Electrolyte for lithium secondary battery and lithium secondary battery comprising same

Abstract

The electrolyte solution for a lithium secondary battery according to an embodiment of the present invention contains an additive, an organic solvent, and a lithium salt, in which the additive contains a sulfonate-based compound represented by a specific chemical formula. A lithium secondary battery including the electrolyte solution for a lithium secondary battery may have improved high temperature characteristics and fast charging performance.

Description

Technical Field

[0001] The present invention relates to an electrolyte for a lithium secondary battery and a lithium secondary battery including the electrolyte. Background Art

[0002] A secondary battery is a battery that can be repeatedly charged and discharged, and secondary batteries are widely used as power sources for portable electronic devices such as mobile phones and laptop computers or electric vehicles.

[0003] Lithium secondary batteries have a high operating voltage and an energy density per unit weight, and are advantageous for charging speed and weight reduction. Therefore, lithium secondary batteries are being actively developed and applied.

[0004] For example, a lithium secondary battery may include an electrode assembly and an electrolyte impregnating the electrode assembly, and the electrode assembly includes a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode.

[0005] For example, the positive electrode may contain a lithium metal oxide capable of reversibly inserting and extracting lithium as a positive electrode active material.

[0006] In addition, when a lithium secondary battery is repeatedly charged and discharged, structural deformation of the lithium metal oxide, side reactions of the electrolyte, etc. may occur. In this case, the life characteristics (e.g., capacity retention rate) of the lithium secondary battery may decrease.

[0007] In particular, when a lithium secondary battery is repeatedly charged and discharged and overcharged, due to internal heat generation, battery swelling (increase in battery thickness due to gas generation inside the battery), increase in internal resistance of the battery, decrease in life characteristics of the battery, etc. occur. Therefore, research is being conducted to add various additives to improve high-temperature characteristics. Summary of the Invention

[0008] (I) Technical Problem to be Solved

[0009] One technical problem of the present invention is to provide an electrolyte for a lithium secondary battery having improved high-temperature stability and a lithium secondary battery including the electrolyte.

[0010] (II) Technical Solution

[0011] According to an exemplary embodiment, there is provided an electrolyte for a lithium secondary battery, the electrolyte for a lithium secondary battery including an additive, an organic solvent, and a lithium salt, wherein the additive includes a compound represented by the following Chemical Formula 1.

[0012] [Chemical Formula 1]

[0013]

[0014] In the Chemical Formula 1, A may be a group represented by the following Chemical Formula 2, R 1 to R 5 may each independently be hydrogen, a C1-C5 alkyl group, a C1-C5 haloalkyl group, a C3-C12 cycloalkyl group, a C6-C12 aryl group, a C1-C5 alkoxy group, a C1-C5 alkylsulfonyl group, a halogen, a nitro group, a cyano group or an isocyanate group, or two adjacent groups among R 1 to R 5 may combine with each other to form a C6-C12 aromatic ring, and the remaining groups among R 1 to R 5 that do not form the aromatic ring may each independently be hydrogen, a C1-C5 alkyl group, a C1-C5 haloalkyl group, a C3-C12 cycloalkyl group, a C6-C12 aryl group, a C1-C5 alkoxy group, a C1-C5 alkylsulfonyl group, a halogen, a nitro group, a cyano group or an isocyanate group.

[0015] [Chemical Formula 2]

[0016]

[0017] In the Chemical Formula 2, L may be a single bond, a C1-C5 alkylene group or a C2-C5 alkenylene group, R 0 may be a halogen, a C1-C5 alkyl group or a C1-C5 haloalkyl group, n may be an integer from 0 to 3, may be the connection point with the benzene ring of Chemical Formula 1.

[0018] According to an exemplary embodiment, the compound may be represented by the following Chemical Formula 1-1.

[0019] [Chemical Formula 1-1]

[0020]

[0021] In the Chemical Formula 1-1, A may be a group represented by the following Chemical Formula 2, R 1 and R 4 to R 9 may each independently be hydrogen, a C1-C5 alkyl group, a C1-C5 haloalkyl group, a C3-C12 cycloalkyl group, a C6-C12 aryl group, a C1-C5 alkoxy group, a C1-C5 alkylsulfonyl group, a halogen, a nitro group, a cyano group or an isocyanate group, or R 1 and R 4 to R 9 two adjacent groups among them may combine with each other to form a C6-C12 aromatic ring, R 1 and R 4 to R 9The remaining groups that do not form the aromatic ring may each independently be hydrogen, C1-C5 alkyl, C1-C5 haloalkyl, C3-C12 cycloalkyl, C6-C12 aryl, C1-C5 alkoxy, C1-C5 alkylsulfonyl, halogen, nitro, cyano or isocyanate group.

[0022] [Chemical Formula 2]

[0023]

[0024] In the Chemical Formula 2, L may be a single bond, C1-C5 alkylene or C2-C5 alkenylene, R 0 may be halogen, C1-C5 alkyl or C1-C5 haloalkyl, n may be an integer from 0 to 3, may be the connection point to the benzene ring of Chemical Formula 1-1.

[0025] According to an exemplary embodiment, the compound may be represented by the following Chemical Formula 1-2.

[0026] [Chemical Formula 1-2]

[0027]

[0028] In the Chemical Formula 1-2, A and A' may each independently be a group represented by the following Chemical Formula 2, R 1 , R 2 , R 4 , R 5 and R 10 to R 13 may each independently be hydrogen, C1-C5 alkyl, C1-C5 haloalkyl, C3-C12 cycloalkyl, C6-C12 aryl, C1-C5 alkoxy, C1-C5 alkylsulfonyl, halogen, nitro, cyano or isocyanate group, R 1 , R 2 , R 4 , R 5 and R 10 to R 13 two adjacent groups among them may combine with each other to form a C6-C12 aromatic ring, R 1 , R 2 , R 4 , R 5 and R 10 to R 13 the remaining groups that do not form the aromatic ring may each independently be hydrogen, C1-C5 alkyl, C1-C5 haloalkyl, C3-C12 cycloalkyl, C6-C12 aryl, C1-C5 alkoxy, C1-C5 alkylsulfonyl, halogen, nitro, cyano or isocyanate group.

[0029] [Chemical Formula 2]

[0030]

[0031] In Formula 2, L may be a single bond, a C1-C5 alkylene group, or a C2-C5 alkenylene group, and R 0 may be a halogen, a C1-C5 alkyl group, or a C1-C5 haloalkyl group, and n may be an integer from 0 to 3, and may be a connection point to the benzene ring of Formula 1-2.

[0032] According to an exemplary embodiment, in Formula 1, one of R 1 to R 5 may be hydrogen, a C1-C5 alkyl group, a C1-C5 haloalkyl group, a C3-C12 cycloalkyl group, a C6-C12 aryl group, a C1-C5 alkoxy group, a C1-C5 alkylsulfonyl group, a halogen, a nitro group, a cyano group, or an isocyanate group, and the rest may be hydrogen.

[0033] According to an exemplary embodiment, in Formula 1, one of R 1 to R 5 may be hydrogen, fluorine, chlorine, bromine, or iodine, and the rest may be hydrogen.

[0034] According to an exemplary embodiment, the content of the additive may be 0.1 wt% to 10 wt% of the total weight of the electrolyte.

[0035] According to an exemplary embodiment, the content of the additive may be 0.2 wt% to 2 wt% of the total weight of the electrolyte.

[0036] According to an exemplary embodiment, the organic solvent may include a linear carbonate-based solvent and a cyclic carbonate-based solvent.

[0037] According to an exemplary embodiment, the cyclic carbonate-based solvent may include at least one selected from ethylene carbonate, propylene carbonate, and butylene carbonate.

[0038] According to an exemplary embodiment, the linear carbonate-based solvent may include at least one selected from dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, and dipropyl carbonate.

[0039] According to an exemplary embodiment, the electrolyte may further include at least one auxiliary additive selected from unsaturated cyclic carbonate-based compounds, fluorine-substituted carbonate-based compounds, sultone-based compounds, cyclic sulfate-based compounds, and phosphate-based compounds.

[0040] According to an exemplary embodiment, the content of the auxiliary additive may be from 0.05% by weight to 10% by weight of the total weight of the electrolyte.

[0041] According to an exemplary embodiment, the content of the auxiliary additive may be from 0.1% by weight to 5% by weight of the total weight of the electrolyte.

[0042] According to an exemplary embodiment, in the electrolyte, the weight ratio of the auxiliary additive to the additive may be from 0.1 to 10.

[0043] According to an exemplary embodiment, there is provided a lithium secondary battery including: an electrode assembly in which a plurality of positive electrodes and a plurality of negative electrodes are repeatedly stacked; a case that houses the electrode assembly; and an electrolyte for a lithium secondary battery as described above, which is housed in the case together with the electrode assembly.

[0044] (III) Advantageous Effects

[0045] The electrolyte for a lithium secondary battery according to an exemplary embodiment of the present invention includes a sulfonyl compound containing an aryl group as an additive, so that a solid electrolyte interphase (SEI) can be formed on the electrode surface.

[0046] Therefore, even after storage at a high temperature, the capacity and resistance of the battery can be maintained, so that a lithium secondary battery having improved high-temperature storage characteristics can be realized. The lithium secondary battery can maintain its capacity even when repeatedly charged and discharged at a high temperature, and thus its high-temperature life characteristics can also be improved.

[0047] In addition, the electrolyte for a lithium secondary battery includes a sulfonyl compound containing an aryl group as an additive, so that a lithium secondary battery having improved fast charging characteristics can be realized, and the charging time of the lithium secondary battery can be shortened. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 is a plan view schematically showing a lithium secondary battery according to an exemplary embodiment.

[0049] Figure 2 is a cross-sectional view schematically showing a lithium secondary battery according to an exemplary embodiment. DETAILED DESCRIPTION

[0050] In this specification, "~-yl compound" may refer to a compound having "~-yl compound" and derivatives of the compound.

[0051] In this specification, "Ca-Cb" may refer to "the number of carbon (C) atoms from a to b".

[0052] The term "aryl" used in this specification refers to a carbocyclic aromatic group having 5 to 10 ring atoms. Representative examples include phenyl, tolyl, xylyl, naphthyl, tetrahydronaphthyl, anthracenyl, fluorenyl, indenyl, azulenyl, etc., but are not limited thereto. The carbocyclic aromatic group may be optionally substituted.

[0053] The term "C1-C5 alkyl" used in this specification refers to an aliphatic hydrocarbon group having 1 to 5 carbon atoms. When the alkyl is used alone or in combination, it may be a straight-chain alkyl or a branched-chain alkyl, respectively. Specifically, the straight-chain alkyl or the branched-chain alkyl may include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, neopentyl, etc. The aliphatic hydrocarbon group may be optionally substituted.

[0054] The terms "halogen" and "halo" used in this specification refer to fluorine (F), chlorine (Cl), bromine (Br), or iodine (I).

[0055] The term "haloalkyl" used in this specification refers to an alkyl in which one or more hydrogen atoms are replaced by halogen atoms. For example, haloalkyl includes -CF3, -CHF2, -CH2F, -CBr3, -CHBr2, -CH2Br, -CCl3, -CHCl2, -CH2CI, -CI3, -CHI2, -CH2I, -CH2-CF3, -CH2-CHF2, -CH2-CH2F, -CH2-CBr3, -CH2-CHBr2, -CH2-CH2Br, -CH2-CCl2, -CH2-CHCl2, -CH2-CH2CI, -CH2-CI3, -CH2-CHI2, -CH2-CH2I, and groups similar thereto. Among them, the definitions of alkyl and halogen are as described above. The haloalkyl may be optionally substituted.

[0056] The term "alkoxy" used in this specification refers to an alkyl group linked to an oxygen atom. For example, alkoxy may include methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, tert-butoxy, pentyloxy, etc. Among them, the definition of alkyl is as described above. The alkoxy may be optionally substituted.

[0057] The term "alkylsulfonyl" used in this specification refers to a sulfonyl group (-S(=O)2-) bonded to an alkyl group. For example, alkylsulfonyl may include methylsulfonyl, ethylsulfonyl, propylsulfonyl, etc. Among them, the definition of alkyl is as described above. The alkylsulfonyl may be optionally substituted.

[0058] The term "cycloalkyl" as used in this specification refers to a cyclic alicyclic hydrocarbon group. The cycloalkyl may include, for example, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, etc. The alicyclic hydrocarbon group may be optionally substituted.

[0059] The term "substituted" as used in this specification may mean that a hydrogen atom of a hydrocarbon group is substituted by a substituent, such that the substituent is further bonded to a carbon atom of the hydrocarbon group. For example, the substituent may include at least one selected from the group consisting of the group represented by the following Chemical Formula 2, C1-C5 alkyl, C1-C5 haloalkyl, C3-C12 cycloalkyl, 5- to 7-membered heterocycloalkyl, C6-C12 aryl, C1-C5 alkoxy, tetrahydrofuranylalkylsulfonate group, halogen, nitro, cyano, and isocyanate group.

[0060] [Chemical Formula 2]

[0061]

[0062] In Chemical Formula 2, L may be a single bond, C1-C5 alkylene, or C2-C5 alkenylene, R 0 may be halogen, C1-C5 alkyl, or C1-C5 haloalkyl, n may be an integer from 0 to 3, may be a point of attachment to the hydrocarbon group. [[ID=*20]]

[0063] The term "heterocycloalkyl" as used in this specification is a group in which at least one carbon in the ring of the cycloalkyl is substituted by a heteroatom such as N, S, O, or P. The hydrogen bonded to the carbon atom or heteroatom of the heterocycloalkyl may be optionally substituted.

[0064] The term "tetrahydrofuranylalkylsulfonate group" as used in this specification refers to a sulfonate group linked to a tetrahydrofuranyl group and an alkylene group. The alkylene group may refer to a straight-chain or branched-chain divalent hydrocarbon group consisting only of single bonds of carbon and hydrogen and to which the rest of the molecule is linked to the group. For example, the tetrahydrofuranylalkylsulfonate group may include tetrahydrofuranylmethylsulfonate group, tetrahydrofuranylethylsulfonate group, etc.

[0065] The electrolyte for a lithium secondary battery according to an exemplary embodiment may include an additive, and the additive includes a compound represented by the following Chemical Formula 1.

[0066] [Chemical Formula 1]

[0067]

[0068] In Chemical Formula 1, A may be a group represented by the following Chemical Formula 2, R 1 to R 5may each independently be hydrogen, a C1-C5 alkyl group, a C1-C5 haloalkyl group, a C3-C12 cycloalkyl group, a C6-C12 aryl group, a C1-C5 alkoxy group, a C1-C5 alkylsulfonyl group, a halogen, a nitro group, a cyano group or an isocyanate group, or R 1 to R 5 two adjacent groups among them may combine with each other to form a C6-C12 aromatic ring, and the remaining groups among R 1 to R 5 that do not form the said aromatic ring may each independently be hydrogen, a C1-C5 alkyl group, a C1-C5 haloalkyl group, a C3-C12 cycloalkyl group, a C6-C12 aryl group, a C1-C5 alkoxy group, a C1-C5 alkylsulfonyl group, a halogen, a nitro group, a cyano group or an isocyanate group.

[0069] [Chemical Formula 2]

[0070]

[0071] In the said Chemical Formula 2, L may be a single bond, a C1-C5 alkylene group or a C2-C5 alkenylene group, R 0 may be a halogen, a C1-C5 alkyl group or a C1-C5 haloalkyl group, n may be an integer from 0 to 3, may be the connection point with the benzene ring of Chemical Formula 1.

[0072] For example, in the said Chemical Formula 1, one of R 1 to R 5 may be hydrogen, a C1-C5 alkyl group, a C1-C5 haloalkyl group, a C3-C12 cycloalkyl group, a C6-C12 aryl group, a C1-C5 alkoxy group, a C1-C5 alkylsulfonyl group, a halogen, a nitro group, a cyano group or an isocyanate group, and the rest may be hydrogen. For example, R 1 , R 2 , R 4 and R 5 may be hydrogen, and R 3 may be the same as defined above.

[0073] For example, in the said Chemical Formula 1, one of R 1 to R 5 may be a substituted C6-C12 aryl group, and the rest may be hydrogen. For example, R 1 , R 2 , R 4 and R 5 may be hydrogen, and R 3 may be a C6-C12 aryl group substituted by a tetrahydrofuranylalkylsulfonate group.

[0074] According to an exemplary embodiment, in the chemical formula 1, A may be a structure represented by the chemical formula 2. That is, A may be a sulfonate group containing a heterocycle. For example, A may be a tetrahydrofuranyl alkylsulfonate group. In some embodiments, A may be a tetrahydrofuranyl methylsulfonate group.

[0075] According to an exemplary embodiment, in Chemical Formula 2, L may be a single bond, a C1-C5 alkylene group, or a C2-C5 alkenylene group. In some embodiments, L may be a C1-C3 alkylene group. For example, L may be a methylene group, an ethylene group, a propylene group, an isopropylene group, a butylene group, an isobutylene group, or the like.

[0076] According to an exemplary embodiment, in the chemical formula 2, R 0 Can be halogen, C1-C5 alkyl or C1-C5 haloalkyl. In some embodiments, R 0 It may be fluorine, a C1-C5 alkyl group or a C1-C5 fluoroalkyl group.

[0077] According to an exemplary embodiment, in Chemical Formula 2, n may be an integer from 0 to 3. In some embodiments, n may be an integer from 0 to 1. In one embodiment, n may be 0.

[0078] According to an exemplary embodiment, in the chemical formula 1, R 1 to R 5 One of them may be hydrogen, fluorine, chlorine, bromine or iodine, and the others may be hydrogen. 3 can be hydrogen, fluorine, chlorine, bromine or iodine, R 1 、R 2 、R 4 and R 5 It may be hydrogen.

[0079] For example, in the chemical formula 1, R 1 to R 5 It may be hydrogen.

[0080] According to an exemplary embodiment, R 1 to R 5 Two adjacent groups can combine to form a C6-C12 aromatic ring, R 1 to R 5 The remaining groups not forming the aromatic ring may each independently be the same as defined above.

[0081] For example, when R 2 and R 3 When combined to form a ring, R 1 、R 4 and R 5 Can be independently the same as defined above.

[0082] According to an exemplary embodiment, when two adjacent groups among R 1 to R 5 combine with each other to form a C6-C12 aromatic ring, they can form a fused ring with the benzene ring of Chemical Formula 1, and thus a structure of the following Chemical Formula 1-1 can be formed.

[0083] For example, when R 2 and R 3 combine to form a benzene ring, they can form a fused ring with the benzene ring of Chemical Formula 1 and a naphthyl structure can be formed.

[0084] The electrolyte for a lithium secondary battery according to an exemplary embodiment includes the compound represented by the Chemical Formula 1, and thus a film with a relatively reduced resistance can be formed on the electrode through, for example, a decomposition reaction of a cyclic ether group. For example, the compound can form an SEI on the surface of the negative electrode.

[0085] Therefore, decomposition of the organic solvent can be effectively prevented, and generation of gas and increase in battery thickness can be significantly reduced. In addition, the film with a relatively reduced resistance can prevent an increase in the initial resistance, which can improve the mobility of lithium ions and thus significantly improve the fast charging performance.

[0086] Therefore, when an additive containing the compound represented by the Chemical Formula 1 is included in the electrolyte for a secondary battery, the room temperature characteristics and the initial resistance characteristics can be improved while improving the high temperature storage characteristics.

[0087] According to an exemplary embodiment, the compound can be represented by the following Chemical Formula 1-1.

[0088] [Chemical Formula 1-1]

[0089]

[0090] In the Chemical Formula 1-1, A can be a group represented by the following Chemical Formula 2, and R 1 and R 4 to R 9 can each independently be hydrogen, a C1-C5 alkyl group, a C1-C5 haloalkyl group, a C3-C12 cycloalkyl group, a C6-C12 aryl group, a C1-C5 alkoxy group, a C1-C5 alkylsulfonyl group, a halogen, a nitro group, a cyano group, or an isocyanate group, or two adjacent groups among R 1 and R 4 to R 9 can combine with each other to form a C6-C12 aromatic ring, and R 1 and R 4 to R 9The remaining groups that do not form the aromatic ring may each independently be hydrogen, a C1-C5 alkyl group, a C1-C5 haloalkyl group, a C3-C12 cycloalkyl group, a C6-C12 aryl group, a C1-C5 alkoxy group, a C1-C5 alkylsulfonyl group, a halogen, a nitro group, a cyano group, or an isocyanate group.

[0091] [Chemical Formula 2]

[0092]

[0093] In the Chemical Formula 2, L may be a single bond, a C1-C5 alkylene group, or a C2-C5 alkenylene group, and R 0 may be a halogen, a C1-C5 alkyl group, or a C1-C5 haloalkyl group, n may be an integer from 0 to 3, may be the connection point to the benzene ring of Chemical Formula 1-1.

[0094] According to an exemplary embodiment, the compound may be represented by the following Chemical Formula 1-2.

[0095] According to an exemplary embodiment, the compound may be represented by the following Chemical Formula 1-2.

[0096] [ [Chemical Formula 1-2]

[0097]

[0098] In the Chemical Formula 1-2, A and A' may each independently be a group represented by the following Chemical Formula 2, and R 1 、R 2 、R 4 、R 5 and R 10 to R 13 may each independently be hydrogen, a C1-C5 alkyl group, a C1-C5 haloalkyl group, a C3-C12 cycloalkyl group, a C6-C12 aryl group, a C1-C5 alkoxy group, a C1-C5 alkylsulfonyl group, a halogen, a nitro group, a cyano group, or an isocyanate group, and R 1 、R 2 、R 4 、R 5 and R 10 to R 13 in which two adjacent groups may combine with each other to form a C6-C12 aromatic ring, and R 1 、R 2 、R 4 、R 5 and R 10 to R 13The remaining groups that do not form the aromatic ring may each independently be hydrogen, a C1-C5 alkyl group, a C1-C5 haloalkyl group, a C3-C12 cycloalkyl group, a C6-C12 aryl group, a C1-C5 alkoxy group, a C1-C5 alkylsulfonyl group, a halogen, a nitro group, a cyano group, or an isocyanate group.

[0099] [Chemical Formula 2]

[0100]

[0101] In Chemical Formula 2, L may be a single bond, a C1-C5 alkylene group, or a C2-C5 alkenylene group, and R 0 may be a halogen, a C1-C5 alkyl group, or a C1-C5 haloalkyl group, and n may be an integer from 0 to 3, and may be the point of attachment to the benzene ring of Chemical Formulas 1-2.

[0102] According to an exemplary embodiment, in Chemical Formulas 1-2, A and A' are each independently represented by Chemical Formula 2, and A and A' may be the same or different.

[0103] According to an exemplary embodiment, the additive may include a compound represented by any one of Chemical Formulas 3 to 6 below.

[0104] [Chemical Formula 3]

[0105]

[0106] [Chemical Formula 4]

[0107]

[0108] [Chemical Formula 5]

[0109]

[0110] [Chemical Formula 6]

[0111]

[0112] For example, when the additive includes a compound represented by Chemical Formula 5, the two sulfonate groups contained in the compound may form a more stable SEI film on the negative electrode, thereby enabling a lithium secondary battery with improved high-temperature storage characteristics. In addition, decomposition of the electrolyte caused by the reaction between the electrolyte and the negative electrode can be suppressed, thereby further reducing gas generation.

[0113] In addition, the two tetrahydrofuran groups contained in the compound can decompose, thereby inducing the formation of a film with a relatively reduced resistance. Therefore, compared with existing additives that provide high-temperature storage characteristics, other characteristics such as the initial resistance value, fast charging characteristics, normal-temperature life, and low-temperature characteristics can be improved simultaneously.

[0114] In one embodiment, considering the formation of a sufficient passivation and stable SEI film, the content of the additive can be adjusted to be 0.1 wt% or more, 0.2 wt% or more, 0.3 wt% or more, 0.4 wt% or more, 0.5 wt% or more, or 1 wt% or more based on the total weight of the electrolyte. In addition, considering the migration of lithium ions in the electrolyte and the activity of the active material, the content of the additive can be adjusted to be 10 wt% or less, 9 wt% or less, 7 wt% or less, 6 wt% or less, 5 wt% or less, 4.5 wt% or less, 4 wt% or less, 3.5 wt% or less, 3 wt% or less, or 2 wt% or less based on the total weight of the electrolyte.

[0115] In an exemplary embodiment, the content of the additive can be 0.1 wt% to 5 wt%. In one embodiment, the content of the additive can be 0.2 wt% to 2 wt%. Within the above range, sufficient passivation of the negative electrode can be achieved while not overly hindering the migration of lithium ions and the activity of the positive electrode active material, and the excellent capacity retention rate at high temperatures and the effect of preventing the increase in battery thickness and resistance can be improved.

[0116] The electrolyte for a lithium secondary battery according to an exemplary embodiment may include an organic solvent. The lithium salt, the additive, and the auxiliary additive may have sufficient solubility in the organic solvent, and the organic solvent may include organic compounds that are non-reactive within the battery.

[0117] For example, the organic solvent may include at least one of a carbonate-based solvent, an ester-based solvent, an ether-based solvent, a ketone-based solvent, an alcohol-based solvent, and an aprotic solvent.

[0118] In one embodiment, the organic solvent may include a carbonate-based solvent.

[0119] According to an exemplary embodiment, the organic solvent may include a linear carbonate-based solvent and a cyclic carbonate-based solvent.

[0120] For example, the linear carbonate-based solvent may include at least one of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl propyl carbonate, ethyl propyl carbonate, and dipropyl carbonate.

[0121] For example, the cyclic carbonate-based solvent may include at least one of ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate.

[0122] In some embodiments, in the organic solvent, based on volume, the content of the linear carbonate-based solvent may be greater than the content of the cyclic carbonate-based solvent.

[0123] For example, the mixing volume ratio of the linear carbonate-based solvent and the cyclic carbonate-based solvent may be from 1:1 to 9:1. In one embodiment, the mixing volume ratio of the linear carbonate-based solvent and the cyclic carbonate-based solvent may be from 1.5:1 to 4:1.

[0124] For example, the ester-based solvent may include at least one of methyl acetate (MA), ethyl acetate (EA), n-propyl acetate (n-PA), 1,1-dimethylethyl acetate (DMEA), methyl propionate (MP), and ethyl propionate (EP).

[0125] For example, the ether-based solvent may include at least one of dibutyl ether, tetraethylene glycol dimethyl ether (TEGDME), diethylene glycol dimethyl ether (DEGDME), dimethoxyethane, tetrahydrofuran (THF), and 2-methyltetrahydrofuran.

[0126] For example, the ketone-based solvent may include cyclohexanone.

[0127] For example, the alcohol-based solvent may include at least one of ethyl alcohol and isopropyl alcohol.

[0128] For example, the aprotic solvent may include at least one of a nitrile-based solvent, an amide-based solvent (e.g., dimethylformamide), a dioxolane-based solvent (e.g., 1,3-dioxolane), and a sulfolane-based solvent.

[0129] The electrolyte for a lithium secondary battery according to an exemplary embodiment may contain a lithium salt. The lithium salt may be represented by Li + X - .

[0130] For example, the anion (X - ) of the lithium salt may be selected from F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - etc.

[0131] In some embodiments, the lithium salt may include at least one of LiBF4 and LiPF6.

[0132] In one embodiment, the lithium salt may be included at a concentration of 0.01 M to 5 M, relative to the organic solvent. In one embodiment, the lithium salt may be included at a concentration of 0.01 M to 2 M, relative to the organic solvent. Within the above concentration range, lithium ions and / or electrons can migrate smoothly during battery charge and discharge.

[0133] According to an exemplary embodiment, the electrolyte may further include at least one auxiliary additive selected from unsaturated cyclic carbonate-based compounds, fluorine-substituted carbonate-based compounds, sultone-based compounds, cyclic sulfate-based compounds, and phosphate-based compounds.

[0134] In one embodiment, considering the role with the main additive including the compound represented by Chemical Formula 1, for example, the content of the auxiliary additive may be adjusted to 10 wt% or less, 9 wt% or less, 8 wt% or less, 7 wt% or less, 6 wt% or less, 5 wt% or less, 4 wt% or less, 3 wt% or less, 2 wt% or less, or 1 wt% or less of the total weight of the non-aqueous electrolyte. In addition, considering the stabilization of the SEI film, the content of the auxiliary additive may be adjusted to 0.01 wt% or more, 0.02 wt% or more, 0.03 wt% or more, 0.05 wt% or more, 0.1 wt% or more, 0.2 wt% or more, 0.3 wt% or more, 0.4 wt% or more, or 0.5 wt% or more. [[ID=]))<).

[0135] According to an exemplary embodiment, the content of the auxiliary additive may be about 0.05 wt% to 10 wt% of the total weight of the non-aqueous electrolyte. According to some embodiments, the content of the auxiliary additive may be 0.1 wt% to 5 wt% of the total weight of the non-aqueous electrolyte. Within the above range, the durability of the electrode protection film can be enhanced without impairing the role of the main additive, and it can contribute to improving high-temperature storage characteristics and other characteristics.

[0136] In one embodiment, in the electrolyte, the weight ratio of the auxiliary additive to the additive may be 0.1 to 10, more than 1 and 10 or less, or 5 to 10. In this case, through the interaction between the main additive and the auxiliary additive, a lithium secondary battery with further improved high-temperature storage characteristics and cycle characteristics can be achieved.

[0137] It should be noted that there seems to be an error in the tag in the original text, which is written as "<). " in the translation. It should be corrected to the correct format for accurate translation and understanding in the future.The unsaturated cyclic carbonate-based compound may include vinylene carbonate (VC), vinyl ethylene carbonate (VEC), etc.

[0138] The fluorine-substituted carbonate-based compound may include fluoroethylenecarbonate (FEC).

[0139] The sultone-based compound may include 1,3-propane sultone, 1,3-propene sultone, 1,4-butane sultone, etc.

[0140] The cyclic sulfate-based compound may include 1,2-ethylene sulfate, 1,2-propylene sulfate, etc.

[0141] The phosphate-based compound may include lithium bis(oxalato)phosphate as an oxalato-phosphate-based compound. Alternatively, the phosphate-based compound may include lithium difluorophosphate (LiPO2F2).

[0142] By adding the auxiliary additive, the durability and stability of the electrode can be further enhanced. For the auxiliary additive, the auxiliary additive may be included in an appropriate amount within a range that does not hinder the migration of lithium ions in the electrolyte.

[0143] According to an exemplary embodiment, in the electrolyte, the weight ratio of the auxiliary additive to the additive may be from 0.1 to 10.

[0144] According to an exemplary embodiment, there is provided a lithium secondary battery including: an electrode assembly in which a plurality of positive electrodes and a plurality of negative electrodes are repeatedly stacked; a case that houses the electrode assembly; and an electrolyte for a lithium secondary battery as described above, the electrolyte for a lithium secondary battery being housed in the case together with the electrode assembly.

[0145] Hereinafter, with reference to the drawings, the lithium secondary battery according to an exemplary embodiment will be described in more detail. Figure 1 and Figure 2 are a schematic plan view and a schematic cross-sectional view, respectively, showing a lithium secondary battery according to an exemplary embodiment. Figure 2 is Figure 1 a cross-sectional view taken along the line I-I' of

[0146] Reference Figure 1 and Figure 2 The lithium secondary battery may include a positive electrode 100 and a negative electrode 130 disposed opposite to the positive electrode 100 .

[0147] For example, the positive electrode 100 may include a positive electrode current collector 105 and a positive electrode active material layer 110 on the positive electrode current collector 105 .

[0148] For example, the positive electrode active material layer 110 may include a positive electrode active material, and may include a positive electrode binder and a conductive material as needed.

[0149] For example, the positive electrode 100 may be manufactured by mixing and stirring a positive active material, a positive binder, a conductive material, a dispersion medium, etc. to prepare a positive electrode slurry, and then coating the positive electrode slurry on the positive electrode collector 105 and drying and rolling the mixture to manufacture the positive electrode 100 .

[0150] For example, the positive electrode current collector 105 may include stainless steel, nickel, aluminum, titanium, copper, or alloys thereof.

[0151] For example, the positive active material may include lithium metal oxide particles that can reversibly intercalate and deintercalate lithium ions.

[0152] In one embodiment, the positive active material may include lithium metal oxide particles containing nickel.

[0153] In some embodiments, the lithium metal oxide particles may contain nickel in an amount of 80 mol % or more relative to the total molar amount of all elements other than lithium and oxygen. In this case, a lithium secondary battery with a high capacity can be realized.

[0154] In some embodiments, in the lithium metal oxide particles, the nickel content may be 83 mol % or more, 85 mol % or more, 90 mol % or more, or 95 mol % or more relative to the total moles of all elements except lithium and oxygen.

[0155] In some embodiments, the lithium metal oxide particles may further include at least one of cobalt and manganese.

[0156] In some embodiments, the lithium metal oxide particles may further include cobalt and manganese. In this case, a lithium secondary battery having excellent power characteristics and puncture stability, etc. can be achieved.

[0157] In one embodiment, the lithium metal oxide particles may be represented by the following Chemical Formula 7.

[0158] [Chemical Formula 7]

[0159] Lix Ni (1-a-b) Co a M b O y

[0160] For example, in Chemical Formula 7, M can be at least one of Al, Zr, Ti, Cr, B, Mg, Mn, Ba, Si, Y, W, and Sr, and 0.9 ≤ x ≤ 1.2, 1.9 ≤ y ≤ 2.1, 0 ≤ a + b ≤ 0.5.

[0161] In some embodiments, a + b can be 0 < a + b ≤ 0.4, 0 < a + b ≤ 0.3, 0 < a + b ≤ 0.2, 0 < a + b ≤ 0.17, 0 < a + b ≤ 0.15, 0 < a + b ≤ 0.12, 0 < a + b ≤ 0.1.

[0162] In one embodiment, the lithium metal oxide particles may further include a coating element or a doping element. For example, the coating element or doping element may include Al, Ti, Ba, Zr, Si, B, Mg, P, Sr, W, La, or an alloy thereof or an oxide thereof. In this case, a lithium secondary battery having further improved life characteristics can be achieved.

[0163] For example, the positive electrode binder may include an organic binder such as polyvinylidene fluoride (PVDF), polyvinylidene fluoride - hexafluoropropylene copolymer (PVDF - co - HFP), polyacrylonitrile, polymethyl methacrylate, etc.; an aqueous binder such as styrene - butadiene rubber (SBR). In addition, for example, the positive electrode binder may also be used together with a thickener such as carboxymethyl cellulose (CMC).

[0164] For example, the conductive material may include a carbon - based conductive material such as graphite, carbon black, graphene, carbon nanotubes; tin, tin oxide, titanium oxide; a perovskite material such as LaSrCoO3, LaSrMnO3, etc., a metal - based conductive material.

[0165] For example, the negative electrode 130 may include a negative electrode current collector 125 and a negative electrode active material layer 120 on the negative electrode current collector 125.

[0166] For example, the negative electrode active material layer 120 may contain a negative electrode active material and may contain a negative electrode binder and a conductive material as needed.

[0167] For example, the negative electrode 130 can be manufactured as follows: a negative electrode active material, a negative electrode binder, a conductive material, a solvent, etc. are mixed and stirred to prepare a negative electrode paste, and then the negative electrode paste is coated on the negative electrode current collector 125 and dried and calendered to manufacture the negative electrode 130.

[0168] For example, the negative electrode current collector 125 can include gold, stainless steel, nickel, aluminum, titanium, copper, or their alloys. More preferably, it can include copper or a copper alloy.

[0169] For example, the negative electrode active material can be a material that allows lithium ions to be inserted and extracted. For example, the negative electrode active material can include a lithium alloy, a carbon-based material, a silicon-based material, etc.

[0170] For example, the lithium alloy can include metal elements such as aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium, indium, etc.

[0171] For example, the carbon-based material can include crystalline carbon, amorphous carbon, carbon composites, carbon fibers, etc.

[0172] For example, the amorphous carbon can be hard carbon, coke, mesocarbon microbead (MCMB) calcined at a temperature below 1500 °C, mesophase pitch-based carbon fiber (MPCF), etc. For example, the crystalline carbon can be natural graphite, graphitized coke, graphitized mesocarbon microbead (MCMB), graphitized mesophase pitch-based carbon fiber (MPCF), etc.

[0173] In one embodiment, the negative electrode active material can contain a silicon-based material. For example, the silicon-based material can include Si, SiO x (0 < x < 2), Si / C, SiO / C, Si Metal, etc. In this case, a lithium secondary battery with a high capacity can be achieved.

[0174] For example, when the negative electrode active material contains a silicon-based material, there may be a problem of an increase in the battery thickness during repeated charge and discharge. The lithium secondary battery according to an exemplary embodiment can alleviate the increase rate of the battery thickness by including the above-mentioned electrolyte.

[0175] In some embodiments, the content of the silicon active material in the negative electrode active material can be 1 wt% to 20 wt%, 1 wt% to 15 wt%, or 1 wt% to 10 wt%.

[0176] The negative electrode binder and the conductive material can be substances that are substantially the same as or similar to the above-mentioned positive electrode binder and conductive material. For example, the negative electrode binder can be an aqueous binder such as styrene-butadiene rubber (SBR). In addition, for example, the negative electrode binder can be used together with a thickener such as carboxymethyl cellulose (CMC).

[0177] For example, a separator 140 can be disposed between the positive electrode 100 and the negative electrode 130.

[0178] In some embodiments, the area of the negative electrode 130 can be larger than the area of the positive electrode 100. In this case, the lithium ions generated from the positive electrode 100 can migrate smoothly to the negative electrode 130 without precipitating in the middle.

[0179] For example, the separator 140 can include a porous polymer membrane made of a polyolefin-based polymer such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, ethylene / methacrylate copolymer, etc. In addition, for example, the separator 140 can include a non-woven fabric formed of glass fibers with a high melting point, polyethylene terephthalate fibers, etc.

[0180] For example, a battery cell can be formed by including the positive electrode 100, the negative electrode 130, and the separator 140.

[0181] For example, an electrode assembly 150 can be formed by stacking a plurality of battery cells. For example, the electrode assembly 150 can be formed by winding, laminating, or z-folding the separator 140.

[0182] The lithium secondary battery according to an exemplary embodiment can include: a positive electrode lead 107 that is connected to the positive electrode 100 and protrudes to the outside of the housing 160; and a negative electrode lead 127 that is connected to the negative electrode 130 and protrudes to the outside of the housing 160.

[0183] For example, the positive electrode 100 and the positive electrode lead 107 can be electrically connected. Similarly, the negative electrode 130 and the negative electrode lead 127 can be electrically connected.

[0184] For example, the positive electrode lead 107 can be electrically connected to the positive electrode current collector 105. In addition, the negative electrode lead 130 can be electrically connected to the negative electrode current collector 125.

[0185] For example, the positive electrode current collector 105 can include a protruding portion (positive electrode tab, not shown) on one side. The positive electrode active material layer 110 may not be formed on the positive electrode tab. The positive electrode tab can be integrally formed with the positive electrode current collector 105 or connected by welding, etc. The positive electrode current collector 105 and the positive electrode lead 107 can be electrically connected through the positive electrode tab.

[0186] Similarly, the negative electrode current collector 125 may include a protruding portion (negative electrode tab, not shown) on one side. The negative electrode active material layer 120 may not be formed on the negative electrode tab. The negative electrode tab may be integrally formed with the negative electrode current collector 125 or connected by welding or the like. The negative electrode current collector 125 and the negative electrode lead 127 may be electrically connected through the negative electrode tab.

[0187] In one embodiment, the electrode assembly 150 may include a plurality of positive electrodes and a plurality of negative electrodes. For example, the plurality of positive electrodes and negative electrodes may be alternately arranged, and a separator may be provided between the positive electrode and the negative electrode. Therefore, a lithium secondary battery according to one embodiment may include a plurality of positive electrode tabs and a plurality of negative electrode tabs respectively protruding from the above-mentioned plurality of positive electrodes and plurality of negative electrodes.

[0188] In one embodiment, the positive electrode tab (or negative electrode tab) may be laminated, rolled, and welded to form a positive electrode tab laminate (or negative electrode tab laminate). The positive electrode tab laminate may be electrically connected to the positive electrode lead 107. In addition, the negative electrode tab laminate may be electrically connected to the negative electrode lead 127.

[0189] For example, the electrode assembly 150 and the electrolyte as described above may be accommodated together in the housing 160 to form a lithium secondary battery.

[0190] The lithium secondary battery may be made, for example, in a cylindrical, prismatic, pouch type, or coin type.

[0191] Hereinafter, with reference to specific experimental examples, the embodiments of the present invention will be further described. The examples and comparative examples included in the experimental examples are only for illustrating the present invention and are not used to limit the scope of the claims. Various changes and modifications can be made to the examples within the scope and technical concept of the present invention, which will be obvious to those skilled in the art, and such variations and modifications are naturally within the scope of the claims.

[0192] Example 1

[0193] (1) Preparation of the compound of Chemical Formula 3

[0194] [Chemical Formula 3]

[0195]

[0196] Add tetrahydrofuran (250 mL), tetrahydrofurfuryl alcohol (10 g, 97.9 mmol), and triethylamine (14.9 g, 146.9 mmol) to a round-bottom flask in sequence, and then cool to 0 °C. Slowly add benzenesulfonyl chloride (12.3 mL, 16.9 mmol) thereto over 0.5 h. After the addition is complete, warm to room temperature and stir for a further 2 h. After the reaction is complete, slowly add 150 mL of saturated aqueous NaHCO3 solution to the reaction mixture, separate the organic layer, and further wash it three times with 100 mL of distilled water. Dry the solvent in the separated organic layer and then purify it by silica gel column to obtain 15.7 g of a colorless liquid (yield 68%).

[0197] 1H-NMR (CDCl3, 600 MHz): 7.94 - 7.92 (d, 2H), 7.68 - 7.65 (t, 1H), 7.58 - 7.55 (t, 2H), 4.12 - 3.99 (m, 3H), 3.79 - 3.72 (m, 2H), 2.01 - 1.95 (m, 1H), 1.90 - 1.86 (m, 2H), 1.70 - 1.65 (m, 1H)

[0198] (2) Preparation of non-aqueous electrolyte

[0199] Prepare a non-aqueous electrolyte as follows: Add 1 wt% of fluoroethylene carbonate (FEC), 0.5 wt% of 1,3 - propanesultone (PS), 0.5 wt% of ethylene sulfate (ESA), and 0.3 wt% of lithium difluorophosphate (EnChem Co., Ltd.) to a mixed solvent composed of ethylene carbonate (EC):ethyl methyl carbonate (EMC):diethyl carbonate (DEC) in a volume ratio of 25:45:30, and dissolve LiPF6 therein such that the concentration of LiPF6 is 1.0 M. Take this solution as the base electrolyte and add 0.3 wt% of the compound of Chemical Formula 3 to prepare the non-aqueous electrolyte.

[0200] (3) Fabrication of lithium secondary battery

[0201] Mix Li[Ni 0.88 Co 0.06 Mn 0.06 O2 as the positive electrode active material, polyvinylidene fluoride (PVDF) as the binder, and carbon as the conductive agent in a weight ratio of 98:1:1, and then disperse them in N-methyl-2-pyrrolidone to prepare a positive electrode slurry. Coat this slurry on an aluminum foil with a thickness of 12 μm, and then dry and calender it to fabricate the positive electrode.

[0202] Artificial graphite and natural graphite as the negative electrode active material, styrene-butadiene rubber as the binder, and carboxymethyl cellulose as the thickener are mixed at a weight ratio of 96:2:2, and then dispersed in water to prepare a negative electrode active material slurry. The slurry is coated on a copper foil with a thickness of 8 μm, and then dried and calendered to manufacture a negative electrode.

[0203] A polyethylene (PE) film separator with a thickness of 13 μm is stacked between the electrodes prepared above, and a soft package with a size of 5 mm in thickness × 50 mm in width × 60 mm in length is used to form a cell, and the non-aqueous electrolyte is injected to manufacture a 2 Ah-class lithium secondary battery for electric vehicles (EV).

[0204] Example 2

[0205] (1) Preparation of the compound of Chemical Formula 4

[0206] [Chemical Formula 4]

[0207]

[0208] Tetrahydrofuran (120 mL), tetrahydrofurfuryl alcohol (9 g, 88.1 mmol), and triethylamine (13.4 g, 132.2 mmol) are successively added to a round-bottom flask, and then cooled to 0 °C. A solution of fluorobenzenesulfonyl chloride (20.6 g, 105.8 mmol) dissolved in tetrahydrofuran (100 mL) is slowly added thereto over 0.5 hour. After the addition is completed, the temperature is raised to room temperature and further stirred for 2 hours. After the reaction is completed, 150 mL of saturated aqueous NaHCO3 solution is slowly added dropwise to the reaction mixture, the organic layer is separated, and further washed three times with 150 mL of distilled water. The solvent in the separated organic layer is dried and then purified by a silica gel column to obtain 17.6 g of a white solid (yield: 96%).

[0209] 1H-NMR (CDCl3, 600 MHz): 7.97 - 7.94 (m, 2H), 7.28 - 7.22 (m, 2H), 4.12 - 4.06 (m, 2H), 4.03 - 4.00 (m, 1H), 3.79 - 3.73 (m, 2H), 2.00 - 1.96 (m, 1H), 1.91 - 1.87 (m, 2H), 1.69 - 1.64 (m, 1H)

[0210] (2) Manufacture of the non-aqueous electrolyte and the lithium secondary battery

[0211] A lithium secondary battery was fabricated by the same method as in Example 1, except that a compound of Chemical Formula 4 was used instead of the compound of Chemical Formula 3 to prepare the non-aqueous electrolyte.

[0212] Comparative Example 1

[0213] A lithium secondary battery was fabricated by the same method as in Example 1, except that 1,3 - propylene sultone (PRS) was used instead of the compound of Chemical Formula 3 in the non-aqueous electrolyte.

[0214] Comparative Example 2

[0215] A lithium secondary battery was fabricated by the same method as in Example 1, except that the compound of Chemical Formula 3 was not added to the non-aqueous electrolyte.

[0216] Experimental Example 1: Evaluation of Initial Performance

[0217] 1) Measurement of Initial Discharge Capacity

[0218] At - 10 °C, the lithium secondary batteries according to the above Examples and Comparative Examples were charged (CC - CV 1.0C 4.2V 0.05C cut-off) and discharged (CC 1.0C 3.0V cut-off) once, and the initial discharge capacity was measured.

[0219] 2) Measurement of Initial Discharge Internal Resistance (DCIR)

[0220] At room temperature (25 °C), the lithium secondary batteries of the Examples and Comparative Examples were charged at 0.5C CC / CV (4.2V 0.05C cut-off), and then discharged at 0.5C CC to SOC 60. At SOC 60, the C-rate was changed to 0.2C, 0.5C, 1C, 1.5C, 2C, 2.5C, and discharge and supplementary charge were performed for 10 seconds respectively, and the initial DCIR was measured.

[0221] Experimental Example 2: Evaluation of High-Temperature Storage Characteristics

[0222] 1) Measurement of Capacity Retention (Ret)

[0223] At 25 °C, the lithium secondary batteries of the Examples and Comparative Examples were repeatedly charged at 0.5C CC / CV (4.2V, 0.05C cut-off) and discharged at 0.5C CC (2.7V cut-off) 3 times, and the discharge capacity C1 of the 3rd time was measured. The charged lithium secondary batteries were stored at 60 °C for 12 weeks, then further placed at room temperature for 30 minutes, and discharged at 0.5C CC (2.75V cut-off), and the discharge capacity C2 was measured. The capacity retention was calculated according to the following Formula 1 and recorded in Table 1 below.

[0224] [Formula 1]

[0225] Capacity retention rate (%) = C2 / C1 × 100 (%)

[0226] 2) Measurement of the increase rate of internal resistance (DCIR)

[0227] At 25°C, the lithium secondary batteries of the examples and comparative examples were charged at 0.5C CC / CV (4.2V, 0.05C cut-off), and then discharged at 0.5C CC to SOC 60. At SOC 60, the C rate was changed to 0.2C, 0.5C, 1C, 1.5C, 2C, 2.5C, and discharge and supplementary charging were carried out for 10 seconds respectively to measure DCIR R1. The charged lithium secondary batteries of the examples and comparative examples were placed in the atmosphere at 60°C for 12 weeks, and then further placed at room temperature for 30 minutes, and DCIR R2 was measured by the same method as above. The increase rate of internal resistance was calculated according to the following formula 2, and the result values were recorded in Table 1 below.

[0228] [Formula 2]

[0229] Increase rate of internal resistance (%) = (R2 - R1) / R1 × 100 (%)

[0230] Experimental Example 3: Evaluation of high-temperature life characteristics

[0231] At 45°C, the lithium secondary batteries of the examples and comparative examples were repeatedly charged at 1.0C CC / CV (4.2V, 0.05C cut-off) and discharged at 1.0C CC (2.7V cut-off) 500 times. At this time, the discharge capacity of the first time was set as C, and the capacity retention rate at high temperature was measured by dividing the discharge capacity of the 500th time by the discharge capacity of the first time.

[0232] Experimental Example 4: Evaluation of fast charging characteristics

[0233] Measure the time required for the lithium secondary batteries of the examples and comparative examples to be charged to a state of charge (SOC) of 8% at 0.33C, and perform step charging at 2.5C - 2.25C - 2C - 1.75C - 1.5C - 1.0C in the range of SOC 8% to 80%, and then charge again at 0.33C (4.2V, 0.05C cut-off) in the range of SOC 80% to 100%. The measured charging time was recorded in Table 1 below.

[0234] [Table 1]

[0235]

[0236] Referring to Table 1, the lithium secondary battery of the embodiment includes an electrolyte containing a compound represented by Chemical Formula 1. Therefore, compared with the case without the additive, the initial resistance and the increase rate of the resistance after high-temperature storage are reduced, and even when charged and discharged repeatedly at high temperature, it still exhibits a high capacity retention rate and has a short charging time, so the fast charging characteristics are also improved.

[0237] In particular, for the charging time, it can be confirmed that, compared with Comparative Example 1 using PRS as an additive instead of the compound represented by Chemical Formula 1, in the case of the lithium secondary battery of Example 1, the charging time is reduced by 6.4%, and in the case of the lithium secondary battery of Example 2, the charging time is reduced by 7.9%.

[0238] On the other hand, compared with the lithium secondary battery of the embodiment, the lithium secondary battery of the comparative example using an electrolyte without the compound represented by Chemical Formula 1 has deteriorated high-temperature characteristics.

[0239] The content described above is only an example of applying the principle of the present invention, and other configurations may be further included without departing from the scope of the present invention.

Claims

1. An electrolyte for a lithium secondary battery, which comprises an additive, an organic solvent, and a lithium salt, Among them, The additive comprises a compound represented by the following Chemical Formula 1, [Chemical Formula 1] In the Chemical Formula 1, A is a group represented by the following Chemical Formula 2, and R 1 to R 5 are each independently hydrogen, a C1-C5 alkyl group, a C1-C5 haloalkyl group, a C3-C12 cycloalkyl group, a C6-C12 aryl group, a C1-C5 alkoxy group, a C1-C5 alkylsulfonyl group, a halogen, a nitro group, a cyano group or an isocyanate group, or two adjacent groups among R 1 to R 5 combine with each other to form a C6-C12 aromatic ring, and the remaining groups among R 1 to R 5 that do not form the aromatic ring are each independently hydrogen, a C1-C5 alkyl group, a C1-C5 haloalkyl group, a C3-C12 cycloalkyl group, a C6-C12 aryl group, a C1-C5 alkoxy group, a C1-C5 alkylsulfonyl group, a halogen, a nitro group, a cyano group or an isocyanate group. [Chemical Formula 2] In Chemical Formula 2, L is a single bond, a C1-C5 alkylene group or a C2-C5 alkenylene group, R 0 is a halogen, a C1-C5 alkyl group or a C1-C5 haloalkyl group, n is an integer from 0 to 3, is the connection point to the benzene ring of Chemical Formula 1.

2. The electrolyte for a lithium secondary battery according to claim 1, wherein, The compound is represented by the following Chemical Formula 1-1, [Chemical Formula 1-1] In Chemical Formula 1-1, A is a group represented by the following Chemical Formula 2, and R 1 and R 4 to R 9 are each independently hydrogen, a C1-C5 alkyl group, a C1-C5 haloalkyl group, a C3-C12 cycloalkyl group, a C6-C12 aryl group, a C1-C5 alkoxy group, a C1-C5 alkylsulfonyl group, a halogen, a nitro group, a cyano group or an isocyanate group, or R 1 and R 4 to R 9 two adjacent groups in combine with each other to form a C6-C12 aromatic ring, R 1 and R 4 to R 9 the remaining groups that do not form the said aromatic ring are each independently hydrogen, a C1-C5 alkyl group, a C1-C5 haloalkyl group, a C3-C12 cycloalkyl group, a C6-C12 aryl group, a C1-C5 alkoxy group, a C1-C5 alkylsulfonyl group, a halogen, a nitro group, a cyano group or an isocyanate group, [Chemical Formula 2] In the chemical formula 2, L is a single bond, a C1-C5 alkylene group or a C2-C5 alkenylene group, and R 0 is a halogen, a C1-C5 alkyl group or a C1-C5 haloalkyl group, n is an integer from 0 to 3, is the connection point to the benzene ring of the chemical formula 1-1.

3. The electrolyte for a lithium secondary battery according to claim 1, wherein, The compound is represented by the following Chemical Formula 1-2, [Chemical Formula 1-2] In Chemical Formula 1-2, A and A' are each independently a group represented by the following Chemical Formula 2, R 1 、R 2 、R 4 、R 5 and R 10 to R 13 each independently represents hydrogen, a C1-C5 alkyl group, a C1-C5 haloalkyl group, a C3-C12 cycloalkyl group, a C6-C12 aryl group, a C1-C5 alkoxy group, a C1-C5 alkylsulfonyl group, a halogen, a nitro group, a cyano group or an isocyanate group, or R 1 、R 2 、R 4 、R 5 and R 10 to R 13 Two adjacent groups in form a C6-C12 aromatic ring, R 1 、R 2 、R 4 、R 5 and R 10 to R 13 The remaining groups that do not form the said aromatic ring are each independently hydrogen, a C1-C5 alkyl group, a C1-C5 haloalkyl group, a C3-C12 cycloalkyl group, a C6-C12 aryl group, a C1-C5 alkoxy group, a C1-C5 alkylsulfonyl group, a halogen, a nitro group, a cyano group or an isocyanate group, [Chemical Formula 2] In the chemical formula 2, L is a single bond, a C1-C5 alkylene group or a C2-C5 alkenylene group, and R 0 is a halogen, a C1-C5 alkyl group or a C1-C5 haloalkyl group, n is an integer from 0 to 3, is the connection point to the benzene ring of the chemical formula 1-2.

4. The electrolyte for a lithium secondary battery according to claim 1, wherein, In the chemical formula 1, one of R 1 to R 5 is hydrogen, C1-C5 alkyl, C1-C5 haloalkyl, C3-C12 cycloalkyl, C6-C12 aryl, C1-C5 alkoxy, C1-C5 alkylsulfonyl, halogen, nitro, cyano or isocyanate group, and the rest are hydrogen.

5. The electrolyte for a lithium secondary battery according to claim 1, wherein, In the chemical formula 1, one of R 1 to R 5 is hydrogen, fluorine, chlorine, bromine or iodine, and the rest are hydrogen.

6. The electrolyte for a lithium secondary battery according to claim 1, wherein, The content of the additive is 0.1% by weight to 10% by weight of the total weight of the electrolyte.

7. The electrolyte for a lithium secondary battery according to claim 1, wherein, The content of the additive is 0.2% by weight to 2% by weight of the total weight of the electrolyte.

8. The electrolyte for a lithium secondary battery according to claim 1, wherein, The organic solvent includes a linear carbonate-based solvent and a cyclic carbonate-based solvent.

9. The electrolyte for a lithium secondary battery according to claim 8, wherein, The cyclic carbonate-based solvent includes at least one selected from ethylene carbonate, propylene carbonate, and butylene carbonate.

10. The electrolyte for a lithium secondary battery according to claim 8, wherein, The linear carbonate-based solvent includes at least one selected from dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, and dipropyl carbonate.

11. The electrolyte for a lithium secondary battery according to claim 1, wherein The electrolyte further comprises at least one auxiliary additive selected from an unsaturated cyclic carbonate-based compound, a fluorine-substituted carbonate-based compound, a sultone-based compound, a cyclic sulfate-based compound, and a phosphate-based compound.

12. The electrolyte for a lithium secondary battery according to claim 11, wherein, The content of the auxiliary additive is 0.05% by weight to 10% by weight of the total weight of the electrolyte.

13. The electrolyte for a lithium secondary battery according to claim 11, wherein, The content of the auxiliary additive is 0.1% by weight to 5% by weight of the total weight of the electrolyte.

14. The electrolyte for a lithium secondary battery according to claim 11, wherein, In the electrolyte, the weight ratio of the auxiliary additive to the additive is 0.1 to 10.

15. A lithium secondary battery, which comprises: An electrode assembly in which a plurality of positive electrodes and a plurality of negative electrodes are repeatedly stacked; A housing that houses the electrode assembly; And The electrolyte for a lithium secondary battery according to Claim 1, and the electrolyte for a lithium secondary battery is housed in the housing together with the electrode assembly.

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