Lithium secondary battery

Abstract

The present invention provides a lithium secondary battery comprising a cathode, an anode, a separator interposed between the cathode and the anode, and a non-aqueous electrolyte, wherein the anode includes an anode active material, the anode active material includes a silicon-based active material, and the non-aqueous electrolyte includes a lithium salt, fluoroethylene carbonate, 1,2-difluoroethylene carbonate, and a coumarin-based compound of a specific chemical formula.

Description

lithium secondary battery Cross-citation with related applications This application claims the benefit of priority to Korean Patent Application No. 10-2023-0126666, filed September 21, 2023, the entire contents of which are incorporated herein by reference. Technology field The present invention relates to a lithium secondary battery. Recently, as the application areas of lithium secondary batteries have rapidly expanded to include not only power supply for electronic devices such as electric, electronic, communication, and computer devices, but also power storage for large-area devices such as automobiles and power storage devices, the demand for high-capacity, high-output, and high-stability lithium secondary batteries is increasing. The above lithium secondary battery can be largely composed of a positive electrode composed of a transition metal oxide containing lithium, a negative electrode capable of storing lithium, an electrolyte that serves as a medium for transferring lithium ions, and a separator. At this time, the negative electrode may include a negative electrode active material such as a carbon-based active material or a silicon-based active material. In the case of the above lithium secondary battery, a film (SEI film) is formed on the positive and / or negative electrodes during the initial activation process, thereby protecting the positive and negative electrodes during battery operation and preventing electrolyte consumption due to electrolyte side reactions. If a robust electrode film is not formed on the positive and / or negative electrodes during this initial activation process, problems such as capacity degradation and reduced lifespan may occur. In particular, silicon-based negative active materials have attracted attention for their higher capacity and higher energy density than carbon-based negative active materials. However, they have the disadvantage of significant volume changes due to lithium insertion and de-insertion. This volume expansion of silicon-based active materials can lower the durability of the already formed SEI film, or cause many problems such as continuous electrolyte consumption and increased SEI film thickness due to the generation of new negative active material surfaces, which in turn leads to capacity degradation and reduced lifespan. One object of the present invention is to provide a lithium secondary battery capable of reducing electrolyte side reactions and improving high-temperature cycle life performance and high-temperature storage performance by forming a flexible and durable film on a negative electrode including a silicon-based active material. [1] The present invention provides a lithium secondary battery comprising: a positive electrode; a negative electrode; a separator interposed between the positive electrode and the negative electrode; and a non-aqueous electrolyte; wherein the negative electrode comprises a negative electrode active material, the negative electrode active material comprises a silicon-based active material, and the non-aqueous electrolyte comprises a lithium salt, fluoroethylene carbonate, 1,2-difluoroethylene carbonate, and a compound represented by the following chemical formula 1. [Chemical Formula 1] In the above chemical formula 1, R1 includes a halogen, a nitrile group, a propargyl group, an ester group, an ether group, a ketone group, a carboxyl group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted alkoxy group, a boron group, a borate group, an isocyanate group, an isothiocyanate group, a silyl group, a siloxane group, a sulfone group, a sulfonate group, a sulfate group, or a combination of two or more thereof, and n is an integer from 0 to 6. [2] The present invention provides a lithium secondary battery according to the above [1], wherein the silicon-based active material includes silicon-based particles, and the silicon-based particles include a compound represented by the following chemical formula A. [Chemical Formula A] SiO x In the above chemical formula A, 0≤x<2. [3] The present invention is a lithium secondary battery, wherein in at least one of the above [1] and [2], the silicon-based particles are made of Si. [4] The present invention provides a lithium secondary battery, wherein in at least one of the above [1] to [3], the compound represented by the chemical formula 1 includes at least one selected from the group consisting of a compound represented by the following chemical formula 1-A and a compound represented by the following chemical formula 1-B. [Chemical Formula 1-A] [Chemical Formula 1-B] In the above chemical formulas 1-A and 1-B, R1 is as defined in the above chemical formula 1. [5] The present invention provides a lithium secondary battery, wherein in at least one of the above [1] to [4], the compound represented by the chemical formula 1 includes at least one selected from the group consisting of compounds represented by the following chemical formulas 1-1 to 1-9. [Chemical Formula 1-1] [Chemical Formula 1-2] [Chemical Formula 1-3] [Chemical Formula 1-4] [Chemical Formula 1-5] [Chemical Formula 1-6] [Chemical Formula 1-7] [Chemical Formula 1-8] [Chemical Formula 1-9] [6] The present invention provides a lithium secondary battery in which, in at least one of the above [1] to [5], the fluoroethylene carbonate is included in the non-aqueous electrolyte in an amount of 3% by volume to 20% by volume. [7] The present invention provides a lithium secondary battery, wherein in at least one of the above [1] to [6], the 1,2-difluoroethylene carbonate is included in the non-aqueous electrolyte in an amount of 10% by volume to 35% by volume. [8] The present invention provides a lithium secondary battery, wherein the compound represented by the chemical formula 1 is included in at least one of the above [1] to [7] in an amount of 0.1 wt% to 10 wt% based on the weight of the non-aqueous electrolyte. [9] The present invention provides a lithium secondary battery in which the volume ratio of the fluoroethylene carbonate and the 1,2-difluoroethylene carbonate is 5:95 to 50:50 in at least one of the above [1] to [8].

[0010] The present invention provides a lithium secondary battery in which, in at least one of the above [1] to [9], the total amount of the fluoroethylene carbonate and the 1,2-difluoroethylene carbonate is more than 10 wt% and less than or equal to 50 wt% based on the total weight of the non-aqueous electrolyte.

[0011] The present invention relates to at least one of the above [1] to

[0010] , wherein the lithium salt is LiCl, LiBr, LiI, LiBF4, LiClO4, LiAlO4, LiAlCl4, LiPF6, LiSbF6, LiAsF6, LiB 10 Cl 10, LiBOB (LiB(C2O4)2), LiCF3SO3, LiFSI (LiN(SO2F)2), LiCH3SO3, LiCF3CO2, LiCH3CO2, and LiBETI (LiN(SO2CF2CF3)2) are provided.

[0012] The present invention relates to a lithium secondary battery, wherein, in at least one of the above [1] to

[0011] , a solid electrolyte interface film is formed on the negative electrode after activation of the lithium secondary battery, and the solid electrolyte interface film comprises an inorganic component, and the inorganic component comprises LiF and CO3. 2- Including the CO3 2- A lithium secondary battery is provided in which the weight ratio of the LiF to the weight of the lithium secondary battery is 1.4 or more. The lithium secondary battery of the present invention is characterized by using a silicon-based active material as a positive electrode active material and using fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate (DFEC) and a compound represented by the chemical formula 1 as a non-aqueous electrolyte component. The above 1,2-difluoroethylene carbonate is used alone and, when decomposed by itself, the CO2 generation reaction is more dominant, causing an undesirable deterioration of battery performance. In this regard, the present invention is characterized by using the compound represented by the above chemical formula 1 together with the 1,2-difluoroethylene carbonate, wherein the compound represented by the above chemical formula 1 is a coumarin-based compound, which is ring-opened upon cathodic reduction to form a radical, and the radical formed at this time can form an inorganic-SEI film such as LiF when defluorinated upon cathodic reduction of the above 1,2-difluoroethylene carbonate, and at the same time, can form a propargyl group (C≡C) due to defluorination and ring-open to form a polymer-SEI film. The organic / inorganic composite film formed from the above components has remarkably excellent chemical and electrochemical stability. Meanwhile, when combining 1,2-difluoroethylene carbonate and the compound represented by the above chemical formula 1, the compounds react and are consumed quickly in the initial process such as the initial activation, so that, although the SEI film reaction during the initial activation and the effect of implementing a flexible and durable SEI film through it are separate, it has a disadvantage in terms of long-term durability. At this time, the present invention includes fluoroethylene carbonate, which has a low consumption rate in the non-aqueous electrolyte and continuously participates in the formation of the SEI film, and through this, the long-term durability of the SEI film can be further improved when applying a silicon-based active material negative electrode, which has an extreme degree of volume expansion and can generate a new negative electrode surface. As a result, the lithium secondary battery according to the present invention, when using a negative electrode including a silicon-based active material, forms and maintains a flexible and highly durable SEI film not only during the initial process but also during battery operation, and thus can have excellent life performance, storage performance, and particularly excellent high-temperature life performance and high-temperature storage performance. Terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best possible manner. It should be understood that the terms “include,” “comprising,” or “having” used in this specification are intended to specify the presence of a feature, number, step, component, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof. Meanwhile, before explaining the present invention, unless otherwise specified, “*” in the present invention means a connected portion (bonding site) between the terminals of the same or different atoms or chemical formulas. In addition, in the description of "carbon atoms a to b" in the present specification, "a" and "b" refer to the number of carbon atoms included in a specific functional group. That is, the functional group may include "a" to "b" carbon atoms. For example, "an alkyl group having 1 to 5 carbon atoms" refers to an alkyl group including 1 to 5 carbon atoms, i.e., CH3-, CH3CH2-, CH3CH2CH2-, (CH3)2CH-, CH3CH2CH2CH2-, (CH3)2CHCH2-, CH3CH2CH2CH2CH2-, (CH3)2CHCH2CH2CH2-, (CH3)2CHCH2CH2CH2-, etc. Additionally, in this specification, both alkyl groups and aryl groups may be substituted or unsubstituted. The above "substitution" means, unless otherwise defined, that at least one hydrogen bonded to carbon is replaced by an element other than hydrogen, for example, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a cycloalkenyl group having 3 to 12 carbon atoms, a cycloalkynyl group having 3 to 12 carbon atoms, a heterocycloalkyl group having 3 to 12 carbon atoms, a heterocycloalkenyl group having 3 to 12 carbon atoms, a heterocycloalkynyl group having 2 to 12 carbon atoms, an aryloxy group having 6 to 12 carbon atoms, a halogen atom, a fluoroalkyl group having 1 to 20 carbon atoms, a nitro group, an aryl group having 6 to 20 carbon atoms, an aryl group having 2 to 20 carbon atoms, an alkyl ... It means substituted with a heteroaryl group having 20 carbon atoms, a haloaryl group having 6 to 20 carbon atoms, etc. Hereinafter, the present invention will be described in more detail. lithium secondary battery The present invention relates to a lithium secondary battery. A lithium secondary battery according to the present invention comprises: a negative electrode; a positive electrode; a separator interposed between the negative electrode and the positive electrode; and a non-aqueous electrolyte; wherein the negative electrode comprises a negative electrode active material, the negative electrode active material comprises a silicon-based active material, and the non-aqueous electrolyte comprises a lithium salt, fluoroethylene carbonate, 1,2-difluoroethylene carbonate, and a compound represented by the following chemical formula 1. [Chemical Formula 1] In the above chemical formula 1, R1 includes a halogen, a nitrile group, a propargyl group, an ester group, an ether group, a ketone group, a carboxyl group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted alkoxy group, a boron group, a borate group, an isocyanate group, an isothiocyanate group, a silyl group, a siloxane group, a sulfone group, a sulfonate group, a sulfate group, or a combination of two or more thereof, and n is an integer from 0 to 6. The lithium secondary battery includes a negative electrode; a positive electrode; a separator; and a non-aqueous electrolyte. Specifically, the lithium secondary battery includes a negative electrode; a positive electrode facing the negative electrode; a separator interposed between the negative electrode and the positive electrode; and a non-aqueous electrolyte. The lithium secondary battery can be manufactured by housing an electrode assembly including the negative electrode; a positive electrode facing the negative electrode; and a separator interposed between the negative electrode and the positive electrode; in a battery case, and then injecting a non-aqueous electrolyte. (1) Cathode The above negative electrode includes a negative electrode active material. The above negative active material includes a silicon-based active material. The above silicon-based active material has the advantage of having a high capacity and high energy density compared to carbon-based active materials such as graphite, but has the disadvantage of a large volume change of the active material during charge and discharge. This volume expansion and contraction of the silicon-based active material causes the disconnection of conductive connections within the negative electrode, which leads to an increase in resistance and a decrease in life performance. In addition, the SEI film of the negative electrode formed during the activation process of a lithium secondary battery can be broken due to the volume change of the silicon-based active material, and this promotes electrolyte side reactions, causing problems such as an increase in resistance due to an increase in SEI film thickness and electrolyte depletion, which can result in a decrease in life performance and storage characteristics. In order to solve these problems, the present invention is characterized by including fluoroethylene carbonate, 1,2-difluoroethylene carbonate, and a compound represented by Chemical Formula 1, which will be described later, in a non-aqueous electrolyte. Through the combined use of the 1,2-difluoroethylene carbonate and the compound represented by Chemical Formula 1, not only can an SEI film with high flexibility, recoverability, and durability be formed upon initial activation, but also fluoroethylene carbonate continuously performs the SEI film formation reaction during the operation of the battery, resulting in the formation of an SEI film with remarkably excellent flexibility, recoverability, and durability simultaneously on an anode including a silicon-based active material, thereby significantly improving the high-temperature life performance and high-temperature storage performance of a lithium secondary battery. On the other hand, when using the non-aqueous electrolyte of a carbon-based active material such as graphite, the corresponding components of the non-aqueous electrolyte may act as resistance and cause unnecessary effects on battery performance, and therefore it is difficult to exhibit the effect on an anode containing only a carbon-based active material. The above silicon-based active material includes silicon-based particles, and the silicon-based particles may include at least one selected from a compound represented by chemical formula A and a silicon-carbon composite. [Chemical Formula A] SiO x In the above chemical formula A, 0≤x<2. In the above chemical formula A, since SiO2 does not react with lithium ions and thus cannot store lithium, it is preferable that x is within the above range. Specifically, the silicon-based particles included in the silicon-based active material may be made of Si, or in the above chemical formula A, x may be 0. Alternatively, the silicon-based particles may include silicon oxide, and for example, in the chemical formula A, 0.7≤x≤1.2, specifically, x=1. The silicon-based active material may further comprise, together with the silicon-based particles, a metal doped into the silicon-based particles. Alternatively, the silicon-based active material may further comprise, together with the silicon-based particles, a metal present on the surface, inside, or both the surface and inside of the silicon-based particles. The metal may be at least one of Li, Mg, Ca, and Al, specifically at least one of Li and Mg, and more specifically Mg. When the above metal is included in a silicon-based active material, it may be included in the silicon-based active material in an amount of 1% to 30% by weight. The above silicon-based active material may further include a carbon coating layer positioned on the surface of the silicon-based particles. The carbon coating layer may include amorphous carbon. When a carbon coating layer is included in the above silicon-based active material, the carbon coating layer may be included in the silicon-based active material in an amount of 0.5 wt% to 10 wt%, specifically 1 wt% to 5 wt%. The average particle diameter (D) of the above silicon-based active material 50 ) may be 1㎛ to 30㎛, preferably 2㎛ to 15㎛, in order to reduce side reactions with the electrolyte while ensuring structural stability during charge and discharge. The above negative active material may further include a carbon-based active material in addition to a silicon-based active material. The above carbon-based active material may include at least one selected from the group consisting of artificial graphite, natural graphite, hard carbon, soft carbon, carbon black, graphene, and fibrous carbon, and preferably may include at least one selected from the group consisting of artificial graphite and natural graphite. The average particle diameter (D) of the above carbon-based active material 50 ) may be 10㎛ to 30㎛, preferably 15㎛ to 25㎛, in order to ensure structural stability during charging and discharging and reduce side reactions with the electrolyte. When the above negative active material includes a silicon-based active material and a carbon-based active material, the weight ratio of the silicon-based active material and the carbon-based active material may be 1:99 to 50:50, specifically 3:97 to 20:80, and more specifically 3:97 to 10:90. In one embodiment, the negative active material may not include a carbon-based active material. The above negative electrode may include a negative electrode current collector; and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. In this case, the negative electrode active material may be included in the negative electrode active material layer. The above negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. Specifically, the negative electrode current collector may be made of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., or an aluminum-cadmium alloy. The above negative electrode current collector may typically have a thickness of 3 to 500 μm. The above-described negative electrode current collector may have fine irregularities formed on its surface to enhance the bonding strength of the negative electrode active material. For example, the above-described negative electrode current collector may be used in various forms, such as a film, sheet, foil, net, porous body, foam, or non-woven fabric. The negative electrode active material layer is disposed on at least one surface of the negative electrode current collector. Specifically, the negative electrode active material layer may be disposed on one or both surfaces of the negative electrode current collector. The above negative active material may be included in the negative active material layer in an amount of 60 wt% to 99 wt%, preferably 75 wt% to 95 wt%. The above negative electrode active material layer may further include a binder and / or a conductive material together with the negative electrode active material. The above binder is used to improve the performance of the battery by improving the adhesion between the negative electrode active material layer and the negative electrode current collector, and may include, for example, at least one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber, and materials in which hydrogens of these are substituted with Li, Na, Ca, etc., and may also include various copolymers thereof. May include. The above binder may be included in the negative electrode active material layer in an amount of 0.5 wt% to 30 wt%, preferably 1 wt% to 15 wt%, and more preferably 5 wt% to 10 wt%. The conductive material is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, panes black, lamp black, and thermal black; conductive fibers such as carbon fiber or metal fiber; conductive tubes such as carbon nanotubes; fluorocarbon; metal powder such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives. The above conductive material may be included in the negative electrode active material layer in an amount of 0.5 wt% to 30 wt%, preferably 1 wt% to 25 wt%. The thickness of the negative electrode active material layer may be 10 µm to 100 µm, preferably 50 µm to 80 µm. The above negative electrode can be manufactured by coating a negative electrode slurry including a negative electrode active material, a binder, a conductive material, and / or a solvent for forming a negative electrode slurry on at least one surface of a negative electrode current collector, and then drying and rolling. The solvent for forming the negative electrode slurry may include at least one selected from the group consisting of distilled water, NMP (N-methyl-2-pyrrolidone), ethanol, methanol, and isopropyl alcohol, preferably distilled water, in order to facilitate dispersion of the negative electrode active material, binder, and / or conductive material. (2) Bipolar The above anode is opposite to the above cathode. The positive electrode may include a positive electrode current collector; and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. The positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. Specifically, the positive electrode current collector may include at least one selected from the group consisting of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, and an aluminum-cadmium alloy, preferably aluminum. The thickness of the above positive electrode collector may typically be 3 to 500 μm. The above-described positive electrode current collector may also form fine irregularities on its surface to enhance the bonding strength of the positive electrode active material. For example, the above-described positive electrode current collector may be used in various forms, such as a film, sheet, foil, net, porous body, foam, or non-woven fabric. The positive electrode active material layer is disposed on at least one surface of the positive electrode current collector. Specifically, the positive electrode active material layer may be disposed on one or both surfaces of the positive electrode current collector. The above positive electrode active material layer may include a positive electrode active material. The above positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically, may include a lithium transition metal composite oxide containing lithium and at least one transition metal composed of nickel, cobalt, manganese, and aluminum, preferably a lithium transition metal composite oxide containing lithium and a transition metal including nickel, cobalt, and manganese. For example, the lithium transition metal composite oxides include lithium-manganese oxides (e.g., LiMnO2, LiMn2O4, etc.), lithium-cobalt oxides (e.g., LiCoO2, etc.), lithium-nickel oxides (e.g., LiNiO2, etc.), lithium-nickel-manganese oxides (e.g., LiNi 1-Y Mn Y O2 (here, 0 <Y<1), LiMn 2-z Ni z O4 (where 0<Z<2), etc.), lithium-nickel-cobalt oxides (e.g., LiNi 1-Y1Co Y1 O2 (here, 0 <Y1<1) 등), 리튬-망간-코발트계 산화물(예를 들면, LiCo 1-Y2 Mn Y2 O2 (here, 0 <Y2<1), LiMn 2-z1 Co z1 O4 (wherein, 0<Z1<2) etc.), lithium-nickel-manganese-cobalt oxides (e.g., Li(Ni p Co q Mn r1 )O2(wherein, 0<p<1, 0<q<1, 0<r1<1, p+q+r1=1) or Li(Ni p1 Co q1 Mn r2 )O4 (wherein, 0<p1<2, 0<q1<2, 0<r2<2, p1+q1+r2=2) etc.), or lithium-nickel-cobalt-transition metal (M) oxide (e.g., Li(Ni p2 Co q2 Mn r3 M S2 )O2(wherein, M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg and Mo, and p2, q2, r3 and s2 are atomic fractions of independent elements, 0<p2<1, 0<q2<1, 0<r3<1, 0<s2<1, p2+q2+r3+s2=1), etc.), and any one or more compounds thereof may be included. Among these, the lithium transition metal composite oxide is LiCoO2, LiMnO2, LiNiO2, lithium nickel-manganese-cobalt oxide (e.g., Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2 or Li(Ni 0.8 Mn 0.1 Co 0.1)O2, etc.), or lithium nickel cobalt aluminum oxide (e.g., Li(Ni 0.8 Co 0.15 Al 0.05 )O2, etc.), and considering the remarkable improvement effect according to the control of the type and content ratio of the constituent elements forming the lithium transition metal composite oxide, the lithium transition metal composite oxide may be Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2 or Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc., and any one of these or a mixture of two or more of them may be used. More specifically, the positive electrode active material may be a lithium-transition metal composite oxide, and may contain nickel in an amount of 60 mol% or more based on the total mole number of transition metals included in the lithium-transition metal composite oxide. Specifically, the positive electrode active material may be a lithium-transition metal composite oxide, and the transition metal may include nickel; and at least one selected from manganese, cobalt, and aluminum, and may contain nickel in an amount of 60 mol% or more, specifically 60 mol% to 90 mol%, based on the total mole number of transition metals. When a lithium-transition metal composite oxide using such a high nickel content is used together with the above-described non-aqueous electrolyte, it is preferable in that it can reduce by-products in the gas phase generated by structural collapse. In addition, the positive electrode active material may include a lithium composite transition metal oxide represented by the following chemical formula B. [Chemical Formula B] Li 1+x (Ni a Co b Mn c M d )O2 In the above chemical formula B, M is at least one selected from W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B and Mo, and 1+x, a, b, c and d are atomic fractions of independent elements, respectively, 0≤x≤0.2, 0.50≤a<1, 0 <b≤0.25, 0<c≤0.25, 0≤d≤0.1, a+b+c+d=1이다. Preferably, the above a, b, c and d may be 0.70≤a≤0.95, 0.025≤b≤0.20, 0.025≤c≤0.20, 0≤d≤0.05, respectively. In addition, the above a, b, c and d may be 0.80≤a≤0.95, 0.025≤b≤0.15, 0.025≤c≤0.15, 0≤d≤0.05, respectively. In addition, the above a, b, c and d may be 0.85≤a≤0.90, 0.05≤b≤0.10, 0.05≤c≤0.10, 0≤d≤0.03, respectively. The above-mentioned positive electrode active material may be included in the positive electrode active material layer at 80 wt% to 99 wt%, preferably 92 wt% to 98.5 wt%, taking into account sufficient capacity of the positive electrode active material. The above-described positive electrode active material layer may further include a binder and / or a conductive material together with the above-described positive electrode active material. The above binder is a component that assists in the binding of the active material and the conductive material and the binding to the current collector, and specifically, may include at least one selected from the group consisting of polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, and fluororubber, preferably polyvinylidene fluoride. The above binder may be included in the positive electrode active material layer at 1 wt% to 20 wt%, preferably 1.2 wt% to 10 wt%, in order to sufficiently secure binding force between components such as the positive electrode active material. The conductive material may be used to assist and improve conductivity in a secondary battery, and is not particularly limited as long as it has conductivity without causing chemical changes. Specifically, the conductive material may include at least one selected from the group consisting of graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, paneth black, lamp black, thermal black; conductive fibers such as carbon fibers or metal fibers; conductive tubes such as carbon nanotubes; fluorocarbons; metal powders such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and polyphenylene derivatives, and preferably, the conductive material may include carbon black in terms of improving conductivity. The above-mentioned conductive material may be included in the positive electrode active material layer at 1 wt% to 20 wt%, preferably 1.2 wt% to 10 wt%, in order to sufficiently secure electrical conductivity. The thickness of the positive electrode active material layer may be 30 µm to 400 µm, preferably 40 µm to 110 µm. The above positive electrode can be manufactured by coating a positive electrode slurry containing a positive electrode active material and optionally a binder, a conductive material, and a solvent for forming a positive electrode slurry on the positive electrode current collector, and then drying and rolling. The solvent for forming the positive electrode slurry may include an organic solvent such as NMP (N-methyl-2-pyrrolidone). The solid content of the positive electrode slurry may be 40 wt% to 90 wt%, specifically 50 wt% to 80 wt%. (3) Membrane The above separator may be interposed between the positive electrode and the negative electrode. In addition, as the separator, a conventional porous polymer film that has been conventionally used as a separator, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, may be used alone or in a laminated manner, or a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. may be used, but is not limited thereto. In addition, a coated separator containing a ceramic component or a polymer material may be used to secure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure. (4) Non-aqueous electrolyte The non-aqueous electrolyte according to the present invention comprises a lithium salt, fluoroethylene carbonate, 1,2-difluoroethylene carbonate, and a compound represented by the following chemical formula 1. The non-aqueous electrolyte may further comprise an organic solvent and an additive, if necessary. 1) Lithium salt As the lithium salt used in the present invention, various lithium salts commonly used in non-aqueous electrolytes for lithium secondary batteries can be used without limitation. For example, the lithium salt may be Li as a cation. + , and the anion is F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , AlO4 - , AlCl4 - , PF6 - , SbF6 - , AsF6 - , B 10 Cl 10 - , BF2C2O4 - , BC4O8- , PF4C2O4 - , PF2C4O8 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , C4F9SO3 - , CF3CF2SO3 - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , CH3SO3 - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - It may include at least one selected from the group consisting of . Specifically, the lithium salt is LiCl, LiBr, LiI, LiBF4, LiClO4, LiAlO4, LiAlCl4, LiPF6, LiSbF6, LiAsF6, LiB 10 Cl 10 , LiBOB (LiB(C2O4)2), LiCF3SO3, LiFSI (LiN(SO2F)2), LiCH3SO3, LiCF3CO2, LiCH3CO2, and LiBETI (LiN(SO2CF2CF3)2). Specifically, the lithium salt may include at least one selected from the group consisting of LiBF4, LiClO4, LiPF6, LiBOB (LiB(C2O4)2), LiCF3SO3, LiTFSI (LiN(SO2CF3)2), LiFSI ((LiN(SO2F)2), and LiBETI (LiN(SO2CF2CF3)2). The lithium salt may be included in the non-aqueous electrolyte at a concentration of 0.5 M to 5 M, specifically at a concentration of 0.8 M to 4 M, and more specifically at a concentration of 0.8 M to 2.0 M. When the concentration of the lithium salt satisfies the above range, the lithium ion yield (Li + The output characteristics of the battery can be improved by improving the transference number and the degree of dissociation of lithium ions. Alternatively, the lithium salt may be included in the non-aqueous electrolyte as a component of the non-aqueous electrolyte, for example, a compound represented by chemical formula 1, a compound represented by chemical formula 2, optionally an organic solvent, and a remainder excluding additives. 2) Fluoroethylene carbonate The above fluoroethylene carbonate (FEC) can be decomposed during the battery operation process to provide a composite component of organic components and inorganic components such as LiF to the SEI film. Such a fluoroethylene carbonate-derived SEI film has excellent long-term durability. In particular, the combination of 1,2-difluoroethylene carbonate and the compound of chemical formula 1 described below, and the product of their reaction, exhibit excellent effects during the initial activation process, but it is difficult to exhibit additional effects during long-term battery operation. At this time, the fluoroethylene carbonate can continuously provide SEI film components when the SEI film is broken and a new negative electrode surface is generated due to the volume expansion of the silicon-based active material during the charge / discharge process of the battery, thereby improving the long-term durability of the SEI film. Meanwhile, the fluoroethylene carbonate has a smaller number of fluorines than 1,2-difluoroethylene carbonate, and contributes less to increasing the overall LiF content of the SEI film, making it difficult to achieve the desired effect by using fluoroethylene carbonate alone. The above fluoroethylene carbonate may mean mono-fluoroethylene carbonate. The above fluoroethylene carbonate may be included in the non-aqueous electrolyte in an amount of 3% to 20% by volume, specifically 5% to 15% by volume, and more specifically 7% to 12% by volume. When present in the above range, an SEI film of an appropriate level can be formed on the negative electrode containing a silicon-based active material, and an increase in resistance, which is a concern when added in excessive amounts, can be prevented. Additionally, the fluoroethylene carbonate may be included in the non-aqueous electrolyte in an amount of 3 wt% to 20 wt%, specifically 5 wt% to 15 wt%, and more specifically 7 wt% to 12 wt%. 3) 1,2-difluoroethylene carbonate The above 1,2-difluoroethylene carbonate is a compound containing two fluorine atoms in its molecular structure, and thus, an increase in the content of inorganic components that contribute to improving the durability of the SEI film, such as LiF, can be expected. In addition, by defluorination of the 1,2-difluoroethylene carbonate, a carbon-carbon triple bond or a propargyl group (C≡C) is formed, and this component can be expected to form a polymer-type SEI film when ring-opening the chemical structure. However, the 1,2-difluoroethylene carbonate itself has a problem in that it is difficult to form an SEI film having the desired organic / inorganic composite component because, when it decomposes, CO2 generation and the formation of a single-molecular structure are more dominant than the opening of a polymer-type ring. To solve these problems, the present invention uses a compound represented by Chemical Formula 1, which will be described later, together with 1,2-difluoroethylene carbonate. The compound represented by Chemical Formula 1 forms a radical upon cathode reduction, thereby promoting the ring-opening reaction of 1,2-difluoroethylene carbonate, thereby inducing the formation of an SEI film having an organic / inorganic composite component and simultaneously improved flexibility, resilience, and durability. That is, it can be understood that the formation of an SEI film derived from 1,2-difluoroethylene carbonate can be preferably implemented only when the compound represented by Chemical Formula 1 is used in combination. That is, the SEI film derived from 1,2-difluoroethylene carbonate by the radical reaction by the compound represented by Chemical Formula 1 has an organic / inorganic composite component, and through this, the flexibility, resilience, and durability of the SEI film can be simultaneously improved. This is very suitable for application to silicon-based active materials that undergo extreme volume expansion / contraction during the initial activation process and battery operation. The above 1,2-difluoroethylene carbonate may be included in the non-aqueous electrolyte in an amount of 10% to 35% by volume, specifically 15% to 30% by volume, and more specifically 17% to 22% by volume. The above 1,2-difluoroethylene carbonate may be included in the non-aqueous electrolyte in an amount of 10 wt% to 35 wt%, specifically 15 wt% to 32 wt%, and more specifically 18 wt% to 25 wt%. The volume ratio of the above fluoroethylene carbonate and the above 1,2-difluoroethylene carbonate may be 5:95 to 50:50, specifically 25:75 to 40:60, and more specifically 28:72 to 35:65. The weight ratio of the above fluoroethylene carbonate and the above 1,2-difluoroethylene carbonate may be 5:95 to 50:50, specifically 15:85 to 45:55, and more specifically 30:70 to 35:65. Meanwhile, the total amount of the fluoroethylene carbonate and the 1,2-difluoroethylene carbonate may be greater than 10 wt% and less than or equal to 50 wt%, specifically 15 wt% to 45 wt%, more specifically 25 wt% to 42 wt%, and even more specifically 30 wt% to 35 wt%, based on the total weight of the non-aqueous electrolyte. Within the above range, the effects of the fluoroethylene carbonate and the 1,2-difluoroethylene carbonate described above can be harmoniously enhanced and expressed. 4) Compound represented by chemical formula 1 The non-aqueous electrolyte of the present invention comprises a compound represented by the following chemical formula 1. [Chemical Formula 1] In the above chemical formula 1, R1 includes a halogen, a nitrile group, a propargyl group, an ester group, an ether group, a ketone group, a carboxyl group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted alkoxy group, a boron group, a borate group, an isocyanate group, an isothiocyanate group, a silyl group, a siloxane group, a sulfone group, a sulfonate group, a sulfate group, or a combination of two or more thereof, and n is an integer from 0 to 6. The compound represented by the above chemical formula 1 has excellent cathodic reducibility and can form radicals during cathodic reduction. As described above, the radicals formed thereby can promote the ring-opening reaction of 1,2-difluoroethylene carbonate, thereby enabling the implementation of an SEI film with high flexibility, resilience, and durability in the initial activation process. In addition, in the case of the compound represented by the above chemical formula 1, upon initial activation, it can be opened to form a polymer-type film of polyethylene oxide on the electrode, and this polymer-type film has excellent flexibility and recoverability. In the above chemical formula 1, R1 may be specifically a halogen (the halogen may be selected from F, Cl, Br, and I, and may be specifically F), a nitrile group, a propargyl group, an ester group, an ether group, or a combination of two or more thereof. Such a substituent may improve the reducibility of the first additive, thereby also realizing the effects of smooth formation of an SEI film and improved lithium ion transfer performance. In the above chemical formula 1, n may be an integer selected from 0 to 6, specifically an integer selected from 1 to 6, and more specifically n may be 1. In the above chemical formula 1, when n is 2 or more, each R1 may be the same or different. Specifically, the compound represented by the above chemical formula 1 may include at least one selected from the group consisting of a compound represented by the following chemical formula 1-A and a compound represented by the following chemical formula 1-B. [Chemical Formula 1-A] [Chemical Formula 1-B] In the above chemical formulas 1-A and 1-B, R1 is as defined in the above chemical formula 1. The compounds represented by the above chemical formulas 1-A and 1-B have structures in which substituents exist at positions 3 and 7 (based on IUPAC nomenclature) of the ring structure, respectively. In this case, it is preferable to synthesize at positions like the above compared to other substitution positions in that it is advantageous. Specifically, the compound represented by the above formula 1 may include at least one selected from the group consisting of compounds represented by the following formulae 1-1 to 1-9. The compound represented by the above formula 1 may specifically include at least one selected from the group consisting of compounds represented by the following formulae 1-1, 1-2, 1-3, 1-4, and 1-9, in that it is more smoothly reduced to the negative electrode and is more advantageous in forming an SEI film, and more specifically, may include at least one selected from the group consisting of compounds represented by the following formulae 1-1 and 1-2, and more specifically, may include a compound represented by the following formula 1-1. [Chemical Formula 1-1] [Chemical Formula 1-2] [Chemical Formula 1-3] [Chemical Formula 1-4] [Chemical Formula 1-5] [Chemical Formula 1-6] [Chemical Formula 1-7] [Chemical Formula 1-8] [Chemical Formula 1-9] The compound represented by the above chemical formula 1 may be included in the non-aqueous electrolyte in an amount of 0.1 wt% to 10 wt%, specifically 1 wt% to 7 wt%, and more specifically 3.5 wt% to 6 wt%. When the content of the compound represented by the above chemical formula 1 is within the above-mentioned range, the ring-opening reaction of 1,2-difluoroethylene carbonate can be sufficiently caused, and concerns about increased resistance when added in excess can be prevented. The weight ratio of the compound represented by the above chemical formula 1 to the weight of the above 1,2-difluoroethylene carbonate may be 0.2 to 1, specifically 0.25 to 0.95, more specifically 0.4 to 0.7. When in the above range, when the content of the compound represented by the above chemical formula 1 is in the above-mentioned range, the ring-opening reaction of 1,2-difluoroethylene carbonate can sufficiently occur, and an organic / inorganic composite SEI film according to the corresponding composition combination can be formed at a sufficient level. The weight ratio of the compound represented by the above chemical formula 1 to the weight of the above fluoroethylene carbonate may be 0.1 to 0.5, specifically 0.15 to 0.45. In addition, the weight ratio of the compound represented by the above chemical formula 1 to the total weight of the above fluoroethylene carbonate and the above 1,2-difluoroethylene carbonate may be 0.1 to 0.3, specifically 0.12 to 0.20. When it is within the above range, it is advantageous in that the initial and long-term life performance of a negative electrode and a lithium secondary battery using a silicon-based active material can be improved to an excellent level. 5) Organic solvents The above non-aqueous electrolyte may further include an organic solvent along with the above-mentioned components. The organic solvent mentioned above is a non-aqueous solvent commonly used in lithium secondary batteries, and is not particularly limited as long as decomposition due to oxidation reactions, etc. during the charging and discharging process of the secondary battery can be minimized. The organic solvent may be included in the non-aqueous electrolyte as a volume percentage (vol%) of the remaining amount excluding the fluoroethylene carbonate and the 1,2-difluoroethylene carbonate. Specifically, the organic solvent may include at least one selected from the group consisting of a cyclic carbonate-based organic solvent, a linear carbonate-based organic solvent, a linear ester-based organic solvent, and a cyclic ester-based organic solvent. Specifically, the organic solvent may include at least one selected from a cyclic carbonate-based organic solvent and a linear carbonate-based organic solvent. Alternatively, the organic solvent may include a linear carbonate-based organic solvent in that the aforementioned fluoroethylene carbonate and 1,2-difluoroethylene carbonate replace the cyclic carbonate organic solvent. The above cyclic carbonate-based organic solvent is a high-viscosity organic solvent having a high dielectric constant and thus capable of dissociating a lithium salt in the electrolyte well. Specifically, the organic solvent may include at least one organic solvent selected from the group consisting of ethylene carbonate (EC), fluoroethylene carbonate (FEC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, and vinylene carbonate, and more specifically, may include ethylene carbonate (EC). Alternatively, the cyclic carbonate-based organic solvent or ethylene carbonate may not be included in the non-aqueous electrolyte of the present invention. In addition, the linear carbonate-based organic solvent is an organic solvent having low viscosity and low dielectric constant, and may specifically include at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethylmethyl carbonate (EMC), methylpropyl carbonate, and ethylpropyl carbonate, and more specifically may include at least one selected from the group consisting of ethylmethyl carbonate (EMC) and diethyl carbonate (DEC), and more specifically may include ethylmethyl carbonate (EMC) and diethyl carbonate (DEC), and even more specifically, ethylmethyl carbonate (EMC) and diethyl carbonate (DEC) are mixed in a ratio of 50:50 to 99:1, specifically 60:40 to 90:10, more specifically 60:40 to 75:25, and even more specifically 62:38 to 66:34. It can be included by volume ratio. When the organic solvent includes a linear carbonate solvent, the ratio of the total volume of the fluoroethylene carbonate and 1,2-difluoroethylene carbonate to the volume of the linear carbonate solvent may be 10:90 to 50:50, specifically 20:80 to 45:55. The linear ester organic solvent may specifically include at least one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate. In addition, the cyclic ester organic solvent may specifically include at least one selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone. Meanwhile, the organic solvent may be used without limitation by adding organic solvents commonly used in non-aqueous electrolytes as needed. For example, at least one organic solvent among an ether-based organic solvent, a glyme-based solvent, and a nitrile-based organic solvent may be additionally included. As the above ether solvent, any one selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether, ethyl propyl ether, 1,3-dioxolane (DOL), and 2,2-bis(trifluoromethyl)-1,3-dioxolane (TFDOL) or a mixture of two or more thereof may be used, but is not limited thereto. The above glyme-based solvent has a high dielectric constant and low surface tension compared to linear carbonate-based organic solvents, and is a solvent with low reactivity with metals, and may include at least one selected from the group consisting of dimethoxyethane (glyme, DME), diethoxyethane, diglyme, tri-glyme, and tetra-glyme (TEGDME), but is not limited thereto. The above nitrile solvent may be at least one selected from the group consisting of acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentane carbonitrile, cyclohexane carbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile, but is not limited thereto. 6) Additives The above non-aqueous electrolyte may further include additives in addition to the aforementioned components. Specifically, the additive may be at least one selected from the group consisting of vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, propane sultone, propene sultone, succinonitrile, adiponitrile, ethylene sulfate, LiODFB (lithium difluorooxalatoborate), LiBOB (lithium bis-(oxalato)borate), TMSPa (tris(trimethylsilyl) phosphate), and TMSPi (tris(trimethylsilyl) phosphite). The above additive may be included in the non-aqueous electrolyte in an amount of 0.1 wt% to 15 wt%, but is not limited thereto. In the lithium secondary battery of the present invention, after activation of the lithium secondary battery, a solid electrolyte interface film is formed on the negative electrode, and the solid electrolyte interface film includes an inorganic component, and the inorganic component is LiF and CO3. 2- Including the CO3 2- The weight ratio of the LiF to the weight of the metal may be 1.4 or more. By the above activation process, the non-aqueous electrolyte component (e.g., fluoroethylene carbonate, 1,2-difluoroethylene carbonate, the compound represented by the above chemical formula 1, etc.) can be decomposed to form a solid electrolyte interface film (SEI film). The above activation process can use any method known in the art without limitation and is not particularly limited. For example, the activation process can be performed by charging to an SOC of 10% or more, specifically, an SOC of 60% or more, and more specifically, an SOC of 100% at a C-rate of 0.1C to 1C at room temperature (20±5°C). Alternatively, the activation process can be performed under a pressure of 0.5 kgf / cm2 to 20 kgf / cm2 at a temperature of 45°C to 60°C depending on the C-rate and SOC conditions. The inorganic component of the above solid electrolyte interface film, its content, can be measured by a method including the following steps. (a) a step of disassembling the activated lithium secondary battery and separating the negative electrode; (b) a step of washing the separated cathode; (c) a step of immersing the washed cathode in an extraction solvent to extract the solid electrolyte interface film on the cathode surface; and (d) a step of analyzing inorganic components in the extraction solvent using capillary electrophoresis; The step of separating the above cathode can be performed under an inert gas atmosphere. The step of washing the separated cathode is to prevent interference by non-aqueous electrolyte components. The washing step can be performed by immersing the cathode in a washing solvent. The washing solvent may include at least one organic solvent selected from the group consisting of a cyclic ether solvent, an ester organic solvent, or a nitrile organic solvent. For example, when a propionate organic solvent is used as the organic solvent for the non-aqueous electrolyte, a carbonate organic solvent may be used as the washing solvent, or when a linear carbonate organic solvent is used as the organic solvent for the non-aqueous electrolyte, a propionate organic solvent may be used as the washing solvent. The above washing step may vary in the washing solvent and washing time used depending on the size of the cathode, specifically 15 cm 2　 35 cm inside 2 Based on the cathode area, the electrode can be immersed in 10 mL to 50 mL of a washing solvent for 15 minutes to 1 hour. After the above washing step, an additional step of drying the electrode under an inert gas atmosphere to remove the used washing solvent may be performed. The drying step may be performed at room temperature (20±5°C) for approximately 5 minutes to 2 hours, depending on the electrode condition. The above extraction solvent may be a highly polar solvent, and the highly polar solvent may include at least one solvent selected from the group consisting of deuterium oxide (D2O), tetrahydrofuran (THF), acetonitrile, acetone, hexamethylphosphoramide (HMPA), N,N-dimethylformamide, and dimethyl sulfoxide. The above solid electrolyte interface film extraction step can be appropriately changed according to experimental conditions such as the size of the electrode, the cycle of the battery, and the storage conditions during extraction. Specifically, based on an electrode area of ​​15 cm2 to 35 cm2, it can be performed by immersing the electrode in 1 mL to 5 mL of an extraction solvent at room temperature (25±5°C) for 12 to 48 hours. Meanwhile, during the extraction step, some electrode metal components dissolved from degraded electrodes may be present in the extraction solvent. In this case, it is difficult to conduct a clear analysis in subsequent steps, so a filtration step may be added to remove these impurities. The above filtration step may appropriately utilize a method such as centrifugation or filtering depending on the content of by-products. Afterwards, analysis of the inorganic components in the extraction solvent obtained after filtration can be performed using the capillary electrophoresis method. In this specification, "capillary electrophoresis" refers to a method of measuring the structure and content of a component by utilizing a chemical phenomenon in which charges in a solution move toward an electrode of opposite charge under an electric field between electrodes, and the structure or content of the component (type) or component does not change depending on specific devices and conditions. In the present invention, measurement can be performed using an AB SCIEX MDQ plus device (Capillary: 75 μm ID, 50 cm; Injection: 0.5 psi, 3 sec; Separation: 20 kV, 0.1 psi; Detector: 230 nm UV) using a SCIEX anion analysis kit (pH5.5) as a run buffer. In addition to the above, the measurement of the components of the solid electrolyte interface film can be referred to Korean Patent Publication No. 10-2020-0005870. In the case of the lithium secondary battery according to the present invention, the CO3 2- The weight ratio of the LiF to the weight of the battery may be 1.4 or more, specifically 1.4 to 3.0, more specifically 1.5 to 2.7, and even more specifically 2.0 to 2.6. When within the above range, it can be evaluated that a composite film of inorganic components and organic components of the SEI film within the negative electrode is formed appropriately at a sufficient level, and in particular, the overall performance of a battery containing a silicon-based negative electrode can be significantly improved. The weight of LiF per area of ​​the above solid electrolyte interfacial film is 100 ㎍ / cm 2 Above, specifically 100㎍ / cm 2 250 ㎍ / cm 2 , more specifically 190㎍ / cm 2 240 ㎍ / cm 2 It could be. CO3 per solid electrolyte interfacial membrane area 2- The weight is 60㎍ / cm 2 Above, specifically 75㎍ / cm 2 100㎍ / cm 2 , more specifically 77㎍ / cm 2 82㎍ / cm 2 It could be. There is no particular limitation on the external shape of the lithium secondary battery of the present invention, but it may be a cylindrical shape using a can, a square shape, a pouch shape, or a coin shape. Hereinafter, the present invention will be described in more detail through specific examples. However, the following examples are merely illustrative and serve to aid understanding of the present invention and do not limit its scope. It will be apparent to those skilled in the art that various modifications and variations are possible within the scope and technical spirit of this disclosure, and such modifications and variations are naturally within the scope of the appended claims. Examples and Comparative Examples Example 1 (Manufacture of non-aqueous electrolyte) An organic solvent was prepared by mixing fluoroethylene carbonate, 1,2-difluoroethylene carbonate, diethyl carbonate, and ethylmethyl carbonate in a volume ratio of 5:20:45:30. A non-aqueous electrolyte was prepared by adding LiPF6 as a lithium salt and a compound represented by the chemical formula 1-1 to the organic solvent. The above lithium salt was added to the non-aqueous electrolyte at a molar concentration of 1.5 M. The compound represented by the above chemical formula 1-1 was added to the non-aqueous electrolyte at a content of 5 wt%. In the above non-aqueous electrolyte, the weight percentage of the fluoroethylene carbonate was 5.5 wt%, and the weight percentage of the 1,2-difluoroethylene carbonate was 22.2 wt%. (Lithium secondary battery manufacturing) Cathode active material (LiNi) 0.85Co 0.05 Mn 0.07 Al 0.03 O2): Conductive agent (carbon nanotube): Binder (polyvinylidene fluoride) was added to N-methyl-2-pyrrolidone (NMP), a solvent, in a weight ratio of 97.74:0.70:1.56 to prepare a positive electrode mixture slurry (solid content 75.5 wt%). The positive electrode mixture slurry was applied to one surface of a positive electrode current collector (Al thin film) having a thickness of 15 ㎛, and dried and roll pressed to prepare a positive electrode. A negative electrode composite slurry (solid content 26 wt%) was prepared by adding a negative electrode active material (Si), a conductive agent (carbon black), and a binder (styrene-butadiene rubber) to distilled water as a solvent in a weight ratio of 70.0:20.3:9.7. The negative electrode composite slurry was applied to one surface of a 15 μm thick negative electrode current collector (Cu thin film), and drying and roll pressing were performed to prepare a negative electrode. A polyethylene porous film separator was interposed between the positive and negative electrodes manufactured above in a dry room, and then the non-aqueous electrolyte manufactured above was injected to manufacture a lithium secondary battery. (Component analysis of solid electrolyte interface film) The lithium secondary battery manufactured above was activated by charging to SOC 100% at a C-rate of 0.33C at room temperature (20±5℃). The above activated lithium secondary batteries were each disassembled under an inert gas atmosphere to form a cathode (area: 65 cm 2 ) was obtained, and the cathode was washed by immersing it in 30 mL of a washing solvent, dimethyl carbonate (DMC), for 30 minutes. Next, the washed electrode was immersed in 10 mL of deuterium oxide (D2O) at room temperature (25±5°C) for 24 hours to perform an extraction step. Next, after the extraction step, the extraction solvent was filtered using a filter, and then the qualitative and quantitative analysis of the inorganic components in the extraction solvent was performed using capillary electrophoresis. Among these, LiF and CO3 2- The results of content analysis are shown in Table 1 below. The above capillary electrophoresis was performed using an AB SCIEX MDQ plus device (Capillary: 75 μm ID, 50 cm; Injection: 0.5 psi, 3 sec; Separation: 20 kV, 0.1 psi; Detector: 230 nm UV) using a SCIEX anion analysis kit (pH5.5) as a run buffer. Example 2 (Manufacture of non-aqueous electrolyte) An organic solvent was prepared by mixing fluoroethylene carbonate, 1,2-difluoroethylene carbonate, diethyl carbonate, and ethylmethyl carbonate in a volume ratio of 15:20:45:20. A non-aqueous electrolyte was prepared by adding LiPF6 as a lithium salt and a compound represented by the chemical formula 1-1 to the organic solvent. The above lithium salt was added to the non-aqueous electrolyte at a molar concentration of 1.5 M. The compound represented by the above chemical formula 1-1 was added to the non-aqueous electrolyte at a content of 5 wt%. In the above non-aqueous electrolyte, the weight percentage of the fluoroethylene carbonate was 15.9 wt%, and the weight percentage of the 1,2-difluoroethylene carbonate was 21.4 wt%. (Lithium secondary battery manufacturing) A lithium secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte manufactured above was used. Example 3 (Manufacture of non-aqueous electrolyte) An organic solvent was prepared by mixing fluoroethylene carbonate, 1,2-difluoroethylene carbonate, diethyl carbonate, and ethylmethyl carbonate in a volume ratio of 10:15:45:30. A non-aqueous electrolyte was prepared by adding LiPF6 as a lithium salt and a compound represented by the chemical formula 1-1 to the organic solvent. The above lithium salt was added to the non-aqueous electrolyte at a molar concentration of 1.5 M. The compound represented by the above chemical formula 1-1 was added to the non-aqueous electrolyte at a content of 5 wt%. In the above non-aqueous electrolyte, the weight percentage of the fluoroethylene carbonate was 11.0 wt%, and the weight percentage of the 1,2-difluoroethylene carbonate was 16.6 wt%. (Lithium secondary battery manufacturing) A lithium secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte manufactured above was used. Example 4 (Manufacture of non-aqueous electrolyte) An organic solvent was prepared by mixing fluoroethylene carbonate, 1,2-difluoroethylene carbonate, diethyl carbonate, and ethylmethyl carbonate in a volume ratio of 10:20:45:25. A non-aqueous electrolyte was prepared by adding LiPF6 as a lithium salt and a compound represented by the chemical formula 1-1 to the organic solvent. The above lithium salt was added to the non-aqueous electrolyte at a molar concentration of 1.5 M. The compound represented by the above chemical formula 1-1 was added to the non-aqueous electrolyte at a content of 5 wt%. In the above non-aqueous electrolyte, the weight percentage of the fluoroethylene carbonate was 10.8 wt%, and the weight percentage of the 1,2-difluoroethylene carbonate was 21.8 wt%. (Lithium secondary battery manufacturing) A lithium secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte manufactured above was used. Example 5 (Manufacture of non-aqueous electrolyte) An organic solvent was prepared by mixing fluoroethylene carbonate, 1,2-difluoroethylene carbonate, diethyl carbonate, and ethylmethyl carbonate in a volume ratio of 10:30:45:15. A non-aqueous electrolyte was prepared by adding LiPF6 as a lithium salt and a compound represented by the chemical formula 1-1 to the organic solvent. The above lithium salt was added to the non-aqueous electrolyte at a molar concentration of 1.5 M. The compound represented by the above chemical formula 1-1 was added to the non-aqueous electrolyte at a content of 5 wt%. In the above non-aqueous electrolyte, the weight percentage of the fluoroethylene carbonate was 10.4 wt%, and the weight percentage of the 1,2-difluoroethylene carbonate was 31.5 wt%. (Lithium secondary battery manufacturing) A lithium secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte manufactured above was used. Example 6 (Manufacture of non-aqueous electrolyte) A non-aqueous electrolyte was prepared in the same manner as Example 1, except that the compound represented by the above chemical formula 1-1 was not used and the compound represented by the above chemical formula 1-2 was included in the non-aqueous electrolyte at a content of 5 wt%. (Lithium secondary battery manufacturing) A lithium secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte manufactured above was used. Example 7 (Manufacture of non-aqueous electrolyte) A non-aqueous electrolyte was prepared in the same manner as Example 1, except that the compound represented by the above chemical formula 1-1 was not used and the compound represented by the above chemical formula 1-3 was included in the non-aqueous electrolyte at a content of 5 wt%. (Lithium secondary battery manufacturing) A lithium secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte manufactured above was used. Example 8 (Manufacture of non-aqueous electrolyte) A non-aqueous electrolyte was prepared in the same manner as Example 1, except that the compound represented by the above chemical formula 1-1 was not used and the compound represented by the above chemical formula 1-4 was included in the non-aqueous electrolyte at a content of 5 wt%. (Lithium secondary battery manufacturing) A lithium secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte manufactured above was used. Example 9 (Manufacture of non-aqueous electrolyte) A non-aqueous electrolyte was prepared in the same manner as Example 1, except that the compound represented by the above chemical formula 1-1 was not used and the compound represented by the above chemical formula 1-9 was included in the non-aqueous electrolyte at a content of 5 wt%. (Lithium secondary battery manufacturing) A lithium secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte manufactured above was used. Comparative Example 1 (Manufacture of non-aqueous electrolyte) An organic solvent was prepared by mixing ethylene carbonate, 1,2-difluoroethylene carbonate, diethyl carbonate, and ethylmethyl carbonate in a volume ratio of 10:20:45:25. A non-aqueous electrolyte was prepared by adding LiPF6 as a lithium salt and a compound represented by the chemical formula 1-1 to the organic solvent. The above lithium salt was added to the non-aqueous electrolyte at a molar concentration of 1.5 M. The compound represented by the above chemical formula 1-1 was added to the non-aqueous electrolyte at a content of 5 wt%. In the above non-aqueous electrolyte, the weight percentage of the ethylene carbonate was 9.6 wt%, and the weight percentage of the 1,2-difluoroethylene carbonate was 22.1 wt%. (Lithium secondary battery manufacturing) A lithium secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte manufactured above was used. Comparative Example 2 (Manufacture of non-aqueous electrolyte) An organic solvent was prepared by mixing fluoroethylene carbonate, diethyl carbonate, and ethylmethyl carbonate in a volume ratio of 10:45:45. A non-aqueous electrolyte was prepared by adding LiPF6 as a lithium salt and a compound represented by the chemical formula 1-1 to the organic solvent. The above lithium salt was added to the non-aqueous electrolyte at a molar concentration of 1.5 M. The compound represented by the above chemical formula 1-1 was added to the non-aqueous electrolyte at a content of 5 wt%. In the above non-aqueous electrolyte, the weight percentage of the fluoroethylene carbonate was 11.6 wt%. (Lithium secondary battery manufacturing) A lithium secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte manufactured above was used. Comparative Example 3 (Manufacture of non-aqueous electrolyte) A non-aqueous electrolyte was prepared in the same manner as in Example 1, except that the compound represented by the above chemical formula 1-1 was not included in the non-aqueous electrolyte. (Lithium secondary battery manufacturing) A lithium secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte manufactured above was used. Comparative Example 4 (Manufacture of non-aqueous electrolyte) An organic solvent was prepared by mixing 1,2-difluoroethylene carbonate, diethyl carbonate, and ethylmethyl carbonate in a volume ratio of 20:45:35. A non-aqueous electrolyte was prepared by adding LiPF6 as a lithium salt and a compound represented by the chemical formula 1-1 to the organic solvent. The above lithium salt was added to the non-aqueous electrolyte at a molar concentration of 1.5 M. The compound represented by the above chemical formula 1-1 was added to the non-aqueous electrolyte at a content of 5 wt%. In the above non-aqueous electrolyte, the weight percentage of the 1,2-difluoroethylene carbonate was 22.6 wt%. (Lithium secondary battery manufacturing) A lithium secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte manufactured above was used. LiF content (μg / cm2 per cathode area) 2 )CO3 2- Content (per cathode area, μg / cm 2 )LiF content / CO3 2- Content Example 1 150851.8 Example 2 140751.9 Example 3 185951.9 Example 4 200802.5 Example 5 135801.7 Example 6 120751.6 Example 7 130801.6 Example 8 120701.7 Example 9 135851.6 Comparative Example 135400.9 Comparative Example 240401 Comparative Example 340351.1 Comparative Example 435301.2 Experimental Example 1: Evaluation of High-Temperature Cycle Charge-Discharge Performance The lithium secondary batteries manufactured in Examples 1 to 9 and Comparative Examples 1 to 4 above were charged to 4.2 V at 45°C under CC / CV, 0.33 C conditions using an electrochemical charger / discharger, and then discharged to 3.0 V under CC, 0.33 C conditions, which was considered one cycle, and 200 cycles of charge / discharge were performed, and the capacity retention rate, resistance increase rate, gas generation amount, and metal elution amount were evaluated as follows. Experimental Example 1-1: Capacity Retention Rate Evaluation After charging and discharging under the above conditions, the capacity retention rate was calculated using the formula below, and the results are shown in Table 2 below. Capacity retention rate (%) = {(discharge capacity after 200 cycles / discharge capacity after 1 cycle)} × 100 Experimental Example 1-2: Evaluation of Resistance Increase Rate After one cycle of charge and discharge, the discharge capacity after one cycle was measured using an electrochemical charger and discharger, the SOC was adjusted to 50%, and then a 2.5C pulse was applied for 10 seconds, and the initial resistance was calculated through the difference between the voltage before and after the pulse was applied. After 200 cycles of charge and discharge, the resistance after 200 cycles was calculated using the same method as above, and the resistance increase rate was calculated using the equation below, and the results are shown in Table 2 below. Resistance increase rate (%) = (Resistance after 200 cycles - Initial resistance) / Initial resistance × 100 Experimental Example 2: Evaluation of High-Temperature Storage Performance The lithium secondary batteries manufactured in Examples 1 to 9 and Comparative Examples 1 to 3 above were charged to 4.2 V / 55 mA under 0.33 C / 4.2 V constant current / constant voltage (CC / CV) conditions at room temperature and discharged to 2.5 V at 0.33 C to perform initial charging and discharging. Afterwards, they were charged to 4.2 V / 55 mA under 0.33 C / 4.2 V constant current / constant voltage (CC / CV) at room temperature and then stored at 60°C. Experimental Example 2-1: Capacity Retention Rate Evaluation After storage, the secondary batteries were charged to 4.2 V / 55 mA under constant current / constant voltage (CC / CV) conditions of 0.33 C / 4.2 V at room temperature and discharged to 2.5 V at 0.33 C to measure the capacity during discharge. Capacity retention rate (%) = (Discharge capacity after 8 weeks of storage / Initial discharge capacity) × 100 Experimental Example 2-2: Resistance Increase Rate Evaluation During the initial charge and discharge, after checking the capacity at room temperature, the battery was charged to SOC 50 based on the discharge capacity, discharged for 10 seconds at a current of 2.5 C, and the resistance was measured based on the difference in voltage drop at this time, which was used as the initial resistance. After 8 weeks of storage at 60°C, the resistance was measured using the same method, which was used as the final resistance, and the resistance increase rate was calculated using the following formula. The results are shown in Table 2 below. Resistance increase rate (%) = (final resistance - initial resistance) / (initial resistance) × 100 Experimental Example 1-1 Experimental Example 1-2 Experimental Example 2-1 Experimental Example 2-2 Capacity retention rate (%) Resistance increase rate (%) Capacity retention rate (%) Resistance increase rate (%) Example 19389410 Example 29479111 Example 3957919 Example 4986958 Example 59699010 Example 6928939 Example 7937928 Example 8938938 Example 9949949 Comparative Example 161555858 Comparative Example 275437145 Comparative Example 376407143 Comparative Example 474417343 Referring to Table 2, it can be confirmed that the lithium secondary batteries according to Examples 1 to 9, which include a non-aqueous electrolyte containing all of fluoroethylene carbonate, 1,2-difluoroethylene carbonate, and a compound represented by Chemical Formula 1, and a negative electrode containing a silicon-based active material, exhibit significantly superior cycle charge-discharge performance and high-temperature storage performance compared to Comparative Examples 1 to 4, which do not. Reference example Reference Example 1 (Manufacture of non-aqueous electrolyte) A non-aqueous electrolyte was prepared using the same method as in Comparative Example 1. (Lithium secondary battery manufacturing) Cathode active material (LiNi) 0.85 Co 0.05 Mn 0.07 Al 0.03 O2): Conductive agent (carbon nanotube): Binder (polyvinylidene fluoride) was added to N-methyl-2-pyrrolidone (NMP), a solvent, in a weight ratio of 97.74:0.70:1.56 to prepare a positive electrode mixture slurry (solid content 75.5 wt%). The positive electrode mixture slurry was applied to one surface of a positive electrode current collector (Al thin film) having a thickness of 15 ㎛, and dried and roll pressed to prepare a positive electrode. A negative electrode mixture slurry (solid content 50 wt%) was prepared by adding a negative electrode active material (a mixture of artificial graphite and natural graphite in a weight ratio of 50.3:49.7): conductive agent (carbon black): binder (styrene-butadiene rubber) to distilled water as a solvent in a weight ratio of 96.7:1.0:2.3. The negative electrode mixture slurry was applied to one surface of an 8 ㎛ thick negative electrode current collector (Cu thin film), and drying and roll pressing were performed to prepare a negative electrode. A polyethylene porous film separator was interposed between the positive and negative electrodes manufactured above in a dry room, and then the non-aqueous electrolyte manufactured above was injected to manufacture a secondary battery. Reference Example 2 A lithium secondary battery was manufactured in the same manner as in Reference Example 1, except that a non-aqueous electrolyte manufactured in the same manner as in Example 4 was used. Reference Example 3 A lithium secondary battery was manufactured in the same manner as in Reference Example 1, except that a non-aqueous electrolyte manufactured in the same manner as in Comparative Example 3 was used. Reference Example 4 A lithium secondary battery was manufactured in the same manner as in Reference Example 1, except that a non-aqueous electrolyte manufactured in the same manner as in Comparative Example 4 was used. Reference Experimental Example 1: Evaluation of High-Temperature Cycle Charge-Discharge Performance The experiment was conducted using the same method as Experimental Example 1 (Experimental Examples 1-1, 1-2). The results are shown in Table 3 below. Reference Experimental Example 2: High-temperature storage performance evaluation The experiment was conducted using the same method as Experimental Example 2 (Experimental Examples 2-1, 2-2). The results are shown in Table 3 below. Reference Experimental Example 1 Reference Experimental Example 2 Capacity Maintenance Rate (%) Resistance Increase Rate (%) Capacity Maintenance Rate (%) Resistance Increase Rate (%) Reference Example 169486252 Reference Example 263525855 Reference Example 366525958 Reference Example 465515953 Referring to Table 3, in the case of the lithium secondary batteries of Reference Examples 1 to 4 using only carbon-based active materials as negative active materials, the performance of Reference Example 2 (using the non-aqueous electrolyte used in Example 4) shows lower capacity retention rate and higher resistance increase rate during cycle charge / discharge and high-temperature storage compared to Reference Example 1 (using the non-aqueous electrolyte used in Comparative Example 1), Reference Example 3 (using the non-aqueous electrolyte used in Comparative Example 3), and Reference Example 4 (using the non-aqueous electrolyte used in Comparative Example 4). This is thought to be because the combined use of fluoroethylene carbonate and 1,2-difluoroethylene carbonate caused unnecessary problems in the carbon-based active material, such as acting as resistance. Therefore, through the experimental results of Table 3 above, it can be understood that the non-aqueous electrolyte of the present invention exhibits the desired life performance and high-temperature storage performance in a negative electrode containing a silicon-based active material and a lithium secondary battery.

Claims

1. Containing a positive electrode; a negative electrode; a separator interposed between the positive electrode and the negative electrode; and a non-aqueous electrolyte; The above negative electrode includes a negative electrode active material, The above negative active material includes a silicon-based active material, The above non-aqueous electrolyte is a lithium secondary battery comprising a lithium salt, fluoroethylene carbonate, 1,2-difluoroethylene carbonate and a compound represented by the following chemical formula 1: [Chemical Formula 1] In the above chemical formula 1, R1 includes a halogen, a nitrile group, a propargyl group, an ester group, an ether group, a ketone group, a carboxyl group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted alkoxy group, a boron group, a borate group, an isocyanate group, an isothiocyanate group, a silyl group, a siloxane group, a sulfone group, a sulfonate group, a sulfate group, or a combination of two or more thereof, and n is an integer from 0 to 6.

2. In claim 1, The above silicon-based active material includes silicon-based particles, The above silicon-based particles are lithium secondary batteries containing a compound represented by the following chemical formula A: [Chemical Formula A] Not. x In the above chemical formula A, 0≤x<2.

3. In claim 2, The above silicon particles are lithium secondary batteries made of Si.

4. In claim 1, A lithium secondary battery comprising at least one compound represented by the above chemical formula 1 selected from the group consisting of a compound represented by the following chemical formula 1-A and a compound represented by the following chemical formula 1-B: [Chemical Formula 1-A] [Chemical Formula 1-B] In the above chemical formulas 1-A and 1-B, R1 is as defined in the above chemical formula 1.

5. In claim 1, A lithium secondary battery comprising at least one compound represented by the above chemical formula 1 selected from the group consisting of compounds represented by the following chemical formulas 1-1 to 1-9: [Chemical Formula 1-1] [Chemical Formula 1-2] [Chemical Formula 1-3] [Chemical Formula 1-4] [Chemical Formula 1-5] [Chemical Formula 1-6] [Chemical Formula 1-7] [Chemical Formula 1-8] [Chemical Formula 1-9] .

6. In claim 1, A lithium secondary battery wherein the above fluoroethylene carbonate is included in the non-aqueous electrolyte at 3% to 20% by volume.

7. In claim 1, A lithium secondary battery wherein the above 1,2-difluoroethylene carbonate is included in the non-aqueous electrolyte at 10 to 35 volume%.

8. In claim 1, A lithium secondary battery, wherein the compound represented by the above chemical formula 1 is included in an amount of 0.1% to 10% by weight based on the weight of the non-aqueous electrolyte.

9. In claim 1, A lithium secondary battery wherein the volume ratio of the above fluoroethylene carbonate and the above 1,2-difluoroethylene carbonate is 5:95 to 50:

50.

10. In claim 1, A lithium secondary battery wherein the total amount of the fluoroethylene carbonate and the 1,2-difluoroethylene carbonate is greater than 10 wt% and less than or equal to 50 wt% based on the total weight of the non-aqueous electrolyte.

11. In claim 1, The above lithium salts are LiCl, LiBr, LiI, LiBF4, LiClO4, LiAlO4, LiAlCl4, LiPF6, LiSbF6, LiAsF6, LiB 10 Cl 10 , LiBOB (LiB(C2O4)2), LiCF3SO3, LiFSI (LiN(SO2F)2), LiCH3SO3, LiCF3CO2, LiCH3CO2, and LiBETI (LiN(SO2CF2CF3)2).

12. In claim 1, After activation of the above lithium secondary battery, a solid electrolyte interface film is formed on the negative electrode, The above solid electrolyte interface film contains an inorganic component, The above inorganic components are LiF and CO3 2- Including, The above CO3 2- A lithium secondary battery having a weight ratio of the LiF to the weight of the lithium secondary battery of 1.4 or more.

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