A gel polymer electrolyte composition with shortened crosslinking time, a secondary battery containing the same, and a method for manufacturing the secondary battery.

Abstract

To provide a gel polymer electrolyte composition attaining a shortened crosslinking time, a secondary battery including the same, and a manufacturing method of the secondary battery.SOLUTION: The present invention relates to a gel polymer electrolyte composition, a secondary battery including the same, and a manufacturing method of a secondary battery. Advantages of the disclosed aspects include increasing process efficiency by reducing the curing time of a gel polymer electrolyte while preventing leakage of an electrolyte.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This application claims priority under Korean Patent Application No. 10-2022-0040568 dated March 31, 2022, and all content disclosed in the said Korean Patent Application is incorporated herein as part of this specification.

[0002] This invention relates to a gel polymer electrolyte composition with a shortened crosslinking time, a secondary battery containing the same, and a method for manufacturing a secondary battery. [Background technology]

[0003] In recent years, rechargeable secondary batteries have been widely used as an energy source for wireless mobile devices. Furthermore, secondary batteries are attracting attention as an energy source for electric vehicles and hybrid electric vehicles, which are being proposed as solutions to address air pollution caused by existing gasoline and diesel vehicles that use fossil fuels. Therefore, the types of applications using secondary batteries have become extremely diverse due to their advantages, and it is expected that secondary batteries will be applied to many more fields and products in the future.

[0004] Rechargeable batteries have a structure in which the electrode assembly is built into the battery case along with the electrolyte, and the electrode assembly exhibits electrical performance when it is sufficiently impregnated and wetted with the electrolyte. However, electrolyte leakage can occur during the charging and discharging process, which can cause battery cell failure and even lead to fire.

[0005] Gel polymer electrolytes are being researched as a method to prevent electrolyte leakage. However, gel polymer electrolytes require a crosslinking process after the electrolyte is injected into the battery. This crosslinking process takes a lot of time, which reduces process efficiency and increases manufacturing costs.

[0006] Therefore, there is a need for a technology that can shorten the curing time due to the cross-linking reaction in the electrolyte while introducing a gel polymer electrolyte to prevent electrolyte leakage.

Summary of the Invention

Problems to be Solved by the Invention

[0007] The present invention was devised to solve the above problems, and an object thereof is to provide a gel polymer electrolyte composition capable of significantly shortening the curing time compared to existing ones, and a secondary battery containing the same.

Means for Solving the Problems

[0008] The present invention provides a composition for a gel polymer electrolyte. In one embodiment, the composition for a gel polymer electrolyte according to the present invention contains an oligomer represented by the following Chemical Formula 1, a curing accelerator which is a monocyclic or polycyclic cyclic amine compound, a polymerization initiator, a non-aqueous solvent, and a lithium salt.

[0009]

Chem.

[0010] In the above Chemical Formula 1, R is an alkylene having 1 to 5 carbon atoms substituted with hydrogen or an alkyl group having 1 to 5 carbon atoms, and m is an integer of 1 to 50.

[0011] In one embodiment, the composition for a gel polymer electrolyte has a curing time in the range of 10 minutes to 50 minutes under heat treatment conditions of 55 to 80°C.

[0012] In a specific embodiment, the content of the oligomer is in the range of 0.1 to 30 parts by weight with respect to 100 parts by weight of the entire composition for a gel polymer electrolyte.

[0013] In another embodiment, the curing accelerator contains one or more of pyrimidine-based, imidazole-based, purine-based, thiadiazole-based, and pyrrole-based.

[0014] In a specific embodiment, the pyrimidine-based curing accelerator is one or more of the following chemical formulas 1-a to 1-g.

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[0022] In specific embodiments, the imidazole-based curing accelerator is one or more of the following chemical formulas 2-a to 2-i.

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[0032] In a specific embodiment, the purine-based curing accelerator is represented by the following chemical formula 3-a.

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[0034] In specific embodiments, the thiadiazole derivative is one or more of the following chemical formulas 4-a to 4-b.

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[0037] In a specific embodiment, the pyrrole-based curing accelerator is one or more of the following chemical formulas 5-a to 5-c.

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[0041] In one embodiment, the content of the curing accelerator is in the range of 0.01 to 10 parts by weight per 100 parts by weight of the entire gel polymer electrolyte composition.

[0042] Furthermore, the present invention provides a method for manufacturing a lithium secondary battery using the gel polymer electrolyte composition described above. In one embodiment, the method for manufacturing a lithium secondary battery according to the present invention includes the step of pouring the gel polymer electrolyte composition described above into a battery case while an electrode assembly including a positive electrode, a negative electrode, and a separation membrane disposed between the positive electrode and the negative electrode is housed in the battery case.

[0043] In one embodiment, the method for manufacturing the lithium secondary battery further includes a step of performing thermal crosslinking for a period of 10 to 50 minutes after pouring the gel polymer electrolyte composition into the battery case.

[0044] In a specific embodiment, the step of performing the thermal crosslinking described above is carried out in the range of 55 to 80°C.

[0045] In another specific embodiment, the manufacturing method according to the present invention further includes a wetting step of waiting for 1 minute to 30 hours between the step of pouring the gel polymer electrolyte composition into the battery case and the step of performing thermal crosslinking.

[0046] In another specific embodiment, the manufacturing method according to the present invention further comprises one or more of the following steps: an activation step and a degassing step, after the step of thermal crosslinking.

[0047] Furthermore, the present invention provides a secondary battery manufactured by the method described above. In one embodiment, the lithium secondary battery according to the present invention includes an electrode assembly comprising a positive electrode, a negative electrode, and a separation membrane disposed between the positive electrode and the negative electrode, a battery case for housing and sealing the electrode assembly, and a gel polymer electrolyte composition injected into the battery case housing the electrode assembly. The gel polymer electrolyte composition is as described above.

[0048] In a specific embodiment, the lithium secondary battery is a pouch-type battery. [Effects of the Invention]

[0049] This invention makes it possible to improve the efficiency of the manufacturing process for secondary batteries using thermally crosslinked gel polymer electrolytes and to improve the quality of the manufactured products. [Brief explanation of the drawing]

[0050] [Figure 1] This is a schematic diagram illustrating the leakage evaluation process for a pouch-type secondary battery according to one embodiment of the present invention. [Modes for carrying out the invention]

[0051] The present invention will now be described in detail. Before that, however, the terms and words used herein and in the claims should not be interpreted in a manner limited to their general or dictionary meanings, but rather in a manner consistent with the technical spirit of the present invention, based on the principle that an inventor may appropriately define the concepts of terms in order to best describe his own invention.

[0052] The present invention provides a composition for gel polymer electrolytes. In one embodiment, the composition for gel polymer electrolytes according to the present invention comprises an oligomer, a curing accelerator which is a monocyclic or polycyclic cyclic amine compound, a polymerization initiator, a non-aqueous solvent, and a lithium salt.

[0053] In this invention, "monocyclic" includes cases where the structural formula contains one cyclic structure. "Polycyclic" means cases where the structural formula contains two or more, specifically 2 to 4, cyclic structures, and includes cases where the two or more cyclic structures are fused or compounded with each other.

[0054] This invention significantly increases the gelation rate of the electrolyte by adding a curing accelerator that promotes the crosslinking reaction of oligomers.

[0055] As one example, the above oligomer can be a PPC (Polypropylene carbonate) series oligomer. In one embodiment, the above oligomer is represented by the following chemical formula 1.

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[0057] In the above chemical formula 1, R is a C1-C5 alkylene substituted with hydrogen or an alkyl group having C1-C5, and m is an integer from 1 to 50.

[0058] Specifically, R is an arylene with 1 to 3 carbon atoms, and more specifically, an arylene with 2 carbon atoms substituted with a methyl group. m is an integer from 1 to 10, an integer from 2 to 5, an integer from 2 to 3, or 2.

[0059] In one embodiment, the oligomer content in the present invention is in the range of 0.1 to 30 parts by weight per 100 parts by weight of the total gel polymer electrolyte composition. More specifically, the oligomer content is in the range of 1 to 10 parts by weight, 2 to 8 parts by weight, or 3 to 5 parts by weight. The oligomer content is within a range that prevents electrolyte leakage when applied to a secondary battery without degrading the performance of the secondary battery.

[0060] The curing temperature of the above gel polymer electrolyte composition may vary depending on the type of polymerization initiator. In one embodiment, the crosslinking reaction of the above gel polymer electrolyte composition proceeds under heat treatment conditions of 55-80°C, 60-75°C, or 62-68°C, in which case the curing time is in the range of 10-50 minutes, 10-40 minutes, or 20-40 minutes. By using a curing accelerator, the curing time of the above gel polymer electrolyte composition can be reduced by 25% or more compared to conventional methods.

[0061] In one embodiment, the curing accelerator comprises one or more of the pyrimidine, imidazole, purine, thiadiazole, and pyrrole types. The present invention also includes cases in which one or more of these curing accelerators are used in combination.

[0062] In a specific embodiment, the pyrimidine-based curing accelerator is one or more of the following chemical formulas 1-a to 1-g.

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[0070] In specific embodiments, the imidazole-based curing accelerator is one or more of the following chemical formulas 2-a to 2-i.

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[0080] In a specific embodiment, the purine-based curing accelerator has the following chemical formula 3-a.

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[0082] In a specific embodiment, the thiadiazole-based curing accelerator is one or more of the following chemical formulas 4-a to 4-b.

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[0085] In a specific embodiment, the pyrrole-based curing accelerator is one or more of the following chemical formulas 5-a to 5-c.

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[0089] In the present invention, the content of the curing accelerator is in the range of 0.01 to 10 parts by weight per 100 parts by weight of the total gel polymer electrolyte composition. Specifically, the content of the curing accelerator is in the range of 0.1 to 10 parts by weight, 0.01 to 5 parts by weight, 0.2 to 5 parts by weight, or 0.5 to 2 parts by weight. Such a content of curing accelerator is within a range that can sufficiently reduce the curing rate while minimizing the amount added.

[0090] Furthermore, the present invention provides a method for manufacturing a lithium secondary battery to which the above-described gel polymer electrolyte is applied. In one embodiment, the method for manufacturing a lithium secondary battery according to the present invention includes the step of pouring a gel polymer electrolyte composition into a battery case while an electrode assembly including a positive electrode, a negative electrode, and a separation membrane disposed between the positive electrode and the negative electrode is housed in the battery case.

[0091] In this invention, a secondary battery is manufactured by injecting the above-described gel polymer electrolyte composition into a battery case containing an electrode assembly. Subsequently, the gel polymer electrolyte composition undergoes a process of gelling by heat treatment. Specifically, the present invention includes a step of performing thermal crosslinking for a range of 10 to 50 minutes after the step of injecting the gel polymer electrolyte composition into the battery case. This thermal crosslinking step is a process that induces the crosslinking reaction of the injected gel polymer electrolyte and causes it to harden. The hardening time is in the range of 10 to 50 minutes, 10 to 40 minutes, or 20 to 40 minutes. The present invention has the effect of reducing the hardening time by 25% or more compared to conventional methods.

[0092] Furthermore, the temperature of the heat treatment in the thermal crosslinking step may vary depending on the type of polymerization initiator added. In the present invention, for example, the curing accelerator represented by the following chemical formula 2 can be used. In this case, the thermal crosslinking step can be performed in a temperature range of 55-80°C, 60-75°C, or 62-68°C.

[0093] In another embodiment, the present invention includes a wetting step of waiting for 1 minute to 30 hours between the step of pouring the gel polymer electrolyte composition into the battery case and the step of performing thermal crosslinking.

[0094] In another embodiment, the present invention includes one or more of the following steps: an activation step and a degassing step, following the step of thermal crosslinking.

[0095] Furthermore, the present invention provides a secondary battery manufactured by the manufacturing method described above. In one embodiment, the secondary battery according to the present invention includes an electrode assembly comprising a positive electrode, one negative electrode, and a separation membrane disposed between the positive electrode and the negative electrode, a battery case for housing and sealing the electrode assembly, and a gel polymer electrolyte composition injected into the battery case housing the electrode assembly. The gel polymer electrolyte composition is as described above.

[0096] Depending on the method of stacking the electrode assemblies, they can be classified into a winding-type jelly roll type and a stacked type in which they are stacked sequentially. Furthermore, secondary batteries can be classified into cylindrical batteries and rectangular batteries in which the electrode assemblies are housed in a cylindrical or rectangular metal can, and pouch-type batteries in which the electrode assemblies are housed in a pouch-type case made of aluminum laminate sheet, depending on the shape of the battery case. The secondary battery of the present invention may be a cylindrical, rectangular, or pouch-type secondary battery, and is preferably a pouch-type secondary battery.

[0097] On the one hand, the above case can be made of a laminate sheet including a metal layer and a resin layer. Specifically, the above laminate sheet can be an aluminum laminate sheet. The battery case of the laminate sheet can be composed of a lower case including a recessed storage part and an outer shell part extending from the above storage part, and an upper case bonded to the above lower case by thermal fusion.

[0098] Hereinafter, the components of the secondary battery of the present invention will be described.

[0099] The positive electrode, which is one of the components of the secondary battery, has a structure in which a positive electrode active material layer is laminated on one or both sides of a positive electrode current collector. In one example, the positive electrode active material layer may include a positive electrode active material, a conductive material, a binder polymer, etc., and may further include a positive electrode additive generally used in the art as needed.

[0100] The above positive electrode active material can be a lithium-containing oxide, and may be the same or different. As the above lithium-containing oxide, a lithium-containing transition metal oxide can be used.

[0101] For example, the lithium-containing transition metal oxide is Li x CoO2 (0.5 < x < 1.3), Li x NiO2 (0.5 < x < 1.3), Li x MnO2 (0.5 < x < 1.3), Li x Mn2O4 (0.5 < x < 1.3), Li x (Ni a Co b Mn c )O2 (0.5 < x < 1.3, 0 < a < 1, 0 < b < 1, 0 < c < 1, a + b + c = 1), Li x Ni 1-y Co y O2 (0.5 < x < 1.3, 0 < y < 1), Li x Co 1-y Mn y O2 (0.5 < x < 1.3, 0 ≤ y < 1), Li x Ni 1-y Mn y O2 (0.5 < x < 1.3, 0 ≤ y < 1), Lix (Ni a Co b Mn c )O4 (0.5 < x < 1.3, 0 < a < 2, 0 < b < 2, 0 < c < 2, a + b + c = 2), Li x Mn 2-z Ni z O4 (0.5 < x < 1.3, 0 < z < 2), Li x Mn 2-z Co z O4 (0.5 < x < 1.3, 0 < z < 2), Li x CoPO4 (0.5 < x < 1.3), and Li x FePO4 (0.5 < x < 1.3), and can be any one selected from the group consisting of or a mixture of two or more thereof. Further, the lithium-containing transition metal oxide can also be coated with a metal or metal oxide such as aluminum (Al). In addition to the lithium-containing transition metal oxide, one or more of a sulfide, selenide, and halide can be used.

[0102] The positive electrode active material can be contained in the positive electrode active material layer in the range of 94.0 to 98.5% by weight. When the content of the positive electrode active material satisfies the above range, it is advantageous in terms of manufacturing a high-capacity battery and imparting sufficient conductivity of the positive electrode and adhesion between electrode materials.

[0103] The current collector used for the positive electrode is a highly conductive metal, and any metal can be used as long as the positive electrode active material slurry can easily adhere thereto and it is non-reactive within the voltage range of the electrochemical device. Specifically, non-limiting examples of the current collector for the positive electrode include foils made of aluminum, nickel, or combinations thereof. The positive electrode active material layer further contains a conductive material.

[0104] Carbon-based conductive materials are frequently used as the conductive material, and include spherical (sphere type) or needle-type carbon-based conductive materials. The spherical carbon-based conductive material, when mixed with a binder, fills the pores, which are the spaces between active material particles, thereby improving physical contact between the active materials, reducing interfacial resistance, and improving the adhesion between the lower positive electrode active material and the current collector.

[0105] The conductive material may be included in the positive electrode active material layer in an amount ranging from 0.5 to 5% by weight. When the content of the conductive material satisfies the above range, it provides sufficient conductivity to the positive electrode and has the effect of reducing the interfacial resistance between the electrode current collector and the active material.

[0106] The binder polymer can be any binder commonly used in the industry without limitation. For example, the binder may be a water-insoluble polymer that is soluble in organic solvents and insoluble in water, or a water-soluble polymer that is insoluble in organic solvents and soluble in water. The water-insoluble polymer may be one selected from the group including polyvinylidene fluoride (PVDF), polyvinylidene chloride (PVDC), polyacrylonitrile (PAN), polypropylene oxide (PPO), polyethylene oxide-propylene oxide copolymer (PEO-PPO), polytetrafluoroethylene (PTFE), polyimide (PI), polyetherimide (PEI), styrene-butadiene rubber (SBR), polyacrylate, and its derivatives.

[0107] The water-soluble polymer may be one or more selected from the group including various cellulose derivatives such as carboxymethylcellulose (CMC), methylcellulose (MC), cellulose acetate phthalate (CAP), hydroxypropyl methylcellulose (HPMC), and hydroxypropyl methylcellulose phthalate (HPMCP).

[0108] The amount of the binder polymer mentioned above is proportional to the amount of conductive material contained in the upper and lower positive electrode active material layers. This is because the binder polymer provides adhesion to the conductive material, which has a relatively small particle size compared to the active material. As the conductive material content increases, more binder polymer is required, and as the conductive material content decreases, less binder polymer can be used.

[0109] The above-described negative electrode has a structure in which a negative electrode active material layer is laminated on one or both sides of a negative electrode current collector. In one example, the negative electrode active material layer includes a negative electrode active material, a conductive material, and a binder polymer, and may further include negative electrode additives commonly used in the industry, as needed.

[0110] The above-mentioned anode active material may include carbon material, lithium metal, silicon, or tin. When carbon material is used as the anode active material, both low-crystalline carbon and high-crystalline carbon can be used. Typical low-crystalline carbons include soft carbon and hard carbon, while typical high-crystalline carbons include natural graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesocarbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch-derived cokes.

[0111] Non-limiting examples of current collectors used in the negative electrode include foils made from copper, gold, nickel, or copper alloys, or combinations thereof. The current collector can also be constructed by laminating substrates made of the above materials.

[0112] Furthermore, the negative electrode may include conductive materials and binders commonly used in the field.

[0113] The above-mentioned separation membrane can be any porous substrate used in lithium secondary batteries, for example, a polyolefin-based porous membrane or nonwoven fabric may be used, but is not particularly limited thereto.

[0114] Examples of the above-mentioned polyolefin-based porous membranes include membranes formed from polyethylene such as high-density polyethylene, linear low-density polyethylene, low-density polyethylene, and ultra-high molecular weight polyethylene, as well as polyolefin polymers such as polypropylene, polybutylene, and polypentene, either individually or as mixtures thereof.

[0115] The above-mentioned nonwoven fabrics include, in addition to polyolefin-based nonwoven fabrics, nonwoven fabrics formed from polymers such as polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, and polyethylenenaphthalene, either individually or as mixtures thereof. The structure of the nonwoven fabric may be a spunbond nonwoven fabric or a meltblown nonwoven fabric composed of long fibers.

[0116] The thickness of the porous substrate described above is not particularly limited, but may be 5 to 50 μm. The size of the pores and the pore density present in the porous substrate are also not particularly limited, but may be 0.01 to 50 μm and 10 to 95%, respectively.

[0117] On the other hand, in order to improve the mechanical strength of the separation membrane composed of the porous substrate and to suppress short circuits between the positive and negative electrodes, the porous substrate may further include a porous coating layer containing inorganic particles and a binder polymer on at least one surface.

[0118] The electrolyte may include an organic solvent and an electrolyte salt, the electrolyte salt being a lithium salt. The lithium salt can be any lithium salt commonly used in non-aqueous electrolytes for lithium secondary batteries, without limitation. For example, Li as a cation. + It contains F as an anion. - Cl - , Br - , I - NO 3- , N(CN) 2- BF 4- , 4- AlO 4- AlCl 4- , PF 6- SbF 6- AsF 6- BF2C2O 4- BC4O 8- (CF3)2PF 4- (CF3)3PF 3- (CF3)4PF 2- (CF3)5PF - (CF3)6P - CF3SO 3- , C4F9SO 3- , CF3CF2SO 3- , (CF3SO2)2N - , (FSO2)2N - CF3CF2(CF3)2CO - (CF3SO2) 2CH - (SF5)3C - (CF3SO2)3C - CF3(CF2)7SO 3- CF3CO 2- CH3CO 2- SCN - , and (CF3CF2SO2)2N - It may include at least one selected from the group consisting of the following.

[0119] The organic solvents included in the electrolyte described above can be any solvent commonly used in electrolytes for secondary batteries, without limitation. For example, ethers, esters, amides, linear carbonates, and cyclic carbonates can be used individually or in combination of two or more. Among these, carbonate compounds, which are typically cyclic carbonates, linear carbonates, or mixtures thereof, may be included.

[0120] Specific examples of the above-mentioned cyclic carbonate compounds include any one or more 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, vinylene carbonate, vinylethylene carbonate, and halides thereof, or mixtures of two or more of these. Examples of these halides include, but are not limited to, fluoroethylene carbonate (FEC).

[0121] Furthermore, specific examples of the linear carbonate compounds mentioned above include, but are not limited to, one 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, or mixtures of two or more of these.

[0122] In particular, among the carbonate-based organic solvents mentioned above, ethylene carbonate and propylene carbonate, which are cyclic carbonates, are high-viscosity organic solvents with high dielectric constants, which can better dissociate lithium salts in the electrolyte. By mixing such cyclic carbonates with linear carbonates with low viscosity and low dielectric constant, such as dimethyl carbonate and diethyl carbonate, in suitable proportions, an electrolyte with higher electrical conductivity can be produced.

[0123] Furthermore, the ether used among the above organic solvents may be, but is not limited to, one selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether, and ethyl propyl ether, or a mixture of two or more of these.

[0124] Furthermore, as the ester among the above organic solvents, one or more selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone may be used, but is not limited to these.

[0125] The electrode assembly may be of the lamination / stack type, in which unit cells are stacked with a separation membrane in between, or of the stack / folding type, in which unit cells are wound by a separation sheet.

[0126] The electrode assembly is manufactured by first coating the positive electrode and negative electrode current collector with electrode active material to form an asphalt layer, then manufacturing the positive electrode and negative electrode with pinholes formed in the electrode tab and electrode plate via a notching device, and finally joining the positive electrode and negative electrode to a separation membrane that does not contain pinholes. The type of separation membrane is not limited, but it may be a porous SRS (Safety-Reinforcing Separators) membrane made of a composite of inorganic and non-porous materials.

[0127] Specifically, the above-mentioned SRS separation membrane is manufactured using inorganic particles and a binder polymer as active layer components on a separation membrane substrate, such as a polyolefin-based example. In this case, it has a uniform pore structure formed by the interstitial volume between the inorganic particles that constitute the active layer, along with the pore structure contained in the separation membrane substrate itself. When using such a porous / inorganic composite separation membrane, there is an advantage in that the increase in battery thickness due to swelling during the formation process can be suppressed compared to when using a general separation membrane. Furthermore, when a polymer that can gel when impregnated with a liquid electrolyte is used as the binder polymer component, it can also be used simultaneously as the electrolyte. In addition, the above-mentioned porous / inorganic composite separation membrane exhibits excellent adhesive properties by adjusting the content of inorganic particles and binder polymers that constitute the active layer components within the separation membrane, thus facilitating the battery assembly process.

[0128] The present invention will be described in more detail below with reference to examples and other examples. Since the present invention can be modified in various ways and may have many different embodiments, specific embodiments will be illustrated and described in detail in the text. However, this is not intended to limit the present invention to any particular form of disclosure, but should be understood as including all modifications, equivalents, or substitutions that fall within the spirit and technical scope of the present invention.

[0129] <Example 1> A gel polymer electrolyte composition was prepared by dissolving LiPF6 as a lithium salt at a concentration of 1 M in a solvent prepared by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7, and then adding additives according to their respective amounts relative to the total weight of the gel polymer electrolyte, as shown in Table 1 below.

[0130] Specifically, the oligomer is added in a content of 4% by weight. In chemical formula 1, the structural formula of the oligomer is such that R is a methyl-substituted alkylene with 2 carbon atoms, and m is an integer in the range of 2 to 3.

[0131] The curing accelerator was added in a 4% by weight content, and the structural formula of the oligomer is as shown in chemical formula 1-c below.

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[0133] As a polymerization initiator, we used FUJIFILM WAKO's V-59 product, an azo-based initiator that is a thermal initiator, at a content of 1% by weight.

[0134] LiNi, with a particle size of 5 μm, is used as the positive electrode active material. 0.5 Mn 1.5 O4 was prepared and mixed with polyvinylidene fluoride and N-methylpyrrolidone (NMP) in a weight ratio of 94:3:3 as a carbon-based conductive agent and binder to form a slurry. This slurry was then cast onto an aluminum sheet, dried in a vacuum oven at 120°C, and then rolled to produce a cathode.

[0135] Separately, a negative electrode active material was prepared by mixing artificial graphite and silicon dioxide (SiO2) in a weight ratio of 9:1. 97 parts by weight of the negative electrode active material and 3 parts by weight of styrene-butadiene rubber (SBR) were mixed with water to form a slurry, which was then cast onto a copper sheet, dried in a vacuum oven at 130°C, and then rolled to produce the negative electrode.

[0136] A separator made of 18 μm polypropylene was placed between the positive and negative electrodes obtained above, and after inserting them into a case, the manufactured gel polymer electrolyte composition was injected. Subsequently, a pouch-type lithium secondary battery was manufactured after a curing time of 30 minutes at 65°C.

[0137] <Examples 2-6> A curing accelerator was added in a 4% by weight content, and the structural formulas of the oligomers were the chemical formulas 2-e, 2-i, 3-a, 4-b, and 5-c shown below, respectively. The gel polymer electrolyte composition was prepared in the same manner as in Example 1.

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[0143] A lithium secondary battery was manufactured using the produced gel polymer electrolyte composition in the same manner as in Example 1.

[0144] <Comparative Example 1> An electrolyte composition was prepared by dissolving LiPF6 as a lithium salt at a concentration of 1 M in a solvent prepared by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7.

[0145] LiNi, with a particle size of 5 μm, is used as the positive electrode active material. 0.5 Mn 1.5 O4 was prepared and mixed with polyvinylidene fluoride and N-methylpyrrolidone (NMP) in a weight ratio of 94:3:3 as a carbon-based conductive agent and binder to form a slurry. This slurry was then cast onto an aluminum sheet, dried in a vacuum oven at 120°C, and then rolled to produce a cathode.

[0146] Separately, a negative electrode active material was prepared by mixing artificial graphite and silicon dioxide (SiO2) in a weight ratio of 9:1. 97 parts by weight of the negative electrode active material and 3 parts by weight of styrene-butadiene rubber (SBR) were mixed with water to form a slurry, which was then cast onto a copper sheet, dried in a vacuum oven at 130°C, and then rolled to produce the negative electrode.

[0147] A separator made of 18 μm polypropylene was interposed between the positive and negative electrodes obtained above, and after inserting them into a case, the manufactured electrolyte composition was injected to produce a pouch-type lithium secondary battery.

[0148] <Comparative Example 2> A gel polymer electrolyte composition was prepared by dissolving LiPF6 as a lithium salt at a concentration of 1 M in a solvent prepared by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7, and then adding additives according to their respective amounts relative to the total weight of the gel polymer electrolyte, as shown in Table 1 below.

[0149] A lithium secondary battery was manufactured using the produced gel polymer electrolyte composition in the same manner as in Example 1, but with a curing time of 30 minutes.

[0150] <Comparative Example 3> A gel polymer electrolyte composition was prepared by dissolving LiPF6 as a lithium salt at a concentration of 1 M in a solvent prepared by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7, and then adding additives according to their respective amounts relative to the total weight of the gel polymer electrolyte, as shown in Table 1 below.

[0151] A lithium secondary battery was manufactured using the produced gel polymer electrolyte composition in the same manner as in Example 1, but with a curing time of 100 minutes.

[0152] <Comparative Example 4> A gel polymer electrolyte composition was prepared by dissolving LiPF6 as a lithium salt at a concentration of 1 M in a solvent prepared by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7, and then adding additives according to their respective amounts relative to the total weight of the gel polymer electrolyte, as shown in Table 1 below.

[0153] A lithium secondary battery was manufactured using the produced gel polymer electrolyte composition in the same manner as in Example 1, but with a curing time of 300 minutes.

[0154] [Table 1]

[0155] <Experimental Example: Evaluation of Leakage> The presence or absence of electrolyte leakage was evaluated for each secondary battery manufactured in Examples 1-6 and Comparative Examples 1-3. Each secondary battery is a large 100Ah class cell.

[0156] The evaluation process is illustrated in Figure 1. Referring to Figure 1, each pouch-type secondary battery 100 is a large battery cell of the 100Ah class. The pouch-type secondary battery 100 has a structure in which the electrode assembly is housed in a pouch-type case. Using the pouch-type case as a reference, a sealing area 120 is formed by heat fusion on all four sides that surround the electrode assembly housing area 110, and the electrode terminals 130 are led out on both sides. One side of the lower end of each pouch-type secondary battery 100 was cut open by about d (d=25cm), tilted at an angle of inclination θ (θ=5°), and stored for one week at room temperature. After that, the amount of electrolyte leakage from each pouch-type secondary battery 100 was measured.

[0157] A decrease of 3% by weight or more compared to the initial infusion volume was determined to indicate electrolyte leakage. The evaluation results are shown in Table 2 below.

[0158] [Table 2]

[0159] Referring to Table 2, no electrolyte leakage was observed in Examples 1-6 even under a curing time of 30 minutes. In contrast, in Comparative Example 1, gelation of the electrolyte did not occur, and therefore leakage was observed. Referring to Comparative Examples 2 and 3, it can be seen that when the curing accelerator according to the present invention is not added, electrolyte leakage is observed under curing times of 30 minutes or 100 minutes. Referring to Comparative Example 4, it can be seen that when the curing accelerator is not added, no leakage is observed under a curing time of 300 minutes. [Explanation of Symbols]

[0160] 100: Pouch-type rechargeable battery 110: Electrode assembly storage area 120: Ceiling area 130: Terminal

Claims

1. Polypropylene carbonate series oligomers, A curing accelerator that is a monocyclic or polycyclic cyclic amine compound. Polymerization initiator, Non-aqueous solvents, and Contains lithium salts, Under heat treatment conditions of 55-80°C, the curing time is in the range of 10-50 minutes. Composition for gel polymer electrolytes.

2. The gel polymer electrolyte composition according to claim 1, wherein the oligomer content is in the range of 0.1 to 30 parts by weight per 100 parts by weight of the entire gel polymer electrolyte composition.

3. The gel polymer electrolyte composition according to claim 1, wherein the curing accelerator comprises one or more of the pyrimidine, imidazole, purine, thiadiazole, and pyrrole types.

4. The gel polymer electrolyte composition according to claim 3, wherein the pyrimidine-based curing accelerator is one or more of the following chemical formulas 1-a to 1-g. 【Chemistry 1】 【Chemistry 2】 【Transformation 3】 【Chemistry 4】 【Transformation 5】 【Transformation 6】 【Transformation 7】

5. The gel polymer electrolyte composition according to claim 3, wherein the imidazole-based curing accelerator is one or more of the following chemical formulas 2-a to 2-i. 【Transformation 8】 【Chemistry 9】 【Chemistry 10】 【Chemistry 11】 【Chemistry 12】 【Chemistry 13】 【Chemistry 14】 【Chemistry 15】 【Chemistry 16】

6. The gel polymer electrolyte composition according to claim 3, wherein the purine-based curing accelerator has the following chemical formula 3-a. 【Chemistry 17】

7. The gel polymer electrolyte composition according to claim 3, wherein the thiadiazole-based curing accelerator is one or more of the following chemical formulas 4-a to 4-b. [Chemistry 18] 【Chemistry 19】

8. The gel polymer electrolyte composition according to claim 3, wherein the pyrrole-based curing accelerator is one or more of the following chemical formulas 5-a to 5-c. 【Chemistry 20】 【Chemistry 21】 【Chemistry 22】

9. The gel polymer electrolyte composition according to claim 1, wherein the content of the curing accelerator is in the range of 0.01 to 10 parts by weight per 100 parts by weight of the entire gel polymer electrolyte composition.

10. With the electrode assembly, which includes a positive electrode, a negative electrode, and a separator membrane placed between the positive and negative electrodes, housed in a battery case, A method for manufacturing a lithium secondary battery, comprising the step of pouring a gel polymer electrolyte composition according to any one of claims 1 to 9 into a battery case.

11. After the step of pouring the gel polymer electrolyte composition into the battery case, A method for manufacturing a lithium secondary battery according to claim 10, further comprising the step of performing thermal crosslinking for a period of 10 to 50 minutes.

12. The method for manufacturing a lithium secondary battery according to claim 11, wherein the step of performing thermal crosslinking is carried out in a temperature range of 55 to 80°C.

13. An electrode assembly including a positive electrode, a negative electrode, and a separator membrane disposed between the positive electrode and the negative electrode, A battery case for housing and sealing the electrode assembly, and A lithium secondary battery comprising a gel polymer electrolyte composition according to any one of claims 1 to 9, which is injected into a battery case containing an electrode assembly.

14. The lithium secondary battery according to claim 13, wherein the lithium secondary battery is a pouch-type battery.

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