Gel polymer electrolyte and lithium secondary battery containing the same

Abstract

The present invention aims to provide a gel polymer electrolyte that has a large effect of suppressing leakage of an organic solvent by trapping the organic solvent in a three-dimensional polymer network, has oxidation safety, flame retardancy, and thermal stability, and has excellent lithium ion conductivity. In order to achieve the above-mentioned object, the present invention provides a gel polymer electrolyte including a crosslinked polymer having a thiol-ene structure, the thiol-ene structure being formed by a click reaction between a thiol group of a thiol compound containing at least four reactive thiol groups per molecule and an acrylic group of a fluorinated polyether diacrylate.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2021-009776 filed on Jul. 29, 2021, and all of the contents disclosed in the document of the Korean patent application are incorporated herein by reference in their entirety.

[0002] The present invention relates to a gel polymer electrolyte, a lithium secondary battery including the same, and a method for manufacturing the same.

Background Art

[0003] Recently, as the application fields of lithium secondary batteries have rapidly expanded not only to power supply for electronic devices such as electric, electronic, communication, and computers but also to power storage supply for large-area devices such as automobiles and power storage devices, the need for secondary batteries with high capacity, high output, and high stability has been increasing.

[0004] A lithium secondary battery is generally manufactured by applying a positive electrode mixture obtained by mixing a positive electrode active material made of a lithium-containing transition metal oxide, a binder, and / or a conductive material onto a positive electrode current collector, and a negative electrode manufactured by applying a negative electrode mixture obtained by mixing a carbon material and / or a silicon material negative electrode active material capable of occluding and releasing lithium ions, a binder, and / or a conductive material onto a negative electrode current collector, laminating the negative electrode on both sides of a separator to form an electrode assembly having a predetermined shape, and then inserting the electrode assembly and an electrolytic solution into a battery case.

[0005] Here, as the electrolyte, it is generally known to use a non-aqueous electrolyte in which a lithium salt is dissolved in a carbonate-based organic solvent such as ethylene carbonate (EC), propylene carbonate (PC), or diethyl carbonate (DEC). However, the carbonate-based organic solvent has drawbacks such as a high possibility of liquid leakage during long-term use, and a risk of fire due to the surrounding temperature and the temperature rise of the battery itself, resulting in low safety. Therefore, attempts have been made to develop an electrolyte for lithium secondary batteries that can complement such drawbacks. Among them, a gel polymer electrolyte that confines a liquid electrolyte within a polymer structure has been proposed as a new electrolyte system.

[0006] However, when using a gel polymer electrolyte in a lithium secondary battery, there is a problem that the performance of the lithium secondary battery deteriorates due to low lithium ion conductivity.

Summary of the Invention

Problems to be Solved by the Invention

[0007] An object of the present invention is to provide a gel polymer electrolyte having oxidation safety, flame retardancy, and thermal stability, a large effect of suppressing liquid leakage of an organic solvent, and excellent lithium ion conductivity.

[0008] Another object of the present invention is to provide a lithium secondary battery having improved various performances such as cycle characteristics and excellent thermal stability by including the gel polymer electrolyte.

[0009] Another object of the present invention is to provide a method for manufacturing the lithium secondary battery.

Means for Solving the Problems

[0010] According to one embodiment, in order to achieve the above object, the present invention provides a gel polymer electrolyte containing a crosslinked polymer having a thiol-ene structure, wherein the thiol-ene structure is formed by a click reaction between a thiol group of a thiol compound containing at least 4 or more reactive thiol groups per molecule and an acrylic group of a fluorinated polyether diacrylate.

[0011] According to another embodiment, the present invention provides a lithium secondary battery including the gel polymer electrolyte.

Advantages of the Invention

[0012] In the crosslinked polymer having a thiol-ene structure contained in the gel polymer electrolyte of the present invention, a chemically crosslinked gel polymer electrolyte is produced by using a click reaction between a thiol group of a thiol compound containing at least 4 or more reactive thiol groups per molecule and an acrylic group of a fluorinated polyether diacrylate. When producing a gel polymer electrolyte by a click reaction, there are almost no side reactions, and since the thiol group and the acrylic group react selectively and quickly, there is an advantage that the acquisition rate of the crosslinked polymer is high.

[0013] In addition, the gel polymer electrolyte of the present invention containing a crosslinked polymer produced by a click reaction entraps an organic solvent within a three-dimensional polymer network and has an excellent effect of preventing liquid leakage of the organic solvent.

[0014] In addition, since the gel polymer electrolyte of the present invention has a crosslinked structure, there are few structural changes even due to changes in the external environment or the passage of time, and thus it has excellent structural, thermal, and mechanical stability.

[0015] In addition, according to the present invention, since a fluorinated ether diacrylate having flame retardant properties is applied as a crosslinking agent, the secondary battery using the gel polymer electrolyte of the present invention has the effects of improved thermal stability and suppressed heat generation amount of the electrode. The gel polymer electrolyte according to the present invention has an effect of excellent oxidation stability due to the fluorine atoms contained in the fluorinated ether diacrylate crosslinking agent.

[0016] Therefore, when using the gel polymer electrolyte of the present invention, not only oxidation stability, flame retardancy and thermal stability are improved, but also cycle life characteristics and safety are improved, and a lithium secondary battery with improved various performances can be realized.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0018] The terms and words used in this specification and claims should not be construed as being limited to their ordinary or dictionary meanings. The inventors should interpret them in accordance with the meaning and concept consistent with the technical idea of the present invention in accordance with the principle that they can appropriately define the concept of the terms in order to explain their invention in the best way.

[0019] In this specification, terms such as "comprising", "including" or "having" are used to specify the presence of implemented features, numbers, steps, components or combinations thereof, and it should be understood that the presence or addition possibility of one or more other features, numbers, steps, components or combinations thereof is not precluded in advance.

[0020] In addition, in the description of "carbon number from a to b" in this specification, "a" and "b" mean the number of carbon atoms contained in a specific functional group. That is, the functional group can contain "a" to "b" carbon atoms. For example, "an alkylene group having 1 to 5 carbon atoms" means an alkylene group containing 1 to 5 carbon atoms, that is, -CH2-, -CH2CH2-, -CH2CH2CH2-, -CH2CH(CH3)-, -CH(CH3)CH2-, -CH(CH3)CH2CH2-, etc.

[0021] In addition, in this specification, the term "alkylene group" means a branched or unbranched divalent saturated hydrocarbon group.

[0022] In addition, in this specification, both the alkyl group and the alkylene group can be either substituted or unsubstituted. The term "substituted" means that at least one or more hydrogens bonded to carbon are substituted with an element other than hydrogen, unless otherwise defined. For example, it means being substituted with an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a cycloalkenyl group having 3 to 12 carbon atoms, a heterocycloalkyl group having 3 to 12 carbon atoms, a heterocycloalkenyl group having 3 to 12 carbon atoms, an aryloxy group having 6 to 12 carbon atoms, a halogen atom, a fluoroalkyl group having 1 to 20 carbon atoms, a nitro group, a nitrile group, an aryl group having 6 to 20 carbon atoms, a heteroaryl group having 2 to 20 carbon atoms, a haloaryl group having 6 to 20 carbon atoms, etc.

[0023] Hereinafter, the present invention will be described in more detail.

[0024] Gel polymer electrolyte The present invention relates to a gel polymer electrolyte containing a crosslinked polymer having a thiol-ene structure, and the thiol-ene structure can be formed by a click reaction between the thiol group of a thiol compound containing at least 4 or more reactive thiol groups per molecule and the acrylic group of a fluorinated polyether diacrylate.

[0025] The thiol compound containing at least 4 or more reactive thiol groups per molecule as described above can be, for example, one or more selected from the group consisting of pentaerythritol tetrakis(3-mercaptopropionate), dipentaerythritol hexakis(3-mercaptopropionate), pentaerythrityl tetrathiols, tetrakis(2-mercaptoethyl)silane, and benzene-1,2,4,5-tetrathiol. By using the thiol compound as described above as a crosslinking agent, a three-dimensional polymer network can be formed. Such a three-dimensional polymer network can confine an organic solvent, and thereby has the effect of preventing liquid leakage of the organic solvent.

[0026] The fluorinated polyether diacrylate can be represented by the following Chemical Formula 1.

[0027]

Chemical formula

[0028] In Chemical Formula 1, R x and R y can each independently be an alkylene group having 1 to 10 carbon atoms, preferably an alkylene group having 1 to 5 carbon atoms, and more preferably an alkylene group having 1 to 3 carbon atoms.

[0029] In Chemical Formula 1, R1 to R4 can each independently be selected from H, an alkyl group having 1 to 10 carbon atoms, and a halogen, preferably at least one or more of R1 to R4 can be a halogen. Most preferably, at least one or more of R1 to R4 can be a fluoro group. By using the polyether diacrylate substituted with fluorine as a crosslinking agent, a gel polymer electrolyte excellent in flame retardancy and thermal stability can be obtained.

[0030] In Chemical Formula 1, n can be an integer of 1 to 5, preferably n can be an integer of 2 to 4.

[0031] In the gel polymer electrolyte of the present invention, the fluorinated polyether diacrylate used as a crosslinking agent can be represented by the following Chemical Formula 1-1. When the perfluorinated polyether diacrylate of Chemical Formula 1-1 is used, a gel polymer electrolyte excellent in flame retardancy and thermal stability can be obtained.

[0032]

Chemical formula

[0033] In Chemical Formula 1, R x and R y can each independently be an alkylene group having 1 to 10 carbon atoms, preferably an alkylene group having 1 to 5 carbon atoms, and more preferably an alkylene group having 1 to 3 carbon atoms.

[0034] In Chemical Formula 1-1, n can be an integer of 1 to 5, preferably n can be an integer of 2 to 4.

[0035] Specifically, the fluorinated polyether diacrylate used as a crosslinking agent in the gel polymer electrolyte of the present invention can be represented by the following Chemical Formula 1-2.

[0036]

Chemical formula

[0037] The weight average molecular weight of the fluorinated polyether diacrylate used as a crosslinking agent in the gel polymer electrolyte of the present invention can be 200 to 2000 g / mol, preferably 200 to 1000 g / mol, and more preferably 300 to 600 g / mol. When the weight average molecular weight of the fluorinated polyether diacrylate satisfies the above range, during the manufacture of a secondary battery, a precursor containing the fluorinated polyether diacrylate can easily impregnate into the cell and can exhibit excellent battery characteristics.

[0038] The gel polymer electrolyte according to the present invention can further contain a lithium salt and an organic solvent in a crosslinked polymer having a thiol-ene structure.

[0039] The lithium salt is used as a mediator for transmitting ions as an electrolyte salt in a lithium secondary battery. Usually, the lithium salt contains, for example, Li as a cation + and, as an anion, F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , B 10 Cl 10 - , AlCl4 - , AlO2 - , PF6 - , CF3SO3 - , CH3CO2 - , CF3CO2 - , AsF6 - , SbF6 - , CH3SO3 - , (CF3CF2SO2)2N - , (CF3SO2)2N - , (FSO2)2N - , BF2C2O4 - , BC4O8 - , PF4C2O4 - , PF2C4O8 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , C4F9SO3 - , CF3CF2SO3 - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , CF3(CF2)7SO3 - and SCN- At least any one selected from the group consisting of

[0040] Specifically, the lithium salt includes LiCl, LiBr, LiI, LiBF4, LiClO4, LiB 10 Cl 10 , LiAlCl4, LiAlO2, LiPF6, LiCF3SO3, LiCH3CO2, LiCF3CO2, LiAsF6, LiSbF6, LiCH3SO3, LiFSI (Lithium bis(fluorosulfonyl)imide, LiN(SO2F)2), LiBETI (lithium bis(perfluoroethanesulfonyl)imide, LiN(SO2CF2CF3)2) and LiTFSI (lithium bis(trifluoromethanesulfonyl)imide, LiN(SO2CF3)2), and can contain a single substance or a mixture of two or more selected from the group consisting of. In addition to these, lithium salts usually used in the electrolyte of lithium secondary batteries can be used without limitation. Among them, LiTFSI is particularly preferred in terms of high thermal stability in the heat treatment process, high ionic conductivity in secondary batteries, and improved flame retardancy.

[0041] The organic solvent can be used without limitation an organic solvent usually used in non-aqueous electrolytes. For example, the organic solvent can contain at least one or more organic solvents selected from the group consisting of cyclic carbonate-based organic solvents, linear carbonate-based organic solvents, linear ester-based organic solvents, cyclic ester-based organic solvents, ether-based organic solvents, glyme-based solvents, and nitrile-based organic solvents.

[0042] The cyclic carbonate-based organic solvent is an organic solvent with a high viscosity, a high dielectric constant, and the ability to well dissociate lithium salts in the electrolyte. Specific examples thereof include at least one or more organic solvents selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, and vinylene carbonate.

[0043] The linear carbonate-based organic solvent is an organic solvent with a low viscosity and a low dielectric constant. Representative examples thereof include at least one or more organic solvents selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate, and ethyl propyl carbonate.

[0044] Examples of the linear ester-based organic solvent include at least one or more organic solvents selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate.

[0045] Examples of the cyclic ester-based organic solvent include at least one or more organic solvents selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone.

[0046] Examples of the ether-based solvent include at least one or more organic solvents selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether, ethyl propyl ether, 1,3-dioxolane (DOL), and 2,2-bis(trifluoromethyl)-1,3-dioxolane (TFDOL).

[0047] The glyme-based solvent has a higher dielectric constant and a lower surface tension than the linear carbonate-based organic solvent, and is a solvent with less reactivity with metals. Examples include at least one or more organic solvents selected from the group consisting of dimethoxyethane (Gleim, DME), diethoxyethane, diglyme, triglyme, and tetra-glyme (TEGDME).

[0048] The nitrile-based solvent includes at least one or more organic solvents selected from the group consisting of acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentanecarbonitrile, cyclohexanecarbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile.

[0049] Specifically, the organic solvent can include a cyclic carbonate-based organic solvent, a linear carbonate-based organic solvent, or a mixed organic solvent thereof. Among them, in terms of low viscosity and improved ionic conductivity of the electrolyte, a linear carbonate-based organic solvent is preferred, and in particular, dimethyl carbonate (DMC) is preferred.

[0050] The gel polymer electrolyte of the present invention can contain a cross-linked polymer having a thiol-ene structure and a lithium salt in a weight ratio of 1:11 to 1:0.5, preferably 1:7 to 1:0.5, and more preferably 1:6 to 1:1. When the weight ratio of the cross-linked polymer having a thiol-ene structure to the lithium salt satisfies the above range, high ionic conductivity and excellent battery characteristics can be exhibited.

[0051] In the gel polymer electrolyte according to the present invention, the crosslinked polymer having a thiol-ene structure can be contained in an amount of 10 to 80 parts by weight, preferably 20 to 80 parts by weight, more preferably 20 to 75 parts by weight, and most preferably 20 to 50 parts by weight with respect to 100 parts by weight of the organic solvent. When the content of the crosslinked polymer having a thiol-ene structure in the organic solvent in the gel polymer electrolyte satisfies the above range, it is possible to ensure high lithium ion conductivity and oxidation stability, reduce the amount of the organic solvent used to prevent liquid leakage, and obtain flame retardant properties.

[0052] The gel polymer electrolyte according to the present invention can have a lithium ion conductivity of 1.0×10 -3 S / cm or more at 25°C, preferably 1.0×10 -3 ~5.0×10 -3 S / cm, more preferably 1.4×10 -3 ~3.0×10 -3 S / cm, and even more preferably 1.5×10 -3 ~3.0×10 -3 S / cm. When the lithium ion conductivity of the gel polymer electrolyte satisfies the above range, the characteristics of a secondary battery at a desired level can be obtained.

[0053] The gel polymer electrolyte according to the present invention can have a lithium ion conductivity of 2.0×10 -3 S / cm or more at 45°C, preferably 2.0×10 -3 ~1.0×10 -2 S / cm, and even more preferably 2.0×10 -3 ~4.0×10 -3 S / cm. When the lithium ion conductivity of the gel polymer electrolyte satisfies the above range, the characteristics of a secondary battery at a desired level can be obtained.

[0054] The ion conductivity can be measured, for example, using a Zahner Electrik, IM6 device, at an amplitude of 50 mV, under conditions in a frequency range of 10 to 1.0×10 6 Hz.

[0055] In order to prevent the gel polymer electrolyte of the present invention from being decomposed in a high-output environment, causing the collapse of the negative electrode, or to further improve characteristics such as low-temperature high-rate discharge characteristics, high-temperature stability, prevention of overcharging, and suppression effect of battery swelling at high temperatures, if necessary, a known electrolyte additive can be further included in the gel polymer electrolyte.

[0056] Such other electrolyte additives can include, as typical examples thereof, at least one or more additives for forming an SEI film selected from the group consisting of cyclic carbonate compounds, halogen-substituted carbonate compounds, sultone compounds, sulfate compounds, phosphate compounds, borate compounds, nitrile compounds, benzene compounds, amine compounds, silane compounds, and lithium salt compounds.

[0057] Examples of the cyclic carbonate compound include vinylene carbonate (VC) or vinyl ethylene carbonate.

[0058] Examples of the halogen-substituted carbonate compound include fluoroethylene carbonate (FEC).

[0059] Examples of the sultone compound include at least one or more compounds selected from the group consisting of 1,3-propane sultone (PS), 1,4-butane sultone, ethene sultone, 1,3-propene sultone (PRS), 1,4-butene sultone, and 1-methyl-1,3-propene sultone.

[0060] Examples of the sulfate compound include ethylene sulfate (Esa), trimethylene sulfate (TMS), or methyl trimethylene sulfate (MTMS).

[0061] The phosphate compound includes one or more compounds selected from the group consisting of lithium difluoro(bisoxalate)phosphate, lithium difluorophosphate, tetramethyltrimethylsilyl phosphate, trimethylsilyl phosphite, tris(2,2,2-trifluoroethyl) phosphate, and tris(trifluoroethyl) phosphite.

[0062] The borate compound includes tetraphenylborate, lithium oxalyldifluoroborate (LiODFB), and lithium bisoxalate borate (LiB(C2O4)2, LiBOB).

[0063] The nitrile compound includes at least one compound selected from the group consisting of succinonitrile, adiponitrile, acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentanecarbonitrile, cyclohexanecarbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile.

[0064] The benzene compound includes fluorobenzene, the amine compound includes triethyl alcoholamine or ethylenediamine, etc., and the silane compound includes tetravinylsilane.

[0065] The lithium salt compound is a compound different from the lithium salt contained in the gel polymer electrolyte, and examples include LiPO2F2 or LiBF4.

[0066] Among such other electrolyte additives, when further containing vinylene carbonate, vinyl ethylene carbonate, succinonitrile, etc., a stronger SEI film can be formed on the surface of the negative electrode during the initial activation process of the secondary battery.

[0067] When containing the LiBF4, generation of gas that can be generated by decomposition of the electrolyte at high temperatures can be suppressed, and the high-temperature stability of the secondary battery can be improved.

[0068] On the other hand, two or more of the other electrolyte additives can be mixed and used, and can be contained in an amount of 0.01 to 2% by weight, 0.01 to 1.5% by weight, and more preferably 0.05 to 1% by weight based on the total weight of the gel polymer electrolyte. When the additive satisfies the above range, the effects of improving ionic conductivity and cycle characteristics are more excellent.

[0069] Lithium secondary battery The present invention can also provide a lithium secondary battery including the gel polymer electrolyte.

[0070] Specifically, the lithium secondary battery can include a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, a separator interposed between the positive electrode and the negative electrode, and the above-described gel polymer electrolyte.

[0071] The lithium secondary battery including the gel polymer electrolyte according to the present invention has improved thermal stability, and when the heat flow is measured by differential scanning calorimetry (DSC), the heat generation amount is 100 J / g or less in the temperature range of 200°C to 300°C, and there may be almost no peak. Specifically, the heat generation amount can be 80 J / g or less in the temperature range of 200°C to 300°C. This is considered to be because the heat absorption characteristics of the ether diacrylate cross-linking agent containing a fluorinated group are excellent and it is more effective in suppressing the heat generation amount of the lithium secondary battery.

[0072] The heat flow measurement by the differential scanning calorimetry (DSC) can be measured using a TA instrument, DSC25 device, and using a Tzero hermetic aluminum pan, the heat generation amount in the temperature range of 0°C to 300°C can be measured at a heating rate of 10°C / min.

[0073] The positive electrode can be manufactured by coating a positive electrode mixture slurry containing a positive electrode active material, a binder, a conductive material, a solvent, etc. on a positive electrode current collector.

[0074] The positive electrode current collector is not particularly limited as long as it does not cause a chemical change in the battery and has conductivity. For example, stainless steel, aluminum, nickel, titanium, fired carbon, or those obtained by surface treatment of the surface of aluminum or stainless steel with carbon, nickel, titanium, silver, etc. can be used.

[0075] The positive electrode active material can include a lithium metal oxide containing one or more metals such as cobalt, manganese, nickel, or aluminum and lithium as a compound capable of reversible intercalation and deintercalation of lithium. More specifically, the lithium metal oxide includes lithium-manganese-based oxides (e.g., LiMnO2, LiMn2O4, etc.), lithium-cobalt-based oxides (e.g., LiCoO2, etc.), lithium-nickel-based oxides (e.g., LiNiO2, etc.), lithium-nickel-manganese-based oxides (e.g., LiNi 1-Y Mn Y O2 (where 0 < Y < 1), LiMn 2-z Ni z O4 (where 0 < Z < 2), etc.), lithium-nickel-cobalt-based oxides (e.g., LiNi 1-Y1 Co Y1 O2 (where 0 < Y1 < 1), etc.), lithium-manganese-cobalt-based oxides (e.g., LiCo 1-Y2 Mn Y2 O2 (where 0 < Y2 < 1), LiMn 2-z1 Co z1 O4 (where 0 < Z1 < 2), etc.), lithium-nickel-manganese-cobalt-based oxides (e.g., Li(Ni p Co q Mn r1 )O2 (where 0 < p < 1, 0 < q < 1, 0 < r1 < 1, p + q + r1 = 1) or Li(Ni p1 Co q1 Mnr2 )O4 (where 0 < p1 < 2, 0 < q1 < 2, 0 < r2 < 2, p1 + q1 + r2 = 2), etc.), or lithium-nickel-cobalt-transition metal (M) oxide (e.g., Li(Ni p2 Co q2 Mn r3 M S2 )O2 (where M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, and p2, q2, r3, and s2 are, as atomic fractions of independent elements, 0 < p2 < 1, 0 < q2 < 1, 0 < r3 < 1, 0 < s2 < 1, and p2 + q2 + r3 + s2 = 1), etc.), and any one or more of these compounds can be included.

[0076] Among them, in terms of being able to enhance the capacity characteristics and stability of the battery, the lithium metal oxide is LiCoO2, LiMnO2, LiNiO2, lithium nickel manganese cobalt oxide (e.g., Li(Ni 1 / 3 Mn 1 / 3 Co 1 / 3 )O2, Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2, and Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc.), or lithium nickel cobalt aluminum oxide (e.g., Li(Ni 0.8 Co 0.15 Al 0.05 )O2, etc.), and any one or more of these mixtures can be used. Preferably, the positive electrode active material can be a lithium-nickel-manganese-cobalt-based oxide.

[0077] The positive electrode active material can be contained in an amount of 60 to 99% by weight, preferably 70 to 99% by weight, more preferably 80 to 98% by weight, based on the total weight of the solid components other than the solvent in the positive electrode mixture slurry.

[0078] The binder is a component that helps bind the active material, conductive material, etc. and bind to the current collector.

[0079] Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene (PE), polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, various copolymers, and the like.

[0080] Usually, the binder can be contained in an amount of 1 to 20% by weight, preferably 1 to 15% by weight, more preferably 1 to 10% by weight, based on the total weight of the solid matter other than the solvent in the positive electrode mixture slurry.

[0081] The conductive material can be added in an amount of 1 to 20% by weight based on the total weight of the solid components in the positive electrode mixture slurry as a component for further improving the conductivity of the positive electrode active material. Such a conductive material is not particularly limited as long as it does not cause a chemical change in the battery and has conductivity. For example, carbon powders such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powders such as natural graphite, artificial graphite, or graphite with a highly developed crystal structure; conductive fibers such as carbon fibers and metal fibers; carbon fluoride powders; conductive powders such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives can be used.

[0082] Generally, the conductive material can be contained in an amount of 1 to 20% by weight, preferably 1 to 15% by weight, more preferably 1 to 10% by weight, based on the total weight of the solid content other than the solvent in the positive electrode active material slurry.

[0083] The solvent can include an organic solvent such as NMP (N-methyl-2-pyrrolidone), and can be used in an amount that results in a preferred viscosity when the positive electrode active material, and optionally a binder, a conductive material, etc. are included. For example, it can be included such that the concentration of the solid content including the positive electrode active material, and optionally the binder and the conductive material, is 50 to 95% by weight, preferably 70 to 95% by weight, more preferably 70 to 90% by weight.

[0084] The negative electrode can be manufactured, for example, by coating a negative electrode active material slurry containing a negative electrode active material, a binder, a conductive material, a solvent, etc. on a negative electrode current collector, or a graphite electrode made of carbon (C) or the metal itself can be used as the negative electrode.

[0085] For example, when manufacturing a negative electrode by coating a negative electrode active material slurry on the negative electrode current collector, the negative electrode current collector generally has a thickness of 3 to 500 μm. Such a negative electrode current collector is not particularly limited as long as it does not cause a chemical change in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, fired carbon, those with a surface treatment of carbon, nickel, titanium, silver, etc. on the surface of copper or stainless steel, aluminum-cadmium alloy, etc. can be used. Also, similar to the positive electrode current collector, fine irregularities can be formed on the surface to strengthen the bonding force of the negative electrode active material, and it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric body, etc.

[0086] Further, the negative electrode active material can include at least one selected from the group consisting of lithium metal, a carbon material capable of reversibly intercalating / deintercalating lithium ions, a metal, an alloy of these metals and lithium, a metal composite oxide, a material capable of doping and dedoping lithium, and a transition metal oxide.

[0087] As the carbon material capable of reversibly intercalating / deintercalating lithium ions, any carbon-based negative electrode active material generally used in a lithium-ion secondary battery can be used without particular limitation. Representative examples thereof include crystalline carbon, amorphous carbon, or both of them can be used. Preferably, crystalline carbon can be used as the negative electrode active material. Examples of the crystalline carbon include graphite such as amorphous, plate-like, flaky, spherical, or fibrous natural graphite or artificial graphite. Examples of the amorphous carbon include soft carbon (low-temperature calcined carbon), hard carbon, mesophase pitch carbide, calcined coke, and the like.

[0088] As the metal or the alloy of these metals and lithium, a metal selected from the group consisting of Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn, or an alloy of these metals and lithium can be used.

[0089] Examples of the metal composite oxide include PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5, Li x Fe2O3(0≦x≦1), Li x WO2(0≦x≦1) and Sn x Me 1-x Me’ y O z(Me: Mn, Fe, Pb, Ge; Me’: Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen; 0 < x ≤ 1; 1 ≤ y ≤ 3; 1 ≤ z ≤ 8) can be selected from the group consisting of those used.

[0090] As substances capable of doping and undoping lithium, Si, SiO x (0 < x ≤ 2), Si-Y alloy (where Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Si), Sn, SnO2, Sn-Y (where Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Sn), etc. can be mentioned, and at least one of these can also be used in combination with SiO2. As the element Y, it can be selected from the group consisting of Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof.

[0091] Examples of the transition metal oxide include lithium-containing titanium composite oxide (LTO), vanadium oxide, lithium vanadate, etc.

[0092] The negative electrode active material can be contained in an amount of 60 to 99% by weight, preferably 70 to 99% by weight, more preferably 80 to 98% by weight, based on the total weight of the solid content in the negative electrode binder slurry.

[0093] The binder is a component that facilitates the binding between the conductive material, the active material, and the current collector. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, various copolymers thereof, and the like.

[0094] Generally, the binder can be contained in an amount of 1 to 20% by weight, preferably 1 to 15% by weight, more preferably 1 to 10% by weight, based on the total weight of the solid components other than the solvent in the negative electrode active material slurry.

[0095] The conductive material can be added in an amount of 1 to 20% by weight based on the total weight of the solid components in the negative electrode active material slurry as a component for further improving the conductivity of the negative electrode active material. Such a conductive material is not particularly limited as long as it does not cause a chemical change in the battery and has conductivity. For example, carbon powders such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powders such as natural graphite, artificial graphite, or graphite with a highly developed crystal structure; conductive fibers such as carbon fibers and metal fibers; carbon fluoride powders; conductive powders such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives can be used.

[0096] The conductive material can be contained in an amount of 1 to 20% by weight, preferably 1 to 15% by weight, more preferably 1 to 10% by weight, based on the total weight of the solids other than the solvent in the negative electrode active material slurry.

[0097] The solvent can include water or an organic solvent such as NMP (N-methyl-2-pyrrolidone), and can be used in an amount that results in a preferred viscosity when including the negative electrode active material, and optionally a binder, a conductive material, etc. For example, the concentration of the solid content including the negative electrode active material, and optionally the binder and the conductive material, can be included such that it is 50% to 95% by weight, preferably 70% to 90% by weight.

[0098] When using the metal itself as the negative electrode, it can be manufactured by physically bonding, rolling, or vapor depositing the metal on the metal thin film itself or the negative electrode current collector. For the vapor deposition method, an electrical vapor deposition method or a chemical vapor deposition method can be used for the metal.

[0099] For example, the metal bonded / rolled / vapor deposited on the metal thin film itself or the negative electrode current collector can include one metal selected from the group consisting of lithium (Li), nickel (Ni), tin (Sn), copper (Cu), and indium (In), or an alloy of two metals, etc.

[0100] Also, as the separator, a conventional porous polymer film used as a separator, for example, a porous polymer film made of a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer can be used alone or laminated, or a conventional porous non-woven fabric, for example, a non-woven fabric made of high melting point glass fibers, polyethylene terephthalate fibers, etc. can be used, but it is not limited thereto. Also, for ensuring heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymer substance can be used, and optionally, it can be used as a single layer or a multi-layer structure.

[0101] The outer shape of the lithium secondary battery case of the present invention is not particularly limited, and it can be a cylindrical shape, a rectangular shape, a pouch type, a coin type, etc. using a can.

[0102] The content of the gel polymer electrolyte with respect to the entire secondary battery can be 10 to 30% by weight, preferably 10 to 25% by weight, and more preferably 10 to 20% by weight. When the content of the gel polymer electrolyte satisfies the above range, there is an advantage that not only high ionic conductivity and thermal stability can be ensured, but also a lithium secondary battery with improved cycle life characteristics and safety can be manufactured.

[0103] The method for manufacturing the lithium secondary battery of the present invention includes the steps of preparing an electrode assembly including the above-described positive electrode, negative electrode, and a separator interposed between the positive electrode and the negative electrode, inserting the electrode assembly into the inside of the battery case, preparing a gel polymer electrolyte precursor solution including a thiol compound containing at least 4 or more reactive thiol groups per molecule, a fluorinated polyether diacrylate, an organic solvent, a lithium salt, and a thermal polymerization initiator, and injecting the precursor solution into the inside of the battery case into which the electrode assembly is inserted and performing heat treatment to carry out a crosslinking reaction.

[0104] The gel polymer electrolyte precursor solution can be manufactured by mixing a thiol compound containing at least 4 or more reactive thiol groups per molecule, a fluorinated polyether diacrylate, an organic solvent, a lithium salt, and a thermal polymerization initiator. Since the thiol compound, the fluorinated polyether diacrylate, the organic solvent, and the lithium salt have been described above, specific descriptions are omitted.

[0105] As the thermal polymerization initiator, for example, one or more selected from the group consisting of peroxide initiators and azo initiators can be used. Specifically, examples of peroxide initiators include t-butyl peroxypivalate, 1-cyclohexyl-1-methylethyl peroxy-2-ethylhexanoate, t-butyl peroxyisopropyl monocarbonate, t-butyltriallylsilyl peroxide, and the like. Specific examples of azo initiators include 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), dimethyl 2,2'-azobis(2-methylpropionate), 2,2'-azobis(N-cyclohexyl-2-methylpropionate), and the like.

[0106] The thermal polymerization initiator can be contained in an amount of 0.005 to 5.0 parts by weight, preferably 0.01 to 3.0 parts by weight, more preferably 0.01 to 1 part by weight, based on 100 parts by weight of the total weight of the thiol compound, fluorinated polyether diacrylate, organic solvent, and lithium salt. When the content of the thermal polymerization initiator satisfies the above range, the thiol-ene structure is excellent in the reactivity of the click reaction between the thiol of the thiol compound containing at least 4 or more reactive thiol groups per molecule and the acrylic group of the fluorinated polyether diacrylate.

[0107] The heat treatment can be carried out at a temperature of 50°C to 80°C, preferably 55°C to 75°C, more preferably 65°C to 75°C. When the heat treatment temperature is less than 50°C, radicals for polymerization are not sufficiently generated, the efficiency of completing the polymerization decreases, and there is a problem that the remaining unreacted cross-linking agent deteriorates the performance of the battery. When the heat treatment temperature exceeds 80°C, there may be a problem that the electrolyte substance deteriorates or the structure is deformed.

[0108] The heat treatment can be carried out for 0.5 to 3 hours, preferably 1.5 to 2.5 hours. When the heat treatment time is less than 0.5 hours, the polymerization reaction cannot proceed sufficiently, a high polymerization conversion rate cannot be ensured, a uniform polymer cannot be obtained, and there is a problem that the remaining unreacted cross-linking agent deteriorates the performance of the battery. When the heat treatment time exceeds 3 hours, there may be problems such as deterioration of the substance or deformation of the structure.

[0109] Hereinafter, the present invention will be described more specifically with reference to specific examples. However, the following examples are for illustrative purposes to facilitate understanding of the present invention and do not limit the scope of the present invention. It is obvious to those skilled in the art that various changes and modifications can be made within the scope of the description and the scope of the technical idea, and it goes without saying that such modifications and changes belong to the scope of the appended claims.

[0110] Examples Example 1 (Production of Gel Polymer Electrolyte Precursor Solution) 0.38 g of pentaerythritol tetrakis(3-mercaptopropionate) and 0.62 g of the fluorinated polyether diacrylate of Chemical Formula 1-2 were mixed so that the number of moles of reactive functional groups was the same, and 5 g of lithium bis(trifluoromethanesulphonyl)imide (LiTFSI) as a lithium salt, 4 g of dimethyl carbonate (DMC) as an organic solvent, and 0.03 g of tert-butyl peroxypivalate (t-BPP) as an initiator were added to produce a gel polymer electrolyte precursor solution containing a cross-linked polymer having a thiol-ene structure.

[0111] (Production of Lithium Secondary Battery) Cathode active material (LiNi 0.6 Co 0.2 Mn 0.2O2): The conductive material (Super P), binder (polyvinylidene fluoride), and solvent N-methyl-2-pyrrolidone (NMP) were added in a weight ratio of 95:3:2 to produce a positive electrode slurry (solid content 75 wt%). The positive electrode slurry was coated on one side of a positive electrode current collector (Al thin film) with a thickness of 20 μm, followed by drying and roll pressing to produce a positive electrode.

[0112] The negative electrode active material (graphite), conductive material (Super P), and binder (polyvinylidene fluoride) were added in a weight ratio of 90:3:7 to the solvent N-methyl-2-pyrrolidone (NMP) to produce a negative electrode slurry (solid content 60 wt%). The negative electrode slurry was coated on one side of a negative electrode current collector (Cu thin film) with a thickness of 15 μm, followed by drying and roll pressing to produce a negative electrode.

[0113] In a glove box, an electrode laminate was assembled with a polyethylene separator interposed between the manufactured positive electrode and negative electrode, and this was inserted into the interior of a battery case. The precursor solution was injected into the battery case, and heat treatment was performed at 70 °C for 2 hours to carry out a cross-linking reaction, thereby manufacturing a secondary battery cell.

[0114] Example 2 A secondary battery cell was manufactured in the same manner as in Example 1, except that 0.76 g of pentaerythritol tetrakis(3-mercaptopropionate) and 1.24 g of the fluorinated polyether diacrylate of Chemical Formula 1-2 were mixed so that the number of moles of reactive functional groups matched, and 4 g of lithium bis(trifluoromethanesulphonyl)imide (LiTFSI) as a lithium salt, 4 g of dimethyl carbonate (DMC) as an organic solvent, and 0.03 g of tert-butyl peroxypivalate (t-BPP) as an initiator were added to produce a gel polymer electrolyte precursor solution.

[0115] Example 3 1.14 g of pentaerythritol tetrakis(3-mercaptopropionate) and 1.86 g of the fluorinated polyether diacrylate of Chemical Formula 1-2 were mixed so that the number of moles of reactive functional groups matched, and 3 g of lithium bis(trifluoromethanesulphonyl)imide (LiTFSI) as a lithium salt, 4 g of dimethyl carbonate (DMC) as an organic solvent, and 0.03 g of tert-butyl peroxypivalate (t-BPP) as an initiator were added. A secondary battery cell was manufactured in the same manner as in Example 1, except that a gel polymer electrolyte precursor solution was prepared.

[0116] Example 4 0.38 g of pentaerythritol tetrakis(3-mercaptopropionate) and 0.62 g of the fluorinated polyether diacrylate of Chemical Formula 1-2 were mixed so that the number of moles of reactive functional groups matched, and 5 g of lithium bis(trifluoromethanesulphonyl)imide (LiTFSI) as a lithium salt, 4 g of dimethyl carbonate (DMC) as an organic solvent, 0.03 g of tert-butyl peroxypivalate (t-BPP) as an initiator, and 0.1 g of vinylene carbonate (VC) as an additive were added. A secondary battery cell was manufactured in the same manner as in Example 1, except that a gel polymer electrolyte precursor solution was prepared.

[0117] Comparative Example 1 (Production of Liquid Electrolyte) 5 g of lithium bis(trifluoromethanesulphonyl)imide (LiTFSI) as a lithium salt and 4 g of dimethyl carbonate (DMC) as an organic solvent were mixed to produce a liquid electrolyte.

[0118] (Manufacture of Lithium Secondary Battery) Positive electrode active material (LiNi 0.6 Co 0.2 Mn 0.2 O2): Conductive material (Super P): Binder (polyvinylidene fluoride) was added to N-methyl-2-pyrrolidone (NMP), which is a solvent, at a weight ratio of 95:3:2 to produce a positive electrode slurry (solid content 75 wt%). The positive electrode slurry was applied to one side of a positive electrode current collector (Al thin film) with a thickness of 20 μm, and drying and roll press were carried out to produce a positive electrode.

[0119] Negative electrode active material (graphite): Conductive material (Super P): Binder (polyvinylidene fluoride) was added to N-methyl-2-pyrrolidone (NMP), which is a solvent, at a weight ratio of 90:3:7 to produce a negative electrode slurry (solid content 60 wt%). The negative electrode slurry was applied to one side of a negative electrode current collector (Cu thin film) with a thickness of 15 μm, and drying and roll press were carried out to produce a negative electrode.

[0120] In a dry room, a polyethylene separator was interposed between the manufactured positive electrode and negative electrode, and then the liquid electrolyte was inserted to manufacture a secondary battery cell.

[0121] Comparative Example 2 0.49 g of pentaerythritol tetrakis(3-mercaptopropionate) and 0.51 g of polyether diacrylate of the following chemical formula A were mixed so that the number of moles of reactive functional groups was the same. 5 g of lithium bis(trifluoromethanesulphonyl)imide (LiTFSI) as a lithium salt, 4 g of dimethyl carbonate (DMC) as an organic solvent, and 0.03 of tert-butyl peroxypivalate (t-BPP) as an initiator were added to produce a gel polymer electrolyte precursor solution. A secondary battery cell was manufactured in the same manner as in Example 1 except for this.

[0122] [Chemical formula]

[0123] Experimental Example 1 - Measurement of Ionic Conductivity The ionic conductivity values at different temperatures of the gel polymer electrolytes produced inside the secondary batteries in Examples 1 to 4 and Comparative Example 2 were measured. Specifically, for the gel polymer electrolytes produced in Examples 1 to 4 and Comparative Example 2, the ionic conductivity was analyzed using Zahner Electrik, IM6, and the results are shown in Table 1 below.

[0124] [Table 1]

[0125] The gel polymer electrolytes of Examples 1 to 4 showed a high ionic conductivity of 1.3×10 -3 S / cm or more at room temperature and 2.0×10 -3 S / cm or more at 45°C. Also, the gel polymer electrolytes of Examples 1 to 4 showed a higher ionic conductivity than the gel polymer electrolyte of Comparative Example 2.

[0126] Experimental Example 2 - Evaluation of Electrochemical Stability To evaluate the electrochemical stability of the electrolytes of Example 1 and Comparative Example 1, linear sweep voltammetry (LSV) was measured. The LSV experiment was carried out at 25°C with a scan rate of 1 mV / s, and the results are shown in Figure 1.

[0127] As shown in Figure 1, it is confirmed that the gel polymer electrolyte of Example 1 produced using fluorinated ether diacrylate is stable without electrochemical decomposition up to 5.3 V. On the other hand, it can be confirmed that the electrolyte of Comparative Example 1 decomposes at about 5.1 V and is inferior in electrochemical stability compared to the gel polymer electrolyte of Example 1.

[0128] Experimental Example 3 - Evaluation of Cycle Characteristics The cycle characteristics of each of the secondary batteries manufactured in Examples 1 to 4 and Comparative Examples 1 and 2 were evaluated.

[0129] Specifically, each of the secondary batteries manufactured in Examples 1 to 4 and Comparative Examples 1 and 2 was charged to 4.2 V at a constant current of 0.1 C at 25°C, and discharged to 3.0 V at a constant current of 0.1 C. One cycle was defined as this process. After performing 100 cycles of charge and discharge, the capacity retention rate with respect to the initial capacity after 100 cycles was measured. The results are shown in Table 2 below.

[0130] [Table 2]

[0131] The secondary batteries of Examples 1 to 4 using the gel polymer electrolyte according to the present invention were superior in life characteristics compared to the secondary battery of Comparative Example 1 using a liquid organic solvent electrolyte. Also, the secondary batteries using Examples 1 to 4 were superior in life characteristics compared to the secondary battery of Comparative Example 2 using a carbon-based polyethylene acrylate cross-linking agent not containing a fluorine group.

[0132] Experimental Example 4 - Evaluation of Thermal Stability Using a differential scanning calorimeter (TA instrument, DSC25), the heat generation amount during charge and discharge of each of the secondary batteries manufactured in Example 1, Comparative Example 1, and Comparative Example 2 was measured. Specifically, 0.0016 g of each of the secondary batteries manufactured in Example 1, Comparative Example 1, and Comparative Example 2 was put into a pressure-resistant pan for DSC measurement. The temperature range for DSC analysis was 25°C to 400°C, and the heating rate was 10°C / min. For each secondary battery, the heat flow due to temperature was measured. The measurement results are shown in FIG. 2.

[0133] From FIG. 2(a), it can be confirmed that the secondary battery of Example 1 is excellent in thermal stability and shows almost no peak in the heat generation amount in the temperature range of 200°C to 300°C, with a heat generation amount of 75.4 J / g.

[0134] On the other hand, referring to FIG. 2(b), clear heat generation peaks were observed in the low-temperature part and the high-temperature part of the secondary battery of Comparative Example 1. In particular, a high heat generation amount of 689.0 J / g was shown in the temperature range of 200°C to 300°C.

[0135] Referring to FIG. 2(c), it can be confirmed that the secondary battery of Comparative Example 2 using a carbon-based polyethylene acrylate crosslinking agent shows a heat generation amount of 139.6 J / g in the temperature range of 200°C to 300°C. The secondary battery using the gel polymer electrolyte of Comparative Example 2 showed a higher heat generation amount than the secondary battery using the gel polymer electrolyte of Example 1 according to the present invention. Therefore, it was found that using a fluorinated polyether diacrylate crosslinking agent is more effective in suppressing heat generation of lithium secondary batteries compared to an acrylate crosslinking agent without a fluorine group substitution.

Claims

1. A gel polymer electrolyte comprising a crosslinked polymer having a thiol-ene structure, wherein the thiol-ene structure is formed by a click reaction between a thiol group of a thiol compound containing at least 4 or more reactive thiol groups per molecule and an acrylic group of a fluorinated polyether diacrylate. Gel polymer electrolyte.

2. The thiol compound is one or more selected from the group consisting of pentaerythritol tetrakis(3-mercaptopropionate), dipentaerythritol hexakis(3-mercaptopropionate), pentaerythrityl tetrathiol, tetrakis(2-mercaptoethyl)silane, and benzene-1,2,4,5-tetrathiol. The gel polymer electrolyte according to claim 1.

3. The fluorinated polyether diacrylate is represented by the following Chemical Formula 1-1. The gel polymer electrolyte according to claim 1: 【Chemical Formula 1】 In Chemical Formula 1-1, R ｘ and R ｙ are each independently an alkylene group having 1 to 10 carbon atoms, n is an integer of 1 to 5.

4. The fluorinated polyether diacrylate is represented by the following Chemical Formula 1-2. The gel polymer electrolyte according to claim 1. 【Chemical Formula 2】

5. The weight average molecular weight of the fluorinated polyether diacrylate is 200 to 2000 g / mol. The gel polymer electrolyte according to claim 1.

6. The gel polymer electrolyte according to claim 1, further comprising a lithium salt and an organic solvent.

7. The weight ratio of the crosslinked polymer having a thiol-ene structure to the lithium salt is 1:11 to 1:0.

5. The gel polymer electrolyte according to claim 6.

8. The crosslinked polymer having a thiol-ene structure is contained in an amount of 10 to 80 parts by weight based on 100 parts by weight of the organic solvent, and is the gel polymer electrolyte according to claim 6.

9. The lithium ion conductivity is 1.0×10 －３ S / cm or more at 25°C, and is the gel polymer electrolyte according to claim 1.

10. The lithium ion conductivity is 2.0×10 －３ S / cm or more at 45°C, and is the gel polymer electrolyte according to claim 1.

11. As an additive, it further contains one or more compounds selected from the group consisting of cyclic carbonate compounds, halogen-substituted carbonate compounds, sultone compounds, sulfate compounds, phosphate compounds, borate compounds, nitrile compounds, benzene compounds, amine compounds, silane compounds and lithium salt compounds, and is the gel polymer electrolyte according to claim 1.

12. The additive is contained in an amount of 0.01 to 2% by weight based on the total weight of the gel polymer electrolyte, and is the gel polymer electrolyte according to claim 11.

13. A lithium secondary battery containing the gel polymer electrolyte according to any one of claims 1 to 12.

14. When measuring the heat flow by differential scanning calorimetry (DSC), in the temperature range of 200°C to 300°C, the heat generation amount is 100 J / g or less, and is the lithium secondary battery according to claim 13.

15. Preparing an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode; Inserting the electrode assembly into the interior of a battery case; A step of preparing a gel polymer electrolyte precursor solution containing a thiol compound having at least 4 or more reactive thiol groups per molecule, a fluorinated polyether diacrylate, an organic solvent, a lithium salt, and a thermal polymerization initiator; A method for manufacturing a lithium secondary battery, comprising: injecting the precursor solution into a battery case into which the electrode assembly is inserted and performing a heat treatment to carry out a crosslinking reaction.

16. The method for manufacturing a lithium secondary battery according to claim 15, wherein the heat treatment is performed at a temperature of 50°C to 80°C for 0.5 to 3 hours.

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