Specification Title of the invention: Solid polymer electrolyte and lithium secondary battery including the same Technical field [One] Mutual citation with related applications [2] This application claims the benefit of priority based on Korean Patent Application No. 10-2018-0016527 filed on February 09, 2018, and all contents disclosed in the documents of the Korean patent application are included as part of this specification. [3] Technical field [4] The present invention relates to a solid polymer electrolyte and a lithium secondary battery using the same, and more particularly, to a solid polymer electrolyte including a porous substrate formed of inorganic fibers including an ethylenic unsaturated group, and a lithium secondary battery including the same. [5] Background [6] As technology development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing, and among such secondary batteries, lithium secondary batteries exhibit high energy density and operating potential, long cycle life, and low self-discharge rate. Batteries are commercialized and widely used. [7] In recent years, in order to overcome the stability problem of a liquid electrolyte, a lithium secondary battery using a solid electrolyte has been in the spotlight. [8] In general, solid electrolytes are polyethylene oxide (PEO) series, polyvinyl acetate (PVA, polyvinyl acetate), polyethylene imine (PEI, polyethyleneimine), polyvinylidene fluoride (PVDF) series, polyacrylonitrile (PAN) series, Polymethyl methacrylate (PMMA) series, or a polymer compound composed of a copolymer thereof, as a main component. [9] On the other hand, a solid polymer electrolyte composed of only polymers has remarkably low mechanical properties, and it is common to use inorganic substances together rather than using only polymers alone. However, if an inorganic material is used, there is a problem in that the ion conductivity may be lowered as it may interfere with the movement of lithium ions, and as an inorganic material and an organic polymer compound are mixed, interfacial resistance is formed, which may deteriorate the performance of the battery. . [10] (Patent Document 1) Korean Patent Publication No. 10-2012-0139058 [11] Detailed description of the invention Technical challenge [12] The present invention is to solve the above problems, and by using a porous substrate formed of inorganic fibers that can be combined with a polymer compound, a solid capable of improving high temperature safety and mechanical performance while maintaining ionic conductivity above a certain level. It is to provide a polymer electrolyte and a lithium secondary battery including the same. [13] Means of solving the task [14] In one aspect, the present invention is a porous substrate formed of inorganic fibers containing an ethylenic unsaturated group; A polymer compound comprising a polymer network in which an oligomer including a (meth)acrylate group is bonded to the inorganic fiber and has a three-dimensional structure; And it provides a solid polymer electrolyte containing; [15] In this case, the ethylenically unsaturated group may be at least one selected from the group consisting of a vinyl group, an acryloxy group, and a methacryloxy group. [16] In another aspect, the present invention comprises the steps of preparing a composition for a polymer electrolyte by dissolving an oligomer and a lithium salt containing a (meth)acrylate group in a solvent; Coating a porous substrate formed of inorganic fibers containing an ethylenically unsaturated group on the polymer electrolyte composition; And it provides a solid polymer electrolyte manufacturing method comprising the step of drying and then curing the coated porous substrate. [17] In another aspect, the present invention provides a lithium secondary battery including the solid polymer electrolyte. [18] Effects of the Invention [19] The solid polymer electrolyte according to the present invention may improve ionic conductivity by improving the mobility of lithium ions in the solid polymer electrolyte by using an inorganic material in the form of fibers. [20] In addition, since the inorganic fiber according to the present invention contains an ethylenically unsaturated group and has a high bonding strength with the organic polymer compound, resistance between the inorganic material and the organic polymer compound interface is higher than when simply mixing an inorganic material and an organic polymer compound. By minimizing the formation, high temperature safety can be improved, and mechanical properties of the battery can be improved. [21] Best mode for carrying out the invention [22] Hereinafter, the present invention will be described in more detail. [23] The terms or words used in the 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. [24] The terms used in the present specification are only used to describe exemplary embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. [25] In the present specification, terms such as "comprises", "includes" or "have" are intended to designate the presence of implemented features, numbers, steps, components, or a combination thereof, and one or more other features or It is to be understood that the possibility of the presence or addition of numbers, steps, elements, or combinations thereof is not preliminarily excluded. [26] On the other hand, in the present invention, unless otherwise specified, "*" means the same or different atoms or a connected portion between the terminal portions of the formula. [27] In the present specification, the weight average molecular weight may mean a value in terms of standard polystyrene measured by GPC (Gel Permeation Chromatograph), and unless otherwise specified, the molecular weight may mean a weight average molecular weight. In this case, the weight average molecular weight may 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 weight average molecular weight is calculated according to the analysis method (system: Alliance 4, column: Ultrahydrogel linear x 2, eluent: 0.1M NaNO 3 ( pH 7.0 phosphate buffer, flow rate: 0.1 mL/min, temp: 40℃, injection: 100µl) [28] [29] [30] The solid polymer electrolyte according to the present invention includes a porous substrate, a polymer compound, and a lithium salt. [31] [32] The porous substrate is formed of inorganic fibers containing an ethylenically unsaturated group. [33] In the case of a conventional liquid electrolyte, there is a high possibility that the electrode material is degraded and the organic solvent is volatilized, and there are safety issues such as heat generation and ignition due to an increase in ambient temperature and the temperature of the battery itself. Therefore, research on a solid polymer electrolyte has been recently conducted. [34] On the other hand, in the case of a solid polymer electrolyte, if it is composed of only a polymer compound, mechanical properties are remarkably low, so it is common to use an inorganic material together. In this case, the inorganic particles are prepared by dispersing them in a polymer compound, and the inorganic particles have a weak binding force with the organic polymer compound, so that aggregation between inorganic particles occurs or there is a problem in that they are separated. [35] In addition, when inorganic particles and organic compounds such as oligomers constituting the polymer compound are physically mixed, the bonding between the organic compound and the inorganic particles is not completely established, so that lithium ions are transferred between the organic compound and the inorganic particles without bonding. This difficult space (dead space) can occur. Accordingly, there is a problem in that the movement of lithium ions may be inhibited, so that the ion conductivity is low, and additional interfacial resistance between the inorganic particles and the organic compound may be generated, thereby deteriorating the performance of the battery. [36] In order to overcome the above problems, in the case of the present invention, by using a porous substrate formed of inorganic fibers instead of inorganic particles, it is possible to prevent inorganic substances from being desorbed and to suppress the movement of lithium ions, thereby improving ionic conductivity. Made it possible. [37] In addition, in the case of the porous substrate formed of the inorganic fiber of the present invention, it may be directly bonded to the oligomer constituting the polymer compound, including an ethylenic unsaturated group on the surface of the inorganic fiber through a polymerization reaction. Therefore, it is possible to improve the performance of the battery by minimizing the interfacial resistance that may occur between the polymer compound and the inorganic material. [38] The inorganic fiber may include an inorganic material commonly used in the art. For example, the inorganic fiber may include at least one element selected from the group consisting of Si, Al, Ti, Zr, Sn, Ce, Mg, Ca, Zn, Y, Pb, Ba, Hf, and Sr. And, preferably, it may include at least one element selected from the group consisting of Si, Al, Ti, and Zr. [39] More specifically, the inorganic fiber is SiO 2 , Al 2 O 3 , TiO 2 , ZrO 2 , SnO 2 , CeO 2 , MgO, CaO, ZnO, Y 2 O 3 , 　Pb(Zr,Ti)O 3　(PZT) , Pb (1-a1) La a1 Zr (1-b1) Ti b1 O 3　(0≤a1≤1, 0≤b1≤1, PLZT), PB(Mg 3 Nb 2/3 )O 3 -PbTiO 3　 ( PMN-PT), BaTiO 3, HfO 2 (hafnia), SrTiO 3　 and the like, and the inorganic materials listed above generally have properties that do not change their physical properties even at a high temperature of 200°C or higher. More preferably, the inorganic fiber may include at least one inorganic material selected from the group consisting of SiO 2 , Al 2 O 3 , TiO 2 and ZrO 2 . [40] Meanwhile, the diameter of the inorganic fiber may be 0.01 μm to 10 μm, preferably 0.01 μm to 9 μm, more preferably 0.01 μm to 8 μm. When the diameter of the inorganic fiber is within the above range, the mechanical properties of the porous substrate may be improved while preventing a decrease in energy density of the battery by adjusting the thickness of the porous substrate formed of the inorganic fiber. Meanwhile, the diameter of the inorganic fiber can be measured by observing the inorganic fiber with a device such as a field emission scanning electron microscope (FE-SEM). [41] Meanwhile, in order to improve the interfacial adhesion between the inorganic fiber and the polymer compound, ethylenically unsaturated groups may be located inside and on the surface of the inorganic fiber by using a coupling agent containing an ethylenically unsaturated group. In this case, a coupling agent containing an ethylenically unsaturated group may be used directly on the inorganic fiber, or after forming a porous substrate with an inorganic fiber, the coupling agent containing the ethylenically unsaturated group may be used. [42] Specifically, the ethylenically unsaturated group may include at least one selected from the group consisting of a vinyl group, an acryloxy group, and a methacryloxy group. [43] Typically, the coupling agent having an ethylenically unsaturated group may be a silane-based compound, for example, methacryloxypropyltrimethoxysilane, vinyl trimethoxysilane, acryloxytrimethoxysilane, methacryloxy Trimethoxysilane or the like can be used. However, the type of the coupling agent is not limited to the compounds listed above. [44] On the other hand, the porous substrate formed of the inorganic fiber refers to a sheet or nonwoven fabric manufactured using the inorganic fiber, and serves as a back bone of the solid polymer electrolyte according to the present invention. [45] For example, the porous substrate may be manufactured by the following method. However, it is not necessarily limited to the following manufacturing method. [46] First, the molten inorganic fiber composition is extruded through a bushing device composed of thousands of fine pores, and then the extruded inorganic fiber composition is pulled by a winding device and rapidly cooled in air to produce an inorganic material having a diameter to be manufactured. It is made of fibers. The prepared inorganic fibers are selectively made of various types of porous substrates such as sheets or nonwovens through a surface coating process (sizing process, sizing), winding process, and post-treatment process. [47] The thickness of the porous substrate may be 1 μm to 200 μm, preferably 5 μm to 200 μm, more preferably 10 μm to 200 μm. When the thickness of the porous substrate is within the above range, short circuit between the positive electrode and the negative electrode may be suppressed, and the mobility of lithium ions may be maintained above a certain level, thereby improving battery performance. [48] The porosity of the porous substrate may be 10% to 80%, preferably 15% to 80%, more preferably 10% to 80%. The porosity of the porous substrate is measured using a Gurley value, which is an index for measuring air permeability. The Gurley index is an index measured based on the time it takes when an air flow rate (100 cm 3) permeates through a standard area under a uniform pressure. When the porosity is within the above range, the lithium ion conductivity may be improved while the mechanical properties of the solid polymer electrolyte are high. [49] [50] Next, the polymer compound will be described. The polymer compound is bonded to the inorganic fiber and includes a polymer network in which an oligomer including a (meth)acrylate group is bonded in a three-dimensional structure. [51] For example, the oligomer may further include an oxyalkylene group. Specifically, the oligomer may be represented by the following formula (1). [52] [Formula 1] [53] [54] In Formula 1, A and A'are each independently a unit containing a (meth)acrylate group, and B is a unit containing an oxyalkylene group. [55] Specifically, the units A and A'are units including a (meth)acrylate group so that oligomers are bonded in a three-dimensional structure to form a polymer network. The units A and A'may be derived from monomers including monofunctional or polyfunctional (meth)acrylate or (meth)acrylic acid. [56] For example, the units A and A'may each independently include at least one or more of units represented by the following Formulas A-1 to A-5. [57] [Formula A-1] [58] [59] [Formula A-2] [60] [61] [Formula A-3] [62] [63] [Formula A-4] [64] [65] [Formula A-5] [66] [67] The unit B may include a unit represented by Formula B-1. [68] [Formula B-1] [69] [70] In Formula B-1, R and R'each independently represent a substituted or unsubstituted linear or branched alkylene group having 1 to 10 carbon atoms, and k is an integer of 1 to 30. [71] For another example, in Formula B-1, R and R'may each independently be -CH 2 CH 2 -or -CHCH 3 CH 2 -. [72] For example, according to one embodiment of the present invention, the oligomer forming a polymer network may be at least one compound selected from the group consisting of the following Formulas 1-1 to 1-5. [73] [Formula 1-1] [74] [75] [Formula 1-2] [76] [77] [Formula 1-3] [78] [79] [Formula 1-4] [80] [81] [Formula 1-5] [82] [83] In Formulas 1-1 to 1-5, n1 to n5 are each independently an integer of 1 to 2,000, preferably an integer of 1 to 1,500, and more preferably an integer of 1 to 1,000. [84] The oligomer according to the present invention may have a weight average molecular weight of about 1,000 to 100,000, preferably 1,000 to 70,000, more preferably 1,000 to 50,000. When the weight average molecular weight of the oligomer is within the above range, the mechanical properties of the solid polymer electrolyte including the polymer network formed of the oligomer may be improved, and lithium ion conductivity may also be improved. [85] [86] [87] Next, a method for preparing a solid polymer electrolyte according to the present invention will be described. The manufacturing method includes (1) preparing a polymer electrolyte composition, (2) coating a porous substrate with the polymer electrolyte composition, and (3) curing the coated porous substrate. [88] [89] (1) Preparation of a composition for a polymer electrolyte [90] The composition for a polymer electrolyte may be prepared by mixing an oligomer and a lithium salt containing the (meth)acrylate group with a solvent, a polymerization initiator, and the like. [91] [92] In this case, the oligomer may be included in an amount of 60 to 95 parts by weight, more preferably 65 to 95 parts by weight, based on 100 parts by weight of the solid content excluding the solvent in the polymer electrolyte composition. When the oligomer is included within the above range, mechanical properties of the solid polymer electrolyte may be improved, and lithium ion transfer characteristics may be maintained above a certain level. In addition, the description of the oligomer is the same as described above and thus is omitted. [93] [94] As the lithium salt, those commonly used in an electrolyte for a lithium secondary battery may be used without limitation. For example, as the cation Li + and include, as an anion 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 -, BC 4 O 8 - , (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 - , (CF 3 SO 2 ) 2 N - , (F 2 SO 2 ) 2 N - , CF 3 CF 2 (CF 3 ) 2 CO - , (CF 3 SO 2 ) 2 CH - , CF 3 (CF 2 ) 7SO 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. The lithium salt may be used alone or in combination of two or more as necessary. The lithium salt can be appropriately changed within a range that can be used normally. [95] [96] The solvent is not particularly limited, but tetrahydrofuran (THF), acetonitrile, N-methyl-2-pyrrolidone (NMP), acetone, and the like may be used. [97] The polymerization initiator may be a conventional polymerization initiator known in the art, and may be at least one selected from the group consisting of an azo compound, a peroxide compound, or a mixture thereof. [98] For example, the polymerization initiator, benzoyl peroxide (benzoyl peroxide), acetyl peroxide (acetyl peroxide), dilauryl peroxide (dilauryl peroxide), di-tert-butyl peroxide (di-tert-butyl peroxide), Organic peroxides such as t-butyl peroxy-2-ethyl-hexanoate, cumyl hydroperoxide, and hydrogen peroxide, or hydro Peroxides and 2,2'-azobis (2-cyanobutane), dimethyl 2,2'-azobis (2-methylpropionate), 2,2'-azobis (methylbutyronitrile), 2 ,2'-azobis (isobutyronitrile) (AIBN; 2,2'-Azobis (iso-butyronitrile)) and 2,2'-azobisdimethyl-valeronitrile (AMVN; 2,2'-Azobisdimethyl- Valeronitrile), but at least one azo compound selected from the group consisting of, but is not limited thereto. [99] The polymerization initiator may be included in an amount of 0.01 to 10 parts by weight, more preferably 0.01 to 5 parts by weight, based on 100 parts by weight of the oligomer. When the polymerization initiator is included within the above range, the mechanical shape of the solid polymer electrolyte may be maintained constant by controlling the molecular weight of the polymer compound. [100] [101] (2) coating step of porous substrate [102] Next, the step of coating the porous substrate will be described. [103] First, it is treated with a coupling agent containing an ethylenically unsaturated group so that the inorganic fibers constituting the porous substrate may contain an ethylenically unsaturated group. More specifically, a porous substrate formed of inorganic fibers is immersed in a solution in which a coupling agent substituted with an ethylenically unsaturated group is dissolved, so that the inorganic fibers constituting the porous substrate and the coupling agent are bonded. When the coupling agent is bonded, the inorganic fiber and the ethylenically unsaturated group included in the coupling agent are connected via the coupling agent, so that the ethylenically unsaturated group can be located inside and on the surface of the porous substrate. [104] Thereafter, the polymer electrolyte composition is coated on a porous substrate formed of inorganic fibers containing the ethylenically unsaturated group. [105] In the case of the coating method, it is not limited to a specific method, and known such as impregnation, slot die, gravure coating, spin coating, spray coating, roll coating, curtain coating, extrusion, casting, screen printing, or inkjet printing. Coating methods can be used. [106] As the porous substrate undergoes the step of coating the polymer electrolyte composition, the ethylenic unsaturated groups located inside and on the surface of the porous substrate react with the oligomer, so that the porous substrate and the oligomer are bonded. The porous substrate, the composition for the polymer electrolyte, and the coupling agent are the same as those described above, and thus the description is omitted. [107] [108] (3) Curing step of the coated porous substrate [109] Finally, a step of drying and curing the coated porous substrate will be described. [110] Even if the porous substrate is coated by the polymer electrolyte composition, the oligomer contained in the polymer electrolyte composition and the inorganic fibers constituting the porous substrate cannot be bonded to each other in the state alone. Therefore, it is necessary to undergo a curing step so that the ethylenic unsaturated group included in the inorganic fiber and the (meth)acrylate group included in the oligomer can be bonded through a radical polymerization reaction and a crosslinking reaction. [111] The curing step is carried out by forming a three-dimensional network of oligomers and inorganic fibers through crosslinking reactions between oligomers and crosslinking reactions between oligomers and inorganic fibers by UV irradiation E-BEAM, gamma rays, room temperature/high temperature aging process, etc. . [112] [113] [114] Next, a lithium secondary battery according to the present invention will be described. A lithium secondary battery according to another embodiment of the present invention includes a positive electrode, a negative electrode, and the solid polymer electrolyte. Specifically, in the case of the solid polymer electrolyte, it may be prepared and introduced in a coated form on an electrode or a porous separator, or may be inserted between the anode and the cathode in a free standing form. Free-standing solid polymer electrolyte is not formed in a solid form by coating and curing a solid polymer constituting the electrolyte on an electrode or a porous separator, but a solid polymer that is cured through a crosslinking reaction before being placed in a battery to exist in the form of a membrane. Means electrolyte. [115] [116] The positive electrode may be prepared by coating a positive electrode active material slurry including a positive electrode active material, a binder, a conductive material, and a solvent on the positive electrode current collector. [117] The positive electrode current collector generally has a thickness of 3 μm to 500 μm, and is not particularly limited as long as it has conductivity without causing a chemical change in the battery. For example, stainless steel, aluminum, nickel, titanium, Calcined carbon, or a surface-treated aluminum or stainless steel surface with carbon, nickel, titanium, silver, or the like may be used. [118] 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-Y1 Mn Y1 O 2 (here, 01 Example 2 >1 Comparative Example 1 >1 Comparative Example 2 120 [184] As shown in Table 5, in the case of Comparative Example 2 using the liquid electrolyte, the rate of change in the thickness of the battery was remarkably increased, which is because the liquid electrolyte is easily volatilized at high temperature and an oxidation reaction occurs at the interface of the electrode, thereby generating a large amount of gas. It is believed that this is because it occurs. In contrast, in the case of Examples 1 and 2, gas is not generated and the battery does not swell even when stored and left at a high temperature using a solid polymer electrolyte. Therefore, it can be confirmed that there is almost no change in the battery thickness. Claims [Claim 1] A porous substrate formed of inorganic fibers containing an ethylenically unsaturated group; A polymer compound comprising a polymer network in which an oligomer including a (meth)acrylate group is bonded to the inorganic fiber and has a three-dimensional structure; And a lithium salt; a solid polymer electrolyte containing. [Claim 2] The solid polymer electrolyte according to claim 1, wherein the ethylenically unsaturated group is at least one selected from the group consisting of a vinyl group, an acryloxy group, and a methacryloxy group. [Claim 3] The solid polymer electrolyte of claim 1, wherein the oligomer further comprises an oxyalkylene group. [Claim 4] The solid polymer electrolyte according to claim 1, wherein the oligomer is represented by the following Formula 1: [Formula 1] In Formula 1, A and A'are each independently a unit containing a (meth)acrylate group, B is a unit containing an oxyalkylene group. [Claim 5] The method of claim 1 wherein the oligomer to the solid polymer electrolyte containing at least one selected from compounds represented by Formula 1-1 to Formula 1-5: [Chemical Formula 1-1] (In the above formula 1-1 n1 is 1 to 2,000) [Formula 1-2] (In Formula 1-2, n2 is 1 to 2,000) [Formula 1-3] (In Formula 1-3, n3 is 1 to 2,000) [ Formula 1-4] (In Formula 1-4, n4 is 1 to 2,000) [Formula 1-5] (In Formula 1-5, n5 is 1 to 2,000) [Claim 6] The solid polymer electrolyte according to claim 1, wherein the inorganic fiber has a diameter of 0.01 μm to 10 μm. [Claim 7] The solid polymer electrolyte of claim 1, wherein the porous substrate has a thickness of 1 μm to 200 μm. [Claim 8] The solid polymer electrolyte of claim 1, wherein the porous substrate has a porosity of 10% to 80%. [Claim 9] Dissolving an oligomer containing a (meth) acrylate group and a lithium salt in a solvent to prepare a composition for a polymer electrolyte; Coating a porous substrate formed of inorganic fibers containing an ethylenically unsaturated group with the polymer electrolyte composition; And drying and curing the coated porous substrate. [Claim 10] A lithium secondary battery comprising the solid polymer electrolyte according to claim 1.