Gel-type polymer electrolyte and lithium metal battery comprising same

Abstract

The present invention relates to a gel-type polymer electrolyte, a lithium metal battery comprising same, and a method for manufacturing same. More specifically, the gel-type polymer electrolyte of the present invention is a gel-type polymer electrolyte for a lithium metal battery, the electrolyte comprising an organic solvent, a fluorine-based lithium salt, an additive, and a crosslinked polymer, wherein the additive includes a cyclophosphazene-based compound, and the content of the cyclophosphazene-based compound is 1 wt% to 30 wt% relative to the total weight of the gel-type polymer electrolyte.

Description

Gel-type polymer electrolyte, and lithium metal battery including the same

[0001] The present invention relates to a gel-type polymer electrolyte and a lithium metal battery containing the same.

[0002] Currently available lithium batteries primarily use carbon-based negative electrode active materials, such as graphite. While carbon-based negative electrode active materials offer high stability due to their lack of volume change during charging and discharging, their low capacity necessitates the development of negative electrode active materials with higher capacities.

[0003] Lithium metal, which has a much larger theoretical capacity compared to carbon-based negative electrode active materials, can be used as a negative electrode active material. During charging and discharging, dendrites can form on the surface of lithium metal due to side reactions with the electrolyte, and as these dendrites grow, they can cause a short circuit between the positive and negative electrodes. Consequently, the lifespan characteristics of a lithium metal battery containing lithium metal may be degraded.

[0004] The problem that the present invention aims to solve is to provide a lithium metal battery with excellent initial discharge efficiency and lifespan characteristics.

[0005] Another problem that the present invention aims to solve is to provide a lithium metal battery with high ion conductivity and excellent thermal stability.

[0006] Another problem that the present invention aims to solve is to provide a method for manufacturing the lithium metal battery.

[0007] According to the concept of the present invention, a gel-type polymer electrolyte may comprise an organic solvent, a fluorinated lithium salt, an additive, and a crosslinking polymer. The additive may comprise a cyclic phosphazene compound, and the content of the cyclic phosphazene compound may be 1% to 30% by weight based on the total weight of the gel-type polymer electrolyte.

[0008] A lithium metal battery according to another concept of the present invention may include: a positive electrode comprising a positive current collector and a positive active material layer on the positive current collector; a negative electrode comprising a negative current collector; a separator disposed between the positive electrode and the negative electrode; and the gel-type polymer electrolyte.

[0009] A method for manufacturing a lithium metal battery according to another concept of the present invention comprises the steps of: forming an electrode assembly by arranging a negative electrode current collector, a separator, and a positive electrode; injecting a composition for forming a gel-type polymer electrolyte into the electrode assembly; and curing the composition for forming a gel-type polymer electrolyte, wherein the composition for forming a gel-type polymer electrolyte comprises an organic solvent, a fluorinated lithium salt, an additive, and a crosslinkable monomer, and the additive may comprise a cyclic phosphazene-based compound.

[0010] A lithium metal battery containing a gel-type polymer electrolyte according to the present invention has excellent initial discharge efficiency and lifespan characteristics.

[0011] In addition, the lithium metal battery containing the gel-type polymer electrolyte according to the present invention has high ion conductivity and excellent thermal safety.

[0012] FIG. 1 is a cross-sectional view of a lithium metal battery according to an exemplary embodiment.

[0013] FIG. 2 is a cross-sectional view of a lithium metal battery according to another exemplary embodiment.

[0014] FIGS. 3 and FIGS. 4 are schematic perspective views of a lithium metal battery according to an exemplary embodiment.

[0015] In order to fully understand the structure and effects of the present invention, preferred embodiments of the present invention are described with reference to the attached drawings. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various forms and various modifications can be made. The description of these embodiments is provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention.

[0016] In this specification, when a component is described as being on another component, it means that it may be formed directly on the other component or that a third component may be interposed between them. Additionally, in the drawings, the thicknesses of the components are exaggerated for the effective description of the technical content. Throughout the specification, parts indicated by the same reference numeral represent the same components.

[0017] The embodiments described herein will be described with reference to cross-sectional and / or plan views, which are exemplary illustrations of the invention. In the drawings, the thicknesses of films and regions are exaggerated for effective description of the technical content. Accordingly, the regions illustrated in the drawings are schematic in nature, and the shapes of the regions illustrated in the drawings are intended to illustrate specific forms of regions of the device and are not intended to limit the scope of the invention. Although terms such as first, second, third, etc., have been used to describe various components in the various embodiments of this specification, these components should not be limited by such terms. These terms are used merely to distinguish one component from another. The embodiments described and illustrated herein also include their complementary embodiments.

[0018] The terms used herein are for describing the embodiments and are not intended to limit the invention. In this specification, the singular form includes the plural form unless specifically stated otherwise in the text. As used herein, 'comprises' and / or 'comprising' do not exclude the presence or addition of one or more other components to the mentioned components.

[0019] Unless otherwise defined in this specification, the particle size may be the average particle size. Additionally, the particle size refers to the average particle size (D50), which means the diameter of the particle whose cumulative volume in the particle size distribution is 50% by volume. The average particle size (D50) may be measured by methods widely known to those skilled in the art, for example, by measuring with a particle size analyzer, or by measuring with a transmission electron microscope (TEM) image or a scanning electron microscope (SEM) image. Alternatively, the average particle size (D50) value may be obtained by measuring using a measuring device utilizing dynamic light scattering, performing data analysis to count the number of particles for each particle size range, and then calculating from this. Alternatively, it may be measured using a laser diffraction method. When measuring by laser diffraction, more specifically, after dispersing the particles to be measured in a dispersion medium, they are introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000) and irradiated with ultrasound of about 28 kHz at an output of 60 W, and then the average particle size (D50) at 50% of the particle size distribution in the measuring device can be calculated.

[0020] In this specification, “metal” includes both metals and metalloids such as silicon and germanium in an elemental or ionic state.

[0021] In this specification, “alloy” means a mixture of two or more metals.

[0022] In this specification, “electrode active material” refers to an electrode material capable of undergoing lithiation and delithiation.

[0023] In this specification, “anode active material” refers to an anode material capable of undergoing lithiation and delithiation.

[0024] In this specification, “anode active material” refers to an anode material capable of undergoing lithiation and delithiation.

[0025] In this specification, “lithiation” and “to lithiate” refer to the process of adding lithium to an electrode active material.

[0026] In this specification, “delithiation” and “to delithiate” refer to the process of removing lithium from an electrode active material.

[0027] In this specification, “charge” and “to charge” refer to the process of providing electrochemical energy to a battery.

[0028] In this specification, “discharge” and “discharge” refer to the process of removing electrochemical energy from a battery.

[0029] In this specification, “anode” and “cathode” refer to electrodes where electrochemical reduction and lithiation occur during the discharge process.

[0030] In this specification, “negative electrode” and “anode” refer to electrodes where electrochemical oxidation and delithiation occur during the discharge process. Although specific embodiments have been described, alternatives, modifications, variations, improvements, and substantial equivalents that are not currently anticipated or cannot be anticipated may arise to the applicant or those skilled in the art. Accordingly, the appended claims, which may be filed and modified, are intended to include all such alternatives, modifications, variations, improvements, and substantial equivalents.

[0031]

[0032] A lithium metal battery according to exemplary embodiments is described in more detail below.

[0033] Referring to FIG. 1, a lithium metal battery (100) according to one embodiment may include a positive electrode (10) comprising a positive current collector (11) and a positive active material layer (12) on the positive current collector (11); a negative electrode (20) comprising a negative current collector (21); a separator (30) disposed between the positive electrode (10) and the negative electrode (20); and a gel-type polymer electrolyte (not shown). The positive electrode (10), the negative electrode (20), and the separator (30) may be impregnated in the gel-type polymer electrolyte (not shown).

[0034] Referring to FIG. 2, the negative electrode (20) of a lithium metal battery (100) according to another embodiment may further include a lithium metal layer (22) disposed between a negative electrode current collector (21) and a separator (30). The lithium metal layer (22) may be a plated layer generated by charging the lithium metal battery (100).

[0035] A lithium metal battery (100) may use lithium metal as a negative electrode active material. During the charging and discharging process of the lithium metal battery, a lithium-containing metal layer may be precipitated and dissolved between the negative electrode current collector (21) and the separator (30). As the charging and discharging of the lithium metal battery is repeated, the lithium-containing metal layer may contain impurities remaining in the electrode, decomposition products of the electrolyte, etc.

[0036] The lithium-containing metal layer may have a rough and hard surface due to the inclusion of such impurities. Lithium dendrites may be deposited on the lithium-containing metal layer having such a rough surface. Lithium dendrites may continuously grow during the charging and discharging process and cause a short circuit between the positive electrode (10) and the negative electrode (20). Additionally, uneven growth of lithium dendrites on the negative electrode (20) during charging can easily cause damage within the cell, and the volume of the cell may expand significantly, making long-term operation difficult.

[0037] The positive electrode (10) and the negative electrode (20) may be spaced apart from each other with a separator (30) in between. The separator (30) may be placed between the positive electrode (10) and the negative electrode (20). The positive electrode (10), the negative electrode (20), and the separator (30) may come into contact with a gel-type polymer electrolyte (not shown).

[0038] A gel-type polymer electrolyte (not shown) may be a medium for transferring lithium ions between a positive electrode (10) and a negative electrode (20). Within the gel-type polymer electrolyte (not shown), the lithium ions may pass through a separator (30) and move toward the positive electrode (10) or the negative electrode (20).

[0039] Referring to FIGS. 3 and 4, the lithium metal battery (100) may include an electrode assembly (40) having a separator (30) interposed between a positive electrode (10) and a negative electrode (20), and a case (50) in which the electrode assembly (40) is housed. The positive electrode (10), the negative electrode (20), and the separator (30) may be impregnated with a gel-type polymer electrolyte (not shown). Referring to FIGS. 3 and 4, the lithium metal battery (100) may include electrode tabs (70), namely a positive electrode tab (71) and a negative electrode tab (72), which serve as electrical passages for inducing current formed in the electrode assembly (40) to the outside.

[0040]

[0041] positive electrode (10)

[0042] A positive electrode (10) for a lithium metal battery may include a positive electrode current collector (11) and a positive electrode active material layer (12) formed on the positive electrode current collector (11). The positive electrode active material layer (12) may include a positive electrode active material and may further include a binder and / or a conductive material. As an example, the positive electrode active material layer (12) may further include an additive that can serve as a sacrificial electrode.

[0043] The content of the positive active material in the positive active material layer (12) may be 90% to 99.5% by weight with respect to 100% by weight of the positive active material layer (12). The content of each of the binder and the conductive material may be 0.5% to 5% by weight with respect to 100% by weight of the positive active material layer (12).

[0044] The above binder can perform the function of adhering the positive active material particles well to each other and also adhering the positive active material well to the positive current collector (11). Representative examples of binders include polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers including ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, nylon, etc., but are not limited thereto.

[0045] The above conductive material can be used to impart conductivity to the electrode. Any electronically conductive material that does not cause chemical changes in the electrode can be used as the conductive material. Examples of conductive materials include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjenblack, carbon fiber, carbon nanofiber, carbon nanotube; metal-based materials containing copper, nickel, aluminum, silver, etc., in the form of metal powder or metal fibers; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0046] The positive current collector (11) can provide a reference surface on which the positive active material layer (12) is placed. The positive current collector (11) 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 current collector (11) may include a plate or a foil.

[0047] Meanwhile, unlike as illustrated in FIG. 1, the positive current collector (11) may be omitted in one embodiment. Although not illustrated, a carbon layer with a thickness of 0.1 μm to 4 μm may be further disposed between the positive current collector (11) and the positive active material layer (12) to increase the bonding strength between the positive current collector (11) and the positive active material layer (12).

[0048]

[0049] positive active material layer (12)

[0050] As the positive active material in the positive active material layer (12), a compound capable of reversible intercalation and deintercalation of lithium (a lithated intercalation compound) may be used. Specifically, one or more of the composite oxides of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof may be used.

[0051] The above composite oxide may be a lithium transition metal composite oxide, and specific examples include a lithium nickel-based oxide, a lithium cobalt-based oxide, a lithium manganese-based oxide, a lithium iron phosphate-based compound, a cobalt-free nickel-manganese-based oxide, or a combination thereof.

[0052] As an example, a compound represented by any one of the following chemical formulas may be used. Li a A 1-bXb O2- 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); LiaNi 1-b-c Mn b Xc 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); 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).

[0053] In the above chemical formula, A is Ni, Co, Mn, or a combination thereof; X is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; and L1 is Mn, Al, or a combination thereof.

[0054] A coating layer may be additionally added to the surface of the aforementioned compound. The coating layer may include, for example, an oxide, a hydroxide, an oxyhydroxide, an oxycarbonate, or a hydroxycarbonate of a coating element. The coating layer may be amorphous or crystalline. The coating element within the coating layer may be selected from the group consisting of Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, and Zr. The method of forming the coating layer may be selected within a range that does not adversely affect the physical properties of the cathode active material. The coating method may include, for example, spray coating or immersion methods.

[0055] For example, the above-mentioned positive electrode active material may be a high-nickel positive electrode active material in which the nickel content relative to 100 mol% of the metal excluding lithium in the lithium transition metal composite oxide is 80 mol% or more, 85 mol% or more, 90 mol% or more, 91 mol% or more, or 94 mol% or more and 99 mol% or less. The high-nickel positive electrode active material can achieve high capacity and can be applied to high-capacity, high-density lithium metal batteries.

[0056]

[0057] Negative electrode (20)

[0058] Referring to FIG. 1, a lithium metal battery (100) according to one embodiment may include a negative electrode (20) including a negative electrode current collector (21). The negative electrode current collector (21) may provide a reference surface on which a lithium metal layer (22), to be described later, is formed.

[0059] The negative electrode current collector (21) may include a material that does not react with lithium, for example, that is, does not form any alloys or compounds with lithium. The material constituting the negative electrode current collector (210) may include at least one metal selected from the group consisting of, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni). The thickness of the negative electrode current collector may be 1 to 20 μm, for example 5 to 15 μm, for example 7 to 10 μm.

[0060] The negative current collector (21) may be composed of one of the metals described above, or may include an alloy of two or more metals or a coating material. The negative current collector (21) is, for example, in the form of a plate or foil. Meanwhile, unlike what is shown in FIG. 1, the negative current collector (21) may be omitted in one embodiment. In the lithium metal battery (100) of FIG. 1, a lithium metal layer (22) may be formed after the operation of an initial cycle.

[0061] Referring to FIG. 2, the negative electrode (20) of a lithium metal battery (100) according to another embodiment may further include a lithium metal layer (22) disposed between a negative electrode current collector (21) and a separator (30). The lithium metal layer (22) may be a plated layer generated by charging the lithium metal battery (100).

[0062] The thickness of the lithium metal layer (22) may 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. By having the lithium metal layer (22) have a thickness within the above-described range, the energy density of the lithium metal battery can be improved.

[0063] The lithium metal layer (22) may include lithium or a lithium alloy. Since the lithium metal layer (22) is a metal layer containing lithium, it may function as, for example, a lithium reservoir. The lithium alloy may be, for example, a Li-Al alloy, a Li-Sn alloy, a Li-In alloy, a Li-Ag alloy, a Li-Au alloy, a Li-Zn alloy, a Li-Ge alloy, a Li-Si alloy, but is not limited to these; any alloy used as a lithium alloy in the relevant technical field may be possible. The lithium metal layer (22) may be composed of one of these alloys or lithium, or may be composed of various types of alloys.

[0064] In another embodiment, the lithium metal layer (22) within the negative electrode (20) may be provided on the negative electrode current collector (21), for example, before assembly of the lithium metal battery (100). When the lithium metal layer (22) is placed on the negative electrode current collector (21) before assembly of the lithium metal battery (100), the lithium metal layer (22) acts as a lithium reservoir because it is a metal layer containing lithium. For example, a lithium foil may be placed on the negative electrode current collector (21) before assembly of the lithium metal battery (100).

[0065] When a lithium metal layer (22) is deposited by charging after assembly of the lithium metal battery (100), the energy density of the lithium metal battery (100) can be increased because the lithium metal layer (22) is not included during assembly of the lithium metal battery (100). The lithium metal layer (22) can be composed mainly of lithium (i.e., metallic lithium). During discharge, the lithium in the lithium metal layer (22) can be ionized and move to the positive electrode (10). In other words, lithium can be used as a negative electrode active material in the lithium metal battery (100). When a lithium metal layer (22) is formed by charging after assembly of the lithium metal battery (100), the negative electrode (20), that is, the region between the negative electrode current collector (21) and the separator (30), may be a Li-free region that does not contain lithium (Li) in the initial state or after complete discharge of the lithium metal battery (100).

[0066]

[0067] Separator (30)

[0068] The separator (30) separates the positive electrode (10) and the negative electrode (20) and provides a pathway for the movement of lithium ions; any separator commonly used in lithium-ion batteries can be used. That is, a separator with low resistance to the movement of ions in the electrolyte and excellent electrolyte moisture retention capacity can be used.

[0069] Depending on the type of lithium metal battery, a separator (30) (or separator) may be provided between the positive electrode (10) and the negative electrode (20). As for this separator (30), polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof 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.

[0070] The separator (30) may include a porous substrate and a coating layer comprising an organic material, an inorganic material, or a combination thereof located on one or both sides of the porous substrate.

[0071] The porous substrate may be a polymer membrane formed from any one of the following: polyolefins such as polyethylene and polypropylene; polyesters such as polyethylene terephthalate and polybutylene terephthalate; polyacetal; polyamide; polyimide; polycarbonate; polyetherketone; polyaryletherketone; polyetherimide; polyamideimide; polybenzimidazole; polyethersulfone; polyphenylene oxide; cyclic olefin copolymer; polyphenylene sulfide; polyethylene naphthalate; glass fiber; Teflon; and polytetrafluoroethylene, or a copolymer or mixture of two or more of these.

[0072] The above organic material may include a polyvinylidene fluoride-based polymer or a (meth)acrylic-based polymer.

[0073] The above inorganic materials are Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, It may include, but is not limited to, inorganic particles selected from SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof.

[0074] The above organic and inorganic materials may exist mixed in a single coating layer, or may exist in a stacked form with a coating layer containing organic materials and a coating layer containing inorganic materials.

[0075] In one embodiment, the thickness of the separator (SEP) may be 1 μm to 15 μm. For example, the thickness of the separator (SEP) may be 3 μm to 15 μm, 3 μm to 12 μm, 5 μm to 12 μm, 3 μm to 10 μm, or 5 μm to 10 μm. If the thickness exceeds the above range, the resistance may increase due to an increase in the lithium ion movement path. If the thickness is below the above range, a short circuit may occur due to insufficient mechanical properties.

[0076]

[0077] Gel-type polymer electrolyte

[0078] The gel-type polymer electrolyte may include an organic solvent, a fluorinated lithium salt, an additive, and a crosslinking polymer. The additive may include a phosphazene-based compound.

[0079] Phosphazene-based compounds may be compounds comprising the structure of Chemical Formula 1 below. In the following chemical formula, n may be an integer of 1 or more. In the following chemical formula, R may be the same or different. In the following chemical formula, R may be, for example, a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, a halogen group, an amino group, or a substituent consisting of two or more of these groups.

[0080] [Chemical Formula 1]

[0081]

[0082] Phosphazene compounds may be low molecular weight phosphazene compounds or high molecular weight phosphazene compounds. Low molecular weight phosphazene compounds may be cyclophosphazenes or linear phosphazenes. High molecular weight phosphazene compounds may be polyphosphazenes.

[0083] Cyclic phosphazene compounds can be classified into cyclotriphosphazene compounds, cyclotetraphosphazene compounds, etc., depending on the number of phosphorus (P) and nitrogen (N) groups constituting the ring. Cyclotriphosphazene compounds can have a ring structure composed of 3 phosphorus (P) and 3 nitrogen (N) groups. Cyclotetraphosphazene compounds can have a ring structure composed of 4 phosphorus (P) and 4 nitrogen (N) groups.

[0084] Phosphazene compounds can contain various functional groups. The physicochemical properties of phosphazene compounds can vary depending on the functional groups. Phosphazene compounds can be flame-retardant depending on their structure or functional groups. Phosphazene compounds have high chemical stability, are biodegradable, and can form high-molecular-weight polymers. Due to these characteristics, phosphazene compounds can be used in various fields, such as biomaterials or plastic manufacturing.

[0085] In lithium batteries using conventional gel-type polymer electrolytes, if heat is continuously accumulated inside the battery, the electrolyte undergoes thermal decomposition to generate large amounts of hydrogen radicals (H·) and hydroxyl radicals (OH·), which can trigger a chain reaction of combustion in the electrolyte. However, when phosphazene is added as an additive, it generates PO· upon combustion, which reacts with H· and HO· to ​​terminate the chain reaction.

[0086] Phosphazene compounds can be classified according to their functional groups into alkyl phosphazene compounds, aryl phosphazene compounds, alkoxy phosphazene compounds, amino phosphazene compounds, halogenated phosphazene compounds, ester phosphazene compounds, imino phosphazene compounds, peroxy phosphazene compounds, carboxyl phosphazene compounds, etc.

[0087] In one embodiment, the additive may be, for example, a halogenated phosphazene-based compound.

[0088] The above halogenated phosphazene compounds can be classified, for example, phosphazene chloride, phosphazene bromide, phosphazene fluoride, phosphazene iodide, etc.

[0089] In one embodiment, the additive may be, for example, a fluorinated phosphazene-based compound.

[0090] Fluorinated phosphazene compounds include, for example, hexafluorocyclotriphosphazene, octafluorocyclotetraphosphazene, decafluorocyclopentaphosphazene, dodecafluorocyclohexaphosphazene, poly(difluorophosphazene), poly(fluoroalkylphosphazene), phenoxy(pentafluoro)cyclotriphosphazene (FPPN), ethoxy(pentafluoro)cyclotriphosphazene (EtPFPN), and methoxy(pentafluoro)cyclotriphosphazene. It may include isopropoxy(pentafluoro)cyclotriphosphazene, butoxy(pentafluoro)cyclotriphosphazene, trifluoromethoxy(pentafluoro)cyclotriphosphazene, or a combination thereof.

[0091] Fluorinated phosphazene compounds can be, for example, cyclic or linear.

[0092] In one embodiment, the additive may be, for example, a cyclic fluorinated phosphazene-based compound.

[0093] The above-mentioned fluorinated cyclic phosphazene compounds include hexafluorocyclotriphosphazene, octafluorocyclotetraphosphazene, decafluorocyclopentaphosphazene, dodecafluorocyclohexaphosphazene, phenoxy(pentafluoro)cyclotriphosphazene (FPPN), ethoxy(pentafluoro)cyclotriphosphazene (EtPFPN), methoxy(pentafluoro)cyclotriphosphazene, and isopropoxy(pentafluoro)cyclotriphosphazene. It may include butoxy(pentafluoro)cyclotriphosphazene, trifluoromethoxy(pentafluoro)cyclotriphosphazene, or a combination thereof.

[0094] In one embodiment, the additive may be, for example, a cyclotriphosphazene-based compound.

[0095] In one embodiment, the additive may be, for example, a fluorinated cyclotriphosphazene-based compound.

[0096] The above-mentioned fluorinated cyclotriphosphazene may include hexafluorocyclotriphosphazene, phenoxy(pentafluoro)cyclotriphosphazene (FPPN), ethoxy(pentafluoro)cyclotriphosphazene (EtPFPN), methoxy(pentafluoro)cyclotriphosphazene, isopropoxy(pentafluoro)cyclotriphosphazene, butoxy(pentafluoro)cyclotriphosphazene, trifluoromethoxy(pentafluoro)cyclotriphosphazene, or a combination thereof.

[0097] The content of the above phosphazene-based compound may be, for example, 1% to 30% by weight, 1% to 25% by weight, 1% to 20% by weight, 2% to 20% by weight, 3% to 20% by weight, or 3% to 15% by weight based on the total weight of the gel-type polymer electrolyte.

[0098] If the above phosphazene-based compound is less than 1% by weight relative to the total weight of the gel-type polymer electrolyte, it may not form enough PO· to ​​terminate the chain thermal decomposition process during the combustion of the electrolyte. In other words, thermal stability may be reduced.

[0099] If the above phosphazene-based compound exceeds 30% by weight relative to the total weight of the gel-type polymer electrolyte, the ionic conductivity may decrease. If the ionic conductivity decreases, the charge / discharge efficiency or lifespan characteristics of the lithium metal battery may be reduced.

[0100] The organic solvent may include a carbonate-based compound. The carbonate-based compound may include, for example, dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, dibutyl carbonate, propylene carbonate, ethylene carbonate (EC), fluoroethylene carbonate (FEC), butylene carbonate, vinylene carbonate, or a combination thereof.

[0101] Fluorinated lithium salts may include, for example, lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium trifluoromethanesulfonate (LiCF3SO3), lithium tetrafluoroborate (LiBF4), lithium perfluorooxalatoborate (LiFOP), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium fluoroethylene carbonate (LiFEC), lithium difluoro(oxalato)borate (LiDFOB), or combinations thereof.

[0102] Fluorinated lithium salts may be added to a liquid electrolyte at concentrations of, for example, 0.1 M to 2 M, 0.2 M to 2 M, 0.3 M to 2 M, 0.4 M to 2 M, 0.5 M to 1.5 M, or 0.6 M to 1.2 M, but are not limited thereto as long as the concentration range can be appropriately selected by a person skilled in the art.

[0103] A cross-linked polymer can be a polymerization product of a cross-linkable monomer.

[0104] The above-mentioned crosslinkable monomers are, for example, trimethylolpropane trimethacrylate (TMPTMA), dipentaerythritol hexaacrylate (DPHA), pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate, trimethylolpropane triacrylate, propoxylate (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) It may include isocyanurate triacrylate (THEICTA), dipentaerythritol pentaacrylate (DPEPA), or a combination thereof.

[0105] The molecular weight of the cross-linked polymer may be 5000 g / mol or less. The molecular weight of the cross-linked polymer may be 100 g / mol to 5000 g / mol. If the molecular weight of the cross-linked polymer is 5000 g / mol or less, the impregnation to the anode may be increased. In addition, the ionic conductivity of the gel-type polymer electrolyte may be improved. If the molecular weight of the cross-linked polymer is less than 1000 g / mol, the ionic conductivity of the electrolyte is low and it may be structurally unstable.

[0106] The content of the crosslinking polymer may be, for example, less than 60 wt%, 1 wt% to 50 wt%, 1 wt% to 45 wt%, 1 wt% to 40 wt%, 1 wt% to 35 wt%, 1 wt% to 30 wt%, 1 wt% to 25 wt%, 1 wt% to 20 wt%, 1 wt% to 15 wt%, 1 wt% to 10 wt%, 1 wt% to 9 wt%, 1 wt% to 8 wt%, 1 wt% to 7 wt%, 1 wt% to 6 wt%, or 1 wt% to 5 wt% based on the total weight of the gel polymer electrolyte, but is not limited thereto as long as it is an appropriate concentration that can form a gel polymer electrolyte by adding it to a liquid electrolyte.

[0107] A gel polymer electrolyte can be formed by crosslinking a composition for forming a gel polymer electrolyte. The method of crosslinking the composition for forming a gel polymer electrolyte is not particularly limited and may be crosslinked by, for example, heat, ultraviolet light, etc. Thermal crosslinking may be used from the perspective of manufacturing efficiency. The composition for forming a gel polymer may include, for example, a thermal initiator. The thermal initiator may be, for example, tert-butyl peroxypivalate (TBPP), t-amyl peroxide, azobis-based, etc., but is not limited to these; any material used as a thermal initiator in the relevant technical field is acceptable. The content of the thermal initiator may be 0.1% by weight or less or 0.05% by weight or less of the total weight of the composition for forming a gel polymer electrolyte. The crosslinking product of the composition for forming a gel polymer electrolyte may be, for example, the result of heat treatment at 40 to 120°C for 1 to 3 hours. The heat treatment conditions may be adjusted according to the type of thermal initiator used.

[0108] The gel-type polymer electrolyte can be manufactured by pouring it into a battery case (50) into which an electrode assembly (40) is inserted and then curing it, and thus has the advantage of being applicable to the existing non-aqueous electrolyte battery manufacturing process.

[0109] The gel-type polymer electrolyte can maintain good processability by maintaining low viscosity when injected into the battery case (50). The gel-type polymer electrolyte can be easily cured by thermal curing or photocuring and thus can have a gel form.

[0110]

[0111] lithium metal battery (100)

[0112] Referring to FIGS. 1 and 2, a lithium metal battery (100) according to one embodiment may include an electrode assembly (40) comprising a positive electrode (10), a negative electrode (20), and a separator (30) disposed between the positive electrode (10) and the negative electrode (20). Although not illustrated, the positive electrode (10), the negative electrode (20), and the separator (30) of the electrode assembly (40) may be supported by a gel-type polymer electrolyte. Since the configuration of the positive electrode (10), the negative electrode (20), the gel-type polymer electrolyte, etc., can be applied as described above, a detailed description is omitted below.

[0113] According to one embodiment, referring to FIG. 1, the negative electrode (20) may include only a negative electrode current collector (21). According to another embodiment, referring to FIG. 2, the negative electrode (20) may include a negative electrode current collector (21) and a lithium metal layer (22) on the negative electrode current collector (21).

[0114] Referring to FIGS. 1 and 2, the anode (10), separator (30), and cathode (20) can be wound, folded, or stacked to form an electrode assembly (40).

[0115] Referring to FIGS. 3 and 4, the formed electrode assembly (40) can be housed in a battery case (50). The battery case (50) may contain a gel-type polymer electrolyte inside. An electrolyte layer can be formed by injecting an electrolyte into the battery case (50). The lithium metal battery (100) may include electrode tabs (70), namely a positive electrode tab (71) and a negative electrode tab (72), which serve as electrical pathways for inducing the current formed in the electrode assembly (40) to the outside. The battery case (50) may include, for example, a cylindrical, prismatic, thin-film type, etc.

[0116] A battery case (50) according to one embodiment may be of the pouch type. An electrode assembly (40) may be laminated in a bicell structure, then impregnated with an electrolyte, and then housed and sealed in a pouch to manufacture a pouch-type lithium metal battery.

[0117] The main body forming the pouch-type battery case according to one embodiment may be composed of a multilayer film, and the multilayer film may include an aluminum (Al) layer, a polymer film, and an adhesive layer. In this case, a pouch-type cell with a flexible and lightweight structure can be manufactured.

[0118] Lithium metal batteries have excellent lifespan and high-rate characteristics, so they can be used, for example, in electric vehicles (EVs). For example, they can be used in plug-in hybrid electric vehicles (PHEVs). In addition, they can be used in fields requiring large amounts of power storage. For example, they can be used in electric bicycles, power tools, etc.

[0119] Multiple lithium metal batteries can be stacked to form a battery module. Multiple battery modules can constitute a battery pack. Such a battery pack can be used in any device requiring high capacity and high output. For example, it can be used in laptops, smartphones, electric vehicles, etc. For example, a battery module may include multiple batteries and a frame that supports them.

[0120] A battery pack may include, for example, a plurality of battery modules and a bus bar connecting them. The battery modules and / or the battery pack may further include a cooling device. A plurality of battery packs may be controlled by a battery management system. The battery management system may include a battery pack and a battery control device connected to the battery pack.

[0121]

[0122] Method for manufacturing a lithium metal battery

[0123] A lithium metal battery according to one embodiment may be manufactured by arranging a negative electrode current collector, a separator, and a positive electrode to form an electrode assembly; housing the electrode assembly in a battery case, and then injecting a composition for forming a gel-type polymer electrolyte into the battery case; and curing the composition for forming a gel-type polymer electrolyte to form the gel-type polymer electrolyte described above.

[0124] A composition for forming a gel-type polymer electrolyte may include a liquid electrolyte comprising an organic solvent, a fluorinated lithium salt, and an additive; a crosslinkable monomer; and a thermal initiator. Since the contents regarding the liquid electrolyte comprising an organic solvent, a fluorinated lithium salt, and an additive, and the crosslinkable monomer can be applied as described above, a detailed description is omitted below.

[0125] The thermal initiator may include, for example, tert-butyl peroxypivalate (TBPP), t-amyl peroxide, benzoyl peroxide (BPO), azobis-isobutyronitrile (AIBN), dicumyl peroxide (DCP), tert-butyl peroxybenzoate (TBPB), lauroyl peroxide, or a combination thereof. The content of the thermal initiator may be 0.1 wt% or less or 0.05 wt% or less of the total weight of the composition for forming a gel-type polymer electrolyte.

[0126] Injecting the composition for forming a gel-type polymer electrolyte into the battery case can be performed under vacuum so that the composition can sufficiently penetrate the positive electrode, negative electrode, and separator.

[0127] Methods for curing a composition for forming a gel-type polymer electrolyte include curing using heat treatment, UV, or high-energy radiation (electron beam, γ-ray). The curing reaction using heat treatment can be carried out for 30 to 120 minutes at a temperature of 40 to 120 ℃, for example, 50 to 90 ℃.

[0128] The above heat treatment varies depending on the type of crosslinkable monomer, but can be performed, for example, at 40 to 120°C. When the heat treatment is performed within the above range, the electrolyte wettability of the separator is increased, thereby providing a lithium metal battery (100) with improved lifespan characteristics.

[0129]

[0130] The creative idea is explained in more detail through the following examples and comparative examples. However, the examples are intended to illustrate the creative idea and do not limit the scope of the creative idea to these examples alone.

[0131]

[0132] Example 1

[0133] (Electrolyte manufacturing)

[0134] A liquid electrolyte was prepared by adding 1 M lithium hexafluorophosphate (LiPF6) and ethoxy(pentafluoro)cyclotriphosphazene (EtPFPN) to an organic solvent mixed with ethylene carbonate (EC) and diethyl carbonate (DEC) in a 1:1 volume ratio. At this time, EtPFPN was added in an amount of 5% by weight relative to the total weight of the gel-type polymer electrolyte.

[0135] A composition for forming a gel-type polymer electrolyte was prepared by adding a crosslinking monomer, TMPTMA (Trimethylolpropane trimethacrylate), and a thermal initiator, tert-Butyl peroxypivalate (TBPP), to form a gel electrolyte. At this time, the content of TMPTMA is 5 wt% of the total weight of the gel-type polymer electrolyte, and the content of TBPP is 0.1 wt% of the total weight of the gel-type polymer electrolyte.

[0136] (Manufacture of cathode current collector)

[0137] A copper foil with a thickness of 10 μm was used as the cathode current collector.

[0138] (Anode manufacturing)

[0139] LiNi 0.8 Co 0.15 Al 0.05 O2(NCA) powder and carbon conductive material (Super-P; Timcal Ltd.) were uniformly mixed in a weight ratio of 90:5, and then a PVDF (polyvinylidene fluoride) binder solution was added to prepare an anode active material slurry with a weight ratio of active material:carbon-based conductive material:binder = 90:5:5.

[0140] The prepared slurry was coated onto an aluminum substrate with a thickness of 20 μm using a doctor blade, dried under reduced pressure at 120 °C, and then rolled into a sheet shape using a roll press to manufacture an anode. The thickness of the anode active material layer was 80 μm.

[0141] (Lithium battery manufacturing)

[0142] A laminate was prepared by placing a polyethylene separator between the manufactured positive and negative current collectors. After injecting the above-prepared gel-type polymer electrolyte forming composition into the prepared laminate, a lithium battery containing a gel-type polymer electrolyte was manufactured by thermally crosslinking in a 70°C oven for 1 hour and 30 minutes.

[0143] The lithium battery had a positive electrode / gel-type polymer electrolyte (separator) / negative electrode current collector structure.

[0144]

[0145] Example 2

[0146] In Example 2, a lithium metal battery was manufactured in the same manner as in Example 1 described above, except that the electrolyte composition was changed. The electrolyte of Example 2 was prepared as follows.

[0147] A liquid electrolyte was prepared by adding 1 M lithium hexafluorophosphate (LiPF6) and phenoxy(pentafluoro)cyclotriphosphazene (FPPN) to an organic solvent mixed with ethylene carbonate (EC) and diethyl carbonate (DEC) in a 1:1 volume ratio. At this time, FPPN was added at 7 wt% of the total weight of the gel-type polymer electrolyte.

[0148] A composition for forming a gel-type polymer electrolyte was prepared by adding a crosslinking monomer, TMPTMA (Trimethylolpropane trimethacrylate), and a thermal initiator, tert-Butyl peroxypivalate (TBPP), to form a gel electrolyte. At this time, the content of TMPTMA is 5 wt% of the total weight of the gel-type polymer electrolyte, and the content of TBPP is 0.1 wt% of the total weight of the gel-type polymer electrolyte.

[0149]

[0150] Example 3

[0151] In Example 3, a lithium metal battery was manufactured in the same manner as in Example 1 described above, except that the electrolyte composition was changed. The electrolyte of Example 3 was prepared as follows.

[0152] A liquid electrolyte was prepared by adding 0.6 M lithium tetrafluoroborate (LiBF4), 0.6 M lithium difluoro(oxalato)borate (LiDFOB), and ethoxy(pentafluoro)cyclotriphosphazene (EtPFPN) to an organic solvent mixed with diethyl carbonate (DEC) and fluoroethylene carbonate (FEC) in a 2:1 volume ratio. At this time, EtPFPN was added to be 7 wt% of the total weight of the gel-type polymer electrolyte.

[0153] A composition for forming a gel-type polymer electrolyte was prepared by adding a crosslinking monomer, DPHA (dipentaerythritol hexacrylate), and a thermal initiator, tert-butyl peroxypivalate (TBPP), to form a gel electrolyte. At this time, the content of DPHA is 7 wt% of the total weight of the gel-type polymer electrolyte, and the content of TBPP is 0.1 wt% of the total weight of the gel-type polymer electrolyte.

[0154]

[0155] Example 4

[0156] In Example 4, a lithium metal battery was manufactured in the same manner as in Example 1 described above, except that the electrolyte composition was changed. The electrolyte of Example 4 was prepared as follows.

[0157] A liquid electrolyte was prepared by adding 1 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and methoxy(pentafluoro)cyclotriphosphazene (MtPFPN) to dimethyl carbonate (DMC). At this time, MtPFPN was added at 12 wt% of the total weight of the gel-type polymer electrolyte.

[0158] A composition for forming a gel-type polymer electrolyte was prepared by adding a crosslinking monomer, DPHA (dipentaerythritol hexacrylate), and a thermal initiator, tert-butyl peroxypivalate (TBPP), to form a gel electrolyte. At this time, the content of DPHA is 10 wt% of the total weight of the gel-type polymer electrolyte, and the content of TBPP is 0.1 wt% of the total weight of the gel-type polymer electrolyte.

[0159]

[0160] Example 5

[0161] In Example 5, a lithium metal battery was manufactured in the same manner as in Example 1 described above, except that the electrolyte composition was changed. The electrolyte of Example 5 was prepared as follows.

[0162] A liquid electrolyte was prepared by adding 0.6 M lithium tetrafluoroborate (LiBF4), 0.6 M lithium difluoro(oxalato)borate (LiDFOB), and phenoxy(pentafluoro)cyclotriphosphazene (FPPN) to an organic solvent mixed with diethyl carbonate (DEC) and fluoroethylene carbonate (FEC) in a 2:1 volume ratio. At this time, FPPN was added to an amount of 10 wt% relative to the total weight of the gel-type polymer electrolyte.

[0163] A composition for forming a gel-type polymer electrolyte was prepared by adding a crosslinking monomer, DPHA (dipentaerythritol hexacrylate), and a thermal initiator, tert-butyl peroxypivalate (TBPP), to form a gel electrolyte. At this time, the content of DPHA is 5 wt% of the total weight of the gel-type polymer electrolyte, and the content of TBPP is 0.1 wt% of the total weight of the gel-type polymer electrolyte.

[0164]

[0165] Comparative Example 1: No addition of phosphazene-based compound

[0166] In Comparative Example 1, a lithium metal battery was manufactured in the same manner as in Example 1 described above, except that the electrolyte composition was changed. In addition, the electrolyte composition of Comparative Example 1 is the same as the electrolyte composition of Example 5, except that the phosphazene-based compound phenoxy(pentafluoro)cyclotriphosphazene (FPPN) was not added.

[0167]

[0168] Comparative Example 2: Excess addition of phosphazene-based compound

[0169] In Comparative Example 2, a lithium metal battery was manufactured in the same manner as in Example 1 described above, except that the electrolyte composition was changed. In addition, the electrolyte composition of Comparative Example 2 is the same as in Example 4, but the content of MtPFPN is 40 wt% instead of 12 wt% relative to the total weight of the gel-type polymer electrolyte.

[0170]

[0171] Table 1 below shows the compositions of the above-described Examples 1 to 5 and Comparative Examples 1 to 3.

[0172] Lithium Salt Organic Solvent Additive (Wt%*) Crosslinkable Monomer (Wt%*) Example 1 LiPF61 MEC, DECEtPFPN (5 wt%) TMPTMA (5 wt%) Example 2 LiPF61 MEC, DECEtPFPN (7 wt%) TMPTMA (5 wt%) Example 3 LiBF 40.6 M, LiDFOB 0.6 MDEC, FECEtPFPN (7 wt%) DPHA (7 wt%) Example 4 LiTFSI1 MDMCMtPFPN (12 wt%) DPHA (10 wt%) Example 5 LiBF 40.6 M, LiDFOB 0.6 MDEC, FECEtPFPN (10 wt%) DPHA (5 wt%) Comparative Example 1 LiBF 40.6 M, LiDFOB 0.6 MDEC, FECEtPFPN (10 wt%) DPHA (5 wt%) Comparative Example 2 LiTFSI1 MDMCMtPFPN (40 wt%) DPHA (10 wt%)

[0173] The above weight % is based on the total weight of the gel-type polymer electrolyte.

[0174] Evaluation Example 1: Measurement of Ionic Conductivity

[0175] The ionic conductivity of the gel-type polymer electrolyte used in the lithium metal batteries of Examples 1 to 5 and Comparative Examples 1 to 3 was measured.

[0176] Ionic conductivity was measured using the AC impedance method. Specifically, ionic conductivity was measured by applying a voltage bias of 10 mV to the electrolyte in the frequency range of 0.1 Hz to 1 MHz, scanning the temperature, and measuring the resistance.

[0177] The measurement results were as shown in Table 2 below. That is, it was confirmed that the ionic conductivity was low when an excess amount of the additive, a phosphazene-based compound, was added as in Comparative Example 2.

[0178]

[0179] Ionic Conductivity (mS / cm) Example 13.7 Example 23.6 Example 33.3 Example 43.2 Example 53.2 Comparative Example 13.7 Comparative Example 21.1

[0180] Evaluation Example 2: Initial Charge / Discharge Efficiency and Lifetime Characteristics of Lithium Metal Batteries

[0181] The initial charge / discharge efficiency and lifespan characteristics of the lithium metal batteries of Examples 1 to 5 and Comparative Examples 1 and 2 were evaluated under the following conditions.

[0182] Constant current charging was performed at 25 ℃ with a current rate of 0.1 C until the voltage reached 4.2 V (vs. Li), and then cut-off was performed at a current rate of 0.05 C while maintaining 4.2 V in constant voltage mode. Subsequently, discharge was performed at a constant current rate of 0.1 C until the voltage reached 3.0 V (vs. Li) during discharge (formation cycle).

[0183] A lithium metal battery that has undergone a formation cycle was charged at a constant current rate of 0.2 C at 25 ℃ until the voltage reached 4.2 V (vs. Li), and then cut off at a current rate of 0.05 C while maintaining 4.2 V in constant voltage mode. Subsequently, it was discharged at a constant current rate of 0.2 C until the voltage reached 3.0 V (vs. Li) during discharge (1st cycle). These cycles were repeated under the same conditions until the capacity retention rate reached 80%.

[0184] In all charge / discharge cycles, a 10-minute pause was taken after each charge / discharge cycle.

[0185] Initial charge / discharge efficiency (ICE) is defined by the following Equation 1:

[0186] <Mathematical Formula 1>

[0187] Initial charge / discharge efficiency [%] = [First cycle discharge capacity / First cycle charge capacity] × 100

[0188] Life characteristics are defined as the number of cycle repetitions until the capacity retention rate reaches 80%, and the capacity retention rate is defined by the following mathematical formula 2.

[0189] <Mathematical Formula 2>

[0190] Capacity Retention Rate [%] = [Discharge Capacity after n cycles / Discharge Capacity at 1st cycle] × 100 (%)

[0191] (where n is a natural number greater than or equal to 2)

[0192] The evaluation results are as shown in Table 3 below.

[0193] Initial Charge / Discharge Efficiency (%) Lifestyle Characteristics (Number of Cycle Repetitions) Example 189.2201 Example 289.4198 Example 389.6225 Example 488.2222 Example 589.1217 Comparative Example 188.1158 Comparative Example 288.586

[0194] Evaluation Example 3: Thermal Stability

[0195] Thermal stability was evaluated by measuring the self-extinguish time of the gel-type polymer electrolyte used in the lithium metal batteries of Examples 1 to 5 and Comparative Examples 1 to 2.

[0196] Self-extinguishing time measurement refers to the time it takes for a sample to extinguish a fire on its own after being exposed to a flame under specific test conditions. To measure this, the gel-type polymer electrolytes used in Examples 1 to 5 and Comparative Examples 1 and 2 were coated to a uniform thickness on a non-combustible substrate. The electrolyte coated on the substrate was exposed to a flame using a torch, and the time until the flame on the burning electrolyte was extinguished was measured. As a result, as shown in Table 4, it was confirmed that the self-extinguishing time in the gel-type polymer electrolyte was significantly reduced when a phosphazene-based compound was added as an additive.

[0197]

[0198] Self-extinguishing time (sec) Example 137 Example 232 Example 330 Example 427 Example 529 Comparative Example 1135 Comparative Example 225

[0199] In summary, it was confirmed that in the case of Examples 1 to 5, it is possible to manufacture a lithium metal battery with excellent thermal stability, as well as excellent ion conductivity, initial charge / discharge efficiency, and lifespan characteristics.

[0200] Although an exemplary embodiment has been described in detail above with reference to the attached drawings, the present creative idea is not limited to such examples. It is obvious that a person skilled in the art to which the present creative idea belongs can derive various variations or modifications within the scope of the technical idea described in the patent claims, and these also naturally fall within the technical scope of the present creative idea.

Claims

1. Comprising an organic solvent, a fluorinated lithium salt, an additive, and a crosslinked polymer, The above additive includes a cyclic phosphazene compound, and The content of the above-mentioned cyclic phosphazene compound is 1% to 30% by weight based on the total weight of the above-mentioned gel-type polymer electrolyte, Gel-type polymer electrolyte for lithium metal batteries.

2. In Paragraph 1, The above additive comprises a halogenated cyclophosphazene-based compound, Gel-type polymer electrolyte for lithium metal batteries.

3. In Paragraph 1, The above additive comprises a fluorinated cyclophosphazene-based compound, Gel-type polymer electrolyte for lithium metal batteries.

4. In Paragraph 3, The above-mentioned fluorinated cyclic phosphazene compounds include hexafluorocyclotriphosphazene, octafluorocyclotetraphosphazene, decafluorocyclopentaphosphazene, dodecafluorocyclohexaphosphazene, phenoxy(pentafluoro)cyclotriphosphazene (FPPN), ethoxy(pentafluoro)cyclotriphosphazene (EtPFPN), methoxy(pentafluoro)cyclotriphosphazene, and isopropoxy(pentafluoro)cyclotriphosphazene. butoxy(pentafluoro)cyclotriphosphazene, trifluoromethoxy(pentafluoro)cyclotriphosphazene, or a combination thereof, comprising butoxy(pentafluoro)cyclotriphosphazene, trifluoromethoxy(pentafluoro)cyclotriphosphazene, or a combination thereof Gel-type polymer electrolyte for lithium metal batteries.

5. In Paragraph 1, The above additive comprises a fluorinated cyclotriphosphazene-based compound, Gel-type polymer electrolyte for lithium metal batteries.

6. In Paragraph 5, The above-mentioned fluorinated cyclotriphosphazene-based compound comprises hexafluorocyclotriphosphazene, phenoxy(pentafluoro)cyclotriphosphazene (FPPN), ethoxy(pentafluoro)cyclotriphosphazene (EtPFPN), methoxy(pentafluoro)cyclotriphosphazene, isopropoxy(pentafluoro)cyclotriphosphazene, butoxy(pentafluoro)cyclotriphosphazene, trifluoromethoxy(pentafluoro)cyclotriphosphazene, or a combination thereof. Gel-type polymer electrolyte for lithium metal batteries.

7. In Paragraph 5, The above-mentioned fluorinated cyclotriphosphazene compound is phenoxy(pentafluoro)cyclotriphosphazene (FPPN), ethoxy(pentafluoro)cyclotriphosphazene (EtPFPN), methoxy(pentafluoro)cyclotriphosphazene (Methoxy(pentafluoro)cyclotriphosphazene), or a combination thereof. Gel-type polymer electrolyte for lithium metal batteries.

8. In Paragraph 1, The above organic solvent includes a carbonate-based compound, Gel-type polymer electrolyte for lithium metal batteries.

9. In Paragraph 8, The above carbonate-based compound comprises dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, dibutyl carbonate, propylene carbonate, ethylene carbonate (EC), fluoroethylene carbonate (FEC), butylene carbonate, vinylene carbonate, or a combination thereof. Gel-type polymer electrolyte for lithium metal batteries.

10. In Paragraph 1, The above-mentioned fluorinated lithium salt comprises lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium trifluoromethanesulfonate (LiCF3SO3), lithium tetrafluoroborate (LiBF4), lithium perfluorooxalatoborate (LiFOP), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium fluoroethylene carbonate (LiFEC), lithium difluoro(oxalato)borate (LiDFOB), or a combination thereof. Gel-type polymer electrolyte for lithium metal batteries.

11. In Paragraph 1, The above-mentioned crosslinked polymer is a polymerization product of crosslinkable monomers, and The above crosslinkable monomers are trimethylolpropane trimethacrylate (TMPTMA), dipentaerythritol hexaacrylate (DPHA), pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate, trimethylolpropane triacrylate, propoxylate (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) Comprising isocyanurate triacrylate (THEICTA), dipentaerythritol pentaacrylate (DPEPA), or a combination thereof, Gel-type polymer electrolyte for lithium metal batteries.

12. In Paragraph 1, The molecular weight of the above-mentioned crosslinked polymer is 100 g / mol to 5000 g / mol, Gel-type polymer electrolyte for lithium metal batteries.

13. In Paragraph 1, The content of the cross-linked polymer is 1% to 50% by weight based on the total weight of the gel-type polymer electrolyte, Gel-type polymer electrolyte for lithium metal batteries.

14. A positive electrode comprising a positive current collector and a positive active material layer on the positive current collector; A cathode including a cathode current collector; A separator disposed between the anode and the cathode; and Comprising the gel-type polymer electrolyte of claim 1, Lithium metal battery.

15. In Paragraph 14, The region between the above-mentioned negative current collector and the above-mentioned separator is a Li-free region that does not contain lithium (Li). Lithium metal battery.

16. In Paragraph 14, The above cathode further includes a lithium metal layer disposed between the cathode current collector and the separator, and The above lithium metal layer comprises lithium or a lithium alloy, Lithium metal battery.

17. In Paragraph 16, The above lithium alloy comprises a Li-Al alloy, a Li-Sn alloy, a Li-In alloy, a Li-Ag alloy, a Li-Au alloy, a Li-Zn alloy, a Li-Ge alloy, a Li-Si alloy, or a combination thereof. Lithium metal battery.

18. A step of forming an electrode assembly by arranging a cathode current collector, a separator, and an anode; A step of injecting a composition for forming a gel-type polymer electrolyte into the electrode assembly; and The method comprises the step of curing the above-mentioned gel-type polymer electrolyte-forming composition, wherein The above-mentioned composition for forming a gel-type polymer electrolyte comprises an organic solvent, a fluorinated lithium salt, an additive, and a crosslinkable monomer, and The above additive comprises a cyclic phosphazene-based compound, Method for manufacturing a lithium metal battery.

19. In Paragraph 18, The content of the above-mentioned cyclic phosphazene compound is 1% to 30% by weight based on the total weight of the above-mentioned gel-type polymer electrolyte, Method for manufacturing a lithium metal battery.

20. In Paragraph 18, The step of curing the above-mentioned gel-type polymer electrolyte-forming composition includes performing a curing reaction using heat treatment, and The above heat treatment is performed at 40 ℃ to 120 ℃, Method for manufacturing a lithium metal battery.

Images