Gel polymer electrolyte, lithium metal battery comprising same, and method for manufacturing lithium metal battery comprising same

Abstract

The present invention relates to a gel polymer electrolyte, a lithium metal battery comprising same, and a method for manufacturing a lithium metal battery comprising same. More specifically, the gel polymer electrolyte comprises: a liquid electrolyte; a lithium salt; a crosslinked polymer; and an additive including a polymer in which at least one functional group is connected to a hydrocarbon backbone, wherein the functional group includes a N-C=O bond, the additive has a weight average molecular weight of 1,000 to 100,000, and the concentration of the additive is 100-10,000 ppm.

Description

Gel polymer electrolyte, lithium metal battery containing the same, and method for producing a lithium metal battery containing the same

[0001] The present invention relates to a gel metal electrolyte for a lithium metal battery, and more particularly, to a gel polymer electrolyte capable of improving battery performance by adding a gel polymer electrolyte additive to induce uniform and dense lithium deposition and reduce side reactions between lithium and the electrolyte, a lithium metal battery comprising the same, and a method for manufacturing a lithium metal battery comprising the same.

[0002]

[0003] Lithium batteries currently on the market primarily use carbon-based anode materials, such as graphite. Carbon-based anode materials exhibit no volume change during charge / discharge, contributing to the stability of lithium batteries. However, their low capacity necessitates the use of higher-capacity, high-capacity anode materials.

[0004] Lithium metal, which has a much higher theoretical electrical capacity than carbon-based anode materials, can be used as an anode active material. However, lithium metal can form dendrites on its surface due to side reactions with the electrolyte during charge / discharge, and these dendrites can grow and cause short circuits between the anode and cathode. Consequently, the lifespan of lithium metal batteries containing lithium metal can be reduced.

[0005]

[0006] The problem to be solved by the present invention is to provide a gel polymer electrolyte additive for a lithium metal battery capable of suppressing lithium dendrites.

[0007] Another problem to be solved by the present invention is to provide a gel polymer electrolyte for a lithium metal battery that reduces side reactions between lithium and the electrolyte.

[0008] Another problem that the present invention seeks to solve is to provide a lithium metal battery having high energy density and excellent lifespan.

[0009]

[0010] According to the concept of the present invention, a gel polymer electrolyte comprises: a liquid electrolyte; a lithium salt; a crosslinked polymer; and an additive comprising a polymer having at least one functional group linked to a hydrocarbon backbone, wherein the functional group comprises an NC=O bond, the additive has a weight average molecular weight of 1,000 to 100,000, and the concentration of the additive may be 100 ppm to 10,000 ppm.

[0011] According to another concept of the present invention, a lithium metal battery may include a negative electrode; a positive electrode; and a gel polymer electrolyte between the negative electrode and the positive electrode.

[0012] According to another concept of the present invention, a method for manufacturing a lithium metal battery may include forming a composition for forming a gel polymer electrolyte by mixing a liquid electrolyte, a lithium salt, a crosslinking agent, and the additives; injecting the composition for forming a gel polymer electrolyte between a positive electrode and a negative electrode; and crosslinking the composition for forming a gel polymer electrolyte to form a gel polymer electrolyte.

[0013]

[0014] The present invention can suppress dendrite formation by reducing side reactions between lithium and electrolyte by adding an additive for a gel polymer electrolyte.

[0015] A lithium metal battery including a gel polymer electrolyte according to the present invention can have improved cycle characteristics and life characteristics.

[0016]

[0017] Figure 1 is a schematic diagram illustrating a lithium metal battery.

[0018] FIG. 2 is a schematic diagram illustrating a lithium metal battery after an initial cycle according to embodiments of the present invention.

[0019] Figure 3 is an enlarged cross-sectional view of a cathode region including a cathode host layer.

[0020] Figure 4a is an enlarged cross-sectional view of part M of Figure 3 before charging.

[0021] Fig. 4b is an enlarged cross-sectional view of the M portion of Fig. 3 after charging.

[0022] Figure 5 is an enlarged view showing the appearance of a gel polymer electrolyte after thermal crosslinking according to embodiments of the present invention.

[0023] Figure 6 is an enlarged view showing the appearance of a gel polymer electrolyte before thermal crosslinking according to embodiments of the present invention.

[0024] Figures 7 to 9 are schematic diagrams illustrating a lithium battery according to one embodiment.

[0025] Figure 10 is a graph showing the performance of a lithium metal battery according to embodiments of the present invention.

[0026]

[0027] To fully understand the structure and effects of the present invention, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various forms and subject to various modifications. However, the description of these embodiments is provided solely to ensure a complete disclosure of the present invention and to fully inform those skilled in the art of the invention of the scope of the invention.

[0028] In this specification, when a component is referred to as being on another component, it means that it can be formed directly on the other component, or a third component may be interposed between them. Furthermore, in the drawings, the thicknesses of the components are exaggerated for the sake of clarity. Parts designated by the same reference numerals throughout the specification represent the same components.

[0029] 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." As used herein, "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components.

[0030] As used herein, “combination thereof” may mean mixtures, laminates, composites, copolymers, alloys, blends, and reaction products of the components.

[0031] In this specification, “metal” may include both metals and metalloids such as silicon and germanium, in either the elemental or ionic state.

[0032] In this specification, “alloy” may mean a mixture of two or more metals.

[0033] In this specification, “positive electrode active material” may mean a positive electrode material capable of undergoing lithiation and delithiation.

[0034] In this specification, “negative electrode active material” may mean a negative electrode material capable of undergoing lithiation and delithiation.

[0035] In this specification, “lithiation” and “lithiating” may refer to a process of adding lithium to a positive electrode active material or a negative electrode active material.

[0036] In this specification, “delithiation” and “delithiate” may refer to a process of removing lithium from a positive electrode active material or a negative electrode active material.

[0037] In this specification, “charging” and “charging” may refer to a process of providing electrochemical energy to a battery.

[0038] In this specification, “discharging” and “discharging” may refer to the process of removing electrochemical energy from a battery.

[0039] In this specification, “positive electrode” may mean an electrode where electrochemical reduction and lithiation occur during a discharge process.

[0040] In this specification, “negative electrode” may mean an electrode where electrochemical oxidation and delithiation occur during a discharge process.

[0041] 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.

[0042]

[0043] FIG. 1 is a schematic conceptual diagram illustrating a lithium metal battery according to embodiments of the present invention. FIG. 2 is an enlarged cross-sectional view of the cathode region of FIG. 1. 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).

[0044] Lithium metal batteries can use lithium metal as the anode active material. During the charge / discharge process, a lithium-containing metal layer can precipitate and dissolve between the anode current collector (COL1) and the electrolyte layer (GPE). As the lithium metal battery is repeatedly charged and discharged, the lithium-containing metal layer can contain residual impurities within the electrode, electrolyte decomposition products, and other substances.

[0045] The lithium-containing metal layer may contain these impurities, resulting in a rough and hard surface. Lithium dendrites may precipitate on the lithium-containing metal layer with this rough surface. Lithium dendrites continuously grow during charge and discharge, potentially causing short circuits between the positive electrode (PEL) and negative electrode (NEL). Furthermore, uneven lithium dendrite growth on the negative electrode (NEL) during charging can easily cause damage within the cell, significantly expanding the cell volume and hindering long-term operation.

[0046] The positive electrode (PEL) and the negative electrode (NEL) can be separated from each other with a separator (SEP) therebetween. The separator (SEP) can be disposed between the positive electrode (PEL) and the negative electrode (NEL). The positive electrode (PEL), the negative electrode (NEL), and the separator (SEP) can be in contact with the electrolyte layer (GPE). The separator (SEP) can be impregnated into the electrolyte layer (GPE). In one embodiment, not only the separator (SEP), but also the positive electrode (PEL) and the negative electrode (NEL) can be impregnated into the electrolyte layer (GPE).

[0047] The electrolyte layer (GPE) may be a medium for transporting lithium ions between the positive electrode (PEL) and the negative electrode (NEL). Within the electrolyte layer (GPE), the lithium ions may pass through the separator (SEP) and move toward the positive electrode (PEL) or the negative electrode (NEL).

[0048]

[0049] Positive electrode (PEL)

[0050] A positive electrode (PEL) for a lithium metal battery may include a positive electrode current collector (COL2) and a positive electrode active material layer (PAL) formed on the positive electrode current collector (COL2). The positive electrode active material layer (PAL) includes a positive electrode active material and may further include a binder and / or a conductive material. For example, the positive electrode active material layer (PAL) may further include an additive that can function as a sacrificial positive electrode.

[0051] The content of the positive active material in the positive active material layer (PAL) may be 90 wt% to 99.5 wt% with respect to 100 wt% of the positive active material layer (PAL). The content of each of the binder and the conductive agent may be 0.5 wt% to 5 wt% with respect to 100 wt% of the positive active material layer (PAL).

[0052] The above binder can serve to adhere positive electrode active material particles well to each other and also to adhere positive electrode active material well to positive electrode current collector (COL2). 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.

[0053] The conductive material may be used to impart conductivity to the electrode. Any conductive material that does not cause a chemical change in the electrode and is electronically conductive may be used. Examples of conductive materials include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic materials containing copper, nickel, aluminum, silver, and the like in the form of metal powder or metal fibers; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0054] Al can be used as the positive electrode collector (COL2), but is not limited thereto.

[0055]

[0056] positive electrode active material

[0057] As the positive active material within the positive active material layer (PAL), a compound capable of reversible intercalation and deintercalation of lithium (lithiated intercalation compound) can be used. Specifically, one or more of a composite oxide of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof can be used.

[0058] 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.

[0059] 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 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 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).

[0060] 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.

[0061] A coating layer (PPL) may be additionally added to the surface of the above-described compound. The coating layer (PPL) may include, for example, an oxide, a hydroxide, an oxyhydroxide of the coating element, an oxycarbonate of the coating element, or a hydroxycarbonate of the coating element of the coating element. The coating layer (PPL) may be amorphous or crystalline. The coating element in the coating layer (PPL) 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 for forming the coating layer (PPL) may be selected within a range that does not adversely affect the physical properties of the positive electrode active material. The coating method may include, for example, spray coating or dipping.

[0062] 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 in the lithium transition metal composite oxide. The high-nickel cathode active material can realize high capacity and thus can be applied to high-capacity, high-density lithium metal batteries.

[0063]

[0064] Separator (SEP)

[0065] Depending on the type of lithium metal battery, a separator (SEP) may be provided between the positive electrode (PEL) and the negative electrode (NEL). The separator (SEP) may be a multilayer film made of polyethylene, polypropylene, polyvinylidene fluoride, or two or more layers thereof. Of course, a mixed multilayer film such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, or a polypropylene / polyethylene / polypropylene three-layer separator may also be used.

[0066] The separator (SEP) may include a porous substrate and a coating layer (PPL) comprising an organic material, an inorganic material, or a combination thereof, positioned on one or both sides of the porous substrate.

[0067] The above 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, Teflon, and polytetrafluoroethylene, or a copolymer or mixture of two or more thereof.

[0068] The organic material may include a polyvinylidene fluoride polymer or a (meth)acrylic polymer.

[0069] 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.

[0070] The organic and inorganic substances may be mixed and present in one coating layer (PPL) or may be present in a laminated form of a coating layer (PPL) containing an organic substance and a coating layer (PPL) containing an inorganic substance.

[0071]

[0072] Electrolyte layer (GPE)

[0073] The electrolyte layer (GPE) according to embodiments of the present invention may include a liquid electrolyte, a solid electrolyte, a gel electrolyte, or a combination thereof.

[0074] In one embodiment, the liquid electrolyte is an organic electrolyte. The organic electrolyte may include an organic solvent and a lithium salt. The organic solvent may be selected without limitation as long as it is used as an organic solvent in the art. 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.

[0075] Lithium salts can be selected without limitation as long as they are used as lithium salts in the relevant technical field. For example, lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, Li(FSO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(C x F 2x+1 SO2)(C y F 2y+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.

[0076] In one embodiment, the solid polymer electrolyte may include a mixture of a lithium salt and a polymer, or may include a polymer having an ion-conducting functional group. The solid polymer electrolyte may be solid at 25°C and 1 atm. The solid polymer electrolyte may not include a liquid.Polymers in the solid polymer electrolyte include, for example, polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyethylene oxide (PEO), poly(styrene-b-ethylene oxide) block copolymer (PS-PEO), poly(styrene-butadiene), poly(styrene-isoprene-styrene), poly(styrene-b-divinylbenzene) block copolymer, poly(styrene-ethylene oxide-styrene) block copolymer, polystyrene sulfonate (PSS), polyvinyl fluoride (PVF), polymethyl methacrylate (PMMA), poly(methylmethacrylate), polyethylene glycol (PEG), polyacrylonitrile (PAN), polytetrafluoroethylene (PTFE), polyethylenedioxythiophene (PEDOT), polypyrrole (PPY), polyacrylonitrile (PAN), Polyaniline, polyacetylene, Nafion, Aquivion, Flemion, Gore, Aciplex, Morgane ADP, sulfonated poly(ether ether ketone) (SPEEK), sulfonated poly(arylene ether ketone ketone sulfone) (SPAEKKS), sulfonated poly(aryl ether ketone) (SPAEK), poly[bis(benzimidazobenzisoquinolinones)] (SPBIBI), poly(styrene sulfonate) (PSS), lithium 9,10-Diphenylanthracene-2-sulfonate (lithium 9,10-diphenylanthracene-2-sulfonate, DPASLi. +) or a combination thereof. The polymer in the solid polymer electrolyte is not limited thereto and may be selected without limitation as long as it is used in a polymer electrolyte in the relevant technical field.

[0077] The lithium salt in the solid polymer electrolyte can be selected from among the lithium salts used in the liquid electrolyte described above. Lithium salts in solid polymer electrolytes include LiSCN, LiN(CN)2, Li(CF3SO2)3C, Li(FSO2)2N(LiFSI), LiC4F9SO3, LiN(SO2CF2CF3)2, LiPF3(C2F5)3, LiCl, LiF, LiBr, LiI, LiB(C2O4)2, LiPF6, LiPF5(CF3), LiPF5(C2F5), LiPF5(C3F7), LiPF4(CF3)2, LiPF4(CF3)(C2F5), LiPF3(CF3)3, LiPF3(CF2CF3)3, LiPF4(C2O4)2, LiBF4, LiBF3(C2F5), lithium bis(oxalato) borate (LiBOB), lithium oxalyldifluoroborate (LIODFB), It may include lithium difluoro(oxalato)borate (LiDFOB), lithium bis(trifluoro methanesulfonyl)imide (LiTFSI, LiN(SO2CF3)2), lithium bis(fluorosulfonyl)imide (LiFSI, LiN(SO2F)2), LiN(SO2C2F5)2, LiCF3SO3, LiAsF6, LiSbF6, LiClO4, or any combination thereof.

[0078] The polymer in the solid polymer electrolyte may contain 10 or more, 20 or more, 50 or more, or 100 or more repeating units. For example, the weight average molecular weight of the polymer in the solid polymer electrolyte may be 1000 Dalton or more, 10,000 Dalton or more, 100,000 Dalton or more, or 1,000,000 Dalton or more.

[0079] In one embodiment, the gel electrolyte may be a gel-polymer electrolyte. The gel-polymer electrolyte may have a gel state or a semi-solid state. The gel-polymer electrolyte may include a liquid electrolyte and a polymer, or may include an organic solvent and a polymer having an ion-conducting functional group. The gel-polymer electrolyte may be in a gel state or a semi-solid state at 25°C and 1 atm.

[0080] For example, a gel polymer electrolyte may have a gel state without containing a liquid. The liquid electrolyte used in the gel polymer electrolyte may be a mixture of a lithium salt and an organic solvent; a mixture of an ionic liquid and an organic solvent; or a mixture of an ionic liquid, a lithium salt, and an organic solvent.

[0081] A gel-polymer electrolyte according to one embodiment of the present invention may include a liquid electrolyte; a lithium salt; a crosslinked polymer, and an additive.

[0082] The polymer in the gel polymer electrolyte may be selected from among the polymers used in the above-described solid polymer electrolyte. The organic solvent in the gel polymer electrolyte may be selected from among the organic solvents used in the above-described liquid electrolyte. The lithium salt in the gel polymer electrolyte may be selected from among the lithium salts used in the above-described liquid electrolyte.

[0083] The ionic liquid in the gel polymer electrolyte may mean a salt or a molten salt in a liquid state at room temperature, which has a melting point below room temperature and is composed only of ions. The ionic liquid comprises a) at least one cation selected from the group consisting of ammonium-based, pyrrolidinium-based, pyridinium-based, pyrimidinium-based, imidazolium-based, piperidinium-based, pyrazolium-based, oxazolium-based, pyridazinium-based, phosphonium-based, sulfonium-based, and triazolium-based cations, and b) BF4. - , PF6 - , AsF6 - , SbF6 - , AlCl4 - , HSO4 - , ClO4 - , CH3SO3 - , CF3CO2 - , Cl - , Br - , I - , BF4 - , SO4 - , CF3SO3 - , (FSO2)2N - , (C2F5SO2)2N - , (C2F5SO2)(CF3SO2)N - , and (CF3SO2)2N - It may include at least one anion selected from the group consisting of .

[0084] The liquid electrolyte in the gel polymer electrolyte may include, but is not necessarily limited to, a carbonate system and at least one of ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and fluoroethylene carbonate (FEC).

[0085] In one embodiment, a gel-polymer electrolyte can be formed by impregnating a solid polymer electrolyte into a liquid electrolyte.

[0086] In one embodiment, the gel-polymer electrolyte may further comprise inorganic particles. The polymer within the gel-polymer electrolyte may comprise at least 10, at least 20, at least 50, or at least 100 repeating units. For example, the weight average molecular weight of the polymer within the gel-polymer electrolyte may be at least 500 Daltons, at least 1000 Daltons, at least 10,000 Daltons, at least 100,000 Daltons, or at least 1,000,000 Daltons.

[0087] In one embodiment of the present invention, the gel polymer electrolyte may include a polymer formed by polymerization of a multifunctional polymerizable monomer, i.e., a cross-linking agent. The cross-linking agent may be a material that is electrochemically stable in an operating environment (e.g., a voltage of about 4.3 V or higher) of a positive electrode using a positive electrode active material having a nickel content of 90 mol% or higher. For example, the crosslinking agent may include at least one selected from the group consisting of pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate (TMPTMA), propoxylated (3) trimethylolpropane triacrylate (PO(3)TMPTA), propoxylated (6) trimethylolpropane triacrylate (PO(6)TMPTA), ethoxylated trimethylolpropane triacrylate, di(trimethylolpropane) tetraacrylate (Di(trimethylolpropane) tetraacrylate), pentaerythritol triacrylate (PETA), propoxylated glyceryl triacrylate, tris(2-hydroxyethyl) isocyanurate triacrylate (THEICTA), and dipentaerythritol pentaacrylate (DPEPA).

[0088] The content of the crosslinked polymer in the gel polymer electrolyte may be 1 to 10 parts by weight, 2 to 8 parts by weight, or 3 to 7 parts by weight based on 100 parts by weight of the total weight of the gel polymer electrolyte. The content of the liquid electrolyte may be 90 to 99 parts by weight, 92 to 98 parts by weight, or 93 to 97 parts by weight based on 100 parts by weight of the total weight of the gel polymer electrolyte.

[0089] According to one embodiment of the present invention, the crosslinked polymer may further comprise a radical thermal initiator. The radical thermal initiator may play a role in causing in-situ polymerization between the crosslinked polymers.

[0090] In one embodiment, the radical thermal initiator may include at least one of tert-butylperoxy (t-BPP), azobisisobutyronitrile (AIBN), and benzoyl peroxide (BPO).

[0091] In one embodiment, the weight ratio of the radical thermal initiator to the total weight of the crosslinked polymer may be from 0.1 wt% to 10 wt%, and may be from 0.3 wt% to 10 wt%, but is not necessarily limited thereto.

[0092] In one embodiment of the present invention, the gel-polymer electrolyte may include an additive comprising a polymer having at least one functional group linked to a hydrocarbon backbone.

[0093] In one embodiment, the functional group may comprise an NC=O bond.

[0094] In one embodiment, the additive may have a weight average molecular weight of from 1,000 to 100,000, but is not necessarily limited to this range.

[0095] In one embodiment, the concentration of the additive within the gel polymer electrolyte may be, but is not necessarily limited to, 100 ppm to 10,000 ppm, 1,000 ppm to 5,000 ppm.

[0096] In one embodiment of the present invention, the additive in the gel-polymer electrolyte may include a polymer represented by the following chemical formula 1.

[0097] [Chemical Formula 1]

[0098]

[0099] In one embodiment, n can be an integer between 10 and 5000.

[0100] In one embodiment, L1 can be a direct linkage or an alkyl group having 1 to 10 carbon atoms.

[0101] In chemical formula 1, A may be a functional group represented by chemical formula 2 below.

[0102] [Chemical Formula 2]

[0103]

[0104] In chemical formula 2, any one of R1, R2, and R3 may be at a position connected to L1 of chemical formula 1.

[0105] In chemical formula 2, the remaining two of R1, R2 and R3 are each independently hydrogen, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 10 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 20 carbon atoms, or the remaining two of R1, R2 and R3 may combine with each other to form a ring having 2 to 6 carbon atoms.

[0106] In one embodiment of the present invention, the additive may include at least one polymer selected from the group consisting of polyvinylpyrrolidone (PVP), polyacrylamide (PAAm), and N-substituted polyacrylamide (N-substituted PAAm).

[0107] In one embodiment, the additive may have a weight average molecular weight of, but is not necessarily limited to, 1,000 to 100,000, or 2,000 to 50,000.

[0108] In one embodiment, the concentration of the additive relative to the gel-polymer electrolyte may be, but is not necessarily limited to, 100 ppm to 10,000 ppm, or 300 ppm to 5,000 ppm.

[0109] According to one embodiment of the present invention, the thermally crosslinked gel-polymer electrolyte before polymerization may be a composition in which a liquid electrolyte, a lithium salt, a crosslinking agent (PM) and an additive are mixed and exist in a liquid state.

[0110] The composition for forming a gel-polymer electrolyte can exist in a gel state after polymerization by heat treatment.

[0111] The crosslinking agent (PM) in the composition for forming a gel polymer electrolyte can be polymerized into a crosslinking polymer by a radical thermal initiator (RHS).

[0112] According to one embodiment of the present invention, the electrolyte layer (GPE) may include the gel polymer electrolyte described above. The separator (SEP) may be impregnated within the gel polymer electrolyte. The pores within the separator (SEP) may be filled with the gel polymer electrolyte.

[0113]

[0114] cathode (NEL)

[0115] Referring back to FIG. 1, the negative electrode (NEL) for a lithium metal battery may include a negative electrode current collector (COL1), and a polymer coating layer (PPL) on the negative electrode current collector (COL1).

[0116] Referring to FIG. 3, the negative electrode (NEL) according to the present embodiments may further include a negative electrode host layer (NHL) on the surface of the negative electrode current collector (COL1). The negative electrode host layer (NHL) may be interposed between the negative electrode current collector (COL1) and the polymer coating layer (PPL).

[0117] The negative electrode collector (COL1) may have a plate or foil shape.

[0118] In one embodiment, the negative electrode current collector (COL1) may include a base film and a metal layer on one or both sides of the base film.

[0119] The base film of the negative electrode current collector (COL1) may include at least one polymer selected from the group consisting of polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), and polyimide (PI). The base film may include an insulating and thermoplastic polymer. The base film of the negative electrode current collector (COL1) may soften or liquefy when a short circuit occurs, thereby blocking battery operation and suppressing a rapid increase in current. The negative electrode current collector (COL1) may additionally include a metal piece and / or a lead tab.

[0120]

[0121] Referring to FIGS. 1 and 2, the polymer coating layer (PPL) may include a polymer configured to suppress the formation of lithium dendrites. The polymer coating layer (PPL) may include a trifluoromethanesulfonimide (TFSI) series polymer. Specifically, the polymer coating layer (PPL) may include a polymer having at least one TFSI functional group bonded to a hydrocarbon backbone. Lithium ions may be bonded to the TFSI functional group.

[0122] The hydrocarbon backbone may have a linear polymer form, a branched polymer form, a network polymer form, or a ladder polymer form. The polymer of the polymer coating layer (PPL) may be a homopolymer, a copolymer, or a combination thereof, and is not particularly limited.

[0123] For example, the polymer coating layer (PPL) may include PMTFSI (Poly(methacrylate TSFI)), PSTFSI (Poly(4-styrenesulfonyl TSFI)), or a combination thereof. The polymer of the polymer coating layer (PPL) may have a weight average molecular weight of 1,000 to 1,000,000.

[0124] In one embodiment of the present invention, the polymer coating layer (PPL) may further include an oxidizing agent. The oxidizing agent may be uniformly dispersed within the polymer of the polymer coating layer (PPL). The oxidizing agent may include a nitrate. The oxidizing agent may include an alkali metal nitrate or an alkaline earth metal nitrate. For example, the oxidizing agent may include at least one selected from the group consisting of LiNO3, KNO3, and Fe(NO3)2.

[0125] In one embodiment, the oxidizing agent may be present in a dissolved form within the polymer coating layer (PPL). In another embodiment, the oxidizing agent may be present in an insoluble form within the polymer coating layer (PPL), for example, in the form of particles.

[0126] Nitrate (NO3) as an oxidizing agent - ) can improve the electrodeposition shape of lithium on the negative electrode current collector (COL1). Nitrate (NO3) of the oxidizing agent - ) can prevent the formation of lithium dendrites.

[0127]

[0128] Referring to FIG. 2, FIG. 2 is a schematic diagram illustrating a lithium metal battery after an initial cycle according to embodiments of the present invention. After charging, lithium is deposited between the polymer coating layer (PPL) and the negative electrode current collector (COL1).

[0129] Referring to FIG. 2, the lithium metal battery of FIG. 1 may form a lithium electrodeposited layer (NAL) after the initial cycle of operation. The negative electrode (NEL) of the lithium metal battery after the initial cycle may further include a lithium electrodeposited layer (NAL). The lithium electrodeposited layer (NAL) may be interposed between the polymer coating layer (PPL) and the current collector (COL1).

[0130] The lithium electrodeposited layer (NAL) can be formed by plating lithium metal between the polymer coating layer (PPL) and the negative electrode current collector (COL1) by charging the lithium metal battery. The lithium electrodeposited layer (NAL) can include lithium metal or a lithium alloy. The lithium alloy can be an alloy of lithium and another metal that can be alloyed with lithium. For example, the lithium alloy can include a lithium-silver alloy, a lithium-zinc alloy, a lithium-magnesium alloy, or a lithium-tin alloy.

[0131] The thickness of the lithium electrodeposited layer (NAL) can be, for example, 50 μm or less, 40 μm or less, 35 μm or less, 30 μm or less, 1 μm to 50 μm, 1 μm to 40 μm, 5 μm to 40 μm, 1 μm to 35 μm, or 10 μm to 35 μm. The energy density of the lithium metal battery can be improved by the lithium electrodeposited layer (NAL) having a thickness in the above-described range.

[0132] In one embodiment, the thickness of the lithium electrodeposited layer (NAL) at maximum charge may be 35 μm or less, 30 μm or less, 28 μm or less, 10 μm to 35 μm, 10 μm to 30 μm, or 10 μm to 28 μm.

[0133] Fig. 3 is a cross-sectional view illustrating a negative electrode according to another embodiment of the present invention. Fig. 3 is an enlarged cross-sectional view of a cross-section of a negative electrode region including a negative electrode host layer (NHL). Referring to Fig. 3, in one embodiment of the present invention, a negative electrode host layer (NHL) may be positioned on a negative electrode current collector (COL1). The negative electrode host layer (NHL) may include a 3D host layer, which will be described later. The negative electrode host layer (NHL) induces uniform lithium deposition and de-deposition during lithium deposition and de-deposition, thereby improving reversibility and life characteristics of the battery. When the battery is discharged, lithium can be de-deposited along the negative electrode host layer (NHL).

[0134] The term “host” used in the present invention refers to a function that can prevent problems such as internal short circuit, discharge, volume expansion of the lithium negative electrode, electrolyte shortage, and acceleration of side reactions by suppressing the growth of lithium dendrites occurring in the lithium negative electrode.

[0135] In one embodiment, the negative host layer (NHL) can be strong enough to maintain its shape without being damaged by the growth of lithium dendrites.

[0136] According to one embodiment, the negative electrode host layer (NHL) can have an appropriate thickness and porosity to prevent volume expansion of the lithium negative electrode due to lithium dendrite growth and to prevent a decrease in energy density of the battery.

[0137] The negative host layer (NHL) may include a negative current collector (COL1) or carbon (C) on the negative current collector (COL1) formed in a 3D structure. The negative host layer (NHL) may be formed in a 3D host-to-host orthogonal shape, may have holes formed in the middle, may be formed in a mesh-like structure, but is not necessarily limited thereto.

[0138] In one embodiment, the thickness of the negative host layer (NHL) may be thicker than the thickness of the lithium electrodeposition layer (NAL) described above. The thickness of the negative host layer (NHL) may be, for example, 60 μm or less, 50 μm or less, 45 μm or less, 40 μm or less, 1 μm to 60 μm, 1 μm to 50 μm, 5 μm to 50 μm, 1 μm to 45 μm, or 10 μm to 45 μm. When the negative host layer (NHL) has a thickness in the above-described range, the energy density of the lithium metal battery may be improved.

[0139] FIG. 4A is an enlarged cross-sectional view of portion M of FIG. 3 before charging. Referring to FIG. 4A, the negative host layer (NHL) may be composed of a plurality of first frames (3DH1), a plurality of second frames (3DH2), and a plurality of pores (HL). In one embodiment, the first and second frames (3DH1, 3DH2) may include the same material as the negative current collector (COL1). In another embodiment, the first and second frames (3DH1, 3DH2) may include a different material from the negative current collector (COL1).

[0140] According to one embodiment, the first and second frames (3DH1, 3DH2) may comprise copper or carbon.

[0141] In one embodiment, the plurality of frames may have lithium affinity and mechanical stability. Furthermore, the plurality of frames may minimize energy loss and maximize the specific surface area of ​​the battery.

[0142] The first frame (3DH1) may be parallel to the Y-axis and may be composed of a plurality of first frames (3DH1). The height of the first frame (3DH1) may be equal to or smaller than the height of the negative host layer (NHL). The height of the first frame (3DH1) refers to the length of the portion parallel to the Y-axis. The height of the first frame (3DH1) may be greater than the thickness of the lithium electrodeposition layer (NAL) described above. The height of the first frame (3DH1) may be, for example, 60 ㎛ or less, 50 ㎛ or less, 45 ㎛ or less, 40 ㎛ or less, 1 ㎛ to 60 ㎛, 1 ㎛ to 50 ㎛, 5 ㎛ to 50 ㎛, 1 ㎛ to 45 ㎛, or 10 ㎛ to 45 ㎛.

[0143] The thickness of the first frame (3DH1) refers to the length of the portion parallel to the X-axis. The thickness of the first frame (3DH1) may be, for example, 1 nm to 50 nm, 5 nm to 30 nm, 10 nm to 30 nm, or 20 nm to 30 nm.

[0144] The structure of the first frame (3DH1) may be formed in a orthogonal shape between the Cu current collector or the carbon layer on the Cu, may have holes in the middle, and may be formed in a structure that is entangled like a net, but is not necessarily limited thereto.

[0145] The second frame (3DH2) may be parallel to the X-axis and may be composed of multiple frames. The horizontal length of the second frame (3DH2) may be equal to or smaller than the horizontal length of the cathode host layer (NHL). The height of the second frame (3DH2) may be equal to the thickness of the first frame (3DH1). The height of the second frame (3DH2) refers to the length of the portion parallel to the Y-axis. The height of the second frame (3DH2) may be, for example, 1 nm to 50 nm, 5 nm to 30 nm, 10 nm to 30 nm, or 20 nm to 30 nm.

[0146] The structure of the second frame (3DH2) can be formed in a orthogonal shape between the Cu current collector or the carbon layer on the Cu, can be formed in a shape with holes in the middle, can be formed in a structure that is entangled like a net, but is not necessarily limited thereto.

[0147] The void (HL) refers to the space other than the space occupied by the first frame (3DH1) and the second frame (3DH2). The void (HL) is an empty space before the initial cycle, but can be filled with lithium metal (LM) after the initial cycle.

[0148] According to one embodiment, the size of the pore (HL) may be, but is not necessarily limited to, 10 nm to 10 um or 20 nm to 90 nm. In this case, the size of the pore (HL) means the length of the longest axis of the pore (HL).

[0149] In one embodiment, the porosity of the negative electrode host layer (NHL) may be 70% to 90% or 80% to 85%. The porosity refers to the ratio of the volume of pores to the total volume, and in the case of the embodiment of the present invention, it refers to the ratio of the volume of pores (HL) to the volume value obtained by multiplying the area of ​​the negative electrode current collector (COL1) by the height of the negative electrode host layer (NHL).

[0150]

[0151] Fig. 4b is an enlarged cross-sectional view of part M of Fig. 3 after charging. Referring to Fig. 4b, lithium metal (LM) can be located in the pore (HL) after the initial cycle. Referring to Fig. 4b, the appearance of a lithium electrodeposited layer (NAL) in which lithium is electrodeposited between negative host layers (NHL) can be confirmed. The negative host layer (NHL) has a 3D structure such as a Cu current collector or a carbon layer on Cu, so that lithium metal (LM) can be electrodeposited within the 3D host. The negative host layer (NHL) can suppress volume changes due to lithium dendrites and lithium electrodeposition / desorption during charge / discharge.

[0152] According to one embodiment, even if deposition and desorption of lithium metal (LM) occur during charge and discharge, no structural change occurs in the negative electrode host layer (NHL).

[0153] In one embodiment, during charging and discharging, lithium metal (LM) can be randomly located in multiple pores (HL).

[0154] Figure 5 is an enlarged view showing the appearance of a gel polymer electrolyte (PEL) after thermal crosslinking. Referring to Figure 5, an electrolyte-forming composition comprising a liquid electrolyte, a crosslinking polymer (PM), an additive (CLA), and a radical thermal initiator (RHS) can be synthesized into a gel polymer (GP) after a thermal crosslinking process.

[0155] Figure 6 is an enlarged view showing the appearance of a gel polymer electrolyte before thermal crosslinking according to embodiments of the present invention. Referring to Figure 6, the radical thermal initiator (RHS) may be positioned at the edge of the polymer monomer (crosslinking agent (PM)), but is not necessarily limited thereto.

[0156] Referring to Figures 5 and 6, radical polymerization is a type of polymerization in which unsaturated monomer molecules are continuously added to terminal free radical reactive sites, called active centers, and the polymerization proceeds in a growth manner. The growing chain radicals can attack the π bonds of monomer molecules, causing the bonds to break symmetrically. As each monomer is added, the active center can be moved to the newly formed chain end.

[0157] Radical polymerization using comonomers containing one or more C=C bonds can produce branched polymer chains rather than simple chain polymers. Monomers containing one or more C=C double bonds in their molecule are called crosslinking monomers. Copolymerization with these monomers can produce branched or network polymers. Junctions within the synthesized nonlinear polymer can be formed by linkages between the C=C double bonds within the crosslinking monomers. The degree of crosslinking depends on the mole fraction of the crosslinked polymer, the difference in reactivity of the C=C bonds present in the monomers used, and the overall conversion. Crosslinked polymers are usually difficult to process, so they are produced directly in an easy-to-use form, and thus, a polymerization process that does not use solvents is used.

[0158] In one embodiment, the crosslinked polymer may be composed of a single molecule or polymer having two or more double bonds. The crosslinked polymer may have a weight average molecular weight of 5,000 to 20,000, 10,000 to 20,000, and 10,000 to 15,000. In addition, the weight ratio of the crosslinked polymer to the total weight of the gel polymer electrolyte may be in the range of 1 wt% to 10 wt%, 3 wt% to 10 wt%, and 5 wt% to 10 wt%.

[0159]

[0160] lithium metal battery

[0161] Referring to FIG. 7, a lithium battery (LBT) according to an 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 accommodated in a battery case (CAS). An electrolyte layer may be formed by injecting an electrolyte into the battery case (CAS). 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, square, thin-film, etc.

[0162] Referring to FIG. 8, 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 the separator (SEP). The 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).

[0163] The formed battery structure (BTS) can be accommodated in a battery case (CAS). An electrode tab (ELT) that serves as an electrical path for conducting the current formed in the battery structure (BTS) to the outside can be included. 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) is not necessarily limited to a square shape, but may be, for example, cylindrical, thin-film, etc.

[0164] Referring to FIG. 9, 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 separator (SEP) may be disposed between the positive electrode (PEL) and the negative electrode (NEL) to form a battery structure (BTS).

[0165] A battery structure (BTS) can be stacked in a bi-cell structure and then accommodated in a battery case (CAS). An electrode tab (ELT) that serves as an electrical path for conducting current formed in the battery structure (BTS) to the outside can be included. 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) is not necessarily limited to a square shape, and may be, for example, cylindrical, thin-film, etc.

[0166] A pouch-type lithium battery may correspond to a lithium battery (LBT) of each of FIGS. 7 to 9 that uses a pouch as a battery case (CAS). The pouch-type lithium battery may include at least one battery structure (BTS). The battery structure (BTS) may be laminated in a bi-cell structure, then impregnated with an electrolyte layer, and accommodated and sealed in a pouch to manufacture a pouch-type lithium battery.

[0167] For example, the above-described positive electrode, negative electrode, and separator may be simply laminated and housed in a pouch in the form of an electrode assembly. The electrode assembly may be wound or folded into a jelly roll shape and then housed in the pouch. An electrolyte layer may be formed by injecting an electrolyte solution into the pouch.

[0168] Lithium batteries have excellent cycle life and high-rate characteristics, making them suitable for use in electric vehicles (EVs). For example, they can be used in plug-in hybrid electric vehicles (PHEVs). They can also be used in applications requiring large amounts of power storage, such as electric bicycles and power tools.

[0169] Multiple lithium batteries can be stacked to form a battery module. Multiple battery modules can form a battery pack. Such a battery pack can be used in any device requiring high capacity and output. Examples include laptops, smartphones, and electric vehicles. For example, a battery module may include multiple batteries and a frame supporting them.

[0170] 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. The 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.

[0171]

[0172] A lithium battery including a solid electrolyte is described in more detail below. A lithium metal battery according to one embodiment of the present invention may be, for example, an all-solid-state lithium battery including a solid electrolyte. By including the aforementioned negative electrode, the all-solid-state lithium battery can have improved capacity and superior lifespan characteristics.

[0173]

[0174] Hereinafter, the present invention will be described in more detail through examples. However, these examples are intended to exemplify the present invention and the scope of the present invention is not limited to these examples.

[0175]

[0176] Example 1

[0177] Diethyl carbonate (DEC) and fluoroethyl carbonate (FEC) are mixed in a 1:1 weight ratio. LiPF6 is dissolved in this solution to a concentration of 1 M to prepare a basic liquid electrolyte. Dipentaerythritol hexaacrylate (DPHA) is dissolved in 4 wt% of the basic liquid electrolyte, and t-butylperoxy pivalate (t-BPP) is added in an amount of 3 wt% relative to DPHA to prepare a precursor electrolyte.

[0178] The final electrolyte is prepared by adding 1000 ppm of polyvinylpyrrolidone (PVP) as an additive to the precursor electrolyte. The molecular weight of the additive (PVP) is 2500.

[0179]

[0180] Example 2

[0181] The final electrolyte is prepared by adding 300 ppm of polyvinylpyrrolidone (PVP) as an additive. The molecular weight of the additive (PVP) is 2500.

[0182]

[0183] Example 3

[0184] The final electrolyte is prepared by adding 5000 ppm of polyvinylpyrrolidone (PVP) as an additive. At this time, the molecular weight of the additive (PVP) is 2500.

[0185]

[0186] Example 4

[0187] The final electrolyte is prepared by adding 300 ppm of polyvinylpyrrolidone (PVP) as an additive. At this time, the molecular weight of the additive (PVP) is 10,000.

[0188]

[0189] Example 5

[0190] The final electrolyte is prepared by adding 300 ppm of polyvinylpyrrolidone (PVP) as an additive. At this time, the molecular weight of the additive (PVP) is 50,000.

[0191]

[0192] Example 6

[0193] The final electrolyte is prepared by adding 300 ppm of polyacrylamide (PAAM) as an additive. At this time, the molecular weight of the additive (PAAM) is 5000.

[0194]

[0195] Example 7

[0196] A precursor electrolyte is prepared by dissolving 4 wt% of trimethylolpropane trimethacrylate (TMPTMA) in a basic liquid electrolyte and adding 3 wt% of t-butylperoxy pivalate (t-BPP) relative to DPHA. Then, 300 ppm of polyvinylpyrrolidone is added as an additive to prepare a final electrolyte. The molecular weight of the additive is 2500.

[0197]

[0198] Example 8

[0199] The final electrolyte is prepared by adding 600 ppm of polyvinylpyrrolidone (PVP) as an additive. The molecular weight of the additive (PVP) is 2500.

[0200]

[0201] Comparative Example 1

[0202] No additives were mixed into the precursor electrolyte.

[0203]

[0204] Comparative Example 2

[0205] 15,000 ppm of polyvinylpyrrolidone (PVP) was mixed as an additive into the precursor electrolyte. At this time, the molecular weight of the additive (PVP) was 2500.

[0206]

[0207] Comparative Example 3

[0208] 30,000 ppm of polyvinylpyrrolidone (PVP) was mixed as an additive into the precursor electrolyte. At this time, the molecular weight of the additive (PVP) was 2500.

[0209]

[0210] Comparative Example 4

[0211] 300 ppm of polyvinylpyrrolidone (PVP) was mixed as an additive into the precursor electrolyte. At this time, the molecular weight of the additive (PVP) was 120,000.

[0212]

[0213] Comparative Example 5

[0214] 300 ppm of polyvinylpyrrolidone (PVP) was mixed as an additive into the precursor electrolyte. At this time, the molecular weight of the additive (PVP) was 150,000.

[0215]

[0216] Production Example 1: Manufacturing of a Lithium Metal Battery

[0217] (Polar electrode manufacturing)

[0218] Li 1.04 Ni 0.8 Co 0.1 Al 0.1O2 A positive electrode active material slurry was prepared by uniformly mixing the powder and carbon conductive material (Super-P; Timcal Ltd.) at a weight ratio of 90:5, and then adding a PVDF (polyvinylidene fluoride) binder solution to obtain a weight ratio of active material:carbon conductive material:binder = 90:5:5.

[0219] The prepared slurry was coated on a 15 ㎛ thick aluminum substrate using a doctor blade. The coating layer was dried under reduced pressure at 120°C and then rolled using a roll press to produce a positive electrode in the form of a sheet.

[0220]

[0221] (Manufacturing of pouch cells)

[0222] A pouch cell was fabricated using the positive electrode, copper foil, and polyolefin separator manufactured in the above-mentioned Fabrication Example 1, and the electrolyte was injected and sealed to fabricate a pouch cell. The fabricated pouch cell was heat-treated at 70°C for 2 hours to induce a cross-linking reaction between dipentaerythritol hexaacrylate (DPHA), thereby obtaining a pouch cell containing a gel polymer electrolyte.

[0223]

[0224] Evaluation Example 1: Lifetime characteristics of lithium metal batteries

[0225] The lithium metal batteries manufactured in Examples 1 to 8 and Comparative Examples 1 to 5 were charged at 45°C at a current rate of 0.1 C for 10 hours. Subsequently, they were discharged at a constant current rate of 0.1 C for 10 hours (1 st cycle, Mars phase).

[0226] The lithium metal batteries manufactured in Examples 1 to 8 and Comparative Examples 1 to 5 were charged at 45°C at a current rate of 0.2 C for 5 hours. Subsequently, they were discharged at a constant current rate of 0.2 C for 5 hours (2 nd Cycle, RPT stage (Reference performance test)).

[0227] The lithium metal batteries manufactured in Examples 1 to 8 and Comparative Examples 1 to 5 were charged at 45°C for 10 hours at a current of 0.33 C rate. Subsequently, they were discharged for 1 hour at a constant current of 0.1 C rate (3 nd cycle, life assessment phase).

[0228] For the above life evaluation step, it was repeated up to 300 cycles under the above conditions.

[0229] The initial charge / discharge efficiency (ICE) and rate characteristics of the lithium metal batteries manufactured in Examples 1 to 8 and Comparative Examples 1 to 5 are shown in Table 1.

[0230] Additionally, the capacity retention rate (CRR) after 100, 200, and 300 cycles was measured and shown in Fig. 10. Here, the capacity retention rate is defined by the following mathematical equation 1:

[0231] <Mathematical Formula 1>

[0232] Capacity retention rate [%] = [Discharge capacity in each cycle / Discharge capacity in the 1st cycle] × 100

[0233] Also, the initial charge-discharge efficiency here is defined by the following mathematical equation 2:

[0234] <Mathematical Formula 2>

[0235] Initial charge / discharge efficiency [%] = [Initial charged capacity / Capacity after discharge] × 100

[0236]

[0237] AdditiveAdditive content (ppm)Additive molecular weightLife (@ 80%)Initial efficiency (%)Rate characteristics (1C / 0.2C)Example 1PVP1000250019281.592.5Example 2PVP300250019081.692.3Example 3PVP5000250018982.091.8Example 4PVP3001000017781.191.6Example 5PVP3005000016180.691.1Example 6PAAM300500017881.292.0Example 7PVP600250019081.392.5Comparative Example 1-0-15578.390.2Comparative Example 2PVP1500025008372.190.2Comparison Example 3PVP3000025006767.778.4Comparison Example 4PVP3001200009278.784.6Comparison Example 5PVP3001500007974.881.5

[0238] As shown in FIG. 10 and Table 1, the lithium batteries of Examples 1 and 2 had improved life characteristics compared to the lithium batteries of Comparative Examples 1, 4, and 5.

[0239] These improved life characteristics of the lithium batteries of Examples 1 and 2 were determined to be due to the suppression of side reactions on the negative electrode surface and the suppression of local current density imbalance by uniformly depositing lithium through a small amount of additive including polyvinylpyrrolidone (PVP).

[0240] In the case of Comparative Example 1, it was determined that the reason was that lithium deposition was not uniform due to the absence of an additive containing polyvinylpyrrolidone (PVP), and thus the imbalance in current density was not effectively suppressed.

[0241] In addition, in the case of Comparative Examples 4 and 5, although additives were included, it was determined that the molecular weight of the polymer additive was greater than a certain level, which reduced the ionic conductivity of the electrolyte and increased the resistance, thereby lowering the battery performance.

[0242] In addition, in the case of Comparative Examples 2 and 3, although additives were included, the additive content was very high, exceeding 10,000 ppm, which reduced the ionic conductivity of the electrolyte and increased the resistance, thereby lowering the battery performance. Referring to Table 1, it can be confirmed that the higher the additive content in the range exceeding 10,000 ppm, the lower the initial efficiency and rate characteristics of the lithium battery.

[0243] Referring to Fig. 10, the capacity retention rates after 100 to 300 cycles of Comparative Example 1, Example 2, Example 8, and Example 1 were measured, respectively, as indicated by #1 to #4. It can be confirmed that the capacity retention rate of Comparative Example 1 (#1) was measured to be the lowest after 200 to 300 cycles. This is because in the case of Comparative Example 1, since there was no additive including polyvinylpyrrolidone (PVP), lithium deposition was not uniform and a side reaction occurred between lithium and the electrolyte, failing to effectively suppress the formation of lithium dendrites.

[0244] Next, looking at Examples 2 (#2) and 8 (#3), where the capacity retention rate was measured to be low, it can be confirmed that the capacity retention rate was measured to be low because the concentration of the additive was relatively low. As in Example 1 (#4) according to the present invention, it was confirmed that the capacity retention rate was relatively the best when the concentration of the additive was 1000 ppm.

[0245]

[0246] Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications can be made within the scope of the claims, the detailed description of the invention, and the attached drawings, and it is obvious that this also falls within the scope of the present invention.

Claims

1. Liquid electrolyte; lithium salt; crosslinked polymers; and An additive comprising a polymer having at least one functional group linked to a hydrocarbon backbone, The above functional group includes an NC=O bond, The above additive has a weight average molecular weight of 1,000 to 100,000, A gel polymer electrolyte having a concentration of the additive of 100 ppm to 10,000 ppm.

2. In paragraph 1, The above additive comprises a polymer represented by the following chemical formula 1, [Chemical Formula 1] In the above chemical formula 1, n is an integer between 10 and 5,000, L1 is a direct linkage or an alkyl group having 1 to 10 carbon atoms, A is a functional group represented by the following chemical formula 2, [Chemical Formula 2] In the above chemical formula 2, one of R1, R2 and R3 is at a position connected to L1 of the above chemical formula 1, The remaining two of R1, R2 and R3 are each independently hydrogen, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 10 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 20 carbon atoms, or the remaining two of R1, R2 and R3 combine with each other to form a ring having 2 to 6 carbon atoms.

3. In paragraph 1, A gel polymer electrolyte, wherein the additive comprises at least one polymer selected from the group consisting of polypyrrolidone (PVP), polyacrylamide (PAAm), and N-substituted polyacrylamide (N-substituted PAAm).

4. In paragraph 1, The above additive is a gel polymer electrolyte having a weight average molecular weight of 1,000 to 100,000.

5. In paragraph 1, The above liquid electrolyte is a gel polymer electrolyte comprising at least one of a carbonate system and ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and fluoroethylene carbonate (FEC).

6. In paragraph 1, The above lithium salts are LiSCN, LiN(CN)2, Li(CF3SO2)3C, Li(FSO2)2N(LiFSI), LiC4F9SO3, LiN(SO2CF2CF3)2, LiPF3(C2F5)3, LiCl, LiF, LiBr, LiI, LiB(C2O4)2, LiPF6, LiPF5(CF3), LiPF5(C2F5), LiPF5(C3F7), LiPF4(CF3)2, LiPF4(CF3)(C2F5), LiPF3(CF3)3, LiPF3(CF2CF3)3, LiPF4(C2O4)2, LiBF4, LiBF3(C2F5), lithium bis(oxalato) borate (LiBOB), lithium oxalyldifluoroborate (LIODFB), lithium A gel polymer electrolyte comprising lithiumdifluoro(oxalato)borate (LiDFOB), lithium bis(trifluoro methanesulfonyl)imide (LiTFSI, LiN(SO2CF3)2), lithium bis(fluorosulfonyl)imide (LiFSI, LiN(SO2F)2), LiN(SO2C2F5)2, LiCF3SO3, LiAsF6, LiSbF6, LiClO4, or any combination thereof.

7. In paragraph 1, The above cross-linked polymer is a gel polymer electrolyte composed of a single molecule or polymer having two or more double bonds.

8. In paragraph 1, The crosslinked polymer is a gel polymer selected from at least one of pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate (TMPTMA), propoxylated (3) trimethylolpropane triacrylate (PO(3)TMPTA), propoxylated (6) trimethylolpropane triacrylate (PO(6)TMPTA), ethoxylated trimethylolpropane triacrylate, di(trimethylolpropane)tetraacrylate, pentaerythritol triacrylate (PETA), propoxylated glyceryl triacrylate, tris(2-hydroxyethyl) isocyanurate triacrylate (THEICTA), and dipentaerythritol pentaacrylate (DPEPA). Electrolyte.

9. In paragraph 1, A gel polymer electrolyte wherein the weight ratio of the crosslinked polymer to the total weight of the gel polymer electrolyte is 1 wt% to 10 wt%.

10. In paragraph 1, A gel polymer electrolyte having a concentration of the above additive of 100 ppm to 10,000 ppm.

11. In paragraph 1, The above crosslinked polymer further comprises a radical thermal initiator that causes in-situ polymerization, A gel polymer electrolyte, wherein the radical thermal initiator comprises at least one of tert-butylperoxy (t-BPP), azobisisobutyronitrile (AIBN), and benzoyl peroxide (BPO).

12. In paragraph 11, A gel polymer electrolyte wherein the weight ratio of the radical thermal initiator to the total weight of the crosslinked polymer is 0.1 wt% to 10 wt%.

13. Cathode; Bipolar; and A lithium metal battery comprising a gel polymer electrolyte according to claim 1 between the negative electrode and the positive electrode.

14. In paragraph 13, The above negative electrode includes a negative electrode active material, and the negative electrode active material includes a carbon-based material; a mixture of a carbon-based material and at least one selected from a metal or a metalloid; a composite of a carbon-based material and at least one selected from a metal or a metalloid; or a combination thereof. A lithium metal battery further comprising a separator on the negative electrode and the gel polymer electrolyte.

15. In paragraph 14, The above separator comprises a porous substrate, A lithium metal battery, wherein the porous substrate comprises at least one of polypropylene and polyethylene.

16. In paragraph 13, A lithium metal battery, wherein the negative electrode further comprises a lithium electrodeposition layer.

17. Forming a composition for forming a gel polymer electrolyte by mixing a liquid electrolyte, a lithium salt, a crosslinking agent, and the additive of claim 1; Injecting the composition for forming the gel polymer electrolyte between the positive and negative electrodes; and A method for manufacturing a lithium metal battery, comprising crosslinking the composition for forming the gel polymer electrolyte to form a gel polymer electrolyte.

18. In paragraph 17, A method for manufacturing a lithium metal battery, wherein the additive comprises the additive of claim 2.

19. In paragraph 17, A method for manufacturing a lithium metal battery, wherein the above cross-linking is performed by heat treatment at 40°C to 120°C.

20. In paragraph 17, A method for manufacturing a lithium metal battery, wherein the weight ratio of the crosslinked polymer to the total weight of the gel polymer electrolyte is 1 wt% to 10 wt%.

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