Non-aqueous electrolyte solution for lithium secondary battery and lithium secondary battery containing the same

Abstract

The present disclosure provides a non-aqueous electrolyte solution for a lithium secondary battery, which can form a solid electrolyte interface (SEI), and a lithium secondary battery having improved battery performance by including the non-aqueous electrolyte solution. Specifically, the non-aqueous electrolyte solution for a secondary battery includes a lithium salt, a non-aqueous organic solvent, a first additive, and a second additive, wherein the non-aqueous electrolyte solution for a secondary battery may include an oligomer as a first additive, the oligomer including a repeating unit derived from a monomer represented by Formula 1 and a repeating unit derived from a monomer represented by Formula 2, and may include at least one selected from the group consisting of a nitrile compound, a lithium salt compound, and a cyclic carbonate compound as a second additive.

Description

Technical Field

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Korean Patent Application Nos. 10-2021-0012449, 10-2021-0012450, and 10-2021-0012451, filed on January 28, 2021, and 10-2022-0011966, filed on January 27, 2022, the disclosures of which are incorporated herein by reference. Technical Field

[0004] The present disclosure provides a nonaqueous electrolyte solution for a lithium secondary battery and a lithium secondary battery including the nonaqueous electrolyte solution. Background Art

[0005] Modern society's reliance on electricity is increasing, and accordingly, electricity production is also increasing. To address the environmental issues arising from this process, renewable energy generation is attracting attention as a next-generation power generation system.

[0006] For renewable energy, due to its intermittent power generation characteristics, large-capacity energy storage devices are essential for stable power supply. Among energy storage devices, lithium-ion batteries have the highest energy density currently commercialized and therefore have attracted much attention.

[0007] Lithium-ion batteries are composed of a positive electrode formed of a transition metal oxide containing lithium, a negative electrode capable of storing lithium, an electrolyte solution containing an organic solvent containing a lithium salt, and a separator.

[0008] Since the positive electrodes in these components store energy through redox reactions of transition metals, transition metal oxides must be substantially contained in the positive electrodes. Furthermore, the negative electrodes, which include lithium, graphite, and / or silicon-based active materials, can exhibit charge and discharge capacities through electrochemical oxidation / reduction reactions at 0.2 V or 0.5 V (vs. (Li / Li+)) or lower, respectively.

[0009] Because the operating voltage range of lithium-, graphite-, and silicon-based active materials is lower than the electrochemical stability window of organic non-aqueous electrolyte solutions, these solutions become electrochemically unstable within the operating voltage range of the negative electrode active material. As a result, while the reductive decomposition of the non-aqueous electrolyte solution proceeds, a passivation layer, known as a solid electrolyte interphase (SEI), forms on the surface of the non-aqueous electrolyte solution.

[0010] SEI is a passivation layer with high lithium ion conductivity but low electronic conductivity, in which it not only suppresses additional reductive decomposition of the electrolyte solution, but also has the property of enabling the operation of lithium ion batteries because it has the property of allowing lithium ion transport but inhibiting electron transport.

[0011] However, SEI is damaged and loses its passivation ability when exposed to high temperatures for a long time. As a result, lithium and electrons in the battery are additionally consumed, and additional electrolyte solution decomposition occurs, leading to a degradation of the battery's electrochemical performance or thermal runaway due to an increase in the battery's internal temperature.

[0012] Furthermore, the performance of the positive electrode deteriorates due to the structural collapse of the positive electrode active material during repeated charge and discharge. Specifically, during the structural collapse of the positive electrode, metal ions that have been dissolved from the positive electrode surface are electro-deposited onto the negative electrode, thereby reducing battery performance. This battery performance degradation phenomenon tends to increase further when the potential of the positive electrode increases or when the battery is exposed to high temperatures.

[0013] To improve these various problems, there is an urgent need to develop a non-aqueous electrolyte solution for lithium secondary batteries that can improve the performance and stability of secondary batteries by forming a strong film on the electrode surface even in a high-temperature environment. Summary of the Invention

[0014] Technical issues

[0015] One aspect of the present disclosure provides a non-aqueous electrolyte solution for a lithium secondary battery, wherein high-temperature safety is enhanced by including an oligomer containing an acrylate-based cyanide (-CN, cyanide) functional group and a compound capable of improving film formation as additives.

[0016] Another aspect of the present disclosure provides a lithium secondary battery including the nonaqueous electrolyte solution for a lithium secondary battery.

[0017] Technical Solution

[0018] According to one aspect of the present disclosure, there is provided a non-aqueous electrolyte solution for a lithium secondary battery, comprising:

[0019] lithium salt; a nonaqueous organic solvent; a first additive; and a second additive,

[0020] wherein the nonaqueous electrolyte solution for a lithium secondary battery includes an oligomer as a first additive, the oligomer comprising a repeating unit derived from a monomer represented by the following formula 1 and a repeating unit derived from a monomer represented by the following formula 2, and

[0021] At least one selected from the group consisting of nitrile compounds, lithium salt compounds, and cyclic carbonate compounds is included as the second additive.

[0022] [Formula 1]

[0023]

[0024] In formula 1,

[0025] R' is hydrogen or an alkyl group having 1 to 3 carbon atoms, and

[0026] R1 is an alkylene group having 1 to 20 carbon atoms or -(R2) o O(R3) p -, wherein R2 and R3 are each independently an alkylene group having 1 to 20 carbon atoms, o is an integer of 1 to 3, and p is an integer of 0 to 3.

[0027] [Formula 2]

[0028]

[0029] In formula 2,

[0030] R" is hydrogen or an alkyl group having 1 to 3 carbon atoms,

[0031] R4 is an alkylene group having 1 to 10 carbon atoms, and

[0032] R5 is an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, a heteroaryl group having 3 to 10 carbon atoms, or a cycloalkyl group having 3 to 10 carbon atoms.

[0033] According to another aspect of the present disclosure, there is provided a lithium secondary battery comprising:

[0034] a positive electrode comprising a positive electrode active material;

[0035] a negative electrode comprising a negative electrode active material;

[0036] a separator disposed between the negative electrode and the positive electrode; and

[0037] The non-aqueous electrolyte solution for a secondary battery of the present disclosure.

[0038] Beneficial effects

[0039] Since the nonaqueous electrolyte solution for a lithium secondary battery of the present disclosure includes an oligomer having an acrylate-based cyanide functional group repeating unit as a first additive, it can suppress side reactions between the positive electrode and the electrolyte solution at high temperatures by forming a strong film on the positive electrode surface.

[0040] In addition, since the non-aqueous electrolyte solution of the present disclosure includes a second additive capable of forming a stable film on the surface of the negative electrode together with the first additive, side reactions between the negative electrode and the electrolyte solution can be prevented by forming a strong passivation film with improved stability and durability on the surface of the negative electrode, and the effect of suppressing resistance increase can be achieved.

[0041] If the nonaqueous electrolyte solution of the present disclosure is included, a lithium secondary battery having improved cycle characteristics and high-temperature stability may be obtained. DETAILED DESCRIPTION

[0042] Hereinafter, the present disclosure will be described in more detail.

[0043] It should be understood that the words or terms used in the specification and claims should not be interpreted as having the meanings defined in commonly used dictionaries. It should be further understood that the words or terms should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and the technical concept of the invention, with the principle that the inventor can appropriately define the meaning to best explain the invention.

[0044] Unless otherwise stated in this disclosure, "*" indicates a moiety attached to the main chain of an oligomer or between the ends of a molecular formula.

[0045] The term "substituted" in the present disclosure refers to that a hydrogen atom bonded to a carbon atom of a compound is replaced by another substituent, wherein the substituted position is not limited, as long as it is the position where the hydrogen atom is substituted, i.e., the position that can be substituted by a substituent. In the above-mentioned substitution, two or more substituents can be substituted, wherein the two or more substituents can be identical or different from each other. The substituent can include at least one selected from oxygen, at least one halogen group, nitrile group, nitro group, hydroxyl group, alkyl group, cycloalkyl group, aryl group and heterocyclic group with 1 to 5 carbon atoms, or can include a structure in which two or more substituents in the example substituents are connected to each other. Specifically, the substituent can be at least one halogen group, hydroxyl group or alkyl group with 1 to 5 carbon atoms.

[0046] In addition, in this specification, unless "only" is used, when the terms "including", "comprising", "consisting of", or "having" are used, other parts may be added. When a component is expressed in the singular, the plural is also included unless otherwise specified.

[0047] In this specification, unless otherwise specifically stated, the expression "%" means % by weight.

[0048] Non-aqueous electrolyte solutions for secondary batteries

[0049] A non-aqueous electrolyte solution for a secondary battery according to the present disclosure includes:

[0050] lithium salt; a non-aqueous organic solvent; a first additive; and a second additive,

[0051] wherein the nonaqueous electrolyte solution for a secondary battery includes an oligomer as a first additive, the oligomer comprising a repeating unit derived from a monomer represented by the following Formula 1 and a repeating unit derived from a monomer represented by the following Formula 2, and

[0052] At least one selected from the group consisting of a nitrile compound, a lithium salt compound, and a cyclic carbonate compound may be included as the second additive.

[0053] [Formula 1]

[0054]

[0055] In formula 1,

[0056] R' is hydrogen or an alkyl group having 1 to 3 carbon atoms, and

[0057] R1 is an alkylene group having 1 to 20 carbon atoms or -(R2) o O(R3) p -, wherein R2 and R3 are each independently an alkylene group having 1 to 20 carbon atoms, o is an integer of 1 to 3, and p is an integer of 0 to 3.

[0058] [Formula 2]

[0059]

[0060] In formula 2,

[0061] R" is hydrogen or an alkyl group having 1 to 3 carbon atoms,

[0062] R4 is an alkylene group having 1 to 10 carbon atoms, and

[0063] R5 is an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, a heteroaryl group having 3 to 10 carbon atoms, or a cycloalkyl group having 3 to 10 carbon atoms.

[0064] (A) Lithium salt

[0065] First, the lithium salt will be described.

[0066] Any lithium salt commonly used in electrolyte solutions for lithium secondary batteries may be used as the lithium salt without limitation. For example, the lithium salt may include Li+ as a cation and may include a cation selected from the group consisting of F - 、Cl - Br - , I - 、NO3 -、N(CN)2 - 、BF4 - 、ClO4 - 、B 10 Cl 10 - 、AlCl4 - 、AlO4 - PF6 - CF3SO3 - 、CH3CO2 - CF3CO2 - 、AsF6 - 、SbF6 - 、CH3SO3 - 、(CF3CF2SO2)2N - 、(CF3SO2)2N - 、(FSO2)2N - 、BF2C2O4 - BC4O8 - PF4C2O4 - PF2C4O8 - 、(CF3)2PF4 - 、(CF3)3PF3 - 、(CF3)4PF2 - 、(CF3)5PF - 、(CF3)6P - 、C4F9SO3 - CF3CF2SO3 - CF3CF2(CF3)2CO - 、(CF3SO2)2CH - CF3(CF2)7SO3 - and SCN - At least one of the constituted group serves as an anion.

[0067] Specifically, the lithium salt may include a lithium salt selected from the group consisting of LiCl, LiBr, LiI, LiBF4, LiClO4, LiB 10 Cl 10, LiAlCl4, LiAlO4, LiPF6, LiCF3SO3, LiCH3CO2, LiCF3CO2, LiAsF6, LiSbF6, LiCH3SO3, LiN(SO2F)2(Lithiumbis(fluorosulfonyl)imide, LiFSI), LiN(SO2CF2CF3)2(lithium bis(pentafluoroethanesulfonyl)imide, LiBETI) and LiN(SO2CF3)2(lithium bis(trifluoromethanesulfonyl)imide, LiTFSI), or a mixture of two or more thereof, and may particularly include at least one selected from the group consisting of LiPF6, LiFSI and LiTFSI having high ionic conductivity.

[0068] The lithium salt may be appropriately varied within the normal usage range, but may be included in the electrolyte solution at a concentration of 0.8M-4.0M, for example, 1.0M-3.0M, to obtain the best effect of forming a film that prevents corrosion on the electrode surface.

[0069] When the concentration of the lithium salt is within the above range, the viscosity of the nonaqueous electrolyte solution can be controlled to achieve optimal impregnation, and by increasing the mobility of lithium ions, the capacity characteristics and cycle characteristics of the lithium secondary battery can be improved.

[0070] (B) Non-aqueous organic solvent

[0071] Furthermore, the nonaqueous organic solvent will be described below.

[0072] Various organic solvents commonly used in non-aqueous electrolyte solutions can be used as the non-aqueous organic solvent without limitation, wherein the type of the non-aqueous organic solvent is not limited as long as the non-aqueous organic solvent can minimize decomposition due to oxidation reaction during charging and discharging of the secondary battery and can exhibit desired characteristics together with the additives.

[0073] Specifically, the non-aqueous organic solvent may include (i) a cyclic carbonate-based organic solvent, (ii) a linear carbonate-based organic solvent, (iii) a linear ester-based organic solvent, or a mixed organic solvent thereof.

[0074] (i) Cyclic carbonate organic solvents are highly viscous organic solvents that can effectively decompose lithium salts in non-aqueous electrolyte solutions due to their high dielectric constant. Specific examples thereof include at least one organic solvent selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentadienyl carbonate, 2,3-pentadienyl carbonate, and vinylene carbonate. The cyclic carbonate organic solvents may include at least one of ethylene carbonate and propylene carbonate.

[0075] (ii) The linear carbonate organic solvent is an organic solvent having low viscosity and low dielectric constant, wherein specific examples of the linear carbonate organic solvent may be at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate, and ethyl propyl carbonate. Specifically, the linear carbonate organic solvent may include dimethyl carbonate and ethyl methyl carbonate.

[0076] (iii) Linear ester organic solvents are solvents that have relatively higher stability than cyclic carbonate organic solvents during high temperature and high pressure operation. They can improve the disadvantage of cyclic carbonate organic solvents in generating gas during high temperature operation and achieve high ionic conductivity.

[0077] As a representative example, (iii) the linear ester organic solvent may include at least one organic solvent selected from methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate, specifically including at least one of ethyl propionate and propyl propionate.

[0078] Furthermore, in order to prepare an electrolyte solution having high ionic conductivity in the present disclosure, the non-aqueous organic solvent may further include (iv) a cyclic ester organic solvent, if necessary.

[0079] (iv) The cyclic ester organic solvent may include at least one selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone.

[0080] Unless otherwise specified, the rest of the non-aqueous electrolyte solution of the present disclosure except the lithium salt, the first additive, and the second additive may be a non-aqueous organic solvent.

[0081] (C) First additive

[0082] The non-aqueous electrolyte solution for a lithium secondary battery of the present disclosure may include an oligomer containing an acrylate-based cyanide (—CN, cyanide) functional group as a first additive.

[0083] Specifically, the oligomer may include a repeating unit derived from a monomer represented by Formula 1 below and a repeating unit derived from a monomer represented by Formula 2 below.

[0084] [Formula 1]

[0085]

[0086] In formula 1,

[0087] R' is hydrogen or an alkyl group having 1 to 3 carbon atoms, and

[0088] R1 is an alkylene group having 1 to 20 carbon atoms or -(R2) o O(R3) p -, wherein R2 and R3 are each independently an alkylene group having 1 to 20 carbon atoms, o is an integer of 1 to 3, and p is an integer of 0 to 3.

[0089] [Formula 2]

[0090]

[0091] In formula 2,

[0092] R" is hydrogen or an alkyl group having 1 to 3 carbon atoms,

[0093] R4 is an alkylene group having 1 to 10 carbon atoms, and

[0094] R5 is an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, a heteroaryl group having 3 to 10 carbon atoms, or a cycloalkyl group having 3 to 10 carbon atoms.

[0095] Specifically, since the oligomer of the present disclosure includes a repeating unit containing an acrylate backbone and a cyanide group (-CN, nitrile group) with a strong binding force to metal ions as a terminal functional group, it can form a stable film by forming a strong bond with the electrode surface, particularly the positive electrode surface. In addition, since the cyanide group easily adsorbs metal ions dissolved from the positive electrode by the charge and discharge process of the secondary battery or the chemical dissolution reaction of the electrolyte solution, the effect of suppressing the dissolution of metal ions from the positive electrode, that is, the effect of suppressing the generation of metal ions in the battery, is excellent. Therefore, the high temperature durability, high temperature storage characteristics and high temperature stability of the secondary battery can be improved.

[0096] The oligomer included as the first additive in the present disclosure may include an oligomer represented by Formula 3 below.

[0097] [Formula 3]

[0098]

[0099] In formula 3,

[0100] R' and R" are each independently hydrogen or an alkyl group having 1 to 3 carbon atoms,

[0101] R1 is an alkylene group having 1 to 10 carbon atoms or -(R2) o O(R3) p -, wherein R2 and R3 are each independently an alkylene group having 1 to 10 carbon atoms, o is an integer from 1 to 3, and p is an integer from 0 to 3,

[0102] R4 is an alkylene group having 1 to 10 carbon atoms,

[0103] R5 is an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, a heteroaryl group having 3 to 10 carbon atoms, or a cycloalkyl group having 3 to 10 carbon atoms, and

[0104] The molar ratio of n:m is in the range of 1:99 to 99:1.

[0105] In the oligomers of the present disclosure, the expression "*" represents a portion connected to the main chain or the end of the oligomer, wherein the two end groups of the oligomer may be the same or different from each other. Specifically, the end of the oligomer may each independently be an alkyl group, an alkoxy group, a hydroxyl group, an aldehyde group, an ester group, a halogen group, a halide group, a vinyl group, a (meth)acrylate group, a carboxyl group, a phenyl group, an amino group, an amide group or a sulfonyl group, and specifically, the end group may be an alkyl group having 1 to 5 carbon atoms.

[0106] Specifically, in Formula 3, R' and R" are each independently hydrogen or an alkyl group having 1 or 2 carbon atoms, R1 is an alkylene group having 1 to 6 carbon atoms or -(R2) o O(R3) p -, wherein R2 and R3 are each independently an alkylene group having 1 to 6 carbon atoms, o is an integer from 1 to 3, p is an integer from 0 to 3, R4 is an alkylene group having 1 to 6 carbon atoms, R5 is an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 8 carbon atoms, a heteroaryl group having 3 to 8 carbon atoms, or a cycloalkyl group having 3 to 8 carbon atoms, and the molar ratio of n:m may be in the range of 20:80 to 90:10.

[0107] In addition, in Formula 3, R' and R" are each independently hydrogen or an alkyl group having 1 or 2 carbon atoms, R1 is an alkylene group having 1 to 6 carbon atoms or -(R2) o O(R3) p-, wherein R2 and R3 are each independently an alkylene group having 1 to 6 carbon atoms, o is an integer from 1 to 3, p is an integer from 0 to 3, R4 is an alkylene group having 1 to 6 carbon atoms, R5 is an aryl group having 6 to 8 carbon atoms, a heteroaryl group having 3 to 8 carbon atoms, or a cycloalkyl group having 3 to 8 carbon atoms, and the molar ratio of n:m may be in the range of 30:70 to 90:10.

[0108] More specifically, the oligomer represented by Formula 3 may include at least one selected from the group consisting of oligomers represented by the following Formulae 3A to 3F.

[0109] [Formula 3A]

[0110]

[0111] In Formula 3A,

[0112] The molar ratio of n1:m1 is in the range of 1:99-99:1.

[0113] [Formula 3B]

[0114]

[0115] In Formula 3B,

[0116] The molar ratio of n2:m2 is in the range of 1:99-99:1.

[0117] [Formula 3C]

[0118]

[0119] In Formula 3C,

[0120] The molar ratio of n3:m3 is in the range of 1:99-99:1.

[0121] [Formula 3D]

[0122]

[0123] In formula 3D,

[0124] The molar ratio of n4:m4 is in the range of 1:99-99:1.

[0125] [Formula 3E]

[0126]

[0127] In Formula 3E,

[0128] The molar ratio of n5:m5 is in the range of 1:99-99:1.

[0129] [Formula 3F]

[0130]

[0131] In Formula 3F,

[0132] The molar ratio of n6:m6 is in the range of 1:99-99:1.

[0133] The weight average molecular weight (Mw) of the oligomer of the present disclosure can be controlled by the number of repeating units and can be in the range of about 1,000 g / mol to about 1,500,000 g / mol, particularly 2,000 g / mol to 1,200,000 g / mol, and more particularly 5,000 g / mol to 500,000 g / mol. When the weight average molecular weight of the oligomer is within the above range, a uniform non-aqueous electrolyte solution with high ionic conductivity can be prepared by ensuring affinity with the solvent of the non-aqueous electrolyte solution.

[0134] Weight average molecular weight can be measured using a gel permeation chromatography (GPC) device, and unless otherwise indicated, molecular weight can represent weight average molecular weight. For example, in the present disclosure, weight average molecular weight is measured using Agilent Technologies' 1200 series under GPC conditions, in which case Agilent Technologies' PL mixed B column can be used, and tetrahydrofuran (THF) can be used as a solvent.

[0135] In addition, the oligomer of the present disclosure may be present in an amount of 0.1 wt % to 5.0 wt % based on the total weight of the non-aqueous electrolyte solution for a lithium secondary battery.

[0136] If the amount of the oligomer is within the above range, the effect of improving stability and high temperature performance can be obtained. Specifically, when the amount of the oligomer is 0.1% by weight or more, a stable film can be formed and flame retardant effects can be achieved, and when the amount of the oligomer is 5.0% by weight or less, the ionic conductivity of the non-aqueous electrolyte solution for lithium secondary batteries can be prevented from decreasing, and the formation of an uneven film on the surface or the increase in side reactions can be prevented. In addition, since the decrease in moisture retention can be prevented by suppressing the increase in the viscosity of the non-aqueous electrolyte solution for lithium secondary batteries, the decrease in capacity characteristics can be improved.

[0137] Specifically, the oligomer of the present disclosure may be present in an amount of 0.1 wt % to 3.0 wt % based on the total weight of the non-aqueous electrolyte solution for a lithium secondary battery.

[0138] (D) Second additive

[0139] The nonaqueous electrolyte solution for a lithium secondary battery of the present disclosure may further include a second additive to obtain a synergistic effect of improving film formation on an electrode surface by mixing with the oligomer included as the first additive.

[0140] The second additive may include at least one selected from the group consisting of a nitrile compound, a lithium salt compound, and a cyclic carbonate compound.

[0141] (D-1) Nitrile compounds

[0142] The non-aqueous electrolyte solution for a lithium secondary battery of the present disclosure may include a nitrile compound as a second additive.

[0143] Due to the low volatility of the solvent, nitrile compounds can improve the safety of non-aqueous electrolyte solutions. For example, they exist in solid form at room temperature and can form a uniform and strong film on the positive and negative electrodes during battery operation to reduce the reaction between the electrodes and the non-aqueous electrolyte solution, which can improve the durability and high-rate charge / discharge characteristics of the battery.

[0144] The nitrile compound may include a compound containing at least one cyanide group (-CN, nitrile group) as a terminal functional group, and specifically may include at least one selected from succinonitrile (SN), adiponitrile (1,4-dicyanobutane or 1,6-adiponitrile), dicyanobutene (DCB), ethylene glycol bis(propionitrile) ether, hexanetrionitrile (HTCN), acetonitrile, propionitrile, butyronitrile, valeronitrile, octanonitrile, heptanenitrile, cyclopentanenitrile, cyclohexanenitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, benzyl cyanide, 2-fluorophenyl acetonitrile and 4-fluorophenyl acetonitrile, more specifically, may include at least one selected from the group consisting of succinonitrile, adiponitrile, dicyanobutene, ethylene glycol bis(propionitrile) ether and hexanetrionitrile (HTCN), which can serve as a supplement capable of forming a more stable solid electrolyte interface (SEI) on the surface of the negative electrode.

[0145] The nitrile compound may be present in a weight ratio of 0.01 to 100 based on the weight of the oligomer as the first additive.

[0146] If the nitrile compound is included within the above-mentioned amount range, since a stable and strong SEI may be formed on the surface of the negative electrode, and the formation of an uneven film due to excessive use of additives or occurrence of side reactions and the increase in resistance due to the negative electrode reduction reaction can be suppressed, the effect of improving high temperature performance and stability can be exhibited.

[0147] Specifically, the weight ratio of the oligomer as the first additive to the nitrile compound may be in the range of 1:0.05 to 1:50, for example, 1:0.1 to 1:30.

[0148] (D-2) Lithium Salt Compound

[0149] The nonaqueous electrolyte solution for a lithium secondary battery of the present disclosure may include a lithium salt compound as a second additive.

[0150] The lithium salt compound is a compound different from the lithium salt contained in the non-aqueous electrolyte solution, wherein it may include a compound in the form of a lithium salt, which can form a uniform and strong film on the positive electrode and the negative electrode during battery operation to reduce the side reaction between the electrode and the non-aqueous electrolyte solution and inhibit the decomposition of the solvent in the non-aqueous electrolyte solution. By including the lithium salt compound, the mobility of lithium ions can be increased, the durability of the battery can be improved, and the high-rate charge / discharge characteristics of the battery can be improved.

[0151] Lithium salt compounds can be divided into (i) phosphate-based lithium and (ii) boron-based lithium.

[0152] (i) The phosphate-based lithium may include lithium difluorophosphate (LiDFP) or lithium difluorobis(oxalato)phosphate (LiDFOP).

[0153] Furthermore, (ii) boron lithium can be divided into (ii-1) boron lithium halide and (ii-2) boron lithium oxalate.

[0154] (ii-1) The boron halide lithium may include lithium tetrafluoroborate (LiBF4) or lithium tetrachloroborate (LiBCl4), and specifically may be lithium tetrafluoroborate (LiBF4).

[0155] As the (ii-2) lithium borooxalate, lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiODFB) or lithium dichloro(oxalato)borate (LiODCB) can be used. In particular, considering the optimization of high-temperature storage characteristics and life characteristics, the (ii-2) lithium borooxalate can be lithium bis(oxalato)borate (LiBOB) or lithium difluoro(oxalato)borate (LiODFB).

[0156] Specifically, the lithium salt compound may include at least one selected from lithium difluorophosphate (LiDFP), lithium difluorobis(oxalato)phosphate (LiDFOP), LiBF4, lithium bis(oxalato)borate (LiBOB) and lithium difluoro(oxalato)borate (LiODFB), and more specifically may include at least one of lithium bis(oxalato)borate (LiBOB) and lithium difluoro(oxalato)borate (LiODFB).

[0157] Since the non-aqueous electrolyte solution for secondary batteries of the present disclosure stabilizes the SEI of the positive and negative electrodes by jointly using a lithium salt compound and an oligomer that can help form a negative electrode film, the overall performance of the lithium secondary battery, such as high-rate charge / discharge characteristics, high-temperature storage characteristics, and life characteristics, can be improved.

[0158] In the case of including the lithium salt compound as the second additive, the lithium salt compound may be present in a weight ratio of 0.01:100 to 1:100 based on the weight of the oligomer as the first additive.

[0159] If the lithium salt compound is included in the above amount range, the free radicals generated as by-products further react with other cyclic carbonates, while destroying the ring (bond) through an oxidation reaction, and a polymerization reaction is carried out in this process. While reacting with this mechanism, a stable film can be formed on the positive electrode surface.

[0160] Specifically, to prevent side reactions caused by residual lithium salt compounds after film formation, the lithium salt compound may be present at a weight ratio of 100 or less, for example, 70 or less. If the weight ratio of the lithium salt compound is greater than 100, performance degradation may occur due to side reactions of the copolymer electrolyte solution caused by free radicals generated during the reduction process. In addition, due to the decomposition of the electrolyte solution and additives, the products of the side reactions may accumulate on the electrode film, thereby increasing the resistance of the battery or causing degradation of high-rate, high-temperature durability, and cycle characteristics.

[0161] In addition, the lithium salt compound may be present at a weight ratio of 0.01 or more to ensure the amount of free radicals. If the weight ratio of the lithium salt compound is less than 0.01, the amount of free radicals generated by the lithium salt compound during the film formation process is absolutely insufficient, thereby reducing the chain reaction of film formation, generating defects on the film surface, and affecting performance degradation.

[0162] Specifically, the oligomer as the first additive and the lithium salt compound may be present in a weight ratio of 1:0.1 to 1:70.

[0163] (D-3) Cyclic carbonate compounds

[0164] The non-aqueous electrolyte solution for a lithium secondary battery of the present disclosure may include a cyclic carbonate-based compound other than the non-aqueous organic solvent as a second additive.

[0165] Cyclic carbonate compounds are additives that can be used with oligomers to aid film formation. Because they form a stable film due to the double bonds contained in their cyclic structure and are reduced on the anode surface, they effectively suppress gas generation and side reactions with the electrolyte solution during anode film formation. Films formed from cyclic carbonate compounds can improve lifespan and high-temperature durability.

[0166] As a representative example, the cyclic carbonate compound may include at least one selected from the group consisting of vinylene carbonate (VC), vinyl ethylene carbonate (VEC) and fluoroethylene carbonate (FEC), and more specifically may include vinyl ethylene carbonate (VEC) and fluoroethylene carbonate (FEC) at the same time.

[0167] Since fluoroethylene carbonate can form a thinner negative electrode film than other fluorine-substituted or unsubstituted cyclic carbonate compounds, it can reduce the resistance in the battery and thus more effectively improve performance. In addition, since fluoroethylene carbonate can inhibit the reduction reaction of ethylene carbonate used as a non-aqueous organic solvent, it can also help improve the cycle characteristics. Therefore, the uniform and strong film thus formed can further improve the durability and high-rate charge / discharge characteristics of the battery by reducing the reaction between the electrode and the non-aqueous organic solvent.

[0168] In the case of including the cyclic carbonate-based compound as the second additive, the cyclic carbonate-based compound may be present in a weight ratio of 0.001 to 150 based on the weight of the oligomer as the first additive.

[0169] If the cyclic carbonate compound is included in the above-mentioned amount ratio, then since a stable and strong SEI may be formed on the negative electrode surface, and since the occurrence of excessive use of additives or side reactions and the increase in resistance due to the negative electrode reduction reaction can be suppressed, it is possible to show the effect of improving high temperature performance and stability. That is, when the weight ratio of the cyclic carbonate compound is more than 0.001, a stable film can be formed on the negative electrode surface, and the effect of improving high temperature life and safety can be shown. In addition, when the weight ratio of the cyclic carbonate compound is less than 150, there will be no uneven film formation due to excessive use and side reactions, and the problem of increased resistance due to the negative electrode reduction reaction, which can improve high temperature performance and safety.

[0170] Specifically, the weight ratio of the oligomer as the first additive to the cyclic carbonate compound may be in the range of 1:0.05 to 1:50, for example, 1:0.1 to 1:30.

[0171] The second additive may be used in an amount of less than 11 wt % based on the total weight of the nonaqueous electrolyte solution, and may be used by appropriately adjusting a relative weight ratio of the second additive to the first oligomer according to each type of the second additive.

[0172] Therefore, since the non-aqueous electrolyte solution for lithium secondary batteries disclosed herein can form a more stable SEI on the positive and negative electrode surfaces by using a second additive that can help film formation together with an oligomer containing an acrylic cyanide terminal functional group, the overall performance of the lithium secondary battery, such as high-rate charge and discharge characteristics, high-temperature storage characteristics, and life characteristics, can be improved.

[0173] (E) Third additive

[0174] In addition, if necessary, the non-aqueous electrolyte solution for a lithium secondary battery of the present disclosure may further include a third additive to prevent negative electrode collapse due to decomposition of the non-aqueous electrolyte solution under a high power environment or to further improve low-temperature high-rate discharge characteristics, high-temperature stability, prevent overcharging, and inhibit battery expansion at high temperatures.

[0175] Examples of the third additive may include at least one selected from the group consisting of sultone compounds, sulfate compounds, phosphate or phosphite compounds, benzene compounds, amine compounds, and silane compounds.

[0176] The sultone compound may be, for example, at least one selected from 1,3-propane sultone (PS), 1,4-butane sultone, ethane sultone, 1,3-propene sultone (PRS), 1,4-butene sultone, and 1-methyl-1,3-propene sultone.

[0177] The sulfate ester compound may be, for example, ethylene sulfate (Esa), trimethylene sulfate (TMS), or methyl trimethylene sulfate (MTMS).

[0178] The phosphate or phosphite compound can be, for example, at least one selected from lithium difluoro(bisoxalato)phosphate, lithium difluorophosphate, tris(trimethylsilyl)phosphate, tris(trimethylsilyl)phosphite, tris(2,2,2-trifluoroethyl)phosphate and tris(trifluoroethyl)phosphite.

[0179] The benzene compound may be fluorobenzene, the amine compound may be triethanolamine or ethylenediamine, and the silane compound may be tetravinylsilane.

[0180] Two or more compounds may be mixed and used as the third additive, and the third additive may be present in an amount of 10 wt % or less based on the total weight of the nonaqueous electrolyte solution to prevent a side reaction caused by an excess of the additive.

[0181] lithium secondary batteries

[0182] Next, a lithium secondary battery according to the present disclosure will be described.

[0183] A lithium secondary battery according to the present disclosure includes:

[0184] a positive electrode comprising a positive electrode active material;

[0185] a negative electrode comprising a negative electrode active material;

[0186] a separator disposed between the negative electrode and the positive electrode; and

[0187] The non-aqueous electrolyte solution for a lithium secondary battery of the present disclosure is described above.

[0188] The lithium secondary battery of the present disclosure may be prepared by forming an electrode assembly in which a positive electrode, a negative electrode, and a separator disposed therebetween are sequentially stacked, such that the electrode assembly is housed in a battery case, and then the nonaqueous electrolyte solution of the present disclosure is injected.

[0189] The preparation method of the lithium secondary battery of the present disclosure may adopt a typical method known in the art. The preparation method of the lithium secondary battery of the present disclosure is specifically described as follows.

[0190] (1) Positive electrode

[0191] The positive electrode according to the present disclosure may include a positive electrode active material layer including a positive electrode active material, and if necessary, the positive electrode active material layer may further include a conductive agent and / or a binder.

[0192] The positive electrode active material is a compound capable of reversibly inserting and deinserting lithium, wherein the positive electrode active material can specifically include a lithium composite metal oxide, which includes lithium and at least one metal selected from the group consisting of nickel (Ni), cobalt (Co), manganese (Mn), iron (Fe) and aluminum (Al), and can particularly include a high nickel (Ni) lithium composite metal oxide in which the Ni content is 0.55 or more.

[0193] Specifically, a typical example of the positive electrode active material can be Li(Ni 0.6 Mn 0.2 Co 0.2 )O2、Li(Ni 0.7 Mn 0.2 0Co 0.10 )O2、Li(Ni0.8 Mn 0.1 Co 0.1 )O2, Li[Ni 0.8 Co 0.15 Al 0.05 O2, Li[Ni 0.86 Mn 0.07 Co 0.05 Al 0.02 O2, or Li(Ni 0.9 Mn 0.05 Co 0.05 )O2.

[0194] For a lithium composite metal oxide having a high Ni content, although it has the advantage of enabling a high-capacity battery, there is a problem that Ni 2+ cations dissolve from the positive electrode into the non-aqueous electrolyte solution, and Ni 2+ cations react with the passivation film (SEI) of the negative electrode to decompose the SEI. As a result, side reactions occur due to a part of the negative electrode active material being exposed to the non-aqueous electrolyte solution, so the capacity and life characteristics decrease and the resistance increases. Therefore, for a lithium composite metal oxide having a high Ni content, although it has the advantage of enabling a high-capacity battery, the life characteristics of the battery may decrease and the resistance may increase. In addition, for a high-Ni positive electrode active material, the collapse of the structure of the positive electrode is accelerated due to high-temperature exposure, and the dissolution of transition metals may be aggravated, especially when HF is present in the non-aqueous electrolyte solution, it may be accelerated.

[0195] Therefore, to solve this problem, the lithium secondary battery of the present disclosure can suppress side reactions of the electrolyte solution by forming a strong film on the electrode surface by using a lithium salt compound and an oligomer containing an acrylate cyanide terminal functional group as components of the non-aqueous electrolyte solution for the lithium secondary battery. In addition, it is possible to prevent a decrease in the high-temperature durability, high-temperature capacity, and life characteristics of the lithium secondary battery.

[0196] In addition, in addition to the above lithium composite metal oxide, if necessary, the positive electrode active material may further include lithium-manganese-based oxides (such as LiMnO2, LiMn2O4, etc.), lithium-cobalt-based oxides (such as LiCoO2, etc.), lithium-nickel-based oxides (such as LiNiO2, etc.), lithium-nickel-manganese-based oxides (such as LiNi 1-Y Mn Y O2 (where 0 < Y < 1), LiMn 2-Z Ni z O4 (where 0 < Z < 2)), lithium-nickel-cobalt-based oxides (such as LiNi 1-Y1 Co Y 1O2 (where 0 < Y1 < 1)), lithium-manganese-cobalt-based oxides (such as LiCo1-Y2 Mn Y2 O2 (where 0 < Y2 < 1), LiMn 2-Z1 Co z1 O4 (where 0 < Z1 < 2)), lithium-nickel-manganese-cobalt-based oxide (e.g., Li(Ni p Co q Mn r1 )O2 (where 0 < p < 1, 0 < q < 1, 0 < r1 < 1, p + q + r1 = 1) or Li(Ni p1 Co q1 Mn r2 )O4 (where 0 < p1 < 2, 0 < q1 < 2, 0 < r2 < 2 and p1 + q1 + r2 = 2), or lithium-nickel-cobalt-transition metal (M) oxide (e.g., Li(Ni p2 Co q2 Mn r3 M S2 )O2 (where M is selected from aluminum (Al), iron (Fe), vanadium (V), chromium (Cr)), titanium (Ti), tantalum (Ta), magnesium (Mg) and molybdenum (Mo), p2, q2, r3, s2 are atomic fractions of each independent element, where 0 < p2 < 1, 0 < q2 < 1, 0 < r3 < 1, 0 < S2 < 1, p2 + q2 + r3 + s2 = 1).

[0197] Based on the total weight of the positive electrode active material layer, the content of the positive electrode active material can be 80 wt% to 98 wt%, for example 85 wt% to 98 wt%. When the content of the positive electrode active material is within the above range, excellent capacity characteristics can be exhibited.

[0198] In addition, the conductive agent is not particularly limited as long as it has conductivity and does not cause adverse chemical changes in the battery. For example, conductive materials such as carbon black, acetylene black, Ketjenblack, channel black, furnace black, lamp black or thermal cracking carbon black can be used; graphite powders such as natural graphite, artificial graphite, graphite with well-developed crystal structures; conductive fibers such as carbon fibers or metal fibers; conductive powders such as fluorocarbon powder, aluminum powder, nickel powder; conductive whiskers such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides such as titanium oxide; or polyphenylene derivatives can be used.

[0199] Based on the total weight of the solid components in the positive electrode active material layer, the addition amount of the conductive agent is usually 1 wt% to 30 wt%.

[0200] In addition, the binder is a component that improves the adhesion between the positive electrode active material particles and the adhesion between the positive electrode active material and the current collector, wherein the binder is generally added in an amount of 1% to 30% by weight based on the total weight of the solid components in the positive electrode active material layer. Examples of binders may include fluororesin binders, including polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); rubber binders, including styrene butadiene rubber (SBR), acrylonitrile-butadiene rubber or styrene-isoprene rubber; cellulose binders, including carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose or regenerated cellulose; polyol binders, including polyvinyl alcohol; polyolefin binders, including polyethylene or polypropylene; polyimide binders; polyester binders; and silane binders.

[0201] The positive electrode of the present disclosure as described above can be prepared by a method for preparing a positive electrode known in the art. For example, the positive electrode can be prepared by coating a positive electrode slurry on a positive electrode current collector, drying it, and then rolling it to form an active material layer, wherein the positive electrode slurry is prepared by dissolving or dispersing the positive electrode active material, a binder and / or a conductive agent in a solution, or the positive electrode can be prepared by casting a positive electrode active material layer on a separate support and then laminating a film separated from the support on the positive electrode current collector.

[0202] The positive electrode current collector is not particularly limited as long as it has conductivity without causing adverse chemical changes to the battery, for example, stainless steel, aluminum, nickel, titanium, sintered carbon or aluminum or stainless steel whose surface has been treated with one of carbon, nickel, titanium, silver, etc. can be used.

[0203] The solvent may include an organic solvent, such as N-methyl-2-pyrrolidone (NMP), and when the positive electrode active material and the optional binder and the conductive agent are included, the solvent may be used in an amount that can obtain the desired viscosity. For example, the solvent may be used in an amount such that the concentration of the solid components in the active material slurry including the positive electrode active material and the optional binder and the conductive agent is in the range of 10 wt % to 90 wt %, for example, 30 wt % to 80 wt %.

[0204] (2) Negative electrode

[0205] Next, the negative electrode will be described.

[0206] The negative electrode according to the present disclosure includes a negative electrode active material layer containing a negative electrode active material, and if necessary, the negative electrode active material layer may further include a conductive agent and / or a binder. In addition, the negative electrode according to the present disclosure may use a lithium metal electrode or a metal electrode such as copper (Cu) or Ni.

[0207] Various negative electrode active materials used in the art may be used, for example, carbon-based negative electrode active materials capable of reversibly inserting / deinserting lithium ions, silicon-based negative electrode active materials that may be doped or undoped with lithium, or mixtures thereof.

[0208] As the carbon-based negative electrode active material, various carbon-based negative electrode active materials used in the art can be used, such as graphite materials such as natural graphite, artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesophase carbon microbeads, mesophase pitch, high-temperature sintered carbon such as petroleum or coal tar pitch derived cokes, soft carbon, and hard carbon. The shape of the carbon-based negative electrode active material is not particularly limited, and various shapes such as irregular shape, planar shape, flake shape, spherical shape, and fibrous shape can be used.

[0209] Preferably, the carbon-based negative electrode active material may include at least one of natural graphite and artificial graphite. More preferably, the carbon-based negative electrode active material may include natural graphite and artificial graphite. When both natural graphite and artificial graphite are used, adhesion to the current collector can be improved to suppress peeling of the active material.

[0210] According to another embodiment, the negative electrode active material may use both a silicon-based negative electrode active material and a carbon-based negative electrode active material.

[0211] For example, the silicon-based negative electrode active material may include metal silicon (Si), silicon oxide (SiO x, where 0 < x < 2), silicon carbide (SiC), and an Si-Y alloy (where Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof, excluding Si). The element Y can be selected from Mg, calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), scandium (Sc), yttrium (Y), Ti, zirconium (Zr), hafnium (Hf), rutherfordium (Rf), V, niobium (Nb), Ta, dubnium (Db), Cr, Mo, tungsten (W), (Sg), technetium (Tc), rhenium (Re), (Bh), Fe, lead (Pb), ruthenium (Ru), osmium (Os), (Hs), rhodium (Rh), iridium (Ir), palladium (Pd), platinum (Pt), copper, silver (Ag), gold (Au), zinc (Zn), cadmium (Cd), boron (B), Al, gallium (Ga), tin (Sn), indium (In), germanium (Ge), phosphorus (P), arsenic (As), antimony (Sb), bismuth (Bi), sulfur (S), selenium (Se), tellurium (Te), polonium (Po), and combinations thereof.

[0212] Since the silicon-based negative electrode active material has higher capacity characteristics than the carbon-based negative electrode active material, better capacity characteristics can be obtained when the silicon-based negative electrode active material is further included.

[0213] The weight ratio of the silicon-based negative electrode active material to the carbon-based negative electrode active material can be in the range of 3:97 to 99:1, for example, 5:95 to 15:85. When the mixing ratio of the silicon-based negative electrode active material and the carbon-based negative electrode active material satisfies the above range, excellent cycle performance can be ensured because the volume expansion of the silicon-based negative electrode active material is suppressed while the capacity characteristics are improved.

[0214] Based on the total weight of the negative electrode active material layer, the content of the negative electrode active material can be 80% by weight to 99% by weight. When the amount of the negative electrode active material satisfies the above range, excellent capacity characteristics and electrochemical characteristics can be obtained.

[0215] Next, the conductive agent is a component used to further improve the conductivity of the negative electrode active material. Based on the total weight of the solid components in the negative electrode active material layer, the addition amount of the conductive agent can be 1% by weight to 20% by weight. Any conductive agent can be used without particular limitation as long as it has conductivity and does not cause adverse chemical changes to the battery. For example, conductive materials such as natural graphite or artificial graphite; carbon blacks such as acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal cracking carbon black; conductive fibers such as carbon fibers or metal fibers; conductive powders such as fluorocarbon powder, aluminum powder, nickel powder; conductive whiskers such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides such as titanium oxide; or polyphenyl derivatives can be used.

[0216] The binder is a component that helps to bind the conductive agent, active material and current collector, wherein the binder is generally added in an amount of 1% to 30% by weight based on the total weight of the solid components in the negative electrode active material layer. Examples of binders include fluororesin binders, including polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); rubber binders, including styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber or styrene-isoprene rubber; cellulose binders, including carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose or regenerated cellulose; polyol binders, including polyvinyl alcohol; polyolefin binders, including polyethylene or polypropylene; polyimide binders; polyester binders; and silane binders.

[0217] The negative electrode can be prepared by a method for preparing a negative electrode known in the art. For example, the negative electrode can be prepared by coating a negative electrode active material slurry on a negative electrode current collector, rolling and drying to form a negative electrode active material layer, wherein the slurry is prepared by dissolving or dispersing the negative electrode active material and optionally a binder and a conductive agent in a solvent, or the negative electrode can be prepared by casting a negative electrode active material layer on a separate support and then laminating a film separated from the support on the negative electrode current collector.

[0218] The negative electrode current collector typically has a thickness of 3 to 500 μm. There are no particular limitations on the negative electrode current collector, as long as it has high conductivity and does not cause adverse chemical changes to the battery. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel whose surface has been treated with one of carbon, nickel, titanium, silver, or the like, or an aluminum-cadmium alloy can be used. Furthermore, as with the positive electrode current collector, to improve the adhesion of the negative electrode active material, microscopic irregularities can be formed on the current collector surface. For example, various shapes such as films, sheets, foils, meshes, porous bodies, foams, and non-woven fabrics can be used.

[0219] The solvent may include water or an organic solvent such as NMP and ethanol, and when the negative electrode active material and, optionally, a binder and a conductive agent are included, the solvent may be used in an amount that can achieve a desired viscosity. For example, the solvent may be used in an amount such that the concentration of the solid content in the active material slurry containing the negative electrode active material and, optionally, a binder and a conductive agent, is in the range of 50% to 75% by weight, for example, 40% to 70% by weight.

[0220] (3) Partition

[0221] The lithium secondary battery according to the present disclosure includes a separator between a positive electrode and a negative electrode.

[0222] The separator separates the negative electrode and the positive electrode and provides a migration path for lithium ions. Any separator can be used without particular limitation as long as it is commonly used as a separator in lithium secondary batteries. In particular, a separator having high moisture retention capacity for electrolyte solutions and low resistance to ion transfer of non-aqueous electrolyte solutions can be used.

[0223] Specifically, a porous polymer film can be used, for example, a porous polymer film prepared from a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure having two or more layers. In addition, a conventional porous non-woven fabric can be used, for example, a non-woven fabric formed from high-melting-point glass fiber or polyethylene terephthalate fiber. In addition, in order to ensure heat resistance or mechanical strength, a coated separator comprising a ceramic component or a polymer material can be used, and a separator having a single-layer or multi-layer structure can be optionally used.

[0224] The lithium secondary battery according to the present disclosure as described above may be applicable to portable devices such as mobile phones, notebook computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0225] Therefore, according to another embodiment of the present disclosure, there are provided a battery module including a lithium secondary battery as a unit battery and a battery pack including the battery module.

[0226] The battery module or battery pack can be used as a power source for a power tool; an electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), and a plug-in hybrid electric vehicle (PHEV); or at least one medium-sized and large-sized device in a power storage system.

[0227] The shape of the lithium secondary battery of the present disclosure is not particularly limited, but a cylindrical type using a can, a prismatic type, a pouch type, or a coin type may be used.

[0228] The lithium secondary battery according to the present disclosure may be used not only in a battery cell used as a power source for small devices but also in unit batteries in medium- and large-sized battery modules including a plurality of battery cells.

[0229] Hereinafter, the present disclosure will be described in more detail with reference to the embodiments. However, the present invention can be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. On the contrary, these exemplary embodiments are provided to make this description thorough and complete and to fully convey the scope of the present disclosure to those skilled in the art.

[0230] [Example]

[0231] I. Examples

[0232] Example 1-1.

[0233] (Preparation of non-aqueous electrolyte solution for lithium secondary batteries)

[0234] LiPF6 was dissolved in a non-aqueous organic solvent in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to obtain a LiPF6 concentration of 1.0 M. A non-aqueous electrolyte solution for a lithium secondary battery was prepared by adding 0.1 wt % of an oligomer represented by Formula 3A (weight average molecular weight (Mw) = 12,000, a molar ratio of n1:m1 of 80:20) as a first additive and 0.05 wt % of LiODFB and 0.05 wt % of LiBOB as a second additive (see Table 1 below).

[0235] (Preparation of lithium secondary batteries)

[0236] The positive electrode active material (LiCoO2), carbon black as a conductive agent, and polyvinylidene fluoride as a binder were added to N-methyl-2-pyrrolidone (NMP) as a solvent in a weight ratio of 98:1:1 to prepare a positive electrode slurry (solid content 40 wt%). This positive electrode slurry was coated on a 20 μm thick positive electrode collector (Al film), dried, and then roll-pressed to prepare a positive electrode.

[0237] The negative electrode active material (graphite), carbon black as a conductive agent, SBR as a binder, and CMC as a thickener were added to NMP at a weight ratio of 95.6:1:2.3:1.1 to prepare a negative electrode slurry (solid content: 90 wt%). This negative electrode slurry was coated on a 10 μm thick copper (Cu) film as a negative electrode current collector, dried, and then roll-pressed to prepare a negative electrode.

[0238] After stacking the positive electrode, the separator formed of a polyethylene porous film and the negative electrode prepared above in sequence to prepare an electrode assembly, the electrode assembly was housed in a pouch-type battery case, and 5 ml of the non-aqueous electrolyte solution for secondary batteries prepared above was injected therein to prepare a pouch-type lithium secondary battery.

[0239] Examples 1-2.

[0240] A lithium secondary battery was prepared in the same manner as in Example 1-1, except that LiPF6 was dissolved in a non-aqueous organic solvent in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 0.1 wt % of an oligomer represented by Formula 3A (weight average molecular weight (Mw) = 12,000, a molar ratio of n1:m1 of 80:20) was added as a first additive, and 0.1 wt % of LiODFB and 5.0 wt % of LiBOB were added as second additives (see Table 1 below) to prepare a non-aqueous electrolyte solution for a secondary battery.

[0241] Examples 1-3.

[0242] A lithium secondary battery was prepared in the same manner as in Example 1-1, except that LiPF6 was dissolved in a non-aqueous organic solvent in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 0.1 wt % of an oligomer represented by Formula 3A (weight average molecular weight (Mw) = 12,000, a molar ratio of n1:m1 of 80:20) was added as a first additive, and 5.0 wt % of LiODFB and 5.0 wt % of LiBOB were added as second additives (see Table 1 below) to prepare a non-aqueous electrolyte solution for a secondary battery.

[0243] Examples 1-4.

[0244] A lithium secondary battery was prepared in the same manner as in Example 1-1, except that LiPF6 was dissolved in a non-aqueous organic solvent in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 0.1 wt % of an oligomer represented by Formula 3A (weight average molecular weight (Mw) = 12,000, a molar ratio of n1:m1 of 80:20) was added as a first additive and 0.05 wt % of LiBOB as a second additive (see Table 1 below) was added to prepare a non-aqueous electrolyte solution for a secondary battery.

[0245] Examples 1-5.

[0246] A lithium secondary battery was prepared in the same manner as in Example 1-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, wherein ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to obtain a LiPF6 concentration of 1.0 M, and then 0.1 wt % of an oligomer represented by Formula 3A (weight average molecular weight (Mw) = 12,000, a molar ratio of n1:m1 of 80:20) was added as a first additive and 0.05 wt % of LiODFB as a second additive (see Table 1 below) was added to prepare a non-aqueous electrolyte solution for a secondary battery.

[0247] Examples 1-6.

[0248] A lithium secondary battery was prepared in the same manner as in Example 1-1, except that LiPF6 was dissolved in a non-aqueous organic solvent in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 3.0 wt % of an oligomer represented by Formula 3A (weight average molecular weight (Mw) = 12,000, a molar ratio of n1:m1 of 80:20) was added as a first additive, and 0.5 wt % of LiODFB and 5.0 wt % of LiBOB were added as second additives (see Table 1 below) to prepare a non-aqueous electrolyte solution for a secondary battery.

[0249] Examples 1-7.

[0250] A lithium secondary battery was prepared in the same manner as in Example 1-1, except that LiPF6 was dissolved in a non-aqueous organic solvent in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 5.0 wt % of an oligomer represented by Formula 3A (weight average molecular weight (Mw) = 12,000, a molar ratio of n1:m1 of 80:20) was added as a first additive, and 0.05 wt % of LiODFB and 5.0 wt % of LiBOB were added as second additives (see Table 1 below) to prepare a non-aqueous electrolyte solution for a secondary battery.

[0251] Examples 1-8.

[0252] A lithium secondary battery was prepared in the same manner as in Example 1-1, except that LiPF6 was dissolved in a non-aqueous organic solvent in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 5.0 wt % of an oligomer represented by Formula 3A (weight average molecular weight (Mw) = 12,000, a molar ratio of n1:m1 of 80:20) was added as a first additive, and 5.0 wt % of LiODFB and 0.05 wt % of LiBOB were added as second additives (see Table 1 below) to prepare a non-aqueous electrolyte solution for a secondary battery.

[0253] Examples 1-9.

[0254] A lithium secondary battery was prepared in the same manner as in Example 1-1, except that LiPF6 was dissolved in a non-aqueous organic solvent in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 5.0 wt % of an oligomer represented by Formula 3A (weight average molecular weight (Mw) = 12,000, a molar ratio of n1:m1 of 80:20) was added as a first additive, and 0.05 wt % of LiODFB and 0.05 wt % of LiBOB were added as second additives (see Table 1 below) to prepare a non-aqueous electrolyte solution for a secondary battery.

[0255] Examples 1-10.

[0256] A lithium secondary battery was prepared in the same manner as in Example 1-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, wherein ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to obtain a LiPF6 concentration of 1.0 M, and then 5.0 wt % of an oligomer represented by Formula 3A (weight average molecular weight (Mw) = 12,000, a molar ratio of n1:m1 of 80:20) was added as a first additive and 5.0 wt % of LiODFB as a second additive (see Table 1 below) was added to prepare a non-aqueous electrolyte solution for a secondary battery.

[0257] Examples 1-11.

[0258] A lithium secondary battery was prepared in the same manner as in Example 1-1, except that the prepared nonaqueous electrolyte solution for a secondary battery included an oligomer represented by Formula 3B (weight average molecular weight (Mw) = 12,500, a molar ratio of n2:m2 of 80:20) instead of the oligomer represented by Formula 3A as the first additive (see Table 1 below).

[0259] Examples 1-12.

[0260] A pouch-type lithium secondary battery was prepared in the same manner as in Example 1-9, except that the prepared non-aqueous electrolytic solution for a secondary battery included an oligomer represented by Formula 3B (weight average molecular weight (Mw) = 12,500, a molar ratio of n2:m2 of 80:20) instead of the oligomer represented by Formula 3A as the first additive (see Table 1 below).

[0261] Examples 1-13.

[0262] A pouch-type lithium secondary battery was prepared in the same manner as in Example 1-1, except that the prepared non-aqueous electrolytic solution for a secondary battery included an oligomer represented by Formula 3C (weight average molecular weight (Mw) = 15,500, a molar ratio of n3:m3 of 80:20) instead of the oligomer represented by Formula 3A as the first additive (see Table 1 below).

[0263] Examples 1-14.

[0264] A pouch-type lithium secondary battery was prepared in the same manner as in Example 1-9, except that the prepared non-aqueous electrolytic solution for a secondary battery included an oligomer represented by Formula 3C (weight average molecular weight (Mw) = 15,500, a molar ratio of n3:m3 of 80:20) instead of the oligomer represented by Formula 3A as the first additive (see Table 1 below).

[0265] Examples 1-15.

[0266] A pouch-type lithium secondary battery was prepared in the same manner as in Example 1-1, except that the prepared non-aqueous electrolytic solution for a secondary battery included an oligomer represented by Formula 3D (weight average molecular weight (Mw) = 13,300, a molar ratio of n4:m4 of 70:30) instead of the oligomer represented by Formula 3A as the first additive (see Table 1 below).

[0267] Examples 1-16.

[0268] A pouch-type lithium secondary battery was prepared in the same manner as in Example 1-9, except that the prepared non-aqueous electrolytic solution for a secondary battery included an oligomer represented by Formula 3D (weight average molecular weight (Mw) = 13,300, a molar ratio of n4:m4 of 70:30) instead of the oligomer represented by Formula 3A as the first additive (see Table 1 below).

[0269] Examples 1-17.

[0270] A pouch-type lithium secondary battery was prepared in the same manner as in Example 1-1, except that LiPF6 was dissolved in a non-aqueous organic solvent in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 0.04 wt % of an oligomer represented by Formula 3A (weight average molecular weight (Mw) = 12,000, a molar ratio of n1:m1 of 80:20) was added as a first additive, and 0.05 wt % of LiODFB and 0.05 wt % of LiBOB were added as second additives (see Table 1 below) to prepare a non-aqueous electrolyte solution for a secondary battery.

[0271] Examples 1-18.

[0272] A pouch-type lithium secondary battery was prepared in the same manner as in Example 1-1, except that LiPF6 was dissolved in a non-aqueous organic solvent in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 0.04 wt % of an oligomer represented by Formula 3A (weight average molecular weight (Mw) = 12,000, a molar ratio of n1:m1 of 80:20) was added as a first additive, and 0.05 wt % of LiODFB and 5.0 wt % of LiBOB were added as second additives (see Table 1 below) to prepare a non-aqueous electrolyte solution for a secondary battery.

[0273] Examples 1-19.

[0274] A pouch-type lithium secondary battery was prepared in the same manner as in Example 1-1, except that LiPF6 was dissolved in a non-aqueous organic solvent in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 0.04 wt % of an oligomer represented by Formula 3A (weight average molecular weight (Mw) = 12,000, a molar ratio of n1:m1 of 80:20) was added as a first additive, and 5.0 wt % of LiODFB and 5.0 wt % of LiBOB were added as second additives (see Table 1 below) to prepare a non-aqueous electrolyte solution for a secondary battery.

[0275] Examples 1-20.

[0276] A pouch-type lithium secondary battery was prepared in the same manner as in Example 1-1, except that LiPF6 was dissolved in a non-aqueous organic solvent in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 6.0 wt % of an oligomer represented by Formula 3A (weight average molecular weight (Mw) = 12,000, a molar ratio of n1:m1 of 80:20) was added as a first additive, and 0.05 wt % of LiODFB and 0.05 wt % of LiBOB were added as second additives (see Table 1 below) to prepare a non-aqueous electrolyte solution for a secondary battery.

[0277] Examples 1-21.

[0278] A pouch-type lithium secondary battery was prepared in the same manner as in Example 1-1, except that LiPF6 was dissolved in a non-aqueous organic solvent in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 6.0 wt % of an oligomer represented by Formula 3A (weight average molecular weight (Mw) = 12,000, a molar ratio of n1:m1 of 80:20) was added as a first additive, and 0.05 wt % of LiODFB and 5.0 wt % of LiBOB were added as second additives (see Table 1 below) to prepare a non-aqueous electrolyte solution for a secondary battery.

[0279] Examples 1-22.

[0280] A pouch-type lithium secondary battery was prepared in the same manner as in Example 1-1, except that LiPF6 was dissolved in a non-aqueous organic solvent in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 6.0 wt % of an oligomer represented by Formula 3A (weight average molecular weight (Mw) = 12,000, a molar ratio of n1:m1 of 80:20) was added as a first additive, and 5.0 wt % of LiODFB and 5.0 wt % of LiBOB were added as second additives (see Table 1 below) to prepare a non-aqueous electrolyte solution for a secondary battery.

[0281] Comparative Example 1-1.

[0282] A pouch-type lithium secondary battery was prepared in the same manner as in Example 1-1, except that ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 and LiPF6 was dissolved therein to obtain a LiPF6 concentration of 1.0 M to prepare a non-aqueous electrolyte solution (see Table 1 below).

[0283] Comparative Example 1-2.

[0284] A pouch-type lithium secondary battery was prepared in the same manner as in Example 1-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, wherein ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to obtain a LiPF6 concentration of 1.0 M, and then a non-aqueous electrolyte solution was prepared by adding 0.05 wt% of LiODFB and 0.05 wt% of LiBOB as a second additive (see Table 1 below).

[0285] Comparative Examples 1-3.

[0286] A pouch-type lithium secondary battery was prepared in the same manner as in Example 1-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, wherein ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to obtain a LiPF6 concentration of 1.0 M, and then 5.0 wt % of LiODFB and 0.05 wt % of LiBOB were added as a second additive (see Table 1 below) to prepare a non-aqueous electrolyte solution.

[0287] Comparative Examples 1-4.

[0288] A pouch-type lithium secondary battery was prepared in the same manner as in Example 1-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, wherein ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to obtain a LiPF6 concentration of 1.0 M, and then only 0.1 wt % of an oligomer represented by Formula 3A (weight average molecular weight (Mw) = 12,000, a molar ratio of n1:m1 of 80:20) was added as a first additive to prepare a non-aqueous electrolyte solution.

[0289] Comparative Examples 1-5.

[0290] A pouch-type lithium secondary battery was prepared in the same manner as in Example 1-1, except that LiPF6 was dissolved in a non-aqueous organic solvent in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 5 wt % of an oligomer represented by the following formula 1A (weight average molecular weight (Mw) = 7,500, o = 40) was added as a first additive, and 5.0 wt % of LiODFB and 0.05 wt % of LiBOB were added as a second additive (see Table 1 below) to prepare a non-aqueous electrolyte solution.

[0291] [Formula 1A]

[0292]

[0293] Comparative Examples 1-6.

[0294] A pouch-type lithium secondary battery was prepared in the same manner as in Example 1-1, except that LiPF6 was dissolved in a non-aqueous organic solvent in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 5 wt % of an oligomer represented by Formula 1A (weight average molecular weight (Mw) = 7,500, o = 40) was added as a first additive, and 0.05 wt % of LiODFB and 0.05 wt % of LiBOB were added as second additives (see Table 1 below) to prepare a non-aqueous electrolyte solution.

[0295] Comparative Examples 1-7.

[0296] A pouch-type lithium secondary battery was prepared in the same manner as in Example 1-1, except that LiPF6 was dissolved in a non-aqueous organic solvent in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 5 wt % of an oligomer represented by the following formula 2A (weight average molecular weight (Mw) = 4,000, p = 40) was added as a first additive, and 0.05 wt % of LiODFB and 0.05 wt % of LiBOB were added as second additives (see Table 1 below) to prepare a non-aqueous electrolyte solution.

[0297] [Formula 2A]

[0298]

[0299] Comparative Examples 1-8.

[0300] A pouch-type lithium secondary battery was prepared in the same manner as in Example 1-1, except that LiPF6 was dissolved in a non-aqueous organic solvent in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 5 wt % of an oligomer represented by Formula 2A (weight average molecular weight (Mw) = 4,000, p = 40) was added as a first additive, and 5.0 wt % of LiODFB and 0.05 wt % of LiBOB were added as second additives (see Table 1 below) to prepare a non-aqueous electrolyte solution.

[0301] Comparative Examples 1-9.

[0302] A pouch-type lithium secondary battery was prepared in the same manner as in Example 1-1, except that the prepared nonaqueous electrolyte solution for a secondary battery included an oligomer represented by the following Formula 4 (weight average molecular weight (Mw) = 13,500, a molar ratio of q:r of 50:50) instead of the oligomer represented by Formula 3A (see Table 1 below).

[0303] [Formula 4]

[0304]

[0305] Comparative Examples 1-10.

[0306] A pouch-type lithium secondary battery was prepared in the same manner as in Example 1-1, except that the prepared nonaqueous electrolyte solution for a secondary battery included an oligomer represented by the following Formula 5 (weight average molecular weight (Mw) = 14,200, a molar ratio of q1:r1 of 60:40) instead of the oligomer represented by Formula 3A (see Table 1 below).

[0307] [Formula 5]

[0308]

[0309] [Table 1]

[0310]

[0311]

[0312] The abbreviations of the compounds in Table 1 are as follows.

[0313] LiBOB:Lithium bis(oxalato)borate

[0314] LiODFB:Lithium difluoro(oxalato)borate

[0315] Example 2-1.

[0316] A pouch-type lithium secondary battery was prepared in the same manner as in Example 1-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, wherein ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to obtain a LiPF6 concentration of 1.0 M, and then 5 wt % of an oligomer represented by Formula 3E (weight average molecular weight (Mw) = 13,000 g / mol, molar ratio n5:m5 = 80:20) was added as a first additive and 0.0005 wt % of succinonitrile as a second additive (see Table 2 below) was added to prepare a non-aqueous electrolyte solution.

[0317] Example 2-2.

[0318] A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 0.1 wt % of an oligomer represented by Formula 3E (weight average molecular weight (Mw) = 13,000 g / mol, molar ratio n5:m5 = 80:20) was added as a first additive, and 0.0005 wt % of succinonitrile and 10.0 wt % of HTCN were added as second additives (see Table 2 below) to prepare a non-aqueous electrolyte solution.

[0319] Examples 2-3.

[0320] A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 0.1 wt % of an oligomer represented by Formula 3E (weight average molecular weight (Mw) = 13,000 g / mol, molar ratio n5:m5 = 80:20) was added as a first additive and 0.0005 wt % of HTCN as a second additive (see Table 2 below) was added to prepare a non-aqueous electrolyte solution.

[0321] Examples 2-4.

[0322] A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 0.1 wt % of an oligomer represented by Formula 3E (weight average molecular weight (Mw) = 13,000 g / mol, molar ratio n5:m5 = 80:20) was added as a first additive, and 10.0 wt % of succinonitrile and 0.0005 wt % of succinonitrile HTCN were added as a second additive (see Table 2 below) to prepare a non-aqueous electrolyte solution.

[0323] Examples 2-5.

[0324] A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, wherein ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to obtain a LiPF6 concentration of 1.0 M, and then 0.1 wt % of an oligomer represented by Formula 3E (weight average molecular weight (Mw) = 13,000 g / mol, molar ratio n5:m5 = 80:20) was added as a first additive and 10.0 wt % of succinonitrile as a second additive (see Table 2 below) was added to prepare a non-aqueous electrolyte solution.

[0325] Examples 2-6.

[0326] A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 0.1 wt % of an oligomer represented by Formula 3E (weight average molecular weight (Mw) = 13,000 g / mol, molar ratio n5:m5 = 80:20) was added as a first additive and 10.0 wt % of HTCN as a second additive (see Table 2 below) was added to prepare a non-aqueous electrolyte solution.

[0327] Examples 2-7.

[0328] A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 0.1 wt % of an oligomer represented by Formula 3F (weight average molecular weight (Mw) = 16,500 g / mol, molar ratio n6:m6 = 70:30) was added as a first additive and 0.0005 wt % of succinonitrile as a second additive (see Table 2 below) was added to prepare a non-aqueous electrolyte solution.

[0329] Examples 2-8.

[0330] A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 0.1 wt % of an oligomer represented by Formula 3F (weight average molecular weight (Mw) = 16,500 g / mol, molar ratio n6:m6 = 70:30) and 0.0005 wt % of succinonitrile and 10.0 wt % of HTCN were added as a second additive (see Table 2 below) to prepare a non-aqueous electrolyte solution.

[0331] Examples 2-9.

[0332] A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, wherein ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to obtain a LiPF6 concentration of 1.0 M, and then 0.1 wt % of an oligomer represented by Formula 3C (weight average molecular weight (Mw) = 15,500 g / mol, molar ratio n3:m3 = 80:20) was added as a first additive and 0.0005 wt % of succinonitrile as a second additive (see Table 2 below) was added to prepare a non-aqueous electrolyte solution.

[0333] Examples 2-10.

[0334] A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 0.1 wt % of an oligomer represented by Formula 3C (weight average molecular weight (Mw) = 15,500 g / mol, molar ratio n3:m3 = 80:20) was added as a first additive and 0.0005 wt % of succinonitrile and 10.0 wt % of HTCN were added as second additives (see Table 2 below) to prepare a non-aqueous electrolyte solution.

[0335] Examples 2-11.

[0336] A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 0.1 wt % of an oligomer represented by Formula 3D (weight average molecular weight (Mw) = 15,000 g / mol, molar ratio n4:m4 = 90:10) was added as a first additive and 0.0005 wt % of succinonitrile as a second additive (see Table 2 below) was added to prepare a non-aqueous electrolyte solution.

[0337] Examples 2-12.

[0338] A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, wherein ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to obtain a LiPF6 concentration of 1.0 M, and then 0.1 wt % of an oligomer represented by Formula 3D (weight average molecular weight (Mw) = 15,000 g / mol, molar ratio n4:m4 = 90:10) was added as a first additive, and 0.0005 wt % of succinonitrile and 10.0 wt % of HTCN were added as a second additive (see Table 2 below) to prepare a non-aqueous electrolyte solution.

[0339] Examples 2-13.

[0340] A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 0.1 wt % of an oligomer represented by Formula 3E (weight average molecular weight (Mw) = 13,000 g / mol, molar ratio n5:m5 = 80:20) was added as a first additive and 0.0001 wt % of succinonitrile as a second additive (see Table 2 below) was added to prepare a non-aqueous electrolyte solution.

[0341] Examples 2-14.

[0342] A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 0.1 wt % of an oligomer represented by Formula 3E (weight average molecular weight (Mw) = 13,000 g / mol, molar ratio n5:m5 = 80:20) was added as a first additive and 0.0001 wt % of HTCN as a second additive (see Table 2 below) was added to prepare a non-aqueous electrolyte solution.

[0343] Examples 2-15.

[0344] A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 0.1 wt % of an oligomer represented by Formula 3E (weight average molecular weight (Mw) = 13,000 g / mol, molar ratio n5:m5 = 80:20) was added as a first additive and 15.0 wt % of succinonitrile as a second additive (see Table 2 below) was added to prepare a non-aqueous electrolyte solution.

[0345] Examples 2-16.

[0346] A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 0.1 wt % of an oligomer represented by Formula 3E (weight average molecular weight (Mw) = 13,000 g / mol, molar ratio n5:m5 = 80:20) was added as a first additive and 15.0 wt % of HTCN as a second additive (see Table 2 below) was added to prepare a non-aqueous electrolyte solution.

[0347] Examples 2-17.

[0348] A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 0.1 wt % of an oligomer represented by Formula 3E (weight average molecular weight (Mw) = 13,000 g / mol, molar ratio n5:m5 = 80:20) was added as a first additive, and 0.0001 wt % of succinonitrile and 10.0 wt % of HTCN were added as second additives (see Table 2 below) to prepare a non-aqueous electrolyte solution.

[0349] Examples 2-18.

[0350] A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 0.1 wt % of an oligomer represented by Formula 3E (weight average molecular weight (Mw) = 13,000 g / mol, molar ratio n5:m5 = 80:20) was added as a first additive, and 10.0 wt % of succinonitrile and 0.0001 wt % of HTCN were added as second additives (see Table 2 below) to prepare a non-aqueous electrolyte solution.

[0351] Examples 2-19.

[0352] A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 6.0 wt % of an oligomer represented by Formula 3E (weight average molecular weight (Mw) = 13,000 g / mol, molar ratio n5:m5 = 80:20) was added as a first additive and 6.0 wt % of succinonitrile and 6.0 wt % of HTCN were added as second additives (see Table 2 below) to prepare a non-aqueous electrolyte solution.

[0353] Examples 2-20.

[0354] A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, wherein ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to obtain a LiPF6 concentration of 1.0 M, and then 6.0 wt % of an oligomer represented by Formula 3E (weight average molecular weight (Mw) = 13,000 g / mol, molar ratio n5:m5 = 80:20) was added as a first additive and 6.0 wt % of succinonitrile as a second additive (see Table 2 below) was added to prepare a non-aqueous electrolyte solution.

[0355] Example 2-21.

[0356] A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to obtain a LiPF6 concentration of 1.0 M, and then 6.0 wt % of an oligomer represented by Formula 3E (weight average molecular weight (Mw) = 13,000 g / mol, molar ratio n5:m5 = 80:20) was added as a first additive and 6.0 wt % of HTCN as a second additive (see Table 2 below) was added to prepare a non-aqueous electrolyte solution.

[0357] Example 2-22.

[0358] A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 0.05 wt % of an oligomer represented by Formula 3E (weight average molecular weight (Mw) = 13,000 g / mol, molar ratio n5:m5 = 80:20) was added as a first additive and 6.0 wt % of succinonitrile as a second additive (see Table 2 below) was added to prepare a non-aqueous electrolyte solution.

[0359] Examples 2-23.

[0360] A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 0.05 wt % of an oligomer represented by Formula 3E (weight average molecular weight (Mw) = 13,000 g / mol, molar ratio n5:m5 = 80:20) was added as a first additive and 6.0 wt % of succinonitrile and 6.0 wt % of HTCN were added as second additives (see Table 2 below) to prepare a non-aqueous electrolyte solution.

[0361] Examples 2-24.

[0362] A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, wherein ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to obtain a LiPF6 concentration of 1.0 M, and then 0.05 wt % of an oligomer represented by Formula 3E (weight average molecular weight (Mw) = 13,000 g / mol, molar ratio n5:m5 = 80:20) was added as a first additive and 6.0 wt % of HTCN as a second additive (see Table 2 below) was added to prepare a non-aqueous electrolyte solution.

[0363] Comparative Example 2-1.

[0364] A pouch-type lithium secondary battery was prepared in the same manner as in Example 2-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 0.1 wt % of an oligomer represented by Formula 3E (weight average molecular weight (Mw) = 13,000 g / mol, molar ratio n5:m5 = 80:20) (see Table 2 below) was added to prepare a non-aqueous electrolyte solution.

[0365] [Table 2]

[0366]

[0367]

[0368] The abbreviations of the compounds in Table 2 are as follows.

[0369] SN: Succinonitrile

[0370] HTCN: adiponitrile

[0371] Example 3-1.

[0372] A pouch-type lithium secondary battery was prepared in the same manner as in Example 1-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, wherein ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 0.1 wt % of an oligomer represented by Formula 3E (weight average molecular weight (Mw) = 15,000 g / mol, molar ratio n5:m5 = 60:40) was added as a first additive, and 0.0001 wt % of ethylene ethylene carbonate and 0.0001 wt % of fluoroethylene carbonate were added as second additives (see Table 3 below) to prepare a non-aqueous electrolyte solution.

[0373] Example 3-2.

[0374] A pouch-type lithium secondary battery was prepared in the same manner as in Example 3-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, wherein ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to obtain a LiPF6 concentration of 1.0 M, and then 0.1 wt % of an oligomer represented by Formula 3E (weight average molecular weight (Mw) = 15,000 g / mol, molar ratio n5:m5 = 60:40) was added as a first additive, and 0.0001 wt % of ethylene ethylene carbonate and 10 wt % of fluoroethylene carbonate were added as second additives (see Table 3 below) to prepare a non-aqueous electrolyte solution.

[0375] Example 3-3.

[0376] A pouch-type lithium secondary battery was prepared in the same manner as in Example 3-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 0.1 wt % of an oligomer represented by Formula 3E (weight average molecular weight (Mw) = 15,000 g / mol, molar ratio n5:m5 = 60:40) was added as a first additive, and 5.0 wt % of ethylene ethylene carbonate and 0.0001 wt % of fluoroethylene carbonate were added as second additives (see Table 3 below) to prepare a non-aqueous electrolyte solution.

[0377] Examples 3-4.

[0378] A pouch-type lithium secondary battery was prepared in the same manner as in Example 3-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 0.1 wt % of an oligomer represented by Formula 3E (weight average molecular weight (Mw) = 15,000 g / mol, molar ratio n5:m5 = 60:40) was added as a first additive, and 5.0 wt % of ethylene ethylene carbonate and 10 wt % of fluoroethylene carbonate were added as second additives (see Table 3 below) to prepare a non-aqueous electrolyte solution.

[0379] Examples 3-5.

[0380] A pouch-type lithium secondary battery was prepared in the same manner as in Example 3-1, except that a non-aqueous electrolyte solution was prepared by adding an oligomer represented by Formula 3F (weight average molecular weight (Mw) = 15,000 g / mol, molar ratio n6:m6 = 50:50) instead of the oligomer represented by Formula 3E as the first additive (see Table 3 below).

[0381] Examples 3-6.

[0382] A pouch-type lithium secondary battery was prepared in the same manner as in Example 3-2, except that a non-aqueous electrolyte solution was prepared by adding an oligomer represented by Formula 3F (weight average molecular weight (Mw) = 15,000 g / mol, molar ratio n6:m6 = 50:50) instead of the oligomer represented by Formula 3E as the first additive (see Table 3 below).

[0383] Examples 3-7.

[0384] A pouch-type lithium secondary battery was prepared in the same manner as in Example 3-1, except that a non-aqueous electrolyte solution was prepared by adding an oligomer represented by Formula 3C (weight average molecular weight (Mw) = 14,300 g / mol, molar ratio n3:m3 = 60:40) instead of the oligomer represented by Formula 3E as the first additive (see Table 3 below).

[0385] Examples 3-8.

[0386] A pouch-type lithium secondary battery was prepared in the same manner as in Example 3-2, except that a non-aqueous electrolyte solution was prepared by adding an oligomer represented by Formula 3C (weight average molecular weight (Mw) = 14,300 g / mol, molar ratio n3:m3 = 60:40) instead of the oligomer represented by Formula 3E as the first additive (see Table 3 below).

[0387] Examples 3-9.

[0388] A pouch-type lithium secondary battery was prepared in the same manner as in Example 3-1, except that a non-aqueous electrolyte solution was prepared by adding an oligomer represented by Formula 3D (weight average molecular weight (Mw) = 12,000 g / mol, molar ratio n4:m4 = 60:40) instead of the oligomer represented by Formula 3E as the first additive (see Table 3 below).

[0389] Examples 3-10.

[0390] A pouch-type lithium secondary battery was prepared in the same manner as in Example 3-2, except that a non-aqueous electrolyte solution was prepared by adding an oligomer represented by Formula 3D (weight average molecular weight (Mw) = 12,000 g / mol, molar ratio n4:m4 = 60:40) instead of the oligomer represented by Formula 3E as the first additive (see Table 3 below).

[0391] Examples 3-11.

[0392] A pouch-type lithium secondary battery was prepared in the same manner as in Example 3-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, wherein ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to obtain a LiPF6 concentration of 1.0 M, and then 0.05 wt % of an oligomer represented by Formula 3E (weight average molecular weight (Mw) = 15,000 g / mol, molar ratio n5:m5 = 60:40) was added as a first additive, and 0.00005 wt % of ethylene ethylene carbonate and 0.00005 wt % of fluoroethylene carbonate were added as second additives (see Table 3 below) to prepare a non-aqueous electrolyte solution.

[0393] Examples 3-12.

[0394] A pouch-type lithium secondary battery was prepared in the same manner as in Example 3-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 6 wt % of an oligomer represented by Formula 3E (weight average molecular weight (Mw) = 15,000 g / mol, molar ratio n5:m5 = 60:40) was added as a first additive and 0.006 wt % of ethylene carbonate and 0.006 wt % of fluoroethylene carbonate were added as second additives (see Table 3 below) to prepare a non-aqueous electrolyte solution.

[0395] Examples 3-13.

[0396] A pouch-type lithium secondary battery was prepared in the same manner as in Example 3-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, wherein ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to obtain a LiPF6 concentration of 1.0 M, and then 0.1 wt % of an oligomer represented by Formula 3E (weight average molecular weight (Mw) = 15,000 g / mol, molar ratio n5:m5 = 60:40) was added as a first additive and 0.0001 wt % of ethylene ethylene carbonate was added as a second additive (see Table 3 below) to prepare a non-aqueous electrolyte solution.

[0397] Examples 3-14.

[0398] A pouch-type lithium secondary battery was prepared in the same manner as in Example 3-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, wherein ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to obtain a LiPF6 concentration of 1.0 M, and then 0.1 wt % of an oligomer represented by Formula 3E (weight average molecular weight (Mw) = 15,000 g / mol, molar ratio n5:m5 = 60:40) was added as a first additive and 0.0001 wt % of fluoroethylene carbonate was added as a second additive (see Table 3 below) to prepare a non-aqueous electrolyte solution.

[0399] Examples 3-15.

[0400] A pouch-type lithium secondary battery was prepared in the same manner as in Example 3-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 0.1 wt % of an oligomer represented by Formula 3E (weight average molecular weight (Mw) = 15,000 g / mol, molar ratio n5:m5 = 60:40) was added as a first additive and 5.0 wt % of ethylene carbonate was added as a second additive (see Table 3 below) to prepare a non-aqueous electrolyte solution.

[0401] Examples 3-16.

[0402] A pouch-type lithium secondary battery was prepared in the same manner as in Example 3-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, wherein ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to obtain a LiPF6 concentration of 1.0 M, and then 0.1 wt % of an oligomer represented by Formula 3E (weight average molecular weight (Mw) = 15,000 g / mol, molar ratio n5:m5 = 60:40) was added as a first additive and 10 wt % of fluoroethylene carbonate was added as a second additive (see Table 3 below) to prepare a non-aqueous electrolyte solution.

[0403] Examples 3-17.

[0404] A pouch-type lithium secondary battery was prepared in the same manner as in Example 3-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 0.1 wt % of an oligomer represented by Formula 3E (weight average molecular weight (Mw) = 15,000 g / mol, molar ratio n5:m5 = 60:40) was added as a first additive and 10 wt % of ethylene carbonate as a second additive (see Table 3 below) was added to prepare a non-aqueous electrolyte solution.

[0405] Examples 3-18.

[0406] A pouch-type lithium secondary battery was prepared in the same manner as in Example 3-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, wherein ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to give a LiPF6 concentration of 1.0 M, and then 0.1 wt % of an oligomer represented by Formula 3E (weight average molecular weight (Mw) = 15,000 g / mol, molar ratio n5:m5 = 60:40) was added as a first additive and 15 wt % of fluoroethylene carbonate as a second additive (see Table 3 below) was added to prepare a non-aqueous electrolyte solution.

[0407] Comparative Example 3-1.

[0408] A pouch-type lithium secondary battery was prepared in the same manner as in Example 3-1, except that LiPF6 was dissolved in a non-aqueous organic solvent, in which ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP) and propyl propionate (PP) were mixed in a volume ratio of 2:1:2.5:4.5 to obtain a LiPF6 concentration of 1.0 M, and then 0.1 wt % of an oligomer represented by Formula 3E (weight average molecular weight (Mw) = 15,000 g / mol, molar ratio n5:m5 = 60:40) (see Table 3 below) was added to prepare a non-aqueous electrolyte solution.

[0409] [Table 3]

[0410]

[0411] The abbreviations of the compounds in Table 3 are as follows.

[0412] VEC: Vinyl Ethylene Carbonate

[0413] FEC: Fluoroethylene carbonate

[0414] II. Experimental Examples

[0415] Experimental Example 1-1: Evaluation of Capacity Retention at High Temperature (45°C)

[0416] The lithium secondary batteries prepared in Examples 1-1 to 1-4, 1-6 to 1-9, and 1-11 to 1-22, and the lithium secondary batteries prepared in Comparative Examples 1-1 and 1-4 to 1-10, were each formed with a current of 200 mA (0.1C rate). The discharge capacity at this time was set as the initial capacity, and the measured resistance was set as the initial resistance.

[0417] Then, a constant current / constant voltage (CC / CV) cycle of charging to 4.2 V at 660 mA (0.33 C, 0.05 C cutoff) and discharging to 2.5 V at 660 mA (0.33 C) was performed as one cycle at high temperature (45°C), and the discharge capacity and resistance were measured after 100 cycles.

[0418] The capacity retention rate was calculated by comparing the discharge capacity after 100 cycles with the initial capacity, and the results are presented in Table 4 below.

[0419] Experimental Example 1-2: Evaluation of high temperature (45°C) storage characteristics

[0420] The lithium secondary batteries prepared in Examples 1-1 to 1-4, 1-6 to 1-9 and 1-11 to 1-22, and the lithium secondary batteries prepared in Comparative Examples 1-1 and 1-4 to 1-10 were each charged to 4.2 V at a rate of 0.33 C under constant current / constant voltage conditions, with a charge cutoff of 0.05 C, and discharged to 2.5 V at 0.33 C. After that, the discharge capacity was set to the initial capacity, and the resistance at this time was set to the initial resistance.

[0421] Each lithium secondary battery was then charged to 4.2 V at a rate of 0.33 C under constant current / constant voltage conditions, with a charge cutoff of 0.05 C. After storage at 60°C for 10 weeks, the residual capacity and resistance were measured. The capacity retention was calculated by comparing the discharge capacity measured after 10 weeks of high-temperature storage with the initial capacity, and the results are presented in Table 4 below.

[0422] [Table 4]

[0423]

[0424]

[0425] Referring to the results in Table 4, for the secondary batteries of Comparative Examples 1-1 and 1-4 to 1-10 that do not include both the first additive and the second additive of the present disclosure, since it is difficult to form a uniform film, it can be understood that compared with the secondary batteries containing the non-aqueous electrolyte solutions of Examples 1-1 to 1-4, 1-6 to 1-9 and 1-11 to 1-22 of the present disclosure, the capacity retention rate after high-temperature cycling and the capacity retention rate after high-temperature storage are both reduced.

[0426] For the lithium secondary batteries of Examples 1-17 to 1-22 containing slightly smaller or larger amounts of the oligomers of the present disclosure, it can be understood that the capacity retention rate is relatively reduced compared to the secondary batteries of Examples 1-1 to 1-4, 1-6 to 1-9 and 1-11 to 1-16, while the film-forming effect is reduced or side reactions are generated.

[0427] Experimental Example 2-1: Evaluation of Capacity Retention at High Temperature (45°C)

[0428] The lithium secondary batteries prepared in Examples 2-1 to 2-24 and the lithium secondary batteries prepared in Comparative Examples 1-9 and 1-10 were formed at a current of 200 mA (0.1 C rate). The discharge capacity at this time was defined as the initial capacity, and the measured resistance was defined as the initial resistance.

[0429] Then, the battery was charged to 4.2 V at a constant current / constant voltage (CC / CV) of 660 mA (0.33 C, 0.05 C cutoff) and discharged to 2.5 V at a CC of 660 mA (0.33 C) as one cycle. After 100 cycles at high temperature (45°C), the discharge capacity was measured.

[0430] The capacity retention rate was calculated by comparing the discharge capacity after 100 cycles with the initial capacity, and the results are presented in Table 5 below.

[0431] Experimental Example 2-2: Evaluation of high temperature (45°C) storage characteristics

[0432] The lithium secondary batteries prepared in Examples 2-1 to 2-24 and the lithium secondary batteries prepared in Comparative Examples 1-9 and 1-10 were each charged to 4.2 V at a rate of 0.33 C under constant current / constant voltage conditions, with a charge cutoff of 0.05 C, and discharged to 2.5 V at 0.33 C, and the discharge capacity was set to the initial capacity, and the resistance at this time was set to the initial resistance.

[0433] Each lithium battery was then recharged to 4.2V at a rate of 0.33C under constant current / constant voltage conditions, with a charge cutoff of 0.05C. After storage at 60°C for 10 weeks, the residual capacity and resistance were measured. The capacity retention was calculated by comparing the discharge capacity measured after 10 weeks of storage at high temperature with the initial capacity, and the results are presented in Table 5 below.

[0434] [Table 5]

[0435]

[0436]

[0437] Referring to Table 5, for the secondary batteries of Comparative Examples 1-9 and 1-10 that do not include both the first additive and the second additive of the present disclosure, since it is difficult to form a uniform film, it can be understood that the capacity retention rate after high-temperature cycling and the capacity retention rate after high-temperature storage are both reduced compared with the secondary batteries respectively containing the non-aqueous electrolyte solutions of Examples 2-1 to 2-24 of the present disclosure.

[0438] For the lithium secondary batteries of Examples 2-1 to 2-18, it can be understood that the capacity retention rate after high-temperature cycling and the capacity retention rate after high-temperature storage are improved compared to the lithium secondary batteries containing slightly more or less oligomers, respectively, containing the non-aqueous electrolyte solutions of Examples 2-19 to 2-24 of the present disclosure. This effect seems to be due to the fact that the film-forming effect is improved when the oligomer and the nitrile compound are contained in a specific content ratio, thereby preventing the increase in resistance caused by the formation of byproducts that may occur on the surface by suppressing electrode failure that may occur during high-temperature performance evaluation and at the same time suppressing side reactions of the electrolyte solution that may occur on the electrode surface.

[0439] Experimental Example 3-1: Evaluation of Capacity Retention at High Temperature (45°C)

[0440] The lithium secondary batteries prepared in Examples 3-1 to 3-10 and 3-13 to 3-18, the lithium secondary battery prepared in Comparative Example 1-1, the lithium secondary batteries prepared in Comparative Examples 1-9 and 1-10, and the lithium secondary battery prepared in Comparative Example 3-1 were formed with a current of 200 mA (0.1C rate), and the discharge capacity at this time was set as the initial capacity, and the measured resistance was set as the initial resistance.

[0441] Then, the battery was charged to 4.2 V at a constant current / constant voltage (CC / CV) of 660 mA (0.33 C, 0.05 C cutoff) and discharged to 2.5 V at a CC of 660 mA (0.33 C) as one cycle. After 100 cycles at high temperature (45°C), the discharge capacity was measured.

[0442] The capacity retention rate was calculated by comparing the discharge capacity after 100 cycles with the initial capacity, and the results are presented in Table 6 below.

[0443] Experimental Example 3-2: Evaluation of high temperature (45°C) storage characteristics

[0444] The lithium secondary batteries prepared in Examples 3-1 to 3-14 and 3-16 to 3-18, the lithium secondary batteries prepared in Comparative Example 1-1, the lithium secondary batteries prepared in Comparative Examples 1-9 and 1-10, and the lithium secondary battery prepared in Comparative Example 3-1 were each charged to 4.2 V at a rate of 0.33 C under constant current / constant voltage conditions, with charging cutoff at 0.05 C, and discharged to 2.5 V at 0.33 C, and the discharge capacity was set to the initial capacity, and the resistance at this time was set to the initial resistance.

[0445] Each lithium battery was then recharged to 4.2 V at a rate of 0.33 C under constant current / constant voltage conditions, with a charge cutoff of 0.05 C. After storage at 60°C for 10 weeks, the residual capacity and resistance were measured. The capacity retention was calculated by comparing the discharge capacity measured after 10 weeks of storage at high temperature with the initial capacity, and the results are presented in Table 6 below.

[0446] [Table 6]

[0447]

[0448] Referring to Table 6, for the lithium secondary batteries according to the embodiments of the present disclosure, it can be understood that the capacity retention rate after high-temperature cycling and the capacity retention rate after high-temperature storage are improved compared to the secondary batteries of Comparative Examples 1-1, 3-1, 1-9, and 1-10, which respectively include non-aqueous electrolyte solutions that do not include both the first additive and the second additive of the present disclosure.

[0449] Specifically, the reason seems to be that since a stable film is formed by including the cyclic carbonate and the oligomer together as additives, an increase in resistance due to the formation of by-products that may occur on the surface can be prevented by suppressing electrode failure that may occur during high-temperature performance evaluation and at the same time suppressing side reactions of the electrolyte solution that may occur on the electrode surface.

[0450] In particular, for the lithium secondary batteries of Examples 3-1 to 3-10, each including a non-aqueous electrolyte solution containing two cyclic carbonate compounds as a second additive, it can be understood that the capacity retention rate after high-temperature cycling and the capacity retention rate after high-temperature storage are further improved compared with the secondary batteries of Examples 3-13 to 3-18, each including a non-aqueous electrolyte solution containing only one cyclic carbonate compound.

[0451] Furthermore, for the secondary battery of Example 3-11, which contained a relatively small amount of oligomer, the absolute amount of oligomer used to form the film was insufficient to form an unstable film. Therefore, it is understood that the capacity retention rate after high-temperature storage was relatively lower than that of the secondary batteries of Examples 3-1 to 3-10. Furthermore, for the secondary battery of Example 3-12, which contained a slightly larger amount of oligomer, it is understood that the capacity retention rate after high-temperature storage was relatively lower than that of the secondary batteries of Examples 3-1 to 3-10. Simultaneously, the lithium ion charge transfer effect was reduced due to the decreased ionic conductivity caused by the increased viscosity of the electrolyte solution.

[0452] Experimental Example 1-3: Safety Evaluation

[0453] The lithium secondary batteries prepared in Examples 1-1 to 1-19 and the lithium secondary batteries prepared in Comparative Examples 1-1 to 1-10 were each charged to 4.2 V at a rate of 0.33 C under constant current / constant voltage conditions, with a charge cutoff of 0.05 C, and discharged to 2.5 V at 0.33 C. The discharge capacity was set to the initial capacity, and the resistance at this time was set to the initial resistance.

[0454] Then, each lithium secondary battery was charged to 4.2 V at a rate of 0.33C under constant current / constant voltage conditions, with a charge cutoff of 0.05C, and each fully charged battery was heated to 140°C at a rate of 5°C / min. A stability evaluation test was performed by observing whether there was fire or explosion while maintaining the temperature at 140°C for 1 hour.

[0455] The results are shown in the following Table 7. In this case, the battery that did not catch fire or explode (pass) was represented by "○", and the battery that caught fire or exploded (fail) was represented by "×".

[0456] [Table 7]

[0457]

[0458]

[0459] Referring to Table 7, for the secondary batteries of Examples 1-1 to 1-16, which respectively include non-aqueous electrolyte solutions containing both the lithium salt compound and the oligomer of the present disclosure, it can be understood that their high-temperature storage stability is better than that of the secondary batteries of Comparative Examples 1-1 to 1-10, which do not include both the first additive and the second additive of the present disclosure.

[0460] For the lithium secondary batteries of Examples 1-17 to 1-19 including a slightly smaller amount of the oligomer of the present disclosure, it can be understood that the high-temperature stability is relatively reduced due to the reduction in film-forming effect compared to the secondary batteries of Examples 1-1 to 1-16.

[0461] Experimental Example 2-3: Safety Evaluation

[0462] The lithium secondary batteries prepared in Examples 2-1 to 2-12 and the lithium secondary batteries prepared in Comparative Examples 1-1 and 2-1 were each charged to 4.2 V at a rate of 0.33 C under constant current / constant voltage conditions, with a charge cutoff of 0.05 C, and discharged to 2.5 V at 0.33 C. The discharge capacity was set to the initial capacity, and the resistance at this time was set to the initial resistance.

[0463] Then, each lithium secondary battery was charged to 4.2 V at a rate of 0.33C under constant current / constant voltage conditions, with a charge cutoff of 0.05C, and each fully charged battery was heated to 140°C at a rate of 5°C / min. A stability evaluation test was performed by observing whether there was fire or explosion while maintaining the temperature at 140°C for 1 hour.

[0464] The results are shown in the following Table 8. In this case, the battery that did not catch fire or explode (pass) was represented by "○", and the battery that caught fire or exploded (fail) was represented by "×".

[0465] [Table 8]

[0466]

[0467]

[0468] Referring to Table 8, it can be understood that the secondary batteries of Examples 2-1 to 2-12, each including the nonaqueous electrolyte solution containing both the first and second additives of the present disclosure, have better high-temperature storage stability than the secondary batteries of Comparative Examples 1-1 and 2-1.

[0469] Experimental Example 3-3: Safety Evaluation

[0470] The lithium secondary batteries prepared in Examples 3-1 to 3-10 and 3-12 and the lithium secondary battery prepared in Comparative Example 3-1 were each charged to 4.2 V at a rate of 0.33 C under constant current / constant voltage conditions, with a charge cutoff of 0.05 C, and discharged to 2.5 V at 0.33 C. The discharge capacity was set to the initial capacity, and the resistance at this time was set to the initial resistance.

[0471] Then, each lithium secondary battery was charged to 4.2 V at a rate of 0.33C under constant current / constant voltage conditions, with a charge cutoff of 0.05C. Each fully charged battery was heated to 140°C at a rate of 5°C / min, and a stability evaluation test was performed by observing for fire or explosion while maintaining the temperature at 140°C for 1 hour.

[0472] The results are shown in the following Table 9. In this case, the battery that did not catch fire or explode (pass) was represented by "○", and the battery that caught fire or exploded (fail) was represented by "×".

[0473] [Table 9]

[0474]

[0475]

[0476] Referring to Table 9, it can be understood that the secondary batteries of Examples 3-1 to 3-10 and 3-12, each including a nonaqueous electrolyte solution containing the oligomer of the present disclosure and two cyclic carbonate compounds, have better high-temperature storage stability than the secondary battery of Comparative Example 3-1.

Claims

1. A non-aqueous electrolyte solution for a lithium secondary battery, the non-aqueous electrolyte solution comprising a lithium salt; a non-aqueous organic solvent; a first additive; and a second additive, wherein the lithium salt is at least one selected from LiPF6, LiFSI, and LiTFSI, the non-aqueous organic solvent comprises a cyclic carbonate organic solvent, a linear carbonate organic solvent, a linear ester organic solvent, or a mixed organic solvent thereof, wherein the cyclic carbonate organic solvent is at least one organic solvent selected from the group consisting of ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentadienyl carbonate, and 2,3-pentadienyl carbonate, wherein the nonaqueous electrolyte solution for a lithium secondary battery comprises an oligomer as a first additive, the oligomer comprising a repeating unit derived from a monomer represented by Formula 1 and a repeating unit derived from a monomer represented by Formula 2, and Containing at least one selected from the group consisting of a nitrile compound, a lithium salt compound, and a cyclic carbonate compound as a second additive: [Formula 1] in, In formula 1, R' is hydrogen or an alkyl group having 1 to 3 carbon atoms, and R1 is an alkylene group having 1 to 20 carbon atoms or -(R2) o O(R3) p -, wherein R2 and R3 are each independently an alkylene group having 1 to 20 carbon atoms, o is an integer from 1 to 3, and p is an integer from 0 to 3; [Formula 2] In formula 2, R" is hydrogen or an alkyl group having 1 to 3 carbon atoms, R4 is an alkylene group having 1 to 10 carbon atoms, and R5 is an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, a heteroaryl group having 3 to 10 carbon atoms, or a cycloalkyl group having 3 to 10 carbon atoms, wherein the lithium salt compound is at least one selected from the group consisting of LiBF4, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium difluorophosphate, and lithium difluorobis(oxalato)phosphate, wherein the nitrile compound comprises at least one selected from the group consisting of succinonitrile, adiponitrile, dicyanobutene, ethylene glycol bis(propionitrile) ether, adiponitrile, acetonitrile, propionitrile, butyronitrile, valeronitrile, octanonitrile, heptanenitrile, cyclopentanenitrile, cyclohexanenitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, benzyl cyanide, 2-fluorophenyl acetonitrile, and 4-fluorophenyl acetonitrile, and The cyclic carbonate compound is at least one selected from the group consisting of vinylene carbonate, vinyl ethylene carbonate, and fluoroethylene carbonate.

2. The nonaqueous electrolyte solution for a lithium secondary battery according to claim 1, wherein the oligomer comprises an oligomer represented by Formula 3: [Formula 3] in, In formula 3, R' and R" are each independently hydrogen or an alkyl group having 1 to 3 carbon atoms, R1 is an alkylene group having 1 to 10 carbon atoms or -(R2) o O(R3) p -, wherein R2 and R3 are each independently an alkylene group having 1 to 10 carbon atoms, o is an integer from 1 to 3, and p is an integer from 0 to 3, R4 is an alkylene group having 1 to 10 carbon atoms, R5 is an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, a heteroaryl group having 3 to 10 carbon atoms, or a cycloalkyl group having 3 to 10 carbon atoms, and The molar ratio of n:m is in the range of 1:99 to 99:

1.

3. The non-aqueous electrolyte solution for a lithium secondary battery according to claim 2, wherein R' and R" are each independently hydrogen or an alkyl group having 1 or 2 carbon atoms, R1 is an alkylene group having 1 to 6 carbon atoms or -(R2) o O(R3) p -, wherein R2 and R3 are each independently an alkylene group having 1 to 6 carbon atoms, o is an integer from 1 to 3, and p is an integer from 0 to 3, R4 is an alkylene group having 1 to 6 carbon atoms, R5 is an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 8 carbon atoms, a heteroaryl group having 3 to 8 carbon atoms, or a cycloalkyl group having 3 to 8 carbon atoms, and The molar ratio of n:m is in the range of 1:99 to 99:

1.

4. The non-aqueous electrolyte solution for a lithium secondary battery according to claim 2, wherein R' and R" are each independently hydrogen or an alkyl group having 1 or 2 carbon atoms, R1 is an alkylene group having 1 to 6 carbon atoms or -(R2) o O(R3) p -, wherein R2 and R3 are each independently an alkylene group having 1 to 6 carbon atoms, o is an integer from 1 to 3, and p is an integer from 0 to 3, R4 is an alkylene group having 1 to 6 carbon atoms, R5 is an aryl group having 6 to 8 carbon atoms, a heteroaryl group having 3 to 8 carbon atoms, or a cycloalkyl group having 3 to 8 carbon atoms, and The molar ratio of n:m is in the range of 1:99 to 99:

1.

5. The non-aqueous electrolyte solution for a lithium secondary battery according to claim 2, wherein the oligomer represented by Formula 3 is at least one selected from the group consisting of oligomers represented by Formulas 3A to 3F: [Formula 3A] in, In Formula 3A, The molar ratio of n1:m1 is in the range of 1:99 to 99:1, [Formula 3B] Wherein, in Formula 3B, The molar ratio of n2:m2 is in the range of 1:99 to 99:1, [Formula 3C] Wherein, in Formula 3C, The molar ratio of n3:m3 is in the range of 1:99 to 99:1, [Formula 3D] Among them, in formula 3D, The molar ratio of n4:m4 is in the range of 1:99 to 99:1, [Formula 3E] Wherein, in Formula 3E, The molar ratio of n5:m5 is in the range of 1:99 to 99:1, [Formula 3F] Wherein, in Formula 3F, The molar ratio of n6:m6 is in the range of 1:99 to 99:

1. 6 . The nonaqueous electrolyte solution for a lithium secondary battery according to claim 1 , wherein the oligomer is present in an amount of 0.1 wt % to 5 wt % based on the total weight of the nonaqueous electrolyte solution. 7 . The nonaqueous electrolyte solution for a lithium secondary battery according to claim 1 , wherein a weight ratio of the oligomer to the nitrile compound is in the range of 1:0.01 to 1:

100. 8 . The nonaqueous electrolyte solution for a lithium secondary battery according to claim 1 , wherein a weight ratio of the oligomer to the lithium salt compound is in the range of 1:0.01 to 1:

100. 9 . The nonaqueous electrolyte solution for a lithium secondary battery according to claim 1 , wherein a weight ratio of the oligomer to the cyclic carbonate compound is in the range of 1:0.001 to 1:

150.

10. A lithium secondary battery comprising: a positive electrode comprising a positive electrode active material; a negative electrode comprising a negative electrode active material; a separator disposed between the negative electrode and the positive electrode; as well as The non-aqueous electrolyte solution for a lithium secondary battery according to claim 1.

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