Polymer electrolyte, lithium metal battery comprising same, and method for manufacturing same

Abstract

A polymer electrolyte according to the present invention comprises: a lithium salt; an organic solvent; a first additive; and a crosslinked polymer polymerized from a crosslinkable monomer, wherein the crosslinkable monomer is at least one of an acrylate-based monomer or a methacrylate-based monomer, and the first additive includes a first compound represented by chemical formula 1. In chemical formula 1, L1 to L3 are each independently a direct bond or a C1-10 alkylene group. [Chemical formula 1]

Description

Polymer electrolyte, lithium metal battery including the same, and method for manufacturing the same

[0001] The invention relates to a polymer electrolyte, a lithium metal battery containing the same, and a method for manufacturing the same.

[0002] Currently commercially available lithium secondary batteries mainly use carbon-based negative electrode active materials such as graphite. Carbon-based negative electrode active materials do not change in volume during charging and discharging, so the stability of lithium secondary batteries is high. The theoretical electric capacity of graphite is small, about 372 mAh / g.

[0003] Lithium metal can be used as a negative electrode active material. The theoretical electric capacity of lithium metal is approximately 3,860 mAh / g, which is larger than that of graphite. During charging and discharging, dendrites may form on the surface of lithium metal due to side reactions with the electrolyte, and the growth of these dendrites can cause a short circuit between the positive and negative electrodes. Consequently, the lifespan characteristics of lithium metal batteries containing lithium metal may be degraded.

[0004] To solve the aforementioned problems, methods have been proposed in which a protective film is introduced to minimize contact between lithium and the electrolyte to reduce side reactions, or in which a gel polymer electrolyte is used to minimize the exposure of the electrolyte on the electrode surface and create a uniform flow of lithium ions throughout the electrode to suppress lithium dendrite growth by introducing the liquid electrolyte into the network of the cross-linked polymer.

[0005] The problem that the present invention aims to solve is to provide a lithium metal battery having improved ion conductivity.

[0006] Another problem that the present invention aims to solve is to provide a lithium metal battery with improved structural stability.

[0007] According to the concept of the present invention, a polymer electrolyte comprises a lithium salt; an organic solvent; a first additive; and a crosslinked polymer polymerized from a crosslinkable monomer, wherein the crosslinkable monomer comprises at least one of an acrylate-based monomer and a methacrylate-based monomer, and the first additive comprises a first compound represented by the following chemical formula 1: wherein L1 to L3 are each independently a direct bond or a C1 to C10 alkylene group.

[0008] [Chemical Formula 1]

[0009]

[0010] According to another concept of the present invention, a lithium metal battery comprises: a positive electrode comprising a positive current collector and a positive active material layer on the positive current collector; a negative electrode comprising a negative current collector; and a polymer electrolyte between the positive electrode and the negative electrode, wherein the polymer electrolyte comprises: a lithium salt; an organic solvent; a first additive; and a crosslinked polymer polymerized from a crosslinkable monomer, wherein the crosslinkable monomer is at least one of an acrylate-based monomer and a methacrylate-based monomer, and the first additive comprises a first compound represented by the following chemical formula 1: wherein L1 to L3 are each independently a direct bond or a C1 to C10 alkylene group.

[0011] [Chemical Formula 1]

[0012]

[0013] According to another concept of the present invention, a method for manufacturing a polymer electrolyte comprises: forming a battery structure by arranging a negative electrode current collector, a separator, and a positive electrode; housing the battery structure in a battery case and then injecting an electrolyte composition into the battery case; and curing the electrolyte composition to form a polymer electrolyte, wherein the electrolyte composition comprises crosslinkable monomers, an initiator, and a first additive, and the first additive comprises a first compound represented by the following chemical formula 1: wherein L1 to L3 are each independently directly bonded or C1 to C10 alkylene groups.

[0014] [Chemical Formula 1]

[0015]

[0016] The polymer electrolyte according to the present invention may include a crosslinked polymer and a first additive. The crosslinked polymer has a matrix structure, and the first additive may be provided in a phase-separated manner within the matrix structure of the crosslinked polymer. By including the first additive, it can serve as a transport pathway for lithium ions. As a result, the ionic conductivity of the polymer electrolyte can be improved. Consequently, a lithium metal battery comprising the polymer electrolyte according to the present invention may have improved electrical characteristics and lifespan characteristics.

[0017] FIG. 1 is a conceptual diagram briefly illustrating a lithium metal battery according to embodiments of the present invention.

[0018] FIG. 2 is a conceptual diagram briefly illustrating a lithium metal battery according to embodiments of the present invention.

[0019] FIGS. 3 to 5 are schematic diagrams illustrating a lithium battery according to one embodiment.

[0020] Figure 6 is an enlarged cross-sectional view of the M region of Figure 1.

[0021] In order to fully understand the structure and effects of the present invention, preferred embodiments of the present invention are described with reference to the attached drawings. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various forms and various modifications can be made. The description of these embodiments is provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention.

[0022] In this specification, when a component is described as being on another component, it means that it may be formed directly on the other component or that a third component may be interposed between them. Additionally, in the drawings, the thicknesses of the components are exaggerated for the effective description of the technical content. Throughout the specification, parts indicated by the same reference numeral represent the same components.

[0023] Unless otherwise specified in this specification, the singular form may also include the plural. Additionally, unless otherwise specified, "A or B" may mean "comprising A, comprising B, or comprising A and B." As used herein, "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components to the mentioned components.

[0024] In this specification, "combination of these" may mean a mixture of components, a laminate, a composite, a copolymer, an alloy, a blend, and a reaction product, etc.

[0025] In this specification, "metal" may include both metals and metalloids such as silicon and germanium in an elemental or ionic state.

[0026] In this specification, "alloy" may mean a mixture of two or more metals.

[0027] In this specification, "anode active material" may refer to an anode material capable of undergoing lithiation and delithiation.

[0028] In this specification, "anode active material" may refer to an anode material capable of undergoing lithiation and delithiation.

[0029] In this specification, "lithiation" and "to lithiate" may refer to the process of adding lithium to a positive electrode active material or a negative electrode active material.

[0030] In this specification, "delithiation" and "to delithiate" may refer to the process of removing lithium from a positive electrode active material or a negative electrode active material.

[0031] In this specification, "charge" and "to charge" may refer to the process of providing electrochemical energy to a battery.

[0032] In this specification, "discharge" and "discharge" may refer to the process of removing electrochemical energy from a battery.

[0033] In this specification, "anode" may refer to an electrode where electrochemical reduction and lithiation occur during the discharge process.

[0034] In this specification, "cathode" may refer to an electrode where electrochemical oxidation and delithiation occur during the discharge process.

[0035] Unless otherwise defined in this specification, the particle size may be the average particle size. Additionally, the particle size refers to the average particle size (D50), which means the diameter of the particle whose cumulative volume in the particle size distribution is 50% by volume. The average particle size (D50) may be measured by methods widely 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) image or a scanning electron microscope (SEM) image. Alternatively, the average particle size (D50) value may be obtained by measuring using a measuring device utilizing dynamic light scattering, performing data analysis to count the number of particles for each particle size range, and then calculating from this. Alternatively, it may be measured using a laser diffraction method. When measuring by laser diffraction, more specifically, after dispersing the particles to be measured 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 ultrasound of about 28 kHz at an output of 60 W, and then the average particle size (D50) at 50% of the particle size distribution in the measuring device can be calculated.

[0036]

[0037] FIG. 1 is a conceptual diagram briefly illustrating a lithium metal battery according to embodiments of the present invention. Referring to FIG. 1, the lithium metal battery may include a positive electrode (PEL), a negative electrode (NEL), a separator (SEP), and an electrolyte layer (GPE).

[0038] In lithium metal batteries, lithium metal can be used as the negative electrode active material. In lithium metal batteries, a lithium-containing metal layer may be precipitated and dissolved between the negative electrode current collector (COL1) and the electrolyte layer (GPE) during the charging and discharging process. As the charging and discharging of the lithium metal battery is repeated, the lithium-containing metal layer may contain impurities remaining in the electrode, decomposition products of the electrolyte, etc.

[0039] The lithium-containing metal layer may have a rough and hard surface due to the inclusion of such impurities. Lithium dendrites may precipitate on the lithium-containing metal layer having such a rough surface. Lithium dendrites continuously grow during the charging and discharging process and can cause a short circuit between the positive electrode (PEL) and the negative electrode (NEL). Furthermore, uneven growth of lithium dendrites on the negative electrode (NEL) during charging can easily cause damage within the cell, and the cell's volume may expand significantly, making long-term operation difficult.

[0040] The positive electrode (PEL) and the negative electrode (NEL) may be spaced apart from each other with a separator (SEP) in between. The separator (SEP) may be placed between the positive electrode (PEL) and the negative electrode (NEL). The positive electrode (PEL), the negative electrode (NEL), and the separator (SEP) may be in contact with the electrolyte layer (GPE). The separator (SEP) may be impregnated within the electrolyte layer (GPE). In one embodiment, not only the separator (SEP) but also the positive electrode (PEL) and the negative electrode (NEL) may be impregnated within the electrolyte layer (GPE).

[0041] The electrolyte layer (GPE) may be a medium for transferring lithium ions between the positive electrode (PEL) and the negative electrode (NEL). Within the electrolyte layer (GPE), the lithium ions may pass through a separator (SEP) and move toward the positive electrode (PEL) or the negative electrode (NEL).

[0042]

[0043] Anode (PEL)

[0044] A positive electrode (PEL) for a lithium metal battery may include a positive current collector (COL2) and a positive active material layer (PAL) formed on the positive current collector (COL2). The positive active material layer (PAL) includes a positive active material and may further include a binder and / or a conductive material. As an example, the positive active material layer (PAL) may further include an additive capable of acting as a sacrificial electrode.

[0045] The content of the positive active material in the positive active material layer (PAL) may be 90% to 99.5% by weight with respect to 100% by weight of the positive active material layer (PAL). The content of each of the binder and the conductive material may be 0.5% to 5% by weight with respect to 100% by weight of the positive active material layer (PAL).

[0046] The above binder can serve to effectively bond the positive active material particles to each other and also to effectively bond the positive active material to the positive current collector (COL2). Representative examples of binders include, but are not limited to, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, nylon, etc.

[0047] The above conductive material can be used to impart conductivity to the electrode. Any electronically conductive material that does not cause chemical changes in the electrode can be used as the conductive material. Examples of conductive materials include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjenblack, carbon fiber, carbon nanofiber, carbon nanotube; metal-based materials containing copper, nickel, aluminum, silver, etc., in the form of metal powder or metal fibers; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0048] The positive current collector (COL2) may include, for example, a plate or foil comprising 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.

[0049]

[0050] Positive active material (PAL)

[0051] As the positive active material in the positive active material layer (PAL), a compound capable of reversible intercalation and deintercalation of lithium (a lithated intercalation compound) may be used. Specifically, one or more composite oxides of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof may be used.

[0052] The above composite oxide may be a lithium transition metal composite oxide, and specific examples include a lithium nickel-based oxide, a lithium cobalt-based oxide, a lithium manganese-based oxide, a lithium iron phosphate-based compound, a cobalt-free nickel-manganese-based oxide, or a combination thereof.

[0053] As an example, a compound represented by any one of the following chemical formulas may be used. Li a 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 Mn 2-b X b About 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 About 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 Mn b X c About 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 Mn 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 Mn 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).

[0054] 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; and L1 is Mn, Al, or a combination thereof.

[0055] A coating layer may be additionally added to the surface of the aforementioned compound. The coating layer may include, for example, an oxide, a hydroxide, an oxyhydroxide, an oxycarbonate, or a hydroxycarbonate of a coating element. The coating layer may be amorphous or crystalline. The coating element within the coating layer may be selected from the group consisting of Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, and Zr. The method of forming the coating layer may be selected within a range that does not adversely affect the physical properties of the cathode active material. The coating method may include, for example, spray coating or immersion methods.

[0056] For example, the above-mentioned positive electrode active material may be a high-nickel positive electrode active material in which the nickel content relative to 100 mol% of the metal excluding lithium in the lithium transition metal composite oxide 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. The high-nickel positive electrode active material can achieve high capacity and can be applied to high-capacity, high-density lithium metal batteries.

[0057]

[0058] Separator (SEP)

[0059] Depending on the type of lithium metal battery, a separator (SEP) may be provided between the positive electrode (PEL) and the negative electrode (NEL). As such a separator (SEP), polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof may be used, and of course, mixed multilayer films 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.

[0060] The separator (SEP) may include a porous substrate and a coating layer comprising an organic material, an inorganic material, or a combination thereof located on one or both sides of the porous substrate.

[0061] The porous substrate may be a polymer membrane formed from any one of the following: polyolefins such as polyethylene and polypropylene; polyesters such as polyethylene terephthalate and polybutylene terephthalate; polyacetal; polyamide; polyimide; polycarbonate; polyetherketone; polyaryletherketone; polyetherimide; polyamideimide; polybenzimidazole; polyethersulfone; polyphenylene oxide; cyclic olefin copolymer; polyphenylene sulfide; polyethylene naphthalate; glass fiber; Teflon; and polytetrafluoroethylene, or a copolymer or mixture of two or more of these.

[0062] The above organic material may include a polyvinylidene fluoride-based polymer or a (meth)acrylic-based polymer.

[0063] The above inorganic materials are Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, It may include, but is not limited to, inorganic particles selected from SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof.

[0064] The above organic and inorganic materials may exist mixed in a single coating layer, or may exist in a stacked form with a coating layer containing organic materials and a coating layer containing inorganic materials.

[0065]

[0066] NEL

[0067] Referring again to FIG. 1, the negative electrode (NEL) for a lithium metal battery may include a negative electrode current collector (COL1).

[0068] The negative electrode current collector (COL1) may include, for example, a material that does not react with lithium, that is, does not form either an alloy or a compound with lithium. The material constituting the negative electrode current collector (COL1) may include at least one metal selected from the group consisting of, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni). The thickness of the negative electrode current collector (COL1) may be 1 to 20 μm, for example 5 to 15 μm, for example 7 to 10 μm.

[0069] The negative current collector (COL1) may be composed of one of the metals described above, or may include an alloy of two or more metals or a coating material. The negative current collector (COL1) is, for example, in the form of a plate or a foil.

[0070] Referring to FIG. 2, the negative electrode (NEL) of a lithium metal battery according to another embodiment may further include a lithium metal layer (NAL) disposed between a negative electrode current collector (COL1) and a separator (SEP). The lithium metal layer (NAL) may be a plated layer generated by charging the lithium metal battery (100).

[0071] The lithium metal layer (NAL) may contain lithium or a lithium alloy. Since the lithium metal layer (NAL) is a metal layer containing lithium, it may function as, for example, a lithium reservoir. The lithium alloy may be, for example, Li-Al alloy, Li-Sn alloy, Li-In alloy, Li-Ag alloy, Li-Au alloy, Li-Zn alloy, Li-Ge alloy, Li-Si alloy, etc., but is not limited to these; any alloy used as a lithium alloy in the relevant technical field may be possible. The lithium metal layer (NAL) may be composed of one of these alloys or lithium, or may be composed of various types of alloys.

[0072] In another embodiment, the lithium metal layer (NAL) within the negative electrode (NEL) may be provided on the negative electrode current collector (COL1), for example, before the assembly of the lithium metal battery. When the lithium metal layer (NAL) is placed on the negative electrode current collector (COL1) before the assembly of the lithium metal battery, the lithium metal layer (NAL) acts as a lithium reservoir because it is a metal layer containing lithium. For example, a lithium foil may be placed on the negative electrode current collector (COL1) before the assembly of the lithium metal battery.

[0073] When a lithium metal layer (NAL) is deposited by charging after the assembly of a lithium metal battery, the energy density of the lithium metal battery can be increased because the lithium metal layer (NAL) is not included during the assembly of the lithium metal battery. The lithium metal layer (NAL) can be composed mainly of lithium (i.e., metallic lithium). During discharge, lithium in the lithium metal layer (NAL) can be ionized and migrate to the positive electrode (PEL). In other words, lithium can be used as the negative electrode active material in a lithium metal battery. When a lithium metal layer (NAL) is formed by charging after the assembly of a lithium metal battery, the negative electrode (NEL), that is, the region between the negative electrode current collector (COL1) and the separator (SEP), may be a Li-free region that does not contain lithium (Li) in the initial state or after complete discharge of the lithium metal battery.

[0074]

[0075] Polymer electrolyte layer (GPE)

[0076] The polymer electrolyte layer (GPE) according to the present invention may comprise a solid electrolyte, a gel electrolyte, or a combination thereof. The polymer electrolyte layer (GPE) may be in a solid state at 25°C and 1 atm. The polymer electrolyte layer (GPE) may be in a gel state at 25°C and 1 atm. The polymer electrolyte layer (GPE) according to the present invention may comprise a lithium salt, an organic solvent, a first additive, and a crosslinking polymer (CP). The polymer electrolyte layer (GPE) will be described in detail with reference to FIG. 1 and FIG. 6. FIG. 6 is an enlarged cross-sectional view of region M in FIG. 1.

[0077] The organic solvent may be selected without limitation as long as it is used as an organic solvent in the relevant technical field. For example, the organic solvent is propylene carbonate, ethylene carbonate, fluoroethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, dibutyl carbonate, benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, dioxolane, 4-methyldioxolane, N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, diethylene glycol, dimethyl ether, or a mixture thereof.

[0078] Lithium salts are materials that are dissolved in organic solvents and act as a source of lithium ions within lithium metal batteries to enable basic operation of the lithium metal battery, and play a role in promoting the transfer of lithium ions between the positive electrode (PEL) and the negative electrode (NEL). Any lithium salt used as a lithium salt in the relevant technical field may be selected without restriction. For example, the lithium salt is LiPF6, LiN(SO₂CF₃)₂ (lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)), LiN(SO₂F)₂ (lithium trifluoromethanesulfonylimide, LiFSI), LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, Li(FSO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(CxF2x+1SO2)(CyF2y+1SO2)(1≤x≤20, 1≤y≤20), LiCl, LiI, or a mixture thereof. For example, the concentration of the lithium salt may be 0.1 M to 5.0 M.

[0079] The crosslinked polymer (CP) according to the present invention may have a matrix structure. The crosslinked polymer (CP) may be a polymer of crosslinkable monomers. For example, the crosslinked polymer (CP) may have chain structures formed by the polymerization of crosslinkable monomers and a crosslinked structure of said chain structures.

[0080] A crosslinked polymer (CP) can be formed by polymerizing from a crosslinkable monomer. The crosslinkable monomer may include at least one of an acrylate-based monomer and a methacrylate-based monomer. The crosslinkable monomer may include at least one of a second compound represented by the following Chemical Formula 2 and a third compound represented by the following Chemical Formula 3.

[0081] [Chemical Formula 2]

[0082]

[0083] In the above chemical formula 2, R1 may be a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C6 to C30 aryl group, or a vinyl group.

[0084] [Chemical Formula 3]

[0085]

[0086] In the above chemical formula 3, R2 may be a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C6 to C30 aryl group, or a vinyl group.

[0087] For example, acrylate monomers include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, acrylonitrile, methacrylonitrile, acrylic acid, methacrylic acid, acrylamide, methacrylamide, bisphenol A dimethacrylate, and trimethylolpropane triacrylate. It may include at least one selected from the group consisting of triacrylate, trimethylolpropane trimethacrylate, acryl hexafluoropropylate, methyl hydroxyethyl acrylate, and acrylic acid-2-hydroxyethyl ester. However, it is not limited thereto.

[0088] Methacrylate monomers include methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, methyl hydroxyethyl methacrylate, ethyl hydroxyethyl methacrylate, butyl hydroxyethyl methacrylate, 2-ethylhexyl hydroxyethyl methacrylate, bisphenol A dimethacrylate, trimethylolpropane trimethacrylate, and dibutyl methacrylate. Methacrylate), Triethylene Glycol Dimethacrylate, Methyl Acrylate Ethyl Methacrylate, Methacryloethyl Amine, Methacryloyl Chloride, Methacryloyl Ethylene Glycol, Pentaerythritol Tetramethacrylate, 2-Ethylhexyl Hydroxypropyl Methacrylate,It may include at least one selected from the group consisting of trimethylolpropane methacrylate and methacrylic acid-2-hydroxyethyl ester. However, it is not limited thereto.

[0089] The polymer electrolyte layer (GPE) may further include an initiator for the polymerization reaction of crosslinkable monomers. For example, the initiator may include at least one of azobis(isobutyronitrile) (AIBN), azobis(2,4-dimethylvaleronitrile) (ADVN), 1,1'-azobis-(cyclohexane-1-carbonitrile) (ACHN), tertbutyl peroxypivalate (BPP), benzoyl peroxide (BPO), and detertbutyl peroxide (DTBP). The content of the initiator may be 3.0 wt% or less or 0.05 wt% or less of the total weight of the polymer electrolyte layer (GPE).

[0090] The crosslinked polymer (CP) may include a crosslinking agent. When the monomers are polymerized to form a chain structure, the crosslinking agent can crosslink between the chain structures. For example, the crosslinking agent of the crosslinked polymer (CP) may include a fourth compound represented by the following chemical formula 4.

[0091] [Chemical Formula 4]

[0092]

[0093] In the above chemical formula 4, R3 is hydrogen or a substituted or unsubstituted C1 to C10 alkyl group, and R4 may be a substituted or unsubstituted C1 to C30 alkyl group or a substituted or unsubstituted C6 to C30 aryl group.

[0094] In one embodiment, the crosslinked polymer (CP) may include a structure such as that of Chemical Formula 5 below.

[0095] [Chemical Formula 5]

[0096]

[0097] In the above chemical formula 5, R1 may be a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C6 to C30 aryl group, or a vinyl group. R3 may be hydrogen or a substituted or unsubstituted C1 to C10 alkyl group, and R4 may be a substituted or unsubstituted C1 to C30 alkyl group or a substituted or unsubstituted C6 to C30 aryl group.

[0098] The first additive according to the present invention may include a first compound represented by the following chemical formula 1.

[0099] [Chemical Formula 1]

[0100]

[0101] In the above Chemical Formula 1, L1 to L3 are each independently directly bonded or C1 to C10 alkylene groups. The first additive may include a functional group capable of coordinating with a cation (e.g., lithium ion). As an example, the first additive may be 1,3,6-hexanetricarbonitrile (HTCN). Specifically, the above Chemical Formula 1 may be represented by the following Chemical Formula 1-1.

[0102]

[0103] The content of the first additive may be 30 to 50 parts by weight per 100 parts by weight of the polymer electrolyte (GPE). The first additive may include a nitrile group. The first additive may have a linear structure. As a result, the first additive can act as an ion transfer channel within the cross-linked polymer to be described later.

[0104] The polymer electrolyte layer (GPE) may further include a second additive. The second additive may be different from the first additive. The second additive may include a functional group capable of coordinating with a cation (e.g., lithium ion). The second additive may include at least one of a nitrile group, an imidazole group, and a triazole group. Preferably, the second additive may include a nitrile group.

[0105] For example, the second additive may include one or more selected from acetonitrile, adiponitrile, succinitrile, propionitrile, phenylacetonitrile, valeronitrile, cyclohexane carbonitrile, imidazole, methylimidazole, benzimidazole, 2-imidazole carboxylic acid, chlordrimazole, 1,2,3-triazole, 1,2,4-triazole, fluconazole, and diazole.

[0106] For example, the second additive may include one or more selected from imidazole, 2-methylimidazole, 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM PF6), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM TFSI), 1,2-dimethylimidazolium methanesulfonate (DMIM MS), 1,2,4-triazole, 1H-1,2,3-triazole, and 1,2,4-triazolium sulfonate (TMS).

[0107] When the polymer electrolyte (GPE) includes a second additive, the total content of the first additive and the second additive may be 30 to 50 parts by weight per 100 parts by weight of the polymer electrolyte. For example, the content of the first additive may be 15 to 40 parts by weight per 100 parts by weight of the polymer electrolyte. The content of the second additive may be 10 to 35 parts by weight per 100 parts by weight of the polymer electrolyte.

[0108] Referring to FIG. 6, a first additive can be provided in a phase-separated manner within a crosslinked polymer (CP). The first additive can form an ion channel (IC) within the matrix structure of the crosslinked polymer (CP). Specifically, the ion channel (IC) can be formed by the functional group of the first additive forming a coordination bond with a cation (e.g., a lithium ion). Through the ion channel (IC), lithium ions (Li + ) can pass through. When the polymer electrolyte layer (GPE) includes a second additive, an ion channel (IC) can be formed by the first additive, the second additive, and the cation forming a coordination bond. For example, the first additive can bind with a lithium ion as shown in Chemical Formula 6 below. Chemical Formula 6 below may be a structure that appears when the N region of FIG. 6 is magnified.

[0109] [Chemical Formula 6]

[0110]

[0111] According to the present invention, the polymer electrolyte according to the present invention may comprise a crosslinked polymer (CP) and a first additive. The crosslinked polymer (CP) has a matrix structure, and the first additive may be provided in a phase-separated manner within the matrix structure of the crosslinked polymer (CP). By including the first additive, it can serve as a transport pathway for lithium ions. As a result, the ion conductivity of the lithium metal battery can be improved. Consequently, the electrical characteristics and lifespan characteristics of the lithium metal battery according to the present invention can be improved.

[0112]

[0113] lithium metal battery

[0114] Referring to FIG. 3, a lithium battery (LBT) according to one embodiment of the present invention may include the aforementioned positive electrode (PEL), the aforementioned negative electrode (NEL), and the separator (SEP). The positive electrode (PEL), the negative electrode (NEL), and the separator (SEP) may be wound or folded to form a battery structure (BTS). The battery structure (BTS) may be housed in a battery case (CAS). An electrolyte may be injected into the battery case (CAS) to form an electrolyte layer. The lithium battery (LBT) may be manufactured by sealing the battery case (CAS) with a cap assembly (CAB). The battery case (CAS) may be cylindrical, but is not necessarily limited to this shape and may be, for example, prismatic, thin-film, etc.

[0115] Referring to FIG. 4, a lithium battery (LBT) according to one embodiment of the present invention may include the above-described positive electrode (PEL), the above-described negative electrode (NEL), and a separator (SEP). A separator (SEP) may be disposed between the positive electrode (PEL) and the negative electrode (NEL) to form a battery structure (BTS).

[0116] A battery structure (BTS) can be stacked in a bicell structure and then housed in a battery case (CAS). It may include an electrode tab (ELT) that serves as an electrical pathway to guide the current formed in the battery structure (BTS) to the outside. An electrolyte layer can be formed by injecting an electrolyte into the battery case (CAS). The battery case (CAS) can be sealed to manufacture a lithium battery (LBT). The battery case (CAS) may be prismatic, but is not necessarily limited to this shape and may be, for example, cylindrical, thin-film, etc.

[0117] Referring to FIG. 5, a lithium battery (LBT) according to one embodiment of the present invention may include the above-described positive electrode (PEL), the above-described negative electrode (NEL), and a separator (SEP). A separator (SEP) is disposed between the positive electrode (PEL) and the negative electrode (NEL), and the positive electrode (PEL), the negative electrode (NEL), and the separator (SEP) may be wound or folded to form a battery structure (BTS).

[0118] The formed battery structure (BTS) can be accommodated in a battery case (CAS). It may include an electrode tab (ELT) that serves as an electrical pathway to guide the current formed in the battery structure (BTS) to the outside. An electrolyte layer can be formed by injecting an electrolyte into the battery case (CAS). The battery case (CAS) can be sealed to manufacture a lithium battery (LBT). The battery case (CAS) may be prismatic, but is not necessarily limited to this shape and may be, for example, cylindrical, thin-film, etc.

[0119] A pouch-type lithium battery may correspond to using a pouch as a battery case (CAS) in each of the lithium batteries (LBT) of FIGS. 3 to 5. A pouch-type lithium battery may include at least one battery structure (BTS). A pouch-type lithium battery may be manufactured by stacking the battery structure (BTS) in a bicell structure, impregnating it into an electrolyte layer, and then housing and sealing it in a pouch.

[0120] For example, the aforementioned anode, cathode, and separator may be simply stacked and accommodated in a pouch in the form of an electrode assembly. The electrode assembly may be wound into a jelly roll or folded and then accommodated in a pouch. An electrolyte layer may be formed by injecting an electrolyte into the pouch.

[0121] Lithium batteries have excellent lifespan and high-rate characteristics, so they can be used, for example, in electric vehicles (EVs). For example, they can be used in plug-in hybrid electric vehicles (PHEVs). In addition, they can be used in fields requiring large amounts of power storage. For example, they can be used in electric bicycles, power tools, etc.

[0122] Multiple lithium batteries can be stacked to form a battery module. Multiple battery modules can constitute 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. For example, a battery module may include multiple batteries and a frame that supports them.

[0123] A battery pack may include, for example, a plurality of battery modules and a bus bar connecting them. The battery modules and / or the battery pack may further include a cooling device. A plurality of battery packs may be controlled by a battery management system. The battery management system may include a battery pack and a battery control device connected to the battery pack.

[0124]

[0125] Method for manufacturing a lithium metal battery

[0126] A lithium metal battery according to the present invention may be manufactured by arranging a negative electrode current collector (COL1), a separator (SEP), and a positive electrode (PEL) to form a battery structure (BTS); housing the battery structure (BTS) in a battery case and then injecting an electrolyte composition into the battery case; and curing the electrolyte composition to form a polymer electrolyte layer (GPE).

[0127] The above electrolyte composition may include an organic solvent, crosslinkable monomers, an initiator, and a first additive. As another example, the above electrolyte composition may further include at least one of a crosslinking agent and a second additive. Since the details regarding the organic solvent, crosslinkable monomers, initiator, first additive, second additive, and crosslinking agent can be applied as described above, a detailed description thereof is omitted below.

[0128] Injecting the electrolyte composition into the battery case can be performed under vacuum so that the composition can sufficiently penetrate the positive electrode, negative electrode, and separator.

[0129] Methods for curing the electrolyte composition include heat treatment, UV, or high-energy radiation (electron beam, γ-ray). The curing reaction using heat treatment can be carried out for 30 to 120 minutes at a temperature of 40 to 120°C, for example, 50 to 90°C.

[0130] Curing the electrolyte composition may include polymerizing crosslinkable monomers to form a crosslinked polymer; and phase-separating a first additive within the matrix structure of the crosslinked polymer. As previously described with reference to FIG. 6, the first additive may form ion channels (IC) within the matrix structure of the crosslinked polymer.

[0131] The polymer electrolyte layer (GPE) can be manufactured by a method in which it is injected into a battery case (CAS) into which a battery structure (BTS) is inserted and then cured, thereby having the advantage of being applicable to existing non-aqueous electrolyte battery manufacturing processes. The polymer electrolyte can maintain good processability by maintaining low viscosity when injected into the battery case (CAS). The gel polymer electrolyte can be easily cured by thermal curing or photocuring and thus can have a gel form. In lithium metal batteries, the polymer electrolyte may also be described as containing a cross-linked polymer or a cured polymer and an electrolyte.

[0132]

[0133] The present invention will be explained in more detail below through examples. However, these examples are intended to illustrate the invention and the scope of the invention is not limited to these examples.

[0134]

[0135] Example 1

[0136] 1. Preparation of polymer electrolyte composition

[0137] A first electrolyte is prepared by dissolving 1.3M LiPF6 in a non-aqueous organic solvent containing ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP), and propyl propionate (PP) in a volume ratio of 10:15:30:45, and dissolving methyl acrylate, 1,6-hexanediol diacrylate, and azobisisobutyronitrile (AIBN) as an initiator.

[0138] A second electrolyte is prepared by dissolving lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and 1,3,6-hexanetricarbonitrile (HTCN) as a first additive in a prepared organic solvent. The first electrolyte and the second electrolyte are mixed and heated at a temperature of 70°C to 80°C for 240 minutes to prepare a polymer electrolyte. The prepared polymer electrolyte may be in a solid state.

[0139]

[0140] Example 2

[0141] Acetonitrile is further dissolved as a second additive in the polymer electrolyte composition. Except for this, the polymer electrolyte is prepared in the same manner as in Example 1.

[0142]

[0143] Comparative Example 1

[0144] The curing of the polymer electrolyte composition was omitted, and a liquid electrolyte was prepared instead of a polymer electrolyte. Additionally, the liquid electrolyte further contained acetonitrile as a second additive. Except for this, the electrolyte was prepared in the same manner as in Example 1.

[0145]

[0146] Comparative Example 2

[0147] The first additive was omitted from the polymer electrolyte composition, and acetonitrile was dissolved as the second additive. Except for this, the polymer electrolyte was prepared in the same manner as in Example 1.

[0148]

[0149] Examples and comparative examples of the present invention manufactured as described above are shown in Table 1 below.

[0150] Electrolyte State 1. Presence or Absence of Additive 2. Presence or Absence of Additive Example 1: Solid Polymer Electrolyte OX Example 2: Solid Polymer Electrolyte OO Comparative Example 1: Liquid Electrolyte OO Comparative Example 2: Solid Polymer Electrolyte XO

[0151] Example 1 of preparation: As a positive electrode active material for a lithium metal battery, 97 wt% of lithium cobalt oxide (LCO, LiCoO2), 2 wt% of polyvinylidene fluoride binder, 1 wt% of carbon nanotube conductive material, and N-methylpyrrolidone solvent are mixed in a mixer to prepare a positive electrode active material layer composition, and the composition is coated onto an aluminum foil, then dried and rolled to produce a positive electrode.

[0152] An electrode assembly is prepared by interposing a separator with a polyethylene polypropylene multilayer structure between a prepared positive electrode and a lithium metal counter electrode. The electrode assembly is inserted into a pouch-type battery case, and a prepared polymer electrolyte composition is injected into the case. Then, the electrolyte composition is cured by heat treatment at 80°C for 1 to 3 hours, thereby manufacturing a half-cell in which a polymer electrolyte is formed.

[0153]

[0154] Evaluation Example 1: Evaluation of Ionic Conductivity of Polymer Electrolytes

[0155] Impedance spectroscopy was performed to evaluate the ionic conductivity of the electrolyte according to each of the examples and comparative examples. The results of the ionic conductivity evaluation of the lithium metal batteries according to each of the examples and comparative examples are shown in Table 2 below.

[0156] Ionic Conductivity (S / cm) Example 16.11 Example 26.42 Comparative Example 17.38 Comparative Example 24.94

[0157] Referring to Table 2, it can be seen that the ionic conductivity of Example 1 is lower than that of Comparative Example 1. This means that the lithium ion mobility was reduced due to the polymer formation reaction. In the case of Comparative Example 2, it can be seen that the ionic conductivity is lower than that of Example 1. From this, it was confirmed that the polymer electrolyte containing HTCN as the first additive has improved ionic conductivity. Thus, it can be seen that the lithium metal battery containing the polymer electrolyte containing the first additive has improved ionic conductivity.

[0158] Evaluation Example 2: Life Characteristics Evaluation

[0159] The lithium metal batteries prepared in Examples 1 and 2 and Comparative Examples 1 and 2 are charged at 25°C with a constant current of 0.1C to an upper voltage limit of 4.4V, and then discharged at a constant current of 0.1C to a discharge termination voltage of 3.0V to perform an initial charge-discharge cycle (formation cycle). Subsequently, charging at 0.5C and discharging at 0.5C within a voltage range of 3.0V to 4.4V are repeated 150 times. The discharge capacity is measured during the 150 cycles, and the discharge capacity for each cycle is shown in FIG. 5, while the discharge capacity after 150 cycles is shown in Table 3 below.

[0160] Solvent composition discharge capacity (@150 th cycles, mAh) Example 1 16.32 Example 2 16.40 Comparative Example 1 12.01 Comparative Example 2 14.28

[0161] Referring to Table 3, it was confirmed that the discharge capacity at 150 cycles for Comparative Examples 1 and 2 was lower than that of Examples 1 and 2. Lifetime characteristics were not improved when only the second additive was included or / when a liquid electrolyte other than a polymer electrolyte was included. On the other hand, it was confirmed that Examples 1 and 2, which are lithium metal batteries containing a polymer electrolyte layer containing the first additive, exhibited excellent lifetime characteristics.

[0162] Although an exemplary embodiment has been described in detail above with reference to the attached drawings, the present creative idea is not limited to such examples. It is obvious that a person skilled in the art to which the present creative idea belongs can derive various variations or modifications within the scope of the technical idea described in the patent claims, and these also naturally fall within the technical scope of the present creative idea.

Claims

1. Lithium salt; Organic solvent; First additive; and A crosslinked polymer polymerized from a crosslinkable monomer, comprising The above-mentioned crosslinkable monomer comprises at least one of an acrylate-based monomer and a methacrylate-based monomer, and The above first additive is a polymer electrolyte comprising a first compound represented by the following chemical formula 1: [Chemical Formula 1] In the above chemical formula 1, L1 to L3 are each independently directly bonded or C1 to C10 alkylene groups.

2. In Paragraph 1, The above-mentioned crosslinkable monomer is a polymer electrolyte comprising a second compound represented by the following chemical formula 2: [Chemical Formula 2] In the above chemical formula 2, R1 is a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C6 to C30 aryl group or vinyl group.

3. In Paragraph 1, The above-mentioned crosslinkable monomer is a polymer electrolyte comprising a third compound represented by the following chemical formula 3: [Chemical Formula 3] In the above chemical formula 3, R2 is a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C6 to C30 aryl group, or a vinyl group.

4. In Paragraph 1, The above chemical formula 1 is a polymer electrolyte represented by the following chemical formula 1-1. [Chemical Formula 1-1] 5. In Paragraph 1, A polymer electrolyte in which the content of the first additive is 30 to 50 parts by weight per 100 parts by weight of the polymer electrolyte.

6. In Paragraph 1, The above-mentioned crosslinked polymer is a polymer electrolyte further comprising a fourth compound represented by the following chemical formula 4: [Chemical Formula 4] In the above chemical formula 4, R3 is hydrogen or a substituted or unsubstituted C1 to C10 alkyl group, and R4 is a substituted or unsubstituted C1 to C30 alkyl group or a substituted or unsubstituted C6 to C30 aryl group.

7. In Paragraph 1, It further includes a second additive, The second additive above is a polymer electrolyte containing nitrile groups.

8. In Paragraph 7, The second additive is a polymer electrolyte selected from one or more of acetonitrile, adiponitrile, succinitrile, propionitrile, phenylacetonitrile, valeronitrile, and cyclohexane carbonitrile.

9. In Paragraph 7, The total content of the first additive and the second additive is 30 to 50 parts by weight per 100 parts by weight of the polymer electrolyte.

10. In Paragraph 1, The above lithium salt is a polymer electrolyte comprising at least one of lithium hexafluorophosphate (LiPF6), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and lithium trifluoromethanesulfonylimide (LiFSI).

11. In Paragraph 1, The above-mentioned cross-linked polymer has a matrix structure, and The first additive is a polymer electrolyte provided in phase separation within the matrix structure of the crosslinked polymer.

12. A positive electrode comprising a positive current collector and a positive active material layer on the positive current collector; A cathode comprising a cathode current collector; and A polymer electrolyte between the anode and the cathode, comprising: The above polymer electrolyte is: Lithium salt; Organic solvent; First additive; and A crosslinked polymer polymerized from a crosslinkable monomer, comprising The above-mentioned crosslinkable monomer is at least one of an acrylate-based monomer and a methacrylate-based monomer, and The above first additive is a lithium metal battery comprising a first compound represented by the following chemical formula 1: [Chemical Formula 1] In the above chemical formula 1, L1 to L3 are each independently directly bonded or C1 to C10 alkylene groups.

13. In Paragraph 12, A lithium metal battery in which the content of the first additive is 30 to 50 parts by weight per 100 parts by weight of the polymer electrolyte.

14. In Paragraph 12, It further includes a second additive, The above second additive is a lithium metal battery containing nitrile groups.

15. In Paragraph 12, A lithium metal battery comprising at least one selected from the group consisting of the above acrylate-based monomer, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, acrylonitrile, methacrylonitrile, acrylic acid, methacrylic acid, acrylamide, methacrylamide, bisphenol A dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, acrylohexafluoropropylate, methylhydroxyethyl acrylate, and acrylic acid-2-hydroxyethyl ester.

16. In Paragraph 12, A lithium metal battery comprising at least one methacrylate monomer selected from the group consisting of methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, methyl hydroxyethyl methacrylate, ethyl hydroxyethyl methacrylate, butyl hydroxyethyl methacrylate, 2-ethylhexyl hydroxyethyl methacrylate, bisphenol A dimethacrylate, trimethylolpropane trimethacrylate, dibutyl methacrylate, triethylene glycol dimethacrylate, methyl acryloyl ethyl methacrylate, methacryl ethylamine, methacryloyl chloride, methacryl ethylene glycol, pentaerythritol tetramethacrylate, 2-ethylhexyl hydroxypropyl methacrylate, trimethylolpropane methacrylate, and methacrylic acid-2-hydroxyethyl ester.

17. Forming a battery structure by arranging a negative current collector, a separator, and a positive electrode; The above-mentioned battery structure is housed in a battery case, and then an electrolyte composition is injected into the battery case; and The above electrolyte composition is cured to form a polymer electrolyte, comprising: The above electrolyte composition comprises crosslinkable monomers, an initiator, and a first additive, and A method for manufacturing a lithium metal battery comprising the first additive being a first compound represented by the following chemical formula 1: [Chemical Formula 1] In the above chemical formula 1, L1 to L3 are each independently directly bonded or C1 to C10 alkylene groups.

18. In Paragraph 17, A method for manufacturing a lithium metal battery comprising at least one of a second compound represented by the following chemical formula 2 and a third compound represented by the following chemical formula 3, wherein the above-mentioned crosslinkable monomers are: [Chemical Formula 2] In the above chemical formula 2, R1 is a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C6 to C30 aryl group or vinyl group, and [Chemical Formula 3] In the above chemical formula 3, R2 is a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C6 to C30 aryl group or vinyl group.

19. In Paragraph 17, Curing the above electrolyte composition is, The above-mentioned crosslinkable monomers are polymerized to form a crosslinked polymer, the crosslinked polymer has a matrix structure; and A method for manufacturing a lithium metal battery comprising the above first additive being phase-separated within the matrix structure.

20. In Paragraph 17, A method for manufacturing a lithium metal battery comprising at least one of the initiator azobis(isobutyronitrile) (AIBN), azobis(2,4-dimethylvaleronitrile) (ADVN), 1,1'-azobis-(cyclohexane-1-carbonitrile) (ACHN), benzoyl peroxide (BPO), tertbutyl peroxypivalate (BPP), and ditertbutyl peroxide (DTBP).

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