Lithium metal battery and manufacturing method therefor

Abstract

The present invention relates to a lithium metal battery and a manufacturing method therefor, and more specifically, comprises: a negative electrode current collector; a positive electrode; an electrolyte layer between the negative electrode current collector and the positive electrode, the electrolyte layer comprising a first electrolyte layer adjacent to the negative electrode current collector, and a second electrolyte layer adjacent to the positive electrode; and a composite separation layer impregnated in the first electrolyte layer. The first electrolyte layer comprises a first gel-polymer electrolyte, the second electrolyte layer comprises a second gel-polymer electrolyte, the weight ratio of a polymer in the first gel-polymer electrolyte and the weight ratio of a polymer in the second gel-polymer electrolyte are different from each other, and the composite separation layer comprises a separator, and an expansion buffer layer on at least one surface of the separator.

Description

Lithium metal battery and method for manufacturing the same

[0001] The present invention relates to a lithium metal battery and a method for manufacturing the same, and more particularly, to a lithium metal battery including a composite separator layer and a method for manufacturing 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 and discharge, contributing to the stability of lithium batteries. However, their low capacity necessitates the use of higher-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 lithium metal battery capable of suppressing lithium dendrites and alleviating volume change.

[0007] Another problem to be solved by the present invention is to provide a method for manufacturing a lithium metal battery capable of suppressing lithium dendrites and alleviating volume changes.

[0008]

[0009] According to the concept of the present invention, a lithium metal battery comprises: an anode current collector; an anode; an electrolyte layer between the anode current collector and the anode, the electrolyte layer comprising a first electrolyte layer adjacent to the anode current collector and a second electrolyte layer adjacent to the anode; and a composite separator layer impregnated within the first electrolyte layer. The first electrolyte layer comprises a first gel-polymer electrolyte, the second electrolyte layer comprises a second gel-polymer electrolyte, and a weight ratio of a polymer within the first gel-polymer electrolyte is different from a weight ratio of a polymer within the second gel-polymer electrolyte, and the composite separator layer comprises a separator and an expansion relief layer on at least one surface of the separator.

[0010] According to another concept of the present invention, a lithium metal battery may include: an anode current collector; a lithium electrodeposition layer on the anode current collector; an electrolyte layer on the lithium electrodeposition layer; a composite separating layer impregnated in the electrolyte layer; and a cathode on the electrolyte layer. The composite separating layer may include a separator and an expansion relief layer on at least one surface of the separator, and a thickness of the expansion relief layer may be configured to change in response to a change in the thickness of the lithium electrodeposition layer.

[0011] According to another concept of the present invention, a method for manufacturing a lithium metal battery may include: preparing a composite separator by forming an expansion relief layer on at least one side of a separator; providing a composite separator on a negative electrode current collector; providing a first electrolyte solution on the composite separator; thermally crosslinking the first electrolyte solution to form a first electrolyte layer, the composite separator being impregnated into the first electrolyte layer; and providing a positive electrode on the first electrolyte layer. Forming the expansion relief layer may include electrospinning a polymer solution onto the separator, and a thickness of the expansion relief layer may be formed to be greater than a thickness of the separator.

[0012]

[0013] The lithium metal battery according to the present invention can effectively accommodate changes in the thickness of the lithium electrodeposition layer by using a composite separator layer including an expansion-relieving layer. Despite changes in the thickness of the lithium electrodeposition layer, the battery according to the present invention can maintain a stable interface between the electrolyte layer and the negative electrode. As a result, the present invention can suppress the formation of lithium dendrites and improve the battery's lifespan characteristics.

[0014]

[0015] FIG. 1 is a schematic diagram illustrating a lithium metal battery according to embodiments of the present invention.

[0016] Figures 2 and 3 are each an enlarged cross-sectional view of area M of Figure 1.

[0017] FIG. 4 and FIG. 5 are schematic diagrams illustrating a lithium metal battery according to another embodiment of the present invention.

[0018] Figure 6 is a conceptual diagram schematically illustrating a cross-linked polymer structure according to embodiments of the present invention.

[0019] Figures 7 to 9 are schematic diagrams illustrating a lithium battery according to one embodiment of the present invention.

[0020] FIGS. 10A to 10G are cross-sectional views illustrating a method for manufacturing a lithium metal battery according to embodiments of the present invention.

[0021]

[0022] 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.

[0023] 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.

[0024] 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.

[0025] As used herein, “combination thereof” may mean mixtures, laminates, composites, copolymers, alloys, blends, and reaction products of the components.

[0026] In this specification, “metal” may include both metals and metalloids such as silicon and germanium, in either the elemental or ionic state.

[0027] In this specification, “alloy” may mean a mixture of two or more metals.

[0028] In this specification, “positive electrode active material” may mean a positive electrode material capable of undergoing lithiation and delithiation.

[0029] In this specification, “negative electrode active material” may mean a negative electrode material capable of undergoing lithiation and delithiation.

[0030] 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.

[0031] 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.

[0032] In this specification, “charging” and “charging” may refer to a process of providing electrochemical energy to a battery.

[0033] In this specification, “discharging” and “discharging” may refer to the process of removing electrochemical energy from a battery.

[0034] In this specification, “positive electrode” may mean an electrode where electrochemical reduction and lithiation occur during a discharge process.

[0035] In this specification, “negative electrode” may mean an electrode where electrochemical oxidation and delithiation occur during a discharge process.

[0036]

[0037] FIG. 1 is a schematic conceptual diagram 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] Lithium metal batteries can use lithium metal as an anode active material. During the charge and discharge process of a lithium metal battery, a lithium-containing metal layer can be precipitated and dissolved. The lithium-containing metal layer can be formed on the upper surface of the anode current collector (COL1) and within the anode host layer (NHL) described below. As the charge and discharge of the lithium metal battery is repeated, the lithium-containing metal layer can contain impurities remaining within the electrode, electrolyte decomposition products, and the like.

[0039] 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.

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

[0041] 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).

[0042]

[0043] cathode (NEL)

[0044] Referring to FIG. 1, a negative electrode (NEL) for a lithium metal battery may include a negative electrode collector (COL1). The negative electrode collector (COL1) may provide a reference surface on which a lithium electrodeposition layer (NAL), which will be described later, is formed. The negative electrode collector (COL1) may include, for example, a material that does not react with lithium, i.e., does not form an alloy or compound with lithium. For example, the negative electrode collector (COL1) may include at least one metal selected from the group consisting of copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni). The thickness of the negative electrode collector (COL1) may be 1 μm to 20 μm, more specifically 5 μm to 15 μm, and more specifically 7 μm to 10 μm.

[0045] The negative electrode current collector (COL1) may be composed of one of the above-described metals, or may include an alloy or coating material of two or more metals. The negative electrode current collector (COL1) may have, for example, a plate or foil shape. Meanwhile, in one embodiment, the negative electrode current collector (COL1) may be omitted.

[0046] Referring to FIG. 3, a lithium metal battery may form a lithium electrodeposited layer (LPL) after the initial cycle. The negative electrode (NEL) of the lithium metal battery after the initial cycle may further include a lithium electrodeposited layer (LPL). The lithium electrodeposited layer (LPL) may be interposed between the negative electrode current collector (COL1) and the first electrolyte layer (GPE1) described below.

[0047] A lithium electrodeposited layer (LPL) may be formed by plating lithium metal on a negative electrode current collector (COL1) during charging of a lithium metal battery. The lithium electrodeposited layer (NAL) may include lithium metal or a lithium alloy. The lithium alloy may be an alloy of lithium and another metal capable of being alloyed with lithium. For example, the lithium alloy may include a lithium-silver alloy, a lithium-zinc alloy, a lithium-magnesium alloy, or a lithium-tin alloy.

[0048] The thickness of the lithium plating layer (LPL) 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 plating layer (LPL) having a thickness in the above-described range.

[0049] In one embodiment, the thickness of the lithium plating layer (LPL) 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.

[0050] FIG. 4 is a schematic conceptual diagram illustrating a lithium metal battery according to another embodiment of the present invention. Referring to FIG. 4, the negative electrode (NEL) may further include a protective layer (PTL) on the negative electrode current collector (COL1). The protective layer (PTL) may directly cover the surface of the negative electrode current collector (COL1). The protective layer (PTL) may be interposed between the negative electrode current collector (COL1) and the first electrolyte layer (GPE1).

[0051] For example, the protective layer (PTL) may include at least one polymer selected from the group consisting of polyvinyl alcohol, polyimide, vinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride, carboxymethyl cellulose, and styrene butyrene rubber. The protective layer (PTL) may further include an inorganic filler in addition to the polymer. For example, the inorganic filler may be selected from the group consisting of SiO2, Al2O3, Al(OH)3, AlO(OH), TiO2, BaTiO3, ZnO2, Mg(OH)2, Aluminum Nitride (AlN), Silicon Carbide (SiC), and Boron Nitride (BoN). For example, the thickness of the protective layer (PTL) may be 1 μm to 20 μm.

[0052] The protective layer (PTL) can reduce side reactions by reducing the contact between lithium and the first electrolyte layer (GPE1), and can suppress lithium dendrite growth by creating a uniform lithium ion flow to the negative electrode (NEL).

[0053] FIG. 5 is a schematic conceptual diagram illustrating a lithium metal battery according to another embodiment of the present invention. Referring to FIG. 5, the negative electrode (NEL) may further include a host layer (HSL) on the negative electrode current collector (COL1). The host layer (HSL) may be interposed between the negative electrode current collector (COL1) and the first electrolyte layer (GPE1).

[0054] The host layer (HSL) can provide a space for lithium to be deposited when the lithium metal battery is charged. For example, the host layer (HSL) can include a space for lithium to be deposited, such as a porous structure. Lithium can be deposited inside the host layer (HSL). The host layer (HSL) can suppress the formation of the lithium electrodeposition layer (LPL) described above with reference to FIG. 3. As a result, the host layer (HSL) can suppress lithium dendrites and suppress an increase in the volume of the battery due to the formation of the lithium electrodeposition layer.

[0055] The host layer (HSL) may include a material with lithium affinity. For example, the host layer (HSL) may include a metal such as carbon or copper. The host layer (HSL) may have a 3D microstructure to maximize the specific surface area and porosity. For example, the host layer (HSL) may have a sponge-like or mesh-like structure.

[0056] The host layer (HSL) may further include a binder for mechanical stability. The binder within the host layer (HSL) may be any polymer used in lithium metal batteries without limitation.

[0057]

[0058] Electrolyte layer (GPE)

[0059] Referring back to FIG. 1, 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.

[0060] 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.

[0061] 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 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 It may include 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.

[0062] For example, the concentration of the lithium salt may be from 0.1 M to 5.0 M.

[0063] In one embodiment, the solid electrolyte may be a solid polymer electrolyte. 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), 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 It may be 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 polymer electrolytes in the relevant technical field.

[0064] The lithium salt in the solid polymer electrolyte can be selected from among the lithium salts used in the liquid electrolyte described above.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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 .

[0070] In one embodiment, a gel-polymer electrolyte can be formed by impregnating a solid polymer electrolyte into a liquid electrolyte.

[0071] 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.

[0072] 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, 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).

[0073] In one embodiment, the content of the crosslinking polymer in the gel-polymer electrolyte may be 1 to 10 wt%, 2 to 8 wt%, or 3 to 7 wt%, based on 100 wt% of the total weight of the gel-polymer electrolyte. The content of the liquid electrolyte may be 90 to 99 wt%, 92 to 98 wt%, or 93 to 97 wt%, based on 100 wt% of the total weight of the gel-polymer electrolyte.

[0074] In another embodiment, the total content of the polymer in the gel-polymer electrolyte may be 5 wt% or less based on 100 wt% of the total weight of the gel-polymer electrolyte. For example, it may be 0.1 wt% to 5 wt%, 0.5 wt% to 5 wt%, 1 wt% to 5 wt%, or 1 wt% to 3 wt%. The content of the liquid electrolyte may be 95 wt% or more based on 100 wt% of the total weight of the gel-polymer electrolyte. For example, it may be 95 wt% to 99.9 wt%, 95 wt% to 99.5 wt%, 95 wt% to 99 wt%, or 95 wt% to 97 wt%.

[0075] In another embodiment, the total content of the polymer in the gel-polymer electrolyte may be greater than or equal to 60 wt% based on 100 wt% of the total weight of the gel-polymer electrolyte. For example, it may be 60 wt% to 90 wt%, 60 wt% to 80 wt%, 65 wt% to 80 wt%, or 70 wt% to 80 wt%. The content of the liquid electrolyte may be less than or equal to 40 wt% based on 100 wt% of the total weight of the gel-polymer electrolyte. For example, it may be 10 wt% to 40 wt%, 20 wt% to 40 wt%, 20 wt% to 35 wt%, or 20 wt% to 30 wt%.

[0076] The electrolyte layer (GPE) according to embodiments of the present invention may include a first electrolyte layer (GPE1) and a second electrolyte layer (GPE2). The first and second electrolyte layers (GPE1, GPE2) will be described below with reference to FIG. 2.

[0077] In one embodiment, each of the first and second electrolyte layers (GPE1, GPE2) may include a gel-polymer electrolyte.

[0078] In one embodiment, the separator (SEP) may be impregnated into the electrolyte layer (GPE). For example, the separator (SEP) may be impregnated into the first electrolyte layer (GPE1).

[0079]

[0080] Composite Separation Layer (CSP)

[0081] FIG. 2 is an enlarged cross-sectional view of area M of FIG. 1. Referring to FIGS. 1 and 2, a composite separation layer (CSP) may be provided between a positive electrode (PEL) and a negative electrode (NEL). The composite separation layer (CSP) may include a separator (SEP) and an expansion buffer layer (EBL) on at least one surface of the separator (SEP). In one embodiment, the composite separation layer (CSP) may include a first expansion buffer layer (EBL1), a second expansion buffer layer (EBL2), and a separator (SEP) therebetween.

[0082] As the separator (SEP), a multilayer film of two or more layers of polyethylene, polypropylene, polyvinylidene fluoride, or these may be used, and 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 be used.

[0083] The separator (SEP) may include a porous substrate. The porous substrate may be a polymer membrane 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.

[0084] The porosity of the separator (SEP) may be 40% to 80%. For example, it may be 40% to 70% or 50% to 70%. The separator (SEP) may have a third thickness (TK3). The third thickness (TK3) may be 2 μm to 40 μm. For example, the third thickness (TK3) of the separator (SEP) may be 2 μm to 40 μm, 3 μm to 30 μm, 3 μm to 15 μm, 3 μm to 12 μm, 5 μm to 12 μm, or 5 μm to 10 μm. If it is greater than the above range, the resistance may increase due to an increase in the lithium ion migration path. If it is less than the above range, a short circuit may occur due to insufficient mechanical properties.

[0085] The first expansion relief layer (EBL1) may be provided on the first surface of the separator (SEP). The first expansion relief layer (EBL1) may be in direct contact with the first surface of the separator (SEP). The first expansion relief layer (EBL1) may include a plurality of pores (POR). The first expansion relief layer (EBL1) may be a porous elastic layer.

[0086] The porosity of the first expansion relief layer (EBL1) may be 40% to 80%. For example, the porosity of the first expansion relief layer (EBL1) may be 40% to 80% or 50% to 80%. In one embodiment, the porosity of the first expansion relief layer (EBL1) may be greater than the porosity of the separator (SEP). The first electrolyte (GPE1) may be filled within the plurality of pores (POR) of the first expansion relief layer (EBL1).

[0087] The first expansion relief layer (EBL1) may include at least one polymer (or engineering plastic) selected from the group consisting of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyacrylonitrile (PAN), polyacrylic acid (PAA), polymethyl methacrylate (PMMA), polyethylene glycol dimethyl ether (NHD), polyetherimide (PEI), polyethylene oxide (PEO), polysiloxane, polypropylene carbonate (PPC), polyethylene carbonate (PEC), polyvinyl chloride (PVC), polyamide-imide (PAI), polyphenylsulfone (PPSU), and polyimide (PI).

[0088] In one embodiment, the first expansion relief layer (EBL1) may further include an inorganic material. The first expansion relief layer (EBL1) may include Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, It may include at least one inorganic particle selected from the group consisting of SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof, but is not limited thereto. The inorganic particle may be provided within a plurality of pores (POR) of the first expansion relief layer (EBL1).

[0089] The first expansion relief layer (EBL1) may have a first thickness (TK1). The first thickness (TK1) may be 10 μm to 60 μm. For example, the first thickness (TK1) of the first expansion relief layer (EBL1) may be 10 μm to 60 μm, 10 μm to 50 μm, 10 μm to 50 μm, 10 μm to 30 μm, or 15 μm to 35 μm. If it exceeds the above range, the resistance may increase due to an increase in the lithium ion migration path. If it is less than the above range, it may be difficult to effectively buffer the volume change of the negative electrode (NEL).

[0090] The first thickness (TK1) of the first expansion relief layer (EBL1) may be greater than the third thickness (TK3) of the separator (SEP). The ratio of the first thickness (TK1) to the third thickness (TK3) (TK1 / TK3) may be 1.1 to 10, 1.1 to 7, or 1.5 to 5.

[0091] The first expansion relief layer (EBL1) may be configured to alleviate the change in volume (or thickness) of the negative electrode (NEL) during charge / discharge of the lithium metal battery. That is, the thickness (TK1) of the first expansion relief layer (EBL1) may change in response to the change in the volume (or thickness) of the negative electrode (NEL). In addition, since the first expansion relief layer (EBL1) includes a porous polymer, it may also perform the function of the host layer (HSL) described above with reference to FIG. 5. For example, lithium may be partially deposited within the pores (POR) of the first expansion relief layer (EBL1).

[0092] The second expansion relief layer (EBL2) may be provided on the second side of the separator (SEP). The second side may face the first side. The second expansion relief layer (EBL2) may be in direct contact with the second side of the separator (SEP). The second expansion relief layer (EBL2) may include a plurality of pores (POR). The second expansion relief layer (EBL2) may be a porous elastic layer.

[0093] The second expansion mitigation layer (EBL2) can have a second thickness (TK2). The second thickness (TK2) can be from 10 μm to 60 μm. For example, the second thickness (TK2) of the second expansion mitigation layer (EBL2) can be from 10 μm to 60 μm, from 10 μm to 50 μm, from 10 μm to 50 μm, from 10 μm to 30 μm, or from 15 μm to 35 μm. The second thickness (TK2) of the second expansion mitigation layer (EBL2) can be greater than, less than, or substantially equal to the first thickness (TK1) of the first expansion mitigation layer (EBL1). The second thickness (TK2) of the second expansion mitigation layer (EBL2) can be greater than the third thickness (TK3) of the separator (SEP). The ratio of the second thickness (TK2) to the third thickness (TK3) (TK2 / TK3) may be from 1.1 to 10, from 1.1 to 7, or from 1.5 to 5.

[0094] In addition, the specific description of the second expansion relief layer (EBL2) may be substantially the same as that described above for the first expansion relief layer (EBL1).

[0095] According to embodiments of the present invention, either one of the first and second expansion relief layers (EBL1, EBL2) may be omitted. According to embodiments of the present invention, the thickness (TK1+TK2+TK3) of the composite separation layer (CSP) may be 25 μm to 180 μm.

[0096] According to embodiments of the present invention, the first and second expansion relief layers (EBL1, EBL2) can buffer the volume change of the negative electrode (NEL). Referring to Fig. 3, when the lithium metal battery is charged, a lithium electrodeposited layer (LPL) is formed on the negative electrode current collector (COL1), so that the volume of the negative electrode (NEL) can increase. At this time, the thickness (TK1') of the first expansion relief layer (EBL1) decreases, and the thickness (TK2') of the second expansion relief layer (EBL2) decreases, so that the increased thickness of the negative electrode (NEL) can be compensated for. Referring to Fig. 2, when the lithium metal battery is discharged, the lithium electrodeposited layer (LPL) can decrease, so that the volume of the negative electrode (NEL) can be reduced. At this time, the thickness (TK1) of the first expansion relief layer (EBL1) increases, and the thickness (TK2) of the second expansion relief layer (EBL2) increases, thereby compensating for the reduced thickness of the cathode (NEL).

[0097] Since the electrolyte layer (GPE) is impregnated within the first and second expansion relief layers (EBL1, EBL2), the thickness of the electrolyte layer (GPE) can also change along with the change in the thickness of the first and second expansion relief layers (EBL1, EBL2). Accordingly, the interface between the electrolyte layer (GPE) and the negative electrode (NEL) and the interface between the electrolyte layer (GPE) and the positive electrode (PEL) can be stably maintained during charge / discharge of the battery. Consequently, the lithium metal battery according to the present invention can effectively suppress the growth of lithium dendrites on the negative electrode (NEL) during repeated cycles.

[0098]

[0099] Positive electrode (PEL)

[0100] Referring back to FIG. 1, the positive electrode (PEL) of the 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.

[0101] 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).

[0102] 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.

[0103] 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.

[0104] The positive electrode current collector (COL2) can provide a reference surface on which the positive electrode active material layer (PAL) is disposed. The positive electrode current collector (COL2) can include, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof. The positive electrode current collector (COL2) can include a plate or a foil. In another embodiment of the present invention, the positive electrode current collector (COL2) can be omitted. The thickness of the positive electrode current collector (COL2) can be, for example, 1 ㎛ to 100 ㎛, 1 ㎛ to 50 ㎛, 5 ㎛ to 25 ㎛, or 10 ㎛ to 20 ㎛. In one embodiment, the positive electrode current collector (COL2) can include, but is not limited to, aluminum (Al).

[0105] 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.

[0106] 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.

[0107] 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 O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni 1-b-c Mn b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni b Co c L 1 d G e O2(0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0≤e≤0.1); Li a NiG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a CoG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1-b G b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Lia 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).

[0108] 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.

[0109] A coating layer may be additionally added to the surface of the above-described compound. The coating layer may include, for example, an oxide, a hydroxide, an oxyhydroxide, an oxycarbonate, or a hydroxycarbonate of the coating element of the coating element. The coating layer may be amorphous or crystalline. The coating element in 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 for forming the coating layer 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.

[0110] 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.

[0111]

[0112] First and second gel-polymer electrolytes

[0113] Referring back to FIGS. 1 and 2, the electrolyte layer (GPE) may include a first electrolyte layer (GPE1) and a second electrolyte layer (GPE2) that are sequentially laminated. The first electrolyte layer (GPE1) may be adjacent to the negative electrode (NEL), and the second electrolyte layer (GPE2) may be adjacent to the positive electrode (PEL). For example, the first electrolyte layer (GPE1) may be in direct contact with the negative electrode current collector (COL1). The second electrolyte layer (GPE2) may be in direct contact with the positive electrode active material layer (PAL).

[0114] According to embodiments of the present invention, a composite separation layer (CSP) may be impregnated within a first electrolyte layer (GPE1). The composite separation layer (CSP) may include a plurality of pores (POR). The first electrolyte layer (GPE1) may fill the plurality of pores (POR). The composite separation layer (CSP) may be spaced apart from the second electrolyte layer (GPE2).

[0115] The surface of the positive active material layer (PAL) may not be flat but may be uneven. For example, the surface of the positive active material layer (PAL) may include a plurality of depressions (DTR). The second electrolyte layer (GPE2) may fill all of the depressions (DTR) of the positive active material layer (PAL). For example, the second electrolyte layer (GPE2) may include protrusions (PRP) that fill each of the depressions (DTR). The surface of the positive active material layer (PAL) may have a relatively large specific surface area due to the depressions (DTR). The second electrolyte layer (GPE2) may include protrusions (PRP) corresponding to the depressions (DTR), thereby improving the contact area with the positive active material layer (PAL).

[0116] The first electrolyte layer (GPE1) may be a cathode-compatible cathode electrolyte layer. For example, the first electrolyte layer (GPE1) may be an anolyte. The second electrolyte layer (GPE2) may be a cathode-compatible cathode electrolyte layer. For example, the second electrolyte layer (GPE2) may be a catholyte.

[0117] The first electrolyte layer (GPE1) faces the lithium electrodeposition layer (LPL, see FIG. 3), and thus can be configured to suppress lithium dendrites during charging and discharging of the battery. The first electrolyte layer (GPE1) can function as a protective film to prevent the second electrolyte layer (GPE2) from directly contacting lithium.

[0118] Since the second electrolyte layer (GPE2) faces the anode, it can be configured to have excellent high-voltage stability. Since the second electrolyte layer (GPE2) faces the anode, it can be configured to have high ionic conductivity.

[0119] According to embodiments of the present invention, the first electrolyte layer (GPE1) may include a first gel-polymer electrolyte, and the second electrolyte layer (GPE2) may include a second gel-polymer electrolyte. As described above, since the first electrolyte layer (GPE1) and the second electrolyte layer (GPE2) are configured to perform different functions, the compositions of the first gel-polymer electrolyte and the second gel-polymer electrolyte may be different from each other.

[0120] In one embodiment, the type of polymer in the first gel-polymer electrolyte may be the same as the type of polymer in the second gel-polymer electrolyte, but the polymer weight ratio in the first gel-polymer electrolyte may be different from the polymer weight ratio in the second gel-polymer electrolyte. For example, the cross-linking agent used to form the polymer of the first gel-polymer electrolyte may be the same as the cross-linking agent used to form the polymer of the second gel-polymer electrolyte, but the content of the cross-linking agent used may be different.

[0121] Hereinafter, the first gel-polymer electrolyte of the first electrolyte layer (GPE1) and the second gel-polymer electrolyte of the second electrolyte layer (GPE2) will be described in more detail.

[0122] The first and second gel-polymer electrolytes may have a gel state or a semi-solid state. The first and second gel-polymer electrolytes may be in a gel state or a semi-solid state at 25°C and 1 atm. The first gel-polymer electrolyte may comprise a liquid electrolyte and a polymer. The second gel-polymer electrolyte may comprise a liquid electrolyte and a polymer. The liquid electrolyte may be a mixture of the above-described 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.

[0123] The above organic solvent, ionic liquid and lithium salt may be selected from the organic solvent, ionic liquid and lithium salt described above in the gel-polymer electrolyte.

[0124] The polymer contained in each of the first and second gel-polymer electrolytes may include a cross-linked polymer (CLP).

[0125] Figure 6 schematically illustrates a cross-linked polymer structure according to embodiments of the present invention. Referring to Figure 6, the cross-linked polymer (CLP) may include a main chain (M) and a plurality of side chains (S) extending from the main chain (M). For example, the plurality of side chains (S) may include a side chain (S1) extending from the main chain (M) and a side chain (S2) extending from the side chain (S1). In addition, the main chain (M) and the plurality of side chains (S) of the cross-linked polymer (1) may include an end portion (E) at which a cross-linking reaction or polymerization reaction is completed.

[0126] Cross-linked polymers (CLPs) can be formed by a cross-linking reaction of a multifunctional polymerizable monomer, i.e., a cross-linking agent. In other words, the cross-linked polymer (CLP) can include repeating units derived from the cross-linking agent. The cross-linking agent can be an electrochemically stable material under the operating environment (e.g., a voltage of approximately 4.3 V or higher) of a positive electrode using a positive electrode active material having a nickel content of 90 mol% or higher.

[0127] In one embodiment, the cross-linking agent may include a functional group capable of cross-linking. For example, the cross-linking agent may include two or more double bond functional groups, and specifically, the double bond functional groups may be (meth)acrylic groups.

[0128] In one embodiment, 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, pentaerythritol triacrylate (PETA), propoxylated glyceryl triacrylate, tris(2-hydroxyethyl) isocyanurate triacrylate (THEICTA), and dipentaerythritol pentaacrylate (DPEPA). there is.

[0129] The crosslinking agent may have a weight average molecular weight in the range of 200 to 2,000, and may be in the range of 200 to 1,000, for example, in the range of 200 to 500. If the weight average molecular weight is less than 200, the density of crosslinking points within the molecular structure of the polymer after crosslinking may be too high, preventing free movement of the lithium salt. If the weight average molecular weight is greater than 2,000, the density of crosslinking points within the molecular structure of the polymer after crosslinking may be too low, reducing the electrolyte blocking ability.

[0130] The crosslinked polymer (CLP) may further comprise repeating units derived from ionic monomers. The ionic monomers may comprise one or more double bond functional groups and ionic functional groups.

[0131] The double bond functional group in the ionic monomer may include an allyl group, an acrylic group, a vinyl group, or any combination thereof. For example, the ionic monomer may include an acrylic group, a vinyl group, or any combination thereof. It may include a cationic functional group, an anionic functional group, or a combination thereof. For example, if the ionic monomer includes a cationic functional group, the ionic monomer may be a cationic monomer. For example, if the ionic monomer includes an anionic functional group, the ionic monomer may be an anionic monomer. For example, if the ionic monomer includes both a cationic functional group and an anionic functional group, the ionic monomer may be a zwitterionic monomer.

[0132] In one embodiment, the polymer included in each of the first and second gel-polymer electrolytes may further include a linear polymer. Linear polymers include polyethylene (PE), styrene-butadiene rubber (SBR), nylon, carboxymethyl cellulose (CMC), polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene (PVDF-HFP), 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, Polyvinyl Fluoride), polyethylene glycol (PEG), polyacrylonitrile (PAN), polytetrafluoroethylene (PTFE), polyethylenedioxythiophene (PEDOT), polypyrrole (PPY), polyacrylonitrile (PAN), It may be polyaniline, polyacetylene, or a combination thereof.

[0133] In one embodiment, the content of linear polymer relative to 100 wt% of the polymer content in the first gel-polymer electrolyte may be 20 wt% or less. For example, it may be 1 wt% to 20 wt%, 5 wt% to 20 wt%, 10 wt% to 20 wt%, or 10 wt% to 15 wt%.

[0134] In one embodiment, the linear polymer content relative to 100 wt% of the polymer content in the second gel-polymer electrolyte may be 20 wt% or less. For example, it may be 1 wt% to 20 wt%, 5 wt% to 20 wt%, 10 wt% to 20 wt%, or 10 wt% to 15 wt%.

[0135] Within the above range, ionic conductivity can be improved while maintaining the mechanical stability of the gel polymer electrolyte. If the linear polymer content exceeds the above range, the mechanical stability of the gel polymer electrolyte may deteriorate.

[0136] In one embodiment, the components of the first gel-polymer electrolyte and the second gel-polymer electrolyte may be the same. Specifically, the types of polymers included in the first and second gel-polymer electrolytes may be the same. For example, the first gel-polymer electrolyte and the second gel-polymer electrolyte may include a crosslinked polymer derived from the same crosslinking agent. The first gel-polymer electrolyte and the second gel-polymer electrolyte may also include a linear polymer derived from the same monomer. Furthermore, the liquid electrolyte components (lithium salt, organic solvent, ionic liquid) constituting the first gel-polymer electrolyte and the second gel-polymer electrolyte may be the same. For example, the first gel-polymer electrolyte and the second gel-polymer electrolyte may include the same lithium salt and organic solvent. Since the first gel-polymer electrolyte and the second gel-polymer electrolyte have the same components, a decrease in ionic conductivity due to a difference in chemical potential can be prevented.

[0137] In one embodiment, the content ratio of the polymer in the first gel-polymer electrolyte may be different from the content ratio of the polymer in the second gel-polymer electrolyte. Specifically, the weight ratio of the polymer in the first gel-polymer electrolyte may be greater than the weight ratio of the polymer in the second gel-polymer electrolyte. That is, by lowering the content ratio of the polymer in the second electrolyte layer (GPE2) filling the depressions (DTR) on the surface of the positive active material layer (PAL) and increasing the content ratio of the polymer in the first electrolyte layer (GPE1) filling the pores (POR) of the composite separator layer (CSP), both ionic conductivity and cell stability can be improved. Through this, the initial discharge efficiency and cycle life characteristics of the lithium metal battery can be improved, and thermal stability can be improved.

[0138] In one embodiment, the polymer content in the first gel-polymer electrolyte may be 60 wt% or more. For example, it may be 60 wt% to 90 wt%, 60 wt% to 80 wt%, 65 wt% to 80 wt%, or 70 wt% to 80 wt%. Within this range, short circuits due to separator shrinkage in a high-temperature environment can be prevented.

[0139] In one embodiment, the polymer content in the second gel-polymer electrolyte may be 5 wt% or less. For example, it may be 0.1 wt% to 5 wt%, 0.5 wt% to 5 wt%, 1 wt% to 5 wt%, or 1 wt% to 3 wt%. Within this range, the impregnation properties and ionic conductivity of the second electrolyte layer may be improved.

[0140] A lithium metal battery according to embodiments of the present invention can improve both ionic conductivity and safety by having the same components of the gel-polymer electrolyte in the first electrolyte layer (GPE1) and the second electrolyte layer (GPE2) but different content ratios.

[0141]

[0142] lithium metal battery

[0143] Referring to FIG. 7, a lithium metal 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 above-described composite separator layer (CSP).

[0144] A positive electrode (PEL), a negative electrode (NEL), and a composite separator (CSP) can be wound or folded to form a battery structure (BTS). The battery structure (BTS) can be accommodated in a battery case (CAS). An electrolyte layer can be formed by injecting an electrolyte into the battery case (CAS). The battery case (CAS) can be sealed with a cap assembly (CAB) to manufacture a lithium metal battery (LBT). The battery case (CAS) is cylindrical, but is not necessarily limited to this shape, and can be, for example, square, thin-film, etc.

[0145] Referring to FIG. 8, a lithium metal battery (LBT) according to one embodiment of the present invention may include the aforementioned positive electrode (PEL), the aforementioned negative electrode (NEL), and the composite separator layer (CSP). The composite separator layer (CSP) is disposed between the positive electrode (PEL) and the negative electrode (NEL), and the positive electrode (PEL), the negative electrode (NEL), and the composite separator layer (CSP) may be wound or folded to form a battery structure (BTS).

[0146] 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 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 metal battery (LBT). The battery case (CAS) is not necessarily limited to a square shape, but may be, for example, cylindrical, thin-film, etc.

[0147] Referring to FIG. 9, a lithium metal battery (LBT) according to one embodiment of the present invention may include the aforementioned positive electrode (PEL), the aforementioned negative electrode (NEL), and the composite separator layer (CSP). The composite separator layer (CSP) may be disposed between the positive electrode (PEL) and the negative electrode (NEL) to form a battery structure (BTS).

[0148] 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 metal battery (LBT). The battery case (CAS) is not necessarily limited to a square shape, and may be, for example, cylindrical, thin-film, etc.

[0149] A pouch-type lithium metal battery may correspond to a lithium metal battery (LBT) of each of FIGS. 7 to 9 that uses a pouch as a battery case (CAS). The pouch-type lithium metal 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 metal battery.

[0150] For example, the above-described positive electrode, negative electrode, and composite separator layers 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.

[0151] Lithium metal 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.

[0152] Multiple lithium metal 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.

[0153] 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.

[0154]

[0155] Manufacturing method

[0156] FIGS. 10A to 10E are cross-sectional views illustrating a method for manufacturing a lithium metal battery according to embodiments of the present invention.

[0157] Referring to FIG. 10A, a separator (SEP) may be prepared. The separator (SEP) may include a porous substrate. A first expansion relief layer (EBL1) and a second expansion relief layer (EBL2) may be formed on each of the two sides of the separator (SEP).

[0158] According to embodiments of the present invention, forming the first and second expansion relief layers (EBL1, EBL2) may include performing an electrospinning process. For example, a polymer solution may be extruded through a needle (NDL) onto one surface of a separator (SEP). The polymer may form a porous film on the surface (i.e., the one surface) of the separator (SEP) by electrospinning. The porous polymer film formed by electrospinning may constitute the expansion relief layers (EBL1, EBL2). For example, the polymer may include at least one selected from the group consisting of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyacrylonitrile (PAN), polyacrylic acid (PAA), polymethyl methacrylate (PMMA), polyethylene glycol dimethyl ether (NHD), polyetherimide (PEI), polyethylene oxide (PEO), polysiloxane, polypropylene carbonate (PPC), polyethylene carbonate (PEC), polyvinyl chloride (PVC), polyamide-imide (PAI), polyphenylsulfone (PPSU), and polyimide (PI).

[0159] According to embodiments of the present invention, the thickness of each of the first and second expansion relief layers (EBL1, EBL2) may be formed to be greater than the thickness of the separator (SEP). The porosity of each of the first and second expansion relief layers (EBL1, EBL2) may be formed to be greater than the porosity of the separator (SEP). The first and second expansion relief layers (EBL1, EBL2) and the separator (SEP) may form a composite separation layer (CSP).

[0160] Referring to FIG. 10b, a negative electrode (NEL), i.e., a negative electrode current collector (COL1), may be provided. The negative electrode current collector (COL1) may include at least one metal selected from the group consisting of copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni). The thickness of the negative electrode current collector (COL1) may be 1 μm to 20 μm, more specifically 5 μm to 15 μm, and more specifically 7 μm to 10 μm.

[0161] A composite separating layer (CSP) may be provided on the negative current collector (COL1). The composite separating layer (CSP) may be laminated on the negative current collector (COL1). The first expansion relief layer (EBL1) of the composite separating layer (CSP) may be in direct contact with the surface of the negative current collector (COL1).

[0162] Referring to FIG. 10c, a first electrolyte solution (GPC1) may be provided on a laminate of a composite separator layer (CSP) and a negative electrode collector (COL1). The separator (SEP) may be impregnated with the first electrolyte solution (GPC1).

[0163] The first electrolyte solution (GPC1) may be a precursor for forming the first electrolyte layer (GPE1) described below. The first electrolyte solution (GPC1) may include a liquid electrolyte, a polymer precursor, and a thermal initiator. The polymer precursor may include a crosslinking agent. The crosslinking agent may form a crosslinked polymer through a crosslinking reaction. The polymer precursor may further include a linear polymer and an ionic monomer.

[0164] The crosslinker, ionic monomer, liquid electrolyte, and linear polymer in the first electrolyte solution (GPC1) are the same as those described above for the first gel-polymer electrolyte.

[0165] For example, the crosslinking agent may include two or more double bond functional groups, and specifically, the double bond functional groups may be (meth)acrylic groups. Specifically, 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, pentaerythritol triacrylate (PETA), propoxylated glyceryl triacrylate, tris(2-hydroxyethyl) isocyanurate triacrylate (THEICTA), and dipentaerythritol pentaacrylate (DPEPA).

[0166] For example, linear polymers include polyethylene (PE), styrene-butadiene rubber (SBR), nylon, carboxymethyl cellulose (CMC), polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene (PVDF-HFP), 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, Polyvinyl Fluoride), polyethylene glycol (PEG), polyacrylonitrile (PAN), polytetrafluoroethylene (PTFE), polyethylenedioxythiophene (PEDOT), polypyrrole (PPY), polyacrylonitrile (PAN), It may include at least one selected from the group consisting of polyaniline and polyacetylene.

[0167] In one embodiment, the content of the linear polymer may be 20 wt% or less relative to 100 wt% of the total content of the polymer precursor in the first electrolyte solution. For example, it may be 1 wt% to 20 wt%, 5 wt% to 20 wt%, 10 wt% to 20 wt%, or 10 wt% to 15 wt%.

[0168] In one embodiment, the content of the liquid electrolyte relative to the total content of 100 wt% of the polymer precursor and the liquid electrolyte in the second electrolyte solution (GPC2) may be 40 wt% or less. For example, it may be 10 wt% to 40 wt%, 20 wt% to 40 wt%, 20 wt% to 35 wt%, or 20 wt% to 30 wt%.

[0169] In one embodiment, the content of the polymer precursor may be 60 wt% or more relative to 100 wt% of the total content of the polymer precursor and the liquid electrolyte in the first electrolyte solution. For example, it may be 60 wt% to 90 wt%, 60 wt% to 80 wt%, 65 wt% to 80 wt%, or 70 wt% to 80 wt%. For example, when the polymer precursor includes all of a crosslinking agent, an ionic monomer, and a linear polymer, the total content of the crosslinking agent, the ionic monomer, and the linear polymer may be within the above range. In another example, when the polymer precursor includes a crosslinking agent, the content of the crosslinking agent may be within the above range.

[0170] In one embodiment, the first electrolyte solution (GPC1) may be provided by inserting a laminate of a composite separator (CSP) and a negative electrode collector (COL1) into a pouch and filling the pouch with the first electrolyte solution (GPC1).

[0171] Referring to FIG. 10d, a first heat treatment process (HEP1) may be performed on a laminate of a composite separating layer (CSP) and a negative electrode current collector (COL1). A first electrolyte layer (GPE1) may be formed from a first electrolyte solution (GPC1) through the first heat treatment process (HEP1). Specifically, a crosslinking agent and an ionic monomer within the first electrolyte solution (GPC1) may polymerize with each other to form a polymer.

[0172] The first electrolyte layer (GPE1) can be in direct contact with the negative electrode current collector (COL1), as previously described with reference to FIG. 2. The composite separator layer (CSP) can be completely impregnated within the first electrolyte layer (GPE1). The first electrolyte layer (GPE1) can fill the pores (POR) of the composite separator layer (CSP).

[0173] Referring to FIG. 10e, a positive electrode (PEL) may be provided on a first electrolyte layer (GPE1). The positive electrode (PEL) may include a positive electrode current collector (COL2) and a positive electrode active material layer (PAL). The positive electrode current collector (COL2) may provide a reference surface on which the positive electrode active material layer (PAL) is disposed. The positive electrode current collector (COL2) may include, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof. The positive electrode active material layer (PAL) may include a compound capable of reversible intercalation and deintercalation of lithium (lithiated intercalation compound).

[0174] Referring to FIG. 10f, a second electrolyte solution (GPC2) may be provided on a stack of a negative electrode current collector (COL1), a composite separator (CSP), and a positive electrode (PEL). The second electrolyte solution (GPC2) may be filled in the space between the first electrolyte layer (GPE1) and the positive electrode active material layer (PAL).

[0175] The second electrolyte solution (GPC2) may be a precursor for forming a second electrolyte layer (GPE2) described below. The second electrolyte solution (GPC2) may include a liquid electrolyte, a polymer precursor, and a thermal initiator. The polymer precursor may include a crosslinking agent. The crosslinking agent may form a crosslinked polymer through a crosslinking reaction. The polymer precursor may further include a linear polymer and an ionic monomer.

[0176] The crosslinker, ionic monomer, liquid electrolyte, and linear polymer in the second electrolyte solution (GPC2) are the same as those described above for the second gel-polymer electrolyte.

[0177] For example, the crosslinking agent may include two or more double bond functional groups, and specifically, the double bond functional groups may be (meth)acrylic groups. Specifically, 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, pentaerythritol triacrylate (PETA), propoxylated glyceryl triacrylate, tris(2-hydroxyethyl) isocyanurate triacrylate (THEICTA), and dipentaerythritol pentaacrylate (DPEPA).

[0178] For example, linear polymers include polyethylene (PE), styrene-butadiene rubber (SBR), nylon, carboxymethyl cellulose (CMC), polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene (PVDF-HFP), 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, Polyvinyl Fluoride), polyethylene glycol (PEG), polyacrylonitrile (PAN), polytetrafluoroethylene (PTFE), polyethylenedioxythiophene (PEDOT), polypyrrole (PPY), polyacrylonitrile (PAN), It may include at least one selected from the group consisting of polyaniline and polyacetylene.

[0179] In one embodiment, the content of the linear polymer may be 20 wt% or less with respect to 100 wt% of the total content of the polymer precursor in the second electrolyte solution (GPC2). For example, it may be 1 wt% to 20 wt%, 5 wt% to 20 wt%, 10 wt% to 20 wt%, or 10 wt% to 15 wt%.

[0180] In one embodiment, the content of the liquid electrolyte relative to the total content of 100 wt% of the polymer precursor and the liquid electrolyte in the second electrolyte solution (GPC2) may be 95 wt% or more. For example, it may be 95 wt% to 99.9 wt%, 95 wt% to 99.5 wt%, 95 wt% to 99 wt%, or 95 wt% to 97 wt%.

[0181] In one embodiment, the content of the polymer precursor may be 5 wt% or less with respect to the total content of 100 wt% of the polymer precursor and the liquid electrolyte in the second electrolyte solution (GPC2). For example, it may be 0.1 wt% to 5 wt%, 0.5 wt% to 5 wt%, 1 wt% to 5 wt%, or 1 wt% to 3 wt%. For example, when the polymer precursor includes all of a crosslinking agent, an ionic monomer, and a linear polymer, the total content of the crosslinking agent, the ionic monomer, and the linear polymer may be within the above range. In another example, when the polymer precursor includes a crosslinking agent, the content of the crosslinking agent may be within the above range.

[0182] In one embodiment, the types of crosslinking agent, ionic monomer, liquid electrolyte, and linear polymer included in the first electrolyte solution (GPC1) and the second electrolyte solution (GPC2) may be the same. The weight ratios of the liquid electrolyte included in the first electrolyte solution (GPC1) and the second electrolyte solution (GPC2) may be different from each other. In other words, the contents of polymer precursors in the first electrolyte solution (GPC1) and the second electrolyte solution (GPC2) may be different from each other.

[0183] In one embodiment, the second electrolyte solution (GPC2) can be provided by inserting a stack of a negative current collector (COL1), a composite separator (CSP), and a positive electrode (PEL) into a pouch and filling the pouch with the second electrolyte solution (GPC2).

[0184] Referring to FIG. 10g, a second heat treatment process (HEP2) may be performed on a laminate of a negative electrode current collector (COL1), a composite separator (CSP), and a positive electrode (PEL). A second electrolyte layer (GPE2) may be formed from a second electrolyte solution (GPC2) through the second heat treatment process (HEP2). Specifically, crosslinking agents within the second electrolyte solution (GPC2) may polymerize with each other to form a polymer.

[0185] The second electrolyte layer (GPE2) can be in direct contact with the positive electrode active material layer (PAL), as previously described with reference to FIG. 2. The second electrolyte layer (GPE2) can be in complete contact with the first electrolyte layer (GPE1). As shown in FIG. 2, the interface (ITF) between the first and second electrolyte layers (GPE1, GPE2) can be uniform and flat.

[0186]

[0187] 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.

[0188] Example 1

[0189] (First electrolyte solution)

[0190] A liquid electrolyte was prepared by dissolving 1.0 M LiPF6 in a non-aqueous organic solvent containing ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 50:50. A first electrolyte precursor was prepared by adding trimethylolpropane trimethacrylate (TMPTMA) as a crosslinking agent to the liquid electrolyte. The content of TMPTMA is 65 wt% based on the total content of the first electrolyte solution.

[0191] (second electrolyte solution)

[0192] A liquid electrolyte was prepared using the same method as described for the first electrolyte solution. A second electrolyte solution was prepared by adding TMPTMA to the liquid electrolyte. The content of TMPTMA was 3 wt% based on the total content of the second electrolyte solution.

[0193] (anode)

[0194] Li 1.04 Ni 0.8 Co 0.1 Al 0.1O2A 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.

[0195] 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.

[0196] The manufactured positive electrode was placed in a pouch, and a second electrolyte solution was injected. The pouch was sealed under vacuum to allow the second electrolyte precursor to be impregnated within the positive electrode for 24 hours. Afterwards, the positive electrode was heat-cured at 70°C for 2 hours, producing a positive electrode containing the second gel-polymer electrolyte.

[0197] (composite separation layer)

[0198] A polyvinylidene fluoride (PVdF) layer was formed on both sides of a 5 μm thick polyethylene membrane by electrospinning. Specifically, a polymer solution of approximately 15 wt% was prepared by mixing polyvinylidene fluoride (PVdF) and a dimethylacetamide (DMAc) solvent. The polymer solution was electrospun onto the surface of the polyethylene membrane to form a polyvinylidene fluoride (PVdF) layer. The polyvinylidene fluoride (PVdF) layer was formed to a thickness of 20 μm. As a result, the total thickness of the composite separator was 45 μm.

[0199] The composite separator layer was placed in a pouch, secured between glass plates, and the first electrolyte solution was injected. The pouch was sealed under vacuum for 24 hours to allow the first electrolyte solution to permeate the composite separator layer. The composite separator layer was then heat-cured at 70°C for 2 hours, producing a composite separator layer containing the first gel-polymer electrolyte.

[0200] (lithium metal battery)

[0201] A pouch cell was manufactured by placing a previously manufactured separator between the previously manufactured positive electrode and a copper foil (negative electrode collector) having a thickness of 10 ㎛.

[0202]

[0203] Example 2

[0204] A polyethylene separator with a thickness of 11 μm was prepared. A polyacrylic acid (PAA) solution was electrospun to form a polyacrylic acid (PAA) layer on both sides of the polyethylene separator. The polyacrylic acid (PAA) layer was formed to a thickness of 20 μm. Otherwise, a lithium metal battery was manufactured using the same method as in Example 1.

[0205]

[0206] Example 3

[0207] A PP / PE / PP separator with a thickness of 13 μm was prepared. A PVdF:PAN (1:1) layer was formed on both sides of the PP / PE / PP separator by electrospinning. The PVdF:PAN layer was formed to a thickness of 30 μm. Otherwise, a lithium metal battery was manufactured in the same manner as in Example 1.

[0208]

[0209] Example 4

[0210] A polyethylene separator with a thickness of 11 μm was prepared. PVdF-HFP layers were formed on both sides of the polyethylene separator by electrospinning. The PVdF-HFP layers were formed to a thickness of 25 μm. Otherwise, a lithium metal battery was manufactured using the same method as in Example 1.

[0211]

[0212] Comparative Example 1

[0213] A 20 μm thick PP / PE / PP separator was prepared. Unlike Example 1, a separate polymer layer was not formed on the surface of the separator by electrospinning. Otherwise, a lithium metal battery was manufactured using the same method as Example 1.

[0214]

[0215] Comparative Example 2

[0216] A 50 μm thick separator coated with ceramic on its surface was prepared. The separator material was polyethylene, and the coated ceramic was alumina. Unlike Example 1, a separate polymer layer was not formed on the surface of the separator by electrospinning. Otherwise, a lithium metal battery was manufactured using the same method as Example 1.

[0217] Comparative Example 3

[0218] A PP / PE / PP separator with a thickness of 20 μm was prepared. A PVdF layer was formed on both sides of the PP / PE / PP separator by electrospinning. The PVdF layer was formed to a thickness of 70 μm. Otherwise, a lithium metal battery was manufactured in the same manner as in Example 1.

[0219]

[0220] Comparative Example 4

[0221] A ceramic-coated separator with a thickness of 50 μm, identical to that of Comparative Example 2, was prepared. A polyacrylic acid (PAA) layer was formed on both sides of the separator by electrospinning. The polyacrylic acid (PAA) layer was formed to a thickness of 20 μm. Otherwise, a lithium metal battery was manufactured using the same method as in Example 1.

[0222]

[0223] The characteristics of the composite separator of the lithium metal battery manufactured through Examples 1 to 4 and Comparative Examples 1 to 4 are shown in Table 1 below.

[0224] Expansion relief layer separator Example 1 PVdF, 20 μm PE, 5 μm Example 2 PAA, 20 μm PE, 11 μm Example 3 PVdF:PAN (1:1), 30 μm PP / PE / PP, 13 μm Example 4 PVdF-HFP, 25 μm PE, 11 μm Comparative Example 1 - PP / PE / PP, 20 μm Comparative Example 2 - Ceramic coated separator, 50 μm Comparative Example 3 PVdF, 70 μm PP / PE / PP, 20 μm Comparative Example 4 PAA, 20 μm Ceramic coated separator, 50 μm

[0225] Evaluation Example 1: Initial discharge efficiency and life characteristics of lithium metal batteries The initial discharge efficiency and life characteristics of the lithium metal batteries (pouch cells) of Examples 1 to 4 and Comparative Examples 1 to 4 were evaluated under the following conditions.

[0226] The battery was charged at a constant current of 0.1 C rate at 25°C until the voltage reached 4.2 V (vs. Li), and then cut-off at a current of 0.05 C rate while maintaining 4.2 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 0.1 C rate until the voltage reached 3.0 V (vs. Li) during discharge (formation cycle).

[0227] A lithium metal battery that had undergone a Mars cycle was charged at a constant current of 0.2 C at 25°C until the voltage reached 4.2 V (vs. Li), and then cut off at a current of 0.05 C while maintaining 4.2 V in constant voltage mode. Subsequently, the battery was discharged at a constant current of 0.2 C until the voltage reached 3.0 V (vs. Li) (1st cycle). This cycle was repeated under the same conditions until the capacity retention rate reached 80%.

[0228] In every charge / discharge cycle, a 10-minute pause was provided after each charge / discharge cycle.

[0229] Initial charge / discharge efficiency (ICE) is defined by the following mathematical equation:

[0230] <Mathematical Formula 1>

[0231] Initial charge / discharge efficiency [%] = [Initial charged capacity / Capacity after discharge] × 100

[0232] The life characteristic is defined as the number of cycles until the capacity retention rate reaches 80%, and the capacity retention rate is defined by the following mathematical expression 2.

[0233] <Mathematical Formula 2>

[0234] Capacity retention rate [%] = [Discharge capacity after n cycles / Discharge capacity in the 1st cycle] × 100

[0235] (However, n is a natural number greater than or equal to 2)

[0236] Additionally, the Coulombic efficiency (CE) was measured over 100 cycles.

[0237] The results of the room temperature charge / discharge experiment are shown in Table 2 below.

[0238] Initial Efficiency (%) CE (%) Lifespan (cycle@80%) Example 189.098.0211 Example 289.198.3222 Example 388.898.1230 Example 488.998.7242 Comparative Example 189.096.9159 Comparative Example 288.796.5149 Comparative Example 386.496.1112 Comparative Example 486.896.0130

[0239] Referring to Table 2, it can be confirmed that the lithium metal batteries according to Examples 1 to 4 have excellent initial efficiency, Coulombic efficiency, and life characteristics. In particular, it was confirmed that the lithium metal batteries according to Examples 1 to 4 stably maintained a capacity retention rate of 80% or more even after 200 cycles. On the other hand, in the case of Comparative Examples 1 and 2 in which the expansion relief layer was omitted, it can be confirmed that the initial efficiency was similar to that of Examples 1 to 4, but the lifespan was rapidly reduced to about 150 cycles. This appears to be due to problems such as the formation of lithium dendrites occurring due to the absence of the expansion relief layer.

[0240] Furthermore, in the case of Comparative Example 3, in which the expansion relief layer was formed excessively thick, it can be confirmed that not only the initial efficiency but also the lifespan was rapidly reduced compared to Examples 1 to 4. In the case of Comparative Example 4, in which the separator was formed excessively thick, it can be confirmed that not only the initial efficiency but also the lifespan was rapidly reduced compared to Examples 1 to 4. That is, it is judged that when the total thickness of the composite separator according to the present invention exceeds about 65㎛, the energy density within the battery is reduced and the resistance is rapidly increased, which causes the above-mentioned problems.

Claims

1. Negative current collector; anode; An electrolyte layer between the negative electrode current collector and the positive electrode, the electrolyte layer including a first electrolyte layer adjacent to the negative electrode current collector, and a second electrolyte layer adjacent to the positive electrode; and Including a composite separation layer impregnated in the first electrolyte layer, The first electrolyte layer comprises a first gel-polymer electrolyte, and the second electrolyte layer comprises a second gel-polymer electrolyte. The weight ratio of the polymer in the first gel-polymer electrolyte and the weight ratio of the polymer in the second gel-polymer electrolyte are different from each other, A lithium metal battery, wherein the composite separation layer comprises a separator and an expansion relief layer on at least one side of the separator.

2. In paragraph 1, A lithium metal battery, wherein the thickness of the expansion relief layer is configured to change in correspondence to a lithium electrodeposition layer formed between the negative electrode current collector and the composite separating layer.

3. In paragraph 1, A lithium metal battery, wherein the thickness of the expansion relief layer is greater than the thickness of the separator.

4. In paragraph 3, The thickness of the above expansion relief layer is 10㎛ to 60㎛, A lithium metal battery, wherein the thickness of the separator is 2 μm to 40 μm.

5. In paragraph 1, A lithium metal battery, wherein the thickness of the composite separating layer is 25 ㎛ to 180 ㎛.

6. In paragraph 1, A lithium metal battery, wherein the porosity of the expansion relief layer is greater than the porosity of the separator.

7. In paragraph 1, A lithium metal battery, wherein the weight ratio of the polymer in the first gel-polymer electrolyte is greater than the weight ratio of the polymer in the second gel-polymer electrolyte.

8. In paragraph 1, A lithium metal battery, wherein the expansion relief layer comprises at least one polymer selected from the group consisting of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyacrylonitrile (PAN), polyacrylic acid (PAA), polymethyl methacrylate (PMMA), polyethylene glycol dimethyl ether (NHD), polyetherimide (PEI), polyethylene oxide (PEO), polysiloxane, polypropylene carbonate (PPC), polyethylene carbonate (PEC), polyvinyl chloride (PVC), polyamide-imide (PAI), polyphenylsulfone (PPSU), and polyimide (PI).

9. In paragraph 1, The above composite separation layer comprises a plurality of pores, A lithium metal battery, wherein the first electrolyte layer fills the plurality of pores.

10. In paragraph 1, A lithium metal battery, wherein the expansion relief layer comprises a first expansion relief layer on a first surface of the separator and a second expansion relief layer on a second surface of the separator.

11. In paragraph 1, The above positive electrode includes a positive electrode current collector, and a positive electrode active material layer on the positive electrode current collector, A lithium metal battery, wherein the second electrolyte layer is in contact with the positive electrode active material layer.

12. In paragraph 11, The above positive electrode active material layer includes a plurality of depressions on its surface, A lithium metal battery, wherein the second electrolyte layer fills the plurality of recesses.

13. In paragraph 1, Further comprising a protective layer between the composite separating layer and the negative electrode current collector, A lithium metal battery, wherein the protective layer comprises at least one polymer selected from the group consisting of polyvinyl alcohol, polyimide, vinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride, carboxymethyl cellulose, and styrene butylene rubber.

14. In paragraph 1, Further comprising a host layer between the composite separating layer and the negative electrode current collector, The above host layer is configured to provide a space for lithium to be deposited, A lithium metal battery, wherein the host layer comprises carbon or metal.

15. Negative current collector; A lithium electrodeposition layer on the above negative electrode current collector; An electrolyte layer on the lithium electrodeposition layer; A composite separation layer impregnated within the electrolyte layer; and Including an anode on the above electrolyte layer, The composite separation layer comprises a separator and an expansion relief layer on at least one side of the separator, A lithium metal battery, wherein the thickness of the expansion relief layer is configured to change in response to a change in the thickness of the lithium electrodeposition layer.

16. In paragraph 15, A lithium metal battery, wherein the thickness of the expansion relief layer is greater than the thickness of the separator.

17. In paragraph 16, The thickness of the above expansion relief layer is 10㎛ to 60㎛, A lithium metal battery, wherein the thickness of the separator is 2 μm to 40 μm.

18. In paragraph 15, A lithium metal battery, wherein the thickness of the composite separating layer is 25 ㎛ to 180 ㎛.

19. Preparing a composite separation layer by forming an expansion relief layer on at least one side of the separator; Providing a composite separating layer on the negative electrode current collector; Providing a first electrolyte solution on the above composite separation layer; Forming a first electrolyte layer by thermally crosslinking the first electrolyte solution, wherein the composite separating layer is impregnated into the first electrolyte layer; and Including providing an anode on the first electrolyte layer, Forming the above expansion relief layer includes electrospinning a polymer solution onto the separator, A method for manufacturing a lithium metal battery, wherein the thickness of the expansion relief layer is formed to be greater than the thickness of the separator.

20. In paragraph 19, Further comprising forming a second electrolyte layer between the first electrolyte layer and the anode, The first electrolyte layer comprises a first gel-polymer electrolyte, and the second electrolyte layer comprises a second gel-polymer electrolyte. A method for manufacturing a lithium metal battery, wherein the weight ratio of the polymer in the first gel-polymer electrolyte is greater than the weight ratio of the polymer in the second gel-polymer electrolyte.

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