A negative electrode including a metal substrate and a protective layer

Abstract

The present invention relates to an anode for a battery comprising a metal substrate and a protective layer disposed directly on at least a portion of the metal substrate, the protective layer comprising a copolymer obtainable by reaction between two or more monomers, a fluoropolymer additive, and a lithium salt. The inventors have demonstrated that the protective layer functions as a self-repairing film on the anode.

Description

[Technical Field]

[0001] The present invention relates to a negative electrode for a battery comprising a metal substrate and a protective layer directly disposed on at least a portion of the metal substrate, a method for preparing a negative electrode, a battery comprising a negative electrode, and the use of a protective layer on the negative electrode. [Background technology]

[0002] As the development of small, lightweight electronic products, electronic devices, and communication devices progresses rapidly, and the need for electric vehicles to address environmental issues becomes increasingly prominent, there is a growing demand for improved performance in rechargeable batteries used as power sources for these products. Among these, lithium metal rechargeable batteries are attracting attention as high-performance batteries due to their high energy density and high reference electrode potential.

[0003] Due to the high reactivity of lithium metal, side reactions between lithium and the liquid electrolyte occur during battery charging and discharging, thereby accelerating the decomposition of the electrolyte. In addition, for various reasons, electron density non-uniformity can occur on the lithium metal surface during battery operation. As a result, dendritic lithium dendrites are formed on the electrode surface, making the electrode surface very rough and potentially causing separator damage. These side reactions reduce the Coulomb efficiency and / or electrochemical stability of lithium metal batteries, leading to a decrease in the lifespan of lithium batteries.

[0004] Therefore, various attempts are being made to stabilize lithium metal and prevent or reduce side reactions between the electrolyte and lithium metal.

[0005] Korean Patent Application Publication No. 20030042288(A) describes a lithium secondary battery in which dendrite growth on the surface of a lithium metal negative electrode can be suppressed by a crosslinked polymer protective film formed on the surface of a lithium metal, wherein the polymer is a crosslinked 1,6-hexanediol diacrylate or a copolymer of 1,6-hexanediol diacrylate and oligo(ethylene glycol) diacrylate.

[0006] U.S. Patent Application Publication No. 2016 / 0372743(A1) relates to a coating on a lithium metal anode for preventing direct contact between lithium metal and a volatile liquid electrolyte. The coating consists of either a single-layer polymer comprising a PVDF homopolymer, an ionic liquid, and LiFSI, or a double-layer polymer coating having a first outer layer of PVDF, an ionic liquid, and LiFSI, and a second inner layer of poly(styrene-acrylonitrile) and LiFSI.

[0007] However, a known drawback of protective layers remains dendrite penetration. Dendrite penetration occurs during charging as lithium is plated onto the anode, forming dendrites that can penetrate the polymer film, thereby tearing it. The reduction in resistance due to breaks in the polymer film leads to localized areas of lower resistance and greater plating in the affected areas, which exacerbates dendrite formation. Dendrite formation is almost unavoidable in these systems, and because the polymer film is thin (approximately 5-10 μm), dendrite formation in the polymer protective layer is very likely to occur. As a result, the Coulomb efficiency, electrochemical stability, and / or lifespan of the lithium metal battery are reduced.

[0008] Therefore, it is necessary to create a protective layer around the negative electrode that can be reformatted around any holes or gaps created by dendrite formation. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Korean Patent Application Publication No. 20030042288(A) [Patent Document 2] U.S. Patent Application Publication No. 2016 / 0372743(A1) [Patent Document 3] Chinese Patent Application Publication No. 111162314(A) [Non-patent literature]

[0010] [Non-Patent Document 1] I. Gadwal, Macromol 2021, 1, 18-36 [Overview of the project] [Problems that the invention aims to solve]

[0011] An object of the present invention is to provide a negative electrode for a battery comprising a metal substrate and a protective layer disposed directly on at least a portion of the metal substrate.

[0012] A further object of the present invention is to provide a method for preparing a negative electrode for a battery, comprising a metal substrate and a protective layer disposed directly on at least a portion of the metal substrate.

[0013] A further object of the present invention is to provide a negative electrode that can be obtained by a method for preparing a negative electrode for a battery according to the present invention.

[0014] A further object of the present invention is to provide a battery comprising a negative electrode, a positive electrode, and an electrolyte composition according to the present invention.

[0015] A further object of the present invention is to provide the use of a protective layer on the negative electrode as a self-healing film to reduce dendrite growth on the negative electrode and / or improve the cycle efficiency of the battery. [Means for solving the problem]

[0016] The objective of the present invention is, a. Metal substrate and b. A protective layer disposed directly on at least a portion of a metal substrate, The protective layer is Copolymers that can be obtained by the reaction between two or more monomers, Fluoropolymer additives and Lithium salts and A protective layer, This is achieved by providing a negative electrode for a battery, including the following:

[0017] To our surprise, as demonstrated in the accompanying examples, the inventors have found that a protective layer comprising a copolymer, a fluoropolymer additive, and a lithium salt functions as a self-healing polymer film. The protective layer according to the present invention is a mechanically robust polymer that also possesses self-healing properties, which is the result of a careful balance between polymer chain mobility, the amount of hydrogen bonding motifs, and the degree of crosslinking.

[0018] While we do not wish to be bound by any theory, the inventors believe that the copolymer according to the present invention contains sufficient hydrogen bonds to break down and reform at ambient temperature, thereby providing self-healing properties for the protective layer.

[0019] Self-healing polymers are known in the art (see, for example, I. Gadwal, Macromol 2021, 1, 18-36), and their application in self-healing polymer electrolytes and secondary lithium batteries based on dynamic chemical bonding has been reported (Chinese Patent Application Publication No. 111162314(A)). However, the inventors have for the first time demonstrated that a protective film according to the present invention, exhibiting self-healing properties, also provides effective anode protection, reduces lithium dendrite growth, and minimizes electrolyte depletion. Furthermore, the protective layer according to the present invention has improved film conductivity, as well as enhanced mechanical and chemical properties, as demonstrated in the appended examples. Finally, the resulting protected anode also significantly extends the cell cycle life compared to an unprotected lithium metal-based reference cell, as shown in the following examples. [Brief explanation of the drawing]

[0020] [Figure 1] SEM (scanning electron microscope) images of each of the three polymer formulations 1-a, 1-b, and 1-c (see also Table 1). [Figure 2]Uncompensated resistance (Ru) measured for each Li-Li symmetric coin cell over 20 hours after cell construction, using unprotected lithium anodes and protected anodes using polymer formulations 1-a, 1-b, and 1-c in a 4.5 M LiFSI electrolyte in DME. (See also Table 1). [Figure 3] Uncompensated resistance (Ru) measured for each Li-Li symmetric coin cell over 20 hours after cell construction in a 4.5 M LiFSI electrolyte in DME, for unprotected lithium anodes and protected anodes using polymer formulations 2-a, 2-b, 2-c, and 2-d (see also Table 2). [Figure 4] These are SEM micrographs of polymer films containing varying amounts of HEAA. Each polymer film was cut with a scalpel, imaged, then immersed overnight (16 hours) in 4.5M LiFSI in DME, rinsed with pure DME, and imaged again. [Figure 5] Total specific discharge capacity of Li-NMC pouch cells containing protected anodes with various PEG-to-HEAA ratios (cycling regime was C / 3 to D / 1, and potential was maintained at the top and bottom of the charge). [Figure 6] Coulomb efficiency of Li-NMC pouch cells containing protected anodes with various PEG-to-HEAA ratios (cycle method C / 3 to D / 1, potential held at the top and bottom of the charge). [Figure 7A] (a) Polymer film conductivity in TTE (3:1, v / v) compared to (4.5 M LiFSI in DME) without thermal annealing; (b) Polymer film conductivity in TTE (3:1, v / v) compared to (4.5 M LiFSI in DME) with thermal annealing. [Figure 7B] (a) Polymer film conductivity in TTE (3:1, v / v) compared to (4.5 M LiFSI in DME) without thermal annealing; (b) Polymer film conductivity in TTE (3:1, v / v) compared to (4.5 M LiFSI in DME) with thermal annealing. [Figure 8]Total specific discharge capacity of Li-NMC pouch cells containing protected anodes with various PEG-to-HEAA ratios, subjected to thermal annealing (cycle method C / 3 to D / 1, potential held at the top and bottom of the charge). [Figure 9] Coulomb efficiency of Li-NMC pouch cells containing protected anodes with various PEG-to-HEAA ratios, subjected to thermal annealing (cycle method C / 3 to D / 1, potential held at the top and bottom of the charge). [Modes for carrying out the invention]

[0021] To enable the execution of the present invention, preferred embodiments are described in detail in the drawings and in the embodiments for carrying out the invention described below. Although the present invention is described with reference to these particular preferred embodiments, it will be understood that the present invention is not limited to these preferred embodiments. On the contrary, the present invention includes a number of substitutes, modifications and equivalents, as will become apparent from the following detailed description and the accompanying drawings.

[0022] As used herein and in the claims, the term “comprising” should not be construed as limiting to the means listed thereafter, nor as excluding other elements or processes. It should be interpreted as specifying the presence of the features, integers, processes, or components described as mentioned, but not as excluding the presence or addition of one or more other features, integers, processes, or components, or groups thereof. Accordingly, the expression “composition comprising components A and B” should not be limited to a composition consisting solely of components A and B. It means, with respect to the present invention, that A and B are the only relevant components of the composition. Thus, the terms “comprising” and “including” encompass the more restrictive terms “consisting essentially of” and “consisting of.”

[0023] As used herein, “optional” or “optionally” means that the event or situation described thereafter may or may not occur, and such description includes both the cases in which such event or situation occurs and the cases in which such event or situation does not occur.

[0024] As used herein, the term "alkyl" has the broadest meaning generally understood in the art and may include linear, branched, or combination thereof. In particular, the term "alkyl," alone or in combination, means a linear or branched alkane derivative group, for example, C F~G Alkyl is defined as a linear or branched alkyl group having F to G carbon atoms, for example, C 1~4 Alkyl refers to linear or branched alkyl groups having 1 to 4 carbon atoms, such as methyl, ethyl, 1-propyl, 2-propyl (isopropyl), 1,5-butyl, 2-butyl, 2-methyl-2-propyl (tert-butyl), and 2-methyl-1-propyl (isobutyl).

[0025] The term "alkanediyl," either alone or in combination, refers to a divalent group derived from a linear or branched alkyl group.

[0026] When used herein, "uncompensated resistor (R)" u The term "cell resistance" is defined as the resistance value including the cell resistance and any small additional resistance. The main contribution to cell resistance comes from, for example, the ionic conductivity of the liquid electrolyte and / or the polymer protective layer. Small resistance contributions come from, for example, metal components such as cables / contacts.

[0027] negative electrode As described above, the first aspect of the present invention is a. Metal substrate and b. A protective layer disposed directly on at least a portion of a metal substrate, The protective layer is Equation (I)

[0028] [Chemical formula] (wherein, R 1 = H or CH3, R 2 is C 2~6 alkanediyl, and the alkanediyl is optionally substituted with one or more substituents selected from halide, C 1~4 alkyl, CF3 or OR 3 , R 3 is hydrogen or C 1~4 alkyl, X 1 = NH or O, and n is an integer selected from 5 to 150, preferably 8 to 100, more preferably 10 to 50), and a first monomer represented by Formula (II)

[0029] [Chemical formula] (wherein, R 4 = H or CH3, R 5 is C 2~6 alkanediyl, and the alkanediyl is optionally substituted with one or more substituents selected from halide, C 1~4 alkyl, CF3 or OR 6 , R 6 is hydrogen or C 1~4 alkyl, X 2 = NH or O, X 3 = SH, NH2 or OH, m is an integer selected from 1 to 10, preferably 1 to 5, and more preferably m = 1), and a second monomer represented by A copolymer obtainable by the reaction between where the weight ratio of the first monomer to the second monomer is 1 to 5 to 8 to 1 (w / w), and the copolymer A fluoropolymer additive selected from the group consisting of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene tetrafluoroethylene copolymer, polychlorotrifluoroethylene, vinylidene fluoride-pentafluoropropylene copolymer, propylene tetrafluoroethylene copolymer, ethylene chlorotrifluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymer, and combinations thereof, Lithium salts and Includes, A protective layer having a copolymer to fluoropolymer additive weight ratio of 1:5 to 8:1 (w / w), The objective is to provide a negative electrode (i.e., anode) for a battery, including [the specified component].

[0030] metal base material One embodiment of the present invention is a negative electrode comprising a metal substrate. In a preferred embodiment, the metal substrate comprises a conductive metal, preferably stainless steel, copper, nickel, iron, cobalt, lithium, lithium alloy, or a combination thereof, more preferably stainless steel, copper, nickel, lithium, lithium alloy, or a combination thereof. In a more preferred embodiment, the metal substrate is a lithium metal substrate or a lithium metal alloy substrate, preferably a lithium metal substrate. As will be understood by those skilled in the art, the metal substrate may be a metal deposited on a support foil such as stainless steel, copper, nickel, iron, or cobalt, or a lithium layer or lithium alloy layer made as a foil or as a layer deposited on a surface.

[0031] Copolymer One embodiment of the present invention is Equation (I)

[0032] [ka] (In the formula, R 1 =H or CH3, R 2 C 2~6 Alkanediyl is a type of halide, C 1~4 Alkyl, CF3, or OR 3 It is optionally substituted with one or more substituents selected from R 3 is hydrogen or C 1~4 Selected from alkyl groups, X 1 A first monomer represented by =NH or O, where n is an integer selected from 5 to 150, preferably 8 to 100, more preferably 10 to 50, Formula (II)

[0033] [ka] (In the formula, R 4 =H or CH3, R 5 C 2~6 Alkanediyl is a type of halide, C 1~4 Alkyl, CF3, or OR 6 It is optionally substituted with one or more substituents selected from R 6 is hydrogen or C 1~4 Selected from alkyl groups, X 2 =NH or O, X 3 A second monomer represented by (=SH, NH2, or OH, where m is an integer selected from 1 to 10, preferably 1 to 5, more preferably m=1), It is a copolymer that can be obtained by a reaction between [the two components].

[0034] One embodiment of the present invention is given by formula (I) (wherein R 1 is H or CH3, preferably H, and R 2 C 2~6 Alkanedil, preferably C 2~4 Alkanediyl, more preferably C2 alkanediyl, where alkanediyl is a halide, C1~4 Alkyl, CF3, or OR 3 It is optionally substituted with one or more substituents selected from R 3 is hydrogen or C 1~4 Selected from alkyl groups, X 1 A first monomer represented by =NH or O, preferably O, where n is an integer selected from 5 to 150, preferably 8 to 100, more preferably 10 to 50.

[0035] A preferred embodiment of the present invention is a first monomer according to the present invention, the first monomer being of formula (III)

[0036] [ka] (wherein o is an integer selected from 5 to 150, preferably 8 to 130, more preferably 10 to 100) is represented by formula (III). In particular, the first monomer represented by formula (III) is poly(ethylene glycol) diacrylate (PEGDA).

[0037] A preferred embodiment of the present invention is a first monomer according to the present invention, wherein the first monomer has a number average molecular weight M greater than 50 g / mol, preferably greater than 100 g / mol, more preferably greater than 200 g / mol, even more preferably greater than 550 g / mol, and most preferably greater than 700 g / mol. n A preferred embodiment of the present invention is a first monomer according to the present invention, the first monomer having a number average molecular weight M of less than 20,000 g / mol, preferably less than 7,000 g / mol, more preferably less than 4,000 g / mol, even more preferably less than 2,000 g / mol, and most preferably less than 1,000 g / mol. nA preferred embodiment of the present invention is a first monomer according to the present invention, the first monomer having a number average molecular weight M of 50 to 20,000 g / mol, preferably 100 to 7,000 g / mol, more preferably 200 to 4,000 g / mol, even more preferably 550 to 2,000 g / mol, and most preferably 700 to 1,000 g / mol. n It has the following specific examples: number average molecular weight M of 250 g / mol, 575 g / mol, 700 g / mol, 4,000 g / mol, or 6,000 g / mol. n A PEGDA having the following characteristics. Preferred examples of the first monomer according to the present invention are number-average molecular weight M of 250 g / mol, 575 g / mol, or 700 g / mol, preferably 700 g / mol. n This is a PEGDA having the following characteristics. PEGDAs with various number-average molecular weights as described above can be commercially purchased from suppliers such as Sigma-Aldrich.

[0038] As demonstrated in the following examples, the first monomer according to the present invention, in particular PEGDA, improves the lithium-ion conductivity of the copolymer and / or protective layer according to the present invention.

[0039] One embodiment of the present invention is a second monomer represented by formula (II), where R 4 =H or CH3, preferably H, R 5 C 2~6 Alkanedil, preferably C 2~4 Alkanediyl, more preferably C2 alkanediyl, where alkanediyl is a halide, C 1~4 Alkyl, CF3, or OR 6 It is optionally substituted with one or more substituents selected from R 6 is hydrogen or C 1~4 Selected from alkyl groups, X 2 =NH or O, preferably NH, X 3 =SH, NH2, or OH, preferably OH, where m is an integer selected from 1 to 10, preferably 1 to 5, most preferably m=1.

[0040] A preferred embodiment of the present invention is a second monomer according to the present invention, the second monomer being of formula (IV)

[0041] [ka] The second monomer, represented by formula (IV) in particular, is N-(2-hydroxyethyl)acrylamide (HEAA). HEAA can be purchased commercially from suppliers such as Sigma-Aldrich and TCI Chemicals.

[0042] As demonstrated in the following examples, the introduction of a second monomer according to the present invention, particularly N-(2-hydroxyethyl)acrylamide (HEAA), into a copolymer yields self-healing properties of the copolymer. The first monomer according to the present invention comprises a hydrogen bond acceptor, for example, a carbonyl functional group of the first monomer represented by formula (I), preferably an ester functional group of the first monomer represented by formula (III). The second monomer according to the present invention comprises a hydrogen bond acceptor, for example, a carbonyl functional group of the second monomer represented by formula (II), preferably an amide functional group of the second monomer represented by formula (IV). The second monomer according to the present invention comprises a hydrogen bond donor, for example, a substituent X of the second monomer represented by formula (II). 3 The hydrogen present in the copolymer is, for example, a thiol, amino, or hydroxyl functional group, preferably the hydrogen of the hydroxyl group of the second monomer represented by formula (IV). The inventors believe that hydrogen bond donors present in the second monomer can form hydrogen bonds with hydrogen bond acceptors present in a further second monomer according to the present invention and / or hydrogen bond acceptors present in the first monomer according to the present invention. The inventors believe that the hydrogen bonding properties of the copolymer result in the self-healing properties of the copolymer and / or protective layer. The hydrogen bonds present in the copolymer according to the present invention have a relatively weak bond strength (1.9 to 6.9 kcal / mol). -1) possesses, which means that their hydrogen bonds can be broken and reformed at ambient temperature.

[0043] As will be understood by those skilled in the art, copolymers according to the present invention can be obtained by a crosslinking step (i.e., radical polymerization) of the corresponding vinyl monomers, for example, the first monomer and the second monomer according to the present invention. In embodiments of the present invention, the initiator that can be used for radical polymerization varies depending on the crosslinking reaction, and all well known photoinitiators or thermal initiators can be used, preferably photoinitiators. Examples of photoinitiators include benzoin, benzoin ethyl ether, benzoin isobutyl ether, alpha-methylbenzoin ethyl ether, benzoin phenyl ether acetophenone, dimethoxyphenyl acetophenone, 2,2-diethoxyacetophenone, 1,1-dichloroacetophenone, trichloroacetophenone, benzophenone, p-chlorobenzophenone, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-2-methylpropiophenone, benzoylbenzoate, anthraquinone, 2-ethylanthraquinone, 2-chloroanthraquinone, 2-methyl-1-(4-methylthiophenyl)-morpholinopropanone-1,2-hydroxy-2-methyl-1-phenylpropan-1-one (Darocure 1173), and 2-methyl-4'-(methylthio)-2-morpholinopropiophenone (Irgacure Examples of thermal initiators include 907), phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (Irgacure 819), 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1,1-hydroxycyclohexylphenyl ketone (Irgacure 184), Michler ketone, benzyldimethyl ketal, thioxanthone, isopropylthioxanthone, chlorothioxanthone, benzyl disulfide, butanediol, carbazole, fluorenone, alphaacyloxime esters, and combinations thereof. Examples of thermal initiators include the peroxide (-OO-) series, benzoyl peroxide, cumylhydroperoxide, etc., and azo compounds (-N=N-) series, azobisisobutyronitrile, azobisovaleronitrile, etc. may also be used.In preferred embodiments of the present invention, the photoinitiator is phenylbis-(2,4,6-trimethylbenzoyl)-phosphine oxide (Irgacure 819) or 2-methyl-4'-(methylthio)-2-morpholinopropiophenone (Irgacure 907), and is preferably Irgacure 819.

[0044] The initiator content is not particularly limited in the present invention, but is preferably within a range that does not affect the properties of the copolymer according to the present invention, the properties of electrodes such as the negative or positive electrode, and the properties of the liquid electrolyte present in the battery. In one embodiment of the present invention, the initiator is used in a range of 1 to 15% by weight based on the total weight of the copolymer, preferably in a range of 1 to 5% by weight based on the total weight of the copolymer, and more preferably in a range of 2 to 4% by weight.

[0045] In embodiments of the present invention, the crosslinking step to give the copolymer according to the present invention is carried out in an organic liquid capable of dissolving the first monomer, the second monomer, and / or the copolymer according to the present invention. Preferably, the organic liquid is a non-aqueous organic liquid. In the present invention, known liquids such as carbonate-based, ester-based, ether-based, ketone-based, alcohol-based, or aprotic liquids may be used as the non-aqueous organic liquid. For example, aprotic organic liquids are selected from the group consisting of N-methyl-2-pyrrolidone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 1-butyrolactone, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, 4-methyl-1,3-dioxene, diethyl ether, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, ethyl propionate, and combinations thereof. Preferred examples of organic liquids are acetonitrile or tetrahydrofuran.

[0046] In embodiments of the present invention, the crosslinking step includes applying heat or irradiating with active energy rays, wherein thermal crosslinking may be performed using a heating method, and the active energy rays may be irradiated with far-infrared rays, ultraviolet rays, or electron beams.

[0047] In embodiments of the present invention, the crosslinking step is carried out by thermal crosslinking or photocrosslinking, preferably by photocrosslinking. In embodiments of the present invention, thermal crosslinking can be carried out at a temperature of 50°C to 200°C, preferably 80°C to 110°C, and the heating time for crosslinking is 30 minutes to 48 hours, more preferably 8 hours to 24 hours. If the heating temperature and time are below the above range, it is difficult to sufficiently form crosslinks, and if the heating temperature and time exceed the above range, side reactions may occur or the material stability may decrease. In preferred embodiments of the present invention, photocrosslinking including irradiation with active energy rays is carried out for 10 seconds to 5 hours, preferably 1 minute to 1 hour, most preferably 2 minutes to 10 minutes. In preferred embodiments of the present invention, photocrosslinking is carried out at a temperature of 5°C to 60°C, preferably 10°C to 50°C, most preferably 20°C to 40°C. If the time of irradiation with active rays is below the above range, it is difficult to sufficiently form crosslinks, and if it exceeds the above range, side reactions may occur or the material stability may decrease.

[0048] As will be understood by those skilled in the art, copolymers can be obtained by the reaction of at least two monomers, a first monomer represented by formula (I) and a second monomer represented by formula (II), but are not limited to reactions between only two different monomers. For example, copolymers can also be obtained by the reaction of three monomers, particularly the first monomer according to the present invention, the second monomer according to the present invention, and a third monomer represented by formula (V) or formula (VI), wherein the third monomer is different from the first and second monomers.

[0049] [ka] (In the formula, R 7 is H or CH3, and R 8 C 2~6 Alkanediyl is a type of halide, C 1~4 Alkyl, CF3, or OR 9 It is optionally substituted with one or more substituents selected from R 9 is hydrogen or C1~4 Selected from alkyl groups, X 4 =NH or O, where p is an integer selected from 5 to 150, preferably 8 to 100, more preferably 10 to 50) or

[0050] [ka] (In the formula, R 10 is H or CH3, and R 11 C 2~6 Alkanediyl is a type of halide, C 1~4 Alkyl, CF3, or OR 12 It is optionally substituted with one or more substituents selected from R 12 is hydrogen or C 1~4 Selected from alkyl groups, X 5 =NH or O, X 6 =SH, NH2, or OH, where q is an integer selected from 1 to 10, preferably from 1 to 5, and more preferably q=1).

[0051] A preferred embodiment of the present invention is a copolymer that can be obtained by the reaction of up to two monomers, the two monomers being a first monomer represented by formula (I) and a second monomer represented by formula (II).

[0052] A very preferred embodiment of the present invention is a copolymer that can be obtained by a reaction between up to two monomers, the first monomer being poly(ethylene glycol) diacrylate and the second monomer being 2-hydroxyethylacrylamide.

[0053] In a preferred embodiment, the weight ratio of the first monomer to the second monomer is 1:5 to 8:1 (w / w), preferably 1:3 to 7:1 (w / w), more preferably 1:2 to 5:1 (w / w), and most preferably 1:2 to 2:1 (w / w).

[0054] In preferred embodiments, the copolymer is present in an amount exceeding 20% ​​by weight, preferably exceeding 30% by weight, and most preferably exceeding 35% by weight, based on the total weight of the protective layer. In preferred embodiments, the copolymer is present in an amount less than 80% by weight, preferably less than 70% by weight, and most preferably less than 60% by weight, based on the total weight of the protective layer. In preferred embodiments, the copolymer is present in an amount in the range of 20 to 80% by weight, preferably in the range of 30 to 70% by weight, and more preferably in the range of 35 to 60% by weight, based on the total weight of the protective layer.

[0055] A specific example of the copolymer according to the present invention is formula (VII)

[0056] [ka] (wherein o is an integer selected from 5 to 150, preferably 8 to 100, more preferably 10 to 50, and r, s, and t are integers independently selected from 1 to 10, preferably 2 to 8, most preferably 3 to 6). However, as will be understood by those skilled in the art, the copolymers according to the present invention are not limited to formula (VII) but are shown as exemplary embodiments.

[0057] In a very preferred embodiment of the present invention, the copolymer according to the present invention, and therefore the protective layer according to the present invention, has self-healing properties, as demonstrated in the attached examples.

[0058] In a preferred embodiment of the present invention, the copolymer and / or protective layer according to the present invention is subjected to a thermal annealing process. As will be understood by those skilled in the art, thermal annealing is a common process used in materials chemistry to relieve stress, improve uniformity, and enhance contact with the substrate. In particular, thermal annealing raises the temperature T of the part coated by the coating from room temperature to a maximum (operating) temperature T. maxThe process involves raising the temperature T to a temperature exceeding the recrystallization temperature of the copolymer and / or protective layer according to the present invention, and then lowering the temperature back to room temperature after the completion of the operation (e.g., cutting). In a very preferred embodiment, the thermal annealing step is performed after UV curing of the copolymer at a temperature in the range of 40 to 100°C, preferably in the range of 50 to 90°C, more preferably in the range of 60 to 80°C, and / or the duration of the thermal annealing is 5 minutes to 10 hours, preferably 15 minutes to 5 hours, most preferably 30 minutes to 90 minutes. In a very preferred embodiment, the thermal annealing step according to the present invention is performed in dry air. Surprisingly, the inventors have found that the thermal annealing step improves the conductivity of the copolymer. In addition, each copolymer subjected to the thermal annealing step appears more homogeneous and has better contact with the lithium metal surface. Furthermore, the inventors have found that after the thermal annealing step, the charge transfer resistance (R) of the negative electrode according to the present invention is reduced. ct They found that ) decreased.

[0059] Fluoropolymer additives As described above, the protective layer according to the present invention includes a fluoropolymer additive, the fluoropolymer additive being polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer, polychlorotrifluoroethylene, vinylidene fluoride-pentafluoropropylene copolymer, The fluoropolymer additive is selected from the group consisting of propylene tetrafluoroethylene copolymer, ethylene chlorotrifluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymer, and combinations thereof. Preferably, the fluoropolymer additive is polyvinylidene fluoride or poly(vinylidene fluoride-co-hexafluoropropylene), and most preferably poly(vinylidene fluoride-co-hexafluoropropylene).

[0060] In preferred embodiments, the fluoropolymer additive is present in an amount of less than 75% by weight, preferably less than 50% by weight, and most preferably less than 20% by weight, based on the total weight of the protective layer. In preferred embodiments, the fluoropolymer additive is present in an amount of more than 0.05% by weight, preferably more than 5% by weight, and most preferably more than 10% by weight, based on the total weight of the protective layer. In preferred embodiments, the fluoropolymer additive is present in an amount of 0.05 to 75% by weight, preferably 5 to 50% by weight, and more preferably 10 to 20% by weight, based on the total weight of the protective layer.

[0061] In preferred embodiments of the present invention, the weight ratio of copolymer to fluoropolymer additive is 1:5 to 8:1 (w / w), preferably 1:2 to 5:1 (w / w), more preferably 1:2 to 4:1 (w / w), and most preferably 2:1 to 4:1 (w / w).

[0062] In one embodiment of the present invention, the fluoropolymer additive has a weight-average molecular weight M greater than 1,000 g / mol, preferably greater than 10,000 g / mol, more preferably greater than 100,000 g / mol, and most preferably greater than 300,000 g / mol. w In one embodiment of the present invention, the fluoropolymer additive has a weight-average molecular weight M of less than 1,000,000 g / mol, preferably less than 800,000 g / mol, more preferably less than 750,000 g / mol, and most preferably less than 600,000 g / mol. w In one embodiment of the present invention, the fluoropolymer additive has a weight-average molecular weight M of 1,000 to 1,000,000 g / mol, preferably 10,000 to 800,000 g / mol, more preferably 100,000 to 750,000 g / mol, and most preferably 300,000 to 600,000 g / mol. w It has. Preferred examples of fluoropolymer additives, particularly poly(vinylidene fluoride-co-hexafluoropropylene), have a weight-average molecular weight of about 400,000 g / mol M w Or a weight-average molecular weight M of approximately 455,000 g / mol w It contains fluoropolymer additives such as poly(vinylidene fluoride-co-hexafluoropropylene) which can be commercially purchased from suppliers such as Sigma-Aldrich.

[0063] In one embodiment of the present invention, the fluoropolymer additive has a number average molecular weight M greater than 250 g / mol, preferably greater than 2,500 g / mol, more preferably greater than 25,000 g / mol, and most preferably greater than 75,000 g / mol. n In one embodiment of the present invention, the fluoropolymer additive has a number average molecular weight M of less than 250,000 g / mol, preferably less than 200,000 g / mol, more preferably less than 190,000 g / mol, and most preferably less than 150,000 g / mol. nIt has. In one embodiment of the present invention, the fluoropolymer additive has a number average molecular weight M of 250 to 250,000 g / mol, preferably 2,500 to 400,000 g / mol, more preferably 25,000 to 190,000 g / mol, and most preferably 75,000 to 150,000 g / mol. n It has. A preferred example of the fluoropolymer additive, particularly poly(vinylidene fluoride-co-hexafluoropropylene), has a number average molecular weight M of about 130,000 g / mol. n or a number average molecular weight M of about 110,000 g / mol. n [[ID=⑥]]It has. Fluoropolymer additives such as poly(vinylidene fluoride-co-hexafluoropropylene) can be commercially purchased from suppliers such as Sigma-Aldrich.

[0064] The inventors have found that, as demonstrated in the attached examples, adding a fluoropolymer additive improves the conductivity of the protective layer, improves the wettability of the protective layer, and enables printing of a homogeneous film of the protective layer.

[0065] Lithium salt As described above, the protective layer according to the present invention contains a lithium salt.

[0066] In one embodiment of the present invention, the lithium salt is Li2CO3, Li2O, Li2C2C4, LiOH, LiX 7 , ROCO2Li, HCOLi, R 13 OLi, Li2O, Li2C2C4, (R 13 OCO2Li)2, (CH2OCO2Li)2, Li2S, LiSCN, LiN(CN)2, LiClO4, LiBF4, LiAsF6, LiPF6, LiCF3SO3, LiC(CF3SO2)3, LiN(SO2C2F5)2, LiN(SO2CF3)2, LiN(SO2F)2, LiSbF6, LiPF3(CF2CF3)3, LiPF3(CF3)3, LiB(C2O4)2 (where R 13 = hydrocarbon and X 7The lithium salt is selected from the group consisting of F, Cl, I, or Br and combinations thereof, preferably from the group consisting of LiSCN, LiN(CN)2, LiClO4, LiI, LiBF4, LiAsF6, LiCF3SO3, LiCF3(SO3)2, LiN(SO2C2F5)2, LiN(SO2CF3)2, LiN(SO2F)2, LiSbF6, LiPF3(CF2CF3)3, LiPF3(CF3)3, LiB(C2O4)2 and combinations thereof, more preferably the lithium salt is LiN(SO2CF3)2 or LiN(SO2F)2, and most preferably the lithium salt is LiN(SO2F)2.

[0067] In a preferred embodiment of the present invention, the amount of lithium salt is greater than 5% by weight based on the total weight of the protective layer, preferably greater than 10% by weight based on the total weight of the protective layer, and most preferably greater than 40% by weight based on the total weight of the protective layer. In a preferred embodiment of the present invention, the amount of lithium salt is less than 70% by weight based on the total weight of the protective layer, preferably less than 65% by weight based on the total weight of the protective layer, and most preferably less than 60% by weight. In a preferred embodiment of the present invention, the amount of lithium salt is 5 to 70% by weight based on the total weight of the protective layer, preferably 10 to 65% by weight based on the total weight of the protective layer, and more preferably 40 to 60% by weight.

[0068] The inventors have found that adding a lithium salt improves the lithium ion conductivity of the protective layer and prevents the protective layer from depleting the lithium ions present in the electrolyte. Furthermore, adding a higher lithium salt content to the protective layer improves the uncompensated resistance R u It decreases.

[0069] protective layer In one embodiment of the present invention, the protective layer has a thickness of 1 to 10 μm, preferably 2 to 7 μm, and more preferably 3 to 6 μm.

[0070] In one embodiment of the present invention, the protective layer is disposed directly on at least a portion of the metal substrate, preferably on the entire surface of the metal substrate. As will be understood by those skilled in the art, the negative electrode according to the present invention includes the protective layer according to the present invention, which forms an outer layer on the metal substrate. In other words, the protective layer is coated on a portion of the surface of the metal substrate, i.e., the protective layer forms a coating on a portion of the surface of the metal substrate, preferably on the entire surface of the metal substrate.

[0071] In preferred embodiments of the present invention, the protective layer according to the present invention has an ionic conductivity greater than 0.01 mS / cm, preferably greater than 0.015 mS / cm, and more preferably greater than 0.05 mS / cm. In preferred embodiments of the present invention, the protective layer has an ionic conductivity less than 0.5 mS / cm, preferably less than 0.2 mS / cm, and more preferably less than 0.1 mS / cm. In preferred embodiments of the present invention, the protective layer according to the present invention has an ionic conductivity in the range of 0.01 to 0.5 mS / cm, preferably in the range of 0.015 to 0.2 mS / cm, and most preferably in the range of 0.05 to 0.1 mS / cm. The ionic conductivity of the protective layer is measured by the uncompensated resistance R measured by electronic impedance spectroscopy (EIS) in a symmetric Li-Li cell. u The ion conductivity is measured by quantification, and is measured after cell construction (meaning, for example, in a battery containing the negative electrode and electrolyte composition according to the present invention).

[0072] A further aspect of the present invention is a method for preparing a protective layer according to the present invention, comprising the following steps: i) A step of adding the first monomer defined above, the second monomer defined above, the initiator defined above, the lithium salt defined above, and the fluoropolymer additive defined above to the organic liquid defined above, ii) A step of subjecting the mixture obtained in step i) to the crosslinking step defined above, iii) Optionally, the crosslinked mixture from step ii) is subjected to the thermal annealing step defined above, Includes.

[0073] A further aspect of the present invention is a protective layer that can be obtained by a method for preparing a protective layer according to the present invention.

[0074] others A further aspect of the present invention is the negative electrode according to the present invention, a. The metal substrate defined above, b. A protective layer that can be obtained by a method for preparing a protective layer according to the present invention, which is directly disposed on at least a portion of a metal substrate, Includes.

[0075] Further aspects of the present invention include the following steps: i) A step of adding the first monomer defined above, the second monomer defined above, the initiator defined above, the lithium salt defined above, and the fluoropolymer additive defined above to the organic liquid defined above, ii) A step of coating at least a portion of a metal substrate, preferably the entire surface of the metal substrate, with the mixture obtained in step i), iii) A step of subjecting the coated metal substrate from step ii) to the crosslinking step defined above, iv) Optionally, the crosslinked coated metal substrate from step iii) is subjected to the thermal annealing process defined above, This is a method for preparing a negative electrode for a battery, including [the specified component].

[0076] In one embodiment of the present invention, as defined above, the amount of solid present in the mixture obtained in step i) (i.e., the sum of the first monomer, the second monomer, the initiator, the lithium salt, and the fluoropolymer) is greater than 1% by weight based on the total weight of the solid and the organic liquid, preferably greater than 2% by weight based on the total weight of the solid and the organic liquid, most preferably greater than 3% by weight. In one embodiment of the present invention, the amount of solid (i.e., the sum of the first monomer, the second monomer, the initiator, the lithium salt, and the fluoropolymer) is less than 10% by weight based on the total weight of the solid and the organic liquid, preferably less than 8% by weight based on the total weight of the solid and the organic liquid, most preferably less than 5% by weight. In one embodiment of the present invention, the amount of solid (i.e., the sum of the first monomer, the second monomer, the initiator, the lithium salt, and the fluoropolymer) is 1 to 10% by weight based on the total weight of the solid and the organic liquid, preferably 2 to 8% by weight based on the total weight of the solid and the organic liquid, most preferably 3 to 5% by weight.

[0077] The coating process may be carried out using methods used in conventional wet processes as understood by those skilled in the art, such as spin coating, spray coating, doctor blade coating, and dip coating.

[0078] Optionally, a drying step is performed after the coating step and / or the thermal annealing step. The drying step is performed at a temperature above the boiling point of the organic liquid and at a temperature equal to the glass transition temperature T of the copolymer and / or protective layer according to the present invention. g The following temperatures may be used to perform the process appropriately. The drying process may also be performed to remove any remaining liquid from the surface of the metal substrate and, at the same time, to improve the adhesion of the copolymer and / or protective layer according to the present invention.

[0079] A further aspect of the present invention is a negative electrode that can be obtained by a method for preparing a negative electrode for a battery according to the present invention.

[0080] battery Further embodiments of the present invention include: a. A negative electrode that can be obtained by the method for preparing a negative electrode for a battery according to the present invention, b. The positive electrode and, c. Electrolyte composition, preferably an electrolyte composition disposed between the positive and negative electrodes, d. Optionally, a separator and, It is a battery that includes [something].

[0081] In a preferred embodiment of the present invention, the battery is a lithium metal battery, preferably a lithium metal secondary battery.

[0082] positive electrode The material for the positive electrode (i.e., cathode) is not particularly limited, and examples include transition metal compounds or specialized metal compounds having a structure that can diffuse lithium ions, and lithium oxides. In particular, examples include LiCoO2, LiNiO2, LiMnO4, and LiFePO4. Preferred positive electrode materials are mixed metal oxides containing lithium, nickel, and optionally manganese, cobalt, and / or aluminum.

[0083] In a preferred embodiment of the present invention, the positive electrode comprises a positive electrode material selected from the group consisting of lithium nickel-manganese-cobalt oxide, lithium nickel-manganese oxide, lithium nickel-cobalt-aluminum oxide, lithium cobalt oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt iron phosphate, lithium sulfide, sulfur, and aluminum, and preferably the positive electrode material is lithium nickel-manganese-cobalt oxide or lithium nickel-cobalt-aluminum oxide.

[0084] The positive electrode can be formed by press-molding the positive electrode material defined above with a known conductive additive or binder, or the positive electrode active material with a known conductive additive or binder, in an organic liquid such as pyrrolidone. This can be obtained by applying the mixture, coating it onto a current collector such as aluminum foil, and then drying it.

[0085] electrolyte composition In one embodiment of the present invention, the electrolyte composition is a liquid electrolyte composition.

[0086] In one embodiment of the present invention, the electrolyte composition comprises a further lithium salt and a further organic liquid, preferably a further non-aqueous organic liquid, more preferably a further aprotic non-aqueous organic liquid.

[0087] In a preferred embodiment of the present invention, further lithium salts include Li2CO3, Li2O, Li2C2O4, LiOH, and LiX 8 ROCO2Li, HCOLi, R 14 OLi, Li2O, Li2C2O4, (ROCO2Li)2, (CH2OCO2Li)2, Li2S, LiSCN, LiN(CN)2, LiClO4, LiBF4, LiAsF6, LiPF6, LiCF3SO3, Li C(CF3SO2)3, LiN(SO2C2F5)2, LiN(SO2CF3)2, LiN(SO2F)2, LiSbF6, LiPF3(CF2CF3)3, LiPF3(CF3)3, LiB(C2O4)2 (in the formula, R 14 =Hydroxides and X 8 The lithium salt is selected from the group consisting of LiSCN, LiN(CN)2, LiClO4, LiI, LiBF4, LiAsF6, LiCF3SO3, LiCF3(SO3)2, LiN(SO2C2F5)2, LiN(SO2CF3)2, LiN(SO2F)2, LiSbF6, LiPF3(CF2CF3)3, LiPF3(CF3)3, LiB(C2O4)2 and combinations thereof, more preferably the lithium salt is LiN(SO2CF3)2 or LiN(SO2F)2, and most preferably the lithium salt is LiN(SO2F)2.

[0088] In a very preferred embodiment, the further lithium salt and the above lithium salt are the same lithium compound.

[0089] As will be understood by those skilled in the art, the lithium salt according to the present invention is present in the protective layer according to the present invention, while the further lithium salt according to the present invention is present in the electrolyte composition according to the present invention.

[0090] In preferred embodiments of the present invention, further organic liquids include N-methyl-2-pyrrolidone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, 4-methyl-1,3-dioxene, diethyl ether, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethyl The non-fluorinated liquid is selected from the group consisting of methyl formate, methyl acetate, triester phosphate, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, ethyl propionate, and combinations thereof. Preferably, the further organic liquid is 1,2-dimethoxyethane or 1,2-diethoxyethane, most preferably 1,2-dimethoxyethane.

[0091] In preferred embodiments, the further organic liquid further comprises a fluorinated liquid, which is a fluorinated ether, a fluorinated carbonate, or a fluorinated aromatic compound. In preferred embodiments, the fluorinated liquid is 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE), bis(2,2,2-trifluoroethyl) ether (BTFE), 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether (TFTFE), tris(2,2,2-trifluoroethyl) orthoformate (TFEO), methoxynononafluorobutane (MOFB), ethoxynononafluorobutane (EOFB), di(2,2,2-trifluoroethyl) carbonate (DTFEC), tris(2,2,2-trifluoroethyl) orthoformate (TFEO), tris(hexafluoroisopropyl) orthoformate (THFiPO), tris(2,2-difluoroethyl) orthoformate (TD The fluorinated liquid is selected from the group consisting of FEO), bis(2,2,2-trifluoroethyl)methyl orthoformate (BTFEMO), tris(2,2,3,3,3-pentafluoropropyl) orthoformate (TPFPO), tris(2,2,3,3-tetrafluoropropyl) orthoformate (TTPO), and combinations thereof. Preferably, the fluorinated liquid is 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE), bis(2,2,2-trifluoroethyl) ether (BTFE), or 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether (TFTFE), and most preferably, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE).

[0092] In preferred embodiments of the present invention, the volume ratio of the non-fluorinated liquid to the fluorinated liquid is 6:1 to 1:2 (vol / vol), preferably 5:1 to 1:1 (vol / vol), and most preferably 4:1 to 2:1 (vol / vol).

[0093] As will be understood by those skilled in the art, the organic liquid according to the present invention is a liquid used in a crosslinking process to give the copolymer according to the present invention, while a further organic liquid according to the present invention is a liquid present in the electrolyte composition according to the present invention.

[0094] In one embodiment of the present invention, the concentration of the further lithium salt in the further organic liquid is greater than 0.2 M, preferably greater than 2 M, and most preferably greater than 4 M. In one embodiment of the present invention, the concentration of the further lithium salt in the further organic liquid is less than 10 M, preferably less than 8 M, and most preferably less than 6 M. In one embodiment of the present invention, the concentration of the further lithium salt in the further organic liquid is in the range of 0.2 to 10 M, preferably in the range of 2 to 8 M, and most preferably in the range of 4 to 6 M.

[0095] Separator To prevent short circuits between the positive and negative electrodes, a separator is usually inserted between the cathode and anode. While the material and shape of the separator are not particularly limited, it is preferable that it allows the electrolyte composition to pass through easily and that the separator is an insulator and chemically stable. Examples include microporous films and sheets made from various polymer materials. Specific examples of polymer materials include polyolefin polymers, nitrocellulose, polyacrylonitrile, polyvinylidene fluoride, polyethylene, and polypropylene. From the viewpoint of electrochemical and chemical stability, polyolefin polymers are preferred.

[0096] others In a preferred embodiment of the present invention, the battery of the present invention has a Coulomb efficiency of at least 93%, preferably at least 94%, more preferably at least 95%, even more preferably at least 96%, even more preferably at least 97%, and most preferably at least 98%. The Coulomb efficiency is evaluated using the following general formula:

[0097]

number

[0098] use A further aspect of the present invention is to provide the use of a protective layer as a self-healing film on a negative electrode including a metal substrate, wherein the protective layer is according to the present invention and the metal substrate is according to the present invention.

[0099] A further aspect of the present invention is to provide the use of a protective layer for reducing dendrite growth on a negative electrode including a metal substrate, wherein the protective layer is according to the present invention and the metal substrate is according to the present invention.

[0100] A further aspect of the present invention provides the use of a protective layer on a negative electrode, comprising a metal substrate, for improving the cycle efficiency of a battery including a negative electrode, preferably by 20%, wherein the protective layer is according to the present invention, preferably subjected to the thermal annealing process defined above, and the metal substrate is according to the present invention. [Examples]

[0101] The present invention is further illustrated in the following embodiments.

[0102] Description of cell preparations and test methods All tested coin cells were of the CR2032 type. Cells were prepared by stacking the positive electrode casing, positive electrode (pre-immersed in electrolyte), Cellguard separator, 50 μL electrolyte droplet, negative electrode, spacer, corrugated spring, and negative electrode casing in that order. A manual welding machine manufactured by MTI was used to press the cells at 80 kg / cm². 2 The welding was performed using pressure.

[0103] Li-Li pouch cells were prepared according to the following specifications: Format = 1 Li (58 × 58 mm) / 1 Sep (62 × 62 mm) / 1 Li (50 × 50 mm), "Nominal Capacity" = 0.1 Ah, Separator = Alumina-coated Targray SH220W22, Lithium = 100 μm thickness (coated or uncoated), Electrolyte Loading = 3.00 μL mAh-1 (i.e., 0.3 mL), C rate = C / 5 D / 5 (standard regime) or C / 3 D / 1, with potential retention (new regime), cycle temperature = 25°C.

[0104] Li-NMC pouch cells were prepared according to the following specifications: Format = 3Li (58x58mm) / 4Sep (62x62mm) / 2NMC (56x54mm), Nominal capacity = 0.48Ah (cathode surface capacity of 4mAh cm²). -2 (Assuming the above), separator = Targray SH220W22 coated with alumina, lithium = 100 μm thickness, electrolyte addition amount = 2.00 μL mAh -1 (i.e., 0.97 mL) or 1.75 μL mAh -1 That is, 0.85 mL), C rate = C / 5 D / 5 (standard regime) or C / 3 D / 1, with potential retention (new regime), cycle temperature = 25°C. The NMC cathode uses LiNi as the positive electrode active material. 0.6 Mn 0.2 Co 0.2 Contains O2, carbon black, and PVDF in a weight ratio of 92:4:4.

[0105] Uncompensated resistance R u This is measured by electrochemical impedance spectroscopy (Nyquist diagram) of Li-Li symmetric coin cells containing lithium metal anodes that are either uncoated or coated with a protective layer. In the tests, frequencies from 1 MHz to 1 Hz were applied.

[0106] The ionic conductivity of the protective layer is determined by the uncompensated resistance R in a symmetric Li-Li cell using electron impedance spectroscopy (EIS). u The quantification of the coefficients is used for measurement, and ionic conductivity is measured after cell construction.

[0107] The cross-section of the protective layer was analyzed using a scanning electron microscope (SEM). A JEOL benchtop SEM was used (samples were imaged under vacuum within the SEM, secondary electron imaging, probe current set to standard, SEM column acceleration voltage).

[0108] Polymer-protected anodes are prepared by adding monomers, lithium salts, initiators, and fluoropolymer additives to an organic solvent in the amounts shown in the table below. These mixtures are coated onto the anode and subjected to UV curing for 5 minutes using Irgacure 819 as a photoinitiator. Optionally, thermal annealing of the polymer is performed after UV curing the polymer-protected anode at 70°C for 1 hour. [Examples]

[0109] To evaluate the effect of the amount of fluoropolymer additive, the following polymer formulations 1-a, 1-b, and 1-c were prepared (see Table 1, PEGDA = 700 g / mol M n Poly(ethylene glycol) diacrylate, LiTFSI=LiN(SO2CF3)2, PVDF-HFP=poly(vinylidene fluoride-co-hexafluoropropylene), THF=tetrahydrofuran).

[0110] [Table 1]

[0111] Figure 1 shows the effect of a decrease in the weight percentage of fluoropolymer additives in the polymer formulation on film continuity. While formulations 1-a and 1-b form homogeneous films on the lithium substrate, excessively reducing the amount of PVDF-HFP (9:1, formulation 1-c) results in a much lower uncompensated resistance (R u This illustrates the formation of discontinuous and patchy films. Figure 2 demonstrates the effect on conductivity, showing that the optimal PEG to PVDF-HFP ratio is 3:1, providing a continuous polymer film and a decrease in Ru compared to formulation 1-a. [Examples]

[0112] To evaluate the effect of lithium salts, the following polymer formulations 2-a, 2-b, 2-c, and 2-d were prepared (see Table 2, PEGDA = 700 g / mol M n Poly(ethylene glycol) diacrylate, LiTFSI=LiN(SO2CF3)2, LiFSI=LiN(SO2F)2, PVDF-HFP=poly(vinylidene fluoride-co-hexafluoropropylene), THF=tetrahydrofuran).

[0113] [Table 2]

[0114] The conductivity data from each of the polymer formulations in Table 2 are shown in Figure 3. The problem with the low film salt content (10 wt%) in the polymer formulations is clear because, over the first 20 hours, the resistance of the Li-Li coin cell increases as the resistant polymer formulation absorbs salt from the electrolyte. u This is because the R of each cell decreases, and this process should be prevented. Increasing the salt content of the polymer formulation from 10% by weight to 50% by weight of the total weight of the formulation results in improved conductivity of the polymer film in each example. u This results in a decrease in (compounds 2-b and 2-d exhibit similar uncompensated resistances of approximately 45-47 Ω). The R of a film containing 50 wt% salt for 0-60 hours is also measured. u The stability indicates that ion movement between the polymer membrane and the electrolyte is in equilibrium from the cell construction, and that depletion of electrolyte salts is avoided. [Examples]

[0115] To evaluate the effect of N-hydroethylacrylamide monomer, the following polymer formulations 3-a, 3-b, 3-c, and 3-d were prepared (see Table 2, PEGDA = 700 g / mol). nPoly(ethylene glycol) diacrylate, HEAA = N-hydroxyethylacrylamide, PVDF-HFP = poly(vinylidene fluoride-co-hexafluoropropylene), THF = tetrahydrofuran).

[0116] [Table 3]

[0117] A protective layer of each formulation was coated onto a lithium substrate, cured, and then cut by drawing a scalpel across the coated surface. The cut samples were imaged by SEM, and then immersed overnight (16 hours) in 4.5 M LiFSI in 1,2-dimethoxyethane (DME). The films were rinsed with pure DME to remove excess LiFSI salts, allowing for clearer SEM micrographs, then dried and observed under SEM. The results for each of the polymer formulations in Table 3 are shown in Figure 4.

[0118] As expected, formulation 4-a (0 wt% HEAA) (1:0) does not exhibit self-healing properties due to the absence of hydrogen bond donors. The protective layer containing the minimum amount of HEAA (formulation 4-b) also does not show evidence of self-healing under these conditions. Increasing the HEAA content to a PEGDA to HEAA weight ratio of 3:1 results in the polymer film resealing at the created incision site. Finally, formulation 4-d (PEGDA to HEAA weight ratio 1:1 w / w) also exhibits substantial self-healing properties (see Figure 4). In addition, it is noteworthy that formulation 4-d appears to have better adhesion to the Li metal surface when observed under SEM compared to the other formulations.

[0119] Next, each polymer formulation was tested in a Li-NMC cell against a reference cell (without polymer). 1.75 μL mAh -1Cells containing the following additive amounts (4.5 M LiFSI in DME) versus TTE (3:1, vol / vol, TTE = 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether) were cycled in a C / 3 to D / 1 cycle using foam (80 × 80 mm) under a fixed volume pressure of 0.06 MPa. Each polymer-protected anode cell functioned similarly to the reference cell (see Figures 5 and 6).

[0120] In the next step, the conductivity of each polymer formulation was evaluated before and after thermal annealing (1 hour at 70°C in dry air). The results are shown in Figures 7(a) and 7(b), respectively. Clearly, thermal annealing improves the conductivity of the polymer formulation. Approximately 0.1 mS.cm -1 Increasing the film conductivity to the minimum threshold is considered essential for successful anode protection. Higher conductivity results in a lower energy barrier to the plating beneath the polymer film, which helps reduce dendrite penetration, decrease the amount of dead lithium, and extend the functionality of the electrolyte and lithium anode. It was also observed that each polymer formulation appeared more homogeneous and had better contact with the lithium surface.

[0121] Next, each polymer formulation after annealing was tested in a Li-NMC cell against a reference cell (without polymer). 1.75 μL mAh -1 Cells containing an additive ratio of (4.5 M LiFSI in DME) to TTE (3:1, vol / vol, TTE = 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether) were cycled in a C / 3 to D / 1 cycle using foam (80 × 80 mm) under a fixed volume pressure of 0.06 MPa. Each heat-annealed polymer-protected cell performed similarly and was up to 20% better than the reference cell (see Figures 8 and 9).

Claims

1. It is the negative electrode for a battery, a. Metal substrate and b. A protective layer disposed directly on at least a portion of the metal substrate, The aforementioned protective layer is Equation (I) 【Chemistry 1】 (wherein R １ = H or CH ３ and R ２ is C ２～６ alkanediyl, and the alkanediyl is optionally substituted with one or more substituents selected from halides, C １～４ alkyl, CF ３ or OR ３ ; R ３ is selected from hydrogen or C １～４ alkyl; X １ = NH or O; and n is an integer selected from 5 to 150), and a first monomer represented by Formula (II) 【Chemistry 2】 (In the formula, R ４ = H or CH ３ And R ５ C ２～６ It is an alkanediyl, and the alkanediyl is a halide, C １～４ Alkyl, CF ３ OR ６ It is optionally substituted with one or more substituents selected from R ６ is hydrogen or C １～４ Selected from alkyl groups, X ２ = NH or O, X ３ =SH,NH ２ A second monomer represented by (or OH, where m is an integer selected from 1 to 10), A copolymer that can be obtained by a reaction between, A copolymer having a weight ratio of 1:5 to 8:1 (w / w) between the first monomer and the second monomer, A fluoropolymer additive selected from the group consisting of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene tetrafluoroethylene copolymer, polychlorotrifluoroethylene, vinylidene fluoride-pentafluoropropylene copolymer, propylene tetrafluoroethylene copolymer, ethylene chlorotrifluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymer, and combinations thereof, Lithium salts and Includes, A protective layer having a weight ratio of 1:5 to 8:1 (w / w) of the copolymer to the fluoropolymer additive, The negative electrode for a battery, including the negative electrode.

2. The negative electrode according to claim 1, wherein the fluoropolymer additive is polyvinylidene fluoride or poly(vinylidene fluoride-co-hexafluoropropylene).

3. The lithium salt is Li ２ CO ３ Li ２ O, Li ２ C ２ O ４ , LiOH, LiX, R １３ OCO ２ Li, HCOLi, R １３ OLi, Li ２ O, Li ２ C ２ O ４ , (R １３ OCO ２ Li) ２ , (CH ２ OCO ２ Li) ２ Li ２ S, LiSCN, LiN(CN) ２ LiClO ４ LiBF ４ LiAsF ６ LiPF ６ LiCF ３ SO ３ LiC (CF ３ SO ２ ) ３ , LiN (SO ２ C ２ F ５ ) ２ , LiN (SO ２ CF ３ ) ２ , LiN (SO ２ F) ２ LiSbF ６ LiPF ３ (CF ２ CF ３ ) ３ LiPF ３ (CF ３ ) ３ LiB(C) ２ O ４ ) ２ (In the formula, R １３ The negative electrode according to claim 1, wherein X is selected from the group consisting of hydrocarbons and F, Cl, I, or Br, and combinations thereof.

4. The negative electrode according to claim 1, wherein the weight ratio of the copolymer to the fluoropolymer additive is 1:2 to 5:1 (w / w).

5. The first monomer is given by formula (III): 【Transformation 3】 The negative electrode according to claim 1, represented by (wherein o is an integer selected from 5 to 150).

6. The second monomer is given by formula (IV): 【Chemistry 4】 The negative electrode according to claim 1, represented by [the specified method].

7. The negative electrode according to claim 1, wherein the weight ratio of the first monomer to the second monomer is 1:3 to 7:1 (w / w).

8. The negative electrode according to claim 1, wherein the copolymer is obtained by the reaction of the first monomer and the second monomer using a photoinitiator.

9. The negative electrode according to claim 1, wherein the amount of the lithium salt is 5 to 70% by weight based on the total weight of the protective layer.

10. The negative electrode according to claim 1, wherein the protective layer has a thickness of 1 to 10 μm.

11. The negative electrode according to claim 1, wherein the copolymer is subjected to a thermal annealing step.

12. A method for preparing a negative electrode for a battery, comprising the following steps: i) A step of adding a first monomer defined in claim 1, a second monomer defined in claim 1, a photoinitiator, a lithium salt defined in claim 1, and a fluoropolymer additive defined in claim 1 to an organic liquid, ii) A step of coating the mixture from step i) onto at least a portion of a metal substrate, iii) A step of subjecting the coated metal substrate from step ii) to a crosslinking step, iv) Optionally, the crosslinked coated metal substrate from step iii) is subjected to a thermal annealing step, Methods that include...

13. a. A negative electrode according to any one of claims 1 to 11, b. The positive electrode and, c. Electrolyte composition and Batteries, including

14. The battery according to claim 13, wherein the positive electrode comprises a positive electrode material selected from the group consisting of lithium nickel-manganese-cobalt oxide, lithium nickel-manganese oxide, lithium nickel-cobalt-aluminum oxide, lithium cobalt oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt iron phosphate, lithium sulfide, sulfur, and aluminum.

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