Gel polymer electrolyte and lithium metal battery comprising same

Abstract

Disclosed is a gel polymer electrolyte comprising: a first polymer including a repeating unit derived from a first crosslinking monomer having three or more reactive functional groups and a repeating unit derived from a second crosslinking monomer having a cyano group (CN); a lithium salt; and a first organic solvent, which is a nitrile-based organic solvent.

Description

Gel polymer electrolyte and lithium metal battery containing the same

[0001] It's about lithium metal batteries.

[0002] Lithium batteries currently on the market primarily use carbon-based anode materials, such as graphite. Carbon-based anode materials exhibit no volume change during charge and discharge, contributing to the stability of lithium batteries. Graphite has a theoretical electrical capacity of 372 mAh / g.

[0003] Lithium metal can be used as an anode material. The theoretical electrical capacity of lithium metal is 3860 mAh / g. However, lithium metal side reactions with the electrolyte during charge and discharge can degrade the lifespan of lithium batteries.

[0004] In a lithium battery, a layer of negative active material is placed between the electrolyte and the negative current collector. By omitting the negative active material layer during lithium battery assembly, the energy density of the lithium battery can be improved.

[0005] During the charge and discharge of a non-anode lithium battery, a lithium metal layer is deposited between the electrolyte and the negative electrode current collector, and the deposited lithium metal layer dissolves. As the lithium battery is repeatedly charged and discharged, the lithium metal layer contains impurities remaining in the electrode due to side reactions with the electrolyte, as well as decomposition products of the electrolyte. The surface of the lithium-containing metal layer containing these impurities becomes rough and hard. Lithium dendrites are deposited on the lithium-containing metal layer with a rough and hard surface. Lithium dendrites continuously grow during the charge and discharge process, causing a short circuit between the positive and negative electrodes. Consequently, the lithium battery deteriorates. Therefore, it is necessary to prevent side reactions between the electrolyte and the lithium metal layer during the charge and discharge process of a lithium battery, and to suppress the growth of lithium dendrites from the lithium metal layer.

[0006] One aspect is that by including a novel gel polymer electrolyte having excellent ionic conductivity, it is possible to provide a lithium battery having improved cycle characteristics and suppressing volume change of the lithium battery during charge and discharge.

[0007] According to one embodiment, a gel polymer electrolyte is provided, comprising: a first polymer including repeating units derived from a first crosslinking monomer having three or more reactive functional groups and repeating units derived from a second crosslinking monomer having a cyano group (CN); a lithium salt; and a first organic solvent that is a nitrile-based organic solvent.

[0008] According to another embodiment, a lithium metal battery is provided, comprising: a positive electrode layer; a negative electrode current collector; and an electrolyte layer disposed between the positive electrode layer and the negative electrode current collector, wherein the electrolyte layer includes the gel polymer electrolyte described above.

[0009]

[0010] *9 According to one aspect, it is possible to provide a lithium battery having improved cycle characteristics and suppressing volume change during charge and discharge by providing a new gel polymer electrolyte having excellent ionic conductivity.

[0011] Figure 1 is a cross-sectional schematic diagram of a lithium battery according to an exemplary embodiment.

[0012] Figure 2 is a conceptual diagram illustrating a reactive functional group and an isolated functional group included in a first polymer according to an exemplary embodiment.

[0013] Figure 3 is a conceptual diagram for explaining reactive functional groups and isolated functional groups included in a polymer.

[0014] Figure 4 is a cross-sectional schematic diagram of a lithium battery according to an exemplary embodiment.

[0015] Figure 5 is a graph showing the radial distribution function (RDF) obtained by performing coordination number analysis on gel polymer electrolytes manufactured according to Example 1 and Comparative Example 1.

[0016] Unless otherwise defined, all terms (including technical and scientific terms) used in this disclosure have the same meaning as commonly understood by those of ordinary skill in the art to which this disclosure pertains. Furthermore, terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning within the context of the relevant technology and this disclosure, and should not be interpreted in an idealized or overly formal sense.

[0017] Exemplary embodiments are described in this disclosure with reference to cross-sectional drawings that are schematic representations of idealized embodiments. As such, variations from the shapes depicted are to be expected, for example, as a result of manufacturing techniques and / or tolerances. Therefore, the embodiments described in this disclosure should not be construed as limited to the specific shapes of regions as depicted in this disclosure, but should encompass variations in shapes resulting from, for example, manufacturing. For example, regions depicted or described as flat may typically have rough and / or non-linear features. Moreover, angles depicted as sharp may be rounded. Therefore, the regions depicted in the drawings are schematic in nature, and their shapes are not intended to depict the precise shapes of the regions, nor are they intended to limit the scope of the claims.

[0018] This creative idea may be embodied in many different forms and should not be construed as limited to the embodiments described in this disclosure. These embodiments are provided so that this disclosure will be thorough and complete, and so that it will fully convey the scope of the creative idea to those skilled in the art. Like reference numerals in the drawings indicate like elements.

[0019] When a component is referred to as being "on" another component, it can be understood that it is either directly on top of the other component or that other components may be intervening between them. Conversely, when a component is referred to as being "directly on" another component, no intervening components are present.

[0020] Although terms such as "first," "second," "third," etc. may be used herein to describe various components, elements, regions, layers, and / or zones, these components, elements, regions, layers, and / or zones should not be limited by these terms. These terms are only used to distinguish one component, element, region, layer, or zone from another component, element, region, layer, or zone. Thus, a first component, element, region, layer, or zone described below may be referred to as a second component, element, region, layer, or zone without departing from the teachings of this disclosure.

[0021] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms including "at least one," unless the content clearly dictates otherwise. "At least one" should not be construed as limiting to the singular. As used herein, the term "and / or" includes any and all combinations of one or more of the listed items. The terms "comprises" and / or "comprising" as used in the detailed description specify the presence of stated features, regions, integers, steps, operations, components, and / or ingredients, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, components, ingredients, and / or groups thereof.

[0022] Spatially relative terms such as "below," "under," "lower," "above," "upper," and the like may be used herein to readily describe the relationship of one component or feature to another. It will be understood that spatially relative terms are intended to encompass different orientations of the device when in use or operation in addition to the orientations depicted in the drawings. For example, if the device in the drawings were turned over, a component described as "below" or "below" another component or feature would then be oriented "above" the other component or feature. Thus, the exemplary term "below" can encompass both the above and below orientations. The device may be arranged in other orientations (rotated 90 degrees or otherwise rotated), and the spatially relative terms used herein may be interpreted accordingly.

[0023] "Group" means a group in the periodic table of elements according to the International Union of Pure and Applied Chemistry ("IUPAC") Group 1-18 classification system.

[0024] In this disclosure, "particle diameter" refers to the average diameter when the particle is spherical, and refers to the average major axis length when the particle is non-spherical. The particle diameter can be measured using a particle size analyzer (PSA). The "particle diameter" is, for example, the average particle diameter. The "average particle diameter" is, for example, D50, the median particle diameter.

[0025] D50 is the size of the particle corresponding to 50% of the cumulative volume, calculated from the particle side with a smaller particle size in the particle size distribution measured by laser diffraction.

[0026] D90 is the size of the particle corresponding to 90% of the cumulative volume, calculated from the particle side with a smaller particle size in the particle size distribution measured by laser diffraction.

[0027] D10 is the size of the particle corresponding to 10% of the cumulative volume, calculated from the particle side with a small particle size in the particle size distribution measured by laser diffraction.

[0028] In this disclosure, “metal” includes both metals and metalloids such as silicon and germanium, in their elemental or ionic states.

[0029] In this disclosure, “alloy” means a mixture of two or more metals.

[0030] In the present disclosure, “electrode active material” means an electrode material capable of undergoing lithiation and delithiation.

[0031] In the present disclosure, “positive electrode active material” means a positive electrode material capable of undergoing lithiation and delithiation.

[0032] In the present disclosure, “negative electrode active material” means a negative electrode material capable of undergoing lithiation and delithiation.

[0033] In the present disclosure, “lithiation” and “lithiating” mean a process of adding lithium to an electrode active material.

[0034] In the present disclosure, “delithiation” and “delithiate” mean a process of removing lithium from an electrode active material.

[0035] In this disclosure, “charging” and “charging” mean a process of providing electrochemical energy to a battery.

[0036] In this disclosure, “discharging” and “discharging” mean the process of removing electrochemical energy from a battery.

[0037] In the present disclosure, “positive electrode” and “cathode” mean an electrode at which electrochemical reduction and lithiation occur during a discharge process.

[0038] In the present disclosure, “cathode” and “anode” mean electrodes where electrochemical oxidation and delithiation occur during a discharge process.

[0039] While specific implementations have been described, alternatives, modifications, variations, improvements, and substantial equivalents that are not currently anticipated or unforeseen may occur to the applicant or those skilled in the art. Accordingly, the appended claims, as filed and as amended, are intended to encompass all such alternatives, modifications, variations, improvements, and substantial equivalents.

[0040] Below, lithium batteries according to exemplary implementation examples are described in more detail.

[0041] According to one embodiment, a lithium battery may include a cathode layer (100); an anode current collector (210); and an electrolyte layer (300) disposed between the cathode layer (100) and the anode current collector (210). The electrolyte layer (300) may include a gel polymer electrolyte. The gel polymer electrolyte may include a first polymer, a lithium salt, and a first organic solvent. The first polymer may include repeating units derived from a first crosslinking monomer including three or more reactive functional groups (1). The first polymer may include repeating units derived from a second crosslinking monomer including a cyano group (CN). The first organic solvent may include a nitrile-based organic solvent.

[0042] Gel polymer electrolytes have excellent ionic conductivity and improved mechanical properties compared to liquid electrolytes, thereby more effectively suppressing volume changes in lithium batteries during charging and discharging.

[0043] The gel polymer electrolyte can effectively prevent deterioration of a lithium battery by suppressing side reactions with the lithium metal layer (240) of the lithium battery during charge and discharge. For example, when charging and discharging a lithium battery, a solid electrolyte interphase (SEI) layer may be formed between a new gel polymer electrolyte and the precipitated lithium metal layer (240). By modifying the composition of the SEI layer to have an increased content of lithium salt decomposition products, side reactions between the gel polymer electrolyte and the lithium metal layer (240) can be more effectively suppressed. In addition, the gel polymer electrolyte and / or the modified SEI layer can effectively prevent internal short circuits of the lithium battery by more effectively suppressing the growth of lithium dendrites from the lithium metal layer (240).

[0044] Since the gel polymer electrolyte contains a lithium salt, the ester group of the first polymer interacts with lithium ions, thereby more effectively altering the solvation structure of the lithium ions. This increases the aggregation of anions derived from the lithium salt, and inorganic components such as fluorine (F) derived from the aggregation of ions during the charge / discharge process can modify the composition of the SEI layer, thereby improving the cycle characteristics of the lithium battery.

[0045] Since the gel polymer electrolyte contains an organic solvent, the carbonyl groups of the organic solvent can interact with lithium ions, effectively altering the solvation structure of lithium ions. This increases the aggregation of anions derived from lithium salts, and inorganic components such as fluorine (F) derived from the aggregation of anions during charge / discharge can modify the composition of the SEI layer, thereby improving the cycling characteristics of lithium batteries.

[0046] As a result, the cycle characteristics of a lithium battery having a gel polymer electrolyte can be improved.

[0047] Figure 1 is a cross-sectional schematic diagram of a lithium battery according to an embodiment.

[0048] Referring to FIG. 1, a lithium metal battery (1000) may include a cathode layer (100); an anode current collector (210); and an electrolyte layer (300) disposed between the cathode layer (100) and the anode current collector (210). The electrolyte layer (300) may include a gel polymer electrolyte. The gel polymer electrolyte may include a first polymer, a lithium salt, and a first organic solvent. The first polymer may include repeating units derived from a first crosslinking monomer including three or more reactive functional groups (1). The first polymer may include a second crosslinking monomer including a cyano group. The first organic solvent may include a nitrile-based organic solvent.

[0049] The electrolyte layer (300) may include a gel polymer electrolyte. The gel polymer electrolyte may include a first polymer, a lithium salt, and a first organic solvent.

[0050] The gel polymer electrolyte can form a gel by including a polymer. The electrolyte without the first polymer can be a liquid electrolyte.

[0051] Referring to FIG. 2, the first polymer may include a reactive functional group (1). The reactive functional group (1) included in the first polymer may interact with lithium ions in the electrolyte layer (300) to move lithium ions, thereby improving the ionic conductivity of the gel polymer electrolyte. The reactive functional group (1) may include, for example, a carboxyl group (COOH), a carbonyl group (C=O), a hydroxyl group (OH), an ester group (COOR), or a combination thereof, but is not particularly limited as long as it is a functional group having a binding force with lithium ions. The reactive functional group (1) according to one embodiment may include an ester group.

[0052] The first polymer may comprise repeating units derived from a first crosslinking monomer having, for example, 3 or more, 4 or more, 5 or more, or 6 or more reactive functional groups (1). The first crosslinking monomer may comprise, for example, 3 to 20, 3 to 10, 3 to 8, or 4 to 6 reactive functional groups (1). The first crosslinking monomer may comprise, for example, 3 to 20, 4 to 15, 5 to 10, or 6 to 10 reactive functional groups (1). When the first crosslinking monomer comprises a reactive functional group (1) in this range, a gel polymer electrolyte comprising a polymer obtained therefrom can provide excellent mechanical properties and ionic conductivity. When the first crosslinking monomer comprises an excessively small number of reactive functional groups (1), the mechanical properties of the gel polymer electrolyte may be excessively deteriorated. By including a first crosslinking monomer having an excessively large number of reactive functional groups (1), the crosslinking density may increase excessively, resulting in excessively low ionic conductivity of the gel polymer.

[0053] The first cross-linking monomer may include an ester group. The first cross-linking monomer may be a monomer including an ester group. By including an ester group in the first cross-linking monomer, the oxidation resistance of the gel polymer electrolyte can be further improved. Therefore, side reactions between the gel polymer electrolyte and the positive electrode and / or side reactions between the gel polymer electrolyte and the solvent due to oxidation of the gel polymer electrolyte in a region adjacent to the positive electrode having a high voltage can be more effectively suppressed. Consequently, deterioration of the gel polymer electrolyte at the interface between the gel polymer electrolyte and the positive electrode can be more effectively prevented.

[0054] The first crosslinking monomer may include, for example, an acrylic monomer containing multiple acrylic groups, a methacrylic monomer containing multiple methacrylic groups, or a combination thereof.

[0055] Acrylic monomers include, for example, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, trimethylolpropane ethoxylate triacrylate, trimethylolpropane propoxylate triacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, pentaerythritol ethoxylate tetraacrylate, dipentaerythritol pentaacrylate, It may contain dipentaerythritol hexaacrylate or a combination thereof.

[0056] The first crosslinking monomer may not include, for example, a glycol-based monomer. The first crosslinking monomer may be, for example, a monomer free of alkylene oxide repeating units. The alkylene oxide repeating units are, for example, ethylene oxide repeating units. Oxidation resistance may be further improved by the first crosslinking monomer not including alkylene oxide repeating units. Accordingly, the gel polymer electrolyte may not be easily oxidized at high voltage by not including repeating units derived from a glycol-based monomer. Deterioration of the gel polymer electrolyte at the interface between the gel polymer electrolyte and the positive electrode may be more effectively suppressed.

[0057] Acrylic monomers that do not contain alkylene oxide repeating units may include, for example, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, trimethylolpropane propoxylate triacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, or combinations thereof.

[0058] Referring to FIGS. 2 and 3, the polymer included in the gel polymer electrolyte may include a reactive functional group (1) and an isolated functional group (2). The isolated functional group (2) may include a functional group that is substantially the same as or different from the reactive functional group (1) described above. The isolated functional group (2) may include a functional group that is substantially the same as the reactive functional group (1) described above. The isolated functional group (2) may be a reactive functional group (1) among the reactive functional groups (1) in which steric hindrance occurs in a portion where the polymer chain is twisted due to the lengthening of the main chain of the polymer included in the gel polymer electrolyte. Such an isolated functional group (2) may not contribute to ionic conductivity because lithium salts are not easily accessible thereto. As a result, it may cause a decrease in the energy density of a lithium battery.

[0059] Referring to FIG. 2, the first polymer of the embodiment may include a cyano group (CN). The cyano group (CN) included in the first polymer can minimize the number of isolated functional groups (2) by improving the morphological characteristics of the first polymer. Consequently, the ionic conductivity of the gel polymer electrolyte can be improved.

[0060] The first polymer may include a repeating unit derived from a second crosslinking monomer containing a cyano group (CN). The second crosslinking monomer may be a monomer containing a cyano group. Since the second crosslinking monomer contains a cyano group, the morphological characteristics of the first polymer may be further improved. Accordingly, the access of a lithium salt to the functional group contained in the first crosslinking monomer may be facilitated. Consequently, side reactions between the gel polymer electrolyte and the positive electrode and / or side reactions between the gel polymer electrolyte and the solvent due to oxidation of the gel polymer electrolyte in a region adjacent to the positive electrode having a high voltage may be more effectively suppressed, and deterioration of the gel polymer electrolyte at the interface between the gel polymer electrolyte and the positive electrode may be more effectively prevented.

[0061] The second crosslinking monomer may comprise repeating units derived from the second crosslinking monomer containing 5 or fewer cyano groups. The second crosslinking monomer may, for example, contain 3 or fewer or 2 or fewer cyano groups. The second crosslinking monomer may, for example, contain one cyano group. The morphological properties of the gel polymer electrolyte may be further improved by the second crosslinking monomer containing cyano groups in this range.

[0062] The second crosslinking monomer may include a repeating unit derived from a second crosslinking monomer containing an ethylene group and a cyano group (CN). The second crosslinking monomer may be a monomer containing an ethylene group and a cyano group. Since the second crosslinking monomer contains an ethylene group, a cyano group (CN) can be stably formed in the first polymer.

[0063] The second crosslinking monomer may include, for example, acrylonitrile, propenenitrile, butenenitrile, pentenenitrile, hexenenitrile, heptenenitrile, octenenitrile, nonenenitrile, decenenitrile, or combinations thereof.

[0064] The second crosslinking monomer may include, for example, acryloisocyanide, propeneisocyanide, buteneisocyanide, penteneisocyanide, hexeneisocyanide, hepteneisocyanide, octeneisocyanide, noneneisocyanide, deceneisocyanide, or combinations thereof.

[0065] The second crosslinking monomer comprising an ethylene group and a cyano group may include a carbon double bond at one end of the compound. The second crosslinking monomer may include, for example, acrylonitrile, propenenitrile, butenenitrile, pentenenitrile, hexanenitrile, hepenenitrile, octenenitrile, nonenenitrile, decenenitrile, or a combination thereof.

[0066] The second crosslinking monomer may have, for example, 5 or fewer carbon atoms. The second crosslinking monomer may include, for example, propenenitrile (Prop-1-enenitrile), butenenitrile (But-3-enenitrile), pentenenitrile (Pent-4-enenitrile), or a combination thereof.

[0067] The first polymer may be a crosslinking product of a first crosslinking monomer and a second crosslinking monomer.

[0068] The molecular weight of the first polymer may be, for example, greater than or equal to 1,000 Daltons, greater than or equal to 10,000 Daltons, or greater than or equal to 100,000 Daltons. The molecular weight of the first polymer may be, for example, from 1,000 Daltons to 5,000,000 Daltons, from 10,000 Daltons to 2,000,000 Daltons, or from 100,000 Daltons to 1,000,000 Daltons. The first polymer may have a two-dimensional and / or three-dimensional network structure within the gel polymer electrolyte.

[0069] The content of the first polymer may be, for example, 0.1 to 15 wt%, 0.2 to 10 wt%, 0.5 to 7 wt%, 1 to 5 wt%, or 2 to 4 wt% based on the total weight of the gel polymer electrolyte. When the gel polymer electrolyte includes the first polymer in this range, a stable gel polymer electrolyte can be formed. If the content of the first polymer is too low, it may be difficult to form a gel. If the content of the first polymer is too high, the gel polymer electrolyte may be excessively hardened, which may cause cracks, etc., to occur within the gel polymer electrolyte during the charge and discharge process of the lithium battery. In addition, cracks, etc., may occur within the gel polymer electrolyte during the charge and discharge process of the lithium battery, and it may be difficult to effectively accommodate the volume change that occurs during the charge and discharge process of the lithium battery. For example, when the lithium battery shrinks, desorption may occur between the gel polymer electrolyte and the positive electrode and / or between the gel polymer electrolyte and the negative electrode, which may rapidly increase the internal resistance.

[0070] The gel polymer electrolyte may contain a lithium salt. The lithium salt may be a borate-based lithium salt. By containing a lithium salt in the gel polymer electrolyte, the ionic conductivity of the gel polymer electrolyte may be improved.

[0071] The lithium salt may include a first lithium salt and a second lithium salt.

[0072] The first lithium salt and the second lithium salt may independently be borate-based lithium salts. Borate-based lithium salts have improved high-temperature stability compared to phosphorous-based lithium salts and can suppress the production of hydrofluoric acid (HF). By including borate-based lithium salts in the first and second lithium salts, the high-temperature cycling characteristics of a lithium battery can be improved.

[0073] The first lithium salt and the second lithium salt may, for example, independently be fluorine-containing borate-based lithium salts. By including the fluorine-containing borate-based lithium salt in the first lithium salt and the second lithium salt, the composition of the SEI layer formed during charge and discharge of the lithium battery can be more effectively modified. For example, by increasing the fluorine (F) content of the SEI layer, the structural stability of the SEI layer can be increased, and side reactions with organic solvents can be effectively suppressed. Consequently, the reversibility of the electrode reaction of the lithium battery can be improved.

[0074] The first lithium salt and the second lithium salt may be, for example, a non-cyclic borate lithium salt and a cyclic borate lithium salt. Since the first lithium salt is a non-cyclic lithium salt, the ionic conductivity of the gel polymer electrolyte can be more effectively increased. Since the second lithium salt is a cyclic lithium salt, the aggregation of anions is increased, so that it can more effectively participate in the composition modification of the SEI layer, and the high-temperature stability of the gel polymer electrolyte can be improved.

[0075] The ionic conductivity of the gel polymer electrolyte may be reduced by not including the first lithium salt. The structural stability of the SEI layer may be reduced by not including the second lithium salt.

[0076] The fluorine-containing borate lithium salt may include, for example, LiBF4, LiBF3(CF3), LiBF3(C2F5), LiBF3(C3F7), LiDFOB or a combination thereof.

[0077] The first lithium salt may include, for example, LiBF4, and the second lithium salt may include, for example, LiDFOB.

[0078] The gel polymer electrolyte may not contain, for example, a phosphorus-based lithium salt. By not containing a phosphorus-based lithium salt, the high-temperature stability of the gel polymer electrolyte is improved and the generation of hydrofluoric acid (HF) can be suppressed.

[0079] The gel polymer electrolyte may not contain, for example, LiBOB. By not containing LiBOB in the gel polymer electrolyte, the ionic conductivity of the gel polymer electrolyte may be further improved and the solubility of the lithium salt in a carbonate solvent may be further improved.

[0080] The contents of the first lithium salt and the second lithium salt in the gel polymer electrolyte can be, for example, independently from each other, from more than 0 to 1.2 M, from 0.1 M to 1.0 M, or from 0.4 M to 0.8 M. By having the first lithium salt and the second lithium salt each having a content in this range, the gel polymer electrolyte can simultaneously provide excellent ionic conductivity and formation of a structurally stable SEI layer.

[0081] The content of the first lithium salt and the second lithium salt may be, for example, from more than 0 to 1.2 M, from 0.1 M to 1.0 M or from 0.4 M to 0.8 M, independently of each other, in the precursor composition for forming the gel polymer electrolyte before adding the first crosslinking monomer and the thermal initiator.

[0082] The content ratio of the first lithium salt and the second lithium salt may be, for example, 1:9 to 9:1, 3:7 to 7:3, or 4:6 to 6:4. When the first lithium salt and the second lithium salt have a content ratio within this range, the gel polymer electrolyte can simultaneously provide excellent ionic conductivity and the formation of a structurally stable SEI layer. The content ratio of the first lithium salt and the second lithium salt may be, for example, a molar ratio.

[0083] The gel polymer electrolyte may include an organic solvent. By including an organic solvent in the gel polymer electrolyte, the interfacial resistance between the gel polymer electrolyte and the positive electrode and / or the interfacial resistance between the gel polymer electrolyte and the lithium metal layer deposited during charging can be more effectively reduced.

[0084] The gel polymer electrolyte may include a first organic solvent. The gel polymer electrolyte may include, for example, a nitrile-based compound. The first organic solvent may be, for example, a nitrile-based organic solvent. By including a nitrile-based organic solvent in the gel polymer electrolyte, a cyano group (CN) may be easily formed in the first polymer.

[0085] The first organic solvent may include, for example, a linear nitrile-based compound. Since the first organic solvent is a linear nitrile-based organic solvent, the viscosity of the precursor composition before crosslinking may be reduced. Since the first organic solvent is a linear nitrile-based organic solvent, the handling of the precursor composition may be easier. The linear nitrile-based compound may include a saturated nitrile-based compound. Since the first organic solvent includes a saturated nitrile-based compound, side reactions between the gel polymer electrolyte and the lithium metal layer may be more effectively suppressed.

[0086] The first organic solvent may include, for example, acetonitrile, propionitrile, butyronitrile, valeronitrile, capronitrile, enanthonitrile, caprylonitrile, pelargonitrile, caprinonitrile, or a combination thereof.

[0087] The first organic solvent may include, for example, a saturated nitrile compound having 5 or fewer carbon atoms. The first organic solvent may include, for example, acetonitrile, propionitrile, butyronitrile, valeronitrile, or a combination thereof.

[0088] The content of the first organic solvent may be, for example, 1 to 20 vol% or 5 to 15 vol% based on the total volume of the first to third organic solvents. By including the first organic solvent in this range, a cyano group (CN) can be stably formed in the first polymer.

[0089] The gel polymer electrolyte may include a second organic solvent and a third organic solvent. The gel polymer electrolyte may include, for example, a carbonate-based compound. The second organic solvent and the third organic solvent may independently include a carbonate-based compound. Since the gel polymer electrolyte includes a carbonate-based organic solvent, the first lithium salt and the second lithium salt can be easily dissolved in the organic solvent, and the viscosity of the precursor composition for forming the gel electrolyte can be reduced.

[0090] The second organic solvent may include, for example, a linear carbonate compound. Since the second organic solvent is a linear carbonate-based organic solvent, the viscosity of the precursor composition before crosslinking may be reduced. Since the second organic solvent is a linear carbonate-based organic solvent, the handling of the precursor composition may be facilitated.

[0091] The third organic solvent may include, for example, a cyclic carbonate compound substituted with a substituent. The substituent of the cyclic carbonate compound may include, for example, a halogen, a cyano group (CN), a nitro group (NO2), or a combination thereof. Since the third organic solvent is a cyclic carbonate-based solvent substituted with a substituent, the first lithium salt and the second lithium salt may be more easily dissolved in the precursor composition for forming a gel electrolyte, and the substituent may be involved in the formation of the SEI layer, thereby improving the structural stability of the SEI layer.

[0092] The second organic solvent may include, for example, diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methyl propyl carbonate, ethyl propyl carbonate, dipropyl carbonate, or a combination thereof. The third organic solvent may include, for example, vinylene carbonate substituted with one or more substituents selected from a halogen, a cyano group (CN), and a nitro group (NO2); vinylethylene carbonate substituted with one or more substituents selected from a halogen, a cyano group (CN), and a nitro group (NO2); fluoroethylene carbonate (FEC); fluoroethylene carbonate substituted with one or more substituents selected from a halogen, a cyano group (CN), and a nitro group (NO2); or a combination thereof. The second organic solvent may include, for example, diethyl carbonate, and the third organic solvent may include, for example, a fluorine-substituted cyclic carbonate compound. The third organic solvent may include, for example, fluoroethylene carbonate. The gel polymer electrolyte may not include, for example, an unsubstituted cyclic carbonate solvent. By not including an unsubstituted cyclic carbonate solvent, the first lithium salt and the second lithium salt can be more easily dissolved in the precursor composition for forming the gel polymer.

[0093] The volume ratio of the second organic solvent and the third organic solvent may be, for example, 5.5:4.5 to 9:1, 6:4 to 9:1, 6:4 to 8:2, or 6:4 to 7:3. When the second organic solvent and the third organic solvent have a volume ratio in this range, a composition for forming a gel electrolyte having excellent lithium salt solubility and low viscosity can be provided. A gel polymer electrolyte obtained from the composition for forming a gel electrolyte having excellent lithium salt solubility and low viscosity can provide excellent mechanical properties and enhanced ionic conductivity.

[0094] The gel polymer electrolyte may not contain, for example, butanediol, thiourea, or a combination thereof. Since the gel polymer electrolyte provides a certain mechanical strength to the negative electrode current collector, a uniform lithium metal layer can be deposited on the negative electrode current collector without these additives.

[0095] A gel polymer electrolyte is a crosslinked product of a precursor composition for forming a gel polymer electrolyte. The precursor composition for forming a gel polymer electrolyte may include, for example, a first crosslinking monomer containing three or more reactive functional groups (1), a second crosslinking monomer containing a cyano group, a lithium salt, and an organic solvent. By crosslinking this precursor composition for forming a gel polymer electrolyte, a gel polymer electrolyte is obtained.

[0096] The sum of the content of the first crosslinking monomer and the content of the second crosslinking monomer may be, for example, 0.1 to 10 wt%, 1 to 8 wt%, or 3 to 6 wt% based on the total weight of the precursor composition for forming a gel polymer electrolyte.

[0097] By crosslinking the first crosslinking monomer, a first polymer including repeating units derived from the first crosslinking monomer can be obtained. By crosslinking the second crosslinking monomer, a first polymer including repeating units derived from the second crosslinking monomer can be obtained. The content ratio of the first crosslinking monomer and the second crosslinking monomer according to one embodiment may be, for example, 20:1 to 1:5, 10:1 to 1:1, or 9:1 to 3:1. When the first crosslinking monomer and the second crosslinking monomer have a content ratio within this range, the gel polymer electrolyte can simultaneously provide excellent ionic conductivity and formation of a structurally stable SEI layer. The content ratio of the first crosslinking monomer and the second crosslinking monomer may be, for example, a molar ratio. For example, the molecular weights of the first crosslinking monomer and the second crosslinking monomer may be 5:1 to 15:1. For example, the molecular weights of the first cross-linking monomer and the second cross-linking monomer may be about 10:1. When the precursor composition for forming a gel polymer electrolyte includes the first cross-linking monomer in this range, a stable gel polymer electrolyte can be formed. If the content of the first cross-linking monomer is too low, it may be difficult to form a gel. If the content of the first cross-linking monomer is too high, the gel polymer electrolyte may be excessively hardened, which may cause cracks or the like to occur within the gel polymer electrolyte during the charge and discharge process. When the precursor composition for forming a gel polymer electrolyte includes the second cross-linking monomer in this range, the morphological characteristics can be further improved.

[0098] The crosslinking method of the precursor composition for forming a gel polymer electrolyte is not particularly limited, and may be crosslinked by, for example, heat, ultraviolet rays, etc. Thermal crosslinking may be used from the viewpoint of manufacturing efficiency. The precursor composition for forming a gel polymer may include, for example, a thermal initiator. The thermal initiator is not limited to, for example, t-amyl peroxide, azobis, etc., and any thermal initiator used in the art may be used. The content of the thermal initiator may be 0.1 wt% or less or 0.05 wt% or less based on the total weight of the precursor composition for forming a gel polymer electrolyte. The crosslinked product of the precursor composition for forming a gel polymer electrolyte may be, for example, a result of heat treatment at 60 to 90°C for 1 to 3 hours. The heat treatment conditions may be adjusted depending on the type of thermal initiator used.

[0099] The ionic conductivity of the gel polymer electrolyte at 25°C and 1 atm can be, for example, 50% or more, 60% or more, 70% or more, or 80% or more of the ionic conductivity of the liquid electrolyte at 25°C and 1 atm excluding the first polymer. The ionic conductivity of the gel polymer electrolyte at 25°C and 1 atm can be, for example, 50% to 99%, 60% to 98%, 70% to 96%, or 80% to 95% of the ionic conductivity of the liquid electrolyte at 25°C and 1 atm excluding the first polymer. When the gel polymer electrolyte has an ionic conductivity in this range, the cycle characteristics of a lithium battery including the gel polymer electrolyte can be further improved. The gel polymer electrolyte may have an ionic conductivity of 0.10 mS / cm, 0.15 mS / cm or more, 0.20 mS / cm or more, or 0.25 mS / cm or more at 25 ℃ and 1 atm. The gel polymer electrolyte may have an ionic conductivity of 0.10 to 10.0 mS / cm, 0.15 to 5 mS / cm or more, 0.20 to 3 mS / cm or more, or 0.25 to 2 mS / cm at 25 ℃ and 1 atm. Since the gel polymer electrolyte has an ionic conductivity in this range, the internal resistance of a lithium battery including the gel polymer electrolyte is reduced, and as a result, the reversibility of the electrode reaction of the lithium battery can be improved. The ionic conductivity can be measured using, for example, an AC impedance analysis method.

[0100] Lithium transference number (t) of gel polymer electrolyte at 25 ℃ and 1 atm Li + ) may be greater than the lithium ion transfer rate at 25 ℃ and 1 atm of the liquid electrolyte excluding the first polymer. The lithium ion transfer rate (lithium transference number, t) of the gel polymer electrolyte at 25 ℃ and 1 atm Li +) may be more than 100%, 105% or more, or 100% or more of the lithium ion transfer rate at 25°C, 1 atm of the liquid electrolyte excluding the first polymer. Since the gel polymer electrolyte has a higher lithium ion transfer rate than the liquid electrolyte, the internal resistance of a lithium battery including the gel polymer electrolyte is reduced, and consequently, the reversibility of the electrode reaction of the lithium battery may be improved. The lithium ion transfer rate can be measured using, for example, an alternating current impedance analysis method. In claim 1, the lithium ion transfer rate of the gel polymer electrolyte at 25°C, 1 atm may be, for example, 0.30 or more, 0.31 or more, 0.32 or more, 0.33 or more, or 0.34 or more.

[0101] The electrolyte layer (300) may further include a porous substrate in addition to the gel polymer electrolyte.

[0102] The porous substrate may be, for example, a porous membrane. The porous membrane may be, for example, a microporous membrane. The porous membrane may be, for example, a woven fabric or a non-woven fabric. The porous membrane may be any material commonly used in lithium batteries. The porous membrane may include, for example, glass fiber, an olefin-based resin, a fluoropolymer, an ester-based resin, an imide-based resin, an acrylic resin, a cellulose-based resin, or a combination thereof. The olefin-based resin may include, for example, polyethylene, polypropylene, or a combination thereof. The fluoropolymer-based resin may include, for example, polyvinylidene fluoride, polytetrafluoroethylene, or a combination thereof. The ester-based resin may include, for example, polyethylene terephthalate, polybutylene terephthalate, or a combination thereof. The imide-based resin may include, for example, polyamideimide, polyetherimide, or a combination thereof. Acrylic resins may include, for example, polyacrylonitrile, polyacrylate, or combinations thereof. Cellulosic resins may include, for example, carboxymethylcellulose, microbial cellulose, plant cellulose, animal cellulose, or combinations thereof.

[0103] A gel polymer electrolyte can be impregnated into a porous substrate. A precursor composition for forming a gel polymer electrolyte can be injected into the porous substrate and then crosslinked to prepare a gel polymer electrolyte impregnated into the porous substrate. The porous substrate can be, for example, a porous membrane having excellent impregnation capability with the precursor composition for forming a gel polymer electrolyte. The porous substrate can be, for example, a separator.

[0104] The porous substrate is manufactured by the following exemplary methods, but is not limited to these methods and may be adjusted according to required conditions.

[0105] First, a porous membrane-forming composition is prepared by mixing a polymer resin, a filler, and a solvent. The porous membrane can be formed, for example, by directly coating the porous membrane-forming composition on the top of an electrode and drying it. Alternatively, the porous membrane-forming composition can be cast on a support and dried, and then the porous membrane peeled from the support and laminated on the top of an electrode to form a porous membrane. The polymer used in the preparation of the porous membrane is not particularly limited, and the resins described above can be used. Any polymer used as a binder for an electrode can be used. The polymer used in the preparation of the porous membrane can include, for example, a vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, or a combination thereof.

[0106] Referring to FIG. 1, a lithium metal battery (1000) according to one embodiment may include a negative electrode layer (200). The negative electrode layer (200) may include a negative electrode current collector (210).

[0107] The negative electrode current collector (210) may include, for example, a material that does not react with lithium, i.e., does not form an alloy or compound with lithium. The material constituting the negative electrode current collector (210) may include, for example, at least one metal selected from the group consisting of copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni). The thickness of the negative electrode current collector may be 1 to 20 μm, for example, 5 to 15 μm, for example, 7 to 10 μm.

[0108] The negative electrode current collector (210) may be composed of one of the above-described metals, or may include an alloy or coating material of two or more metals. The negative electrode current collector (210) is, for example, in the form of a plate or foil. In another embodiment, the negative electrode current collector (210) may be omitted.

[0109] Fig. 4 is for explaining a lithium metal battery (1000) according to another embodiment. Referring to Fig. 4, the lithium metal battery (1000) according to one embodiment may further include a lithium metal layer (240) disposed between the negative electrode current collector (210) and the electrolyte layer (300) by charging.

[0110] The lithium metal layer (240) may include lithium or a lithium alloy. Since the lithium metal layer (240) is a metal layer including lithium, it may function as a lithium reservoir, for example. The lithium alloy may be, but is not limited to, a Li-Al alloy, a Li-Sn alloy, a Li-In alloy, a Li-Ag alloy, a Li-Au alloy, a Li-Zn alloy, a Li-Ge alloy, a Li-Si alloy, etc., and any lithium alloy used in the art may be used. The lithium metal layer (240) may be formed of one of these alloys or lithium, or may be formed of several types of alloys. The lithium metal layer (240) may be, for example, a plated layer.

[0111] Thickness (d) of lithium metal layer (240) 240 ) is not particularly limited, but may be, for example, 1 μm to 500 μm, 1 μm to 200 μm, 1 μm to 150 μm, 1 μm to 100 μm, or 1 μm to 50 μm. If the thickness of the lithium metal layer (240) is too thin, it may be difficult for the lithium metal layer (240) to perform the role of a lithium reservoir. If the thickness of the lithium metal layer (240) is too thick, the mass and volume of the lithium metal battery (1000) may increase, and the cycle characteristics of the lithium metal battery (1000) may rather deteriorate.

[0112] In another implementation example, the lithium metal layer (240) in the negative electrode layer (200) may be provided between the negative electrode current collector (210) and the negative electrode coating layer (220), for example, before assembling the lithium metal battery (1000). When the lithium metal layer (240) is disposed between the negative electrode current collector (210) and the negative electrode coating layer (220) before assembling the lithium metal battery (1000), the lithium metal layer (240) acts as a lithium reservoir because it is a metal layer containing lithium. For example, a lithium foil may be disposed between the negative electrode current collector (210) and the negative electrode coating layer (220) before assembling the lithium metal battery (1000).

[0113] When the lithium metal layer (240) is precipitated by charging after assembling the lithium metal battery (1000), the energy density of the lithium metal battery (1000) can increase because the lithium metal layer (240) is not included when assembling the lithium metal battery (1000). When charging the lithium metal battery (1000), the charging can exceed the charging capacity of the negative electrode coating layer (220). That is, the negative electrode coating layer (220) is overcharged. At the initial stage of charging, lithium can be absorbed into the negative electrode coating layer (220). When charging exceeds the capacity of the negative electrode coating layer (220), lithium can be precipitated, for example, between the negative electrode coating layer (220) and the negative electrode current collector (210). The precipitated lithium can form a lithium metal layer (230).

[0114] The lithium metal layer (240) may be mainly composed of lithium (i.e., metallic lithium). When discharging, lithium in the lithium metal layer (240) may be ionized and move to the positive electrode layer (100). In other words, lithium may be used as an anode active material in the lithium metal battery (1000). In addition, since the anode coating layer (220) covers the lithium metal layer (240), the anode coating layer (220) may protect the lithium metal layer (240) and simultaneously suppress the precipitation and growth of lithium dendrites. Therefore, the anode coating layer (220) may suppress short-circuiting and capacity degradation of the lithium metal battery (1000) and improve the cycle characteristics of the lithium metal battery (1000).

[0115] When a lithium metal layer (240) is formed by charging after assembling a lithium metal battery (1000), the negative electrode layer (200), i.e., the negative electrode current collector (210) and the negative electrode coating layer (220) and the region between them may be a Li-free region that does not contain lithium (Li) in the initial state of the lithium metal battery (1000) or in the state after complete discharge.

[0116] Referring to FIG. 1, a lithium metal battery (1000) according to one embodiment may include a cathode layer (100). The cathode layer (100) may include a cathode current collector (110) and a cathode active material layer (120) disposed on one surface of the cathode current collector (110). The cathode active material layer (120) may include a cathode active material, a conductive material, and a binder.

[0117] The positive electrode current collector (110) can provide a reference surface on which the positive electrode active material layer (120) is arranged. The positive electrode current collector (110) can include a plate or foil including, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof.

[0118] Meanwhile, unlike that illustrated in FIG. 1, in one embodiment, the positive electrode current collector (110) may be omitted. Although not illustrated, a carbon layer having a thickness of 0.1 μm to 4 μm may be additionally disposed between the positive electrode current collector (110) and the positive electrode active material layer (120) to increase the bonding strength between the positive electrode current collector (110) and the positive electrode active material layer (120).

[0119] The cathode active material is a material that can reversibly absorb and desorb lithium ions. The cathode active material may include, but is not necessarily limited to, lithium transition metal oxides such as lithium cobalt oxide (LCO), lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCM), lithium manganate, and lithium iron phosphate, nickel sulfide, copper sulfide, lithium sulfide, iron oxide, or vanadium oxide. The cathode active materials may be used alone or as a mixture of two or more.

[0120] Lithium transition metal oxides include, for example, Li a A 1-b B b D2(0.90≤a≤1, 0≤b≤0.5), Li a E 1-b B b O 2-c D c (0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05), LiE 2-b B b O 4-c D c (0≤b≤0.5, 0≤c≤0.05), Li a Ni 1-b-c Co b B c D α (0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α<2), Li aNor 1-b-c Co b B c O 2-α F α (0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α<2), Li a Nor 1-b-c Mn b B c D α (0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α≤2), Li a Nor 1-b-c Mn b B c O 2-α F α (0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α<2), Li a Nor b E c G d O2(0.90≤a≤1, 0≤b≤0.9, 0≤c≤0.5, 0.001≤d≤0.1), Li a Nor b Co c Mn d GeO2(0.90≤a≤1, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0.001≤e≤0.1), Li a NiG b O2(0.9≤a≤1, 0.001≤b≤0.1), Li a CoG b O2(0.90≤a≤1, 0.001≤b≤0.1), Li a MnG b O2(0.90≤a≤1, 0.001≤b≤0.1), Li a Mn2GbO4(0.90≤a≤1, 0.001≤b≤0.1), QO2, QS2, LiQS2, V2O5, LiV2O5, LiIO2, LiNiVO4, Li 3-f J2(PO4)3(0≤f≤2), Li 3-fA compound represented by any one of Fe2(PO4)3(0≤f≤2), LiFePO4. In these compounds, the capital letter “A” is Ni, Co, Mn, or a combination thereof, the capital letter “B” is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof, the capital letter “D” is O, F, S, P, or a combination thereof, the capital letter “E” is Co, Mn, or a combination thereof, the capital letter “F” is F, S, P, or a combination thereof, the capital letter “G” is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof, the capital letter “Q” is Ti, Mo, Mn, or a combination thereof, the capital letter “I” is Cr, V, Fe, Sc, Y, or a combination thereof, and the capital letter “J” is V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

[0121] The cathode active material may include, for example, a lithium salt of a transition metal oxide having a layered rock salt type structure among the lithium transition metal oxides described above. The "layered rock salt type structure" is, for example, a cubic rock salt type structure. <111> It is a structure in which oxygen atomic layers and metal atomic layers are alternately and regularly arranged in a direction, and thereby each atomic layer forms a two-dimensional plane. The "cubic rock salt structure" refers to the sodium chloride type (NaCl type) structure, which is a type of crystal structure, and specifically refers to a structure in which the face-centered cubic lattice (fcc) formed by each cation and anion is arranged with a displacement of half of the ridge of the unit lattice. Lithium transition metal oxides having this layered rock salt structure include, for example, LiNi x Co y Al z O2(NCA) or LiNi x Co y Mn zO2(NCM) (0 <x<1,0<y<1, 0<z<1, x+y+z=1) 등의 삼원계 리튬전이금속산화물일 수 있다. 양극 활물질이 층상암염형 구조를 갖는 삼원계 리튬전이금속산화물을 포함하는 경우, 리튬금속전지(1000)의 에너지 밀도가 커지고 열안정성이 향상될 수 있다.

[0122] The above-described compound included in the positive electrode active material may be covered by a coating layer (not shown). The positive electrode active material may also be a mixture of the above-described compound and a compound to which a coating layer is added. Meanwhile, the coating layer added to the surface of the positive electrode active material may include, for example, an oxide, a hydroxide, an oxyhydroxide, an oxycarbonate, or a hydroxycarbonate of the coating elements below. The compound forming the coating layer is amorphous or crystalline. The coating elements included in the coating layer may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof. The coating layer may include, for example, Li2O-ZrO2 (LZO). The method for forming the coating layer is selected within a range that does not adversely affect the physical properties of the positive electrode active material. The method for forming the coating layer includes, for example, spray coating, dipping, etc.

[0123] When the positive electrode active material contains nickel (Ni) as a ternary lithium transition metal oxide such as NCA or NCM, for example, the capacity density of the lithium metal battery (1000) can be increased, thereby reducing metal dissolution of the positive electrode active material in a charged state. As a result, the cycle characteristics of the lithium metal battery (1000) in a charged state are improved. Meanwhile, the “cycle characteristics” are characteristics indicating the degree to which the lithium metal battery (1000) is deteriorated due to charge / discharge of the lithium metal battery (1000). A lithium metal battery (1000) having high cycle characteristics may have a small degree of deterioration of the lithium metal battery (1000) due to charge / discharge, and a lithium metal battery (1000) having low cycle characteristics may have a large degree of deterioration of the lithium metal battery (1000) due to charge / discharge.

[0124] The shape of the positive electrode active material may include particle shapes such as a sphere or an ellipsoid, for example. The particle size and content of the positive electrode active material are not particularly limited.

[0125] The positive electrode active material layer (120) may include a conductive material. The conductive material may be one that increases the conductivity of the positive electrode active material by providing conductivity without causing a chemical change in the lithium metal battery (1000). The conductive material may include a carbon-based material. The conductive material may include, for example, one or more selected from graphite, carbon black, acetylene black, carbon nanofibers, and carbon nanotubes.

[0126] The positive electrode active material layer (120) may further include a binder. The binder may include a material for binding the positive electrode active material and conductive material included in the positive electrode active material layer (120) and improving bonding strength with the positive electrode current collector (110). The binder may include, for example, polyvinylidene fluoride, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, and polymethyl methacrylate.

[0127] The positive electrode active material layer (120) may further include additives such as fillers, coating agents, dispersants, and ion conductive aids in addition to the positive electrode active material, conductive agent, and binder described above.

[0128] The following examples and comparative examples further illustrate the present invention. However, these examples are intended to illustrate the present invention and do not limit the scope of the present invention.

[0129] (Precursor composition and electrolyte)

[0130] Manufacturing Example 1: Organic solvent (FEC / DEC / BN = 42:48:10) + lithium salt (LiDFOB / LiBF4 = 1:1) + monomer (DPHA / acrylonitrile = 6:1)

[0131] A liquid electrolyte was prepared by adding 0.6 M LiBF4 and 0.6 M LiDFOB (lithium difluoro(oxalate)borate) to a 42:48:10 volume ratio mixed solvent of fluoroethylene carbonate (FEC), diethyl carbonate (DEC), and butyronitrile.

[0132] Dipentaerythritol hexaacrylate (DPHA) as a first crosslinking monomer and acrylonitrile as a second crosslinking monomer were added to a liquid electrolyte at a molar ratio of 6:1. t-Amyl peroxide was added as a thermal initiator to prepare a precursor composition for forming a gel polymer electrolyte.

[0133] The DPHA content included in the precursor composition for forming a gel electrolyte was 2 wt% with respect to the total weight of the precursor composition for forming a gel electrolyte, and the t-amyl peroxide content was 0.02 wt% with respect to the total weight of the precursor composition for forming a gel electrolyte.

[0134] After impregnating the prepared precursor composition for forming a gel electrolyte into a polyethylene separator, a gel polymer electrolyte was prepared by thermal crosslinking in an oven at 70°C for 1 hour and 30 minutes.

[0135] Manufacturing Example 2: Organic solvent (FEC / DEC / BN = 42:48:10) + lithium salt (LiDFOB / LiBF4 = 1:1) + monomer (DPHA / acrylonitrile = 3:1)

[0136] A precursor composition for forming a gel polymer electrolyte and a gel polymer electrolyte were prepared in the same manner as in Manufacturing Example 1, except that dipentaerythritol hexaacrylate (DPHA) as a first crosslinking monomer and acrylonitrile as a second crosslinking monomer were added to the liquid electrolyte at a molar ratio of 3:1.

[0137] Manufacturing Example 3: Organic solvent (FEC / DEC / BN = 42:48:10) + lithium salt (LiDFOB / LiBF4 = 1:1) + monomer (DPHA / 3-butenenitrile = 6:1)

[0138] A precursor composition for forming a gel polymer electrolyte and a gel polymer electrolyte were prepared in the same manner as in Manufacturing Example 1, except that dipentaerythritol hexaacrylate (DPHA) as a first crosslinking monomer and But-3-enenitrile as a second crosslinking monomer were added to the liquid electrolyte at a molar ratio of 6:1.

[0139] Manufacturing Example 4: Organic solvent (FEC / DEC / PN = 42:48:10) + lithium salt (LiDFOB / LiBF4 = 1:1) + monomer (DPHA / acrylonitrile = 6:1)

[0140] A precursor composition for forming a gel polymer electrolyte and a gel polymer electrolyte were prepared in the same manner as in Manufacturing Example 1, except that a mixed solvent of fluoroethylene carbonate (FEC), diethyl carbonate (DEC), and propionitrile in a volume ratio of 42:48:10 was used in the organic solvent.

[0141] Manufacturing Example 5: Organic solvent (FEC / DEC / AN = 42:48:10) + lithium salt (LiDFOB / LiBF4 = 1:1) + monomer (DPHA / acrylonitrile = 6:1)

[0142] A precursor composition for forming a gel polymer electrolyte and a gel polymer electrolyte were prepared in the same manner as in Manufacturing Example 1, except that a mixed solvent of fluoroethylene carbonate (FEC), diethyl carbonate (DEC), and acetonitrile (42:48:10 by volume) was used in the organic solvent.

[0143] Comparative Manufacturing Example 1: Organic solvent (FEC / DEC = 47:53) + lithium salt (LiDFOB / LiBF4 = 1:1)

[0144] A precursor composition for forming an electrolyte was prepared in the same manner as in Manufacturing Example 1, except that a 47:53 volume ratio mixed solvent of fluoroethylene carbonate (FEC) and diethyl carbonate (DEC) was used in the organic solvent without adding a monomer or a thermal cross-linking agent. The prepared composition is a liquid electrolyte.

[0145] A liquid electrolyte was prepared by impregnating a polyethylene separator with the prepared precursor composition for forming a gel electrolyte.

[0146] Comparative Manufacturing Example 2: Organic solvent (FEC / DEC / BN = 42:48:10) + lithium salt (LiDFOB / LiBF4 = 1:1) + monomer (acrylonitrile)

[0147] A precursor composition for forming a gel polymer electrolyte and a gel polymer electrolyte were each prepared in the same manner as in Manufacturing Example 1, except that the first crosslinking monomer was not added to the liquid electrolyte.

[0148] Comparative Manufacturing Example 3: Organic solvent (FEC / DEC = 47:53) + lithium salt (LiDFOB / LiBF4 = 1:1) + monomer (DPHA / acrylonitrile = 6:1)

[0149] A precursor composition for forming a gel polymer electrolyte and a gel polymer electrolyte were prepared in the same manner as in Manufacturing Example 1, except that a mixed solvent of fluoroethylene carbonate (FEC) and diethyl carbonate (DEC) in a volume ratio of 47:53 was used in the organic solvent.

[0150] (lithium battery)

[0151] Example 1

[0152] (Manufacturing of negative electrode collector)

[0153] Copper foil with a thickness of 10 μm was used as the negative electrode collector.

[0154] (Polar electrode manufacturing)

[0155] LiNi 0.8 Co 0.15 Al 0.05 O2(NCA) powder and carbon conductive material (Super-P; Timcal Ltd.) were uniformly mixed at a weight ratio of 90:5, and then a PVDF (polyvinylidene fluoride) binder solution was added to prepare a positive electrode active material slurry so that the weight ratio of active material:carbon conductive material:binder = 90:5:5.

[0156] The manufactured slurry was coated on a 20 ㎛ thick aluminum substrate using a doctor blade, dried under reduced pressure at 120 ℃, and then rolled using a roll press into a sheet shape to manufacture a positive electrode. The thickness of the positive electrode active material layer was 80 ㎛.

[0157] (lithium battery manufacturing)

[0158] A polyethylene separator was placed between the manufactured positive and negative electrode current collectors to prepare a laminate. The precursor composition for forming a gel polymer electrolyte manufactured in Manufacturing Example 1 was injected into the prepared laminate, and then thermally crosslinked in an oven at 70°C for 1 hour and 30 minutes to manufacture a lithium battery including a gel polymer electrolyte.

[0159] Lithium batteries have a positive electrode / gel polymer electrolyte (separator) / negative electrode current collector structure.

[0160] Examples 2 to 5

[0161] A lithium battery was manufactured in the same manner as in Example 1, except that the precursor compositions for forming a gel electrolyte manufactured in Manufacturing Examples 2 to 5 were used instead of the precursor composition for forming a gel electrolyte manufactured in Manufacturing Example 1.

[0162] Comparative Examples 1 to 3

[0163] A lithium battery was manufactured in the same manner as in Example 1, except that the precursor compositions for forming a gel electrolyte manufactured in Comparative Manufacturing Examples 1 to 3 were used instead of the precursor composition for forming a gel electrolyte manufactured in Manufacturing Example 1. The lithium battery of Comparative Example 1, which includes the liquid electrolyte of Comparative Manufacturing Example 1, was prepared without thermal cross-linking.

[0164]

[0165] Evaluation Example 1: Coordination number analysis of gel polymer electrolyte

[0166] To obtain statistical information on the interaction between lithium and reactive functional groups, coordination number analysis was performed on the gel polymer electrolytes prepared according to Example 1 and Comparative Example 1. The peak of the Radial Distribution Function (RDF) for the Li-O pair was measured for each lithium, and the graph obtained from the RDF peak magnitude value is shown in Fig. 5.

[0167] In Example 1, it was confirmed that the RDF peak magnitude at the peak corresponding to the Li-O bond was measured to be greater than in Comparative Example 1.

[0168] Evaluation Example 2: Charge / Discharge Test

[0169] A high-temperature (45°C) charge-discharge test was performed on the lithium batteries of Examples 1 to 5 and Comparative Examples 1 to 3 under the following conditions.

[0170] The lithium battery was charged at a constant current of 0.2 C at 45°C until the voltage reached 4.3 V. Subsequently, it was discharged at a constant current of 0.5 C until the voltage reached 3.6 V. The discharge capacity for one charge-discharge cycle was measured.

[0171] These charge-discharge cycles were repeated 80 times, and the discharge capacity for 80 charge-discharge cycles was measured.

[0172] In all charge / discharge cycles, a 5-minute pause was provided after each charge / discharge cycle. The results of the room-temperature charge / discharge experiments are shown in Table 1 below. The capacity retention rate is defined by the following mathematical equation (1).

[0173] <Mathematical Formula 1>

[0174] Capacity retention rate [%] = [80 th Discharge capacity in cycle / 1 st Discharge capacity in cycle] × 100(%)

[0175] Initial Capacity (mAh) Capacity Retention Rate [@80 cycle, &] Example 1 (FEC / DEC / BN = 42:48:10) + (DPHA / acrylonitrile = 6:1) 40.273197.02 Example 2 (FEC / DEC / BN = 42:48:10) + (DPHA / acrylonitrile = 3:1) 40.181391.65 Example 3 (FEC / DEC / BN = 42:48:10) + (DPHA / 3-butenenitrile = 6:1) 38.117293.73 Example 4 (FEC / DEC / PN = 42:48:10) + (DPHA / acrylonitrile = 6:1) 37.2096.04 Example 5 (FEC / DEC / AN = 42:48:10) +(DPHA / acrylonitrile = 6:1)40.704488.93 Comparative Example 1 (FEC / DEC = 47:53)41.822179.69 Comparative Example 2 (FEC / DEC / BN = 42:48:10) +(acrylonitrile)36.078877.18 Comparative Example 3 (FEC / DEC = 47:53) +(DPHA / acrylonitrile = 6:1)36.484887.86

[0176] As shown in Table 1, the lithium batteries of Examples 1 to 5 have improved life characteristics compared to the lithium batteries of Comparative Examples 1 to 3. Although exemplary embodiments have been described in detail with reference to the attached drawings, the present invention is not limited to these examples. It is obvious that a person having ordinary skill in the art to which the present invention pertains can derive various modifications or variations within the scope of the technical ideas described in the claims, and these also naturally fall within the technical scope of the present invention.

Claims

A first polymer comprising a repeating unit derived from a first crosslinking monomer having three or more reactive functional groups, and a repeating unit derived from a second crosslinking monomer having a cyano group (CN); lithium salt; and A gel polymer electrolyte comprising a first organic solvent which is a nitrile-based organic solvent. In the first paragraph, The first crosslinking monomer contains an ester group, The above first crosslinking monomer is an acrylic monomer, The above acrylic monomers are trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, trimethylolpropane ethoxylate triacrylate, trimethylolpropane propoxylate triacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, pentaerythritol ethoxylate tetraacrylate, dipentaerythritol pentaacrylate, A gel polymer electrolyte comprising dipentaerythritol hexaacrylate or a combination thereof. In the first paragraph, The second crosslinking monomer comprises an ethylene group and a cyano group (CN), The second crosslinking monomer is acrylonitrile, propenenitrile, butenenitrile, pentenenitrile, hexenenitrile, heptenenitrile, octenenitrile, nonenenitrile, decenenitrile, acryloisocyanide, propeneisocyanide, buteneisocyanide, penteneisocyanide, hexeneisocyanide, hepteneisocyanide, octeneisocyanide, noneneisocyanide. A gel polymer electrolyte comprising nonenisocyanide, deceneisocyanide, or a combination thereof. In the first paragraph, The second crosslinking monomer comprises an ethylene group and a cyano group (CN), The second crosslinking monomer contains a carbon double bond at one terminal of the compound, A gel polymer electrolyte, wherein the second crosslinking monomer comprises acrylonitrile, propenenitrile, butenenitrile, pentenenitrile, hexanenitrile, heptenenitrile, octenenitrile, nonenenitrile, decenenitrile, or a combination thereof. In the first paragraph, A gel polymer electrolyte, wherein the content of the first polymer is 0.1 to 15 wt% of the total weight of the gel polymer electrolyte. In the first paragraph, The above lithium salt comprises a first lithium salt and a second lithium salt, The first lithium salt and the second lithium salt each independently contain a fluorine-containing borate lithium salt, A gel polymer electrolyte, wherein the fluorine-containing borate lithium salt comprises LiBF4, LiBF3(CF3), LiBF3(C2F5), LiBF3(C3F7), LiDFOB or a combination thereof. In the first paragraph, The contents of the first lithium salt and the second lithium salt are each greater than 0 and less than or equal to 1.2 M, A gel polymer electrolyte in which the content ratio of the first lithium salt and the second lithium salt is 1:9 to 9:

1. In the first paragraph, The first organic solvent comprises a linear nitrile compound, A gel polymer electrolyte, wherein the first organic solvent comprises acetonitrile, propionitrile, butyronitrile, valeronitrile, capronitrile, enanthonitrile, caprylonitrile, pelargonitrile, caprinonitrile, or a combination thereof. In the first paragraph, a second organic solvent; and Further comprising a third organic solvent, The second organic solvent and the third organic solvent include a carbonate compound, The second organic solvent comprises a linear carbonate compound, The third organic solvent comprises a cyclic carbonate compound substituted with a substituent, A gel polymer electrolyte, wherein the substituent comprises a halogen, a cyano group (CN), a nitro group (NO2), or a combination thereof. In paragraph 9, A gel polymer electrolyte, wherein the content of the first organic solvent is 1 to 20 vol% based on the total volume of the first to third organic solvents. In paragraph 9, A gel polymer electrolyte, wherein the second organic solvent comprises diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methyl propyl carbonate, ethyl propyl carbonate, dipropyl carbonate, or a combination thereof. In paragraph 9, A gel polymer electrolyte comprising the third organic solvent, wherein the third organic solvent comprises vinylene carbonate substituted with one or more substituents selected from a halogen, a cyano group (CN), and a nitro group (NO2); vinylethylene carbonate substituted with one or more substituents selected from a halogen, a cyano group (CN), and a nitro group (NO2); fluoroethylene carbonate (FEC); fluoroethylene carbonate substituted with one or more substituents selected from a halogen, a cyano group (CN), and a nitro group (NO2); or a combination thereof. In paragraph 9, A gel polymer electrolyte, wherein the volume ratio of the second organic solvent and the third organic solvent is 5.5:4.5 to 9:

1. In the first paragraph, The above gel polymer electrolyte is a crosslinked product of the precursor composition, The precursor composition comprises the first crosslinking monomer, the second crosslinking monomer and a thermal initiator, The sum of the content of the first crosslinking monomer and the content of the second crosslinking monomer is 0.1 to 10 wt% with respect to the total weight of the precursor composition, The above thermal initiator comprises t-amyl peroxide, azobis or a combination thereof, The above crosslinked product is a gel polymer electrolyte which is the result of heat treatment at 60 to 90°C for 1 to 3 hours. In the first paragraph, A gel polymer electrolyte having an ionic conductivity of 0.10 mS / cm or more at 25°C and 1 atm. In the first paragraph, A gel polymer electrolyte having a lithium ion transfer rate of 0.30 or more at 25 ℃1 atm. bipolar layer; negative current collector; and It includes an electrolyte layer disposed between the positive electrode layer and the negative electrode current collector, A lithium metal battery, wherein the electrolyte layer comprises the gel polymer electrolyte of claim 1. In Article 17, The above electrolyte layer further includes a porous substrate, The above porous substrate is a porous membrane, The above porous membrane is a woven or non-woven fabric, The above porous substrate includes an olefin resin, a fluorine resin, an ester resin, an imide resin, an acrylic resin, a cellulose resin, or a combination thereof, The above olefin resin includes polyethylene, polypropylene or a combination thereof, The above fluorine resin includes polyvinylidene fluoride, polytetrafluoroethylene or a combination thereof, The above ester resin includes polyethylene terephthalate, polybutylene terephthalate or a combination thereof, The above imide resin includes polyamideimide, polyetherimide or a combination thereof, The above acrylic resin includes polyacrylonitrile, polyacrylate or a combination thereof, A lithium metal battery, wherein the cellulose-based resin comprises carboxymethyl cellulose, microbial cellulose, plant cellulose, animal cellulose, or a combination thereof. In Article 17, A lithium metal battery, wherein the negative electrode current collector comprises at least one metal selected from the group consisting of copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni). In Article 17, Further comprising a lithium metal layer disposed between the negative electrode current collector and the electrolyte layer, The above lithium metal layer comprises lithium or a lithium alloy, A lithium metal battery, wherein the lithium alloy comprises a Li-Al alloy, a Li-Sn alloy, a Li-In alloy, a Li-Ag alloy, a Li-Au alloy, a Li-Zn alloy, a Li-Ge alloy, a Li-Si alloy, or a combination thereof.

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