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

Abstract

The present invention relates to a non-aqueous electrolyte solution for lithium secondary batteries, comprising an oligomer represented by Formula 1, a lithium salt and an organic solvent, and a lithium secondary battery comprising the non-aqueous electrolyte solution.

Description

Technical Field

[0001] This application claims priority to Korean Patent Application No. 10-2021-0006096, filed on January 15, 2021, and Korean Patent Application No. 10-2021-0006097, filed on January 15, 2021, the disclosures of which are incorporated herein by reference.

[0002] The present invention relates to a non-aqueous electrolyte solution for lithium secondary batteries and a lithium secondary battery comprising the non-aqueous electrolyte solution. Background Technology

[0003] Recently, as the application of lithium secondary batteries has rapidly expanded not only to the power supply field of electrical, electronic, communication and electronic equipment (such as computers), but also to the energy storage field of automobiles or large-area devices such as energy storage devices, the demand for secondary batteries with high stability, high capacity and high output is also increasing.

[0004] Typically, the positive and negative electrodes are prepared by coating a positive current collector and a negative current collector with a material, respectively. This material consists of a positive active material formed from a lithium-containing transition metal oxide, or a carbon or silicon negative active material capable of intercalating and deintercalating lithium ions, mixed with an optional binder and conductive agent. Electrode assemblies of a predetermined shape are formed by stacking these electrodes on both sides of a separator. The lithium secondary battery is then fabricated by inserting the electrode assemblies and a non-aqueous electrolyte solution into a battery casing. Here, to ensure battery performance, almost entirely a formation and aging process is performed.

[0005] The formation process is the step of activating a secondary battery after assembly through repeated charging and discharging. During charging, lithium ions from the lithium-containing transition metal oxide used as the positive electrode are transferred and intercalated into the carbon-based negative electrode active material used as the negative electrode. In this process, the highly reactive lithium ions react with the electrolyte to form compounds such as Li₂CO₃, Li₂O, and LiOH, which form a solid electrolyte interface (SEI) on the electrode surface. Since the SEI is closely related to lifetime and capacity retention, its formation is a crucial factor.

[0006] In particular, high capacity, high output, and long lifespan are crucial for lithium-ion rechargeable batteries used in automobiles. Since high capacity is achieved by using high-energy-density but low-stability positive electrode active materials, methods have been investigated to form a stable active material-electrolyte interface (SEI) by protecting the surface of the positive electrode active material. Furthermore, regarding the negative electrode, the decomposition of surface species in the electrolyte solution leads to side reactions, necessitating the formation of a robust and low-resistivity SEI.

[0007] In particular, since the SEI gradually collapses during high-temperature storage, leading to problems such as electrode exposure, it is necessary to develop an additive for the electrolyte solution to help form an SEI that can suppress side reactions during high-temperature storage.

[0008] Furthermore, non-aqueous electrolyte solutions have drawbacks, including a high likelihood of electrode material degradation and organic solvent evaporation, as well as poor safety due to combustion caused by increased ambient and battery temperatures. Therefore, it is necessary to develop an electrolyte for lithium secondary batteries that can compensate for these drawbacks while ensuring both performance and safety. Summary of the Invention

[0009] Technical issues

[0010] One aspect of the present invention provides a non-aqueous electrolyte solution comprising oligomers and a lithium secondary battery having improved safety and high-temperature performance by comprising the non-aqueous electrolyte solution.

[0011] Technical solution

[0012] According to one aspect of the present invention, a non-aqueous electrolyte solution for lithium secondary batteries is provided, comprising: an oligomer represented by Formula 1; a lithium salt; and an organic solvent.

[0013] [Formula 1]

[0014]

[0015] In Equation 1,

[0016] R is an aliphatic hydrocarbon group or an aromatic hydrocarbon group.

[0017] R' is an unsubstituted or substituted alkyl group having 1-5 carbon atoms.

[0018] R1 to R4 may be the same as or different from each other, and each is independently an unsubstituted or substituted alkyl group having 1-3 carbon atoms.

[0019] R5 is an unsubstituted or substituted alkyl group having 1-5 carbon atoms.

[0020] n, m, and x are the multiplicity of each unit.

[0021] Where n is an integer from 1 to 10, m is an integer from 1 to 5, and x is an integer from 1 to 200, and

[0022] E and E' are either the same as or different from each other, and are each independently represented by Equation 2.

[0023] [Equation 2]

[0024]

[0025] In Equation 2,

[0026] Ra and Rb may be the same as or different from each other, and each is independently hydrogen, an alkyl group having 1-6 carbon atoms that is unsubstituted or substituted with a halogen group, or an alkenyl group having 1-6 carbon atoms that is unsubstituted or substituted with a halogen group.

[0027] Rc and Rd may be the same as or different from each other, and each is independently hydrogen or an alkyl group having 1-5 carbon atoms.

[0028] Rb and Rc can bond to each other to form cycloalkyl groups including O, and

[0029] p and k are both repetition numbers.

[0030] Where p is an integer between 0 and 4, and

[0031] k is an integer between 1 and 3.

[0032] According to another aspect of the present invention, a lithium secondary battery is provided, comprising: a positive electrode containing a positive electrode active material; a negative electrode containing a negative electrode active material; a separator disposed between the positive electrode and the negative electrode; and a non-aqueous electrolyte solution.

[0033] Beneficial effects

[0034] According to the present invention, a non-aqueous electrolyte solution capable of forming a thinner and denser protective film on the electrode surface can be prepared by further including oligomers with a specific structure in an organic solvent in which lithium salts are dissolved. Furthermore, lithium secondary batteries with improved safety and high-temperature life can be prepared using this non-aqueous electrolyte solution. Detailed Implementation

[0035] The invention will be described in more detail below to allow for a clearer understanding of it.

[0036] The term "*-" in this specification indicates a site that is connected to the main chain of the oligomer or to other monomers, substituents, or end groups in the chemical formula.

[0037] The term "substitution" refers to the replacement of a hydrogen atom bonded to a carbon atom in a compound by another substituent. The position of the substitution is not limited, as long as it is the position where the hydrogen atom is replaced. That is, the position where the substituent can be substituted. When two or more substituents are substituted, the two or more substituents can be the same or different.

[0038] In this specification, "substituted or unsubstituted" means that the compound is substituted by at least one substituent selected from deuterium, oxygen, halogen group, nitrile group, nitro group, hydroxyl group, alkyl group, cycloalkyl group, aryl group and heterocyclic group, is substituted by a substituent formed by two or more substituents linked together in the examples above, or has no substituents.

[0039] In this specification, alkyl, alkenyl, alkynyl, and aryl refer to groups that have two bonding sites in the alkyl, alkenyl, alkynyl, and aryl groups, respectively, i.e., divalent groups.

[0040] Non-aqueous electrolyte solution

[0041] In one embodiment of the invention, the non-aqueous electrolyte solution for a lithium secondary battery comprises an oligomer represented by Formula 1; a lithium salt; and an organic solvent.

[0042] [Formula 1]

[0043]

[0044] In Equation 1,

[0045] R is an aliphatic hydrocarbon group or an aromatic hydrocarbon group.

[0046] R' is an unsubstituted or substituted alkyl group having 1-5 carbon atoms.

[0047] R1 to R4 may be the same as or different from each other, and each is independently an unsubstituted or substituted alkyl group having 1-3 carbon atoms.

[0048] R5 is an unsubstituted or substituted alkyl group having 1-5 carbon atoms.

[0049] n, m, and x are the number of repetitions in each unit.

[0050] Where n is an integer from 1 to 10, m is an integer from 1 to 5, and x is an integer from 1 to 200, and

[0051] E and E' are either the same as or different from each other, and are each independently represented by the following equation 2.

[0052] [Equation 2]

[0053]

[0054] In Equation 2,

[0055] Ra and Rb may be the same as or different from each other, and each is independently hydrogen, an alkyl group having 1-6 carbon atoms that is unsubstituted or substituted with a halogen group, or an alkenyl group having 1-6 carbon atoms that is unsubstituted or substituted with a halogen group.

[0056] Rc and Rd may be the same as or different from each other, and each is independently hydrogen or an alkyl group having 1-5 carbon atoms.

[0057] Rb and Rc can bond to each other to form cycloalkyl groups including O, and

[0058] p and k are both repetition numbers.

[0059] Where p is an integer between 0 and 4, and

[0060] k is an integer between 1 and 3.

[0061] (a) Oligomers represented by Formula 1

[0062] In one embodiment of the invention, since the oligomer represented by Formula 1 has the ability to dissociate lithium salts, it can improve the mobility of lithium ions, especially since it contains components that are electrochemically very stable and compatible with lithium ions (Li). + The low-reactivity siloxane group (-Si-O-) serves as the repeating unit of the main chain, thus allowing control over lithium ions (Li). + The oligomers reduce the side reactions of lithium salt and the decomposition of lithium salt, thereby reducing the generation of gases such as CO or CO2 during overcharging. Therefore, oligomers can improve the safety of secondary batteries by suppressing high-temperature ignition.

[0063] In particular, since the end group includes the structure of Formula 2, it can reduce the reactivity with the negative electrode compared with highly reactive end groups such as acrylate end groups, thereby reducing the resistance of the battery.

[0064] In one embodiment of the invention, the weight-average molecular weight (Mw) of the oligomer represented by Formula 1 can be controlled by the number of repeating units, and can be from about 1,000 g / mol to about 100,000 g / mol, particularly from 1,000 g / mol to 50,000 g / mol, and even more particularly from 1,000 g / mol to 10,000 g / mol. When the weight-average molecular weight of the oligomer is greater than 100,000 g / mol, there is a problem of reduced ionic conductivity due to its low solubility in non-aqueous electrolyte solutions.

[0065] Weight-average molecular weight was measured by gel permeation chromatography (GPC). Specifically, a Waters Styragel HR3 / HR4 (THF) column was used as the chromatographic column, tetrahydrofuran (THF) (filtered at 0.45 μm) was used as the solvent, and the flow rate was 1.0 mL / min with a sample concentration of 1 mg / mL. 100 μL of sample was injected, and the column temperature was set to 40 °C. A Waters RI detector was used as the detector, and polystyrene (PS) was used as the standard. Data processing was performed using Empower3.

[0066] In one embodiment of the invention, Ra to Rd of Formula 2 may each be hydrogen or an alkyl group having 1 to 6 carbon atoms.

[0067] In one embodiment of the invention, Rb and Rc of Formula 2 are each alkyl groups having 1-3 carbon atoms and can be bonded to each other to form an O-containing cycloalkyl group, such as tetrahydrofuranyl.

[0068] In one embodiment of the present invention, formula 2 can be represented by formula 2-1 or formula 2-2.

[0069] [Equation 2-1]

[0070] *-(CH2)p'(CH2)2-OH

[0071] In Equation 2-1,

[0072] p' is the repetition number, where p' is an integer between 0 and 4.

[0073] [Equation 2-2]

[0074]

[0075] In Equation 2-2,

[0076] p” and s are the repetition numbers.

[0077] Where p” is an integer between 0 and 4, and

[0078] s is 1 or 2.

[0079] In one embodiment of the present invention, p' can be an integer from 0 to 2, p" can be 0 or 1, and s can be 1.

[0080] In one embodiment of the present invention, E and E' in Formula 1 can each be *-(CH2)3-OH or

[0081] In one embodiment of the present invention, the aliphatic hydrocarbon group R in Formula 1 may be selected from unsubstituted or substituted alkyl groups having 1-20 carbon atoms, unsubstituted or substituted cycloalkyl groups having 4-20 carbon atoms, unsubstituted or substituted heterocycloalkyl groups having 2-20 carbon atoms, unsubstituted or substituted olefinic groups having 2-20 carbon atoms, and unsubstituted or substituted alkynyl groups having 2-20 carbon atoms.

[0082] The aromatic hydrocarbon group of R can be selected from unsubstituted or substituted aryl groups having 6-20 carbon atoms, or unsubstituted or substituted heteroaryl groups having 2-20 carbon atoms.

[0083] Preferably, R in Formula 1 can be an aliphatic hydrocarbon group, specifically, it can be an unsubstituted or cycloalkane group with 4-20 carbon atoms substituted with an alkyl group having 1-3 carbon atoms.

[0084] In one embodiment of the present invention, R' of Formula 1 may be an alkyl group having 1-5 carbon atoms, preferably an alkyl group having 2-4 carbon atoms, and more preferably a propene group.

[0085] In one embodiment of the present invention, Formula 1 can be represented by the following Formula 1-1.

[0086] [Equation 1-1]

[0087]

[0088] In Equation 1-1,

[0089] R, R1 to R5, E, E', n, m and x are the same as those defined in Equation 1.

[0090] Specifically, Equation 1 can be represented by Equation 1A below.

[0091] [Formula 1A]

[0092]

[0093] In Equation 1A,

[0094] n, m, and x are the same as those defined in Equation 1.

[0095] In one embodiment of the invention, the amount of oligomer can be in the range of 0.1% to 5% by weight, preferably 0.2% to 3% by weight, and more preferably 0.5% to 1% by weight, based on the total weight of the non-aqueous electrolyte solution.

[0096] When the amount of oligomer is within the above range, it is desirable from the perspective of improving battery capacity and ensuring high-temperature safety. Specifically, when the amount of oligomer is less than 0.1% by weight, the effect of adding oligomer is not significant, and when the amount of oligomer is greater than 5% by weight, there is a problem that the initial capacity decreases due to the increase in resistance.

[0097] (b) Additives

[0098] In one embodiment of the invention, the non-aqueous electrolyte solution may further include at least one additive selected from the group consisting of lithium salt additives and nitrile additives, and may preferably include lithium salt additives or nitrile additives.

[0099] Lithium salt additives can be at least one selected from the group consisting of lithium tetrafluoroborate (LiBF4), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiODFB), lithium difluorophosphate (LiDFP), and lithium difluorobis(oxalato)phosphate (LiDFOP), and the lithium salt is different from lithium salt additives. Oligomers represented by Formula 1 can help improve the safety and high-temperature life of lithium secondary batteries, but have the limitation of reduced battery capacity due to increased interfacial resistance between the electrode and electrolyte. However, when lithium salt additives are used simultaneously, a thinner and denser film can be formed through electrochemical reactions, thus increasing battery capacity and further improving high-temperature life.

[0100] In one embodiment of the invention, the amount of lithium salt additive can range from 0.05% to 5% by weight, preferably from 0.1% to 3% by weight, and more preferably from 0.5% to 2% by weight, based on the total weight of the non-aqueous electrolyte solution.

[0101] Ideally, when the amount of lithium salt additive is within the above range, it can adequately compensate for the problem caused by the increase in resistance during the formation of the oligomer film.

[0102] In one embodiment of the present invention, the non-aqueous electrolyte solution may include two or more different types of lithium salt additives, and may preferably include LiODFB and LiBOB.

[0103] In one embodiment of the present invention, the weight ratio of LiODFB to LiBOB can be in the range of 10:90 to 90:10, preferably 20:80 to 80:20, and more preferably 40:60 to 60:40.

[0104] The nitrile additives may be at least one selected from the group consisting of succinonitrile (SN), adiponitrile (ADN), sebaconitrile (SBN), dicyanobutene (DCB), hexanetricarbonitrile (HTCN), 1,2,3-tris(2-cyanoethoxy)propane (TCEP), and ethylene glycol bis(propionitrile) ether (ASA3).

[0105] When oligomers represented by Formula 1 are used together with nitrile additives, a synergistic effect of further improving high-temperature life can be obtained compared with the use of oligomers alone, since the nitrile additives control the dissolution of transition metals from the cathode.

[0106] In one embodiment of the invention, the amount of nitrile additives can range from 0.05% by weight to 10% by weight, preferably from 1% by weight to 7% by weight, and more preferably from 2.5% by weight to 5% by weight, based on the total weight of the non-aqueous electrolyte solution.

[0107] When the amount of nitrile additives is less than 0.05% by weight, the effect of controlling transition metal dissolution is not significant. When the amount of nitrile additives is greater than 10% by weight, there are problems with decreased wetting and decreased ionic conductivity due to increased viscosity.

[0108] In one embodiment of the invention, the non-aqueous electrolyte solution may contain two or more different types of nitrile additives, and may preferably contain dicyanobutylene and hexamethylenetrionitrile.

[0109] In one embodiment of the present invention, the weight ratio of dicyanobutene to triadimenol can be in the range of 10:90 to 90:10, preferably 20:80 to 60:40, and more preferably 30:70 to 50:50.

[0110] In addition, the non-aqueous electrolyte solution of the present invention may optionally contain the following other additives as needed to prevent electrolyte decomposition or further improve the low-temperature high-rate discharge characteristics, high-temperature stability, prevent overcharging, and suppress battery expansion at high temperatures.

[0111] Other additives may be at least one compound selected from carbonate compounds, halogen-substituted carbonate compounds, sulfonyl lactone compounds, sulfate compounds, phosphate compounds, borate compounds, amine compounds, silane compounds, imide compounds, and benzene compounds.

[0112] The carbonate compound may be at least one selected from vinylene carbonate (VC) and ethylene ethylene carbonate (VEC), and specifically may be vinylene carbonate.

[0113] Halogen-substituted carbonate compounds can be fluoroethylene carbonate (FEC).

[0114] Sulfolactone compounds are materials capable of forming a stable solid electrolyte interphase (SEI) film on the negative electrode surface through a reduction reaction. The sulfonolactone compound may be at least one selected from 1,3-propanesulfonolactone (PS), 1,4-butanesulfonolactone, ethylenesulfonolactone, 1,3-propenesulfonolactone (PRS), 1,4-butenesulfonolactone, and 1-methyl-1,3-propenesulfonolactone, and may specifically be 1,3-propanesulfonolactone (PS).

[0115] Sulfate compounds are materials that can undergo electrolysis on the negative electrode surface to form a stable SEI film that will not crack even during high-temperature storage. The sulfate compounds can be at least one selected from ethylene sulfate (Esa), propylene sulfate (TMS), or methyl propylene sulfate (MTMS).

[0116] The phosphate compound may be at least one selected from lithium difluoro(bis(oxalate)phosphate), lithium difluorophosphate, tri(trimethylsilyl)phosphate, tri(trimethylsilyl)phosphite, tri(2,2,2-trifluoroethyl)phosphate and tri(trifluoroethyl)phosphite.

[0117] Borate compounds can be lithium tetraphenylborate.

[0118] The amine compound may be at least one selected from triethanolamine and ethylenediamine, and the silane compound may be tetravinylsilane.

[0119] Imide compounds can be N,N'-dicyclohexylcarbodiimide (DCC).

[0120] Benzene compounds can be at least one selected from monofluorobenzene, difluorobenzene, trifluorobenzene, and tetrafluorobenzene.

[0121] Based on the total weight of the non-aqueous electrolyte solution, the amount of other additives can range from 0.1 wt% to 15 wt%, for example, 5 wt% to 15 wt%. When the amount of other additives is less than 0.1 wt%, the effect of improving the low-temperature capacity, high-temperature storage characteristics, and high-temperature life characteristics of the battery is not significant, and when the content of other additives is greater than 15 wt%, excessive side reactions in the electrolyte solution may occur during the charging and discharging process of the battery.

[0122] (c) Lithium salts

[0123] In addition to lithium salt additives, any lithium salt commonly used in the electrolyte solution of lithium secondary batteries can be used as a lithium salt. Specifically, the lithium salt can be at least one selected from lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), preferably LiPF6.

[0124] The lithium salt can be appropriately varied within the range of normal use, but specifically, it can be included in the electrolyte solution at a concentration of 0.1M to 4.0M, for example, 1.0M to 2.5M. If the concentration of the lithium salt is greater than 4.0M, the lithium ion migration effect in the non-aqueous electrolyte solution may be reduced due to the increased viscosity of the electrolyte solution.

[0125] (d) Organic solvents

[0126] In the non-aqueous electrolyte solution according to embodiments of the present invention, the type of organic solvent is not limited, as long as the organic solvent can minimize decomposition caused by oxidation reactions during the charging and discharging of the secondary battery, and can exhibit the desired properties together with the additives. For example, carbonate organic solvents, ether organic solvents, or ester organic solvents can be used alone, or a mixture of two or more of them.

[0127] The carbonate organic solvent in the organic solvent can include at least one selected from cyclic carbonate organic solvents and linear carbonate organic solvents. Specifically, the cyclic carbonate organic solvent can be at least one selected from ethylene carbonate (EC), propylene carbonate (PC), 1,2-butenyl carbonate, 2,3-butenyl carbonate, 1,2-pentadienyl carbonate, 2,3-pentadienyl carbonate, and fluoroethylene carbonate (FEC), specifically a mixed solvent of ethylene carbonate having a high dielectric constant and propylene carbonate having a relatively lower melting point than ethylene carbonate.

[0128] In addition, linear carbonate organic solvents are organic solvents with low viscosity and low dielectric constant. The linear carbonate organic solvent can be at least one selected from dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, methyl ethyl carbonate (EMC), methyl propyl carbonate and ethyl propyl carbonate, specifically dimethyl carbonate.

[0129] The ether organic solvent may be selected from at least one of dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether and ethyl propyl ether, but is not limited thereto.

[0130] Ester organic solvents can be at least one selected from straight-chain ester organic solvents and cyclic ester organic solvents.

[0131] The linear ester organic solvent may be at least one selected from methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate and butyl propionate, but is not limited thereto.

[0132] Cyclic ester organic solvents may be selected from at least one of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone and ε-caprolactone, but are not limited thereto.

[0133] High-viscosity cyclic carbonate organic solvents can be used as organic solvents because they readily dissociate lithium salts in electrolytes due to their high dielectric constant. Furthermore, to prepare electrolytes with higher conductivity, low-viscosity and low-dielectric-constant linear carbonate compounds (such as dimethyl carbonate and diethyl carbonate), as well as linear ester compounds and cyclic carbonate organic solvents, can be mixed in appropriate proportions and used as organic solvents.

[0134] Specifically, cyclic carbonate compounds and straight-chain ester compounds can be mixed and used as organic solvents, and the weight ratio of cyclic carbonate compounds to straight-chain ester compounds in the organic solvent may be in the range of 10:90 to 70:30.

[0135] The remaining portion of the total weight of the non-aqueous electrolyte solution of the present invention, excluding organic solvents, may be organic solvents, except for components other than, for example, oligomers, lithium salts and additives, unless otherwise stated.

[0136] Lithium secondary batteries

[0137] Next, the lithium secondary battery according to the present invention will be described.

[0138] The lithium secondary battery according to the present invention includes a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, a separator disposed between the positive electrode and the negative electrode, and the aforementioned non-aqueous electrolyte solution. Since the non-aqueous electrolyte solution has already been described above, its description is omitted; the other components will be described below.

[0139] The lithium secondary battery of the present invention can be prepared according to typical methods known in the art. For example, after forming an electrode assembly consisting of a positive electrode, a negative electrode, and a separator disposed between the positive and negative electrodes stacked in sequence, the lithium secondary battery of the present invention can be prepared by inserting the electrode assembly into a battery casing and then injecting a non-aqueous electrolyte solution according to the present invention.

[0140] (a) Positive electrode

[0141] A positive electrode can be prepared by coating a positive electrode current collector with a slurry containing a mixture of positive electrode active material, binder, conductive agent and solvent.

[0142] There are no particular restrictions on the positive current collector, as long as it is conductive and will not cause adverse chemical changes to the battery. For example, it can be made of stainless steel, aluminum, nickel, titanium, sintered carbon, or aluminum or stainless steel with a surface treatment using one of carbon, nickel, titanium, silver, etc.

[0143] The positive electrode active material is a compound capable of reversibly inserting and deintercalating lithium, wherein the positive electrode active material can be selected from LiNiO2, including LCO (LiCoO2), LNO (LiNiO2), LMO (LiMnO2), LiMn2O4, LiCoPO4, LFP (LiFePO4), LiNiMnCoO2, and NMC (LiNiCoMnO2). 1-x-y-z Co x M 1 y M 2 z O2(M 1 and M 2Each independently selected from the group consisting of aluminum (Al), nickel (Ni), cobalt (Co), iron (Fe), manganese (Mn), vanadium (V), chromium (Cr), titanium (Ti), tungsten (W), tantalum (Ta), magnesium (Mg), and molybdenum (Mo), and x, y, and z are each independently the atomic fraction of the oxide constituent element, where 0 ≤ x < 0.5, 0 ≤ y < 0.5, 0 ≤ z < 0.5, and x + y + z = 1) of at least one.

[0144] Specifically, the positive electrode active material may include a lithium metal oxide, which includes lithium and at least one metal, such as cobalt, manganese, nickel, or aluminum.

[0145] More specifically, the lithium metal oxide may be selected from lithium manganese oxides such as LiMnO2 and LiMn2O4; lithium cobalt-based oxides such as LiCoO2; lithium nickel oxides such as LiNiO2; such as LiNi 1-Y Mn Y O2 (where 0 < Y < 1) and LiMn 2- z Ni z O4 (where 0 < z < 2) of lithium nickel manganese oxides; such as LiNi 1-Y1 Co Y1 O2 (where 0 < Y1 < 1)) of lithium nickel cobalt oxides; such as LiCo 1-Y2 Mn Y2 O2 (where 0 < Y2 < 1) and LiMn 2-z1 Co​​​​​​​​​​​​​​​​​​​​​​​​Among these materials, from the perspective of improving battery capacity characteristics and stability, lithium metal oxides can be LiCoO2, LiMnO2, LiNiO2, and lithium nickel manganese cobalt oxides (e.g., Li(Ni)O2). 1 / 3 Mn 1 / 3 Co 1 / 3 O2, Li(Ni) 0.6 Mn 0.2 Co 0.2 O2, Li(Ni) 0.5 Mn 0.3 Co 0.2 O2, Li(Ni) 0.7 Mn 0.15 Co 0.15 O2, Li(Ni) 0.8 Mn 0.1 Co 0.1 (O2, etc.), or lithium nickel cobalt aluminum oxide (e.g., Li(Ni) 0.8 Co 0.15 Al 0.05 The lithium metal oxide can be selected from Li(Ni)O2, etc., and the composition and content ratio of the constituent elements forming the lithium metal oxide are controlled according to the specific requirements. When considering significant improvement effects, the lithium metal oxide can be selected from Li(Ni)O2, etc. 0.6 Mn 0.2 Co 0.2 O2, Li(Ni) 0.5 Mn 0.3 Co 0.2 O2, Li(Ni) 0.7 Mn 0.15 Co 0.15 )O2 and Li(Ni 0.8 Mn 0.1 Co 0.1 At least one of O2.

[0147] Based on the total weight of solids excluding solvent in the cathode mixture slurry, the content of cathode active material is 60% to 99% by weight, preferably 70% to 99% by weight, and more preferably 80% to 98% by weight.

[0148] Adhesives are components used to help bond active and conductive materials together, as well as to bond with current collectors.

[0149] Examples of adhesives may include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene (PE), polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber (SBR), fluororubber and various copolymers thereof.

[0150] Typically, based on the total weight of solids excluding solvent in the cathode mixture slurry, the binder content can be from 1% to 20% by weight, preferably from 1% to 15% by weight, and more preferably from 1% to 10% by weight.

[0151] Conductive agents are components used to further improve the conductivity of positive electrode active materials.

[0152] There are no particular restrictions on conductive materials, as long as they are conductive and do not cause chemical changes in the battery. Examples include graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal cracking black; conductive fibers such as carbon fiber and metal fiber; metal powders such as fluorocarbon powder, aluminum powder, and nickel powder; conductive whiskers such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides such as titanium oxide; and conductive materials such as polystyrene derivatives.

[0153] Typically, based on the total weight of solids excluding solvent in the positive electrode mixture slurry, the content of conductive material is from 1% to 20% by weight, preferably from 1% to 15% by weight, and more preferably from 1% to 10% by weight.

[0154] The solvent may include an organic solvent, such as N-methyl-2-pyrrolidone (NMP), and when a positive electrode active material and optionally a binder and conductive material are included, the solvent may be used in an amount to achieve a preferred viscosity. For example, the solvent content may be such that the concentration of solids including the positive electrode active material and optionally the binder and conductive material is in the range of 50% to 95% by weight, preferably 50% to 80% by weight, more preferably 55% to 70% by weight.

[0155] (b) Negative electrode

[0156] A negative electrode can be prepared by coating a negative electrode slurry containing a negative electrode active material, a binder, a conductive material, a solvent, etc., onto a negative electrode current collector, and then drying and rolling the coated negative electrode current collector.

[0157] Negative electrode current collectors typically have a thickness ranging from 3 μm to 500 μm. There are no particular limitations on the type of negative electrode current collector, as long as it possesses high conductivity without causing chemical changes in the battery. Examples include copper; stainless steel; aluminum; nickel; titanium; sintered carbon; copper or stainless steel with surface treatment using one of carbon, nickel, titanium, or silver; or aluminum-cadmium alloys. Furthermore, similar to positive electrode current collectors, negative electrode current collectors can have fine surface roughness to improve the bonding strength with the negative electrode active material, and they can be used in various shapes, such as films, sheets, foils, meshes, porous bodies, foams, and nonwoven fabrics.

[0158] In addition, the negative electrode active material may include at least one selected from lithium metal, a carbon material capable of reversibly inserting / extracting lithium ions, a metal or an alloy of a metal and lithium, a metal composite oxide, a material doped and undoped with lithium, and a transition metal oxide.

[0159] As the carbon material capable of reversibly inserting / extracting lithium ions, carbon-based negative electrode active materials commonly used in lithium ion secondary batteries can be used without particular limitation, and representative examples thereof may include crystalline carbon, amorphous carbon, or a combination thereof. Examples of crystalline carbon may include graphite such as irregular, planar, flaky, spherical, or fibrous natural graphite or artificial graphite, and examples of amorphous carbon may include soft carbon (low-temperature fired carbon), hard carbon, mesophase pitch carbide, fired coke, and the like.

[0160] As the metal or the alloy of lithium and a metal, a metal selected from copper (Cu), nickel (Ni), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), silicon (Si), antimony (Sb), lead (Pb), indium (In), zinc (Zn), barium (Ba), radium (Ra), germanium (Ge), aluminum (Al), and tin (Sn), or an alloy of lithium and a metal can be used.

[0161] As the metal composite oxide, one selected from PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5, Li X Fe2O3 (0 ≤ X ≤ 1), Li X WO2 (0 ≤ X ≤ 1), and Sn x Me 1-X Me' y O z (Me: Mn, Fe, Pb, Ge; Me': Al, boron (B), phosphorus (P), Si, elements of Groups I, II, and III of the periodic table, or a halogen; 0 < x ≤ 1; 1 ≤ y ≤ 3; 1 ≤ z ≤ 8) can be used.

[0162] The material capable of doping and undoping lithium may include Si, SiO x(0 < x ≤ 2), Si-Y alloy (where Y is an element selected from alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof, but not including Si), Sn, SnO2, Sn-Y (where Y is an element selected from alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof, but not including Sn), and a mixture of SiO2 and at least one of them can also be used. Element Y can be selected from Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db (dubnium), Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof.

[0163] The transition metal oxide can include lithium titanium composite oxide (LTO), vanadium oxide, and lithium vanadium oxide.

[0164] In the present invention, the negative electrode active material can be graphite.

[0165] Based on the total weight of the solids other than the solvent in the negative electrode mixture slurry, the content of the negative electrode active material is 60 wt% to 99 wt%, preferably 70 wt% to 99 wt%, more preferably 80 wt% to 98 wt%.

[0166] The binder is a component used to assist the bonding between the conductive material, the active material, and the current collector. Examples of the binder can include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber (SBR), fluororubber, and various copolymers thereof.

[0167] Based on the total weight of the solids other than the solvent in the negative electrode mixture slurry, the content of the binder is 1 wt% to 20 wt%, preferably 1 wt% to 15 wt%, more preferably 1 wt% to 10 wt%.

[0168] Conductive agents are components used to further improve the conductivity of negative electrode active materials. There are no particular limitations on conductive agents, as long as they are conductive and do not cause adverse chemical changes in the battery. Examples include graphite such as natural or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal cracking black; conductive fibers such as carbon fibers and metal fibers; metal powders such as fluorocarbon powder, aluminum powder, and nickel powder; conductive whiskers such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides such as titanium oxide; and conductive materials such as polystyrene derivatives.

[0169] Based on the total weight of solids excluding solvent in the negative electrode mixture slurry, the content of conductive agent can be from 1% to 20% by weight, preferably from 1% to 15% by weight, and more preferably from 1% to 10% by weight.

[0170] The solvent may include water; or organic solvents, such as N-methyl-2-pyrrolidone (NMP) and alcohols, and when the negative electrode active material, as well as optional binders and conductive materials, are included, the solvent may be used in an amount to achieve the desired viscosity. For example, the solvent content may be such that the concentration of the solids comprising the negative electrode active material, as well as optional binders and conductive materials, is in the range of 50% by weight to 95% by weight, for example, 70% by weight to 90% by weight.

[0171] When the metal itself is used as the negative electrode, the negative electrode can be manufactured by physically bonding, rolling, or depositing the metal onto the metal thin film itself or the negative electrode current collector. Electrodeposition of metal or chemical vapor deposition can be used as the deposition methods described above.

[0172] For example, the metal bonded / rolled / deposited on the metal film itself or on the negative electrode current collector can be a metal selected from the group consisting of nickel (Ni), tin (Sn), copper (Cu) and indium (In), or an alloy of two of these metals.

[0173] (c) partition

[0174] The lithium secondary battery according to the present invention includes a separator between the positive electrode and the negative electrode.

[0175] The separator serves to block internal short circuits between two electrodes and to impregnate the electrolyte. The separator is prepared by mixing polymer resin, filler and solvent to form a separator composition, coating the separator composition directly onto the electrode and drying it to form a separator membrane, or by casting the separator composition onto a support and drying it, and then laminating the separator membrane peeled off from the support onto the electrode.

[0176] Commonly used porous polymer membranes, such as those prepared from polyolefin polymers like ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers, can be used alone or in layers as separators. Additionally, typical porous nonwoven fabrics, such as those formed from high-melting-point glass fibers, polyethylene terephthalate fibers, etc., can be used, but the invention is not limited thereto.

[0177] In this case, porous separators typically have pore sizes ranging from 0.01 μm to 50 μm and porosities ranging from 5% to 95%. Furthermore, porous separators typically have thicknesses ranging from 5 μm to 300 μm.

[0178] The lithium secondary battery according to the present invention, as described above, can be used in portable devices such as mobile phones, laptops, and digital cameras, as well as electric vehicles such as hybrid electric vehicles (HEVs).

[0179] Therefore, according to another embodiment of the present invention, a battery module including a lithium secondary battery as a unit battery and a battery pack including the battery module are provided.

[0180] Battery modules or battery packs can be used as a power source for at least one medium-sized and large device, such as power tools, electric vehicles including electric vehicles (EVs), hybrid electric vehicles and plug-in hybrid electric vehicles (PHEVs), and energy storage systems.

[0181] The shape of the lithium secondary battery of the present invention is not particularly limited, but it can be cylindrical, prismatic, pouch or coin-shaped.

[0182] The lithium secondary battery according to the present invention can be used not only as a battery unit for powering small devices, but also as a unit battery in medium and large battery modules comprising multiple battery units.

[0183] The present invention will be described in detail below with reference to specific embodiments.

[0184] Implementation

[0185] <Example>

[0186] Example 1.

[0187] (Preparation of non-aqueous electrolyte solutions)

[0188] A non-aqueous electrolyte solution with a total weight of 100 wt% was prepared by mixing 1.2 M LiPF6, 0.5 wt% of an oligomer represented by Formula 1A (Mw: 6,000 g / mol, m = 1, n = 1, x = 10), 0.5 wt% of VEC (ethylene ethylene carbonate), 4 wt% of PS (1,3-propanesulfonate lactone), 7 wt% of FEC (fluoroethylene carbonate), 2 wt% of SN (succinate), 3 wt% of HTCN (1,3,6-hexamethylenetrionitrile), 0.1 wt% of DCC (N,N'-dicyclohexylcarbodiimide), 0.5 wt% of LiBOB, 0.5 wt% of LiODFB, and the remaining organic solvent. In this case, a non-aqueous organic solvent of ethylene carbonate (EC): propylene carbonate (PC): ethyl propionate (EP): propyl propionate (PP) in a volume ratio of 20:10:20:50 was used as the organic solvent.

[0189] [Formula 1A]

[0190]

[0191] (Preparation of lithium secondary batteries)

[0192] LiCoO2, carbon black, and polyvinylidene fluoride (PVDF) were added to N-methyl-2-pyrrolidone (NMP) as a solvent in a weight ratio of 94:3:3 to prepare a positive electrode mixture slurry. This positive electrode mixture slurry was coated onto an aluminum (Al) film with a thickness of approximately 20 μm, which served as the positive electrode current collector. The film was then dried and rolled to prepare the positive electrode.

[0193] Graphite, PVDF, and carbon black, used as negative electrode active materials, were added to NMP as a solvent in a weight ratio of 96:3:1 to prepare a negative electrode mixture slurry. This negative electrode mixture slurry was coated onto a 10 μm thick copper (Cu) film, which served as the negative electrode current collector, and then dried and rolled to prepare the negative electrode.

[0194] A lithium secondary battery is prepared by sequentially stacking a positive electrode, a separator formed by three layers of polypropylene / polyethylene / polypropylene (PP / PE / PP), and a negative electrode, and injecting 5 mL of a pre-prepared non-aqueous electrolyte solution into the electrode assembly.

[0195] Example 2.

[0196] The lithium secondary battery was prepared in the same manner as in Example 1, except that the amount of oligomer represented by Formula 1A was changed to 1 wt% during the preparation of the non-aqueous electrolyte solution in Example 1.

[0197] Example 3.

[0198] The lithium secondary battery was prepared in the same manner as in Example 2, except that LiBOB was not added during the preparation of the non-aqueous electrolyte in Example 2, and the amount of LiODFB was changed to 1% by weight.

[0199] Example 4.

[0200] The lithium secondary battery was prepared in the same manner as in Example 2, except that LiDFOP was added instead of LiBOB during the preparation of the non-aqueous electrolyte solution in Example 2.

[0201] Example 5.

[0202] The lithium secondary battery was prepared in the same manner as in Example 2, except that LiBF4 was added instead of LiBOB during the preparation of the non-aqueous electrolyte solution in Example 2.

[0203] Example 6.

[0204] The lithium secondary battery was prepared in the same manner as in Example 2, except that LiDFP was added instead of LiBOB during the preparation of the non-aqueous electrolyte solution in Example 2.

[0205] Example 7.

[0206] The lithium secondary battery was prepared in the same manner as in Example 2, except that LiBOB was not added during the preparation of the non-aqueous electrolyte solution in Example 2.

[0207] Example 8.

[0208] The lithium secondary battery was prepared in the same manner as in Example 7, except that DCB (dicyanobutylene) was added instead of HTCN during the preparation of the non-aqueous electrolyte solution in Example 7.

[0209] Example 9.

[0210] The lithium secondary battery was prepared in the same manner as in Example 7, except that ADN (adiponitrile) was added instead of HTCN during the preparation of the non-aqueous electrolyte solution in Example 7.

[0211] Example 10.

[0212] The lithium secondary battery was prepared in the same manner as in Example 7, except that DCB (dicyanobutylene) was added instead of SN during the preparation of the non-aqueous electrolyte solution in Example 7.

[0213] Example 11.

[0214] The lithium secondary battery was prepared in the same manner as in Example 10, except that the amounts of DCB and HTCN were changed to 1% by weight and 1.5% by weight, respectively, during the preparation of the non-aqueous electrolyte solution in Example 10.

[0215] Compare with Example 1.

[0216] The lithium secondary battery was prepared in the same manner as in Example 1, except that no oligomer represented by Formula 1A and no LiBOB were added during the preparation of the non-aqueous electrolyte solution in Example 1.

[0217] Compare with Example 2.

[0218] The lithium secondary battery was prepared in the same manner as in Example 2, except that in the preparation of the non-aqueous electrolyte solution in Example 2, the oligomer represented by formula B (Mw: 6,500 g / mol, m = 1, n = 1, x = 10) was used instead of the oligomer represented by formula 1A, and LiBOB was not added.

[0219] [Formula B]

[0220]

[0221] Compare Example 3.

[0222] The lithium secondary battery was prepared in the same manner as in Example 7, except that no oligomer represented by Formula 1A and no SN and HTCN were added during the preparation of the non-aqueous electrolyte solution in Example 7.

[0223] Compare Example 4.

[0224] The lithium secondary battery was prepared in the same manner as in Example 7, except that no oligomer represented by Formula 1A was added during the preparation of the non-aqueous electrolyte solution in Example 7.

[0225] Compare Example 5.

[0226] The lithium secondary battery was prepared in the same manner as in Example 7, except that, in the preparation of the non-aqueous electrolyte solution in Example 7, the oligomer represented by Formula B (Mw: 6,500 g / mol, m = 1, n = 1, x = 10) was used instead of the oligomer represented by Formula 1A.

[0227] <Experimental Example>

[0228] Experimental Example 1: Initial Capacity Measurement and Lifetime Characteristic Evaluation (High Temperature)

[0229] After each lithium secondary battery in the examples and comparative examples was activated at 25°C at a rate of 0.2C, the gas in each battery was removed by a degassing process. Under constant current / constant voltage (CC / CV) conditions at 45°C, each degassed lithium secondary battery was charged to 4.45V at a rate of 0.7C, charging was stopped at 0.05C, and then discharged to 3.0V at a rate of 0.5C under constant current.

[0230] One charge / discharge cycle was defined as one charge / discharge operation. The initial discharge capacity (one cycle) was measured and listed as the initial capacity in Table 1 below. Furthermore, after 300 cycles, the capacity retention relative to the initial discharge capacity was measured and listed in Table 1 below. The charge / discharge process was performed using a PNE-0506 charger / discharger (manufacturer: PNE solution).

[0231] Experimental Example 2: Thermal Safety Evaluation

[0232] A hot box evaluation test was conducted, in which each lithium secondary battery prepared in the examples and comparative examples was heated to 140°C at a heating rate of 5°C / min in a fully charged state of charge (SOC) of 100%, and then left to stand for one hour to confirm whether the battery was ignited.

[0233] The results are listed in Table 1 below, where a battery ignited is indicated as "failed" and a battery not ignited is indicated as "passed".

[0234] [Table 1]

[0235]

[0236]

[0237] Based on the results in Table 1, it can be confirmed that, compared with the batteries of Comparative Examples 1-5 that do not contain the oligomers represented by Formula 1 of the present invention, the batteries of Examples 1-11 that contain the oligomers represented by Formula 1 of the present invention in the electrolyte solution have better initial capacity, lifespan and thermal safety.

[0238] Specifically, compared with Examples 1-11, Comparative Examples 1, 3, and 4, which did not use oligomers, and Comparative Examples 2 and 5, which used oligomers with the modified end groups of Formula 1 of the present invention, were found to have poor initial capacity and capacity retention. In particular, for Comparative Examples 1, 3, and 4, which did not use oligomers at all, it was confirmed that not only was the capacity retention less than 80%, but they were also susceptible to heat and failed the thermal stability evaluation.

[0239] Furthermore, for Comparative Examples 2 and 5 using oligomers of Formula B, it was confirmed that the initial capacity was reduced compared to Comparative Example 1, which did not contain any oligomers. That is, it can be understood that the initial capacity may be reduced when the end-group structure of Formula 1 of the present invention is not followed.

[0240] Furthermore, when comparing Examples 2 and 3, which were carried out under the same conditions except for lithium salt additives, it can be understood that, even if the total amount of lithium salt additives is the same, Example 2, which mixes the two lithium salt additives, has better initial capacity and lifetime characteristics than Example 3.

[0241] Furthermore, it can be confirmed that Example 2, which uses a combination of LiODFB and LiBOB, exhibits the best lifetime characteristics compared to Examples 2 and 4 to 6, which use a mixture of two lithium salt additives.

[0242] Based on the fact that the initial capacity and capacity retention of Examples 10 and 11 were the best in Examples 7 to 11 under the same conditions of oligomer and lithium salt additives, it can be understood that DCB and HTCN among nitrile additives are the most effective in improving battery capacity and life.

Claims

1. A non-aqueous electrolyte solution for lithium secondary batteries, comprising: Oligomers represented by Formula 1; Lithium salts; and Organic solvents: [Formula 1] In Equation 1, R is an aliphatic hydrocarbon group or an aromatic hydrocarbon group. R' is an unsubstituted or substituted alkyl group having 1-5 carbon atoms. R1 to R4 may be the same as or different from each other, and each is independently an unsubstituted or substituted alkyl group having 1-3 carbon atoms. R5 is an unsubstituted or substituted alkyl group having 1-5 carbon atoms. n, m, and x are the number of repetitions in each unit. Where n is an integer from 1 to 10, m is an integer from 1 to 5, and x is an integer from 1 to 200, and E and E' are either the same as or different from each other, and are each independently represented by Equation 2. [Equation 2] In Equation 2, Ra and Rb may be the same as or different from each other, and each is independently hydrogen, an alkyl group having 1-6 carbon atoms that is unsubstituted or substituted with a halogen group, or an alkenyl group having 1-6 carbon atoms that is unsubstituted or substituted with a halogen group. Rc and Rd may be the same as or different from each other, and each is independently hydrogen or an alkyl group having 1-5 carbon atoms. Rb and Rc can bond to each other to form cycloalkyl groups including O, and Both p and k are repeated numbers. Where p is an integer between 0 and 4, and k is an integer between 1 and 3.

2. The non-aqueous electrolyte solution for lithium secondary batteries according to claim 1, wherein formula 2 is represented by formula 2-1 or formula 2-2: [Equation 2-1] *-(CH2) p' (CH2)2-OH in, In Equation 2-1, p' is the repetition number, where p' is an integer between 0 and 4. [Equation 2-2] In Equation 2-2, p” and s are the repetition numbers. Where p” is an integer between 0 and 4, and s is 1 or 2.

3. The non-aqueous electrolyte solution for lithium secondary batteries according to claim 1, wherein, In Formula 1, the aliphatic hydrocarbon group of R is selected from unsubstituted or substituted alkyl groups having 1-20 carbon atoms, unsubstituted or substituted cycloalkyl groups having 4-20 carbon atoms, unsubstituted or substituted heterocycloalkyl groups having 2-20 carbon atoms, unsubstituted or substituted olefinic groups having 2-20 carbon atoms, and unsubstituted or substituted alkynyl groups having 2-20 carbon atoms. The aromatic hydrocarbon group of R is selected from aryl groups having 6-20 unsubstituted or substituted carbon atoms, and heteroaryl groups having 2-20 unsubstituted or substituted carbon atoms.

4. The non-aqueous electrolyte solution for lithium secondary batteries according to claim 1, wherein formula 1 is represented by formula 1-1: [Equation 1-1] in, In Equation 1-1, R, R1 to R5, E, E', n, m and x are defined in the same way as in Equation 1.

5. The non-aqueous electrolyte solution for lithium secondary batteries according to claim 1, wherein the amount of the oligomer is in the range of 0.1% to 5% by weight based on the total weight of the non-aqueous electrolyte solution.

6. The non-aqueous electrolyte solution for lithium secondary batteries according to claim 1, further comprising at least one additive selected from the group consisting of lithium salt additives and nitrile additives.

7. The non-aqueous electrolyte solution for lithium secondary batteries according to claim 6, wherein the lithium salt additive is at least one selected from the group consisting of lithium tetrafluoroborate, lithium bis(oxalate)borate, lithium difluoro(oxalate)borate, lithium difluorophosphate, and lithium difluorobis(oxalate)phosphate, and... The lithium salt is different from the lithium salt additives.

8. The non-aqueous electrolyte solution for lithium secondary batteries according to claim 6, wherein the amount of the lithium salt additive is in the range of 0.05% by weight to 5% by weight based on the total weight of the non-aqueous electrolyte solution.

9. The non-aqueous electrolyte solution for lithium secondary batteries according to claim 1 further comprises lithium difluoro(oxalate)borate and lithium bis(oxalate)borate.

10. The non-aqueous electrolyte solution for lithium secondary batteries according to claim 9, wherein the weight ratio of lithium difluoro(oxalate)borate to lithium bis(oxalate)borate is in the range of 10:90 to 90:

10.

11. The non-aqueous electrolyte solution for lithium secondary batteries according to claim 6, wherein the nitrile additive is at least one selected from the group consisting of succinic anhydride, adiponitrile, sebaconitrile, dicyanobutene, triaconitrile, 1,2,3-tris(2-cyanoethoxy)propane and ethylene glycol bis(propionitrile) ether.

12. The non-aqueous electrolyte solution for lithium secondary batteries according to claim 6, wherein the amount of the nitrile additive is in the range of 0.05% by weight to 10% by weight based on the total weight of the non-aqueous electrolyte solution.

13. The non-aqueous electrolyte solution for lithium secondary batteries according to claim 1, further comprising dicyanobutylene and hexamethylenetrionitrile.

14. The non-aqueous electrolyte solution for lithium secondary batteries according to claim 13, wherein the weight ratio of dicyanobutylene to hexatrionitrile is in the range of 10:90 to 90:

10.

15. A lithium secondary battery, comprising: A cathode containing positive electrode active materials; A negative electrode containing a negative electrode active material; A partition is disposed between the positive electrode and the negative electrode; and The non-aqueous electrolyte solution according to claim 1.

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