Specification Title of the invention: separator for secondary battery 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. 10-2018-0006795 filed on January 18, 2018, and all contents disclosed in the documents of the Korean patent application are included as part of this specification. [3] [4] Technical field [5] The present invention relates to a separator for a secondary battery and a lithium secondary battery including the same, and more particularly, to a separator for a secondary battery capable of improving the performance and safety of a lithium secondary battery, and a lithium secondary battery including the same. [6] Background [7] 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. [8] In addition, as interest in environmental issues has increased in recent years, electric vehicles (EVs) and hybrid electric vehicles (HEVs) that can replace vehicles using fossil fuels such as gasoline vehicles and diesel vehicles, which are one of the main causes of air pollution. There is a lot of research on the back. [9] These electric vehicles (EV) and hybrid electric vehicles (HEV) use nickel-metal hydride (Ni-MH) secondary batteries or lithium secondary batteries with high energy density, high discharge voltage, and output stability as a power source. When used in an electric vehicle, it must be used for 10 years or more under severe conditions, as well as high energy density and high power output in a short time. Therefore, energy density, safety, and long life are far superior to those of conventional small lithium secondary batteries. Characteristics are inevitably required. [10] In general, a lithium secondary battery is manufactured using a negative electrode and a positive electrode, a separator interposed therebetween, and an electrolyte that is a transport medium for lithium ions. [11] Among them, the separator is an inert material that does not participate in the electrochemical reaction or provides a path for lithium ions to move to operate the battery, and as a material that separates the physical contact between the positive electrode and the negative electrode, it has a great effect on the performance and stability of the battery. Mitch is one of the core materials. [12] Separator manufacturing methods are largely divided into wet and dry methods. In the wet manufacturing method, a polymer material and a low molecular weight wax are mixed, the film is extruded at high temperature, and the wax is extracted using a solvent (solvent) to form a microporous structure. The dry manufacturing method is a multi-layered structure that is bonded with a film of 2-3 layers using polyethylene (PE) and polypropylline (PP). It's the way. [13] On the other hand, lithium secondary batteries can easily generate heat due to kinetic energy generated during repeated charging and discharging, and the separator is vulnerable to this heat. In particular, in the case of a separator using polyethylene (PE), it may start to melt (melt) around 130℃ and cause a'shut down' phenomenon in which the pores are closed, and at 150℃ or higher, it completely melts and an internal short circuit It may not prevent it and may collapse (meltdown or destroy mechanical integrity). [14] In order to overcome this problem, studies have been continued to enhance durability, such as using a dip coating method in which inorganic particles and a polymeric binder are coated on the surface of a separator. [15] Meanwhile, conventional secondary batteries have mainly used an electrolyte in a liquid state, particularly an ion conductive organic liquid electrolyte in which a salt is dissolved in a non-aqueous organic solvent. [16] However, when the electrolyte in a liquid state is used, there is a high possibility that the electrode material is degraded and the organic solvent is volatilized, and there is a problem in safety such as combustion due to an increase in ambient temperature and the temperature of the battery itself. In particular, the lithium secondary battery has a problem in that the thickness of the battery is expanded by generating gas in the battery due to decomposition of the carbonate organic solvent and/or side reaction between the organic solvent and the electrode during charging and discharging. Therefore, deterioration of battery performance and safety is essentially caused. [17] In general, the safety of the battery is improved in the order of liquid electrolyte [39] The separator for a secondary battery according to the present invention includes a substrate and a coating layer formed on the surface of the substrate, the coating layer includes an organic binder and inorganic particles, and the organic binder includes an ethylenically unsaturated group. [40] The thickness of the separator may be 0.1 to 20 µm, preferably 0.5 to 20 µm, more preferably 1.0 to 20 µm. When the thickness of the separator is formed within the above range, it is preferable that the thickness of the separator is formed within the above range since resistance in the battery can be prevented from increasing and movement of lithium ions can be maintained smoothly. [41] [42] As the substrate, a porous substrate may be used, and in general, the porous substrate may be used without particular limitation as long as it can be used as a material for a separator of an electrochemical device. Such porous substrates include, for example, polyolefin, polyethylene, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polycarbonate, polyimide, polyether ether ketone, polyether sulfone, polyphenylene oxide, A nonwoven fabric or a porous polymer film formed of at least one of polymer resins such as polyphenylene sulfide and polyethylene naphthalene, or a laminate of two or more of them, but is not particularly limited thereto. [43] [44] The coating layer is for enhancing the durability of the separator substrate, is formed on the surface of the substrate, and includes an organic binder and inorganic particles, wherein the organic binder includes an ethylenically unsaturated group. [45] [46] Conventionally, an inorganic coating layer coated with inorganic particles on the surface of a substrate was used to improve the durability and conductivity of the separator, but the inorganic particles have no reactivity with the electrolyte, so the adhesion between the electrolyte and the separator decreases, leading to a short circuit inside the battery. There are safety issues such as. [47] The separator according to the present invention forms a coating layer using an organic binder with inorganic particles, and the organic binder contains an ethylenically unsaturated group. The organic binder containing the ethylenically unsaturated group may undergo a radical polymerization reaction with an oligomer contained in the composition for a gel polymer electrolyte. [48] More specifically, the composition for a gel polymer electrolyte may include an oligomer containing a (meth)acrylate group, and the functional group is a functional group capable of radical polymerization with an ethylenic unsaturated group contained in the organic binder. Accordingly, the oligomer and the organic binder are bonded through a radical polymerization reaction in the curing process of the gel polymer electrolyte composition to form a polymer network having a three-dimensional structure, and as a result, the adhesion between the separator and the gel polymer electrolyte is improved. At this time, when the adhesion between the separator and the gel polymer electrolyte is improved, the internal resistance of the battery is reduced, and the transfer characteristics of lithium ions are improved, so that the output characteristics and life characteristics of the battery may be improved. [49] In addition, when the adhesion between the separator and the gel polymer electrolyte is improved, the mechanical strength of the secondary battery is improved to prevent a short circuit inside the battery even when subjected to an external impact, and to suppress thermal runaway or ignition. It can be improved. [50] The organic binder contains an ethylenically unsaturated group. For example, 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. [51] Meanwhile, the organic binder is an alkylene group in which at least one halogen element (F, Cl, Br, I) is substituted, in addition to the functional group, an alkylene oxide group, an alkyl substituted with a halogen element (F, Cl, Br, I) A unit including at least one or more selected from the group consisting of a ren oxide group, an imide group, and a celluloid may be further included. [52] At this time, in the case of the ethylenically unsaturated group, it may be located at the end portion of the polymer main chain composed of the units or the side portion of the polymer main chain, and the number or position of the attached functional groups is not specified. [53] For example, the unit including an alkylene group in which at least one halogen element is substituted may be represented by at least one or more selected from units represented by the following Formula X-1 or X-2. [54] [Formula X-1] [55] [56] In Formula X-1, m1 is an integer ranging from 1 to 100. [57] [Formula X-2] [58] [59] In Formula X-2, m2 and m3 are each independently an integer of 1 to 100. [60] For example, a unit containing an alkylene oxide group may be represented by the following Formula X-3. [61] [Formula X-3] [62] [63] In Formula X-3, m4 is an integer ranging from 1 to 100. [64] For example, a unit containing an alkylene oxide group in which the halogen element is substituted may be represented by Formula X-4 below. [65] [Formula X-4] [66] [67] In Formula X-4, m5 is an integer ranging from 1 to 100. [68] For example, the unit containing the imide group may be represented by the following Formula X-5. [69] [Formula X-5] [70] [71] For example, the celluloid-containing unit may be represented by Formula X-6 below. [72] [Formula X-6] [73] [74] In Formula X-6, m7 is an integer of 1 to 100. [75] Specifically, the compound used as the organic binder is a compound in which an ethylenically unsaturated group is substituted at the end portion of the polymer main chain or the side portion of the main chain consisting of at least one unit selected from the group consisting of Formulas X-1 to X-6. [76] For example, in the case of a polymer or copolymer containing units represented by Formulas X-1 to X-6, it is generally formed by a free radical polymerization reaction or the like. At this time, at the end of the polymerization reaction, end-capping is performed to prevent further polymerization from occurring at the end or side of the main chain of the polymer or copolymer. An oxide group and an alkyl group are attached. [77] For example, in the case of treating the end with a functional group containing a halogen element, a halogenated compound such as sodium chloride (NaCl) may be used as an end-capping agent, but limited to the above method Also, the type of the end capping agent is not limited to the above material. [78] Specifically, when a functional group including a halogen element is positioned at the end or side portion, it may react with a (meth)acrylate compound or a vinyl compound. By the above reaction, an organic binder in which the halogen element has an ethylenically unsaturated group such as a (meth)acryloxy group or a vinyl group can be prepared. [79] The organic binder may be included in an amount of 1 to 80 parts by weight, preferably 5 to 60 parts by weight, more preferably 5 to 40 parts by weight, based on 100 parts by weight of the coating layer. When the organic binder is included within the above range, it is possible to prevent separation of inorganic particles included in the coating layer, and a separator for a secondary battery having improved mechanical properties may be provided. [80] [81] The inorganic particles form an interstitial volume between the particles to form microscopic pores and at the same time serve as a type of spacer capable of maintaining a physical shape. In addition, since the inorganic particles can transfer and move lithium ions, lithium ion conductivity can be improved. At this time, by adjusting the size of the inorganic particles, the content of the inorganic particles, and the composition of the inorganic particles and the polymer, microscopic pores can be formed, and the pore size and porosity can be controlled. [82] The inorganic particles may include inorganic particles commonly used in the art. For example, the inorganic particles 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. [83] More specifically, the inorganic particles are 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 particles may include at least one inorganic material selected from the group consisting of SiO 2 , Al 2 O 3 , TiO 2 and ZrO 2 . [84] The inorganic particles may be included in an amount of 20 to 99 parts by weight, preferably 40 to 95 parts by weight, more preferably 60 to 90 parts by weight, based on 100 parts by weight of the coating layer. When the inorganic particles are included within the above range, the inorganic particles may be prevented from being separated from the coating layer, and durability of the separator for a secondary battery may be improved. [85] [86] 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, a separator interposed between the positive electrode and the negative electrode and including a coating layer, and a gel polymer electrolyte disposed between the positive electrode and the negative electrode and the separator. [87] [88] 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. [89] 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. [90] 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, 0