Gel polymer electrolyte for lithium battery and lithium battery comprising same

Abstract

Provided are: a gel polymer electrolyte for a lithium battery; and a lithium battery comprising same. The gel polymer electrolyte for a lithium battery comprises a gel polymer and a liquid electrolyte. The gel polymer is i) a crosslinked product of a multifunctional acrylic monomer having three or more polymerizable functional groups, or ii) a crosslinked product of a first polymerizable monomer and a second polymerizable monomer, wherein the first polymerizable monomer is a multifunctional acrylic monomer having three or more polymerizable functional groups, and the second polymerizable monomer is a urethane acrylic monomer having two or more polymerizable functional groups, a polymerizable monomer containing a perfluoropolyether (PFPE) unit and having two or more polymerizable functional groups, or a combination thereof. The liquid electrolyte contains a lithium salt, an organic solvent, and butyronitrile, and the lithium salt includes lithium difluoro (oxalato) borate and lithium tetrafluoroborate.

Description

Gel polymer electrolyte for lithium batteries and lithium batteries containing the same

[0001] The present invention relates to a gel polymer electrolyte for a lithium battery and a lithium battery including the same.

[0002] Lithium batteries 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. However, their low capacity necessitates the use of higher-capacity anode materials.

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

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

[0005] A method using a solid electrolyte with high modulus and high lithium ion mobility to control lithium dendrites has been proposed.

[0006] However, among solid electrolytes, polymer solid electrolytes exhibit low ionic conductivity at room temperature, making practical application difficult. In contrast, gel polymer electrolytes are easy to manufacture and exhibit excellent electrochemical performance. However, their lithium ion transfer rates are not satisfactory, requiring further improvement.

[0007] One aspect is to provide a gel polymer electrolyte for lithium batteries with improved lithium ion conductivity.

[0008] Another aspect is to provide a lithium battery with improved cycle characteristics including the gel polymer electrolyte described above.

[0009] According to one embodiment, a gel polymer electrolyte for a lithium battery comprising a gel polymer and a liquid electrolyte,

[0010] The gel polymer is i) a crosslinked product of a multifunctional acrylic monomer having three or more polymerizable functional groups; or ii) a crosslinked product of a first polymerizable monomer and a second polymerizable monomer, wherein the first polymerizable monomer is a multifunctional acrylic monomer having three or more polymerizable functional groups, and the second polymerizable monomer is a urethane acrylic monomer having two or more polymerizable functional groups, a polymerizable monomer containing a perfluoropolyether (PFPE) unit and having two or more polymerizable functional groups, or a combination thereof.

[0011] The above liquid electrolyte comprises a lithium salt, an organic solvent and butyronitrile,

[0012] A gel polymer electrolyte for a lithium battery is provided, wherein the lithium salt includes a first lithium salt and a second lithium salt, and the first lithium salt and the second lithium salt independently include a fluorine-containing borate-based lithium salt.

[0013] According to another aspect, a lithium battery comprising a negative electrode current collector, a positive electrode, and an electrolyte layer disposed between the positive electrode and the negative electrode is provided, wherein the electrolyte layer comprises the gel polymer electrolyte described above.

[0014] A lithium metal layer is further included between the negative electrode current collector and the electrolyte layer, and the lithium metal layer includes a lithium metal foil, a lithium metal powder, a lithium alloy foil, a lithium alloy powder, or a combination thereof.

[0015] The electrolyte layer includes a separator, and the separator includes a porous substrate. The porous substrate is a porous membrane, and the porous membrane is a woven fabric or a non-woven fabric.

[0016] The above porous substrate includes an olefin resin, a fluorine resin, an ester resin, an imide resin, an acrylic resin, a cellulose resin, or a combination thereof.

[0017] 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, and the above imide resin includes polyamideimide, polyetherimide or a combination thereof.

[0018] The acrylic resin includes polyacrylonitrile, polyacrylate, or a combination thereof, and the cellulose resin includes carboxymethylcellulose, microbial cellulose, plant cellulose, animal cellulose, or a combination thereof.

[0019] The above negative electrode collector comprises copper (Cu), nickel (Ni), nickel-coated copper, stainless steel (SUS), iron (Fe), cobalt (Co), or an alloy thereof. And the lithium battery comprises a negative electrode active material layer, a protective layer, or a combination thereof between the negative electrode collector and the electrolyte layer.

[0020] According to one aspect, a gel polymer electrolyte for a lithium battery having improved lithium ion conductivity and a lithium battery using the same having high rate characteristics and lifespan characteristics are provided.

[0021] Figure 1a shows the results of a scanning electron microscope analysis of a gel polymer electrolyte manufactured according to Example 1.

[0022] Figure 1b shows the results of a scanning electron microscope analysis of a gel polymer electrolyte manufactured according to Comparative Example 1.

[0023] Figure 2 is a drawing for explaining the laminated structure of a lithium battery according to an embodiment.

[0024] Figure 3 is a drawing for explaining the laminated structure of a lithium battery according to another embodiment.

[0025] Figure 4 is a drawing for explaining the laminated structure of a lithium battery according to an embodiment.

[0026] Figure 5 is a schematic diagram of a lithium battery according to another embodiment.

[0027] Figure 6 is a schematic diagram of a lithium battery according to another embodiment.

[0028] <Explanation of symbols>

[0029] 1 lithium battery 2, 20 cathode

[0030] 3, 10 anode 4 separator

[0031] 5 Battery case 6 Cap assembly

[0032] 7 Battery structure 8 Electrode tab

[0033] The present inventive concept described below is capable of various modifications and embodiments. Specific embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the present inventive concept to specific embodiments, but rather to encompass all modifications, equivalents, or alternatives within the technical scope of the present inventive concept.

[0034] The terminology used below is only used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. Hereinafter, the terms "comprises" or "has" and the like are intended to indicate the presence of a feature, number, step, operation, component, part, ingredient, material, or combination thereof described in the specification, but should be understood to not preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, ingredients, materials, or combinations thereof. The " / " used below may be interpreted as "and" or "or" depending on the context.

[0035] In order to clearly express various layers and regions in the drawings, the thickness is shown enlarged or reduced. Similar parts are designated by the same drawing reference numerals throughout the specification. When a part such as a layer, film, region, or plate is said to be "on" or "above" another part throughout the specification, this includes not only cases where it is directly above the other part, but also cases where there is another part in between. Terms such as first, second, etc. may be used throughout the specification to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. In this specification and the drawings, components having substantially the same functional configuration are referred to by the same reference numerals, and redundant descriptions are omitted.

[0036] Unless otherwise specified herein, when a part such as a layer, film, region, or plate is said to be “on top of” another part, this includes not only cases where it is “directly on top of” the other part, but also cases where there is another part in between.

[0037] Unless otherwise specified herein, the singular may also include the plural. Furthermore, unless otherwise specified, "A or B" may mean "including A, including B, or including A and B."

[0038] As used herein, “combination thereof” may mean mixtures, laminates, composites, copolymers, alloys, blends, and reaction products of the components.

[0039] Unless otherwise defined herein, the particle size may be the average particle size. In addition, the particle size refers to the average particle size (D50), which means the diameter of particles with a cumulative volume of 50% by volume in a particle size distribution. The average particle size (D50) can be measured by a method well known to those skilled in the art, for example, by measuring with a particle size analyzer, or by measuring with a transmission electron microscope (TEM) photograph or a scanning electron microscope (SEM) photograph. Alternatively, the average particle size (D50) value can be obtained by measuring with a measuring device that utilizes dynamic light-scattering, performing data analysis to count the number of particles for each particle size range, and calculating from the counted number. Alternatively, the average particle size (D50) value can be obtained by measuring with a laser diffraction method. When measuring by laser diffraction, more specifically, after the particles to be measured are dispersed in a dispersion medium, they are introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000) and irradiated with ultrasonic waves of approximately 28 kHz at an output of 60 W, and the average particle size (D50) based on 50% of the particle size distribution in the measuring device can be calculated.

[0040] In the present disclosure, the "particle diameter" of a particle 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 of a particle can be measured using a particle size analyzer (PSA). The "particle diameter" of a particle is, for example, the average particle diameter. The average particle diameter is, for example, the median particle diameter (D50). The median particle diameter (D50) is the size of a particle corresponding to 50% of the cumulative volume, calculated from the side of particles having a small particle size in a size distribution of particles measured by, for example, laser diffraction. The average particle diameter and average major axis length of a particle can be measured using a scanning electron microscope. When the particle size is measured using a scanning electron microscope, it is determined as the average value of 30 or more randomly selected particles having a size of 1 μm or more, excluding fine particles.

[0041] In the present disclosure, “metal” includes both metals and metalloids such as silicon and germanium, in their elemental or ionic states, and “alloy” means a mixture of two or more metals.

[0042] In the present disclosure, “positive electrode active material” means a positive electrode material capable of undergoing lithiation and delithiation, and “negative electrode active material” means a negative electrode material capable of undergoing lithiation and delithiation.

[0043] In the present disclosure, “lithiation” and “lithiating” mean a process of adding lithium to a positive electrode active material or a negative electrode active material, and “delithiation” and “delithiating” mean a process of removing lithium from a positive electrode active material or a negative electrode active material.

[0044] In the present disclosure, “charging” and “charging” mean a process of providing electrochemical energy to a battery, and “discharging” and “discharging” mean a process of removing electrochemical energy from a battery.

[0045] In the present disclosure, “positive electrode” and “cathode” mean an electrode where electrochemical reduction and lithiation occur during a discharge process, and “negative electrode” and “anode” mean an electrode where electrochemical oxidation and delithiation occur during a discharge process.

[0046] In this disclosure, “length” and “thickness” represent average length and average thickness, respectively. Length and thickness can be measured using a scanning electron microscope.

[0047] Hereinafter, a gel polymer electrolyte for a lithium battery, a lithium battery including the same, and a method for manufacturing the same according to exemplary embodiments are described in more detail.

[0048] Gel polymer electrolytes for lithium batteries are easy to manufacture and have excellent electrochemical performance, but their ion transfer rate of lithium ions is insufficient, requiring improvement.

[0049] Accordingly, in order to solve the above-described problem, the present disclosure provides a gel polymer electrolyte for a lithium battery with improved lithium ion mobility by transferring lithium cations and anions to the polymer chains and concentrating the distribution of lithium ions in the gel polymer chains contained in the gel polymer electrolyte.

[0050] A gel polymer electrolyte for a lithium battery comprising a gel polymer and a liquid electrolyte according to an embodiment, wherein the gel polymer is i) a crosslinked product of a multifunctional acrylic monomer having three or more polymerizable functional groups; or ii) a crosslinked product of a first polymerizable monomer and a second polymerizable monomer, wherein the first polymerizable monomer is a multifunctional acrylic monomer having three or more polymerizable functional groups, and the second polymerizable monomer is a urethane acrylic monomer having two or more polymerizable functional groups, a polymerizable monomer containing a perfluoropolyether (PFPE) unit and having two or more polymerizable functional groups, or a combination thereof, wherein the liquid electrolyte comprises a lithium salt, an organic solvent, and butyronitrile, wherein the lithium salt comprises a first lithium salt and a second lithium salt, and wherein the first lithium salt and the second lithium salt independently comprise a fluorine-containing borate-based lithium salt.

[0051] In the present disclosure, the terms “first polymerizable monomer” and “second polymerizable monomer” may be referred to as “first cross-linkable monomer” and “second cross-linkable monomer,” respectively.

[0052] In a gel polymer electrolyte according to one embodiment, butyronitrile acts as a mediator that enables anions to move to the cathode together with lithium cations. Butyronitrile is a neutral molecule with improved anion interaction in addition to lithium cation interaction, and a gel polymer electrolyte formed using a liquid electrolyte containing such butyronitrile can provide a lithium battery with improved longevity and reduced resistance.

[0053] The content of butyronitrile is 3 wt% to 45 wt%, 5 wt% to 40 wt%, or 10 wt% to 35 wt% based on 100 wt% of the total weight of the electrolyte. When the content of butyronitrile is within the above range, the interaction with lithium cations and anions is excellent, so that a gel polymer electrolyte with improved lithium ion conductivity can be formed.

[0054] In a lithium battery according to an embodiment, if butyronitrile, which has excellent affinity for both cations and anions, is used on the negative electrode surface, cations and anions (e.g., difluorooxalateborate anions or tetrafluoroborate anions) are combined with butyronitrile, so that when Li cations move from the positive electrode to the negative electrode, the content of anions on the negative electrode surface increases, and a film including high-performance anions is formed on the surface when lithium cations are electrodeposited. In a general electrolyte, the structure of lithium metal surface / cation / solvent is formed, and the solvent is decomposed to form an SEI, and the formation of an organic SEI may deteriorate the performance of the lithium battery.

[0055] However, in a lithium battery according to one embodiment, the use of butyronitrile can form an SEI with an increased inorganic (anion) content on the lithium metal surface. As a result, the performance of the lithium battery is improved.

[0056] If butyronitrile is not added to the gel polymer electrolyte according to the embodiment, electrons are supplied to lithium ions on the negative electrode current collector, forming a lithium electrodeposited layer. The solvent components present around the lithium ions decompose, forming an SEI layer containing organic substances on the lithium metal surface. However, if the SEI layer contains organic substances, the life characteristics of the lithium battery may be reduced.

[0057] By utilizing butyronitrile, anions can be induced to migrate along with the initial lithium ions from the anode to the cathode during charging. This results in the presence of more anions at the cathode, resulting in the formation of a robust film enriched in boron and fluorine anions through the presence of abundant clustered solvation structures.

[0058] When the content of butyronitrile is within the above range, the number of clusters in which ions are not completely dissociated and three or more ions exist simultaneously increases, and these clusters have different configurations even though the constituent materials themselves are the same, so they form a film before other structures. Such butyronitrile has excellent cation and anion interactions, so it has excellent affinity for cations and anions. Therefore, when it is used, the number of anions in addition to cations around lithium increases, so that an SEI (Solid Electrolyte Interphase) layer with increased inorganic content can be formed on the lithium metal surface. At this time, the thickness of the SEI layer is 50 nm or less, 30 nm or less, or 1 to 25 nm. When an SEI layer with increased inorganic content exists on the lithium metal surface in this way, a lithium battery with improved life characteristics can be manufactured.

[0059] If the content of butyronitrile is less than 3 wt% based on 100 wt% of the total weight of the electrolyte, the effect of anions existing other than the solvent around lithium is minimal, and if it exceeds 45 wt%, solvents such as vinylene carbonate (VC), vinylethylene carbonate (VEC), and fluoroethylene carbonate (FEC) are not contained in the cluster containing the lithium salt and solvent, so they hardly participate in the formation of the SEI film. As a result, the SEI (Solid Electrolyte Interphase) film is formed only with the salt and butyronitrile, which may deteriorate the performance of the lithium battery.

[0060] The content of the above carbonate compound is 30 to 95 wt%, or 40 to 90 wt%, based on 100 wt% of the total weight of butyronitrile and the carbonate compound.

[0061] When the content of the carbonate compound is within the above range, lithium mobility is improved, enabling the manufacture of a lithium battery with improved initial capacity and lifespan characteristics. If the content of the carbonate compound exceeds 95 wt%, the proportion of clusters of an appropriate size may decrease, resulting in changes in the SEI film composition.

[0062] According to an embodiment, the carbonate compound contained in the liquid electrolyte includes FEC and diethyl carbonate (DEC), and the mixing weight ratio of FEC and DEC is 1:10 to 1:1, 1:8 to 1:1, 1:5 to 1:1, or 1:3 to 1:1.

[0063] According to one embodiment, a gel polymer electrolyte can be formed in a semi-solid state by confining a liquid in a polymer matrix obtained by polymerization. At this time, if a gel polymer electrolyte is manufactured using a polymerizable monomer (crosslinking monomer) for manufacturing the polymer matrix, a monomer having a strong affinity for lithium ions and a monomer having a strong affinity for anions, the movement of lithium ions through the polymer chain can be facilitated. In this way, lithium ions can be uniformly deposited on the negative electrode current collector through the polymer chain, and lithium can be delivered and uniformly deposited at a uniform concentration on the negative electrode current collector without an increase in dendritic lithium deposition.

[0064] The multifunctional acrylic monomer having three or more polymerizable functional groups, the first polymerizable monomer, and the second polymerizable monomer have strong affinity for lithium cations and anions, so that the gel polymer electrolyte obtained from them can facilitate the movement of lithium ions through the polymer chain. Therefore, by using such a gel polymer electrolyte, a lithium battery with improved life characteristics can be manufactured. Here, the lithium cations and anions are derived from a lithium salt, and for example, when LiPF6 is used as the lithium salt, the anion can be, for example, PF6-.

[0065] A gel polymer electrolyte according to an embodiment can be manufactured using a composition for forming a gel polymer electrolyte. The composition for forming a gel polymer electrolyte contains a polymerizable monomer for forming a gel polymer, a liquid electrolyte, and an initiator.

[0066] When a gel polymer electrolyte is formed using a liquid electrolyte containing a polymerizable monomer and butyronitrile by a single embodiment, butyronitrile exists around the gel polymer formed from the polymerizable monomer, and the use of butyronitrile can form an SEI with an increased inorganic (anion) content on the lithium metal surface. In addition, when a gel polymer and a carbonate compound such as FEC are used, lithium ions move and exist in large numbers around the gel polymer, thereby increasing lithium mobility.

[0067] The multifunctional acrylic monomer having three or more polymerizable functional groups and the multifunctional acrylic monomer containing a urethane group have strong lithium cation (Li+) interaction and anion interaction, so that lithium cation ions are transferred through the polymer chain, and the lithium cation transport rate (Li+ transferenece number) and lithium ion mobility are greatly increased. Here, the lithium cation and anion are, for example, the cation and anion of a lithium salt, and when LiPF6 is used as the lithium salt, the anion is, for example, PF6 - am.

[0068] A gel polymer electrolyte for a lithium battery according to one embodiment is a gel polymer electrolyte for a lithium battery comprising a gel polymer and a liquid electrolyte, wherein the gel polymer is i) a crosslinked product of a multifunctional acrylic monomer having three or more polymerizable functional groups; or ii) a crosslinked product of a first polymerizable monomer and a second polymerizable monomer, wherein the first polymerizable monomer is a multifunctional acrylic monomer having three or more polymerizable functional groups, and the second polymerizable monomer is a urethane acrylic monomer having two or more polymerizable functional groups, a polymerizable monomer containing a perfluoropolyether (PFPE) unit and having two or more polymerizable functional groups, or a combination thereof.

[0069] And the liquid electrolyte includes a lithium salt, an organic solvent, and butyronitrile, and the lithium salt includes lithium difluoro(oxalato)borate (LiDFOB) and lithium tetrafluoroborate (LiBF4).

[0070] A multifunctional acrylic first polymerizable monomer having three or more polymerizable functional groups has, for example, three or more polymerizable functional groups, for example, three to six polymerizable functional groups. When the multifunctional acrylic first polymerizable monomer has three or more polymerizable functional groups, a gel polymer electrolyte having excellent physical properties can be obtained. These polymerizable 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, Dipentaerythritol hexaacrylate (DPHA), or a combination thereof.

[0071] The ester (COO) group of the first polymerizable monomer can play a role in holding lithium salt and anions. By utilizing this, when lithium ions move from the positive electrode to the negative electrode during the initial charge, the anions can be induced to move together. As a result, it is possible to induce the presence of more anions at the negative electrode, which results in the formation of a robust film by enriching clustered solvation structures. Here, when the film is a lithium salt and a fluorine-containing borate lithium salt is used, a robust film rich in the anions boron and fluorine can be formed.

[0072] A urethane acrylic monomer having two or more functional groups is a compound represented by the following chemical formula 1, a compound represented by the following chemical formula 2, or a combination thereof.

[0073] <Chemical Formula 1>

[0074]

[0075] In chemical formula 1, n is an integer from 1 to 100, and R a and R b are the same or different from each other, and are substituted or unsubstituted C1-C10 alkylene groups, EG represents an ethylene group, DEG represents a diethylene glycol residue, and TMP represents a trimethylolpropane residue.

[0076] <Chemical Formula 2>

[0077]

[0078] In chemical formula 2, each R independently represents a hydrogen atom or a C1-C3 alkyl group.

[0079] In chemical formula 1, n is an integer from 3 to 80, an integer from 5 to 50, or an integer from 5 to 30. For example, in a substituted alkylene, at least one hydrogen atom of the alkylene may be replaced with a C1-C3 alkylene group.

[0080] The compound of the above chemical formula 1 or the compound of the above chemical formula 2 is a polyfunctional acrylic monomer containing a urethane group.

[0081] The compound represented by the above chemical formula 1 may include, for example, a compound represented by the following chemical formula 1-1.

[0082] <Chemical Formula 1-1>

[0083]

[0084] In chemical formula 1-1, n1 is an integer from 1 to 100, EG is a residue of ethylene glycol, DEG is a residue of diethylene glycol, and trimethylolpropane is a residue.

[0085] In Chemical Formula 1-1, n1 is an integer from 3 to 80, an integer from 5 to 50, or an integer from 5 to 30. The compound of Chemical Formula 1 and the compound of Chemical Formula 1-1 described above can be prepared using the preparation method disclosed in Korean Patent Publication No. 10-1326629, and Korean Patent Publication No. 10-1326629 is incorporated herein by reference and is cited herein.

[0086] The compound of the above-described chemical formula 1 has an isonate group at the terminal, and the method for producing this compound is described as follows.

[0087] A polyester polyol is prepared by mixing C1-C10 aliphatic dicarboxylic acids, diethylene glycol, ethylene glycol, and trimethylolpropane, adding a reaction catalyst, and heat-treating the mixture. Here, the polyester polyol is obtained through an ester reaction between a C1-C10 aliphatic dicarboxylic acid and the alcohols diethylene glycol, ethylene glycol, and trimethylolpropane. Titanium isopropoxide is used as the reaction catalyst.

[0088] By adding isocyanatoethyl methacrylate to the above polyester polyol, a reaction between the polyester polyol and isocyanatoethyl methacrylate occurs to form polyurethane, thereby producing a compound of chemical formula 1 having isocyanate at both ends.

[0089] C1-C10 aliphatic dicarboxylic acids include diadipic acid, succinic acid, sebacic acid, or combinations thereof.

[0090] The reaction of the polyester polyol and isocyanatoethyl methacrylate forms polyurethane by reacting at least a portion of the hydroxyl groups of the polyester polyol with isocyanatoethyl methacrylate. Monomethyl ether hydroquinone as a polymerization inhibitor, butylated hydroxy toluene as an antioxidant, and dibutyl tin dilaulate as a reaction catalyst may be added to the reaction of the polyester polyol and isocyanatoethyl methacrylate.

[0091] The weight average molecular weight of the compound of the above-described chemical formula 1 and the compound of the chemical formula 1-1 may be in the range of 10,000 to 100,000. The range of n in chemical formula 1 and chemical formula 3 may be used to have such a weight average molecular weight.

[0092] Since a urethane acrylic monomer having two or more functional groups has high mechanical strength and elasticity by including a urethane moiety, when it is used as a second polymerizable monomer to form a crosslinked product with the first polymerizable monomer, a gel polymer electrolyte having elasticity while maintaining high mechanical strength can be manufactured.

[0093] As a second polymerizable monomer, a monomer containing a multifunctional functional group having a structure similar to a urethane-containing multifunctional acrylic monomer may be added. As other monomers containing such a multifunctional functional group, for example, one or more selected from the group consisting of urethane acrylate methacrylate, urethane epoxy methacrylate, and Arkema's product names Satomer N3DE180 and N3DF230 may be used.

[0094] When a polyfunctional acrylic monomer containing a urethane group is used as a polymerizable monomer, it can act as a diluent in the electrolyte, thereby reducing the viscosity of the composition for forming a gel polymer electrolyte. The viscosity of the composition for forming a gel polymer electrolyte is 4 to 10 cps. Therefore, using a composition having such a viscosity can facilitate injection into a battery structure.

[0095] The polymerizable monomer containing the above PFPE unit and having three or more polymerizable functional groups contains a perfluoroether unit, thereby exhibiting an effect of increasing the ionic conductivity of the gel polymer electrolyte, and improving oxidation stability, thereby enhancing high-voltage stability compared to the case where a polymerizable monomer not containing a PFPE unit is used. For example, a compound represented by the following chemical formula 3 or chemical formula 3-1 may be mentioned.

[0096] <Chemical Formula 3>

[0097]

[0098] In chemical formula 3, R1 is hydrogen or a C1-C6 alkyl group, m and n are each greater than 0, and the sum of m+n is in the range of 2 to 300 or in the range of 2 to 100. For example, m is a number from 1 to 150, or from 1 to 100, and n is a number from 1 to 150, or from 1 to 100.

[0099] <Chemical Formula 3-1>

[0100]

[0101] In Chemical Formula 3-1, p and q are greater than 0, the sum of p+q is in the range of 2 to 300, or in the range of 2 to 100, p is a number from 1 to 150, or a number from 1 to 100, and q is a number from 1 to 150 or 1 to 100.

[0102] The weight average molecular weight of the compound represented by the above chemical formula 3 or chemical formula 3-1 is 400 to 10,000, 400 to 5,000, or 500 to 3,000.

[0103] In this specification, the weight average molecular weight of the compound can be measured by gel permeation chromatography (GPC).

[0104] In the polymerizable monomer containing the above PFPE unit and having two or more polymerizable functional groups, the number of polymerizable functional groups may be three or more, or four or more. The compound of the above chemical formula 3 has four (meth)acrylic groups, which are crosslinking functional groups, and thus can form a network capable of trapping a large amount of liquid while using a small amount compared to a case where a compound having less than three crosslinking functional groups is used.

[0105] The above second polymerizable monomer is a compound represented by the following chemical formula 4, a compound represented by the following chemical formula 5, or a combination thereof.

[0106] <Chemical Formula 4>

[0107]

[0108] In chemical formula 4, m and n are greater than 0, and the sum of m+n is in the range of 2 to 300 or in the range of 2 to 100. For example, m is a number from 1 to 150, or from 1 to 100, and n is a number from 1 to 150, or from 1 to 100.

[0109] <Chemical Formula 5>

[0110]

[0111] In chemical formula 5, m and n are greater than 0, and the sum of m+n is in the range of 2 to 300 or in the range of 2 to 100. For example, m is a number from 1 to 150, or from 1 to 100, and n is a number from 1 to 150, or from 1 to 100.

[0112] A polymerizable monomer containing the above PFPE unit and having three or more polymerizable functional groups is commercially available under the trade name Fluorolink. ® AD 1700 PFPE - commercially available as perfluoropolyether (PFPE) urethane acrylate (Solvay Specialty Polymers Italy SpA).

[0113] The mixing weight ratio of the first polymerizable monomer, which is a multifunctional acrylic monomer, and at least one second polymerizable monomer selected from a urethane acrylic monomer having two or more functional groups and a polymerizable monomer containing a PFPE unit and three or more polymerizable functional groups is in the range of 1:10 to 10:1. The weight ratio of the first polymerizable monomer and the second polymerizable monomer is, for example, 5:1 to 1:1 or 3:1 to 1:1. When the weight ratio of the first polymerizable monomer and the second polymerizable monomer is in the above range, a gel polymer electrolyte with improved ionic conductivity and physical properties can be formed.

[0114] The gel polymer electrolyte made of a crosslinked product obtained from the first polymerizable monomer and the second polymerizable monomer is Li + Cations such as and PF6 - The interaction with anions such as is very strong. This strong interaction can be confirmed to be caused by the difference in electron density distribution in DFT (Discrete Fourier Transform) simulation.

[0115] The above gel polymer electrolyte-containing separator is manufactured separately in the form of a self-supporting membrane, and a lithium battery can be manufactured by positioning the gel polymer electrolyte-containing separator on top of the negative electrode current collector and protective layer and placing the positive electrode on top of it.

[0116] Alternatively, a lithium battery having a separator containing a gel polymer electrolyte can be manufactured by forming a battery structure by positioning a negative electrode current collector and a protective layer and arranging a separator and a positive electrode on top of the battery structure, injecting a composition for forming a gel polymer electrolyte into the battery structure, and performing heat treatment.

[0117] A lithium battery according to an embodiment includes a negative electrode current collector; a protective layer formed on the negative electrode current collector; a separator; a gel polymer electrolyte; and a positive electrode, and includes a negative electrode active material layer disposed between the negative electrode current collector and the protective layer, or the negative electrode active material layer is absent (free), the protective layer includes boron nitride (BN) and a binder, and the gel polymer electrolyte contains a gel polymer, boron nitride (BN), butyronitrile, and a liquid electrolyte.

[0118] In a lithium battery according to an embodiment, the thickness of the protective layer is 1 to 10 μm, and the thickness of the separator is 5 to 20 μm. In the present disclosure, the thickness represents an average thickness. When the thickness of the protective layer and the separator are within the above range, a lithium battery having improved ionic conductivity and physical properties and improved lifespan characteristics can be provided.

[0119] In the above gel polymer electrolyte, the liquid electrolyte contains an organic solvent, which acts as a medium through which ions involved in the electrochemical reaction of the battery can move. The organic solvent may be a carbonate-based, ester-based, ether-based, ketone-based, or alcohol-based solvent, an aprotic solvent, or a combination thereof.

[0120] Examples of the above carbonate solvents that can be used include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC).

[0121] Ester solvents that can be used include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, and caprolactone.

[0122] Examples of ether solvents that can be used include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and tetrahydrofuran. In addition, examples of ketone solvents that can be used include cyclohexanone. Examples of alcohol solvents that can be used include ethyl alcohol and isopropyl alcohol, and examples of aprotic solvents that can be used include nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double bond, an aromatic ring, or an ether group); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane and 1,4-dioxolane; and sulfolanes.

[0123] The above organic solvents can be used alone or in combination of two or more.

[0124] In addition, when using a carbonate solvent, a cyclic carbonate and a chain carbonate can be mixed and used, and the cyclic carbonate and the chain carbonate can be mixed in a volume ratio of 1:1 to 1:9.

[0125] According to one embodiment, the carbonate compound includes fluoroethylene carbonate (FEC) and diethyl carbonate (DEC), and the mixing weight ratio of the FEC and DEC is 1:10 to 1:1.

[0126] The above liquid electrolyte may further include a nitrile compound. The nitrile compound

[0127] The compound is at least one selected from among succinonitrile (SN), adiponitrile (1,4-dicyanobutane or 1,6-hexanedinitrile), dicyanobutene (DCB), ethylene glycol bis(propionitrile) ether, hexanetricarbonitrile (HTCN), acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentane carbonitrile, cyclohexane carbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile. The content of the above nitrile compound is 1 to 5 parts by weight based on 100 parts by weight of the total weight of the gel polymer electrolyte. Such a nitrile compound can be used to manufacture a gel polymer electrolyte with excellent high-voltage stability and improved ionic conductivity.

[0128] The lithium salt is a substance that dissolves in an organic solvent and acts as a source of lithium ions within the battery, enabling the basic operation of a lithium secondary battery and promoting the movement of lithium ions between the positive and negative electrodes. Lithium difluorobis(oxalato)phosphate (LiDFOB) and LiBF4 are used as the lithium salt. The concentration of the lithium salt is, for example, 0.1 M to 5.0 M, 0.2 M to 4.0 M, or 0.3 M to 4.0 M.

[0129] Lithium salts include LiPF6, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide (LiFSI), LiC4F9SO3, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2) (wherein x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium bis(oxalato)borate (LiBOB) may further include one or more selected from the group consisting of lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, and lithium bis(oxalato)borate (LiBOB). The concentration of the lithium salt is, for example, from 0.1 M to 5.0 M.

[0130] According to one embodiment, the lithium salt includes a first lithium salt and a second lithium salt.

[0131] The ionic conductivity of the gel polymer electrolyte can be improved by including a first lithium salt and a second lithium salt.

[0132] 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.

[0133] 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.

[0134] 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.

[0135] The ionic conductivity of the gel polymer electrolyte may be reduced by not including the second lithium salt. The structural stability of the SEI layer may be reduced by not including the second lithium salt.

[0136] Fluorine-containing borate lithium salts may include, for example, LiBF4, LiBF3(C2F5), compounds represented by chemical formulae 5 to 16, or combinations thereof.

[0137] <Chemical Formula 5> <Chemical Formula 6>

[0138]

[0139] <Chemical Formula 7> <Chemical Formula 8>

[0140]

[0141] <Chemical Formula 9> <Chemical Formula 10>

[0142]

[0143] <Chemical Formula 11> <Chemical Formula 12>

[0144]

[0145] <Chemical Formula 13> <Chemical Formula 14>

[0146]

[0147] <Chemical Formula 15> <Chemical Formula 16>

[0148]

[0149] 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 5 to 16.

[0150] The first lithium salt may include LiBF4, and the second lithium salt may include, for example, LiDFOB (lithium difluoro(oxalate)borate).

[0151] The liquid electrolyte according to the embodiment includes LiBFOB, LiBF4, butryonitrile (BN), and FEC as described above, and includes a carbonate compound.

[0152] 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.

[0153] The gel polymer electrolyte may not contain, for example, lithium bis(oxalato)borate (LiBOB). By not containing lithium bis(oxalato)borate (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.

[0154] 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.

[0155] The content of the first lithium salt and the second lithium salt may be, for example, greater than 0 to 1.2 M, 0.1 M to 1.0 M, or 0.4 M to 0.8 M, for the precursor composition for forming a gel polymer electrolyte (e.g., the composition for forming a gel polymer electrolyte) before adding the first polymerizable monomer and the second polymerizable monomer and the thermal initiator independently of each other.

[0156] 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.

[0157] 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 polymer electrolyte can be lowered. The first organic solvent includes, for example, a linear carbonate compound. Since the first organic solvent is a linear carbonate solvent, the viscosity of the precursor composition for forming a gel polymer electrolyte before crosslinking can be lowered. The precursor composition can be easier to handle. 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 solvent substituted with a substituent, the first lithium salt and the second lithium salt can be more easily dissolved in the precursor composition for forming a gel electrolyte, and the substituent can participate in the formation of the SEI layer, thereby improving the structural stability of the SEI layer. The first organic solvent can 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.

[0158] The gel polymer electrolyte may be present within the separator and at the interface between the separator and the positive electrode. The gel polymer electrolyte may be contained within a portion of the positive electrode.

[0159] The weight average molecular weight of the first polymerizable monomer is 500 to 50,000, 1000 to 45,000. If the weight average molecular weight of the first polymerizable monomer is less than the above range, the density of crosslinking points within the molecular structure of the polymer after crosslinking may be too high, preventing free movement of the lithium salt. If the weight average molecular weight is greater than the above range, the density of crosslinking points within the molecular structure of the polymer after crosslinking may be too low, reducing the electrolyte blocking ability.

[0160] The weight average molecular weight of the second polymerizable monomer is 500 to 50,000. When the weight average molecular weight of the second polymerizable monomer is within the above range, a lithium battery having excellent effects of improving ionic conductivity and increasing lifespan can be manufactured.

[0161] The gel polymer electrolyte may further include one or more selected from an ionic liquid and a polymer ionic liquid.

[0162] The ionic liquid may include at least one selected from the group consisting of diethylmethylammonium trifluoromethanesulfonate ([dema][TfO]), dimethylpropylammonium trifluoromethanesulfonate ([dmpa][TfO]), N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide ([DEMA][TFSI]), N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide ([PP13][TFSI]), N-butyl-N-methyl pyrrolidinium bis(trifluoromethanesulfonyl)imide ([Py14][TFSI]), and methylpropylpiperidiniumtrifluoromethanesulfonylimide ([mpp][TFSI]).

[0163] The above gel polymer electrolyte-containing separator can be manufactured separately in the form of a self-supporting membrane, and a lithium battery can be manufactured by positioning the gel polymer electrolyte-containing separator on top of a negative electrode current collector and a protective layer, and placing the positive electrode on top of the separator. Here, a protective layer cannot be provided.

[0164] Alternatively, a lithium battery having a separator containing a gel polymer electrolyte can be manufactured by forming a battery structure by positioning a negative electrode current collector and a protective layer and arranging a separator and a positive electrode thereon, injecting a composition for forming a gel polymer electrolyte into the battery structure, and heat-treating the composition.

[0165] According to another aspect, a lithium battery is provided, which includes 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 includes the gel polymer electrolyte described above.

[0166] The ionic conductivity of the above gel polymer electrolyte at 25°C and 1 atm is 0.30 mS / cm or more, for example, 0.38 mS / cm or more, and the ionic conductivity at 45°C and 1 atm is 0.42 mS / cm or more, or 0.47 mS / cm or more. Using a gel polymer electrolyte having such ionic conductivity can provide a lithium battery with improved cycle characteristics.

[0167] The above lithium battery may further include a separator on the negative electrode current collector. The separator may contain a gel polymer electrolyte.

[0168] A lithium battery may have a structure including a positive electrode; a negative electrode current collector; a separator disposed between the positive electrode and the negative electrode current collector; and a gel-type polymer electrolyte disposed on top of the separator. The gel-type polymer electrolyte may be disposed between the separator and the positive electrode.

[0169] The negative electrode active material layer or protective layer may be disposed between the negative electrode current collector and the separator, or the negative electrode active material layer or protective layer may be absent (free).

[0170] Figure 2 illustrates a laminated structure of a lithium battery according to an embodiment. Here, the lithium battery is, for example, a lithium metal battery.

[0171] A lithium battery (1) comprises a negative electrode (20) including a negative electrode collector (21), and the negative electrode (20) has a structure in which an electrolyte layer (30) is disposed between the negative electrode collector (21) and the positive electrode (10). In the negative electrode (20), a negative electrode active material layer is absent. Although not shown in Fig. 1, a protective layer may be formed on the negative electrode collector (21).

[0172] The electrolyte layer (30) contains a gel polymer electrolyte. The electrolyte layer (30) may further include a separator. The separator may include a porous substrate or the porous substrate and a coating layer formed thereon.

[0173] The positive electrode (10) contains a positive electrode active material layer (12) and a positive electrode current collector (11). The separator (30) contains a gel polymer electrolyte.

[0174] When the electrolyte layer includes a porous substrate, a gel polymer electrolyte may be disposed between the porous substrate and the anode. The porous substrate may contain a gel polymer electrolyte.

[0175] According to one embodiment, a gel polymer electrolyte may be contained in the positive electrode (10).

[0176] A lithium metal layer (22) may be further disposed between the negative electrode current collector (21) and the electrolyte layer (30), as shown in Fig. 3. The lithium metal layer corresponds to the negative electrode active material layer. The lithium metal layer may include lithium metal or a lithium alloy.

[0177] A protective layer may be positioned between the lithium metal layer and the electrolyte layer. The protective layer is a lithium ion conductive buffer layer, and as an electrolyte layer, it can prevent or reduce contact between the separator containing the gel polymer electrolyte and the lithium metal layer. It also inhibits the formation and growth of lithium dendrites positioned on the negative electrode current collector.

[0178] The lithium metal layer can also be placed during battery assembly.

[0179] In a lithium battery according to an embodiment, the thickness expansion rate of the negative electrode, expressed by the following mathematical formula 1, is 150% or less.

[0180] <Formula 1>

[0181] Cathode thickness expansion rate (%) = [thickness of lithium precipitation layer formed on the negative electrode current collector after 100 cycles of charging / thickness of lithium precipitation layer formed on the negative electrode current collector after formation] × 100

[0182] For example, the thickness expansion ratio of the negative electrode may be 140% or less, 139% or less, 138% or less, 136% or less, 105 to 136%, or 110 to 136%. By including a binder including a crosslinked polymer with increased modulus, the strength of the binder in the protective layer may be increased, thereby suppressing or reducing volume change of the negative electrode during charge and discharge. Charge and discharge conditions may refer to the evaluation examples.

[0183] The binder of the protective layer can be, for example, vinylidenefluoride-hexafluoropropylene (VDF-HFP) copolymer, polyethylene oxide, polypropylene oxide, polydimethylsiloxane, polyacrylonitrile, polymethyl(meth)acrylate, polyvinyl chloride, polyvinylidene fluoride, polyvinylidenefluoride-co-hexafluoropropylene, polyethyleneimine, polyphenylene terephthalamide, polymethoxypolyethyleneglycol(meth)acrylate, poly2-methoxy ethylglycidyl ether, or a combination thereof.

[0184] The binder of the above protective layer may include, for example, a crosslinked polymer of a first polymer and a second polymer, which is a crosslinking reaction product of a first polymer containing a hydroxyl group and a second polymer having a crosslinkable functional group.

[0185] The weight ratio of the first polymer and the second polymer is 50:50 to 99:1, and the second polymer is at least one selected from among fluorinated polyamic acid and fluorinated polyimide having a carboxyl group.

[0186] The protective layer is dense, increasing its density and strength, allowing free lithium ion movement and enhancing lithium ion transport, thereby improving lithium electrodeposition characteristics. Consequently, ionic conductivity is improved, thereby enhancing the high-rate characteristics of lithium batteries. Furthermore, by positioning the protective layer on the negative electrode active material layer, side reactions between the negative electrode active material layer and the electrolyte can be effectively blocked, suppressed, or reduced.

[0187] The protective layer may further comprise an inorganic material. The inorganic material is selected from the group consisting of silica (SiO2), alumina (Al2O3), titanium oxide (TiO2), lithium titanium oxide (LiTiO2), barium titanium oxide (BaTiO2), lithium alumina (LiAlO2), and zeolite, or a mixture thereof.

[0188] The mixing weight ratio of the first polymer containing a hydroxyl group and the second polymer is adjusted to be in the range of 50:50 to 99:1, 50:50 to 90:10, or 60:40 to 90:10.

[0189] When a protective layer according to an embodiment of the present invention exists on the surface of a negative electrode active material layer including lithium metal, the generation and / or growth of lithium dendrites on the negative electrode current collector can be effectively prevented. In addition, the cycle characteristics and stability of the above-described negative electrode and a lithium 500,000-cell battery employing the same are improved.

[0190] The above hydroxyl group-containing first polymer is carboxymethyl cellulose (CMC); polyvinyl alcohol (PVA); Vinyl acetate, butyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 2-hydroxyethylene glycol (meth)acrylate, 2-hydroxypropylene glycol (meth)acrylate, acrylic acid, methacrylic acid, 2-(meth)acryloyloxy acetic acid, 3-(meth)acryloyloxy propinic acid, 4-(meth)acryloyloxy butyric acid, itaconic acid, maleic acid, 2-isocyanatoethyl (meth)acrylate, 3-isocyanatopropyl (meth)acrylate, A polymerization reaction product of one or more monomers selected from among 4-isocyanatobutyl (meth)acrylate, (meth)acrylamide, ethylene di(meth)acrylate, diethylene glycol (meth)acrylate, triethylene glycol di(meth)acrylate, trimethylene propane tri(meth)acrylate, trimethylene propane triacrylate, 1,3-butanediol (meth)acrylate, 1,6-hexanediol di(meth)acrylate, allyl acrylate, and N-vinyl caprolactam, or a hydrolyzate thereof, may be mentioned.

[0191] The first polymer may be polyvinyl alcohol (PVA). For example, polyvinyl alcohol may be a hydrolyzate obtained by hydrolyzing polyvinyl acetate with an alkali.

[0192] The degree of saponification of polyvinyl alcohol is 60 to 99%, 70 to 95%, 75 to 90% or 80

[0193] The degree of saponification of polyvinyl alcohol can be 85 to 90%. For example, the degree of saponification of polyvinyl alcohol can be 85 to 90%.

[0194] The properties of the protective layer can be further improved within the above saponification range.

[0195] The weight average molecular weight of the first polymer may be 10,000 to 500,000 Dalton, 10,000 to 400,000 Dalton, 10,000 to 300,000 Dalton, 10,000 to 200,000 Dalton, 50,000 to 150,000 Dalton, 70,000 to 100,000 Dalton, or 80,000 to 100,000 Dalton. The physical properties of the protective layer may be further improved within the weight average molecular weight range of the first polymer.

[0196] The protective layer may further include a second polymer having a functional group capable of crosslinking with the first polymer containing a hydroxyl group. In this case, the protective layer further includes a crosslinked polymer of the first polymer and the second polymer.

[0197] The second polymer comprises at least one selected from among fluorinated polyamic acid and fluorinated polyimide having a carboxyl group.

[0198] The above fluorinated polyamic acid is represented by the following chemical formula 17 or 18, and the above fluorinated polyimide is a polymer represented by the following chemical formula 19 or 20.

[0199] [Chemical Formula 17]

[0200]

[0201] [Chemical Formula 18]

[0202]

[0203] [Chemical Formula 19]

[0204]

[0205] [Chemical Formula 20]

[0206]

[0207] In the above equations, n and m are the mole fractions within the repeating unit, respectively, and 0 <n≤1, 0≤m<1, n+m=1이다.

[0208] For example, in the second polymer, a repeating unit including a crosslinking group and a crosslinking group

[0209] The mole fraction of repeating units that do not contain each other is 0 <n≤0.5, 0.5≤m<1 및 n+m=1일 수 있다. 예를 들어, 상기 제2 고분자에서 가교기를 포함하는 반복단위와 가교기를 포함하지 않는 반복단위의 몰분율이 각각 0.1≤n≤0.4, 0.6≤m≤0.9 및 n+m=1일 수 있다. 예를 들어, 상기 제2 고분자에서 가교기를 포함하는 반복단위와 가교기를 포함하지 않는 반복단위의 몰분율이 각각 0.15≤n≤0.35, 0.65≤m≤0.85 및 n+m=1일 수 있다. 예를 들어, 상기 제2 고분자에서 가교기를 포함하는 반복단위와 가교기를 포함하지 않는 반복단위의 몰분율이 각각 0.2≤n≤0.3, 0.7≤m≤0.8 및 n+m=1일 수 있다. 상기 몰분율 범위에서 더욱 향상된 물성을 제공할 수 있다.

[0210] In one embodiment, the ratio of n and m is 1:1.5 to 1:5, 1:2 to 1:4, or 1:3.

[0211] For example, the second polymer may be a random copolymer. For example, the above

[0212] The second polymer may be a block copolymer.

[0213] The weight average molecular weight of the second polymer may be 10,000 to 1,200,000 Dalton, 10,000 to 1,100,000 Dalton, 10,000 to 1,000,000 Dalton, 10,000 to 500,000 Dalton, 100,000 to 500,000 Dalton, 100,000 to 400,000 Dalton, for example, 100,000 to 300,000 Dalton. The physical properties of the protective layer may be further improved within the weight average molecular weight range of the second polymer.

[0214] In the above protective layer, the weight ratio of the first polymer containing a hydroxyl group to the second polymer may be 99:1 to 50:50, 95:5 to 55:45, 95:5 to 60:40, 95:5 to 65:35, or 90:10 to 70:30. In the above range of the weight ratio of the first polymer to the second polymer, the physical properties of the protective layer may be further improved.

[0215] The hydroxyl groups of the first polymer and the carboxyl groups of the second polymer react with each other to form an ester bond, thereby forming a third polymer crosslinked with the first and second polymers. The formation of the third polymer enhances the stability of the protective layer, and in the case of halogen groups such as fluorine functional groups, it can improve interfacial stability by reducing the formation of irreversible lithium inclusions.

[0216] The weight average molecular weight of the third polymer may be from 10,000 to 1,500,000 Daltons. For example, the weight average molecular weight of the third polymer may be from 10,000 to 1,200,000 Daltons. For example, the weight average molecular weight of the third polymer in the binder may be from 10,000 to 1,100,000 Daltons. For example, the weight average molecular weight of the third polymer may be from 10,000 to 1,000,000 Daltons. For example, the weight average molecular weight of the third polymer may be from 10,000 to 500,000 Daltons. For example, the weight average molecular weight of the third polymer may be from 100,000 to 400,000 Daltons. For example, the weight average molecular weight of the third polymer may be 100,000 to 300,000 Dalton. The properties of the protective layer may be further improved within the weight average molecular weight range of the third polymer.

[0217] The protective layer according to an embodiment includes a crosslinked polymer of polyvinyl alcohol and polyamic acid. The polyamic acid is, for example, a polymer represented by the chemical formula 9 or 10 described above.

[0218] In another embodiment, the crosslinked polymer of the protective layer is a crosslinked polymer of polyvinyl alcohol and fluorinated polyimide (PVA / PI-f). The fluorinated polyimide is a polymer represented by the chemical formula 11 or 12 described above.

[0219] The above protective layer may contain a polar functional group binder and may be free of lithium salt.

[0220] The protective layer may further contain a lithium salt, and when containing a lithium salt, excellent ionic conductivity of the protective layer can be secured. The lithium salt may be one or more of materials such as LiSCN, LiN(CN)2, LiClO4, LiBF4, LiAsF6, LiPF6, LiCF3SO3, LiC(CF3SO2)3, LiC(FSO2)3, LiN(SO2C2F5)2, LiN(SO2CF3)2, LiN(SO2F)2, LiSbF6, LiPF3(CF2CF3)3, LiPF3(CF3)3, and LiB(C2O4)2.

[0221] In one embodiment, a lithium metal layer may be disposed between the negative electrode current collector and the electrolyte layer. The lithium metal layer may be disposed during battery assembly or may be formed during charging. The lithium metal layer corresponds to the negative electrode active material layer.

[0222] The lithium metal layer comprises a lithium metal foil, a lithium metal powder, a lithium alloy foil, a lithium alloy powder, or a combination thereof, wherein the lithium alloy contains lithium and a first metal.

[0223] The lithium alloy contains lithium and a first metal, wherein the first metal is indium (In), silicon (Si), gallium (Ga), tin (Sn), aluminum (Al), zirconium (Zr), niobium (Nb), germanium (Ge), antimony (Sb), bismuth (Bi), gold (Au), platinum (Pt), palladium (Pd), magnesium (Mg), silver (Ag), zinc (Zn), chromium, cesium, sodium, potassium, calcium, yttrium, tantalum, hafnium, barium, vanadium, strontium, lanthanum, or a combination thereof.

[0224] Lithium alloys are alloys of lithium and other metals that can be alloyed with lithium, such as lithium-silver alloys, lithium-zinc alloys, lithium-magnesium alloys, and lithium-tin alloys. The negative electrode active material layer including a lithium metal foil may be, for example, a lithium metal layer. The negative electrode active material layer including a lithium alloy foil may be, for example, a lithium alloy layer. The negative electrode active material layer including lithium metal powder and / or lithium alloy powder may be introduced by coating a slurry including lithium powder and a binder onto a negative electrode current collector. The binder may be, for example, a fluorine-based binder such as polyvinylidene fluoride (PVDF). The negative electrode active material layer may not include a carbon-based negative electrode active material. Therefore, the negative electrode active material layer may be formed of a metal-based negative electrode active material.

[0225] The thickness of the lithium metal layer may be, for example, 1 μm to 50 μm, 1 μm to 30 μm, 5 μm to 30 μm, 10 μm to 30 μm, 10 μm to 50 μm, or 10 μm to 80 μm. When the lithium metal layer has a particle size in this range, the cycle characteristics and life characteristics of the lithium battery can be further improved.

[0226] 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.

[0227] 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), the volume change during charge and discharge of the lithium battery (1) can be suppressed. As a result, deterioration due to the volume change of the lithium battery (1) can be suppressed or reduced.

[0228] For example, in the XPS (X-ray Photoelectron Spectroscopy) analysis of the surface of the lithium metal layer (22), the intensity of the peak derived from fluorine (F) may be greater than the intensity of the peak derived from oxygen (O). In the XPS analysis of the surface of the lithium metal layer (22), the peak intensity derived from, for example, fluorine (F) element may be greater than 100%, 105% or more, 110% or more, or 120% or more of the peak intensity derived from oxygen (O) element in the XPS analysis of the surface of the lithium metal layer (23). In the XPS analysis of the surface of the lithium metal layer (22), the peak intensity derived from, for example, 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 oxygen (O). The structural stability of the SEI layer formed on the surface of the lithium metal layer (22) can be improved by mainly including an inorganic compound containing 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.

[0229] After assembling the lithium battery (1), a lithium metal layer (22) is deposited by charging, and since the lithium metal layer (23) is not included when assembling the lithium battery (1), the energy density of the lithium battery (1) increases. When the lithium metal layer (23) 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.

[0230] The particle size of the lithium powder may be, for example, 0.1 ㎛ to 3 ㎛, 0.1 ㎛ to 2 ㎛, or 0.1 ㎛ to 2 ㎛. When the lithium powder has a thickness in this range, the life characteristics of the lithium battery can be further improved.

[0231] The cathode may further include a cathode active material layer.

[0232] The negative electrode active material layer contains a carbon-based compound; a mixture of at least one selected from a carbon-based material and a first metal; a composite of at least one selected from a carbon-based material and a first metal; or a combination thereof, wherein the carbon-based material includes amorphous carbon, and the average particle size of the amorphous carbon is from 10 nm to 100 nm. The carbon-based material includes carbon black, carbon nanotubes, carbon nanofibers, fullerenes, activated carbon, carbon fibers, or a combination thereof.

[0233] The first metal is indium (In), silicon (Si), gallium (Ga), tin (Sn), aluminum (Al), titanium (Ti), zirconium (Zr), niobium (Nb), germanium (Ge), antimony (Sb), bismuth (Bi), gold (Au), platinum (Pt), palladium (Pd), magnesium (Mg), silver (Ag), zinc (Zn), nickel, iron, cobalt, chromium, cesium, sodium, potassium, calcium, yttrium, tantalum, hafnium, barium, vanadium, strontium, lanthanum, or a combination thereof.

[0234] A lithium metal layer may be further disposed between the negative electrode current collector and one surface of the protective layer.

[0235] There is. A lithium metal layer can be further disposed on the other surface opposite to the one surface of the above protective layer.

[0236] The thickness of the protective layer is 1 to 10 μm, 1 to 8 μm, 1 to 7 μm, 2 to 6 μm, or 3 to 5 μm. When the thickness of the protective layer is within the above range, the internal resistance increases, and the energy density of the lithium battery is not reduced, and the energy density is excellent and the high-rate characteristics and life characteristics are improved.

[0237] In a lithium battery according to one embodiment, the electrolyte layer may further contain an electrolyte. The electrolyte may be a liquid electrolyte, a solid electrolyte, a gel electrolyte, or a combination thereof.

[0238] The above solid electrolyte includes an oxide-based solid electrolyte, a sulfide-based solid electrolyte, a polymer solid electrolyte, or a combination thereof. A gel electrolyte may have a gel state, for example, without including a polymer.

[0239] The above gel electrolyte comprises a polymer gel electrolyte. The positive electrode comprises a positive electrode current collector and a positive electrode active material layer, and at least one of the positive electrode current collector and the negative electrode current collector comprises a base film and a metal layer disposed on one or both sides of the base film, and the base film comprises a polymer, and the polymer comprises polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof.

[0240] The above metal layer includes indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof.

[0241] The thickness of the negative electrode active material layer may be, for example, 0.1 ㎛ to 500 ㎛, 1 ㎛ to 500 ㎛, or 10 ㎛ to 500 ㎛, but is not necessarily limited to this range and may be adjusted according to the required shape, capacity, etc. of the lithium battery. When the thickness of the negative electrode active material layer is within the above range, the cycle characteristics are improved without lowering the energy density of the lithium battery.

[0242] A lithium battery according to an embodiment does not include a negative electrode active material layer disposed between a negative electrode current collector (21) and a protective layer. An anode not including a negative electrode active material layer may include a negative electrode active material layer by plating lithium metal between a negative electrode current collector (21) and a protective layer by charging after being introduced into a lithium battery together with a positive electrode and an electrolyte. The negative electrode active material layer may be a lithium plating layer (plated lithium layer).

[0243] Lithium batteries may further include a separator.

[0244] The pore diameter of the separator is generally 0.01 to 10 μm, and the thickness can generally be 5 to 20 μm. Examples of such separators include sheets or non-woven fabrics made of olefin-based polymers such as polypropylene, glass fiber, or polyethylene. When a solid polymer electrolyte is used as the electrolyte, the solid polymer electrolyte may also function as the separator.

[0245] Specific examples of the above separation membrane include polyethylene, polypropylene, or a multilayer membrane of two or more layers thereof, and mixed multilayer membranes such as a polyethylene / polypropylene two-layer separation membrane, a polyethylene / polypropylene / polyethylene three-layer separation membrane, and a polypropylene / polyethylene / polypropylene three-layer separation membrane may be used.

[0246] In a lithium battery according to an embodiment, the liquid electrolyte contains a lithium salt and an organic solvent.

[0247] As the organic solvent, for example, an aprotic organic solvent such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, tetrahydroxy franc, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolan, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxy methane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl pyropionate, ethyl propionate, etc. can be used. Carbonate solvents such as propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, and diethyl carbonate can be used.

[0248] The above lithium salt can be any one that is commonly used in lithium secondary batteries, and as a material that is easily dissolved in the non-aqueous solvent, for example, one or more of the following materials can be used: LiSCN, LiN(CN)2, LiClO4, LiBF4, LiAsF6, LiPF6, LiCF3SO3, LiC(CF3SO2)3, LiC(FSO2)3, LiN(SO2C2F5)2, LiN(SO2CF3)2, LiN(SO2F)2, LiSbF6, LiPF3(CF2CF3)3, LiPF3(CF3)3, and LiB(C2O4)2.

[0249] The concentration of the lithium salt may be, for example, 1 to 5 M, for example, 1 to 2.5 M, in the liquid electrolyte. In the above range, a sufficient amount of lithium ions required for charging and discharging a lithium battery can be generated.

[0250] When a gel-type polymer electrolyte exists in the pores of a porous substrate, the interfacial resistance between the positive electrode, negative electrode, and separator is minimized or reduced, and lithium movement becomes easier.

[0251] According to one embodiment, the negative electrode active material layer can be arranged during the assembly of the lithium battery. According to another embodiment, the negative electrode active material layer can be a negative electrode active material layer by plating lithium metal after charging. The negative electrode active material layer can be a lithium plating layer (plated lithium layer).

[0252] The above negative electrode active material layer includes lithium metal or a lithium alloy.

[0253] When the negative electrode active material layer is placed at the time of assembly, it may include only a carbon-based material, a carbon-based material, and at least one selected from metals and metalloids.

[0254] The carbon-based material includes amorphous carbon, and the average particle diameter of the amorphous carbon is 10 nm to 100 nm, and the carbon-based material includes carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), graphene, or a combination thereof.

[0255] The above negative active material layer includes a lithium metal foil, a lithium metal powder, a lithium alloy foil, a lithium alloy powder, or a combination thereof, wherein the lithium alloy contains lithium and a first metal.

[0256] The first metal is indium (In), silicon (Si), gallium (Ga), tin (Sn), aluminum (Al), titanium (Ti), zirconium (Zr), niobium (Nb), germanium (Ge), antimony (Sb), bismuth (Bi), gold (Au), platinum (Pt), palladium (Pd), magnesium (Mg), silver (Ag), zinc (Zn), nickel, iron, cobalt, chromium, cesium, sodium, potassium, calcium, yttrium, tantalum, hafnium, barium, vanadium, strontium, lanthanum, or a combination thereof.

[0257] The negative electrode active material layer (22) may include, for example, lithium foil, lithium powder, or a combination thereof. The lithium foil may include, for example, lithium metal foil, lithium alloy foil, or a combination thereof. The lithium powder may include lithium metal powder, lithium alloy powder, or a combination thereof. A lithium alloy is an alloy of lithium and another metal that can be alloyed with lithium, such as a lithium-silver alloy, a lithium-zinc alloy, a lithium-magnesium alloy, or a lithium-tin alloy. The negative electrode active material layer including a lithium metal foil may be, for example, a lithium metal layer. The negative electrode active material layer including a lithium alloy foil may be, for example, a lithium alloy layer. The negative electrode active material layer including a lithium metal powder and / or a lithium alloy powder may be introduced by coating a slurry including lithium powder and a binder, etc., on a negative electrode current collector. The binder may be, for example, a fluorine-based binder such as polyvinylidene fluoride (PVDF). The negative electrode active material layer may not include a carbon-based negative electrode active material. Therefore, the negative electrode active material layer can be made of a metal-based negative electrode active material.

[0258] The negative electrode current collector is composed of a material that does not react with lithium, i.e., does not form an alloy or compound. The material constituting the negative electrode current collector includes, but is not limited to, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni), and any material that is used as an electrode current collector in the relevant technical field may be used. The negative electrode current collector may be composed of one of the above-mentioned metals, or may be composed of an alloy or a coating material of two or more metals. The negative electrode current collector is, for example, in the form of a plate or foil.

[0259] In one embodiment of the present invention, the positive electrode collector uses a plate or foil made of, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof. The thickness of the positive electrode collector is, for example, 1 µm to 100 µm, 1 µm to 50 µm, 5 µm to 25 µm, or 10 µm to 20 µm.

[0260] The negative electrode active material layer may contain a negative electrode active material and a binder.

[0261] The negative active material has, for example, a particle form. The average particle diameter of the negative active material having a particle form is, for example, 10 nm to 4 ㎛, 10 nm to 1 ㎛, 10 nm to 500 nm, 10 nm to 100 nm, or 20 nm to 80 nm. When the negative active material has an average particle diameter in this range, reversible plating and / or dissolution of lithium can be facilitated during charge and discharge. The average particle diameter of the negative active material is, for example, a median diameter (D50) measured using a laser particle size distribution analyzer.

[0262] The negative electrode active material may include, for example, at least one selected from a carbon-based negative electrode active material and a metal or metalloid negative electrode active material. The carbon-based negative electrode active material may be, for example, amorphous carbon. Examples of the carbon-based negative electrode active material include, but are not limited to, carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), graphene, etc., and any material classified as amorphous carbon in the relevant technical field may be used. Amorphous carbon is carbon that has no crystallinity or very low crystallinity, and is distinguished from crystalline carbon or graphite-based carbon. The metal or metalloid negative electrode active material includes, but is not limited to, one or more selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn), and any metal or metalloid negative electrode active material that forms an alloy or compound with lithium in the relevant technical field may be used. For example, nickel (Ni) does not form an alloy with lithium, and therefore is not a metal negative electrode active material in the present specification. The negative electrode active material layer includes a type of negative electrode active material among these negative electrode active materials, or includes a mixture of a plurality of different negative electrode active materials. For example, the negative electrode active material layer may include a mixture of amorphous carbon and one or more selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). The mixing ratio of the mixture (e.g., amorphous carbon and one or more metals) may be, for example, 10:1 to 1:2, 10:1 to 1:1, 7:1 to 1:1, 5:1 to 1:1, or 4:1 to 2:1 by weight.The negative electrode active material included in the negative electrode active material layer may include a mixture of first particles made of, for example, amorphous carbon and second particles made of a metal or a metalloid. The metal includes, for example, gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). The content of the second particles is 8 to 60 wt%, 10 to 50 wt%, 15 to 40 wt%, or 20 to 30 wt% based on the total weight of the mixture. When the second particles have a content in this range, the cycle characteristics of, for example, a lithium battery are further improved.

[0263] The binder included in the negative electrode active material layer may be, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, etc., but is not necessarily limited thereto, and any binder used in the relevant technical field may be used. The binder may be composed of a single binder or a plurality of different binders. When the negative electrode active material layer does not include a binder, the negative electrode active material layer can be easily separated from the negative electrode current collector (21). The content of the binder included in the negative electrode active material layer may be, for example, 1 to 20 wt% based on the total weight of the negative electrode active material layer.

[0264] The thickness of the negative electrode active material layer may be, for example, 0.1 μm to 500 μm, or 100 μm to 50 μm. The thickness of the negative electrode active material layer may be, for example, 1% to 50%, 1% to 30%, 1% to 10%, or 1% to 5% of the thickness (100%) of the positive electrode active material layer. When the thickness of the negative electrode active material layer is within the above range, the energy density and cycle characteristics of a lithium battery employing the negative electrode are improved without decreasing the cycle characteristics of the lithium battery.

[0265] When the thickness of the negative electrode active material layer decreases, the charge capacity of the negative electrode active material layer also decreases, for example. The charge capacity of the negative electrode active material layer may be, for example, 0.1% to 50%, 1% to 30%, 1% to 10%, 1% to 5%, or 1% to 2% of the charge capacity of the positive electrode active material layer. If the charge capacity of the negative electrode active material layer is too small, lithium dendrites formed between the negative electrode active material layer and the negative electrode current collector may collapse the negative electrode active material layer, making it difficult to improve the cycle characteristics of the lithium battery. If the charge capacity of the negative electrode active material layer increases excessively, the energy density of the lithium battery using the negative electrode (20) may decrease, and it may be difficult to improve the cycle characteristics. The charge capacity of the positive electrode active material layer is obtained by multiplying the charge capacity density (mAh / g) of the positive electrode active material by the mass of the positive electrode active material in the positive electrode active material layer. When multiple types of positive electrode active materials are used, the charge capacity density × mass value is calculated for each positive electrode active material, and the sum of these values ​​is the charge capacity of the positive electrode active material layer. The charge capacity of the negative electrode active material layer is also calculated in the same way. That is, the charge capacity of the negative electrode active material layer is obtained by multiplying the charge capacity density (mAh / g) of the negative electrode active material by the mass of the negative electrode active material in the negative electrode active material layer. When multiple types of negative electrode active materials are used, the charge capacity density × mass value is calculated for each negative electrode active material, and the sum of these values ​​is the capacity of the negative electrode active material layer. Here, the charge capacity density of the positive electrode active material and the negative electrode active material is the estimated capacity using an all-solid-state half-cell using lithium metal as a counter electrode. The charge capacity of the positive electrode active material layer and the negative electrode active material layer are directly measured by measuring the charge capacity using an all-solid-state half-cell. The charge capacity density is obtained by dividing the measured charge capacity by the mass of each active material. Alternatively, the charge capacity of the positive electrode active material layer and the negative electrode active material layer may be the initial charge capacity measured at the first charge cycle.

[0266] [Lithium battery]

[0267] According to one embodiment, a lithium battery includes a positive electrode; a negative electrode; and an electrolyte disposed between the positive electrode and the negative electrode. The lithium battery may further include a separator. Such a lithium battery may provide excellent life characteristics. The lithium battery may be, but is not limited to, a lithium primary battery, a lithium metal battery, a lithium-sulfur battery, a lithium-air battery, etc., and any lithium battery used in the art may be used.

[0268] Lithium batteries are manufactured by, for example, the following exemplary methods, but are not necessarily limited to these methods and are adjusted according to required conditions.

[0269] (anode)

[0270] First, a positive electrode active material composition is prepared by mixing a positive electrode active material, a conductive agent (e.g., an electronic conductor), a binder, and a solvent. The prepared positive electrode active material composition is directly coated on an aluminum current collector and dried to produce a positive electrode plate having a positive electrode active material layer formed thereon. Alternatively, the positive electrode active material composition is cast on a separate support, and then the film obtained by peeling from the support is laminated on the aluminum current collector to produce a positive electrode plate having a positive electrode active material layer formed thereon.

[0271] A compound capable of reversible intercalation and deintercalation of lithium (a lithiated intercalation compound) can be used as a cathode active material. Specifically, one or more of a composite oxide of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof can be used.

[0272] The above composite oxide may be a lithium transition metal composite oxide, and specific examples thereof include lithium nickel-based oxide, lithium cobalt-based oxide, lithium manganese-based oxide, lithium iron phosphate-based compound, cobalt-free nickel-manganese-based oxide, or a combination thereof.

[0273] As an example, a compound represented by any one of the following chemical formulas may be used: Lia A 1-b X b O 2-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a Mr 2-b X b O 4-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a Ni 1-b-c Co b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni 1-b-c Mr b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni b Co c L 1 d G e O2(0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0≤e≤0.1); Li a NiG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a CoG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mr 1-b G b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn2G b O4(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mr 1-g G g PO4(0.90≤a≤1.8, 0≤g≤0.5); Li (3-f) Fe2(PO4)3(0≤f≤2); Li a FePO4(0.90≤a≤1.8).

[0274] In the above chemical formula, A is Ni, Co, Mn, or a combination thereof; X is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; L 1 is Mn, Al or a combination thereof.

[0275] For example, the cathode active material may be a high-nickel cathode active material in which the nickel content is 80 mol% or more, 85 mol% or more, 90 mol% or more, 91 mol% or more, or 94 mol% or more and 99 mol% or less, based on 100 mol% of metals excluding lithium. The high-nickel cathode active material can realize high capacity and thus can be applied to high-capacity, high-density lithium secondary batteries.

[0276] The cathode active material is, for example, Li a Ni x Co y M z O 2-b A b (1.0≤a≤1.2, 0≤b≤0.2, 0.8≤x<1, 0 <y≤0.3, 0<z≤0.3, 및 x+y+z=1이고, M은 망간(Mn), 니오븀(Nb), 바나듐(V), 마그네슘(Mg), 갈륨(Ga), 실리콘(Si), 텅스텐(W), 몰리브덴(Mo), 철(Fe), 크롬(Cr), 구리(Cu), 아연(Zn), 티타늄(Ti), 알루미늄(Al), 보론(B) 또는 이들의 조합이고, A는 F, S, Cl, Br 또는 이들의 조합), LiNi x Co y Mn z O2(0.8≤x≤0.95, 0≤y≤0.2, 0 <z≤0.2 및 x+y+z=1), LiNi x Co y Al zO2(0.8≤x≤0.95, 0≤y≤0.2, 0 <z≤0.2 및 x+y+z=1), LiNi x Co y Mn z Al w O2(0.8≤x≤0.95, 0≤y≤0.2, 0 <z≤0.2, 0<w≤0.2, 및 x+y+z+w=1), Li a Co x M y O 2-b A b (1.0≤a≤1.2, 0≤b≤0.2, 0.9≤x≤1, 0≤y≤0.1, and x+y=1, M is manganese (Mn), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B) or a combination thereof, and A is F, S, Cl, Br or a combination thereof), Li a Ni x Mn y M' z O 2-b A b (1.0≤a≤1.2, 0≤b≤0.2, 0 <x≤0.3, 0.5≤y<1, 0<z≤0.3, 및 x+y+z=1이고, M'는 코발트(Co), 니오븀(Nb), 바나듐(V), 마그네슘(Mg), 갈륨(Ga), 실리콘(Si), 텅스텐(W), 몰리브덴(Mo), 철(Fe), 크롬(Cr), 구리(Cu), 아연(Zn), 티타늄(Ti), 알루미늄(Al), 보론(B) 또는 이들의 조합이고, A는 F, S, Cl, Br 또는 이들의 조합), Li a M1 x M2 y PO 4-b X b(Here, 0.90≤a≤1.1, 0≤x≤0.9, 0≤y≤0.5, 0.9 <x+y<1.1, 0≤b≤2 이며, M1이 크롬(Cr), 망간(Mn), 철(Fe), 코발트(Co), 니켈(Ni), 구리(Cu), 지르코늄(Zr) 또는 이들의 조합이며, M2가 마그네슘(Mg), 칼슘(Ca), 스트론튬(Sr), 바륨(Ba), 티탄(Ti), 아연(Zn), 보론(B), 니오븀(Nb), 갈륨(Ga), 인듐(In), 몰리브덴(Mo), 텅스텐(W), 알루미늄(Al), 실리콘(Si), 크롬(Cr), 바나듐(V), 스칸듐(Sc), 이트륨(Y) 또는 이들의 조합이며, X가 O, F, S, P 또는 이들의 조합), Li a M3 z PO4 (0.90≤a≤1.1, 0.9≤z≤1.1, and M3 is chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr), or a combination thereof).

[0277] The conductive material may include, but is not limited to, carbon black, graphite particles, natural graphite, artificial graphite, acetylene black, Ketjen black, carbon fibers; carbon nanotubes; metal powders or metal fibers or metal tubes such as copper, nickel, aluminum, and silver; and conductive polymers such as polyphenylene derivatives. Any conductive material used in the relevant technical field may be used. Alternatively, the anode may not include a separate conductive material, for example.

[0278] As binders, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene (PTFE), mixtures of the above-mentioned polymers, styrene butadiene rubber-based polymers, etc. are used, and as solvents, N-methylpyrrolidone (NMP), acetone, water, etc. are used, but are not necessarily limited to these, and any solvent used in the relevant technical field may be used.

[0279] A positive electrode for a lithium secondary battery may include a current collector and a positive electrode active material layer formed on the current collector. The positive electrode active material layer includes a positive electrode active material and may further include a binder and / or a conductive material.

[0280] For example, the anode may further include an additive that can act as a sacrificial anode.

[0281] The content of the positive electrode active material may be 90 wt% to 99.5 wt% with respect to 100 wt% of the total weight of the positive electrode active material layer, and the contents of the binder and the conductive material may be 0.5 wt% to 5 wt%, respectively, with respect to 100 wt% of the total weight of the positive electrode active material layer.

[0282] The above binder serves to adhere the positive electrode active material particles well to each other and also to adhere the positive electrode active material well to the positive electrode current collector. Representative examples of the binder include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, nylon, etc.

[0283] The conductive material is used to provide conductivity to the electrode, and any material that does not cause chemical changes and is electronically conductive can be used in the battery. Examples of the conductive material include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials containing copper, nickel, aluminum, silver, etc. in the form of metal powder or metal fiber; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0284] The positive electrode collector uses a plate or foil made of, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof. The thickness of the positive electrode collector is, for example, 1 ㎛ to 100 ㎛, 1 ㎛ to 50 ㎛, 5 ㎛ to 25 ㎛, or 10 ㎛ to 20 ㎛.

[0285] The cathode current collector may include, for example, a base film and a metal layer disposed on one or both sides of the base film. The base film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof. The base film may be, for example, an insulator. Since the base film includes an insulating thermoplastic polymer, when a short circuit occurs, the base film may soften or liquefy, thereby blocking battery operation and suppressing a sudden increase in current. The metal layer may include, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), or an alloy thereof. The metal layer can act as an electrochemical fuse and cut off in case of overcurrent to prevent short circuits. The limit current and maximum current can be controlled by adjusting the thickness of the metal layer. The metal layer can be plated or deposited on the base film. As the thickness of the metal layer decreases, the limit current and / or maximum current of the positive electrode current collector decreases, thereby improving the stability of the lithium battery in case of a short circuit. A lead tab can be added to the metal layer for external connection. The lead tab can be welded to the metal layer or the metal layer / base film laminate by ultrasonic welding, laser welding, spot welding, etc. During welding, the base film and / or the metal layer melt, so that the metal layer can be electrically connected to the lead tab. To strengthen the welding between the metal layer and the lead tab, a metal chip can be added between the metal layer and the lead tab.The metal piece may be a thin piece of the same material as the metal of the metal layer. The metal piece may be, for example, a metal foil, a metal mesh, etc. The metal piece may be, for example, aluminum foil, copper foil, SUS foil, etc. After the metal piece is placed on the metal layer, the lead tab may be welded to the metal piece / metal layer laminate or the metal piece / metal layer / base film laminate. During welding, the base film, the metal layer, and / or the metal piece may melt, so that the metal layer or the metal layer / metal piece laminate may be electrically connected to the lead tab. A metal chip and / or a lead tab may be added to a portion of the metal layer. The base film may have a thickness of, for example, 1 to 50 μm, 1.5 to 50 μm, 1.5 to 40 μm, or 1 to 30 μm. When the base film has a thickness in this range, the weight of the electrode assembly can be more effectively reduced. The melting point of the base film may be, for example, 100 to 300°C, 100 to 250°C or less, or 100 to 200°C. Since the base film has a melting point within this range, the base film can be melted and easily bonded to the lead tab during the welding process of the lead tab. To improve the adhesion between the base film and the metal layer, a surface treatment such as corona treatment may be performed on the base film. The thickness of the metal layer may be, for example, 0.01 to 3 μm, 0.1 to 3 μm, 0.1 to 2 μm, or 0.1 to μm. Since the metal layer has a thickness within this range, conductivity can be maintained while ensuring the stability of the electrode assembly. The thickness of the metal piece may be, for example, 2 to 10 μm, 2 to 7 μm, or 4 to 6 μm. Since the metal piece has a thickness within this range, the connection between the metal layer and the lead tab can be performed more easily. By having this structure as the cathode current collector, the weight of the cathode can be reduced, and as a result, the energy density of the cathode and lithium battery can be improved. (Electrolyte)

[0286] Next, an electrolyte is prepared. The electrolyte may be, for example, a liquid electrolyte, a solid electrolyte, a gel electrolyte, or a combination thereof. The electrolyte is, for example, an organic electrolyte. The liquid electrolyte is as mentioned in the liquid electrolyte of the gel polymer electrolyte.

[0287] The solid electrolyte is, for example, an oxide-based solid electrolyte, a sulfide-based solid electrolyte, a polymer solid electrolyte, or a combination thereof.

[0288] (cathode)

[0289] The cathode contains a cathode current collector.

[0290] Although not shown in the drawing, the negative electrode current collector (21) may include, for example, a base film and a metal layer disposed on one or both sides of the base film. The base film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof. The polymer may be an insulating polymer. Since the base film includes an insulating thermoplastic polymer, when a short circuit occurs, the base film may soften or liquefy, thereby blocking battery operation and suppressing a rapid increase in current. The metal layer may include, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), or an alloy thereof. The metal layer may correspond to, for example, the first metal substrate. The metal layer may additionally include a coating layer including a second metal. The negative electrode current collector (21) may additionally include a metal piece and / or a lead tab. For more specific details on the base film, metal layer, metal chip, and lead tab of the negative electrode current collector (21), refer to the positive electrode current collector. By having such a structure, the negative electrode current collector (21) can reduce the weight of the negative electrode, thereby improving the energy density of the negative electrode and the lithium battery.

[0291] A negative electrode active material layer may be formed on the negative electrode current collector. The negative electrode active material layer may be formed as a lithium deposition layer after charging. Alternatively, the negative electrode active material layer may be formed using a negative electrode active material during battery assembly.

[0292] The method of forming a negative electrode active material layer using a negative electrode active material can be manufactured in the same manner as described above, except that the negative electrode active material is used instead of the positive electrode active material when forming the positive electrode active material layer.

[0293] The lithium battery may further include, for example, a thin film comprising an element capable of forming an alloy with lithium on one surface of the negative electrode current collector. The thin film is disposed between the negative electrode current collector and the negative electrode active material layer. The thin film includes, for example, an element capable of forming an alloy with lithium. The element capable of forming an alloy with lithium includes, but is not limited to, gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, etc., and any element capable of forming an alloy with lithium in the art may be used. The thin film may be composed of one of these metals or an alloy of several types of metals. By disposing the thin film on one surface of the negative electrode current collector, for example, the deposition shape of the first negative electrode active material layer deposited between the thin film and the negative electrode active material layer becomes flatter, and the cycle characteristics of the lithium battery may be further improved.

[0294] (electrolyte layer)

[0295] The electrolyte layer contains a gel polymer electrolyte and may further include a separator.

[0296] Any separator commonly used in lithium batteries can be used.

[0297] As such a separator, a multilayer membrane of two or more layers of polyethylene, polypropylene, polyvinylidene fluoride, or these may be used, and of course, a mixed multilayer membrane such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, or a polypropylene / polyethylene / polypropylene three-layer separator may be used.

[0298] The above separator may include a porous substrate and a coating layer including an organic material, an inorganic material, or a combination thereof located on one or both sides of the porous substrate.

[0299] The above porous substrate is a porous membrane, and the porous membrane is a woven fabric or a non-woven fabric,

[0300] The porous substrate includes an olefin resin, a fluorine resin, an ester resin, an imide resin, an acrylic resin, a cellulose resin, or a combination thereof, and the olefin resin includes polyethylene, polypropylene, or a combination thereof.

[0301] The fluorine-based resin includes polyvinylidene fluoride, polytetrafluoroethylene, or a combination thereof, the ester-based resin includes polyethylene terephthalate, polybutylene terephthalate, or a combination thereof, the imide-based resin includes polyamideimide, polyetherimide, or a combination thereof, the acrylic-based resin includes polyacrylonitrile, polyacrylate, or a combination thereof, and the cellulose-based resin includes carboxymethyl cellulose, microbial cellulose, plant cellulose, animal cellulose, or a combination thereof.

[0302] The porous substrate may be a polymer film formed of any one polymer selected from polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyacetal, polyamide, polyimide, polycarbonate, polyether ketone, polyarylether ketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene oxide, cyclic olefin copolymer, polyphenylene sulfide, polyethylene naphthalate, glass fiber, and polytetrafluoroethylene (e.g., Teflon), or a copolymer or mixture of two or more thereof.

[0303] The organic material may include a polyvinylidene fluoride polymer or a (meth)acrylic polymer.

[0304] The above inorganic materials are Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, It may include inorganic particles selected from, but not limited to, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof.

[0305] The organic and inorganic substances may be mixed and present in one coating layer, or a coating layer including an organic substance and a coating layer including an inorganic substance may be present in a laminated form.

[0306] A lithium battery according to an embodiment may further include a solid electrolyte. The solid electrolyte is, for example, an oxide-based solid electrolyte, a sulfide-based solid electrolyte, or a combination thereof.

[0307] Solid electrolytes are, for example, oxide-based solid electrolytes. Oxide-based solid electrolytes are Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (0 <x<2, 0≤y<3), Li3PO4, Li x Ti y (PO4)3(0 <x<2, 0<y<3), Li x Al y Ti z (PO4)3(0 <x<2, 0<y<1, 0<z<3), Li 1+x+y (Al, Ga) x (Ti, Ge) 2-x Si y P 3-y O 12 (0≤x≤1 0≤y≤1), Li x La y TiO3(0 <x<2, 0<y<3), Li2O, LiOH, Li2CO3, LiAlO2, Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2, Li 3+x La3M2O 12 (M = Te, Nb, or Zr, x is an integer from 1 to 10) is one or more selected from. The solid electrolyte is manufactured by a sintering method, etc. For example, the oxide-based solid electrolyte is Li7La3Zr2O 12 (LLZO) and Li3+x La3Zr 2-a M a O 12 A garnet-type solid electrolyte selected from (M doped LLZO, M=Ga, W, Nb, Ta, or Al, x is an integer from 1 to 10).

[0308] The sulfide-based solid electrolyte may include, for example, lithium sulfide, silicon sulfide, phosphorus sulfide, boron sulfide, or a combination thereof. The sulfide-based solid electrolyte particles may include Li2S, P2S5, SiS2, GeS2, B2S3, or a combination thereof. The sulfide-based solid electrolyte particles may be Li2S or P2S5. Sulfide-based solid electrolyte particles are known to have high lithium ion conductivity compared to other inorganic compounds. For example, the sulfide-based solid electrolyte includes Li2S and P2S5. When the sulfide solid electrolyte material constituting the sulfide-based solid electrolyte includes Li2S-P2S5, the mixing molar ratio of Li2S to P2S5 may be, for example, in a range of about 50:50 to about 90:10. In addition, Li3PO4, halogen, halogen compound, Li 2+2x Zn 1-x GeO4("LISICON", 0≤x<1), Li 3+y PO 4-x N x( "LIPON", 0 <x<4, 0<y<3), Li 3.25 Ge 0.25 P 0.75 S4("ThioLISICON"), Li2O-Al2O3-TiO2-P2O 5(An inorganic solid electrolyte prepared by adding "LATP") etc. to an inorganic solid electrolyte of Li2S-P2S5, SiS2, GeS2, B2S3, or a combination thereof can be used as a sulfide solid electrolyte. Non-limiting examples of sulfide solid electrolyte materials include Li2S-P2S5; Li2S-P2S5-LiX (X=halogen element); Li2S-P2S5-Li2O; Li2S-P2S5-Li2O-LiI; Li2S-SiS2; Li2S-SiS2-LiI; Li2S-SiS2-LiBr; Li2S-SiS2-LiCl; Li2S-SiS2-B2S3-LiI; Li2S-SiS2-P2S5-LiI; Li2S-B2S3; Li2S -P2S5-Z m S n (0 <m<10, 0<n<10, Z=Ge, Zn 또는 Ga); Li2S-GeS2; Li2S-SiS2-Li3PO4; 및 Li2S-SiS2-Li p MO q (0 <p<10, 0<q<10, M=P, Si, Ge, B, Al, Ga 또는 In)을 포함한다. 이와 관련하여, 황화물계 고체전해질 재료는 황화물계 고체전해질 물질의 원료 시작 물질(예를 들면, Li2S, P2S5, 등)을 용융 담금질법(melt quenching method), 기계적 밀링법 등에 의해 처리함으로써 제조될 수 있다. 또한, 소성(calcinations) 공정이 상기 처리 후에 수행될 수 있다. 황화물계 고체전해질은 비정질이거나, 결정질이거나, 이들이 혼합된 상태일 수 있다.

[0309] (lithium battery)

[0310] Referring to Figure 4-6, a lithium battery (1) according to one embodiment includes a positive electrode (3), a negative electrode (2), and a separator (4). The separator is contained in the electrolyte layer according to one embodiment.

[0311] The separator may contain a gel-type polymer electrolyte disposed on at least one surface thereof, and the gel-type polymer electrolyte may be contained within the separator. Here, the gel-type polymer electrolyte may be a gel polymer electrolyte according to one embodiment.

[0312] A gel polymer electrolyte (not shown) may be placed between the electrolyte and the positive electrode. As shown in FIGS. 5 and 6, 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). According to one embodiment, as shown in FIG. 4, an organic electrolyte is injected into the battery case (5) 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. As shown in FIGS. 5 and 6, the lithium battery (1) includes an electrode tab (8) containing a positive electrode tab and a negative electrode tab. The electrode tab (8) may serve as an electrical path for guiding a current formed in the battery assembly (7) to the outside.

[0313] A separator (4) is disposed between the positive electrode (3) and the negative electrode (2), thereby forming a battery structure. The gel-like polymer electrolyte between the separator and the positive electrode is not shown. The pouch-type lithium battery corresponds to the lithium batteries of FIGS. 5 and 6, which use a pouch as a battery case, respectively. The pouch-type lithium battery includes one or more battery structures. An electrolyte is disposed between the positive electrode and the negative electrode, or an electrolyte and a separator are disposed, thereby forming a battery structure. The battery structures are laminated in a bi-cell structure, then impregnated with a liquid electrolyte, and accommodated and sealed in a pouch, thereby completing a pouch-type lithium battery. For example, 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 jelly-roll-shaped electrode assembly and then accommodated in a pouch. Subsequently, an organic electrolyte is injected into the pouch and sealed, thereby completing the lithium battery.

[0314] The lithium battery of the present disclosure has excellent discharge capacity and lifespan characteristics, as well as high energy density, and is therefore used in, for example, electric vehicles (EVs). For example, it is used in hybrid vehicles such as plug-in hybrid electric vehicles (PHEVs). It is also used in applications requiring large amounts of power storage, such as electric bicycles, power tools, and power walls.

[0315] 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.

[0316] [Method for manufacturing lithium batteries]

[0317] A lithium battery according to an embodiment can be manufactured through the steps of: preparing a negative electrode current collector; preparing a separator; preparing a positive electrode; preparing a battery assembly by laminating the negative electrode current collector, the separator, and the positive electrode; injecting a composition for forming a gel polymer electrolyte including a crosslinking monomer for forming a gel polymer and a liquid electrolyte into the battery assembly; and performing crosslinking to form a gel polymer electrolyte.

[0318] A composition for forming a gel polymer electrolyte according to an embodiment of the present invention contains a first polymerizable monomer and a second polymerizable monomer.

[0319] In the composition for forming the gel polymer electrolyte, the total content of the first polymerizable monomer and the second polymerizable 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 composition for forming the gel polymer electrolyte. When the content is within this range, a stable gel polymer electrolyte can be formed.

[0320] In a lithium battery according to an embodiment, a separator containing a gel polymer electrolyte can be formed in situ by injecting a composition for forming a gel polymer electrolyte into a battery assembly as described above and heat-treating the composition. Alternatively, a separator containing a gel polymer electrolyte can be manufactured separately to form a self-supporting film, which is then placed on a negative electrode current collector and a positive electrode placed on top of the self-supporting film, thereby manufacturing a lithium battery.

[0321] In the composition for forming the above gel polymer electrolyte, the polymerizable monomer is i) a multifunctional acrylic monomer having three or more polymerizable functional groups; or ii) at least one second polymerizable monomer selected from a multifunctional acrylic monomer having three or more polymerizable functional groups, which is a first polymerizable monomer, a urethane acrylic monomer having two or more polymerizable functional groups, and a polymerizable monomer containing a perfluoropolyether (PFPE) unit and having two or more polymerizable functional groups, and the liquid electrolyte includes a lithium salt, an organic solvent, and butyronitrile, and the lithium salt includes lithium difluoro(oxalato)borate (LiDFOB) and lithium tetrafluoroborate (LiBF4).

[0322] The crosslinking method of the composition for forming a gel polymer electrolyte is not particularly limited and may be crosslinked, for example, by heat, ultraviolet rays, etc. From the viewpoint of manufacturing efficiency, thermal crosslinking using heat treatment may be used. The composition for forming a gel polymer electrolyte 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 composition for forming a gel polymer electrolyte. The crosslinked product of the 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.

[0323] The separator may include a gel-type polymer electrolyte. Here, the gel-type polymer electrolyte may be a gel-type polymer electrolyte according to one embodiment. The separator may further include a liquid electrolyte.

[0324] A step of forming a protective layer on the negative electrode current collector may be further included.

[0325] The step of forming the above protective layer can be performed by coating and heat treating a composition for forming a protective layer comprising at least one binder precursor and a binder selected from boron nitride on a negative electrode current collector. Here, the binder precursor may include, for example, the first polymer and the second polymer, and the binder refers to the binder mentioned in the above-described protective layer.

[0326] A solvent such as N-methylpyrrolidone or dimethylformamide may be added to the composition for forming the protective layer. The content of the solvent may be 0.05 to 5 parts by weight based on 100 parts by weight of the total weight of boron nitride and binder.

[0327] The above protective layer may further include a lithium salt. The content of the lithium salt is 30 to 80 parts by weight, 40 to 60 parts by weight, or 45 to 55 parts by weight based on 100 parts by weight of the total weight of the binder and the lithium salt.

[0328] The composition for forming the protective layer may further include a second polymer having a crosslinkable functional group with the first polymer containing a hydroxyl group. The protective layer formed from the composition for forming the protective layer further includes a crosslinked polymer of the first polymer and the second polymer. Here, the mixing weight ratio of the first polymer containing a hydroxyl group and the second polymer is adjusted to be in the range of 50:50 to 99:1, 50:50 to 99:1, or 60:40 to 90:10.

[0329] The above second polymer is at least one selected from among fluorinated polyamic acid and fluorinated polyimide having a carboxyl group.

[0330] When the second polymer is a fluorinated polyamic acid having a carboxyl group, a composition for forming a protective layer containing the same may be coated on a negative electrode current collector, dried, and then further heat-treated to cause a crosslinking reaction between the first polymer and the second polymer, thereby forming a protective layer containing a crosslinked polymer. The heat-treatment may vary depending on the composition of the first polymer and the second polymer, but may be performed at, for example, 80 to 200°C, 100 to 200°C, 150 to 200°C, or 150 to 190°C. When the heat-treatment temperature is within the above range, the protective layer formed on the electrode surface can minimize or reduce exposure of the electrolyte at the electrode surface and create a uniform lithium ion flow throughout the electrode, thereby effectively suppressing lithium dendrite growth.

[0331] 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.

[0332] (Preparation of polymer solution for forming a protective layer)

[0333] Manufacturing Example 1: Manufacturing of a polymer solution containing polyvinyl alcohol and a fluorinated polyamic acid of the following chemical formula 18.

[0334] Polyvinyl alcohol was purchased from Sigma-Aldrich. The synthesis process of fluorinated polyamic acid of chemical formula 10 is as follows.

[0335] First, after filling a round-bottom flask with nitrogen, 4.9411 g (0.00154 mol) of 2,2'-bis(trifluoromethyl)benzidine (TFDB) and 0.7825 g (0.00051 mol) of diaminobenzoic acid (DABA) were added, followed by adding 131 g of N-methylpyrrolidone (NMP) and completely dissolving using a mechanical stirrer. Next, 9.2764 g (0.0209 mol) of 4,4'-(hexafluoroisopropylidene) (6FDA) was added and stirred at room temperature (25°C) for 24 hours, thereby producing a polyamic acid represented by the following chemical formula 17. The polyamic acid is a random copolymer. The molar ratio of 6FDA:TFDB:DABA was 4:3:1.

[0336] In chemical formula 9, the molar ratio of n:m was 1:3.

[0337] By adding 10 g of a LiOH aqueous solution having 0.5 equivalents in carboxylic acid equivalent ratio to a polyamic acid (6FDA:TFDB:DABA, acid equivalent 210 g / eq) represented by the following chemical formula 17, a water-soluble polyamic acid represented by the following chemical formula 18 was prepared in which 0.5 equivalents of COOH among the COOH of the polyamic acid was replaced with COO-Li+.

[0338] [Chemical Formula 17]

[0339]

[0340] In the above equation, n is 0.25, m is 0.75, and the sum of n and m is 1.

[0341] A water-soluble polyamic acid represented by the following chemical formula 18 and polyvinyl alcohol (weight average molecular weight, Mw = 89,000, hydrolysis +99%) were mixed at a weight ratio of 20:80 to prepare a polymer solution having a solid content of 10 wt%.

[0342] [Chemical Formula 18]

[0343]

[0344] In the above equation, n is 0.25, m is 0.75, and the sum of n and m is 1.

[0345] Manufacturing Example 2: Manufacturing of compound DRIC of the following chemical formula 1-1

[0346] <Chemical Formula 1-1>

[0347]

[0348] In chemical formula 1-1, EG represents a residue of ethylene glycol, DEG represents a residue of diethylene glycol, TMP represents a residue of trimethylolpropane, and n1 is 10.

[0349] Adipic acid (AA) 150.6 g, diethylene glycol (DG) 115.14 g, ethylene glycol (EG) 81.05 g, and trimethylolpropane (TMP) 21.32 g were added to a reaction vessel at room temperature (25°C) and the temperature was increased to 220°C. Titanium isopropoxide (TIP) was added to the reaction vessel. After the mixture reached full vacuum, it was subjected to a primary reaction at 220°C for 10 hours to obtain a polyester polyol. The polyol was first cooled to 130°C, vacuum-treated at 130°C for 2 hours, and then cooled to 75°C for a second time. 18.24 g of isocyanato ethyl methacrylate (ICEMA), 0.54 g of monomethyl ether hydroquinone (MEHQ), 0.566 g of butylated hydroxy toluene (BHT), and 0.526 g of dibutyl-tin-dilaulate (DBTDL) were added to the polyester polyol, and a secondary reaction was performed at 70 to 80°C for 3 hours to obtain compound DRIC of the chemical formula 1-1.

[0350] (Manufacture of gel polymer electrolyte and lithium battery)

[0351] Example 1: Negative current collector / / Separator + GPE (gel polymer (DPHA / AD1700 (3 / 1) 4%) + LE, LE (butyronitrile + LiDFOB + LiBF4) / positive electrode

[0352] A copper foil with a thickness of 10 μm was prepared as a negative current collector.

[0353] A polyethylene single film having a thickness of 20 μm was laminated as a separator on top of copper foil, and a positive electrode was laminated on the other side of the separator to manufacture a laminate. A composition for forming a gel polymer electrolyte was injected into the prepared laminate, and heat-treated at 70°C for 120 minutes to manufacture a lithium battery in which a gel polymer electrolyte was formed in the pores of the separator. The lithium battery had a structure of positive electrode / gel polymer electrolyte (separator) / negative electrode current collector. The content of the gel polymer in the gel polymer electrolyte was 4 parts by weight based on 100 parts by weight of the gel polymer electrolyte, and the content of the liquid electrolyte was 96 parts by weight.

[0354] The composition for forming the above gel polymer electrolyte was prepared by mixing dipentaerythritol hexaacrylate (DPHA), a 6-functional crosslinking agent that is a crosslinking monomer, Fluorolink AD1700 (MW: 1,500) from Solvay, and benzoin ethyl ether (Sigma-Aldrich, 240.30 g / mol) as a liquid electrolyte and initiator. The total content of the crosslinking monomer in the composition for forming the gel polymer electrolyte is 4 wt% based on 100 wt% of the total weight of the composition for forming the gel polymer electrolyte, and the mixing weight ratio of DPHA and AD1700 is 3:1.

[0355] The liquid electrolyte used was a 2:1 volume ratio mixed solvent of diethyl carbonate (DEC) and fluoroethylene carbonate (FEC), in which 0.6 M LiBF4 and 0.6 M LiDFOB (lithium difluoro(oxalate)borate) and butyronitrile were added. The content of butyronitrile in the liquid electrolyte was 8.74 wt% based on the total weight of the liquid electrolyte, and the content of FEC was 36.7 wt% based on the total weight of the liquid electrolyte.

[0356] In the composition for forming the above gel polymer electrolyte, 4 parts by weight of DPHA, a crosslinking monomer, 96 parts by weight of a liquid electrolyte, and an initiator were contained based on 100 parts by weight of the total weight of the composition for forming the gel polymer electrolyte. The initiator was used in an amount of 5 parts by weight based on 100 parts by weight of the crosslinking monomer.

[0357] The above anode was manufactured according to the following method.

[0358] Li, the positive electrode active material 1.04 Ni 0.88 Co 0.1 Al 0.02 O2 powder and carbon conductive material (Super-P; Timcal Ltd.) were uniformly mixed at a weight ratio of 90:5, and then a PVDF (polyvinylidene fluoride) binder solution was added to prepare a cathode active material slurry so that the weight ratio of cathode active material:carbon conductive material:binder = 90:5:5.

[0359] The manufactured positive electrode active material slurry was coated on a 15 ㎛ thick aluminum substrate using a doctor blade, dried under reduced pressure at 120°C, and rolled using a roll press to form a sheet to manufacture a positive electrode.

[0360] In the lithium battery manufactured according to the above process, a lithium precipitation layer was formed between the negative electrode collector and the separator.

[0361] Example 2: Negative electrode current collector / separator + GPE (gel polymer (DPHA / DRIC (3 / 1) 4%) + LE, LE (butyronitrile + LiDFOB + LiBF4) / positive electrode

[0362] A gel polymer electrolyte and a lithium battery were manufactured in the same manner as in Example 1, except that dipentaerythritol hexaacrylate (DPHA), a 6-functional crosslinking agent that is a crosslinking monomer, and Fluorolink AD1700 (MW: 1,500) from Solvay were used instead of DPHA and DRIC of the following chemical formula 1-1.

[0363] <Chemical Formula 1-1>

[0364]

[0365] In chemical formula 1-1, n1 is an integer of 5, EG represents an ethylene residue, DEG represents a diethylene glycol residue, and TMP represents a trimethylolpropane residue.

[0366] Example 3: GPE (gel polymer (DPHA / AD1700 (1 / 1) 4%) + LE, LE (butyronitrile + LiDFOB + LiBF4)

[0367] A gel polymer electrolyte and a lithium battery were manufactured in the same manner as in Example 1, except that the mixing weight ratio of DPHA and AD1700 was changed to 1:1 when manufacturing a composition for forming a gel polymer electrolyte.

[0368] Example 4: GPE (gel polymer (DPHA / DRIC (1 / 1) 4%) + LE, LE (butyronitrile + LiDFOB + LiBF4)

[0369] A gel polymer electrolyte and a lithium battery were manufactured in the same manner as in Example 2, except that the mixing weight ratio of DPHA and DRIC was changed to 1:1 when manufacturing a composition for forming a gel polymer electrolyte.

[0370] Example 5: GPE (gel polymer (DPHA / AD1700 (3 / 1) 10%) + LE, LE (butyronitrile + LiDFOB + LiBF4)

[0371] A gel polymer electrolyte and a lithium battery were manufactured in the same manner as in Example 1, except that the total content of DPHA and AD1700 was changed to 10 wt% based on the total weight of the gel polymer electrolyte composition when manufacturing the composition for forming a gel polymer electrolyte.

[0372] Example 6: GPE (gel polymer (TMPTMA / AD1700 (3 / 1) 4%) + LE, LE (butyronitrile + LiDFOB + LiBF4)

[0373] A gel polymer electrolyte and a lithium battery were manufactured in the same manner as in Example 1, except that TMPTMA (trimethylolpropanetrimethacrylate) was used instead of DPHA when manufacturing a composition for forming a gel polymer electrolyte.

[0374] Example 7

[0375] A gel polymer electrolyte and a lithium battery were manufactured in the same manner as in Example 1, except that a protective layer was further formed on the negative electrode current collector according to the following process and a separator was placed on top of it.

[0376] According to Manufacturing Example 1, the water-soluble polyamic acid represented by the following chemical formula 18 and polyvinyl alcohol (weight average molecular weight, Mw=78,000, degree of saponification 88%, Polysciences, 15132) were mixed in a weight ratio of 20:80 to obtain a polymer solution having a solid content of 10 wt%. This polymer solution, hexagonal crystalline boron nitride (average particle diameter: 100 nm, spherical particles), and lithium salt LiPF6 were mixed, and this was mixed with NMP as a solvent to prepare a composition for forming a protective layer. At this time, the contents of the polymer, boron nitride (BN), and lithium salt of the polymer solution were adjusted so that the mixing weight ratio of (PVA / PIF):BN:lithium salt in the protective layer was 50:0.5:50. And the content of the solvent was 900 parts by weight based on 100 parts by weight of the polymer.

[0377] [Chemical Formula 18]

[0378]

[0379] In the above equation, n is 0.25 and m is 0.75.

[0380] The composition for forming the protective layer was coated on the top of a copper foil having a thickness of 10 μm, which is a negative electrode collector, and dried in a vacuum oven at 80°C for 30 minutes, followed by heat treatment at 180°C for 30 minutes to prepare a negative electrode.

[0381] By the above heat treatment, the carboxyl group of the fluorine-substituted polyamic acid and the hydroxyl group of the polyvinyl alcohol react to form an ester linker, thereby producing a cross-linked polymer of the fluorine-substituted polyimide and polyvinyl alcohol. The cross-linked polymer has a three-dimensional network structure in which the fluorine-substituted polyimide (PIF) of the following chemical formula 20 and the polyvinyl alcohol are cross-linked at multiple points.

[0382] <Chemical Formula 20>

[0383]

[0384] In the above formula, n is 0.25, m is 0.75, and the weight average molecular weight of the polyimide of chemical formula 20 is approximately 2,000,000.

[0385] Comparative Example 1: Negative electrode current collector / separator + GPE (gel polymer (DPHA / AD1700 (3 / 1) 4%) + LE (LiDFOB + LiBF4, butyronitrile-free) / positive electrode

[0386] A gel polymer electrolyte and a lithium battery were manufactured in the same manner as in Example 1, except that butyronitrile was not used in the preparation of the liquid electrolyte of the composition for forming a gel polymer electrolyte.

[0387] Comparative Example 2: Negative electrode current collector / separator + GPE (gel polymer (DPHA) 4%) + LE (LiDFOB + LiBF4, butyronitrile-free) / positive electrode

[0388] A gel polymer electrolyte and a lithium battery were manufactured in the same manner as in Example 1, except that only DPHA was used instead of DPHA and AD1700 as a crosslinking monomer when manufacturing a composition for forming a gel polymer electrolyte, and butyronitrile was not used when manufacturing a liquid electrolyte.

[0389] Comparative Example 3: Negative electrode current collector / separator + GPE (gel polymer (bifunctional monomer (PEO-DMA) + AD1700 3:1) 4%) + LE (LiDFOB + LiBF4, butyronitrile-free) / positive electrode

[0390] A gel polymer electrolyte and a lithium battery were manufactured in the same manner as in Example 1, except that PEO-DMA and AD1700 were used instead of DPHA and AD1700 as crosslinking monomers when manufacturing a composition for forming a gel polymer electrolyte, and butyronitrile was not used when manufacturing a liquid electrolyte. PEO-DMA is poly(ethylene glycol) dimethacrylate disclosed in Example 2C of WO2017 / 153310A.

[0391] Evaluation Example 1: High Temperature (45℃) Lifespan

[0392] The charge / discharge characteristics of the lithium batteries of Examples 1-4, 6-7 and Comparative Examples 1-2 were evaluated under the following conditions.

[0393] The battery was charged at a constant current of 0.1 C rate at 45°C until the voltage reached 4.3 V (vs. Li), and then cut-off at a current of 0.05 C rate while maintaining 4.3 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 0.1 C rate until the voltage reached 3.6 V (vs. Li) during discharge (formation cycle).

[0394] The lithium battery, which had undergone a Mars cycle, was charged at a constant current of 0.2 C rate at 45°C until the voltage reached 4.3 V (vs. Li), and then cut-off at a current of 0.05 C rate while maintaining 4.3 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 0.5 C rate until the voltage reached 3.6 V (vs. Li) (1 st cycle). These cycles are 160 thThe cycle was repeated under the same conditions.

[0395] In all charge / discharge cycles, a 10-minute pause was provided after each charge / discharge cycle. Some of the results of the high-temperature charge / discharge experiments are shown in Table 1.

[0396] In Table 2 below, the number of cycles refers to the number of cycles required for the discharge capacity to decrease to 80% of the standard capacity after the second cycle.

[0397] Distinction condition Cycle number (n) @ 80% Example 1 GPE (gel polymer (DPHA / AD1700 (3 / 1) 4%) + LE, LE (butyronitrile + LiDFOB + LiBF4) 223 Example 2 GPE (gel polymer (DPHA / DRIC (3 / 1) 4%) + LE, LE (butyronitrile + LiDFOB + LiBF4) 231 Example 3 GPE (gel polymer (DPHA / AD1700 (1 / 1) 4%) + LE, LE (butyronitrile + LiDFOB + LiBF4) 215 Example 4 GPE (gel polymer (DPHA / DRIC (1 / 1) 4%) + LE, LE (butyronitrile + LiDFOB + LiBF4) 211 Example 6GPE (gel polymer (TMPTMA / AD1700 (3 / 1) 4%) + LE, LE (butyronitrile + LiDFOB + LiBF4) 203 Example 7 In case of forming a protective layer compared to Example 1 225 Comparative Example 1 GPE (gel polymer (DPHA / AD1700 (3 / 1) 4%) + LE (LiDFOB + LiBF4, butyronitrile-free) 186 Comparative Example 2 GPE (gel polymer (DPHA) 4%) + LE (LiDFOB + LiBF4, butyronitrile-free) 174

[0398] As can be seen in Table 1, the lithium batteries of Examples 1 to 6 had improved life characteristics compared to the lithium batteries of Comparative Examples 1 and 2.

[0399] Evaluation Example 2: High-rate characteristics

[0400] The lithium batteries manufactured in Example 1-7 and Comparative Example 1-3 were charged at a constant current of 0.1 C rate at 25°C until the voltage reached 4.3 V (vs. Li), and then cut-off at a current of 0.05 C rate while maintaining 4.3 V in constant voltage mode. Subsequently, the batteries were discharged at a constant current of 0.1 C rate until the voltage reached 3.6 V (vs. Li) during discharge (formation cycle).

[0401] The lithium battery, which had undergone a Mars cycle, was charged at a constant current of 0.2 C rate at 25°C until the voltage reached 4.3 V (vs. Li), and then cut-off at a current of 0.05 C rate while maintaining 4.3 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 0.2 C rate until the voltage reached 3.6 V (vs. Li) (1 st cycle).

[0402] 1 st The cycled lithium battery was charged at a constant current of 0.2 C at 25°C until the voltage reached 4.3 V (vs. Li), and then cut off at a current of 0.05 C while maintaining 4.3 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 0.5 C until the voltage reached 2.8 V (vs. Li) (2 nd cycle).

[0403] 2 nd Cycle 7 th The cycle was repeated under the same conditions.

[0404] 7 thThe cycled lithium battery was charged at a constant current of 0.33 C at 25°C until the voltage reached 4.35 V (vs. Li), and then cut off at a current of 0.05 C while maintaining 4.35 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 1 C until the voltage reached 2.8 V (vs. Li) (8 th cycle).

[0405] 8 th Cycle 14 th The cycle was repeated under the same conditions.

[0406] 14 th The cycled lithium battery was charged at a constant current of 0.33 C at 25°C until the voltage reached 4.35 V (vs. Li), and then cut off at a current of 0.05 C while maintaining 4.35 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 2 C until the voltage reached 2.8 V (vs. Li) (15 th cycle).

[0407] 15th cycle 18 th The cycle was repeated under the same conditions.

[0408] 18 st The cycled lithium battery was charged at a constant current of 0.33 C at 25°C until the voltage reached 4.35 V (vs. Li), and then cut off at a current of 0.05 C while maintaining 4.35 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 3 C until the voltage reached 2.8 V (vs. Li) (18 th cycle). 18 th Cycle 30 th The cycle was repeated under the same conditions.

[0409] In all the above charge / discharge cycles, a pause of 10 minutes was allowed after each charge / discharge cycle.

[0410] Some of the results of the above charge-discharge experiment are shown in Table 2 below.

[0411] The high-rate characteristic is defined by Equation 3 below.

[0412] <Formula 2>

[0413] High rate characteristic [%] = [30 th Discharge capacity in cycle (3C rate) / 1 st Discharge capacity in cycle (0.2C rate)] × 100

[0414] Classification Condition High Rate Characteristics (%) Example 1 GPE (Gel Polymer (DPHA / AD1700 (3 / 1) 4%) + LE, LE (Butyronitrile + LiDFOB + LiBF4) 46.7 Example 2 GPE (Gel Polymer (DPHA / DRIC (3 / 1) 4%) + LE, LE (Butyronitrile + LiDFOB + LiBF4) 42.1 Example 3 GPE (Gel Polymer (DPHA / AD1700 (1 / 1) 4%) + LE, LE (Butyronitrile + LiDFOB + LiBF4) 43.8 Example 4 GPE (Gel Polymer (DPHA / DRIC (1 / 1) 4%) + LE, LE (Butyronitrile + LiDFOB + LiBF4) 41.5 Example 6GPE(Gel polymer(TMPTMA / AD1700(3 / 1) 4%)+ LE, LE(Butyronitrile+LiDFOB+LiBF4)39.8Example 7When protective layer is formed compared to Example 142.2Comparative Example 1GPE(Gel polymer(DPHA / AD1700(3 / 1) 4%)+ LE(LiDFOB+LiBF4, butyronitrile free), DPHA / AD1700(3 / 1) 4% (Dahn base)32.3Comparative Example 2GPE(Gel polymer(DPHA) 4%)+ LE(LiDFOB+LiBF4, butyronitrile free), DPHA 4% (Dahn base)31.5Comparative Example 3GPE(Gel polymer(PE0-DMA / AD1700(3 / 1) 4%)+ LE, LE(Butyronitrile + LiDFOB + LiBF4)36.4

[0415] As can be seen in Table 2, the lithium batteries of Examples 1 to 4, Example 6, and Example 7 had improved rate characteristics compared to the lithium batteries of Comparative Examples 1 to 3.

[0416] The lithium batteries of Examples 1 to 4, Example 6, and Example 7 contained a gel polymer electrolyte in which more anions interacted with the gel polymer chain, thereby reducing the binding energy when Li moved between O (oxygen) atoms in the chain, enabling rapid movement of Li ions, and thereby improving the rate characteristics. In addition, the lithium battery of Example 5, although not shown in Table 3, exhibited rate characteristics similar to those of the lithium battery of Example 1.

[0417] Evaluation Example 3: Ionic Conductivity

[0418] In the lithium batteries of Example 1-7 and Comparative Example 1-2, the ionic conductivity of the gel polymer electrolyte at room temperature (25°C) and high temperature (45°C) was evaluated according to the following method.

[0419] Ionic conductivity was measured at 25°C using a lithium symmetric cell and an impedance analyzer (Solartron 1260A Impedance / Gain-Phase Analyzer coupled with Solartron 1287 Electrochemical Interface). Ionic conductivity was 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 a 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.

[0420] 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 3 below.

[0421] Classification conditionsRoom temperature ionic conductivity (mS / cm)High temperature ionic conductivity (mS / cm)Example 1GPE(gel polymer (DPHA / AD1700(3 / 1) 4%)+LE, LE(butyronitrile+LiDFOB+LiBF4)0.450.68Example 2GPE(gel polymer (DPHA / DRIC(3 / 1) 4%)+LE, LE(butyronitrile+LiDFOB+LiBF4)0.410.59Example 3GPE(gel polymer (DPHA / AD1700(1 / 1) 4%)+LE, LE(butyronitrile+LiDFOB+LiBF4)0.440.65Example 4GPE(gel polymer (DPHA / DRIC(1 / 1) 4%)+LE, LE(butyronitrile+ LiDFOB + LiBF4) 0.40 0.56 Example 6 GPE (gel polymer (TMPTMA / AD1700 (3 / 1) 4%) + LE, LE (butyronitrile + LiDFOB + LiBF4) 0.38 0.48 Example 7 When a protective layer was formed compared to Example 1 0.35 0.44 Comparative Example 1 GPE (gel polymer (DPHA / AD1700 (3 / 1) 4%) + LE (LiDFOB + LiBF4, butyronitrile-free), DPHA / AD1700 (3 / 1) 4% (Dahn base) 0.28 0.39 Comparative Example 2 GPE (gel polymer (DPHA) 4%) + LE (LiDFOB + LiBF4, butyronitrile-free), DPHA 4% (Dahn base) 0.26 0.41

[0422] As shown in Table 3, the gel polymer electrolytes of Examples 1-4 and 6-7 were found to have higher ionic conductivity at room temperature and high temperature than the gel polymer electrolytes of Comparative Examples 1 and 2. In addition, the gel polymer electrolyte of Example 5, although not shown in the table, exhibited ionic conductivity characteristics similar to those of Example 1.

[0423] Evaluation Example 4: Scanning Electron Microscopy Analysis

[0424] Scanning electron microscopy analysis was performed on the gel polymer electrolytes manufactured according to Example 1 and Comparative Example 1. The results of the scanning electron microscopy analysis are shown in Figs. 1a and 1b.

[0425] Referring to Fig. 1a, the gel polymer electrolyte of Example 1 contained butyronitrile, so that lithium transfer occurred only through the polymer chain, enabling a more uniform lithium supply than the gel polymer electrolyte of Comparative Example 1 of Fig. 1b.

[0426] Evaluation Example 5: Thickness expansion rate of the cathode

[0427] The charge / discharge characteristics of the lithium batteries of Examples 1-4, 6-7 and Comparative Example 1-4 were evaluated under the following conditions, and the thickness expansion rate of the negative electrode was investigated.

[0428] The battery was charged at a constant current of 0.1 C rate at 25°C until the voltage reached 4.3 V (vs. Li), and then cut-off at a current of 0.05 C rate while maintaining 4.3 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 0.1 C rate until the voltage reached 3.6 V (vs. Li) (formation cycle).

[0429] The lithium battery, which had undergone a Mars cycle, was charged at a constant current of 0.2 C rate at 25°C until the voltage reached 4.3 V (vs. Li), and then cut-off at a current of 0.05 C rate while maintaining 4.3 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 0.5 C rate until the voltage reached 3.6 V (vs. Li) (1 st cycle). These cycles are 100 th The cycle was repeated under the same conditions.

[0430] In all charge / discharge cycles, a 10-minute pause was allowed after each charge / discharge cycle. The room-temperature cathode thickness expansion rate was calculated according to Equation 1 below and is shown in Table 4 below.

[0431] <Formula 1>

[0432] Cathode thickness expansion rate (%) = [thickness of lithium precipitation layer formed on the negative electrode current collector after 100 cycles of charging / thickness of lithium precipitation layer formed on the negative electrode current collector after formation] × 100

[0433] Conditions of classification Thickness expansion ratio of the negative electrode (%) Example 1 GPE (gel polymer (DPHA / AD1700 (3 / 1) 4%) + LE, LE (butyronitrile + LiDFOB + LiBF4) 127.4 Example 2 GPE (gel polymer (DPHA / DRIC (3 / 1) 4%) + LE, LE (butyronitrile + LiDFOB + LiBF4) 133.1 Example 3 GPE (gel polymer (DPHA / AD1700 (1 / 1) 4%) + LE, LE (butyronitrile + LiDFOB + LiBF4) 135.5 Example 4 GPE (gel polymer (DPHA / DRIC (1 / 1) 4%) + LE, LE (butyronitrile + LiDFOB + LiBF4) 136.9 Example 6GPE(Gel polymer(TMPTMA / AD1700(3 / 1) 4%)+ LE, LE(Butyronitrile+LiDFOB+LiBF4)141.3Example 7When protective layer is formed compared to Example 1125.5Comparative Example 1GPE(Gel polymer(DPHA / AD1700(3 / 1) 4%)+ LE(LiDFOB+LiBF4, butyronitrile free), DPHA / AD1700(3 / 1) 4% (Dahn base)151.3Comparative Example 2GPE(Gel polymer(DPHA) 4%)+ LE(LiDFOB+LiBF4, butyronitrile free), DPHA 4% (Dahn base)159.8Comparative Example 3GPE(Gel polymer(PE0-DMA / AD1700(3 / 1) 4%)+ LE, LE(Butyronitrile + LiDFOB + LiBF4)173.5

[0434] As can be seen in Table 4, the lithium batteries of Examples 1 to 4, 6 and 7 had an improved thickness expansion rate of the negative electrode of 150% or less, unlike the lithium batteries of Comparative Examples 1 to 3. Although exemplary embodiments have been described in detail with reference to the attached drawings, the present invention is not limited to these examples. It is obvious that a person having ordinary skill in the art to which the present invention pertains can derive various changes or modifications within the scope of the technical ideas described in the claims, and these also naturally fall within the technical scope of the present invention.

Claims

1. A gel polymer electrolyte for a lithium battery comprising a gel polymer and a liquid electrolyte. The above gel polymer is i) a crosslinked product of a multifunctional acrylic monomer having three or more polymerizable functional groups; or ii) a crosslinked product of a first polymerizable monomer and a second polymerizable monomer, wherein the first polymerizable monomer is a multifunctional acrylic monomer having three or more polymerizable functional groups, and the second polymerizable monomer is a urethane acrylic monomer having two or more polymerizable functional groups, a polymerizable monomer containing a perfluoropolyether (PFPE) unit and having two or more polymerizable functional groups, or a combination thereof. The above liquid electrolyte contains a lithium salt, an organic solvent and butyronitrile, A gel polymer electrolyte for a lithium battery, wherein the lithium salt comprises a first lithium salt and a second lithium salt, and the first lithium salt and the second lithium salt independently comprise a fluorine-containing borate-based lithium salt.

2. A gel polymer electrolyte for a lithium battery, wherein the content of butyronitrile in the first paragraph is 5 to 15 wt% based on 100 wt% of the total weight of the liquid electrolyte.

3. In the first paragraph, a multifunctional compound having three or more polymerizable functional groups Acrylic monomers include trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, trimethylolpropane ethoxylate triacrylate, trimethylolpropane propoxylate triacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, pentaerythritol ethoxylate tetraacrylate, dipentaerythritol pentaacrylate, A gel polymer electrolyte for lithium batteries, comprising dipentaerythritol hexaacrylate (DPHA) or a combination thereof.

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

5. In the first paragraph, the content of the liquid electrolyte is 90 to 96 parts by weight based on 100 parts by weight of the total weight of the gel polymer electrolyte. A gel polymer electrolyte for a lithium battery, wherein the content of the gel polymer is 4 to 10 parts by weight based on 100 parts by weight of the total weight of the gel polymer electrolyte.

6. In the first paragraph, the fluorine-containing borate lithium salt is LiBF 4 , LiBF 3 (C 2 F 5 ), a gel polymer electrolyte for a lithium battery, comprising a compound represented by the following chemical formulas 5 to 16 or a combination thereof. <Chemical Formula 5> <Chemical Formula 6> <Chemical Formula 7> <Chemical Formula 8> <Chemical Formula 9> <Chemical Formula 10> <Chemical Formula 11> <Chemical Formula 12> <Chemical Formula 13> <Chemical Formula 14> <Chemical Formula 15> <Chemical Formula 16> 7. In the 6th paragraph, the first lithium salt is LiBF 4 A gel polymer electrolyte for a lithium battery, wherein the second lithium salt comprises a compound selected from compounds represented by the chemical formulas 5 to 16, and the concentration of the lithium salt is 0.1 to 5 M.

8. In the first paragraph, the lithium salt is lithium difluoro(oxalato)borate (LiDFOB) and lithium tetrafluoroborate (LiBF). 4 ) and The above lithium difluorodioxalatoborate (LiDFOB) and lithium tetrafluoroborate (LiBF) 4 ) A gel polymer electrolyte for a lithium battery, wherein the mixing weight ratio of the polymer is 1:2 to 1:0.

3.

9. In paragraph 1, the organic solvent contains a carbonate compound, The above carbonate compounds include fluoroethylene carbonate (FEC) and diethyl carbonate (DEC). The mixing weight ratio of the above FEC and DEC is 1:10 to 1:1, A gel polymer electrolyte for a lithium battery, wherein the content of the fluoroethylene carbonate is 5 to 45 wt% based on the total weight of the liquid electrolyte.

10. 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, A lithium battery, wherein the electrolyte layer comprises a gel polymer electrolyte according to any one of claims 1 to 9.

11. A lithium battery according to claim 10, further comprising a lithium metal layer disposed between the negative electrode collector and the electrolyte layer.

12. A lithium battery according to claim 11, wherein the lithium metal layer comprises a lithium metal foil, a lithium metal powder, a lithium alloy foil, a lithium alloy powder, or a combination thereof.

13. In the 12th paragraph, the lithium alloy of the lithium alloy foil and lithium alloy powder contains lithium and a first metal, A lithium battery wherein the first metal is indium (In), silicon (Si), gallium (Ga), tin (Sn), aluminum (Al), zirconium (Zr), niobium (Nb), germanium (Ge), antimony (Sb), bismuth (Bi), gold (Au), platinum (Pt), palladium (Pd), magnesium (Mg), silver (Ag), zinc (Zn), chromium, cesium, sodium, potassium, calcium, yttrium, tantalum, hafnium, barium, vanadium, strontium, lanthanum or a combination thereof.

14. A lithium battery according to claim 10, wherein the electrolyte layer includes a separator, and the separator includes a porous substrate.

15. In the 14th paragraph, the porous substrate is a porous membrane, The above porous membrane is a woven or 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.

16. A lithium battery in claim 10, wherein the negative electrode collector comprises copper (Cu), nickel (Ni), nickel-coated copper, stainless steel (SUS), iron (Fe), cobalt (Co), or an alloy thereof.

17. A lithium battery according to claim 10, wherein the ionic conductivity of the gel polymer electrolyte at 25°C and 1 atm is 0.3 mS / cm or more, and the ionic conductivity at 45°C and 1 atm is 0.42 mS / cm or more.

18. A lithium battery comprising a negative electrode active material layer, a protective layer, or a combination thereof, disposed between the negative electrode current collector and the electrolyte layer in the 10th paragraph.

19. In the 18th paragraph, the protective layer comprises a crosslinked polymer of a first polymer and a second polymer, and the second polymer comprises at least one selected from a fluorinated polyamic acid having a carboxyl group and a fluorinated polyimide. A lithium battery, wherein the fluorinated polyamic acid is a polymer represented by the following chemical formula 17 or chemical formula 18, and the fluorinated polyimide is a polymer represented by the following chemical formula 19 or chemical formula 20: [Chemical Formula 17] [Chemical Formula 18] [Chemical Formula 19] [Chemical formula 20] In the above equations, n and m are the mole fractions within the repeating unit, respectively, and are 0 <n≤1, 0≤m<1, n+m=1이다.

20. In the 10th paragraph, the positive electrode includes a positive electrode current collector and a positive electrode active material layer, At least one of the positive electrode current collector and the negative electrode current collector includes a base film and a metal layer disposed on one or both sides of the base film, The above base film contains a polymer, The above polymer comprises polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI) or a combination thereof, A lithium battery, wherein the metal layer comprises indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof.

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