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

Abstract

Disclosed are a gel-type polymer electrolyte, a lithium metal battery comprising same, and a method for manufacturing same, the electrolyte including: a lithium salt; an organic solvent including a first compound represented by chemical formula 1 and a second compound which is a fluorine-substituted cyclic carbonate-based compound; and a cross-linked polymer having two or more functional groups, wherein the weight ratio of the first compound and the second compound is 20:1 to 1:5 (chemical formula 1 is the same as described in the specification).

Description

Gel-type polymer electrolyte, lithium metal battery containing the same, and method for manufacturing the same

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

[0002]

[0003] Currently commercially available lithium secondary batteries mainly use carbon-based negative electrode active materials such as graphite. Carbon-based negative electrode active materials do not change in volume during charging and discharging, so the stability of lithium secondary batteries is high. The theoretical electric capacity of graphite is small, about 372 mAh / g.

[0004] Lithium metal can be used as a negative electrode active material. The theoretical electric capacity of lithium metal is approximately 3,860 mAh / g, which is larger than that of graphite. During charging and discharging, dendrites may form on the surface of lithium metal due to side reactions with the electrolyte, and the growth of these dendrites can cause a short circuit between the positive and negative electrodes. Consequently, the lifespan characteristics of lithium metal batteries containing lithium metal may be degraded.

[0005] To solve the aforementioned problems, methods have been proposed in which a protective film is introduced to minimize contact between lithium and the electrolyte to reduce side reactions, or in which a gel polymer electrolyte is used to minimize the exposure of the electrolyte on the electrode surface and create a uniform flow of lithium ions throughout the electrode to suppress lithium dendrite growth by introducing the liquid electrolyte into the network of the cross-linked polymer.

[0006]

[0007] One aspect is to provide a lithium metal battery with improved lifespan characteristics.

[0008] Another aspect is to provide a lithium metal battery with improved swelling resistance.

[0009]

[0010] According to one embodiment, a gel-type polymer electrolyte is provided, comprising: a lithium salt; an organic solvent comprising a first compound represented by the following chemical formula 1 and a second compound which is a fluorine-substituted cyclic carbonate-based compound; and a crosslinked polymer having two or more functional groups, wherein the weight ratio of the first compound to the second compound is 20:1 to 1:5.

[0011] [Chemical Formula 1]

[0012]

[0013] In the above chemical formula 1,

[0014] L1 is a single-bonded or substituted or unsubstituted C1 to C10 alkylene group, and

[0015] R1 is a substituted or unsubstituted C1 to C10 alkyl group, and

[0016] X1, X2, and X3 are each one of the same or different halogen elements.

[0017] According to another embodiment, a lithium metal battery is provided comprising: a positive electrode including a positive current collector and a positive active material layer on the positive current collector; a negative electrode current collector; a separator disposed between the positive electrode and the negative electrode current collector; and the gel-type polymer electrolyte described above.

[0018] A method for manufacturing a lithium metal battery is provided, comprising: forming an electrode assembly by arranging a negative electrode current collector, a separator, and a positive electrode according to another embodiment; 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 of claim 1.

[0019]

[0020] In one aspect, by employing a gel polymer electrolyte mixed with different types of solvents, it is possible to provide a lithium metal battery with improved lifespan characteristics, reduced gas generation, and improved swelling.

[0021]

[0022] FIG. 1 is a cross-sectional view of a lithium metal battery according to an exemplary embodiment.

[0023] FIG. 2 is a cross-sectional view of a lithium metal battery according to another exemplary embodiment.

[0024] FIGS. 3 and 4 are schematic perspective views of a lithium metal battery according to an exemplary embodiment.

[0025]

[0026] The present inventive concept described below is subject to various modifications and may have various embodiments, and specific embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the present inventive concept to specific embodiments and should be understood to include all modifications, equivalents, or substitutions that fall within the scope of the description of the present inventive concept.

[0027] The terms used below are used merely to describe specific embodiments and are not intended to limit the creative concept. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the following, terms such as “comprising” or “having” are intended to indicate the existence of the features, numbers, steps, actions, components, parts, components, materials, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, components, materials, or combinations thereof. The “ / ” used below may be interpreted as “and” or “or” depending on the context.

[0028] In the drawings, thicknesses have been enlarged or reduced to clearly represent various layers and regions. Throughout the specification, the same reference numerals have been used for similar parts. Throughout the specification, when a part such as a layer, film, region, or plate is described as being “on” or “above” another part, this includes not only cases where it is directly above another part but also cases where there is another part in between. Throughout the specification, terms such as “first,” “second,” etc., may be used to describe various components, but the components should not be limited by these terms. In this specification and drawings, components having substantially the same functional configuration are referred to by the same reference numerals to avoid redundant descriptions.

[0029] In the present disclosure, the “size” of a particle is, for example, the “particle diameter” of the particle. The “particle diameter” of the particle represents the average diameter when the particle is spherical and represents the average major axis length when the particle is non-spherical. The particle diameter of the particle can be measured using a particle size analyzer (PSA). The “particle diameter” of the particle is, for example, the average particle diameter. The average particle diameter is, for example, the median particle diameter (D50). The median particle diameter (D50) is the particle size corresponding to the 50% cumulative volume calculated from the side of the particle having a small particle size in the particle size distribution measured, for example by laser diffraction.

[0030] In the present disclosure, “metal” includes both metals and metalloids such as silicon and germanium in an elemental or ionic state.

[0031] In this disclosure, “alloy” means a mixture of two or more metals.

[0032] In the present disclosure, “anode active material” refers to an anode material capable of undergoing lithiation and delithiation.

[0033] In the present disclosure, “anode active material” refers to an anode material capable of undergoing lithiation and delithiation.

[0034] In the present disclosure, “lithiation” and “to lithiate” refer to the process of adding lithium to a positive electrode active material or a negative electrode active material.

[0035] In the present disclosure, “delithiation” and “to delithiate” refer to the process of removing lithium from a positive electrode active material or a negative electrode active material.

[0036] In this disclosure, “charge” and “to charge” refer to the process of providing electrochemical energy to a battery.

[0037] In this disclosure, “anode” and “cathode” refer to electrodes where electrochemical reduction and lithiation occur during the discharge process.

[0038] In this disclosure, “cathode” and “anode” refer to electrodes where electrochemical oxidation and delithiation occur during the discharge process.

[0039] A cathode according to exemplary embodiments, a lithium secondary battery including the same, and a method for manufacturing the same will be described in more detail below.

[0040] A lithium metal battery (100) according to one embodiment may include an electrode assembly (40).

[0041] Referring to FIG. 1, an electrode assembly (40) according to one embodiment may include an anode (10) comprising an anode current collector (11) and an anode active material layer (12) on the anode current collector (11); a cathode (20) comprising a cathode current collector (21); a separator (30) disposed between the anode (10) and the cathode (20); and a gel-type polymer electrolyte (not shown). The anode (10), the cathode (20), and the separator (30) may be impregnated with a gel-type polymer electrolyte (not shown).

[0042] 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.

[0043] Gel-type polymer electrolyte

[0044] The gel-type polymer electrolyte can be manufactured by a method in which it is poured into a battery case (50) into which an electrode assembly (40) is inserted and then cured, and thus has the advantage of being applicable to the existing non-aqueous electrolyte battery manufacturing process. The gel-type polymer electrolyte can maintain good processability by maintaining low viscosity when poured 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. In a lithium metal battery, the gel-type polymer electrolyte may be described as containing a cross-linked polymer or a cured polymer and an electrolyte.

[0045] A gel-type polymer electrolyte according to one embodiment may comprise a lithium salt; an organic solvent comprising a first compound comprising a compound represented by the following chemical formula 1; a second compound comprising a fluorine-substituted cyclic carbonate-based compound; and a crosslinked polymer having two or more functional groups.

[0046] [Chemical Formula 1]

[0047]

[0048] In the above chemical formula 1,

[0049] L1 is a single-bonded or substituted or unsubstituted C1 to C10 alkylene group, and

[0050] R1 is a substituted or unsubstituted C1 to C10 alkyl group, and

[0051] X1, X2, and X3 can each be any one of the same or different halogen elements.

[0052] A lithium salt is a substance that is dissolved in an organic solvent and acts as a source of lithium ions within a lithium metal battery (100), enabling the operation of the basic lithium metal battery and promoting the ionization of lithium ions between the positive electrode (10) and the negative electrode (20). Lithium salts include, for example, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide (LiFSI), LiC4F9SO3, LiN(C x F 2x+1 SO2)(C y F 2y+1 It may include one or more selected from SO2)(x and y are integers from 1 to 20), lithium trifluoromethane sulfonate, lithium tetrafluoroethane sulfonate, lithium difluoro(oxalate)borate (LiDFOB), lithium difluorobis(oxalate)phosphate (LiDFBOP), and lithium bis(oxalate)borate (LiBOB).

[0053] For example, a gel-type polymer electrolyte according to one embodiment may include lithium difluoro(oxalate)borate (LiDFOB) and LiBF4 as lithium salts. By including the two types of lithium salts in the gel-type polymer electrolyte, lifespan characteristics can be significantly improved. A gel-type polymer electrolyte according to one embodiment can achieve superior lifespan characteristics compared to a case where neither of the two types of lithium salts is included. A gel-type polymer electrolyte according to one embodiment may include LiDFOB and LiBF4 as lithium salts in a molar ratio of 20:80 to 80:20, for example, 30:70 to 70:30, or 40:60 to 60:40. By including the lithium salts in such molar ratios, the lifespan characteristics of the lithium metal battery can be improved.

[0054] The concentration of the lithium salt in the gel-type polymer electrolyte may be 0.3 M to 4 M, for example, 0.6 M to 3 M, 0.8 M to 2.5 M, or 1.0 M to 2.0 M. When the concentration of the lithium salt satisfies these ranges, the gel-type polymer electrolyte can exhibit excellent lithium conductivity, maintain an appropriate concentration when injected into a battery case, and effectively maintain a gel form after curing.

[0055] The organic solvent can serve as a medium through which ions involved in the electrochemical reaction of the lithium metal battery (100) can move. A gel-type polymer electrolyte according to one embodiment may include a first compound and a second compound to be described later.

[0056] An organic solvent according to one embodiment may include a first compound represented by the following chemical formula 1.

[0057] [Chemical Formula 1]

[0058]

[0059] In the above chemical formula 1,

[0060] L1 is a single-bonded or substituted or unsubstituted C1 to C10 alkylene group, and

[0061] R1 is a substituted or unsubstituted C1 to C10 alkyl group, and

[0062] X1, X2, and X3 are each one of the same or different halogen elements.

[0063] The first compound described above contains a trihalomethyl group within its molecule, which allows it to have a relatively high reduction potential. This first compound is reduced relatively earlier than other compounds in an organic solvent, thereby suppressing gas generation due to side reactions and forming a robust SEI layer on the cathode surface.

[0064] According to one embodiment, X1 to X3 in Chemical Formula 1 may be fluorine elements (F). In this case, the first compound may have a relatively high reduction potential as it contains a trifluoromethyl group within the molecule. This first compound is reduced relatively earlier than other compounds in an organic solvent, thereby suppressing gas generation due to side reactions and forming a robust SEI layer on the cathode surface.

[0065] According to another embodiment, the above chemical formula 1 can be represented by the following chemical formula 1-1.

[0066] [Chemical Formula 1-1]

[0067]

[0068] In the above chemical formula 1-1,

[0069] R1 is a substituted or unsubstituted C1 to C10 alkyl group.

[0070] According to another embodiment, the above chemical formula 1 can be represented by the following chemical formula 1-2.

[0071] [Chemical Formula 1-2]

[0072]

[0073] In the above chemical formula 1-2,

[0074] L1 is a single bond or a substituted or unsubstituted C1 to C10 alkylene group.

[0075] According to another embodiment, the above chemical formula 1 can be represented by the following chemical formula 1-3.

[0076] [Chemical Formula 1-3]

[0077]

[0078] The content of the first compound according to one embodiment may include 10 to 40 parts by weight based on 100 parts by weight of the gel-type polymer electrolyte. For example, the content of the first compound according to one embodiment may include 15 to 35 parts by weight based on 100 parts by weight of the gel-type polymer electrolyte, 20 to 35 parts by weight, and 25 to 35 parts by weight.

[0079] An organic solvent according to one embodiment may include a second compound which is a fluorine-substituted cyclic carbonate-based compound. The second compound may include, for example, fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), or a combination thereof. In this case, the gel-type polymer electrolyte can achieve excellent lifetime characteristics while maintaining good processability.

[0080] According to one embodiment, the content of the second compound may include 5 to 30 parts by weight based on 100 parts by weight of the gel-type polymer electrolyte. For example, according to one embodiment, the content of the second compound may include 10 to 25 parts by weight based on 100 parts by weight of the gel-type polymer electrolyte, 10 to 20 parts by weight, and 10 to 17 parts by weight.

[0081] The organic solvent can appropriately adjust the mixing ratio of the first compound and the second compound according to the desired battery performance. For example, according to one embodiment, the weight ratio of the first compound and the second compound in the organic solvent may be 20:1 to 1:5. According to another embodiment, the weight ratio of the first compound and the second compound in the organic solvent may be 10:1 to 1:2, or 5:1 to 1:1, or 3:1 to 1:1. When the organic solvent has such a mixing ratio, it can effectively reduce gas generation while having excellent lifespan characteristics.

[0082] An organic solvent according to one embodiment may further comprise a third compound which is a chain-type carbonate-based compound. The third compound may include, for example, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methyl ethyl carbonate (MEC), or a combination thereof.

[0083] According to one embodiment, the content of the third compound may comprise 30 to 80 parts by weight based on 100 parts by weight of the gel-type polymer electrolyte. For example, according to one embodiment, the content of the third compound may comprise 40 to 70 parts by weight and 50 to 60 parts by weight based on 100 parts by weight of the gel-type polymer electrolyte.

[0084] The above organic solvent may further include solvents used in general non-aqueous electrolytes. For example, it may further include carbonate-based solvents, ester-based solvents, or combinations thereof. In addition, the above solvent may not include ether-based solvents. When a lithium cobalt-based oxide is applied as the positive electrode active material, a problem may occur in which ether-based components in the electrolyte decompose in a high voltage range, so the organic solvent of the gel-type polymer electrolyte according to one embodiment may be designed not to include ether-based solvents.

[0085] In addition to the chain-type carbonate compounds described above, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc., may be additionally used as the carbonate-based solvents.

[0086] The above ester-based solvents may include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methylpropionate, ethylpropionate, decanolide, mevalonolactone, valerolactone, caprolactone, etc.

[0087] A cross-linked polymer according to one embodiment may have two or more functional groups. The cross-linked polymer included in the gel-type polymer electrolyte has two or more functional groups, which is advantageous for cross-linking and curing within the battery case and can exhibit excellent lifespan characteristics.

[0088] The above functional group may be, for example, an ester group (-C(=O)O-), a carbonate group (-OC(=O)O-), an acrylate group, a methacrylate group, or a combination thereof. Accordingly, the cross-linked polymer may be described as an ester-based polyfunctional polymer or a carbonate-based polyfunctional polymer. The gel-type polymer electrolyte may comprise a polymer containing two or more functional groups selected from ester groups, carbonate groups, acrylate groups, and methacrylate groups, and not containing ether groups. Accordingly, the safety of the lithium metal battery can be ensured and lifespan characteristics can be dramatically improved while enhancing processability.

[0089] A crosslinked polymer according to one embodiment may be a polymerization product of a crosslinkable monomer. The crosslinkable monomer may be a compound containing three or more carbon-carbon double bonds. That is, the crosslinked polymer can be understood as a compound containing three or more carbon-carbon double bonds that has been polymerized, crosslinked, or cured. A compound containing three or more carbon-carbon double bonds may be, for example, a compound containing three or more acrylic groups (CH2=CH-C(=O)O-). In the crosslinked polymer, the carbon-carbon double bonds participate in reactions such as polymerization or crosslinking during the process in which the gel-type polymer electrolyte is cured within the battery case, and thus may not be detected in the final battery. In the cured gel-type polymer electrolyte state, they may be detected as ester groups or carbonate groups, etc.

[0090] Crosslinkable monomers are, for example, trimethylolpropane trimethacrylate (TMPTMA), diethylene glycol diacrylate (DEGDA), diethylene glycol dimethacrylate (DEGDMA), triethylene glycol diacrylate (TEGDA), triethylene glycol dimethacrylate (TEGDMA), tetraethylene glycol diacrylate (TTEGDA), glycidyl methacrylate, polyethylene glycol diacrylate (PEGDA), polyethylene glycol dimethacrylate (PEGDMA), polypropylene glycol diacrylate (PPGDA), dipropylene glycol diacrylate (DPGDA), tripropylene glycol diacrylate (TPGDA), dianol diacrylate (DDA), dianol dimethacrylate (DDMA), and ethoxylated trimethylolpropane triacrylate (ETPTA). Acrylate-functionalized ethylene oxide, butanediol dimethacrylate, ethoxylated neopentyl glycol diacrylate (NPEOGDA), propoxylated neopentyl glycol diacrylate (NPEOGDA), trimethylolpropane triacrylate (TMPTA), trimethylolpropane trimethacrylate (TMPTMA), pentaerythritol triacrylate (PETA), ethoxylated propoxylated trimethylolpropane triacrylate (TMPEOTA) / (TMPPOTA), propoxylated glyceryl triacrylate, tris(2-hydroxyethyl)isocyanurate triacrylate (THEICTA), pentaerythritol tetraacrylate (PETTA), Dipentaerythritol pentaacrylate (DPEPA), ditrimethylol propane tetraacrylate (DTMPTTA);It may include diglycidyl ester, diallyl suberate; acrylamide, divinylbenzene, or a combination thereof.

[0091] The content of the cross-linked polymer may include 32 to 10 parts by weight based on 100 parts by weight of the gel-type polymer electrolyte. For example, it may include 2 to 8 parts by weight, 2 to 6 parts by weight, or 2 to 5 parts by weight. When these content ranges are satisfied, the gel-type polymer electrolyte can be effectively manufactured and the lifespan characteristics of the lithium metal battery can be improved.

[0092] anode

[0093] Referring to FIGS. 1 and FIGS. 2, a positive electrode (10) according to one embodiment may include a positive electrode current collector (11) and a positive electrode active material layer (12) on the positive electrode current collector (11).

[0094] 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, a plate or foil comprising indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof.

[0095] Meanwhile, unlike as illustrated in FIGS. 1 and 2, 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).

[0096] The positive active material layer (12) may include a positive active material. The positive active material is a material capable of reversibly absorbing and desorbing lithium ions. The positive active material may include, for example, lithium transition metal oxides such as lithium cobalt oxide (LCO), lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCM), lithium manganate, and lithium iron phosphate, as well as nickel sulfide, copper sulfide, lithium sulfide, iron oxide, or vanadium oxide, but is not necessarily limited to these. Each positive active material may be a single material or a mixture of two or more materials.

[0097] Lithium transition metal oxides are, for example, Li a A 1-b B b D2(0.90≤a≤1, 0≤b≤0.5), Li a E 1-b B b O 2-c D c (0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05), LiE 2-b B b O 4-c D c (0≤b≤0.5, 0≤c≤0.05), Li a Ni 1-b-c Co b B c D α (0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α<2), Li a Ni 1-b-c Co b B c O 2-α F α (0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α<2), Li a Ni 1-b-c Mn b Bc D α (0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α≤2), Li a Nor 1-b-c Mn b B c O 2-α F α (0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α<2), Li a Nor b E c G d O2(0.90≤a≤1, 0≤b≤0.9, 0≤c≤0.5, 0.001≤d≤0.1), Li a Nor b Co c Mn d GeO2(0.90≤a≤1, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0.001≤e≤0.1), Li a NiG b O2(0.9≤a≤1, 0.001≤b≤0.1), Li a CoG b O2(0.90≤a≤1, 0.001≤b≤0.1), Li a MnG b O2(0.90≤a≤1, 0.001≤b≤0.1), Li a Mn2GbO4(0.90≤a≤1, 0.001≤b≤0.1), QO2, QS2, LiQS2, V2O5, LiV2O5, LiIO2, LiNiVO4, Li 3-f J2(PO4)3(0≤f≤2), Li 3-fIt is a compound represented by any one of Fe2(PO4)3 (0≤f≤2) or LiFePO4. In such compounds, the uppercase “A” is Ni, Co, Mn, or a combination thereof; the uppercase “B” is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; the uppercase “D” is O, F, S, P, or a combination thereof; the uppercase “E” is Co, Mn, or a combination thereof; the uppercase “F” is F, S, P, or a combination thereof; the uppercase “G” is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; the uppercase “Q” is Ti, Mo, Mn, or a combination thereof; the uppercase “I” is Cr, V, Fe, Sc, Y, or a combination thereof; and the uppercase “J” is V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

[0098] The positive electrode active material may include, for example, a lithium salt of a transition metal oxide having a layered rock salt type structure among the lithium transition metal oxides described above. The "layered rock salt type structure" is, for example, a cubic rock salt type structure. <111> It is a structure in which oxygen and metal atomic layers are alternately and regularly arranged in a specific direction, thereby forming a two-dimensional plane for each atomic layer. The "cubic rock salt type structure" represents a sodium chloride (NaCl) type structure, which is a type of crystal structure; specifically, it exhibits a structure in which face-centered cubic lattices (fcc) formed by cations and anions, respectively, are offset from each other by half the ridge of the unit lattice. Lithium transition metal oxides having such a layered rock salt type structure are, for example, LiNi x Co y Al z O2(NCA) or LiNi x Co y Mn zO2(NCM) (0 <x<1,0<y<1, 0<z<1, x+y+z=1) 등의 삼원계 리튬전이금속산화물일 수 있다. 양극 활물질이 층상암염형 구조를 갖는 삼원계 리튬전이금속산화물을 포함하는 경우, 리튬 금속 전지(100)의 에너지 밀도가 커지고 열안정성이 향상될 수 있다.

[0099] The aforementioned compound contained in the positive electrode active material may be covered by a coating layer (not shown). The positive electrode active material may also be a mixture of the aforementioned compound and the compound to which the coating layer is added. Meanwhile, the coating layer added to the surface of the positive electrode active material may include, for example, oxides, hydroxides, oxyhydroxides, oxycarbonates, or hydroxycarbonates of the following coating elements. The compounds forming this coating layer are amorphous or crystalline. The coating elements included in the coating layer may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof. The coating layer may include, for example, Li2O-ZrO2 (LZO). The method for forming the coating layer is selected within a range that does not adversely affect the physical properties of the positive electrode active material. The method for forming the coating layer is, for example, spray coating or immersion.

[0100] When the positive electrode active material is a ternary lithium transition metal oxide such as NCA or NCM and contains nickel (Ni), the capacity density of the lithium metal battery (100) is increased, and the metal leaching of the positive electrode active material in the charged state can be reduced. As a result, the cycle characteristics of the lithium metal battery (100) in the charged state are improved. Meanwhile, “cycle characteristics” is a characteristic that indicates the degree of degradation of the lithium metal battery (100) due to charging and discharging of the lithium metal battery (100). A lithium metal battery (100) with high cycle characteristics has a small degree of degradation due to charging and discharging, while a lithium metal battery (100) with low cycle characteristics may have a large degree of degradation due to charging and discharging.

[0101] The shape of the positive electrode active material may include particle shapes such as spheres or ellipsoids. The particle size and content of the positive electrode active material are not particularly limited.

[0102] The positive active material layer (12) may include a conductive material. The conductive material may have conductivity without causing chemical changes in the lithium metal battery (100), thereby increasing the conductivity of the positive active material. The conductive material may include a carbon-based material. The conductive material may include, for example, one or more selected from graphite, carbon black, acetylene black, carbon nanofibers, and carbon nanotubes.

[0103] The positive active material layer (12) may further include a binder. The binder may include a material for bonding the positive active material and conductive material contained in the positive active material layer (12) and for improving the bonding strength with the positive current collector (11). The binder may include, for example, polyvinylidene fluoride, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, and polymethyl methacrylate.

[0104] The positive active material layer (12) may further include additives such as fillers, coating agents, dispersants, and ion-conducting aids in addition to the positive active material, conductive material, and binder described above.

[0105] cathode

[0106] 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).

[0107] The negative electrode current collector (210) 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.

[0108] The negative current collector (210) 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 (210) is, for example, in the form of a plate or foil.

[0109] 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).

[0110] 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.

[0111] 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).

[0112] 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).

[0113] Separator

[0114] The separator (30) separates the positive electrode (10) and the negative electrode (20) and provides a pathway for the movement of lithium ions; any material commonly used in lithium-ion batteries can be used. That is, a material having low resistance to the movement of electrolyte ions and excellent electrolyte moisture retention capacity can be used. For example, it may include glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene, or a combination thereof, and may be in the form of a non-woven fabric or a woven fabric. For example, polyolefin-based polymer separators such as polyethylene and polypropylene are mainly used in lithium-ion batteries, and a coated separator containing ceramic components or polymer materials may be used to ensure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0115] lithium metal battery

[0116] 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.

[0117] 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).

[0118] Referring to FIGS. 1 and 2, the positive electrode (10), the separator (30), and the negative electrode (20) may be wound, folded, or stacked to form an electrode assembly (40). Referring to FIGS. 3 and 4, the formed electrode assembly (40) may be housed in a battery case (50). The battery case (50) may contain a gel-type polymer electrolyte inside. In one embodiment, the battery case (50) may be pouch-type. In one embodiment, the main body forming the pouch-type battery case 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.

[0119] Method for manufacturing a lithium metal battery

[0120] 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.

[0121] The above composition for forming a gel-type polymer electrolyte may include a crosslinkable monomer, a lithium salt, an organic solvent, and a thermal initiator. Since the details regarding the crosslinkable monomer, lithium salt, and organic solvent can be applied as described above, a detailed description is omitted below. The thermal initiator may include, for example, t-amyl peroxide, benzoyl peroxide (BPO), azobisisobutyronitrile (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.

[0122] 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.

[0123] 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 ℃.

[0124] The above heat treatment varies depending on the type of crosslinkable monomer, but for example, it can be performed 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 (1000) with improved lifespan characteristics.

[0125]

[0126] 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.

[0127]

[0128] Example 1 (DEC / FEC / MTFA = 58 / 12 / 30wt%)

[0129] 1. Preparation of a composition for forming a gel-type polymer electrolyte

[0130] Trimethylolpropane trimethacrylate (TMPTMA) is prepared as a polymer precursor.

[0131] A solution is prepared by mixing diethyl carbonate (DEC), fluoroethylene carbonate (FEC), and a compound represented by the following chemical formula 1-3 in a mass ratio of 58:12:30 as organic solvents. Lithium difluoro(oxalateto)borate (LiDFOB) and LiBF4 are dissolved as lithium salts in the prepared organic solvent at a molar concentration of 0.6 M each to prepare an electrolyte (total 1.2 M). A gel-type polymer electrolyte composition is prepared by mixing the prepared electrolyte with a polymer precursor in a weight ratio of 97:3.

[0132] [Chemical Formula 1-3]

[0133]

[0134] (CAS # 431-47-0 or lower, MTFA)

[0135]

[0136] 2. Manufacture of lithium metal batteries

[0137] Li 1.02 Co 0.9823 Al 0.0127 Mg 0.005 A cathode active material layer composition is prepared by mixing 96 wt% of O2 cathode active material, 2 wt% of polyvinylidene fluoride binder, 2 wt% of carbon nanotube conductive material, and N-methylpyrrolidone solvent in a mixer, and the composition is coated onto aluminum foil, then dried and rolled to produce a cathode.

[0138] An electrode assembly is prepared by interposing a separator with a polyethylene polypropylene multilayer structure between the prepared positive electrode and the lithium metal counter electrode. The electrode assembly is inserted into a pouch-type battery case, and a prepared gel-type polymer electrolyte composition is injected into the case. Then, the electrolyte composition is cured by heat treatment at 70°C for 3 hours, thereby manufacturing a half-cell in which a gel-type polymer electrolyte is formed.

[0139] Example 2 (DEC / FEC / MTFA = 58 / 17 / 25wt%)

[0140] A lithium metal battery was prepared in the same manner as in Example 1, except that a solution was prepared by mixing diethyl carbonate (DEC), fluoroethylene carbonate (FEC), and a compound represented by the chemical formula 1-3 in a mass ratio of 58:17:25 as organic solvents.

[0141] Example 3 (DEC / FEC / MTFA = 58 / 21 / 21wt%)

[0142] A lithium metal battery was prepared in the same manner as in Example 1, except that a solution was prepared by mixing diethyl carbonate (DEC), fluoroethylene carbonate (FEC), and a compound represented by the chemical formula 1-3 in a mass ratio of 58:21:21 as organic solvents.

[0143] Comparative Example 1 (DEC / FEC = 58 / 42wt%)

[0144] A lithium metal battery was manufactured in the same manner as in Example 1, except that a solution was prepared by mixing diethyl carbonate (DEC) and fluoroethylene carbonate (FEC) in a mass ratio of 58:42 as organic solvents.

[0145] Comparative Example 2 (DEC / MTFA = 58 / 42wt%)

[0146] A lithium metal battery was prepared in the same manner as in Example 1, except that a solution was prepared by mixing diethyl carbonate (DEC) and a compound represented by the chemical formula 1-3 in a mass ratio of 58:42 as an organic solvent.

[0147] Comparative Example 3 (DEC / MTFA = 68 / 32wt%)

[0148] A lithium metal battery was prepared in the same manner as in Example 1, except that a solution was prepared by mixing diethyl carbonate (DEC) and a compound represented by the chemical formula 1-3 in a mass ratio of 68:32 as an organic solvent.

[0149] Comparative Example 4 (DEC / FEC / MTFA = 58 / 37 / 5wt%)

[0150] A lithium metal battery was prepared in the same manner as in Example 1, except that a solution was prepared by mixing diethyl carbonate (DEC), fluoroethylene carbonate (FEC), and a compound represented by the chemical formula 1-3 in a mass ratio of 58:37:5 as organic solvents.

[0151]

[0152] Evaluation Example 1: Life Characteristics Evaluation

[0153] The batteries prepared in Examples 1 to 3 and Comparative Examples 1 to 4 are charged at 25°C with a constant current of 0.1C to an upper voltage limit of 4.25V, and then discharged at a constant current of 0.1C to a discharge termination voltage of 3.5V to perform an initial charge-discharge cycle (formation cycle). Subsequently, charging at 0.5C and discharging at 0.5C within a voltage range of 3.5V to 4.25V are repeated 150 times. The discharge capacity after 150 cycles is shown in Table 1 below.

[0154] Solvent composition discharge capacity (@150 th cycles, mAh) Example 1 (DEC / FEC / MTFA = 58 / 12 / 30wt%) 24.07 Example 2 (DEC / FEC / MTFA = 58 / 17 / 25wt%) 23.43 Example 3 (DEC / FEC / MTFA = 58 / 21 / 21wt%) 22.7 Comparative Example 1 (DEC / FEC = 58 / 42wt%) 20.04 Comparative Example 2 (DEC / MTFA = 58 / 42wt%) 18.98 Comparative Example 3 (DEC / MTFA = 68 / 32wt%) 12.39 Comparative Example 4 (DEC / FEC / MTFA = 58 / 37 / 5wt%) 21.75

[0155] Referring to Table 1, it was confirmed that Examples 1 to 3, which are lithium metal batteries using an appropriate mixture of FEC and MTFA in an organic solvent, exhibit excellent lifespan characteristics.

[0156] Evaluation Example 2: Evaluation of Gas Generation Amount

[0157] The batteries prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were charged at 25°C with a constant current of 0.1C to an upper voltage limit of 4.25V, and then discharged with a constant current of 0.1C to a discharge termination voltage of 3.5V to perform an initial charge-discharge cycle (formation cycle). Afterward, the batteries were removed, placed in a jig, and burst, and the change in internal gas pressure was converted into volume to measure the amount of gas generated. The amount of gas generated was expressed as the amount of gas generated per unit weight of the positive active material contained in the lithium metal battery.

[0158] Again, the batteries prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were charged at 25°C with a constant current of 0.1C to an upper voltage limit of 4.25V, and then discharged with a constant current of 0.1C to a discharge termination voltage of 3.5V to perform an initial charge-discharge cycle (formation cycle). Subsequently, charging at 0.5C and discharging at 0.5C within a voltage range of 3.5V to 4.25V were repeated 50 times. Afterward, the batteries were removed, placed in a jig, and burst, and the change in internal gas pressure was converted into volume to measure the amount of gas generated. The amount of gas generated was expressed as the amount of gas generated per unit weight of the positive active material contained in the lithium metal battery.

[0159] The evaluation results are shown in Table 2 below.

[0160]

[0161] Solvent Composition After Formation (cc / g) After 50 Cycles (cc / g) Example 1 (DEC / FEC / MTFA = 58 / 12 / 30wt%) 0.20 0.53 Example 2 (DEC / FEC / MTFA = 58 / 17 / 25wt%) 0.23 0.57 Example 3 (DEC / FEC / MTFA = 58 / 21 / 21wt%) 0.27 0.63 Comparative Example 1 (DEC / FEC = 58 / 42wt%) 0.51 0.98 Comparative Example 2 (DEC / MTFA = 58 / 42wt%) 0.17 0.42 Comparative Example 3 (DEC / MTFA = 68 / 32wt%) 0.16 0.43 Comparative Example 4 (DEC / FEC / MTFA = 58 / 37 / 5wt%) 0.36 0.69

[0162] Referring to Table 2, Comparative Example 1, which used a solvent not containing MTFA, had a higher amount of gas generation compared to the other examples. In Comparative Example 4, MTFA and FEC were mixed, but the mass ratio of MTFA was relatively low at 5%, so the gas generation suppression effect was not prominent. On the other hand, it can be confirmed that Examples 1 to 3 exhibited an excellent gas generation suppression effect.

[0163] synthesis

[0164] Referring to Evaluation Example 2, it was confirmed that the effect of suppressing gas generation was improved in the gel polymer electrolyte containing MTFA compared to Comparative Example 1, which does not contain it.

[0165] However, by referring to Evaluation Example 1 together, it was confirmed that the lifespan characteristics of Comparative Examples 2 and 3, in which MTFA was applied without FEC, deteriorated.

[0166] In the present disclosure, it was confirmed that a lithium metal battery containing a gel polymer electrolyte with excellent lifespan characteristics and gas generation is suppressed by mixing MTFA and FEC in an appropriate ratio can be provided.

[0167]

[0168] Although an exemplary embodiment has been described in detail above with reference to the attached drawings, the present creative idea is not limited to such examples. It is obvious that a person skilled in the art to which the present creative idea belongs can derive various variations or modifications within the scope of the technical idea described in the patent claims, and these also naturally fall within the technical scope of the present creative idea.

Claims

1. Lithium salt; An organic solvent comprising a first compound represented by the following chemical formula 1 and a second compound which is a fluorine-substituted cyclic carbonate-based compound; and A cross-linked polymer having two or more functional groups, comprising A gel-type polymer electrolyte in which the weight ratio of the first compound and the second compound is 20:1 to 1:5: [Chemical Formula 1] In the above chemical formula 1, L1 is a single-bonded or substituted or unsubstituted C1 to C10 alkylene group, and R1 is a substituted or unsubstituted C1 to C10 alkyl group, and X1, X2, and X3 are each one of the same or different halogen elements.

2. In Paragraph 1, A gel-type polymer electrolyte in which X1 to X3 in Chemical Formula 1 above are fluorine elements (F).

3. In Paragraph 1, The above chemical formula 1 is a gel-type polymer electrolyte represented by the following chemical formula 1-1: [Chemical Formula 1-1] In the above chemical formula 1-1, R1 is a substituted or unsubstituted C1 to C10 alkyl group.

4. In Paragraph 1, The above chemical formula 1 is a gel-type polymer electrolyte represented by the following chemical formula 1-2: [Chemical Formula 1-2] In the above chemical formula 1-2, L1 is a single bond or a substituted or unsubstituted C1 to C10 alkylene group.

5. In Paragraph 1, The above Chemical Formula 1 is a gel-type polymer electrolyte represented by the following Chemical Formula 1-3: [Chemical Formula 1-3] .

6. In Paragraph 1, A gel-type polymer electrolyte, wherein the content of the first compound is 10 to 40 parts by weight based on 100 parts by weight of the gel-type polymer electrolyte.

7. In Paragraph 1, The second compound is a gel-type polymer electrolyte comprising fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), or a combination thereof.

8. In Paragraph 1, A gel-type polymer electrolyte in which the weight ratio of the first compound and the second compound is 3:1 to 1:

1.

9. In Paragraph 1, The above functional group comprises an ester group, a carbonate group, an acrylate group, a methacrylate group, or a combination thereof, in a gel-type polymer electrolyte.

10. In Paragraph 1, The above-mentioned crosslinked polymer is a polymerization product of crosslinkable monomers, and The above-mentioned crosslinkable monomers are trimethylolpropane trimethacrylate (TMPTMA), diethylene glycol diacrylate (DEGDA), diethylene glycol dimethacrylate (DEGDMA), triethylene glycol diacrylate (TEGDA), triethylene glycol dimethacrylate (TEGDMA), tetraethylene glycol diacrylate (TTEGDA), glycidyl methacrylate, polyethylene glycol diacrylate (PEGDA), polyethylene glycol dimethacrylate (PEGDMA), polypropylene glycol diacrylate (PPGDA), dipropylene glycol diacrylate (DPGDA), tripropylene glycol diacrylate (TPGDA), dianol diacrylate (DDA), dianol dimethacrylate (DDMA), ethoxylated trimethylolpropane triacrylate (ETPTA), and acrylates. Acrylate-functionalized ethylene oxide, butanediol dimethacrylate, ethoxylated neopentyl glycol diacrylate (NPEOGDA), propoxylated neopentyl glycol diacrylate (NPEOGDA), trimethylolpropane triacrylate (TMPTA), trimethylolpropane trimethacrylate (TMPTMA), pentaerythritol triacrylate (PETA), ethoxylated propoxylated trimethylolpropane triacrylate (TMPEOTA) / (TMPPOTA), propoxylated glyceryl triacrylate, tris(2-hydroxyethyl) isocyanurate triacrylate (THEICTA), pentaerythritol tetraacrylate (PETTA), dipentaerythritol Pentaacrylate (DPEPA), ditrimethylolpropane tetraacrylate (DTMPTTA);A gel-type polymer electrolyte comprising a diglycidyl ester, diallyl suberate; acrylamide, divinylbenzene, or a combination thereof.

11. In Paragraph 1, A gel-type polymer electrolyte in which the content of the cross-linked polymer is 2 to 10 parts by weight based on 100 parts by weight of the gel-type polymer electrolyte.

12. In Paragraph 1, The above organic solvent is a gel-type polymer electrolyte further comprising a third compound which is a chain-type carbonate-based compound.

13. In Paragraph 12, The above-mentioned third compound is a gel-type polymer electrolyte comprising dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methyl ethyl carbonate (MEC), or a combination thereof.

14. In Paragraph 1, The above lithium salt is a gel-type polymer electrolyte comprising lithium difluoro(oxalate)borate (LiDFOB) and LiBF4.

15. 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 A lithium metal battery comprising the gel-type polymer electrolyte of claim 1.

16. In Paragraph 15, A lithium metal battery, wherein the above-mentioned cathode further comprises a lithium metal layer disposed between the cathode current collector and the separator.

17. In Paragraph 16, The above lithium metal layer comprises lithium or a lithium alloy, and The above lithium alloy is a lithium metal battery comprising 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.

18. Forming an electrode assembly by arranging a negative current collector, a separator, and a positive electrode; The above electrode assembly is housed in a battery case, and then a composition for forming a gel-type polymer electrolyte is injected into the battery case; and A method for manufacturing a lithium metal battery comprising curing the above-mentioned composition for forming a gel-type polymer electrolyte to form the gel-type polymer electrolyte of claim 1.

19. In Paragraph 18, The process of curing the above-mentioned composition for forming a gel-type polymer electrolyte to form a gel-type polymer electrolyte includes a curing reaction using heat treatment, and A method for manufacturing a lithium metal battery in which the above heat treatment is performed at 40 to 120 ℃.

20. In Paragraph 18, A method for manufacturing a lithium metal battery, wherein the above-described composition for forming a gel-type polymer electrolyte comprises a crosslinkable monomer, a lithium salt, an organic solvent, and a thermal initiator.

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