Additive for electrolyte, electrolyte for rechargeable lithium battery, and rechargeable lithium battery including the same

Abstract

The present invention provides an electrolyte additive represented by Chemical Formula 1, an electrolyte for a lithium secondary battery containing the same, and a lithium secondary battery. The details regarding the above chemical formula 1 are as described in the specification.

Description

Technology Field

[0001] The present invention relates to an electrolyte additive, an electrolyte for a lithium secondary battery containing the same, and a lithium secondary battery. Background Technology

[0003] Lithium secondary batteries are rechargeable and have an energy density more than three times higher per unit weight than conventional lead-acid batteries, nickel-cadmium batteries, nickel-hydrogen batteries, and nickel-zinc batteries, and can be fast-charged. As a result, they are being commercialized for laptops, mobile phones, power tools, and electric bicycles, and research and development to further improve energy density is actively underway.

[0004] These lithium secondary batteries are used by injecting an electrolyte into a battery cell comprising a positive electrode containing a positive electrode active material capable of intercalating and deintercalating lithium, and a negative electrode containing a negative electrode active material capable of intercalating and deintercalating lithium.

[0005] The above electrolyte acts as a medium for transporting lithium ions between the negative and positive electrodes, and generally, an organic solvent in which a lithium salt is dissolved is used; this electrolyte is important in determining the stability and performance of the lithium secondary battery.

[0006] The above electrolyte is commonly used by adding lithium salts such as LiPF6, LiBF4, and LiFSI to a mixed solvent of high-dielectric cyclic carbonates such as propylene carbonate and ethylene carbonate and linear carbonates such as diethyl carbonate, ethylmethyl carbonate, and dimethyl carbonate. As battery development in various fields becomes more active, the development of batteries with guaranteed stability over a wide temperature range is considered important, and in terms of electrolytes, the development of an optimal combination of organic solvents and additives that can improve room-temperature life characteristics while suppressing the increase in resistance during high-temperature storage is also considered important. The problem to be solved

[0008] One embodiment provides an electrolyte additive that improves the room temperature life characteristics of a lithium secondary battery while suppressing the increase in resistance during high-temperature storage.

[0009] Another embodiment provides an electrolyte for a lithium secondary battery comprising the above additive.

[0010] Another embodiment provides a lithium secondary battery comprising the above-mentioned electrolyte. means of solving the problem

[0012] One embodiment provides an electrolyte additive represented by the following chemical formula 1:

[0013] [Chemical Formula 1]

[0014]

[0015] In the above chemical formula 1,

[0016] X is a halogen atom;

[0017] L 1 to L 3 Each is a single bond, *-O-*, *-C(=O)O-*, a substituted or unsubstituted C1 to C10 alkylene group, a substituted or unsubstituted C2 to C10 alkenylene group, or a substituted or unsubstituted C2 to C10 alkynylene group;

[0018] A is a substituent represented by the following chemical formula 2;

[0019] [Chemical Formula 2]

[0020]

[0021] X 1 To X 5 are each nitrogen atoms or CR;

[0022] The above X 1 To X 5 At least two of them are nitrogen atoms;

[0023] Each of the above Rs is a hydrogen atom, or two or more adjacent Rs are bonded to each other to form a substituted or unsubstituted C6 to C10 aromatic ring.

[0024] The above X 1 To X 5 Three of them could be nitrogen atoms.

[0025] The above A may be a substituent represented by the following chemical formula 2-1 or 2-2:

[0026] [Chemical Formula 2-1]

[0027]

[0028] [Chemical Formula 2-2]

[0029] .

[0030] The above L 1 is a substituted or unsubstituted C1 to C10 alkylene group, and L 2 and L 3 All of them can be single bonds.

[0031] The above Chemical Formula 1 can be represented by the following Chemical Formula 1-1 or Chemical Formula 1-2:

[0032] [Chemical Formula 1-1]

[0033]

[0034] [Chemical Formula 1-2]

[0035]

[0036] In the above chemical formulas 1-1 and 1-2,

[0037] X is a halogen atom;

[0038] The above L 1 is a substituted or unsubstituted C1 to C10 alkylene group.

[0039] The above X may be a fluorine atom.

[0040] The above chemical formula 1 can be represented by the following chemical formula 1-1-1 or chemical formula 1-2-1:

[0041] [Chemical Formula 1-1-1]

[0042]

[0043] [Chemical Formula 1-2-1]

[0044] .

[0046] Another embodiment provides an electrolyte for a lithium secondary battery comprising a non-aqueous organic solvent, a lithium salt, and an electrolyte additive according to the above-described embodiment.

[0047] The above electrolyte additive may be included in an amount of 0.1 to 10 parts by weight per 100 parts by weight of the total electrolyte for a lithium secondary battery.

[0048] The above non-aqueous organic solvent may include carbonate-based, ester-based, ether-based, ketone-based, alcohol-based, or aprotic solvents.

[0049] The above-mentioned non-aqueous organic solvent may be a carbonate-based solvent including ethylene carbonate (EC), ethylmethyl carbonate (EMC), and dimethyl carbonate (DMC).

[0050] The above lithium salts are LiPF6, LiBF4, LiSbF6, LiAsF6, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide): LiFSI), LiC4F9SO3, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiN(C x F 2x+1 SO2)(C y F 2y+1It may include one or more selected from the group consisting of SO2)(where x and y are integers from 1 to 20), LiCl, LiI, LiB(C2O4)2 (lithium bis(oxalato) borate: LiBOB), LiDFOB (lithium difluoro(oxalato) borate) and Li[PF2(C2O4)2] (lithium difluoro(bis oxalato) phosphate).

[0051] The concentration of the lithium salt may be 0.1M to 2.0M.

[0052] Another embodiment provides a lithium secondary battery comprising: a positive electrode comprising a positive active material; a negative electrode comprising a negative active material; and an electrolyte for a lithium secondary battery according to the other embodiment described above.

[0053] The above positive active material may include a nickel-based positive active material.

[0054] The above positive active material is Li x Ni y Mn (1-y) O2(where, 0.5≤x≤1.8, 0 <y<1)로 표시되는 화합물을 포함할 수 있다.

[0055] The negative electrode active material may include graphite, silicon, or a combination thereof. Effects of the invention

[0057] An electrolyte additive of one embodiment is included in the electrolyte to improve the room temperature life characteristics of a lithium secondary battery while suppressing the increase in resistance during high-temperature storage. Brief explanation of the drawing

[0059] FIG. 1 is a schematic diagram illustrating a lithium secondary battery according to one embodiment of the present invention. Figures 2 and 3 are graphs showing the results of the CV characteristic evaluation for a cathode half cell of one evaluation example of the present invention, respectively. Figures 4 and 5 are graphs showing the results of the CV characteristic evaluation for an anode half cell of one evaluation example of the present invention, respectively. Specific details for implementing the invention

[0060] Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples and are not intended to limit the present invention, and the present invention is defined only by the scope of the claims to be followed.

[0061] In this specification, "substitution" means that, unless otherwise defined, at least one hydrogen of a substituent or compound is substituted with a deuterium, a halogen group, a hydroxyl group, an amino group, a substituted or unsubstituted C1 to C30 amine group, a nitro group, a substituted or unsubstituted C1 to C40 silyl group, a C1 to C30 alkyl group, a C1 to C10 alkylsilyl group, a C6 to C30 arylsilyl group, a C3 to C30 cycloalkyl group, a C3 to C30 heterocycloalkyl group, a C6 to C30 aryl group, a C2 to C30 heteroaryl group, a C1 to C20 alkoxy group, a C1 to C10 fluoroalkyl group, a cyano group, or a combination thereof.

[0062] In one example of the present invention, "substitution" means that at least one hydrogen in a substituent or compound is substituted with deuterium, a halogen group, a C1 to C30 alkyl group, a C1 to C10 alkylsilyl group, a C6 to C30 arylsilyl group, a C3 to C30 cycloalkyl group, a C3 to C30 heterocycloalkyl group, a C6 to C30 aryl group, a C2 to C30 heteroaryl group, a C1 to C10 fluoroalkyl group, or a cyano group. Furthermore, in a specific example of the present invention, "substitution" means that at least one hydrogen in a substituent or compound is substituted with deuterium, a halogen group, a C1 to C20 alkyl group, a C6 to C30 aryl group, a C1 to C10 fluoroalkyl group, or a cyano group. In addition, in a specific example of the present invention, "substitution" means that at least one hydrogen in the substituent or compound is substituted with deuterium, a halogen group, a C1 to C5 alkyl group, a C6 to C18 aryl group, a C1 to C5 fluoroalkyl group, or a cyano group. In addition, in a specific example of the present invention, "substitution" means that at least one hydrogen in the substituent or compound is substituted with deuterium, a cyano group, a halogen group, a methyl group, an ethyl group, a propyl group, a butyl group, a phenyl group, a biphenyl group, a terphenyl group, a trifluoromethyl group, or a naphthyl group.

[0063] Additionally, unless otherwise defined in this specification, "*" signifies a part connected to the same or different atoms or chemical formulas.

[0064] Lithium secondary batteries can be classified into lithium-ion batteries, lithium-ion polymer batteries, and lithium polymer batteries depending on the type of separator and electrolyte used; classified into cylindrical, prismatic, coin, and pouch types depending on their shape; and divided into bulk and thin-film types depending on their size. Since the structures and manufacturing methods of these batteries are widely known in this field, a detailed description is omitted.

[0065] Here, a cylindrical lithium secondary battery is described as an example of a lithium secondary battery. FIG. 1 schematically shows the structure of a lithium secondary battery according to one embodiment. Referring to FIG. 1, a lithium secondary battery (100) according to one embodiment includes a battery cell comprising a positive electrode (114), a negative electrode (112) positioned opposite to the positive electrode (114), a separator (113) disposed between the positive electrode (114) and the negative electrode (112), and an electrolyte (not shown) impregnating the positive electrode (114), the negative electrode (112), and the separator (113); a battery container (120) containing the battery cell; and a sealing member (140) sealing the battery container (120).

[0067] (Electrolyte Additive)

[0068] Hereinafter, an electrolyte additive according to one embodiment is described.

[0069] In lithium secondary batteries, the non-aqueous electrolyte decomposes during initial charging and discharging, forming a film with passivation capabilities on the surfaces of the positive and negative electrodes, which can improve high-temperature storage characteristics; however, the said film is HF generated by the thermal decomposition of lithium salts (such as LiPF6) widely used in lithium-ion batteries. - and PF5 - It can be degraded by acids such as [specific acid]. Due to the attack of such acids, the leaching of transition metal elements occurs at the anode, and changes in the surface structure lead to an increase in the electrode's surface resistance. Furthermore, as metal elements acting as redox centers are lost, the theoretical capacity decreases, which can result in a decrease in the actual capacity. In addition, these leached transition metal ions are electrodeposited on the cathode, which reacts in a strong reduction potential band; this not only consumes electrons but also destroys the film during deposition, exposing the cathode surface and causing additional electrolyte decomposition reactions. Consequently, there is a problem in which the cell's capacity continuously decreases as the cathode resistance increases and irreversible capacity increases.

[0070] On the other hand, the electrolyte additive of one embodiment can solve the above problem. Specifically, the additive according to one embodiment of the present invention is represented by the following chemical formula 1.

[0071] [Chemical Formula 1]

[0072]

[0073] In the above chemical formula 1,

[0074] X is a halogen atom;

[0075] L 1 to L 3 Each is independently a single bond, *-O-*, *-C(=O)O-*, a substituted or unsubstituted C1 to C10 alkylene group, a substituted or unsubstituted C2 to C10 alkenylene group, or a substituted or unsubstituted C2 to C10 alkynylene group;

[0076] A is a substituent represented by the following chemical formula 2;

[0077] [Chemical Formula 2]

[0078]

[0079] X 1 To X 5 are each nitrogen atoms or CR;

[0080] The above X 1 To X 5 At least two of them are nitrogen atoms;

[0081] Each of the above Rs is a hydrogen atom, or two or more adjacent Rs are bonded to each other to form a substituted or unsubstituted C6 to C10 aromatic ring.

[0083] The sulfonyl group substituted with the above halogen atom (X) can lower the interfacial resistance between the anode and the electrolyte, accelerate the movement of lithium ions on the surface of the anode or anode, and suppress the decomposition of the anode or anode active material by forming a lithium salt-based Solid Electrolyte Interphase (SEI) on the surface of the anode or anode. In particular, as shown in the evaluation examples described below, the additive can be oxidized preferentially over the solvent forming a protective film on the anode surface, thereby forming a lithium salt-based SEI on the surface and passivating it.

[0084] In addition, two or more nitrogen atoms included in the substituent represented by the above chemical formula 2 provide lone pairs of electrons, and PF5 - By capturing and stabilizing the LiPF6 salt, the acid caused by the decomposition of the lithium salt can be removed.

[0085] Meanwhile, the above L 1 to L 3 The sulfonyl group substituted with the halogen atom (X) directly combines with the substituent represented by Chemical Formula 2 or connects them by means of a linker.

[0086] Accordingly, the electrolyte additive represented by the above chemical formula 1 has a sulfonyl group substituted with the halogen atom (X) and a substituent represented by the above chemical formula 2 directly bonded or a linker (L 1 , L 2 , L 3 A structure connected by (or a combination thereof) can solve the aforementioned problems and improve the room temperature life characteristics of a lithium secondary battery while suppressing the increase in resistance during high-temperature storage.

[0087] The electrolyte additive represented by the above chemical formula 1 is described in more detail below.

[0089] In the sulfonyl group substituted with the halogen atom (X), the halogen atom (X) may be a fluorine atom (F), a chlorine atom (Cl), a bromine atom (Br), or an iodine atom (I). Specifically, the halogen atom (X) may be a fluorine atom (F) or a chlorine atom (Cl). For example, the halogen atom (X) may be a fluorine atom (F).

[0090] The above A may be a pentagonal aromatic ring containing three nitrogen atoms or a derivative thereof. Specifically, it may be a substituent represented by the above chemical formula 2, and the X 1 To X 5 Three of them may be nitrogen atoms. For example, the above A may be a substituent represented by the following chemical formula 2-1 or 2-2:

[0091] [Chemical Formula 2-1]

[0092]

[0093] [Chemical Formula 2-2]

[0094]

[0095] The above L 1 is a substituted or unsubstituted C1 to C10 alkylene group, and L 2 and L 3 All of them can be single bonds. Specifically, the above L 1 may be a substituted or unsubstituted C1 to C5 alkylene group. More specifically, it may be a substituted or unsubstituted C1 to C3 alkylene group. For example, the above L 1 It may be an unsubstituted C2 alkylene group (*-CH2CH2-*).

[0096] The above Chemical Formula 1 can be represented by the following Chemical Formula 1-1 or Chemical Formula 1-2:

[0097] [Chemical Formula 1-1]

[0098]

[0099] [Chemical Formula 1-2]

[0100]

[0101] In the above chemical formulas 1-1 and 1-2, X is a halogen atom; and L 1 is a substituted or unsubstituted C1 to C10 alkylene group.

[0102] Representative examples of the above chemical formula 1 are as follows:

[0103] [Chemical Formula 1-1-1]

[0104]

[0105] [Chemical Formula 1-2-1]

[0106] .

[0108] (Electrolyte)

[0109] An electrolyte for a lithium secondary battery according to another embodiment of the present invention comprises a non-aqueous organic solvent, a lithium salt, and the aforementioned electrolyte additive.

[0111] The above additive may be included in an amount of 0.1 to 10 parts by weight per 100 parts by weight of the total electrolyte for a lithium secondary battery.

[0112] Specifically, the above additive may be included in an amount of 0.1 parts by weight or more, 0.2 parts by weight or more, 0.3 parts by weight or more, or 0.5 parts by weight or more, based on 100 parts by weight of the total electrolyte for a lithium secondary battery; and in an amount of 10 parts by weight or less, 5.0 parts by weight or less, 3.0 parts by weight or less, or 0.5 to 1.0 parts by weight.

[0113] When the content range of the additive is as described above, it is possible to realize a lithium secondary battery with improved lifespan and output characteristics by preventing an increase in resistance at high temperatures.

[0115] The above electrolyte for a lithium secondary battery may further include at least one other additive selected from vinylene carbonate (VC), fluoroethylene carbonate (FEC), difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, vinylethylene carbonate (VEC), adiponitrile (AN), succinonitrile (SN), 1,3,6-hexane tricyanide (HTCN), propensulfone (PST), propanesulfone (PS), lithium tetrafluoroborate (LiBF4), lithium difluorophosphate (LiPO2F2), and 2-fluorobiphenyl (2-FBP).

[0116] By further including the aforementioned other additives, the lifespan can be further improved, or gases generated at the anode and cathode during high-temperature storage can be effectively controlled.

[0117] The above other additives may be included in an amount of 0.2 to 20 parts by weight per 100 parts by weight of the total electrolyte for the lithium secondary battery, and specifically, may be included in an amount of 0.2 to 15 parts by weight, for example, 0.2 to 10 parts by weight.

[0118] When the content of other additives is as described above, the increase in film resistance can be minimized, thereby contributing to the improvement of battery performance.

[0120] The above-mentioned non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0121] The above-mentioned non-aqueous organic solvent may be a carbonate-based, ester-based, ether-based, ketone-based, alcohol-based, or aprotic solvent.

[0122] The above carbonate-based solvents may include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), ethylmethyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc. The above ester-based solvents may include methyl acetate, ethyl acetate, n-propyl acetate, t-butyl acetate, methylpropionate, ethylpropionate, propylpropionate, decanolide, mevalonolactone, caprolactone, etc. The above ether-based solvents may include dibutyl ether, tetraglame, deglame, dimethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, etc. In addition, cyclohexanone, etc. may be used as the ketone-based solvent. Furthermore, ethyl alcohol, isopropyl alcohol, etc. may be used as the alcohol-based solvent, and R may be used as the aprotic solvent. 1 -CN(R 1 Nitriles such as dimethylformamide, amides such as dioxolanes such as 1,3-dioxolane, sulfolanes, etc., may be used. (It is a hydrocarbon group with a straight, branched, or ring structure having 2 to 20 carbon atoms and may include a double bond direction ring or ether bond.)

[0123] The above-mentioned non-aqueous organic solvents may be used alone or in a mixture of one or more. When used in a mixture of one or more, the mixing ratio can be appropriately adjusted according to the desired battery performance, which is widely understood by those working in the field.

[0124] In addition, for the above carbonate-based solvent, it is preferable to use a mixture of cyclic carbonates and chain carbonates. In this case, using a mixture of cyclic carbonates and chain carbonates in a volume ratio of 1:9 to 9:1 can result in excellent performance of the electrolyte.

[0125] In particular, in one embodiment of the present invention, the non-aqueous organic solvent may contain the cyclic carbonate and the chain carbonate in a volume ratio of 2:8 to 5:5, and additionally, the cyclic carbonate and the chain carbonate may be contained in a volume ratio of 2:8 to 4:6.

[0126] More specifically, the cyclic carbonate and the chain carbonate may be included in a volume ratio of 2:8 to 3:7.

[0127] For example, the above-mentioned non-aqueous organic solvent may be a carbonate-based solvent comprising ethylene carbonate (EC), ethylmethyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 2:4:4.

[0128] The above-mentioned non-aqueous organic solvent may further include an aromatic hydrocarbon organic solvent in addition to the carbonate-based solvent. In this case, the carbonate-based solvent and the aromatic hydrocarbon solvent may be mixed in a volume ratio of 1:1 to 30:1.

[0129] As the above aromatic hydrocarbon solvent, an aromatic hydrocarbon compound of the following chemical formula 4 may be used.

[0130] [Chemical Formula 4]

[0131]

[0132] In the above chemical formula 3, R 3 to R 8The groups are identical or different from each other and are selected from the group consisting of hydrogen, halogen, alkyl groups having 1 to 10 carbon atoms, haloalkyl groups having 1 to 10 carbon atoms, and combinations thereof.

[0133] Specific examples of the above aromatic hydrocarbon solvents include benzene, fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-trifluorobenzene, 1,2,4-trifluorobenzene, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2,3-trichlorobenzene, 1,2,4-trichlorobenzene, iodobenzene, 1,2-diiodobenzene, 1,3-diiodobenzene, 1,4-diiodobenzene, 1,2,3-triiodobenzene, 1,2,4-triiodobenzene, toluene, fluorotoluene, 2,3-difluorotoluene, 2,4-difluorotoluene. It is selected from the group consisting of 2,5-difluorotoluene, 2,3,4-trifluorotoluene, 2,3,5-trifluorotoluene, chlorotoluene, 2,3-dichlorotoluene, 2,4-dichlorotoluene, 2,5-dichlorotoluene, 2,3,4-trichlorotoluene, 2,3,5-trichlorotoluene, iodotoluene, 2,3-diiodotoluene, 2,4-diiodotoluene, 2,5-diiodotoluene, 2,3,4-triiodotoluene, 2,3,5-triiodotoluene, xylene, and combinations thereof.

[0135] The above lithium salt is a material that dissolves in a non-aqueous organic solvent and acts as a source of lithium ions within the battery, enabling the operation of a basic lithium secondary battery and facilitating the movement of lithium ions between the anode and cathode. Representative examples of such lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide): LiFSI), LiC4F9SO3, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, and LiN(C x F2x+1 SO2)(C y F 2y+1 Examples include one or more selected from the group consisting of SO2)(where x and y are integers from 1 to 20), LiCl, LiI, LiB(C2O4)2 (lithium bis(oxalato) borate: LiBOB), LiDFOB (lithium difluoro(oxalato) borate), and Li[PF2(C2O4)2] (lithium difluoro(bis oxalato) phosphate). It is preferable to use a lithium salt concentration within the range of 0.1M to 2.0M. Specifically, the lithium salt concentration may be 0.1M or higher, 0.5M or higher, 1.0M or higher, or 1.15M or higher; and 2.0M or lower, 1.8M or lower, 1.5M or lower, or 1.3M or lower. When the lithium salt concentration is within the above range When included, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and allow lithium ions to move effectively.

[0137] (Lithium secondary battery)

[0138] Another embodiment of the present invention provides a lithium secondary battery comprising a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material; and the aforementioned electrolyte.

[0140] The above positive electrode comprises a positive current collector and a positive active material layer located on the positive current collector, and the positive active material layer comprises a positive active material.

[0141] As the above-mentioned positive electrode active material, a compound capable of reversible intercalation and deintercalation of lithium (a lithated intercalation compound) may be used.

[0142] Specifically, at least one type of composite oxide of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof may be used as the positive electrode active material. Such a positive electrode active material may be one or more types of lithium composite oxides represented by the following chemical formula 5.

[0143] [Chemical Formula 5]

[0144] Li x M 1 y M 2 z M 3 1-y-z O 2±a X a

[0145] In the above chemical formula 5,

[0146] 0.5≤x≤1.8, 0≤a≤0.1, 0 <y≤1, 0≤z≤1, 0<y+z≤1, M 1 , M 2 and M 3 Each comprises one or more elements selected from metals such as Ni, Co, Mn, Al, B, Ba, Ca, Ce, Cr, Fe, Mo, Nb, Si, Sr, Mg, Ti, V, W, Zr, or La and combinations thereof, and X comprises one or more elements selected from F, S, P, or Cl.

[0147] The positive active material corresponding to the above chemical formula 5 is LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiNi a Mn b Co c O2(a+b+c=1), LiNi a Mn b Co c Al d O2(a+b+c+d=1) and LiNi e Co f Al g It may be at least one type selected from the group consisting of O2(e+f+g=1).

[0148] Of course, a composite oxide may be used in which a portion of the metal is substituted with a metal other than another metal, or at least one phosphate compound of the composite oxide selected from the group consisting of, for example, LiFePO4, LiCoPO4, and LiMnPO4, or a composite oxide having a coating layer on its surface may be used, or a composite oxide having a coating layer may be mixed and used. This coating layer may include at least one coating element compound selected from the group consisting of oxide of the coating element, hydroxide of the coating element, oxyhydroxide of the coating element, oxycarbonate of the coating element, and hydroxycarbonate of the coating element. The compounds forming these coating layers may be amorphous or crystalline. As the coating elements included in the coating layer, Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof may be used. For the coating layer formation process, any coating method may be used as long as the above-mentioned compounds are coated using these elements in a manner that does not adversely affect the physical properties of the cathode active material (e.g., spray coating, immersion method, etc.). Since this is a matter that is well understood by those skilled in the field, a detailed explanation will be omitted.

[0149] More specifically, a nickel-based cathode active material that necessarily includes nickel may be used as the cathode active material. In this case, in Chemical Formula 5, M 1 It can be Ni. For example, the above LiNi b Mn c Co d O2(b+c+d=1), LiNi b Mn c Co d Al e O2(b+c+d+e=1) and LiNi b Co d Al eThe positive active material selected in O2(b+d+e=1) may be a high nickel (high Ni) based positive active material. The above LiNi b Mn c Co d O2(b+c+d=1) and LiNi b Mn c Co d Al e In the case of O2(b+c+d+e=1), the nickel content may be 60% or more (b ≥ 0.6) or 80% or more (b ≥ 0.8). The above LiNi b Co d Al e In the case of O2(b+d+e=1), the nickel content may be 60% or more (b ≥ 0.6), and more specifically, 80% or more (b ≥ 0.8).

[0150] Meanwhile, as the above-mentioned positive active material, a nickel-based cobalt-free (Co-free) positive active material that necessarily includes nickel but does not include cobalt may be used. In this case, the above-mentioned chemical formula 5 may be represented by the following chemical formula 5-1:

[0151] [Chemical Formula 5-1]

[0152] Li x Ni y Mn (1-y) O2

[0153] 0.5≤x≤1.8, 0 <y<1일 수 있다.

[0154] The content of the above positive active material may be 90% to 98% by weight with respect to the total weight of the positive composition.

[0155] The content of the conductive material and binder may each be 1% to 5% by weight with respect to the total weight of the anode composition.

[0156] The above conductive material is used to impart conductivity to the positive electrode, and any electronically conductive material that does not cause chemical changes can be used in the battery being constructed. Examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, and carbon fibers; metal-based materials such as metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; or conductive materials including mixtures thereof.

[0157] The above binder serves to adhere the positive active material particles well to each other and also to adhere the positive active material well to the current collector. Representative examples include polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc., but are not limited thereto.

[0158] Al may be used as the anode current collector, but is not limited thereto.

[0160] The above cathode includes a cathode active material layer comprising a cathode current collector and a cathode active material formed on the cathode current collector.

[0161] The above-mentioned negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

[0162] As a material capable of reversibly intercalating / deintercalating the above lithium ions, any carbon-based negative electrode active material commonly used in lithium secondary batteries can be used, and representative examples include crystalline carbon, amorphous carbon, or a combination thereof. Examples of the above crystalline carbon include graphite such as amorphous, plate-like, flake-like, spherical, or fibrous natural graphite or artificial graphite, and examples of the above amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, etc.

[0163] As the above lithium metal alloy, an alloy of a metal selected from the group consisting of lithium, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn may be used.

[0164] Materials capable of doping and undoping the above lithium include Si, Si-C complexes, SiOx (0 < x < 2), Si-Q alloys (wherein Q is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements excluding Si, Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof), Sn, SnO2, and Sn-R 11 (Above R 11 Examples include elements selected from the group consisting of alkali metals, alkaline earth metals, group 13 elements, group 14 elements excluding Sn, group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof, and at least one of these may be mixed with SiO2 and used.

[0165] The above elements Q and R 11For the arbor, one may be selected from the group consisting of Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof.

[0166] Examples of the above transition metal oxides include vanadium oxide, lithium vanadium oxide, or lithium titanium oxide.

[0167] In a specific embodiment, the negative electrode active material may include graphite, silicon, or a combination thereof. More specifically, it may include at least one of a graphite and Si composite.

[0168] The above Si composite comprises a core containing Si-based particles and an amorphous carbon coating layer, for example, the Si-based particles include Si particles, Si-C composites, and SiO. x It may include one or more of (0 < x ≤ 2) and Si alloys.

[0169] For example, the above Si composite may include a void in the center of a core containing the above Si-based particles, the radius of the center may be 30% to 50% of the radius of the above cathode active material, and the average particle size of the above Si-based particles may be 10 nm to 200 nm.

[0170] In this specification, the average particle size may be the particle size (D50) at 50% by volume ratio in the cumulative size-distribution curve.

[0171] When the average particle size of the above Si-based particles falls within the above range, volume expansion occurring during charging and discharging can be suppressed, and the disruption of the conductive path due to particle fragmentation during charging and discharging can be prevented.

[0172] The core containing the above Si-based particles further includes amorphous carbon, wherein the central part does not contain amorphous carbon, and the amorphous carbon may exist only on the surface of the negative electrode active material.

[0173] At this time, the surface region refers to the area from the outermost surface of the center to the outermost surface of the cathode active material.

[0174] In addition, Si-based particles are substantially uniformly incorporated throughout the cathode active material, that is, they can exist at a substantially uniform concentration in the center and on the surface.

[0175] The above amorphous carbon may be soft carbon, hard carbon, mesophase pitch carbide, calcined coke, or a combination thereof.

[0176] For example, the above Si-C composite may include Si particles and crystalline carbon.

[0177] The above Si particles may be included in an amount of 1 to 60 weight% with respect to the total weight of the Si-C composite, for example, 3 It may be included in an amount of up to 60 weight%.

[0178] The above crystalline carbon may be, for example, graphite, and specifically may be natural graphite, artificial graphite, or a combination thereof.

[0179] The average particle size of the crystalline carbon above may be 5 μm to 30 μm.

[0180] When the above-mentioned cathode active material includes graphite and Si composites together, the graphite and Si composites may be included in the form of a mixture, and in this case, the graphite and Si composites may be included in a weight ratio of 99:1 to 50:50.

[0181] More specifically, the graphite and Si composite may be included in a weight ratio of 97:3 to 80:20 or 95:5 to 80:20.

[0182] As the above amorphous carbon precursor, coal-based pitch, mesophase pitch, petroleum-based pitch, coal-based oil, petroleum-based heavy oil, or polymer resins such as phenolic resin, furan resin, and polyimide resin may be used.

[0183] The content of the negative electrode active material in the above negative electrode active material layer may be 95% to 99% by weight with respect to the total weight of the negative electrode active material layer.

[0184] In one embodiment of the present invention, the negative electrode active material layer comprises a binder and may optionally further comprise a conductive material. The content of the binder in the negative electrode active material layer may be 1% to 5% by weight with respect to the total weight of the negative electrode active material layer. Additionally, when further comprising a conductive material, the negative electrode active material may be used in an amount of 90% to 98% by weight, the binder in an amount of 1% to 5% by weight, and the conductive material in an amount of 1% to 5% by weight.

[0185] The above binder serves to effectively bond the negative electrode active material particles to each other and also to effectively bond the negative electrode active material to the current collector. As the binder, a water-insoluble binder, a water-soluble binder, or a combination thereof may be used.

[0186] Examples of the above-mentioned water-insoluble binders include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or combinations thereof.

[0187] Examples of the above water-soluble binders include rubber-based binders or polymer resin binders. The above rubber-based binder may be selected from styrene-butadiene rubber, acrylated styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluororubber, and combinations thereof. The above polymer resin binder may be selected from polytetrafluoroethylene, ethylene-propylene copolymer, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, ethylene-propylene-diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0188] When a water-soluble binder is used as the above-mentioned cathode binder, a cellulose-based compound capable of imparting viscosity may be further included as a thickener. As this cellulose-based compound, one or more types such as carboxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, or alkali metal salts thereof may be mixed and used. Na, K, or Li may be used as the alkali metal. The content of such a thickener may be 0.1 to 3 parts by weight per 100 parts by weight of the cathode active material.

[0189] The above conductive material is used to impart conductivity to the electrode, and any electronically conductive material that does not cause chemical changes can be used in the battery being constructed. Examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, and carbon fibers; metal-based materials such as metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; or conductive materials comprising a mixture thereof.

[0190] The above-mentioned cathode current collector may be selected from the group consisting of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof.

[0192] Depending on the type of lithium secondary battery, a separator may be present between the positive and negative electrodes. Such a separator may be a porous substrate; or a composite porous substrate.

[0193] The porous substrate is a substrate containing pores through which lithium ions can move. The porous substrate may be, for example, polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof, and of course, a mixed multilayer film such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, or a polypropylene / polyethylene / polypropylene three-layer separator may be used.

[0194] The above composite porous substrate may be in the form of a porous substrate and a functional layer located on the porous substrate. From the perspective of enabling the addition of additional functions, the functional layer may be, for example, at least one of a heat-resistant layer and an adhesive layer, and for example, the heat-resistant layer may include a heat-resistant resin and optionally a filler.

[0195] In addition, the adhesive layer may include an adhesive resin and optionally a filler.

[0196] The above filler may be an organic filler or an inorganic filler.

[0198] Examples and comparative examples of the present invention are described below. However, the following examples are merely one example of the present invention, and the present invention is not limited to the following examples.

[0200] (Synthesization Example: Synthesis of Additives)

[0201] The additive was prepared according to the procedure disclosed below: [J. Org. Chem., Vol. 44, No. 22, 1979]. A suitable triazole was reacted with ethensulfonyl fluoride (ESF) in dimethylformamide (DMF).

[0203] Synthesis Example 1: Synthesis of a compound represented by Chemical Formula 1-1-1

[0204] A solution of 5.5 g of ESF (0.05 mol) in 10 mL of DMF was added to a solution of 5.96 g of benzotriazole (0.05 mol) in 20 mL of DMF. The reaction mixture was stirred at 45°C for 4 hours. DMF was removed by rotary evaporation at 60°C, and toluene was added to the residue. The precipitated product was filtered, washed with toluene, and dried under vacuum to obtain a compound represented by the following chemical formula 1-1-1 (2-(1H-1,2,3-benzotriazole-1-yl)ethanesulfonyl fluoride).

[0205] [Chemical Formula 1-1-1]

[0206]

[0207] 1H NMR (400 MHz, CDCl3) 4.17 (m, 2H), 5.17 (t, 2H), 7.44 (1m, 1H), 7.60 (m, 1H), 8.10 (d, 1H); 19F NMR (376MHz, CDCl3) 57.44.

[0209] Synthesis Example 2: Synthesis of a compound represented by Chemical Formula 1-2-1

[0210] A solution of ESF (7.72 g, 0.07 mol) in 10 mL of DMF was added to a solution of triazole (4.49 g, 0.065 mol) in DMF (25 mL). The reaction mixture was stirred at room temperature for 4 hours. DMF was removed by rotary evaporation at 60°C, and toluene was added to the residue. The precipitated product was filtered, washed with toluene, and dried under vacuum to obtain a compound represented by the following chemical formula 1-2-1 (2-(1H-1,2,4-triazole-1-yl)ethanesulfonyl fluoride).

[0211] [Chemical Formula 1-2-1]

[0212] .

[0213] 1H NMR (400 MHz, CDCl3) 4.01 (m, 2H), 4.73 (t, 2H), 8.01 (s, 1H), 8.19 (s, 1H); 19F NMR (376MHz, CDCl3) 57.83.

[0215] Comparative Synthesis Example 1: Synthesis of a compound represented by chemical formula A

[0216] The compound represented by the chemical formula 1-1-1 (4.5 g, 0.02 mol) and glacial acetic acid (30 ml) were reacted at 100°C for 48 hours. Subsequently, the reaction mixture was reduced under vacuum, and acetone was added to the residue. The precipitated product was filtered, washed with anhydrous acetone, and dried under vacuum to obtain the compound represented by the chemical formula A below.

[0217] [Chemical Formula A]

[0218]

[0220] Comparative Synthesis Example 2: Synthesis of a compound represented by chemical formula B

[0221] Methyl vinylsulfone (5.3g, 0.05mol) and potassium bicarbonate were added to a solution of benzotriazole (5.96g, 0.05mol) in methyl ethyl ketone (MEK) (50ml) and reacted. After refluxing the reaction mixture for 24 hours, the solvent was removed by rotary evaporation and dried under vacuum to obtain a compound represented by the following chemical formula B.

[0222] [Chemical Formula B]

[0223]

[0225] (Example: Preparation of electrolyte)

[0226] Example 1

[0227] The electrolyte of Example 1 was prepared by mixing the following lithium salt, a non-aqueous organic solvent, and an additive.

[0228] Lithium salt: LiPF6 1.15 M

[0229] Non-aqueous organic solvent: Ethylene carbonate: Ethylmethyl carbonate: Dimethyl carbonate (volume ratio of EC: EMC:DMC = 20:40:40)

[0230] Additive: 0.5 parts by weight of a compound represented by chemical formula 1-1-1

[0231] (However, in the above electrolyte composition, “parts by weight” refers to the relative weight of the additive to 100 parts by weight of the total electrolyte (lithium salt + non-aqueous organic solvent) excluding the additive.)

[0233] Example 2

[0234] The electrolyte of Example 2 was prepared in the same manner as Example 1, except that a compound represented by the chemical formula 1-2-1 was used instead of the compound represented by the chemical formula 1-1-1 as an electrolyte additive.

[0235] In addition, a lithium secondary battery of Example 2 was prepared in the same manner as Example 1, except that the electrolyte of the above example was used.

[0237] Example 3

[0238] The electrolyte of Example 3 was prepared in the same manner as Example 1, except that 0.2 parts by weight of the compound represented by the chemical formula 1-1-1 was used as an electrolyte additive.

[0239] In addition, a lithium secondary battery of Example 3 was prepared in the same manner as Example 1, except that the electrolyte of the above example was used.

[0241] Example 4

[0242] The electrolyte of Example 4 was prepared in the same manner as Example 1, except that 1.0 part by weight of the compound represented by the chemical formula 1-1-1 was used as an electrolyte additive.

[0243] In addition, a lithium secondary battery of Example 4 was prepared in the same manner as Example 1, except that the electrolyte of the above example was used.

[0245] Example 5

[0246] The electrolyte of Example 5 was prepared in the same manner as Example 2, except that 1.0 part by weight of the compound represented by the chemical formula 1-2-1 was used as an electrolyte additive.

[0247] In addition, the lithium secondary battery of Example 5 was manufactured in the same manner as Example 5, except that the electrolyte of the above example was used.

[0249] Comparative Example 1 (Ref.)

[0250] A lithium secondary battery was manufactured using the same method as in Example 1 above, except that no additives were used.

[0252] Comparative Example 2

[0253] The electrolyte of Comparative Example 2 was prepared in the same manner as Example 1, except that a compound represented by the chemical formula A was used instead of the compound represented by the chemical formula A as an electrolyte additive.

[0254] In addition, a lithium secondary battery of Comparative Example 2 was prepared in the same manner as Example 1, except that the electrolyte of the above example was used.

[0256] Comparative Example 3

[0257] The electrolyte of Comparative Example 3 was prepared in the same manner as Example 1, except that a compound represented by the chemical formula B was used instead of the compound represented by the chemical formula A as an electrolyte additive.

[0258] In addition, a lithium secondary battery of Comparative Example 3 was prepared in the same manner as Example 1, except that the electrolyte of the above example was used.

[0260] The electrolyte additive compositions according to Examples 1 to 8 and Comparative Examples 1 to 3 above are shown in Table 1 below.

[0262] Lithium salt (M) Non-aqueous organic solvents (volume ratio) Additives (parts by weight) LiPF6 EC EMC DMC Comparative Example 1 (Ref.) 1.15 2 4 4 - Comparative Example 2 1.15 2 4 4 0.5 parts by weight of chemical formula A Comparative Example 3 1.15 2 4 4 0.5 parts by weight of chemical formula B Example 1 1.15 2 4 4 10.5 parts by weight of the chemical formula Example 2 1.15 2 4 4 20.5 parts by weight of the chemical formula Example 3 1.15 2 4 4 10.2 parts by weight of the chemical formula Example 4 1.15 2 4 4 11.0 parts by weight of the chemical formula Example 5 1.15 2 4 4 21.0 parts by weight of the chemical formula

[0263] For reference, in Table 1 above, the molar concentration (M) of the lithium salt refers to the amount (number of moles) of the lithium salt dissolved per 1 L of electrolyte, and the volume ratio of the non-aqueous organic solvent refers to the volume ratio of EC:EMC:DMC, and The weight part of the additive It refers to the relative weight of the additive to 100 weights of the total electrolyte (lithium salt + non-aqueous organic solvent) excluding the additive.

[0265] (Evaluation Example: Evaluation of lithium secondary batteries)

[0266] Evaluation 1: Room temperature life characteristics and resistance characteristics before and after high-temperature storage

[0267] (1) Room temperature lifespan characteristics

[0268] For the lithium secondary batteries according to Examples 1 to 5 and Comparative Examples 1 to 3, room temperature life characteristics were evaluated, and the results are shown in Table 2.

[0269] Specifically, after charging and discharging a lithium secondary battery for 150 cycles under conditions of 25℃, 0.33C charging (CC / CV, 4.3V, 0.025C Cut-off) / 1.0C discharging (CC, 2.5V Cut-off), the lifespan (capacity retention rate) was calculated according to Equation 1 below.

[0270] [Equation 1]

[0271] Capacity retention rate = (Capacity after 150 cycles / Capacity after 1 cycle) * 100

[0272] (2) Resistance characteristics before and after high-temperature storage

[0273] For the lithium secondary batteries according to Examples 1 to 5 and Comparative Examples 1 to 3, the direct current internal resistance (DC-IR) characteristics before and after high-temperature storage were evaluated, and the results are shown in Table 2.

[0274] Specifically, for a lithium secondary battery, the initial DC resistance (DC-IR) was measured using the △V / △I (change in voltage / change in current) value, the maximum energy state inside the battery was made to a fully charged state (SOC 100%), and after storing it at a high temperature (60℃) for 30 days in this state, the DC resistance was measured and the DC-IR increase rate (%) was calculated according to Equation 2 below.

[0275] [Equation 2]

[0276] DC-IR Growth Rate = (DC-IR after 30 days of storage at 60℃ - Initial DC-IR) / Initial DC-IR * 100

[0278] Life (Capacity Retention Rate) (@25℃, 150 Cycles) Initial DC-IR@25℃(mΩ) DC-IR after 30 days @ 60℃ (mΩ) Change rate of DC-IR after 30 days @ 60℃ (%) Comparative Example 1 79.2 4.23 7.13 68.6 Comparative Example 2 80.2 4.52 7.69 70.2 Comparative Example 3 80.5 4.48 7.69 71.3 Example 1 84.2 4.02 6.08 51.2 Example 2 83.0 4.18 7.02 67.9 Example 3 81.1 4.22 6.56 55.4 Example 4 83.7 3.99 6.05 51.7 Example 5 82.5 4.33 7.28 68.2

[0279] Referring to Table 2, the electrolyte additive of one embodiment is included in the electrolyte to improve the room temperature life characteristics of the lithium secondary battery while suppressing the increase in resistance during high-temperature storage.

[0281] Evaluation Example 2: Circulating Current Characteristics

[0282] For the lithium secondary batteries according to Examples 1 and 2 and Comparative Example 1, cyclic voltammetry characteristics were evaluated for cases where the working electrode was a negative electrode and a positive electrode, respectively, and the results are shown in FIGS. 2 and 3.

[0283] (1) Cathode half cell

[0284] Artificial graphite with a D50 of 5 μm as a negative electrode active material, polyvinylidene fluoride as a binder, and acetylene black as a conductive material are mixed in a weight ratio of 96:2:2, respectively. N A negative electrode active material slurry was prepared by dispersing it in methylpyrrolidone.

[0285] The above cathode active material slurry was coated onto an Al foil with a thickness of 14 μm, dried at 110°C, and then pressed to produce an anode.

[0286] A lithium secondary battery in the form of a CR2032 coin-half cell was manufactured by using a 10 μm thick Li foil as the cathode (positive electrode), assembling a 25 μm thick polyethylene separator as the negative electrode, and injecting the electrolyte.

[0287] One to three cycles of the lithium secondary battery were performed at a scan rate of 0.1 mV / s while varying the applied voltage from 3 V to 0 V. Through this, cyclic voltammetry characteristics were evaluated, and the results are shown in Figures 2 and 3.

[0288] (2) Positive half cell

[0289] LiNi with a D50 of 5 μm as the positive electrode active material0.8 Mn 0.2 O2, polyvinylidene fluoride as a binder, and acetylene black as a conductive material are mixed in a weight ratio of 96:2:2, respectively. N - A positive electrode active material slurry was prepared by dispersing in methylpyrrolidone.

[0290] The above positive active material slurry was coated onto an Al foil with a thickness of 14 μm, dried at 110°C, and then pressed to produce a positive electrode.

[0291] A 10 μm thick Li foil was used as the counter electrode (negative electrode), and while using the above positive electrode, a 25 μm polyethylene separator was assembled to manufacture an electrode assembly, and the above electrolyte was injected to produce a CR2032 type coin-half cell lithium secondary battery by a conventional method.

[0292] One to three cycles of the lithium secondary battery were performed at a scan rate of 0.1 mV / s while varying the applied voltage from 3 V to 4.5 V. Through this, cyclic voltammetry characteristics were evaluated, and the results are shown in Figures 4 and 5.

[0293] FIGS. 2 to 5 show that an additive according to one embodiment can form SEI on the surface of the cathode or anode to passivate it.

[0294] In particular, when using a nickel-based cobalt-free (Co-free) cathode active material that necessarily contains nickel but does not contain cobalt as the cathode active material, the additive is oxidized preferentially over the solvent that forms a protective film on the cathode surface, thereby forming a lithium salt-based SEI on the surface and enabling passivation.

[0296] In summary, the electrolyte additive of one embodiment represented by Examples 1 to 5 above comprises, wherein the sulfonyl group substituted with the halogen atom (X) and the substituent represented by Formula 2 are directly bonded or a linker (L 1, L 2 , L 3 A structure connected by (or a combination thereof) can solve the aforementioned problems and improve the room temperature life characteristics of a lithium secondary battery while suppressing the increase in resistance during high-temperature storage.

[0298] Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto and can be implemented with various modifications within the scope of the claims, the detailed description of the invention, and the attached drawings, and it is obvious that such modifications also fall within the scope of the present invention. Explanation of the symbols

[0300] 100: Lithium secondary battery 112: Cathode 113: Separator 114: Bipolar 120: Battery container 140: Encapsulated member

Claims

Claim 1 Electrolyte additive represented by the following chemical formula 1-1 or chemical formula 1-2: [Chemical formula 1-1] [Chemical Formula 1-2] In the above chemical formulas 1-1 and 1-2, X is a fluorine atom (F); and L 1 is a substituted or unsubstituted C1 to C10 alkylene group. Claim 2 delete Claim 3 delete Claim 4 delete Claim 5 delete Claim 6 delete Claim 7 In claim 1, the electrolyte additive represented by the following chemical formula 1-1-1 or chemical formula 1-2-1: [Chemical formula 1-1-1] [Chemical Formula 1-2-1] . Claim 8 Electrolyte for a lithium secondary battery comprising a non-aqueous organic solvent, a lithium salt, and an electrolyte additive according to claim 1. Claim 9 In claim 8, the electrolyte for a lithium secondary battery is included in an amount of 0.1 to 10 parts by weight per 100 parts by weight of the total electrolyte for a lithium secondary battery. Claim 10 In claim 8, the above-mentioned non-aqueous organic solvent is an electrolyte for a lithium secondary battery comprising a carbonate-based, ester-based, ether-based, ketone-based, alcohol-based, or aprotic solvent. Claim 11 In claim 10, the above-mentioned non-aqueous organic solvent is a carbonate-based solvent comprising ethylene carbonate (EC), ethylmethyl carbonate (EMC), and dimethyl carbonate (DMC), an electrolyte for a lithium secondary battery. Claim 12 In claim 8, the lithium salt is LiPF6, LiBF4, LiSbF6, LiAsF6, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide): LiFSI), LiC4F9SO3, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiN(C x F 2x+1 SO2)(C y F 2y+1 An electrolyte for a lithium secondary battery comprising one or more selected from the group consisting of SO2)(where x and y are integers from 1 to 20), LiCl, LiI, LiB(C2O4)2 (lithium bis(oxalato) borate: LiBOB), LiDFOB (lithium difluoro(oxalato) borate) and Li[PF2(C2O4)2](lithium difluoro(bis oxalato) phosphate). Claim 13 In claim 12, the electrolyte for a lithium secondary battery has a concentration of lithium salt of 0.1M to 2.0M. Claim 14 A lithium secondary battery comprising: a positive electrode including a positive active material; a negative electrode including a negative active material; and an electrolyte for a lithium secondary battery according to any one of claims 8 to 13. Claim 15 In paragraph 14, the above positive active material is a lithium secondary battery comprising a nickel-based positive active material. Claim 16 In Clause 15, the above positive active material is Li x Ni y Mn (1-y) O2(where, 0.5≤x≤1.8, 0 <y<1)로 표시되는 화합물을 포함하는 리튬 이차 전지. Claim 17 In paragraph 15, the negative electrode active material comprises graphite, silicon, or a combination thereof in a lithium secondary battery.

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