Lithium battery

Abstract

Provided is a lithium battery comprising: a positive electrode; a negative electrode current collector; and an electrolyte layer disposed between the positive electrode and the negative electrode current collector, wherein the electrolyte layer comprises a gel polymer electrolyte, the gel polymer electrolyte comprises a first polymer, a first lithium salt, a second lithium salt, a first organic solvent, and a second organic solvent, the first polymer comprises a repeating unit derived from a first cross-linking monomer including three or more reactive functional groups, and the first lithium salt and the second lithium salt each independently include a borate-based lithium salt.

Description

lithium batteries

[0001] It's about lithium 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] In a non-anode lithium battery, the anode active material layer is omitted during lithium battery assembly. By omitting the anode active material layer in the lithium battery, the energy density of the lithium battery is improved.

[0006] During the charging and discharging of a lithium-ion battery, a lithium metal layer is deposited between the electrolyte and the negative electrode current collector, and the deposited lithium metal layer is dissolved. As the lithium battery is repeatedly charged and discharged, the lithium metal layer contains impurities and electrolyte decomposition products that remain in the electrode due to side reactions with 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.

[0007] 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.

[0008] According to the implementation example

[0009] A cathode; a cathode current collector; and an electrolyte layer disposed between the cathode and the cathode current collector,

[0010] The above electrolyte layer includes a gel polymer electrolyte,

[0011] The above gel polymer electrolyte comprises a first polymer, a first lithium salt, a second lithium salt, a first organic solvent, and a second organic solvent,

[0012] The first polymer comprises a repeating unit derived from a first crosslinking monomer containing three or more reactive functional groups,

[0013] A lithium battery is provided, wherein the first lithium salt and the second lithium salt independently include a borate-based lithium salt.

[0014] According to one aspect, by providing a novel gel polymer electrolyte having excellent ion conductivity, it is possible to provide a lithium battery having suppressed volume change during charge and discharge and improved cycle characteristics.

[0015] Figure 1 is a cross-sectional schematic diagram of a lithium battery according to an exemplary embodiment.

[0016] Figure 2 is a cross-sectional schematic diagram of a lithium battery according to an exemplary embodiment.

[0017] Figure 3a is a scanning electron microscope image of the surface of a lithium metal layer formed after the first cycle of charging in the lithium battery of Example 3.

[0018] Figure 3b is a scanning electron microscope image of a cross-section of a lithium metal layer formed after the first cycle of charging in the lithium battery of Example 3.

[0019] Figure 4a is a scanning electron microscope image of the surface of a lithium metal layer formed after the first cycle of charging in the lithium battery of Comparative Example 1.

[0020] Figure 4b is a scanning electron microscope image of the surface of a lithium metal layer formed after the first cycle of charging in the lithium battery of Comparative Example 1.

[0021] Figure 5a is a scanning electron microscope image of the surface of a lithium metal layer formed after the 60th cycle of charging in the lithium battery of Example 3.

[0022] Figure 5b is a scanning electron microscope image of a cross-section of a lithium metal layer formed after the 60th cycle of charging in the lithium battery of Example 3.

[0023] Figure 6a is a scanning electron microscope image of the surface of a lithium metal layer formed after the 60th cycle of charging in the lithium battery of Comparative Example 1.

[0024] Figure 6b is a scanning electron microscope image of the surface of the lithium metal layer formed after the 60th cycle of charging in the lithium battery of Comparative Example 1.

[0025] Figure 7 is an XPS spectrum of the surface of the lithium metal layer after 20 cycles of the lithium battery manufactured in Example 3.

[0026] Figure 8 is an XPS spectrum of the surface of the lithium metal layer after 20 cycles of the lithium battery manufactured in Comparative Example 1.

[0027] Figure 9 is an infrared spectrum for the gel polymer electrolyte of Example 3 and the liquid electrolyte of Comparative Example 1.

[0028] Figure 10 is a Raman spectrum for the gel polymer electrolyte of Example 3 and the liquid electrolyte of Comparative Example 1.

[0029] Figure 11 is a schematic diagram of a lithium battery according to an exemplary embodiment.

[0030] Figure 12 is a schematic diagram of a lithium battery according to an exemplary embodiment.

[0031] Figure 13 is a schematic diagram of a lithium battery according to an exemplary embodiment.

[0032] Figure 14 is a schematic diagram of a lithium battery according to an exemplary embodiment.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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 can be arranged in other orientations (rotated 90 degrees or otherwise rotated), and the spatially relative terms used herein can be interpreted accordingly.

[0040] "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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] In this disclosure, “metal” includes both metals and metalloids such as silicon and germanium, in their elemental or ionic states.

[0046] In this disclosure, “alloy” means a mixture of two or more metals.

[0047] In the present disclosure, “electrode active material” means an electrode material capable of undergoing lithiation and delithiation.

[0048] In the present disclosure, “positive electrode material” means a positive electrode material capable of undergoing lithiation and delithiation.

[0049] In the present disclosure, “negative electrode active material” means a negative electrode material capable of undergoing lithiation and delithiation.

[0050] In the present disclosure, “lithiation” and “lithiating” mean a process of adding lithium to an electrode active material.

[0051] In the present disclosure, “delithiation” and “delithiate” mean a process of removing lithium from an electrode active material.

[0052] In this disclosure, “charging” and “charging” mean a process of providing electrochemical energy to a battery.

[0053] In this disclosure, “discharging” and “discharging” mean the process of removing electrochemical energy from a battery.

[0054] In the present disclosure, “positive electrode” and “cathode” mean an electrode at which electrochemical reduction and lithiation occur during a discharge process.

[0055] In the present disclosure, “cathode” and “anode” mean electrodes where electrochemical oxidation and delithiation occur during a discharge process.

[0056] 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.

[0057] Below, lithium batteries according to exemplary implementation examples are described in more detail.

[0058] [Lithium battery]

[0059] According to one embodiment, a lithium battery includes a positive electrode; a negative electrode current collector; and an electrolyte layer disposed between the positive electrode and the negative electrode current collector. The electrolyte layer includes a gel polymer electrolyte. The gel polymer electrolyte includes a first polymer, a first lithium salt, a second lithium salt, a first organic solvent, and a second organic solvent. The first polymer includes repeating units derived from a first crosslinking monomer including three or more reactive functional groups. The first lithium salt and the second lithium salt independently include a borate-based lithium salt.

[0060] 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.

[0061] The gel polymer electrolyte can effectively prevent deterioration of a lithium battery by suppressing side reactions with the lithium metal layer during charge and discharge of the lithium battery. 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 a precipitated lithium metal layer. 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 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.

[0062] Since the gel polymer electrolyte includes the first lithium salt and the second lithium salt, the ester group of the first polymer can interact with lithium ions to more effectively change the solvation structure of the lithium ions. The aggregation of anions derived from the first lithium salt and the second lithium salt increases, and inorganic components such as fluorine (F) derived from the aggregation of anions during the charge / discharge process can modify the composition of the SEI layer, thereby improving the cycle characteristics of the lithium battery.

[0063] Since the gel polymer electrolyte includes a first organic solvent and a second organic solvent, the carbonyl groups of the organic solvents can interact with lithium ions to more effectively change the solvation structure of the lithium ions. The aggregation of anions derived from the first lithium salt and the second lithium salt increases, and inorganic components such as fluorine (F) derived from the aggregation of anions during the charge / discharge process can modify the composition of the SEI layer, thereby improving the cycle characteristics of the lithium battery.

[0064] As a result, the cycle characteristics of a lithium battery having a gel polymer electrolyte can be improved.

[0065] Figure 1 is a cross-sectional schematic diagram of a lithium battery according to an embodiment.

[0066] Referring to FIG. 1, a lithium metal battery (1) includes a positive electrode (10); a negative electrode current collector (21); and an electrolyte layer (30) disposed between the positive electrode (10) and the negative electrode current collector (21). The electrolyte layer (30) includes a gel polymer electrolyte. The gel polymer electrolyte includes a first polymer, a first lithium salt, a second lithium salt, a first organic solvent, and a second organic solvent. The first polymer includes a repeating unit derived from a first crosslinking monomer including three or more reactive functional groups. The first lithium salt and the second lithium salt independently include a borate-based lithium salt.

[0067] [Electrolyte layer]

[0068] The electrolyte layer (30) includes a gel polymer electrolyte. The gel polymer electrolyte includes a first polymer, a first lithium salt, a second lithium salt, a first organic solvent, and a second organic solvent.

[0069] A gel polymer electrolyte can form a gel by including a first polymer. An electrolyte without a first polymer is a liquid electrolyte.

[0070] The first polymer comprises repeating units derived from a first crosslinking monomer, for example, comprising 3 or more, 4 or more, 5 or more, or 6 or more reactive functional groups. The first crosslinking monomer may comprise, for example, 3 to 20, 3 to 10, 3 to 8, or 4 to 6 reactive functional groups. The first crosslinking monomer may comprise, for example, 3 to 20, 4 to 15, 5 to 10, or 6 to 10 reactive functional groups. When the first crosslinking monomer comprises reactive functional groups in this range, a gel polymer electrolyte comprising the first 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, the mechanical properties of the gel polymer electrolyte may be excessively deteriorated. If the first crosslinking monomer has an excessively large number of reactive functional groups, the crosslinking density may increase excessively, which may excessively lower the ionic conductivity of the gel polymer.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] The first polymer may be a crosslinking product of the first crosslinking monomer.

[0077] The molecular weight of the first polymer may be, for example, greater than or equal to 1000 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 1000 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.

[0078] The content of the first polymer may be, for example, 0.1 to 10 wt%, 0.2 to 8 wt%, 0.5 to 6 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 or the like to occur within the gel polymer electrolyte during the charge and discharge process, 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.

[0079] The gel polymer electrolyte includes a first lithium salt and a second lithium salt. By including the first lithium salt and the second lithium salt in the gel polymer electrolyte, the ionic conductivity of the gel polymer electrolyte can be improved.

[0080] The first and second lithium salts are borate-based lithium salts. Compared to phosphorus-based lithium salts, borate-based lithium salts exhibit improved high-temperature stability 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 lithium batteries can be improved.

[0081] The first lithium salt and the second lithium salt may, for example, be independently a fluorine-containing borate-based lithium salt. By including a 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.

[0082] 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.

[0083] 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.

[0084] Fluorine-containing borate lithium salts may include, for example, LiBF4, LiBF3(C2F5), compounds represented by chemical formulas 1 to 12, or combinations thereof.

[0085] <Chemical Formula 1> <Chemical Formula 2>

[0086]

[0087] <Chemical Formula 3> <Chemical Formula 4>

[0088]

[0089] <Chemical Formula 5> <Chemical Formula 6>

[0090]

[0091] <Chemical Formula 7> <Chemical Formula 8>

[0092]

[0093] <Chemical Formula 9> <Chemical Formula 10>

[0094]

[0095] <Chemical Formula 11> <Chemical Formula 12>

[0096] .

[0097] The first lithium salt may include, for example, LiBF4, and the second lithium salt may include a compound selected from compounds represented by chemical formulas 1 to 12.

[0098] The first lithium salt may include LiBF4, and the second lithium salt may include, for example, a compound of formula 1.

[0099] 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.

[0100] 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 the carbonate solvent may be further improved.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] The gel polymer electrolyte includes a first organic solvent and a second organic solvent. By including the first organic solvent and the second 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. The first organic solvent and the second organic solvent include, for example, a carbonate-based compound. The first organic solvent and the second organic solvent are, for example, carbonate-based organic solvents. By including the first carbonate-based organic solvent and the second carbonate-based organic solvent in the gel polymer electrolyte, 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 lowered. The first organic solvent includes, for example, a linear carbonate compound. By including the first organic solvent as a linear carbonate-based solvent, the viscosity of the precursor composition before crosslinking can be lowered. The handling of the precursor composition may be easier. The second organic solvent includes, for example, a cyclic carbonate compound substituted with a substituent. The substituent of the cyclic carbonate compound includes, for example, a halogen, a cyano group (CN), a nitro group (NO2), or a combination thereof. Since the second 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 participate in the formation of the SEI layer, thereby improving the structural stability of the SEI layer. The first 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 second organic solvent may include, for example, vinylene carbonate substituted with one or more substituents selected from halogen, cyano group (CN), and nitro group (NO2); vinylethylene carbonate substituted with one or more substituents selected from halogen, cyano group (CN), and nitro group (NO2); fluoroethylene carbonate (FEC); fluoroethylene carbonate substituted with one or more substituents selected from halogen, cyano group (CN), and nitro group (NO2); or a combination thereof. The first organic solvent may include, for example, diethyl carbonate, and the second organic solvent may include, for example, a fluorine-substituted cyclic carbonate compound. The second 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 a gel polymer. The volume ratio of the first organic solvent and the second organic solvent can 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 first organic solvent and the second organic solvent have a volume ratio within 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.

[0105] 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 even without these additives.

[0106] 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 includes, for example, a first crosslinking monomer including three or more reactive functional groups, a first lithium salt, a second lithium salt, a first organic solvent, and a second organic solvent. By crosslinking this precursor composition for forming a gel polymer electrolyte, a gel polymer electrolyte is obtained. By crosslinking the first crosslinking monomer, a first polymer including repeating units derived from the first crosslinking monomer is obtained. The content of the first crosslinking monomer may be, for example, 0.1 to 10 wt%, 0.2 to 8 wt%, 0.5 to 6 wt%, 1 to 5 wt%, or 2 to 4 wt% based on the total weight of the precursor composition for forming a gel polymer electrolyte. A precursor composition for forming a gel polymer electrolyte can form a stable gel polymer electrolyte by including the first cross-linking monomer within this range. 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 / discharge process.

[0107] The crosslinking method of the precursor composition for forming a gel polymer electrolyte is not particularly limited, and may be crosslinked, for example, by 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.

[0108] 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.

[0109] Lithium transference number (t) of gel polymer electrolyte at 25 ℃ and 1 atm Li + ) can 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 110% 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 as a result, 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.

[0110] [Electrolyte: Porous substrate]

[0111] The electrolyte layer (30) may further include a porous substrate in addition to the gel polymer electrolyte.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] [cathode]

[0117] Referring to FIG. 1, a lithium battery (1) according to one embodiment includes a negative electrode (20), and the negative electrode (20) includes a negative electrode collector (21).

[0118] [Cathode: Negative current collector]

[0119] The negative electrode current collector (21) includes, for example, a metal substrate. The metal substrate includes a first metal as a main component or is made of the first metal. The metal substrate includes a first metal as a main component or is made of the first metal. The content of the first metal included in the metal substrate is, for example, 90 wt% or more, 95 wt% or more, 99 wt% or more, or 99.9 wt% or more based on the total weight of the metal substrate. The metal substrate may be made of, for example, a material that does not react with lithium, i.e., does not form an alloy and / or compound with lithium. The first metal is, for example, copper (Cu), nickel (Ni), stainless steel (SUS), iron (Fe), and cobalt (Co), but is not necessarily limited thereto, and any metal used as a current collector in the relevant technical field may be used. The first metal substrate may be made of, for example, one of the above-described metals, or may be made of an alloy of two or more metals. The metal substrate is, for example, in the form of a sheet or foil. The thickness of the negative electrode current collector (21) may be, for example, 5 µm to 50 µm, 10 µm to 50 µm, 10 µm to 40 µm, or 10 µm to 30 µm, but is not necessarily limited to this range and may be selected depending on the characteristics of the required lithium metal battery.

[0120] The negative electrode current collector (21) may further include a coating layer (not shown) containing a second metal on a metal substrate. The negative electrode current collector (21) may include, for example, a metal substrate; and a coating layer disposed on the metal substrate and containing a second metal. The second metal has a higher Mohs hardness than the first metal. That is, since the coating layer containing the second metal is harder than the metal substrate containing the first metal, deterioration of the first metal substrate can be prevented. The Mohs hardness of the material constituting the metal substrate is, for example, 5.5 or less. The Mohs hardness of the first metal is, for example, 5.5 or less, 5.0 or less, 4.5 or less, 4.0 or less, 3.5 or less, or 3.0 or less. The Mohs hardness of the first metal may be, for example, 2.0 to 6.0. The Mohs hardness of the material constituting the coating layer is, for example, 6.0 or more. For example, the Mohs hardness of the second metal is 6.0 or more, 6.5 or more, 7.0 or more, 7.5 or more, 8.0 or more, 8.5 or more, or 9.0 or more. The Mohs hardness of the second metal may be, for example, 6.0 to 12. If the Mohs hardness of the second metal is too low, it may be difficult to suppress deterioration of the negative electrode current collector. If the Mohs hardness of the second metal is too high, processing may not be easy. The second metal is, for example, one or more selected from titanium (Ti), manganese (Mn), niobium (Nb), tantalum (Ta), iridium (Ir), vanadium (V), rhenium (Re), osmium (Os), tungsten (W), chromium (Cr), boron (B), ruthenium (Ru), and rhodium (Rh). The thickness of the coating layer can be, for example, 10 nm to 1 μm, 50 nm to 500 nm, 50 nm to 200 nm, or 50 nm to 150 nm.

[0121] Alternatively, the negative electrode current collector (21) may include, for example, a base film and a metal layer disposed on one or both sides of the base film. The base film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof. The base film may be, for example, an insulator. Since the base film includes an insulating thermoplastic polymer, when a short circuit occurs, the base film softens or liquefies, thereby blocking battery operation and suppressing a sudden increase in current. The metal layer may include, for example, copper (Cu), nickel (Ni), stainless steel (SUS), iron (Fe), and cobalt (Co) or an alloy thereof. The metal layer may act as an electrochemical fuse and cut off in the event of an overcurrent, thereby performing a short circuit prevention function. The limit current and maximum current can be controlled by adjusting the thickness of the metal layer. The metal layer can be plated or deposited on the base film. When the thickness of the metal layer is reduced, the limit current and / or maximum current of the negative electrode current collector (21) decreases, thereby improving the stability of the lithium battery in the event of a short circuit. A lead tab can be added on the metal layer for connection to the outside. The lead tab can be welded to the metal layer or the metal layer / base film laminate by ultrasonic welding, laser welding, spot welding, etc. During welding, the base film and / or the metal layer melts, so that the metal layer can be electrically connected to the lead tab. In order to strengthen the welding of the metal layer and the lead tab, a metal chip can be added between the metal layer and the lead tab. The metal chip can be a thin piece of the same material as the metal of the metal layer.The metal piece may be, for example, a metal foil, a metal mesh, etc. The metal piece may be, for example, an aluminum foil, a copper foil, a SUS foil, etc. After the metal piece is placed on the metal layer, the lead tab may be welded to the metal piece / metal layer laminate or the metal piece / metal layer / base film laminate by welding the lead tab. During welding, the base film, the metal layer, and / or the metal piece may melt, so that the metal layer or the metal layer / metal piece laminate may be electrically connected to the lead tab. A metal chip and / or a lead tab may be added to a portion of the metal layer. The base film may have a thickness of, for example, 1 to 50 ㎛, 1.5 to 50 ㎛, 1.5 to 40 ㎛, 1 to 30 ㎛, 1 to 20 ㎛, or 1 to 10 ㎛. When the base film has a thickness in this range, the weight of the electrode assembly can be more effectively reduced. The melting point of the base film may be, for example, 100 to 300°C, 100 to 250°C or less, or 100 to 200°C. Since the base film has a melting point within this range, the base film can be melted and easily bonded to the lead tab during the welding process of the lead tab. To improve the adhesion between the base film and the metal layer, a surface treatment such as corona treatment may be performed on the base film. The thickness of the metal layer may be, for example, 0.01 to 3 μm, 0.1 to 3 μm, 0.1 to 2 μm, or 0.1 to μm. Since the metal layer has a thickness within this range, conductivity can be maintained while ensuring the stability of the electrode assembly. The thickness of the metal piece may be, for example, 2 to 10 μm, 2 to 7 μm, or 4 to 6 μm. Since the metal piece has a thickness within this range, the connection between the metal layer and the lead tab can be performed more easily. By having this structure, the negative electrode current collector (21) can reduce the weight of the negative electrode and consequently improve the energy density of the negative electrode and lithium battery.

[0122] [Cathode: Lithium metal layer]

[0123] Referring to Fig. 2, the lithium battery (1) further includes a lithium metal layer (22) disposed between the negative electrode current collector (21) and the electrolyte layer (30) after being charged. The lithium metal layer (22) corresponds to the negative electrode active material layer.

[0124] The lithium metal layer (22) is a metal layer containing lithium or a lithium alloy. The lithium metal layer contains lithium or a lithium alloy. The lithium metal layer (22) acts as, for example, a lithium reservoir. The lithium alloy includes, 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 (22) may be made of one of these alloys or lithium, or may be made of several types of alloys. The lithium metal layer (22) is, for example, a plated layer. The lithium metal layer (22) is deposited between the electrolyte layer (30) and the negative electrode current collector (21), for example, during the charging process of the lithium battery (1).

[0125] The thickness of the lithium metal layer (22) is not particularly limited, but is, for example, 1 to 200 μm, 1 to 150 μm, 1 to 100 μm, 1 to 50 μm, 1 to 30 μm, 1 to 22 μm, or 1 μm to 10 μm. If the thickness of the lithium metal layer (22) is too thin, it is difficult for the lithium metal layer (22) to perform the role of a lithium reservoir. If the thickness of the lithium metal layer (22) is too thick, the volume of the lithium battery (1) may excessively increase, and the cycle characteristics of the lithium battery (1) may rather deteriorate.

[0126] The thickness of the lithium metal layer (22) may be, for example, smaller than the thickness of the electrolyte layer (30). The thickness of the lithium metal layer (22) may be, for example, 70% or less, 60% or less, 50% or less, 40% or less, or 30% or less of the thickness of the electrolyte layer (30). The thickness of the lithium metal layer (22) may be, for example, 1 to 70%, 1 to 60%, 1 to 50%, 1 to 40%, or 1 to 30% of the thickness of the electrolyte layer (30). Since the thickness of the lithium metal layer (22) is smaller than the thickness of the electrolyte layer (30), volume change during charge and discharge of the lithium battery (1) can be suppressed. As a result, deterioration due to volume change of the lithium battery (1) can be suppressed.

[0127] The thickness of the lithium metal layer (22) may be, for example, smaller than the thickness of the positive electrode active material layer (12). The thickness of the lithium metal layer (22) may be, for example, 70% or less, 60% or less, 50% or less, 40% or less, or 30% or less of the thickness of the positive electrode active material layer (12). The thickness of the lithium metal layer (22) may be, for example, 1 to 70%, 1 to 60%, 1 to 50%, 1 to 40%, or 1 to 30% of the thickness of the positive electrode active material layer (12). Since the thickness of the lithium metal layer (22) is smaller than the thickness of the positive electrode active material layer (30), a volume change during charge and discharge of the lithium battery (1) can be suppressed. As a result, deterioration due to a volume change of the lithium battery (1) can be suppressed.

[0128] In the XPS analysis of the surface of the lithium metal layer (22), for example, the peak intensity derived from the fluorine (F) element may be greater than the peak intensity derived from the oxygen (O) element. In the XPS analysis of the surface of the lithium metal layer (22), for example, the peak intensity derived from the fluorine (F) element may be greater than 100%, 105% or more, 110% or more, or 120% or more of the peak intensity derived from the oxygen (O) element. In the XPS analysis of the surface of the lithium metal layer (22), for example, the peak intensity derived from the fluorine (F) element may be greater than 100% to 200%, 105% to 200%, 110% to 200%, or 120% to 200% of the peak intensity derived from the oxygen (O) element. The structural stability of the SEI layer formed on the surface of the lithium metal layer (22) may be improved by mainly including an inorganic compound including fluorine (F). As a result, the cycle characteristics of the lithium battery (1) can be improved. In contrast, when the SEI layer formed on the surface of the lithium metal layer (22) mainly includes an organic compound containing oxygen (O), the structural stability of the SEI layer can be reduced. The peak derived from the fluorine (F) element can be, for example, a peak derived from the fluorine (F) 1s orbital. The peak derived from the oxygen (O) element can be, for example, a peak derived from the oxygen (O) 1s orbital.

[0129] After assembling the lithium battery (1), a lithium metal layer (22) is deposited by charging, and since the lithium metal layer (22) is not included during the assembly of the lithium battery (1), the energy density of the lithium battery (1) increases. When the lithium metal layer (22) is additionally disposed by charging after assembling the lithium battery (1), the region between the negative electrode (20), i.e., the negative electrode current collector (21), and the electrolyte layer (30) is a Li-free region that does not include lithium (Li), for example, in the initial state of the lithium battery (1) or in the state after complete discharge.

[0130] [anode]

[0131] Referring to FIG. 1, a lithium battery (1) according to one embodiment includes a positive electrode (10), and the positive electrode (10) includes a positive electrode current collector (11) and a positive electrode active material layer (12) disposed on one surface of the positive electrode current collector (11).

[0132] [Anode: Anode active material layer]

[0133] The cathode active material layer (12) includes a cathode active material. The cathode active material is, for example, a lithium-containing metal oxide, and any one used in the relevant technical field can be used. The cathode active material can be, for example, at least one of a composite oxide of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof, and a specific example thereof is Li. a A 1-b B' b D2 (in the above formula, 0.90 ≤ a ≤ 1, and 0 ≤ b ≤ 0.5); Li a E 1-b B' b O 2-c D c (In the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); LiE 2-b B' b O 4-c D c (In the above formula, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b B' c D α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Co b B' c O 2-α F' α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mnb B' c D α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Mn b B' c O 2-α F' α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni b E c G d O2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1); Li a Ni b Co c Mn d G e O2 (in the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0.001 ≤ e ≤ 0.1); Li a NiG b O2 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a CoG b O2 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a MnG b O2 (in the above formula, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a Mn2G b O4 (wherein 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); QO2; QS2; LiQS2; V2O5; LiV2O5; LiI'O2; LiNiVO4; Li (3-f) J2(PO4)3(0 ≤ f ≤ 2); Li (3-f)A compound represented by any one of the chemical formulas Fe2(PO4)3(0≤ f ≤ 2); LiFePO4 can be used.

[0134] In the chemical formula representing the above-described compound, A is Ni, Co, Mn, or a combination thereof; B' is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F' is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; I' is Cr, V, Fe, Sc, Y, or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof. It is also possible to use a compound having a coating layer added to the surface of the above-described compound, or it is also possible to use a mixture of the above-described compound and the compound having a coating layer added. The coating layer added to the surface of the above-mentioned compound includes a coating element compound of, for example, an oxide, a hydroxide, an oxyhydroxide of the coating element, an oxycarbonate of the coating element, or a hydroxycarbonate of the coating element of the coating element. The compound forming the coating layer is amorphous or crystalline. The coating elements included in the coating layer are Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof. The method for forming the coating layer is selected within a range that does not adversely affect the physical properties of the positive electrode active material. The coating method includes, for example, spray coating and dipping. Since the specific coating method is well understood by those working in the relevant field, a detailed description thereof will be omitted.

[0135] The cathode active material may include, for example, a lithium transition metal oxide represented by the following chemical formulas 1 to 8:

[0136] <Chemical Formula 1>

[0137] Li a Ni x Co y M z O 2-b A b

[0138] In the above chemical formula 1,

[0139] 1.0≤a≤1.2, 0≤b≤0.2, 0.8≤x<1, 0≤y≤0.3, 0 <z≤0.3, 및 x+y+z=1이고,

[0140] M is manganese (Mn), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B), or a combination thereof,

[0141] A is F, S, Cl, Br or a combination thereof,

[0142] <Chemical Formula 2>

[0143] LiNi x Co y Mn z O2

[0144] <Chemical Formula 3>

[0145] LiNi x Co y Al z O2

[0146] In the above chemical formulas 2 and 3, 0.8≤x≤0.95, 0≤y≤0.2, 0 <z≤0.2 및 x+y+z=1이며,

[0147] <Chemical Formula 4>

[0148] LiNi x Co y Mn z Al w O2

[0149] In the above chemical formula 4, 0.8≤x≤0.95, 0≤y≤0.2, 0 <z≤0.2, 0<w≤0.2, 및 x+y+z+w=1이며,

[0150] <Chemical Formula 5>

[0151] Li a Co x M y O 2-b A b

[0152] In the above chemical formula 5,

[0153] 1.0≤a≤1.2, 0≤b≤0.2, 0.9≤x≤1, 0≤y≤0.1, and x+y=1,

[0154] M is manganese (Mn), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B), or a combination thereof,

[0155] A is F, S, Cl, Br or a combination thereof,

[0156] <Chemical Formula 6>

[0157] Li a Ni x Mn y M' z O 2-b A b

[0158] In the above chemical formula 6,

[0159] 1.0≤a≤1.2, 0≤b≤0.2, 0 <x≤0.3, 0.5≤y<1, 0<z≤0.3, 및 x+y+z=1이고,

[0160] M' is cobalt (Co), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B) or a combination thereof,

[0161] A is F, S, Cl, Br or a combination thereof,

[0162] <Chemical Formula 7>

[0163] Li a M1x M2 y PO 4-b X b

[0164] In the above chemical formula 7, 0.90≤a≤1.1, 0≤x≤0.9, 0≤y≤0.5, 0.9 <x+y<1.1, 0≤b≤2 이며,

[0165] M1 is chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr) or a combination thereof,

[0166] M2 is magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), titanium (Ti), zinc (Zn), boron (B), niobium (Nb), gallium (Ga), indium (In), molybdenum (Mo), tungsten (W), aluminum (Al), silicon (Si), chromium (Cr), vanadium (V), scandium (Sc), yttrium (Y) or a combination thereof, and X is O, F, S, P or a combination thereof.

[0167] <Chemical Formula 8>

[0168] Li a M3 z PO4

[0169] In the above chemical formula 8, 0.90≤a≤1.1, 0.9≤z≤1.1,

[0170] M3 is chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr), or a combination thereof.

[0171] The cathode active material layer (12) may further include a conductive material. Examples of the conductive material include, but are not limited to, carbon black, graphite particles, natural graphite, artificial graphite, acetylene black, Ketjen black, carbon fibers; carbon nanotubes; metal powders or metal fibers or metal tubes such as copper, nickel, aluminum, and silver; and conductive polymers such as polyphenylene derivatives. Any conductive material used in the art may be used. Alternatively, the cathode may not include a separate conductive material, for example.

[0172] The cathode active material layer (12) may further include, for example, a binder. Examples of binders that may be used include vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene (PTFE), a mixture of the aforementioned polymers, and a styrene butadiene rubber-based polymer.

[0173] The content of the positive electrode active material included in the positive electrode active material layer (12) may be 80 wt% to 99 wt%, 90 wt% to 99 wt%, or 95 wt% to 99 wt% of the total weight of the positive electrode active material layer (12).

[0174] The conductive material content including the positive electrode active material layer (12) may be 0.1 wt% to 10 wt% or 0.1 wt% to 5 wt% of the total weight of the positive electrode active material layer (12).

[0175] The binder content including the positive electrode active material layer (12) may be 0.1 wt% to 10 wt% or 0.1 wt% to 5 wt% of the total weight of the positive electrode active material layer (12).

[0176] The contents of the cathode active material, conductive agent, and binder contained in the cathode are at levels typically used in lithium batteries. Depending on the intended use and configuration of the lithium battery, one or more of the conductive agent and binder may be omitted.

[0177] [Anode: Anode current collector]

[0178] The material constituting the positive electrode current collector (11) can be any material that does not react with lithium, that is, any material that does not form an alloy or compound with lithium and has conductivity. The positive electrode current collector (11) is, for example, a metal or an alloy. The positive electrode current collector (11) can be made of, for example, aluminum (Al), indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), germanium (Ge) or an alloy thereof. The positive electrode current collector (11) can have a shape selected from, for example, a sheet, a foil, a film, a plate, a porous body, a mesoporous body, a body containing through-holes, a polygonal ring body, a mesh body, a foam body, and a non-woven body, but is not necessarily limited to these shapes, and any shape used in the relevant technical field can be used.

[0179] Alternatively, the cathode current collector (11) may include, for example, a base film and a metal layer disposed on one or both sides of the base film. The base film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof. The polymer may be an insulating polymer. Since the base film includes an insulating thermoplastic polymer, when a short circuit occurs, the base film may soften or liquefy, thereby blocking battery operation and suppressing a sudden increase in current. The metal layer may include, for example, aluminum (Al), indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), germanium (Ge), or an alloy thereof. The positive electrode current collector (11) may additionally include a metal piece and / or a lead tab. For more specific details regarding the base film, metal layer, metal piece (metal chip), and lead tab of the positive electrode current collector (11), refer to the positive electrode current collector (11) described above. By having such a structure, the positive electrode current collector (11) can reduce the weight of the positive electrode, and consequently, improve the energy density of the positive electrode and the lithium battery.

[0180] [Lithium Battery Manufacturing Method]

[0181] According to one embodiment, a method for manufacturing a lithium battery includes the steps of: preparing a precursor composition for forming a gel polymer electrolyte; preparing an assembly by laminating a negative electrode collector, a porous membrane, and a positive electrode; injecting a precursor composition for forming a gel electrolyte into the assembly; and crosslinking the injected precursor composition for forming a gel electrolyte to prepare a lithium battery having an electrolyte layer including a gel polymer electrolyte. The gel polymer electrolyte includes a first polymer, a first lithium salt, a second lithium salt, a first organic solvent, and a second organic solvent, wherein the first polymer includes a repeating unit derived from a first crosslinking monomer including three or more reactive functional groups, and the first lithium salt and the second lithium salt independently include a borate-based lithium salt. In a lithium battery manufactured by this method, the gel polymer electrolyte has excellent ionic conductivity and improved mechanical properties compared to a liquid electrolyte, thereby more effectively suppressing volume changes of the lithium battery during charge and discharge. As a result, deterioration of the lithium battery is prevented and the cycle characteristics of the lithium battery are improved.

[0182] A precursor composition for forming a gel polymer electrolyte is prepared. The precursor composition for forming a gel polymer electrolyte includes a first crosslinking monomer, a thermal initiator, and a liquid electrolyte. The liquid electrolyte includes a first lithium salt, a second lithium salt, a first organic solvent, and a second organic solvent. The content of the first crosslinking monomer may be, for example, 1 to 20 wt% of the total weight of the composition for forming a positive electrode electrolyte. The thermal initiator is not limited to t-aminopropyl peroxide or an azobis-based thermal initiator, but any thermal initiator used in the art may be used. The types of the second crosslinking monomer and the liquid electrolyte refer to the gel polymer electrolyte described above. The precursor composition for forming a gel electrolyte is prepared, for example, by adding the first crosslinking monomer and the thermal initiator to the liquid electrolyte. The content of the first lithium salt and the second lithium salt may, for example, be independently greater than 0 to 1.2 M with respect to the liquid electrolyte.

[0183] A positive electrode is prepared. For example, a positive electrode active material composition is prepared by mixing a positive electrode active material, a conductive agent, a binder, and a solvent. The prepared positive electrode active material composition is directly coated on a positive electrode current collector and dried to produce a positive electrode plate having a positive electrode active material layer formed thereon. Alternatively, the positive electrode active material composition is cast on a separate support, and then the film obtained by peeling from the support is laminated on a positive electrode current collector to produce a positive electrode plate having a positive electrode active material layer formed thereon. The solvent is, for example, N-methylpyrrolidone, but is not particularly limited. It is also possible to form pores inside the electrode plate by further adding a plasticizer or a pore forming agent to the positive electrode active material composition. The positive electrode can be prepared by the methods described above, but is not necessarily limited thereto. The types and contents of the positive electrode active material, conductive agent, and binder refer to the positive electrode active material layer described above.

[0184] Prepare a negative current collector. A negative current collector is, for example, copper foil. For more specific information about the negative current collector, refer to the negative electrode section above.

[0185] Prepare a porous membrane. For example, a polyethylene separator is used. For more detailed information about the porous membrane, refer to the electrolyte layer section described above.

[0186] An assembly is prepared by laminating a negative electrode collector, a porous membrane, and a positive electrode. The assembly is contained in a can or pouch. The porous membrane refers to the positive electrode electrolyte described above.

[0187] A composition for forming a positive electrode electrolyte is injected into the assembly. By injecting the composition for forming a positive electrode electrolyte into the assembly contained in a can or pouch, the composition for forming a positive electrode electrolyte is impregnated into the porous membrane and the positive electrode active material layer.

[0188] A lithium metal battery including a positive electrode electrolyte is prepared by crosslinking the injected composition for forming a positive electrode electrolyte. Crosslinking is performed, for example, by thermal crosslinking or ultraviolet crosslinking. Thermal crosslinking may be performed, for example, at a temperature of 60 to 80°C for 1 to 2 hours, but is not limited to these conditions and may be appropriately selected depending on the required degree of crosslinking. By crosslinking the composition for forming a positive electrode electrolyte, a positive electrode electrolyte is formed in a region where a porous membrane and a positive electrode active material layer are arranged. The positive electrode electrolyte is arranged in the pores included in the positive electrode active material layer and the pores included in the porous membrane.

[0189] The manufactured lithium battery (1) may have a structure as shown in FIGS. 11 to 14 below, for example.

[0190] Referring to FIG. 11, a lithium battery (1) according to an embodiment includes a positive electrode (3), the above-described negative electrode (2), and a separator (4). The positive electrode (3), the negative electrode (2), and the separator (4) are wound or folded to form a battery structure (7). The formed battery structure (7) is accommodated in a battery case (5). A composition for forming a positive electrode electrolyte is injected into the battery case (5), cross-linked, and sealed with a cap assembly (6), thereby completing the lithium battery (1). The battery case (5) is cylindrical, but is not necessarily limited to this shape, and may be, for example, square, thin-film, etc.

[0191] Referring to FIG. 12, a lithium battery (1) according to an embodiment includes a positive electrode (3), the above-described negative electrode (2), and a separator (4). The positive electrode (3), the negative electrode (2), and the separator (4) are wound, folded, or laminated to form a battery structure (7). The formed battery structure (7) is accommodated in a battery case (5). A composition for forming a positive electrode electrolyte is injected into the battery case (5), cross-linked, and sealed to complete the lithium battery (1). The battery case (5) is square, but is not necessarily limited to this shape, and may be, for example, cylindrical, thin-film, etc. A positive electrode lead tab (3') and a positive electrode terminal (3") are electrically connected to the positive electrode (3). A negative electrode lead tab (2') and a negative electrode terminal (2") are electrically connected to the negative electrode (2).

[0192] Referring to FIG. 13, a lithium battery (1) according to one embodiment includes a positive electrode (3), the aforementioned negative electrode (2), and a separator (4). A separator (4) is disposed between the positive electrode (3) and the negative electrode (2), and the positive electrode (3), the negative electrode (2), and the separator (4) are wound or folded to form a battery structure (7). The formed battery structure (7) is accommodated in a battery case (5). An electrode tab (8) that serves as an electrical path for guiding a current formed in the battery structure (7) to the outside may be included. A composition for forming a positive electrode electrolyte is injected into the battery case (5), crosslinked, and sealed, thereby completing the lithium battery (1). The battery case (5) is not necessarily limited to a square shape, but may be, for example, a cylindrical shape, a thin film shape, etc.

[0193] Referring to FIG. 14, a lithium battery (1) according to one embodiment includes a positive electrode (3), the aforementioned negative electrode (2), and a separator (4). A separator (4) is disposed between the positive electrode (3) and the negative electrode (2), thereby forming a battery structure. A battery structure (7) is stacked in a bi-cell structure and then accommodated in a battery case (5). An electrode tab (8) serving as an electrical path for guiding a current formed in the battery structure (7) to the outside may be included. A composition for forming a positive electrode electrolyte is injected into the battery case (5), cross-linked, and sealed, thereby completing the lithium metal battery (1). The battery case (5) is not necessarily limited to a square shape, but may be, for example, a cylindrical shape, a thin film shape, etc.

[0194] A pouch-type lithium metal battery uses a pouch as a case for the lithium battery of FIGS. 11 to 14. The pouch-type lithium battery may include one or more battery structures. A separator is disposed between a positive electrode and a negative electrode to form a battery structure. A plurality of battery structures are laminated in the thickness direction, then impregnated with an organic electrolyte, and accommodated and sealed in a pouch to complete the pouch-type lithium metal battery. For example, although not shown in the drawing, the above-described positive electrode, negative electrode, and separator may be simply laminated and accommodated in a pouch in the form of an electrode assembly, or may be wound or folded into a jellyroll-shaped electrode assembly and then accommodated in a pouch. Subsequently, a composition for forming a positive electrode electrolyte is injected into the pouch, and thermal cross-linking and sealing are performed to complete the lithium battery.

[0195] The lithium battery of the present disclosure has excellent lifespan characteristics and high energy density, making it suitable for use in, for example, electric vehicles (EVs). For example, it is used in hybrid vehicles such as plug-in hybrid electric vehicles (PHEVs). It is also used in applications requiring large amounts of power storage, such as electric bicycles and power tools.

[0196] Lithium batteries are stacked in multiple layers to form a battery module, and the multiple battery modules form a battery pack. Such a battery pack can be used in any device requiring high capacity and high output. For example, it can be used in laptops, smartphones, electric vehicles, etc. The battery module includes, for example, multiple batteries and a frame that holds them. The battery pack includes, for example, multiple battery modules and a bus bar that connects them. The battery module and / or the battery pack may further include a cooling device. The multiple battery packs are controlled by a battery management system. The battery management system includes a battery pack and a battery control device connected to the battery pack.

[0197] The present invention is explained in more detail through the following examples and comparative examples. However, the examples are intended to illustrate the present invention and are not intended to limit the scope of the present invention.

[0198] (Precursor composition and electrolyte)

[0199] Preparation Example 1: DEC / FEC (2:1)+LiDFOB+LiBF4+DPHA 2 wt%

[0200] A liquid electrolyte was prepared by adding 0.6 M LiBF4 and 0.6 M LiDFOB (lithium difluoro(oxalate)borate) to a 2:1 volume ratio mixed solvent of diethyl carbonate (DEC) and fluoroethylene carbonate (FEC).

[0201] A precursor composition for forming a gel polymer electrolyte was prepared by adding DPHA (dipentaerythritol hexaacrylate), an ester crosslinking agent represented by the following chemical formula 13, as a first crosslinking monomer to a liquid electrolyte, and t-amyl peroxide as a thermal initiator.

[0202] <Chemical Formula 13>

[0203]

[0204] 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.

[0205] After impregnating the prepared precursor composition for forming a gel electrolyte into a polyethylene (PE) separator, a gel polymer electrolyte was prepared by thermal crosslinking in an oven at 70°C for 1 hour and 30 minutes.

[0206] Preparation Example 2: DEC / FEC (2:1)+LiDFOB+LiBF4+DPHA 3 wt%

[0207] 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 DPHA content was changed to 3 wt%.

[0208] Preparation Example 3: DEC / FEC (2:1)+LiDFOB+LiBF4+DPHA 4 wt%

[0209] 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 DPHA content was changed to 4 wt%.

[0210] Preparation Example 4: DEC / FEC (9:1)+LiDFOB+LiBF4+DPHA 2 wt%

[0211] 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 the mixing volume ratio of DEC and FEC was changed from 2:1 to 9:1.

[0212] Manufacturing Example 5: DEC / FEC(2:1)+LiDFOB+LiBF4+DETA 2 wt%

[0213] 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 DETA (pentaerythritol triacrylate) represented by the following chemical formula 14 was used instead of DPHA.

[0214] <Chemical Formula 14>

[0215]

[0216] Manufacturing Example 6: DEC / FEC(2:1)+LiDFOB+LiBF4+PETTA 2 wt%

[0217] 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 PETTA (pentaerythritol tetraacrylate) represented by the following chemical formula 15 was used instead of DPHA.

[0218] <Chemical Formula 15>

[0219]

[0220] Manufacturing Example 7: DEC / FEC(2:1)+LiDFOB+LiBF4+TriPEA 2 wt%

[0221] 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 TriPEA (tripentaerythritol acrylate, Viscoat#802) represented by the following chemical formula 16 was used instead of DPHA.

[0222] <Chemical Formula 16>

[0223]

[0224] In the above formula, R is hydrogen or -C(=O)-CH=CH2, n is 1 to 3, the n=1 content is 10-20%, the n=2 content is 55=65%, and the n=3 content is 5-15%.

[0225] Preparation Example 8: DEC / FEC (2:1)+LiDFOB+LiBF4+DPHA 10 wt%

[0226] 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 DPHA content was changed to 10 wt%.

[0227] Comparative Manufacturing Example 1: DEC / FEC(2:1)+LiDFOB+LiBF4+DPHA 0 wt%

[0228] A precursor composition for forming an electrolyte was prepared in the same manner as in Manufacturing Example 1, except that DPHA and a thermal cross-linking agent were not added. The prepared composition is a liquid electrolyte.

[0229] A liquid electrolyte was prepared by impregnating a polyethylene separator with the prepared precursor composition for forming a gel electrolyte.

[0230] Comparative Manufacturing Example 2: DEC / FEC (2:1) + LiDFOB + LiBF4 + NPGDA 2 wt%

[0231] 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 NPGDA (neopentyl glycol diacrylate) represented by the following chemical formula 16 was used instead of DPHA.

[0232] <Chemical Formula 16>

[0233]

[0234] Comparative Manufacturing Example 3: DEC / FEC (2:1) + LiBF4 + DPHA 2 wt%

[0235] 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 LiDFOB was omitted and LiBF41.2 M was used alone.

[0236] Comparative Manufacturing Example 4: DEC / FEC (2:1) + LiDFOB + DPHA 2 wt%

[0237] 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 LiBF4 was omitted and only LiDFOB 1.2 M was used.

[0238] Comparative Manufacturing Example 5: DEC / FEC (2:1) + LiPF6 + DPHA 2 wt%

[0239] 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 LiPF61.2 M was used alone instead of LiBF4 and LiDFOB.

[0240] Comparative Manufacturing Example 6: DEC / FEC(3:0)+LiDFOB+LiBF4+DPHA 2 wt%

[0241] 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 FEC was omitted and DEC alone was used as an organic solvent.

[0242] Comparative Manufacturing Example 7: DEC / FEC(0:3)+LiDFOB+LiBF4+DPHA 2 wt%

[0243] 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 DEC was omitted and only FEC was used as an organic solvent.

[0244] (lithium battery)

[0245] Example 1

[0246] (Cathode collector manufacturing)

[0247] Copper foil with a thickness of 10 ㎛ was used as the negative electrode collector.

[0248] (Polar electrode manufacturing)

[0249] LiNi 0.8 Co 0.15 Al 0.05O2(NCA) powder and carbon conductive material (Super-P; Timcal Ltd.) were uniformly mixed at a weight ratio of 90:5, and then 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.

[0250] 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 ㎛.

[0251] (lithium battery manufacturing)

[0252] 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 cross-linked in an oven at 70°C for 1 hour and 30 minutes to manufacture a lithium battery including a gel polymer electrolyte.

[0253] Lithium batteries have a positive electrode / gel polymer electrolyte (separator) / negative electrode current collector structure.

[0254] Examples 2 to 8

[0255] 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 8 were used instead of the precursor composition for forming a gel electrolyte manufactured in Manufacturing Example 1.

[0256] Comparative Examples 1 to 7

[0257] 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 7 were used instead of the precursor composition for forming a gel electrolyte manufactured in Manufacturing Example 1. The lithium battery of Comparative Example 1 including the liquid electrolyte of Comparative Manufacturing Example 1 was prepared without thermal cross-linking.

[0258] Evaluation Example 1: Measurement of ionic conductivity of gel polymer electrolyte

[0259] For the electrolytes manufactured in Manufacturing Examples 1 to 8 and Comparative Manufacturing Examples 1 to 7, ionic conductivity (σ) and lithium ion transference number (t) were measured using a lithium symmetric cell and an impedance analyzer (Solartron 1260A Impedance / Gain-Phase Analyzer coupled with Solartron 1287 Electrochemical Interface) at 25°C. + ) were measured. The ionic conductivity and lithium ion transfer rate were derived using the AC impedance method combined with the steady-state current method. First, the initial lithium interfacial resistance (Ro) was measured from the impedance spectrum in the frequency range of 0.1 Hz to 100 kHz, then a small DC voltage (<10 mV) was applied until the steady-state current (Iss) was obtained (time >3000 s), and finally, the steady-state lithium interfacial resistance (Rss) was measured from the impedance spectrum in the frequency range of 0.1 Hz to 100 kHz. Using the parameters obtained from the impedance response and the steady-state current response, the lithium ion transfer rate (t + ) was derived.

[0260] The lithium symmetric cell has a Li / electrolyte / Li structure, with a positive electrolyte membrane positioned between lithium electrodes, and is sealed within the cell. Some of the measurement results are shown in Table 1 below.

[0261] Ion Conductivity [mS / cm] Lithium Ion Transfer Rate Comparison Manufacturing Example 1 DEC / FEC(2:1)+LiDFOB+LiBF4+DPHA 0 wt% 0.32 0.28 Manufacturing Example 1 DEC / FEC(2:1)+LiDFOB+LiBF4+DPHA 2 wt% 0.26 0.31 Manufacturing Example 2 DEC / FEC(2:1)+LiDFOB+LiBF4+DPHA 3 wt% 0.21 0.32 Manufacturing Example 3 DEC / FEC(2:1)+LiDFOB+LiBF4+DPHA 4 wt% 0.19 0.34

[0262] As shown in Table 1, the ionic conductivity of the gel polymer electrolytes of Preparation Examples 1 to 3 exhibited an ionic conductivity of at least 50% of the ionic conductivity of the liquid electrolyte of Comparative Preparation Example 1. The gel polymer electrolytes of Preparation Examples 1 to 3 provided an ionic conductivity in a range similar to the ionic conductivity of the liquid electrolyte of Comparative Preparation Example 1.

[0263] Although not shown in Table 1, the ionic conductivities of the gel polymer electrolytes of Preparation Examples 7 and 8 were lower than those of the gel polymer electrolytes of Preparation Examples 1 to 3. This was believed to be because the crosslinking density increased and the fluidity decreased in the gel polymer electrolytes of Preparation Examples 7 and 8 compared to the gel polymer electrolytes of Preparation Examples 1 to 3.

[0264] Evaluation Example 2: Charge / Discharge Test

[0265] A high-temperature (45°C) charge-discharge test was performed on the lithium batteries of Examples 1 to 8 and Comparative Examples 1 to 7 under the following conditions.

[0266] The lithium battery was charged at a constant current of 0.2 C rate at 45°C until the voltage reached 4.3 V (vs. Li). Subsequently, it was discharged at a constant current of 0.5 C rate until the voltage reached 3.6 V (vs. Li).

[0267] This charge-discharge cycle was repeated 160 times.

[0268] 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 2 below. The capacity retention rate is defined by the following mathematical equation (1).

[0269] <Mathematical Formula 1>

[0270] Capacity retention rate [%] = [160 th Discharge capacity in cycles / 1 st Discharge capacity in cycles] Х 100

[0271] Capacity Retention [%] Example 1 DEC / FEC(2:1)+LiDFOB+LiBF4+DPHA 2 wt% 67.0 Example 2 DEC / FEC(2:1)+LiDFOB+LiBF4+DPHA 3 wt% 67.1 Example 3 DEC / FEC(2:1)+LiDFOB+LiBF4+DPHA 4 wt% 72.4 Example 4 DEC / FEC(9:1)+LiDFOB+LiBF4+DPHA 2 wt% 60.0 Example 5 DEC / FEC(2:1)+LiDFOB+LiBF4+PETA 2 wt% 63.4 Example 6 DEC / FEC(2:1)+LiDFOB+LiBF4+PETTA 2 wt% 66.2 Example 7 DEC / FEC(2:1)+LiDFOB+LiBF4+TriPEA 2 wt% 66.8 Example 8 DEC / FEC(2:1)+LiDFOB+LiBF4+DPHA 10 wt% 65.5 Comparative Example 1 DEC / FEC(2:1)+LiDFOB+LiBF4+DPHA 0 wt% 49.1 Comparative Example 2 DEC / FEC(2:1)+LiDFOB+LiBF4+NPGDA 2 wt% 52.6 Comparative Example 3 DEC / FEC(2:1)+LiBF4+DPHA 2 wt% 58.2 Comparative Example 4 DEC / FEC(2:1)+LiDFOB+DPHA 2 wt% 59.1 Comparative Example 5 DEC / FEC(2:1)+LiPF6+DPHA 2 wt% 42.7 Comparative Example 6 DEC / FEC(3:0)+ LiDFOB+LiBF4+DPHA 2 wt%53.0 Comparative Example 7 DEC / FEC(0:3)+ LiDFOB+LiBF4+DPHA 2 wt%56.4

[0272] As shown in Table 2, the lithium batteries of Examples 1 to 8 had improved life characteristics compared to the lithium batteries of Comparative Examples 1 to 7.

[0273] The lithium batteries of Examples 1 to 6 having a number of crosslinkers of 3 or more had improved life characteristics compared to the lithium battery of Comparative Example 2 having a number of crosslinkers of 2.

[0274] For example, the lithium batteries of Examples 1 to 3 including a gel polymer electrolyte have improved life characteristics compared to the lithium battery of Comparative Example 1 including a liquid electrolyte.

[0275] Evaluation Example 3: Confirmation of the surface and cross-section of the lithium metal layer

[0276] Scanning electron microscope images of the surface and cross-section of the lithium metal layer formed after the first cycle of charging of the lithium battery manufactured in Example 3 and Comparative Example 1 and the surface and short side of the lithium metal layer formed after the 60th cycle of charging are shown in FIGS. 3 a to 6b.

[0277] Figure 3a is a scanning electron microscope image of the surface of a lithium metal layer formed after the first cycle of charging in the lithium battery of Example 3.

[0278] Figure 3b is a scanning electron microscope image of a cross-section of a lithium metal layer formed after the first cycle of charging in the lithium battery of Example 3.

[0279] Figure 4a is a scanning electron microscope image of the surface of a lithium metal layer formed after the first cycle of charging in the lithium battery of Comparative Example 1.

[0280] Figure 4b is a scanning electron microscope image of the surface of a lithium metal layer formed after the first cycle of charging in the lithium battery of Comparative Example 1.

[0281] Figure 5a is a scanning electron microscope image of the surface of a lithium metal layer formed after the 60th cycle of charging in the lithium battery of Example 3.

[0282] Figure 5b is a scanning electron microscope image of a cross-section of a lithium metal layer formed after the 60th cycle of charging in the lithium battery of Example 3.

[0283] Figure 6a is a scanning electron microscope image of the surface of a lithium metal layer formed after the 60th cycle of charging in the lithium battery of Comparative Example 1.

[0284] Figure 6b is a scanning electron microscope image of the surface of the lithium metal layer formed after the 60th cycle of charging in the lithium battery of Comparative Example 1.

[0285] As shown in FIGS. 3a and 4a, after the first cycle of charging, it was confirmed that the surface of the lithium metal layer deposited in the lithium battery of Example 3 had fewer pores and was formed more densely compared to the surface of the lithium metal layer deposited in the lithium battery of Comparative Example 1.

[0286] As shown in FIGS. 3b and 4b, after the first cycle of charging, the thickness of the lithium metal layer formed in the lithium battery of Example 3 was 29.2 μm, which was reduced by more than 10% compared to the thickness of the lithium metal layer formed in the lithium battery of Comparative Example 1, which was 33.1 μm.

[0287] As shown in FIGS. 5a and 6a, after the 60th cycle of charging, it was confirmed that the surface of the lithium metal layer deposited in the lithium battery of Example 3 had fewer pores and was formed more densely compared to the surface of the lithium metal layer deposited in the lithium battery of Comparative Example 1.

[0288] As shown in FIGS. 5b and 6b, after the 60th cycle of charging, the thickness of the lithium metal layer formed in the lithium battery of Example 3 was 33.3 μm, which was reduced by about 15% compared to the thickness of the lithium metal layer formed in the lithium battery of Comparative Example 1, which was 39.1 μm.

[0289] It was confirmed that the lithium battery of Example 3, which has a gel polymer electrolyte with improved mechanical properties, increases the density of the lithium metal layer precipitated during the charging process compared to the lithium battery of Comparative Example 1 having a liquid electrolyte, and also reduces the change in the thickness of the lithium battery, i.e., the change in the volume of the lithium battery.

[0290] Evaluation Example 4: XPS Spectrum Evaluation

[0291] The lithium batteries manufactured in Example 3 and Comparative Example 1 were charged to the 20th cycle under the charge / discharge conditions of Evaluation Example 3, and then the lithium batteries were disassembled to measure the XPS spectra on the surface of the lithium metal layer. The results are shown in Figs. 7a and 7b. The XPS spectra for the oxygen (O) 1s orbital and the fluorine (F) 1s orbital were measured using Qunatum 2000 (Physical Electronics).

[0292] Figure 7 is an XPS spectrum of the surface of the lithium metal layer after 20 cycles of the lithium battery manufactured in Example 3. The peak attributed to the fluorine (F) 1s orbital was larger than the peak attributed to the oxygen (O) 1s orbital.

[0293] Figure 8 is an XPS spectrum of the surface of the lithium metal layer after 20 cycles of the lithium battery manufactured in Comparative Example 1. The peak attributed to the fluorine (F) 1s orbital was smaller than the peak attributed to the oxygen (O) 1s orbital.

[0294] As shown in Fig. 7, the fluorine (F) content on the surface of the lithium metal layer in the lithium battery of Example 3 was higher than the oxygen (O) content.

[0295] As shown in Fig. 8, the fluorine (F) content on the surface of the lithium metal layer in the lithium battery of Example 3 was lower than the oxygen (O) content.

[0296] In the lithium battery of Example 3, it was determined that the fluorine (F) content was high because the SEI layer on the surface of the lithium metal layer mainly contained inorganic substances resulting from the anion decomposition of lithium salt.

[0297] In the lithium battery of Comparative Example 1, it was determined that the oxygen (O) content was high because the SEI layer on the surface of the lithium metal layer mainly contained organic substances that were the result of decomposition of the organic solvent.

[0298] Evaluation Example 5: IR Spectrum Evaluation

[0299] Infrared spectra were measured for the gel polymer electrolyte of Example 3 and the liquid electrolyte of Comparative Example 1, and the results are shown in Fig. 9.

[0300] In Fig. 9, the upper part is for the liquid electrolyte of Comparative Example 1, and the lower part is for the gel polymer electrolyte of Example 3.

[0301] As shown in Fig. 9, the peaks (i.e., DPHA C=O…) due to the interaction of the ester group of the first polymer and the lithium cation in the gel polymer electrolyte of Example 3. Li + ) was obtained.

[0302] Therefore, it was confirmed that the solvation structure of lithium can be changed differently from that of a liquid electrolyte by the interaction between the ester group of the gel polymer electrolyte of Example 3 and the lithium cation.

[0303] Evaluation Example 6: Raman Spectrum Evaluation

[0304] Raman spectra were measured for the gel polymer electrolyte of Example 3 and the liquid electrolyte of Comparative Example 1, and the results are shown in Fig. 10.

[0305] In Fig. 10, the upper part is for the liquid electrolyte of Comparative Example 1, and the lower part is for the gel polymer electrolyte of Example 3.

[0306] As shown in Fig. 10, the area of ​​the peak (i.e., AGGs) due to the aggregation of anions of lithium salt in the gel polymer electrolyte of Example 3 was 48.4%, and the area of ​​the peak (i.e., AGGs) due to the aggregation of anions of lithium salt in the liquid electrolyte of Comparative Example 1 was 35.7%. It was confirmed that anion aggregation increased in the gel polymer electrolyte of Example 3 compared to the liquid electrolyte of Comparative Example 1.

[0307] In the gel polymer electrolyte of Example 3, as the aggregation of anions increases, the relative charge of the aggregation of anions changes, thereby increasing the anion concentration within the electric double layer. It was confirmed that the increased anions can change the composition of the SEI layer by participating in the formation of the SEI layer during the charge / discharge process.

[0308] As a result, the cycle characteristics of the lithium battery of Example 3 can be improved by forming an SEI layer with improved structural stability during the charge / discharge process in the lithium battery including the gel polymer electrolyte of Example 3 compared to the lithium battery including the liquid electrolyte of Comparative Example 1.

[0309] While exemplary embodiments have been described in detail with reference to the attached drawings, the present invention is not limited to these examples. It is self-evident that those skilled in the art to which the present invention pertains can devise various modifications or variations within the scope of the technical concepts described in the patent claims, and these also naturally fall within the technical scope of the present invention.

[0310] [Explanation of symbols]

[0311] 1 lithium battery 2, 20 cathode

[0312] 2' negative lead tab 2" negative terminal

[0313] 3, 10 positive 3' positive lead tab

[0314] 3" positive terminal 4 separator

[0315] 5 Battery case 6 Cap assembly

[0316] 7 Battery structure 8 Electrode tab

[0317] 11. Anode current collector 12. Anode active material layer

[0318] 21 Negative current collector 22 Negative active material layer, lithium metal layer

[0319] 30 electrolytes

[0320] According to one aspect, by providing a novel gel polymer electrolyte having excellent ion conductivity, it is possible to provide a lithium battery having suppressed volume change during charge and discharge and improved cycle characteristics.

Claims

1. A positive electrode; a negative electrode current collector; and an electrolyte layer disposed between the positive electrode and the negative electrode current collector, The above electrolyte layer comprises a gel polymer electrolyte, The above gel polymer electrolyte comprises a first polymer, a first lithium salt, a second lithium salt, a first organic solvent and a second organic solvent, The first polymer comprises a repeating unit derived from a first crosslinking monomer containing three or more reactive functional groups, A lithium battery, wherein the first lithium salt and the second lithium salt independently comprise a borate-based lithium salt.

2. 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, Containing dipentaerythritol hexaacrylate or a combination thereof; A lithium battery, wherein the first polymer is a crosslinking product of the first crosslinking monomer.

3. A lithium battery according to claim 1, wherein the content of the first polymer is 0.1 to 10 wt% of the total weight of the gel polymer electrolyte.

4. In the first paragraph, the first lithium salt and the second lithium salt independently include a fluorine-containing borate lithium salt, A lithium battery, wherein the fluorine-containing borate lithium salt comprises LiBF4, LiBF3(C2F5), a compound represented by the following chemical formulas 1 to 12, or a combination thereof. <Chemical Formula 1> <Chemical Formula 2> <Chemical Formula 3> <Chemical Formula 4> <Chemical Formula 5> <Chemical Formula 6> <Chemical Formula 7> <Chemical Formula 8> <Chemical Formula 9> <Chemical Formula 10> <Chemical Formula 11> <Chemical Formula 12> .

5. In the first paragraph, the first lithium salt comprises LiBF4, and the second lithium salt comprises a compound selected from compounds represented by the chemical formulas 1 to 12. A lithium battery wherein a phosphorous-based lithium salt is free in the gel polymer electrolyte.

6. In the first paragraph, the contents of the first lithium salt and the second lithium salt are each more than 0 and less than 1.2 M, A lithium battery, wherein the content ratio of the first lithium salt and the second lithium salt is 1:9 to 9:

1.

7. In the first paragraph, the first organic solvent and the second organic solvent include a carbonate compound, The first organic solvent comprises a linear carbonate compound, and the second organic solvent comprises a cyclic carbonate compound substituted with a substituent. A lithium battery, wherein the substituent comprises a halogen, a cyano group (CN), a nitro group (NO2), or a combination thereof.

8. A lithium battery according to claim 1, wherein the first 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.

9. A lithium battery according to claim 1, wherein the second 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.

10. In the first paragraph, the first organic solvent comprises diethyl carbonate, and the second organic solvent comprises a fluorine-substituted cyclic carbonate compound. A lithium battery wherein the unsubstituted cyclic carbonate compound is free in the above gel polymer electrolyte.

11. A lithium battery according to claim 1, wherein the volume ratio of the first organic solvent and the second organic solvent is 5.5:4.5 to 9:

1.

12. A lithium battery according to claim 1, wherein butanediol, thiourea or a combination thereof is free in the gel polymer electrolyte.

13. In the first paragraph, the gel polymer electrolyte is a crosslinked product of the precursor composition, The content of the first crosslinking monomer is 0.1 to 10 wt% of the total weight of the precursor composition, The above precursor composition comprises a thermal initiator, The above-mentioned thermal initiator is t-amyl peroxide, azobis. A lithium battery, wherein the cross-linked product is a result of heat treatment at 60 to 90° C. for 1 to 3 hours.

14. A lithium battery according to claim 1, wherein the ionic conductivity of the gel polymer electrolyte at 25°C and 1 atm is 50% or more of the ionic conductivity of the liquid electrolyte excluding the first polymer at 25°C and 1 atm.

15. A lithium battery according to claim 1, wherein the ionic conductivity of the gel polymer electrolyte at 25°C and 1 atm is 0.10 mS / cm or more.

16. In the first paragraph, the lithium ion transference number (t) of the gel polymer electrolyte at 25 ℃ and 1 atm Li + ) is a lithium battery having a lithium ion transfer rate at 25°C and 1 atm greater than that of the liquid electrolyte excluding the first polymer.

17. A lithium battery according to claim 1, wherein the lithium ion transfer rate of the gel polymer electrolyte at 25°C and 1 atm is 0.30 or more.

18. In the first paragraph, the electrolyte layer further includes a porous substrate, The above porous substrate is a porous membrane, and the above porous membrane is a woven fabric or a non-woven fabric, The above porous substrate comprises 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 battery, wherein the cellulose-based resin comprises carboxymethyl cellulose, microbial cellulose, plant cellulose, animal cellulose, or a combination thereof.

19. A lithium battery according to claim 1, wherein the negative electrode collector comprises copper (Cu), nickel (Ni), nickel-coated copper, stainless steel (SUS), iron (Fe), cobalt (Co), or an alloy thereof.

20. In the first paragraph, a lithium metal layer is further included between the electrolyte layer and the negative electrode current collector, A lithium battery in which the intensity of the fluorine peak is greater than that of the oxygen peak in the XPS analysis of the surface of the lithium metal layer.

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