Lithium metal negative electrode, manufacturing method thereof and lithium metal battery comprising same

Abstract

A lithium metal negative electrode according to one specific embodiment includes a lithium metal layer and a protective layer formed on at least one surface of the lithium metal layer, where the protective layer includes lithium-philic inorganic particles, and at least one peak appears in a region of 1750-1880 cm-1 when the protective layer is subjected to FT-IR analysis. The lithium metal negative electrode includes a protective layer having excellent ionic conductivity and mechanical strength and capable of inducing a uniform lithium electrodeposition behavior, thereby effectively suppressing growth of lithium dendrites, and thus can provide a lithium metal battery having excellent cycle life, capacity characteristics, safety, and the like at the time of electrodeposition / desorption.

Description

Technical Field

[0001] The present invention relates to a lithium metal negative electrode, a manufacturing method thereof and a lithium metal battery comprising the same. Background Art

[0002] Interest in electric vehicles (EVs) that can replace fossil fuel-based vehicles, one of the main causes of air pollution, continues to increase, and in recent years, lithium secondary batteries that have high charging voltage and power stability and are mainly used as power sources for electric vehicles (EVs) are being actively developed.

[0003] In addition, in recent years, lithium metal, which has a relatively high capacity (3860 mAh / g) and a low redox potential (-3.04 V vs. SHE), has attracted much attention as one of the promising negative electrode materials, and research on lithium metal batteries including such lithium metal anodes (Lithium Metal Anode; LMA) is also underway.

[0004] However, when lithium metal is used as the negative electrode, there are problems such as (1) low coulombic efficiency during charge / discharge due to the high reactivity of lithium metal to the electrolyte and (2) the formation of lithium dendrites, which makes it difficult to ensure the cycle characteristics and stability of the battery. Therefore, a technology that effectively controls these problems is needed. Summary of the Invention

[0005] (1) Technical issues to be resolved

[0006] A specific embodiment aims to provide a lithium metal anode that induces uniform lithium electrodeposition and inhibits the growth of lithium dendrites, thereby effectively improving the electrochemical performance, efficiency, safety, etc. of the battery.

[0007] Another embodiment aims to provide a lithium metal battery having excellent electrochemical performance, lifespan characteristics, safety, etc.

[0008] (2) Technical solution

[0009] According to a specific embodiment, the lithium metal negative electrode comprises: a lithium metal layer; and a protective layer, wherein the protective layer is formed on at least one side of the lithium metal layer, wherein the protective layer comprises lithium-philic inorganic particles, and when the protective layer is subjected to FT-IR analysis, the wavelength of the protective layer is 1750-1880 cm -1 At least one peak appears in the region.

[0010] The protective layer may include an organic-inorganic composite polymer.

[0011] The organic-inorganic composite polymer may have a structure in which lithium-philic inorganic particles are three-dimensionally connected to each other through chemical bonds.

[0012] When the protective layer is subjected to FT-IR analysis, the -1 The area and 1820-1880cm -1 At least one peak can appear in each region.

[0013] When the protective layer is subjected to FT-IR analysis, the peak area ratio according to the following formula 1 may be greater than 1.

[0014] [Formula 1]

[0015] R P =I / A

[0016] In the formula 1, R P is the peak area ratio, A is at 1680-1750cm -1 The peak area in the region of 1750-1800 cm -1 The area and 1820-1880cm -1 The total area of each peak region appearing in the region.

[0017] The protective layer may include one or more substances selected from the group consisting of LiF and Li3N.

[0018] The lithiophilic inorganic particles may comprise metals, metal oxides, metal nitrides, or combinations thereof.

[0019] The lithium-philic inorganic particles may include Au, Ag, Pt, Al, Mg, Zn, Ni, Se, Te, Bi, Pb, Ga, Cd, Hg, Pd, Sc, Y, Ca, Sr, Ba, NiO, ZnO, SnO, Cu x O (x is 1 or 2), GeO, Ag x O (x is 1 or 2), Sb2O y (y is 3, 4 or 5), CuZn or a combination thereof.

[0020] The diameter of the lithiophilic inorganic particles may be less than 500 nm.

[0021] The thickness of the protective layer may be 0.1-20 μm.

[0022] According to a specific embodiment, a method for manufacturing a lithium metal negative electrode includes the following steps: step S1, modifying lithium-philic inorganic particles so that the surface of the lithium-philic inorganic particles has amino groups; step S2, imidizing the modified lithium-philic inorganic particles with dianhydride to prepare an organic-inorganic composite polymer; and step S3, using a composition containing the organic-inorganic composite polymer to form a protective layer on at least one side of the lithium metal layer.

[0023] The step S1 may include dispersing the lithiophilic inorganic particles in an organic solution.

[0024] The organic solution may include a compound represented by Chemical Formula 1 below.

[0025] [Chemical Formula 1]

[0026]

[0027] In the chemical formula 1, R 1 It is one or more organic groups selected from the group consisting of an alkylene group, an arylene group, a heterocyclic group and an alkylene oxide group which may be substituted.

[0028] The organic solution may include 1-20 mol / L of the compound represented by Chemical Formula 1.

[0029] The dianhydride may contain fluorine element.

[0030] A lithium metal battery according to one embodiment includes the lithium metal negative electrode described in any one of the above embodiments.

[0031] (3) Beneficial effects

[0032] According to a specific embodiment, a lithium metal anode can be provided, which includes a protective layer having excellent ionic conductivity and mechanical strength and inducing uniform lithium electrodeposition behavior, thereby effectively suppressing the growth of lithium dendrites.

[0033] According to another specific embodiment, a lithium metal battery having excellent cycle life, capacity characteristics, safety, etc. during charge / discharge can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1a to Figure 1b FIG. 1 is a diagram showing a method for forming an organic-inorganic composite polymer according to one embodiment in sequential steps.

[0035] Figure 2 is a conceptual diagram illustrating a cross section of a lithium metal anode according to one specific embodiment.

[0036] Figure 31 and 2 are diagrams sequentially illustrating a method for manufacturing a lithium metal negative electrode according to one specific embodiment.

[0037] Figures 4a to 4c Graphs showing FT-IR analysis results of lithium metal negative electrodes according to Examples and Comparative Examples.

[0038] Figure 5 Graphs showing evaluation results of electrodeposition / desorption characteristics of lithium metal batteries including lithium metal negative electrodes according to Examples and Comparative Examples. Best Practice

[0039] Hereinafter, preferred embodiments will be described with reference to various embodiments. However, the embodiments are not limited to the specific embodiments described below, but can be modified into various other forms.

[0040] Hereinafter, in this specification, unless otherwise specifically defined, when describing a layer, membrane, film, region, plate or the like as being “above” or “on” another part, this may include not only the case where it is “directly” “above” the other part, but also the case where there is another part in between.

[0041] Hereinafter, in this specification, unless otherwise specifically defined, "a combination thereof" may refer to a mixture or copolymerization of the aforementioned compositions. In addition, "a combination thereof" may refer to the simultaneous use or provision of two or more of the aforementioned compositions.

[0042] In this specification, "polymer" refers to a molecule of relatively high molecular weight, and the structure of the "polymer" can be a structure in which units derived from low molecular weight monomers are repeated multiple times. The "polymer" can include organic polymers composed of organic matter, inorganic polymers composed of inorganic matter, organic-inorganic composite polymers containing organic matter and inorganic matter, or a combination thereof, and can also include polymers composed of monomers of the same type and copolymers thereof. In addition, the copolymer can include alternating copolymers, block copolymers, random copolymers, branched copolymers, crosslinked copolymers, or a combination thereof.

[0043] In this specification, an "organic-inorganic composite polymer" refers to a polymer in which chemical bonds are formed between inorganic particles by reacting monomers containing inorganic particles with each other or reacting monomers containing inorganic particles with other compounds. Specifically, the "organic-inorganic composite polymer" may refer to a polymer having a structure in which the inorganic particles are three-dimensionally connected to each other, and more specifically, may refer to a polymer having a network structure in which the inorganic particles are three-dimensionally cross-linked and connected to each other.

[0044] As mentioned above, research is underway on using lithium metal, which has relatively high capacity and low redox potential characteristics, as the negative electrode. However, due to problems such as the formation of lithium dendrites, it is difficult to ensure the cycle characteristics and stability of the battery.

[0045] In a lithium metal negative electrode according to a specific embodiment, a protective layer is included on at least one side of the lithium metal layer, and the protective layer can effectively suppress the growth of lithium dendrites by inducing uniform lithium electro-deposition behavior, thereby substantially solving the above-mentioned problems and contributing to providing a lithium metal battery with excellent ionic conductivity, cycle life, capacity characteristics and safety. Figures 1a to 5 , and make the specific content public.

[0046] Figure 1a to Figure 1b FIG. 1 is a diagram showing a method for forming an organic-inorganic composite polymer according to one embodiment in sequential steps.

[0047] Figure 2 is a conceptual diagram illustrating a cross section of a lithium metal anode according to one specific embodiment.

[0048] Figure 3 1 and 2 are diagrams sequentially illustrating a method for manufacturing a lithium metal negative electrode according to one specific embodiment.

[0049] Figures 4a to 4c Graphs showing FT-IR analysis results of lithium metal negative electrodes according to Examples and Comparative Examples.

[0050] Figure 5 Graphs showing evaluation results of electrodeposition / desorption characteristics of lithium metal batteries including lithium metal negative electrodes according to Examples and Comparative Examples.

[0051] Lithium metal anode

[0052] According to a specific embodiment, the lithium metal negative electrode 100 includes a lithium metal layer 10 and a protective layer 20 formed on at least one side of the lithium metal layer, wherein the protective layer contains lithium-philic inorganic particles 1, and when the protective layer 20 is subjected to FT-IR analysis, the wavelength of the protective layer 20 is 1750-1880 cm -1 At least one peak appears in the region.

[0053] As described above, the protection layer 20 can effectively suppress the growth of lithium dendrites by inducing uniform lithium electrodeposition behavior on at least one side of the lithium metal layer 10 .

[0054] The protective layer 20 includes lithium-philic inorganic particles 1. Wherein, lithium-philic refers to an affinity for lithium. When a substance with a low affinity for lithium and lithium coexist, lithium metal will selectively be electrodeposited first. On the other hand, lithium-philic substances with a high affinity for lithium reduce the initial nucleation resistance of the lithium electrodeposition reaction, thereby inducing uniform electrodeposition of lithium metal, thereby inhibiting the growth of lithium dendrites. Therefore, the lithium-philic inorganic particles 1 can induce uniform electrodeposition of lithium metal and can inhibit the growth of lithium dendrites, thereby improving the stability and cell performance of lithium metal batteries.

[0055] The lithium-philic inorganic particles 1 refer to particles containing lithium-philic inorganic substances, and the lithium-philic inorganic particles 1 may contain metals, metal oxides, metal nitrides, or combinations thereof. For example, the lithium-philic inorganic particles may contain Au, Ag, Pt, Al, Mg, Zn, Ni, Se, Te, Bi, Pb, Ga, Cd, Hg, Pd, Sc, Y, Ca, Sr, Ba, NiO, ZnO, SnO, Cu x O (x is 1 or 2), GeO, Ag x O (x is 1 or 2), Sb2O y (y is 3, 4 or 5), CuZn or a combination thereof. In addition, the lithium-philic inorganic particles may be substantially composed of the above-mentioned lithium-philic inorganic substances.

[0056] As described above, these lithiophilic inorganic substances can undergo electrochemical reactions with lithium and induce uniform electrodeposition of lithium ions. Therefore, when a protective layer 20 comprising the lithiophilic inorganic particles 1 is formed on at least one side of the lithium metal layer 10, the growth of lithium dendrites can be suppressed during the charge / discharge process of the battery, thereby effectively preventing problems such as a reduction in irreversible capacity and internal short circuits in the battery.

[0057] In a specific embodiment, the lithium-philic inorganic particles 1 may include Ag, Ag x O (x is 1 or 2) or a combination thereof. Specifically, the lithium-philic inorganic particles 1 can be silver nanoparticles (AgNPs) containing silver (Ag). When the lithium-philic inorganic particles 1 contain silver (Ag), they can form an alloy with lithium, thereby facilitating the generation of initial lithium nuclei and more effectively reducing lithium electrodeposition resistance.

[0058] The diameter of the lithium-philic inorganic particles 1 may be less than 500 nm. Specifically, the diameter of the lithium-philic inorganic particles 1 may be greater than 0.1 nm, greater than 1 nm, greater than 10 nm, or greater than 20 nm, and may be less than 400 nm or less than 300 nm. When the size of the lithium-philic inorganic particles 1 is too small, the specific surface area is reduced, and thus, in the particle surface modification step described below, it may be difficult for the functional groups on the surface of the inorganic particles to polymerize. Therefore, when the lithium-philic inorganic particles 1 are nanoparticles having a diameter within the above range, the dispersibility is excellent, so that in the particle surface modification step described below, functional groups can be appropriately formed on the surface of the inorganic particles, and the imidization reaction due to the polymerization between the functional groups can be easily performed.

[0059] The protective layer 20 may include an organic-inorganic composite polymer, which may have a structure in which the lithiophilic inorganic particles 1 are three-dimensionally connected to each other by chemical bonds. When the protective layer includes the organic-inorganic composite polymer as described above, the lithiophilic inorganic particles 1 may be present within the protective layer 20 in a network structure in which the particles are three-dimensionally cross-linked and connected to each other by organic chemical bonds. The structure of the organic-inorganic composite polymer differs from the structure of a mixture formed by physically mixing a single organic polymer having the above-mentioned chemical bonds and the lithiophilic inorganic particles. Specifically, the structure can be distinguished by whether the lithiophilic inorganic particles are three-dimensionally connected to each other by chemical bonds.

[0060] The chemical bond formed between the lithium-philic inorganic particles 1 may be an imide bond. Specifically, the lithium-philic inorganic particles 1 may exist in the protective layer 20 in the following structure, that is, through the amino group (Amino Group) formed as a functional group (Functional Group) on the particle surface, a compound (PI) having an imide bond is formed between the particles and the particles are cross-linked and connected to each other (see Figure 1b and Figure 2 ). Therefore, when infrared analysis (IR) is performed on the protective layer 20, a peak representing an imide bond may appear.

[0061] Generally, when Fourier transform infrared spectroscopy (FT-IR) is performed by a FT-IR instrument, the -1 When at least one peak appears in the region of 1750-1800 cm -1 The area and 1820-1880cm -1 When at least one peak appears in the region of 1750-1880 cm, it indicates that there is an imide bond in the specific material. -1 At least one peak may appear in the region of 1750-1800 cm-1 The area and 1820-1880cm -1 At least one peak may appear in the region of -1 The term "region" refers to a region distinguished by absorbance according to wavenumbers in FT-IR analysis.

[0062] When the protective layer 20 is analyzed by FT-IR, the peak area ratio according to the following formula 1 may be greater than 1.

[0063] [Formula 1]

[0064] R P =I / A

[0065] In the formula 1, R P is the peak area ratio, A is at 1680-1750cm -1 The peak area in the region of 1750-1800 cm -1 The area and 1820-1880cm -1 The total area of each peak region appearing in the region.

[0066] Specifically, when the protective layer 20 is analyzed by FT-IR, the peak area ratio according to Formula 1 may be greater than 1.1, greater than 3, greater than 6, or greater than 8, and may be less than 30, less than 20, or less than 15.

[0067] In the formula 1, R P It represents the ratio of the area of the imide C=O peak region (I) to the area of the acid C=O peak region (A) in FT-IR analysis. A represents the area of 1680-1750 cm where the acid C=O peak appears. -1 The peak area in the range of 1750-1800 cm where the imide C=O peak appears is shown in Figure 2. -1 The area and 1820-1880cm -1 The total area of each peak region in the region of . In this case, the area of the peak region can be calculated by measuring the infrared absorbance of the wave number region where the peak appears using an FT-IR instrument and integrating the area of each peak using the OriginPro 2021b program. For example, the area (A) of the acid C=O peak region can be obtained by using the second derivative method to obtain the baseline and then integrating the 1680-1750 cm -1 The peak corresponding to the wave number is fitted into a Gaussian curve to obtain the area and the obtained area is integrated for calculation.

[0068] In this specification, when the protective layer 20 is subjected to FT-IR analysis, the wavelengths in the region of 1750-1800 cm-1 and 1820-1880 cm-1 are -1 When at least one peak appears in each of the regions and the peak area ratio characteristics according to Formula 1 are as described above, it can be determined that the protective layer comprises an organic-inorganic composite polymer having a structure in which the lithiophilic inorganic particles 1 are three-dimensionally connected to each other by chemical bonds. Since the lithiophilic inorganic particles 1 included in the protective layer 20 of the lithium metal negative electrode 100 are cross-linked and connected to each other in a three-dimensional structure via organic bonds, the lithium metal negative electrode can have very excellent mechanical / electrochemical properties, charge / discharge characteristics, etc.

[0069] According to a specific embodiment, when the protective layer 20 is subjected to FT-IR analysis, the imide peak area ratio according to the following formula 2 may be greater than 1.

[0070] [Formula 2]

[0071] R I =I1 / I2

[0072] In Formula 2, R I is the imide peak area ratio, I1 is at 1750-1800cm -1 The area of the peak region appearing in the region of 1820-1880 cm -1 The area of the peak region that appears in the region.

[0073] Specifically, when the protective layer 20 is analyzed by FT-IR, the imide peak area ratio according to Formula 2 may be greater than or equal to 2 or greater than 2.5, and may be less than or equal to 10 or less than or equal to 5.

[0074] When the protective layer 20 is subjected to FT-IR analysis and the imide peak area ratio characteristic according to Formula 2 is as described above, the organic-inorganic composite polymer contained in the protective layer can be formed into a more excellent structure, thereby further improving the performance of the lithium metal negative electrode.

[0075] The protective layer 20 may contain one or more substances selected from LiF and Li3N. The lithium fluoride (LiF) and lithium nitride (Li3N) are inorganic compounds formed by the reaction of the fluorine and nitrogen elements in the protective layer 20 with lithium ions during the charge / discharge process of the battery. The lithium fluoride (LiF) and lithium nitride (Li3N) can further improve the uniform electrodeposition characteristics and mechanical strength of the lithium metal during the charge / discharge of the battery. When the protective layer 20 contains one or more substances selected from LiF and Li3N, the mechanical strength, lifespan characteristics, electrochemical properties, ionic conductivity, etc. of the lithium metal negative electrode 100 can be further improved.

[0076] The thickness of the protective layer 20 may be 0.1-20 μm. Specifically, the thickness of the protective layer 20 may be greater than 1 μm, and may be less than 10 μm or less than 2 μm. When the thickness of the protective layer 20 is within the above range, the mechanical strength and electrochemical performance of the lithium metal negative electrode can be significantly improved.

[0077] The lithium metal negative electrode 100 can be manufactured by the following negative electrode manufacturing method.

[0078] Negative electrode manufacturing method

[0079] According to a specific embodiment, a method for manufacturing a lithium metal negative electrode 100 includes the following steps: step S1, modifying the lithium-philic inorganic particles 1 so that the surface of the lithium-philic inorganic particles has amino groups; step S2, imidizing the modified lithium-philic inorganic particles with dianhydride to prepare an organic-inorganic composite polymer; and step S3, using a composition containing the organic-inorganic composite polymer to form a protective layer 20 on at least one side of the lithium metal layer 10.

[0080] In the manufacturing method of the lithium metal negative electrode 100, in order to form an imide bond between the lithium-philic inorganic particles 1 contained in the protective layer 20 formed on at least one side of the lithium metal layer 10, so that the lithium-philic inorganic particles 1 exist in the protective layer 20 in a mutually cross-linked structure, the method includes step S1: modifying the lithium-philic inorganic particles 1 so that the surface of the lithium-philic inorganic particles 1 has one or more amino groups as functional groups.

[0081] The step S1 may include dispersing the lithium-philic inorganic particles 1 in an organic solution. The organic solution may contain a compound represented by the following Chemical Formula 1.

[0082] [Chemical Formula 1]

[0083]

[0084] In the chemical formula 1, R 1 It is one or more organic groups selected from the group consisting of an alkylene group, an arylene group, a heterocyclic group and an alkylene oxide group which may be substituted.

[0085] The number of carbon atoms in the alkylene group is not particularly limited. For example, the alkylene group may be an alkylene group having 1 to 20 carbon atoms, 1 to 15 carbon atoms, 1 to 10 carbon atoms, 1 to 6 carbon atoms, or 1 to 4 carbon atoms. When the alkylene group is an alkylene group having 2 carbon atoms, the compound represented by Chemical Formula 1 may correspond to 2-aminoethanethiol.

[0086] The arylene group refers to a monovalent or divalent residue derived from an aromatic compound or a derivative thereof containing a benzene ring or a structure containing two or more benzene rings sharing two or one carbon atom and condensed or bonded. The arylene group may be optionally substituted with one or more substituents. The number of carbon atoms in the arylene group is not particularly limited, but the arylene group may be an arylene group having 6 to 30 carbon atoms, 6 to 25 carbon atoms, 6 to 22 carbon atoms, 6 to 18 carbon atoms, 6 to 14 carbon atoms, or 6 to 12 carbon atoms.

[0087] For example, the arylene group may be a phenyl group, a naphthyl group, an anthracenyl group, a phenanthrenyl group, a pyrenyl group, a peryl group, a chrysyl group, a fluorenyl group, or a combination thereof. When the arylene group is a phenyl group having 6 carbon atoms, the compound represented by Chemical Formula 1 may be 2-aminobenzenethiol or 4-aminobenzenethiol.

[0088] The heterocyclic group refers to a ring containing one or more heteroatoms other than carbon, and for example, the heteroatoms may be O, N, Se, S, etc. The heterocyclic group may be optionally substituted with one or more substituents, and the number of carbon atoms in the heterocyclic group is not particularly limited, but the heterocyclic group may be a heterocyclic group with 2 to 60 carbon atoms.

[0089] Illustratively, the heterocyclic group can be pyridyl, N-oxide pyridyl, pyrimidinyl, pyridazinyl, furanyl, tetrahydrofuranyl, thienyl, tetrahydrothienyl, tetrahydropyranyl, oxazolyl, isoxazolyl, oxadiazolyl, thiazolyl, isothiazolyl, thiadiazolyl, pyrrolyl, imidazolyl, triazolyl, pyrazolyl, tetrazolyl, or a combination thereof.

[0090] The epoxyalkyl group may be optionally substituted with one or more substituents, and the number of carbon atoms of the epoxyalkyl group is not particularly limited. For example, the epoxyalkyl group may be an epoxyalkyl group having 2 to 20 carbon atoms, and may be ethylene oxide, propylene oxide, or the like.

[0091] The compound represented by the chemical formula 1 is a compound having a thiol group and an amino group at both ends. Specifically, R 1 When the lithium-philic inorganic particles 1 are dispersed using an organic solution containing the above-mentioned compound, the lithium-philic inorganic particles 1 can be modified so that a structure in which the thiol group is attached to the particle surface and the amino group is present on the outermost side can be easily formed (see Figure 1a ).

[0092] The organic solution may contain 1-20 mol / L of the compound represented by Chemical Formula 1. Specifically, the organic solution may contain 5-15 mol / L of the compound represented by Chemical Formula 1. When the concentration of the compound represented by Chemical Formula 1 is too low, it may be difficult to form amino groups on the surface of the lithiophilic metal particles. When the concentration of the compound represented by Chemical Formula 1 is too high, it may be difficult to uniformly disperse the lithiophilic metal particles in the solution. Therefore, when the organic solution contains the compound represented by Chemical Formula 1 within the above range, amino groups can be excellently formed on the surface of the lithiophilic metal particles without causing problems such as dispersibility in the solution.

[0093] The organic solution may further include a commonly used organic solvent. For example, the organic solution may include tetrahydrofuran (THF) as the organic solvent, but the type of organic solvent is not particularly limited. The organic solution may disperse the compound represented by Chemical Formula 1 using the organic solvent as described above.

[0094] The step S1 may further include the following steps: stirring the organic solution in which the lithium-philic inorganic particles 1 are dispersed; filtering the stirred organic solution; and drying the filtrate. The stirring process of the organic solution may be performed for 1-5 hours, the filtering process of the organic solution may be performed by washing the solid matter with an organic solvent such as tetrahydrofuran (THF), and the drying process of the filtrate may be performed at room temperature for 12-48 hours.

[0095] The method for manufacturing the lithium metal negative electrode 100 includes step S2: performing an imidization reaction on the modified lithium-philic inorganic particles in step S1 with a dianhydride to prepare a polymer. Specifically, the imidization reaction can be performed by reacting amino groups formed on the surface of the modified lithium-philic inorganic particles with a dianhydride to form a polyamic acid (PAA); and heat-treating the polyamic acid to form an imide bond.

[0096] The step of forming the amic acid can be performed by adding dianhydride to a solution of the modified lithiophilic inorganic particles dispersed in an organic solvent such as diethylformamide (DEF) and stirring the solution. The stirring process can be performed at room temperature for 12-48 hours.

[0097] In the step S2, the weight ratio of the modified lithiophilic inorganic particles to the dianhydride can be 1:50 to 1:200. When the content of the modified lithiophilic inorganic particles is too high, the degree of polymerization of the polymer may be reduced. When the content of the dianhydride is too high, not only may the polymer have a low degree of polymerization, but problems may also occur due to the presence of unreacted materials. Therefore, when the weight ratio of the modified lithiophilic inorganic particles to the dianhydride is appropriately adjusted to the above range, a polymer can be formed with substantially no unreacted materials remaining, and a polyimide polymer having a high degree of polymerization adjusted to a suitable level or higher can be obtained.

[0098] The dianhydride may contain fluorine element. Exemplarily, the dianhydride may be 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (4,4'-(hexafluoroisopropylidene) diphthalic anhydride, 6FDA), 2,2'-bis(trifluoromethyl) diaminobiphenyl (2,2'-Bis(trifluoromethyl)benzidine, TFMN), etc., and is not limited thereto. When the dianhydride containing fluorine element as described above is reacted with the modified lithium-philic inorganic particles, an amide bond compound (F-PI) containing fluorine element may be formed. Exemplarily, when the dianhydride is 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), the amide bond compound (F-PI) containing fluorine element may include a compound represented by the following Chemical Formula 2.

[0099] [Chemical Formula 2]

[0100]

[0101] When the dianhydride containing fluorine element as described above is applied, an imide bond compound (F-PI) containing fluorine element can be formed in the protective layer 20. The LIF formed in the protective layer 20 by the reaction of the fluorine element with lithium ions can further improve the uniform electrodeposition characteristics of lithium metal during battery charging / discharging, and can further improve the life characteristics, electrochemical properties, ionic conductivity, etc. of the lithium metal negative electrode 100.

[0102] In the step of forming the imide bond, the heat treatment process can be performed in a vacuum, the heat treatment time can be 0.5-3 hours, and the heat treatment temperature can be 100-300°C.

[0103] The method for manufacturing the lithium metal negative electrode 100 includes step S3: forming a protective layer 20 on at least one side of the lithium metal layer 10 using a composition containing the polymer prepared in step S2. Specifically, step S3 can be performed by adding the polymer to an organic solvent such as tetrahydrofuran (THF) and stirring to prepare a composition; and coating the composition on at least one side of the lithium metal layer 10 and drying the composition.

[0104] During the preparation of the composition, the polymer content in the composition can be 5-20% by weight. When the polymer content in the composition is too high, the viscosity increases, which may cause problems in producing a protective layer with an appropriate thickness. When the polymer content in the composition is too low, due to the very low concentration, problems may occur in producing a uniform protective layer. Therefore, when the polymer content in the composition is appropriately adjusted to the above range, a uniform protective layer with a thickness controllable within an appropriate range can be produced. In addition, when preparing the composition, the stirring process can be carried out for 12-48 hours.

[0105] In the process of drying after coating the composition on at least one side of the lithium metal layer 10, the coating process may be performed by bar coating, casting, etc., but is not limited thereto. In addition, the drying process may be performed at room temperature.

[0106] lithium metal batteries

[0107] A lithium metal battery according to a specific embodiment may include the aforementioned lithium metal negative electrode 100. Specifically, the lithium metal battery may include the aforementioned lithium metal negative electrode 100, a positive electrode, and an electrolyte layer located between the negative electrode and the positive electrode.

[0108] The positive electrode is not particularly limited, and the positive electrode may include lithium-transition metal oxides such as lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4) or lithium nickel oxide (LiNiO2), or lithium-transition metal composite oxides in which a portion of these transition metals is replaced by other transition metals as the positive electrode active material. Specifically, the lithium-transition metal composite oxide may be a compound having the chemical formula Li x Ni a Co b Mn c Al d O yNCM-based cathode active material represented by (0 < x ≤ 1.1, 2 ≤ y ≤ 2.02, 0 < a < 1, 0 < b < 1, 0 < c < 1, 0 < d < 1, 0 < a + b + c + d ≤ 1). In addition, the cathode active material may also be a lithium iron phosphate (LFP)-based cathode active material represented by the chemical formula LiFePO4. Additionally, the cathode may be (1) a cathode for a lithium-sulfur battery using polysulfide containing sulfur (S) element as an active material or (2) a cathode for a lithium-air battery using oxygen (O2) in the air as an active material.

[0109] The electrolyte contained in the electrolyte layer is not particularly limited and may include at least one of conventional liquid electrolytes and solid electrolytes. Exemplarily, the liquid electrolyte may contain: lithium salts such as LiPF6, Lithium-(bis)-trifluoromethanesulfonimide (LiTFSI); and organic solvents such as ether-based solvents and carbonate-based solvents. In addition, the solid electrolyte may be an oxide-based solid electrolyte such as Li7La3Zr2O 12 (LLZO); a sulfide-based solid electrolyte such as Li2S-P2S5; or (1) a solid polymer electrolyte formed by adding a polymer resin such as a polyether-based polymer to a lithium salt, (2) a polymer-based solid electrolyte such as a polymer gel electrolyte obtained by impregnating a polymer resin with an organic electrolyte solution containing an organic solvent and a lithium salt.

[0110] When the lithium metal battery includes the above-mentioned lithium metal anode 100, the growth of lithium dendrites can be effectively suppressed through the protective layer 20 that can induce uniform lithium electrodeposition behavior, and thus it can have excellent cycle life, capacity characteristics, safety, etc. during charging / discharging. Detailed implementation methods

[0111] Examples

[0112] 1. Lithium metal anode

[0113] 1) Fabrication of the anode

[0114] (1) Example 1

[0115] A) Modification of lithiophilic inorganic particles

[0116] 2-aminoethanethiol, a compound having both a thiol group and an amino group, was dispersed in tetrahydrofuran (THF) at 10 mol / L to prepare an organic solution. 3 g of silver nanoparticles (AgNPs; Sigma-Aldrich), lithium-philic inorganic particles with a diameter of less than 150 nm, were dispersed in 4.5 mL of the organic solution and stirred for 2 hours to form a solid. The solid was then washed with tetrahydrofuran (THF) and filtered. The final filtrate was dried at room temperature for 24 hours to produce silver nanoparticles (Ag-NH2) with amino groups on the surface.

[0117] B) Preparation of the composition

[0118] 0.04 g of the prepared silver nanoparticles were added to 18 g of diethylformamide (DEF), and 4.44 g of a dianhydride containing fluorine (F) (4,4'-(hexafluoroisopropylidene) diphthalic anhydride, 6FDA) was added to the solution. The mixture was then stirred at room temperature for 18 hours to prepare a polyamic acid solution containing silver nanoparticles. At this point, the weight ratio of the silver nanoparticles to the dianhydride (6FDA) in the solution was 1:100, and the solid content of the solution was set to 20%.

[0119] Subsequently, for an imidization reaction, the solution was heat-treated at 200° C. under vacuum for 1 hour to obtain a polymer (F-Ag-PI) containing silver nanoparticles and having an imide bond. The polymer was added to a tetrahydrofuran (THF) solvent so that the content of the polymer was 10 wt % based on the total content of the composition, and stirred for 24 hours to obtain a composition containing a polymer containing silver nanoparticles and having an imide bond.

[0120] C) Forming a protective layer

[0121] The composition was coated on the surface of a lithium metal layer having a thickness of 100 μm by casting, and then dried at room temperature to prepare the lithium metal negative electrode of Example 1 having a protective layer formed on one side of the lithium metal layer.

[0122] (2) Example 2

[0123] The lithium metal negative electrode of Example 2 was manufactured by the same method as Example 1, except that the heat treatment temperature for the imidization reaction was set to 120°C.

[0124] (3) Comparative Examples 1 to 3

[0125] A) Comparative Example 1

[0126] The lithium metal negative electrode of Comparative Example 1 was manufactured by the same method as Example 1, except that an organic solution prepared by dispersing 0.01 mol / L of 2-aminoethanethiol in tetrahydrofuran (THF) solvent was used.

[0127] B) Comparative Example 2

[0128] 3.36 g of diamine (2,2'-bis(trifluoromethyl)benzidine; TFDB) was added to 31 g of diethylformamide (DEF). 4.44 g of dianhydride (4,4'-(hexafluoroisopropylidene)diphthalic anhydride, 6FDA) was added to the solution, and the mixture was stirred at room temperature for 18 hours to produce a polyamic acid solution that did not contain silver nanoparticles, unlike Example 1. The molar ratio of diamine (TFDB) to dianhydride (6FDA) was 1.05:1, and the solids content of the solution was set to 20%.

[0129] Subsequently, for the imidization reaction, the solution was heat-treated at a temperature of 200°C and under vacuum for 1 hour to obtain a polymer (F-PI) having an imide bond, and the polymer was added to a tetrahydrofuran (THF) solvent so that the content of the polymer was 10% by weight, and stirred for 24 hours to obtain a composition comprising a polymer having an imide bond but not containing silver nanoparticles. The composition was coated on the surface of a lithium metal layer having a thickness of 100 μm and then dried at room temperature to obtain a lithium metal negative electrode of Comparative Example 2 having a protective layer formed on one side of the lithium metal layer.

[0130] C) Comparative Example 3

[0131] A lithium metal negative electrode of Comparative Example 3 was manufactured in which a separate protective layer was not formed on one side of the lithium metal layer.

[0132] 2) Analysis of negative electrode materials (FT-IR)

[0133] The protective layers included in the negative electrode samples of Examples 1 to 2 and Comparative Example 1 manufactured as described above were analyzed using a Fourier transform infrared spectroscopy (FT-IR) instrument (Thermo Scientific; Nicolet 6700) and Resolution Pro S / W program, and the results are shown in FIG. Figures 4a to 4c middle.

[0134] Specifically, (1) the measurement mode was selected as the Attenuated Total Reflection (ATR) mode, (2) the instrument configuration conditions were set to the IR Source: [MIR Source], the Beam Splitter: [KBr], the Beam Path: [Internal], the Detector: [DTGS], the Aperture / Source: [Open], etc., and (3) the method settings were set to the Resolution: [8 cm -1 ]、No. of Scan:[16 scans]、Scan Range:[4000-650cm -1 ], speed (Speed): [5kHz], sampling interval (Sampling Interval): [2], etc., (4) after measuring the background spectrum (Background Spectrum), (5) loading the sample onto the ATR crystal (crystal), and then measuring the FT-IR spectrum.

[0135] In addition, the area of the peak region is calculated by measuring the infrared absorbance of the wave number region where the peak appears using an FT-IR instrument and integrating the area of each peak. Specifically, using the OriginPro 2021b program, the peak area of 1500-2000 cm -1 The area of each peak calculated as described above is used as a reference, and the peak area ratio and the imide peak area ratio are calculated according to the following formula 1 and formula 2.

[0136] [Formula 1]

[0137] R P =I / A

[0138] In the formula 1, R P is the peak area ratio, A is at 1680-1750cm -1 The peak area in the region of 1750-1800 cm -1 The area and 1820-1880cm -1 The total area of each peak region appearing in the region.

[0139] [Formula 2]

[0140] R I =I1 / I2

[0141] In Formula 2, R I is the imide peak area ratio, I1 is at 1750-1800cm -1 The area of the peak region appearing in the region of 1820-1880 cm -1 The area of the peak region that appears in the region.

[0142] 2. Lithium Metal Batteries

[0143] 1) Battery Manufacturing

[0144] A lithium metal battery sample including the lithium metal negative electrode prepared as described above was manufactured. In this case, the lithium metal battery sample was a battery sample manufactured as follows: the battery sample was a symmetrical cell (Symmetric Cell) using lithium metal as a working electrode and a counter electrode, and these electrodes were arranged on both sides, and contained ethylene carbonate (EC) / ethyl methyl carbonate (EMC) (3:7 v / v) containing 1M LiPF6 and 2 wt% fluoroethylene carbonate (FEC) as an electrolyte between the two electrodes.

[0145] 2) Battery evaluation (lifespan characteristics)

[0146] The overvoltage characteristics of the lithium metal symmetrical batteries of Example 1 and Comparative Examples 1 to 3 prepared as described above were evaluated based on lithium electrodeposition / desorption. Specifically, the lithium metal battery samples were evaluated at 25°C, with a unit area capacity of 2 mAh and a unit area current density of 1 mA, and the overvoltage (overpotential) of the battery generated during lithium oxidation / reduction was measured.

[0147] See also Figures 4a to 4c In the case of Example 1 and Example 2, in which 2-aminoethanethiol was dispersed in tetrahydrofuran (THF) solvent at 10 mol / L, the organic solution was obtained. When FT-IR was analyzed, the wavelength range of the organic solution was 1750-1880 cm -1 There are two peaks in the imide C=O peak region, specifically, at 1750-1800 cm -1 There is a peak in the region of 1820-1880 cm -1 There is a peak in the region ( Figure 4a). In addition, when the protective layer was subjected to FT-IR analysis, the peak area ratios of Example 1 and Example 2 according to Formula 1 were both greater than 1 (Example 1: 9.44, Example 2: 5.97), and the imide peak area ratios of Example 1 and Example 2 according to Formula 2 were also greater than 1 (Example 1: 2.57, Example 2: 2.60) ( Figure 4b and Figure 4c ).

[0148] On the other hand, in the case of Comparative Example 1 using an organic solution prepared by dispersing 2-aminoethanethiol at 0.01 mol / L in tetrahydrofuran (THF) solvent, the FT-IR analysis showed that the ions at 1680-1750 cm -1 A peak appears in the acid C=O peak region at 1750-1880 cm -1 There is no peak in the imide C=O peak region ( Figure 4a ). It is judged that this is because, in Examples 1 and 2, amino groups are easily formed on the surfaces of the silver nanoparticles modified with the organic solution containing 10 mol / L of 2-aminoethanethiol, so that the particles are connected to each other through imide bonds. On the other hand, in Comparative Example 1, amino groups are not easily formed on the surfaces of the silver nanoparticles modified with the organic solution containing a relatively small amount (0.01 mol / L) of 2-aminoethanethiol, so that the particles cannot be connected to each other through imide bonds, and the added dianhydride is not used for the imidization reaction and decomposes, thereby forming an acid.

[0149] See also Figure 5In the case of lithium metal batteries including the negative electrode of Comparative Example 1 (unlike Example 1, the protective layer included in the negative electrode of Comparative Example 1 did not have a peak in the imide C=O peak region when FT-IR analysis was performed on the protective layer included in the negative electrode of Comparative Example 1), the negative electrode of Comparative Example 2 (not containing silver nanoparticles), and the negative electrode of Comparative Example 3 (not including a protective layer), a relatively large overvoltage began to appear from a specific point after a certain number of electrodeposition / desorption cycles. Specifically, in Comparative Example 1, a large overvoltage appeared after 71 electrodeposition / desorption cycles (284 hours), in Comparative Examples 2 and 3, overvoltage began to appear at the beginning of the electrodeposition / desorption cycles, in Comparative Example 2, a voltage of several mV was displayed after 66 electrodeposition / desorption cycles (284 hours), and in Comparative Example 3, a voltage of several mV was displayed after 99 electrodeposition / desorption cycles (395 hours). According to judgment, this is because, when including (1) a negative electrode including a protective layer that is not properly formed on the lithium metal layer due to the failure to properly form an imide bond, (2) a negative electrode including a protective layer that is not properly formed on the lithium metal layer due to the absence of silver nanoparticles, or (3) a negative electrode not including a protective layer on the lithium metal layer, the growth of dendrites cannot be effectively suppressed during the electrodeposition / desorption process of the battery, resulting in excessive resistance inside the battery, and during long-term electrodeposition / desorption, the dendrites will grow significantly, resulting in a short circuit inside the battery.

[0150] On the other hand, in the case of the battery of Example 1, which includes a negative electrode with a protective layer appropriately formed on the lithium metal layer, stable electrodeposition / desorption cycles are performed without generating a large overvoltage even after a long period of charge / discharge cycles. It is believed that this is because, in the case of Example 1, the lithium-philic inorganic substance (Ag) contained in the protective layer induces uniform lithium electrodeposition behavior, thereby suppressing the growth of dendrites, etc., and due to the large amount of LiF, etc. contained in the protective layer, the protective layer has excellent mechanical strength.

[0151] Therefore, it is judged that when a protective layer comprising 1) lithium-philic inorganic particles and 2) imide bonds, etc. is appropriately formed on at least one side of the lithium metal layer, the electrochemical properties of the lithium metal negative electrode and the lithium metal battery including the lithium metal negative electrode can be improved, thereby effectively improving its efficiency and safety.

[0152] The embodiments of the present invention have been described in detail above, but the scope of the present invention is not limited thereto, and it is obvious to those skilled in the art that various modifications and variations can be made without departing from the technical concept of the present invention described in the claims.

[0153] [Explanation of Reference Signs]

[0154] 1: Lithium-philic inorganic particles

[0155] 10: Lithium metal layer

[0156] 20: Protective layer

[0157] 100: Lithium metal anode

[0158] PI: Imide bond compound

[0159] I: Imide C=O peak region

[0160] A: Acid C=O peak area

[0161] Industrial Applicability

[0162] As described above, the features of the present invention can be applied in whole or in part to a lithium metal anode, a method for manufacturing the same, and a lithium metal battery including the same.

Claims

1. A lithium metal negative electrode, comprising: lithium metal layer; as well as a protective layer formed on at least one side of the lithium metal layer, wherein the protective layer comprises lithium-philic inorganic particles, When the protective layer was subjected to FT-IR analysis, the -1 At least one peak appears in the region.

2. The lithium metal negative electrode according to claim 1, wherein The protective layer comprises an organic-inorganic composite polymer, and the organic-inorganic composite polymer has a structure in which lithium-philic inorganic particles are three-dimensionally connected to each other by forming chemical bonds.

3. The lithium metal negative electrode according to claim 1, wherein When the protective layer is subjected to FT-IR analysis, the -1 The area and 1820-1880cm -1 At least one peak appears in each region.

4. The lithium metal negative electrode according to claim 3, wherein When the protective layer is subjected to FT-IR analysis, the peak area ratio according to the following formula 1 is greater than 1, [Formula 1] R P =I / A In the formula 1, R P is the peak area ratio, A is at 1680-1750cm -1 The peak area in the region of 1750-1800 cm -1 The area and 1820-1880cm -1 The total area of each peak region appearing in the region.

5. The lithium metal negative electrode according to claim 1, wherein The protective layer contains one or more substances selected from the group consisting of LiF and Li3N.

6. The lithium metal negative electrode according to claim 1, wherein The lithiophilic inorganic particles include metals, metal oxides, metal nitrides, or combinations thereof.

7. The lithium metal negative electrode according to claim 1, wherein The lithium-philic inorganic particles include Au, Ag, Pt, Al, Mg, Zn, Ni, Se, Te, Bi, Pb, Ga, Cd, Hg, Pd, Sc, Y, Ca, Sr, Ba, NiO, ZnO, SnO, Cu x O, GeO, Ag x O, Sb2O y , CuZn or a combination thereof, the Cu x O wherein x is 1 or 2, the Ag x O wherein x is 1 or 2, and the Sb2O y where y is 3, 4, or 5.

8. The lithium metal negative electrode according to claim 1, wherein The diameter of the lithium-philic inorganic particles is less than 500 nm.

9. The lithium metal negative electrode according to claim 1, wherein The thickness of the protective layer is 0.1-20 μm.

10. A method for manufacturing a lithium metal negative electrode, comprising the following steps: Step S1, modifying the lithium-philic inorganic particles so that the surfaces of the lithium-philic inorganic particles have amino groups; Step S2, performing an imidization reaction on the modified lithium-philic inorganic particles and dianhydride to prepare an organic-inorganic composite polymer; as well as In step S3, a protective layer is formed on at least one side of the lithium metal layer using the composition containing the organic-inorganic composite polymer.

11. The method for manufacturing a lithium metal negative electrode according to claim 10, wherein: The step S1 includes dispersing lithium-philic inorganic particles in an organic solution, wherein the organic solution contains a compound represented by the following chemical formula 1: [Chemical Formula 1] In the chemical formula 1, R 1 It is one or more organic groups selected from substituted or unsubstituted alkylene groups, arylene groups, heterocyclic groups and alkylene oxide groups.

12. The method for manufacturing a lithium metal negative electrode according to claim 11, wherein: The organic solution contains 1-20 mol / L of the compound represented by Chemical Formula 1.

13. The method for manufacturing a lithium metal negative electrode according to claim 10, wherein: The dianhydride contains fluorine element.

14. A lithium metal battery comprising the lithium metal negative electrode according to any one of claims 1 to 9.

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