Title of the invention: Lithium secondary battery comprising a composition for a gel polymer electrolyte and a gel polymer electrolyte formed therefrom Technical field [One] Cross-reference with related application(s) [2] This application claims the benefit of priority based on Korean Patent Application No. 2018-0114102 filed on September 21, 2018, and all contents disclosed in the documents of the Korean patent application are incorporated as part of this specification. [3] [4] Technical field [5] The present invention relates to a lithium secondary battery comprising a composition for a gel polymer electrolyte and a gel polymer electrolyte formed therefrom. Background [6] Recently, as the electric, electronic, telecommunication and computer industries rapidly develop, demand for high-performance, high-stability secondary batteries is gradually increasing. In particular, according to the trend of miniaturization and weight reduction of these electronic and communication devices, there is a demand for thinning and miniaturization of a lithium secondary battery, which is a core component in this field. [7] Lithium secondary batteries can be divided into lithium ion batteries using a liquid electrolyte and lithium polymer batteries using a polymer electrolyte, depending on the applied electrolyte. [8] Although the lithium ion battery has the advantage of high capacity, there is a risk of leakage and explosion because it uses a liquid electrolyte containing a lithium salt, and there is a disadvantage that the battery design becomes complicated due to countermeasures. [9] On the other hand, since the lithium polymer battery uses a solid polymer electrolyte or a gel polymer electrolyte containing a liquid electrolyte as an electrolyte, it improves stability and has flexibility, so that it can be developed in various forms such as small size or thin film type. [10] The secondary battery to which the gel polymer electrolyte is applied can be manufactured by two methods as follows. [11] First, an electrolyte composition was prepared by mixing a polymerization initiator and a polymerizable monomer or oligomer in a liquid electrolyte in which a lithium salt was dissolved in a non-aqueous organic solvent, and then infused into a battery containing an electrode assembly, and gelled under appropriate temperature and time conditions ( It can be prepared by crosslinking). [12] However, the above method has a disadvantage in that it is not easy to secure mechanical strength even after gelation due to poor wetting in the cell due to high viscosity and surface tension of the solution before injection. [13] In another method, the electrolyte composition is coated on one surface of an electrode and a separator, cured (gelled) using heat or UV to form a gel polymer electrolyte, and then the electrode and/or the gel polymer electrolyte is formed. An electrode assembly may be manufactured by winding or stacking a separator, and then inserted into a battery case and then re-injected with an existing liquid electrolyte. [14] However, this method requires a process of irradiating heat or UV for gelation, and in the case of a gel-coated separator, there is a problem of reducing the performance and stability of the battery by absorbing moisture. Moreover, since polyethylene separators used as conventional separators have high heat shrinkage, a short circuit occurs between the positive electrode and the negative electrode when used under abnormal conditions in which the temperature rises, thereby deteriorating the stability of the battery. [15] Accordingly, there is a need for development of a method for manufacturing a gel polymer electrolyte having improved stability at high temperatures while securing mechanical strength and ion transfer capability. [16] Prior art literature [17] Korean Patent Publication No. 2018-0026358 Detailed description of the invention Technical challenge [18] In order to solve the above problems, the present invention is to provide a composition for a gel polymer electrolyte comprising a polymerizable oligomer having a polymerizable substituent and an ionic monomer having a crosslinking reactive group. [19] In addition, the present invention is formed by thermal polymerization of the composition for a gel polymer electrolyte, to provide a gel polymer electrolyte having improved mechanical strength and electrochemical stability. [20] In addition, the present invention is to provide a lithium secondary battery with improved electrochemical stability by including the gel polymer electrolyte. Means of solving the task [21] Specifically, in one embodiment of the present invention [22] Lithium salt, [23] Organic solvent, [24] Oligomer represented by the following formula (1), [25] A compound represented by the following formula (2) and [26] Composition for a gel polymer electrolyte containing a polymerization initiator: [27] [Formula 1] [28] [29] In Formula 1, [30] R 1 is an alkylene group having 1 to 5 carbon atoms or -R 1 ′-O-, wherein R 1 ′ is an alkylene group having 1 to 5 carbon atoms, [31] R 2 is an alkylene group having 1 to 5 carbon atoms or -OR 2 ′-, wherein R 2 ′ is an alkylene group having 1 to 5 carbon atoms, [32] R 4 , R 5 , R 6 , and R 7 are each independently hydrogen or an alkyl group having 1 to 3 carbon atoms, [33] R and R 3 are each independently an aliphatic hydrocarbon group or an aromatic hydrocarbon group, [34] R 8 and R 9 are each an alkylene group having 1 to 5 carbon atoms, [35] R a , R b , R c and R d are each independently hydrogen or an alkyl group having 1 to 3 carbon atoms, [36] x, y, z and o are each independently an integer of 1 to 100, [37] c and c1 are each independently an integer of 1 to 3, [38] d and d1 are each independently an integer of 0 to 2. [39] [40] [Formula 2] [41] [42] In Formula 2, [43] R 10 is hydrogen or an alkyl group having 1 to 4 carbon atoms, [44] R 11 is an alkylene group having 1 to 6 carbon atoms unsubstituted or substituted with fluorine, [45] M is one or more alkali metal ions selected from lithium (Li), sodium (Na) and potassium (K), and A is , or . [46] [47] In addition, another embodiment of the present invention provides a gel polymer electrolyte formed by thermal polymerization of the composition for a gel polymer electrolyte of the present invention. [48] [49] In addition, another embodiment of the present invention provides a lithium secondary battery including the gel polymer electrolyte of the present invention. Effects of the Invention [50] The oligomer represented by Formula 1 included in the composition for a gel polymer electrolyte of the present invention includes an acrylate group as a hydrophilic part and a siloxane group and a urethane group as a hydrophobic part in the structure, and gives the role of a surfactant in the battery. The impregnation property of the solvent composition can be improved. In addition, the compound represented by Formula 2 contained in the composition for a gel polymer electrolyte of the present invention contains a double bond and an alkali metal ion, which are crosslinking reactive groups in the structure, so as to improve the crosslinking effect and ion transfer ability of the gel polymer electrolyte. It works. Therefore, when using the composition for a gel polymer electrolyte of the present invention including the oligomer represented by Formula 1 and the compound represented by Formula 2, a lithium secondary battery having a gel polymer electrolyte having improved mechanical properties and electrochemical stability Can be implemented. Best mode for carrying out the invention [51] Hereinafter, the present invention will be described in more detail to aid understanding of the present invention. At this time, terms or words used in the present specification and claims should not be construed as being limited to a conventional or dictionary meaning, and the inventor appropriately defines the concept of terms in order to describe his own invention in the best way. It should be interpreted as a meaning and concept consistent with the technical idea of ​​the present invention based on the principle that it can be done. [52] Meanwhile, prior to describing the present invention, in the description of "carbon number a to b" in the specification, "a" and "b" mean the number of carbon atoms included in a specific functional group. That is, the functional group may include "a" to "b" carbon atoms. For example, "an alkylene group having 1 to 5 carbon atoms" is an alkylene group containing a carbon atom having 1 to 5 carbon atoms, that is, -CH 2 -, -CH 2 CH 2 -, -CH 2 CH 2 CH 2 -,- It means CH 2 (CH 2 )CH-, -CH(CH 2 )CH 2 -and -CH(CH 2 )CH 2 CH 2 -. [53] In addition, in the present specification, the term "alkylene group" refers to a branched or unbranched divalent unsaturated hydrocarbon group. In one embodiment, the alkylene group may be substituted or unsubstituted. The alkylene group includes, but is not limited to, a methylene group, ethylene group, propylene group, isopropylene group, butylene group, isobutylene group, tert-butylene group, pentylene group, 3-pentylene group, and the like, and each of these It may be optionally substituted in other embodiments. [54] In addition, in the present specification, "substitution" means that at least one hydrogen bonded to carbon is substituted with an element other than hydrogen, unless otherwise defined, for example, an alkyl group having 1 to 5 carbon atoms or a fluorine element Means substituted with. [55] In addition, in the present specification, terms such as "comprise", "include", or "have" are intended to designate the presence of implemented features, numbers, steps, elements, or a combination thereof, but one or more other It is to be understood that the possibility of the presence or addition of features or numbers, steps, components, or combinations thereof is not preliminarily excluded. [56] Meanwhile, in the present specification, the term "molecular weight" means a weight average molecular weight (Mw) unless otherwise defined, and the weight average molecular weight (Mw) of the polymer or oligomer of the present invention is gel permeation unless otherwise defined. It can be measured using chromatography (Gel Permeation Chromatography: GPC). [57] Meanwhile, in the present specification, the electrochemical (oxidation) stability was measured according to a linear sweep voltammetry (LSV). A potentiostat (EG&G, model 270A) was used as a measuring device, and the measurement temperature was 60°C. [58] On the other hand, in this specification, the tensile strength is measured using Lloyd LR-10K at a rate of 5 mm per minute at 25°C and about 30% relative humidity using an electrolyte specimen manufactured collectively through ASTM standard D638 (Type V specimens). I did. [59] Meanwhile, in the present specification, the ion conductivity may be measured using an AC impedance measurement method. Specifically, it was measured in a frequency band of 100 MHz to 0.1 Hz using a VMP3 measuring equipment and a precision impedance analyzer (4294A). [60] [61] Composition for gel polymer electrolyte [62] The composition for a gel polymer electrolyte according to the present invention is [63] Lithium salt, [64] Organic solvent, [65] Oligomer represented by the following formula (1), [66] A compound represented by the following formula (2) and [67] It contains a polymerization initiator. [68] [Formula 1] [69] [70] In Formula 1, [71] R 1 is an alkylene group having 1 to 5 carbon atoms or -R 1 ′-O-, wherein R 1 ′ is an alkylene group having 1 to 5 carbon atoms, [72] R 2 is an alkylene group having 1 to 5 carbon atoms or -OR 2 ′-, wherein R 2 ′ is an alkylene group having 1 to 5 carbon atoms, [73] R 4 , R 5 , R 6 , and R 7 are each independently hydrogen or an alkyl group having 1 to 3 carbon atoms, [74] R and R 3 are each independently an aliphatic hydrocarbon group or an aromatic hydrocarbon group, [75] R 8 and R 9 are each an alkylene group having 1 to 5 carbon atoms, [76] R a , R b , R c and R d are each independently hydrogen or an alkyl group having 1 to 3 carbon atoms, [77] x, y, z and o are each independently an integer of 1 to 100, [78] c and c1 are each independently an integer of 1 to 3, [79] d and d1 are each independently an integer of 0 to 2. [80] [81] [Formula 2] [82] [83] In Formula 2, [84] R 10 is hydrogen or an alkyl group having 1 to 4 carbon atoms, [85] R 11 is an alkylene group having 1 to 6 carbon atoms unsubstituted or substituted with fluorine, [86] M is one or more alkali metal ions selected from lithium (Li), sodium (Na) and potassium (K), and A is , or . [87] [88] (1) lithium salt [89] As the lithium salt, various lithium salts in which an electrolyte for a lithium secondary battery is commonly used may be used without limitation. For example, the lithium salt is Li cation + a, and the anion include F - , Cl - , Br - , I - , NO 3 - , N (CN) 2 - , ClO 4 - , BF 4 - , B 10 Cl 10 - , AlO 4 - , AlCl 4 - , PF 6 - , CF 3 SO 3 - , CH 3CO 2 - , CH 3 SO 3 - , CF 3 CO 2 - , AsF 6 - , SbF 6 - , BF 2 C 2 O 4 - , BC 4 O 8 - , (CF 3 ) 2 PF 4 - , (CF 3 ) 3 PF 3 - , (CF 3 ) 4PF 2 - , (CF 3 ) 5 PF - , (CF 3 ) 6 P - , C 4 F 9 SO 3 - , CF 3 CF 2 SO 3 - , (FSO 2 ) 2 N - , (CF 3 SO 2 ) 2 N - , CF 3 CF 2 (CF 3) 2 CO - , (CF 3 SO 2 ) 2 CH - , (SF 5 ) 3 C - , (CF 3 SO 2 ) 3 C - , CF 3 (CF 2 ) 7 SO 3 - , SCN - , and (CF 3 CF 2 the SO 2 ) 2 N -Any one selected from the group consisting of may be included, and in addition to these, a lithium salt commonly used in an electrolyte solution of a lithium secondary battery may be used without limitation. [90] Specifically, the lithium salt is LiCl, LiBr, LiI, LiClO 4 , LiBF 4 , LiB 10 Cl 10 , LiAlO 4 , LiAlCl 4 , LiPF 6 , LiCF 3 SO 3 , LiCH 3 CO 2 , LiCH 3 SO 3 , LiCF 3 CO 2 , LiAsF 6 , LiSbF 6 , LiFSI (Lithium bis(fluorosulfonyl)imide, LiN(SO 2 F) 2), LiBETI (lithium bisperfluoroethanesulfonimide, LiN(SO 2 CF 2 CF 3 ) 2 and LiTFSI (lithium (bis) trifluoromethanesulfonimide, LiN(SO 2 CF 3 ) 2 )), a single substance or a mixture of two or more selected from the group consisting of And, specifically, at least one of LiPF 6 , LiFSI and LiTFSI may be mentioned. [91] The lithium salt may be appropriately changed within a range that is usually usable, but in order to obtain an optimum effect of forming an anti-corrosion film on the electrode surface, a concentration of 1.0M to 6.0M, specifically 1.5M to 4.0M in the composition for a gel polymer electrolyte Can be included as [92] When the concentration of the lithium salt satisfies the above range, the ion transport characteristics (ie, cation transport rate (transference number)) of a high lithium cation (Li + ) are improved due to an increase in the lithium cation present in the composition for a gel polymer electrolyte. In addition, it is possible to improve the cycle capacity characteristics by bringing about an effect of reducing resistance during the diffusion of lithium ions. [93] That is, in the case of the composition for a gel polymer electrolyte, by including a lithium salt of 1.0M or more, it is possible to impart ionic conductivity and reduce resistance due to depletion of lithium ions during high rate charging and discharging. If the concentration of the lithium salt is 1.0M or less, the cycle life characteristics and capacity characteristics of the lithium secondary battery may be deteriorated. In addition, when the maximum concentration of the lithium salt exceeds 6.0M, the viscosity of the composition for the gel polymer electrolyte is excessively increased, so that the electrolyte wettability is deteriorated, and thus the overall performance of the secondary battery may be deteriorated. [94] On the other hand, when the concentration of the lithium salt is 4M or more, the viscosity of the electrolyte may increase, but as described later, a part of the oligomer contained in the composition for the gel polymer electrolyte acts as a surfactant and lowers the surface tension, so that the gel polymer electrolyte It is possible to prevent the impregnation property of the solvent composition from deteriorating. [95] [96] (2) organic solvent [97] The organic solvent is not limited as long as it can minimize decomposition due to an oxidation reaction or the like in the charging and discharging process of the secondary battery, and can exhibit desired properties together with additives. [98] The organic solvent may include a cyclic carbonate-based organic solvent, a linear carbonate-based organic solvent, or a mixed organic solvent thereof. [99] The cyclic carbonate-based organic solvent is an organic solvent having a high viscosity and has a high dielectric constant, and is an organic solvent capable of dissociating lithium salts in an electrolyte well.Specific examples thereof are 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. It may include. [100] In addition, the linear carbonate-based organic solvent is an organic solvent having a low viscosity and a low dielectric constant, and representative examples thereof are dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethylmethyl carbonate ( EMC), at least one organic solvent selected from the group consisting of methylpropyl carbonate and ethylpropyl carbonate may be used, and specifically, ethylmethyl carbonate (EMC) may be included. [101] The organic solvent is preferably a mixed organic solvent of a cyclic carbonate-based organic solvent and a linear carbonate-based organic solvent in order to prepare an electrolyte solution having a high ionic conductivity. [102] In addition, the organic solvent may further include a linear ester-based organic solvent and/or a cyclic ester-based organic solvent to the cyclic carbonate-based organic solvent and/or the linear carbonate-based organic solvent. [103] Such a linear ester-based organic solvent may be at least one organic solvent selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate. Can be lifted. [104] In addition, the cyclic ester-based organic solvent may include at least one organic solvent among γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone. [105] Meanwhile, the organic solvent may be used by adding an organic solvent commonly used in an electrolyte solution for a lithium secondary battery, without limitation, if necessary. For example, it may further include at least one organic solvent of an ether-based organic solvent, a glyme-based organic solvent, and a nitrile-based organic solvent. [106] The ether solvents include dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methylpropyl ether, ethylpropyl ether, 1,3-dioxolane (DOL) and 2,2-bis (trifluoromethyl ) Any one selected from the group consisting of -1,3-dioxolane (TFDOL), or a mixture of two or more of them may be used, but the present invention is not limited thereto. [107] The glyme-based solvent has a higher dielectric constant and lower surface tension than a linear carbonate-based organic solvent, and is a solvent with less reactivity with a metal, such as dimethoxyethane (glyme, DME), diglyme, and tri-glyme. It may include at least one or more selected from the group consisting of (Triglyme), and tetra-glyme. [108] The nitrile solvent is acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentane carbonitrile, cyclohexane carbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile , Difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile may be one or more selected from the group consisting of. [109] [110] (3) oligomer [111] The composition for a gel polymer electrolyte of the present invention is a compound having a crosslinkable substituent capable of forming a polymer matrix, which is a basic skeleton of a gel polymer electrolyte, while being oxidized by a polymerization reaction when the temperature rises, and containing at least one acrylate group at the terminal. It includes an oligomer represented by the following formula (1). [112] [Formula 1] [113] [114] In Formula 1, [115] R 1 is an alkylene group having 1 to 5 carbon atoms or -R 1 ′-O-, wherein R 1 ′ is an alkylene group having 1 to 5 carbon atoms, [116] R 2 is an alkylene group having 1 to 5 carbon atoms or -OR 2 ′-, wherein R 2 ′ is an alkylene group having 1 to 5 carbon atoms, [117] R 4 , R 5 , R 6 , and R 7 are each independently hydrogen or an alkyl group having 1 to 3 carbon atoms, [118] R and R 3 are each independently an aliphatic hydrocarbon group or an aromatic hydrocarbon group, [119] R 8 and R 9 are each an alkylene group having 1 to 5 carbon atoms, [120] R a , R b , R c and R d are each independently hydrogen or an alkyl group having 1 to 3 carbon atoms, [121] x, y, z and o are each independently an integer of 1 to 100, [122] c and c1 are each independently an integer of 1 to 3, [123] d and d1 are each independently an integer of 0 to 2. [124] [125] Specifically, in Formula 1, R 1 is -R 1 ′-O-, wherein R 1 ′ is an alkylene group having 1 to 5 carbon atoms, R 2 is -OR 2 ′-, wherein R 2 ′ is a carbon number 1 to 5 alkylene groups, R 4 , R 5 , R 6 , and R 7 are each independently an alkyl group having 1 to 3 carbon atoms, and R 8 and R 9 are each independently an alkylene group having 1 to 3 carbon atoms, R a , R b , R c and R d may each independently be hydrogen. [126] More specifically, in Formula 1, R 1 is -R 1 ′-O-, wherein R 1 ′ is an alkylene group having 2 to 5 carbon atoms, R 2 is -OR 2 ′-, wherein R 2 ′ is Is an alkylene group having 2 to 5 carbon atoms, R 4 , R 5 , R 6 , and R 7 are each independently an alkyl group having 1 to 3 carbon atoms, and R 8 and R 9 are each independently an alkylene group having 1 or 2 carbon atoms , R a , R b , R c and R d may each independently be hydrogen. [127] [128] In addition, in Formula 1, R and R 3 may be at least one aliphatic hydrocarbon group selected from the group consisting of an alicyclic hydrocarbon group and a linear hydrocarbon group. [129] The alicyclic hydrocarbon group is a substituted or unsubstituted cycloalkylene group having 4 to 20 carbon atoms; A substituted or unsubstituted C4 to C20 cycloalkylene group; A substituted or unsubstituted C4 to C20 cycloalkenylene group; And it may be at least one selected from the group consisting of a substituted or unsubstituted C2 to C20 heterocycloalkylene group, among which it is preferable that it is a substituted or unsubstituted C4 to C20 cycloalkylene group. [130] The linear hydrocarbon group is a substituted or unsubstituted alkylene group having 1 to 20 carbon atoms; A substituted or unsubstituted C1-C20 alkylene group; A substituted or unsubstituted C 1 to C 20 alkoxyl group; A substituted or unsubstituted alkenylene group having 2 to 20 carbon atoms; And it may be at least one selected from the group consisting of a substituted or unsubstituted alkynylene group having 2 to 20 carbon atoms. [131] In addition, in Formula 1, R and R 3 may be an aromatic hydrocarbon group. [132] The aromatic hydrocarbon group is a substituted or unsubstituted arylene group having 6 to 20 carbon atoms; And it may be at least one selected from the group consisting of a substituted or unsubstituted heteroarylene group having 4 to 20 carbon atoms. [133] [134] More specifically, the oligomer represented by Formula 1 may be at least one selected from the group consisting of compounds represented by the following Formulas 1a and 1b. [135] [Formula 1a] [136] [137] In Formula 1a, [138] x1, y1, z1, and o1 are each independently an integer of 1 to 100. [139] [140] [Formula 1b] [141] [142] In Formula 1b, [143] x2, y2, z2, and o2 are each independently an integer of 1 to 100. [144] [145] Since the oligomer represented by Formula 1 contains an acrylate group as a hydrophilic portion, a siloxane group (-[Si-O]-) and a urethane group as a hydrophobic portion in the structure, a hydrophilic portion inside the battery (anode, separator (SRS layer)) Since it can exhibit affinity in a balanced manner in the hyperhydrophobic portion (cathode, membrane fabric), it can impart the role of a surfactant. Therefore, it is possible to improve the impregnation property of the composition for the gel polymer electrolyte by lowering the surface tension of the electrode and the separator. [146] On the other hand, in the case of a polymer having an alkylene oxide skeleton used in the manufacture of a conventional gel polymer electrolyte, since the reduction stability is low, a film can be formed on the surface of the negative electrode during initial charging. However, since such a film is easily destroyed at a high temperature to cause side reactions, there is a disadvantage of increasing the interface resistance between the electrode and the gel polymer electrolyte. [147] On the other hand, the oligomer represented by Formula 1 is not only electrochemically stable and has high reduction stability, but also has the ability to dissociate lithium salts, thereby minimizing the reduction reaction on the surface of the negative electrode and improving lithium ion mobility. have. [148] Therefore, in the case of the composition for a gel polymer electrolyte of the present invention, compared with the composition for a gel polymer electrolyte containing a polymer having a conventional alkylene oxide skeleton, side reactions with the electrode are reduced, the mechanical strength is high, and between the electrode and the electrolyte The interfacial stability effect can produce an improved gel polymer electrolyte. [149] [150] On the other hand, the weight average molecular weight (MW) of the oligomer represented by Formula 1 is 1,000 g/mol to 100,000 g/mol, specifically 1,000 g/mol to 50,000 g/mol, more specifically 1,000 g/mol to 10,000 g/ mol, more specifically 3,000 g/mol to 7,000 g/mol, and the range can be adjusted by the number of repeating units. When the weight average molecular weight of the oligomer is within the above range, the mechanical strength of the non-aqueous electrolyte containing the oligomer can be effectively improved. [151] If the weight average molecular weight of the oligomer represented by Chemical Formula 1 is less than 1,000 g/mol, appropriate mechanical strength cannot be expected, and the use of a more polymerization initiator is required, or a difficult additional polymerization process is required. There is a disadvantage that the process becomes complicated. On the other hand, when the weight average molecular weight exceeds 100,000 g/mol, the oligomer physical properties themselves become rigid, and the affinity with the electrolyte solvent decreases, making it difficult to dissolve, and thus formation of a uniform and excellent gel polymer electrolyte cannot be expected. [152] The weight average molecular weight can be measured using Agilent's 1200 series under Gel Permeation Chromatography (GPC) conditions. For example, after preparing a sample sample of a certain concentration, the GPC measurement system alliance 4 device is stabilized, and when the device is stabilized, a standard sample and a sample sample are injected into the device to obtain a chromatogram, and then the molecular weight can be calculated according to the analysis method. Yes (system: Alliance 4, column: Ultrahydrogel linear×2, eluent: 0.1M NaNO 3 (pH 7.0 phosphate buffer, flow rate: 0.1 mL/min, solvent: THF, temp: 40℃, injection: 100μL) [153] [154] (4) compound represented by formula 2 [155] The composition for a gel polymer electrolyte according to the present invention includes a compound represented by the following formula (2) as an ionic monomer having a crosslinking reactive group in order to improve the crosslinking effect. [156] [Formula 2] [157] [158] In Formula 2, [159] R 10 is hydrogen or an alkyl group having 1 to 4 carbon atoms, [160] R 11 is an alkylene group having 1 to 6 carbon atoms unsubstituted or substituted with fluorine, [161] M is one or more alkali metal ions selected from lithium (Li), sodium (Na) and potassium (K), and A is , or . [162] [163] In Formula 2, R 10 is hydrogen or an alkyl group having 1 to 3 carbon atoms, R 11 is an alkylene group having 2 to 5 carbon atoms substituted or unsubstituted with fluorine, M is a lithium (Li) ion, A is , or to be. [164] [165] Specifically, the compound represented by Formula 2 may include at least one selected from the group consisting of compounds represented by the following Formulas 2a to 2c. [166] [Formula 2a] [167] [168] [169] [Formula 2b] [170] [171] [172] [Formula 2c] [173] [174] [175] The compound represented by Formula 2 contains a double bond (C=C), which is a crosslinking reactive group, in the structure, so that it is easy to crosslink with the oligomer represented by Formula 1 to prepare a gel polymer electrolyte with improved mechanical strength. have. [176] Moreover, since the compound represented by Formula 2 is an ionic monomer having a single ionic carrier structure containing both anions and alkali metal cations in the structure, ion transfer is possible without additionally supplying a lithium salt. The polymer formed by the polymerization reaction with the displayed oligomer acts as a huge anion, and by the hopping of alkali metal cations in the polymer, the alkali metal cations move uniformly and efficiently, increasing the ion transfer effect. I can make it. Therefore, it is possible to prepare a gel polymer electrolyte with improved ionic conductivity. [177] [178] On the other hand, the composition for a gel polymer electrolyte of the present invention may contain at least one or more compounds of Formulas 2a to 2c, and specifically, may be used by mixing two or more. [179] For example, when the compound of Formula 2a and the compound of Formula 2b are mixed and used, the weight ratio of the compound of Formula 2a: the compound of Formula 2b may be 1:10 to 10:1, specifically 5:5. . Alternatively, when the compound of Formula 2b: the compound of Formula 2c is mixed and used, the weight ratio of the compound of Formula 2b: the compound of Formula 2c may be 1:10 to 10:1, specifically 5:5. [180] [181] On the other hand, the mixed (solid content) content of the oligomer represented by Formula 1 and the compound represented by Formula 2 is 0.1% to 60% by weight, specifically 1% to 30% by weight based on the total weight of the composition for the gel polymer electrolyte %, more specifically 1% to 20% by weight. [182] When the mixed (solid content) content of the oligomer represented by Formula 1 and the compound represented by Formula 2 satisfies the above range, a gel polymer electrolyte having excellent mechanical strength and ionic conductivity may be prepared. That is, when the mixed solid content of the oligomer represented by Formula 1 and the compound represented by Formula 2 is 0.1% by weight or more, a gel polymer electrolyte having a high ionic conductivity and a stable network structure can be prepared. In addition, when the mixed (solid content) content of the oligomer represented by Formula 1 and the compound represented by Formula 2 is 60% by weight or less, while securing the impregnating property of the gel polymer electrolyte, the effect of moving lithium ions is increased. Sufficient ion conductivity can be secured. [183] [184] Meanwhile, the weight ratio of the oligomer represented by Chemical Formula 1 to the compound represented by Chemical Formula 2 in the composition for the gel polymer electrolyte is 0.2:99.8 to 99.8:0.2, specifically 10:90 to 80:20, more specifically 40: It may be 60 to 80:20. [185] Depending on the weight ratio of the compound represented by Formula 2 to the oligomer represented by Formula 1, the cation (eg, Li + ) in the polymer formed by the polymerization reaction of the oligomer represented by Formula 1 and the compound represented by Formula 2 The amount may vary. That is, when the mixing ratio of the oligomer represented by Formula 1 and the compound represented by Formula 2 satisfies the above range, the content of cations increases and can be uniformly moved and distributed. Accordingly, the ionic conductivity of the gel polymer electrolyte Can increase. [186] On the other hand, when the weight ratio of the compound represented by Formula 2 to the oligomer represented by Formula 1 is less than 0.2, since the content of the oligomer represented by Formula 1, which is a high molecular weight, increases, the physical strength of the gel polymer electrolyte increases, while The amount of cations in the polymer formed by the polymerization reaction of the oligomer represented by Formula 1 and the compound represented by Formula 2 decreases, so that the ion transfer ability of the gel polymer electrolyte may be lowered. [187] Therefore, when the oligomer represented by Formula 1 is 0.2 weight ratio, specifically 10 weight ratio or more, the polymer matrix by the oligomer can be easily formed and a polymer network having excellent mechanical strength can be formed, so that the overall performance is improved. Polymer electrolytes can be prepared. In addition, if the oligomer represented by Formula 1 is 99.8, specifically 80 weight ratio or less, it is possible to prevent disadvantages such as an increase in resistance due to the addition of an excessive amount of oligomer and restriction of movement of lithium ions, for example, a decrease in ionic conductivity, and an appropriate By securing the viscosity, it is possible to improve the impregnation property of the composition for a gel polymer electrolyte. [188] In other words, if the content of the compound represented by Formula 2 is within the above range, not only can the single cationic species be transferred without adding a salt, but also the cation is more efficiently transferred due to the ion transfer characteristics of the macro anion, so that the ionic conductivity It is possible to prepare an improved gel polymer electrolyte. Specifically, when the compound represented by Formula 2 is contained in an amount of 0.2 weight ratio or more, specifically 20 weight ratio or more, the amount of cation can be secured, thereby improving the mobility of lithium ions in the gel polymer electrolyte, and 99.8 weight ratio, specifically It should be included in a weight ratio of 80 or less to secure the mechanical properties of the gel polymer electrolyte. [189] [190] (5) polymerization initiator [191] The composition for a gel polymer electrolyte of the present invention may include a polymerization initiator to perform a radical reaction required when preparing a gel polymer electrolyte. [192] The polymerization initiator may be a conventional thermal or photopolymerization initiator known in the art. For example, the polymerization initiator may be decomposed by heat to form a radical, and reacted with an oligomer represented by Formula 1 by free radical polymerization to form a gel polymer electrolyte. [193] More specifically, non-limiting examples of the polymerization initiator are benzoyl peroxide, acetyl peroxide, dilauryl peroxide, di-tert-butyl peroxide (di-tert- butyl peroxide), t-butyl peroxy-2-ethyl-hexanoate, cumyl hydroperoxide and hydrogen peroxide Peroxides or hydroperoxides and 2,2'-azobis (2-cyanobutane), 2,2'-azobis (methylbutyronitrile), 2,2'-azobis (isobutyronitrile) ( At least one azo compound selected from the group consisting of AIBN; 2,2'-Azobis (iso-butyronitrile)) and 2,2'-azobisdimethyl-valeronitrile (AMVN; 2,2'-Azobisdimethyl-Valeronitrile) And the like, but are not limited thereto. [194] The polymerization initiator is decomposed by heat in the battery, for example, 30°C to 100°C, or decomposed at room temperature (5°C to 30°C) to form a radical, and the polymerizable oligomer is acrylated by free radical polymerization. It can react with the system compound to form a gel polymer electrolyte. [195] The polymerization initiator may be included in an amount of 0.01 to 20 parts by weight, specifically 0.1 to 10 parts by weight, based on 100 parts by weight of the oligomer represented by Formula 1. [196] When the polymerization initiator is in the range of 0.01 to 20 parts by weight, the gel polymer conversion rate can be increased to ensure gel-gel polymer electrolyte properties, and the pre-gel reaction is prevented, thereby improving the impregnation of the composition for the gel polymer electrolyte into the electrode. I can make it. [197] [198] (6) oxygen scavenger [199] In addition, the composition for a gel polymer electrolyte of the present invention may further include an oxygen scavenger as an additive. [200] In general, when the radical reaction required in the preparation of the gel polymer electrolyte is carried out in the presence of oxygen, the reaction is stabilized by quenching by oxygen, and the chain polymerization reaction efficiency is reduced, resulting in a gel of monomer and/or oligomer. ) It is known that the conversion rate is reduced. That is, since radicals generated from the polymerization initiator easily react with oxygen and are consumed, radical polymerization reactivity in the presence of oxygen decreases. [201] Accordingly, the composition for a gel polymer electrolyte of the present invention may further include an oxygen scavenger in order to improve injection properties by controlling gelation reactivity at room temperature and in an oxygen atmosphere. . In the case of the gel polymer electrolyte composition having such a configuration, even when gelling is performed in an oxygen atmosphere, the influence of oxygen can be reduced, and the polymerization reaction effect can be enhanced. [202] The oxygen scavenger may include at least one of a trisalkylsilylphosphite-based compound and a trisarylsilylphosphite-based compound. That is, the trisalkylsilylphosphite-based compound or trisarylsilylphosphite-based compound contained in the oxygen scavenger consumes oxygen while converting the phosphite structure to a phosphate structure, so that radicals generated from the polymerization initiator are converted to oxygen. Can be prevented from being removed. [203] Representative examples of the trisalkylsilylphosphite-based compound are tris-2,2,2-trifluoroethyl phosphite (TFEPi), tris(methylsilyl) phosphite (TMSPi, Tris(methylsilyl) phosphite), tris(ethyl Silyl) phosphite (TESPi), tris(propylsilyl) phosphite (TPSPi), and at least one selected from the group consisting of tris(butylsilyl) phosphite. In addition, as the trisarylsilyl phosphite-based compound, trisphenylsilyl phosphite may be mentioned. At this time, the use of a fluorine-based oxygen scavenger containing a fluorine element as the oxygen scavenger is preferably avoided. [204] The composition for a gel polymer electrolyte of the present invention includes an oxygen scavenger, so that a pre-gel reaction does not occur even at room temperature. [205] The oxygen scavenger may be included in an amount of 0.01 to 10% by weight based on the total weight of the composition for the gel polymer electrolyte. When the oxygen scavenger is included in the range of 0.01% by weight to 10% by weight, specifically 0.5% by weight to 10% by weight, the conversion rate of the polymerization reaction is reduced at room temperature and in the presence of oxygen, thereby suppressing the gelation phenomenon. Specifically, when the content of the oxygen scavenger is 0.01% by weight or more, since the oxygen scavenger effect is excellent and the polymerization reaction conversion rate may be increased, the mechanical strength of the gel polymer electrolyte may be improved. In addition, when it is less than 10% by weight, it is possible to prevent an increase in resistance due to residual additives. [206] [207] (7) additional additives [208] The composition for a gel polymer electrolyte of the present invention prevents cathodic collapse due to decomposition in a high-power environment during the manufacture of the gel polymer electrolyte, or prevents the occurrence of cathodic collapse, low-temperature high-rate discharge characteristics, high-temperature stability, overcharge prevention, high-temperature swelling improvement, resistance reduction, life improvement , In order to further improve the gas reduction effect, etc., additional additives may be additionally included as needed. [209] Specific examples of such additional additives include vinylene carbonate (VC), vinylethylene carbonate (VEC), ethylene sulfate (Esa), trimethylene sulfate (TMS), and methyl trimethylene sulfate. ; MTMS), 1,3-propane sultone (PS), succinonitrile (SN), adiponitrile (Adn), ethylene sulfite, 1,3-propene sultone (PRS), fluoroethylene carbonate (FEC) , Lithium difluoro(bisoxalato)phosphate, lithium difluorophosphate, lithium oxalyldifluoroborate, LiBr, LiF, LiI, succinyl anhydride, CsNO 3 , In(TFSI) 3 , Tris(2,2,2-trifluoroethyl)phosphate (TFEPa) and 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether, F3-EMC (2,2, 2-trifluoroethyl methyl carbonate), difluoroethyl acetate (di-FEC), fluorobenzene, difluorobenzene, hexafluorobenzene, and at least one selected from the group consisting of LiBF 4 . . [210] Among these additional additives, vinylene carbonate, vinylethylene carbonate, or succinonitrile can form a stable SEI film on the surface of the negative electrode together with lithium difluorophosphate during the initial activation process of the secondary battery. [211] The LiBF 4 is added to the lithium secondary battery to suppress the generation of gas that may be generated due to decomposition of the gel polymer electrolyte composition at high temperature, thereby improving high temperature stability of the secondary battery. [212] At least one of the additional additives may be mixed and included in an amount of 0.01 to 5% by weight, specifically 0.1 to 3% by weight, and preferably 0.5 to 3% by weight, based on the total amount of the composition for a gel polymer electrolyte. If the content of the additional additive is less than 0.01% by weight, the effect of improving the low-temperature output and improving the high-temperature storage characteristics and high-temperature life characteristics of the battery is insignificant. There is a possibility that side reactions in the composition for gel polymer electrolyte may occur excessively. In particular, when the additives for forming the SEI film are added in an excessive amount, they may not be sufficiently decomposed at high temperature, and thus may be present as unreacted or precipitated in the composition for gel polymer electrolyte at room temperature. Accordingly, a side reaction may occur in which the lifespan or resistance characteristics of the secondary battery are deteriorated. [213] [214] Gel polymer electrolyte [215] In addition, the present invention provides a gel polymer electrolyte formed by polymerization of the composition for a gel polymer electrolyte. [216] As for the polymerization method for preparing the gel polymer electrolyte of the present invention, a conventional polymerization method may be used without limitation. [217] For example, i) a composition for a gel polymer electrolyte comprising a lithium salt, an organic solvent, a polymerization initiator, an oligomer represented by Formula 1, and a compound represented by Formula 2 was prepared, and then injected into a battery and subjected to a thermal polymerization reaction. In this way, a gel polymer electrolyte including a polymer matrix can be prepared. [218] Or, ii) polymerization between the oligomer represented by Formula 1 and the compound represented by Formula 2 in the presence of a polymerization initiator inside the electrochemical device to form a polymer matrix, and then a nonaqueous electrolyte containing a lithium salt and an organic solvent It can also be prepared by further impregnation. [219] At this time, the polymerization reaction may be carried out through heat, e-beam and gamma ray processes, and specifically, a thermal polymerization method of heating at 50 to 100°C for about 1 to 8 hours is preferable. [220] The radical polymerization reaction for gelation may be carried out under an inert condition in which oxygen in the atmosphere, which is a radical scavenger, is blocked. Alternatively, when an oxygen scavenger is additionally included in the gel polymer electrolyte composition of the present invention, a polymerization reaction for preparing the gel polymer electrolyte may be performed even in the presence of general air or oxygen. In other words, since the oxygen scavenger contained in the gel polymer electrolyte during the polymerization reaction reduces the influence of oxygen and improves the reactivity of the oligomers, the polymerization reaction progresses to such an extent that a large amount of unreacted monomer is hardly present even in a general air or oxygen atmosphere. (extent of reaction) can be increased. As a result, disadvantages such as deterioration in charge/discharge performance caused by the conventional unreacted monomer remaining in the battery can be improved. Particularly, the oxygen scavenger can further impart a flame retardant enhancing effect of the gel polymer electrolyte by containing a flame retardant functional group. [221] [222] Lithium secondary battery [223] In addition, in an embodiment of the present invention, a lithium secondary battery including the gel polymer electrolyte of the present invention may be provided. [224] The lithium secondary battery of the present invention can be prepared by injecting the composition for a gel polymer electrolyte of the present invention into an electrode assembly formed by sequentially stacking a positive electrode, a negative electrode, and a separator selectively interposed between the positive electrode and the negative electrode, followed by curing. [225] At this time, the positive electrode, the negative electrode, and the separator constituting the electrode assembly may be prepared by a conventional method when manufacturing a lithium secondary battery. [226] [227] (1) anode [228] First, the positive electrode may be manufactured by forming a positive electrode mixture layer on a positive electrode current collector. The positive electrode mixture layer may be formed by coating a positive electrode active material slurry including a positive electrode active material, a binder, a conductive material, and a solvent on a positive electrode current collector, followed by drying and rolling. [229] The positive electrode current collector is not particularly limited as long as it has conductivity without causing chemical changes to the battery, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or carbon on the surface of aluminum or stainless steel. , Nickel, titanium, silver, or the like may be used. [230] The positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically, may include at least one metal such as cobalt, manganese, nickel, or aluminum, and a lithium composite metal oxide containing lithium. have. More specifically, the lithium composite metal oxide is a lithium-manganese oxide (eg, LiMnO 2 , LiMn 2 O 4, etc.), a lithium-cobalt oxide (eg, LiCoO 2, etc.), a lithium-nickel oxide (E.g., LiNiO 2 ), lithium-nickel-manganese oxide (e.g., LiNi 1-Y Mn Y O 2 (here, 0