Secondary battery

Abstract

Disclosed is a secondary battery comprising: a cathode layer; an anode layer; and a flexible electrolyte layer disposed between the cathode layer and the anode layer, wherein: the cathode layer includes a cathode current collector and a cathode active material layer disposed on at least one surface of the cathode current collector; the anode layer includes an anode current collector and a first anode active material layer disposed on one surface of the anode current collector; and an initial charge capacity of the first anode active material layer is less than 50% of an initial charge capacity of the cathode active material layer.

Description

secondary batteries

[0001] It's about secondary batteries.

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

[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 using solid 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 secondary battery having improved cycle characteristics by placing a flexible electrolyte layer between the positive electrode layer and the negative electrode layer.

[0006] According to the implementation example

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

[0008] 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,

[0009] The above 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,

[0010] A secondary battery is provided, wherein the initial charge capacity of the first negative electrode active material layer is less than 50% of the initial charge capacity of the positive electrode active material layer.

[0011] According to one aspect, by arranging a flexible electrolyte layer between the positive electrode layer and the negative electrode layer, the interfacial resistance between the positive electrode layer and / or the negative electrode layer and the electrolyte layer is reduced, and cracking of the solid electrolyte layer, etc. is suppressed during the charge / discharge process, thereby providing a secondary battery having improved cycle characteristics.

[0012] Figure 1 is a cross-sectional view of a secondary battery according to an exemplary embodiment.

[0013] Figure 2 is a cross-sectional view of a secondary battery according to an exemplary embodiment.

[0014] Figure 3 is a cross-sectional view of a secondary battery according to an exemplary embodiment.

[0015] Figure 4 is a cross-sectional view of a secondary battery according to an exemplary embodiment.

[0016] Figure 5 is a schematic diagram of a secondary battery according to an exemplary embodiment.

[0017] Figure 6 is a schematic diagram of a secondary battery according to an exemplary embodiment.

[0018] Figure 7 is a schematic diagram of a secondary battery according to an exemplary embodiment.

[0019] Unless otherwise defined, all terms (including technical and scientific terms) used in this disclosure have the same meaning as commonly understood by those of ordinary skill in the art to which this disclosure pertains. Furthermore, terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning within the context of the relevant technology and this disclosure, and should not be interpreted in an idealized or overly formal sense.

[0020] Exemplary embodiments are described in this disclosure with reference to cross-sectional drawings that are schematic representations of idealized embodiments. As such, variations from the shapes depicted are to be expected, for example, as a result of manufacturing techniques and / or tolerances. Therefore, the embodiments described in this disclosure should not be construed as limited to the specific shapes of regions as depicted in this disclosure, but should encompass variations in shapes resulting from, for example, manufacturing. For example, regions depicted or described as flat may typically have rough and / or non-linear features. Moreover, angles depicted as sharp may be rounded. Therefore, the regions depicted in the drawings are schematic in nature, and their shapes are not intended to depict the precise shapes of the regions, nor are they intended to limit the scope of the claims.

[0021] This creative idea may be embodied in many different forms and should not be construed as limited to the embodiments described in this disclosure. These embodiments are provided so that this disclosure will be thorough and complete, and so that it will fully convey the scope of the creative idea to those skilled in the art. Like reference numerals in the drawings indicate like elements.

[0022] When a component is referred to as being "on" another component, it can be understood that it is either directly on top of the other component or that other components may be intervening between them. Conversely, when a component is referred to as being "directly on" another component, no intervening components are present.

[0023] Although terms such as "first," "second," "third," etc. may be used herein to describe various components, elements, regions, layers, and / or zones, these components, elements, regions, layers, and / or zones should not be limited by these terms. These terms are only used to distinguish one component, element, region, layer, or zone from another component, element, region, layer, or zone. Thus, a first component, element, region, layer, or zone described below may be referred to as a second component, element, region, layer, or zone without departing from the teachings of this disclosure.

[0024] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms including "at least one," unless the content clearly dictates otherwise. "At least one" should not be construed as limiting to the singular. As used herein, the term "and / or" includes any and all combinations of one or more of the listed items. The terms "comprises" and / or "comprising" as used in the detailed description specify the presence of stated features, regions, integers, steps, operations, components, and / or ingredients, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, components, ingredients, and / or groups thereof.

[0025] Spatially relative terms such as "below," "under," "lower," "above," "upper," and the like may be used herein to readily describe the relationship of one component or feature to another. It will be understood that spatially relative terms are intended to encompass different orientations of the device when in use or operation in addition to the orientations depicted in the drawings. For example, if the device in the drawings were turned over, a component described as "below" or "below" another component or feature would then be oriented "above" the other component or feature. Thus, the exemplary term "below" can encompass both the above and below orientations. The device may be arranged in other orientations (rotated 90 degrees or otherwise rotated), and the spatially relative terms used herein may be interpreted accordingly.

[0026] "Group" means a group in the periodic table of elements according to the International Union of Pure and Applied Chemistry ("IUPAC") Group 1-18 classification system.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] In the present disclosure, "viscosity" can be measured using a viscometer, for example, a rotational viscometer such as Brookfield's LV DV-II + Pro Viscometer (cone-plate type). The 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.

[0032] 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.

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

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

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

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

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

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

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

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

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

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

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

[0044] While specific implementations have been described, alternatives, modifications, variations, improvements, and substantial equivalents that are not currently anticipated or unforeseen may occur to the applicant or those skilled in the art. Accordingly, the appended claims, as filed and as amended, are intended to encompass all such alternatives, modifications, variations, improvements, and substantial equivalents.

[0045]

[0046] Hereinafter, secondary batteries according to exemplary implementation examples will be described in more detail.

[0047] [Secondary battery]

[0048] A secondary battery according to one embodiment includes a positive electrode layer; a negative electrode layer; and a flexible electrolyte layer disposed between the positive electrode layer and the negative electrode layer, wherein the positive electrode layer includes a positive electrode current collector and a positive electrode active material layer disposed on one or both surfaces (e.g., at least one surface of the positive electrode current collector) of the positive electrode current collector, and 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, and wherein an initial charge capacity of the first negative electrode active material layer is less than 50% of an initial charge capacity of the positive electrode active material layer.

[0049] By including a flexible electrolyte layer between the positive electrode layer and the negative electrode layer in the secondary battery, the interfacial resistance between the positive electrode layer and / or the negative electrode layer and the electrolyte layer is reduced, and the flexible electrolyte layer can more easily accommodate changes in the volume of the positive electrode layer and / or the negative electrode layer during charge and discharge of the secondary battery. The flexible electrolyte layer can prevent or reduce detachment of the positive electrode layer and / or the negative electrode layer from the electrolyte layer by having improved adhesion to the positive electrode layer and / or the negative electrode layer compared to an inflexible electrolyte layer due to its flexibility. The inflexible electrolyte layer is, for example, an inorganic solid electrolyte layer. Since the flexible electrolyte layer has a low possibility of cracking, etc., it can suppress or reduce non-uniformity of ionic conductivity within the flexible electrolyte layer during charge and discharge of the secondary battery. In contrast, the inflexible electrolyte layer can increase non-uniformity of ionic conductivity within the solid electrolyte layer compared to local cracking, etc. during charge and discharge of the secondary battery. The flexible electrolyte layer suppresses the formation of defects such as pinholes within the electrolyte layer, thereby more effectively suppressing or reducing the growth of lithium dendrites through such defects during the charge / discharge process of the secondary battery, and thereby the short circuit of the secondary battery. The flexible electrolyte layer provides improved moisture stability compared to the non-flexible electrolyte layer, thereby suppressing or reducing side reactions caused by moisture, such as gas generation, within the secondary battery. The reduction in ionic conductivity of the electrolyte layer within the secondary battery can be more effectively suppressed or reduced. Therefore, the cycle characteristics of the secondary battery can be further improved. For example, the high-rate characteristics and life characteristics of the secondary battery can be improved.

[0050] Referring to FIGS. 1 to 4, a secondary battery (1) includes a positive electrode layer (10); a negative electrode layer (20); and a flexible electrolyte layer (30) disposed between the positive electrode layer (10) and the negative electrode layer (20). The positive electrode layer (10) includes a positive electrode current collector (11) and a positive electrode active material layer (12) disposed on one or both surfaces of the positive electrode current collector (11) (e.g., at least one surface of the positive electrode current collector (11)). 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). The initial charge capacity of the first negative electrode active material layer (22) is less than 50% of the initial charge capacity of the positive electrode active material layer (12).

[0051]

[0052] [Electrolyte layer]

[0053] [Electrolyte layer: organic electrolyte]

[0054] Referring to FIGS. 1 to 4, the secondary battery (1) includes an electrolyte layer (30) disposed between a positive electrode layer (10) and a negative electrode layer (20). The electrolyte layer (30) has flexibility. The electrolyte layer (30) may include, for example, an organic electrolyte. The electrolyte layer (30) may be, for example, an organic electrolyte layer. The electrolyte layer (30) may not include, or may exclude, an inorganic electrolyte. The electrolyte layer (30) may not include, or may exclude, an inorganic electrolyte layer (30). The electrolyte layer (30) may not include, for example, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or a combination thereof. The flexibility of the electrolyte layer (30) may be further improved by the electrolyte layer (30) not including an inorganic solid electrolyte.

[0055] The electrolyte layer (30) may include, for example, a polymer electrolyte, a liquid electrolyte, or a combination thereof. The viscosity of the polymer electrolyte may be higher than that of the liquid electrolyte, for example. The viscosity of the liquid electrolyte may be, for example, 10 cps or more at 25°C and 1 atm. The liquid electrolyte may be, for example, a high-viscosity liquid electrolyte having a viscosity of 10 cps or more at 25°C and 1 atm.

[0056] 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.

[0057] 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.

[0058] The polymer gel electrolyte may include, for example, a liquid electrolyte and a polymer, or may include an organic solvent and a polymer having an ion-conducting functional group. The 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 be, for example, a polymer itself that is in a gel state without including a liquid.

[0059] The lithium salt used in the polymer electrolyte and / or liquid electrolyte is not 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.

[0060] 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.

[0061] 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 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] Monomers containing an imide group include, for example, cyclohexylmaleimide, isopropylmaleimide, N-cyclohexylmaleimide, and itaconimide.

[0069] 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.

[0070] The carboxylic acid anhydride group-containing monomer is, for example, an acid anhydride of the unsaturated polycarboxylic acid described above.

[0071] 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.

[0072] Oligomeric ionic liquids and polymeric ionic liquids can be, for example, the result of polymerization of ionic liquid monomers.

[0073] 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-. By polymerizing these ionic liquid monomers, an oligomeric ionic liquid or a polymeric ionic liquid can be obtained.

[0074] A liquid electrolyte is an electrolyte that is in a liquid state, for example, at 25°C and 1 atm. The viscosity of the liquid electrolyte may be, 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 may be, for example, 10 to 1000 cps, 15 to 500 cps, 20 to 300 cps, 25 to 200 cps, or 30 to 100 cps at 25°C 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, it can more effectively accommodate the volume change during charge and discharge of the positive electrode layer (10) and / or the negative electrode layer (10), more effectively reduce the interfacial resistance between the positive electrode layer (10), the negative electrode layer (10) and / or the electrolyte layer (30), and provide improved bonding force between the positive electrode layer (10), the negative electrode layer (10) and / or the electrolyte layer (30). As a result, the cycle characteristics of the secondary battery (1) can be improved. If the viscosity of the liquid electrolyte is excessively low, the above-described effect may be minimal.

[0075] The liquid electrolyte may include, for example, an ionic liquid.

[0076] The ionic liquid may be represented, for example, by one of the following chemical formulas 1 to 2:

[0077] <Chemical Formula 1> <Chemical Formula 2>

[0078]

[0079] In the above chemical formula 1, X1 is -N(R2)(R3)(R4) or -P(R2)(R3)(R4),

[0080] 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,

[0081] In the above chemical formula 2,

[0082] 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)=,

[0083] 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.

[0084] The ionic liquid may be represented, for example, by one of the following chemical formulas 3 to 4:

[0085] <Chemical Formula 3>

[0086]

[0087] <Chemical Formula 4>

[0088]

[0089] In the above chemical formula 3, Z is N or P,

[0090] 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,

[0091] In the above chemical formula 4, Z is N or P,

[0092] 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.

[0093] The ionic liquid may be represented, for example, by one of the following chemical formulas 5 to 10:

[0094] <Chemical Formula 5> <Chemical Formula 6> <Chemical Formula 7>

[0095]

[0096] <Chemical Formula 8> <Chemical Formula 9> <Chemical Formula 10>

[0097]

[0098] 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,

[0099] 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.

[0100] Ionic liquids contain anions, for example BF4 - , PF6 - , AsF6 - , SbF6 - , AlCl4 - , HSO4 - , ClO4 - , CH3SO3 - , CF3CO2- , Cl - , Br - , I - , SO4 2- , PF6 - , ClO4 - , 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.

[0101] 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.

[0102] 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. The molecular weight of the ionic liquid is, for example, 50 to 1000 Dalton, 100 to 900 Dalton, 100 to 800 Dalton, or 100 to 500 Dalton.

[0103] The electrolyte layer (30) may be, for example, a self-standing film. The electrolyte layer (30) may be, for example, a flexible self-standing film. Since the electrolyte layer (30) is a self-standing film, the secondary battery manufacturing process can be further simplified and the process efficiency of the secondary battery manufacturing process can be improved.

[0104] [Electrolyte layer: porous membrane]

[0105] The electrolyte layer (30) may further include a flexible porous membrane.

[0106] The flexible porous membrane may include, for example, polyolefin. Polyolefin has excellent short-circuit prevention properties and can also improve the stability of secondary batteries through its shutdown effect. For example, the flexible porous membrane may be a membrane made of a resin such as polyolefins such as polyethylene, polypropylene, polybutene, polyvinyl chloride, and mixtures or copolymers thereof, but is not necessarily limited thereto, and any porous membrane usable in the relevant technical field may be used. For example, a porous membrane made of a polyolefin resin; a porous membrane woven with polyolefin fibers; a non-woven fabric including polyolefin; an aggregate of insulating material particles, etc. may be used. For example, a porous membrane including polyolefin has excellent applicability of a binder solution for producing a coating layer formed on the porous membrane, and can increase the ratio of active materials in the battery by reducing the film thickness of the composite membrane, thereby increasing the capacity per unit volume.

[0107] For example, the polyolefin used as a material for the porous membrane may be a homopolymer, copolymer, or mixture thereof, such as polyethylene or polypropylene. The polyethylene may be low-density, medium-density, or high-density polyethylene, and from the perspective of mechanical strength, high-density polyethylene may be used. In addition, two or more types of polyethylene may be mixed for the purpose of providing flexibility. The polymerization catalyst used in the preparation of polyethylene is not limited, and a Ziegler-Natta catalyst, a Phillips catalyst, a metallocene catalyst, etc. may be used. From the viewpoint of achieving both mechanical strength and high permeability, the weight average molecular weight of polyethylene may be, for example, 100,000 to 12,000,000 Dalton, 100,000 to 8,000,000 Dalton, 100,000 to 5,000,000 Dalton, or 200,000 to 3,000,000 Dalton. Polypropylene may be a homopolymer, a random copolymer, or a block copolymer, and these may be used alone or in combination of two or more. In addition, the polymerization catalyst is not limited, and a Ziegler-Natta catalyst or a metallocene catalyst, etc. may be used. In addition, the stereoregularity is not limited, and isotactic, syndiotactic, or atactic may be used, but inexpensive isotactic polypropylene can be used. Polyolefins may contain additives such as polyolefins other than polyethylene or polypropylene and antioxidants.

[0108] For example, the porous membrane may include polyolefins such as polyethylene and polypropylene, and a multilayer membrane having two or more layers may be used, and a mixed multilayer membrane such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, a polypropylene / polyethylene / polypropylene three-layer separator, etc. may be used, but is not limited thereto, and any material and configuration that can be used as a porous substrate in the relevant technical field may be used.

[0109] For example, the porous membrane may include a diene polymer prepared by polymerizing a monomer composition including a diene monomer. The diene monomer may be a conjugated diene monomer or a non-conjugated diene monomer. For example, the diene monomer includes at least one selected from the group consisting of 1,3-butadiene, isoprene, 2-chloro-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3-pentadiene, chloroprene, vinylpyridine, vinylnorbornene, dicyclopentadiene, and 1,4-hexadiene, but is not necessarily limited thereto, and any diene monomer that can be used in the art may be used.

[0110] The thickness of the porous membrane may be, for example, 1 to 100 μm, 1 to 30 μm, 5 to 20 μm, 5 to 15 μm, or 5 to 10 μm. If the thickness of the porous membrane is too thin, it may be difficult to maintain the mechanical properties of the porous membrane, and if the thickness of the porous membrane is too thick, the internal resistance of the secondary battery may increase.

[0111] The porosity of the porous membrane may be, for example, 5 to 95 vol%, 10 to 90 vol%, 20 to 80 vol%, or 30 to 70 vol%. If the porosity is too low, the internal resistance of the electrolyte layer (30) may increase excessively. If the porosity of the porous membrane is too high, it may be difficult to maintain the mechanical properties of the porous membrane. The porosity of the porous membrane can be measured, for example, by a nitrogen adsorption method.

[0112] The pore size of the porous membrane may be, for example, 0.01 to 10 μm, 0.01 to 5 μm, 0.01 to 2 μm, 0.01 to 1 μm, 0.01 to 0.5 μm, or 0.1 to 0.5 μm. If the pore size of the porous membrane is too small, the internal resistance of the electrolyte layer (30) may excessively increase, and if the pore size of the porous substrate is excessively large, the possibility of a short circuit in the secondary battery may increase. The pore size of the porous membrane can be measured, for example, by a nitrogen adsorption method.

[0113] The electrolyte layer (30) may be comprised of a composite membrane. The composite membrane may further comprise a coating layer disposed on one or both sides (e.g., at least one side of the porous membrane) of the above-described porous membrane.

[0114] In a composite membrane, the coating layer may include, for example, a filler. The filler is not limited and any filler that can be used in the art may be used.

[0115] In a composite membrane, a filler can act as a support. When the porous membrane tends to shrink at high temperatures, the filler can support the porous membrane and suppress shrinkage of the porous membrane. By including a filler in the coating layer disposed on the composite membrane, sufficient porosity can be secured and mechanical properties can be improved. Improved structural stability of a secondary battery including such a composite membrane can be secured. The average particle diameter of the filler included in the coating layer can be 300 nm to 2 ㎛, 300 nm to 1.5 ㎛, or 300 nm to 1.0 ㎛. The average particle diameter of the filler can be defined as the number average particle diameter of particles measured using, for example, a laser scattering particle size distribution analyzer (e.g., Horiba LA-920). By using a filler having such an average particle diameter, the coating layer can be easily formed to an appropriate thickness. A composite membrane including such a coating layer can have an appropriate porosity. If the average particle size of the filler is too small, the mechanical properties of the composite membrane may deteriorate.

[0116] The filler may be an inorganic particle, an organic particle, or a combination thereof. The inorganic particle may be a metal oxide, a metalloid oxide, or a combination thereof. Specifically, the inorganic particle may be alumina, silica, boehmite, magnesia, or a combination thereof. The alumina, silica, etc. have a small particle size, making it easy to prepare a dispersion. For example, the inorganic particle may be Al2O3, SiO2, TiO2, SnO2, CeO2, NiO, CaO, ZnO, MgO, ZrO2, Y2O3, SrTiO3, BaTiO3, MgF2, Mg(OH)2 or a combination thereof. The inorganic particles may be, but are not limited to, spheres, plates, fibers, etc., and any form usable in the relevant technical field may be used. The organic particles may be cross-linked polymers. The organic particles may be highly cross-linked polymers that do not exhibit a glass transition temperature (Tg). When highly cross-linked polymers are used, heat resistance is improved, and shrinkage of the porous substrate at high temperatures can be effectively suppressed. The organic particles may include, but are not limited to, acrylate compounds and derivatives thereof, diallyl phthalate compounds and derivatives thereof, polyimide compounds and derivatives thereof, polyurethane compounds and derivatives thereof, copolymers thereof, or combinations thereof, and any form usable as a filler in the relevant technical field may be used. For example, the filler may be a cross-linked polystyrene particle or a cross-linked polymethyl methacrylate particle. The filler may be a secondary particle formed by agglomeration of primary particles. In a separator including a filler as a secondary particle, the porosity of the coating layer is increased, thereby providing a lithium battery with excellent high-power characteristics. The glass transition temperature of the organic particles may be measured, for example, by a Differential Scanning Calorimeter (DSC), a Dynamic Mechanical Analyzer (DMA), a Thermomechanical Analyzer (TMA), and / or a Thermogravimetric Analyzer (TGA).

[0117] In the composite membrane, a coating layer may be disposed on, for example, both sides of the porous membrane. The thickness of the coating layer may be 0.1 to 5 ㎛, 0.5 to 5 ㎛, or 0.5 to 3 ㎛ based on one side. When the thickness of the coating layer satisfies the above range, a composite membrane including the coating layer can provide improved adhesion and air permeability. In addition, since the coating layer is disposed on both sides of the porous substrate, the adhesion between the composite binder and the electrode active material layer can be further improved, thereby suppressing volume change of the lithium battery. The coating layers disposed on both sides of the composite membrane may have the same composition. Since the coating layers having the same composition are disposed on both sides of the composite membrane, the same adhesive force acts on the positive electrode layer and / or the negative electrode layer on one side and the other side of the composite membrane, thereby uniformly suppressing volume change of the secondary battery.

[0118] In the composite membrane, the coating layer may include, for example, a blend of a binder and a filler. The coating layer may include a blend of binder and filler in which the binder and filler are uniformly mixed. By including a blend of binder and filler in the coating layer, the adhesion between the porous substrate and the electrode active material layer may be further improved compared to a multilayer structure in which the binder and filler are arranged in separate layers. The mixed weight ratio of binder:filler in the coating layer may be 1:1 to 1:8. For example, the binder:filler ratio in the coating layer may be 1:1.5 to 1:7, 1:2 to 1:6, or 1:2 to 1:5. Within these binder-filler ratio ranges, improved adhesion and air permeability may be achieved simultaneously.

[0119] The binder included in the coating layer may be a fluorinated polymer. The binder included in the coating layer may be a fluorinated polymer in which some or all of the hydrogens connected to the carbon atoms included in the binder are replaced with fluorine. For example, the fluorinated polymer may be a polymer including repeating units derived from one or more monomers selected from a vinylidene fluoride monomer, a tetrafluoroethylene monomer, and a hexafluoropropylene monomer. For example, the binder included in the coating layer may be a fluorinated homopolymer. The binder included in the coating layer may be a copolymer. The binder included in the coating layer may be a fluorinated copolymer. The fluorinated copolymer included in the coating layer may be a copolymer of a tetrafluoroethylene monomer and another monomer. Other monomers used together with the tetrafluoroethylene monomer may be one or more fluorine-containing monomers selected from the group consisting of vinylidene fluoride, hexafluoropropylene, chlorotrifluoroethylene, and perfluoroalkyl vinyl ether. For example, the fluorinated copolymer included in the coating layer may be a tetrafluorinated ethylene-vinylidene fluoride copolymer, a tetrafluorinated ethylene-hexafluoropropylene copolymer, a tetrafluorinated ethylene-chlorotrifluoroethylene copolymer, a tetrafluorinated ethylene-perfluoroalkyl vinyl ether, etc. The fluorinated copolymer included in the coating layer may be a copolymer of a vinylidene fluoride monomer and another monomer. For example, the fluorinated copolymer included in the coating layer may be a copolymer of a vinylidene fluoride monomer and one or more fluorine-containing monomers selected from the group consisting of hexafluoropropylene, chlorotrifluoroethylene, fluorovinyl, and perfluoroalkyl vinyl ether. Specifically, the vinylidine monomer may be a vinylidene fluoride homopolymer, a vinylidene fluoride-hexafluoropropylene copolymer, a vinylidene fluoride-chlorotrifluoroethylene copolymer, etc. The fluorinated polymer included in the coating layer may additionally include a hydrophilic functional group. By additionally including the hydrophilic functional group, improved adhesion to the electrode active material layer can be achieved. The hydrophilic functional group is a polar functional group.The hydrophilic functional group additionally included in the fluoropolymer included in the coating layer may be at least one selected from the group consisting of a carboxylic acid group, a sulfonic acid group, a phosphoric acid group, an acid anhydride group, a hydroxyl group, and salts thereof, but is not necessarily limited thereto, and any group that can be used as a hydrophilic functional group in the relevant technical field may be used. The weight average molecular weight of the fluoropolymer included in the coating layer may be 100,000 dalton or more. For example, the weight average molecular weight of the fluoropolymer included in the coating layer may be 100,000 to 1,500,000 dalton. For example, the weight average molecular weight of the fluoropolymer included in the coating layer may be 300,000 to 1,500,000 dalton. For example, the weight average molecular weight of the fluoropolymer included in the coating layer may be 500,000 to 1,500,000 dalton. For example, the weight average molecular weight of the fluoropolymer included in the coating layer may be 1,000,000 to 1,500,000 dalton. The weight average molecular weight is a polystyrene conversion value obtained by gel permeation chromatography. Within the range of the weight average molecular weight of the fluoropolymer included in the coating layer, the adhesive strength with the positive electrode active material layer may be further improved. If the weight average molecular weight of the fluoropolymer included in the coating layer is too small, the adhesive strength is reduced, and if the weight average molecular weight is large, it is not easy to manufacture the binder composition.

[0120]

[0121] [Anode layer]

[0122] [Anode layer: cathode active material]

[0123] Referring to FIGS. 1 to 4, the positive electrode layer (10) includes a positive electrode current collector (11); and a positive electrode active material layer (12) disposed on one or both sides of the positive electrode current collector (11) (e.g., at least one side of the positive electrode current collector (11)).

[0124] The cathode active material layer (12) may include, for example, an alkali metal-containing sulfide-based cathode active material or an alkali metal-containing oxide-based cathode active material. The alkali metal may include, for example, lithium or sodium. The cathode active material layer (12) may include, for example, a lithium-containing sulfide-based cathode active material, a lithium-containing oxide-based cathode active material, a sodium-containing sulfide-based cathode active material, or a sodium-containing oxide-based cathode active material.

[0125] The cathode active material layer (12) may include, for example, a Li2S-containing complex as an alkali metal-containing sulfide-based cathode active material.

[0126] 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 layer may be accelerated due to a change in the volume of the cathode layer during charge and discharge. As a result, the cycle characteristics of the secondary battery (1) may be deteriorated.

[0127] 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.

[0128] 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 cathode layer including these is maintained high because the interfacial resistance between Li2S and the other material is maintained. Therefore, the cycle characteristics of a secondary battery (1) including these may be deteriorated. In contrast, in a Li2S-containing composite, the interfacial resistance between Li2S and the other material is reduced because Li2S and the other material are mechanochemically or chemically complexed, so the internal resistance of a cathode layer including these is reduced. Therefore, the cycle characteristics of a secondary battery (1) including a LiS-containing composite can be improved.

[0129] 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 a fibrous carbon-based material, i.e., the ratio of the diameter and length of the fibrous carbon-based material, can be measured from a Scanning Electron Microscopy (SEM) image.

[0130] 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.

[0131] 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 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 positive electrode layer. The sulfide-based solid electrolyte has, for example, a 1×10 -5 It can have an ionic conductivity of S / cm or more. The oxide-based solid electrolyte contains, for example, Li, O, and transition metal elements, and may optionally contain other elements. The oxide-based solid electrolyte has an ionic conductivity of, for example, 1×10 at room temperature. -5 It may be a solid electrolyte having an ionic conductivity of S / cm or more. The oxide-based solid electrolyte may be selected from among the oxide-based solid electrolytes used in the anode layer.

[0132] 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.

[0133] 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 Li2S and a lithium halide. The complex of Li2S 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 deteriorate the life characteristics of the secondary battery (1).

[0134] 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.

[0135] 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.

[0136] 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.

[0137] 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.

[0138] 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.

[0139] 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 secondary battery (1) including the composite can provide further improved ionic conductivity and / or electronic conductivity.

[0140] 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 nitride refers to the composite of Li2S and a metal nitride described above.

[0141] The cathode active material layer (12) may additionally include, for example, a sulfide-based compound that is distinct from the above-described cathode active material. 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 (12) additionally including a sulfide-based compound, the cycle characteristics of the 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).

[0142] The cathode active material layer (12) may include, for example, lithium metal oxide as an alkali metal-containing oxide-based cathode active material.

[0143] Any lithium metal oxide commonly used in the art can be used without limitation. For example, the lithium metal oxide can be at least one compound oxide of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof. Specific examples thereof include Li a A 1-b B' b D2 (in the above formula, 0.90 ≤ a ≤ 1, and 0 ≤ b ≤ 0.5); Li a E 1-b B' b O 2-c D c (In the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); LiE 2-b B' b O 4-c D c (In the above formula, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Lia Ni 1-b-c Co b B' c D α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Co b B' c O 2-α' F' α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b B' c D α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Mn b B' c O 2-α F' α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni b E c G d O2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1); Li a Ni b Co c Mn d G e O2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0.001 ≤ e ≤ 0.1); Li a NiG b O2 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a CoG bO2 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a MnG b O2 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a Mn2G b O4 (wherein 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); QO2; V2O5; LiV2O5; LiI'O2; LiNiVO4; Li (3-f) J2(PO4)3(0 ≤ f ≤ 2); Li (3-f) A compound represented by any one of the chemical formulas Fe2(PO4)3(0 ≤ f ≤ 2); LiFePO4 can be used.

[0144] In the chemical formula representing the above-described compound, A is Ni, Co, Mn, or a combination thereof; B' is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F' is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; I' is Cr, V, Fe, Sc, Y, or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof. It is also possible to use a compound having a coating layer added to the surface of the above-described compound, or it is also possible to use a mixture of the above-described compound and the compound having a coating layer added. The coating layer added to the surface of the above-mentioned compound includes a coating element compound of, for example, an oxide, a hydroxide, an oxyhydroxide of the coating element, an oxycarbonate of the coating element, or a hydroxycarbonate of the coating element of the coating element. The compound forming the coating layer is amorphous or crystalline. The coating elements included in the coating layer are Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof. The method for forming the coating layer is selected within a range that does not adversely affect the physical properties of the positive electrode active material. The coating method includes, for example, spray coating and dipping. Since the specific coating method is well understood by those working in the relevant field, a detailed description thereof will be omitted.

[0145] The cathode active material layer (12) may include, for example, a lithium transition metal oxide represented by the following chemical formulas 11 to 18 as an alkali metal-containing oxide-based cathode active material:

[0146] <Chemical Formula 11>

[0147] Li a Ni x Coy M z O 2-b A b

[0148] In the above chemical formula 11,

[0149] 1.0≤a≤1.2, 0≤b≤0.2, 0.8≤x<1, 0≤y≤0.3, 0 <z≤0.3, 및 x+y+z=1이고,

[0150] M is manganese (Mn), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B), or a combination thereof,

[0151] A is F, S, Cl, Br or a combination thereof,

[0152] <Chemical Formula 12>

[0153] LiNi x Co y Mn z O2

[0154] <Chemical Formula 13>

[0155] LiNi x Co y Al z O2

[0156] In the above chemical formulas 12 to 13, 0.8≤x≤0.95, 0≤y≤0.2, 0 <z≤0.2 및 x+y+z=1이며,

[0157] <Chemical Formula 14>

[0158] LiNi x Co y Mn z Al w O2

[0159] In the above chemical formula 14, 0.8≤x≤0.95, 0≤y≤0.2, 0 <z≤0.2, 0<w≤0.2, 및 x+y+z+w=1이며,

[0160] <Chemical Formula 15>

[0161] Li a Cox M y O 2-b A b

[0162] In the above chemical formula 15,

[0163] 1.0≤a≤1.2, 0≤b≤0.2, 0.9≤x≤1, 0≤y≤0.1, and x+y=1,

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

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

[0166] <Chemical Formula 16>

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

[0168] In the above chemical formula 16,

[0169] 1.0≤a≤1.2, 0≤b≤0.2, 0 <x≤0.3, 0.5≤y<1, 0<z≤0.3, 및 x+y+z=1이고,

[0170] M' is cobalt (Co), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B) or a combination thereof,

[0171] A is F, S, Cl, Br or a combination thereof,

[0172] <Chemical Formula 17>

[0173] Li a M1 x M2 y PO 4-b Xb

[0174] In the above chemical formula 17, 0.90≤a≤1.1, 0≤x≤0.9, 0≤y≤0.5, 0.9 <x+y<1.1, 0≤b≤2 이며,

[0175] M1 is chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr) or a combination thereof,

[0176] M2 is magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), titanium (Ti), zinc (Zn), boron (B), niobium (Nb), gallium (Ga), indium (In), molybdenum (Mo), tungsten (W), aluminum (Al), silicon (Si), chromium (Cr), vanadium (V), scandium (Sc), yttrium (Y) or a combination thereof, and X is O, F, S, P or a combination thereof.

[0177] <Chemical Formula 18>

[0178] Li a M3 z PO4

[0179] In the above chemical formula 18, 0.90≤a≤1.1, 0.9≤z≤1.1,

[0180] M3 is chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr), or a combination thereof.

[0181]

[0182] [Anode layer: solid electrolyte]

[0183] The cathode active material layer (12) may further include, for example, a solid electrolyte. The solid electrolyte may include, for example, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or a combination thereof.

[0184] 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.

[0185] The sulfide-based solid electrolyte may include, for example, an argyrodite type solid electrolyte represented by the following chemical formula 19:

[0186] <Chemical Formula 19>

[0187] Li + 12-n-x A n+ X 2- 6-x Y - x

[0188] In the above formula, A is P, As, Ge, Ga, Sb, Si, Sn, Al, In, Ti, V, Nb or Ta, X is S, Se or Te, Y is Cl, Br, I, F, CN, OCN, SCN or N3, and 1≤n≤5, 0≤x≤2. The sulfide-based solid electrolyte is, for example, Li 7-x PS 6-x Cl x , 0≤x≤2, Li 7-xPS 6-x Br x , 0≤x≤2, and Li 7-x PS 6-x I x , may be an argyrodite-type compound including at least one selected from 0≤x≤2. The sulfide-based solid electrolyte may be, for example, an argyrodite-type compound including at least one selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0189] Oxide-based solid electrolytes include, for example, Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (0 <x<2, 0≤y<3), BaTiO3, Pb(Zr,Ti)O3(PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT)(0≤x<1, 0≤y<1), PB(Mg3Nb 2 / 3 )O3-PbTiO3(PMN-PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, Li3PO4, Li x Ti y (PO4)3(0 <x<2, 0<y<3), Li x Al y Ti z (PO4)3(0 <x<2, 0<y<1, 0<z<3), 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 yTiO3(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.

[0190] 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.

[0191] 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 layer (10) 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.

[0192] [Anode layer: conductive material]

[0193] 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).

[0194] 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 or exclude a separate carbon-based material in addition to the composite cathode active material including the carbon-based material. Since the cathode active material layer (12) 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.

[0195] [Anode layer: binder]

[0196] 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.

[0197] [Anode layer: Other additives]

[0198] 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.

[0199] As fillers, coating agents, dispersants, ion conductivity aids, etc. that the positive electrode active material layer (12) may include, known materials generally used in the electrode of a secondary battery (1) may be used.

[0200] [Anode layer: Anode current collector]

[0201] 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.

[0202] 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 perform a short-circuit prevention function by being cut in case of overcurrent. The limit current and maximum current can be controlled by adjusting the thickness of the metal layer. The metal layer can be plated or deposited on the base film. When the thickness of the metal layer is reduced, the limit current and / or 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. 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 1 μm. Since the metal layer has a thickness within this range, conductivity can be maintained while ensuring the stability of the electrode assembly. The thickness of the metal piece may be, for example, 2 to 10 μm, 2 to 7 μm, or 4 to 6 μm. Since the metal piece has a thickness within this range, the connection between the metal layer and the lead tab can be performed more easily. By having this structure, the positive electrode current collector (11) can reduce the weight of the positive electrode layer and consequently improve the energy density of the positive electrode and lithium battery.

[0203]

[0204] [Cathode layer]

[0205] [Cathode layer: negative electrode active material]

[0206] Referring to FIGS. 1 to 5, 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.

[0207] 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.

[0208] 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.

[0209] The negative electrode active material included in the first negative electrode active material layer (22) includes, for example, at least one selected from among a carbon-based negative electrode active material and a metal or semi-metal negative electrode active material.

[0210] Carbon-based negative electrode materials include, for example, amorphous carbon, crystalline carbon, porous carbon, or a combination thereof.

[0211] 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.

[0212] 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.

[0213] 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.

[0214] 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 secondary battery (1). When the negative electrode active material has this composition, the cycle characteristics of the secondary battery (1) are further improved.

[0215] 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, the secondary battery (1) are further improved.

[0216] 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 secondary battery (1) including the first negative electrode active material layer (22) are further improved.

[0217] 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.

[0218] The carbon-based support is, for example, amorphous carbon. Amorphous carbon includes, but is not limited to, carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), graphene, activated carbon, carbon nanofibers (CNF), carbon nanotubes (CNT), etc., and any material classified as amorphous carbon in the relevant technical field is possible. Amorphous carbon is carbon that has no crystallinity or very low crystallinity, and is distinguished from crystalline carbon or graphitic carbon. Carbon-based materials, e.g., carbonaceous materials, are, for example, carbon-based negative electrode active materials.

[0219] 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.

[0220] [Cathode layer: binder]

[0221] 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.

[0222] Since the first negative electrode active material layer (22) includes a binder, the first negative electrode active material layer (22) is stabilized on the negative electrode current collector (21). In addition, cracking of the first negative electrode active material layer (22) is suppressed despite changes in the volume and / or relative position of the first negative electrode active material layer (22) during the charge and discharge process. For example, if the first negative electrode active material layer (22) does not include a binder, the first negative electrode active material layer (22) can be easily separated from the negative electrode current collector (21). As the first negative electrode active material layer (22) is separated from the negative electrode current collector (21), the possibility of a short circuit occurring increases as the negative electrode current collector (21) comes into contact with the electrolyte layer (30) at the exposed portion of the negative electrode current collector (21). The first negative electrode active material layer (22) is manufactured by, for example, applying a slurry in which the material constituting the first negative electrode active material layer (22) is dispersed onto the negative electrode current collector (21) and drying the slurry. By including a binder in the first negative electrode active material layer (22), stable dispersion of the negative electrode active material in the slurry is possible. For example, when applying the slurry onto the negative electrode current collector (21) by screen printing, it is possible to suppress clogging of the screen (for example, clogging by aggregates of the negative electrode active material).

[0223] [Cathode layer: Other additives]

[0224] The first negative electrode active material layer (22) may further include additives used in conventional secondary batteries (1), such as fillers, coating agents, dispersants, and ion conductive aids.

[0225] [Cathode layer: first cathode active material layer]

[0226] 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 (12). The initial charge capacity of the first negative electrode active material layer may be, for example, 0.1 to 50%, 0.5 to 45%, 1 to 40%, 1 to 30%, 1 to 20%, or 5 to 10% of the initial charge capacity of the positive electrode active material layer (12).

[0227] 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 (12) is, for example, 0.005 to 0.5 or 0.005 to 0.45. The initial charge capacity of the positive electrode active material layer (12) is Li / Li + About the first open circuit voltage (1 st It is determined by charging from the open circuit voltage to the maximum charging voltage. The initial charging capacity of the first negative electrode active material layer (22) is Li / Li + About the second open circuit voltage (2 nd The maximum charge voltage is determined by charging from 0.01 V to 0.01 V. The maximum charge voltage is determined by 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) and the initial charge capacity (A) of the positive electrode active material layer (12) 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 anode layer, the measurement is performed from the first open circuit voltage (OCV) to the maximum charge voltage, for example, 3.0 V (vs. Li / Li +) can be performed for an operating voltage of up to 0.01 V for the cathode, for example, lithium metal, from the second open circuit voltage (OCV). For example, a solid-state half-cell having a cathode active material layer (12) 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 (12) 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 (12) can be determined by the maximum voltage of the battery satisfying the safety conditions according to JISC8712:2015 of the Japanese Standards Association.

[0228] 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 secondary battery (1). If the charge capacity of the first negative electrode active material layer (22) increases excessively, the energy density of the secondary battery (1) decreases and the internal resistance of the secondary battery (1) due to the first negative electrode active material layer (22) increases, making it difficult to improve the cycle characteristics of the secondary battery (1).

[0229] 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 secondary battery (1). If the thickness of the first negative electrode active material layer (22) increases excessively, the energy density of the secondary battery (1) decreases and the internal resistance of the secondary battery (1) due to the first negative electrode active material layer (22) increases, making it difficult to improve the cycle characteristics of the 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.

[0230] [Cathode layer: second cathode active material layer]

[0231] Referring to FIG. 3, the 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 the secondary battery (1).

[0232] The thickness of the second negative electrode active material layer (24) is not 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 secondary battery (1) may increase, and the cycle characteristics of the secondary battery (1) may rather deteriorate.

[0233] Alternatively, in the 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 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 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 secondary battery (1).

[0234] When the second negative electrode active material layer (24) is precipitated by charging after assembling the secondary battery (1), the energy density of the secondary battery (1) increases because the second negative electrode active material layer (24) is not included when assembling the secondary battery (1). When charging the 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 layer (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), the second negative electrode active material layer (24), and the metal layer is ionized and moves toward the positive electrode layer (10). Therefore, it is possible to use lithium as the negative electrode active material in the 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 secondary battery (1), and consequently improves the cycle characteristics of the secondary battery (1).In addition, when the second negative electrode active material layer (24) is placed by charging after assembling the 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 area between them are Li-free areas that do not contain lithium (Li) in the initial state of the secondary battery (1) or in the state after complete discharge.

[0235] [Cathode layer: negative current collector]

[0236] 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.

[0237] Referring to FIG. 2, the 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 relevant technical field 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 secondary battery (1) can be further improved.

[0238] 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 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.

[0239] 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.

[0240] [Cathode layer: first inert member]

[0241] Referring to Fig. 4, the secondary battery (1) further includes a first inert member (40) arranged on the other surface of the negative electrode collector (21). The first inert member (40) is, for example, a conductive flame-retardant inert member.

[0242] The first inert member (40) includes, for example, a matrix, a filler, and a conductive material. The matrix includes, for example, a substrate and a reinforcing material. The first inert member (40) may further include a filler, a binder, and the like.

[0243] 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 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 secondary battery (1) occurring during charging and discharging of the secondary battery (1) can be effectively accommodated and deformation of the first inactive member (40) due to the volume changes of the secondary battery (1) 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 includes, for example, at least one selected from pulp fibers and polymer fibers. The strength of the matrix is ​​improved by including a reinforcing material in the matrix. Therefore, the matrix can prevent excessive volume change during charging and discharging of the secondary battery (1) and deformation of the secondary battery. The reinforcing material included in the matrix includes, for example, a second fibrous material. By including the second fibrous material in the reinforcing material, the strength of the matrix can be increased more uniformly. The second fibrous material is, for example, a material having an aspect ratio of 3 or more, 5 or more, or 10 or more. The first fibrous material is, for example, a material having an aspect ratio of 3 to 100, 5 to 100, or 10 to 100. The second fibrous material is, for example, a flame retardant material. Since the second fibrous material is a flame retardant material, ignition due to thermal runaway occurring during the charging and discharging process of the secondary battery (1) or due to external impact can be effectively suppressed. The second fibrous material is, for example, a glass fiber, a metal oxide fiber, a ceramic fiber, or the like.

[0244] The first inert member (40) includes a filler and a conductive material in addition to the matrix.

[0245] The filler can be disposed inside the matrix, on the surface of the matrix, or on both the inside and the surface. The filler is, for example, an inorganic material. The filler included in the conductive flame-retardant inert member is, for example, a moisture getter. The filler removes moisture remaining in the secondary battery (1) by adsorbing moisture, for example, at a temperature below 100°C, thereby preventing deterioration of the secondary battery (1). In addition, when the temperature of the secondary battery (1) increases to 150°C or higher due to thermal runaway occurring during the charging / discharging process of the secondary battery (1) or an external impact, the filler can release the adsorbed moisture, thereby effectively suppressing ignition of the 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 conductive 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 conductive flame-retardant inert member.

[0246] 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 first 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).

[0247] The first inert member (40) may further include, for example, a binder. The binder may include, for example, a curable polymer or a non-curable polymer. The curable polymer is a polymer that cures by heat and / or pressure. The curable polymer is, for example, a solid at room temperature. The flame-retardant inert member includes, for example, a heat-pressure curable film and / or a cured product thereof. The heat-pressure curable polymer is, for example, TSA-66 from Toray.

[0248] The first inert member (40) may additionally include other materials in addition to the above-described substrate, reinforcing material, filler, conductive material, and binder. The conductive flame-retardant inert member may further include one or more selected from among paper, an insulating polymer, an ion-conductive polymer, an insulating inorganic material, an oxide-based solid electrolyte, and a sulfide-based solid electrolyte, for example. The insulating polymer may be an olefin-based polymer such as polypropylene (PP), polyethylene (PE), or the like.

[0249] The density of the substrate or the density of the reinforcing material included in the first inert member (40) 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).

[0250] The first inert member (40) is a member that does not contain an electrochemically active material, for example, an electrode active material. An electrode active material is a material that absorbs / releases lithium. The first inert member (40) is a member made of a material other than an electrode active material and used in the relevant technical field.

[0251] The content of the conductive material included in the first inert member (40) 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 first inert member (50).

[0252] The Young's modulus of the first inert member (40) is, for example, smaller than the elastic modulus of the negative electrode collector (21). The Young's modulus of the first inert member (40) 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 first 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 first inert member (40) 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 first inert member (40) 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. The elastic modulus (Young's modulus) of the first inert member (40) and the negative electrode current collector (21) can be measured, for example, by a method according to ASTM D412.

[0253] Since the first inert member (40) is conductive, it can function as a negative electrode current collector (50). In addition, since the first inert member (40) 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 secondary battery (1). Consequently, the first inert member (40) can effectively alleviate the internal stress caused by the volume change of the secondary battery (1) during charging and discharging of the secondary battery (1), thereby improving the cycle characteristics of the secondary battery (1).

[0254] The thickness of the first inert member (40) is, for example, greater than the thickness of the first negative electrode active material layer (22). Since the first inert member (40) has a greater thickness than the first negative electrode active material layer (22), the volume change of the negative electrode layer (20) during charge and discharge can be more effectively accommodated. 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 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 (50). The thickness of the first inert member (40) is, for example, 1 ㎛ to 300 ㎛, 10 ㎛ to 300 ㎛, 50 ㎛ to 300 ㎛, or 100 ㎛ to 200 ㎛. If the thickness of the first inert member (40) is too thin, it may be difficult to provide the intended effect, and if the thickness of the first inert member (40) is too thick, the energy density of the secondary battery (1) may be reduced. The shape of the first inert member (50) is not limited and may be selected according to the shape of the secondary battery (1). The first inert member (40) may be, for example, in the shape of a sheet, a rod, or a gasket. The first inert member (40) may be disposed on, for example, one side or both sides of one secondary battery (1). The first inert member (40) may be disposed between, for example, a plurality of stacked secondary batteries (1). The first inactive member (40) may be arranged, for example, between each of the plurality of stacked secondary batteries (1), on the uppermost surface and / or the lowermost surface.

[0255] 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 absorbs a change in the volume of the negative electrode layer (20) that occurs during the charge / discharge process of the secondary battery (1), and provides an adhesive force between the support layer and other layers, thereby improving the film strength of the first inert member (40). The support layer provides support to the first inert member (40), prevents unevenness of pressure applied to the secondary battery (1) during the pressurization process or the charging / discharging process, and prevents deformation of the secondary battery (1).

[0256]

[0257] [Secondary battery manufacturing]

[0258] Referring to FIG. 5, a secondary battery (1a) according to one embodiment includes a positive electrode layer (10a), a negative electrode layer (20a), and a flexible electrolyte layer (30a). The positive electrode layer (10a), the negative electrode layer (20a), and the electrolyte layer (30a) are wound or folded to form a battery structure (70a). The formed battery structure (70a) is accommodated in a battery case (50a). The secondary battery (1a) is completed by sealing the battery case (50a) with a cap assembly (60a). The battery case (50a) is cylindrical, but is not necessarily limited to this shape, and may be, for example, square, thin-film, etc. Alternatively, the positive electrode layer (10a), the negative electrode layer (20a), and the porous membrane (30a) are wound or folded to form the battery structure (70a). The formed battery structure (70a) is accommodated in a battery case (50a). A high-viscosity liquid electrolyte or polymer electrolyte forming composition is injected into the battery case (50a) and sealed with a cap assembly (60a), thereby completing the secondary battery (1a). If a polymer electrolyte forming composition is used, heat treatment is added. The secondary battery (1a) is, for example, a lithium battery.

[0259] Referring to FIG. 6, a secondary battery (1b) according to one embodiment includes a positive electrode layer (10b), a negative electrode layer (20b), and a flexible electrolyte layer (30b). An electrolyte layer (30b) is disposed between the positive electrode layer (10b) and the negative electrode layer (20b), and the positive electrode layer (10b), the negative electrode layer (20b), and the electrolyte layer (30b) are wound or folded to form a battery structure (70b). The formed battery structure (70b) is accommodated in a battery case (50b), thereby completing the secondary battery (1b). An electrode tab (80b) that serves as an electrical path for guiding the current formed in the battery structure (70b) to the outside may be included. Alternatively, a composition for forming a high-viscosity liquid electrolyte or a polymer electrolyte is injected into the battery case (50a) and sealed with a cap assembly (60a), thereby completing the secondary battery (1a). When a composition for forming a polymer electrolyte is used, heat treatment is added. The secondary battery (1b) is, for example, a lithium battery.

[0260] Referring to FIG. 7, a secondary battery (1c) according to one embodiment includes a positive electrode layer (10c), a negative electrode layer (20c), and a flexible electrolyte layer (30c). An electrolyte layer (30c) is disposed between the positive electrode layer (10c) and the negative electrode layer (20c) to form a battery structure (70c). The battery structures (70c) are stacked and then accommodated in a battery case (50c), thereby completing the secondary battery (1c). An electrode tab (80c) that serves as an electrical path for guiding the current formed in the battery structure (70c) to the outside may be included. The battery case (50c) is not necessarily limited to a square shape, but may be, for example, a cylindrical shape, a thin film shape, etc. Alternatively, a high-viscosity liquid electrolyte or polymer electrolyte forming composition is injected into a battery case (50c) and sealed with a cap assembly (60c), thereby completing a secondary battery (1c). If a polymer electrolyte forming composition is used, heat treatment is added. The secondary battery (1c) is, for example, a lithium battery.

[0261] A pouch-type lithium battery corresponds to the secondary batteries of FIGS. 5 to 7, each of which uses a pouch as a battery case. The pouch-type secondary battery includes one or more battery structures. A separator is disposed between a positive electrode and a negative electrode to form a battery structure. The battery structures are laminated in a bi-cell structure, then impregnated with an electrolyte, and accommodated and sealed in a pouch to complete the pouch-type lithium battery. For example, although not shown in the drawings, the above-described positive electrode, negative electrode, and separator may be simply laminated and accommodated in a pouch in the form of an electrode assembly, or may be wound or folded into a jelly-roll-shaped electrode assembly and then accommodated in a pouch. Subsequently, an organic electrolyte is injected into the pouch and sealed to complete the secondary battery.

[0262] Secondary batteries have excellent lifespan and high-rate characteristics, making them suitable for use in electric vehicles (EVs). Examples include plug-in hybrid electric vehicles (PHEVs). They are also used in applications requiring large amounts of power storage, such as electric bicycles and power tools.

[0263] Secondary batteries are stacked in multiple layers to form a battery module, and the multiple battery modules form a battery pack. Such a battery pack can be used in any device requiring high capacity and high output. For example, it can be used in laptops, smartphones, electric vehicles, etc. The battery module includes, for example, multiple batteries and a frame that holds them. The battery pack includes, for example, multiple battery modules and a bus bar that connects them. The battery module and / or the battery pack may further include a cooling device. The multiple battery packs are controlled by a battery management system. The battery management system includes a battery pack and a battery control device connected to the battery pack.

[0264] 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.

[0265] Example 1: Li2S-LiI-CNF cathode layer / flexible electrolyte layer (separator + thermosetting polymer) / Ag-C cathode layer, thermal curing after lamination assembly.

[0266] (Manufacturing of composite cathode active materials)

[0267] 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.

[0268] (Anode layer manufacturing)

[0269] The Li2S-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.

[0270] The positive electrode was manufactured by placing the positive electrode active material on one side of a positive electrode current collector made of aluminum foil coated on one side and plate pressing at a pressure of 200 MPa for 10 minutes. The thickness of the positive electrode was approximately 120 μm. The thickness of the positive electrode active material layer (12) was approximately 100 μm, and the thickness of the carbon-coated aluminum foil was approximately 20 μm.

[0271] The initial charge capacity of the positive electrode layer was measured by the above-described half-cell. For Examples 1 to 3 and 7, the ratio (B / A) of the initial charge capacity (B) of the first negative electrode active material layer to the initial charge capacity (A) of the positive electrode active material layer was less than 30% (i.e., less than 0.3), respectively. The initial charge capacity of the positive electrode active material layer was measured from the first open circuit voltage to Li / Li. + was determined by charging up to a maximum charging voltage of 2.8 V. In addition, the initial charge capacity of the first negative active material layer was determined from the second open circuit voltage to Li / Li + It was determined by charging up to 0.01 V.

[0272] (Cathode layer manufacturing)

[0273] A 10 ㎛ thick SUS (stainless steel) 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.

[0274] 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 2The surface of the first negative electrode active material layer of the laminate was flattened by cold roll pressing at a pressure of 5 m / sec. The negative electrode layer was manufactured by the above process. The thickness of the first negative electrode active material layer included in the negative electrode layer was approximately 15 μm. The initial charge capacity of the negative electrode was measured by the above-described half-cell.

[0275] (thermosetting electrolyte composition)

[0276] 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.

[0277] <Chemical Formula A>

[0278]

[0279] 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.

[0280] (Manufacturing of secondary batteries)

[0281] A polypropylene separator (celgard 3501) was prepared as a flexible porous separator. The separator was impregnated with the thermosetting electrolyte composition.

[0282] Referring to Fig. 8, a separator was placed on the cathode layer so that the lithium metal layer was in contact with the separator, and a positive electrode layer was placed on the separator to prepare a laminate.

[0283] 85 prepared laminates o Plate press and heat treatment were performed at a pressure of 0.5 MPa for 1 hour at C.

[0284] By simultaneously performing heat treatment and pressure treatment of the laminate, the thermosetting composition was thermally cured to form a polymer gel electrolyte. A polymer electrolyte layer was formed between the positive and negative electrode layers.

[0285] The pressurized laminate was placed in a pouch and vacuum-sealed to manufacture a secondary battery. Parts of the positive and negative current collectors were extended outside the sealed secondary battery to be used as positive and negative electrode terminals.

[0286] Example 2: Li2S-LiI-CNF cathode layer / flexible electrolyte layer (separator + thermosetting polymer) / Ag-C cathode layer, thermal curing before stack assembly.

[0287] A secondary battery was manufactured in the same manner as Example 1, except that an electrolyte layer impregnated with a polymer gel electrolyte in a separator was separately prepared and placed on the cathode layer, and an anode layer was placed on the electrolyte layer.

[0288] The electrolyte layer was manufactured using the following method.

[0289] A polypropylene separator (celgard 3501) was placed as a flexible porous separator on the substrate. A thermosetting electrolyte composition was applied onto the separator, thereby impregnating the separator with the thermosetting electrolyte composition, and heat treatment was performed at 85°C for 2 hours to prepare an electrolyte layer in which the separator was impregnated with a polymer gel electrolyte.

[0290] Example 3: Li2S-LiI-CNF cathode layer / flexible electrolyte layer (separator + high-viscosity liquid electrolyte) / Ag-C cathode layer

[0291] A secondary battery was manufactured in the same manner as in Example 1, except that a liquid electrolyte containing an ionic liquid was applied instead of a thermosetting electrolyte composition on the separator and the temperature during pressurization was changed to 25°C.

[0292] A liquid electrolyte containing an ionic liquid was prepared as follows.

[0293] (high viscosity liquid electrolyte)

[0294] 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.

[0295] As an ionic liquid, 1-methyl-1-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide represented by the following chemical formula B was used.

[0296] The viscosity of the liquid electrolyte was 22.5 cps at 1 atm and 25 ℃.

[0297] <Chemical Formula B>

[0298]

[0299] Example 4: NCM cathode layer / flexible electrolyte layer (separator + thermosetting polymer) / Ag-C cathode layer, thermal curing after lamination assembly.

[0300] Instead of the anode layer containing Li2S-LiI-CNF composite as the anode layer, LiNi coated with Li2O-ZrO2 (LZO) prepared as follows 0.8 Co 0.15 Mn 0.05 A lithium secondary battery was manufactured in the same manner as in Example 1, except that an O2(NCM)-containing cathode layer was used.

[0301] (Anode layer manufacturing)

[0302] LiNi coated with Li2O-ZrO2 (LZO) as a cathode active material 0.8 Co 0.15 Mn 0.05 O2(NCM) was prepared. The LZO-coated cathode active material was prepared according to the method disclosed in Korean Patent Publication No. 10-2016-0064942. Li6PS5Cl, an argyrodite-type crystal (D50 = 0.5 μm, crystalline), was prepared as a solid electrolyte. Polytetrafluoroethylene (PTFE) binder was prepared as a binder. Carbon nanofibers (CNF) were prepared as a conductive agent. These materials were mixed with xylene solvent at a weight ratio of cathode active material: solid electrolyte: conductive agent: binder = 84: 11.5: 3: 1.5, and the slurry was molded into a sheet shape, and then vacuum-dried at 40°C for 8 hours to prepare a cathode sheet. The prepared cathode sheet was placed on the carbon layer of a cathode current collector composed of aluminum foil coated with a carbon layer on one side, and 85 o The positive electrode layer was manufactured by heated roll pressing of C. The total thickness of the positive electrode layer was approximately 120 μm. The thickness of each positive electrode active material layer was approximately 95 μm, and the thickness of the carbon-coated aluminum foil was approximately 25 μm.

[0303] The initial charge capacity of the positive electrode layer was measured by the above-described half-cell. For Examples 4 to 6, the ratio (B / A) of the initial charge capacity (B) of the first negative electrode active material layer to the initial charge capacity (A) of the positive electrode active material layer was less than 30% (i.e., less than 0.3). The initial charge capacity of the positive electrode active material layer was measured from the first open circuit voltage to Li / Li. + was determined by charging up to a maximum charging voltage of 4.25 V. In addition, the initial charge capacity of the first negative electrode active material layer was determined from the second open circuit voltage to Li / Li + It was determined by charging up to 0.01 V.

[0304] Example 5: NCM cathode layer / flexible electrolyte layer (separator + thermosetting polymer) / Ag-C cathode layer, thermal curing before laminate assembly.

[0305] A secondary battery was manufactured in the same manner as Example 4, except that an electrolyte layer impregnated with a polymer gel electrolyte in a separator was separately prepared and placed on the cathode layer, and a cathode layer was placed on the electrolyte layer.

[0306] The electrolyte layer was manufactured using the following method.

[0307] A polypropylene separator (celgard 3501) was placed as a flexible porous separator on the substrate. A thermosetting electrolyte composition was applied onto the separator, thereby impregnating the separator with the thermosetting electrolyte composition, and heat treatment was performed at 85°C for 2 hours to prepare an electrolyte layer in which the separator was impregnated with a polymer gel electrolyte.

[0308] Example 6: NCM cathode layer / flexible electrolyte layer (separator + high-viscosity liquid electrolyte) / Ag-C cathode layer

[0309] Instead of the cathode layer containing Li2S-LiI-CNF composite as the cathode layer, LiNi coated with Li2O-ZrO2 (LZO) prepared in Example 3 0.8 Co 0.15 Mn 0.05A lithium secondary battery was manufactured in the same manner as in Example 3, except that an O2(NCM)-containing cathode layer was used.

[0310] Example 7: Li2S-LiI-CNF cathode layer / flexible electrolyte layer (separator + thermosetting polymer) / Ag-C cathode layer / elastic sheet, thermal curing after lamination assembly

[0311] A 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 the secondary battery.

[0312] 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.

[0313] 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.

[0314] Comparative Example 1: S-carbon (C) anode layer / flexible electrolyte layer (separator + low-viscosity liquid electrolyte) / Li-metal anode layer, low-viscosity liquid electrolyte used

[0315] (Manufacturing of composite cathode active materials)

[0316] Sulfur (S) and carbon-based materials were mixed in a weight ratio of 70:30 and then heat-treated at 160°C to produce a sulfur-carbon composite. The carbon-based material was a carbon nanotube (CNT) with a specific surface area of ​​300 m2 / g and a particle diameter of 30 μm.

[0317] (Anode layer manufacturing)

[0318] A slurry having a solid content of 25 wt% was prepared by mixing a sulfur-carbon composite, a conductive agent, and a binder in a weight ratio of 90:5:5 and dissolving the mixture in water. The slurry was bar-coated on a carbon-coated aluminum foil current collector, dried at 50°C for 2 hours, and then rolled to prepare a cathode layer. Vapor-grown carbon fiber (VGCF) was used as the conductive agent, and polyvinylidene fluoride (PVDF) was used as the binder. The thickness of the cathode layer was approximately 120 μm. The thickness of the cathode active material layer was approximately 100 μm, and the thickness of the carbon-coated aluminum foil was approximately 20 μm.

[0319] (Cathode layer manufacturing)

[0320] A 20 ㎛ thick lithium metal foil was placed as a negative electrode active material layer on a 10 ㎛ thick SUS foil as a negative electrode current collector to prepare a negative electrode layer.

[0321] (Manufacturing of low-viscosity liquid electrolyte)

[0322] 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 ℃.

[0323] (Secondary battery manufacturing)

[0324] A polypropylene separator (celgard 3501) was prepared as a flexible porous separator.

[0325] A separator was placed on the cathode layer so that the lithium metal layer was in contact with the separator, and a stack was prepared by placing the anode layer on the separator.

[0326] 85 prepared laminates o Plate pressing was performed at a pressure of 0.5 MPa for 1 hour at C.

[0327] The pressurized laminate was placed in a pouch, filled with a low-viscosity liquid electrolyte, and vacuum-sealed. Portions of the positive and negative current collectors were extended outside the sealed battery to serve as positive and negative electrode terminals.

[0328] Comparative Example 2: Li2S-LiI-CNT anode layer / solid electrolyte layer (sulfide-based solid electrolyte) / Li-metal anode layer, inorganic solid electrolyte layer

[0329] (Manufacturing of composite cathode active materials)

[0330] Li2S, LiI, and carbon nanotubes (CNTs) were mixed in a weight ratio of 70:20:10. The mixture was mechanically milled using a ball mill to prepare a Li2S-LiI-CNT composite. The milling conditions were 25°C, 300 rpm, and 12 h.

[0331] A Li2S-LiI-CNT composite was used as a composite cathode active material.

[0332] (Anode layer manufacturing)

[0333] The cathode layer was prepared in the same manner as in Example 1, except that the Li2S-LiI-CNT composite was used.

[0334] (Cathode layer manufacturing)

[0335] A 20 ㎛ thick lithium metal foil was placed as a negative electrode active material layer on a 10 ㎛ thick SUS foil as a negative electrode current collector to prepare a negative electrode layer.

[0336] (Manufacturing of solid electrolyte layer)

[0337] Li6PS5Cl solid electrolyte in the form of argyrodite crystals (D 50=3.0 mm, crystalline), a mixture was prepared by adding 1.5 parts by weight of an acrylic binder to 98.5 parts by weight of the solid electrolyte. Octyl acetate was added to the prepared mixture and stirred to prepare a slurry. The prepared slurry was applied using a bar coater onto a 15 μm thick nonwoven fabric placed on a 75 μm thick PET substrate, and dried in air at 80°C for 10 minutes to prepare a laminate. The prepared laminate was vacuum-dried at 80°C for 2 hours to prepare a solid electrolyte layer.

[0338] (Manufacturing of secondary batteries)

[0339] A solid electrolyte layer was placed on the cathode layer so that the lithium metal layer was in contact with the solid electrolyte layer, and a layer was prepared by placing the anode layer on the solid electrolyte layer.

[0340] 85 prepared laminates o Plate press treatment was performed at a pressure of 500 MPa for 30 min at C.

[0341] The pressurized laminate was placed in a pouch and vacuum-sealed to manufacture a secondary battery. Portions of the positive and negative current collectors were extended outside the sealed battery to serve as positive and negative terminals.

[0342] Comparative Example 3: Li2S-LiI-CNF cathode layer / flexible electrolyte layer (separator + thermosetting polymer) / Cu current collector, thermal curing after laminate assembly, no use of negative electrode active material layer

[0343] A secondary battery was manufactured in the same manner as in Example 1, except that the first negative electrode active material layer containing carbon black (CB) and silver (Ag) particles was omitted. The battery had a structure in which the negative electrode current collector was directly disposed on the electrolyte layer.

[0344] Comparative Example 4: NCM cathode layer / solid electrolyte layer (sulfide-based solid electrolyte) / Li-metal cathode layer, inorganic solid electrolyte layer

[0345] Instead of the anode layer containing Li2S-LiI-CNT composite as the anode layer, LiNi coated with Li2O-ZrO2 (LZO) prepared in Example 4 0.8 Co 0.15 Mn 0.05 A lithium secondary battery was manufactured in the same manner as in Comparative Example 2, except that an O2(NCM)-containing cathode layer was used.

[0346]

[0347] Evaluation Example 1: Life Characteristics Evaluation

[0348] The charge / discharge characteristics of the secondary batteries manufactured in Examples 1 to 7, Comparative Examples 1 to 3, and Reference Example 1 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.

[0349] In the first cycle, the lithium battery was charged at a constant current of 0.05 C rate at 45°C until the voltage reached 2.7 V (vs. Li). Subsequently, the battery was discharged at a constant current of 0.05 C rate until the voltage reached 1.0 V (vs. Li).

[0350] Next, the lithium battery was charged at a constant current of 0.1 C rate at 45°C until the voltage reached 2.7 V (vs. Li). Subsequently, the discharge cycle was repeated at a constant current of 0.1 C rate until the voltage reached 1.0 V (vs. Li). The discharge capacity of the first cycle was taken as the standard capacity.

[0351] The charge-discharge characteristics of the secondary batteries manufactured in Examples 4 to 6 were evaluated by the following charge-discharge test. The charge-discharge test was performed by placing the all-solid-state secondary batteries in a constant temperature bath at 45°C.

[0352] In the first cycle, the lithium battery was charged at a constant current of 0.05 C rate at 45°C until the voltage reached 4.2 V (vs. Li). Subsequently, the battery was discharged at a constant current of 0.05 C rate until the voltage reached 2.5 V (vs. Li).

[0353] Next, the lithium battery was charged at a constant current of 0.1 C rate at 45°C until the voltage reached 4.2 V (vs. Li). Then, the discharge cycle was repeated at a constant current of 0.1 C rate until the voltage reached 2.5 V (vs. Li).

[0354] The discharge capacity of the first cycle was taken as the standard capacity.

[0355] After the second cycle, charging and discharging were performed up to 150 cycles under the same conditions as the first cycle. The measurement results are shown in Table 1 below.

[0356] The cycle count is the number of cycles required for the discharge capacity to decrease to 80% of the standard capacity after the second cycle. As the cycle count increases, the battery is considered to have better or more suitable life characteristics.

[0357] Number of cycles [times] Example 1 (Li2S-LiI-CNF positive electrode active material, GPE + porous separator, Ag-C negative electrode active material, thermal curing after laminate assembly) 510 Example 2 (Same as Example 1, but thermal curing before laminate assembly) 320 Example 3 (Li2S-LiI-CNF positive electrode active material, high viscosity electrolyte + porous separator, Ag-C negative electrode active material) 408 Example 4 (NCM positive electrode active material, GPE + porous separator, Ag-C negative electrode active material, thermal curing after laminate assembly) 720 Example 5 (Same as Example 4, but thermal curing before laminate assembly) 505 Example 6 (NCM positive electrode active material, high viscosity electrolyte + porous separator, Ag-C negative electrode active material) 601 Example 7 (Addition of elastic sheet to the outside of the negative electrode) (Example 1) + Negative elastic sheet)430Comparative Example 1 (S-carbon positive electrode active material, low viscosity electrolyte + porous separator, Li metal negative electrode active material)8Comparative Example 2 (Li2S-LiI-CNT positive electrode active material, sulfide-based solid electrolyte layer, Li-metal negative electrode active material)32Comparative Example 3 (Direct contact between electrolyte layer and Cu negative electrode current collector)5Comparative Example 4 (NCM positive electrode active material, sulfide-based solid electrolyte layer, Li-metal negative electrode active material)102

[0358] As shown in Table 1, the secondary batteries of Examples 1 to 7 have improved life characteristics compared to the secondary batteries of Comparative Examples 1 to 3.

[0359] The secondary batteries of Examples 1 to 7 provided improved life characteristics by reducing the interfacial resistance between the positive electrode layer, the negative electrode layer, and the electrolyte layer by including a flexible electrolyte, and effectively accommodating changes in the volume of the positive electrode layer and the negative electrode layer during the charge and discharge process.

[0360] In the secondary battery of Comparative Example 1, the electrode capacity was reduced due to polysulfide generated from sulfur (S) dissolving in the liquid electrolyte during the charge / discharge process, and the life characteristics were reduced due to the dissolved polysulfide causing a side reaction with the negative electrode layer.

[0361] In the secondary battery of Comparative Example 2, cracks and other defects occurred in the solid electrolyte layer during the pressurized manufacturing process and the charging and discharging process of the secondary battery, and short circuits occurred due to the growth of lithium dendrites through these defects. As a result, the life characteristics of the secondary battery were deteriorated.

[0362] In the secondary battery of Comparative Example 3, the polymer electrolyte layer was in direct contact with the negative electrode collector, and thus, during the charging and discharging process of the secondary battery, lithium metal was precipitated and dissolved on the surface of the negative electrode collector, and thus the life characteristics of the secondary battery were deteriorated due to the formation of dendrites and the creation of isolated lithium metal.

[0363]

[0364] Evaluation Example 2: High-Rate Characteristic Evaluation

[0365] After the life evaluation of Evaluation Example 1, the high-rate characteristics of the secondary batteries manufactured in Examples 1 to 7 and Comparative Examples 1 to 4 were evaluated by the following charge-discharge test. The charge-discharge test was performed by placing the secondary batteries in a constant temperature bath at 45°C.

[0366] The lithium battery was charged at a constant current of 0.1 C rate at 45°C until the voltage reached 2.7 V (vs. Li). Subsequently, it was discharged at a constant current of 0.1 C rate until the voltage reached 1.0 V (vs. Li) (first cycle).

[0367] The lithium battery that had undergone the first cycle was charged at a constant current of 0.1 C rate at 45°C until the voltage reached 2.7 V (vs. Li). Subsequently, it was discharged at a constant current of 0.2 C rate until the voltage reached 1.0 V (vs. Li) (second cycle).

[0368] The lithium battery that had undergone the second cycle was charged at a constant current of 0.12 C rate at 45°C until the voltage reached 2.7 V (vs. Li). Subsequently, it was discharged at a constant current of 0.5 C rate until the voltage reached 1.0 V (vs. Li) (third cycle).

[0369] The lithium battery that had undergone the third cycle was charged at a constant current of 0.1 C rate at 45°C until the voltage reached 2.7 V (vs. Li). Subsequently, it was discharged at a constant current of 1.0 C rate until the voltage reached 1.0 V (vs. Li) (4th cycle).

[0370] After the life evaluation of Evaluation Example 1, the lithium batteries manufactured in Examples 4 to 6 and Comparative Example 4 were charged at a constant current of 0.1 C rate at 45°C until the voltage reached 2.5 V (vs. Li). Subsequently, they were discharged at a constant current of 0.1 C rate until the voltage reached 2.5 V (vs. Li) (first cycle).

[0371] The lithium battery that had undergone the first cycle was charged at a constant current of 0.1 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 2.5 V (vs. Li) (second cycle).

[0372] The lithium battery that had undergone the second cycle was charged at a constant current of 0.1 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 2.5 V (vs. Li) (third cycle).

[0373] The lithium battery that had undergone the third cycle was charged at a constant current of 0.1 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 2.5 V (vs. Li) (4th cycle).

[0374] 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).

[0375] <Mathematical Formula 1>

[0376] High rate characteristics [%] = [Discharge capacity at the 4th cycle (1.0 C) / Discharge capacity at the 1st cycle (0.1 C)] Х 100

[0377] High rate characteristics (1C / 0.1C) [%] Example 1 (Li2S-LiI-CNF positive electrode active material, GPE + porous separator, Ag-C negative electrode active material, thermal curing after laminate assembly) 87.5 Example 2 (Same as Example 1, but thermal curing before laminate assembly) 78.1 Example 3 (Li2S-LiI-CNF positive electrode active material, high viscosity electrolyte + porous separator, Ag-C negative electrode active material) 83.2 Example 4 (NCM positive electrode active material, GPE + porous separator, Ag-C negative electrode active material, thermal curing after laminate assembly) 92.2 Example 5 (Same as Example 4, but thermal curing before laminate assembly) 87.2 Example 6 (NCM positive electrode active material, high viscosity electrolyte + porous separator, Ag-C negative electrode active material) 89.9 Example 7 (Addition of elastic sheet to the outside of the negative electrode) (Example 1 + negative electrode elastic sheet) 85.5 Comparative Example 1 (S-carbon positive electrode active material, low viscosity electrolyte + porous separator, Li metal negative electrode active material) 8.1 Comparative Example 2 (Li2S-LiI-CNT positive electrode active material, sulfide-based solid electrolyte layer, Li-metal negative electrode active material) 16.5 Comparative Example 3 (Direct contact between electrolyte layer and Cu negative electrode current collector) 25.0 Comparative Example 4 (NCM positive electrode active material, sulfide-based solid electrolyte layer, Li-metal negative electrode active material) 56.2

[0378] As shown in Table 2, the secondary batteries of Examples 1 to 3 and Example 7 containing sulfide-based cathode active materials had improved high-rate characteristics compared to the secondary batteries of Comparative Examples 1 to 3 containing sulfur-based or sulfide-based cathode active materials.

[0379] In addition, the secondary batteries of Examples 4 to 6 including an oxide-based cathode active material had improved high-rate characteristics compared to the secondary battery of Comparative Example 4 including an oxide-based cathode active material.

[0380] [Explanation of symbols]

[0381] 1, 1a, 1b, 1c secondary battery 10, 10a, 10b, 10c positive electrode layer

[0382] 11. Cathode current collector 12. Cathode active material layer

[0383] 20, 20a, 20b 30a cathode layer 21 cathode current collector

[0384] 22 First negative electrode active material layer 30, 30a, 30b, 30c electrolyte layer

[0385] 40 First inert member 50a, 50b, 50c battery case

[0386] 60a, 60b, 60c cap assembly 70a, 70b, 70c battery assembly

[0387] According to one aspect, by arranging a flexible electrolyte layer between the positive electrode layer and the negative electrode layer, the interfacial resistance between the positive electrode layer and / or the negative electrode layer and the electrolyte layer is reduced, and cracking of the solid electrolyte layer, etc. is suppressed during the charge / discharge process, thereby providing a secondary battery having improved cycle characteristics.

Claims

1. It comprises an anode layer; a cathode layer; and a flexible electrolyte layer disposed between the anode layer and the cathode layer, The above positive electrode layer includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, The above 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, A secondary battery, wherein the initial charge capacity of the first negative electrode active material layer is less than 50% of the initial charge capacity of the positive electrode active material layer.

2. A secondary battery according to claim 1, wherein the electrolyte layer comprises 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.

3. A secondary battery in the second paragraph, 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 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 secondary battery according to claim 2, 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 fifth paragraph, a transition battery, wherein the ionic liquid is represented by one of the following chemical formulas 1 to 2: <Chemical Formula 1> <Chemical Formula 2> In the above chemical formula 1, X1 is -N(R2)(R3)(R4) or -P(R2)(R3)(R4), 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, In the above chemical formula 2, 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, X2 is =N(R5)(R6), -N(R5)=, =P(R5)(R6) or -P(R5)=, The substituents, R5, and R6 substituted on the ring 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, Y - is an anion.

7. In the first paragraph, the electrolyte layer is a self-standing film, A secondary battery, wherein the electrolyte layer further includes a flexible porous membrane.

8. A secondary battery in the first paragraph, wherein the positive electrode active material layer includes an alkali metal-containing sulfide-based positive electrode active material or an alkali metal-containing oxide-based positive electrode active material, and the alkali metal includes lithium or sodium.

9. In the 8th paragraph, the alkali metal-containing sulfide-based cathode active material includes a Li2S-containing complex, A secondary battery, wherein the above 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 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 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 9th paragraph, the Li2S-containing complex includes a composite of Li2S, a lithium salt, and a carbon-based material, Based on 100 parts by weight of the above Li2S-containing complex, 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. The above cathode active material layer further includes a sulfide-based solid electrolyte, A secondary battery, wherein the carbon-based material in the above cathode active material layer is disposed only in the Li2S-containing composite.

13. A secondary battery according to claim 8, wherein the alkali metal-containing oxide-based cathode active material comprises a lithium transition metal oxide represented by one of the chemical formulas 11 to 18: <Chemical Formula 11> Li a Ni x Co y M z O 2-b A b In the above chemical formula 11, 1.0≤a≤1.2, 0≤b≤0.2, 0.8≤x<1, 0≤y≤0.3, 0 <z≤0.3, 및 x+y+z=1이고, M is manganese (Mn), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B), or a combination thereof, A is F, S, Cl, Br or a combination thereof, <Chemical Formula 12> LiNi x Co y Mr z O2 <Chemical Formula 13> LiNi x Co y Al z O2 In the above chemical formulas 12 to 13, 0.8≤x≤0.95, 0≤y≤0.2, 0 <z≤0.2 및 x+y+z=1이며, <Chemical Formula 14> LiNi x Co y Mr z Al w O2 In the above chemical formula 14, 0.8≤x≤0.95, 0≤y≤0.2, 0 <z≤0.2, 0<w≤0.2, 및 x+y+z+w=1이며, <Chemical Formula 15> Li a Co x M y O 2-b A b In the above chemical formula 15, 1.0≤a≤1.2, 0≤b≤0.2, 0.9≤x≤1, 0≤y≤0.1, and x+y=1, M is manganese (Mn), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B), or a combination thereof, A is F, S, Cl, Br or a combination thereof, <Chemical Formula 16> Li a Ni x Mr y M' z O 2-b A b In the above chemical formula 16, 1.0≤a≤1.2, 0≤b≤0.2, 0 <x≤0.3, 0.5≤y<1, 0<z≤0.3, 및 x+y+z=1이고, M' is cobalt (Co), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B) or a combination thereof, A is F, S, Cl, Br or a combination thereof, <Chemical Formula 17> Yes a M1 x M2 y PO 4-b X b In the above chemical formula 17, 0.90≤a≤1.1, 0≤x≤0.9, 0≤y≤0.5, 0.9 <x+y<1.1, 0≤b≤2 이며, M1 is chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr) or a combination thereof, M2 is magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), titanium (Ti), zinc (Zn), boron (B), niobium (Nb), gallium (Ga), indium (In), molybdenum (Mo), tungsten (W), aluminum (Al), silicon (Si), chromium (Cr), vanadium (V), scandium (Sc), yttrium (Y) or a combination thereof, and X is O, F, S, P or a combination thereof. <Chemical Formula 18> Li a M3 z PO4 In the above chemical formula 18, 0.90≤a≤1.1, 0.9≤z≤1.1, M3 is chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr), or a combination thereof.

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

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

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

17. A 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.

18. In the first paragraph, a second negative electrode active material layer is further included, wherein the second negative electrode active material layer Between the negative electrode current collector and the first negative electrode active material layer and / or It is placed between the negative electrode collector and the electrolyte layer, A secondary battery, wherein the second negative electrode active material layer is a metal layer, and the metal layer includes lithium or a lithium alloy.

19. In the first paragraph, 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 secondary battery, wherein the metal layer comprises indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof.

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

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