Lithium metal battery and manufacturing method therefor

Abstract

Disclosed are a lithium metal battery and a manufacturing method therefor, the lithium metal battery comprising: a negative electrode current collector; a protective layer formed on the negative electrode current collector; a separator; a gel polyelectrolyte; and a positive electrode, wherein the protective layer includes boron nitride (BN) and a binder, and the gel polyelectrolyte contains a gel polymer, boron nitride (BN), a nitrile-based compound, and a liquid electrolyte.

Description

Lithium metal battery and manufacturing method thereof

[0001] It relates to a lithium metal battery and a method for manufacturing the same.

[0002] Lithium metal batteries currently on the market primarily use carbon-based anode materials, such as graphite. Carbon-based anode materials exhibit no volume change during charge / discharge, enhancing the stability of lithium metal batteries. However, their low capacity necessitates the use of higher-capacity anode materials.

[0003] Lithium metal, which has a much larger theoretical electric capacity than carbon-based negative electrode materials, can be used as a negative electrode material.

[0004] When lithium metal is charged and discharged, lithium dendrites are formed on the surface of the lithium metal due to a side reaction with the electrolyte, and the growth of the dendrites can cause a short circuit between the positive and negative electrodes, which can reduce the life characteristics of a lithium metal battery containing lithium metal.

[0005] A method using a solid electrolyte with high modulus and high lithium ion transport rate was proposed to control lithium dendrites.

[0006] However, among solid electrolytes, solid polymer electrolytes have low ionic conductivity at room temperature, and solid ceramic electrolytes are difficult to put into practical use due to difficulties in manufacturing and handling.

[0007] In comparison, gel polymer electrolytes are easy to manufacture and have excellent ionic conductivity and electrochemical performance, but their mechanical strength and ionic conductivity must be further improved.

[0008] One aspect is to provide a lithium metal battery with improved ionic conductivity and mechanical properties.

[0009] Another aspect is to provide a method for manufacturing the above-described lithium metal battery.

[0010] According to one embodiment, a lithium metal battery includes a negative electrode current collector; a protective film formed on the negative electrode current collector; a separator; a gel polymer electrolyte; and a positive electrode.

[0011] The above protective film includes boron nitride (BN) and a binder, and a lithium metal battery is provided in which the gel polymer electrolyte contains a gel polymer, boron nitride (BN), a nitrile compound, and a liquid electrolyte.

[0012] It may include a negative electrode active material layer disposed between the negative electrode current collector and the protective film.

[0013] According to another aspect, a method for manufacturing a lithium metal battery is provided, comprising: preparing a negative electrode current collector; forming a protective film comprising boron nitride and a binder on the negative electrode current collector; preparing a separator; preparing a positive electrode; preparing a battery assembly by laminating the negative electrode current collector, the separator, and the positive electrode; injecting a composition for forming a gel polymer electrolyte comprising a crosslinking monomer for forming a gel polymer, a liquid electrolyte, boron nitride, and a nitrile-based compound into the battery assembly; and performing a heat treatment to form a gel polymer electrolyte.

[0014] The step of forming a protective film comprising boron nitride and a binder on the negative electrode current collector includes coating and heat-treating a composition for forming a protective film comprising at least one binder precursor and a binder and boron nitride on the negative electrode current collector, and the protective film further comprises a lithium salt.

[0015] According to one aspect, a lithium metal battery is provided with improved ionic conductivity and physical properties and improved life cycle characteristics by adding boron nitride to a protective film and a gel polymer electrolyte.

[0016] Figure 1 is a drawing for explaining the laminated structure of a lithium metal battery according to an embodiment.

[0017] Figure 2 is a drawing for explaining the laminated structure of a lithium metal battery according to another embodiment.

[0018] Figure 3 is a drawing for explaining the laminated structure of a lithium metal battery according to another embodiment.

[0019] Figure 4 is a schematic diagram of a lithium metal battery according to an embodiment.

[0020] Figure 5 is a schematic diagram of a lithium metal battery according to another embodiment.

[0021] Figure 6 is a schematic diagram of a lithium metal battery according to another embodiment.

[0022] [Explanation of symbols]

[0023] 1: Lithium metal battery 2, 20: Cathode

[0024] 3, 10: Anode 4: Separator

[0025] 5: Battery case 6: Cap assembly

[0026] 7: Battery structure 8: Electrode tab

[0027] The present inventive concept described below is capable of various modifications and embodiments. Specific embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the present inventive concept to specific embodiments, but rather to encompass all modifications, equivalents, or alternatives within the technical scope of the present inventive concept.

[0028] The terminology used below is only used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. Hereinafter, the terms "comprises" or "has" and the like are intended to indicate the presence of a feature, number, step, operation, component, part, ingredient, material, or combination thereof described in the specification, but should be understood to not preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, ingredients, materials, or combinations thereof. The " / " used below may be interpreted as "and" or "or" depending on the context.

[0029] In order to clearly express various layers and regions in the drawings, the thickness is shown enlarged or reduced. Similar parts are designated by the same drawing reference numerals throughout the specification. When a part such as a layer, film, region, or plate is said to be "on" or "above" another part throughout the specification, this includes not only cases where it is directly above the other part, but also cases where there is another part in between. Terms such as first, second, etc. may be used throughout the specification to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. In this specification and the drawings, components having substantially the same functional configuration are referred to by the same reference numerals, and redundant descriptions are omitted.

[0030] Unless otherwise specified herein, when a part such as a layer, film, region, or plate is said to be “on top of” another part, this includes not only cases where it is “directly on top of” the other part, but also cases where there is another part in between.

[0031] Unless otherwise specified herein, the singular may also include the plural. Furthermore, unless otherwise specified, "A or B" may mean "including A, including B, or including A and B."

[0032] As used herein, “combination thereof” may mean mixtures, laminates, composites, copolymers, alloys, blends, and reaction products of the components.

[0033] In the present disclosure, the "size" of a particle refers to the average diameter if the particle is spherical, and refers to the average major axis length if the particle is non-spherical. The particle diameter can be measured using a particle size analyzer (PSA).

[0034] Unless otherwise defined herein, the particle size may be the average particle size. In addition, the particle size refers to the average particle size (D50), which means the diameter of particles with a cumulative volume of 50% by volume in a particle size distribution. The average particle size (D50) can be measured by a method well known to those skilled in the art, for example, by measuring with a particle size analyzer, or by measuring with a transmission electron microscope (TEM) photograph or a scanning electron microscope (SEM) photograph. Alternatively, the average particle size (D50) value can be obtained by measuring with a measuring device that utilizes dynamic light-scattering, performing data analysis to count the number of particles for each particle size range, and calculating from the counted number. Alternatively, the average particle size (D50) value can be obtained by measuring with a laser diffraction method. When measuring by laser diffraction, more specifically, after the particles to be measured are dispersed in a dispersion medium, they are introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000) and irradiated with ultrasonic waves of approximately 28 kHz at an output of 60 W, and the average particle size (D50) based on 50% of the particle size distribution in the measuring device can be calculated.

[0035] In the present disclosure, “metal” includes both metals and metalloids such as silicon and germanium, in their elemental or ionic states, and “alloy” means a mixture of two or more metals.

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

[0037] In the present disclosure, “lithiation” and “lithiating” mean a process of adding lithium to a positive electrode active material or a negative electrode active material, and “delithiation” and “delithiating” mean a process of removing lithium from a positive electrode active material or a negative electrode active material.

[0038] In the present disclosure, “charging” and “charging” mean a process of providing electrochemical energy to a battery, and “discharging” and “discharging” mean a process of removing electrochemical energy from a battery.

[0039] In the present disclosure, “positive electrode” and “cathode” mean an electrode where electrochemical reduction and lithiation occur during a discharge process, and “negative electrode” and “anode” mean an electrode where electrochemical oxidation and delithiation occur during a discharge process.

[0040] In the present disclosure, the aspect ratio represents the ratio (L1 / L2) of the major axis length L1 (e.g., length) and the minor axis length L2 (e.g., diameter). Here, the aspect ratio, major axis length, minor axis length, length, and diameter represent the average aspect ratio, average major axis length, average minor axis length, average length, and average diameter. The aspect ratio can be evaluated using a scanning electron microscope.

[0041] In the present disclosure, the terms “thickness” and “length” mean average thickness and average length, respectively.

[0042] Hereinafter, a lithium metal battery and a method for manufacturing the same according to exemplary embodiments are described in more detail.

[0043] A non-cathode lithium metal battery is a battery that uses only a cathode current collector without a cathode active material layer. When charging, lithium ions transferred from the cathode are deposited on the surface of the cathode current collector, and when discharging, the lithium deposited on the cathode current collector is eluted again and inserted into the cathode, thereby operating the battery.

[0044] Non-cathode lithium metal batteries offer the advantage of maximizing energy density per volume / weight of the battery by omitting lithium metal as the anode active material. However, lithium metal precipitates during operation, and the uneven current concentration during oxidation / reduction causes lithium dendrites to grow. These dendrites not only cause lithium anode loss, reducing battery capacity and lifespan, but can also cause short-circuiting between the anode and cathode, posing safety concerns.

[0045] To solve the above-mentioned problem, a method was proposed in which a protective film is introduced on the top of the negative electrode current collector to minimize contact between lithium and the electrolyte, thereby reducing side reactions, thereby minimizing exposure of the electrolyte on the electrode surface and creating a uniform flow of lithium ions throughout the electrode, thereby suppressing lithium dendrite growth.

[0046] A lithium metal battery according to an embodiment includes: a negative electrode current collector; a protective film formed on the negative electrode current collector; a separator; a gel polymer electrolyte; and a positive electrode, wherein the protective film includes boron nitride (BN) and a binder, and the gel polymer electrolyte contains a gel polymer, boron nitride (BN), a nitrile compound, and a liquid electrolyte.

[0047] The protective film and gel polymer electrolyte of a lithium metal battery according to an embodiment of the present invention contain boron nitride.

[0048] Boron nitride possesses Lewis acid properties, allowing it to interact with polymers. When added as an additive to protective films and gel polymer electrolytes, boron nitride increases the strength and ionic conductivity of the protective film, gel polymer electrolyte, and separator containing them. As a result, lithium metal batteries equipped with these protective films, gel polymer electrolytes, and separators exhibit reduced resistance and improved cycle life.

[0049] The size of boron nitride is, for example, 0.01 um (10 nm) to 10 um, 0.1 um (100 nm) to 5 um, 0.1 um (100 nm) to 3 um, 0.1 um (100 nm) to 2 um, or 0.1 um (100 nm) to 1 um. In addition, the content of boron nitride in the gel polymer electrolyte according to one embodiment can be controlled to be equal to or smaller than the content of boron nitride in the protective film. When the content of boron nitride is in this range, the protective film has properties effective in suppressing dendrites during lithium electrodeposition, and the ionic conductivity of the gel polymer electrolyte increases, thereby manufacturing a lithium metal battery with increased life characteristics.

[0050] In the protective film, the content of boron nitride is 5 parts by weight or less, 0.01 to 5 parts by weight, 0.05 to 5 parts by weight, 0.1 to 5 parts by weight, 0.2 to 5 parts by weight, or 0.5 to 3 parts by weight, based on 100 parts by weight of the total weight of the protective film. When the content of boron nitride in the protective film is within the above range, the mechanical properties are improved without deterioration in ionic conductivity.

[0051] The content of boron nitride in the gel polymer electrolyte is 5 parts by weight or less, 0.01 to 5 parts by weight, 0.05 to 5 parts by weight, 0.05 to 3 parts by weight, or 0.1 to 3 parts by weight, based on 100 parts by weight of the gel polymer electrolyte. When the content of boron nitride in the gel polymer electrolyte is within the above range, a gel polymer electrolyte having improved mechanical properties without deterioration in ionic conductivity can be obtained.

[0052] In a lithium metal battery according to an embodiment, the thickness of the protective film is 1 to 10 um, and the thickness of the separator is 5 to 20 um. When the thickness of the protective film and the separator are within the above ranges, a lithium metal battery having improved ionic conductivity and physical properties and improved lifespan characteristics can be provided.

[0053] The above gel polymer electrolyte contains a gel polymer, boron nitride, a nitrile compound, and a liquid electrolyte.

[0054] Nitrile compounds have a melting point of 30°C or higher and are solid or solid-like substances at room temperature. These nitrile compounds exhibit excellent stability and ionic conductivity.

[0055] The nitrile compound may include, for example, one or more selected from the group consisting of succinonitrile, adiponitrile, pimelonitrile, suberonitrile, sebaconitrile, butyronitrile, acetonitrile, and propionitrile. The content of the nitrile compound is 0.01 to 5 parts by weight, 0.05 to 3 parts by weight, or 0.1 to 3 parts by weight based on 100 parts by weight of the total weight of the gel polymer electrolyte.

[0056] Nitrile compounds include, for example, succinonitrile.

[0057] The liquid electrolyte contains a lithium salt and a non-aqueous organic solvent. The non-aqueous organic solvent acts as a medium through which ions involved in the electrochemical reaction of the battery can move. The non-aqueous organic solvent may be a carbonate, ester, ether, ketone, or alcohol solvent, an aprotic solvent, or a combination thereof.

[0058] Examples of carbonate solvents that can be used include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), fluoroethylene carbonate (FEC), and difluoroethylene carbonate (2FEC).

[0059] Ester solvents that can be used include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, caprolactone, fluorinated ethyl acetate, and fluorinated propyl acetate.

[0060] Examples of ether solvents that can be used include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and tetrahydrofuran. In addition, examples of ketone solvents that can be used include cyclohexanone. Examples of alcohol solvents that can be used include ethyl alcohol and isopropyl alcohol, and examples of aprotic solvents that can be used include nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double bond, an aromatic ring, or an ether group); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane and 1,4-dioxolane; and sulfolanes.

[0061] The above non-aqueous organic solvents can be used alone or in combination of two or more.

[0062] In addition, when using a carbonate solvent, a cyclic carbonate and a chain carbonate can be mixed and used, and the cyclic carbonate and the chain carbonate can be mixed in a volume ratio of 1:1 to 1:9.

[0063] The above lithium salt is a substance that dissolves in an organic solvent and acts as a source of lithium ions in the battery, enabling the basic operation of a lithium secondary battery and promoting the movement of lithium ions between the positive and negative electrodes. Representative examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide (LiFSI), LiC4F9SO3, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2) (wherein x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalato)phosphate (LiDFOB), lithium bis(oxalato)borate (LiBOB). The concentration of the lithium salt is, for example, from 0.1 M to 5.0 M.

[0064] The gel polymer electrolyte may be present within the separator and at the interface between the separator and the positive electrode. The gel polymer electrolyte may be contained within a portion of the positive electrode.

[0065] The above gel polymer is a crosslinked product of i) a multifunctional acrylic monomer having three or more polymerizable functional groups; or ii) a crosslinked product of a first polymerizable monomer having three or more polymerizable functional groups, and at least one second polymerizable monomer selected from a urethane acrylic monomer having two or more polymerizable functional groups and a polymerizable monomer containing a perfluoropolyether (PFPE) unit and having two or more polymerizable functional groups.

[0066] A multifunctional acrylic monomer having three or more polymerizable functional groups has, for example, three or more polymerizable functional groups, for example, three to six polymerizable functional groups. When the multifunctional acrylic monomer, which is the first polymerizable monomer, has three or more polymerizable functional groups, a gel polymer electrolyte having excellent physical properties can be obtained. Such polymerizable monomers are, for example, pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate (TMPTMA), propoxylated(3) trimethylolpropane triacrylate (PO(3)TMPTA), propoxylated(6) trimethylolpropane triacrylate (PO(6)TMPTA), ethoxylated trimethylolpropane triacrylate, di(trimethylolpropane) tetraacrylate, pentaerythritol triacrylate (PETA), propoxylated glyceryl triacrylate, tris(2-hydroxyethyl) isocyanurate triacrylate (THEICTA), dipentaerythritol pentaacrylate (DPEPA), or combinations thereof.

[0067] A urethane acrylic monomer having two or more functional groups is a compound represented by the following chemical formula 1, a compound represented by the following chemical formula 2, or a combination thereof.

[0068] <Chemical Formula 1>

[0069]

[0070] In chemical formula 1, n is an integer from 1 to 100, and R a and R b are the same or different from each other, and are substituted or unsubstituted C1-C10 alkylene groups, EG represents an ethylene glycol residue, DEG represents a diethylene glycol residue, and TMP represents a trimethylolpropane residue.

[0071] <Chemical Formula 2>

[0072]

[0073] In the above chemical formula 2, each R is independently a hydrogen atom or a C1-C3 alkyl group.

[0074] The compound of the above chemical formula 1 or the compound of the above chemical formula 2 is a polyfunctional acrylic monomer containing a urethane group.

[0075] The compound represented by the above chemical formula 1 may include, for example, a compound represented by the following chemical formula 1-1.

[0076] <Chemical Formula 1-1>

[0077]

[0078] In chemical formula 1-1, n1 is an integer from 1 to 100, EG is a residue of ethylene glycol, DEG is a residue of diethylene glycol, and trimethylolpropane is a residue.

[0079] In chemical formula 1-1, n1 is an integer from 3 to 80, an integer from 5 to 50, or an integer from 5 to 30.

[0080] The compound of the above-described chemical formula 1 and the compound of the chemical formula 1-1 can be manufactured using the manufacturing method disclosed in Korean Patent Publication No. 10-1326629, and Korean Patent Publication No. 10-1326629 is incorporated herein by reference and cited herein.

[0081] The compound of the above-described chemical formula 1 has an isonate group at the terminal, and the method for producing this compound is described as follows.

[0082] A polyester polyol is prepared by mixing C1-C10 aliphatic dicarboxylic acids, diethylene glycol, ethylene glycol, and trimethylolpropane, adding a reaction catalyst, and heat-treating the mixture. Here, the polyester polyol is obtained through an ester reaction between a C1-C10 aliphatic dicarboxylic acid and the alcohols diethylene glycol, ethylene glycol, and trimethylolpropane. Titanium isopropoxide is used as the reaction catalyst.

[0083] By adding isocyanatoethyl methacrylate to the above polyester polyol, a reaction between the polyester polyol and isocyanatoethyl methacrylate occurs to form polyurethane, thereby producing a compound of chemical formula 1 having isocyanate at both ends.

[0084] C1-C10 aliphatic dicarboxylic acids include diadipic acid, succinic acid, sebacic acid, or combinations thereof.

[0085] The reaction of the polyester polyol and isocyanatoethyl methacrylate forms polyurethane by reacting at least a portion of the hydroxyl groups of the polyester polyol with isocyanatoethyl methacrylate. Monomethyl ether hydroquinone as a polymerization inhibitor, butylated hydroxy toluene as an antioxidant, and dibutyl tin dilaulate as a reaction catalyst may be added to the reaction of the polyester polyol and isocyanatoethyl methacrylate.

[0086] The weight average molecular weight of the compound of the above-described chemical formula 1 and the compound of the chemical formula 1-1 may be in the range of 10,000 to 100,000. The range of n in chemical formula 1 and chemical formula 3 may be used to have such a weight average molecular weight.

[0087] Since the polyfunctional acrylic monomer containing a urethane group has high mechanical strength and elasticity by including a urethane moiety, when forming a copolymer structure with a polyfunctional block copolymer, a gel polymer electrolyte having high mechanical strength and elasticity can be manufactured.

[0088] Since a urethane acrylic monomer having two or more functional groups has high mechanical strength and elasticity by including a urethane moiety, when it is used as a second polymerizable monomer to form a crosslinked product with the first polymerizable monomer, a gel polymer electrolyte having elasticity while maintaining high mechanical strength can be manufactured.

[0089] As a second polymerizable monomer, a monomer containing a multifunctional functional group having a structure similar to a urethane-containing multifunctional acrylic monomer may be added. As other monomers containing such a multifunctional functional group, for example, one or more selected from the group consisting of urethane acrylate methacrylate, urethane epoxy methacrylate, and Arkema's product names Satomer N3DE180 and N3DF230 may be used.

[0090] When a polyfunctional acrylic monomer containing a urethane group is used as a polymerizable monomer, it can act as a diluent in the electrolyte, thereby reducing the viscosity of the composition for forming a gel polymer electrolyte. The viscosity of the composition for forming a gel polymer electrolyte is 4 to 10 cps. Therefore, using a composition having such a viscosity can facilitate injection into a battery structure.

[0091] The multifunctional acrylic monomer having three or more polymerizable functional groups and the multifunctional acrylic monomer containing a urethane group have strong lithium cation (Li+) interaction and anion interaction, so that lithium cation ions are transferred through the polymer chain and anions are trapped, thereby greatly increasing the lithium cation transport rate (Li+ transferenece number). Here, the lithium cation and anion are, for example, the cation and anion of a lithium salt, and when LiPF6 is used as the lithium salt, the anion is, for example, PF6 - am.

[0092] The polymerizable monomer containing the above PFPE (perfluoropolyether) unit and having two or more polymerizable functional groups contains a perfluoroether unit and has excellent ionic conductivity, and examples thereof include a compound represented by the following chemical formula 3 or chemical formula 3-1.

[0093] <Chemical Formula 3>

[0094]

[0095] In chemical formula 3, R1 is hydrogen or a C1-C6 alkyl group, m and n are each greater than 0, and the sum of m+n is in the range of 2 to 300 or in the range of 1 to 100. For example, m is a number from 1 to 150, or from 1 to 100, and n is a number from 1 to 150, or from 1 to 100.

[0096] <Chemical Formula 3-1>

[0097]

[0098] In Chemical Formula 3-1, p and q are greater than 0, the sum of p+q is in the range of 2 to 300, or in the range of 1 to 100, p is a number from 1 to 150, or a number from 1 to 100, and q is a number from 1 to 150 or 1 to 100.

[0099] The weight average molecular weight of the compound represented by the above chemical formula 3 or chemical formula 3-1 is, for example, 400 to 10,000, 400 to 5,000, or 500 to 3,000.

[0100] In the polymerizable monomer containing the above PFPE unit and having two or more polymerizable functional groups, the number of polymerizable functional groups may be three or more, or four or more.

[0101] The compound of the above chemical formula 3 has four (meth)acrylic groups, which are crosslinking functional groups, and thus can form a network capable of trapping a large amount of liquid while using a small amount compared to a case where a compound having less than three crosslinking functional groups is used.

[0102] The above second polymerizable monomer is, for example, a compound represented by the following chemical formula 4, a compound represented by the following chemical formula 5, or a combination thereof.

[0103] <Chemical Formula 4>

[0104]

[0105] In chemical formula 4, m and n are greater than 0, and the sum of m+n is in the range of 2 to 300 or in the range of 1 to 100. For example, m is a number from 1 to 150, or from 1 to 100, and n is a number from 1 to 150, or from 1 to 100.

[0106] <Chemical Formula 5>

[0107]

[0108] In chemical formula 5, m and n are greater than 0, and the sum of m+n is in the range of 2 to 300. The sum of m+n is, for example, in the range of 1 to 100. For example, m is a number from 1 to 150, or from 1 to 100, and n is a number from 1 to 150, or from 1 to 100.

[0109] The polymerizable monomer containing the above PFPE unit and having three or more polymerizable functional groups is commercially available as Sangpungmyeong Fluorolink AD 1700 PFPE - perfluoropolyether (PFPE) urethane acrylate (Solvay Specialty Polymers Italy SpA).

[0110] The mixing weight ratio of the first polymerizable monomer, which is a multifunctional acrylic monomer, and at least one second polymerizable monomer selected from a urethane acrylic monomer having two or more functional groups and a polymerizable monomer containing a PFPE unit and three or more polymerizable functional groups is in the range of 1:10 to 10:1. The weight ratio of the first polymerizable monomer and the second polymerizable monomer is, for example, 5:1 to 1:1 or 3:1 to 1:1. When the weight ratio of the first polymerizable monomer and the second polymerizable monomer is in the above range, a gel polymer electrolyte with improved ionic conductivity and physical properties can be formed.

[0111] The size of boron nitride contained in the protective film and gel polymer electrolyte is, for example, 0.01 um to 10 um, 0.02 um to 10 um, 0.02 um (20 nm) to 0.1 um (100 nm), or 40 to 80 nm. When the size of boron nitride is within the above range, the ionic conductivity characteristics are excellent.

[0112] In the above gel polymer electrolyte, the content of boron nitride is 5 parts by weight or less, 0.1 to 5 parts by weight, 0.1 to 3 parts by weight, or 0.1 to 1 part by weight based on 100 parts by weight of the total weight of the gel polymer electrolyte. When the content of boron nitride in the gel polymer electrolyte is within the above range, a gel polymer electrolyte having excellent ion conductivity can be produced.

[0113] A gel polymer electrolyte contains 90 to 97 parts by weight of a liquid electrolyte, 90 to 96 parts by weight of a liquid electrolyte, 90 to 95 parts by weight of a liquid electrolyte, or 92 to 94 parts by weight of a gel polymer (crosslinked polymer), 1 to 9 parts by weight, 1 to 8 parts by weight, or 2 to 8 parts by weight of a gel polymer (crosslinked polymer), 5 parts by weight or less, 0.01 to 5 parts by weight, 0.05 to 5 parts by weight, or 0.1 to 3 parts by weight of boron nitride, and 0.01 to 5 parts by weight, 0.05 to 5 parts by weight, or 0.1 to 3 parts by weight of a nitrile compound.

[0114] The gel polymer electrolyte contains 90 to 95 parts by weight, 91 to 94 parts by weight, or 92 to 93 parts by weight of a liquid electrolyte and 1 to 8 parts by weight, 2 to 7 parts by weight, 2 to 6 parts by weight, or 3 to 5 parts by weight of a crosslinked polymer. When the contents of the liquid electrolyte and the crosslinked polymer in the gel polymer electrolyte are within the above ranges, ionic conductivity is improved.

[0115] The gel polymer electrolyte made of a crosslinked product obtained from the first polymerizable monomer and the second polymerizable monomer is Li + Cations such as and PF6 - The interaction with anions such as is very strong. This strong interaction can be confirmed to be caused by the difference in electron density distribution in the DFT simulation.

[0116] Boron nitride has a hexagonal crystal structure, a cubic crystal structure, and a wurtzite crystal structure depending on pressure and temperature. In the present disclosure, boron nitride having a hexagonal crystal structure is used because it has superior chemical stability and mechanical properties.

[0117] In the present disclosure, the purity of boron nitride is 98% or more, and in the X-ray diffraction spectrum, the (002) plane peak (c-axis lattice constant) is within 3.33 to 3.36 Å, and the (102) plane peak appears at an intensity ratio of 100:3 or more with respect to the (002) plane peak, which may be hexagonal crystal boron nitride.

[0118] Boron nitride can be nano-sized microcrystals or fibrous. The nano-sized microcrystals have particle diameters ranging from 20 to 200 nm, 50 to 200 nm, and an average size of 5 to 50 nm. The fibrous boron nitride has a length of 30 μm or more and 5 mm or less, and an aspect ratio of 10 to 50.

[0119] The above gel polymer electrolyte-containing separator is manufactured separately in the form of a self-supporting membrane, and a lithium metal battery can be manufactured by positioning the gel polymer electrolyte-containing separator on top of the negative electrode current collector and protective film and placing the positive electrode on top of it.

[0120] Alternatively, a lithium metal battery having a separator containing a gel polymer electrolyte can be manufactured by forming a battery structure by positioning a negative electrode current collector and a protective film, and arranging a separator and a positive electrode on top of the battery structure, and injecting a composition for forming a gel polymer electrolyte into the battery structure and performing heat treatment.

[0121] The negative electrode active material layer may be disposed between the negative electrode current collector and the protective film, or the negative electrode active material layer may be absent (free).

[0122] Figure 1 shows a laminated structure of a lithium metal battery according to an embodiment.

[0123] A lithium metal battery (1) has a negative electrode (20) including a negative electrode current collector (21), and the negative electrode active material layer is absent.

[0124] A protective film (22) is formed between the negative electrode current collector (21) and the separator (30).

[0125] A positive electrode (10) is sequentially arranged on top of the above separator (30). The positive electrode (10) contains a positive electrode active material layer (12) and a positive electrode current collector (11). A gel polymer electrolyte is contained within the separator (30).

[0126] As shown in Fig. 2, a gel polymer electrolyte (31) can be placed between the separator (30) and the anode (10). Although not shown in Figs. 1 and 2, the gel polymer electrolyte can be contained in the anode (10).

[0127] Between the negative electrode current collector (21) and the protective film (22), a negative electrode active material layer (23) may be further disposed as shown in Fig. 3. The negative electrode active material layer may include lithium metal or a lithium alloy.

[0128] A lithium precipitation layer, a lithium electrodeposition induction layer, or a combination thereof may be further included between the negative electrode current collector (21) and the protective film (22).

[0129] The protective film is a lithium-ion conductive buffer layer that prevents the separator containing the gel polymer electrolyte from contacting lithium metal. It also inhibits the formation and growth of lithium dendrites on the negative electrode current collector.

[0130] The thickness expansion rate of the negative electrode of a lithium metal battery according to an embodiment is 150% or less.

[0131] <Formula 1>

[0132] Cathode thickness expansion rate (%) = [thickness of lithium precipitation layer formed on the negative electrode current collector after 100 cycles of charging / thickness of lithium precipitation layer formed on the negative electrode current collector after formation] × 100

[0133] For example, the thickness expansion ratio of the negative electrode may be 140% or less, 139% or less, 138% or less, 136% or less, 105 to 136%, or 110 to 136%. By including a binder including a crosslinked polymer with increased modulus, the strength of the binder is increased, thereby suppressing volume changes of the negative electrode during charge and discharge. Charge and discharge conditions may refer to the evaluation examples.

[0134] The binder of the protective film according to one embodiment can be, for example, vinylidenefluoride-hexafluoropropylene (VDF-HFP) copolymer, polyethylene oxide, polypropylene oxide, polydimethylsiloxane, polyacrylonitrile, polymethyl(meth)acrylate, polyvinyl chloride, polyvinylidene fluoride, polyvinylidenefluoride-co-hexafluoropropylene, polyethyleneimine, polyphenylene terephthalamide, polymethoxypolyethyleneglycol(meth)acrylate, poly2-methoxy ethylglycidyl ether, or a combination thereof.

[0135] According to another embodiment, the binder of the protective film may include a crosslinked polymer of the first polymer and the second polymer, wherein the first polymer containing a hydroxyl group and the second polymer having a crosslinkable functional group are crosslinking reaction products.

[0136] The weight ratio of the first polymer and the second polymer is 50:50 to 99:1, and is adjusted to be in the range of 50:50 to 90:10, or 60:40 to 90:10.

[0137] The second polymer is at least one selected from among fluorinated polyamic acid and fluorinated polyimide having a carboxyl group.

[0138] The protective film according to the present invention is dense, with increased density and strength, allowing free lithium ion movement and enhanced lithium ion transport, thereby improving lithium electrodeposition characteristics. Consequently, ionic conductivity is improved, thereby enhancing the high-rate characteristics of lithium metal batteries. Furthermore, by positioning the protective film on the negative electrode active material layer, side reactions between the negative electrode active material layer and the electrolyte can be effectively blocked and suppressed.

[0139] Boron nitride may have a form selected from the group consisting of nanoflakes, nanoparticles, nanoplates, nanotubes, nanoribbons, fullerenes, and combinations thereof. The boron nitride may be, for example, in the form of nanoflakes or in a two-dimensional form.

[0140] The crosslinked polymer-containing protective film may further include an inorganic material. The inorganic material is selected from the group consisting of silica (SiO2), alumina (Al2O3), titanium oxide (TiO2), lithium titanium oxide (LiTiO2), barium titanium oxide (BaTiO2), lithium alumina (LiAlO2), and zeolite, or a mixture thereof.

[0141] When a protective film according to an embodiment of the present invention exists on the surface of a negative electrode active material layer containing lithium metal, the generation and / or growth of lithium dendrites on the negative electrode current collector can be effectively prevented. In addition, the cycle characteristics and stability of a negative electrode containing the above-described protective film and a lithium metal battery employing the same are improved.

[0142] The above hydroxyl group-containing first polymer is carboxymethyl cellulose (CMC); polyvinyl alcohol (PVA); Vinyl acetate, butyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 2-hydroxyethylene glycol (meth)acrylate, 2-hydroxypropylene glycol (meth)acrylate, acrylic acid, methacrylic acid, 2-(meth)acryloyloxy acetic acid, 3-(meth)acryloyloxy propyl acid, 4-(meth)acryloyloxy butyric acid, itaconic acid, maleic acid, 2-isocyanatoethyl (meth)acrylate, 3-isocyanatopropyl (meth)acrylate, A polymerization reaction product of one or more monomers selected from among 4-isocyanatobutyl (meth)acrylate, (meth)acrylamide, ethylene di(meth)acrylate, diethylene glycol (meth)acrylate, triethylene glycol di(meth)acrylate, trimethylene propane tri(meth)acrylate, trimethylene propane triacrylate, 1,3-butanediol (meth)acrylate, 1,6-hexanediol di(meth)acrylate, allyl acrylate, and N-vinyl caprolactam, or a hydrolyzate thereof, may be mentioned.

[0143] The first polymer may be polyvinyl alcohol (PVA). For example, polyvinyl alcohol may be a hydrolyzate obtained by hydrolyzing polyvinyl acetate with an alkali.

[0144] The degree of saponification of polyvinyl alcohol is 60 to 99%, 70 to 95%, 75 to 90% or 80

[0145] The degree of saponification of polyvinyl alcohol can be 85 to 90%. For example, the degree of saponification of polyvinyl alcohol can be 85 to 90%.

[0146] There is. The properties can be further improved by the protective film within the above saponification range.

[0147] The weight average molecular weight of the first polymer may be 10,000 to 500,000 Dalton, 10,000 to 400,000 Dalton, 10,000 to 300,000 Dalton, 10,000 to 200,000 Dalton, 50,000 to 150,000 Dalton, 70,000 to 100,000 Dalton, or 80,000 to 100,000 Dalton. The physical properties of the protective film may be further improved within the weight average molecular weight range of the first polymer.

[0148] The above protective film may further include a second polymer having a functional group capable of crosslinking with the first polymer containing a hydroxyl group. In this case, the protective film further includes a crosslinked polymer of the first polymer and the second polymer.

[0149] The second polymer comprises at least one selected from among fluorinated polyamic acid and fluorinated polyimide having a carboxyl group.

[0150] The above fluorinated polyamic acid may be, for example, a polymer represented by the following chemical formula 6 or 7, and the above fluorinated polyimide may be a polymer represented by the following chemical formula 8 or 9.

[0151] [Chemical Formula 6]

[0152]

[0153] [Chemical Formula 7]

[0154]

[0155] [Chemical Formula 8]

[0156]

[0157] [Chemical Formula 9]

[0158]

[0159] In the above formulas, M is an alkali metal, Ar1 and Ar3 are each independently an aromatic ring group selected from a substituted or unsubstituted tetravalent arylene group having 6 to 24 carbon atoms or a substituted or unsubstituted tetravalent heteroarylene group having 4 to 24 carbon atoms, wherein the aromatic ring group is one aromatic ring, a ring in which two or more aromatic rings are fused, or a ring in which two or more aromatic rings are connected by a single bond, -O-, -S-, -C(=O)-, -S(=O)2-, -Si(Ra)(Rb)- (Ra and Rb are each independently an alkyl group having 1 to 10 carbon atoms), a substituted or unsubstituted alkylene group having 1 to 10 carbon atoms, or -C(=O)-NH-,

[0160] Ar2 and Ar4 are independently an aromatic ring group selected from a substituted or unsubstituted divalent arylene group having 6 to 24 carbon atoms or a substituted or unsubstituted divalent heteroarylene group having 4 to 24 carbon atoms, wherein the aromatic ring group is a ring connected by one aromatic ring, a fused ring of two or more aromatic rings, a single bond, -O-, -S-, -C(=O)-, -S(=O)2-, -Si(Ra)(Rb)- (Ra and Rb are independently an alkyl group having 1 to 10 carbon atoms), a substituted or unsubstituted alkylene group having 1 to 10 carbon atoms, or -C(=O)-NH-.

[0161] At least one of Ar1 to Ar4 is substituted with a halogen group, X1 is a first functional group, -COOH, -OH, -CO-NH2, or -COH,

[0162] n and m are the mole fractions within the repeating unit, respectively, and 0 <n≤1, 0≤m<1, n+m=1이다.

[0163] The halogen group may be a fluorine group, a chlorine group, a bromine group, or an iodine group. For example, the halogen group may be a fluorine group.

[0164] Here, Ar1 and Ar3 are independently selected from the following chemical formulae 1a and 1b, and Ar2 and Ar4 can be independently selected from the following chemical formulae 1c to 1e.

[0165] there is.

[0166] [Chemical Formula 1a]

[0167]

[0168] [Chemical Formula 1b]

[0169]

[0170] [Chemical Formula 1c]

[0171]

[0172] [Chemical Formula 1d]

[0173]

[0174] [Chemical Formula 1e]

[0175]

[0176] In the above formulas, R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 , R 12 , R 13 , R 14 , R 15 and R 16 are each independently hydrogen, halogen, -COOH, -OH, -CO-NH2, -COH, a halogen-substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a halogen-substituted or unsubstituted aryl group having 6 to 20 carbon atoms, or a halogen-substituted or unsubstituted heteroaryl group having 2 to 20 carbon atoms; provided that R1 to R 16At least one of which is a halogen group or a group substituted with a halogen group; A1, A2 and A3 are each independently a single bond, -O-, -C(=O)-, -S-, -S(=O)2-, -Si(Ra)(Rb)- (Ra and Rb are each independently an alkyl group having 1 to 10 carbon atoms), an alkylene group having 1 to 10 carbon atoms substituted or unsubstituted with a halogen, or -C(=O)-NH-; provided that the above chemical formulas 1c to 1e, which become Ar2, are R5 to R 16 At least one of the first functional groups is -COOH, -OH, -CO-NH2, or -COH.

[0177] For example, in the above chemical formulas 1a to 1e, R1 to R 16 are each independently a hydrogen atom, a halogen atom, a hydroxyl group, -CH3, or -CF3, provided that the above chemical formulas 1c to 1e, which become Ar2, are R5 to R 16 At least one of the first functional groups is -COOH, -OH, -CO-NH2, or -COH; A2 and A3 can each independently be a single bond, -O-, -CO-, -S-, -SO2-, -C(CH3)2-, -CONH-, -C(CF3)2-, -CH2-, or -CF2-.

[0178] The above polyamic acid may be, for example, a polymer represented by the following chemical formula 10 or 11, and the above polyimide may be a polymer represented by the following chemical formula 12 or 13.

[0179] [Chemical Formula 10]

[0180]

[0181] [Chemical Formula 11]

[0182]

[0183] [Chemical Formula 12]

[0184]

[0185] [Chemical Formula 13]

[0186]

[0187] In the above formulas, M is lithium or sodium,

[0188] R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 , and R 12 are independently hydrogen, halogen, -COOH, -OH, -CO-NH2, -COH, an alkyl group having 1 to 10 carbon atoms substituted or unsubstituted with a halogen, an aryl group having 6 to 20 carbon atoms substituted or unsubstituted with a halogen, or a heteroaryl group having 2 to 20 carbon atoms substituted or unsubstituted with a halogen, provided that R1 to R 12 At least one of which is a halogen group or a group substituted with a halogen group,

[0189] A1 and A2 are each independently a single bond, -O-, -S-, -C(=O)-, -S(=O)2-, -Si(Ra)(Rb)- (Ra and Rb are each independently an alkyl group having 1 to 10 carbon atoms), an alkylene group having 1 to 10 carbon atoms which is unsubstituted or substituted with halogen, or -C(=O)-NH-;

[0190] However, at least one of R5, R6, R7, and R8 is -COOH, -OH, -CO-NH2, or -COH, and n and m are each a mole fraction within the repeating unit, 0 <n≤1, 0≤m<1, n+m=1이다.

[0191] The halogen group may be a fluorine group, a chlorine group, a bromine group, or an iodine group. For example, the halogen group may be a fluorine group. Here, Ar1 and Ar3 may be independently selected from the chemical formulae 1a and 1b, and Ar2 and Ar4 may be independently selected from the chemical formulae 1c to 1e.

[0192] The above polyamic acid is represented by the following chemical formula 14 or 15, and the above polyimide is a polymer represented by the following chemical formula 16 or 17.

[0193] [Chemical Formula 14]

[0194]

[0195] [Chemical Formula 15]

[0196]

[0197] [Chemical Formula 16]

[0198]

[0199] [Chemical Formula 17]

[0200]

[0201] In the above equations, n and m are the mole fractions within the repeating unit, respectively, and 0 <n≤1, 0≤m<1, n+m=1이다.

[0202] For example, in the second polymer, a repeating unit including a crosslinking group and a crosslinking group

[0203] The mole fraction of repeating units that do not contain each other is 0 <n≤0.5, 0.5≤m<1 및 n+m=1일 수 있다. 예를 들어, 상기 제2 고분자에서 가교기를 포함하는 반복단위와 가교기를 포함하지 않는 반복단위의 몰분율이 각각 0.1≤n≤0.4, 0.6≤m≤0.9 및 n+m=1일 수 있다. 예를 들어, 상기 제2 고분자에서 가교기를 포함하는 반복단위와 가교기를 포함하지 않는 반복단위의 몰분율이 각각 0.15≤n≤0.35, 0.65≤m≤0.85 및 n+m=1일 수 있다. 예를 들어, 상기 제2 고분자에서 가교기를 포함하는 반복단위와 가교기를 포함하지 않는 반복단위의 몰분율이 각각 0.2≤n≤0.3, 0.7≤m≤0.8 및 n+m=1일 수 있다. 상기 몰분율 범위에서 더욱 향상된 물성을 제공할 수 있다.

[0204] For example, the second polymer may be a random copolymer. For example, the second polymer may be a block copolymer.

[0205] The weight average molecular weight of the second polymer may be 10,000 to 1,200,000 Dalton, 10,000 to 1,100,000 Dalton, 10,000 to 1,000,000 Dalton, 100,000 to 500,000 Dalton, 100,000 to 400,000 Dalton, for example, 100,000 to 300,000 Dalton. The properties of the protective film may be further improved within the weight average molecular weight range of the second polymer.

[0206] In the above protective film, the weight ratio of the first polymer and the second polymer containing a hydroxyl group included in the third polymer may be 99:1 to 50:50, 95:5 to 55:45, 95:5 to 60:40, 95:5 to 65:35, or 90:10 to 70:30. The physical properties of the protective film may be further improved within the weight ratio range of the first polymer to the second polymer.

[0207] The hydroxyl groups of the first polymer and the carboxyl groups of the second polymer react with each other to form an ester bond, thereby forming a third polymer crosslinked with the first and second polymers. The formation of the third polymer enhances the stability of the protective film, and in the case of halogen groups such as fluorine functional groups, it can improve interfacial stability by reducing the formation of irreversible lithium inclusions.

[0208] The protective film according to an embodiment includes a crosslinked polymer of polyvinyl alcohol and polyamic acid as a crosslinked polymer. The polyamic acid is, for example, a polymer represented by the chemical formula 9 or 10 described above.

[0209] In another embodiment, the crosslinked polymer of the protective film is a crosslinked polymer of polyvinyl alcohol and fluorinated polyimide (PVA / PI-f). The fluorinated polyimide is a polymer represented by the chemical formula 11 or 12 described above.

[0210] The above protective film may include a binder and be free of lithium salt.

[0211] The protective film may further contain a lithium salt, and when containing a lithium salt, excellent ionic conductivity of the protective film can be secured. The lithium salt may be one or more of materials such as LiSCN, LiN(CN)2, LiClO4, LiBF4, LiAsF6, LiPF6, LiCF3SO3, LiC(CF3SO2)3, LiC(FSO2)3, LiN(SO2C2F5)2, LiN(SO2CF3)2, LiN(SO2F)2, LiSbF6, LiPF3(CF2CF3)3, LiPF3(CF3)3, and LiB(C2O4)2.

[0212] In the negative electrode according to an embodiment, the negative electrode active material layer includes lithium metal foil, lithium metal powder, lithium alloy foil, lithium alloy powder, or a combination thereof, wherein the lithium alloy contains lithium and a first metal.

[0213] The negative electrode active material layer contains a carbon-based compound; a mixture of at least one selected from a carbon-based material and a first metal; a composite of at least one selected from a carbon-based material and a first metal; or a combination thereof, wherein the carbon-based material includes amorphous carbon, and the average particle size of the amorphous carbon is from 10 nm to 100 nm. The carbon-based material includes carbon black, carbon nanotubes, carbon nanofibers, fullerenes, activated carbon, carbon fibers, or a combination thereof.

[0214] The first metal is indium (In), silicon (Si), gallium (Ga), tin (Sn), aluminum (Al), titanium (Ti), zirconium (Zr), niobium (Nb), germanium (Ge), antimony (Sb), bismuth (Bi), gold (Au), platinum (Pt), palladium (Pd), magnesium (Mg), silver (Ag), zinc (Zn), nickel, iron, cobalt, chromium, cesium, sodium, potassium, calcium, yttrium, tantalum, hafnium, barium, vanadium, strontium, lanthanum, or a combination thereof.

[0215] A lithium metal layer may be further disposed between the negative electrode current collector and one surface of the protective film.

[0216] There is. A lithium metal layer can be further disposed on the other side opposite to the above-mentioned one side of the above-mentioned protective film.

[0217] The thickness of the protective film is 1 to 10 μm, 1 to 8 μm, 1 to 7 μm, 2 to 6 μm, or 3 to 5 μm. When the thickness of the protective film is within the above range, the internal resistance is reduced, and the energy density of the lithium metal battery is not reduced, and the energy density is excellent and the high-rate characteristics and life characteristics are improved.

[0218] According to another aspect, the positive electrode; the negative electrode according to an embodiment; and the positive electrode and the negative electrode

[0219] A lithium metal battery including an electrolyte disposed therebetween is provided.

[0220] The electrolyte may be a liquid electrolyte, a solid electrolyte, a gel electrolyte, or a combination thereof. The electrolyte is, for example, an organic electrolyte. An organic electrolyte is prepared by dissolving a lithium salt in an organic solvent, for example.

[0221] The above solid electrolyte includes an oxide-based solid electrolyte, a sulfide-based solid electrolyte, a polymer solid electrolyte, or a combination thereof. A gel electrolyte may have a gel state, for example, without including a polymer.

[0222] The above gel electrolyte comprises a polymer gel electrolyte. The positive electrode comprises a positive electrode current collector and a positive electrode active material layer, and at least one of the positive electrode current collector and the negative electrode current collector comprises a base film and a metal layer disposed on one or both sides of the base film, the base film comprises a polymer, and the polymer comprises polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof, and 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.

[0223] The lithium metal may include, for example, a lithium metal foil, a lithium alloy foil, or a combination thereof. The lithium powder may include, for example, a lithium metal powder, a lithium alloy powder, or a combination thereof. A lithium alloy is an alloy of lithium and another metal that can be alloyed with lithium, such as a lithium-silver alloy, a lithium-zinc alloy, a lithium-magnesium alloy, or a lithium-tin alloy. The negative electrode active material layer including a lithium metal foil may be, for example, a lithium metal layer. The negative electrode active material layer including a lithium alloy foil may be, for example, a lithium alloy layer. The negative electrode active material layer including a lithium metal powder and / or a lithium alloy powder may be introduced by coating a slurry including lithium powder and a binder onto a negative electrode current collector. The binder may be, for example, a fluorine-based binder such as polyvinylidene fluoride (PVDF). The negative electrode active material layer may not include a carbon-based negative electrode active material. Therefore, the negative electrode active material layer may be formed of a metal-based negative electrode active material.

[0224] The thickness of the lithium metal may be, for example, 1 μm to 50 μm, 1 μm to 30 μm, or 10 μm to 30 μm, or 10 μm to 80 μm. When the lithium metal has a thickness in this range, the life characteristics of the lithium battery including the protective film can be further improved. The particle size of the lithium powder may be, for example, 0.1 μm to 3 μm, 0.1 μm to 2 μm, or 0.1 μm to 2 μm. When the lithium powder has a thickness in this range, the life characteristics of the lithium battery including the protective film can be further improved.

[0225] The thickness of the negative electrode active material layer may be, for example, 0.1 ㎛ to 500 ㎛, 1 ㎛ to 500 ㎛, or 10 ㎛ to 500 ㎛, but is not necessarily limited to this range and may be adjusted according to the shape, capacity, etc. of the required lithium metal battery. When the thickness of the negative electrode active material layer is within the above range, the cycle characteristics are improved without lowering the energy density of the lithium metal battery.

[0226] A lithium metal battery according to an embodiment does not include a negative electrode active material layer disposed between a negative electrode current collector (21) and a protective film (22). An anode not including a negative electrode active material layer may include a negative electrode active material layer by plating lithium metal between the negative electrode current collector (21) and the protective film (22) upon charging after being introduced into a lithium battery together with a positive electrode and an electrolyte. The negative electrode active material layer may be a lithium plating layer (plated lithium layer).

[0227] Lithium metal batteries may further include a separator.

[0228] The pore diameter of the separator is generally 0.01 to 10 μm, and the thickness can generally be 5 to 20 μm. Examples of such separators include sheets or non-woven fabrics made of olefin-based polymers such as polypropylene, glass fiber, or polyethylene. When a solid polymer electrolyte is used as the electrolyte, the solid polymer electrolyte may also function as the separator.

[0229] Among the above separation membranes, specific examples of olefin-based polymers include polyethylene, polypropylene, or a multilayer membrane of two or more layers thereof, and mixed multilayer membranes such as a polyethylene / polypropylene two-layer separation membrane, a polyethylene / polypropylene / polyethylene three-layer separation membrane, and a polypropylene / polyethylene / polypropylene three-layer separation membrane may be used.

[0230] In a lithium metal battery according to an embodiment, the liquid electrolyte contains a lithium salt and an organic solvent.

[0231] As the organic solvent, for example, an aprotic organic solvent such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, tetrahydroxy franc, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolan, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxy methane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl pyropionate, ethyl propionate, etc. can be used. Carbonate solvents such as propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, and diethyl carbonate can be used.

[0232] The above lithium salt can be any one that is commonly used in lithium secondary batteries, and as a material that is easily dissolved in the non-aqueous solvent, for example, one or more of the following materials can be used: LiSCN, LiN(CN)2, LiClO4, LiBF4, LiAsF6, LiPF6, LiCF3SO3, LiC(CF3SO2)3, LiC(FSO2)3, LiN(SO2C2F5)2, LiN(SO2CF3)2, LiN(SO2F)2, LiSbF6, LiPF3(CF2CF3)3, LiPF3(CF3)3, and LiB(C2O4)2.

[0233] The concentration of the lithium salt may be, for example, 1 to 5 M, for example, 1 to 2.5 M, in the liquid electrolyte. In the above range, a sufficient amount of lithium ions required for charging and discharging a lithium metal battery can be generated.

[0234] When a gel-type polymer electrolyte exists in the pores of a porous substrate, the interfacial resistance between the positive electrode, negative electrode, and separator is minimized, and lithium movement becomes easier.

[0235] According to one embodiment, the negative electrode active material layer may be disposed during the assembly of the lithium metal battery. According to another embodiment, the negative electrode active material layer may include a negative electrode active material layer by plating lithium metal after charging. The negative electrode active material layer may be a plated lithium layer.

[0236] The above negative electrode active material layer includes lithium metal or a lithium alloy.

[0237] When the negative electrode active material layer is placed at the time of assembly, it may include only a carbon-based material, a carbon-based material, and at least one selected from metals and metalloids.

[0238] The carbon-based material includes amorphous carbon, and the average particle diameter of the amorphous carbon is 10 nm to 100 nm, and the carbon-based material includes carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), graphene, or a combination thereof.

[0239] The above negative active material layer includes a lithium metal foil, a lithium metal powder, a lithium alloy foil, a lithium alloy powder, or a combination thereof, wherein the lithium alloy contains lithium and a first metal.

[0240] The first metal is indium (In), silicon (Si), gallium (Ga), tin (Sn), aluminum (Al), titanium (Ti), zirconium (Zr), niobium (Nb), germanium (Ge), antimony (Sb), bismuth (Bi), gold (Au), platinum (Pt), palladium (Pd), magnesium (Mg), silver (Ag), zinc (Zn), nickel, iron, cobalt, chromium, cesium, sodium, potassium, calcium, yttrium, bismuth, tantalum, hafnium, barium, vanadium, strontium, lanthanum, or a combination thereof.

[0241] The negative electrode active material layer (22) may include, for example, lithium foil, lithium powder, or a combination thereof. The lithium foil may include, for example, lithium metal foil, lithium alloy foil, or a combination thereof. The lithium powder may include lithium metal powder, lithium alloy powder, or a combination thereof. A lithium alloy is an alloy of lithium and another metal that can be alloyed with lithium, such as a lithium-silver alloy, a lithium-zinc alloy, a lithium-magnesium alloy, or a lithium-tin alloy. The negative electrode active material layer including a lithium metal foil may be, for example, a lithium metal layer. The negative electrode active material layer including a lithium alloy foil may be, for example, a lithium alloy layer. The negative electrode active material layer including a lithium metal powder and / or a lithium alloy powder may be introduced by coating a slurry including lithium powder and a binder, etc., on a negative electrode current collector. The binder may be, for example, a fluorine-based binder such as polyvinylidene fluoride (PVDF). The negative electrode active material layer may not include a carbon-based negative electrode active material. Therefore, the negative electrode active material layer can be made of a metal-based negative electrode active material.

[0242] The negative electrode current collector is composed of a material that does not react with lithium, i.e., does not form an alloy or compound. The material constituting the negative electrode current collector includes, but is not limited to, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni), and any material that is used as an electrode current collector in the relevant technical field may be used. The negative electrode current collector may be composed of one of the above-mentioned metals, or may be composed of an alloy or a coating material of two or more metals. The negative electrode current collector is, for example, in the form of a plate or foil.

[0243] In one embodiment of the present invention, the positive electrode collector 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 thickness of the positive electrode collector is, for example, 1 µm to 100 µm, 1 µm to 50 µm, 5 µm to 25 µm, or 10 µm to 20 µm.

[0244] The negative electrode active material layer may contain a negative electrode active material and a binder.

[0245] The negative active material has, for example, a particle form. The average particle diameter of the negative 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 100 nm, or 20 nm to 80 nm. When the negative active material has an average particle diameter in this range, reversible plating and / or dissolution of lithium can be facilitated during charge and discharge. The average particle diameter of the negative active material is, for example, a median diameter (D50) measured using a laser particle size distribution analyzer.

[0246] The negative electrode active material may include, for example, at least one selected from a carbon-based negative electrode active material and a metal or metalloid negative electrode active material. The carbon-based negative electrode active material may be, for example, amorphous carbon. Examples of the carbon-based negative electrode active material include, but are not limited to, carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), graphene, etc., and any material classified as amorphous carbon in the relevant technical field may be used. Amorphous carbon is carbon that has no crystallinity or very low crystallinity, and is distinguished from crystalline carbon or graphite-based carbon. 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 in the present specification. The negative electrode active material layer 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 negative electrode active material layer may include a mixture of amorphous carbon and one or more selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). The mixing ratio of the mixture may be, for example, 10:1 to 1:2, 10:1 to 1:1, 7:1 to 1:1, 5:1 to 1:1, or 4:1 to 2:1 by weight.The negative electrode active material included in the negative electrode active material layer may include a mixture of first particles made of, for example, amorphous carbon and second particles made of a metal or a metalloid. The metal includes, for example, gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). The content of the second particles is 8 to 60 wt%, 10 to 50 wt%, 15 to 40 wt%, or 20 to 30 wt% based on the total weight of the mixture. When the second particles have a content in this range, the cycle characteristics of, for example, a lithium metal battery are further improved.

[0247] The binder included in the negative electrode active material layer 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. When the negative electrode active material layer does not include a binder, the negative electrode active material layer can be easily separated from the ceramic coating layer (21) or the negative electrode current collector (21). The content of the binder included in the negative electrode active material layer may be, for example, 1 to 20 wt% based on the total weight of the negative electrode active material layer.

[0248] The thickness of the negative electrode active material layer may be, for example, 0.1 ㎛ to 500 ㎛, or 100 ㎛ to 50 ㎛. The thickness of the negative electrode active material layer may be, for example, 1% to 50%, 1% to 30%, 1% to 10%, or 1% to 5% of the thickness of the positive electrode active material layer. If the thickness of the negative electrode active material layer is too thin, lithium dendrites formed between the negative electrode active material layer and the negative electrode current collector may collapse the negative electrode active material layer, making it difficult to improve the cycle characteristics of the lithium metal battery. If the thickness of the negative electrode active material layer increases excessively, the energy density of the lithium metal battery employing the negative electrode (20) may decrease, and it may be difficult to improve the cycle characteristics.

[0249] When the thickness of the negative electrode active material layer decreases, the charge capacity of the negative electrode active material layer also decreases, for example. The charge capacity of the negative electrode active material layer may be, for example, 0.1% to 50%, 1% to 30%, 1% to 10%, 1% to 5%, or 1% to 2% of the charge capacity. If the charge capacity of the negative electrode active material layer is too small, lithium dendrites formed between the negative electrode active material layer and the negative electrode current collector may collapse the negative electrode active material layer, making it difficult to improve the cycle characteristics of the lithium metal battery. If the charge capacity of the negative electrode active material layer increases excessively, the energy density of the lithium metal battery using the negative electrode (20) may decrease, and it may be difficult to improve the cycle characteristics. The charge capacity of the positive electrode active material layer is obtained by multiplying the charge capacity density (mAh / g) of the positive electrode active material by the mass of the positive electrode active material in the positive electrode active material layer. When multiple 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 charge capacity of the positive electrode active material layer. The charge capacity of the negative electrode active material layer is also calculated in the same way. That is, the charge capacity of the negative electrode active material layer 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 negative electrode active material layer. When multiple types of negative electrode active materials are used, the charge capacity density × mass value is calculated for each negative electrode active material, and the sum of these values ​​is the capacity of the negative electrode active material layer. Here, the charge capacity density of the positive electrode active material and the negative electrode active material is the estimated capacity using an all-solid-state half-cell using lithium metal as a counter electrode. The charge capacity of the positive electrode active material layer and the negative electrode active material layer are directly measured by measuring the charge capacity using an all-solid-state half-cell. The charge capacity density is obtained by dividing the measured charge capacity by the mass of each active material. Alternatively, the charge capacity of the positive electrode active material layer and the negative electrode active material layer may be the initial charge capacity measured at the first charge cycle.

[0250] [Lithium metal battery]

[0251] According to one embodiment, a lithium metal battery includes a positive electrode; a negative electrode; and an electrolyte disposed between the positive electrode and the negative electrode. The lithium metal battery may further include a separator. Such a lithium metal battery can simultaneously provide excellent lifespan characteristics. The lithium metal battery may be, but is not limited to, a lithium primary battery, a lithium secondary battery, a lithium-sulfur battery, a lithium-air battery, etc., and any lithium metal battery used in the art may be used.

[0252] Lithium metal batteries are manufactured by, for example, the following exemplary methods, but are not necessarily limited to these methods and are adjusted according to required conditions.

[0253] (anode)

[0254] First, a positive electrode active material composition is prepared by mixing a positive electrode active material, a conductive agent, a binder, and a solvent. The prepared positive electrode active material composition is directly coated on an aluminum current collector and dried to produce a positive electrode plate having a positive electrode active material layer formed thereon. Alternatively, the positive electrode active material composition is cast on a separate support, and then the film obtained by peeling from the support is laminated on the aluminum current collector to produce a positive electrode plate having a positive electrode active material layer formed thereon.

[0255] A compound capable of reversible intercalation and deintercalation of lithium (a lithiated intercalation compound) can be used as a cathode active material. Specifically, one or more of a composite oxide of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof can be used.

[0256] The above composite oxide may be a lithium transition metal composite oxide, and specific examples thereof include lithium nickel-based oxide, lithium cobalt-based oxide, lithium manganese-based oxide, lithium iron phosphate-based compound, cobalt-free nickel-manganese-based oxide, or a combination thereof.

[0257] As an example, a compound represented by any one of the following chemical formulas may be used: Lia A 1-b X b O 2-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a Mr 2-b X b O 4-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a Ni 1-b-c Co b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni 1-b-c Mr b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni b Co c L 1 d G e O2(0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0≤e≤0.1); Li a NiG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a CoG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mr 1-b G b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn2G b O4(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mr 1-g G g PO4(0.90≤a≤1.8, 0≤g≤0.5); Li (3-f) Fe2(PO4)3(0≤f≤2); Li a FePO4(0.90≤a≤1.8).

[0258] In the above chemical formula, A is Ni, Co, Mn, or a combination thereof; X 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; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; L 1 is Mn, Al or a combination thereof.

[0259] For example, the cathode active material may be a high-nickel cathode active material in which the nickel content is 80 mol% or more, 85 mol% or more, 90 mol% or more, 91 mol% or more, or 94 mol% or more and 99 mol% or less, based on 100 mol% of metals excluding lithium in a lithium transition metal composite oxide. The high-nickel cathode active material can realize high capacity and thus can be applied to high-capacity, high-density lithium secondary batteries.

[0260] The cathode active material is, for example, Li a Ni x Co y M z O 2-b A b (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, M은 망간(Mn), 니오븀(Nb), 바나듐(V), 마그네슘(Mg), 갈륨(Ga), 실리콘(Si), 텅스텐(W), 몰리브덴(Mo), 철(Fe), 크롬(Cr), 구리(Cu), 아연(Zn), 티타늄(Ti), 알루미늄(Al), 보론(B) 또는 이들의 조합이고, A는 F, S, Cl, Br 또는 이들의 조합), LiNi x Co y Mn z O2(0.8≤x≤0.95, 0≤y≤0.2, 0 <z≤0.2 및 x+y+z=1), LiNi x Co y Al z O2(0.8≤x≤0.95, 0≤y≤0.2, 0 <z≤0.2 및 x+y+z=1), LiNix Co y Mn z Al w O2(0.8≤x≤0.95, 0≤y≤0.2, 0 <z≤0.2, 0<w≤0.2, 및 x+y+z+w=1), Li a Co x M y O 2-b A b (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, and A is F, S, Cl, Br or a combination thereof), Li a Ni x Mn y M' z O 2-b A b (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'는 코발트(Co), 니오븀(Nb), 바나듐(V), 마그네슘(Mg), 갈륨(Ga), 실리콘(Si), 텅스텐(W), 몰리브덴(Mo), 철(Fe), 크롬(Cr), 구리(Cu), 아연(Zn), 티타늄(Ti), 알루미늄(Al), 보론(B) 또는 이들의 조합이고, A는 F, S, Cl, Br 또는 이들의 조합), Li a M1 x M2 y PO 4-b X b(Here, 0.90≤a≤1.1, 0≤x≤0.9, 0≤y≤0.5, 0.9 <x+y<1.1, 0≤b≤2 이며, M1이 크롬(Cr), 망간(Mn), 철(Fe), 코발트(Co), 니켈(Ni), 구리(Cu), 지르코늄(Zr) 또는 이들의 조합이며, M2가 마그네슘(Mg), 칼슘(Ca), 스트론튬(Sr), 바륨(Ba), 티탄(Ti), 아연(Zn), 보론(B), 니오븀(Nb), 갈륨(Ga), 인듐(In), 몰리브덴(Mo), 텅스텐(W), 알루미늄(Al), 실리콘(Si), 크롬(Cr), 바나듐(V), 스칸듐(Sc), 이트륨(Y) 또는 이들의 조합이며, X가 O, F, S, P 또는 이들의 조합), Li a M3 z PO4 (0.90≤a≤1.1, 0.9≤z≤1.1, and M3 is chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr), or a combination thereof).

[0261] The conductive material may include, but is not limited to, carbon black, graphite particles, natural graphite, artificial graphite, acetylene black, Ketjen black, carbon fibers; carbon nanotubes; metal powders or metal fibers or metal tubes such as copper, nickel, aluminum, and silver; and conductive polymers such as polyphenylene derivatives. Any conductive material used in the relevant technical field may be used. Alternatively, the anode may not include a separate conductive material, for example.

[0262] As binders, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene (PTFE), mixtures of the above-mentioned polymers, styrene butadiene rubber-based polymers, etc. are used, and as solvents, N-methylpyrrolidone (NMP), acetone, water, etc. are used, but are not necessarily limited to these, and any solvent used in the relevant technical field may be used.

[0263] A positive electrode for a lithium secondary battery may include a current collector and a positive electrode active material layer formed on the current collector. The positive electrode active material layer includes a positive electrode active material and may further include a binder and / or a conductive material.

[0264] For example, the anode may further include an additive that can act as a sacrificial anode.

[0265] The content of the positive electrode active material may be 90 wt% to 99.5 wt% with respect to 100 wt% of the positive electrode active material layer, and the contents of the binder and conductive material may be 0.5 wt% to 5 wt%, respectively, with respect to 100 wt% of the positive electrode active material layer.

[0266] The above binder serves to adhere the positive electrode active material particles well to each other and also to adhere the positive electrode active material well to the current collector. Representative examples of the binder include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, nylon, etc.

[0267] The conductive material is used to provide conductivity to the electrode, and any material that does not cause chemical changes and is electronically conductive can be used in the battery. Examples of the conductive material include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials containing copper, nickel, aluminum, silver, etc. in the form of metal powder or metal fiber; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0268] The positive electrode collector 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 thickness of the positive electrode collector is, for example, 1 ㎛ to 100 ㎛, 1 ㎛ to 50 ㎛, 5 ㎛ to 25 ㎛, or 10 ㎛ to 20 ㎛.

[0269] The cathode current collector 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 may soften or liquefy, thereby blocking battery operation and suppressing a sudden 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 cut off in case of overcurrent to prevent short circuits. 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. As the thickness of the metal layer decreases, the limit current and / or maximum current of the positive electrode current collector decreases, thereby improving the stability of the lithium battery in case of a short circuit. A lead tab can be added to the metal layer for external connection. The lead tab can be welded to the metal layer or the metal layer / base film laminate by ultrasonic welding, laser welding, spot welding, etc. During welding, the base film and / or the metal layer melt, so that the metal layer can be electrically connected to the lead tab. To strengthen the welding between the metal layer and the lead tab, a metal chip can be added between the metal layer and the lead tab.The metal piece may be a thin piece of the same material as the metal of the metal layer. The metal piece may be, for example, a metal foil, a metal mesh, etc. The metal piece may be, for example, aluminum foil, copper foil, SUS foil, etc. After the metal piece is placed on the metal layer, the lead tab may be welded to the metal piece / metal layer laminate or the metal piece / metal layer / base film laminate. During welding, the base film, the metal layer, and / or the metal piece may melt, so that the metal layer or the metal layer / metal piece laminate may be electrically connected to the lead tab. A metal chip and / or a lead tab may be added to a portion of the metal layer. The base film may have a thickness of, for example, 1 to 50 μm, 1.5 to 50 μm, 1.5 to 40 μm, or 1 to 30 μm. When the base film has a thickness in this range, the weight of the electrode assembly can be more effectively reduced. The melting point of the base film may be, for example, 100 to 300°C, 100 to 250°C or less, or 100 to 200°C. Since the base film has a melting point within this range, the base film can be melted and easily bonded to the lead tab during the welding process of the lead tab. To improve the adhesion between the base film and the metal layer, a surface treatment such as corona treatment may be performed on the base film. The thickness of the metal layer may be, for example, 0.01 to 3 μm, 0.1 to 3 μm, 0.1 to 2 μm, or 0.1 to μm. Since the metal layer has a thickness within this range, conductivity can be maintained while ensuring the stability of the electrode assembly. The thickness of the metal piece may be, for example, 2 to 10 μm, 2 to 7 μm, or 4 to 6 μm. Since the metal piece has a thickness within this range, the connection between the metal layer and the lead tab can be performed more easily. By having this structure as the cathode current collector, the weight of the cathode can be reduced, and as a result, the energy density of the cathode and lithium battery can be improved. (Electrolyte)

[0270] Next, an electrolyte is prepared. The electrolyte may be, for example, a liquid electrolyte, a solid electrolyte, a gel electrolyte, or a combination thereof. The electrolyte is, for example, an organic electrolyte. The liquid electrolyte is as mentioned in the liquid electrolyte of the gel polymer electrolyte.

[0271] The solid electrolyte is, for example, an oxide-based solid electrolyte, a sulfide-based solid electrolyte, a polymer solid electrolyte, or a combination thereof.

[0272] Solid electrolytes are, for example, oxide-based solid electrolytes. Oxide-based solid electrolytes are 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)(O≤x<1, O≤y<1), PB(Mg3Nb 2 / 3 )O3-PbTiO3(PMN-PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, Li3PO4, Li x Ti y (PO4)3(0 <x<2, 0<y<3), Li x Al y Ti z (PO4)3(0 <x<2, 0<y<1, 0<z<3), Li 1+x+y (Al, Ga) x (Ti, Ge) 2-x Si y P 3-y O 12 (0≤x≤1 0≤y≤1), Li x La y TiO3(0 <x<2, 0<y<3), Li2O, LiOH, Li2CO3, LiAlO2, Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2, Li3+x La3M2O 12 (M = Te, Nb, or Zr, x is an integer from 1 to 10) is one or more selected from. The solid electrolyte is manufactured by a sintering method, etc. For example, the oxide-based solid electrolyte is Li7La3Zr2O 12 (LLZO) and Li 3+x La3Zr 2-a M a O 12 A garnet-type solid electrolyte selected from (M doped LLZO, M=Ga, W, Nb, Ta, or Al, x is an integer from 1 to 10).

[0273] The sulfide-based solid electrolyte may include, for example, lithium sulfide, silicon sulfide, phosphorus sulfide, boron sulfide, or a combination thereof. The sulfide-based solid electrolyte particles may include Li2S, P2S5, SiS2, GeS2, B2S3, or a combination thereof. The sulfide-based solid electrolyte particles may be Li2S or P2S5. Sulfide-based solid electrolyte particles are known to have high lithium ion conductivity compared to other inorganic compounds. For example, the sulfide-based solid electrolyte includes Li2S and P2S5. When the sulfide solid electrolyte material constituting the sulfide-based solid electrolyte includes Li2S-P2S5, the mixing molar ratio of Li2S to P2S5 may be, for example, in a range of about 50:50 to about 90:10. In addition, Li3PO4, halogen, halogen compound, Li 2+2x Zn 1-x GeO4("LISICON", 0≤x<1), Li 3+y PO 4-x N x( "LIPON", 0 <x<4, 0<y<3), Li 3.25 Ge 0.25 P 0.75 S4("ThioLISICON"), Li2O-Al2O3-TiO2-P2O 5(An inorganic solid electrolyte prepared by adding "LATP") etc. to an inorganic solid electrolyte of Li2S-P2S5, SiS2, GeS2, B2S3, or a combination thereof can be used as a sulfide solid electrolyte. Non-limiting examples of sulfide solid electrolyte materials include Li2S-P2S5; Li2S-P2S5-LiX (X=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 (0 <m<10, 0<n<10, Z=Ge, Zn 또는 Ga); Li2S-GeS2; Li2S-SiS2-Li3PO4; 및 Li2S-SiS2-Li p MO q (0 <p<10, 0<q<10, M=P, Si, Ge, B, Al, Ga 또는 In)을 포함한다. 이와 관련하여, 황화물계 고체전해질 재료는 황화물계 고체전해질 물질의 원료 시작 물질(예를 들면, Li2S, P2S5, 등)을 용융 담금질법(melt quenching method), 기계적 밀링법 등에 의해 처리함으로써 제조될 수 있다. 또한, 소성(calcinations) 공정이 상기 처리 후에 수행될 수 있다. 황화물계 고체전해질은 비정질이거나, 결정질이거나, 이들이 혼합된 상태일 수 있다.

[0274] The polymer solid electrolyte may, for example, comprise a mixture of a lithium salt and a polymer, or a polymer having ion-conducting functional groups. The polymer solid electrolyte may be, for example, a polymer electrolyte that is solid at 25°C and 1 atm. The polymer solid electrolyte may not, for example, comprise a liquid.The polymer solid electrolyte comprises a polymer, and the polymer is, for example, polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyethylene oxide (PEO), poly(styrene-b-ethylene oxide) block copolymer (PS-PEO), poly(styrene-butadiene), poly(styrene-isoprene-styrene), poly(styrene-b-divinylbenzene) block copolymer, poly(styrene-ethylene oxide-styrene) block copolymer, polystyrene sulfonate (PSS), polyvinyl fluoride (PVF), polymethyl methacrylate (PMMA, poly(methylmethacrylate), polyethylene glycol (PEG), polyacrylonitrile (PAN), polytetrafluoroethylene (PTFE), polyethylenedioxythiophene (PEDOT), polypyrrole (PPY), Polyacrylonitrile (PAN), polyaniline, polyacetylene, Nafion, Aquivion, Flemion, Gore, Aciplex, Morgane ADP, sulfonated poly(ether ether ketone) (SPEEK), sulfonated poly(arylene ether ketone ketone sulfone) (SPAEKKS), sulfonated poly(aryl ether ketone) (SPAEK), poly[bis(benzimidazobenzisoquinolinones)] (SPBIBI), poly(styrene sulfonate) (PSS), lithium 9,10-Diphenylanthracene-2-sulfonate (lithium 9,10-diphenylanthracene-2-sulfonate, DPASLi. +) or a combination thereof, but is not limited thereto, and any lithium salt that can be used in polymer electrolytes in the relevant technical field is possible. The lithium salt can be any lithium salt that can be used in the relevant technical field. The lithium salt is, for example, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2) (x and y are each 1 to 20), LiCl, LiI or a mixture thereof, etc. The polymer included in the polymer solid electrolyte may be, for example, a compound including 10 or more, 20 or more, 50 or more or 100 or more repeating units. The weight average molecular weight of the polymer included in the polymer solid electrolyte may be, for example, 1000 Dalton or more, 10,000 Dalton or more, 100,000 Dalton or more or 1,000,000 Dalton or more.

[0275] A gel electrolyte is, for example, a polymer gel electrolyte. A gel electrolyte can have a gel state without containing a polymer, for example.

[0276] A polymer gel electrolyte may include, for example, a liquid electrolyte and a polymer, or an organic solvent and a polymer having an ion-conducting functional group. The 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, for example, have a gel state without containing a liquid. The liquid electrolyte used in the polymer gel electrolyte may be, for example, an ionic liquid, a mixture of a lithium salt and an organic solvent; a mixture of a lithium salt and an organic solvent; a mixture of an ionic liquid and an organic solvent; or a mixture of a lithium salt, an ionic liquid, and an organic solvent. The polymer used in the polymer gel electrolyte may be selected from among the polymers used in solid polymer electrolytes. The organic solvent may be selected from among the organic solvents used in liquid electrolytes. The lithium salt may be selected from among the lithium salts used in solid polymer electrolytes. An ionic liquid refers to a salt that has a melting point below room temperature, is composed solely of ions, and is liquid at room temperature or a molten salt at room temperature. The ionic liquid may include, for example, one or more cations selected from among a) ammonium compounds, pyrrolidinium compounds, pyridinium compounds, pyrimidinium compounds, imidazolium compounds, piperidinium compounds, pyrazolium compounds, oxazolium compounds, pyridazinium compounds, phosphonium compounds, sulfonium compounds, triazolium compounds, and mixtures thereof, and b) one or more anions selected from among BF4-, PF6-, AsF6-, SbF6-, AlCl4-, HSO4-, ClO4-, CH3SO3-, CF3CO2-, Cl-, Br-, I-, SO4-, CF3SO3-, (FSO2)2N-, (C2F5SO2)2N-, (C2F5SO2)(CF3SO2)N-, and (CF3SO2)2N-. A polymer solid electrolyte can form a polymer gel electrolyte, for example, by being impregnated into a liquid electrolyte in a secondary battery. The polymer gel electrolyte may further include inorganic particles. The polymer included in the polymer gel electrolyte may be, for example, a compound containing 10 or more, 20 or more, 50 or more, or 100 or more repeating units.The weight average molecular weight of the polymer included in the polymer gel electrolyte may be, for example, 500 Dalton or more, 1000 Dalton or more, 10,000 Dalton or more, 100,000 Dalton or more, or 1,000,000 Dalton or more.

[0277] (cathode)

[0278] The cathode contains a cathode current collector.

[0279] 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 metal layer may correspond to, for example, the first metal substrate. The metal layer may additionally include a coating layer including a second metal. The negative electrode current collector (21) may additionally include a metal piece and / or a lead tab. For more specific details on the base film, metal layer, metal chip, and lead tab of the negative electrode current collector (21), refer to the positive electrode current collector. By having such a structure, the negative electrode current collector (21) can reduce the weight of the negative electrode, thereby improving the energy density of the negative electrode and the lithium battery.

[0280] A negative electrode active material layer may be formed on the negative electrode current collector. The negative electrode active material layer may be formed as a lithium deposition layer after charging. Alternatively, the negative electrode active material layer may be formed using a negative electrode active material during battery assembly.

[0281] The method of forming a negative electrode active material layer using a negative electrode active material can be manufactured in the same manner as described above, except that the negative electrode active material is used instead of the positive electrode active material when forming the positive electrode active material layer.

[0282] A lithium metal battery may further include, for example, a thin film comprising an element capable of forming an alloy with lithium on one surface of an anode current collector. The thin film is disposed between the anode current collector and the anode active material layer. The thin film includes, for example, an element capable of forming an alloy with lithium. The element capable of forming an alloy with lithium includes, but is not limited to, gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, etc., and any element capable of forming an alloy with lithium in the art may be used. The thin film may be composed of one of these metals or an alloy of several types of metals. By disposing the thin film on one surface of the anode current collector, for example, the deposition shape of the first anode active material layer deposited between the thin film and the anode active material layer becomes flatter, and the cycle characteristics of the lithium metal battery may be further improved.

[0283] (Separator)

[0284] A separator may be further placed between the anode and cathode.

[0285] Any separator commonly used in lithium metal batteries can be used.

[0286] As such a separator, a multilayer membrane of two or more layers of polyethylene, polypropylene, polyvinylidene fluoride, or these may be used, and of course, a mixed multilayer membrane such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, or a polypropylene / polyethylene / polypropylene three-layer separator may be used.

[0287] The above separator may include a porous substrate and a coating layer including an organic material, an inorganic material, or a combination thereof located on one or both sides of the porous substrate.

[0288] The above porous substrate may be a polymer film formed of any one polymer selected from polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyacetal, polyamide, polyimide, polycarbonate, polyether ketone, polyarylether ketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene oxide, cyclic olefin copolymer, polyphenylene sulfide, polyethylene naphthalate, glass fiber, Teflon, and polytetrafluoroethylene, or a copolymer or mixture of two or more thereof.

[0289] The organic material may include a polyvinylidene fluoride polymer or a (meth)acrylic polymer.

[0290] The above inorganic materials are Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, It may include inorganic particles selected from, but not limited to, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof.

[0291] The organic and inorganic substances may be mixed and present in one coating layer, or a coating layer including an organic substance and a coating layer including an inorganic substance may be present in a laminated form.

[0292] A lithium metal battery according to one embodiment may further include a solid electrolyte. The solid electrolyte is, for example, an oxide-based solid electrolyte, a sulfide-based solid electrolyte, or a combination thereof.

[0293] (lithium metal battery)

[0294] Referring to FIG. 4, a lithium metal battery (1) according to one embodiment includes a positive electrode (3), the above-described negative electrode (2), and a separator (4). A gel-type polymer electrolyte (not shown) may be disposed between the electrolyte and the positive electrode. The positive electrode (3), the negative electrode (2), and the separator (4) are wound or folded to form a battery structure (7). The formed battery structure (7) is accommodated in a battery case (5). An organic electrolyte is injected into the battery case (5) and sealed with a cap assembly (6), thereby completing the lithium metal battery (1). The battery case (5) is cylindrical, but is not necessarily limited to this shape, and may be, for example, square, thin-film, etc.

[0295] Referring to FIG. 5, a lithium metal battery (1) according to one embodiment includes a positive electrode (3), a negative electrode (2), and a separator (4). A separator (4) is disposed between the positive electrode (3) and the negative electrode (2), and the positive electrode (3), the negative electrode (2), and the separator (4) are wound or folded to form a battery structure (7). The formed battery structure (7) is accommodated in a battery case (5). An electrode tab (8) that serves as an electrical path for guiding the current formed in the battery structure (7) to the outside may be included. An organic electrolyte is injected into the battery case (5) and sealed to complete the lithium metal battery (1). The battery case (5) is not necessarily limited to a square shape, but may be, for example, a cylindrical shape, a thin film shape, etc.

[0296] Referring to FIG. 6, a lithium metal battery (1) according to one embodiment includes a positive electrode (3), a negative electrode (2) according to one embodiment, and a separator (4). A separator (4) is disposed between the positive electrode (3) and the negative electrode (2), thereby forming a battery structure. A gel-type polymer electrolyte between the separator and the positive electrode is not shown. A battery structure (7) is stacked in a bi-cell structure and then accommodated in a battery case (5). An electrode tab (8) that serves as an electrical path for guiding the current formed in the battery structure (7) to the outside may be included. An organic electrolyte is injected into the battery case (5) and sealed, thereby completing the lithium metal battery (1). The battery case (5) is not necessarily limited to a square shape, but may be, for example, a cylindrical shape, a thin-film shape, etc.

[0297] A pouch-type lithium metal battery corresponds to the lithium metal batteries of FIGS. 5 and 6, each of which uses a pouch as a battery case. The pouch-type lithium metal battery includes one or more battery structures. An electrolyte is disposed between a positive electrode and a negative electrode, or an electrolyte and a separator are disposed to form a battery structure. The battery structures are laminated in a bi-cell structure, then impregnated with a liquid electrolyte, and accommodated and sealed in a pouch, thereby completing a pouch-type lithium metal 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 jellyroll-shaped electrode assembly and then accommodated in a pouch. Subsequently, an organic electrolyte is injected into the pouch and sealed, thereby completing a lithium metal battery.

[0298] The lithium metal battery of the present disclosure has excellent discharge capacity and cycle life characteristics, as well as high energy density, and is therefore used in, for example, electric vehicles (EVs). For example, it is used in hybrid vehicles such as plug-in hybrid electric vehicles (PHEVs). It is also used in applications requiring large amounts of power storage, such as electric bicycles and power tools.

[0299] Lithium metal 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.

[0300] [Method for manufacturing lithium metal batteries]

[0301] According to one embodiment, a lithium metal battery can be manufactured by the steps of: preparing an anode current collector; forming a protective film including boron nitride and a binder on the anode current collector; preparing a separator; preparing a cathode; laminating the anode current collector, the separator, and the cathode to prepare a battery assembly; injecting a composition for forming a gel polymer electrolyte including a crosslinking monomer for forming a gel polymer, a liquid electrolyte, boron nitride, and a nitrile compound into the battery assembly; and performing a heat treatment to form a gel polymer electrolyte.

[0302] The step of forming a protective film comprising boron nitride and a binder on the negative electrode current collector may be performed by coating and heat-treating a composition for forming a protective film comprising at least one selected from a binder precursor and a binder and boron nitride on the negative electrode current collector. Here, the binder precursor may include, for example, a first polymer and a second polymer, and the binder refers to the binder mentioned in the above-described protective film.

[0303] A solvent such as N-methylpyrrolidone or dimethylformamide may be added to the composition for forming the protective film. The content of the solvent may be 0.05 to 5 parts by weight based on 100 parts by weight of the total weight of boron nitride and binder.

[0304] The above protective film may further include a lithium salt. The content of the lithium salt is 30 to 80 parts by weight, 40 to 60 parts by weight, or 45 to 55 parts by weight based on 100 parts by weight of the total weight of the binder and the lithium salt.

[0305] In a lithium metal battery according to an embodiment, a separator containing a gel polymer electrolyte can be formed in situ by injecting a composition for forming a gel polymer electrolyte into a battery assembly as described above and heat-treating the composition. Alternatively, a separator containing a gel polymer electrolyte can be manufactured separately to form a self-supporting film, which is then placed on a negative electrode current collector and a positive electrode placed on top of the self-supporting film, thereby manufacturing a lithium metal battery.

[0306] The composition for forming a protective film may further include a second polymer having a crosslinkable functional group with the first polymer containing a hydroxyl group. The protective film formed from the composition for forming a protective film further includes a crosslinked polymer of the first polymer and the second polymer. Here, the mixing weight ratio of the first polymer containing a hydroxyl group and the second polymer is adjusted to be in the range of 50:50 to 99:1, 50:50 to 99:1, or 60:40 to 90:10.

[0307] The above second polymer is at least one selected from among fluorinated polyamic acid and fluorinated polyimide having a carboxyl group.

[0308] When the second polymer is a fluorinated polyamic acid having a carboxyl group, a composition for forming a protective film containing the same may be coated on a negative electrode current collector and dried, and then further heat treatment may be performed to cause a crosslinking reaction between the first polymer and the second polymer to form a protective film containing a crosslinked polymer. The heat treatment may vary depending on the composition of the first polymer and the second polymer, but may be performed at, for example, 80 to 200°C, 100 to 200°C, 150 to 200°C, or 150 to 190°C. When the heat treatment temperature is within the above range, the protective film formed on the electrode surface can minimize exposure of the electrolyte at the electrode surface and create a uniform lithium ion flow throughout the electrode, thereby effectively suppressing lithium dendrite growth.

[0309] The composition for forming the protective film may further contain a lithium salt.

[0310] The above lithium metal battery may further include a separator. The separator may further include a liquid electrolyte and / or a gel-type polymer electrolyte.

[0311] 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.

[0312] Manufacturing Example 1: Manufacturing of a polymer solution containing polyvinyl alcohol and a fluorinated polyamic acid of the following chemical formula 15.

[0313] Polyvinyl alcohol was purchased from Sigma-Aldrich. The synthesis process of fluorinated polyamic acid of chemical formula 10 is as follows.

[0314] First, after filling a round-bottom flask with nitrogen, 4.9411 g (0.00154 mol) of 2,2'-bis(trifluoromethyl)benzidine (TFDB) and 0.7825 g (0.00051 mol) of diaminobenzoic acid (DABA) were added, followed by adding 131 g of N-methylpyrrolidone (NMP) and completely dissolving using a mechanical stirrer. Next, 9.2764 g (0.0209 mol) of 4,4'-(hexafluoroisopropylidene) (6FDA) was added and stirred at room temperature (25°C) for 24 hours, thereby producing a polyamic acid represented by the following chemical formula 9. The polyamic acid is a random copolymer. The molar ratio of 6FDA:TFDB:DABA was 4:3:1.

[0315] In chemical formula 14, the molar ratio of n:m was 1:3.

[0316] By adding 10 g of a LiOH aqueous solution having 0.5 equivalents in carboxylic acid equivalent ratio to a polyamic acid (6FDA:TFDB:DABA, acid equivalent 210 g / eq) represented by the following chemical formula 14, a water-soluble polyamic acid represented by the following chemical formula 15 was prepared in which 0.5 equivalents of COOH among the COOH of the polyamic acid was replaced with COO-Li+.

[0317] [Chemical Formula 14]

[0318]

[0319] In the above chemical formula 14, n is 0.25 and m is 0.75.

[0320] A water-soluble polyamic acid represented by the following chemical formula 15 and polyvinyl alcohol (weight average molecular weight, Mw = 89,000, hydrolysis +99%) were mixed at a weight ratio of 20:80 to prepare a polymer solution having a solid content of 10 wt%.

[0321] [Chemical Formula 15]

[0322]

[0323] In the above chemical formula 15, n is 0.25 and m is 0.75.

[0324] Manufacturing Example 2: Manufacturing of compound DRIC of the following chemical formula 1-1

[0325] <Chemical Formula 1-1>

[0326]

[0327] In chemical formula 1-1, EG represents a residue of ethylene glycol, DEG represents a residue of diethylene glycol, TMP represents a residue of trimethylolpropane, and n1 is 10.

[0328] Adipic acid (AA) 150.6 g, diethylene glycol (DG) 115.14 g, ethylene glycol (EG) 81.05 g, and trimethylolpropane (TMP) 21.32 g were added to a reaction vessel at room temperature (25°C) and the temperature was increased to 220°C. Titanium isopropoxide (TIP) was added to the reaction vessel. After the mixture reached full vacuum, it was subjected to a primary reaction at 220°C for 10 hours to obtain a polyester polyol. The polyol was first cooled to 130°C, vacuum-treated at 130°C for 2 hours, and then cooled to 75°C for a second time. 18.24 g of isocyanato ethyl methacrylate (ICEMA), 0.54 g of monomethyl ether hydroquinone (MEHQ), 0.566 g of butylated hydroxy toluene (BHT), and 0.526 g of dibutyl-tin-dilaulate (DBTDL) were added to the polyester polyol, and a secondary reaction was performed at 70 to 80°C for 3 hours to obtain compound DRIC of the chemical formula 1-1.

[0329] Example 1:

[0330] Negative current collector / protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / separator+GPE(gel polymer+BN+SN+LE)(BN=0.1%) / positive electrode

[0331] A water-soluble polyamic acid represented by the following chemical formula 15 obtained according to Manufacturing Example 1, and

[0332] Polyvinyl alcohol mixed in a weight ratio of 20:80 to form a polymer solution with a solid content of 10% by weight,

[0333] Hexagonal boron nitride (average particle size: 100 nm, spherical particles) and lithium salt LiPF6 were mixed, and then mixed with NMP as a solvent to prepare a composition for forming a protective film. At this time, the contents of the polymer, boron nitride, and lithium salt of the polymer solution were adjusted so that the mixing weight ratio of (PVA / PI-F)+BN+lithium salt in the protective film was 50:0.5:50. Here, PVA / PI-F refers to a crosslinked polymer of polyimide and polyvinyl alcohol of the following chemical formula 17 described below. And the content of the solvent is 900 parts by weight based on 100 parts by weight of the polymer.

[0334] [Chemical Formula 15]

[0335]

[0336] In the above chemical formula 15, n is 0.25 and m is 0.75.

[0337] The composition for forming a protective film was coated on a copper foil having a thickness of 10 μm, which is a negative electrode current collector, and dried in a vacuum oven at 80°C for 30 minutes, followed by heat treatment at 180°C for 30 minutes to prepare a negative electrode. The negative electrode had a structure in which a protective film having a thickness of 3 μm was coated on a lithium metal thin film disposed on a copper current collector.

[0338] The above heat treatment causes the carboxyl group of the polyamic acid of the above chemical formula 15 and the hydroxyl group of the polyvinyl alcohol to react to form an ester linker, thereby forming a crosslinked polymer (PVA / PI-F) of the polyimide of the following chemical formula 17 and the polyvinyl alcohol. The crosslinked polymer has a three-dimensional network structure in which the polyimide of the following chemical formula 17 and the polyvinyl alcohol are crosslinked at multiple points.

[0339] [Chemical Formula 17]

[0340]

[0341] In the above chemical formula 17, n is 0.25, m is 0.75, and the weight average molecular weight of the polyimide of chemical formula 17 is about 2,000,000.

[0342] A polyethylene single film having a thickness of 20 μm was laminated as a separator, and a positive electrode was laminated on the other side of the separator to manufacture a laminate. A composition for forming a gel polymer electrolyte was injected into the prepared laminate, and heat-treated at 70°C for 120 minutes to manufacture a lithium metal battery in which a gel polymer electrolyte was formed in the pores of the separator. The lithium metal battery had a structure of positive electrode / gel polymer electrolyte (separator) / protective film / negative electrode current collector. The content of boron nitride in the gel polymer electrolyte was 0.1 part by weight based on 100 parts by weight of the gel polymer electrolyte.

[0343] The composition for forming the above gel polymer electrolyte was prepared by mixing dipentaerythritol hexaacrylate (DPHA), a 6-functional crosslinking agent, which is a crosslinking monomer, hexagonal crystalline boron nitride (average particle diameter: 0.1 μm (100 nm), spherical particles), a liquid electrolyte, succinonitrile, and benzoin ethyl ether (Sigma-Aldrich, 240.30 g / mol) as an initiator. As the liquid electrolyte, 0.6 M LiBF4 and 0.6 M LiDFOB (lithium difluoro(oxalate)borate) were added to a 2:1 volume ratio mixed solvent of diethyl carbonate (DEC) and fluoroethylene carbonate (FEC).

[0344] Based on 100 parts by weight of the total weight of the composition for forming the gel polymer electrolyte, the content of the crosslinking monomer is 4 parts by weight of DPHA and 0.1 parts by weight of boron nitride. In addition, the content of the initiator was 5 parts by weight based on 100 parts by weight of the crosslinking monomer. The content of succinonitrile was 0.1 parts by weight based on 100 parts by weight of the total weight of the composition for forming the gel polymer electrolyte.

[0345] The above anode was manufactured according to the following method.

[0346] Li 1.04 Ni 0.88 Co 0.1 Al 0.02 O2 powder and carbon conductive material (Super-P; Timcal Ltd.) were uniformly mixed at a weight ratio of 90:5, and then a PVDF (polyvinylidene fluoride) binder solution was added to prepare a positive electrode active material slurry with a weight ratio of active material:carbon conductive material:binder = 90:5:5.

[0347] The manufactured slurry was coated on a 15 ㎛ thick aluminum substrate using a doctor blade, dried under reduced pressure at 120°C, and rolled using a roll press to form a sheet to manufacture a positive electrode.

[0348] The lithium metal battery manufactured according to the above process has a structure in which a lithium precipitation layer is formed between the negative electrode current collector and the separator before and after charging and discharging.

[0349] Example 2: Negative current collector / protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / separator+GPE (gel polymer+BN+SN+LE) (BN=1%) / positive electrode

[0350] A gel polymer electrolyte and a lithium metal battery having the same were manufactured in the same manner as in Example 1, except that the content of boron nitride in the composition for forming a gel polymer electrolyte was changed from 0.1 part by weight to 1 part by weight so that the content of boron nitride was 0.1 part by weight based on 100 parts by weight of the total weight of the gel polymer electrolyte.

[0351] Example 3: Negative current collector / protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / separator+GPE (gel polymer+BN+SN+LE) (BN=0.1%) / positive electrode

[0352] A gel polymer electrolyte and a lithium metal battery having the same were manufactured in the same manner as in Example 1, except that trimethylolpropane trimethacrylate (TMPTMA) was used instead of DPHA as a crosslinking monomer in the manufacture of the gel polymer electrolyte.

[0353] Example 4: Negative current collector / protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / separator+GPE(gel polymer+BN+SN+LE) (BN=0.01%) (change in BN size compared to Example 1) / positive electrode

[0354] A gel-type polymer electrolyte and a lithium metal battery were manufactured in the same manner as in Example 1, except that the average particle size of boron nitride was changed from 0.1 um (100 nm) to 1 um.

[0355] Example 5:

[0356] Negative current collector / protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / separator+GPE(gel polymer+BN+SN+EL)(BN=0.1%) / positive electrode

[0357] A gel-type polymer electrolyte and a lithium metal battery were manufactured in the same manner as in Example 1, except that the content of succinonitrile in the composition for forming a gel polymer electrolyte was changed to 1 wt%.

[0358] Example 6

[0359] A gel polymer electrolyte and a lithium metal battery were manufactured in the same manner as in Example 1, except that fibrous boron nitride with an average fiber length of 60 μm was used as the boron nitride in the protective film and gel polymer electrolyte. The fibrous boron nitride was manufactured according to the manufacturing method disclosed in Korean Patent Application Publication No. 2000-0029823.

[0360] Comparative Example 1: BN Free (negative current collector / protective film (PVA / PI-F+lithium salt=50:0.5:50) / separator+GPE (gel polymer+SN+LE) / positive electrode)

[0361] A gel polymer electrolyte and a lithium metal battery were manufactured in the same manner as in Example 1, except that boron nitride was not used in the manufacture of the protective film and gel polymer electrolyte.

[0362] Comparative Example 2: SN Free

[0363] (Cathode current collector / protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / separator+GPE(gel polymer+BN+LE) (BN=0.01%) / anode gel polymer electrolyte forming composition) Except that succinonitrile was not used, the same procedure as Example 1 was performed to manufacture a gel-type polymer electrolyte and a lithium metal battery.

[0364] Comparative Example 3:

[0365] Negative current collector / protective film (PVA / PIF+lithium salt=50:0.5:50) / separator+GPE(gel polymer+BN+SN+LE) / positive electrode (BN=0.1%)

[0366] A gel polymer electrolyte and a lithium metal battery were manufactured in the same manner as in Example 1, except that boron nitride was not used in the preparation of a composition for forming a gel polymer electrolyte.

[0367] Evaluation Example 1: Lifespan at room temperature (25℃)

[0368] The charge / discharge characteristics of the lithium metal batteries of Example 1-6 and Comparative Example 1-3 were evaluated under the following conditions.

[0369] The battery was charged at a constant current of 0.1 C rate at 25°C until the voltage reached 4.3 V (vs. Li), and then cut-off at a current of 0.05 C rate while maintaining 4.3 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 0.1 C rate until the voltage reached 3.6 V (vs. Li) (formation cycle).

[0370] The lithium metal battery, which had undergone a Mars cycle, was charged at a constant current of 0.2 C rate at 25°C until the voltage reached 4.3 V (vs. Li), and then cut-off at a current of 0.05 C rate while maintaining 4.3 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 0.5 C rate until the voltage reached 3.6 V (vs. Li) (1 st cycle). These cycles are 300 th The cycle was repeated under the same conditions.

[0371] 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 1. The cycle number refers to the number of cycles required for the discharge capacity to decrease to 80% of the standard capacity after the second cycle. As the cycle number increases, the battery is considered to have better life characteristics.

[0372] Differentiation conditions Number of cycles (n) Example 1 Protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / Separator+GPE(gel polymer+BN+SN+LE) Content of BN in GPE: 0.1% Average particle size of BN in protective film and GPE: 0.1 um (100 nm) 174 Example 2 Protective film with change in BN content in GPE compared to Example 1 (PVA / PI-F+BN+lithium salt=50:0.5:50) / Separator+GPE(gel polymer+BN+SN+LE) Content of BN in GPE: 1% Average particle size of BN in protective film and GPE: 0.1 um (100 nm) 158 Example 3 Type of crosslinking monomer in GPE compared to Example 1 Change of protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / separator+GPE(gel polymer+BN+SN+LE) BN content in GPE: 0.1% Average particle size of BN in protective film and GPE: 0.1um (100nm) 162 Example 4 Change of BN size in protective film compared to Example 1 Protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / separator+GPE(gel polymer+BN+SN+LE) Average particle size of BN in protective film and GPE: 1um 155 Example 5 Change of BN content in protective film compared to Example 1 Protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / separator+GPE(gel polymer+BN+SN+LE) BN content in protective film: 1%143Example 6Use of fibrous boron nitride151Comparative Example 1BN FREE in GPE, protective film (PVA / PI-F+lithium salt=50:0.5:50) / separator+GPE(gel polymer+SN+EL)87Comparative Example 2SN FREE in GPE, protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / separator+GPE(gel polymer+BN+EL)111Comparative Example 3BN FREE in protective filmProtective film (PVA / PI-F+lithium salt=50:0.5:50) / separator+GPE(gel polymer+BN+SN+EL)126

[0373] As shown in Table 1, the lithium metal battery of Comparative Example 1 had a deteriorated lifespan due to lithium and electrolyte side reactions caused by dendrite growth in the absence of boron nitride in the protective film, and the lithium metal battery of Comparative Example 2 had an insufficient lifespan due to the insufficient ionic conductivity increase effect caused by the non-inclusion of succinonitrile in the GPE. The lithium metal battery of Comparative Example 3 had insufficient mechanical properties because the protective film did not contain BN. In the lithium metal batteries of Comparative Examples 1 to 3, the protective film did not have a sufficient effect of suppressing the growth of anode dendrites, and thus, compared to the cases of Examples 1 to 5, when the protective film was formed on the anode current collector, the physical properties of the protective film increased without deteriorating the ionic conductivity, resulting in a deterioration in the capacity retention characteristics of the lithium metal battery.

[0374] In comparison, the lithium metal batteries of Examples 1 to 3 showed improved lifespan characteristics compared to the lithium metal batteries of Comparative Examples 1 to 3 due to increased ionic conductivity and improved physical properties as boron nitride was added to the gel polymer electrolyte and protective film contained in the separator. In the lithium metal battery of Example 4, compared to the lithium metal battery of Example 1, when the size of boron nitride contained in the gel polymer electrolyte and protective film increased, the dispersibility was somewhat reduced and the specific surface area decreased, thereby reducing the lifespan increase effect. In addition, the lithium metal battery of Example 5 showed improved lifespan characteristics due to the increased content of boron nitrite in the protective film, which increased the dendrite inhibition effect compared to Example 1.

[0375] Evaluation Example 2: High Temperature (45℃) Lifespan

[0376] The charge / discharge characteristics of the lithium metal batteries of Example 1-6 and Comparative Example 1-3 were evaluated under the following conditions.

[0377] The battery was charged at a constant current of 0.1 C rate at 45°C until the voltage reached 4.3 V (vs. Li), and then cut-off at a current of 0.05 C rate while maintaining 4.3 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 0.1 C rate until the voltage reached 3.6 V (vs. Li) during discharge (formation cycle).

[0378] The lithium metal battery, which had undergone a Mars cycle, was charged at a constant current of 0.2 C rate at 45°C until the voltage reached 4.3 V (vs. Li), and then cut-off at a current of 0.05 C rate while maintaining 4.3 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 0.5 C rate until the voltage reached 3.6 V (vs. Li) (1 st cycle). These cycles are 160 th The cycle was repeated under the same conditions.

[0379] In all charge / discharge cycles, a 10-minute pause was observed after each charge / discharge cycle. Some of the results of the high-temperature charge / discharge experiments are shown in Table 2.

[0380] Differentiation conditions Number of cycles (n) Example 1 Protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / Separator+GPE(gel polymer+BN+SN+LE) Content of BN in GPE: 0.1% Average particle size of BN in protective film and GPE: 0.1 um (100 nm) 135 Example 2 Change in the content of BN in GPE compared to Example 1 Protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / Separator+GPE(gel polymer+BN+SN+LE) Content of BN in GPE: 1% Average particle size of BN in protective film and GPE: 0.1 um (100 nm) 111 Example 3 Type of crosslinking monomer in GPE compared to Example 1 Change of protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / Separator+GPE(gel polymer+BN+SN+LE) BN content in GPE: 0.1% Average particle size of BN in protective film and GPE: 0.1um (100nm) 135 Example 4 Change of BN size in protective film compared to Example 1 Protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / Separator+GPE(gel polymer+BN+SN+LE) Average particle size of BN in protective film and GPE: 1um 108 Example 5 Change of BN content in protective film compared to Example 1 Protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / Separator+GPE(gel polymer+BN+SN+LE) BN content in protective film: 1%107Example 6Use of fibrous boron nitride125Comparative Example 1BN FREE in GPE, protective film (PVA / PI-F+lithium salt=50:0.5:50) / separator+GPE(gel polymer+SN+EL)52Comparative Example 2SN FREE in GPE, protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / separator+GPE(gel polymer+BN+EL)77Comparative Example 3BN FREE in protective filmProtective film (PVA / PI-F+lithium salt=50:0.5:50) / separator+GPE(gel polymer+BN+SN+EL)79

[0381] Referring to Table 2, it was found that the lithium metal batteries of Examples 1 to 6 had significantly improved high-temperature life characteristics compared to the lithium metal batteries of Comparative Examples 1 to 3.

[0382] Evaluation Example 3: Thickness expansion rate of the cathode

[0383] In the lithium metal batteries of Example 1-6 and Comparative Example 1-3, the charge / discharge characteristics were evaluated under the following conditions, and the thickness expansion rate of the negative electrode was investigated.

[0384] The battery was charged at a constant current of 0.1 C rate at 25°C until the voltage reached 4.3 V (vs. Li), and then cut-off at a current of 0.05 C rate while maintaining 4.3 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 0.1 C rate until the voltage reached 3.6 V (vs. Li) (formation cycle).

[0385] The lithium metal battery, which had undergone a Mars cycle, was charged at a constant current of 0.2 C rate at 25°C until the voltage reached 4.3 V (vs. Li), and then cut-off at a current of 0.05 C rate while maintaining 4.3 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 0.5 C rate until the voltage reached 3.6 V (vs. Li) (1 st cycle). These cycles are 100 th The cycle was repeated under the same conditions.

[0386] 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 1 below.

[0387] <Formula 1>

[0388] Cathode thickness expansion rate (%) = [thickness of lithium precipitation layer formed on the negative electrode current collector after 100 cycles of charging / thickness of lithium precipitation layer formed on the negative electrode current collector after formation] × 100

[0389] Conditions of classification Thickness expansion ratio of the negative electrode (%)Example 1Protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / Separator+GPE(gel polymer+BN+SN+LE) Content of BN in GPE: 0.1% Average particle size of BN in protective film and GPE: 0.1um (100nm)111Example 2 Change in the content of BN in GPE compared to Example 1Protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / Separator+GPE(gel polymer+BN+SN+LE) Content of BN in GPE: 1% Average particle size of BN in protective film and GPE: 0.1um (100nm)115Example 3 Type of crosslinking monomer in GPE compared to Example 1 Change of protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / separator+GPE(gel polymer+BN+SN+LE) BN content in GPE: 0.1% Average particle size of BN in protective film and GPE: 0.1um (100nm) 121 Example 4 Change of BN size in protective film compared to Example 1 Protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / separator+GPE(gel polymer+BN+SN+LE) Average particle size of BN in protective film and GPE: 1um 125 Example 5 Change of BN content in protective film compared to Example 1 Protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / separator+GPE(gel polymer+BN+SN+LE) BN content in protective film: 1%136Example 6Use of fibrous boron nitride127Comparative Example 1BN FREE in GPE, protective film (PVA / PI-F+lithium salt=50:0.5:50) / separator+GPE(gel polymer+SN+EL)205Comparative Example 2SN FREE in GPE, protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / separator+GPE(gel polymer+BN+EL)198Comparative Example 3BN FREE in protective filmProtective film (PVA / PI-F+lithium salt=50:0.5:50) / separator+GPE(gel polymer+BN+SN+EL)192

[0390] As can be seen in Table 3, the lithium metal batteries of Examples 1 to 6 had an improved thickness expansion rate of the negative electrode of 150% or less, unlike the lithium metal batteries of Comparative Examples 1 to 3.

[0391] Evaluation Example 4: Ionic Conductivity

[0392] The ionic conductivity of the protective film in the lithium metal batteries of Example 1-6 and Comparative Example 1-3 was investigated and is shown in Table 4 below. The ionic conductivity was measured by applying a voltage bias of 10 mV to the protective film in the frequency range of 1 Hz to 1 MHz, scanning the temperature, and measuring the resistance.

[0393] Distinction condition Ion conductivity (mS / cm) Example 1 Protective membrane (PVA / PI-F+BN+lithium salt=50:0.5:50) / Separator+GPE(gel polymer+BN+SN+LE) Content of BN in GPE: 0.1% Average particle size of BN in protective membrane and GPE: 0.1um (100nm) 0.47 Example 2 Change in the content of BN in GPE compared to Example 1 Protective membrane (PVA / PI-F+BN+lithium salt=50:0.5:50) / Separator+GPE(gel polymer+BN+SN+LE) Content of BN in GPE: 1% Average particle size of BN in protective membrane and GPE: 0.1um (100nm) 0.41 Example 3 Type of crosslinking monomer in GPE compared to Example 1 Change of protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / Separator+GPE(gel polymer+BN+SN+LE) Content of BN in GPE: 0.1% Average particle size of BN in the protective film and GPE: 0.1um (100nm) 0.43 Example 4 Change of BN size in the protective film compared to Example 1 Protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / Separator+GPE(gel polymer+BN+SN+LE) Average particle size of BN in the protective film and GPE: 1um 0.42 Example 5 Change of BN content in the protective film compared to Example 1 Protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / Separator+GPE(gel polymer+BN+SN+LE) Content of BN in the protective film: 1%0.42Example 6Use of boron nitride on fiber0.48Comparative Example 1BN FREE in GPE, protective film (PVA / PI-F+lithium salt=50:0.5:50) / separator+GPE(gel polymer+SN+EL)0.32Comparative Example 2SN FREE in GPE, protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / separator+GPE(gel polymer+BN+EL)0.33Comparative Example 3BN FREE in protective filmProtective film (PVA / PI-F+lithium salt=50:0.5:50) / separator+GPE(gel polymer+BN+SN+EL)0.35

[0394] As shown in Table 4, it was found that the protective films of the lithium metal batteries of Examples 1 to 6 had higher ionic conductivity than the lithium metal batteries of Comparative Examples 1 to 3.

[0395] Evaluation Example 5: Mechanical Properties Evaluation

[0396] In the lithium metal batteries of Examples 1 to 6 and Comparative Examples 1 to 3, the modulus, hardness, and recovery rate of the protective film were evaluated and measured using a microindenter (DUH-211, Shimadzu). The force applied to the protective film was 10 mN.

[0397] The measurement results are shown in Table 5 below. Extension is the distance that the tip of the microindenter moves into the sample until a certain force is applied to the tip, and recovery is the ratio of the distance that the tip moves toward the sample surface from the point where the tip moves the most into the sample to the point where the force applied to the tip becomes zero, to the distance that the tip has moved into the sample. Modulus is the indentation modulus, and hardness is the indentation hardness, and they are calculated from the force applied to the tip from the sample according to the movement distance of the microindenter tip.

[0398] Classification Conditions Modulus (Mpa) Hardness (N / mm) 2) Recovery rate (%) Example 1 Protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / Separator+GPE(gel polymer+BN+SN+LE) Content of BN in GPE: 0.1% Average particle size of BN in protective film and GPE: 0.1um (100nm) 287026.677.2 Example 2 Change in the content of BN in GPE compared to Example 1 Protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / Separator+GPE(gel polymer+BN+SN+LE) Content of BN in GPE: 1% Average particle size of BN in protective film and GPE: 0.1um (100nm) 222023.375.5 Example 3 Type of crosslinking monomer in GPE compared to Example 1 Change of protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / Separator+GPE(Gel polymer+BN+SN+LE) Content of BN in GPE: 0.1% Average particle size of BN in protective film and GPE: 0.1um (100nm) 2940 27.16 9.3 Example 4 Change of BN size in protective film compared to Example 1 Protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / Separator+GPE(Gel polymer+BN+SN+LE) Average particle size of BN in protective film and GPE: 1um 2580 25.56 2.4 Example 5 Content of BN in protective film compared to Example 1 Change Protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / Separator+GPE(gel polymer+BN+SN+LE) Content of BN in the protective film: 1% 287027.375.1 Example 6 Use of fibrous boron nitride 315035.183.1 Comparative example 1 BN FREE in GPE, protective film (PVA / PI-F+lithium salt=50:0.5:50) / Separator+GPE(gel polymer+SN+EL) 153013.160.0 Comparative example 2 SN FREE in GPE, protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / Separator+GPE(gel polymer+BN+EL) 171015.255.3 Comparative example 3 BN in the protective film FREE protective film (PVA / PI-F+lithium salt=50:0.5:50) / separator+GPE(gel polymer+BN+SN+EL)209021.162.1

[0399] As shown in Table 5, the protective films of Examples 1 to 6 showed increased modulus, i.e., elastic modulus, compared to the protective films of Comparative Examples 1 to 3, thereby increasing the strength of the binder and suppressing electrode expansion. This increase in modulus is believed to be due to the formation of a cross-linked polymer.

[0400] In comparison, the protective films of Comparative Examples 1 to 3 had significantly poor modulus, hardness, and strength.

[0401] Evaluation Example 6: High-rate characteristics

[0402] The lithium metal batteries manufactured in Example 1-6 and Comparative Example 1-3 were charged at a constant current of 0.1 C rate at 25°C until the voltage reached 4.3 V (vs. Li), and then cut-off was achieved at a current of 0.05 C rate while maintaining 4.3 V in constant voltage mode. Subsequently, the batteries were discharged at a constant current of 0.1 C rate until the voltage reached 3.6 V (vs. Li) during discharge (formation cycle).

[0403] The lithium metal battery, which had undergone a Mars cycle, was charged at a constant current of 0.2 C rate at 25°C until the voltage reached 4.3 V (vs. Li), and then cut-off at a current of 0.05 C rate while maintaining 4.3 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 0.5 C rate until the voltage reached 3.6 V (vs. Li) (1 st cycle).

[0404] 1 st The cycled lithium metal battery was charged at a constant current of 0.2 C at 25°C until the voltage reached 4.3 V (vs. Li), and then cut off at a current of 0.05 C while maintaining 4.3 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 0.2 C until the voltage reached 2.8 V (vs. Li) (2nd cycle).

[0405] 2 nd Cycle 7 th The cycle was repeated under the same conditions.

[0406] 7 th The cycled lithium battery was charged at a constant current of 0.33 C at 25°C until the voltage reached 4.35 V (vs. Li), and then cut off at a current of 0.05 C while maintaining 4.35 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 0.5 C until the voltage reached 2.8 V (vs. Li) (8 rd cycle).

[0407] 8th cycle 17 th The cycle was repeated under the same conditions.

[0408] 17 th The cycled lithium metal battery was charged at a constant current of 0.33 C at 25°C until the voltage reached 4.35 V (vs. Li), and then cut off at a current of 0.05 C while maintaining 4.35 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 1 C until the voltage reached 2.8 V (vs. Li) (18 th cycle).

[0409] 18 th Cycle 25 th The cycle was repeated under the same conditions.

[0410] 25 st The cycled lithium metal battery was charged at a constant current of 0.33 C at 25°C until the voltage reached 4.35 V (vs. Li), and then cut off at a current of 0.05 C while maintaining 4.35 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 2 C until the voltage reached 2.8 V (vs. Li) (26 thcycle).

[0411] 26th cycle 35 th The cycle was repeated under the same conditions.

[0412] 35 st The cycled lithium metal battery was charged at a constant current of 0.33 C at 25°C until the voltage reached 4.35 V (vs. Li), and then cut off at a current of 0.05 C while maintaining 4.35 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 3 C until the voltage reached 2.8 V (vs. Li) (36 th cycle).

[0413] 36 th The cycled lithium metal battery was charged at a constant current of 0.33 C at 25°C until the voltage reached 4.35 V (vs. Li), and then cut off at a current of 0.05 C while maintaining 4.35 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 0.2 C until the voltage reached 2.8 V (vs. Li) (46 th cycle), these cycles are 100 th The cycle was repeated under the same conditions.

[0414] In all the above charge / discharge cycles, a pause of 10 minutes was allowed after each charge / discharge cycle.

[0415] Some of the results of the above charge-discharge experiment are shown in Table 6 below.

[0416] The high-rate characteristic is defined by Equation 2 below.

[0417] <Formula 2>

[0418] High rate characteristic [%] = [25 st Discharge capacity in cycles (1C rate) / 2 nd Discharge capacity in cycle (0.2C rate)] × 100

[0419] Distinction condition High rate characteristics (%) Example 1 Protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / Separator+GPE(gel polymer+BN+SN+LE) Content of BN in GPE: 0.1% Average particle size of BN in protective film and GPE: 0.1um (100nm) 80 Example 2 Change in the content of BN in GPE compared to Example 1 Protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / Separator+GPE(gel polymer+BN+SN+LE) Content of BN in GPE: 1% Average particle size of BN in protective film and GPE: 0.1um (100nm) 78 Example 3 Type of crosslinking monomer in GPE compared to Example 1 Change of protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / Separator+GPE(gel polymer+BN+SN+LE) BN content in GPE: 0.1% Average particle size of BN in protective film and GPE: 0.1um (100nm) 76 Example 4 Change of BN size in protective film compared to Example 1 Protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / Separator+GPE(gel polymer+BN+SN+LE) Average particle size of BN in protective film and GPE: 1um 77 Example 5 Change of BN content in protective film compared to Example 1 Protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / Separator+GPE(gel polymer+BN+SN+LE) BN content in protective film: 1%75Example 6Use of fibrous boron nitride79Comparative Example 1BN FREE in GPE, protective film (PVA / PI-F+lithium salt=50:0.5:50) / separator+GPE(gel polymer+SN+EL)67Comparative Example 2SN FREE in GPE, protective film (PVA / PI-F+BN+lithium salt=50:0.5:50) / separator+GPE(gel polymer+BN+EL)68Comparative Example 3BN FREE in protective filmProtective film (PVA / PI-F+lithium salt=50:0.5:50) / separator+GPE(gel polymer+BN+SN+EL)72

[0420] Referring to Table 6, the lithium metal batteries of Examples 1 to 6 have improved ion conductivity characteristics due to the improved lithium ion transport of the protective film formed on the negative electrode current collector containing boron nitrite. As a result, the high-rate characteristics of the lithium metal batteries of Examples 1 to 6 were significantly increased compared to the lithium metal battery of Comparative Example 1 having a separator containing a gel polymer electrolyte that did not contain boron nitrite and the lithium metal battery having a separator containing a gel polymer electrolyte that did not contain succinonitrile. From this, it was found that the physical strength of the protective film containing the gel polymer electrolyte of Examples 1 to 6 was increased, further increasing stability, and thus the high-rate characteristics were improved due to the improved ion conductivity.

[0421] While exemplary embodiments have been described in detail with reference to the attached drawings, the present invention is not limited to these examples. It is self-evident that those skilled in the art to which the present invention pertains can devise various modifications or variations within the scope of the technical concepts described in the patent claims, and these also naturally fall within the technical scope of the present invention.

Claims

1. A lithium metal battery comprising a negative electrode current collector; a protective film formed on the negative electrode current collector; a separator; a gel polymer electrolyte; and a positive electrode. The above protective film comprises boron nitride (BN) and a binder, The above gel polymer electrolyte is a lithium metal battery containing a gel polymer, boron nitride (BN), a nitrile compound, and a liquid electrolyte.

2. In paragraph 1, the nitrile compound is a compound having a melting point of 30°C or higher, The above nitrile compound is at least one selected from the group consisting of succinonitrile, adiponitrile, pimelonitrile, suberonitrile, sebaconitrile, butyronitrile, acetonitrile, and propionitrile. A lithium metal battery, wherein the content of the nitrile compound is 0.01 to 5 parts by weight based on 100 parts by weight of the total weight of the gel polymer electrolyte.

3. A lithium metal battery according to claim 1, wherein the size of the boron nitride is 0.01 um to 10 um, and the content of the boron nitride of the gel polymer electrolyte is controlled to be equal to or smaller than the content of the boron nitride of the protective film.

4. In the first paragraph, the content of boron nitride in the protective film is 5 parts by weight or less based on 100 parts by weight of the total weight of the protective film, A lithium metal battery, wherein the content of the binder is 40 to 60 parts by weight based on 100 parts by weight of the total weight of the protective film.

5. In the first paragraph, the protective film further includes a lithium salt, A lithium metal battery, wherein the mixing weight ratio of the binder and the lithium salt is 1:9 to 9:

1.

6. In the first paragraph, the gel polymer has i) three or more polymerizable functional groups. A crosslinked product of a multifunctional acrylic monomer; or ii) A lithium metal battery, which is a crosslinked product of a first polymerizable monomer, a multifunctional acrylic monomer having three or more polymerizable functional groups, and at least one second polymerizable monomer selected from a urethane acrylic monomer having two or more polymerizable functional groups and a polymerizable monomer containing a perfluoropolyether (PFPE) unit and having two or more polymerizable functional groups.

7. In the 6th paragraph, the multifunctional acrylic monomer having three or more polymerizable functional groups is pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate (TMPTMA), propoxylated (3) trimethylolpropane triacrylate (PO(3)TMPTA), propoxylated (6) trimethylolpropane triacrylate (PO(6)TMPTA), ethoxylated trimethylolpropane triacrylate, di(trimethylolpropane) tetraacrylate (Di(trimethylolpropane) tetraacrylate), pentaerythritol triacrylate (PETA), propoxylated glyceryl triacrylate, tris(2-hydroxyethyl) isocyanurate triacrylate (THEICTA), dipentaerythritol Pentaacrylate (DPEPA), or a combination thereof, lithium metal battery.

8. In paragraph 6, the urethane acrylic monomer having two or more functional groups is a compound represented by the following chemical formula 1, a compound represented by the following chemical formula 2, or a combination thereof. The polymerizable monomer containing the perfluoropolyether (PFPE) unit and having two or more polymerizable functional groups is a compound represented by the following chemical formula 3, a compound represented by the following chemical formula 3-1, or a combination thereof, a lithium metal battery: <Chemical Formula 1> In chemical formula 1, n is an integer from 1 to 100, and R a and R b are the same or different from each other, and are substituted or unsubstituted C1-C10 alkylene groups, EG represents an ethylene glycol residue, DEG represents a diethylene glycol residue, TMP represents a trimethylolpropane residue, <Chemical Formula 2> In chemical formula 2, each R is independently a hydrogen atom or a C1-C3 alkyl group, <Chemical Formula 3> In chemical formula 3, R1 is hydrogen or a C1-C6 alkyl group, m and n are greater than 0, the sum of m+n is in the range of 2 to 300, m is a number from 1 to 150, n is a number from 1 to 150, <Chemical Formula 3-1> In Chemical Formula 3-1, p and q are greater than 0, the sum of p+q is in the range of 2 to 300, p is a number from 1 to 150, and q is a number from 1 to 150.

9. A lithium metal battery in the first paragraph, wherein the content of boron nitride in the gel polymer electrolyte is 5 parts by weight or less based on 100 parts by weight of the total weight of the gel polymer electrolyte.

10. A lithium metal battery in which the thickness expansion rate of the negative electrode represented by the following formula 1 in the first paragraph is 150% or less: <Formula 1> Thickness expansion rate of the negative electrode (%) = [Thickness of the lithium precipitation layer formed on the negative electrode current collector after 100 cycles of charging / Thickness of the lithium precipitation layer formed on the negative electrode current collector after formation] × 100 11. In the first paragraph, the protective film further includes a second polymer having a functional group capable of crosslinking with the first polymer containing a hydroxyl group, A lithium metal battery, wherein the second polymer is at least one selected from among fluorinated polyamic acid and fluorinated polyimide having a carboxyl group.

12. In the 11th paragraph, the first polymer containing a hydroxyl group is carboxymethyl cellulose (CMC); polyvinyl alcohol (PVA); Vinyl acetate, butyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 2-hydroxyethylene glycol (meth)acrylate, 2-hydroxypropylene glycol (meth)acrylate, acrylic acid, methacrylic acid, 2-(meth)acryloyloxy acetic acid, 3-(meth)acryloyloxy propyl acid, 4-(meth)acryloyloxy butyric acid, itaconic acid, maleic acid, 2-isocyanatoethyl (meth)acrylate, 3-isocyanatopropyl (meth)acrylate, A polymerization reaction product of one or more monomers selected from among 4-isocyanatobutyl (meth)acrylate, (meth)acrylamide, ethylene di(meth)acrylate, diethylene glycol (meth)acrylate, triethylene glycol di(meth)acrylate, trimethylene propane tri(meth)acrylate, trimethylene propane triacrylate, 1,3-butanediol (meth)acrylate, 1,6-hexanediol di(meth)acrylate, allyl acrylate, and N-vinyl caprolactam, or a hydrolyzate thereof, A lithium metal battery, wherein the second polymer is a polyamic acid represented by the following chemical formula 14 or 15, a polyimide represented by the following chemical formula 16 or 17, or a combination thereof: [Chemical Formula 14] [Chemical Formula 15] [Chemical Formula 16] [Chemical Formula 17] In the above equations, n and m are the mole fractions within the repeating unit, respectively, and 0 <n≤1, 0≤m<1, n+m=1이다.

13. A lithium metal battery according to claim 1, wherein the binder is a vinylidene fluoride-hexafluoropropylene (VDF-HFP) copolymer, polyethylene oxide, polypropylene oxide, polydimethylsiloxane, polyacrylonitrile, polymethyl(meth)acrylate, polyvinyl chloride, polyvinylidene fluoride, polyvinylidene fluoride-co-hexafluoropropylene, polyethyleneimine, polyphenylene terephthalamide, polymethoxypolyethylene glycol(meth)acrylate, poly2-methoxy ethyl glycidyl ether, or a combination thereof.

14. A lithium metal battery comprising a negative electrode active material layer disposed between the negative electrode current collector and the protective film in the first paragraph.

15. A lithium metal battery according to claim 14, wherein the negative electrode active material layer comprises a carbon-based compound; a mixture of at least one selected from a carbon-based material and a first metal; a composite of at least one selected from a carbon-based material and a first metal; or a combination thereof.

16. In the first paragraph, a metal layer is further included between the negative electrode current collector and the protective film, and the metal layer includes lithium metal foil, lithium metal powder, lithium alloy foil, lithium alloy powder, or a combination thereof. The above lithium alloy contains lithium and a first metal, The first metal is indium (In), silicon (Si), gallium (Ga), tin (Sn), aluminum (Al), titanium (Ti), zirconium (Zr), niobium (Nb), germanium (Ge), antimony (Sb), bismuth (Bi), gold (Au), platinum (Pt), palladium (Pd), magnesium (Mg), silver (Ag), zinc (Zn), nickel, iron, cobalt, chromium, cesium, sodium, potassium, calcium, yttrium, tantalum, hafnium, barium, vanadium, strontium, lanthanum, or a combination thereof.

17. In the first paragraph, the lithium metal battery further includes an electrolyte, The above electrolyte is a liquid electrolyte, a solid electrolyte, a gel electrolyte or a combination thereof, The above solid electrolyte includes an oxide-based solid electrolyte, a sulfide-based solid electrolyte, a polymer solid electrolyte, or a combination thereof, A lithium metal battery, wherein the gel electrolyte comprises a polymer gel electrolyte.

18. In paragraph 1, The above positive electrode includes a positive electrode current collector and a positive electrode active material layer, At least one of the positive electrode current collector and the negative electrode current collector includes a base film and a metal layer disposed on one or both sides of the base film, The above base film comprises a polymer, and the polymer comprises polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI) or a combination thereof, A lithium metal battery, wherein the metal layer comprises indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof.

19. Step of preparing the negative electrode collector; A step of forming a protective film containing boron nitride and a binder on a negative electrode current collector; Step for preparing a membrane; Steps to prepare the anode; A step of preparing a battery assembly by laminating a negative electrode collector, a separator, and a positive electrode; A step of injecting a composition for forming a gel polymer electrolyte, including a crosslinking monomer for forming a gel polymer, a liquid electrolyte, boron nitride, and a nitrile-based compound, into the battery assembly; and A method for manufacturing a lithium metal battery, comprising a step of forming a gel polymer electrolyte by performing heat treatment, for manufacturing the lithium metal battery of claim 1.

20. In paragraph 19, The step of forming a protective film containing boron nitride and a binder on the negative electrode current collector comprises coating and heat-treating a composition for forming a protective film containing boron nitride and at least one selected from a binder precursor and a binder on the negative electrode current collector. A method for manufacturing a lithium metal battery, wherein the protective film further comprises a lithium salt.

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