Non-aqueous electrolyte and lithium secondary battery comprising same

Abstract

The present invention relates to a non-aqueous electrolyte comprising: a lithium salt; an organic solvent; and an additive, wherein the additive comprises a compound represented by chemical formula A according to the present invention.

Description

Non-aqueous electrolyte and lithium secondary battery including the same

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0199368 filed December 27, 2024 and Korean Patent Application No. 10-2025-0210945 filed December 26, 2025, the entire contents of which are incorporated herein.

[0003]

[0004] Technology field

[0005] The present invention relates to a non-aqueous electrolyte and a lithium secondary battery containing the same.

[0006]

[0007] With the development of the information society leading to advancements in personal IT devices and computer networks, and the accompanying increase in overall societal dependence on electrical energy, there is a growing demand for the development of technologies to efficiently store and utilize electrical energy.

[0008] Rechargeable batteries are the most suitable technology for various applications among developed technologies. Among these, there is growing interest in lithium-ion batteries, which not only allow for miniaturization sufficient for application in personal IT devices but also possess the highest energy density. In particular, lithium-ion batteries are being applied in the electric vehicle and power storage markets. To this end, it is necessary to ensure high energy density, high power output characteristics, and safety for lithium-ion batteries, as well as secure long lifespan characteristics.

[0009] Generally, lithium secondary batteries are manufactured by injecting or impregnating a non-aqueous electrolyte into an electrode assembly consisting of a positive electrode, a negative electrode, and a porous separator. In this regard, the electrolyte of a lithium secondary battery is typically a non-aqueous solution containing lithium salts, organic solvents, etc., and the organic solvent is typically a carbonate-based organic solvent, while a carbon-based active material is mainly used as the negative electrode active material.

[0010] Meanwhile, during the operation of a lithium secondary battery, as lithium ions repeatedly insert into and extract from the negative and positive electrodes, the organic solvent and lithium salt constituting the electrolyte undergo reductive decomposition on the surface of the negative electrode to form a solid electrolyte interphase (SEI) film composed of various organic and inorganic materials. At this time, various byproducts are formed due to the decomposition of the organic solvent and lithium salt during the formation of the SEI film; therefore, methods involving the combined use of various additives are emerging to prevent the degradation of the electrochemical characteristics of the secondary battery caused by these byproducts.

[0011] However, if the amount of additive for forming the SEI film is excessively large, a problem arises where the battery resistance increases; conversely, if the amount of additive is excessively small, the negative electrode is not sufficiently protected, leading to a problem where the amount of gas generated due to solvent decomposition during cycling increases rapidly.

[0012] Therefore, there is a need for an additive that can reduce gas generation by sufficiently protecting the cathode while lowering resistance.

[0013]

[0014] One objective of the present invention is to solve the above-mentioned problems by using an additive comprising a compound represented by Formula A according to the present invention, thereby providing a non-aqueous electrolyte capable of reducing gas generation while achieving excellent resistance characteristics, and a lithium secondary battery comprising the same.

[0015]

[0016] However, the problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below.

[0017]

[0018] [1] The present invention provides a non-aqueous electrolyte comprising a lithium salt; an organic solvent; and an additive, wherein the additive comprises a compound represented by the following chemical formula A.

[0019] [Chemical Formula A]

[0020]

[0021] In the above chemical formula A,

[0022] L1 and L2 are each independently an alkylene group, ester group, sulfone group, sulfonate group, sulfate group having 1 to 10 carbon atoms, or a combination of two or more of these, and

[0023] R1 is selected from the substituents represented by the following chemical formulas B-1 and B-2, and

[0024] [Chemical Formula B-1]

[0025]

[0026] [Chemical Formula B-2]

[0027]

[0028] R2 is selected from substituents represented by the following chemical formulas C-1 to C-3, and

[0029] [Chemical Formula C-1]

[0030]

[0031] [Chemical Formula C-2]

[0032]

[0033] [Chemical Formula C-3]

[0034]

[0035] In the above formulas B-1 to B-2 and C-1 to C-3,

[0036] X1 and X2 are each independently *-O-* or *-C(R X1 R X2 It is one of )-* and,

[0037] R3 to R7, the above R x1 and R x2 Each is independently hydrogen, halogen, nitrile group, ester group, ether group, ketone group, carboxyl group, substituted or unsubstituted alkyl group, substituted or unsubstituted alkenyl group, substituted or unsubstituted alkynyl group, substituted or unsubstituted alkoxy group, boron group, borate group, isocyanate group, isothiocyanate group, silyl group, siloxane group, sulfone group, sulfonate group, sulfate group, or a combination of two or more of these, n1 to n4 are integers selected independently from 1 to 3, m1 and m2 are integers selected independently from 1 to 2, and * is a bonding site.

[0038] [2] In the present invention [1], the R1 may be selected from the substituents represented by the following formulas B-1-1, B-1-2, B-1-3, B-1-4, B-1-5, B-1-6, B-2-1 and B-2-2.

[0039] [Chemical Formula B-1-1]

[0040]

[0041] [Chemical Formula B-1-2]

[0042]

[0043] [Chemical Formula B-1-3]

[0044]

[0045] [Chemical Formula B-1-4]

[0046]

[0047] [Chemical Formula B-1-5]

[0048]

[0049] [Chemical Formula B-1-6]

[0050]

[0051] [Chemical Formula B-2-1]

[0052]

[0053] [Chemical Formula B-2-2]

[0054]

[0055] The above * is the connection site.

[0056] [3] In the present invention [1] or [2], the R2 may be selected from the substituents represented by the following formulas C-1-1, C-1-2, C-2-1 and C-3-1.

[0057] [Chemical Formula C-1-1]

[0058]

[0059] [Chemical Formula C-1-2]

[0060]

[0061] [Chemical Formula C-2-1]

[0062]

[0063] [Chemical Formula C-3-1]

[0064]

[0065] The above * is the connection site.

[0066] [4] In at least one of [1] to [3] of the present invention, in the formula A, L1 is a methylene group and L2 may be an ethylene group.

[0067] [5] In at least one of [1] to [4], the present invention may include at least one compound represented by the formula A selected from the group consisting of the following formulas: formula Aa, formula Ab, formula Ac, and formula Ad.

[0068] [Chemical Formula Aa]

[0069]

[0070] [Chemical Formula Ab]

[0071]

[0072] [Chemical Formula Ac]

[0073]

[0074] [Chemical Formula Ad]

[0075]

[0076] [6] In at least one of [1] to [5], the additive may be included in an amount of 0.01% to 10% by weight based on the total weight of the non-aqueous electrolyte.

[0077] [7] The present invention provides a lithium secondary battery comprising: a positive electrode; a negative electrode disposed opposite to the positive electrode; and at least one of [1] to [6] a non-aqueous electrolyte.

[0078] [8] In the present invention [7], the cathode may include a carbon-based cathode active material.

[0079] [9] In the present invention, the carbon-based cathode active material may include natural graphite in accordance with [7] or [8].

[0080]

[0010] The present invention relates to at least one of [7] to [9], wherein the carbon-based negative electrode active material has a BET specific surface area of ​​2 m² 2 / g to 8m 2 It can be / g.

[0081]

[0011] In at least one of [7] to

[0010] of the present invention, the carbon-based negative electrode active material may have an average particle size of 10 μm to 100 μm.

[0082]

[0083] An additive comprising a compound represented by chemical formula A according to the present invention includes a carbonyl group and two structures represented by a specific chemical formula within the main chain, thereby forming a robust and uniform film while forming an SEI film having excellent mechanical strength, high temperature stability, and Li ion affinity, which can improve resistance characteristics, high temperature life characteristics, high temperature storage characteristics, and gas generation characteristics.

[0084]

[0085] Terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0086] The terms used in this invention are used merely to describe exemplary embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise.

[0087] In the present invention, terms such as “comprising,” “having,” or “having” are intended to specify the existence of the implemented features, numbers, steps, components, or combinations thereof, and should be understood as not excluding in advance the existence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0088] In the present invention, the “BET specific surface area” is measured by the BET method and, preferably, can be calculated from the amount of nitrogen gas adsorbed at liquid nitrogen temperature (77K) using BEL Japan’s BELSORP-mino II.

[0089] In the present invention, "average particle size" refers to the particle size (D) at 50% of the volume cumulative amount of the volume cumulative particle size distribution of the powder to be measured. 50 ...means. The above average particle size can be measured using the laser diffraction method. The laser diffraction method generally enables the measurement of particle sizes ranging from the submicron range to several millimeters, and can obtain results with high reproducibility and high resolution. For example, the average particle size can be measured by dispersing the powder to be measured in a dispersion medium, introducing it into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000), irradiating it with ultrasound of approximately 28 kHz at an output of 60 W, obtaining a volume-cumulative particle size distribution graph, and then determining the particle size corresponding to 50% of the volume-cumulative amount.

[0090] In addition, in the description of "a to b carbon atoms" within this specification, "a" and "b" refer to the number of carbon atoms included in a specific functional group. That is, the functional group may include "a" to "b" carbon atoms. For example, "alkyl group having 1 to 5 carbon atoms" refers to an alkyl group containing 1 to 5 carbon atoms, namely CH3-, CH3CH2-, CH3CH2CH2-, (CH3)2CH-, CH3CH2CH2CH2-, (CH3)2CHCH2-, CH3CH2CH2CH2CH2-, (CH3)2CHCH2CH2-, etc.

[0091] In addition, in this specification, alkyl groups or aryl groups may all be substituted or unsubstituted. Unless otherwise defined, the term "substitution" above means that at least one hydrogen bonded to a carbon is substituted with an element other than hydrogen, for example, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a cycloalkenyl group having 3 to 12 carbon atoms, a cycloalkynyl group having 3 to 12 carbon atoms, a heterocycloalkyl group having 3 to 12 carbon atoms, a heterocycloalkynyl group having 2 to 12 carbon atoms, an aryloxy group having 6 to 12 carbon atoms, a halogen atom, a fluoroalkyl group having 1 to 20 carbon atoms, a nitro group, an aryl group having 6 to 20 carbon atoms, and a group having 2 to It means that it is substituted with a heteroaryl group of 20 carbon atoms, a haloaryl group having 6 to 20 carbon atoms, etc.

[0092]

[0093] In the case of additives included in conventional non-aqueous electrolytes, various types of compounds were used in combination to prevent the formation of byproducts generated during the SEI film formation process or to more easily form an SEI film with excellent physical and chemical properties.

[0094] However, if the amount of additive for forming the SEI film is excessively large, a problem arises where the battery resistance increases; conversely, if the amount of additive is excessively small, the negative electrode is not sufficiently protected, leading to a problem where the amount of gas generated due to solvent decomposition during cycling increases rapidly.

[0095] Accordingly, the inventors have made continuous efforts to develop an additive capable of reducing gas generation while lowering resistance and sufficiently protecting the cathode. As a result, they discovered that when an additive containing a compound represented by Formula A according to the present invention is included in a non-aqueous electrolyte, excellent resistance, high-temperature lifespan, and high-temperature storage characteristics are achieved, thereby completing the present invention.

[0096]

[0097] The present invention will be described in a preferred manner below.

[0098] The non-aqueous electrolyte according to the present invention and the lithium secondary battery including the same comprise at least one of the configurations disclosed below, and may comprise any combination of technically feasible configurations among the configurations below.

[0099]

[0100] Non-aqueous electrolytes

[0101] According to one embodiment of the present invention, the non-aqueous electrolyte according to the present invention comprises a lithium salt; an organic solvent; and an additive; and the additive may comprise a compound represented by the following chemical formula A.

[0102] [Chemical Formula A]

[0103]

[0104] In the above chemical formula A,

[0105] L1 and L2 are each independently an alkylene group, ester group, sulfone group, sulfonate group, sulfate group having 1 to 10 carbon atoms, or a combination of two or more of these, and

[0106] R1 is selected from the substituents represented by the following chemical formulas B-1 and B-2, and

[0107] [Chemical Formula B-1]

[0108]

[0109] [Chemical Formula B-2]

[0110]

[0111] R2 is selected from substituents represented by the following chemical formulas C-1 to C-3, and

[0112] [Chemical Formula C-1]

[0113]

[0114] [Chemical Formula C-2]

[0115]

[0116] [Chemical Formula C-3]

[0117]

[0118] In the above formulas B-1 to B-2 and C-1 to C-3,

[0119] X1 and X2 are each independently *-O-* or *-C(R X1 R X2 It is one of )-* and,

[0120] R3 to R7, the above R x1 and R x2 Each is independently hydrogen, halogen, nitrile group, ester group, ether group, ketone group, carboxyl group, substituted or unsubstituted alkyl group, substituted or unsubstituted alkenyl group, substituted or unsubstituted alkynyl group, substituted or unsubstituted alkoxy group, boron group, borate group, isocyanate group, isothiocyanate group, silyl group, siloxane group, sulfone group, sulfonate group, sulfate group, or a combination of two or more of these, n1 to n4 are integers selected independently from 1 to 3, m1 and m2 are integers selected independently from 1 to 2, and * is a bonding site.

[0121] In the case of the above chemical formula A, a carbonyl group is included in the center of the main chain, a functional group including a double bond between sulfur (S) and oxygen (O) is present on one side, and a functional group including a double bond between carbon (C) and oxygen (O) is present on the other side. At this time, the carbonyl group located in the center of the main chain has excellent Li affinity, so excellent resistance characteristics can be achieved when forming an SEI film. The functional group including the double bond between sulfur (S) and oxygen (O) has low reactivity with HF at high temperatures when forming an SEI film, so a film that is stable and highly durable even at high temperatures can be formed, thereby achieving excellent high-temperature lifespan and high-temperature storage characteristics. The functional group including the double bond between carbon (C) and oxygen (O) forms a thin SEI film with excellent durability, and has high Li affinity, which can lower the resistance of the SEI film, thereby achieving excellent high-temperature lifespan and high-temperature storage characteristics.

[0122] Furthermore, in the case of the additive according to the present invention, excellent effects can be achieved because the aforementioned carbonyl group and two functional groups are included within the main chain. For example, when a compound having a functional group containing a double bond between sulfur (S) and oxygen (O), a compound having a functional group containing a double bond between carbon (C) and oxygen (O), and a compound containing a carbonyl group are used separately, the molecular weight decreases as the compound is separated. Consequently, when forming an SEI film on the cathode surface, the coverage ability becomes inferior, and a problem arises where the reactive site relatively increases. Therefore, problems arise such as inferior high-temperature lifespan and high-temperature storage characteristics due to electrolyte side reactions, and a high rate of resistance increase. Additionally, since the content of each compound must be increased to achieve sufficient performance, a problem of poor resistance characteristics occurs.

[0123] In addition, even if two functional groups are included in the main chain, if the carbonyl group is not located in the center of the main chain, the Li affinity is inferior, so the resistance of the SEI film cannot be lowered, and the high-temperature life and high-temperature storage characteristics become inferior.

[0124] Furthermore, in compounds where a carbonyl group is located in the center of the main chain, if both sides have functional groups containing a double bond between sulfur (S) and oxygen (O) or a double bond between carbon (C) and oxygen (O), even if a carbonyl group is present in the compound, it is not possible to form an SEI film with excellent mechanical and chemical properties through the coexistence of each functional group. Consequently, a problem arises in which the resistance of the SEI film cannot be lowered, while the high-temperature lifespan and high-temperature storage characteristics become inferior.

[0125]

[0126] Hereinafter, the composition included in the non-aqueous electrolyte according to the present invention will be described in more detail.

[0127]

[0128] (1) Lithium salt

[0129] First, the above lithium salt will be explained.

[0130]

[0131] According to one embodiment of the present invention, the non-aqueous electrolyte according to the present invention may include a lithium salt.

[0132] According to one embodiment of the present invention, the lithium salt can be any that are commonly used in non-aqueous electrolytes without limitation, for example, Li as a cation + It includes, and as anion, F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , AlO4 -, AlCl4 - , PF6 - , SbF6 - , AsF6 - , B 10 Cl 10 - , BF2C2O4 - , BC4O8 - , PF4C2O4 - , PF2C4O8 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , C4F9SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , CH3SO3 - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - At least one selected from the group consisting of may be cited. Preferably, the lithium salt is LiCl, LiBr, LiI, LiBF4, LiClO4, LiAlO4, LiAlCl4, LiPF6, LiSbF6, LiAsF6, LiB 10 Cl 10At least one selected from the group consisting of LiBOB (LiB(C2O4)2), LiCF3SO3, LiFOBLiTFSI (LiN(SO2CF3)2), LiFSI (LiN(SO2F)2), LiCH3SO3, LiCF3CO2, LiDFOB (Lithium difluoro(oxalato)borate), LiDFBP (lithium difluoro(bisoxalato)phosphate), LiTFOP (lithium tetrafluoro(oxalato)phosphate), LiDFP (LiPO2F2), LiCH3CO2, and LiBETI (LiN(SO2CF2CF3)2) can be cited. The above lithium salt may preferably comprise a single substance or a mixture of two or more substances selected from the group consisting of LiBF4, LiClO4, LiPF6, LiBOB (LiB(C2O4)2), LiCF3SO3, LiTFSI (LiN(SO2CF3)2), LiFSI (LiN(SO2F)2) and LiBETI (LiN(SO2CF2CF3)2), and more preferably may comprise LiPF6.

[0133] According to one embodiment of the present invention, the lithium salt may be appropriately modified within a range that is typically usable, but in order to obtain an optimal effect of forming a corrosion-preventing film on the electrode surface, it may be included in the electrolyte at a concentration of 0.1 M to 3.0 M, preferably 0.8 M to 2.0 M. When the concentration of the lithium salt satisfies the above range, the viscosity of the non-aqueous electrolyte can be controlled to achieve optimal impregnation, and the mobility of lithium ions can be improved to obtain an effect of improving the capacity characteristics and cycle characteristics of the lithium secondary battery.

[0134]

[0135] (2) Organic solvent

[0136] According to one embodiment of the present invention, the non-aqueous electrolyte according to the present invention may include an organic solvent.

[0137]

[0138] According to one embodiment of the present invention, the organic solvent is a non-aqueous solvent commonly used in lithium secondary batteries, and is not particularly limited as long as it minimizes decomposition due to oxidation reactions, etc., during the charging and discharging process of the secondary battery.

[0139] Preferably, the organic solvent may include a cyclic carbonate-based organic solvent and a linear carbonate-based organic solvent.

[0140] The above-mentioned cyclic carbonate-based organic solvent is a high-viscosity organic solvent that has a high dielectric constant and can effectively dissociate lithium salts in the electrolyte. It may preferably 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-pentylene carbonate, 2,3-pentylene carbonate, and vinylene carbonate, and more preferably may include ethylene carbonate.

[0141] The above cyclic carbonate-based organic solvent may be included in the organic solvent in an amount of 10 volume% to 30 volume%.

[0142]

[0143] In addition, the linear carbonate-based organic solvent is an organic solvent having low viscosity and low dielectric constant, and preferably may include at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethylmethyl carbonate (EMC), methylpropyl carbonate, and ethylpropyl carbonate, and more preferably may include ethylmethyl carbonate (EMC).

[0144] The above linear carbonate-based organic solvent may be included in the organic solvent in an amount of 60% to 90% by volume.

[0145]

[0146] According to one embodiment of the present invention, the organic solvent may include ethylene carbonate, ethylmethyl carbonate, and dimethyl carbonate. In this case, excellent resistance characteristics and high temperature characteristics can be achieved.

[0147] Preferably, the organic solvent may contain 10 to 30 volume% of ethylene carbonate, 60 to 80 volume% of ethylmethyl carbonate, and 1 to 20 volume% of dimethyl carbonate. Preferably, it may contain 15 to 25 volume% of ethylene carbonate, 65 to 75 volume% of ethylmethyl carbonate, and 5 to 15 volume% of dimethyl carbonate.

[0148] Meanwhile, the above organic solvent may be used without limitation by adding organic solvents commonly used in non-aqueous electrolytes as needed. For example, it may additionally include at least one organic solvent among ester-based organic solvents, ether-based organic solvents, glycine-based solvents, and nitrile-based organic solvents.

[0149] The above ester-based organic solvent may include at least one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate and butyl propionate, γ-butyrolactone, γ-valerolactone, γ-caprolactone, δ-valerolactone and ε-caprolactone.

[0150] As the above ether-based solvent, any one selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methylpropyl ether, ethyl propyl ether, 1,3-dioxolane (DOL), and 2,2-bis(trifluoromethyl)-1,3-dioxolane (TFDOL), or a mixture of two or more of these may be used, but is not limited thereto.

[0151] The above-mentioned glyme-based solvent has a high dielectric constant and low surface tension compared to linear carbonate-based organic solvents and is a solvent with low reactivity with metals. It may include at least one selected from the group consisting of dimethoxyethane (glyme, DME), diethoxyethane, diglyme, triglyme, and tetraglyme (TEGDME), but is not limited thereto.

[0152] The above nitrile-based solvent may be one or more selected from the group consisting of acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanitrile, cyclopentane carbonitrile, cyclohexane carbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile, but is not limited thereto.

[0153] Meanwhile, the remainder of the above-mentioned non-aqueous electrolyte, excluding the lithium salt and additives, may all be organic solvents unless otherwise noted.

[0154]

[0155] (3) Additives

[0156] According to one embodiment of the present invention, the non-aqueous electrolyte according to the present invention may include an additive, and preferably, the additive may include a compound represented by the following chemical formula A.

[0157] [Chemical Formula A]

[0158]

[0159] In the above formula A, L1 and L2 may each independently be an alkylene group having 1 to 10 carbon atoms, an ester group, a sulfone group, a sulfonate group, a sulfate group, or a combination of two or more of these, preferably an alkylene group having 1 to 5 carbon atoms, and more preferably an alkylene group having 1 to 3 carbon atoms. Even more preferably, L1 may be a methylene group and L2 may be an ethylene group. When the above conditions are satisfied, it is possible to form an SEI film with excellent coverage ability and durability while achieving stable reactivity without impairing the effect of the combination of the carbonyl group located in the center of the main chain and R1 and R2.

[0160] The above R1 may be selected from among the substituents represented by the following chemical formulas B-1 and B-2. In this case, since the reactivity with HF at high temperatures is low when forming the SEI film, a film that is stable and highly durable even at high temperatures can be formed, thereby enabling excellent high-temperature life and high-temperature storage characteristics while lowering the resistance of the SEI film.

[0161] [Chemical Formula B-1]

[0162]

[0163] [Chemical Formula B-2]

[0164]

[0165] In the above chemical formulas B-1 to B-2, X1 and X2 are each independently *-O-* or *-C(R X1 R X2 It may be one of )-* and preferably *-O-*. When the above conditions are satisfied, the structure may be easily reduced, so that excellent high-temperature life and high-temperature storage characteristics can be achieved while lowering the resistance of the SEI film.

[0166] The above R3 to R4, the above R x1 and R x2Each may independently be hydrogen, halogen, nitrile group, ester group, ether group, ketone group, carboxyl group, substituted or unsubstituted alkyl group, substituted or unsubstituted alkenyl group, substituted or unsubstituted alkynyl group, substituted or unsubstituted alkoxy group, boron group, borate group, isocyanate group, isothiocyanate group, silyl group, siloxane group, sulfone group, sulfonate group, sulfate group, or a combination of two or more of these, and preferably R3 to R4, R x1 and R x2 Each can be hydrogen independently.

[0167] The above n1 and n2 may be integers selected independently from 1 to 3.

[0168] The above m1 and m2 may be integers selected independently from 1 to 2, preferably 2. When the above conditions are satisfied, oxidation stability is high and the reduction reaction amount is excellent, and as a result, the cathode can be protected stably, so excellent high-temperature life and high-temperature storage characteristics can be realized while lowering the resistance of the SEI film.

[0169] The above * is the connection site.

[0170]

[0171] Preferably, the R1 may be selected from the substituents represented by the following chemical formulas B-1-1, B-1-2, B-1-3, B-1-4, B-1-5, B-1-6, B-2-1, and B-2-2; more preferably, it may be selected from the substituents represented by the following chemical formulas B-1-2, B-1-4, B-1-5, B-1-6, B-2-1, and B-2-2; even more preferably, it may be selected from the substituents represented by the following chemical formulas B-1-4, B-2-1, and B-2-2; even more preferably, it may be selected from the substituents represented by the following chemical formulas B-2-1 and B-2-2; and even more preferably, it may be the substituent represented by the following chemical formula B-2-2. In this case, since polymerization reactions are possible at the double bonds between carbons (C), the coverage capability is excellent. Furthermore, due to high oxidation stability, the reduction reaction rate is excellent, and consequently, the cathode can be protected stably. Consequently, excellent high-temperature lifespan and high-temperature storage characteristics can be achieved while lowering the resistance of the SEI film. Additionally, when double bonds between carbons (C) within the cyclic ring are present, a stable SEI layer can be formed at the cathode through reduction reactions, thereby enabling even better high-temperature lifespan and high-temperature storage characteristics.

[0172] [Chemical Formula B-1-1]

[0173]

[0174] [Chemical Formula B-1-2]

[0175]

[0176] [Chemical Formula B-1-3]

[0177]

[0178] [Chemical Formula B-1-4]

[0179]

[0180] [Chemical Formula B-1-5]

[0181]

[0182] [Chemical Formula B-1-6]

[0183]

[0184] [Chemical Formula B-2-1]

[0185]

[0186] [Chemical Formula B-2-2]

[0187]

[0188] The above * is the connection site.

[0189]

[0190] The above R2 may be selected from among the substituents represented by the following chemical formulas C-1 to C-3. In this case, while forming a thin SEI film with excellent durability, the high affinity for Li can lower the resistance of the SEI film, thereby enabling excellent high-temperature life and high-temperature storage characteristics while lowering the resistance of the SEI film.

[0191] [Chemical Formula C-1]

[0192]

[0193] [Chemical Formula C-2]

[0194]

[0195] [Chemical Formula C-3]

[0196]

[0197] In the above C-1 to C-3 formulas, R5 to R7 may each independently be hydrogen, halogen, nitrile group, ester group, ether group, ketone group, carboxyl group, substituted or unsubstituted alkyl group, substituted or unsubstituted alkenyl group, substituted or unsubstituted alkynyl group, substituted or unsubstituted alkoxy group, boron group, borate group, isocyanate group, isothiocyanate group, silyl group, siloxane group, sulfone group, sulfonate group, sulfate group, or a combination of two or more of these, and preferably R5 may be fluorine (F), and R6 and R7 may each independently be hydrogen.

[0198] The above n3 and n4 may be integers selected from 1 to 3.

[0199] The above * is the connection site.

[0200]

[0201] Preferably, the R2 may be selected from the substituents represented by the following chemical formulas C-1-1, C-1-2, C-2-1, and C-3-1, and more preferably, may be the substituent represented by the chemical formula C-3-1. In this case, since polymerization reaction at the double bond between carbon (C) and carbon (C) is possible, the coverage ability is excellent and the Li affinity may be high. Furthermore, while forming a thin SEI film with excellent durability of the double bond between carbon (C) and carbon (C) present in the ring structure, it is possible to achieve excellent high-temperature life and high-temperature storage characteristics while lowering the resistance of the SEI film.

[0202] [Chemical Formula C-1-1]

[0203]

[0204] [Chemical Formula C-1-2]

[0205]

[0206] [Chemical Formula C-2-1]

[0207]

[0208] [Chemical Formula C-3-1]

[0209]

[0210] The above * is the connection site.

[0211]

[0212] According to one embodiment of the present invention, the compound represented by the formula A may include at least one selected from the group consisting of the following formulas Aa, Ab, Ac, and Ad; preferably, the compound represented by the formula A may include at least one selected from the group consisting of the following formulas Aa and Ab; more preferably, the compound represented by the formula A may be the compound represented by the following formula Aa. In this case, the affinity for Li may be excellent, the reactivity with HF at high temperatures when forming the SEI film may be low, the oxidation stability may be excellent, the coverage ability when forming the SEI film on the cathode surface may be improved, and a thin SEI film with excellent durability may be formed, thereby enabling excellent high-temperature life and high-temperature storage characteristics while lowering the resistance of the SEI film.

[0213] [Chemical Formula Aa]

[0214]

[0215] [Chemical Formula Ab]

[0216]

[0217] [Chemical Formula Ac]

[0218]

[0219] [Chemical Formula Ad]

[0220]

[0221] According to one embodiment of the present invention, the additive may be included in an amount of 0.01% to 10% by weight based on the total weight of the non-aqueous electrolyte, preferably 0.01% or more, 0.05% or more, 0.1% or more, 0.15% or more, 0.2% or more, 10% or less, 7.5% or less, 5% or less, 2.5% or less, 2% or less, 1.5% or less, 1.25% or less, 1% or less, 0.9% or less, or 0.8% or less by weight, and more preferably 0.2% to 0.8% by weight. When the compound represented by the chemical formula A is used in the above-described content range, a SEI film that is flexible, durable, and has excellent coverage ability can be formed on the cathode, while preventing an increase in resistance. In addition, one feature of the present invention is that it forms an excellent SEI film even when using a small amount of additive, thereby ensuring excellent processability and preventing an increase in resistance.

[0222]

[0223] lithium secondary battery

[0224] Hereinafter, a lithium secondary battery according to the present invention will be described.

[0225] A lithium secondary battery according to the present invention comprises: a positive electrode; a negative electrode disposed opposite to the positive electrode; and a non-aqueous electrolyte according to the present invention. Optionally, the lithium secondary battery according to the present invention may further comprise a separator interposed between the positive electrode and the negative electrode.

[0226] The components are described below.

[0227]

[0228] (1) positive electrode

[0229] The anode according to the present invention comprises an anode active material. Preferably, the anode may comprise an anode active material layer comprising an anode active material, and more preferably, may comprise an anode current collector; and an anode active material layer comprising an anode active material located on the anode current collector.

[0230]

[0231] Hereinafter, each component of the anode according to the present invention will be described in detail.

[0232]

[0233] 1) Positive current collector

[0234] Various positive current collectors used in the relevant technical field may be used as the positive current collector. For example, the positive current collector may be stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, etc. The positive current collector may typically have a thickness of 3 to 500 μm, and fine irregularities may be formed on the surface of the positive current collector to increase the adhesion of the positive active material. The positive current collector may be used in various forms, such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0235]

[0236] 2) Anode active material layer

[0237] The positive active material layer may be located on the positive current collector, and preferably, may be located on one or both sides of the positive current collector. The positive active material layer may be a single layer or a multilayer structure of two or more layers.

[0238] The above positive active material layer may include a positive active material, a positive conductive material, and a positive binder.

[0239] The above-mentioned positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and preferably may include a lithium transition metal composite oxide comprising lithium and at least one transition metal comprising nickel, cobalt, manganese, and aluminum, and preferably a lithium transition metal composite oxide comprising lithium and a transition metal comprising nickel, cobalt, and manganese.

[0240] For example, the above lithium transition metal composite oxide includes a lithium-manganese oxide (e.g., LiMnO2, LiMn2O4, etc.), a lithium-cobalt oxide (e.g., LiCoO2, etc.), a lithium-nickel oxide (e.g., LiNiO2, etc.), and a lithium-nickel-manganese oxide (e.g., LiNi 1-Y Mn Y O2(here, 0 <Y<1), LiMn 2-z Ni z O4 (where 0 < Z < 2), etc.), lithium-nickel-cobalt oxides (e.g., LiNi 1-Y1 Co Y1 O2(here, 0 <Y1<1) 등), 리튬-망간-코발트계 산화물(예를 들면, LiCo 1-Y2 Mn Y2 O2(here, 0 <Y2<1), LiMn 2-z1 Co z1 O4 (where 0 < Z1 < 2), etc.), lithium-nickel-manganese-cobalt oxides (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, p1+q1+r2=2), etc.), or lithium-nickel-cobalt-transition metal (M) oxide (e.g., Li(Ni p2 Co q2 Mn r3 M S2Examples include )O2 (wherein M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, and p2, q2, r3, and s2 are each atomic fractions of independent elements, such that 0 < p2 < 1, 0 < q2 < 1, 0 < r3 < 1, 0 < s2 < 1, and p2 + q2 + r3 + s2 = 1), etc., and any one or more of these compounds may be included. Among these, the lithium transition metal composite oxide is LiCoO2, LiMnO2, LiNiO2, and lithium nickel-manganese-cobalt oxide (for example, Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2 or Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc.), or lithium nickel-cobalt-aluminum oxide (e.g., Li(Ni 0.8 Co 0.15 Al 0.05 It may be )O2, etc., and considering the significant improvement effect resulting from controlling the type and content ratio of constituent elements forming the lithium transition metal composite oxide, the lithium transition metal composite oxide is Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2 or Li(Ni 0.8 Mn 0.1 Co 0.1 It may be O2, etc., and any one of these or a mixture of two or more may be used.

[0241] More preferably, the positive electrode active material may be a lithium transition metal composite oxide containing 60 mol% or more of nickel based on the total molar amount of the transition metal contained in the lithium transition metal composite oxide. Preferably, the positive electrode active material may be a lithium transition metal composite oxide, wherein the transition metal comprises nickel; and at least one selected from manganese, cobalt, and aluminum, and may contain 60 mol% or more, preferably 60 mol% to 90 mol%, based on the total molar amount of the transition metal. When such a lithium transition metal composite oxide containing a high amount of nickel is used together with the aforementioned non-aqueous electrolyte, it is desirable in that it can reduce gaseous by-products generated by structural collapse.

[0242] In addition, the above positive active material may include a lithium complex transition metal oxide represented by the following chemical formula 1.

[0243] [Chemical Formula 1]

[0244] Li 1+x (Ni a Co b Mn c Al d M 1 e )O2

[0245] In the above chemical formula 1, M 1 ... is one or more selected from W, Cu, Fe, V, Cr, Ti, Zr, Zn, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, where 1+x, a, b, c, d, and e are the atomic fractions of independent elements, 0≤x≤0.2, 0.50≤a<1, 0 <b≤0.25, 0<c≤0.25, 0≤d≤0.1, 0≤e≤0.1, a+b+c+d+e=1이다.

[0246] Preferably, a, b, c, d, and e are each 0.70≤a≤0.95, 0.025≤b≤0.20, 0.025≤c≤0.20, 0 <d≤0.1, 0≤e≤0.05일 수 있다.

[0247] In addition, the above a, b, c, d, and e are respectively 0.80≤a≤0.95, 0.025≤b≤0.15, 0.025≤c≤0.15, 0 <d≤0.08, 0≤e≤0.05일 수 있다.

[0248] In addition, the above a, b, c, d, and e are respectively 0.85≤a≤0.90, 0.05≤b≤0.10, 0.05≤c≤0.10, 0 <d≤0.05, 0≤e≤0.05일 수 있다.

[0249]

[0250] The above positive active material may be included in an amount of 90% to 99% by weight, preferably 92% to 98% by weight, and more preferably 94% to 98% by weight, based on the total weight of the positive active material layer. If the above range is satisfied, the energy density and capacity characteristics of the lithium secondary battery to which the positive material is applied can be improved.

[0251]

[0252] The above-mentioned positive electrode conductive material is used to impart conductivity to the electrode, and in the battery being constructed, it may be used without special limitations as long as it possesses electronic conductivity without causing chemical changes. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, carbon nanotube; metal powder or metal fiber such as copper, nickel, aluminum, or silver; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and one of these alone or a mixture of two or more may be used. The above-mentioned positive electrode conductive material may typically be included in an amount of 0.1 to 10 weight%, preferably 0.1 to 8 weight%, and more preferably 0.1 to 5 weight% based on the total weight of the positive electrode active material layer.

[0253] The above-mentioned anode binder serves to improve adhesion between anode material particles and adhesion between the anode material and the anode current collector. Specific examples include fluoropolymer-based binders comprising polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); rubber-based binders comprising styrene butadiene rubber (SBR), acrylonitrile-butadiene rubber, or styrene-isoprene rubber; cellulose-based binders comprising carboxyl methyl cellulose (CMC), starch, hydroxypropyl cellulose, or regenerated cellulose; polyalcohol-based binders comprising polyvinyl alcohol; polyolefin-based binders comprising polyethylene or polypropylene; polyimide-based binders; and polyester-based binders. Examples include silane-based binders, and one of these alone or a mixture of two or more may be used. The anode binder may be included in an amount of 1 to 10 weight%, preferably 0.5 to 10 weight%, and more preferably 1 to 8 weight% based on the total weight of the anode active material layer.

[0254]

[0255] The above-mentioned anode may be manufactured by methods known in the art. For example, the above-mentioned anode may be manufactured by mixing an anode active material, an anode binder, and an anode conductive material in a solvent to prepare an anode slurry, applying the anode slurry onto an anode current collector, and then drying and rolling, or by casting the anode slurry onto a separate support and then laminating the film obtained by peeling it off from the support onto an anode current collector. In this case, the solvent for the anode slurry may be any anode slurry solvents generally used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, water, or a mixture thereof, but is not limited thereto.

[0256] The above solvent can be used in an amount that dissolves or disperses the anode powder, anode conductive material, and anode binder, and has a viscosity such that the anode slurry can be uniformly coated.

[0257]

[0258] (2) Cathode

[0259] The cathode according to the present invention comprises a cathode active material. Preferably, the cathode may comprise a cathode active material layer comprising a cathode active material, and more preferably, may comprise a cathode current collector; and a cathode active material layer comprising a cathode active material located on the cathode current collector.

[0260]

[0261] 1) Cathode current collector

[0262] The above-mentioned negative current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. In addition, the above-mentioned negative current collector may typically have a thickness of 3 to 500 μm, and, similar to the positive current collector, fine irregularities may be formed on the surface of the current collector to strengthen the bonding strength of the negative active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0263]

[0264] 2) Cathode active material layer

[0265] The above negative electrode active material layer may be located on the negative electrode current collector, and preferably may be located on one or both sides of the negative electrode current collector. The above negative electrode active material layer may have a single-layer structure or a multi-layer structure of two or more layers.

[0266] When the negative electrode active material layer is a multilayer structure composed of two or more layers, the types and / or contents of the negative electrode active material, negative electrode binder, and / or negative electrode conductive material in each layer may differ from one another. By forming the negative electrode active material layer into a multilayer structure and varying the composition of each layer, the performance characteristics of the battery, such as rapid charging performance and output characteristics, can be appropriately controlled.

[0267]

[0268] Meanwhile, as the above-mentioned negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; and SiO₂ β Examples include metal oxides capable of doping and dedoping lithium, such as (0 < β < 2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the metal compound and carbonaceous material, such as Si-C composites or Sn-C composites, and any one or more of these may be used.

[0269] Meanwhile, both low-crystallinity carbon and high-crystallinity carbon can be used as the aforementioned carbonaceous materials. Representative examples of low-crystallinity carbon include soft carbon and hard carbon, while representative examples of high-crystallinity carbon include amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch-derived cokes.

[0270] According to one embodiment of the present invention, the negative electrode active material may include a carbon-based negative electrode active material. In this case, the carbon-based negative electrode active material may include, for example, natural graphite, artificial graphite, graphitized carbon fiber, amorphous carbon, soft carbon, hard carbon, or a combination thereof. More preferably, the carbon-based negative electrode active material may include natural graphite and artificial graphite. Even more preferably, the negative electrode active material may include natural graphite. Satisfying the above conditions may be desirable in terms of maximizing the effect of the non-aqueous electrolyte according to the present invention.

[0271]

[0272] The above carbon-based negative electrode active material has a BET specific surface area of ​​2 m² 2 / g to 8m 2 It can be / g, preferably 2m 2 / g or more, 2.05m 2 / g or more or 2.1m 2 It can be more than / g, and 8m 2 / g or less, 7m 2 / g or less, 6m 2 / g or less, 5m 2 / g or less, 4m 2 / g or less, 3.5m 2 / g or less, 3m 2 / g or less or 2.9 m 2 It may be less than / g, and more preferably 2.1m 2 / g to 2.9m 2It may be / g. When the above range is satisfied, a uniform and stable SEI film can be formed, gas generation can be reduced, and excellent energy density and output characteristics can be realized. In addition, while carbon-based cathode active materials with a high specific surface area require excessive additive consumption for SEI film formation, using the non-aqueous electrolyte according to the present invention has the advantage of maximizing effectiveness by forming an SEI film with excellent mechanical and chemical properties with a low resistance, even with a small amount of additives.

[0273]

[0274] The carbon-based negative electrode active material may have an average particle size of 10㎛ to 100㎛, preferably 10㎛ or more, 100㎛ or less, 75㎛ or less, 50㎛ or less, 40㎛ or less, 30㎛ or less, or 20㎛ or less, and more preferably 10㎛ to 20㎛. When the above range is satisfied, the diffusion distance of lithium ions is shortened to achieve excellent output characteristics, while volume expansion is mitigated and thermal stability is increased, and excellent lifespan characteristics can be achieved.

[0275]

[0276] The above-mentioned negative electrode active material may be included in an amount of 80% to 98% by weight, preferably 90% to 98% by weight, and more preferably 93% to 98% by weight, based on the total weight of the negative electrode active material layer. When the content of the negative electrode active material satisfies the above range, excellent energy density can be achieved.

[0277]

[0278] Meanwhile, the above-mentioned cathode active material layer may further include a cathode conductive material and / or a cathode binder together with the cathode active material.

[0279] The cathode conductive material is used to impart conductivity to the cathode, and in the battery being constructed, it can be used without special restrictions as long as it has electronic conductivity without causing chemical changes. Specific examples include carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, carbon nanotube; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and one of these alone or a mixture of two or more of them may be used.

[0280] The above-mentioned cathode conductive material may typically be included in an amount of 0.1 to 10 weight%, preferably 0.1 to 8 weight%, and more preferably 0.1 to 5 weight% based on the total weight of the cathode active material layer.

[0281] The above-mentioned cathode binder serves to improve adhesion between cathode active material particles and adhesion between the cathode active material and the cathode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one of these alone or a mixture of two or more may be used.

[0282] The above-mentioned cathode binder may be included in an amount of 0.1 to 10 weight%, preferably 0.5 to 10 weight%, and more preferably 1 to 8 weight% based on the total weight of the cathode active material layer.

[0283]

[0284] The above cathode may be manufactured by methods known in the art. For example, the cathode may be manufactured by mixing a cathode active material, a cathode binder, and / or a cathode conductive material in a solvent to prepare a cathode slurry, applying the cathode slurry onto a cathode current collector, and then drying and rolling, or by casting the cathode slurry onto a separate support and then laminating the film obtained by peeling it off from the support onto a cathode current collector.

[0285] Meanwhile, solvents commonly used in the relevant technical field may be used as the solvent for the cathode slurry, for example, dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, water, or mixtures thereof, but are not limited thereto. The solvent may be used in an amount that dissolves or disperses the cathode active material, cathode conductive material, and cathode binder, and has a viscosity such that the cathode slurry can be uniformly coated.

[0286]

[0287] (3) Non-aqueous electrolyte

[0288] The non-aqueous electrolyte according to the present invention has been described above and is therefore omitted.

[0289]

[0290] (4) Separator

[0291] The above separator physically separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions; any separator typically used in lithium secondary batteries can be used without any special restrictions. In this case, the separator may be interposed between the positive electrode and the negative electrode.

[0292] Preferably, a porous polymer film made of a polyolefin-based 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 of two or more layers thereof may be used. In addition, a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fibers or polyethylene terephthalate fibers, may be used. Furthermore, a coated separator containing a ceramic component or a polymer material may be used to ensure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0293]

[0294] The lithium secondary battery according to the present invention as described above can be usefully applied to portable devices such as mobile phones, laptop computers, and digital cameras, as well as electric vehicles such as hybrid electric vehicles (HEVs).

[0295]

[0296] According to one embodiment of the present invention, a battery module comprising a lithium secondary battery according to the present invention as a unit cell and a battery pack comprising the same are provided.

[0297] The above battery module or battery pack can be used as a power source for one or more medium-to-large devices, including a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0298]

[0299] The present invention will be explained in more detail below through specific embodiments. However, the following embodiments are intended only to enable a person skilled in the art to fully understand and easily implement the present invention, and the scope of the rights of the present invention is not limited to the following embodiments.

[0300]

[0301] Example 1

[0302] (Preparation of non-aqueous electrolytes)

[0303] An organic solvent was prepared by mixing ethylene carbonate (EC), ethylmethyl carbonate (EMC) and dimethyl carbonate (DMC) in a volume ratio of 20:70:10.

[0304] LiPF6 was dissolved in the above organic solvent as a lithium salt to a molar concentration of 1.0 M.

[0305] In addition, a non-aqueous electrolyte was prepared by adding a compound represented by the chemical formula Aa and ethylene sulfate to an organic solvent in which the lithium salt was dissolved.

[0306] The compound represented by the chemical formula Aa was included at 0.4% by weight based on the total weight of the non-aqueous electrolyte, and the ethylene sulfate was included at 1.0% by weight based on the total weight of the non-aqueous electrolyte.

[0307]

[0308] (Manufacturing of lithium secondary batteries)

[0309] Cathode active material (Li 1.0 Ni 0.86 Co 0.05 Mn 0.07 Al 0.02 An anode slurry was prepared by adding O2, a conductive material (carbon black), and a binder (PVdF) to the solvent N-methyl-2-pyrrolidone (NMP) in a weight ratio of 97.5:1.0:1.5. Then, the anode slurry was applied to one surface of an anode current collector (Al thin film), and an anode was manufactured by drying and roll pressing.

[0310] Natural graphite as cathode active material (average particle size: 15㎛, BET specific surface area: 2.5m² 2 A cathode slurry was prepared by adding carbon black as a conductive material and PVdF as a binder to water, which is a solvent, in a weight ratio of 97:1:2 (g / g). Then, the cathode slurry was applied to one surface of a cathode current collector (Cu thin film), and a cathode was manufactured by drying and roll pressing.

[0311] An electrode assembly was manufactured by sequentially stacking the above-mentioned positive electrode, polyolefin-based porous separator, and negative electrode, and then the electrode assembly was housed in a battery case, and then the manufactured non-aqueous electrolyte was injected to manufacture a lithium secondary battery.

[0312]

[0313] Example 2

[0314] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that a compound represented by the chemical formula Aa was added in an amount of 0.1% by weight based on the total weight of the non-aqueous electrolyte.

[0315]

[0316] Example 3

[0317] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that a compound represented by the chemical formula Aa was added in an amount of 2.0 wt% based on the total weight of the non-aqueous electrolyte.

[0318]

[0319] Example 4

[0320] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that instead of the compound represented by the chemical formula Aa above, a compound represented by the chemical formula Ab below was added in an amount of 0.4% by weight based on the total weight of the non-aqueous electrolyte.

[0321] [Chemical Formula Ab]

[0322]

[0323]

[0324] Comparative Example 1

[0325] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that the compound represented by the chemical formula Aa above was not added.

[0326]

[0327] Comparative Example 2

[0328] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that instead of the compound represented by the chemical formula Aa above, PES (prop-1-ene-1,3 sultone) was added at a content of 0.5 wt% based on the total weight of the non-aqueous electrolyte.

[0329]

[0330] Comparative Example 3

[0331] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that vinylene carbonate (VC) was added in an amount of 0.5% by weight based on the total weight of the non-aqueous electrolyte instead of the compound represented by the chemical formula Aa above.

[0332]

[0333] Comparative Example 4

[0334] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that instead of the compound represented by the chemical formula Aa above, PES (prop-1-ene-1,3 sultone) was added at a content of 0.25 wt% based on the total weight of the non-aqueous electrolyte and vinylene carbonate (VC) was added at a content of 0.25 wt% based on the total weight of the non-aqueous electrolyte.

[0335]

[0336] Comparative Example 5

[0337] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that instead of the compound represented by the chemical formula Aa above, a compound represented by the chemical formula X-1 below was added at a content of 0.4% by weight based on the total weight of the non-aqueous electrolyte.

[0338] [Chemical Formula X-1]

[0339]

[0340]

[0341] Comparative Example 6

[0342] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that instead of the compound represented by the chemical formula Aa above, a compound represented by the chemical formula X-2 below was added at a content of 0.4% by weight based on the total weight of the non-aqueous electrolyte.

[0343] [Chemical Formula X-2]

[0344]

[0345]

[0346] Comparative Example 7

[0347] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that instead of the compound represented by the chemical formula Aa above, a compound represented by the chemical formula X-3 below was added at a content of 0.4% by weight based on the total weight of the non-aqueous electrolyte.

[0348] [Chemical Formula X-3]

[0349]

[0350]

[0351] The above non-aqueous electrolytes are summarized and shown in Table 1 below.

[0352]

[0353] Additive Additive Component Ratio Additive Content (Weight%) Based on Total Weight of Electrolyte Example 1 Chemical Formula A-a 0.4 Example 2 Chemical Formula A-a 0.1 Example 3 Chemical Formula A-a 2.0 Example 4 Chemical Formula A-b 0.4 Comparative Example 1 -- Comparative Example 2 PES(prop-1-ene-1,3 sultone) 0.5 Comparative Example 3 Vinylene Carbonate (VC) 0.5 Comparative Example 4 PES(prop-1-ene-1,3 sultone) 0.25 Vinylene Carbonate (VC) 0.25 Comparative Example 5 Chemical Formula X-1 0.4 Comparative Example 6 Chemical Formula X-2 0.4 Comparative Example 7 Chemical Formula X-3 0.4

[0354] Experimental Example 1: Initial Resistance Measurement

[0355] Each lithium secondary battery prepared in Examples 1 to 4 and Comparative Examples 1 to 7 was charged at 25°C with a constant current of 0.33C until it reached 4.2V, and discharged with a constant current of 0.33C to reach 2.5V to measure the discharge capacity.

[0356] Afterwards, the State of Charge (SOC) was set to 50% based on the above discharge capacity. At a State of Charge (SOC) of 50%, the DC internal resistance was calculated through the voltage drop that occurred when a discharge pulse of 2.5C was applied for 10 seconds, and this resistance was set as the initial resistance.

[0357] Based on the initial resistance of Example 1, the difference in each initial resistance was expressed as a percentage and is shown in Table 2 below.

[0358]

[0359] Experimental Example 2: Evaluation of High-Temperature Life Characteristics

[0360] 1) Measurement of dosage retention rate

[0361] Each lithium secondary battery prepared in Examples 1 to 4 and Comparative Examples 1 to 7 was charged to 4.2V at a rate of 0.33C under CC-CV conditions at 45℃, and discharged to 2.5V at a rate of 0.33C under CC conditions. The above charging and discharging was performed for 300 cycles, with the above cycle being one cycle.

[0362] The capacity retention rate was calculated by substituting the capacity after the first cycle and the capacity after the 300th cycle into Equation 1 below. The results are shown in Table 2 below.

[0363] [Equation 1]

[0364] Capacity Retention Rate (%) = (Discharge Capacity after 300 Cycles / Discharge Capacity after 1 Cycle) × 100

[0365]

[0366] 2) Measure resistance increase rate

[0367] Each lithium secondary battery prepared in Examples 1 to 4 and Comparative Examples 1 to 7 was charged to 4.2V at a rate of 0.33C under CC-CV conditions at 45℃, and discharged to 2.5V at a rate of 0.33C under CC conditions. The above charging and discharging was performed for 300 cycles, with the above cycle being one cycle.

[0368] At this time, the SOC was set to 50% based on the discharge capacity of the first cycle, and the DC internal resistance was calculated through the voltage drop that occurred when a discharge pulse of 2.5C was applied for 10 seconds immediately after the first cycle. The DC internal resistance was calculated through the voltage drop that occurred when a discharge pulse of 2.5C was applied for 10 seconds immediately after the 300th cycle, and the resistance increase rate was calculated by substituting these values ​​into Equation 2 below. The results are shown in Table 2 below.

[0369] [Equation 2]

[0370] Resistance increase rate (%) = {(Resistance after 300 cycles - Resistance after 1 cycle) / (Resistance after 1 cycle)} × 100

[0371]

[0372] Experimental Example 3: Evaluation of High-Temperature Storage Characteristics

[0373] 1) Measurement of dosage retention rate

[0374] Each lithium secondary battery prepared in Examples 1 to 4 and Comparative Examples 1 to 7 was charged to 4.2V at a rate of 0.33C under CC-CV conditions at 25°C and discharged to 2.5V under CC conditions at a rate of 0.33C to measure the initial discharge capacity, then charged again to 4.2V at 25°C under CC-CV conditions at a rate of 0.33C and stored each lithium secondary battery at 60°C for 12 weeks.

[0375] Afterward, the lithium secondary battery was transferred to a charging / discharging device at room temperature (25℃), then charged to 4.2V at a rate of 0.33C under CC-CV conditions, and discharged to 2.5V at a rate of 0.33C under CC conditions to measure the discharge capacity, and then the capacity retention rate during high-temperature storage was calculated by substituting the values ​​into Equation 3 below. The results are shown in Table 2 below.

[0376] [Equation 3]

[0377] Capacity Retention Rate (%) = (Discharge Capacity after 12 Weeks of High-Temperature Storage / Initial Discharge Capacity) × 100

[0378]

[0379] 2) Measure resistance increase rate

[0380] Each lithium secondary battery prepared in Examples 1 to 4 and Comparative Examples 1 to 7 was charged to 4.2V at a rate of 0.33C under CC-CV conditions at 45℃, and discharged to 2.5V at a rate of 0.33C under CC conditions. After that, the SOC was set to 50% based on the discharge capacity of the above cycle, and the DC internal initial resistance was calculated through the voltage drop that appeared when a discharge pulse was applied at 2.5C for 10 seconds.

[0381] After that, the batteries were charged to 4.2V at a rate of 0.33C under CC-CV conditions, and each of the above lithium secondary batteries were stored at 60℃ for 12 weeks.

[0382] Subsequently, the above lithium secondary battery was transferred to a charge / discharger at room temperature (25℃), the SOC was set to 50%, and the DC internal resistance was calculated through the voltage drop observed when a discharge pulse of 2.5C was applied for 10 seconds. The resistance increase rate during high-temperature storage was then calculated by substituting the values ​​into Equation 4 below. The results are shown in Table 2 below.

[0383] [Equation 4]

[0384] Resistance increase rate (%) = {(Resistance after 12 weeks of high-temperature storage - Initial resistance) / (Initial resistance)} × 100

[0385]

[0386] Initial Resistance (%) High-Temperature Life Characteristics High-Temperature Storage Characteristics Capacity Retention Rate (%) Resistance Growth Rate (%) Capacity Retention Rate (%) Resistance Growth Rate (%) Example 1 - 94.2 14.2 96.6 11.2 Example 2 - 0.3 93.9 15.6 96.2 12.4 Example 3 - 1.2 93.7 17.1 95.8 14.5 Example 4 - 2.4 92.4 23.6 94.5 20.8 Comparative Example 1 - 13.6 90.2 38.6 93.1 32.2 Comparative Example 2 - 25.4 91.1 32.9 93.6 26.1 Comparative Example 3 - 34.2 91.1 34.5 93.5 24.9 Comparative Example 4 - 3.9 91.8 30.8 93.9 26.8 Comparative Example 55.291.929.694.124.5 Comparative Example 65.791.529.694.028.6 Comparative Example 76.091.631.793.730.5

[0387] Referring to Table 2 above, it can be seen that in the case of Examples 1 to 4, the initial resistance, high-temperature life characteristics, and high-temperature storage characteristics are all superior compared to Comparative Examples 1 to 7.

[0388] Specifically, in the case of Examples 1 to 4 according to the present invention, a carbonyl group is included in the center of the main chain, a functional group including a double bond between sulfur (S) and oxygen (O) is present on one side, and a functional group including a double bond between carbon (C) and oxygen (O) is included on the other side, so it can be seen that the initial resistance, high-temperature life characteristics, and high-temperature storage characteristics are all superior compared to Comparative Examples 1 to 7.

[0389] In particular, when comparing Example 1 and Comparative Example 4, it can be confirmed that even when PES and VC are used in combination at a similar content to Example 1, the initial resistance, high-temperature life characteristics, and high-temperature storage characteristics are all inferior to Example 1 because the molecular weight of each added compound is lower compared to Example 1.

[0390] In addition, when comparing Example 1 and Comparative Example 5, it can be confirmed that even when the additive is added in the same amount as in Example 1, the carbonyl group is not positioned in the center of the main chain, and thus the Li affinity is inferior compared to Example 1, resulting in inferior initial resistance, high-temperature life characteristics, and high-temperature storage characteristics.

[0391] In addition, when comparing Example 1 with Comparative Examples 6 and 7, even if the additive is added in the same amount as in Example 1, VC or PES is placed on both sides of the compound in Comparative Examples 6 and 7, respectively. Since a SEI film with excellent mechanical and chemical properties cannot be formed through the coexistence of VC and PES even if carbonyl groups are present in the compound, it can be confirmed that the initial resistance, high-temperature life characteristics, and high-temperature storage characteristics are all inferior compared to Example 1.

Claims

1. comprising a lithium salt; an organic solvent; and an additive; and The above additive is a non-aqueous electrolyte comprising a compound represented by the following chemical formula A: [Chemical Formula A] In the above chemical formula A, L1 and L2 are each independently an alkylene group, ester group, sulfone group, sulfonate group, sulfate group having 1 to 10 carbon atoms, or a combination of two or more of these, and R1 is selected from the substituents represented by the following chemical formulas B-1 and B-2, and [Chemical Formula B-1] [Chemical Formula B-2] R2 is selected from substituents represented by the following chemical formulas C-1 to C-3, and [Chemical Formula C-1] [Chemical Formula C-2] [Chemical Formula C-3] In the above formulas B-1 to B-2 and C-1 to C-3, X1 and X2 are each independently *-O-* or *-C(R X1 R X2 It is one of )-* and, R3 to R7, the above R x1 and R x2 Each is independently hydrogen, halogen, nitrile group, ester group, ether group, ketone group, carboxyl group, substituted or unsubstituted alkyl group, substituted or unsubstituted alkenyl group, substituted or unsubstituted alkynyl group, substituted or unsubstituted alkoxy group, boron group, borate group, isocyanate group, isothiocyanate group, silyl group, siloxane group, sulfone group, sulfonate group, sulfate group, or a combination of two or more of these, n1 to n4 are integers selected independently from 1 to 3, and m1 and m2 are integers selected independently from 1 to 2, and * is the connection site.

2. In Claim 1, The above R1 is a non-aqueous electrolyte selected from substituents represented by the following chemical formulas B-1-1, B-1-2, B-1-3, B-1-4, B-1-5, B-1-6, B-2-1, and B-2-2: [Chemical Formula B-1-1] [Chemical Formula B-1-2] [Chemical Formula B-1-3] [Chemical Formula B-1-4] [Chemical Formula B-1-5] [Chemical Formula B-1-6] [Chemical Formula B-2-1] [Chemical Formula B-2-2] The above * is the connection site.

3. In Claim 1, The above R2 is a non-aqueous electrolyte selected from substituents represented by the following chemical formulas C-1-1, C-1-2, C-2-1, and C-3-1: [Chemical Formula C-1-1] [Chemical Formula C-1-2] [Chemical Formula C-2-1] [Chemical Formula C-3-1] The above * is the connection site.

4. In Claim 1, A non-aqueous electrolyte in which, in the above chemical formula A, L1 is a methylene group and L2 is an ethylene group.

5. In Claim 1, A non-aqueous electrolyte comprising at least one selected from the group consisting of the following chemical formulas Aa, Ab, Ac, and Ad: [Chemical Formula Aa] [Chemical Formula Ab] [Chemical Formula Ac] [Chemical Formula Ad] 6. In Claim 1, The above additive is included in an amount of 0.01% to 10% by weight based on the total weight of the above non-aqueous electrolyte.

7. A lithium secondary battery comprising: a positive electrode; a negative electrode disposed opposite to the positive electrode; and a non-aqueous electrolyte according to claim 1.

8. In Claim 7, The above-mentioned negative electrode comprises a carbon-based negative electrode active material, in a lithium secondary battery.

9. In Claim 8, The above carbon-based negative electrode active material comprises natural graphite, in a lithium secondary battery.

10. In Claim 8, The above carbon-based negative electrode active material has a BET specific surface area of ​​2 m² 2 / g to 8m 2 / g lithium secondary battery.

11. In Claim 8, The above carbon-based negative electrode active material is a lithium secondary battery having an average particle size of 10㎛ to 100㎛.

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