Specification Title of the invention: Polymer electrolyte for secondary battery and lithium secondary battery containing the same Technical field [One] Cross-reference with related application(s) [2] This application claims the benefit of priority based on Korean Patent Application No. 2017-0116831 filed on September 12, 2017 and Korean Patent Application No. 2018-0102273 filed on August 29, 2018, and The content is incorporated as part of this specification. [3] [4] Technical field [5] The present invention relates to a polymer electrolyte for a secondary battery and a lithium secondary battery including the same. Background [6] With the rapid development of the electric, electronic, communication and computer industries, the demand for high-performance and high-stability secondary batteries is gradually increasing. In particular, according to the trend of miniaturization and weight reduction of these electronic (communication) devices, thin film and miniaturization of lithium secondary batteries, which are core parts in this field, are required. [7] Lithium secondary batteries can be divided into lithium ion batteries using a liquid electrolyte and lithium polymer batteries using a polymer electrolyte according to the applied electrolyte. [8] In the case of a lithium ion battery, there is an advantage of high capacity, but there is a risk of leakage and explosion due to the use of a liquid electrolyte containing a lithium salt, and there is a disadvantage in that the battery design becomes complicated due to countermeasures. [9] On the other hand, in the case of a lithium polymer battery, since a solid polymer electrolyte or a gel polymer electrolyte is used as an electrolyte, it is possible to develop a variety of forms such as small size or thin film type while improving stability while improving stability. [10] However, the solid or gel polymer electrolyte has a disadvantage in that it has a lower ionic conductivity value than that of a liquid electrolyte. [11] For example, in the case of polyethylene oxide used in the manufacture of a polymer electrolyte, since the cation of the electrolyte salt is stabilized while forming a complex by coordinating with oxygen atoms present in the polyethylene oxide, it is stable despite being in a solid state without a solvent. It can exist in an ionic state. However, since the polyethylene oxide has a semi-crystalline structure at room temperature, there is a disadvantage in that it exhibits a low ionic conductivity value of about 1.0 × 10 -8 S/cm at room temperature by interfering with the movement of the dissociated electrolyte salt . [12] Therefore, in the case of a secondary battery to which such a solid or gel polymer electrolyte is applied, there is a problem that it is not suitable for commercialization because energy characteristics and the like decrease. [13] Accordingly, it can be said that the development of a polymer electrolyte material capable of securing high ionic conductivity, processability and mechanical strength while maintaining a solid phase is urgent. [14] [15] Prior art literature [16] Korean Patent Registration Publication 10-0538680 Detailed description of the invention Technical challenge [17] In order to solve the above problems, the present invention is to provide a polymer electrolyte for a secondary battery having high ionic conductivity. [18] In addition, the present invention is to provide a polymer electrolyte composition for preparing the polymer electrolyte for a secondary battery. [19] In addition, the present invention is to provide a method for manufacturing a secondary battery using the polymer electrolyte composition. [20] In addition, in the present invention, by including the polymer electrolyte for a secondary battery, it is intended to provide a lithium secondary battery with improved electrochemical stability at high voltage and high temperature. Means of solving the task [21] Specifically, in one embodiment of the present invention [22] It provides a polymer electrolyte for a secondary battery comprising a unit A derived from a lithium salt and a polymer (a) represented by the following Formula 1: [23] [Formula 1] [24] [25] In Formula 1, [26] R 1 , R 2 and R 3 are each independently hydrogen or -CH 2 -CH=CH 2 , [27] At least one or more of R 1 , R 2 and R 3 is -CH 2 -CH=CH 2 , [28] a, b and c are each the number of repeat units, [29] a, b, and c are each independently an integer of 1 to 10,000. [30] [31] The polymer (a) represented by Formula 1 may be at least one selected from the group consisting of polymers represented by Formulas 1a to 1c below. [32] [Formula 1a] [33] [34] In Formula 1a, [35] a1, b1 and c1 are each the number of repeat units, [36] a1, b1 and c1 are each independently an integer of 1 to 10,000. [37] [38] [Formula 1b] [39] [40] In Formula 1b, [41] a2, b2 and c2 are each the number of repeat units, [42] a2, b2, and c2 are each independently an integer of 1 to 10,000. [43] [44] [Formula 1c] [45] [46] In Formula 1c, [47] a3, b3 and c3 are each the number of repeat units, [48] a3, b3, and c3 are each independently an integer of 1 to 10,000. [49] [50] Meanwhile, in the polymer electrolyte, the weight ratio of the lithium salt: the unit A derived from the polymer (a) represented by Formula 1 may be 1:1 to 1:9, specifically 1:1 to 1:6. [51] The polymer electrolyte may further include an oxygen inhibitor (O 2 inhibitor). [52] [53] In addition, in an embodiment of the present invention [54] It provides a composition for a polymer electrolyte comprising a lithium salt, an organic solvent, and the polymer (a) represented by Chemical Formula 1. [55] The lithium salt: the weight ratio of the polymer (a) represented by Formula 1 may be 1:1 to 1:9, specifically 1:1 to 1:6. [56] The polymer electrolyte composition may further include a polymerization initiator. [57] The composition for the polymer electrolyte may further include an oxygen inhibitor (O 2 inhibitor). [58] [59] In addition, in an embodiment of the present invention [60] Coating the composition for a polymer electrolyte of the present invention on at least one surface of the anode, the cathode, and the separator; And [61] It provides a method for manufacturing a secondary battery comprising; thermosetting the polymer electrolyte composition to form a polymer electrolyte for a secondary battery. [62] [63] In addition, in another embodiment of the present invention [64] Coating the composition for a polymer electrolyte of the present invention on a substrate; [65] Thermosetting the polymer electrolyte composition to form a polymer electrolyte for a secondary battery; [66] Separating the polymer electrolyte from the substrate; And [67] It provides a method for manufacturing a secondary battery comprising; interposing the separated polymer electrolyte on at least one surface of a negative electrode, a positive electrode, and a separator. [68] [69] In addition, an embodiment of the present invention provides a lithium secondary battery including the polymer electrolyte for a secondary battery of the present invention. Effects of the Invention [70] According to the present invention, it is possible to provide a polymer electrolyte capable of implementing not only mechanical strength but also excellent ionic conductivity by including a lithium salt and a unit A derived from a polymer having a specific structure. Further, by including this, it is possible to manufacture a lithium secondary battery with enhanced electrochemical stability at high voltage and high temperature. Best mode for carrying out the invention [71] Hereinafter, the present invention will be described in more detail. [72] The terms or words used in the present specification and claims should not be construed as being limited to their usual or dictionary meanings, and the inventor may appropriately define 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 there is. [73] 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 a gel permeation chromatography (Gel Permeation Chromatography) : GPC) can be used. For example, after preparing a sample sample of a certain concentration, the GPC measurement system alliance 4 device is stabilized. 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 (system: Alliance 4, column: Ultrahydrogel linearX2, eluent: 0.1M NaNO 3 (pH 7.0). phosphate buffer, flow rate: 0.1 mL/min, temp: 40℃, injection: 100μL) [74] Meanwhile, in the present specification, the ion conductivity can be measured using an AC impedance measurement method. Specifically, it is possible to measure in a frequency band of 100 MHz to 0.1 Hz using a VMP3 measuring device and a precision impedance analyzer 4294A. [75] 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. [76] In the present invention, the tensile strength was measured by using Lloyd LR-10K at a rate of 5 mm per minute at 25° C. and about 30% relative humidity of an electrolyte specimen manufactured collectively through ASTM standard D638 (Type V specimens). [77] [78] Currently, secondary batteries containing polymer electrolytes have less solution leakage compared to secondary batteries containing liquid electrolyte alone as an ion transport medium, thus improving the reliability and safety of the battery, reducing the thickness, simplifying the package, and reducing the weight. have. In addition, since the polymer electrolyte has inherently good processability and flexibility, when used in an electrochemical device such as a battery, it is easy to form a laminated structure with the electrode, and according to the volume change of the electrode due to ion occlusion and release. There is an advantage in that the shape of the polymer electrolyte interface can be changed. [79] However, since the polymer electrolyte has relatively low ionic conductivity compared to the liquid electrolyte, the secondary battery using the same has a disadvantage in that the charge/discharge current density is limited at room temperature to be low, thereby increasing the battery resistance. [80] In the present invention, by improving these problems, it is intended to provide a polymer electrolyte for secondary batteries having excellent mechanical strength as well as ionic conductivity, and a secondary battery including the same. [81] [82] Hereinafter, a polymer electrolyte for a secondary battery, a composition for a polymer electrolyte for preparing the same, and a lithium secondary battery including the same will be described in more detail. [83] Polymer electrolyte [84] Specifically, in one embodiment of the present invention [85] A polymer electrolyte comprising a lithium salt and a unit A derived from a polymer (a) represented by the following formula (1) is provided. [86] [Formula 1] [87] [88] In Formula 1, [89] R 1 , R 2 and R 3 are each independently hydrogen or -CH 2 -CH=CH 2 , [90] At least one of R 1 , R 2 and R 3 is -CH 2 -CH=CH 2 (that is, R 1 , R 2 and R 3 are not all hydrogen), [91] a, b and c are each the number of repeat units, [92] a, b, and c are each independently an integer of 1 to 10,000, specifically 5 to 8,000. [93] [94] (1) lithium salt [95] First, the polymer electrolyte of the present invention may contain a lithium salt in order to increase lithium ion transport characteristics. The lithium salt is Li cation + to contain the anion is F - , Cl - , Br - , I - , NO 3 - , N (CN) 2 - , BF 4 - , ClO 4 - , AlO 4 - , AlCl 4 - , PF 6 - , SbF 6 - , AsF 6 - , BF 2 C 2 O 4 -, B (C 2 O 4 ) 2 - , (CF 3 ) 2 PF 4 - , (CF 3 ) 3 PF 3 - , (CF 3 ) 4 PF 2 - , (CF 3 ) 5 PF - , (CF 3 ) 6 P - , CF 3 SO 3 - , C 4 F 9 SO 3 - , CF 3 CF 2 SO 3 - , (FSO 2 ) 2 N - , CF 3 CF 2 (CF 3 ) 2 CO - , (CF 3 SO 2 ) 2 N - , (SF 5 ) 3 C - , (CF 3 SO 2 ) 3 C -, CF 3 (CF 2 ) 7 SO 3 - , CF 3 CO 2 - , CH 3 CO 2 - , SCN - , and (CF 3 CF 2 SO 2 ) 2 N - can include at least one selected from the group consisting of have. [96] The lithium salt may be used alone or in combination of two or more as necessary. [97] [98] (2) Unit derived from polymer (a) represented by formula (1) (A) [99] In addition, the polymer electrolyte according to an embodiment of the present invention may include a unit A derived from polymer (a) represented by Chemical Formula 1. That is, the polymer electrolyte includes a polymer network formed by crosslinking the ends (double bonds) of the polymer (a) represented by Formula 1, and the unit A is represented by Formula 1 included in the polymer network. It means a polymerization repeating unit derived from polymer (a). [100] Meanwhile, in the polymer electrolyte, the weight ratio of the lithium salt: the unit A derived from the polymer (a) represented by Formula 1 is 1:1 to 1:9, specifically 1:1 to 1:6, specifically 1: It may be from 1.5 to 1:6. [101] In the case where the content of the unit A derived from the polymer (a) represented by Chemical Formula 1 per 1 weight of the lithium salt in the polymer electrolyte is 9 weight ratio or less, it is advantageous for polymer electrolyte molding and the oxidation potential may increase, It is possible to suppress the decrease in mechanical strength due to the reduction in battery performance at high temperature and high voltage. In addition, it is possible to improve the ion transfer characteristics due to the lithium salt in the polymer electrolyte. [102] In addition, when the content of the unit A derived from the polymer (a) represented by Formula 1 with respect to 1 weight of the lithium salt in the polymer electrolyte is 1 weight ratio or more, not only the formation of a polymer matrix is ​​easy, but also excellent mechanical properties are secured. can do. If the content of the unit A derived from the polymer (a) represented by Formula 1 is less than 1 weight ratio, the ratio of the lithium salt in the polymer electrolyte increases, so that the supply of lithium ions is smooth and the ion transport characteristics can be improved. The mechanical properties of the polymer electrolyte may be relatively deteriorated. [103] Meanwhile, the weight average molecular weight (Mw) of the polymer (a) represented by Formula 1 is 1,000 g/mol to 1,000,000 g/mol, specifically 5,000 g/mol to 500,000 g/mol, more specifically 10,000 g/mol to 200,000 g/mol. [104] When the weight average molecular weight of the polymer (a) represented by Chemical Formula 1 is within the above range, ion transport capability of the polymer electrolyte may be improved, and electrochemical stability may be secured. [105] The weight average molecular weight (Mw) of the polymer (a) represented by Chemical Formula 1 can be measured using gel permeation chromatography (GPC). For example, after preparing a sample sample of a certain concentration, the GPC measurement system alliance 4 device is stabilized. 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 (system: Alliance 4, column: Ultrahydrogel linearX2, eluent: 0.1M NaNO 3 (pH 7.0). phosphate buffer, flow rate: 0.1 mL/min, temp: 40℃, injection: 100μL) [106] [107] Meanwhile, the polymer (a) represented by Formula 1 may be at least one selected from the group consisting of polymers represented by the following Formulas 1a to 1c. [108] [Formula 1a] [109] [110] In Formula 1a, [111] a1, b1 and c1 are each the number of repeat units, [112] a1, b1 and c1 are each independently an integer of 1 to 10,000, specifically 5 to 8,000. [113] [114] [Formula 1b] [115] [116] In Formula 1b, [117] a2, b2 and c2 are each the number of repeat units, [118] a2, b2 and c2 are each independently an integer of 1 to 10,000, specifically 5 to 8,000. [119] [120] [Formula 1c] [121] [122] In Formula 1c, [123] a3, b3 and c3 are each the number of repeat units, [124] a3, b3 and c3 are each independently an integer of 1 to 10,000, specifically 5 to 8,000. [125] [126] (3) oxygen inhibitor [127] In addition, the polymer electrolyte according to an embodiment of the present invention may further include an oxygen inhibitor (O 2 inhibitor). [128] The oxygen inhibitor may include tris(2,2,2-trifluoroethyl) phosphite as a representative example thereof. [129] The oxygen inhibitor may be included in an amount of 0.1% to 10% by weight based on the total weight of the solid content in the polymer electrolyte. When the oxygen inhibitor is included in the above content ratio, an oxygen generation suppressing effect and a side reaction prevention effect may be obtained, so that the crosslinking polymerization reaction of the polymer (A) can be more efficiently improved. [130] [131] (4) Unit B [132] In addition, the polymer electrolyte according to an embodiment of the present invention may further include unit B. [133] The unit B may be derived from compounds containing a polymerizable functional group for crosslinking in a molecule. [134] The compound containing the polymerizable functional group is a representative example of a multifunctional (meth)acrylate compound containing at least one acrylate group, or a vinyl group, an epoxy group, an ether group, an allyl group, and a (meth)acrylic group. And a compound having at least one polymerizable functional group selected from the group consisting of. At this time, when there are two or more polymerizable functional groups in the compound, these polymerizable functional groups may have the same structure or different from each other. [135] Specifically, the compound having a polymerizable functional group is representative examples thereof, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, Hexyl acrylate, hexyl methacrylate, ethylhexyl acrylate, ethylhexyl methacrylate, 2,2,2-trifluoroethyl acrylate, 2,2,2-trifluoroethyl methacrylate, 2,2 ,3,3-tetrafluoropropyl acrylate, 2,2,3,3-tetrafluoropropyl methacrylate, tetraethylene glycol diacrylate, Polyethylene glycol diacrylate diacrylate, molecular weight 50~20,000), 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate (1,6-hexandiol diacrylate), trimethylolpropane triacrylate ( trimethylolpropane triacrylate), trimethylolpropane ethoxylate triacrylate, trimethylolpropane propoxylate triacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol tetra Acrylate (pentaerythritol tetraacrylate),At least one compound selected from the group consisting of pentaerythritol ethoxylate tetraacrylate, dipentaerythritol pentaacrylate, and dipentaerythritol hexaacrylate. I can. [136] In addition, phosphate compounds, pyrophosphate compounds, polyethylene glycol diglycidylether, 1,5-hexadiene diepoxide, glycerol Propoxylate triglycidyl ether, vinylcyclohexene dioxide, 1,2,7,8-diepoxyoctane (1,2,7,8-diepoxyoctane), 4-vinylcyclo Hexene dioxide (4-vinylcyclohexene dioxide), butyl glycidyl ether, diglycidyl 1,2-cyclohexanedicarboxylate, ethylene glycol diglycidyl ether ( ethylene glycol diglycidyl ether), glycerol triglycidyl ether, and at least one compound selected from the group consisting of glycidyl methacrylate. [137] The unit B may be included in an amount of 1 to 100 parts by weight, specifically 1 to 50 parts by weight, and more specifically 1 to 30 parts by weight, based on 100 parts by weight of the unit A. [138] When the unit B is included in the content ratio, it is possible to improve the electrochemical stability of the secondary battery by further improving the oxidation potential window and ion transfer capability while securing mechanical strength. [139] At this time, the unit B may be included in the form of a polymer network cross-linked with the unit A, or may be included in the form of a polymer network consisting of only the unit B. [140] [141] Meanwhile, the polymer electrolyte of the present invention may be a free-standing polymer electrolyte including a lithium salt and a unit A derived from the polymer (a) represented by Formula 1 above. [142] In addition, the polymer electrolyte of the present invention may be a self-supporting polymer electrolyte including a lithium salt, a unit A derived from the polymer (a) represented by Chemical Formula 1, and optionally a unit B. [143] [144] The ionic conductivity of the polymer electrolyte of the present invention may be 1.0 × 10 -4 S/cm or more, specifically 2.7 × 10 -4 S/cm to 3.8 × 10 -4 S/cm. [145] The ionic conductivity can be measured using an AC impedance measurement method. The ionic conductivity may be measured in a frequency band of 100 MHz to 0.1 Hz using a VMP3 measuring device and a precision impedance analyzer 4294A. [146] [147] Composition for polymer electrolyte [148] In addition, the present invention provides a composition for a polymer electrolyte comprising a lithium salt, an organic solvent, and a polymer (a) represented by Formula 1 above. [149] [150] (1) Lithium salt and polymer represented by Formula 1 (a) [151] First, in the method of the present invention, descriptions of the lithium salt contained in the polymer electrolyte composition and the polymer (a) represented by Chemical Formula 1 are duplicated with those described above, and thus description thereof will be omitted. [152] However, with respect to the content of the lithium salt and the polymer (a) represented by Formula 1, the weight ratio of the lithium salt: the polymer (a) represented by Formula 1 in the polymer electrolyte composition may be 1:1 to 1:9, Specifically, it may be 1:1 to 1:6, more specifically 1:2 to 1:4. [153] When the polymer (a) and lithium salt represented by Formula 1 are included in the above ratio in the polymer electrolyte composition, the desired amount of unit A may be included in the polymer electrolyte after drying and curing, and thus excellent mechanical strength And it is possible to prepare a polymer electrolyte having ionic conductivity and the like. Specifically, when the weight ratio of the polymer (a) represented by Formula 1 to 1 weight of the lithium salt is 9 or less, it is advantageous for polymer electrolyte molding, has advantages such as an increase in oxidation potential, and suppresses a decrease in mechanical strength due to excessive content. Deterioration of battery performance at high temperatures and high voltages can be suppressed. In addition, when the weight ratio of the polymer (a) represented by Formula 1 to 1 weight of the lithium salt is 1 or more, not only the formation of the polymer matrix is ​​easy, but also excellent mechanical properties can be secured. At this time, when the weight ratio of the polymer (a) represented by Formula 1 to 1 weight of the lithium salt is less than 1, the ratio of the lithium salt increases, thereby facilitating the supply of lithium ions and improving the ion transport characteristics, while the mechanical properties are relatively It can be degraded. [154] [155] Meanwhile, the polymer electrolyte of the present invention may be used by appropriately mixing one or more polymers represented by Formula 1, specifically, polymers represented by Formulas 1a to 1c, depending on the effect to be implemented. [156] That is, in the case of a polymer represented by Formula 1c containing an acrylate group at all terminals, the crosslinking performance is superior to that of the polymer represented by Formula 1a or 1b. Therefore, when it is desired to achieve higher mechanical properties and stability under high voltage, a polymer electrolyte having a dense polymer network structure may be prepared by increasing the content of the polymer represented by Formula 1c. Further, in the case of the polymer represented by Formula 1a containing one acrylate group at the terminal, the crosslinking performance is lower than that of the polymer represented by Formula 1b or 1c. Therefore, when the content of the polymer represented by Formula 1a is high, a polymer electrolyte having a relatively loose polymer network structure is formed compared to the case where the content of the polymer represented by Formula 1c is high. In this case, while the mechanical properties of the polymer electrolyte are relatively low, since the movement of lithium ions is advantageous, the effect of improving ionic conductivity can be realized. [157] [158] (2) organic solvent [159] In addition, the organic solvent used in the preparation of the polymer electrolyte composition is not particularly limited as long as decomposition by oxidation reactions, etc. can be minimized during the charging and discharging process of the secondary battery. Any organic solvent can be used. [160] Representative examples of the organic solvent include N,N'-dimethylacetamide, N-methyl-2-pyrrolidone (hereinafter, abbreviated as "NMP"), dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), acetonitrile (AN), propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), fluorine Roethylene carbonate (FEC), gamma-butyrolactone (GBL), 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyl tetrahydrofuran (THF), dimethyl sulfoxide, 1,3-dioxolone (DOL), 1,4-dioxane, formamide, dimethylformamide, dioxolone, acetonitrile, nitromethane, methyl formate, methyl acetate (EA), ethyl propionate (EP), Methyl acetate (MA), methyl propionate (MP), dimethoxy ethane (DME) phosphoric acid tryster, diethyl ether, trimethoxy methane, triglyme, tetraglyme (TEGDME), sulfolane, A single substance selected from the group consisting of methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, methyl propionate, and ethyl propionate, or a mixture of two or more thereof may be included. [161] More specifically, the organic solvent preferably includes an organic solvent having a low boiling point such as acetonitrile or an organic solvent having excellent volatility such as N-methyl-2-pyrrolidone to facilitate removal. [162] The amount of the organic solvent is not particularly limited as long as it is an amount capable of uniformly mixing the polymer (a) and lithium salt represented by the formula (1) and coating with a uniform thickness. After that, it is preferable to use it in a small amount as possible to facilitate removal. [163] Specifically, the organic solvent is about 5 parts by weight to 1,000 parts by weight, specifically 30 parts by weight to 500 parts by weight, more specifically, based on 100 parts by weight of the total solid content including the lithium salt and the polymer (a) represented by Formula 1 It may be used in an amount of 30 parts by weight to 200 parts by weight. In this case, when the organic solvent is used in an amount of 30 parts by weight or less to prepare a composition for a polymer electrolyte in a stiff slurry state, the solubility may be increased by slightly applying heat of 45° C. or less to facilitate application. [164] When the amount of the organic solvent is within the above range, the polymer electrolyte composition can be uniformly coated with a sufficient thickness, and the organic solvent can be easily removed during the production of the polymer electrolyte. It is possible to prevent decrease in strength and the like. [165] [166] (3) polymerization initiator [167] In addition, the composition for a polymer electrolyte of the present invention may optionally further include a polymerization initiator in order to improve the polymerization reaction effect. [168] The polymerization initiator may be a conventional polymerization initiator known in the art. For example, the polymerization initiator may be used by selecting one or more selected from the group consisting of a UV polymerization initiator, a photo polymerization initiator, and a thermal polymerization initiator, and specifically, a UV polymerization initiator or a thermal polymerization initiator may be used. [169] Specifically, the UV polymerization initiator is representative examples of 2-hydroxy-2-methylpropiophenone, 1-hydroxy-cyclohexylphenyl-ketone, benzophenone, 2-hydroxy-1-[4-(2-hydroxyl) Roxyethoxy)phenyl]-2-methyl-1-propanone, oxy-phenylacetic acid 2-[2-oxo-2 phenyl-acetoxy-ethoxy]-ethyl ester, oxy-phenyl-acetic 2- [2-hydroxyethoxy]-ethyl ester, alpha-dimethoxy-alpha-phenylacetophenone, 2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl)phenyl]-1 -Butanone, 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone, diphenyl (2,4,6-trimethylbenzoyl)-phosphine Oxide, bis(2,4,6-trimethylbenzoyl)-phenyl phosphine oxide, bis(ethane 5-2,4-cyclopentadien-1-yl), bis[2,6-difluoro-3-( 1H-pyrrol-1-yl)phenyl] titanium, 4-isobutylphenyl-4'-methylphenyliodonium, hexafluorophosphate, and may include at least one selected from the group consisting of methyl benzoyl formate. [170] In addition, the photo or thermal polymerization initiators are representative examples thereof, 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, 2,2 '-Azobis(2-cyanobutane), 2,2'-azobis(methylbutyronitrile), 2,2'-azobis(isobutyronitrile) (AIBN; 2,2'-Azobis(iso -butyronitrile)) and 2,2'-azobisdimethyl-valeronitrile (AMVN; 2,2'-Azobisdimethyl-Valeronitrile). [171] The polymerization initiator is decomposed by UV or heat of 30° C. to 100° C. in the battery, or decomposed by light at room temperature (5° C. to 30° C.) to form a radical, and the free radical polymerization is expressed as Formula 1 The polymer (a) displayed may form a crosslinking bond to form a polymer electrolyte. [172] Meanwhile, when a polymerization initiator is included in the preparation of the polymer electrolyte composition, the polymerization initiator may be used in an amount of 0.1 parts by weight or more based on 100 parts by weight of the polymer (a). That is, when the polymerization initiator is contained in an amount of 0.1 parts by weight or more, the polymerization reaction between the polymer (a) compounds represented by Formula 1 can be performed more smoothly and quickly. [173] On the other hand, when the polymerization initiator is included in the preparation of the polymer electrolyte composition, the polymerization initiator is usually decomposed to initiate a chain polymerization reaction when performing drying and curing reactions on the polymer composition, and then part of it is converted to gas. It is removed while being decomposed, and at this time, some residues of the polymerization initiator remaining without decomposition and removal may be included in a trace amount in the prepared polymer electrolyte. [174] Therefore, in order to prevent side reactions and increased resistance to the polymerization initiator, the polymerization initiator is not used in an excessive amount, and specifically 10 parts by weight or less based on 100 parts by weight of the polymer (a) represented by Formula 1, It may be used in an amount of 5 parts by weight or less, more preferably 2 parts by weight or less. [175] That is, when the polymerization initiator is contained in an amount of 10 parts by weight, specifically 5 parts by weight or less, the polymerization rate can be controlled in the polymer electrolyte, so that the unreacted polymerization initiator remains, thereby preventing a disadvantage that adversely affects the battery performance later. . [176] [177] (4) oxygen inhibitor [178] In addition, the composition for a polymer electrolyte of the present invention may optionally further include an oxygen inhibitor (O 2 inhibitor) in order to suppress the generation of oxygen during the polymerization reaction and increase the polymerization reaction effect . [179] As described above, the oxygen inhibitor may include tris(2,2,2-trifluoroethyl) phosphite as a representative example thereof. [180] The oxygen inhibitor may be included in an amount of 0.1% to 10% by weight based on the total weight of the polymer electrolyte composition. When included in the above content ratio, an oxygen suppression effect and a side reaction prevention effect may be obtained, so that the crosslinking polymerization reaction may proceed more efficiently. [181] [182] (5) Compound having a polymerizable functional group [183] In addition, the composition for a polymer electrolyte of the present invention may optionally further include a compound having a polymerizable functional group. [184] Since the description of the compound having the polymerizable functional group overlaps with the above description, the description thereof will be omitted. [185] Meanwhile, the compound having the polymerizable functional group may be included in an amount of 1 to 100 parts by weight, specifically 5 to 50 parts by weight, and more specifically 5 to 30 parts by weight based on 100 parts by weight of the polymer (a) represented by Formula 1 . [186] When the compound having the polymerizable functional group is included in the above content ratio, the mechanical strength and the oxidation potential window may be further improved. [187] [188] Secondary battery manufacturing method [189] In addition, in an embodiment of the present invention [190] Coating the composition for a polymer electrolyte of the present invention on at least one surface of the negative electrode, the positive electrode, and the separator; And [191] It is possible to provide a method for manufacturing a secondary battery comprising a step of thermosetting the polymer electrolyte composition to form the polymer electrolyte of the present invention. [192] [193] In addition, in an embodiment of the present invention [194] Coating the composition for a polymer electrolyte on a substrate; [195] Thermosetting the polymer electrolyte composition to form the polymer electrolyte of the present invention; [196] Separating the polymer electrolyte membrane from the substrate; And [197] It may provide a method for manufacturing a secondary battery comprising; interposing the separated polymer electrolyte membrane on at least one surface of the cathode, the anode, and the separator. [198] [199] In the method of the present invention, coating a composition for a polymer electrolyte on at least one surface of a cathode, an anode, and a separator, or coating a composition for a polymer electrolyte on a substrate may be performed using a conventional solution casting method known in the art. have. [200] In this case, the substrate may include a glass substrate, PET (polyethylene terephthalate), Teflon, or a fluorinated ethylene propylene copolymer (FEP) film. [201] [202] In addition, in the method of the present invention, the curing process of the polymer electrolyte composition may be performed by performing a thermal process, and in addition, a UV curing process may be performed. [203] Specifically, the curing step may be performed for 5 hours to 24 hours at a temperature range of 40°C to 70°C under an inert condition. [204] When the curing process is carried out in an inert atmosphere, the reaction between oxygen and radicals in the atmosphere, which is a radical scavenger, is fundamentally blocked, thereby increasing the extent of reaction so that almost no unreacted polymer exists. I can make it. Accordingly, it is possible to prevent a decrease in mechanical strength and ion transfer capability caused by a large amount of unreacted polymer remaining inside the battery. As the inert atmosphere condition, a gas having low reactivity known in the art may be used, and in particular, at least one inert gas selected from the group consisting of nitrogen, argon, helium, and xenon may be used. [205] By this curing step, a polymer electrolyte having improved mechanical strength may be prepared by crosslinking the polymers (a) represented by Formula 1 with each other. [206] The polymer electrolyte of the present invention may be a self-supporting polymer electrolyte comprising a lithium salt and a unit A derived from the polymer (a) represented by Formula 1. [207] [208] Lithium secondary battery [209] In addition, an embodiment of the present invention provides a lithium secondary battery including the polymer electrolyte for a secondary battery of the present invention. This lithium secondary battery can be manufactured by the above-described secondary battery manufacturing method. [210] The polymer electrolyte is prepared by polymerizing the polymer electrolyte composition of the present invention, and the thickness of the electrolyte may be about 0.5 μm to 300 μm in consideration of ion conductivity. When the thickness of the electrolyte is 0.5 μm or more, the strength of the membrane can be secured, and when the thickness of the electrolyte is less than 300 μm, protons (H + ), which are ion transporters, can easily pass, thereby preventing an increase in volume per unit performance of the secondary battery specification. It is possible to manufacture a secondary battery. [211] [212] On the other hand, the positive electrode and negative electrode used for manufacturing the lithium secondary battery of the present invention may be manufactured by a conventional method. [213] 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 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. [214] 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. [215] The positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically, may include a lithium composite metal oxide containing lithium and at least one metal such as cobalt, manganese, nickel or aluminum. 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