One]Cross-Citation with Related Application(s) [2]This application claims the benefit of priority based on Korean Patent Application No. 2019-0024104 dated February 28, 2019, and all contents disclosed in the literature of the Korean patent application are incorporated as a part of this specification. [3] [4] technical field [5] The present invention relates to an electrolyte for a lithium secondary battery having excellent high temperature characteristics and a lithium secondary battery including the same. background [6] As personal IT devices and computer networks are developed due to the development of the information society, and the overall society's dependence on electric energy increases accordingly, technology development for efficiently storing and utilizing electric energy is required. [7] The secondary battery-based technology is the most suitable technology for various uses and can be miniaturized and thus applied to personal IT devices and the like, and may also be applied to large devices such as power storage devices. [8] Among secondary battery technologies, a lithium ion battery, which is a battery system with the highest theoretical energy density, is in the spotlight. [9] A lithium ion battery is largely composed of a positive electrode composed of a transition metal oxide containing lithium, a negative electrode capable of storing lithium, an electrolyte serving as a medium for transferring lithium ions, and a separator. In the case of a double electrolyte, as it is known as a component that has a great influence on the stability, safety, etc. of a battery, a lot of research is being conducted on this. [10] On the other hand, during the activation process of the battery, the electrolyte undergoes a reductive decomposition reaction, and the reductive decomposition product forms a solid electrolyte interphase (SEI) film that transmits lithium ions on the negative electrode interface but inhibits further decomposition of the electrolyte. [11] The SEI film does not have electron conductivity, but has ion conductivity, and thus serves to assist the movement of lithium ions. [12] On the other hand, if the SEI membrane does not have sufficient passivation ability to suppress the further electrolyte decomposition, the electrolyte is further decomposed during storage and the charged graphite is self-discharged, and as a result, the potential of the entire secondary battery is lowered. . For example, under high-temperature conditions, the by-product generated by the decomposition reaction of lithium salt contained in the electrolyte decomposes the SEI film formed on the surfaces of the positive and negative electrodes after activation, thereby lowering the passivation ability of the SEI film, and this causes the electrolyte to additionally decomposition, causing a problem in which self-discharge is induced. [13] Accordingly, in order to maintain the passivation ability of the SEI membrane under high-temperature conditions, it is urgent to study an electrolyte including a component capable of suppressing the generation of decomposition products of salts. [14] [15] Prior art literature [16] Laid-open Patent Publication No. 10-2017-0132239 DETAILED DESCRIPTION OF THE INVENTION technical challenge [17] An object of the present invention is to solve the above problems, and to provide an electrolyte for a lithium secondary battery capable of removing by-products generated according to the decomposition reaction of lithium salts at high temperatures. [18] In addition, an object of the present invention is to provide a lithium secondary battery having improved high-temperature lifespan characteristics and high-temperature storage characteristics by including the electrolyte for a lithium secondary battery. means of solving the problem [19] According to one embodiment, the present invention includes a lithium salt, a first additive, a second additive and an organic solvent, wherein the first additive includes a compound represented by the following Chemical Formula 1, and the second additive includes the following Chemical Formula 2 It provides an electrolyte for a lithium secondary battery comprising a compound represented by. [20] [Formula 1] [21] [22] (In Formula 1, R is a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms, the ring A includes one or more nitrogen atoms, and is a substituted or unsubstituted group containing at least one double bond in the ring. It is a heterocyclic ring having 3 to 8 carbon atoms) [23] [24] [Formula 2] [25] [26] (In Formula 2, R' is F, CF 3 , CHF 2 , CH 2 F, C 2 HF 4 , C 2 H 2 F 3 , C 2 H 3 F 2 , C 2 F 5 , C 3 F 7 , C 3 H 2 F 5 , C 3 H 4 F 3 , C 4 F 9 , C 4 H 2 F 7 , C 4 H 4 F 5 , C 5 F 11 , C 3 F 5 OCF 3 , C 2 F 4 OCF 3 , C 2 H 2 F 2 OCF 3 and CF 2 OCF 3 selected from the group consisting of: at least one functional group that becomes [27] [28] In addition, the present invention is a positive electrode; cathode; and an electrolyte for a lithium secondary battery of the present invention; provides a lithium secondary battery comprising. Effects of the Invention [29] The compound represented by Formula 1 and the compound represented by Formula 2 included in the electrolyte for a lithium secondary battery of the present invention are compounds including an N atom in the structure, wherein the N atom acts as a Lewis base to form an electrolyte decomposition product under high temperature conditions. By removing the generated Lewis acid, it is possible to suppress further decomposition of the organic solvent in the electrolyte. Therefore, it is possible to prevent the SEI film formed on the electrode interface from being damaged by the reaction by-products in advance, thereby minimizing the increase in resistance in the battery, and minimizing the deterioration of the battery life characteristics, so that the high temperature life characteristics and high temperature storage characteristics are improved. An improved lithium secondary battery can be implemented. Brief description of the drawing [30] The following drawings attached to the present specification illustrate preferred embodiments of the present invention, and serve to further understand the technical spirit of the present invention together with the above-described content of the present invention, so the present invention is limited to the matters described in those drawings It should not be construed as being limited. [31] 1 is a graph showing a capacity retention rate and a resistance increase rate of a secondary battery measured according to Experimental Example 1. Referring to FIG. [32] 2 is a graph showing a resistance increase rate of a secondary battery measured according to Experimental Example 2. Referring to FIG. Best mode for carrying out the invention [33] Hereinafter, the present invention will be described in more detail. [34] The terms or words used in the present specification and claims are not to be construed as being limited to their ordinary or dictionary meanings, and the inventor may properly define the concept of the term in order to best describe his invention. It should be interpreted as meaning and concept consistent with the technical idea of ​​the present invention based on the principle that there is. [35] The terminology used herein is used to describe exemplary embodiments only, and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. [36] In this specification, terms such as "comprise", "comprising" or "have" are intended to designate the presence of an embodied feature, number, step, element, or a combination thereof, but one or more other features or It should be understood that the existence or addition of numbers, steps, elements, or combinations thereof is not precluded in advance. [37] [38] [39] The electrolyte for a lithium secondary battery according to the present invention includes a lithium salt, a first additive, a second additive and an organic solvent, wherein the first additive includes a compound represented by the following formula (1), and the second additive includes the following formula The compound represented by 2 is included. [40] [Formula 1] [41] [42] (In Formula 1, R is a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms, the ring A includes one or more nitrogen atoms, and is a substituted or unsubstituted group containing at least one double bond in the ring. It is a heterocyclic ring having 3 to 8 carbon atoms) [43] [44] [Formula 2] [45] [46] (In Formula 2, R' is F, CF 3 , CHF 2 , CH 2 F, C 2 HF 4 , C 2 H 2 F 3 , C 2 H 3 F 2 , C 2 F 5 , C 3 F 7 , C 3 H 2 F 5 , C 3 H 4 F 3 , C 4 F 9 , C 4 H 2 F 7 , C 4 H 4 F 5 , C 5 F 11 , C 3 F 5 OCF 3 , C 2 F 4 OCF 3 , C 2 H 2 F 2 OCF 3 and CF 2 OCF 3 selected from the group consisting of: at least one functional group that becomes [47] [48] [49] (1) lithium salt [50] First, the lithium salt will be described. [51] A lithium salt is used as a medium for ion transfer in a lithium secondary battery. Typically, the lithium salt is LiPF 6 , LiBF 4 , LiSbF 6 , LiAsF 6 , LiClO 4 , LiN(C 2 F 5 SO 2 ) 2 , LiN(CF 3 SO 2 ) 2 , CF 3 SO 3 Li, LiC(CF) 3 SO 2 ) 3 , LiC 4 BO 8 , LiTFSI, LiFSI and LiClO 4It may include at least one compound selected from the group consisting of, preferably LiPF 6 and/or LiBF 4 . [52] Among lithium salts, LiPF 6 and/or LiBF 4 are widely used because of their relatively high ionic conductivity compared to other lithium salts. However, when the organic solvent contained in the electrolyte is decomposed at a high temperature, the decomposition product of the organic solvent reacts with PF 6 − , which is an anion of a lithium salt generated by dissolving a lithium salt in the organic solvent, such as PF 5 Lewis such as Lewis acid may generate by-products. In the case of a Lewis acid by-product, it promotes a spontaneous decomposition reaction of the organic solvent and causes a side reaction that collapses the SEI film formed on the electrode interface. If the side reaction is not suppressed, the resistance in the battery may rapidly increase, and the capacity characteristics of the battery may be deteriorated. [53] More specifically, when LiPF 6 is used as the lithium salt , PF 6 − , which is an anion, loses electrons from the negative electrode side, and PF 5 may be generated. At this time, the chemical reaction as shown in Scheme 1 below may proceed in a chain. [54] [Scheme 1] [55] [56] When the chain reaction proceeds, decomposition of an organic solvent or a side reaction with the SEI film may occur due to other by-products including HF generated, thereby continuously decreasing battery performance. [57] [58] (2) the first additive [59] The electrolyte for a lithium secondary battery of the present invention uses an additive including a compound represented by the following Chemical Formula 1 in order to remove by-products generated according to the chain reaction as shown in Scheme 1 above. [60] [Formula 1] [61] [62] In Formula 1, R is a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms, ring A includes one or more nitrogen atoms, and substituted or unsubstituted carbon atoms including at least one double bond in the ring 3 to 8 heterocyclic rings. [63] For example, the compound represented by Chemical Formula 1 may be one or more compounds selected from the group consisting of compounds represented by the following Chemical Formulas 1A to 1C. [64] [Formula 1A] [65] [66] [67] [Formula 1B] [68] [69] [70] [Formula 1C] [71] [72] [73] In Formulas 1A to 1C, R is a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms, and R 1 to R 3 are each independently hydrogen, an alkyl group having 1 to 5 carbon atoms, and one or more hydrogen atoms are halogen. It is selected from the group consisting of an alkyl group having 1 to 5 carbon atoms substituted with an element. [74] More specifically, the compound represented by Formula 1 may be selected from the group consisting of compounds represented by Formulas 1A-1 to 1A-5. [75] [Formula 1A-1] [76] [77] [78] [Formula 1A-2] [79] [80] [81] [Formula 1A-3] [82] [83] [84] [Formula 1A-4] [85] [86] [87] [Formula 1A-5] [88] [89] [90] PF 5 , which is one of the by-products generated when lithium salt dissolved in an organic solvent is decomposed under high-temperature conditions , corresponds to a Lewis acid compound. The Lewis acid compound such as PF 5 may react with the organic solvent or components constituting the SEI film on the electrode interface to cause a decomposition reaction. Therefore, in order to suppress the decomposition reaction of the SEI film under high-temperature conditions, and to solve problems such as increased resistance in the battery and deterioration of battery life characteristics due to the generation of decomposition reaction products, it is necessary to remove the Lewis acid compound, which is a high-temperature decomposition product of lithium salt. have. [91] A Lewis acid compound is a chemical species that accepts an electron pair, and a Lewis base is a chemical species that can donate an electron pair. A compound having a strong electron donor property can be used as a Lewis base. [92] Therefore, in the present invention, a compound corresponding to a Lewis base capable of reacting with a Lewis acid was used as an additive included in the electrolyte. Ring A in the compound represented by Formula 1 includes at least one nitrogen element having a lone pair of electrons, and includes a triple bond at the terminal portion to supply electrons to a Lewis acid compound such as PF 5 , SEI formed on the electrode Instead of the components constituting the membrane , a Lewis acid-base reaction with PF 5 is performed. Accordingly, it is possible to prevent damage to the SEI film formed on the electrode by removing PF 5 in advance. [93] On the other hand, in the case of the triple bond positioned at the terminal of the compound represented by Formula 1, the SEI component can be modified, and the SEI film can be more stably formed, thereby improving the high-temperature stability of the SEI film itself. [94] Meanwhile, the first additive may be included in an amount of 0.02 parts by weight to 1.0 parts by weight, preferably 0.3 parts by weight to 1.0 parts by weight, more preferably 0.1 parts by weight to 0.7 parts by weight based on 100 parts by weight of the electrolyte for a lithium secondary battery. When the first additive is included within the above range, while sufficiently removing the Lewis acid compound, the SEI film may be stably formed. [95] [96] (3) second additive [97] In addition, the electrolyte for a lithium secondary battery of the present invention includes a compound represented by the following formula (2) as a second additive. [98] [Formula 2] [99] [100] In Formula 2, R' is F, CF 3 , CHF 2 , CH 2 F, C 2 HF 4 , C 2 H 2 F 3 , C 2 H 3 F 2 , C 2 F 5 , C 3 F 7 , C 3 H 2 F 5 , C 3 H 4 F 3 , C 4 F 9 , C 4 H 2 F 7 , C 4 H 4 F 5 , C 5 F 11 , C 3 F 5 OCF 3 , C 2 F 4 OCF 3 , C 2 H 2 F 2 OCF 3 and CF 2 OCF 3 selected from the group consisting of: is one or more functional groups. [101] The compound represented by Chemical Formula 2 is decomposed to form an SEI film formed on the surface of the anode, and the SEI film including the decomposition product of the compound represented by Chemical Formula 2 is more difficult than when only the compound represented by Chemical Formula 1 is used. It can be formed rigidly to improve the high-temperature durability of the battery. [102] More specifically, as the compound represented by Formula 2, lithium 4,5-dicyano-2-(trifluoromethyl)imidazole (LiTDI) may be used. [103] The second additive may be included in an amount of 0.02 parts by weight to 1.0 parts by weight, more preferably 0.3 parts by weight to 1.0 parts by weight, preferably 0.3 parts by weight to 0.7 parts by weight based on 100 parts by weight of the electrolyte for a lithium secondary battery. When the lithium imidazole salt represented by Formula 2 is included within the above range, the increase in initial resistance of the battery may be minimized, and a stable SEI film may be formed on the negative electrode to improve high temperature durability. [104] [105] (4) other additives [106] On the other hand, the electrolyte for a lithium secondary battery according to the present invention does not significantly increase the initial resistance, and forms a stable film on the surface of the negative electrode and the positive electrode, suppresses the decomposition of the solvent in the electrolyte, and serves as a complement to improve the mobility of lithium ions It may additionally include other additives that can do this. [107] For example, the other additives include a vinyl silane compound, a phosphate or phosphite compound, a sulfite compound, a sulfone compound, a sulfate compound, a sultone compound, a halogen-substituted carbonate compound, a nitrile compound, or a borate compound. It may include one or more compounds selected from the group consisting of compounds, and lithium salt-based compounds. [108] The vinyl silane compound may be electrochemically reduced on the surface of the negative electrode to form a stable SEI, thereby improving battery durability. More specifically, the vinyl silane-based compound may include tetravinyl silane and the like. [109] The phosphate-based or phosphite-based compound is a component that is electrochemically decomposed on the surfaces of the positive electrode and the negative electrode to help form the SEI film, and may improve the lifespan characteristics of the secondary battery. More specifically, lithium difluoro(bisoxalato)phosphate, lithium difluorophosphate, tetramethyl trimethyl silyl phosphate, trimethyl silyl phosphite, tris(2,2,2-trifluoroethyl)phosphate and tris( trifluoroethyl) at least one compound selected from the group consisting of phosphite. [110] The sulfite-based compound is ethylene sulfite, methyl ethylene sulfite, ethyl ethylene sulfite, 4,5-dimethyl ethylene sulfite, 4,5-diethyl ethylene sulfite, propylene sulfite, 4,5-dimethyl propylene sulfite at least one compound selected from the group consisting of phite, 4,5-diethyl propylene sulfite, 4,6-dimethyl propylene sulfite, 4,6-diethyl propylene sulfite, and 1,3-butylene glycol sulfite may include [111] The sulfone-based compound may include at least one compound selected from the group consisting of divinyl sulfone, dimethyl sulfone, diethyl sulfone, methylethyl sulfone, and methylvinyl sulfone. [112] The sulfate-based compound may include at least one compound selected from the group consisting of ethylene sulfate (Esa), trimethylene sulfate (TMS), and methyl trimethylene sulfate (MTMS). . [113] The sultone-based compound is 1,3-propane sultone (PS), 1,4-butane sultone, ethenesultone, 1,3-propene sultone (PRS), 1,4-butene sultone, and 1-methyl-1; at least one compound selected from the group consisting of 3-propene sultone. [114] As the halogen-substituted carbonate-based compound, fluoroethylene carbonate (FEC) may be included. [115] In addition, the nitrile-based compound is succinonitrile (SN), adiponitrile (Adn), acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptannitrile, cyclopentane carbonitrile, cyclohexane Carbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile It may include one or more compounds selected from the group consisting of. [116] The borate-based compound may include lithium oxalyldifluoroborate (LiODFB) or lithium bisoxalatoborate (LiB(C 2 O 4 ) 2 : LiBOB). [117] The lithium salt-based compound is a compound different from the lithium salt included in the electrolyte, and may include at least one compound selected from the group consisting of LiPO 2 F 2 and LiBF 4 . [118] The other additives may be included in an amount of 20 parts by weight or less, preferably 10 parts by weight or less, based on 100 parts by weight of the electrolyte for a lithium secondary battery. When the content of the additives exceeds the above range, side reactions in the electrolyte may excessively occur during charging and discharging of the lithium secondary battery, and may not be sufficiently decomposed at high temperature, and may exist as unreacted or precipitated in the electrolyte, thus Lifespan or resistance characteristics of the secondary battery may be reduced. [119] [120] (5) organic solvents [121] Next, the organic solvent will be described. [122] In the present invention, the organic solvent is a solvent commonly used in lithium secondary batteries, for example, an ether compound, an ester (Acetate, Propionate) compound, an amide compound, a linear carbonate compound, a cyclic carbonate compound, or a nitrile compound, respectively. It can be used individually or in mixture of 2 or more types. [123] Among them, the organic solvent may be typically a carbonate compound, which is a cyclic carbonate compound, a linear carbonate compound, or a mixture thereof. [124] Specific examples of the cyclic carbonate compound include ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene There is a single compound or a mixture of at least two or more selected from the group consisting of carbonate, vinylene carbonate, and halides thereof. In addition, specific examples of the linear carbonate compound include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethylmethyl carbonate (EMC), methylpropyl carbonate (MPC) and ethylpropyl carbonate (EPC) A compound selected from the group consisting of or a mixture of at least two or more may be representatively used, but the present invention is not limited thereto. [125] In particular, propylene carbonate and ethylene carbonate, which are the cyclic carbonate compounds, are highly viscous organic solvents and have a high dielectric constant to well dissociate lithium salts in the electrolyte. When a low-viscosity, low-dielectric constant linear carbonate compound is mixed in an appropriate ratio, an electrolyte having high electrical conductivity can be prepared, and thus can be used more preferably. [126] In addition, as esters in the organic solvent, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone and a single compound or a mixture of at least two or more selected from the group consisting of ε-caprolactone, but is not limited thereto. [127] [128] [129] Next, a lithium secondary battery according to the present invention will be described. [130] A lithium secondary battery according to an embodiment of the present invention includes a positive electrode, a negative electrode, a separator selectively interposed between the positive electrode and the negative electrode, and an electrolyte for the lithium secondary battery. At this time, since the electrolyte for a lithium secondary battery is the same as the above-described content, a detailed description thereof will be omitted. [131] [132] (1) Anode [133] The positive electrode may be prepared by coating a positive electrode active material slurry including a positive electrode active material, a binder for an electrode, a conductive material for an electrode, a solvent, and the like on a positive electrode current collector. [134] The positive electrode current collector 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 carbon on the surface of aluminum or stainless steel. , nickel, titanium, silver, etc. may be used. In this case, the positive electrode current collector may form fine irregularities on the surface to strengthen the bonding force of the positive electrode active material, and may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a nonwoven body, and the like. [135] The positive active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically, may include a lithium composite metal oxide including lithium and one or more metals 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-based oxide (eg, LiCoO 2 , etc.), lithium-nickel-based oxide (eg, LiNiO 2 , etc.), lithium-nickel-manganese oxide (eg, LiNi 1-Y1 Mn Y1 O 2 (here, 0