes have been proposed. Solid electrolytes have a lower risk of ignition compared to liquid electrolytes.

[0004] By using a solid electrolyte instead of a liquid electrolyte in rechargeable batteries, the possibility of fire and explosion can be reduced. Rechargeable batteries using solid electrolytes can offer improved safety. [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The problem that this invention aims to solve is to provide a solid-state secondary battery having improved cycle characteristics by arranging an organic electrolyte on the surface and / or inside the solid electrolyte layer. [Means for solving the problem]

[0006] In one embodiment, a solid-state secondary battery is presented comprising: a positive electrode layer; a negative electrode layer; a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer; and a first organic electrolyte disposed between the positive electrode layer and the solid electrolyte layer, a second organic electrolyte disposed between the negative electrode layer and the solid electrolyte layer, a third organic electrolyte disposed within the solid electrolyte layer, or a combination thereof, wherein the first organic electrolyte, the second organic electrolyte, and the third organic electrolyte independently comprise a polymer electrolyte, a liquid electrolyte, or a combination thereof, the viscosity of the liquid electrolyte is 10 cps or more at 25°C and 1 atm, the 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 positive electrode active material layer comprises a Li2S-containing composite, and the negative electrode layer comprises a negative electrode current collector and a first negative electrode active material layer disposed on one side of the negative electrode current collector. [Effects of the Invention]

[0007] In one embodiment, by additionally arranging an organic electrolyte on the surface and / or inside the solid electrolyte layer, defects in the solid electrolyte layer are suppressed during the charge-discharge process, and the internal resistance of the solid secondary battery is reduced, thereby providing a solid secondary battery with improved lifespan and high efficiency characteristics. [Brief explanation of the drawing]

[0008] [Figure 1a] This is a cross-sectional view of a solid-state secondary battery according to an exemplary embodiment. [Figure 1b] This is a cross-sectional view of a solid-state secondary battery according to an exemplary embodiment. [Figure 1c] This is a cross-sectional view of a solid-state secondary battery according to an exemplary embodiment. [Figure 2a] This is a cross-sectional view of a solid-state secondary battery according to an exemplary embodiment. [Figure 2b] This is a cross-sectional view of a solid-state secondary battery according to an exemplary embodiment. [Figure 2c] This is a cross-sectional view of a solid-state secondary battery according to an exemplary embodiment. [Figure 3a] This is a cross-sectional view of a solid-state secondary battery according to an exemplary embodiment. [Figure 3b]This is a cross-sectional view of a solid-state secondary battery according to an exemplary embodiment. [Figure 3c] This is a cross-sectional view of a solid-state secondary battery according to an exemplary embodiment. [Figure 4a] This is a schematic diagram illustrating the change in organic electrolyte concentration with respect to position in a solid electrolyte layer according to an exemplary embodiment. [Figure 4b] This is a schematic diagram illustrating the change in organic electrolyte concentration with respect to position in a solid electrolyte layer according to an exemplary embodiment. [Figure 4c] This is a schematic diagram illustrating the change in organic electrolyte concentration with respect to position in a solid electrolyte layer according to an exemplary embodiment. [Figure 5] This is a cross-sectional view of a solid-state secondary battery according to an exemplary embodiment. [Figure 6] This is a cross-sectional view of a solid-state secondary battery according to an exemplary embodiment. [Figure 7] This is a cross-sectional view of a solid-state secondary battery according to an exemplary embodiment. [Figure 8] This is a cross-sectional view of a solid-state secondary battery according to an exemplary embodiment. [Figure 9] This is a cross-sectional view of a solid-state secondary battery according to an exemplary embodiment. [Figure 10] This is a cross-sectional view of a solid-state secondary battery according to an exemplary embodiment. [Figure 11] This is a cross-sectional view of a solid-state secondary battery according to an exemplary embodiment. [Modes for carrying out the invention]

[0009] Unless otherwise specifically defined, all terms used in this invention (including technical and scientific terms) have the same meaning as those generally understood by a person of ordinary skill in the art to which this invention pertains. Furthermore, terms as defined in commonly used dictionaries should be interpreted to have a meaning consistent with their meaning in the relevant art and in the context of this disclosure, and should not be interpreted in an idealized or overly formal sense.

[0010] The present invention is described with reference to illustrative cross-sectional views, which are schematic diagrams of idealized embodiments. Thus, deformations from the illustrated shapes must be expected, for example, as a result of manufacturing techniques and / or tolerances. Therefore, the embodiments described herein should not be construed as being limited to specific shapes of regions as illustrated herein, and should include, for example, deviations of shape caused by manufacturing. For example, a region illustrated or described as flat may typically be rough and / or have nonlinear features. Furthermore, sharply illustrated corners may also be rounded. Therefore, the regions illustrated in the drawings are essentially schematic, and their shapes are not intended to illustrate the exact shape of the regions and are not intended to limit the scope of the claims.

[0011] This inventive idea can be embodied in various other forms and should not be construed as being limited to the embodiments described herein. Examples are provided to ensure that the invention is thorough and complete, and to fully convey the scope of this inventive idea to those with ordinary skill in the art. Same reference numerals refer to the same components.

[0012] When one component is said to be "on top of" another, one will understand that it is either directly above the other component or that the other component may be interposed between them. In contrast, when one component is said to be "directly on top of" another, there is no component interposed between them.

[0013] The terms "first," "second," "third," etc., may be used in the present invention to describe a variety of components, elements, regions, layers, and / or areas, but these components, elements, regions, layers, and / or areas should not be limited by these terms. These terms are used to distinguish one component, element, region, layer, or area from other elements, elements, regions, layers, or areas. Accordingly, the first component, element, region, layer, or area described below may be referred to as the second component, element, region, layer, or area without deviating from the teachings of the present invention.

[0014] The terminology used in this invention is for the purpose of describing specific embodiments only and is not intended to limit the present invention. The singular form used in this application includes plural forms, including “at least one,” unless the content expressly indicates otherwise. “At least one” should not be construed as limiting to the singular. The term “and / or” as used in this invention includes all any combination of one or more of the list items. The terms “including” and / or “including” as used in the detailed description specify the presence of expressed features, regions, integers, stages, operations, components, and / or ingredients, and do not exclude the presence or addition of one or more other features, regions, integers, stages, operations, components, ingredients, and / or groups thereof.

[0015] Spatially relative terms such as “down,” “underside,” “bottom,” “up,” “top,” and “top” may be used here to easily describe the relationship between one component or feature and other components or features. Spatially relative terms will be understood to be intended to include different orientations of the device when used or operating, in addition to the orientation illustrated in the drawings. For example, if the device in the drawings is inverted, a component described as “below” or “below” other components or features will be oriented “above” other components or features. Thus, the exemplary term “down” may encompass both up and down. The device may be positioned in other orientations (rotated by 90° or in different directions), and the spatially relative terms used in this invention may be interpreted accordingly.

[0016] "Group" refers to a group of elements in the periodic table according to the International Union of Pure and Applied Chemistry ("IUPAC") classification system of groups 1-18.

[0017] In this specification, "particle size" refers to the average diameter if the particle is spherical, and to the average major axis length if the particle is non-spherical. Particle size can be measured using a particle size analyzer (PSA). "Particle size" is, for example, the average particle size. "Average particle size" is, for example, the median particle size, D50.

[0018] D50 is the particle size that corresponds to the 50% cumulative volume calculated from the smallest particle size in the particle size distribution measured by laser diffraction.

[0019] D90 is the particle size that corresponds to the 90% cumulative volume calculated from the smallest particle size in the particle size distribution measured by laser diffraction.

[0020] D10 is the particle size that corresponds to the 10% cumulative volume, calculated from the smallest particle size in the particle size distribution measured by laser diffraction.

[0021] In this invention, "viscosity" can be measured using Brookfield's LV DV-II + Pro Viscometer (cone-plate type). Viscosity can be measured, for example, by dissolving an ionic liquid in dimethylformamide (DMF) at a concentration of 35 wt%, and then measuring at 1 atm and 25°C. For example, when measuring viscosity, the spindle is set to S40, rpm 15, and the sample loading volume is 1 mL.

[0022] In this invention, "weight-average molecular weight" may refer to a converted value relative to standard polystyrene measured by GPC (Gel Permeation Chromatography). The molecular weight is, for example, the weight-average molecular weight. For example, weight-average molecular weight measurement using GPC can be performed using an Agilent 1200 series, an Agilent PL mixed B column, and THF as the solvent.

[0023] In this invention, "metal" includes both metals and metalloids such as silicon and germanium, in either an elemental or ionic state.

[0024] In this invention, "alloy" means a mixture of two or more metals.

[0025] In this invention, "electrode active material" means an electrode material that can be lithium-treated and delithiated.

[0026] In this invention, "positive electrode active material" means a positive electrode material that can be lithium-ionized and delithiated.

[0027] In this invention, "negative electrode active material" means a negative electrode material that can be lithium-treated and delithiated.

[0028] In this invention, "lithification" and "lithification" refer to the process of adding lithium to the electrode active material.

[0029] In this invention, "desitization" and "to delithiate" refer to the process of removing lithium from the electrode active material.

[0030] In this invention, "charging" and "to charge" refer to the process of providing electrochemical energy to a battery.

[0031] In this invention, "discharge" and "to discharge" refer to the process of removing electrochemical energy from a battery.

[0032] In this invention, "positive electrode" and "cathode" refer to electrodes in which electrochemical reduction and lithiumization occur during the discharge process.

[0033] In this invention, "negative electrode" and "anode" refer to electrodes in which electrochemical oxidation and delithiation occur during the discharge process.

[0034] While specific embodiments have been described, alternatives, modifications, variations, improvements, and substantial equivalents that are not currently anticipated or foreseeable may arise for the applicant or those skilled in the art. Accordingly, the claims of the filed and modifiable appendix are intended to include all such alternatives, modifications, variations, improvements, and substantial equivalents.

[0035] The following describes a solid-state secondary battery according to an exemplary embodiment in more detail.

[0036] [Solid secondary battery] A 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; comprising a first organic electrolyte disposed between the positive electrode layer and the solid electrolyte layer, a second organic electrolyte disposed between the negative electrode layer and the solid electrolyte layer, a third organic electrolyte disposed within the solid electrolyte layer, or a combination thereof, wherein the first organic electrolyte, the second organic electrolyte, and the third organic electrolyte independently comprise a polymer electrolyte, a liquid electrolyte, or a combination thereof, the viscosity of the liquid electrolyte is 10 cps or more at 25°C and 1 atm, the 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 positive electrode active material layer comprises a Li2S-containing composite, and the negative electrode layer comprises a negative electrode current collector and a first negative electrode active material layer disposed on one side of the negative electrode current collector. The solid-state secondary battery may further include one or more of the following: a first intermediate layer disposed between the positive electrode layer and the solid electrolyte layer, and a second intermediate layer disposed between the negative electrode layer and the solid electrolyte layer. The first intermediate layer may contain the first organic electrolyte. The second intermediate layer may contain the second organic electrolyte.

[0037] By including a high-viscosity organic electrolyte between the positive electrode layer and the solid electrolyte layer, between the negative electrode layer and the solid electrolyte layer, or within the solid electrolyte layer of a solid-state secondary battery, the interfacial resistance between the positive electrode layer and / or the negative electrode layer and the solid electrolyte layer is reduced, allowing the solid electrolyte layer to more easily accommodate volume changes in the positive electrode layer and / or the negative electrode layer during charging and discharging of the solid-state secondary battery. Furthermore, the high-viscosity organic electrolyte can suppress the formation of defects such as cracks in the solid electrolyte layer by filling pinholes and other defects on the surface of the solid electrolyte layer. The high-viscosity organic electrolyte can suppress gas generation due to side reactions and thus suppress the decrease in ionic conductivity by reducing the contact area between the solid electrolyte layer and oxygen. The cycle characteristics of the solid-state secondary battery can be further improved. For example, the efficiency characteristics and lifespan characteristics of the solid-state secondary battery can be improved.

[0038] Referring to Figures 1a-1c, 2a-2c, 3a-3c, 4a-4c, and 5-9, the solid-state secondary battery 1 includes a high-viscosity organic electrolyte 100 disposed on one or more of the following: one surface 30a of the solid electrolyte layer, the other surface 30b of the solid electrolyte layer 30 facing the aforementioned surface 30a, and the interior 30c of the solid electrolyte layer. The high-viscosity organic electrolyte 100 has improved flexibility compared to inorganic electrolytes. The high-viscosity organic electrolyte 100 includes a polymer electrolyte, a liquid electrolyte, or a combination thereof, and has a viscosity of 10 cps or more at 25°C. The viscosity unit cps is centipoise.

[0039] Referring to Figures 1a-1c, 2a-2c, 3a-3c, 4a-4c, and 5-9, the solid-state secondary battery 1 includes a positive electrode layer 10; a negative electrode layer 20; and a solid electrolyte layer 30 disposed between the positive electrode layer 10 and the negative electrode layer 20. It includes a first organic electrolyte 100a disposed between the positive electrode layer 10 and the solid electrolyte layer 30, a second organic electrolyte 100b disposed between the negative electrode layer 20 and the solid electrolyte layer 30, a third organic electrolyte 100c disposed within the solid electrolyte layer 30, or a combination thereof. The first organic electrolyte 100a, the second organic electrolyte 100b, and the third organic electrolyte 100c independently include a polymer electrolyte, a liquid electrolyte, or a combination thereof. The viscosity of the liquid electrolyte is 10 cps or more at 25°C and 1 atm. The positive electrode layer 10 includes a positive electrode current collector 11 and a positive electrode active material layer 12 disposed on one or both sides of the positive electrode current collector 11, wherein the positive electrode active material layer 12 includes a Li2S-containing composite. The negative electrode layer 20 includes a negative electrode current collector 21 and a first negative electrode active material layer 22 disposed on one side of the negative electrode current collector 21.

[0040] [Solid electrolyte layer] [Solid electrolyte layer: organic electrolyte] Referring to Figures 1a to 1c, the solid electrolyte layer 30 includes, for example, one or more of the following: a first organic electrolyte 100a disposed between the positive electrode layer 10 and the solid electrolyte layer 30, a second organic electrolyte 100b disposed between the negative electrode layer 20 and the solid electrolyte layer 30, and a third organic electrolyte 100c disposed within the solid electrolyte layer 30.

[0041] Referring to Figure 1a, the solid electrolyte layer 30 includes, for example, a first organic electrolyte 100a disposed on one surface 30a of the solid electrolyte layer or on one surface of the positive electrode layer 10. By arranging one surface of the positive electrode layer 10 on one surface 30a of the solid electrolyte layer, the first organic electrolyte 100a is disposed between the positive electrode layer 10 and the solid electrolyte layer 30. By arranging the flexible first organic electrolyte 100a between the positive electrode layer 10 and the solid electrolyte layer 30, the interfacial resistance between the positive electrode layer 10 and the solid electrolyte layer 30 can be reduced. Pinholes disposed on the other surface 30b of the solid electrolyte layer can be filled with the first organic electrolyte 100a. By providing the first organic electrolyte 100a, the internal resistance of the solid secondary battery 1 is reduced, and the solid electrolyte layer 30 can more easily accommodate the volume change of the positive electrode layer 10 during charging and discharging of the solid secondary battery 1.

[0042] Referring to Figure 1b, the solid electrolyte layer 30 includes, for example, a second organic electrolyte 100b disposed on the other surface 30b of the solid electrolyte layer opposite to the one surface 30a, or on one surface of the negative electrode layer 20. By arranging one surface of the negative electrode layer 20 on the other surface 30b of the solid electrolyte layer, the second organic electrolyte 100b is disposed between the negative electrode layer 20 and the solid electrolyte layer 30. By arranging the flexible second organic electrolyte 100b between the negative electrode layer 20 and the solid electrolyte layer 30, the interfacial resistance between the negative electrode layer 20 and the solid electrolyte layer 30 can be reduced. Pinholes disposed on the one surface 30a of the solid electrolyte layer can be filled with the second organic electrolyte 100b. By providing the second organic electrolyte 100b, the internal resistance of the solid secondary battery 1 is reduced, and the solid electrolyte layer 30 can more easily accommodate the volume change of the negative electrode layer 20 during charging and discharging of the solid secondary battery 1.

[0043] Referring to Figure 1c, the solid electrolyte layer 30 includes, for example, a third organic electrolyte 100c disposed within the solid electrolyte layer 30. The presence of the flexible third organic electrolyte 100c inside the solid electrolyte layer 30c can reduce the internal resistance of the solid electrolyte layer 30. Pinholes disposed inside the solid electrolyte layer 30c can be filled with the third organic electrolyte 100c. The inclusion of the third organic electrolyte 100c reduces the internal resistance of the solid secondary battery 1, and the solid electrolyte layer 30 can more easily accommodate volume changes of the positive electrode layer 10 and / or negative electrode layer 20 during charging and discharging of the solid secondary battery 1.

[0044] Referring to Figure 2a, the solid-state secondary battery 1 may further include, for example, a first intermediate layer 60 disposed between the positive electrode layer 10 and the solid electrolyte layer 30. The first intermediate layer 60 may include a first organic electrolyte 100a. For example, the first organic electrolyte 100a may form the first intermediate layer 60 between the positive electrode layer 10 and the solid electrolyte layer 30. By including the first intermediate layer 60 in the solid-state secondary battery 1, the interfacial resistance between the positive electrode layer 10 and the solid electrolyte layer 30 may be further reduced. The cycle characteristics of the solid-state secondary battery 1 may be further improved.

[0045] Referring to Figure 2b, the solid-state secondary battery 1 may further include, for example, a second intermediate layer 70 disposed between the negative electrode layer 20 and the solid electrolyte layer 30. The second intermediate layer 70 may include a second organic electrolyte 100b. For example, the second organic electrolyte 100b may form the second intermediate layer 70 between the negative electrode layer 20 and the solid electrolyte layer 30. By including the second intermediate layer 70 in the solid-state secondary battery 1, the interfacial resistance between the negative electrode layer 20 and the solid electrolyte layer 30 may be further reduced. The cycle characteristics of the solid-state secondary battery 1 may be further improved.

[0046] Referring to Figure 2c, the solid-state secondary battery 1 may simultaneously include a first intermediate layer 60 and a second intermediate layer 70. By including both the first and second intermediate layers 60 and 70 in the solid-state secondary battery 1, the interfacial resistance between the positive electrode layer 10 and the solid electrolyte layer 30 and the interfacial resistance between the negative electrode layer 20 and the solid electrolyte layer 30 can be further reduced. As the internal resistance of the solid-state secondary battery 1 is further reduced, the cycle characteristics of the solid-state secondary battery 1 can be further improved.

[0047] The first organic electrolyte 100a, the second organic electrolyte 100b, and the third organic electrolyte 100c are, respectively, a polymer solid electrolyte, a polymer gel electrolyte, a liquid electrolyte, or a combination thereof. The first organic electrolyte 100a, the second organic electrolyte 100b, and the third organic electrolyte 100c may be, for example, identical to or different from each other.

[0048] The organic electrolyte 100 includes, for example, a polymer electrolyte. The viscosity of the polymer electrolyte is even higher than that of, for example, a liquid electrolyte.

[0049] A polymer electrolyte is an electrolyte containing a polymer. Polymer electrolytes may include, for example, polymer solid electrolytes, polymer gel electrolytes, or combinations thereof.

[0050] Polymer electrolytes can be classified into polymer solid electrolytes or polymer gel electrolytes, for example, depending on whether or not they contain a liquid. Alternatively, polymer electrolytes can be classified into polymer solid electrolytes or polymer gel electrolytes depending on their state at 25°C and 1 atm. Polymer solid electrolytes may contain, for example, a mixture of lithium salt and polymer, or a polymer having ion-conducting active groups. Polymer solid electrolytes are also polymer electrolytes that are in a solid state at 25°C and 1 atm. Polymer solid electrolytes do not contain liquid.

[0051] Polymer gel electrolytes may, for example, contain a liquid electrolyte and a polymer, or an organic solvent and a polymer having an ionic conductive working group. Liquid electrolytes may also be, for example, an ionic liquid, a mixture of a lithium salt and an ionic liquid, a mixture of a lithium salt and an organic solvent, a mixture of an ionic liquid and an organic solvent, or a mixture of a lithium salt, an ionic liquid, and an organic solvent. Polymer gel electrolytes may also be polymer electrolytes that are in a gel state at 25°C and 1 atm. Polymer gel electrolytes may, for example, not contain a liquid and may be in a gel state. In this invention, "ionic liquid" is a compound consisting of ions and having a melting point of 100°C or lower.

[0052] Lithium salts used in polymer electrolytes and / or liquid electrolytes are not particularly limited, and any lithium salt usable as an electrolyte lithium salt in the art may be used. Examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, and LiN(C) x F 2x+1 SO2)(C y F 2y+1 SO2) (where x and y are 1 to 20, respectively), LiCl, LiI, or mixtures thereof, etc.

[0053] The polymer electrolyte may include, for example, a polymer containing repeating units having a thermopolymerizable functional group, a thermoset of the polymer, an oligomer containing repeating units having a thermopolymerizable functional group, a thermoset of the oligomer, a monomer having a thermopolymerizable functional group, a thermoset of the monomer, an oligomeric ionic liquid, a polymeric ionic liquid, or a combination thereof.

[0054] Polymers containing repeating units having thermopolymerizable functional groups, thermosets of such polymers, and oligomers containing repeating units having thermopolymerizable functional groups may further contain repeating units that do not have thermopolymerizable functional groups. The repeating units that do not have thermopolymerizable functional groups are not particularly limited, and any repeating units derived from unsaturated group-containing monomers used in the production of copolymers in the art can be used. The repeating units that do not have thermopolymerizable functional groups are, for example, acrylic monomers such as methyl acrylate and ethyl acrylate.

[0055] Thermally polymerizable functional groups may include, for example, cyano groups, hydroxyl groups, amino groups, amide groups, imide groups, carboxyl groups, acid anhydride groups, or combinations thereof.

[0056] Polymers and / or oligomers containing repeating units having a thermally polymerizable functional group may include, for example, repeating units derived from cyano group-containing monomers, repeating units derived from hydroxyl group-containing monomers, repeating units derived from acid anhydride group-containing monomers, repeating units derived from amino group-containing monomers, repeating units derived from amide group-containing monomers, repeating units derived from imide group-containing monomers, repeating units derived from carboxyl group-containing monomers, or combinations thereof. Monomers having a thermally polymerizable functional group may include, for example, cyano group-containing monomers, hydroxyl group-containing monomers, amino group-containing monomers, amide group-containing monomers, imide group-containing monomers, carboxyl group-containing monomers, acid anhydride group-containing monomers, or combinations thereof.

[0057] Cyano group-containing monomers include, for example, unsaturated carboxylic acid nitrile monomers such as acrylonitrile, methacrylonitrile, and vinylidene cyanide; cyanoalkyl ester monomers of unsaturated carboxylic acids such as 2-cyanoethyl (meth)acrylate, 2-cyanopropyl (meth)acrylate, and 3-cyanopropyl (meth)acrylate; and CH=CH-C(=O)-(OCH2CH2) n -CN(n=1~20), etc.

[0058] Examples of hydroxyl group-containing monomers include hydroxyalkyl ester monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate.

[0059] Examples of amino group-containing monomers include aminoalkyl ester monomers of unsaturated carboxylic acids such as aminomethyl (meth)acrylate, methylaminomethyl (meth)acrylate, dimethylaminomethyl (meth)acrylate, 2-aminoethyl (meth)acrylate, 2-methylaminoethyl (meth)acrylate, 2-ethylaminoethyl (meth)acrylate, 2-dimethylaminoethyl (meth)acrylate, 2-diethylaminoethyl (meth)acrylate, 2-n-propylaminoethyl (meth)acrylate, 2-n-butylaminoethyl (meth)acrylate, 2-aminopropyl (meth)acrylate, 2-methylaminopropyl (meth)acrylate, 2-dimethylaminopropyl (meth)acrylate, 3-aminopropyl (meth)acrylate, 3-methylaminopropyl (meth)acrylate, and 3-dimethylaminopropyl (meth)acrylate.

[0060] Amide group-containing monomers include, for example, unsaturated carboxylic acid amide monomers such as (meth)acrylamide, α-chloroacrylamide, N,N'-methylenebis(meth)acrylamide, N,N'-ethylenebis(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, N-2-hydroxyethyl(meth)acrylamide, N-2-hydroxypropyl(meth)acrylamide, N-3-hydroxypropyl(meth)acrylamide, crotonamide, maleic acid diamide, fumaric acid diamide, and diacetone acrylamide; N-di These include unsaturated carboxylic acid amide monomers such as methylaminomethyl(meth)acrylamide, N-2-aminoethyl(meth)acrylamide, N-2-methylaminoethyl(meth)acrylamide, N-2-ethylaminoethyl(meth)acrylamide, N-2-dimethylaminoethyl(meth)acrylamide, N-2-diethylaminoethyl(meth)acrylamide, N-3-aminopropyl(meth)acrylamide, N-3-methylaminopropyl(meth)acrylamide, and N-3-dimethylaminopropyl(meth)acrylamide.

[0061] Examples of imide group-containing monomers include cyclohexylmaleimide, isopropylmaleimide, N-cyclohexylmaleimide, and itaconimide.

[0062] Examples of carboxyl group-containing monomers include unsaturated monocarboxylic acid monomers such as (meth)acrylic acid and crotonic acid; unsaturated polycarboxylic acid monomers such as maleic acid, fumaric acid, itaconic acid, citraconic acid, and mesaconic acid; and alkyl ester monomers or amide monomers containing free carboxyl groups of the aforementioned unsaturated polycarboxylic acids.

[0063] Examples of monomers containing carboxylic acid anhydride groups include the acid anhydrides of the unsaturated polycarboxylic acids mentioned above.

[0064] Thermosetting products of polymers containing repeating units having thermopolymerizable functional groups, thermosetting products of oligomers containing repeating units having thermopolymerizable functional groups, and thermosetting products of monomers having thermopolymerizable functional groups are obtained by heat-treating the polymer containing repeating units having thermopolymerizable functional groups, the oligomer containing repeating units having thermopolymerizable functional groups, and the monomer having thermopolymerizable functional groups, respectively, at temperatures such as 50-200°C, 50-150°C, 50-100°C, or 50-70°C. The heat treatment time is, for example, 1-120 minutes, 5-100 minutes, 10-80 minutes, or 30-80 minutes.

[0065] Oligomeric ionic liquids and polymeric ionic liquids are, for example, the polymerization results of ionic liquid monomers.

[0066] Ionic liquid monomers 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- The unsaturated monomers can be selected from among CF3SO3-, (FSO2)2N-, (C2F5SO2)2N-, (C2F5SO2)(CF3SO2)N-, and (CF3SO2)2N-, which contain one or more anions selected from these. Such ionic liquid monomers can be polymerized to obtain oligomeric ionic liquids or polymeric ionic liquids.

[0067] Organic electrolyte 100 includes, for example, a liquid electrolyte, the viscosity of which is, for example, 10 cps or more, 15 cps or more, 20 cps or more, 25 cps or more, or 30 cps at 25°C and 1 atm. The viscosity of the liquid electrolyte is, for example, 10 cps to 1000 cps, 15 cps to 500 cps, 20 cps to 400 cps, 25 cps to 200 cps, 30 cps to 100 cps at 25°C and 1 atm. The viscosity of the liquid electrolyte is, for example, 10 cps to 1000 cps, 10 cps to 500 cps, 10 cps to 400 cps, 10 cps to 200 cps, or 10 cps to 100 cps at 25°C and 1 atm. The viscosity of the liquid electrolyte can be measured using Brookfield's LV DV-II + Pro Viscometer (cone-plate type). Having a high viscosity within this range of liquid electrolytes can more effectively accommodate volume changes during charging and discharging of the positive electrode layer 10 and / or negative electrode layer 20, more effectively reduce interfacial resistance at the interfaces between the positive electrode layer 10, negative electrode layer 20, and solid electrolyte layer 30, and provide improved bonding strength between the positive electrode layer 10, negative electrode layer 20, and solid electrolyte layer 30. As a result, the cycle characteristics of the solid-state secondary battery 1 can be improved. If the viscosity of the liquid electrolyte is excessively low, the above-mentioned effects will be negligible.

[0068] Liquid electrolytes may include, for example, ionic liquids.

[0069] Ionic liquids can be represented, for example, by the following chemical formulas 1 and 2. [ka]

[0070] In the above chemical formula 1, X1 is -N(R2)(R3)(R4) or -P(R2)(R3)(R4), and R1, R2, R3, and R4 are each independently a halogen-substituted or unsubstituted C1-C30 alkyl group, a halogen-substituted or unsubstituted C1-C30 alkoxy group, a halogen-substituted or unsubstituted C6-C30 aryl group, a halogen-substituted or unsubstituted C6-C30 aryloxy group, a halogen-substituted or unsubstituted C3-C30 heteroaryl group, a halogen-substituted or unsubstituted C3-C30 heteroaryloxy group, a halogen-substituted or unsubstituted C4-C30 cycloalkyl group, a halogen-substituted or unsubstituted C3-C30 heterocycloalkyl group, or a halogen-substituted or unsubstituted C2-C100 alkylene oxide group. In the aforementioned chemical formula 2, [ka] X2 is a heterocycloalkyl or heteroaryl ring containing 1 to 3 heteroatoms and 2 to 30 carbon atoms, wherein the ring is substituted or unsubstituted, and X2 is =N(R5)(R6), -N(R5)=, =P(R5)(R6), or -P(R5)=. The substituents R5 and R6 substituted on the ring are, independently, hydrogen, a halogen-substituted or unsubstituted C1-C30 alkyl group, a halogen-substituted or unsubstituted C1-C30 alkoxy group, a halogen-substituted or unsubstituted C6-C30 aryl group, a halogen-substituted or unsubstituted C6-C30 aryloxy group, a halogen-substituted or unsubstituted C3-C30 heteroaryl group, a halogen-substituted or unsubstituted C3-C30 heteroaryloxy group, a halogen-substituted or unsubstituted C4-C30 cycloalkyl group, a halogen-substituted or unsubstituted C3-C30 heterocycloalkyl group, or a halogen-substituted or unsubstituted C2-C100 alkylene oxide group. - It is an anion.

[0071] Ionic liquids can be represented, for example, by the following chemical formulas 3 and 4.

Chem.

[0072] In the chemical formula 3, Z is N or P, R7, R8, R9 and R 10 are each independently a C1-C30 alkyl group substituted or unsubstituted with halogen, a C6-C30 aryl group substituted or unsubstituted with halogen, a C3-C30 heteroaryl group substituted or unsubstituted with halogen, a C4-C30 cycloalkyl group substituted or unsubstituted with halogen, or a C3-C30 heterocycloalkyl group substituted or unsubstituted with halogen, In the chemical formula 4, Z is N or P, R 11 、R 12 、R 13 、R 14 、R 15 、R 16 、and R 17 are each independently hydrogen, a C1-C30 alkyl group substituted or unsubstituted with halogen, a C6-C30 aryl group substituted or unsubstituted with halogen, a C3-C30 heteroaryl group substituted or unsubstituted with halogen, a C4-C30 cycloalkyl group substituted or unsubstituted with halogen, or a C3-C30 heterocycloalkyl group substituted or unsubstituted with halogen, and Y - is an anion.

[0073] The ionic liquid can be represented, for example, by the following chemical formulas 5 to 10.

Chem.

[0074] In the chemical formulas 5 to 10, R 18 、R 19 、R 20 and R 21Each of these is independently a halogen-substituted or unsubstituted C1-C30 alkyl group, a halogen-substituted or unsubstituted C6-C30 aryl group, a halogen-substituted or unsubstituted C3-C30 heteroaryl group, a halogen-substituted or unsubstituted C4-C30 cycloalkyl group, or a halogen-substituted or unsubstituted C3-C30 heterocycloalkyl group. R 22 , R 23 , R 24 , R 25 , R 26 , and R 27 Each of these is independently hydrogen, a halogen-substituted or unsubstituted C1-C30 alkyl group, a halogen-substituted or unsubstituted C6-C30 aryl group, a halogen-substituted or unsubstituted C3-C30 heteroaryl group, a halogen-substituted or unsubstituted C4-C30 cycloalkyl group, or a halogen-substituted or unsubstituted C3-C30 heterocycloalkyl group, Y - It is an anion.

[0075] Ionic liquids contain anions, and anions are, for example, BF4 - PF6 - AsF6 - SbF6 - AlCl4 - HSO4 - ClO4 - CH3SO3 - CF3CO2 - Cl - , Br - , I - SO4 2- , BOB - (bis(oxalate)borate), CF3SO3 - , (FSO2)2N - , (C2F5SO2)2N - ,(C2F5SO2)(CF3SO2)N - , (CF3SO2)2N - (CF3)3PF3 - (CF3)4PF2 - (CF3)5PF - (CF3)6P -, SF5CF2SO3 - ,SF5CHFCF2SO3 - CF3CF2(CF3)2CO - (CF3SO2) 2CH - (SF5)3C - , C2N3 - (O(CF3)2C2(CF3)2O)2PO - , (FSO2)2N - , (CF3SO2)2N - Or it may include combinations of these.

[0076] The anions of ionic liquids represented by chemical formulas 1 to 10 can also be selected from among the anions mentioned above.

[0077] Ionic liquids may include, for example, 1-methyl-1-propylpyrrolidinium bis(fluorosulfonyl)imide, 1-methyl-1-butylpyrrolidinium bis(fluorosulfonyl)imide, 1-methyl-1-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide, 1-methyl-1-butylpyrrolidinium bis(trifluoromethanesulfonyl)imide, or combinations thereof.

[0078] The molecular weight of ionic liquids is, for example, 1000 Daltons or less, 900 Daltons or less, 800 Daltons or less, or 500 Daltons or less.

[0079] Referring to Figures 3a to 3c, the solid electrolyte layer 30 may further include one or more of the first organic electrolyte and the second organic electrolyte disposed inside the solid electrolyte layer 30c.

[0080] Referring to Figure 3a, the solid electrolyte layer 30 may include a first organic electrolyte 100a disposed on one surface 30a of the solid electrolyte and extending from that surface 30a to the interior 30c of the solid electrolyte layer. By simultaneously distributing the first organic electrolyte 100a at the interface between the solid electrolyte layer 30 and the positive electrode layer 10 and in the interior 30c of the solid electrolyte layer, the interfacial resistance between the solid electrolyte layer 30 and the positive electrode layer 10 is further reduced, and the solid electrolyte layer 30 can more easily accommodate volume changes of the positive electrode layer 10. The first organic electrolyte 100a may extend from one surface 30a of the solid electrolyte layer toward the negative electrode layer 20 to a region corresponding to 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less of the total thickness of the solid electrolyte layer 30.

[0081] Referring to Figure 3b, the solid electrolyte layer 30 may include a second organic electrolyte 100b disposed on the other surface 30b of the solid electrolyte and extending from the other surface 30b to the interior 30c of the solid electrolyte layer. By simultaneously distributing the second organic electrolyte 100b at the interface between the solid electrolyte layer 30 and the negative electrode layer 20 and in the interior 30c of the solid electrolyte layer, the interfacial resistance between the solid electrolyte layer 30 and the negative electrode layer 20 is further reduced, and the solid electrolyte layer 30 can more easily accommodate volume changes of the negative electrode layer 20. The second organic electrolyte 100b may extend from the other surface 30b of the solid electrolyte layer toward the positive electrode layer 10 to a region corresponding to 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less of the total thickness of the solid electrolyte layer 30.

[0082] Referring to Figure 3c, the solid electrolyte layer 30 may simultaneously include a first organic electrolyte 100a disposed on one surface 30a of the solid electrolyte and extending from that surface 30a to the interior 30c of the solid electrolyte layer, and a second organic electrolyte 100b disposed on the other surface 30b of the solid electrolyte and extending from that other surface 30b to the interior 30c of the solid electrolyte layer. By distributing the first organic electrolyte 100a at the interface between the solid electrolyte layer 30 and the positive electrode layer 10 and the interior 30c of the solid electrolyte layer, and distributing the second organic electrolyte 100b at the interface between the solid electrolyte layer 30 and the negative electrode layer 20 and the interior 30c of the solid electrolyte layer, the interfacial resistance between the solid electrolyte layer 30 and the positive electrode layer 10 and the interfacial resistance between the solid electrolyte layer 30 and the negative electrode layer 20 are further reduced, and the solid electrolyte layer 30 can more effectively accommodate the volume changes of the positive electrode layer 10 and the negative electrode layer 20. The first organic electrolyte 100a and the second organic electrolyte 100b may be arranged extending from one surface 30a and the other surface 30b of the solid electrolyte layer to regions corresponding to 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less of the total thickness of the solid electrolyte layer 30, respectively.

[0083] The solid electrolyte includes one surface 30a and another surface 30b facing the first surface 30a. One surface 30a of the solid electrolyte layer is adjacent to the positive electrode layer 10, and the other surface 30b of the solid electrolyte layer is adjacent to the negative electrode layer 20. One surface 30a of the solid electrolyte layer is in contact with, for example, the positive electrode layer 10. The other surface 30b of the solid electrolyte layer is in contact with, for example, the negative electrode layer 20.

[0084] Figures 4a to 4c illustrate the organic electrolyte concentration C contained in the solid electrolyte layer 30 at different positions from one surface 30a to the other surface 30b of the solid electrolyte layer.

[0085] Referring to Figure 4a, the solid electrolyte layer 30 may have a concentration gradient of the first organic electrolyte 100a that decreases from one surface 30a of the solid electrolyte layer toward the negative electrode layer 20. Although not shown in the drawing, the concentration gradient of the first organic electrolyte 100a may decrease in various inclines. The concentration gradient of the first organic electrolyte 100a may decrease in a constant incline or in a changing incline. The concentration of the first organic electrolyte 100a may decrease continuously or discontinuously from one surface 30a of the solid electrolyte layer to the other surface 30b of the solid electrolyte layer. For example, if the solid electrolyte layer 30 has a multilayer structure, the concentration of the first organic electrolyte 100a may decrease in a stepwise manner from one surface 30a of the solid electrolyte layer to the other surface 30b of the solid electrolyte layer. The solid electrolyte layer 30 having such a concentration gradient of the first organic electrolyte 100a can more effectively accommodate volume changes in the positive electrode layer 10 in regions where the concentration of the first organic electrolyte 100a is high, and can provide improved structural stability in regions where the concentration of the first organic electrolyte 100a is low or zero.

[0086] Referring to Figure 4b, the solid electrolyte layer 30 may have a concentration gradient of the second organic electrolyte 100b that decreases from the other surface 30b of the solid electrolyte layer toward the positive electrode layer 10. Although not shown in the drawing, the concentration gradient of the second organic electrolyte 100b may decrease in various inclines. The concentration gradient of the second organic electrolyte 100b may decrease in a constant incline or in a changing incline. The concentration of the second organic electrolyte 100b may decrease continuously or discontinuously from the other surface 30b of the solid electrolyte layer toward one surface 30a of the solid electrolyte layer. For example, if the solid electrolyte layer 30 has a multilayer structure, the concentration of the second organic electrolyte 100b may decrease in a stepwise manner from the other surface 30b of the solid electrolyte layer toward one surface 30a of the solid electrolyte layer. The solid electrolyte layer 30 having such a concentration gradient of the second organic electrolyte 100b can more effectively accommodate the volume change of the negative electrode layer 20 in regions where the concentration of the second organic electrolyte 100b is high, and can provide improved structural stability in regions where the concentration of the second organic electrolyte 100b is low or zero.

[0087] Referring to Figure 4c, the solid electrolyte layer 30 may simultaneously have a concentration gradient of the first organic electrolyte 100a decreasing from one surface 30a of the solid electrolyte layer toward the negative electrode layer 20, and a concentration gradient of the second organic electrolyte 100b decreasing from the other surface 30b of the solid electrolyte layer toward the positive electrode layer 10. Although not shown in the drawing, the concentration gradients of the first organic electrolyte 100a and the second organic electrolyte 100b may decrease in various ways, for example. The concentration gradients of the first organic electrolyte 100a and the second organic electrolyte 100b may decrease in a constant or variable manner from the other surface 30b of the solid electrolyte layer toward one surface 30a of the solid electrolyte layer. For example, by having a multilayer structure, the concentrations of the first organic electrolyte 100a and the second organic electrolyte 100b can decrease, for example, in a stepwise manner from one surface 30a and the other surface 30b of the solid electrolyte layer to the interior 30c of the solid electrolyte layer. By having such a concentration gradient of the first organic electrolyte 100a and the second organic electrolyte 100b in the solid electrolyte layer 30, it is possible to more effectively accommodate the volume changes of the positive electrode layer 10 and the negative electrode layer 20 in regions where the concentrations of the first organic electrolyte 100a and the second organic electrolyte 100b are high, and to provide improved structural stability in regions where the concentrations of the first organic electrolyte 100a and the second organic electrolyte 100b are low or zero, for example, in the central region of the solid electrolyte layer 30.

[0088] [Solid electrolyte layer: solid electrolyte] Referring to Figures 1a to 9, the solid electrolyte layer 30 is positioned between the positive electrode layer 10 and the negative electrode layer 20 and contains a solid electrolyte. The solid electrolyte includes, for example, an inorganic solid electrolyte.

[0089] The solid electrolyte may include, for example, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or a combination thereof.

[0090] Solid electrolytes are, for example, sulfide-based solid electrolytes. Sulfide-based solid electrolytes include, 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-ZmSn, where m and n are positive numbers, and Z is one of Ge, Zn, or Ga, Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q p and 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 , one or more selected from 0 ≤ x ≤ 2. Sulfide-based solid electrolytes are produced by processing starting materials such as Li2S and P2S5 by methods such as melt-quenching or mechanical milling. After such processing, heat treatment can be performed. Solid electrolytes can be amorphous, crystalline, or a mixture of both. Solid electrolytes can also be, for example, those sulfide-based solid electrolyte materials mentioned above that contain at least sulfur (S), phosphorus (P), and lithium (Li) as constituent elements. For example, solid electrolytes can also be materials containing Li2S-P2S5. When utilizing Li2S-P2S5 as a sulfide-based solid electrolyte material to form a solid electrolyte, the molar ratio of Li2S to P2S5 is, for example, in the range of Li2S:P2S5 = 20:80~90:10, 25:75~90:10, 30:70~70:30, and 40:60~60:40.

[0091] Sulfide-based solid electrolytes may include, for example, argyrodite-type solid electrolytes represented by the following chemical formula 11. <Chemical formula 11> Li + 12-n-x A n+ X 2- 6-x Y - x

[0092] In the above formula, A is P, As, Ge, Ga, Sb, Si, Sn, Al, In, Ti, V, Nb, or Ta, X is S, Se, or Te, Y is Cl, Br, I, F, CN, OCN, SCN, or N3, and 1 ≤ n ≤ 5 and 0 ≤ x ≤ 2. A sulfide-based solid electrolyte is, for example, Li 7-x PS 6-x Cl x , 0≦x≦2, Li 7-x PS 6-x Br x , 0≦x≦2, and Li 7-x PS 6-x I x It is also an argyrodite-type compound containing one or more values ​​selected from 0 ≤ x ≤ 2. Sulfide-based solid electrolytes are also argyrodite-type compounds containing one or more values ​​selected from, for example, Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0093] The densities of argyrodite-type solid electrolytes are 0.1-2.0 g / cc, 0.5-2.0 g / cc, 1.0-2.0 g / cc, or 1.5-2.0 g / cc. Having argyrodite-type solid electrolytes in such a range of densities reduces the internal resistance of the solid secondary battery 1.

[0094] This can effectively suppress penetration of the solid electrolyte layer by lithium.

[0095] Oxide-based solid electrolytes include, for example, Li1+x+y Al x Ti 2-x Si y P 3-y O 12 (0 < x < 2, 0 ≤ y < 3), BaTiO3, Pb(Zr,Ti)O3 (PZT), Pb 1-x La x Zr 1-y Ti y O3 (PLZT) (0 ≤ x < 1, 0 ≤ y < 1), PB(Mg3Nb 2 / 3 )O3 - PbTiO3 (PMN - PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, Li3PO4, Li x Ti y (PO4)3 (0 < x < 2, 0 < y < 3), Li x Al y Ti z (PO4)3 (0 < x < 2, 0 < y < 1, 0 < z < 3), Li 1+x+y (Al, Ga) x (Ti, Ge) 2-x Si y P 3-y O 12 (0 ≤ x ≤ 1, 0 ≤ y ≤ 1), Li x La y TiO3 (0 < x < 2, 0 < y < 3), Li2O, LiOH, Li2CO3, LiAlO2, Li2O - Al2O3 - SiO2 - P2O5 - TiO2 - GeO2, Li 3+x La3M2O 12 (M = Te, Nb, or Zr, 0 ≤ x ≤ 10), or a combination thereof. The oxide-based solid electrolyte is produced, for example, by a sintering method or the like.

[0096] The oxide-based solid electrolyte is, for example, Li7La3Zr2O 12 (LLZO) and Li 3+x La3Zr 2-a M a O 12 (M doped LLZO, M = Ga, W, Nb, Ta, or Al, 0 < a < 2, 0 ≤ x ≤ 10), which is a garnet-type solid electrolyte selected therefrom.

[0097] The solid electrolyte layer 30 is also impermeable to lithium polysulfide. Therefore, it can block side reactions between lithium polysulfide, which is generated during the charging and discharging of the sulfide-based positive electrode active material, and the negative electrode layer. Consequently, the cycle characteristics of the solid secondary battery 1 including the solid electrolyte layer 30 can be improved.

[0098] [Solid electrolyte layer: binder] The solid electrolyte layer 30 may, for example, contain a binder. Examples of binders included in the solid electrolyte layer 30 include styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, and polyethylene, but are not limited to these; any binder usable in the relevant art can be used. The binder in the solid electrolyte layer 30 is the same as, but may differ from, the binder in the positive electrode active material layer 12 and the negative electrode active material layer 22. The binder is optional.

[0099] The binder content of the solid electrolyte layer 30 is 0.1-10 wt%, 0.1-5 wt%, 0.1-3 wt%, 0.1-1 wt%, 0-0.5 wt%, or 0-0.1 wt% relative to the total weight of the solid electrolyte layer 30.

[0100] [Positive electrode layer] [Cathode layer: Cathode active material] Referring to Figures 1a to 9, the positive electrode 10 includes a positive electrode current collector 11 and a positive electrode active material layer 12 disposed on one or both sides of the positive electrode current collector 11. The positive electrode active material layer 12 includes a Li2S-containing composite as the positive electrode active material.

[0101] The positive electrode active material layer 12 may contain 10-90 parts by weight, 30-90 parts by weight, 40-90 parts by weight, 40-80 parts by weight, 50-80 parts by weight, or 50-70 parts by weight of Li2S-containing composite per 100 parts by weight. If the content of Li2S-containing composite decreases excessively, the energy density of the secondary battery decreases. If the content of Li2S-containing composite increases excessively, the deterioration of the positive electrode may be accelerated due to volume changes in the positive electrode during charging and discharging. As a result, the cycle characteristics of the secondary battery 1 may deteriorate.

[0102] Li2S-containing composites include, for example, composites of Li2S and carbon-based materials, composites of Li2S, carbon-based materials and solid electrolytes, composites of Li2S and solid electrolytes, composites of Li2S, carbon-based materials and lithium salts, composites of Li2S and lithium salts, composites of Li2S and metal carbides, composites of Li2S, carbon-based materials and metal carbides, composites of Li2S and metal nitrides, composites of Li2S, carbon-based materials and metal nitrides, or combinations thereof.

[0103] Li2S-containing composites are distinguished from simple mixtures of Li2S and other materials. In simple mixtures of Li2S and other materials, the interfacial resistance between Li2S and the other materials is maintained, resulting in a high internal resistance of the positive electrode containing them. Therefore, the cycle characteristics of solid-state secondary batteries 1 containing them may be degraded. On the other hand, in Li2S-containing composites, the interfacial resistance between Li2S and the other materials is reduced due to the mechanochemical or chemical compounding of Li2S and the other materials, thus reducing the internal resistance of the positive electrode containing them. Therefore, the cycle characteristics of solid-state secondary batteries 1 containing Li2S-containing composites may be improved.

[0104] Composites of Li2S and carbon-based materials include carbon-based materials. Carbon-based materials can be, for example, any material containing carbon atoms that is used as a conductive material in the art. Carbon-based materials can also be, for example, crystalline carbon, amorphous carbon, or a combination thereof. Carbon-based materials can also be, for example, calcined carbon precursors. Carbon-based materials can also be, for example, carbon nanostructures. Carbon nanostructures can be, for example, one-dimensional carbon nanostructures, two-dimensional carbon nanostructures, three-dimensional carbon nanostructures, or a combination thereof. Carbon nanostructures can also be, for example, carbon nanotubes, carbon nanofibers, carbon nanobelts, carbon nanorods, graphene, or a combination thereof. Carbon-based materials can also be, for example, porous carbon-based materials or non-porous carbon-based materials. Porous carbon-based materials may, for example, include periodic and regular two-dimensional or three-dimensional pores. Porous carbon-based materials include, for example, carbon blacks such as Ketjenblack, acetylene black, Denka black, thermal black, and channel black; graphite, activated carbon, or combinations thereof. The form of carbon-based materials may be, for example, particulate, sheet-like, or flake-like; however, any form suitable for use as a carbon-based material in the relevant art is acceptable. Carbon-based materials may include, for example, fibrous carbon-based materials. The aspect ratios of fibrous carbon-based materials are, for example, 2-30, 2-20, 2-10, 2-8, 2-5, or 2-4. Fibrous carbon-based materials may include fibrous carbon nanostructures. Fibrous carbon nanostructures may include, for example, carbon nanofibers, carbon nanotubes, carbon nanobelts, carbon nanorods, or combinations thereof. The aspect ratio of fibrous carbon-based materials can be measured, for example, by scanning electron microscopy (SEM) or transmission electron microscopy (TEM).

[0105] The method for producing composites of Li2S and carbon-based materials may be a dry method, a wet method, or a combination thereof, but is not limited to these; any method used in the relevant art is acceptable. Examples of methods for producing composites of Li2S and carbon-based materials include milling, heat treatment, and vapor deposition, but is not necessarily limited to these; any method used in the relevant art is acceptable.

[0106] 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 any material used as an ion-conducting material in the art, for example. 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. A sulfide-based solid electrolyte contains, for example, Li, S, and P, and may further selectively contain halogen elements. The sulfide-based solid electrolyte can be selected from among the sulfide-based solid electrolytes used in the solid electrolyte layer. A sulfide-based solid electrolyte has a capacity of, for example, 1 × 10⁻⁶ at room temperature. -5 It may have an ionic conductivity of S / cm or higher. Oxide-based solid electrolytes may contain, for example, Li, O, and transition metal elements, and may further selectively contain other elements. Oxide-based solid electrolytes may have a conductivity of, for example, 1 × 10⁻⁶ at room temperature. -5 These are also solid electrolytes having an ionic conductivity of S / cm or higher. Oxide-based solid electrolytes can be selected from among the oxide-based solid electrolytes used in the solid electrolyte layer. The ionic conductivity of the solid electrolyte can be measured, for example, by electrochemical impedance spectroscopy.

[0107] The Li2S-solid electrolyte composite includes a solid electrolyte. The term "solid electrolyte" refers to the Li2S-carbon-based material-solid electrolyte composite described above.

[0108] A complex of Li2S and a lithium salt contains Li2S and a lithium salt. A lithium salt is, for example, a binary compound or a ternary compound. A lithium salt is a compound that does not contain sulfur (S). A lithium salt is also, for example, a binary compound consisting of lithium and one element selected from groups 13 to 17 of the periodic table. A lithium salt is also, for example, a ternary compound consisting of lithium and two elements selected from groups 13 to 17 of the periodic table. Binary compounds include, for example, LiI, LiBr, LiCl, LiF, LiH, Li2O, Li2Se, Li2Te, Li3N, Li3P, Li3As, Li3Sb, Li3Al2, LiB3, or combinations thereof. The ternary compounds include, for example, Li3OCl, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiNO3, Li2CO3, LiBH4, Li2SO4, Li3BO3, Li3PO4, Li4NCl, Li5NCl2, Li3BN2, or combinations thereof. The lithium salt is one or more lithium halide compounds selected in particular from LiF, LiCl, LiBr, and LiI. The Li2S and lithium salt composite is also, for example, the Li2 and lithium halide composite. The Li2 and lithium salt composite may provide further improved ionic conductivity by including a lithium halide compound. The Li2S and lithium salt composite is distinguished from a simple mixture of Li2S, a carbon-based material, and a lithium salt. The simple mixture of Li2S and a lithium salt provides high interfacial resistance because it cannot maintain a dense interface between Li2S and the lithium salt, which may consequently reduce the lifetime characteristics of the solid-state secondary battery 1.

[0109] The composite of Li2S, carbon-based material, and lithium salt includes the carbon-based material and the lithium salt. The carbon-based material refers to the composite of Li2S and carbon-based material described above. The lithium salt refers to the composite of Li2S and lithium salt described above.

[0110] The Li2S-metal carbide composite contains a metal carbide. The metal carbide is, for example, a two-dimensional metal carbide. The two-dimensional metal carbide is, for example, Mn+1 C n T x It is expressed as (where 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). A two-dimensional metal carbide is, for example, Ti2CT. x , (Ti 0.5 Nb 0.5 )2CT x Nb2CT x V2CT x Ti3C2T x , (V 0.5 , Cr 0.5 )3C2T x Ti3CNT x Ta4C3T x Nb4C3T x Or a combination of these. The surface of the two-dimensional metal carbide is terminated with O, OH and / or F.

[0111] The composite of Li2S, carbon-based material, and metal carbide includes the carbon-based material and the metal carbide. The carbon-based material refers to the composite of Li2S and carbon-based material described above. The metal carbide refers to the composite of Li2S and metal carbide described above.

[0112] The Li2S and metal nitride composite contains a metal nitride. The metal nitride is, for example, a two-dimensional metal nitride. The two-dimensional metal nitride is, for example, M n+1 N n T x It is expressed as (where 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). The surface of the two-dimensional metal nitride is terminated with O, OH and / or F.

[0113] Li2S-containing composites are also composites of Li2S, lithium salts, and carbon-based materials. For example, Li2S-containing composites are also composites of Li2S, lithium salts, and fibrous carbon-based materials.

[0114] For example, a composite of Li2S, lithium salt, and carbon-based material may contain 10 to 80 parts by weight of Li2S, 1 to 40 parts by weight of lithium salt, and 1 to 20 parts by weight of carbon-based material per 100 parts by weight of the composite. The Li2S content of the composite is, 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 LiS per 100 parts by weight of the composite. The lithium salt content of the composite is, 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 lithium salt per 100 parts by weight of the composite. The carbon-based material content of the composite is, for example, 1 to 20 parts by weight, 5 to 20 parts by weight, or 5 to 15 parts by weight of carbon-based material per 100 parts by weight of the composite. By having a composite material composition of Li2S, lithium salt, and carbon-based materials within this range, the solid-state secondary battery 1 containing the composite may provide further improved ionic and / or electronic conductivity.

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

[0116] The positive electrode active material layer 12 may further contain, for example, a sulfide-based compound distinct from the positive electrode active material described above. The sulfide-based compound may also contain, for example, a metal element other than Li and a sulfur element. The sulfide-based compound may also contain, for example, a metal element belonging to groups 1 to 14 of the periodic table with an atomic weight of 10 or more and a sulfur element. The sulfide-based compound may also be, for example, FeS2, VS2, NaS, MnS, FeS, NiS, CuS, or a combination thereof. The inclusion of a sulfide-based compound in the positive electrode active material layer can further improve the cycle characteristics of the solid-state secondary battery 1. The content of such sulfide-based compounds in the positive electrode 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 positive electrode active material layer 12.

[0117] [Positive electrode layer: solid electrolyte] The positive electrode active material layer 12 may further contain, for example, a solid electrolyte. The solid electrolyte may be, for example, a sulfide-based solid electrolyte. The solid electrolyte contained in the positive electrode 10 may be the same as or different from the solid electrolyte contained in the solid electrolyte layer 30. For detailed information regarding the solid electrolyte, please refer to the section on the solid electrolyte layer 30.

[0118] The solid electrolyte contained in the positive electrode active material layer 12 has a smaller D50 average particle size compared to the solid electrolyte contained in the solid electrolyte layer 30. For example, the D50 average particle size of the solid electrolyte contained in the positive electrode active material layer 12 is 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, or 20% or less of the D50 average particle size of the solid electrolyte contained in the solid electrolyte layer 30. The D50 average particle size is, for example, the median particle size (D50). The median particle size (D50) is, for example, the particle size corresponding to the 50% cumulative volume calculated from the particle size with the smallest particle size in the particle size distribution measured by laser diffraction.

[0119] The positive electrode active material layer 12 may contain 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 of solid electrolyte per 100 parts by weight. If the content of the solid electrolyte is excessively reduced, the internal resistance of the positive electrode may increase, which may degrade the cycle characteristics of the secondary battery. If the content of the sulfide-based solid electrolyte is excessively increased, the energy density of the secondary battery 1 may decrease.

[0120] [Positive electrode layer: conductive material] The positive electrode active material layer 12 may further contain a conductive material. The conductive material may be, for example, a carbon-based conductive material, a metallic 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 to these; any material used as a carbon-based conductive material in the art may be used. The metallic conductive material may be, for example, metal powder, metal fiber, or a combination thereof; any material used as a metallic conductive material in the art may be used. The conductive material content in the positive electrode active material layer 12 may be, for example, 1 wt% to 30 wt%, 1 wt% to 20 wt%, or 1 wt% to 10 wt% of the total weight of the positive electrode active material layer 12.

[0121] The positive electrode active material layer 12 contains a carbon-based material, and the carbon-based material may be present only in the composite positive electrode active material. The positive electrode active material layer 12 does not contain any additional carbon-based material outside of the composite positive electrode active material containing the carbon-based material. By not including additional carbon-based material in the positive electrode active material layer, the energy density of the positive electrode and the secondary battery 1 can be improved and the manufacturing process can be simplified.

[0122] [Positive electrode layer: Binder] The positive electrode active material layer 12 may further contain a binder. The binder may be, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc., but is not limited to these; any binder usable in the art may be used. The binder content of 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 is optional.

[0123] [Positive electrode layer: Other additives] In addition to the positive electrode active material, solid electrolyte, binder, and conductive material described above, the positive electrode active material layer 12 may further contain additives such as fillers, coating agents, dispersants, and ion conductivity enhancers.

[0124] As fillers, coating agents, dispersants, ion conductivity enhancers, etc. that the positive electrode active material layer 12 may contain, known materials generally used for electrodes in solid-state secondary batteries 1 can be used.

[0125] [Positive electrode layer: Positive electrode current collector] The positive electrode current collector 11 may be 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 current collector 11 is optional. The thickness of the positive electrode current collector 11 may be, for example, 1 μm to 100 μm, 1 μm to 50 μm, 5 μm to 25 μm, or 10 μm to 20 μm.

[0126] The positive electrode current collector 11 may include, for example, a base film and a metal layer disposed on one or both sides of the base film. The base film may include, for example, a polymer. The polymer may also 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 also be, for example, an insulator. By including an insulating thermoplastic polymer in the base film, the base film may soften or liquefy when a short circuit occurs, interrupting 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 alloys thereof. The metal layer can act as an electrochemical fuse, cutting off during overcurrents to prevent short circuits. The limit current and maximum current can be adjusted by adjusting the thickness of the metal layer. The metal layer can be plated or deposited onto the base film. Reducing the thickness of the metal layer reduces the limit current and / or maximum current of the positive electrode current collector 11, thereby improving the stability of the lithium battery during short circuits. A lead tab can be added to the metal layer for external connection. The lead tab can be welded to the metal layer or the metal layer / base film laminate by ultrasonic welding, laser welding, spot welding, etc. During welding, the base film and / or metal layer melt, while the metal layer is electrically connected to the lead tab. To further strengthen the weld between the metal layer and the lead tab, a metal chip can be added between the metal layer and the lead tab. The metal chip is also a thin piece of the same material as the metal layer. Metal pieces can also be, for example, metal foil or metal mesh. Examples of metal pieces include aluminum foil, copper foil, and SUS foil.After placing a metal chip on a metal layer, the lead tab can be welded to a metal chip / metal layer laminate or a metal chip / metal layer / base film laminate by welding the lead tab to the metal chip. During welding, the base film, metal layer, and / or metal chip melt, and the metal layer or metal layer / metal chip laminate can be electrically connected to the lead tab. A metal chip and / or lead tab can be added to a portion of the metal layer phase. The thickness of the base film is, for example, 1-50 μm, 1.5-50 μm, 1.5-40 μm, or 1-30 μm. Having the base film in such a thickness range can further effectively reduce the weight of the electrode assembly. The melting point of the base film is also, for example, 100-300°C, 100-250°C or less, or 100-200°C. Having the base film in such a melting point range allows the base film to melt during the process of welding the lead tab and easily bond to 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 is, for example, 0.01 to 3 μm, 0.1 to 3 μm, 0.1 to 2 μm, or 0.1 μm. Having the metal layer in this thickness range ensures the stability of the electrode assembly while maintaining conductivity. The thickness of the metal piece is also, for example, 2 to 10 μm, 2 to 7 μm, or 4 to 6 μm. Having the metal piece in this thickness range makes it easier to connect the metal layer to the lead tab. Having such a structure in the positive electrode current collector 11 reduces the weight of the positive electrode, and as a result, the energy density of the positive electrode and the lithium battery can be improved.

[0127] [Positive electrode layer: First inert component] Referring to Figures 8 and 9, the positive electrode 10 includes a positive electrode current collector 11 and a positive electrode active material layer 12 disposed on one surface of the positive electrode current collector. A first inactive member 40 is disposed on one side surface of the positive electrode 10. Referring to Figure 8, the first inactive member 40 is disposed on one side surface of the positive electrode active material layer 12 and the positive electrode current collector 11. Referring to Figure 9, the first inactive member 40 is disposed on one side surface of the positive electrode active material layer 12 and is positioned between the solid electrolyte layer 30 and the positive electrode current collector 11 facing the solid electrolyte layer 30. The first inactive member 40 is not disposed on one side surface of the positive electrode current collector 11.

[0128] The inclusion of the first inert member 40 prevents cracking of the solid electrolyte layer 30 during the manufacturing and / or charging / discharging of the solid secondary battery 1, thereby improving the cycle characteristics of the solid secondary battery 2. In a solid secondary battery 1 without the first inert member 40, uneven pressure is applied to the solid electrolyte layer 30 in contact with the positive electrode 10 during the manufacturing and / or charging / discharging of the solid secondary battery 1, causing cracks to occur in the solid electrolyte layer 30, and the growth of lithium metal through these cracks increases the likelihood of short circuits.

[0129] In the solid-state secondary battery 1, the thickness of the first inert member 40 is greater than or equal to the thickness of the positive electrode active material layer 12. On the other hand, in the solid-state secondary battery 1, the thickness of the first inert member 40 is substantially the same as the thickness of the positive electrode 10. Since the thickness of the first inert member 40 is the same as the thickness of the positive electrode 10, a uniform pressure is applied between the positive electrode 10 and the solid electrolyte layer 30, and the positive electrode 10 and the solid electrolyte layer 30 are in close contact, which can reduce the interfacial resistance between the positive electrode 10 and the solid electrolyte layer 30. In addition, the solid electrolyte layer 30 is sufficiently sintered during the pressurized manufacturing process of the solid-state secondary battery 1, which reduces the internal resistance of the solid electrolyte layer 30 and the solid-state secondary battery 1 containing it.

[0130] The first inert member 40 surrounds the side surface of the positive electrode 10 and is in contact with the solid electrolyte layer 30. By surrounding the side surface of the positive electrode 10 and being in contact with the solid electrolyte layer 30, the first inert member 40 can effectively suppress cracks in the solid electrolyte layer 30 that occur due to the pressure difference during the pressurization process in the solid electrolyte layer 30 that is not in contact with the positive electrode 20. The first inert member 40 surrounds the side surface of the positive electrode 10 and is separated from the negative electrode 20, more specifically, from the first negative electrode active material layer 22. The first inert member 40 surrounds the side surface of the positive electrode 10, is in contact with the solid electrolyte layer 30, and is separated from the negative electrode 20. Therefore, a short circuit will not occur due to physical contact between the positive electrode 10 and the first negative electrode active material layer 22, or the possibility of a short circuit occurring due to lithium overcharging, etc., is suppressed. For example, by placing the first inert member 40 on one side surface of the positive electrode active material layer 12 and simultaneously on one side surface 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 further effectively suppressed.

[0131] Referring to Figures 8 and 9, the first inert member 40 extends from one side of the positive electrode 30 to the end of the solid electrolyte layer 30. By extending the first inert member 40 to the end of the solid electrolyte layer 30, cracks that occur at the end of the solid electrolyte layer 30 can be suppressed. The end of the solid electrolyte layer 30 is the outermost part that is in contact with the side of the solid electrolyte layer 30. The first inert member 40 extends to the outermost part that is in contact with the side of the solid electrolyte layer 30. The first inert member 40 is separated from the negative electrode 20, and more specifically, from the first negative electrode active material layer 22. The first inert member 40 extends to the end of the solid electrolyte layer 30, but does not come into contact with the negative electrode 20. The first inert member 40 fills, for example, the space that extends from one side of the positive electrode 30 to the end of the solid electrolyte layer 30.

[0132] Referring to Figures 8 and 9, the width of the first inert member 40 extending from one side of the positive electrode 10 to the end of the solid electrolyte layer 30 is, for example, 1-30%, 1-25%, 1-20%, 1-15%, 1-10%, or 1-5% of the width between one side of the positive electrode 10 and the other side facing that side. If the width of the first inert member 40 is excessively large, the energy density of the solid secondary battery 1 will decrease. If the width of the first inert member 40 is excessively small, the effect of placing the first inert member 40 will be negligible.

[0133] The area of ​​the positive electrode 10 is smaller than the area of ​​the solid electrolyte layer 30 that is in contact with the positive electrode 10. The first inert member 40 is positioned to surround the side surface of the positive electrode 10 and compensate for the area difference between the positive electrode 10 and the solid electrolyte layer 30. By the area of ​​the first inert member 40 compensating for the difference between the area of ​​the positive electrode 10 and the area of ​​the solid electrolyte layer 30, cracks in the solid electrolyte layer 30 caused by the pressure difference during the pressing process are effectively suppressed. For example, the sum of the area of ​​the positive electrode 10 and the area of ​​the first inert member 40 is the same as the area of ​​the solid electrolyte layer 30.

[0134] The area of ​​the positive electrode 10 is, for example, less than 100%, 99% or less, 98% or less, 97% or less, 96% or less, or 95% or less of the area of ​​the solid electrolyte layer 30. The area of ​​the positive electrode 10 is, for example, 50% to less than 100%, 50% to 99%, 55% to 98%, 60% to 97%, 70% to 96%, 80% to 95%, or 85% to 95% of the area of ​​the solid electrolyte layer 30.

[0135] If the area of ​​the positive electrode 10 is the same as or larger than the area of ​​the solid electrolyte layer 30, the positive electrode 10 and the first negative electrode active material layer 22 may come into physical contact, causing a short circuit, or the possibility of a short circuit occurring due to lithium overcharging or the like increases. The area of ​​the positive electrode 10 is, for example, the same as the area of ​​the positive electrode active material layer 12. The area of ​​the positive electrode 10 is, for example, the same as the area 11 of the positive electrode current collector.

[0136] The area of ​​the first 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 positive electrode 10. The area of ​​the first 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 positive electrode 10.

[0137] 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.

[0138] In the present invention, “identical” area, length, width, thickness and / or form includes all cases having “substantially identical” area, length, width, thickness and / or form, except when the area, length, width, thickness and / or form are intentionally made to differ from one another. “Identical” area, length, width and / or thickness includes unintended differences in the area, length, width and / or thickness of the objects being compared, for example, less than 3%, less than 2%, less than 1%, less than 0.5%, or less than 0.1%.

[0139] The thickness of the first 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 first 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 first inert member 40.

[0140] The first inert member 40 is also a gasket. By using a gasket as the first inert member 40, cracks in the solid electrolyte layer 30 caused by the pressure difference during the pressurization process can be effectively suppressed.

[0141] The first inert member 40 has, for example, a single-layer structure. On the other hand, although not shown in the drawings, the first inert member 40 may have a multilayer structure. In the first inert member 40 having a multilayer structure, each layer may have a different composition from the others. The first inert member having a multilayer structure may have, for example, a two-layer, three-layer, four-layer, or five-layer structure. The first inert member 40 having a multilayer structure may include, for example, one or more adhesive layers and one or more support layers. The adhesive layer effectively prevents separation between the positive electrode 10 and the solid electrolyte layer 30 due to volume changes of the positive electrode 10 that occur during the charging and discharging process of the solid secondary battery 10, and improves the film strength of the first inert member 40 by providing bonding force between the support layer and the other layers. The support layer provides support force to the first inert member 40, prevents non-uniformity of the pressure applied to the solid electrolyte layer 30 during the pressurizing process or charging and discharging process, and prevents deformation of the solid secondary battery 1 when manufactured.

[0142] The first inert member 40 is, for example, a flame-retardant inert member. By providing flame retardancy, the flame-retardant inert member can prevent thermal runaway and ignition of the solid-state secondary battery 1. As a result, the stability of the solid-state secondary battery 1 is further improved. By absorbing residual moisture in the solid-state secondary battery 1, the flame-retardant inert member prevents deterioration of the solid-state secondary battery 1 and improves its lifespan characteristics.

[0143] The flame-retardant inert member includes, for example, a matrix and a filler. The matrix includes, for example, a base material and a reinforcing material. The matrix includes, for example, a fibrous base material and a fibrous reinforcing material. The matrix may have elasticity because it includes a base material. Therefore, the matrix can effectively accommodate the volume change during charging and discharging of the solid secondary battery 1 and can be positioned in various locations. The base material included in the matrix includes, for example, a first fibrous material. The base material including the first fibrous material can effectively accommodate the volume change of the positive electrode 30 that occurs during the charging and discharging process of the solid secondary battery 1 and effectively suppress the deformation of the inert member 40 due to the volume change of the positive electrode 30. The first fibrous material is, for example, a material with an aspect ratio of 5 or more, 20 or more, or 50 or more. The first fibrous material is, for example, a material with an aspect ratio of 5 to 1000, 20 to 1000, or 50 to 1000. The first fibrous material is, for example, an insulating material. The first fibrous material being an insulating material effectively prevents short circuits between the positive electrode 30 and the negative electrode 20 caused by lithium dendrites and the like that generated during the charging and discharging process of the solid-state secondary battery 1. The first fibrous material includes, for example, one or more selected from pulp fibers, insulating polymer fibers, and ion-conducting polymer fibers. The inclusion of a reinforcing material in the matrix improves the strength of the matrix. Therefore, the matrix can prevent excessive volume changes during the charging and discharging of the solid-state secondary battery 1 and prevent deformation of the solid-state secondary battery. The reinforcing material included in the matrix includes, for example, a second fibrous material. The inclusion of a second fibrous material in the reinforcing material can further uniformly increase the strength of the matrix. The second fibrous material is, for example, a material with an aspect ratio of 3 or more, 5 or more, or 10 or more. The first fibrous material is, for example, a material with an aspect ratio of 3 to 100, 5 to 100, or 10 to 100. The second fibrous material is, for example, a flame-retardant material. The second fibrous material being a flame-retardant material can effectively suppress ignition caused by thermal runaway during the charging and discharging process of the solid secondary battery 1 or by external impact. The second fibrous material is, for example, glass fiber, metal oxide fiber, or ceramic fiber.

[0144] The flame-retardant inert member includes a filler in addition to the matrix. The filler may be located inside the matrix, on the matrix surface, or both inside and on 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 prevents the deterioration of the solid-state secondary battery 1 by removing moisture remaining inside the solid-state secondary battery 1 by adsorbing moisture at temperatures below 100°C. Furthermore, if the temperature of the solid-state secondary battery 1 rises above 150°C due to thermal runaway caused by the charging / discharging process or external shock, the filler can release the adsorbed moisture and effectively suppress ignition of the solid-state secondary battery 1. In other words, the filler is, for example, a flame retardant. The filler is, for example, a metal hydroxide with moisture-adsorbing properties. The metal hydroxides contained in the filler are, for example, Mg(OH)2, Fe(OH)3, Sb(OH)3, Sn(OH)4, Ti(OH)3, Zr(OH)4, Al(OH)3, or combinations thereof. The content of the filler in the flame-retardant inert member is, for example, 10-80 parts by weight, 20-80 parts by weight, 30-80 parts by weight, 40-80 parts by weight, 50-80 parts by weight, 60-80 parts by weight, or 65-80 parts by weight per 100 parts by weight of the flame-retardant inert member.

[0145] The flame-retardant inert member may further include, for example, a binder. The binder may include, for example, a curable polymer or a non-curable polymer. A curable polymer is a polymer that is cured by heat and / or pressure. A curable polymer is, for example, a solid at room temperature. The flame-retardant inert member includes, for example, a heat- and pressure-curable film and / or its cured product. An example of a heat- and pressure-curable polymer is Toray's TSA-66.

[0146] The flame-retardant inert member may further include other materials in addition to the base material, reinforcing material, filler, and binder described above. The flame-retardant inert member may further include, for example, one or more selected from paper, insulating polymers, ion-conducting polymers, insulating inorganic materials, oxide-based solid electrolytes, and sulfide-based solid electrolytes. The insulating polymer may also be an olefin-based polymer such as polypropylene (PP) or polyethylene (PE).

[0147] The density of the base material or reinforcing material contained 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 contained in the positive electrode active material layer 12.

[0148] The first inert member 40 is a member that does not contain an electrochemically active substance, such as an electrode active material. An electrode active material is a substance that intercalates / releases lithium. The first inert member 40 is a member made of a substance other than an electrode active material, which is used in the art.

[0149] [Negative electrode layer] [Negative electrode layer: negative electrode active material] Referring to Figures 1a to 11, the negative electrode layer 20 includes a first negative electrode active material layer 22. The first negative electrode active material layer 22 includes, for example, a negative electrode active material and a binder.

[0150] The negative electrode active material contained in the first negative electrode active layer 22 is, for example, a negative electrode material that can form an alloy or compound with lithium.

[0151] The negative electrode active material contained in the first negative electrode active material layer 22 has, for example, a particle form. The average particle size of the negative electrode active material having a particle form is, for example, 4 μm or less, 3 μm or less, 2 μm or less, 1 μm or less, 500 nm or less, 300 nm or less, or 100 nm or less. The average particle size of the negative electrode active material having a particle form is, for example, 10 nm to 4 μm, 10 nm to 3 μm, 10 nm to 2 μm, 10 nm to 1 μm, 10 nm to 500 nm, 10 nm to 300 nm, or 10 nm to 100 nm. Having an average particle size in such a range of negative electrode active material makes reversible absorption and / or desorbing of lithium during charging and discharging even easier. The average particle size of the negative electrode active material is, for example, the median diameter (D50) measured using a laser particle size analyzer.

[0152] The negative electrode active material contained in the first negative electrode active material layer 22 includes, for example, one or more selected from carbon-based negative electrode active materials and metal or semimetallic negative electrode active materials.

[0153] Carbon-based negative electrode active materials include, for example, amorphous carbon, crystalline carbon, porous carbon, or combinations thereof.

[0154] Carbon-based negative electrode active materials are particularly amorphous carbon. Amorphous carbons include, for example, carbon black (CB), acetylene black (AB), furnace black (FB), Ketjen black (KB), and graphene, but are not necessarily limited to these; any material classified as amorphous carbon in the relevant technical field can be used. Amorphous carbon is carbon that does not have crystallinity or has very low crystallinity, and is distinguished from crystalline carbon or graphite-based carbon.

[0155] Carbon-based negative electrode active materials are, for example, porous carbon. The pore volume of porous carbon is, for example, 0.1 cc / g to 10.0 cc / g, 0.5 cc / g to 5 cc / g, or 0.1 cc / g to 1 cc / g. The average pore diameter of porous carbon is, for example, 1 nm to 50 nm, 1 nm to 30 nm, or 1 nm to 10 nm. The BET specific surface area of ​​porous carbon is, for example, 100 m². 2 / g~3000m 2 It is / g.

[0156] The metallic or metalloid anode 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). Any metallic or metalloid anode active material that can be used in the art to form an alloy or compound with lithium is acceptable. For example, nickel (Ni) does not form an alloy with lithium and is therefore not a metallic anode active material.

[0157] The first negative electrode active material layer 22 contains either one type of negative electrode active material or a mixture of multiple different negative electrode active materials. For example, the first negative electrode active material layer 22 contains only amorphous carbon, or 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). Alternatively, the first negative electrode active material layer 22 may contain a mixture of amorphous carbon and one or more selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). The mixing ratio of amorphous carbon and gold, etc., is by weight and is, for example, 99:1 to 1:99, 10:1 to 1:2, 5:1 to 1:1, or 4:1 to 2:1, but is not necessarily limited to these ranges and is selected according to the required characteristics of the solid-state secondary battery 1. Having such a composition in the negative electrode active material further improves the cycle characteristics of the solid-state secondary battery 1. The negative electrode active material contained in the first negative electrode active material layer 22 includes, for example, a mixture of first particles made of amorphous carbon and second particles made of a metal or 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). Unlike metalloids, metalloids are semiconductors. The content of the second particles is 1-99% by weight, 1-60% by weight, 8-60% by weight, 10-50% by weight, 15-40% by weight, or 20-30% by weight based on the total weight of the mixture. Having the second particles in such a range of content further improves the cycle characteristics of the solid-state secondary battery 1, for example.

[0158] On the other hand, the first negative electrode active material layer 22 contains a composite negative electrode active material. The composite negative electrode active material may include, for example, a carbon-based support and a metallic negative electrode active material supported on the carbon-based support. Having such a structure in the composite negative electrode active material prevents uneven distribution of the metallic negative electrode active material within the first negative electrode active material layer, resulting in a uniform distribution. As a result, the cycle characteristics of the solid-state secondary battery 1 containing the first negative electrode active material layer 22 are further improved.

[0159] The metallic anode active material supported on a carbon-based support includes, for example, metals, metal oxides, composites of metals and metal oxides, or combinations thereof. Metals include, for example, gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), tellurium (Te), and zinc (Zn). Metal oxides include, for example, gold (Au) oxide, platinum (Pt) oxide, palladium (Pd) oxide, silicon (Si) oxide, silver (Ag) oxide, aluminum (Al) oxide, bismuth (Bi) oxide, tin (Sn) oxide, tellurium (Te) oxide, and zinc (Zn) oxide. Metal oxides include, for example, Au x O y (0 <x≦2、0<y≦3)、Pt x O y (0 <x≦1、0<y≦2)、Pd x O y (0 <x≦1、0<y≦1)、Six O y (0 < x ≤ 1, 0 < y ≤ 2), Ag x O y (0 < x ≤ 2, 0 < y ≤ 1), Al x O y (0 < x ≤ 2, 0 < y ≤ 3), Bi x O y (0 < x ≤ 2, 0 < y ≤ 3), Sn x O y (0 < x ≤ 1, 0 < y ≤ 2), Te x O y (0 < x ≤ 1, 0 < y ≤ 3), Zn x O y (0 < x ≤ 1, 0 < y ≤ 1) or combinations thereof may be included. The composite of metal and metal oxide is, for example, Au x O<00千0162>(0 < x ≤ 2, 0 < y ≤ 3) composite, Pt and Pt x O y (0 < x ≤ 1, 0 < y ≤ 2) composite, Pd and Pd x O y (0 < x ≤ 1, 0 < y ≤ 1) composite, Si and Si x O y (0 < x ≤ 1, 0 < y ≤ 2) composite, Ag and Ag x O y (0 < x ≤ 2, 0 < y ≤ 1) composite, Al and Al x O y (0 < x ≤ 2, x x O y \ (0 < x ≤ 2, 0 < y ≤ 3) composite, Bi and Bi x O y (0 < x ≤ 1, 0 < y ≤ 2) composite, Te and Te x O y (0 < x ≤ 1, 0 < y ≤ 3), Zn and Zn x O y (0 < x ≤ 1, + (0 < x ≤ 1, 0 < y ≤ 1) composite, or combinations thereof may be included.

[0160] It should be noted that there seems to be an error in the original text where "<00千016>" is likely incorrect. I've translated it as best as possible with the assumption it might be a typo. If this is a crucial part, it would need to be corrected in the original for a more accurate translation.Carbon-based supports include, for example, amorphous carbon. Amorphous carbon includes, for example, carbon black (CB), acetylene black (AB), furnace black (FB), Ketjen black (KB), graphene, activated carbon, carbon nanofibers (CNF), and carbon nanotubes (CNT), but is not necessarily limited to these; any material classified as amorphous carbon in the relevant art can be used. Amorphous carbon is carbon that does not have crystallinity or has very low crystallinity, and is distinguished from crystalline carbon or graphite-based carbon. Carbonaceous materials include, for example, carbon-based negative electrode active materials.

[0161] The composite anode active material may, for example, have a particulate form. The particle size of the composite anode active material having a particulate form is, for example, 10 nm to 4 μm, 10 nm to 1 μm, 10 nm to 500 nm, 10 nm to 200 nm, or 10 nm to 100 nm. Having a particle size in such a range for the composite anode active material makes the reversible absorption and / or desorbing of lithium during charging and discharging even easier. The metallic anode active material supported on a support may, for example, have a particulate form. The particle size of the metallic anode active material may, for example, be 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, for example, have a particulate form. The particle size of the carbon-based support can be, for example, 10 nm to 2 μm, 10 nm to 1 μm, 10 nm to 500 nm, 10 nm to 200 nm, or 10 nm to 100 nm. Having particle sizes within this range allows for more uniform distribution within the first anode active material layer. The carbon-based support can also be, for example, nanoparticles with a particle size of 500 nm or less. The particle size of the composite anode active material, the metallic anode active material, and the carbon-based support are, for example, average particle sizes. The average particle size is, for example, the median diameter (D50) measured using a laser particle size analyzer. Alternatively, the average particle size can be automatically determined using software from electron microscope images, or manually determined.

[0162] [Negative electrode layer: Binder] The binder contained in the first negative electrode active material layer 22 is, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, etc., but is not necessarily limited to these, and any binder that can be used in the art can be used. The binder may consist of one or more different binders.

[0163] The inclusion of a binder in the first negative electrode active material layer 22 stabilizes the first negative electrode active material layer 22 on the negative electrode current collector 21. Furthermore, cracking of the first negative electrode active material layer 22 is suppressed despite volume changes and / or relative positional changes of the first negative electrode active material layer 22 during the charge-discharge process. For example, if the first negative electrode active material layer 22 does not contain a binder, the first negative electrode active material layer 22 can be easily separated from the negative electrode current collector 21. When the first negative electrode active material layer 22 detaches from the negative electrode current collector 21, the exposed portion of the negative electrode current collector 21 comes into contact with the solid electrolyte layer 30, increasing the likelihood of a short circuit. The first negative electrode active material layer 22 is manufactured, for example, by coating a slurry in which the materials constituting the first negative electrode active material layer 22 are dispersed onto the negative electrode current collector 21 and drying it. By incorporating a binder into the first negative electrode active material layer 22, stable dispersion of the negative electrode active material in the slurry is possible. For example, when the slurry is applied onto the negative electrode current collector 21 by screen printing, screen clogging (e.g., clogging due to aggregates of the negative electrode active material) can be suppressed.

[0164] [Negative electrode layer: Other additives] The first negative electrode active material layer 22 may further contain additives used in conventional solid-state secondary batteries 1, such as fillers, coating agents, dispersants, and ion conductivity enhancers.

[0165] [Negative electrode layer: solid electrolyte] The first negative electrode active material layer 22 may further contain a solid electrolyte. The solid electrolyte is, for example, a material selected from among the solid electrolytes contained in the solid electrolyte layer 30. The solid electrolyte contained in the first negative electrode active material layer 22 may act at the reaction site where the formation of lithium metal is initiated within the first negative electrode active material layer 22, act in the space where the formed lithium metal is stored, or act as a pathway for transporting lithium ions. The solid electrolyte is optional.

[0166] In the first negative electrode active material layer 22, the solid electrolyte content is high in the region adjacent to the solid electrolyte layer 30, for example, and low in the region adjacent to the negative electrode current collector 21. The solid electrolyte in the first negative electrode active material layer 22 may have a concentration gradient in which the concentration decreases from the region adjacent to the solid electrolyte layer 30 to the region adjacent to the negative electrode current collector 21.

[0167] [Negative electrode layer: first negative electrode active material layer] The initial charge capacity of the first negative electrode active material layer is, for example, 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less of the initial charge capacity of the positive electrode active material layer.

[0168] The ratio (B / A) of the initial charge capacity (B) of the first negative electrode active material layer 22 to the initial charge capacity (A) of the positive electrode active material layer is 0.005 to 0.45. The initial charge capacity of the positive electrode active material layer 12 is calculated from the first open circuit voltage as Li / Li + The initial charge capacity of the first negative electrode active material layer 22 is determined by charging up to the maximum charging voltage. + The maximum charging voltage is determined by the type of positive electrode active material. The maximum charging voltage can also be, for example, 1.5V, 2.0V, 2.5V, 3.0V, 3.5V, 4.0V, 4.2V, or 4.3V. For example, the maximum charging voltage for Li2S or Li2S composite is Li / Li + It is also 2.5V for this. For example, the maximum charging voltage for Li2S or Li2S composite is Li / Li +It is also 3.0V. The ratio (B / A) of the initial charge capacity (B) of the first negative electrode active material layer 22 to the initial charge capacity (A) of the positive electrode active material layer is, for example, 0.01~0.45, 0.01~0.4, 0.01~0.3, 0.01~0.2, or 0.05~0.1. The initial charge capacity (mAh) of the positive electrode active material layer 12 is obtained by multiplying the charge specific capacity (mAh / g) of the positive electrode active material by the mass (g) of the positive electrode active material in the positive electrode active material layer 12. When multiple types of positive electrode active materials are used, the charge specific capacity × mass value is calculated for each positive electrode active material, and the sum of these values ​​is the initial charge capacity of the positive electrode active material layer 12. The initial charge capacity of the first negative electrode active material layer 22 is calculated in 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. If multiple types of negative electrode active materials are used, the charge capacity density x mass value is calculated for each negative electrode active material, and the sum of these values ​​is the initial charge capacity of the first negative electrode active material layer 22. The charge capacity densities of the positive electrode active material and the negative electrode active material can be measured using a solid half-cell with lithium metal as the relative electrode. The initial charge capacities of the positive electrode active material layer 12 and the first negative electrode active material layer 22 are constant at a current density, for example, 0.1 mA / cm². 2 This can be measured directly using a solid half-cell. With respect to the positive electrode, the measurement is taken from the first open-circuit voltage (OCV) to the maximum charging voltage, for example, 3.0V (vs. Li / Li + The measurement can be performed for operating voltages up to 3.0V. For the negative electrode, the measurement can be performed for operating voltages from the second open-circuit voltage (OCV) up to 0.01V for the negative electrode, for example, lithium metal. For example, a solid half-cell with a positive electrode active material layer can be measured from the first open-circuit voltage up to 3.0V at a rate of 0.1mA / cm². 2 A solid half-cell, charged with a constant current and having a first negative electrode active material layer, draws 0.1 mA / cm² from the second open-circuit voltage up 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 / cm². 2 , or 0.5 mA / cm 2Furthermore, a solid-state half-cell having a positive electrode active material layer can be charged, for example, from a first open-circuit voltage to 2.5V, 2.0V, 3.5V, or 4.0V. The maximum charging voltage of the positive electrode active material layer can be determined by the maximum voltage of a battery that satisfies the safety conditions according to JISC8712:2015 of the Japanese Industrial Standards Association.

[0169] If the initial charge capacity of the first negative electrode active material layer 22 is excessively small, the thickness of the first negative electrode active material layer 22 becomes very thin, so lithium dendrites formed between the first negative electrode active material layer 22 and the negative electrode current collector 21 during repeated charge-discharge processes cause the first negative electrode active material layer 22 to disintegrate, making it difficult to improve the cycle characteristics of the 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 solid-state secondary battery 1 decreases, the internal resistance of the 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 solid-state secondary battery 1.

[0170] 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, 1-50%, 1-40%, 1-30%, 1-20%, 1-10%, or 1-5% of the thickness of the positive electrode active material layer 12. The thickness of the first negative electrode active material layer 22 is, for example, 1 μm to 20 μm, 2 μm to 15 μm, or 3 μm to 10 μm. If the thickness of the first negative electrode active material layer 22 is excessively thin, lithium dendrites formed between the first negative electrode active material layer 22 and the negative electrode current collector 21 will cause the first negative electrode active material layer 22 to disintegrate, making it difficult to improve the cycle characteristics of the solid-state secondary battery 1. If the thickness of the first negative electrode active material layer 22 increases excessively, the energy density of the solid-state secondary battery 1 decreases, and the internal resistance of the 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 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.

[0171] [Negative electrode layer: second negative electrode active material layer] Referring to Figure 7, the solid-state secondary battery 1 further includes a second negative electrode active material layer 24 which, after being charged, is placed, 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 metallic layer containing lithium or a lithium alloy. The metallic layer contains lithium or a lithium alloy. Therefore, since the second negative electrode active material layer 24 is a metallic layer containing lithium, it acts, for example, as a lithium reservoir. Examples of lithium alloys include, but are not limited to, Li-Al alloys, Li-Sn alloys, Li-In alloys, Li-Ag alloys, Li-Au alloys, Li-Zn alloys, Li-Ge alloys, and Li-Si alloys; any alloy usable as a lithium alloy in the art can be used. The second negative electrode active material layer 24 may consist of one of these alloys or lithium, or of various 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, for example, between the first negative electrode active material layer 22 and the negative electrode current collector 21 during the charging process of the solid-state secondary battery 1.

[0172] The thickness of the second negative electrode active material layer 24 is not particularly limited, but for example, it can be 1 μm to 500 μm, 1 μm to 200 μm, 1 μm to 150 μm, 1 μm to 100 μm, or 1 μm to 50 μm. If the thickness of the second negative electrode active material layer 24 is excessively thin, it will be difficult for the second negative electrode active material layer 24 to perform its role as a lithium reservoir. If the thickness of the second negative electrode active material layer 24 is excessively thick, the mass and volume of the solid-state secondary battery 1 will increase, which may actually degrade the cycle characteristics of the solid-state secondary battery 1.

[0173] On the other hand, in the solid-state secondary battery 1, the second negative electrode active material layer 24 may be placed, for example, between the negative electrode current collector 21 and the first negative electrode active material layer 22 before the assembly of the solid-state secondary battery 1. When the second negative electrode active material layer 24 is placed between the negative electrode current collector 21 and the first negative electrode active material layer 22 before the assembly of the solid-state secondary battery 1, the second negative electrode active material layer 24 acts as a lithium reservoir because it is a lithium-containing metal layer. For example, lithium foil may be placed between the negative electrode current collector 21 and the first negative electrode active material layer 22 before the assembly of the solid-state secondary battery 1.

[0174] When the second negative electrode active material layer 24 is deposited by charging the solid-state secondary battery 1 after assembly, the energy density of the solid-state secondary battery 1 increases because the second negative electrode active material layer 24 is not included during the assembly of the solid-state secondary battery 1. When the solid-state secondary battery 1 is charged, it is charged beyond the charging capacity of the first negative electrode active material layer 22. That is, the first negative electrode active material layer 22 is overcharged. In the initial stages of charging, lithium is absorbed into the first negative electrode active material layer 22. The negative electrode active material contained in the first negative electrode active material layer 22 forms an alloy or compound with lithium ions that have moved from the positive electrode 10. If the capacity of the first negative electrode active material layer 22 is exceeded during charging, for example, lithium is deposited on the back surface of the first negative electrode active material layer 22, i.e., between the negative electrode current collector 21 and the first negative electrode active material layer 22, and the deposited lithium forms a metal layer corresponding to the second negative electrode active material layer 24. 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 including a substance in the negative electrode active material contained in the first negative electrode active material layer 22 that forms an alloy or compound with lithium. During discharge, the lithium in the first negative electrode active material layer 22 and the second negative electrode active material layer 24, i.e., the metallic layer, is ionized and moves toward the positive electrode 10. Therefore, lithium can be used as the negative electrode active material in the solid-state secondary battery 1. Furthermore, 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 metallic layer, and also plays a role in suppressing the deposition and growth of lithium dendrites. Therefore, short circuits and capacity degradation of the solid-state secondary battery 1 are suppressed, and as a result, the cycle characteristics of the solid-state secondary battery 1 are improved. Furthermore, when the second negative electrode active material layer 24 is positioned by charging after the assembly of the solid secondary battery 1, the negative electrode 20, that is, the negative electrode current collector 21, the first negative electrode active material layer 22, and the region between them, are lithium (Li)-free regions that do not contain lithium in the initial state or after complete discharge of the solid secondary battery 1.

[0175] [Negative electrode layer: negative electrode current collector] The negative electrode current collector 21 is made of a material that does not react with lithium, i.e., does not form any alloys or compounds. The materials constituting the negative electrode current collector 21 include, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni), but are not necessarily limited to these; any material that can be used as an electrode current collector in the art can be used. The negative electrode current collector 21 may consist of one of the above-mentioned metals, or an alloy or coating material of two or more metals. The negative electrode current collector 21 may be in the form of a plate or foil, for example.

[0176] Referring to Figure 6, the 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 current collector 21. The thin film 23 is placed between the negative electrode current 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. Examples of elements capable of forming an alloy with lithium include, but are not limited to, gold, silver, zinc, tin, indium, silicon, aluminum, and bismuth; any element capable of forming an alloy with lithium in the art can be used. The thin film 23 is composed of one of these metals or an alloy of several metals. By placing the thin film 23 on one surface of the negative electrode current collector 21, for example, the deposition morphology of the second negative electrode active material layer 24 deposited between the thin film 23 and the first negative electrode active material layer 22 can be further flattened, thereby further improving the cycle characteristics of the solid-state secondary battery 1.

[0177] 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, the function of the thin film 23 is difficult to achieve. If the thickness of the thin film 23 is excessively thick, the thin film 23 itself may absorb lithium, reducing the amount of lithium deposited at the negative electrode, lowering the energy density of the solid-state battery, and potentially degrading the cycle characteristics of the solid-state secondary battery 1. The thin film 23 can be disposed on the negative electrode current collector 21 by, for example, vacuum deposition, sputtering, or plating, but is not necessarily limited to these methods; any method that can form the thin film 23 in the relevant art can be used.

[0178] Although not shown in the drawings, the negative electrode current collector 21 may include, for example, a base film and a metal layer disposed on one or both sides of the base film. The base film may include, for example, a polymer. The polymer may also be, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof. The polymer may also be an insulating polymer. By including an insulating thermoplastic polymer in the base film, the base film may soften or liquefy in the event of a short circuit, interrupting 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 alloys thereof. The negative electrode current collector 21 may further include metal pieces and / or lead tabs. For more specific details regarding the base film, metal layer, metal chip, and lead tab of the negative electrode current collector 21, please refer to the positive electrode current collector 11 described above. Having such a structure in the negative electrode current collector 21 reduces the weight of the negative electrode, and as a result, can improve the energy density of the negative electrode and the lithium battery.

[0179] [Negative electrode layer: Second inert component] Referring to Figures 10 and 11, the solid-state secondary battery 1 further includes a second inert member 50 disposed on the other side of the negative electrode current collector 21.

[0180] The second inert member 50 is distinguished from the first inert member 40 in that it is conductive by further containing a conductive material. The second inert member 50 is, for example, a conductive flame-retardant inert member.

[0181] Examples of conductive materials include graphite, carbon black, acetylene black, Ketjen black, Denka black, carbon fiber, carbon nanotubes (CNTs), graphene, metal fibers, and metal powders. The electronic conductivity of the second inert member 50 at 25°C is, for example, 100 times or more, 1000 times or more, or 10000 times or more, the electronic conductivity of the first inert member 40 at 25°C.

[0182] The second inert member 50 includes, for example, a matrix, a filler, and a conductive material. The matrix includes, for example, a base material and a reinforcing material. The second inert member 50 may further include a filler, a binder, etc. The content of the conductive material in the second inert member 50 is, for example, 1 to 30 parts by weight, 1 to 20 parts by weight, 1 to 15 parts by weight, 1 to 10 parts by weight, 5 to 40 parts by weight, 5 to 30 parts by weight, or 5 to 35 parts by weight per 100 parts by weight of the second inert member 50.

[0183] The Young's modulus of the second inert member 50 is, for example, even smaller than the Young's modulus of the negative electrode current collector 21. The Young's modulus of the second inert member 50 is, for example, 50% or less, 30% or less, 10% or less, or 5% or less of the Young's modulus of the negative electrode current collector 21. The Young's modulus of the second inert member 50 is, for example, 0.01% to 50%, 0.1 to 30%, 0.1 to 10%, or 1 to 5% of the Young's modulus of the negative electrode current collector 21. The Young's modulus of the second inert member 50 is, for example, 100 MPa or less, 50 MPa or less, 30 MPa or less, 10 MPa or less, or 5 MPa or less. The elastic modulus of the second inert member 50 is, for example, 0.01 to 100 MPa, 0.1 to 50 MPa, 0.1 to 30 MPa, 0.1 to 10 MPa, or 1 to 5 MPa.

[0184] Since the second inert member 50 is conductive, it can perform its role as a negative electrode current collector 21. Furthermore, since the second inert member 50 has a lower elastic modulus than the negative electrode current collector 50, it can more effectively accommodate the volume change of the negative electrode layer 20 during charging and discharging of the solid secondary battery 1. As a result, the second inert member 50 can effectively relieve the internal stress caused by the volume change of the solid secondary battery 1 during charging and discharging, thereby improving the cycle characteristics of the solid secondary battery 1.

[0185] The thickness of the second inert member 50 is, for example, greater than the thickness of the first negative electrode active material layer 22. Having a greater thickness for the second inert member 50 than for the first negative electrode active material layer 22 allows for more effective accommodation of volume changes in the negative electrode layer 20 during charging and discharging. The thickness of the first negative electrode active material layer 22 is 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less of the thickness of the second inert member 50. 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 second inert member 50. The thickness of the second inert member 50 is, for example, 1 μm to 300 μm, 10 μm to 300 μm, 50 μm to 300 μm, or 100 μm to 200 μm. If the thickness of the second inert member 50 is excessively thin, it will be difficult to provide the intended effect, and if the thickness of the second inert member 50 is excessively thick, the energy density of the solid-state secondary battery 1 may decrease. The form of the second inert member 50 is not particularly limited and can be selected depending on the form of the solid-state secondary battery 1. The second inert member 50 can also be, for example, in the form of a sheet, a rod, or a gasket. The second inert member 50 can be placed, for example, on one or both sides of a single solid-state secondary battery 1. The second inert member 50 can be placed, for example, between a plurality of stacked solid-state secondary batteries 1. The second inert member 50 can be placed, for example, between each of the stacked solid-state secondary batteries 1, on the top surface and / or the bottom surface.

[0186] The present invention will be explained in more detail through the following examples and comparative examples. However, these examples are for illustrative purposes only and do not limit the scope of the present invention.

[0187] Example 1: Positive electrode layer / First intermediate layer / Sulfide solid electrolyte layer / Second intermediate layer / Negative electrode layer, Thermosetting polymer gel electrolyte (Manufacturing of composite cathode active materials) Li2S and LiI were mixed in a weight ratio of 30:20. The mixture was mechanically milled using a ball mill to produce a Li2S-LiI composite. The milling conditions were 25°C and 600 rpm for 10 hours. The milling energy applied to the sample during milling was 20 G. Next, the Li2S-LiI composite and carbon nanofiber (CNF) were mixed in a weight ratio of 50:10. The mixture was mechanically milled using a ball mill to produce a Li2S-LiI-CNF composite. The milling conditions were 25°C and 600 rpm for 10 hours. 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.

[0188] (Positive electrode layer manufacturing) The Li2S-LiI-CNF composite described above was prepared as the positive electrode active material. Li6PS5Cl, an argyrodite-type crystalline material (D50 = 1.0 μm, crystalline), was prepared as the solid electrolyte. PTFE was prepared as the binder. These materials were mixed in a weight ratio of composite positive electrode active material:solid electrolyte:binder = 60:40:1.2 to prepare the positive electrode mixture. The positive electrode mixture was obtained by dry mixing using a ball mill.

[0189] A positive electrode was manufactured by placing a positive electrode mixture on one surface of a positive electrode current collector made of aluminum foil coated with carbon on one side, and then plate-pressing it 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 area of ​​the positive electrode active material layer and the positive electrode current collector were the same.

[0190] (Negative electrode layer manufacturing) A 10 μm thick SUS foil was prepared as the negative electrode current collector. In addition, carbon black (CB) with a primary particle size of approximately 30 nm and silver (Ag) particles with an average particle diameter of approximately 60 nm were prepared as the negative electrode active material.

[0191] A mixed powder of carbon black (CB) and silver (Ag) particles in a 3:1 weight ratio was placed in a container. 4g of an NMP solution containing 7% by weight of PVDF binder (Kureha Corporation #9300) was added to prepare the mixed solution. Next, NMP was gradually added to this mixed solution while stirring to produce a slurry. The prepared slurry was applied to a SUS sheet using a bar coater and dried in air at 80°C for 10 minutes. The resulting laminate was then vacuum-dried at 40°C for 10 hours. The dried laminate was subjected to a temperature of 5 ton·f / cm². 2 The surface of the first negative electrode active material layer of the laminate was flattened by cold roll pressing at a pressure of 5 m / sec. The negative electrode layer was fabricated by the above process. The thickness of the first negative electrode active material layer contained within the negative electrode layer was approximately 15 μm. The area of ​​the first negative electrode active material layer and the negative electrode current collector were the same.

[0192] (Manufacturing of solid electrolyte layer) A mixture was prepared by adding 1.5 parts by weight of an acrylic binder to 98.5 parts by weight of an argyrodite-type crystalline Li6PS5Cl solid electrolyte (D50 = 5.0 mm, crystalline). Octyl acetate was added to the prepared mixture while stirring to produce a slurry. The produced slurry was applied using a bar coater onto a 15 mm thick nonwoven fabric placed on a 75 mm thick PET substrate, and dried in air at 80°C for 10 minutes to obtain a laminate. The obtained laminate was vacuum dried at 80°C for 2 hours. The solid electrolyte layer was manufactured by the above process.

[0193] (First inert member) A slurry of cellulose fiber, glass fiber, aluminum hydroxide (Al(OH)3), an acrylic binder, and a solvent was molded into a gasket, and then the solvent was removed to produce a flame-retardant inert material as the first inert material.

[0194] The weight ratio of pulp fiber (cellulose fiber), glass fiber, aluminum hydroxide (Al(OH)3), and acrylic binder was 20:8:70:2. The thickness of the inert material was 120 μm.

[0195] Before placing the manufactured flame-retardant inert material onto the solid electrolyte layer, the material was subjected to vacuum heat treatment at 80°C for 5 hours to remove moisture and other contaminants.

[0196] (Thermosetting electrolyte composition) Into a 20 L four-neck flask equipped with a stirrer, a thermometer, and a cooling tube, distilled water was introduced as a solvent, and 2-(N,N-dimethylamino)ethyl acrylate, methyl acrylate, and acrylonitrile were introduced in a certain molar ratio, and a small amount of potassium persulfate was introduced as an initiator. The reaction was carried out for 18 hours while maintaining the temperature of the reaction solution stable between 65 °C and 70 °C. Then, after cooling to room temperature, the pH of the reaction solution was adjusted to 7-8 using a 25% aqueous ammonia solution to produce an acrylic polymer which is poly(2-(N,N-dimethylamino)ethyl acrylate-co-methyl acrylate-co-acrylonitrile) copolymer represented by the following Chemical Formula A. (The molar ratio of 2-(N,N-dimethylamino)ethyl acrylate, methyl acrylate, and acrylonitrile was 20:15:65. The weight-average molecular weight of the acrylic binder was about 60,000 Dalton. The weight-average molecular weight of the acrylic polymer was measured using gel permeation chromatography (GPC) as a relative value with respect to a polystyrene standard sample.) [Chemical Formula]

[0197] After dissolving 1.0 M of LiPF6 and 1.0 M of LiTFSI respectively in 94 g of a non-aqueous organic solvent in which ethylene carbonate (EC):dimethyl carbonate (DMC) was mixed at a volume ratio of 15:85, 5.0 g of the acrylic polymer represented by the above Chemical Formula A was added to produce a thermosetting electrolyte composition.

[0198] (Manufacture of Solid Secondary Battery) The above-mentioned thermosetting electrolyte composition was respectively coated on one surface of the solid electrolyte layer and on the other surface facing the one surface.

[0199] Referring to FIG. 8, the solid electrolyte layer was disposed such that the first negative electrode active material layer contacted one surface of the solid electrolyte layer on the negative electrode layer, and the positive electrode layer was disposed on the other surface of the solid electrolyte layer. A gasket surrounding the positive electrode layer and contacting the solid electrolyte layer was disposed around the positive electrode layer to prepare a laminate. The thickness of the gasket was about 120 μm. The flame-retardant inert member was used as the gasket. The gasket was disposed so as to contact the side surface of the positive electrode layer and the solid electrolyte layer. The positive electrode layer was disposed at the center of the solid electrolyte layer, and the gasket surrounded the positive electrode layer and extended to the end portion of the solid electrolyte layer. The area of the positive electrode layer was about 90% of the area of the solid electrolyte layer, and the gasket was disposed over the entire remaining 10% area of the solid electrolyte layer where the positive electrode layer was not disposed.

[0200] Next, the laminate was subjected to plate pressing and heat treatment at 85 °C under a pressure of 2.5 MPa for 1 hour. Such a pressing treatment sintered the solid electrolyte layer and improved the battery characteristics. The thickness of the sintered solid electrolyte layer was about 45 μm. The density of the Li6PS5Cl solid electrolyte, which is an Argyrodite-type crystal contained in the sintered solid electrolyte layer, was 1.47 g / cc. The area of the solid electrolyte layer was the same as the area of the negative electrode layer.

[0201] Also, by proceeding with the heat treatment simultaneously with the pressing treatment, the thermosetting composition was thermally cured to form a polymer gel electrolyte. A first intermediate layer 60 (polymer gel electrolyte layer) was disposed between the positive electrode layer and the solid electrolyte layer, and a second intermediate layer 70 (polymer gel electrolyte layer) was disposed between the negative electrode layer and the solid electrolyte layer. Further, by thermally curing the thermosetting composition diffused inside the solid electrolyte layer during the pressing process, a polymer gel electrolyte was also disposed inside the solid electrolyte layer.

[0202] The pressed laminate was placed in a pouch and vacuum-sealed. A part of the positive electrode current collector and the negative electrode current collector was extended outside the sealed battery and used as the positive electrode layer terminal and the negative electrode layer terminal.

[0203] Example 2: Positive electrode layer / first intermediate layer / sulfide solid electrolyte layer / negative electrode layer, thermosetting polymer gel electrolyte A solid-state secondary battery was manufactured in the same manner as in Example 1, except that the thermosetting electrolyte composition was applied to only one surface of the solid electrolyte layer, and not applied to the other surface of the solid electrolyte layer.

[0204] A first intermediate layer 60 (polymer gel electrolyte layer) is placed between the positive electrode layer and the solid electrolyte layer, but a second intermediate layer 70 is not placed between the negative electrode layer and the solid electrolyte layer.

[0205] Example 3: Positive electrode layer / Sulfide solid electrolyte layer / Second intermediate layer / Negative electrode layer, Thermosetting polymer gel electrolyte A solid-state secondary battery was manufactured in the same manner as in Example 1, except that the thermosetting electrolyte composition was not applied to one surface of the solid electrolyte layer, but only to the other surface of the solid electrolyte layer.

[0206] A first intermediate layer 60 is not placed between the positive electrode layer and the solid electrolyte layer, but a second intermediate layer 70 (polymer gel electrolyte layer) is placed between the negative electrode layer and the solid electrolyte layer.

[0207] Example 4: Positive electrode layer / First intermediate layer / Sulfide solid electrolyte layer / Second intermediate layer / Negative electrode layer, High viscosity liquid electrolyte A solid-state secondary battery was manufactured in the same manner as in Example 1, except that a liquid electrolyte containing an ionic liquid was applied to one and the other surface of the solid electrolyte layer, respectively, and the heat treatment process was omitted.

[0208] The liquid electrolyte containing the ionic liquid was prepared as follows.

[0209] A liquid electrolyte was prepared by dissolving 1.0 M LiPF6 and 1.0 M LiTFSI in 65 g of a non-aqueous organic solvent, which was a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 15:85, and then adding 35 g of an ionic liquid represented by the following chemical formula B.

[0210] As the ionic liquid, 1-methyl-1-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide, represented by the following chemical formula B, was used.

[0211] The viscosity of the liquid electrolyte was 22.5 cps at 1 atm and 25°C. [ka]

[0212] Example 5: Positive electrode layer / First intermediate layer / Sulfide solid electrolyte layer / Negative electrode layer, High viscosity liquid electrolyte A solid-state secondary battery was manufactured in the same manner as in Example 4, except that the ionic liquid-containing liquid electrolyte was applied to only one side of the solid electrolyte layer, and the ionic liquid-containing liquid electrolyte was not applied to the other side of the solid electrolyte layer.

[0213] An ionic liquid-containing liquid electrolyte layer is placed between the positive electrode layer and the solid electrolyte layer, but no ionic liquid-containing liquid electrolyte layer is placed between the negative electrode layer and the solid electrolyte layer.

[0214] Example 6: Positive electrode layer / Sulfide solid electrolyte layer / Second intermediate layer / Negative electrode layer, High viscosity liquid electrolyte A solid-state secondary battery was manufactured in the same manner as in Example 4, except that the ionic liquid-containing liquid electrolyte was not applied to one surface of the solid electrolyte layer, but only to the other surface of the solid electrolyte layer.

[0215] While no ionic liquid-containing liquid electrolyte layer is placed between the positive electrode layer and the solid electrolyte layer, an ionic liquid-containing liquid electrolyte layer is placed between the negative electrode layer and the solid electrolyte layer.

[0216] Example 7: Positive electrode layer / First intermediate layer / Sulfide solid electrolyte layer / Second intermediate layer / Negative electrode layer, Cured polymer gel electrolyte A thermosetting electrolyte composition was applied to one side and the other side of the solid electrolyte layer, and heat treatment was carried out at 85 °C for 2 hours. A solid secondary battery was manufactured in the same manner as in Example 1, except that a polymer gel electrolyte thermally cured on one side and the other side of the solid electrolyte layer was disposed in advance before manufacturing the laminate.

[0217] Example 8: Positive electrode layer / First intermediate layer / Sulfide solid electrolyte layer / Second intermediate layer / Negative electrode layer, thermosetting polymer gel electrolyte, elastic sheet member A solid secondary battery was manufactured in the same manner as in Example 1, except that a sheet-shaped conductive flame-retardant member having the same area and form as the laminate was further disposed on the outer surface of the negative electrode current collector of the pressurized laminate before putting the pressurized laminate into the pouch, and vacuum-sealed.

[0218] The conductive flame-retardant inert member sheet was prepared by the following method. The conductive flame-retardant inert member sheet can act as an elastic sheet.

[0219] A slurry obtained by mixing pulp fiber (cellulose fiber), glass fiber, aluminum hydroxide (Al(OH)3), an acrylic binder, a conductive material (Denka black) and a solvent was formed into a sheet shape and then dried to produce a flame-retardant inert member. The weight ratio of pulp fiber (cellulose fiber), glass fiber, aluminum hydroxide (Al(OH)3), an acrylic binder, and the conductive material was 20:8:50:2:20. The thickness of the conductive flame-retardant inert member was 120 μm. The manufactured conductive flame-retardant inert member was vacuum heat-treated at 80 °C for 5 hours before being disposed on the negative electrode current collector to remove moisture and the like of the conductive flame-retardant inert member.

[0220] Example 9: Positive electrode layer / First intermediate layer / Sulfide solid electrolyte layer / Second intermediate layer / Negative electrode layer, thermosetting polymer gel electrolyte, Ag-supported carbon An all-solid-state secondary battery was manufactured in the same manner as in Example 2, except that carbon black supported with silver particles was used as the negative electrode active material instead of a mixture of carbon black and silver particles.

[0221] (Manufacturing of carbon black with supported silver particles) Carbon black was dispersed in a 1.0 M sulfuric acid solution, stirred for 2 hours, then filtered and dried to prepare acid-treated carbon black.

[0222] A mixed solvent consisting of 1500g of distilled water, 1500g of ethanol, and 30g of glycerol was mixed with 10g of acid-treated carbon black and stirred. Then, 2g of AgNO3 was added and stirred to prepare a mixed solution. The particle size of the carbon black was 80nm. A reducing agent was added to the mixed solution to reduce and support silver ions onto the carbon black. The carbon black with supported silver particles was filtered, washed, and dried to prepare a composite anode active material. Scanning electron microscopy 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 silver-containing particle content in the composite anode active material was 5wt%. The average particle size of the silver particles was 10nm.

[0223] Comparative Example 1: Use of a positive electrode layer / sulfide solid electrolyte layer / negative electrode layer and a low viscosity liquid electrolyte. A solid-state secondary battery was manufactured in the same manner as in Example 1, except that a liquid electrolyte was applied to one and the other surface of the solid electrolyte layer, and the heat treatment process was omitted.

[0224] The liquid electrolyte was prepared as follows:

[0225] A liquid electrolyte was prepared by dissolving 1.0 M LiPF6 in 100 g of a non-aqueous organic solvent mixture of ethylene carbonate (EC) and ethyl methyl carbonate (DEC) in a volume ratio of 30:70. The viscosity of the liquid electrolyte was less than 5 cps at 1 atm and 25°C.

[0226] Comparative example 2: Positive electrode layer / sulfide solid electrolyte layer / negative electrode layer, thermosetting electrolyte composition not used A solid-state secondary battery was manufactured in the same manner as in Example 1, except that a thermosetting electrolyte composition was not applied to one and the other surfaces of the solid electrolyte layer, and the heat treatment process was omitted.

[0227] Reference Example 1: Lithium Metal Anode A solid-state secondary battery was manufactured in the same manner as in Example 1, except that a 20 μm thick lithium metal foil 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.

[0228] Reference example 2: First inactive member not used (free) A solid-state secondary battery was manufactured using the same method as in Example 1, except that flame-retardant inert materials (i.e., gaskets) were not used during the manufacturing of the all-solid-state secondary battery.

[0229] Evaluation Example 1: Lifetime Characteristics Evaluation The charge-discharge characteristics of the solid-state secondary batteries manufactured in Examples 1-8, Reference Examples 1 and 2, and Comparative Examples 1 and 2 were evaluated by the following charge-discharge tests.

[0230] The charge-discharge test was performed by placing the solid-state rechargeable battery in a constant temperature bath at 45°C.

[0231] The first cycle involved charging the battery at a constant current of 0.1C for 12.5 hours until the battery voltage reached 2.5V to 2.8V. Subsequently, the battery was discharged at a constant current of 0.1C for 12.5 hours until the battery voltage reached 0.3V.

[0232] The discharge capacity of the first cycle was set as the standard capacity.

[0233] After the first cycle, charging and discharging were performed under the same conditions as the first cycle for up to 150 cycles. Some of the measurement results are shown in Table 1 below.

[0234] The cycle count refers to the number of cycles required for the discharge capacity to decrease to 80% of the standard capacity after the first cycle. A higher cycle count is considered to indicate better lifespan characteristics. [Table 1]

[0235] As shown in Table 1, the solid-state secondary batteries of Examples 1 to 8 showed improved lifespan characteristics compared to the solid-state secondary batteries of Reference Example 1 and Comparative Examples 1 and 2.

[0236] The solid-state secondary batteries of Examples 1 to 8 exhibit improved lifespan characteristics by reducing interfacial resistance between the solid electrolyte layer and the positive electrode layer, and between the solid electrolyte layer and the negative electrode layer, relatively increasing the flexibility of the solid electrolyte layer itself, and suppressing pinhole formation, thereby more effectively accommodating volume changes in the positive and / or negative electrode layers during charging and discharging. Furthermore, improved adhesion at the interface between the solid electrolyte layer and the positive electrode layer, the interface between the solid electrolyte layer and the negative electrode layer, and within the solid electrolyte layer, along with improved uniformity of ionic conductivity, further enhances lifespan characteristics. Additionally, the reduced contact area between the solid electrolyte layer and moisture suppresses gas generation due to side reactions, thereby preventing a decrease in ionic conductivity.

[0237] In the solid-state secondary battery of Example 7, the diffusion of the polymer gel electrolyte within the solid electrolyte layer was restricted, resulting in a reduced lifespan compared to the solid-state secondary battery of Example 1.

[0238] Although not shown in Table 1, the solid-state secondary battery of Example 9 showed improved lifespan characteristics compared to the solid-state secondary battery of Example 1, which was a simple mixture of silver particles and carbon particles, by using carbon supported with silver particles. The solid-state secondary battery of Comparative Example 1 used a low-viscosity liquid electrolyte, resulting in only a minimal effect from the addition of an organic electrolyte compared to the high-viscosity liquid electrolytes of Examples 4-6.

[0239] In Comparative Example 2, the absence of an organic electrolyte increased the formation of pinholes in the solid electrolyte layer. During charging and discharging, volume changes in the positive and / or negative electrode layers promoted the occurrence of defects such as cracks in the solid electrolyte layer, and the growth of lithium dendrites through these defects reduced the battery's lifespan.

[0240] In Reference Example 1, the solid-state secondary battery experienced a decrease in its lifespan due to accelerated degradation of the solid electrolyte layer, such as cracking, caused by increased growth of lithium dendrites from the lithium metal anode.

[0241] In Reference Example 2, a short circuit occurred in the solid-state rechargeable battery before the completion of the first cycle, making it impossible to measure its life characteristics.

[0242] Evaluation Example 2: High-Frequency Characteristic Evaluation The high efficiency characteristics of the solid-state secondary batteries manufactured in Examples 1-8, Reference Example 1, and Comparative Examples 1 and 2 were evaluated by the following charge-discharge tests. The charge-discharge tests were performed by placing the solid-state secondary batteries in a constant temperature bath at 45°C.

[0243] The lithium batteries manufactured in Examples 1-8, Reference Example 1, and Comparative Examples 1 and 2 were charged at 45°C with a current of 0.1 Crate until the voltage reached 2.5V (vs.Li), and then cut off with a current of 0.05 Crate while maintaining 2.5V in constant voltage mode. Subsequently, they were discharged with a constant current of 0.1 Crate until the voltage reached 0.3V (vs.Li) (formation cycle).

[0244] A lithium battery that had undergone a chemical conversion cycle was charged with a constant current of 0.2 Crate at 45°C until the voltage reached 2.5V (vs.Li). Subsequently, it was discharged with a constant current of 0.2 Crate until the voltage reached 0.3V (vs.Li) (first cycle).

[0245] The lithium battery, after completing the first cycle, was charged with a constant current of 0.2 Crate at 45°C until the voltage reached 2.5V (vs.Li). Subsequently, it was discharged with a constant current of 0.33 Crate until the voltage reached 0.3V (vs.Li) (second cycle).

[0246] The lithium battery, after completing the second cycle, was charged with a constant current of 0.2 Crate at 45°C until the voltage reached 2.5V (vs.Li). Subsequently, it was discharged with a constant current of 0.5 Crate until the voltage reached 0.3V (vs.Li) (third cycle).

[0247] A lithium battery that had undergone the third cycle was charged with a constant current of 0.2 Crate at 45°C until the voltage reached 2.5V (vs.Li). Subsequently, it was discharged with a constant current of 1.0 Crate until the voltage reached 0.3V (vs.Li) (fourth cycle).

[0248] A 10-minute stop period was observed after each charge / discharge cycle in all charge / discharge cycles. Some of the results from the room-temperature charge / discharge experiments are shown in Table 2 below. The high-efficiency characteristic is defined by Equation 1 below. <Formula 1> High efficiency performance [%] = [Discharge capacity in the 4th cycle / Discharge capacity in the 1st cycle] × 100 [Table 2]

[0249] As shown in Table 2, the solid-state secondary batteries of Examples 1 to 8 had similar high-efficiency characteristics to the solid-state secondary batteries of Reference Example 1 and Comparative Examples 1 and 2. [Industrial applicability]

[0250] In one embodiment, by additionally arranging an organic electrolyte on the surface and / or inside the solid electrolyte layer, defects in the solid electrolyte layer are suppressed during the charge-discharge process, and the internal resistance of the solid secondary battery is reduced, thereby providing a solid secondary battery with improved lifespan and high efficiency characteristics. [Explanation of Symbols]

[0251] 1 Solid state secondary battery 10 Positive electrode layer 11 Positive electrode current collector 12 Cathode active material layer 20 Negative electrode layer 21 Negative electrode current collector 22 First negative electrode active material layer 30 Solid electrolyte layer 30a All solid electrolyte layer 30b Other side of solid electrolyte layer 30c Inside the solid electrolyte layer 40 First inert member 50 Second inert member 60 First Meso-Marginal Layer 70 Second Meso-Marginal Layer 100 organic electrolytes 100a Organic Electrolyte No. 1 100b Second organic electrolyte 100c 3rd organic electrolyte

Claims

1. A positive electrode layer; a negative electrode layer; a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer; and The electrolyte comprises a first organic electrolyte disposed between the positive electrode layer and the solid electrolyte layer, a second organic electrolyte disposed between the negative electrode layer and the solid electrolyte layer, a third organic electrolyte disposed within the solid electrolyte layer, or a combination thereof. The first organic electrolyte, the second organic electrolyte, and the third organic electrolyte independently comprise a polymer electrolyte, a liquid electrolyte, or a combination thereof, and the viscosity of the liquid electrolyte is 10 cps or more at 25°C and 1 atm. The positive electrode layer includes a positive electrode current collector and a positive electrode active material layer disposed on one or both sides of the positive electrode current collector, wherein the positive electrode active material layer is Li ２ Contains S-containing complex, A solid-state secondary battery in which 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.

2. The present invention further includes a first intermediate layer disposed between the positive electrode layer and the solid electrolyte layer, a second intermediate layer disposed between the negative electrode layer and the solid electrolyte layer, or a combination thereof. The solid-state secondary battery according to claim 1, wherein the first intermediate layer contains the first organic electrolyte and the second intermediate layer contains the second organic electrolyte.

3. The solid-state secondary battery according to claim 1, wherein the polymer electrolyte comprises a polymer having repeating units having a thermopolymerizable functional group, a thermoset of the polymer, an oligomer having repeating units having a thermopolymerizable functional group, a thermoset of the oligomer, a monomer having a thermopolymerizable functional group, a thermoset of the monomer, an oligomeric ionic liquid, a polymeric ionic liquid, or a combination thereof.

4. The solid-state secondary battery according to claim 3, wherein the thermally polymerizable functional group comprises a cyano group, a hydroxyl group, an amino group, an amide group, an imide group, a carboxyl group, an acid anhydride group, or a combination thereof.

5. The solid-state secondary battery according to claim 1, wherein the liquid electrolyte comprises an ionic liquid, and the viscosity of the liquid electrolyte is 15 cps or more at 25°C and 1 atm.

6. The solid electrolyte layer further comprises one or more of a first organic electrolyte and a second organic electrolyte disposed inside the solid electrolyte layer. The solid electrolyte layer includes one surface adjacent to the positive electrode layer and the other surface adjacent to the negative electrode layer. It has a concentration gradient of the first organic electrolyte that decreases from the aforementioned surface toward the negative electrode layer, The second organic electrolyte has a concentration gradient that decreases from the other surface toward the positive electrode layer, or The solid-state secondary battery according to claim 1, which simultaneously has a concentration gradient of the first organic electrolyte and a concentration gradient of the second organic electrolyte.

7. The solid electrolyte layer contains an inorganic solid electrolyte, The solid-state secondary battery according to claim 1, wherein the inorganic solid electrolyte includes a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or a combination thereof.

8. The sulfide-based solid electrolyte is Li ２ S-P ２ S ５ 、Li ２ S-P ２ S ５ -LiX, X is a halogen element, Li ２ S-P ２ S ５ -Li ２ O, Li ２ S-P ２ S ５ -Li ２ O-LiI, Li ２ S-SiS ２ 、Li ２ S-SiS ２ -LiI, Li ２ S-SiS<00-00021>-LiBr, Li ２ S-SiS ２ -LiCl, Li ２ S-SiS ２ -B ２ S ３ -LiI, Li ２ S-SiS ２ -P ２ S ５ -LiI, Li ２ S-B ２ S ３ 、Li ２ S-P ２ S ５ -Z ｍ S ｎ 、m, n are positive numbers, Z is one of Ge, Zn or Ga, Li ２ S-GeS ２ 、Li ２ S-SiS ２ -Li ３ PO ４ 、Li ２ S-SiS ２ -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<0-00054>Br ｘ 、0≤x≤2、and Li ７－ｘ PS ６－ｘ I ｘ , one or more selected from 0 ≤ x ≤ 2, The sulfide-based solid electrolyte comprises an argyrodite-type solid electrolyte. The argyrodite-type solid electrolyte is Li ６ PS ５ Cl, Li ６ PS ５ Br and Li ６ PS ５ Includes one or more selected from I, The solid-state secondary battery according to claim 7, wherein the density of the argyrodite-type solid electrolyte is 1.0 to 2.0 g / cc.

9. The Li ２ S-containing complex is Li ２ S and carbon-based composite, Li ２ A composite of S, carbon-based materials, and a solid electrolyte, Li ２ S and solid electrolyte complex, Li ２ A composite of S, carbon-based materials, and lithium salts, Li ２ A composite of S and lithium salt, Li ２ S and metal carbide composite, Li ２ S, carbon-based materials, and metal carbide composites, Li ２ Composite of S and metal nitride, Li ２ A solid-state secondary battery according to claim 1, comprising a composite of S, a carbon-based material, and a metal nitride, or a combination thereof.

10. The lithium salt is a binary compound or a ternary compound, The binary compound is LiI, LiBr, LiCl, LiF, LiH, Li ２ O, Li ２ Se, Li ２ Te, Li ３ N, Li ３ P, Li ３ As, Li ３ Sb, Li ３ Al ２ LiB ３ or a combination of these, where the ternary compound is Li ３ OCl, LiPF ６ 、LiBF ４ 、LiSbF ６ 、LiAsF ６ 、LiClO ４ 、LiAlO ２ 、LiAlCl ４ 、LiNO ３ 、Li ２ CO ３ 、LiBH ４ 、Li ２ SO ４ 、Li ３ BO ３ 、Li ３ PO ４ 、Li ４ NCl, Li ５ NCl ２ 、Li ３ BN ２ or a combination thereof, the solid secondary battery according to claim 9.

11. The carbon-based material includes a fibrous carbon-based material, The solid-state secondary battery according to claim 9, wherein the fibrous carbon-based material comprises a carbon nanostructure, and the carbon nanostructure comprises carbon nanofibers, carbon nanotubes, carbon nanobelts, carbon nanorods, or a combination thereof.

12. The Li ２ S-containing complex is Li ２ It contains a composite of S, lithium salt, and carbon-based material. Li ２ The mixture contains 10 to 80 parts by weight of S, 1 to 40 parts by weight of lithium salt, and 1 to 20 parts by weight of carbon-based material. The positive electrode active material layer further contains a sulfide-based solid electrolyte, In the positive electrode active material layer, the carbon-based material is Li ２ The solid secondary battery according to claim 1, wherein the sulfur is arranged only in the sulfur-containing composite.

13. The first negative electrode active material layer comprises a negative electrode active material and a binder. The solid-state secondary battery according to claim 1, wherein the negative electrode active material has a particle form and the average particle size of the negative electrode active material is 4 μm or less.

14. The anode active material comprises one or more selected from carbon-based anode active materials and metal or semimetallic anode active materials. The carbon-based anode active material includes amorphous carbon, crystalline carbon, porous carbon, or a combination thereof. The solid-state secondary battery according to claim 1, wherein the metal or metalloid anode active material includes gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), zinc (Zn), or a combination thereof.

15. The first negative electrode active material layer comprises a negative electrode active material, and the negative electrode active material comprises a mixture of first particles containing amorphous carbon and second particles containing metal or metalloid. The solid secondary battery according to claim 1, wherein the content of the second particles is 1 to 60 wt% based on the total weight of the mixture.

16. The solid-state secondary battery according to claim 1, wherein the initial charge capacity of the first negative electrode active material layer is 50% or less of the initial charge capacity of the positive electrode active material layer.

17. The first negative electrode active material layer comprises a negative electrode active material, the negative electrode active material comprising a carbon-based support and a metallic negative electrode active material supported on the carbon-based support, The aforementioned metallic negative electrode active material includes a metal, a metal oxide, a composite of a metal and a metal oxide, or a combination thereof. The metallic anode active material has a particle form, and the particle size of the metallic anode active material is 1 nm to 200 nm. The carbon-based support has a particle form, and the particle size of the carbonaceous material is 10 nm to 2 μm. The present invention further includes 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, in one or more locations. The solid-state secondary battery according to claim 1, wherein the second negative electrode active material layer is a metal layer, and the metal layer contains lithium or a lithium alloy.

18. One or more of the positive electrode current collector and the negative electrode current collector include a base film and a metal layer disposed on one or both sides of the base film. The base film comprises a polymer, and the polymer comprises polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof. The solid-state secondary battery according to claim 1, 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.

19. The solid-state secondary battery according to claim 1, further comprising a first inert member disposed on one side surface of the positive electrode, wherein the first inert member includes a flame-retardant inert member.

20. The solid-state secondary battery according to claim 1, further comprising a second inert member disposed on the other surface of the negative electrode current collector, wherein the second inert member comprises a conductive flame-retardant inert member.

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