Solid secondary battery

Abstract

Provided is a solid secondary battery 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 in the solid electrolyte layer, or a combination thereof. The first organic electrolyte, the second organic electrolyte, and the third organic electrolyte each independently include a polymer electrolyte, a liquid electrolyte, or a combination thereof, and the liquid electrolyte has a viscosity of 10 cps or more at 25℃ and 1 atmospheric pressure. The positive electrode layer includes a positive electrode current collector and a positive electrode active material layer disposed on one side or both sides of the positive electrode current collector, the positive electrode active material layer includes a Li2S-containing composite, and the negative electrode layer includes a negative electrode current collector and a first negative electrode active material layer disposed on one side of the negative electrode current collector.

Description

solid secondary batteries

[0001] It's about solid secondary batteries.

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

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

[0004] By adopting solid electrolytes instead of liquid electrolytes in secondary batteries, the risk of fire or explosion can be reduced. Secondary batteries using solid electrolytes can offer improved safety.

[0005] One aspect is to provide a solid secondary battery having improved cycle characteristics by disposing an organic electrolyte on the surface and / or inside the solid electrolyte layer.

[0006] According to the implementation example

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

[0008] It includes 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.

[0009] 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.

[0010] The above 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, and the positive electrode active material layer includes a Li2S-containing complex,

[0011] A solid secondary battery is provided, wherein the negative electrode layer includes a negative electrode current collector and a first negative electrode active material layer disposed on one surface of the negative electrode current collector.

[0012] According to one aspect, by additionally arranging an organic electrolyte on the surface and / or inside of a 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 having improved life characteristics and high-rate characteristics.

[0013] Figures 1a to 1c are cross-sectional views of a solid secondary battery according to an exemplary embodiment.

[0014] Figures 2a to 2c are cross-sectional views of a solid secondary battery according to an exemplary embodiment.

[0015] Figures 3a to 3c are cross-sectional views of a solid secondary battery according to an exemplary embodiment.

[0016] Figures 4a to 4c are schematic diagrams showing changes in the concentration of an organic electrolyte depending on the location in a solid electrolyte layer according to an exemplary embodiment.

[0017] Figure 5 is a cross-sectional view of a solid secondary battery according to an exemplary embodiment.

[0018] Figure 6 is a cross-sectional view of a solid secondary battery according to an exemplary embodiment.

[0019] Fig. 7 is a cross-sectional view of a solid secondary battery according to an exemplary embodiment.

[0020] Figure 8 is a cross-sectional view of a solid secondary battery according to an exemplary embodiment.

[0021] Figure 9 is a cross-sectional view of a solid secondary battery according to an exemplary embodiment.

[0022] Fig. 10 is a cross-sectional view of a solid secondary battery according to an exemplary embodiment.

[0023] Fig. 11 is a cross-sectional view of a solid secondary battery according to an exemplary embodiment.

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

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

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

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

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

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

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

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

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

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

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

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

[0036] In the present disclosure, "viscosity" can be measured using a Brookfield LV DV-II + Pro Viscometer (cone-plate type). Viscosity can be measured, for example, at 1 atm and 25°C after dissolving an ionic liquid in dimethyl formamide (DMF) at a concentration of 35 wt%. For example, when measuring viscosity, the spindle is S40, rpm 15, and the sample loading amount is 1 mL.

[0037] In the present disclosure, "weight average molecular weight" may refer to a conversion value for 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 utilize the Agilent 1200 series, the Agilent PL mixed B column, and THF as the solvent.

[0038] In this disclosure, “metal” includes both metals and metalloids such as silicon and germanium, in their elemental or ionic states.

[0039] In this disclosure, “alloy” means a mixture of two or more metals.

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

[0041] In the present disclosure, “positive electrode material” means a positive electrode material capable of undergoing lithiation and delithiation.

[0042] In the present disclosure, “negative electrode active material” means a negative electrode material capable of undergoing lithiation and delithiation.

[0043] In the present disclosure, “lithiation” and “lithiating” mean a process of adding lithium to an electrode active material.

[0044] In the present disclosure, “delithiation” and “delithiate” mean a process of removing lithium from an electrode active material.

[0045] In this disclosure, “charging” and “charging” mean a process of providing electrochemical energy to a battery.

[0046] In this disclosure, “discharging” and “discharging” mean the process of removing electrochemical energy from a battery.

[0047] In the present disclosure, “positive electrode” and “cathode” mean an electrode at which electrochemical reduction and lithiation occur during a discharge process.

[0048] In the present disclosure, “cathode” and “anode” mean electrodes where electrochemical oxidation and delithiation occur during a discharge process.

[0049] While specific implementations have been described, alternatives, modifications, variations, improvements, and substantial equivalents that are not currently anticipated or unforeseen may occur to the applicant or those skilled in the art. Accordingly, the appended claims, as filed and as amended, are intended to encompass all such alternatives, modifications, variations, improvements, and substantial equivalents.

[0050]

[0051] Below, solid secondary batteries according to exemplary implementation examples are described in more detail.

[0052] [Solid secondary battery]

[0053] According to one embodiment, a solid secondary battery 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, and includes 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 include 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 surface or both surfaces of the positive electrode current collector, the positive electrode active material layer includes a Li2S-containing composite, and the negative electrode layer includes a negative electrode current collector and a first negative electrode active material layer disposed on one surface of the negative electrode current collector. The solid secondary battery may further include at least one of 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 include the first organic electrolyte. The second intermediate layer may include the second organic electrolyte.

[0054] 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 secondary battery, the interfacial resistance between the positive electrode layer and / or the negative electrode layer and the solid electrolyte layer is reduced, and the solid electrolyte layer can more easily accommodate changes in the volume of the positive electrode layer and / or the negative electrode layer during charging and discharging of the solid secondary battery. In addition, the high-viscosity organic electrolyte can suppress the formation of defects such as cracks in the solid electrolyte layer by filling pinholes on the surface of the solid electrolyte layer. The high-viscosity organic electrolyte can suppress gas generation due to side reactions and suppress the decline in ionic conductivity by reducing the contact area between the solid electrolyte layer and oxygen. The cycle characteristics of the solid secondary battery can be further improved. For example, the high-rate characteristics and life characteristics of the solid secondary battery can be improved.

[0055] Referring to FIGS. 1a-1c, 2a-2c, 3a-3c, 4a-4c and FIGS. 5 to 9, a solid secondary battery (1) includes a high-viscosity organic electrolyte (100) disposed on at least one of one surface (30a) of a solid electrolyte layer, the other surface (30b) of the solid electrolyte layer (30) facing the one surface (30a) and the inside (30c) of the solid electrolyte layer. The high-viscosity organic electrolyte (100) has improved flexibility compared to an inorganic electrolyte. 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.

[0056] Referring to FIGS. 1a-1c, 2a-2c, 3a-3c, 4a-4c and 5 to 9, a solid secondary battery (1) includes a positive electrode layer (10); a negative electrode layer (10); and a solid electrolyte layer (30) disposed between the positive electrode layer (10) and the negative electrode layer (10). The solid secondary battery 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 (10) 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 surfaces of the positive electrode current collector (11), and the positive electrode active material layer (12) includes a Li2S-containing complex. The negative electrode layer (20) includes a negative electrode current collector (21) and a first negative electrode active material layer (22) disposed on one surface of the negative electrode current collector (21).

[0057]

[0058] [Solid electrolyte layer]

[0059] [Solid electrolyte layer: organic electrolyte]

[0060] Referring to FIGS. 1A to 1C, the solid electrolyte layer (30) includes, for example, at least one of 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 (10) and the solid electrolyte layer (30), and a third organic electrolyte (100c) disposed within the solid electrolyte layer (30).

[0061] Referring to FIG. 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 disposed on one surface of the anode layer (10). By disposing one surface of the anode layer (10) on one surface (30a) of the solid electrolyte layer, the first organic electrolyte (100a) is disposed between the anode layer (10) and the solid electrolyte layer (30). By disposing the flexible first organic electrolyte (100a) between the anode layer (10) and the solid electrolyte layer (30), the interface resistance between the anode layer (10) and the solid electrolyte layer (30) can be reduced. A pin-hole 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 change in volume of the positive electrode layer (10) during charging and discharging of the solid secondary battery (1).

[0062] Referring to FIG. 1b, the solid electrolyte layer (30) includes, for example, a second organic electrolyte (100b) disposed on the other side (30b) opposite to the one side (30a) of the solid electrolyte layer or disposed on one side of the cathode layer (10). By disposing one side of the cathode layer (10) on the other side (30b) of the solid electrolyte layer, the second organic electrolyte (100b) is disposed between the cathode layer (10) and the solid electrolyte layer (30). By disposing the second organic electrolyte (100b) having flexibility between the cathode layer (10) and the solid electrolyte layer (30), the interfacial resistance between the cathode layer (10) and the solid electrolyte layer (30) can be reduced. A pin-hole disposed on one side (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 change in volume of the negative electrode layer (10) during charging and discharging of the solid secondary battery (1).

[0063] Referring to FIG. 1c, the solid electrolyte layer (30) includes, for example, a third organic electrolyte (100c) disposed within the solid electrolyte layer (30). By disposing the third organic electrolyte (100c) having flexibility within the solid electrolyte layer (30c), the internal resistance of the solid electrolyte layer (30) can be reduced. A pin-hole disposed within the solid electrolyte layer (30c) can be filled with the third organic electrolyte (100c). By providing the third organic electrolyte (100c), the internal resistance of the solid secondary battery (1) is reduced, and the solid electrolyte layer (30) can more easily accommodate changes in the volume of the positive electrode layer (10) and / or the negative electrode layer (10) during charging and discharging of the solid secondary battery (1).

[0064] Referring to FIG. 2a, the solid 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 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 secondary battery (1) may be further improved.

[0065] Referring to FIG. 2b, the solid secondary battery (1) may further include, for example, a second intermediate layer (70) disposed between the negative electrode layer (10) 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 (10) and the solid electrolyte layer (30). By including the second intermediate layer (70) in the solid secondary battery (1), the interfacial resistance between the negative electrode layer (10) and the solid electrolyte layer (30) may be further reduced. The cycle characteristics of the solid secondary battery (1) may be further improved.

[0066] Referring to FIG. 2c, the solid secondary battery (1) can include a first intermediate layer (60) and a second intermediate layer (70) at the same time. Since the solid secondary battery (1) includes the first intermediate layer (60) and the second intermediate layer (70) at the same time, the interfacial resistance between the positive electrode layer (10) and the solid electrolyte layer (30) and the interfacial resistance between the negative electrode layer (10) and the solid electrolyte layer (30) can be further reduced. Since the internal resistance of the solid secondary battery (1) is further reduced, the cycle characteristics of the solid secondary battery (1) can be further improved.

[0067] The first organic electrolyte (100a), the second organic electrolyte (100b), and the third organic electrolyte (100c) are each 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, the same or different from each other.

[0068] The organic electrolyte (100) includes, for example, a polymer electrolyte. The viscosity of the polymer electrolyte may be higher than that of, for example, a liquid electrolyte.

[0069] A polymer electrolyte is an electrolyte containing a polymer. The polymer electrolyte may include, for example, a polymer solid electrolyte, a polymer gel electrolyte, or a combination thereof.

[0070] Polymer electrolytes can be classified, for example, as solid polymer electrolytes or gel polymer electrolytes, depending on whether they contain liquid. Alternatively, polymer electrolytes can be classified, for example, as solid polymer electrolytes or gel polymer electrolytes, depending on their state at 25°C and 1 atm. Solid polymer electrolytes can include, for example, a mixture of a lithium salt and a polymer, or a polymer having an ion-conducting functional group. Solid polymer electrolytes can be, for example, polymer electrolytes that are solid at 25°C and 1 atm. Solid polymer electrolytes may not contain liquid.

[0071] The polymer gel electrolyte may include, for example, a liquid electrolyte and a polymer, or an organic solvent and a polymer having an ion-conducting functional group. The liquid electrolyte may be, for example, an ionic liquid, a mixture of a lithium salt and an ionic liquid, a mixture of a lithium salt and an organic solvent, a mixture of an ionic liquid and an organic solvent, or a mixture of a lithium salt, an ionic liquid, and an organic solvent. The polymer gel electrolyte may be, for example, a polymer electrolyte that is in a gel state at 25°C and 1 atm. The polymer gel electrolyte may have a gel state without including a liquid, for example. In the present disclosure, an "ionic liquid" is a compound composed of ions and has a melting point of 100°C or lower.

[0072] The lithium salt used in the polymer electrolyte and / or liquid electrolyte is not particularly limited and any lithium salt that can be used as an electrolyte in the relevant technical field may be used. Lithium salts include, for example, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2)(x, y are 1 to 20, respectively), LiCl, LiI or mixtures thereof.

[0073] The polymer electrolyte may include, for example, a polymer including a repeating unit having a thermopolymerizable functional group, a thermosetting product of the polymer, an oligomer including a repeating unit having a thermopolymerizable functional group, a thermosetting product of the oligomer, a monomer having a thermopolymerizable functional group, a thermosetting product of the monomer, an oligomeric ionic liquid, a polymeric ionic liquid, or a combination thereof.

[0074] A polymer comprising a repeating unit having a thermopolymerizable functional group, a thermosetting product of the polymer, and an oligomer comprising a repeating unit having a thermopolymerizable functional group may additionally include a repeating unit that does not have a thermopolymerizable functional group. The repeating unit that does not have a thermopolymerizable functional group is not particularly limited, and any repeating unit derived from an unsaturated monomer commonly used in the production of copolymers in the relevant technical field may be used. The repeating unit that does not have a thermopolymerizable functional group may be, for example, an acrylic monomer such as methyl acrylate or ethyl acrylate.

[0075] The thermopolymerizable functional group may include, for example, 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.

[0076] The polymer comprising a repeating unit having a thermopolymerizable functional group and / or the oligomer comprising a repeating unit having a thermopolymerizable functional group may include, for example, repeating units derived from a cyano group-containing monomer, repeating units derived from a hydroxyl group-containing monomer, repeating units derived from an acid anhydride group-containing monomer, repeating units derived from an amino group-containing monomer, repeating units derived from an amide group-containing monomer, repeating units derived from an imide group-containing monomer, repeating units derived from a carboxyl group-containing monomer, or a combination thereof. The thermopolymerizable functional group-containing monomer may include, for example, a cyano group-containing monomer, a hydroxyl group-containing monomer, an amino group-containing monomer, an amide group-containing monomer, an imide group-containing monomer, a carboxyl group-containing monomer, an acid anhydride group-containing monomer, or a combination thereof.

[0077] Cyano group-containing monomers include, for example, unsaturated carboxylic acid nitrile monomers such as acrylonitrile, methacrylonitrile, and vinylidene cyanide; unsaturated carboxylic acid cyanoalkyl ester monomers such as 2-cyanoethyl(meth)acrylate, 2-cyanopropyl(meth)acrylate, and 3-cyanopropyl(meth)acrylate; CH=CH-C(=O)-(OCH2CH2) n -CN (n=1 to 20), etc.

[0078] Examples of hydroxyl group-containing monomers include (meth)acrylic acid hydroxyalkyl ester monomers such as (meth)acrylic acid 2-hydroxyethyl, (meth)acrylic acid 2-hydroxypropyl, (meth)acrylic acid 3-hydroxypropyl, (meth)acrylic acid 2-hydroxybutyl, (meth)acrylic acid 3-hydroxybutyl, (meth)acrylic acid 4-hydroxybutyl, etc.

[0079] Amino group-containing monomers include, for example, 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, 3-dimethylaminopropyl (meth)acrylate, etc. Aminoalkyl ester monomers, etc.

[0080] 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, crotonic acid amide, maleic acid diamide, fumaric acid diamide, and diacetone acrylamide; These include unsaturated carboxylic acid amide monomers such as N-dimethylaminomethyl(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.

[0081] Monomers containing an imide group include, for example, cyclohexylmaleimide, isopropylmaleimide, N-cyclohexylmaleimide, and itaconimide.

[0082] Carboxyl group-containing monomers include, for example, 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; alkyl ester monomers containing free carboxyl groups of the above-described unsaturated polycarboxylic acids or amide monomers containing free carboxyl groups.

[0083] The carboxylic acid anhydride group-containing monomer is, for example, an acid anhydride of the unsaturated polycarboxylic acid described above.

[0084] A thermosetting product of a polymer including a repeating unit having a thermopolymerizable functional group, a thermosetting product of an oligomer including a repeating unit having a thermopolymerizable functional group, and a thermosetting product of a monomer including a thermopolymerizable functional group can be obtained by heat-treating a polymer including a repeating unit having a thermopolymerizable functional group, an oligomer including a repeating unit having a thermopolymerizable functional group, and a monomer including a thermopolymerizable functional group, respectively, at, for example, 50 to 200°C, 50 to 150°C, 50 to 100°C, or 50 to 70°C. The heat-treatment time can be, for example, 1 to 120 minutes, 5 to 100 minutes, 10 to 80 minutes, or 30 to 80 minutes.

[0085] Oligomeric ionic liquids and polymeric ionic liquids can be, for example, the result of polymerization of ionic liquid monomers.

[0086] The ionic liquid monomer comprises, for example, a) one or more cations selected from ammonium, pyrrolidinium, pyridinium, pyrimidinium, imidazolium, piperidinium, pyrazolium, oxazolium, pyridazinium, phosphonium, sulfonium, triazolium and mixtures thereof, and b) BF4-, PF6-, AsF6-, SbF6-, AlCl4-, HSO4-, ClO4-, CH3SO3-, CF3CO2-, Cl-, Br-, I-, SO4 2- , CF3SO3-, (FSO2)2N-, (C2F5SO2)2N-, (C2F5SO2)(CF3SO2)N-, and (CF3SO2)2N-. An oligomeric ionic liquid or a polymeric ionic liquid can be obtained by polymerizing these ionic liquid monomers.

[0087] The organic electrolyte (100) includes, for example, a liquid electrolyte, and the viscosity of the liquid electrolyte 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, or 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, and 10 cps to 100 cps at 25 ℃ and 1 atm. The viscosity of the liquid electrolyte can be measured using a Brookfield LV DV-II + Pro Viscometer (cone-plate type). Since the liquid electrolyte has a high viscosity in this range, the volume change during charge and discharge of the positive electrode layer (10) and / or the negative electrode layer (10) can be more effectively accommodated, and the interfacial resistance between the positive electrode layer (10), the negative electrode layer (10), and the solid electrolyte layer (30) can be more effectively reduced, and an improved bonding force can be provided between the positive electrode layer (10), the negative electrode layer (10), and the solid electrolyte layer (30). As a result, the cycle characteristics of the solid secondary battery (1) can be improved. If the viscosity of the liquid electrolyte is excessively low, the above-described effect may be minimal.

[0088] The liquid electrolyte may include, for example, an ionic liquid.

[0089] Ionic liquids can be represented, for example, by the following chemical formulas 1 and 2:

[0090] <Chemical Formula 1> <Chemical Formula 2>

[0091]

[0092] In the above chemical formula 1, X1 is -N(R2)(R3)(R4) or -P(R2)(R3)(R4),

[0093] R1, R2, R3 and R4 are each independently an unsubstituted or halogen-substituted C1-C30 alkyl group, an unsubstituted or halogen-substituted C1-C30 alkoxy group, an unsubstituted or halogen-substituted C6-C30 aryl group, an unsubstituted or halogen-substituted C6-C30 aryloxy group, an unsubstituted or halogen-substituted C3-C30 heteroaryl group, an unsubstituted or halogen-substituted C3-C30 heteroaryloxy group, an unsubstituted or halogen-substituted C4-C30 cycloalkyl group, an unsubstituted or halogen-substituted C3-C30 heterocycloalkyl group, or an unsubstituted or halogen-substituted C2-C100 alkylene oxide group,

[0094] In the above chemical formula 2,

[0095] is a heterocycloalkyl ring or heteroaryl ring containing 1 to 3 heteroatoms and 2 to 30 carbon atoms, wherein the ring is substituted or unsubstituted by a substituent, and X2 is =N(R5)(R6), -N(R5)=, =P(R5)(R6) or -P(R5)=,

[0096] The substituents substituted on the above ring, R5, and R6 are each independently hydrogen, an unsubstituted or halogen-substituted C1-C30 alkyl group, an unsubstituted or halogen-substituted C1-C30 alkoxy group, an unsubstituted or halogen-substituted C6-C30 aryl group, an unsubstituted or halogen-substituted C6-C30 aryloxy group, an unsubstituted or halogen-substituted C3-C30 heteroaryl group, an unsubstituted or halogen-substituted C3-C30 heteroaryloxy group, an unsubstituted or halogen-substituted C4-C30 cycloalkyl group, an unsubstituted or halogen-substituted C3-C30 heterocycloalkyl group, or an unsubstituted or halogen-substituted C2-C100 alkylene oxide group, and Y- is an anion.

[0097] Ionic liquids can be represented, for example, by the following chemical formulas 3 to 4:

[0098] <Chemical Formula 3> <Chemical Formula 4>

[0099]

[0100] In the above chemical formula 3, Z is N or P,

[0101] R7, R8, R9 and R 10 are each independently an unsubstituted or halogen-substituted C1-C30 alkyl group, an unsubstituted or halogen-substituted C6-C30 aryl group, an unsubstituted or halogen-substituted C3-C30 heteroaryl group, an unsubstituted or halogen-substituted C4-C30 cycloalkyl group, or an unsubstituted or halogen-substituted C3-C30 heterocycloalkyl group,

[0102] In the above chemical formula 4, Z is N or P,

[0103] R 11 , R 12 , R 13 , R 14 , R 15 , R 16 , and R 17 are each independently hydrogen, an unsubstituted or halogen-substituted C1-C30 alkyl group, an unsubstituted or halogen-substituted C6-C30 aryl group, an unsubstituted or halogen-substituted C3-C30 heteroaryl group, an unsubstituted or halogen-substituted C4-C30 cycloalkyl group, or an unsubstituted or halogen-substituted C3-C30 heterocycloalkyl group, and Y - is an anion.

[0104] Ionic liquids can be represented, for example, by the following chemical formulae 5 to 10:

[0105] <Chemical Formula 5> <Chemical Formula 6> <Chemical Formula 7>

[0106]

[0107] <Chemical Formula 8> <Chemical Formula 9> <Chemical Formula 10>

[0108]

[0109] In chemical formulas 5 to 10, R 18 , R 19 , R 20 and R 21 are each independently an unsubstituted or halogen-substituted C1-C30 alkyl group, an unsubstituted or halogen-substituted C6-C30 aryl group, an unsubstituted or halogen-substituted C3-C30 heteroaryl group, an unsubstituted or halogen-substituted C4-C30 cycloalkyl group, or an unsubstituted or halogen-substituted C3-C30 heterocycloalkyl group,

[0110] R 22 , R 23 , R 24 , R 25 , R 26 , and R 27 are each independently hydrogen, an unsubstituted or halogen-substituted C1-C30 alkyl group, an unsubstituted or halogen-substituted C6-C30 aryl group, an unsubstituted or halogen-substituted C3-C30 heteroaryl group, an unsubstituted or halogen-substituted C4-C30 cycloalkyl group, or an unsubstituted or halogen-substituted C3-C30 heterocycloalkyl group, and Y - is an anion.

[0111] Ionic liquids contain anions, 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 a combination thereof may be included. The anion of the ionic liquid represented by chemical formulae 1 to 10 may also be selected from the anions described above.

[0112] The ionic liquid 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 a combination thereof.

[0113] The molecular weight of the ionic liquid is, for example, 1000 Dalton or less, 900 Dalton or less, 800 Dalton or less, or 500 Dalton or less.

[0114] Referring to FIGS. 3a to 3c, the solid electrolyte layer (30) may further include at least one of the first organic electrolyte and the second organic electrolyte disposed inside the solid electrolyte layer (30c).

[0115] Referring to FIG. 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 the one surface (30a) to the inside (30c) of the solid electrolyte layer. By simultaneously disposing the first organic electrolyte (100a) at the interface between the solid electrolyte layer (30) and the positive electrode layer (10) and the inside (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 changes in the volume of the positive electrode layer (10). The first organic electrolyte (100a) may be arranged to extend from one side (30a) of the solid electrolyte layer toward the cathode layer (10) to an area 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).

[0116] Referring to FIG. 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 inside (30c) of the solid electrolyte layer. By simultaneously disposing the second organic electrolyte (100b) at the interface between the solid electrolyte layer (30) and the cathode layer (10) and the inside (30c) of the solid electrolyte layer, the interfacial resistance between the solid electrolyte layer (30) and the cathode layer (10) is further reduced, and the solid electrolyte layer (30) can more easily accommodate changes in the volume of the cathode layer (10). The second organic electrolyte (100b) may be arranged to extend from the other surface (30b) of the solid electrolyte layer toward the anode layer (10) to an area 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).

[0117] Referring to FIG. 3c, the solid electrolyte layer (30) may include a first organic electrolyte (100a) disposed on one side (30a) of the solid electrolyte and extending from the one side (30a) to the inside of the solid electrolyte layer (30c), and a second organic electrolyte (100b) disposed on the other side (30b) of the solid electrolyte and extending from the other side (30b) to the inside of the solid electrolyte layer (30c). By disposing a 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 disposing a second organic electrolyte (100b) at the interface between the solid electrolyte layer (30) and the negative electrode layer (10) 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 (10) are further reduced, and the solid electrolyte layer (30) can more effectively accommodate changes in the volume of the positive electrode layer (10) and the negative electrode layer (10). The first organic electrolyte (100a) and the second organic electrolyte (100b) may be arranged to extend from one side (30a) and the other side (30b) of the solid electrolyte layer, respectively, to an area 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).

[0118] The solid electrolyte layer includes one side (30a) and another side (30b) opposite to the one side (30a). One side (30a) of the solid electrolyte layer is adjacent to the positive electrode layer (10), and the other side (30b) of the solid electrolyte layer is adjacent to the negative electrode layer (10). One side (30a) of the solid electrolyte layer is in contact with, for example, the positive electrode layer (10). The other side (30b) of the solid electrolyte layer is in contact with, for example, the negative electrode layer (10).

[0119] Figures 4a to 4c illustrate the organic electrolyte concentration (C) included in the solid electrolyte layer (30) according to the position from one side (30a) of the solid electrolyte layer to the other side (30b) of the solid electrolyte layer.

[0120] Referring to FIG. 4a, the solid electrolyte layer (30) may have a first organic electrolyte (100a) concentration gradient that decreases from one side (30a) of the solid electrolyte layer toward the cathode layer (10). Although not shown in the drawing, the first organic electrolyte (100a) concentration gradient may decrease at various slopes, for example. The first organic electrolyte (100a) concentration gradient may decrease at a constant slope or at a varying slope. The concentration of the first organic electrolyte (100a) may decrease, for example, continuously or discontinuously from one side (30a) of the solid electrolyte layer to the other side (30b) of the solid electrolyte layer. For example, since the solid electrolyte layer (30) has a multilayer structure, the concentration of the first organic electrolyte (100a) can decrease, for example, in a stepwise manner from one side (30a) of the solid electrolyte layer to the other side (30b) of the solid electrolyte layer. Since the solid electrolyte layer (30) has such a concentration gradient of the first organic electrolyte (100a), the volume change of the positive electrode layer (10) can be more effectively accommodated in an area where the concentration of the first organic electrolyte (100a) is high, and improved structural stability can be provided in an area where the concentration of the first organic electrolyte (100a) is low or zero.

[0121] Referring to FIG. 4b, the solid electrolyte layer (30) may have a second organic electrolyte (100b) concentration gradient 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 second organic electrolyte (100b) concentration gradient may decrease at various slopes, for example. The second organic electrolyte (100b) concentration gradient may decrease at a constant slope or at a varying slope. The concentration of the second organic electrolyte (100b) may decrease, for example, continuously or discontinuously from the other surface (30b) of the solid electrolyte layer to one surface (30a) of the solid electrolyte layer. For example, since the solid electrolyte layer (30) has a multilayer structure, the concentration of the second organic electrolyte (100b) can decrease, for example, in a stepwise manner from the other surface (30b) of the solid electrolyte layer to one surface (30a) of the solid electrolyte layer. Since the solid electrolyte layer (30) has such a concentration gradient of the second organic electrolyte (100b), the volume change of the cathode layer (10) can be more effectively accommodated in an area where the concentration of the second organic electrolyte (100b) is high, and improved structural stability can be provided in an area where the concentration of the second organic electrolyte (100b) is low or zero.

[0122] Referring to FIG. 4c, the solid electrolyte layer (30) can simultaneously have a first organic electrolyte (100a) concentration gradient that decreases from one surface (30a) of the solid electrolyte layer toward the cathode layer (10) and a second organic electrolyte (100b) concentration gradient that decreases from the other surface (30b) of the solid electrolyte layer toward the anode layer (10). Although not shown in the drawing, the first organic electrolyte (100a) concentration gradient and the second organic electrolyte (100b) concentration gradient can decrease at various slopes, for example. The first organic electrolyte (100a) concentration gradient and the second organic electrolyte (100b) concentration gradient can decrease at a constant slope or at varying slopes. The concentration of the first organic electrolyte (100a) and the concentration of the second organic electrolyte (100b) may decrease, for example, continuously or discontinuously from the other surface (30b) of the solid electrolyte layer to one surface (30a) of the solid electrolyte layer. For example, since the solid electrolyte layer (30) has a multilayer structure, the concentration of the first organic electrolyte (100a) and the concentration of the second organic electrolyte (100b) may decrease, for example, in a stepwise manner from one surface (30a) and the other surface (30b) of the solid electrolyte layer to the inside (30c) of the solid electrolyte layer. Since the solid electrolyte layer (30) has the first organic electrolyte (100a) concentration gradient and the second organic electrolyte (100b) concentration gradient, the volume change of the positive electrode layer (10) and the negative electrode layer (10) can be more effectively accommodated in the region where the concentration of the first organic electrolyte (100a) and the second organic electrolyte (100b) is high, and improved structural stability can be provided in the region where the concentration of the first organic electrolyte (100a) and the second organic electrolyte (100b) is low or zero, for example, in the central region of the solid electrolyte layer (30).

[0123] [Solid electrolyte layer: solid electrolyte]

[0124] Referring to FIGS. 1A to 9, a solid electrolyte layer (30) is disposed between the positive electrode layer (10) and the negative electrode layer (20) and includes a solid electrolyte. The solid electrolyte includes, for example, an inorganic solid electrolyte.

[0125] The solid electrolyte may include, for example, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or a combination thereof.

[0126] The solid electrolyte is, for example, a sulfide-based solid electrolyte. The sulfide-based solid electrolyte is, for example, Li2S-P2S5, Li2S-P2S5-LiX, where X is a halogen element, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n , m, n are positive numbers, Z is one of Ge, Zn or Ga, Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q , p, q are positive numbers, M is one of P, Si, Ge, B, Al, Ga In, Li 7-x PS 6-x Cl x , 0≤x≤2, Li 7-x PS 6-x Br x , 0≤x≤2, and Li 7-x PS 6-x I x, at least one selected from 0≤x≤2. The sulfide-based solid electrolyte is manufactured by treating starting materials such as Li2S and P2S5 by a melting rapid cooling method or a mechanical milling method. In addition, heat treatment may be performed after the treatment. The solid electrolyte may be amorphous, crystalline, or a mixture thereof. In addition, the solid electrolyte may be, for example, one containing sulfur (S), phosphorus (P), and lithium (Li) as at least constituent elements among the above-described sulfide-based solid electrolyte materials. For example, the solid electrolyte may be a material containing Li2S-P2S5. When using a sulfide-based solid electrolyte material containing Li2S-P2S5 to form a solid electrolyte, the mixing molar ratio of Li2S and P2S5 is, for example, in the range of Li2S:P2S5=20:80 to 90:10, 25:75 to 90:10, 30:70 to 70:30, 40:60 to 60:40.

[0127] The sulfide-based solid electrolyte may include, for example, an argyrodite type solid electrolyte represented by the following chemical formula 11:

[0128] <Chemical Formula 11>

[0129] Li + 12-n-x A n+ X 2- 6-x Y - x

[0130] In the above formula, A is P, As, Ge, Ga, Sb, Si, Sn, Al, In, Ti, V, Nb or Ta, X is S, Se or Te, Y is Cl, Br, I, F, CN, OCN, SCN or N3, and 1≤n≤5, 0≤x≤2. The sulfide-based solid electrolyte is, for example, Li 7-x PS 6-x Cl x , 0≤x≤2, Li7-x PS 6-x Br x , 0≤x≤2, and Li 7-x PS 6-x I x , may be an argyrodite-type compound including at least one selected from 0≤x≤2. The sulfide-based solid electrolyte may be, for example, an argyrodite-type compound including at least one selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0131] The density of the argyrodite-type solid electrolyte may be 0.1 to 2.0 g / cc, 0.5 to 2.0 g / cc, 1.0 to 2.0 g / cc, or 1.5 to 2.0 g / cc. Since the argyrodite-type solid electrolyte has a density in this range, the internal resistance of the solid secondary battery (1) is reduced, and penetration of the solid electrolyte layer by Li can be effectively suppressed.

[0132] Oxide solid electrolytes include, for example, Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (0 <x<2, 0≤y<3), BaTiO3, Pb(Zr,Ti)O3(PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT)(0≤x<1, 0≤y<1), PB(Mg3Nb 2 / 3 )O3-PbTiO3(PMN-PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, Li3PO4, Li x Ti y (PO4)3(0 <x<2, 0<y<3), Li xAl y Ti z (PO4)3(0 <x<2, 0<y<1, 0<z<3), Li 1+x+y (Al, Ga) x (Ti, Ge) 2-x Si y P 3-y O 12 (0≤x≤1 0≤y≤1), Li x La y TiO3(0 <x<2, 0<y<3), Li2O, LiOH, Li2CO3, LiAlO2, Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2, Li 3+x La3M2O 12 (M = Te, Nb, or Zr, 0≤x≤10), or a combination thereof. The oxide-based solid electrolyte is manufactured, for example, by a sintering method.

[0133] Oxide-based solid electrolytes include, for example, Li7La3Zr2O 12 (LLZO) and Li 3+x La3Zr 2-a M a O 12 (M doped LLZO, M=Ga, W, Nb, Ta, or Al, 0 <a<2, 0≤x≤10) 중에서 선택된 가넷계(Garnet-type) 고체전해질이다.

[0134] The solid electrolyte layer (30) may be impermeable to lithium polysulfide. Accordingly, side reactions between lithium polysulfide generated during charging and discharging of the sulfide-based positive electrode active material and the negative electrode layer can be prevented. Accordingly, the cycle characteristics of the solid secondary battery (1) (1) including the solid electrolyte layer (30) can be improved.

[0135] [Solid electrolyte layer: binder]

[0136] The solid electrolyte layer (30) may include, for example, a binder. The binder included in the solid electrolyte layer (30) is not limited to, but may include, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc., and any binder used in the relevant technical field may be used. The binder of the solid electrolyte layer (30) may be the same as or different from the binder included in the positive electrode active material layer (12) and the negative electrode active material layer (22). The binder may be omitted.

[0137] The binder content included in the solid electrolyte layer (30) is 0.1 to 10 wt%, 0.1 to 5 wt%, 0.1 to 3 wt%, 0.1 to 1 wt%, 0 to 0.5 wt%, or 0 to 0.1 wt% with respect to the total weight of the solid electrolyte layer (30).

[0138]

[0139] [Anode layer]

[0140] [Anode layer: cathode active material]

[0141] Referring to FIGS. 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.

[0142] The Li2S-containing composite may be included in an amount of 10 to 90 parts by weight, 30 to 90 parts by weight, 40 to 90 parts by weight, 40 to 80 parts by weight, 50 to 80 parts by weight, or 50 to 70 parts by weight, based on 100 parts by weight of the cathode active material layer (12). If the content of the Li2S-containing composite is excessively reduced, the energy density of the secondary battery is lowered. If the content of the Li2S-containing composite is excessively increased, the deterioration of the cathode may be accelerated due to a change in the volume of the cathode during charge and discharge. As a result, the cycle characteristics of the secondary battery (1) may be deteriorated.

[0143] The Li2S-containing composite includes, for example, a composite of Li2S and a carbon-based material, a composite of Li2S and a carbon-based material and a solid electrolyte, a composite of Li2S and a solid electrolyte, a composite of Li2S and a carbon-based material and a lithium salt, a composite of Li2S and a lithium salt, a composite of Li2S and a metal carbide, a composite of Li2S and a carbon-based material and a metal carbide, a composite of Li2S and a metal nitride, a composite of Li2S and a carbon-based material and a metal nitride, or a combination thereof.

[0144] A Li2S-containing composite is distinguished from a simple mixture of Li2S and another material. In a simple mixture of Li2S and another material, the internal resistance of a positive electrode including these is maintained high because the interfacial resistance between Li2S and the other material is maintained. Therefore, the cycle characteristics of a solid secondary battery (1) including these may be deteriorated. In contrast, in a Li2S-containing composite, the interfacial resistance between Li2 and the other material is reduced because Li2S and the other material are mechanochemically or chemically complexed, so the internal resistance of a positive electrode including these is reduced. Therefore, the cycle characteristics of a solid secondary battery (1) including a Li2S-containing composite can be improved.

[0145] The composite of Li2S and a carbon-based material includes a carbon-based material. The carbon-based material can be, for example, any material containing carbon atoms that is used as a conductive material in the art. The carbon-based material can be, for example, crystalline carbon, amorphous carbon, or a combination thereof. The carbon-based material can be, for example, a sintered product of a carbon precursor. The carbon-based material can be, for example, a carbon nanostructure. The carbon nanostructure can be, for example, a one-dimensional carbon nanostructure, a two-dimensional carbon nanostructure, a three-dimensional carbon nanostructure, or a combination thereof. The carbon nanostructure can be, for example, a carbon nanotube, a carbon nanofiber, a carbon nanobelt, a carbon nanorod, graphene, or a combination thereof. The carbon-based material can be, for example, a porous carbon-based material or a non-porous carbon-based material. The porous carbon-based material can include, for example, periodic and regular two-dimensional or three-dimensional pores. The porous carbon-based material may be, for example, carbon black such as Ketjen Black, acetylene black, Denka Black, thermal black, channel black, or the like; graphite, activated carbon, or a combination thereof. The form of the carbon-based material may be, for example, but not limited to, particle form, sheet form, flake form, or the like, and any form that is used as a carbon-based material in the art may be used. The carbon-based material may include, for example, a fibrous carbon-based material. The aspect ratio of the fibrous carbon-based material may be, for example, 2 to 30, 2 to 20, 2 to 10, 2 to 8, 2 to 5, or 2 to 4. The fibrous carbon-based material may include a fibrous carbon nanostructure. The fibrous carbon nanostructure may include, for example, carbon nanofibers, carbon nanotubes, carbon nanobelts, carbon nanorods, or a combination thereof. The aspect ratio of the fibrous carbon-based material may be measured, for example, by scanning electron microscopy (SEM) or transmission electron microscopy (TEM).

[0146] The method for manufacturing a composite of Li2S and a carbon-based material may be, but is not limited to, a dry method, a wet method, or a combination thereof, and any method used in the relevant technical field may be used. The method for manufacturing a composite of Li2S and a carbon-based material may be, but is not necessarily limited to, milling, heat treatment, deposition, etc., and any method used in the relevant technical field may be used.

[0147] A composite of Li2S, a carbon-based material, and a solid electrolyte includes a carbon-based material and a solid electrolyte. The carbon-based material refers to the composite of Li2S and a carbon-based material described above. The solid electrolyte can be, for example, any material used as an ion-conducting material in the relevant technical field. The solid electrolyte is, for example, an inorganic solid electrolyte. The solid electrolyte is, for example, a crystalline solid electrolyte, an amorphous solid electrolyte, or a combination thereof. The solid electrolyte is, for example, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or a combination thereof. The sulfide-based solid electrolyte includes, for example, Li, S, and P, and may optionally further include a halogen element. The sulfide-based solid electrolyte can be selected from among the sulfide-based solid electrolytes used in the solid electrolyte layer. The sulfide-based solid electrolyte has, for example, a molecular weight of 1×10 at room temperature. -5 It can have an ionic conductivity of S / cm or more. The oxide-based solid electrolyte contains, for example, Li, O, and transition metal elements, and may optionally contain other elements. The oxide-based solid electrolyte has, for example, an ionic conductivity of 1×10 at room temperature. -5 It may be a solid electrolyte having an ionic conductivity of S / cm or higher. The oxide-based solid electrolyte may be selected from among 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.

[0148] The composite of Li2S and a solid electrolyte includes a solid electrolyte. The solid electrolyte refers to the composite of Li2S, a carbon-based material, and a solid electrolyte described above.

[0149] A complex of Li2S and a lithium salt includes 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). The lithium salt can be, for example, a binary compound composed of lithium and one element selected from groups 13 to 17 of the periodic table of elements. The lithium salt can be, for example, a ternary compound composed of lithium and two elements selected from groups 13 to 17 of the periodic table of elements. The binary compound includes, for example, LiI, LiBr, LiCl, LiF, LiH, Li2O, Li2Se, Li2Te, Li3N, Li3P, Li3As, Li3Sb, Li3Al2, LiB3, or a combination thereof. The ternary compound includes, for example, Li3OCl, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiNO3, Li2CO3, LiBH4, Li2SO4, Li3BO3, Li3PO4, Li4NCl, Li5NCl2, Li3BN2, or a combination thereof. The lithium salt is particularly one or more lithium halide compounds selected from LiF, LiCl, LiBr, and LiI. The complex of Li2S and a lithium salt can be, for example, a complex of Li2 and a lithium halide. The complex of Li2 and a lithium salt can provide improved ionic conductivity by including a lithium halide compound. The complex of Li2S and a lithium salt is distinguished from a simple mixture of Li2S, a carbon-based material, and a lithium salt. A simple mixture of Li2S and a lithium salt may provide high interfacial resistance by failing to maintain a dense interface between Li2S and a lithium salt, which may consequently reduce the life characteristics of a solid secondary battery (1).

[0150] A composite of Li2S, a carbon-based material, and a lithium salt includes a carbon-based material and a lithium salt. The carbon-based material refers to the composite of Li2S and a carbon-based material described above. The lithium salt refers to the composite of Li2S and a lithium salt described above.

[0151] The composite of Li2S and metal carbide includes metal carbide. The metal carbide is, for example, a two-dimensional metal carbide. The two-dimensional metal carbide is, for example, M n+1 C n T x (M is a transition metal, T is a terminal group, T is O, OH and / or F, n=1, 2, or 3, and x is the number of terminal groups) is expressed as 2D metal carbides, for example, Ti2CT x , (Ti 0.5 , Nb 0.5 )2CT x , Nb2CT x , V2CT x , Ti3C2T x , (V 0.5 , Cr 0.5 )3C2T x , Ti3CNT x , Ta4C3T x , Nb4C3T x or a combination thereof. The surface of the two-dimensional metal carbide is terminated with O, OH and / or F.

[0152] A composite of Li2S, a carbon-based material, and a metal carbide includes a carbon-based material and a metal carbide. The carbon-based material refers to the composite of Li2S and a carbon-based material described above. The metal carbide refers to the composite of Li2S and a metal carbide described above.

[0153] The complex of Li2S and metal nitride includes a metal nitride. The metal nitride is, for example, a two-dimensional metal nitride. The two-dimensional metal nitride is, for example, M n+1 N n T x(M is a transition metal, T is a terminal group, T is O, OH and / or F, n=1, 2, or 3, and x is the number of terminal groups) is expressed as The surface of the two-dimensional metal nitride is terminated with O, OH and / or F.

[0154] The Li2S-containing composite may be, in particular, a composite of Li2S, a lithium salt, and a carbon-based material. The Li2S-containing composite may be, for example, a composite of Li2S, a lithium salt, and a fibrous carbon-based material.

[0155] The composite of Li2S, a lithium salt, and a carbon-based material may include, for example, 10 to 80 parts by weight of Li2S, 1 to 40 parts by weight of the lithium salt, and 1 to 20 parts by weight of the carbon-based material, relative to 100 parts by weight of the composite. The Li2S content included in the composite may be, for example, 10 to 80 parts by weight, 20 to 70 parts by weight, 30 to 60 parts by weight, or 40 to 60 parts by weight of LiS, relative to 100 parts by weight of the composite. The lithium salt content included in the composite may be, for example, 10 to 40 parts by weight, 15 to 40 parts by weight, 20 to 40 parts by weight, or 25 to 35 parts by weight of the lithium salt, relative to 100 parts by weight of the composite. The carbon-based material content included in the composite may be, for example, 1 to 20 parts by weight, 5 to 20 parts by weight, or 5 to 15 parts by weight of the carbon-based material, relative to 100 parts by weight of the composite. By having the composite having a composition of Li2S, lithium salt and carbon-based material in this range, a solid secondary battery (1) including the composite can provide further improved ionic conductivity and / or electronic conductivity.

[0156] A composite of Li2S, a carbon-based material, and a metal nitride includes a carbon-based material and a metal nitride. The carbon-based material refers to the composite of Li2S and a carbon-based material described above. The metal carbide refers to the composite of Li2S and a metal nitride described above.

[0157] The cathode active material layer (12) may additionally include, for example, a sulfide-based compound that is distinct from the cathode active material described above. The sulfide-based compound may be, for example, a compound containing a metal element other than Li and the element sulfur. The sulfide-based compound may be, for example, a compound containing a metal element belonging to Groups 1 to 14 of the Periodic Table of Elements having an atomic weight of 10 or more and the element sulfur. The sulfide-based compound may be, for example, FeS2, VS2, NaS, MnS, FeS, NiS, CuS, or a combination thereof. By the cathode active material layer additionally including a sulfide-based compound, the cycle characteristics of the solid secondary battery (1) may be further improved. The content of the sulfide-based compound included in the cathode active material layer (12) may be 10 wt% or less, 5 wt% or less, 3 wt% or less, or 1 wt% or less of the total weight of the cathode active material layer (12).

[0158] [Anode layer: solid electrolyte]

[0159] The positive electrode active material layer (12) may further include, for example, a solid electrolyte. The solid electrolyte may be, for example, a sulfide-based solid electrolyte. The solid electrolyte included in the positive electrode (10) may be the same as or different from the solid electrolyte included in the solid electrolyte layer (30). For more details on the solid electrolyte, refer to the section on the solid electrolyte layer (30).

[0160] The solid electrolyte included in the positive electrode active material layer (12) may have a smaller average D50 particle diameter than the solid electrolyte included in the solid electrolyte layer (30). For example, the average D50 particle diameter of the solid electrolyte included in the positive electrode active material layer (12) may be 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, or 20% or less of the average D50 particle diameter of the solid electrolyte included in the solid electrolyte layer (30). The average D50 particle diameter is, for example, a median particle diameter (D50). The median particle diameter (D50) is, for example, the size of particles corresponding to 50% of the cumulative volume, calculated from the side of particles having a small particle size in a size distribution of particles measured by laser diffraction.

[0161] The solid electrolyte may be included in an amount of 10 to 60 parts by weight, 10 to 50 parts by weight, 20 to 50 parts by weight, or 30 to 50 parts by weight, based on 100 parts by weight of the positive electrode active material layer (12). If the content of the solid electrolyte is excessively reduced, the internal resistance of the positive electrode may increase, thereby deteriorating the cycle characteristics of the secondary battery. If the content of the sulfide-based solid electrolyte is excessively increased, the energy density of the secondary battery (1) may be reduced.

[0162] [Anode layer: conductive material]

[0163] The cathode active material layer (12) may further include a conductive material. The conductive material may be, for example, a carbon-based conductive material, a metal-based conductive material, or a combination thereof. The carbon-based conductive material may be, for example, graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or a combination thereof, but is not limited thereto, and any material used as a carbon-based conductive material in the art may be used. The metal-based conductive material may be, for example, metal powder, metal fiber, or a combination thereof, but is not limited thereto, and any material used as a metal-based conductive material in the art may be used. The content of the conductive material included in the cathode active material layer (12) may be, for example, 1 wt% to 30 wt%, 1 wt% to 20 wt%, or 1 wt% to 10 wt% of the total weight of the cathode active material layer (12).

[0164] The cathode active material layer (12) includes a carbon-based material, and the carbon-based material may be disposed only in the composite cathode active material. The cathode active material layer (12) may not additionally include a separate carbon-based material other than the composite cathode active material including the carbon-based material. Since the cathode active material layer does not include a separate carbon-based material, the energy density of the cathode and the secondary battery (1) can be improved and the manufacturing process can be simplified.

[0165] [Anode layer: binder]

[0166] The positive electrode active material layer (12) may further include a binder. The binder may be, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc., but is not limited thereto, and any binder used in the relevant technical field may be used. The binder content included in the positive electrode active material layer (12) may be, for example, 1 wt% to 10 wt% of the total weight of the positive electrode active material layer (12). The binder may be omitted.

[0167] [Anode layer: Other additives]

[0168] The cathode active material layer (12) may further include additives such as fillers, coating agents, dispersants, and ion conductive aids in addition to the cathode active material, solid electrolyte, binder, and conductive agent described above.

[0169] As fillers, coating agents, dispersants, ion conductivity aids, etc. that the positive electrode active material layer (12) may include, known materials generally used in electrodes of solid secondary batteries (1) may be used.

[0170] [Anode layer: Anode current collector]

[0171] The positive electrode collector (11) uses a plate or foil made of, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof. The positive electrode collector (11) may be omitted. The thickness of the positive electrode collector (11) is, for example, 1 µm to 100 µm, 1 µm to 50 µm, 5 µm to 25 µm, or 10 µm to 20 µm.

[0172] The cathode current collector (11) may include, for example, a base film and a metal layer disposed on one or both sides of the base film. The base film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof. The base film may be, for example, an insulator. Since the base film includes an insulating thermoplastic polymer, when a short circuit occurs, the base film softens or liquefies, thereby blocking battery operation and suppressing a rapid increase in current. The metal layer may include, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), or an alloy thereof. The metal layer can act as an electrochemical fuse and be cut off in case of overcurrent to prevent a short circuit. The limit current and the maximum current can be controlled by adjusting the thickness of the metal layer. The metal layer can be plated or deposited on the base film. As the thickness of the metal layer decreases, the limit current and / or the maximum current of the positive electrode current collector (11) decreases, thereby improving the stability of the lithium battery in case of a short circuit. A lead tab can be added on the metal layer for connection to the outside. The lead tab can be welded to the metal layer or the metal layer / base film laminate by ultrasonic welding, laser welding, spot welding, etc. During welding, the base film and / or the metal layer melt, so that the metal layer can be electrically connected to the lead tab. In order to strengthen the welding of the metal layer and the lead tab, a metal chip can be added between the metal layer and the lead tab.The metal piece may be a thin piece of the same material as the metal of the metal layer. The metal piece may be, for example, a metal foil, a metal mesh, etc. The metal piece may be, for example, aluminum foil, copper foil, SUS foil, etc. After the metal piece is placed on the metal layer, the lead tab may be welded to the metal piece / metal layer laminate or the metal piece / metal layer / base film laminate. During welding, the base film, the metal layer, and / or the metal piece may melt, so that the metal layer or the metal layer / metal piece laminate may be electrically connected to the lead tab. A metal chip and / or a lead tab may be added to a portion of the metal layer. The base film may have a thickness of, for example, 1 to 50 μm, 1.5 to 50 μm, 1.5 to 40 μm, or 1 to 30 μm. When the base film has a thickness in this range, the weight of the electrode assembly can be more effectively reduced. The melting point of the base film may be, for example, 100 to 300°C, 100 to 250°C or less, or 100 to 200°C. Since the base film has a melting point within this range, the base film can be melted and easily bonded to the lead tab during the welding process of the lead tab. To improve the adhesion between the base film and the metal layer, a surface treatment such as corona treatment may be performed on the base film. The thickness of the metal layer may be, for example, 0.01 to 3 μm, 0.1 to 3 μm, 0.1 to 2 μm, or 0.1 to μm. Since the metal layer has a thickness within this range, conductivity can be maintained while ensuring the stability of the electrode assembly. The thickness of the metal piece may be, for example, 2 to 10 μm, 2 to 7 μm, or 4 to 6 μm. Since the metal piece has a thickness within this range, the connection between the metal layer and the lead tab can be performed more easily. By having this structure, the positive electrode collector (11) can reduce the weight of the positive electrode and consequently improve the energy density of the positive electrode and lithium battery.

[0173] [Anode layer: first inert member]

[0174] Referring to FIGS. 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 side of the positive electrode current collector. A first inactive member (40) is disposed on one side of the positive electrode (10). Referring to FIG. 8, the first inactive member (40) is disposed on one side of the positive electrode active material layer (12) and the positive electrode current collector (11). Referring to FIG. 9, the first inactive member (40) is disposed on one side of the positive electrode active material layer (12) and between the solid electrolyte layer (30) and the positive electrode current collector (11) facing the solid electrolyte layer (30). The first inactive member (40) is not disposed on one side of the positive electrode current collector (11).

[0175] By including the first inert member (40), cracking of the solid electrolyte layer (30) is prevented during the manufacture and / or charging and discharging of the solid secondary battery (1), thereby improving the cycle characteristics of the solid secondary battery (2). In the solid secondary battery (1) that does not include the first inert member (40), when the manufacture and / or charging and discharging of the solid secondary battery (1) is performed, uneven pressure is applied to the solid electrolyte layer (30) in contact with the positive electrode (10), which increases the possibility of cracking in the solid electrolyte layer (30), and thus causing a short circuit due to the growth of lithium metal through the cracks.

[0176] In the solid 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). Alternatively, in the solid secondary battery (1), the thickness of the first inert member (40) is substantially equal to the thickness of the positive electrode (10). Since the thickness of the first inert member (40) is equal to the thickness of the positive electrode (10), a uniform pressure is applied between the positive electrode (10) and the solid electrolyte layer (30), and the positive electrode (10) and the solid electrolyte layer (30) are sufficiently adhered to each other, so that the interfacial resistance between the positive electrode (10) and the solid electrolyte layer (30) can be reduced. In addition, since the solid electrolyte layer (30) is sufficiently sintered during the pressurized manufacturing process of the solid secondary battery (1), the internal resistance of the solid electrolyte layer (30) and the solid secondary battery (1) including the same is reduced.

[0177] The first inert member (40) surrounds the side surface of the positive electrode (10) and is in contact with the solid electrolyte layer (30). Since the first inert member (40) surrounds the side surface of the positive electrode (10) and is in contact with the solid electrolyte layer (30), cracks in the solid electrolyte layer (30) that occur due to a pressure difference during the pressing process in the solid electrolyte layer (30) that does not come into contact with the positive electrode (20) can be effectively suppressed. The first inert member (40) surrounds the side surface of the positive electrode (10) and is separated from the negative electrode (20), more specifically, the first negative electrode active material layer (22). The 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, the possibility of a short circuit occurring due to physical contact between the positive electrode (10) and the first negative electrode active material layer (22) or a short circuit occurring due to overcharging of lithium, etc., is suppressed. For example, the first inert member (40) is disposed on one side of the positive electrode active material layer (12) and simultaneously disposed on one side of the positive electrode current collector (11), thereby more effectively suppressing the possibility of a short circuit occurring due to contact between the positive electrode current collector (11) and the negative electrode (20).

[0178] Referring to FIGS. 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 occurring 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), 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 contact the negative electrode (20). The first inert member (40) fills a space extending from, for example, one side of the anode (30) to the end of the solid electrolyte layer (30).

[0179] Referring to FIGS. 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 to 30%, 1 to 25%, 1 to 20%, 1 to 15%, 1 to 10%, or 1 to 5% of the width between one side of the positive electrode (10) and the other side opposite to the one side. If the width of the first inert member (40) is excessively large, the energy density of the solid secondary battery (1) is reduced. If the width of the first inert member (40) is excessively small, the effect of arranging the first inert member (40) is minimal.

[0180] The area of ​​the anode (10) is smaller than the area of ​​the solid electrolyte layer (30) in contact with the anode (10). The first inert member (40) is arranged to surround the side of the anode (10) to compensate for the area difference between the anode (10) and the solid electrolyte layer (30). By compensating for the difference between the area of ​​the anode (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 anode (10) and the area of ​​the first inert member (40) is equal to the area of ​​the solid electrolyte layer (30).

[0181] The area of ​​the anode (10) is, for example, less than 100%, 99% or less, 98% or less, 97% or less, 96% or less, or 95% or less of the area of ​​the solid electrolyte layer (30). The area of ​​the anode (10) is, for example, 50% to less than 100%, 50% to 99%, 55% to 98%, 60% to 97%, 70% to 96%, 80% to 95%, or 85% to 95% of the area of ​​the solid electrolyte layer (30).

[0182] If the area of ​​the positive electrode (10) is equal to or larger than the area of ​​the solid electrolyte layer (30), the possibility of a short circuit occurring due to physical contact between the positive electrode (10) and the first negative electrode active material layer (22) or due to overcharging of lithium increases. The area of ​​the positive electrode (10) is, for example, equal to the area of ​​the positive electrode active material layer (12). The area of ​​the positive electrode (10) is, for example, equal to the area (11) of the positive electrode current collector.

[0183] 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 anode (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 anode (10).

[0184] 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).

[0185] As used herein, “same” area, length, width, thickness, and / or shape includes all instances of having “substantially the same” area, length, width, thickness, and / or shape, except where the area, length, width, thickness, and / or shape are intentionally different from each other. “Same” area, length, width, and / or thickness includes a range where the unintentional difference in the area, length, width, and / or thickness of the compared objects is, for example, less than 3%, less than 2%, less than 1%, less than 0.5%, or less than 0.1%.

[0186] 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).

[0187] The first inert member (40) may be a gasket. By using a gasket as the first inert member (40), cracks in the solid electrolyte layer (30) caused by a pressure difference during the pressing process can be effectively suppressed.

[0188] The first inert member (40) has, for example, a single-layer structure. Alternatively, although not shown in the drawing, the first inert member (40) may have a multi-layer structure. In the first inert member (40) having a multi-layer structure, each layer may have a different composition. The first inert member having a multi-layer structure may have, for example, a two-layer structure, a three-layer structure, a four-layer structure, or a five-layer structure. The first inert member (40) having a multi-layer structure may include, for example, one or more adhesive layers and one or more support layers. The adhesive layer effectively prevents, for example, a separation between the positive electrode (10) and the solid electrolyte layer (30) due to a change in the volume of the positive electrode (10) that occurs during the charge / discharge process of the solid secondary battery (10), and improves the film strength of the first inert member (40) by providing a bonding force between the support layer and other layers. The support layer provides support to the first inert member (40), prevents unevenness of pressure applied to the solid electrolyte layer (30) during the pressurization process or the charge / discharge process, and prevents deformation of the shape of the solid secondary battery (1) being manufactured.

[0189] The first inert member (40) is, for example, a flame-retardant inert member. The flame-retardant inert member prevents thermal runaway and ignition of the solid secondary battery (1) by providing flame retardancy. Consequently, the safety of the solid secondary battery (1) is further enhanced. The flame-retardant inert member prevents deterioration of the solid secondary battery (1) by absorbing residual moisture within the solid secondary battery (1), thereby improving the lifespan characteristics of the solid secondary battery (1).

[0190] The flame-retardant inert member includes, for example, a matrix and a filler. The matrix includes, for example, a substrate and a reinforcing material. The matrix includes, for example, a fibrous substrate and a fibrous reinforcing material. Since the matrix includes the substrate, the matrix can have elasticity. Therefore, the matrix can effectively accommodate volume changes during charging and discharging of the solid secondary battery (1) and can be arranged at various positions. The substrate included in the matrix includes, for example, a first fibrous material. Since the substrate includes the first fibrous material, the volume changes of the positive electrode (30) occurring during the charging and discharging process of the solid secondary battery (1) can be effectively accommodated and deformation of the inert member (40) due to the volume changes of the positive electrode (30) can be effectively suppressed. The first fibrous material is, for example, a material having an aspect ratio of 5 or more, 20 or more, or 50 or more. The first fibrous material is, for example, a material having an aspect ratio of 5 to 1000, 20 to 1000, or 50 to 1000. The first fibrous material is, for example, an insulating material. Since the first fibrous material is an insulating material, a short circuit between the positive electrode (30) and the negative electrode (20) caused by lithium dendrites, etc., generated during the charge and discharge process of the solid secondary battery (1) can be effectively prevented. The first fibrous material includes, for example, at least one selected from pulp fibers, insulating polymer fibers, and ion-conductive polymer fibers. The strength of the matrix is ​​improved by the inclusion of a reinforcing material in the matrix. Therefore, the matrix can prevent excessive volume change during charge and discharge of the solid secondary battery (1) and deformation of the solid secondary battery. The reinforcing material included in the matrix includes, for example, a second fibrous material. Since the reinforcing material includes the second fibrous material, the strength of the matrix can be increased more uniformly. The second fibrous material is, for example, a material having an aspect ratio of 3 or more, 5 or more, or 10 or more.The first fibrous material is, for example, a material having an aspect ratio of 3 to 100, 5 to 100, or 10 to 100. The second fibrous material is, for example, a flame-retardant material. Since the second fibrous material is a flame-retardant material, it can effectively suppress ignition due to thermal runaway that occurs during the charging / discharging process of the solid secondary battery (1) or due to external impact. The second fibrous material is, for example, glass fiber, metal oxide fiber, ceramic fiber, etc.

[0191] The flame-retardant inert member includes a filler in addition to a matrix. The filler may be disposed within the matrix, on the surface of the matrix, or on both the interior and the surface. The filler is, for example, an inorganic material. The filler included in the flame-retardant inert member is, for example, a moisture getter. The filler removes moisture remaining in the solid secondary battery (1) by adsorbing moisture, for example, at a temperature below 100°C, thereby preventing deterioration of the solid secondary battery (1). In addition, when the temperature of the solid secondary battery (1) increases to 150°C or higher due to thermal runaway occurring during the charge / discharge process of the solid secondary battery (1) or an external impact, the filler releases the adsorbed moisture, thereby effectively suppressing ignition of the solid secondary battery (1). That is, the filler is, for example, a flame retardant. The filler is, for example, a metal hydroxide having moisture adsorption properties. The metal hydroxide contained in the filler is, for example, Mg(OH)2, Fe(OH)3, Sb(OH)3, Sn(OH)4, TI(OH)3, Zr(OH)4, Al(OH)3, or a combination thereof. The content of the filler contained in the flame-retardant inert member is, for example, 10 to 80 parts by weight, 20 to 80 parts by weight, 30 to 80 parts by weight, 40 to 80 parts by weight, 50 to 80 parts by weight, 60 to 80 parts by weight, or 65 to 80 parts by weight, based on 100 parts by weight of the flame-retardant inert member.

[0192] The flame-retardant inert member may further comprise, for example, a binder. The binder may comprise, for example, a curable polymer or a non-curable polymer. A curable polymer is a polymer that cures by heat and / or pressure. A curable polymer is, for example, a solid at room temperature. The flame-retardant inert member may comprise, for example, a heat-pressure curable film and / or a cured product thereof. An example of a heat-pressure curable polymer is TSA-66 from Toray.

[0193] The flame-retardant inert member may additionally include other materials in addition to the above-described substrate, reinforcing material, filler, and binder. The flame-retardant inert member may further include one or more selected from among paper, an insulating polymer, an ion-conducting polymer, an insulating inorganic material, an oxide-based solid electrolyte, and a sulfide-based solid electrolyte. The insulating polymer may be, for example, an olefin-based polymer such as polypropylene (PP) or polyethylene (PE).

[0194] The density of the substrate or the density of the reinforcing material included in the flame-retardant inert member may be, for example, 10% to 300%, 10% to 150%, 10% to 140%, 10% to 130%, or 10% to 120% of the density of the positive electrode active material included in the positive electrode active material layer (12).

[0195] The first inert member (40) is a member that does not contain an electrochemically active material, for example, an electrode active material. The electrode active material is a material that absorbs / releases lithium. The first inert member (40) is a member made of a material other than the electrode active material and used in the relevant technical field.

[0196]

[0197] [Cathode layer]

[0198] [Cathode layer: negative electrode active material]

[0199] Referring to FIGS. 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.

[0200] The negative electrode active material included in the first negative electrode active material layer (22) is, for example, a negative electrode material that can form an alloy or compound with lithium.

[0201] The negative electrode active material included in the first negative electrode active material layer (22) has, for example, a particle form. The average particle diameter of the negative electrode active material having a particle form is, for example, 4 ㎛ or less, 3 ㎛ or less, 2 ㎛ or less, 1 ㎛ or less, 500 nm or less, 300 nm or less, or 100 nm or less. The average particle diameter of the negative electrode active material having a particle form is, for example, 10 nm to 4 ㎛, 10 nm to 3 ㎛, 10 nm to 2 ㎛, 10 nm to 1 ㎛, 10 nm to 500 nm, 10 nm to 300 nm, or 10 nm to 100 nm. When the negative electrode active material has an average particle diameter in this range, reversible absorption and / or desorption of lithium can be facilitated during charge and discharge. The average particle size of the negative electrode active material is, for example, the median diameter (D50) measured using a laser particle size distribution meter.

[0202] The negative electrode active material included in the first negative electrode active material layer (22) includes, for example, at least one selected from among a carbon-based negative electrode active material and a metal or metalloid negative electrode active material.

[0203] Carbon-based negative electrode materials include, for example, amorphous carbon, crystalline carbon, porous carbon, or a combination thereof.

[0204] The carbon-based negative electrode material is, in particular, amorphous carbon. Amorphous carbon includes, but is not limited to, carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), and graphene, and any material classified as amorphous carbon in the relevant technical field is acceptable. Amorphous carbon is carbon that has no crystallinity or very low crystallinity, and is distinguished from crystalline carbon or graphite-based carbon.

[0205] The carbon-based negative electrode active material may be, for example, porous carbon. The porous carbon has a pore volume of, for example, 0.1 cc / g to 10.0 cc / g, 0.5 cc / g to 5 cc / g, or 0.1 cc / g to 1 cc / g. The porous carbon has an average pore diameter of, for example, 1 nm to 50 nm, 1 nm to 30 nm, or 1 nm to 10 nm. The porous carbon has a BET surface area of, for example, 100 m 2 / g to 3000 m 2 / g is.

[0206] The metal or metalloid negative electrode active material includes, but is not limited to, one or more selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn), and any metal or metalloid negative electrode active material that forms an alloy or compound with lithium in the relevant technical field may be used. For example, nickel (Ni) does not form an alloy with lithium and therefore is not a metal negative electrode active material.

[0207] The first negative electrode active material layer (22) includes a type of negative electrode active material among these negative electrode active materials, or includes a mixture of a plurality of different negative electrode active materials. For example, the first negative electrode active material layer (22) includes only amorphous carbon, or includes at least one selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). Alternatively, the first negative electrode active material layer (22) includes a mixture of amorphous carbon and at least one selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). The mixing ratio of the mixture of amorphous carbon and gold, etc., is a weight ratio, for example, 99:1 to 1:99, 10:1 to 1:2, 5:1 to 1:1, or 4:1 to 2:1, but is not necessarily limited to this range and is selected according to the required characteristics of the solid secondary battery (1). When the negative electrode active material has this composition, the cycle characteristics of the solid secondary battery (1) are further improved.

[0208] The negative electrode active material included in the first negative electrode active material layer (22) includes, for example, a mixture of first particles made of amorphous carbon and second particles made of a metal or a metalloid. The metal or metalloid includes, for example, gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). Alternatively, the metalloid is a semiconductor. The content of the second particles is 1 to 99 wt%, 1 to 60 wt%, 8 to 60 wt%, 10 to 50 wt%, 15 to 40 wt%, or 20 to 30 wt% based on the total weight of the mixture. When the second particles have a content in this range, the cycle characteristics of, for example, a solid secondary battery (1) are further improved.

[0209] Alternatively, the first negative electrode active material layer (22) includes a composite negative electrode active material. The composite negative electrode active material may include, for example, a carbon-based support and a metal-based negative electrode active material supported on the carbon-based support. Since the composite negative electrode active material has such a structure, the metal-based negative electrode active material can be prevented from being localized within the first negative electrode active material layer and a uniform distribution can be achieved. As a result, the cycle characteristics of the solid secondary battery (1) including the first negative electrode active material layer (22) are further improved.

[0210] The metal-based negative electrode active material supported on the carbon-based support includes, for example, a metal, a metal oxide, a composite of a metal and a metal oxide, or a combination thereof. The metal includes, for example, gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), tellurium (Te), and zinc (Zn). The metal oxide includes, for example, gold (Au) oxide, platinum (Pt) oxide, palladium (Pd) oxide, silicon (Si) oxide, silver (Ag) oxide, aluminum (Al) oxide, bismuth (Bi) oxide, tin (Sn) oxide, tellurium (Te) oxide, and zinc (Zn) oxide. The metal oxide includes, for example, Au x O y (0 <x≤2, 0<y≤3), Pt x O y (0 <x≤1, 0<y≤2), Pd x O y (0 <x≤1, 0<y≤1), Si x O y (0 <x≤1, 0<y≤2), Ag x O y (0 <x≤2, 0<y≤1), Al x O y (0 <x≤2, 0<y≤3), Bi x O y (0 <x≤2, 0<y≤3), Sn x O y (0 <x≤1, 0<y≤2), Te x O y(0 <x≤1, 0<y≤3), Zn x The y (0 <x≤1, 0<y≤1) 또는 이들의 조합을 포함할 수 있다. 금속과 금속산화물의 복합체는 예를 들어 Au와 Au x The y (0 <x2, 0<y3)의 복합체, Pt와 Pt x The y (0 <x≤1, 0<y≤2)의 복합체, Pd와 Pd x The y (0 <x≤1, 0<y≤1)의 복합체, Si와 Si x The y (0 <x≤1, 0<y≤2)의 복합체, Ag 와 Ag x The y (0 <x≤2, 0<y≤1)의 복합체, Al과 Al x The y (0 <x≤2, 0<y≤3)의 복합체, Bi와 Bi x The y (0 <x≤2, 0<y≤3)의 복합체, Sn과 Sn x The y (0 <x≤1, 0<y≤2)의 복합체, Te과 Te x The y (0 <x≤1, 0<y≤3), Zn과 Zn x The y (0 <x≤1, 0<y≤1)의 복합체, 또는 이들의 조합을 포함할 수 있다.

[0211] The carbonaceous support is, for example, amorphous carbon. Amorphous carbon includes, but is not limited to, carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), graphene, activated carbon, carbon nanofibers (CNF), carbon nanotubes (CNT), etc., and any material classified as amorphous carbon in the relevant technical field is possible. Amorphous carbon is carbon that has no crystallinity or very low crystallinity, and is distinguished from crystalline carbon or graphite carbon. Carbonaceous materials are, for example, carbonaceous negative electrode active materials.

[0212] The composite negative electrode active material may have, for example, a particle form. The particle size of the composite negative electrode active material having a particle form is, for example, 10 nm to 4 ㎛, 10 nm to 1 ㎛, 10 nm to 500 nm, 10 nm to 200 nm, or 10 nm to 100 nm. When the composite negative electrode active material has a particle size in this range, reversible absorption and / or desorption of lithium may be facilitated during charge and discharge. The metal-based negative electrode active material supported on the support may have, for example, a particle form. The particle size of the metal-based negative electrode active material may be, for example, 1 nm to 200 nm, 1 nm to 150 nm, 5 nm to 100 nm, or 10 nm to 50 nm. The carbon-based support may have, for example, a particle form. The particle size of the carbon-based support may be, for example, 10 nm to 2 ㎛, 10 nm to 1 ㎛, 10 nm to 500 nm, 10 nm to 200 nm, or 10 nm to 100 nm. By having a particle size in this range, the carbon-based support can be more uniformly arranged within the first negative electrode active material layer. The carbon-based support may be, for example, nanoparticles having a particle size of 500 nm or less. The particle sizes of the composite negative electrode active material, the particle sizes of the metal-based negative electrode active material, and the particle sizes of the carbon-based support are, for example, average particle sizes. The average particle size is, for example, the median diameter (D50) measured using a laser particle size distribution analyzer. Alternatively, the average particle size may be determined automatically using software, for example, from an electron microscope image, or manually by a manual method.

[0213] [Cathode layer: binder]

[0214] The binder included in the first negative electrode active material layer (22) is, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, etc., but is not necessarily limited thereto and any binder used in the relevant technical field may be used. The binder may be composed of a single binder or a plurality of different binders.

[0215] Since the first negative electrode active material layer (22) includes a binder, the first negative electrode active material layer (22) is stabilized on the negative electrode current collector (21). In addition, cracking of the first negative electrode active material layer (22) is suppressed despite changes in the volume and / or relative position of the first negative electrode active material layer (22) during the charge and discharge process. For example, if the first negative electrode active material layer (22) does not include a binder, the first negative electrode active material layer (22) can be easily separated from the negative electrode current collector (21). As the first negative electrode active material layer (22) is detached from the negative electrode current collector (21), the possibility of a short circuit occurring increases at the exposed portion of the negative electrode current collector (21) due to the negative electrode current collector (21) coming into contact with the solid electrolyte layer (30). The first negative electrode active material layer (22) is manufactured by, for example, applying a slurry in which the material constituting the first negative electrode active material layer (22) is dispersed onto the negative electrode current collector (21) and drying the slurry. By including a binder in the first negative electrode active material layer (22), stable dispersion of the negative electrode active material in the slurry is possible. For example, when applying the slurry onto the negative electrode current collector (21) by screen printing, it is possible to suppress clogging of the screen (for example, clogging by aggregates of the negative electrode active material).

[0216] [Cathode layer: Other additives]

[0217] The first negative electrode active material layer (22) may further include additives used in conventional solid secondary batteries (1), such as fillers, coating agents, dispersants, and ion conductive aids.

[0218] [Cathode layer: solid electrolyte]

[0219] The first negative electrode active material layer (22) may further include a solid electrolyte. The solid electrolyte may be, for example, a material selected from among the solid electrolytes included in the solid electrolyte layer (30). The solid electrolyte included in the first negative electrode active material layer (22) may act as a reaction site where lithium metal formation begins within the first negative electrode active material layer (22), as a space where the formed lithium metal is stored, or as a path for transferring lithium ions. The solid electrolyte may be omitted.

[0220] In the first negative electrode active material layer (22), the content of the solid electrolyte may be high, for example, in an area adjacent to the solid electrolyte layer (30), and low, for example, in an area adjacent to the negative electrode current collector (21). In the first negative electrode active material layer (22), the solid electrolyte may have a concentration gradient in which the concentration decreases, for example, from an area adjacent to the solid electrolyte layer (30) to an area adjacent to the negative electrode current collector (21).

[0221] [Cathode layer: first cathode active material layer]

[0222] The initial charge capacity of the first negative electrode active material layer may be, 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.

[0223] The ratio (B / A) of the initial charge capacity (B) of the first negative electrode active material layer (22) and the initial charge capacity (A) of the positive electrode active material layer is 0.005 to 0.45. The initial charge capacity of the positive electrode active material layer (12) is the first open circuit voltage (1 st Li / Li from open circuit voltage) +It is determined by charging up to the maximum charging voltage. The initial charging capacity of the first negative electrode active material layer (22) is determined by charging up to the maximum charging voltage. The initial charging capacity of the first negative electrode active material layer (22) is determined by charging up to the maximum charging voltage. nd Li / Li from open circuit voltage) + It is determined at a charge of up to 0.01 V for the cathode active material. The maximum charge voltage is determined depending on the type of cathode active material. The maximum charge voltage can be, for example, 1.5 V, 2.0 V, 2.5 V, 3.0 V, 3.5 V, 4.0 V, 4.2 V, or 4.3 V. For example, the maximum charge voltage of Li2S or Li2S composite is Li / Li + can be 2.5 V for Li2S or Li2S complex. For example, the maximum charging voltage of Li / Li +It can be 3.0 V for. The ratio (B / A) of the initial charge capacity (B) of the first negative electrode active material layer (22) to the initial charge capacity (A) of the positive electrode active material layer is, for example, 0.01 to 0.45, 0.01 to 0.4, 0.01 to 0.3, 0.01 to 0.2, or 0.05 to 0.1. The initial charge capacity (mAh) of the positive electrode active material layer (12) is obtained by multiplying the charge capacity density (charge specific capacity) (mAh / g) of the positive electrode active material by the mass (g) of the positive electrode active material in the positive electrode active material layer (12). When several types of positive electrode active materials are used, the charge capacity density × mass value is calculated for each positive electrode active material, and the sum of these values ​​is the initial charge capacity of the positive electrode active material layer (12). The initial charge capacity of the first negative electrode active material layer (22) is also calculated in the same way. The initial charge capacity of the first negative electrode active material layer (22) is obtained by multiplying the charge capacity density (mAh / g) of the negative electrode active material by the mass of the negative electrode active material in the first negative electrode active material layer (22). When several types of negative electrode active materials are used, the charge capacity density Х mass value is calculated for each negative electrode active material, and the sum of these values ​​is the initial charge capacity of the first negative electrode active material layer (22). The charge capacity density of each of the positive electrode active material and the negative electrode active material can be measured using a solid half-cell using lithium metal as a counter electrode. The initial charge capacity of each of the positive electrode active material layer (12) and the first negative electrode active material layer (22) is obtained by multiplying the charge capacity density (mAh / g) of the negative electrode active material by the mass value of the negative electrode active material in the first negative electrode active material layer (22). 2 can be directly measured using a solid-state half-cell. For the positive electrode, the measurement is made from the first open circuit voltage (OCV) to the maximum charge voltage, e.g., 3.0 V (vs. Li / Li +) can be performed for an operating voltage of up to 0.01 V for the cathode, for example, lithium metal, from the second open circuit voltage (OCV). For example, a solid-state half-cell having a cathode active material layer can measure a current of 0.1 mA / cm from the first open circuit voltage to 3.0 V. 2 The solid half-cell having the first negative active material layer is charged with a constant current of 0.1 mA / cm from the second open circuit voltage to 0.01 V. 2 It can be charged with a constant current. The current density during constant current charging is, for example, 0.2 mA / cm 2 , or 0.5 mA / cm 2 A solid-state battery having a positive electrode active material layer can be charged from a first open circuit voltage to, for example, 2.5 V, 2.0 V, 3.5 V, or 4.0 V. The maximum charge voltage of the positive electrode active material layer can be determined by the maximum voltage of the battery that satisfies the safety conditions according to JISC8712:2015 of the Japanese Standards Association.

[0224] If the initial charge capacity of the first negative electrode active material layer (22) is too small, the thickness of the first negative electrode active material layer (22) becomes very thin, so that lithium dendrites formed between the first negative electrode active material layer (22) and the negative electrode current collector (21) during repeated charge / discharge processes collapse the first negative electrode active material layer (22), making it difficult to improve the cycle characteristics of the solid secondary battery (1). If the charge capacity of the first negative electrode active material layer (22) increases excessively, the energy density of the solid secondary battery (1) decreases and the internal resistance of the solid 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 secondary battery (1).

[0225] The thickness of the first negative electrode active material layer (22) is, for example, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 5% or less of the thickness of the positive electrode active material layer (12). The thickness of the first negative electrode active material layer (22) is, for example, 1 to 50%, 1 to 40%, 1 to 30%, 1 to 20%, 1 to 10%, or 1 to 5% of the thickness of the positive electrode active material layer (12). The thickness of the first negative electrode active material layer (22) is, for example, 1 µm to 20 µm, 2 µm to 15 µm, or 3 µm to 10 µm. If the thickness of the first negative electrode active material layer (22) is too thin, lithium dendrites formed between the first negative electrode active material layer (22) and the negative electrode current collector (21) collapse the first negative electrode active material layer (22), making it difficult to improve the cycle characteristics of the solid secondary battery (1). If the thickness of the first negative electrode active material layer (22) increases excessively, the energy density of the solid secondary battery (1) decreases and the internal resistance of the solid 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 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.

[0226] [Cathode layer: second cathode active material layer]

[0227] Referring to FIG. 7, the solid secondary battery (1) further includes, after being charged, a second negative electrode active material layer (24) disposed, for example, between the negative electrode current collector (21) and the first negative electrode active material layer (22). The second negative electrode active material layer (24) is a metal layer containing lithium or a lithium alloy. The metal layer contains lithium or a lithium alloy. Therefore, since the second negative electrode active material layer (24) is a metal layer containing lithium, it functions as, for example, a lithium reservoir. The lithium alloy is, for example, a Li-Al alloy, a Li-Sn alloy, a Li-In alloy, a Li-Ag alloy, a Li-Au alloy, a Li-Zn alloy, a Li-Ge alloy, a Li-Si alloy, etc., but is not limited thereto, and any lithium alloy used in the art may be used. The second negative electrode active material layer (24) may be made of one of these alloys or lithium, or may be made of several types of alloys. The second negative electrode active material layer (24) is, for example, a plated layer. The second negative electrode active material layer (24) is deposited between the first negative electrode active material layer (22) and the negative electrode current collector (21), for example, during the charging process of a solid secondary battery (1).

[0228] The thickness of the second negative electrode active material layer (24) is not particularly limited, but is, for example, 1 ㎛ to 500 ㎛, 1 ㎛ to 200 ㎛, 1 ㎛ to 150 ㎛, 1 ㎛ to 100 ㎛, or 1 ㎛ to 50 ㎛. If the thickness of the second negative electrode active material layer (24) is too thin, it is difficult for the second negative electrode active material layer (24) to perform the role of a lithium reservoir. If the thickness of the second negative electrode active material layer (24) is too thick, the mass and volume of the solid secondary battery (1) may increase, and the cycle characteristics of the solid secondary battery (1) may rather deteriorate.

[0229] Alternatively, in the solid secondary battery (1), the second negative electrode active material layer (24) may be disposed between the negative electrode current collector (21) and the first negative electrode active material layer (22), for example, before assembling the solid secondary battery (1). When the second negative electrode active material layer (24) is disposed between the negative electrode current collector (21) and the first negative electrode active material layer (22) before assembling the solid secondary battery (1), the second negative electrode active material layer (24) acts as a lithium reservoir because it is a metal layer containing lithium. For example, a lithium foil may be disposed between the negative electrode current collector (21) and the first negative electrode active material layer (22) before assembling the solid secondary battery (1).

[0230] When the second negative electrode active material layer (24) is precipitated by charging after assembling the solid secondary battery (1), the energy density of the solid secondary battery (1) increases because the second negative electrode active material layer (24) is not included when assembling the solid secondary battery (1). When charging the solid secondary battery (1), the charging is performed in excess of the charging capacity of the first negative electrode active material layer (22). That is, the first negative electrode active material layer (22) is overcharged. At the beginning of charging, lithium is absorbed into the first negative electrode active material layer (22). The negative electrode active material included in the first negative electrode active material layer (22) forms an alloy or compound with the lithium ions that have moved from the positive electrode (10). When charging exceeds the capacity of the first negative electrode active material layer (22), for example, lithium is deposited on the back surface of the first negative electrode active material layer (22), that is, between the negative electrode current collector (21) and the first negative electrode active material layer (22), and a metal layer corresponding to the second negative electrode active material layer (24) is formed by the deposited lithium. The second negative electrode active material layer (24) is a metal layer mainly composed of lithium (i.e., metallic lithium). This result is obtained, for example, by the negative electrode active material included in the first negative electrode active material layer (22) including a material that forms an alloy or compound with lithium. During discharge, lithium in the first negative electrode active material layer (22) and the second negative electrode active material layer (24), that is, the metal layer, is ionized and moves toward the positive electrode (10). Therefore, it is possible to use lithium as the negative electrode active material in a solid secondary battery (1). In addition, since the first negative electrode active material layer (22) covers the second negative electrode active material layer (24), it functions as a protective layer for the second negative electrode active material layer (24), i.e., the metal layer, and at the same time, it suppresses the precipitation and growth of lithium dendrites. Accordingly, it suppresses short circuit and capacity reduction of the solid secondary battery (1), and consequently improves the cycle characteristics of the solid secondary battery (1).In addition, when the second negative electrode active material layer (24) is placed by charging after assembling the solid secondary battery (1), the negative electrode (20), i.e., the negative electrode current collector (21) and the first negative electrode active material layer (22) and the region between them are Li-free regions that do not contain lithium (Li) in the initial state or the state after complete discharge of the solid secondary battery (1).

[0231] [Cathode layer: negative electrode collector]

[0232] The negative electrode current collector (21) is composed of, for example, a material that does not react with lithium, i.e., does not form an alloy or a compound. The material constituting the negative electrode current collector (21) is, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni), but is not necessarily limited thereto, and any material that can be used as an electrode current collector in the relevant technical field can be used. The negative electrode current collector (21) may be composed of one type of the above-described metal, or may be composed of an alloy or a coating material of two or more types of metals. The negative electrode current collector (21) is, for example, in the form of a plate or foil.

[0233] Referring to FIG. 6, the solid 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 disposed 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. The element capable of forming an alloy with lithium includes, but is not limited to, gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, etc., and any element capable of forming an alloy with lithium in the art may be used. The thin film (23) is composed of one of these metals or an alloy of several types of metals. By placing the thin film (23) on one surface of the negative electrode current collector (21), for example, the deposition shape of the second negative electrode active material layer (24) deposited between the thin film (23) and the first negative electrode active material layer (22) becomes flatter, and the cycle characteristics of the solid secondary battery (1) can be further improved.

[0234] The thickness of the thin film (23) is, for example, 1 nm to 800 nm, 10 nm to 700 nm, 50 nm to 600 nm, or 100 nm to 500 nm. If the thickness of the thin film (23) is less than 1 nm, it may be difficult for the function of the thin film (23) to be exerted. If the thickness of the thin film (23) is excessively thick, the thin film (23) itself absorbs lithium, which reduces the amount of lithium precipitated from the negative electrode, thereby lowering the energy density of the solid-state battery and deteriorating the cycle characteristics of the solid-state secondary battery (1). The thin film (23) may be disposed on the negative electrode current collector (21) by, for example, a vacuum deposition method, a sputtering method, a plating method, or the like, but is not necessarily limited to these methods, and any method capable of forming the thin film (23) in the relevant technical field may be used.

[0235] Although not shown in the drawing, the negative electrode current collector (21) may include, for example, a base film and a metal layer disposed on one or both sides of the base film. The base film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof. The polymer may be an insulating polymer. Since the base film includes an insulating thermoplastic polymer, when a short circuit occurs, the base film may soften or liquefy, thereby blocking battery operation and suppressing a rapid increase in current. The metal layer may include, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), or an alloy thereof. The negative electrode current collector (21) may additionally include a metal piece and / or a lead tab. For more specific details regarding the base film, metal layer, metal chip, and lead tab of the negative electrode collector (21), refer to the positive electrode collector (11) described above. By having this structure, the negative electrode collector (21) can reduce the weight of the negative electrode, and consequently, improve the energy density of the negative electrode and lithium battery.

[0236] [Cathode layer: second inert member]

[0237] Referring to FIGS. 10 to 11, the solid secondary battery (1) further includes a second inactive member (50) disposed on the other surface of the negative electrode collector (21).

[0238] The second inert member (50) is distinguished from the first inert member (40) in that it has conductivity by additionally including a conductive material. The second inert member (50) is, for example, a conductive flame-retardant inert member.

[0239] The conductive material is, for example, graphite, carbon black, acetylene black, Ketjen black, Denka black, carbon fiber, carbon nanotube (CNT), graphene, metal fiber, metal powder, etc. The 25°C electronic conductivity of the second inert member (50) is, for example, 100 times or more, 1000 times or more, or 10000 times or more, of the 25°C electronic conductivity of the first inert member (40).

[0240] The second inert member (50) includes, for example, a matrix, a filler, and a conductive material. The matrix includes, for example, a substrate and a reinforcing material. The second inert member (50) may further include a filler, a binder, etc. The content of the conductive material included 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, based on 100 parts by weight of the second inert member (50).

[0241] The Young's modulus of the second inert member (50) is, for example, smaller than the elastic modulus of the negative electrode 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 elastic modulus of the negative electrode 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 elastic modulus of the negative electrode 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.

[0242] Since the second inert member (50) is conductive, it can function as a negative electrode current collector (21). In addition, since the second inert member (50) has a lower elastic coefficient 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). Consequently, the second inert member (50) can effectively alleviate the internal stress caused by the volume change of the solid secondary battery (1) during charging and discharging of the solid secondary battery (1), thereby improving the cycle characteristics of the solid secondary battery (1).

[0243] The thickness of the second inert member (50) is, for example, greater than the thickness of the first negative electrode active material layer (22). Since the second inert member (50) has a greater thickness than the first negative electrode active material layer (22), the volume change of the negative electrode layer (20) can be more effectively accommodated during charge and discharge. 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 ㎛ to 300 ㎛, 10 ㎛ to 300 ㎛, 50 ㎛ to 300 ㎛, or 100 ㎛ to 200 ㎛. If the thickness of the second inert member (50) is too thin, it may be difficult to provide the intended effect, and if the thickness of the second inert member (50) is too thick, the energy density of the solid secondary battery (1) may be reduced. The shape of the second inert member (50) is not particularly limited and may be selected according to the shape of the solid secondary battery (1). The second inert member (50) may be, for example, in the shape of a sheet, a rod, or a gasket. The second inert member (50) may be, for example, disposed on one side or both sides of one solid secondary battery (1). The second inert member (50) may be disposed, for example, between a plurality of stacked solid secondary batteries (1). The second inert member (50) may be disposed, for example, between each of the plurality of stacked solid secondary batteries (1), on the uppermost surface and / or the lowermost surface.

[0244] The present invention is explained in more detail through the following examples and comparative examples. However, the examples are intended to illustrate the present invention and are not intended to limit the scope of the present invention.

[0245] Example 1: Anode layer / first intermediate layer / sulfide solid electrolyte layer / second intermediate layer / cathode layer, thermosetting polymer gel electrolyte

[0246] (Manufacturing of composite cathode active materials)

[0247] Li2S and LiI were mixed at a weight ratio of 30:20. The mixture was mechanically milled using a ball mill to prepare a Li2S-LiI composite. The milling conditions were 25°C, 600 rpm for 10 h. The milling energy applied to the sample during milling was 20 G. Subsequently, the Li2S-LiI composite and carbon nanofibers (CNF) were mixed at a weight ratio of 50:10. The mixture was mechanically milled using a ball mill to prepare a Li2S-LiI-CNF composite. The milling conditions were 25°C, 600 rpm for 10 h. The milling energy applied to the sample during milling was 20 G. The Li2S-LiI-CNF composite was used as a composite cathode active material.

[0248] (Anode layer manufacturing)

[0249] The Li2S-LiI-CNF composite described above was prepared as a cathode active material. Li6PS5Cl, an argyrodite-type crystal (D50=1.0 μm, crystalline), was prepared as a solid electrolyte. PTFE was prepared as a binder. These materials were mixed in a weight ratio of composite cathode active material: solid electrolyte: binder = 60:40:1.2 to prepare a cathode mixture. The cathode mixture was obtained by dry mixing using a ball mill.

[0250] The positive electrode was manufactured by placing the positive electrode active material mixture on one side of a positive electrode current collector made of aluminum foil coated on one side and plate pressing at a pressure of 200 MPa for 10 minutes. The thickness of the positive electrode was approximately 120 μm. The thickness of the positive electrode active material layer was approximately 100 μm, and the thickness of the carbon-coated aluminum foil was approximately 20 μm. The areas of the positive electrode active material layer and the positive electrode current collector were the same.

[0251] (Cathode layer manufacturing)

[0252] A 10 ㎛ thick SUS foil was prepared as a negative electrode current collector. In addition, carbon black (CB) particles with a primary particle diameter of approximately 30 nm and silver (Ag) particles with an average particle diameter of approximately 60 nm were prepared as negative electrode active materials.

[0253] 4 g of a mixed powder containing carbon black (CB) and silver (Ag) particles in a weight ratio of 3:1 was placed in a container, and 4 g of an NMP solution containing 7 wt% PVDF binder (Kureha #9300) was added thereto to prepare a mixed solution. Then, a slurry was prepared by stirring the mixed solution while adding NMP little by little to the mixed solution. The prepared slurry was applied to a SUS sheet using a bar coater and dried in the air at 80°C for 10 minutes. The laminate thus obtained was vacuum-dried at 40°C for 10 hours. The dried laminate was dried at 5 ton·f / cm 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 manufactured by the above process. The thickness of the first negative electrode active material layer included in the negative electrode layer was approximately 15 ㎛. The areas of the first negative electrode active material layer and the negative electrode current collector were the same.

[0254] (Manufacturing of solid electrolyte layer)

[0255] Li6PS5Cl solid electrolyte in the form of argyrodite crystals (D 50=5.0 mm, crystalline), 1.5 parts by weight of an acrylic binder was added to 98.5 parts by weight of the solid electrolyte to prepare a mixture. Octyl acetate was added to the prepared mixture and stirred to prepare a slurry. The prepared slurry was applied 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. A solid electrolyte layer was prepared by the above process.

[0256] (First inert member)

[0257] A slurry containing pulp fiber (cellulose fiber), glass fiber, aluminum hydroxide (Al(OH)3), an acrylic binder, and a solvent was formed into a gasket shape, and then the solvent was removed to manufacture a flame-retardant inert member as a first inert member.

[0258] 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 ㎛.

[0259] Before placing the manufactured flame-retardant inert material on the solid electrolyte layer, moisture, etc. of the flame-retardant inert material was removed by vacuum heat treatment at 80°C for 5 hours.

[0260] (thermosetting electrolyte composition)

[0261] In a 20 L four-necked flask equipped with a stirrer, a thermometer, and a condenser, distilled water was added as a solvent, 2-(N,N-dimethylamino)ethyl acrylate, methyl acrylate, and acrylonitrile were added at a constant molar ratio, and a small amount of potassium persulfate was added as an initiator. The reaction was carried out for 18 hours while maintaining the temperature of the reaction solution to be stable between 65°C and 70°C. Then, after cooling to room temperature, the pH of the reaction solution was adjusted to 7 to 8 using a 25% ammonia aqueous solution, thereby producing an acrylic polymer, which is a poly(2-(N,N-dimethylamito)ethyl acrylate-co-methyl acrylate-co-acrylonitrile) copolymer represented by the following chemical formula A. The molar ratio of (2-(N,N-dimethylamito)ethyl acrylate, methyl acrylate, and acrylonitrile was 20:15:65. The weight average molecular weight of the acrylic binder was approximately 60,000 Dalton. The weight average molecular weight of the acrylic polymer was measured using gel permeation chromatography (GPC) as a relative value to a polystyrene standard sample.

[0262] <Chemical Formula A>

[0263]

[0264] LiPF6 (1.0 M) and LiTFSI (1.0 M) were dissolved in 94 g of a non-aqueous organic solvent containing ethylene carbonate (EC) and dimethyl carbonate (DMC) in a volume ratio of 15:85, and then 5.0 g of an acrylic polymer represented by the above chemical formula A was added to prepare a thermosetting electrolyte composition.

[0265] (Manufacturing of solid secondary batteries)

[0266] The thermosetting electrolyte composition described above was applied to one side of the solid electrolyte layer and the other side opposite to the one side.

[0267] Referring to Fig. 8, a solid electrolyte layer was placed on the negative electrode layer such that the first negative electrode active material layer was in contact with one surface of the solid electrolyte layer, and a positive electrode layer was placed on the other surface of the solid electrolyte layer. A laminate was prepared by placing a gasket surrounding the positive electrode layer and in contact with the solid electrolyte layer. The thickness of the gasket was approximately 120 ㎛. The above-described flame-retardant inert material was used as the gasket. The gasket was placed so as to be in contact with the side surface of the positive electrode layer and the solid electrolyte layer. The positive electrode layer was placed at the center of the solid electrolyte layer, and the gasket was placed so as to surround the positive electrode layer and extend to the end of the solid electrolyte layer. The area of ​​the positive electrode layer was approximately 90% of the area of ​​the solid electrolyte layer, and the gasket was placed on the entire remaining 10% of the area of ​​the solid electrolyte layer where the positive electrode layer was not placed.

[0268] Next, the laminate is 85 o The solid electrolyte layer was plate pressed and heat treated at a pressure of 2.5 MPa for 1 hour at C. This pressurization process sintered the solid electrolyte layer, thereby improving the battery characteristics. The thickness of the sintered solid electrolyte layer was approximately 45 ㎛. 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 that of the negative electrode layer.

[0269] In addition, the thermosetting composition was thermoset by heat treatment simultaneously with the pressurization treatment, thereby forming 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. In addition, the thermosetting composition diffused into the solid electrolyte layer during the pressurization process was thermoset, thereby forming a polymer gel electrolyte within the solid electrolyte layer as well.

[0270] The pressurized laminate was placed in a pouch and vacuum-sealed. Parts of the positive and negative current collectors were extended outside the sealed battery and used as positive and negative electrode terminals.

[0271] Example 2: Anode layer / first intermediate layer / sulfide solid electrolyte layer / cathode layer, thermosetting polymer gel electrolyte

[0272] A solid secondary battery was manufactured in the same manner as Example 1, except that the thermosetting electrolyte composition was applied only to one side of the solid electrolyte layer and the thermosetting electrolyte composition was not applied to the other side of the solid electrolyte layer.

[0273] A first intermediate layer (60) (polymer gel electrolyte layer) is disposed between the positive electrode layer and the solid electrolyte layer, but a second intermediate layer (70) is not disposed between the negative electrode layer and the solid electrolyte layer.

[0274] Example 3: Anode layer / sulfide solid electrolyte layer / second intermediate layer / cathode layer, thermosetting polymer gel electrolyte

[0275] A solid secondary battery was manufactured in the same manner as Example 1, except that the thermosetting electrolyte composition was not applied to one side of the solid electrolyte layer and the thermosetting electrolyte composition was applied only to the other side of the solid electrolyte layer.

[0276] The first intermediate layer (60) is not disposed between the positive electrode layer and the solid electrolyte layer, but the second intermediate layer (70) (polymer gel electrolyte layer) is disposed between the negative electrode layer and the solid electrolyte layer.

[0277] Example 4: Anode layer / first intermediate layer / sulfide solid electrolyte layer / second intermediate layer / cathode layer, high viscosity liquid electrolyte

[0278] A solid 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 side and the other side of the solid electrolyte layer, respectively, and the heat treatment process was omitted.

[0279] A liquid electrolyte containing an ionic liquid was prepared as follows.

[0280] LiPF6 (1.0 M) and LiTFSI (1.0 M) were dissolved in 65 g of a non-aqueous organic solvent containing ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 15:85, and then 35 g of an ionic liquid represented by the following chemical formula B was added to prepare a liquid electrolyte.

[0281] As an ionic liquid, 1-methyl-1-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide represented by the following chemical formula B was used.

[0282] The viscosity of the liquid electrolyte was 22.5 cps at 1 atm and 25 ℃.

[0283] <Chemical Formula B>

[0284]

[0285] Example 5: Anode layer / first intermediate layer / sulfide solid electrolyte layer / cathode layer, high viscosity liquid electrolyte

[0286] A solid secondary battery was manufactured in the same manner as Example 4, except that the liquid electrolyte containing an ionic liquid was applied only to one side of the solid electrolyte layer and the liquid electrolyte containing an ionic liquid was not applied to the other side of the solid electrolyte layer.

[0287] An ionic liquid-containing liquid electrolyte layer is placed between the anode layer and the solid electrolyte layer, but an ionic liquid-containing liquid electrolyte layer is not placed between the cathode layer and the solid electrolyte layer.

[0288] Example 6: Anode layer / sulfide solid electrolyte layer / second intermediate layer / cathode layer, high viscosity liquid electrolyte

[0289] A solid secondary battery was manufactured in the same manner as Example 4, except that the liquid electrolyte containing an ionic liquid was not applied to one side of the solid electrolyte layer, and the liquid electrolyte containing an ionic liquid was applied only to the other side of the solid electrolyte layer.

[0290] An ionic liquid-containing liquid electrolyte layer is not disposed between the anode layer and the solid electrolyte layer, but an ionic liquid-containing liquid electrolyte layer is disposed between the cathode layer and the solid electrolyte layer.

[0291] Example 7: Anode layer / first intermediate layer / sulfide solid electrolyte layer / second intermediate layer / cathode layer, cured polymer gel electrolyte

[0292] A solid secondary battery was manufactured in the same manner as in Example 1, except that a thermosetting polymer gel electrolyte was first placed on one side and the other side of the solid electrolyte layer before manufacturing the laminate by applying a thermosetting electrolyte composition to one side and the other side of the solid electrolyte layer and performing a heat treatment at 85°C for 2 hours.

[0293] Example 8: Anode layer / first intermediate layer / sulfide solid electrolyte layer / second intermediate layer / cathode layer, thermosetting polymer gel electrolyte, elastic sheet member

[0294] A solid secondary battery was manufactured in the same manner as in Example 1, except that a sheet-shaped conductive flame-retardant material having the same area and shape as the laminate was additionally placed on the outer surface of the negative electrode collector of the pressed laminate before placing the pressed laminate in a pouch, and vacuum-sealed to manufacture a solid secondary battery.

[0295] A 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.

[0296] A slurry containing pulp fibers (cellulose fibers), glass fibers, aluminum hydroxide (Al(OH)3), an acrylic binder, a conductive agent (Denka black), and a solvent was formed into a sheet shape and then dried to manufacture a flame-retardant inert member. The weight ratio of pulp fibers (cellulose fibers), glass fibers, aluminum hydroxide (Al(OH)3), an acrylic binder, and a conductive agent was 20:8:50:2:20. The thickness of the conductive flame-retardant inert member was 120 ㎛. The manufactured conductive flame-retardant inert member was heat-treated in a vacuum at 80°C for 5 hours before being placed on a negative electrode current collector to remove moisture, etc., from the conductive flame-retardant inert member.

[0297] Example 9: Anode layer / first intermediate layer / sulfide solid electrolyte layer / second intermediate layer / cathode layer, thermosetting polymer gel electrolyte, Ag-supported carbon

[0298] An all-solid-state secondary battery was manufactured in the same manner as Example 2, except that the silver particle-supported carbon black described below was used instead of the mixture of carbon black and silver particles as the negative electrode active material.

[0299] (Manufacture of carbon black loaded with silver particles)

[0300] Carbon black was dispersed in a 1.0 M sulfuric acid solution, stirred for 2 hours, filtered, and dried to prepare acid-treated carbon black.

[0301] 10 g of acid-treated carbon black was added to a mixed solvent of 1500 g of distilled water, 1500 g of ethanol, and 30 g of glycerol, and stirred, followed by adding 2 g of AgNO3 and stirring to prepare a mixed solution. The particle size of the carbon black was 80 nm. A reducing agent was added to the mixed solution to reduce and support silver ions on the carbon black. The carbon black supported with silver-containing particles was filtered, washed, and dried to prepare a composite negative electrode active material. Scanning electron microscope and XPS measurements confirmed that multiple silver-containing particles were supported on the carbon black particles. The silver-containing particles were silver particles, silver oxide (Ag2O) particles, and composite particles of silver (Ag) and silver oxide (Ag2O). The content of silver-containing particles included in the composite negative electrode active material was 5 wt%. The average particle size of the silver particles was 10 nm.

[0302]

[0303] Comparative Example 1: Anode layer / sulfide solid electrolyte layer / cathode layer, use of low-viscosity liquid electrolyte

[0304] A solid secondary battery was manufactured in the same manner as Example 1, except that a liquid electrolyte was applied to one side and the other side of the solid electrolyte layer, respectively, and the heat treatment process was omitted.

[0305] The liquid electrolyte was prepared as follows.

[0306] A liquid electrolyte was prepared by dissolving 1.0 M LiPF6 in 100 g of a non-aqueous organic solvent containing 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 ℃.

[0307] Comparative Example 2: Anode layer / sulfide solid electrolyte layer / cathode layer, no thermosetting electrolyte composition used

[0308] A solid secondary battery was manufactured in the same manner as Example 1, except that the thermosetting electrolyte composition was not applied to one side and the other side of the solid electrolyte layer, and the heat treatment process was also omitted.

[0309]

[0310] Reference Example 1: Lithium metal cathode

[0311] A solid secondary battery was manufactured in the same manner as in Example 1, except that a lithium metal foil having a thickness of 20 μm was used instead of the first negative electrode active material layer containing carbon black (CB) and silver (Ag) particles as the negative electrode active material layer.

[0312] Reference Example 2: First inert member not used (free)

[0313] A solid secondary battery was manufactured in the same manner as Example 1, except that a flame-retardant inert material (i.e., a gasket) was not used during the manufacture of the all-solid-state secondary battery.

[0314]

[0315] Evaluation Example 1: Life Characteristics Evaluation

[0316] The charge / discharge characteristics of the solid secondary batteries manufactured in Examples 1 to 8, Reference Examples 1 to 2, and Comparative Examples 1 to 2 were evaluated by the following charge / discharge test.

[0317] Charge and discharge tests were performed by placing the solid secondary battery in a constant temperature bath at 45°C.

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

[0319] The discharge capacity of the first cycle was taken as the standard capacity.

[0320] After the first cycle, charging and discharging were performed up to 150 cycles under the same conditions as the first cycle. Some of the measurement results are shown in Table 1 below.

[0321] The cycle count is the number of cycles required for the discharge capacity to decrease to 80% of the standard capacity after the first cycle. As the cycle count increases, it is considered that the battery has better life characteristics.

[0322] Number of Cycles [Times] Example 1 (Double-Sided Thermally Polymerized GPE Coated SE Film) 520 Example 2 (Anode-Side Thermally Polymerized GPE Coated SE Film) 415 Example 3 (Cathode-Side Thermally Polymerized GPE Coated SE Film) 380 Example 4 (Double-Sided High-Viscosity Electrolytic Jack Coated SE Film) 450 Example 5 (Anode-Side High-Viscosity Electrolyte Coated SE Film) 342 Example 6 (Cathode-Side High-Viscosity Electrolyte Coated SE Film) 310 Example 7 (Double-Sided GPE Coated SE Film, Pre-Polymerized) 420 Example 8 (Elastic Sheet Added to Anode) 540 Reference Example 1 (Li Metal Foil Used Instead of Ag-C Layer on Anode) 20 Comparative Example 1 (Double-Sided Low-Viscosity Electrolyte Coated SE Film) 150 Comparative Example 2 (Double-Sided Uncoated SE Film) 200

[0323] As shown in Table 1, the solid secondary batteries of Examples 1 to 8 had improved life characteristics compared to the solid secondary batteries of Reference Example 1 and Comparative Examples 1 to 2.

[0324] The solid secondary batteries of Examples 1 to 8 have improved life characteristics by more effectively accommodating changes in the volume of the positive electrode layer and / or the negative electrode layer during charge and discharge due to a decrease in the interfacial resistance between the solid electrolyte layer and the positive electrode layer and between the solid electrolyte layer and the negative electrode layer, a relative increase in the flexibility of the solid electrolyte layer itself, and suppression of pinhole formation. In addition, the life characteristics are improved by improving the 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, and by improving the uniformity of ionic conductivity. In addition, by reducing the contact area between the solid electrolyte layer and moisture, gas generation due to side reactions is suppressed, and a decrease in ionic conductivity is suppressed.

[0325] In the solid secondary battery of Example 7, the life characteristics were lowered compared to the solid secondary battery of Example 1 due to the limited diffusion of the polymer gel electrolyte into the solid electrolyte layer.

[0326] Although not shown in Table 1, the solid secondary battery of Example 9 showed improved life characteristics compared to the solid 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 secondary battery of Comparative Example 1 showed minimal effect of adding organic electrolyte compared to the high viscosity liquid electrolyte of Examples 4 to 6 by using a low viscosity liquid electrolyte.

[0327] Since the solid secondary battery of Comparative Example 2 does not include an organic electrolyte, the formation of pinholes in the solid electrolyte layer increases, and the occurrence of defects such as cracks in the solid electrolyte layer is promoted due to changes in the volume of the positive electrode layer and / or the negative electrode layer during charging and discharging, and the life characteristics are deteriorated due to the growth of lithium dendrites through these defects.

[0328] In the solid secondary battery of Reference Example 1, the life characteristics of the solid secondary battery were deteriorated due to accelerated deterioration such as cracking of the solid electrolyte layer caused by increased growth of lithium dendrites from the lithium metal negative electrode.

[0329] In the solid secondary battery of Reference Example 2, a short circuit occurred before the first cycle was completed, making it impossible to measure the life characteristics.

[0330]

[0331] Evaluation Example 2: High-Rate Characteristic Evaluation

[0332] The high-rate characteristics of the solid secondary batteries manufactured in Examples 1 to 8, Reference Example 1, and Comparative Examples 1 to 2 were evaluated by the following charge-discharge test. The charge-discharge test was performed by placing the solid secondary batteries in a constant temperature bath at 45°C.

[0333] The lithium batteries manufactured in Examples 1 to 8, Reference Example 1, and Comparative Examples 1 to 2 were charged at a constant current of 0.1 C rate at 45°C until the voltage reached 2.5 V (vs. Li), and then cut-off was achieved at a current of 0.05 C rate while maintaining 2.5 V in constant voltage mode. Subsequently, the batteries were discharged at a constant current of 0.1 C rate until the voltage reached 0.3 V (vs. Li) during discharge (formation cycle).

[0334] The lithium battery that had undergone the Mars cycle was charged at a constant current of 0.2 C rate at 45°C until the voltage reached 2.5 V (vs. Li). Subsequently, it was discharged at a constant current of 0.2 C rate until the voltage reached 0.3 V (vs. Li) (first cycle).

[0335] The lithium battery that had undergone the first cycle was charged at a constant current of 0.2 C rate at 45°C until the voltage reached 2.5 V (vs. Li). Subsequently, it was discharged at a constant current of 0.33 C rate until the voltage reached 0.3 V (vs. Li) (second cycle).

[0336] The lithium battery that had undergone the second cycle was charged at a constant current of 0.2 C rate at 45°C until the voltage reached 2.5 V (vs. Li). Subsequently, it was discharged at a constant current of 0.5 C rate until the voltage reached 0.3 V (vs. Li) (third cycle).

[0337] The lithium battery that had undergone the third cycle was charged at a constant current of 0.2 C rate at 45°C until the voltage reached 2.5 V (vs. Li). Subsequently, it was discharged at a constant current of 1.0 C rate until the voltage reached 0.3 V (vs. Li) (4th cycle).

[0338] In all charge / discharge cycles, a 10-minute pause was observed after each charge / discharge cycle. Some of the results of the room-temperature charge / discharge experiments are shown in Table 2 below. The high-rate characteristics are defined by the following mathematical equation (1).

[0339] <Mathematical Formula 1>

[0340] High-rate characteristic [%] = [Discharge capacity in the 4th cycle / Discharge capacity in the 1st cycle] Х 100

[0341] High rate characteristics (1C / 0.2C) [%] Example 1 (Double-sided thermally polymerizable GPE coated SE film) 96 Example 2 (Anode-side thermally polymerizable GPE coated SE film) 92 Example 3 (Cathode-side thermally polymerizable GPE coated SE film) 89 Example 4 (Double-sided high-viscosity electrolytic jack coated SE film) 94 Example 5 (Anode-side high-viscosity electrolyte coated SE film) 90 Example 6 (Cathode-side high-viscosity electrolyte coated SE film) 88 Example 7 (Double-sided GPE coated SE film, pre-polymerized) 90 Example 8 (Elastic sheet added to the cathode) 96 Reference Example 1 (Li metal used instead of Ag-C at the cathode) 95 Comparative Example 1 (Double-sided low-viscosity electrolyte coated SE film) 96 Comparative Example 2 (Double-sided uncoated SE film) 88

[0342] As shown in Table 2, the solid secondary batteries of Examples 1 to 8 had similar high-rate characteristics to the solid secondary batteries of Reference Example 1 and Comparative Examples 1 to 2.

[0343] [Explanation of symbols]

[0344] 1 Solid secondary battery 10 Cathode layer

[0345] 11. Cathode current collector 12. Cathode active material layer

[0346] 20 Cathode layer 21 Cathode current collector

[0347] 22 First negative electrode active material layer 30 Solid electrolyte layer

[0348] 30a solid electrolyte layer one side 30b solid electrolyte layer other side

[0349] 30c solid electrolyte layer inside 40 first inert member

[0350] 50 Second inert member 60 First intermediate layer

[0351] 70 Second intermediate layer 100 Organic electrolyte

[0352] 100a first organic electrolyte 100b second organic electrolyte

[0353] 100c third organic electrolyte

[0354] According to one aspect, by additionally arranging an organic electrolyte on the surface and / or inside of a 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 having improved life characteristics and high-rate characteristics.

Claims

1. Anode layer; cathode layer; a solid electrolyte layer disposed between the anode layer and the cathode layer; and It includes 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 above 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, and the positive electrode active material layer includes a Li2S-containing complex, A solid secondary battery, wherein the negative electrode layer includes a negative electrode current collector and a first negative electrode active material layer disposed on one surface of the negative electrode current collector.

2. In the first paragraph, it 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. A solid secondary battery, wherein the first intermediate layer comprises the first organic electrolyte and the second intermediate layer comprises the second organic electrolyte.

3. A solid secondary battery according to claim 1, wherein the polymer electrolyte comprises a polymer including a repeating unit having a thermopolymerizable functional group, a thermosetting product of the polymer, an oligomer including a repeating unit having a thermopolymerizable functional group, a thermosetting product of the oligomer, a monomer having a thermopolymerizable functional group, a thermosetting product of the monomer, an oligomeric ionic liquid, a polymeric ionic liquid, or a combination thereof.

4. A solid 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. A solid 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. In the first paragraph, the solid electrolyte layer further includes at least one of the first organic electrolyte and the 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, or having a first organic electrolyte concentration gradient that decreases from the above-mentioned one side toward the cathode layer, or having a second organic electrolyte concentration gradient that decreases from the surface toward the anode layer. A solid secondary battery having the first organic electrolyte concentration gradient and the second organic electrolyte concentration gradient simultaneously.

7. In the first paragraph, the solid electrolyte layer includes an inorganic solid electrolyte, A solid secondary battery, wherein the above-mentioned inorganic solid electrolyte comprises a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or a combination thereof.

8. In the 7th paragraph, the sulfide-based solid electrolyte is Li2S-P2S5, Li2S-P2S5-LiX, X is a halogen element, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n , m, n are positive numbers, Z is one of Ge, Zn or Ga, Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q , p, q are positive numbers, M is one of P, Si, Ge, B, Al, Ga In, Li 7-x PS 6-x Cl x , 0≤x≤2, Li 7-x PS 6-x Br x , 0≤x≤2, and Li 7-x PS 6-x I x , at least one selected from 0≤x≤2, The above sulfide-based solid electrolyte includes an argyrodite-type solid electrolyte, The above argyrodite-type solid electrolyte comprises at least one selected from Li6PS5Cl, Li6PS5Br and Li6PS5I, A solid secondary battery, wherein the density of the above argyrodite-type solid electrolyte is 1.0 to 2.0 g / cc.

9. A solid secondary battery according to claim 1, wherein the Li2S-containing complex comprises a complex of Li2S and a carbon-based material, a complex of Li2S and a carbon-based material and a solid electrolyte, a complex of Li2S and a solid electrolyte, a complex of Li2S and a carbon-based material and a lithium salt, a complex of Li2S and a lithium salt, a complex of Li2S and a metal carbide, a complex of Li2S and a carbon-based material and a metal carbide, a complex of Li2S and a metal nitride, a complex of Li2S and a carbon-based material and a metal nitride, or a combination thereof.

10. In the 9th paragraph, the lithium salt is a binary compound or a ternary compound, The above binary compound comprises LiI, LiBr, LiCl, LiF, LiH, Li2O, Li2Se, Li2Te, Li3N, Li3P, Li3As, Li3Sb, Li3Al2, LiB3 or a combination thereof, A solid secondary battery, wherein the ternary compound comprises Li3OCl, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiNO3, Li2CO3, LiBH4, Li2SO4, Li3BO3, Li3PO4, Li4NCl, Li5NCl2, Li3BN2 or a combination thereof.

11. In the 9th paragraph, the carbon-based material includes a fibrous carbon-based material, A solid secondary battery, wherein the above-mentioned fibrous carbon-based material includes a carbon nanostructure, and the carbon nanostructure includes carbon nanofibers, carbon nanotubes, carbon nanobelts, carbon nanorods, or a combination thereof.

12. In the first paragraph, the Li2S-containing complex includes a composite of Li2S, a lithium salt, and a carbon-based material, It comprises 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 for 100 parts by weight of the above complex, The above cathode active material layer further includes a sulfide-based solid electrolyte, A solid secondary battery, wherein a carbon-based material is disposed only in the Li2S-containing composite in the above-described positive electrode active material layer.

13. In the first paragraph, the first negative electrode active material layer includes a negative electrode active material and a binder, A solid secondary battery in which the negative electrode active material has a particle form and the average particle diameter of the negative electrode active material is 4 ㎛ or less.

14. In the first paragraph, the negative electrode active material includes at least one selected from a carbon-based negative electrode active material and a metal or metalloid negative electrode active material, The above carbon-based negative electrode active material includes amorphous carbon, crystalline carbon, porous carbon, or a combination thereof. A solid secondary battery, wherein the metal or metalloid negative electrode active material comprises gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), zinc (Zn), or a combination thereof.

15. In the first paragraph, the first negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes a mixture of first particles including amorphous carbon and second particles including a metal or a metalloid, A solid secondary battery, wherein the content of the second particles is 1 to 60 wt% based on the total weight of the mixture.

16. A solid secondary battery in the first paragraph, 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. In the first paragraph, the first negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes a carbon-based support; and a metal-based negative electrode active material supported on the carbon-based support. The above metal-based negative electrode active material includes a metal, a metal oxide, a complex of a metal and a metal oxide, or a combination thereof, The above metal-based negative electrode active material has a particle form, and the particle size of the metal-based negative electrode active material is 1 nm to 200 nm, The above carbon-based support has a particle shape, and the particle size of the carbonaceous material is 10 nm to 2 ㎛, Further comprising a second negative electrode active material layer disposed between the negative electrode current collector and the first negative electrode active material layer and between the negative electrode current collector and the electrolyte layer, A solid secondary battery, wherein the second negative electrode active material layer is a metal layer, and the metal layer includes lithium or a lithium alloy.

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

19. A solid secondary battery further comprising a first inert member disposed on one side of the positive electrode, wherein the first inert member comprises a flame-retardant inert member.

20. A solid secondary battery further comprising a second inert member disposed on the other surface of the negative electrode collector in the first paragraph, wherein the second inert member comprises a conductive flame-retardant inert member.

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