Non-aqueous electrolyte and lithium secondary battery comprising the same

Abstract

The present invention provides a nonaqueous electrolyte and a lithium secondary battery comprising the same. The nonaqueous electrolyte of the present invention includes a lithium salt, an organic solvent, and an additive. The additive includes a cyclic borate compound to prevent the nonaqueous electrolyte of the lithium secondary battery from being decomposed in a high power environment and causing deterioration of a negative electrode, or to further improve low-temperature high-rate discharge characteristics, high-temperature stability, overcharge prevention, and battery swelling suppression effect at high temperature, etc.

Description

[0001] Cross-references to related applications

[0002] This application is based on and claims priority to Korean Patent Application No. 10-2024-0073345, filed with the Korean Intellectual Property Office on June 4, 2024, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] This invention relates to a non-aqueous electrolyte and a lithium secondary battery containing the same. Background Technology

[0004] In recent years, as the application fields of lithium secondary batteries have rapidly expanded to power supply for electronic devices such as electrical, electronic, communication and computer equipment, as well as power storage / supply for large-area devices such as automobiles and power storage devices, the demand for high-capacity, high-output and high-stability secondary batteries is increasing.

[0005] For example, as lithium-ion batteries develop towards higher capacity and higher output, the possibility of abnormal temperature rises during charging / discharging increases due to various reasons. This can lead to the so-called thermal runaway phenomenon, where a spark can ignite and cause an explosion at high temperatures. In the event of thermal runaway, the fire is not easily extinguished, therefore safety is considered one of the more critical issues to be addressed in high-capacity and high-output lithium-ion batteries. Summary of the Invention

[0006] [Technical Issues]

[0007] This invention provides a non-aqueous electrolyte that can improve the lifespan and storage performance of lithium secondary batteries during operation at high temperatures and high voltages, and prevents resistance increase to a significant extent.

[0008] Furthermore, the present invention provides a lithium secondary battery including the aforementioned non-aqueous electrolyte.

[0009] [Technical Solution]

[0010] The present invention provides a non-aqueous electrolyte comprising a lithium salt, an organic solvent, and an additive, wherein the additive comprises a compound represented by Formula 1.

[0011] [Formula 1]

[0012] In Formula 1, L1 is an alkylene group having 1 to 10 carbon atoms, and L2 is a directly bonded or -C(R 25 (R) 26 )- L3 is direct bonding or -C(R 35 (R)36 )- R1 is an unsaturated hydrocarbon group with 2 to 10 carbon atoms. 21 R 22 R 23 R 24 R 25 R 26 R 31 R 32 R 33 R 34 R 35 R 36 R4 and R4 are each independently hydrogen or alkyl groups having 1 to 5 carbon atoms, and It is a bonding site.

[0013] Furthermore, the present invention provides a lithium secondary battery comprising: a positive electrode; a negative electrode facing the positive electrode; a separator disposed between the positive electrode and the negative electrode; and the aforementioned non-aqueous electrolyte.

[0014] [Beneficial Effects]

[0015] The non-aqueous electrolyte of the present invention is characterized by comprising a cyclic borate ester compound (a compound represented by Formula 1) as an additive, wherein the compound contains two cyclic borate ester groups and an unsaturated hydrocarbon group in its structure. Cyclic borate ester groups can form a highly durable SEI film due to their high density (compactness) and promote lithium transport characteristics at the electrode surface; however, reactivity degradation becomes a problem due to steric hindrance. The cyclic borate ester compound contained in the non-aqueous electrolyte of the present invention contains an unsaturated hydrocarbon group, which facilitates the proximity of the cyclic borate ester groups to the electrode and improves reactivity. Therefore, it is easier to form an SEI film derived from the aforementioned cyclic borate ester compound. Furthermore, the cyclic borate ester compound contains two cyclic borate ester groups, which can provide a large amount of film components on the electrode surface that are beneficial for improving durability. In addition, the lithium salt exhibits excellent stabilization effect due to the presence of numerous boron sites.

[0016] Therefore, lithium secondary batteries incorporating the non-aqueous electrolyte of the present invention can exhibit improved lifespan and storage performance, such as improved lifespan and storage performance at high temperatures and high voltages. Attached Figure Description

[0017] The following figures illustrate exemplary embodiments of the invention and, together with the detailed description that follows, serve to further understand the technical concept of the invention. Therefore, the invention should not be construed as limited to the matters shown in the figures.

[0018] Figure 1 The structure of a lithium secondary battery according to one embodiment of the present invention is shown.

[0019] Figure 2 It shows that it includes the following: Figure 1 A diagram of a vehicle with a battery pack composed of lithium secondary batteries.

[0020] In some of the accompanying drawings, corresponding components have the same reference numerals. Those skilled in the art will understand that the drawings simply and clearly depict the elements and are not necessarily drawn to scale. For example, to facilitate understanding of the various embodiments, the dimensions of some elements shown in the drawings may be exaggerated compared to other elements. Furthermore, elements of known technology that are useful or necessary in commercially viable embodiments may not typically be depicted so as not to hinder the spirit of the various embodiments of the invention. Detailed Implementation

[0021] The words and terms used in the detailed description and claims herein should not be construed as limited to their usual or dictionary meanings, but should be interpreted as having meanings and concepts corresponding to the technical ideas of the invention, in accordance with the principle that the inventors may appropriately define terms and concepts to best describe the invention.

[0022] As used herein, it should be understood that the terms “comprising,” “including,” or “having” are intended to specify the presence of a feature, number, step, component, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0023] Furthermore, unless otherwise stated herein, prior to the explanation of this invention, " "" refers to the connection part (bonding site) between the ends of the same or different atoms or formulas.

[0024] In the description of "carbon number a to b" in the specification, "a" and "b" refer to the number of carbon atoms contained in a specific functional group. That is, the functional group can include "a" to "b" carbon atoms. For example, "alkyl group with 1 to 5 carbon atoms" can include alkyl groups having 1 to 5 carbon atoms, such as CH3-, CH3CH2-, CH3CH2CH2-, (CH3)2CH-, CH3CH2CH2CH2-, (CH3)2CHCH2-, CH3CH2CH2CH2CH2-, and (CH3)2CHCH2CH2-.

[0025] Furthermore, in this specification, alkyl, alkenyl, silyl, siloxane, and aryl groups may each be substituted or unsubstituted. Unless otherwise defined, the term "substitution" as used above means that at least one hydrogen atom bonded to a carbon atom is replaced by an element other than hydrogen, such as an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a cycloalkenyl group having 3 to 12 carbon atoms, a cycloalkynyl group having 3 to 12 carbon atoms, a heterocycloalkyl group having 3 to 12 carbon atoms, a heterocycloalkenyl group having 3 to 12 carbon atoms, a heterocycloalkynyl group having 2 to 12 carbon atoms, an aryloxy group having 6 to 12 carbon atoms, a halogen atom, a fluoroalkyl group having 1 to 20 carbon atoms, a nitro group, an aryl group having 6 to 20 carbon atoms, a heteroaryl group having 2 to 20 carbon atoms, or a haloaryl group having 6 to 20 carbon atoms.

[0026] Lithium-ion secondary batteries typically consist of a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, a separator separating the positive and negative electrodes, and an electrolyte serving as a medium for transporting lithium ions through the separator. According to one embodiment, carbon-based active materials, silicon-based active materials, etc., can be used for the negative electrode active material, and lithium transition metal oxides, such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), and lithium nickel-cobalt-manganese composite transition metal oxides, can be used for the positive electrode active material.

[0027] In recent years, to improve the energy density of the cathode in lithium-ion batteries, lithium nickel-cobalt-manganese composite transition metal oxides with a nickel content of approximately 80 mol% or more relative to the transition metal have been studied. However, as the nickel content of lithium nickel-cobalt-manganese composite transition metal oxides increases, the thermal stability of the cathode decreases.

[0028] To prevent such problems, when the nickel content in lithium-nickel-cobalt-manganese composite transition metal oxides is reduced, the operating voltage needs to be increased to achieve the required energy density. During this high-voltage operation, issues such as electrolyte side reactions at the positive electrode, reduced high-temperature durability, and / or increased resistance may be exacerbated.

[0029] In view of these points, the present invention provides a non-aqueous electrolyte that can improve the life performance and storage performance of lithium secondary batteries during operation at high temperatures and high voltages, and can suppress or prevent resistance increase to a significant extent.

[0030] The invention will be described in more detail below.

[0031] refer to Figure 1One embodiment of the lithium secondary battery 100 of the present invention includes an electrode assembly, a non-aqueous electrolyte 140, and a battery casing 150. The electrode assembly consists of a positive electrode 110, a negative electrode 120 facing the positive electrode 110, and a separator 130 disposed between the positive electrode 110 and the negative electrode 120. The battery casing 150 houses the electrode assembly and the non-aqueous electrolyte 140.

[0032] The lithium secondary battery 100 can be manufactured by storing the electrode assembly in the battery casing 150 and then injecting the aforementioned non-aqueous electrolyte 140.

[0033] The lithium secondary battery 100 of one embodiment of the present invention can be manufactured in, for example, prismatic, pouch, coin or cylindrical shapes, depending on the manufacturing form.

[0034] Non-aqueous electrolytes

[0035] In one embodiment of the present invention, the non-aqueous electrolyte 140 comprises a lithium salt, an organic solvent, and an additive. The additive comprises a compound represented by Formula 1.

[0036] [Formula 1]

[0037] In Formula 1, L1 is an alkylene group having 1 to 10 carbon atoms, and L2 is a directly bonded or -C(R 25 (R) 26 )- L3 is direct bonding or -C(R 35 (R) 36 )- R1 is an unsaturated hydrocarbon group with 2 to 10 carbon atoms. 21 R 22 R 23 R 24 R 25 R 26 R 31 R 32 R 33 R 34 R 35 R 36 R4 and R4 are each independently hydrogen or alkyl groups having 1 to 5 carbon atoms, and It is a bonding site.

[0038] (1) Lithium salts

[0039] For the lithium salt used in this invention, there are no limitations on the use of various lithium salts commonly used in the non-aqueous electrolyte 140 of lithium secondary batteries 100. For example, the lithium salt may contain Li. +It is a cation, and may contain at least one selected from the following as an anion: F - Cl - ,Br - I - NO3 - N(CN)2 - BF4 - ClO4 - AlO4 - AlCl4 - PF6 - SbF6 - AsF6 - B 10 Cl 10 - BF2C2O4 - BC4O8 - PF4C2O4 - PF2C4O8 - (CF3)2PF4 - (CF3)3PF3 - (CF3)4PF2 - (CF3)5PF - (CF3)6P - CF3SO3 - C4F9SO3 - CF3CF2SO3 - (FSO2)2N - CF3CF2(CF3)2CO - (CF3SO2)2CH - CH3SO3 - CF3(CF2)7SO3 - CF3CO2 - CH3CO2 - SCN - and (CF3CF2SO2)2N - .

[0040] For example, lithium salts may include those selected from LiCl, LiBr, LiI, LiBF4, LiClO4, LiAlO4, LiAlCl4, LiPF6, LiSbF6, LiAsF6, and LiB. 10 Cl 10The lithium salt may include at least one selected from LiBF4, LiClO4, LiPF6, LiBOB (LiB(C2O4)2), LiCF3SO3, LiTFSI (LiN(SO2CF3)2), LiFSI (LiN(SO2F)2), and LiBETI (LiN(SO2CF2CF3)2). According to one embodiment, the lithium salt may include at least one selected from LiBF4, LiClO4, LiPF6, LiBOB (LiB(C2O4)2), LiCF3SO3, LiTFSI (LiN(SO2CF3)2), LiFSI (LiN(SO2F)2), and LiBETI (LiN(SO2CF2CF3)2).

[0041] Lithium salts can be included in non-aqueous electrolytes at concentrations of about 0.5 M to 5 M, for example, about 0.8 M to 4 M, or 0.8 M to 2.0 M. When the concentration of the lithium salt meets these ranges, the lithium-ion yield (Li) can be increased. + This improves the battery's output characteristics by increasing the transference number and the degree of lithium ion dissociation.

[0042] (2) Organic solvents

[0043] Organic solvents are generally non-aqueous solvents used in lithium secondary batteries 100, and there are no particular restrictions, as long as they can minimize decomposition caused by oxidation reactions, etc., during the charging / discharging of the secondary battery.

[0044] For example, the organic solvent may include at least one selected from cyclic carbonate organic solvents, linear carbonate organic solvents, linear ester organic solvents, and cyclic ester organic solvents.

[0045] According to one embodiment, the organic solvent may include cyclic carbonate organic solvents, linear carbonate organic solvents, or mixtures thereof.

[0046] Cyclic carbonate organic solvents are high-viscosity organic solvents. These solvents, due to their high dielectric constant, enable the good dissociation of lithium salts in electrolytes, and may include, for example, at least one organic solvent selected from ethylene carbonate (EC), fluoroethylene carbonate (FEC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentene carbonate, 2,3-pentene carbonate, and vinylene carbonate. According to one embodiment, the organic solvent may include at least one selected from ethylene carbonate (EC) and fluoroethylene carbonate (FEC).

[0047] Linear carbonate organic solvents are organic solvents with low viscosity and low dielectric constant, and may include at least one selected from, for example, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate, and ethyl propyl carbonate. According to one embodiment, the organic solvent may include at least one selected from ethyl methyl carbonate (EMC) and diethyl carbonate (DEC).

[0048] The organic solvent can be a mixture of cyclic carbonate organic solvents and linear carbonate organic solvents. Cyclic carbonate organic solvents and linear carbonate organic solvents can be mixed in a volume ratio of about 5:95 to 40:60, for example, 7:93 to 25:75. When the mixing ratio of cyclic carbonate organic solvents and linear carbonate organic solvents meets the above range, both high dielectric constant and low viscosity characteristics can be achieved, and excellent ionic conductivity characteristics can be exhibited.

[0049] In order to manufacture an electrolyte with high ionic conductivity, in addition to at least one carbonate organic solvent selected from cyclic carbonate organic solvents and linear carbonate organic solvents, the organic solvent may further include at least one ester organic solvent selected from linear ester organic solvents and cyclic ester organic solvents.

[0050] Straight-chain ester organic solvents may include, for example, at least one selected from methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate.

[0051] In addition, cyclic ester organic solvents may include, for example, at least one selected from γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone and ε-caprolactone.

[0052] For organic solvents, organic solvents commonly used for non-aqueous electrolytes may be added and used without limitation, if necessary. For example, at least one organic solvent selected from ether organic solvents, glycol diether solvents, and nitrile organic solvents may also be included.

[0053] For ether solvents, any one or a mixture of two or more of dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether, ethyl propyl ether, 1,3-dioxolane (DOL) and 2,2-bis(trifluoromethyl)-1,3-dioxolane (TFDOL) can be used, but the present invention is not limited thereto.

[0054] Glycol diether solvents are solvents that have a high dielectric constant, low surface tension and low reactivity with metals compared to straight-chain carbonate organic solvents, and may include at least one selected from dimethoxyethane (glycol dimethyl ether, DME), diethoxyethane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether (TEGDME), but the present invention is not limited thereto.

[0055] Nitrile solvents may be selected from at least one of acetonitrile, propionitrile, butyronitrile, valerate, octanoic acid, heptanoic acid, cyclopentaneformitrile, cyclohexaneformitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile, but are not limited thereto.

[0056] (3) Additives

[0057] In addition to the lithium salt and organic solvent mentioned above, the non-aqueous electrolyte 140 also includes additives.

[0058] For additives, for example, to prevent or inhibit the decomposition of the non-aqueous electrolyte of the lithium secondary battery in a high-power environment (which can lead to the deterioration of the negative electrode), or to further improve the low-temperature high-rate discharge characteristics, high-temperature stability, overcharge prevention and high-temperature battery expansion suppression effect, it is necessary to additionally include additives capable of forming an SEI (solid electrolyte interface) film in the non-aqueous electrolyte 140.

[0059] Additives include compounds represented by Formula 1 below.

[0060] [Formula 1]

[0061] In Formula 1, L1 is an alkylene group having 1 to 10 carbon atoms, and L2 is a directly bonded or -C(R 25 (R) 26 )- L3 is direct bonding or -C(R 35 (R) 36 )- R1 is an unsaturated hydrocarbon group with 2 to 10 carbon atoms. 21 R 22 R 23 R 24 R 25 R 26 R 31 R 32 R 33 R 34 R 35 R 36 R4 and R4 are each independently hydrogen or alkyl groups having 1 to 5 carbon atoms, and It is a bonding site.

[0062] Typically, in the case of cyclic borate esters, a highly durable SEI film due to its high density (compactness) can be formed at the electrode (positive and / or negative electrode), while simultaneously promoting lithium transport properties. However, after solvation by organic solvents, cyclic borate esters become too bulky to be easily accessible to the negative electrode. This reduced accessibility then becomes a factor in reduced reactivity. In this regard, the compound represented by Formula 1 of the present invention contains an unsaturated hydrocarbon group in its structure. This unsaturated hydrocarbon group is highly reactive due to its LUMO (lowest unoccupied molecular orbital) characteristics and is easily accessible to the electrode. Therefore, the cyclic borate ester group present with the unsaturated hydrocarbon group is also easily accessible to the electrode. This can promote the reactivity of the cyclic borate ester at the electrode. This effect cannot be achieved by substituents other than the unsaturated hydrocarbon group (e.g., allyl or propargyl) (e.g., alkyl groups, etc.).

[0063] Furthermore, the cyclic borate ester compounds contain two cyclic borate ester groups, which can provide a large amount of film components on the electrode surface that are beneficial to improving durability. In addition, due to the large number of boron sites, the lithium salt exhibits excellent stabilization effects. For example, when only one cyclic borate ester group is present in the compound, its effect on improving the durability of the SEI film is minimal, and its effect on improving the life performance of lithium-ion secondary batteries under high voltage and high temperature conditions is insufficient. On the other hand, when three or more cyclic borate ester groups are present in the compound, excessive steric hindrance leads to reduced reactivity, making it difficult to achieve effective protection of the electrode through the SEI film.

[0064] In Formula 1 above, R1 can be an unsaturated hydrocarbon group having 2 to 10 carbon atoms. In this case, the unsaturated hydrocarbon group can refer to a hydrocarbon group containing a carbon-carbon double bond or a hydrocarbon group containing a carbon-carbon triple bond. R1 can be a substituent selected from Formulas 1-a and 1-b below. Specifically, R1 can be a substituent shown in Formula 1-a below.

[0065] [Equation 1-a]

[0066] [Equation 1-b]

[0067] In equation 1-a above, R a It can be a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. It is a bonding site.

[0068] In Formula 1, L1 can be an alkylene group having 1 to 10 carbon atoms, for example, in terms of achieving the reactivity enhancement effect of the cyclic borate ester group by means of an unsaturated hydrocarbon group, it can be an alkylene group having 1 to 5 carbon atoms, a methylene or an ethylene, or according to one embodiment, it can be a methylene group.

[0069] In Equation 1, R 21 R 22 R 23 R 24 R 31 R 32 R 33 R 34 R4 and R5 can each be independently hydrogen or an alkyl group having 1 to 5 carbon atoms, can each be independently, for example, hydrogen or an alkyl group having 1 to 3 carbon atoms, can each be independently hydrogen or methyl, or can each be hydrogen. According to one embodiment, within the above range, a stable SEI film formation reaction can be achieved without reducing the reactivity of the cyclic borate ester group and the unsaturated hydrocarbon group.

[0070] L2 can be direct bonding or -C(R 25 (R) 26 )- Furthermore, L3 can be directly bonded or -C(R 35 (R) 36 )- Here, in -C(R 25 (R) 26 )- and -C(R 35 (R) 36 )- In this context, C refers to the element carbon. Furthermore, This refers to the bonding site. For example, L2 and L3 can each be directly bonded. Furthermore, when L2 and L3 are each... -C(R 25 (R) 26 )- or -C(R 35 (R) 36 )- At that time, R 25 R 26 R 35 and R 36Each group can be independently hydrogen or an alkyl group having 1 to 5 carbon atoms, or each group can be independently hydrogen or an alkyl group having 1 to 3 carbon atoms, or each group can be independently hydrogen or methyl. Within the above ranges, a stable SEI film formation reaction can be achieved without reducing the reactivity of the cyclic borate ester group and the unsaturated hydrocarbon group.

[0071] The compound represented by Formula 1 may include at least one of the compounds represented by Formulas 1-1 to 1-8 below, may include at least one of the compounds represented by Formulas 1-1 to 1-4 below, or may include at least one of the compounds represented by Formulas 1-1 and 1-3 below.

[0072] [Equation 1-1]

[0073] [Equation 1-2]

[0074] [Equation 1-3]

[0075] [Equations 1-4]

[0076] [Equations 1-5]

[0077] [Equations 1-6]

[0078] [Equations 1-7]

[0079] [Equations 1-8]

[0080] The content of the compound represented by Formula 1 relative to the weight of the non-aqueous electrolyte 140 can be from about 0.01% by weight to 10% by weight, for example, from about 0.05% by weight to 5% by weight, from about 0.1% by weight to 3% by weight, from about 0.3% by weight to 1.5% by weight, or from about 0.5% by weight to 1% by weight, or according to one embodiment, the content can be from 0.5% by weight to 0.8% by weight. When the compound represented by Formula 1 is used within the above content range, a flexible SEI film with excellent durability can be formed at the negative electrode while suppressing or preventing an increase in resistance.

[0081] In addition to the compound represented by Formula 1, the additive may further include additional additives. Additional additives may be included in the non-aqueous electrolyte 140 to suppress or prevent the decomposition of the non-aqueous electrolyte in high-power environments (which can lead to negative electrode degradation), or to obtain low-temperature high-rate discharge characteristics, high-temperature stability, overcharge prevention, and high-temperature battery swelling suppression effects. When additional additives are included, the compound represented by Formula 1 may be referred to as the first additive, and the additional additive may be referred to as the second additive.

[0082] For example, the additive may be selected from at least one of the following: lithium difluorophosphate (LiDFP), vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, propane sulpholactone, propene sulpholactone, succinic acid, adiponitrile, ethylene sulfate, lithium bis(oxalate)borate (LiBOB), 3-trimethoxysilyl-propyl-N-aniline (TMSPa) and tri(trimethylsilyl)phosphite (TMSPi), compounds represented by formula 2 below and compounds represented by formula 3 below.

[0083] [Equation 2]

[0084] [Formula 3]

[0085] In Formula 3, R5 includes halogen, nitrile, propargyl, ester, ether, ketone, carboxyl, alkyl, alkenyl, substituted or unsubstituted alkynyl, alkoxy, boronyl, borate ester, isocyanate ester, isothiocyanate ester, silyl, siloxane, sulfone, sulfonate ester, sulfate ester, or a combination of two or more of these. n is an integer selected from 0 to 6.

[0086] The compound represented by Formula 3 may be selected from at least one of the compounds represented by, for example, Formulas 3-1 to 3-9 below.

[0087] [Equation 3-1]

[0088] [Equation 3-2]

[0089] [Equation 3-3]

[0090] [Equation 3-4]

[0091] [Equation 3-5]

[0092] [Equation 3-6]

[0093] [Equation 3-7]

[0094] [Equation 3-8]

[0095] [Equation 3-9]

[0096] The additional additives may be present in the non-aqueous electrolyte at a concentration of about 0.1% to 15% by weight, for example, about 0.3% to 3% by weight.

[0097] Lithium secondary batteries

[0098] According to one embodiment, the present invention provides a lithium secondary battery 100 comprising the above-described non-aqueous electrolyte 140.

[0099] The lithium secondary battery 100 of the present invention includes: a positive electrode 110; a negative electrode 120 facing the positive electrode 110; a separator 130 disposed between the positive electrode 110 and the negative electrode 120; and the aforementioned non-aqueous electrolyte 140.

[0100] According to one embodiment, the lithium secondary battery 100 can be manufactured by storing an electrode assembly in a battery casing 150 and then injecting the aforementioned non-aqueous electrolyte 140. The electrode assembly includes a positive electrode 110; a negative electrode 120 facing the positive electrode 110; and a separator 130 disposed between the positive electrode 110 and the negative electrode 120. Here, as described above, the lithium secondary battery 100 of one embodiment of the present invention can be manufactured in, for example, a prismatic, pouch, coin, or cylindrical shape, depending on the manufacturing form.

[0101] Following the description of the non-aqueous electrolytes, the negative electrode, positive electrode, and membrane will be described below.

[0102] (1) Positive electrode

[0103] The positive electrode 110 may include a positive electrode active material.

[0104] Positive electrode active materials are compounds that allow reversible insertion and extraction, and there are no particular limitations, as long as they are positive electrode active materials used in the relevant field. Examples of positive electrode active materials can include: layered compounds such as lithium cobalt oxide (LiCoO2) and lithium nickel oxide (LiNiO2) or compounds substituted with one or more transition metals; lithium iron oxides, such as LiFe3O4; lithium iron phosphates, such as LiFePO4; lithium manganese oxides, such as Li... 1+c1 Mn 2-c1O4 (0 ≤ c1 ≤ 0.33), LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, and Cu2V2O7; lithium nickel oxides of the Ni-site type represented by the formula LiNi 1-c2 M c2 O2 (where M is at least one selected from Co, Mn, Al, Cu, Fe, Mg, B, and Ga, and satisfies approximately 0.01 ≤ c2 ≤ 0.3); and lithium manganese composite oxides represented by the formula LiMn 2-c3 M c3 O2 (where M is at least one selected from Co, Ni, Fe, Cr, Zn, and Ta, and satisfies approximately 0.01 ≤ c3 ≤ 0.1) or Li2Mn3MO8 (where M is at least one selected from Fe, Co, Ni, Cu, and Zn), but not limited thereto. The positive electrode may also be a Li metal positive electrode.

[0105] According to one embodiment, the positive electrode active material may include at least one selected from lithium cobalt oxide (LiCoO2), lithium nickel cobalt manganese oxide, over-lithiated manganese-rich oxide, and lithium iron phosphate.

[0106] The lithium nickel cobalt manganese oxide having a high nickel content may be represented by the following formula A. The positive electrode active material may include a lithium transition metal oxide represented by the following formula A.

[0107] [Formula A]

[0108] Li 1+x (Ni a Co b Mn c M d )O2

[0109] In formula A, M is at least one selected from W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo. 1 + x, a, b, c, and d are the atomic fractions of the respective elements, x satisfies approximately 0 ≤ x ≤ 0.2, a satisfies approximately 0 < a < 1, b satisfies approximately 0 < b < 1, c satisfies approximately 0 < c < 1, d satisfies approximately 0 ≤ d ≤ 0.1, and a + b + c + d = 1.

[0110] According to one embodiment, in formula A, x may satisfy approximately 0 ≤ x ≤ 0.5, for example, approximately 0 ≤ x ≤ 0.2.

[0111] In formula A, a may satisfy approximately 0.5 ≤ a ≤ 0.7, for example, approximately 0.55 ≤ a ≤ 0.65.

[0112] In formula A, b can satisfy about 0 < b ≤ 0.15. b corresponds to the molar percentage of Co in the metals other than lithium in the lithium transition metal oxide represented by formula A. According to the present invention, by reducing the Co content, a cost advantage can be obtained, and the ratio of Mn can be relatively increased, thereby improving the structural stability of the positive electrode active material. For example, in formula A, b can satisfy about 0 < b ≤ 0.1.

[0113] In formula A, b / a can satisfy about 0 < b / a ≤ 0.2. Within the corresponding range, the ratio of Co in the transition metals is appropriately adjusted so that the increase in irreversibility within the structure is not large. Therefore, by forming a positive electrode film with an additive, the effect of improving performance can be easily exhibited. According to one embodiment, in formula A, b / a can satisfy about 0.05 ≤ b / a ≤ 0.2.

[0114] In formula A, c = 1 - a - b - d, and a / c satisfies about 1 ≤ a / c ≤ 3. c corresponds to the molar percentage of Mn in the metals other than lithium in the lithium transition metal oxide represented by formula A. According to the present invention, since the molar ratio of Ni to Mn is adjusted to satisfy 1 ≤ a / c ≤ 3, the structural stability of the positive electrode active material can be improved. According to one embodiment, a / c can satisfy about 1.5 ≤ a / c ≤ 2.5.

[0115] In formula A, M can be understood as a doping element of the lithium transition metal oxide and can be at least one selected from, for example, W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo. Here, d can satisfy 0 ≤ d ≤ 0.1, for example, 0 ≤ d ≤ 0.05.

[0116] In formula A, a / (b × c) can be about 18 to 50, for example, about 18 to 40, or about 20 to 35. Within the above range, the contents of nickel, cobalt, and manganese in formula A are coordinately adjusted. Therefore, by forming a positive electrode film with an additive, the effect of improving performance can be enhanced while improving the structural stability of the positive electrode active material.

[0117] The lithium-rich manganese oxide can include a compound represented by the following formula B.

[0118] [Formula B]<00,00469>

[0119] Li 1+s [Ni t [[ID=!5]]Co u Mn v M 1 w O 2+z

[0120] In formula B, M 1It is selected from at least one of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, wherein s satisfies approximately 0.05 ≤ s ≤ 1, t satisfies approximately 0 ≤ t ≤ 0.5, u satisfies approximately 0 ≤ u ≤ 0.3, v satisfies approximately 0.5 ≤ v < 1.0, w satisfies approximately 0 ≤ w ≤ 0.2, and 0 ≤ z ≤ 1. For example, in equation B, s can satisfy approximately 0.05 ≤ s ≤ 1.0, t can satisfy approximately 0.1 ≤ t ≤ 0.5, u can satisfy approximately 0 ≤ u ≤ 0.1, v can satisfy approximately 0.5 ≤ v < 1.0, 0 ≤ w ≤ 0.2, and 0 ≤ z ≤ 1. Alternatively, in equation B, 0.10≤s≤0.50, t can satisfy approximately 0.1≤t≤0.5, u can satisfy approximately 0≤u≤0.1, v can satisfy approximately 0.6≤v<1.0, w can satisfy approximately 0≤w≤0.1, and z can satisfy approximately 0≤z≤0.50.

[0121] Lithium iron phosphate can include compounds represented by the following formula C.

[0122] [Formula C]

[0123] Li 1+e Fe 1-g M 2 g (PO 4-f )X f

[0124] In equation C, M 2 X is at least one element selected from Co, Ni, Mn, Al, Mg, Ti, and V, and X is F, S, or N. g satisfies approximately 0 ≤ g ≤ 0.5; e satisfies approximately -0.5 ≤ e ≤ +0.5; and f satisfies approximately 0 ≤ f ≤ 0.1. Formula C can be represented by, for example, LiFePO4 (g=0, e=0, and f=0).

[0125] The positive electrode 110 may include a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector.

[0126] There are no particular limitations on the positive electrode current collector, as long as it has high conductivity and does not cause chemical changes in the battery. For example, the positive electrode current collector may include at least one selected from copper, stainless steel, aluminum, nickel, titanium, calcined carbon, and aluminum-cadmium alloys, such as aluminum.

[0127] Positive current collectors can typically have a thickness of about 3 μm to 500 μm.

[0128] In positive electrode current collectors, the bonding strength of the positive electrode active material can be enhanced by forming fine irregularities on the surface. For example, positive electrode current collectors can be used in various forms, such as membranes, sheets, foils, meshes, porous bodies, foams, and nonwoven fabrics.

[0129] The positive electrode active material layer can be disposed on at least one surface of the positive electrode current collector. For example, the positive electrode active material layer can be disposed on one or both surfaces of the positive electrode current collector.

[0130] The positive electrode active material layer may include the aforementioned positive electrode active material.

[0131] In addition to the aforementioned positive electrode active material, the positive electrode active material layer may optionally further include an adhesive and / or a conductive material.

[0132] Adhesives are components that facilitate the adhesion of active materials to conductive materials and to current collectors, and may include, for example, at least one selected from polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, and fluororubber, such as polyvinylidene fluoride.

[0133] To ensure sufficient bonding between components such as the positive electrode active material, the binder content in the positive electrode active material layer can be from about 1% to 20% by weight, for example, from about 1.2% to 10% by weight.

[0134] Conductive materials can be used to assist and improve the conductivity in secondary batteries, and there are no particular limitations, as long as they are conductive and do not cause chemical changes. For example, positive electrode conductive materials may include at least one selected from: graphite, such as natural or artificial graphite; carbon black, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermally cracked carbon black; conductive fibers, such as carbon fibers or metal fibers; conductive tubes, such as carbon nanotubes; fluorocarbons; metal powders, such as aluminum or nickel powder; conductive whiskers, such as zinc oxide or potassium titanate; conductive metal oxides, such as titanium oxide; and polyphenylene derivatives, and for the purpose of improving conductivity, may include, for example, carbon nanotubes.

[0135] To ensure sufficient conductivity, the content of conductive material in the positive electrode active material layer can be from about 1% to 20% by weight, for example, from about 1.2% to 10% by weight.

[0136] The thickness of the positive electrode active material layer can be from about 5 μm to 500 μm, for example, from about 20 μm to 200 μm.

[0137] The positive electrode can be manufactured by coating a positive electrode slurry onto a positive electrode current collector, followed by drying and rolling. The positive electrode slurry includes a positive electrode active material and optional binders, conductive materials, and solvents for forming the positive electrode slurry.

[0138] (2) Negative electrode

[0139] The negative electrode 120 can face the positive electrode 110.

[0140] The negative electrode 120 may include a negative electrode active material.

[0141] The negative electrode active material is a material that enables reversible insertion / extraction of lithium ions, and may include at least one selected from carbon-based active materials, (semi)metallic active materials and lithium metal, or may include, for example, at least one selected from carbon-based active materials and (semi)metallic active materials.

[0142] The carbon-based active material may include at least one selected from graphite, hard carbon, soft carbon, carbon black, graphene, and fibrous carbon, or, according to one embodiment, may include graphite. Graphite may be, for example, at least one selected from artificial graphite and natural graphite.

[0143] In terms of reducing side reactions with the electrolyte while ensuring structural stability during charging / discharging, the average particle size (D) of carbon-based active materials is crucial. 50 The diameter can be from about 10 μm to 30 μm, for example, from about 15 μm to 25 μm.

[0144] According to one embodiment, the (semi)metallic active material may include: at least one (semi)metal selected from Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, V, Ti, and Sn; an alloy of lithium with at least one (semi)metal selected from Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, V, Ti, and Sn; an oxide of at least one (semi)metal selected from Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, V, Ti, and Sn; lithium titanium oxide (LTO); or lithium vanadium oxide.

[0145] According to one embodiment, (semi)metallic active materials may include silicon-based active materials.

[0146] Silicon-based active materials may include SiO xCompounds represented by (0≤x<2) are used. SiO2 does not react with lithium ions and therefore cannot store lithium. Therefore, x can satisfy the above range, and according to one embodiment, the silicon-based active material can be SiO.

[0147] In terms of reducing side reactions with the electrolyte while ensuring structural stability during charging / discharging, the average particle size (D) of silicon-based active materials is crucial. 50 The diameter can range from about 1 μm to 30 μm, for example, from about 2 μm to 15 μm.

[0148] The negative electrode 120 may include a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. Here, the negative electrode active material may be included in the negative electrode active material layer.

[0149] There are no particular restrictions on the negative electrode current collector, as long as it has high conductivity and does not cause chemical changes in the corresponding battery. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloys can be used as negative electrode current collectors.

[0150] Negative current collectors can typically have a thickness of about 3 μm to 500 μm.

[0151] Similar to positive electrode current collectors, in negative electrode current collectors, the bonding strength of the negative electrode active material can also be enhanced by forming fine irregularities on the surface. For example, negative electrode current collectors can be used in various forms, such as membranes, sheets, foils, meshes, porous bodies, foams, and nonwoven fabrics.

[0152] The negative electrode active material layer can be disposed on at least one surface of the negative electrode current collector, for example, on one or both surfaces of the negative electrode current collector.

[0153] The content of the negative electrode active material in the negative electrode active material layer can be from about 60% to 99% by weight, for example, from about 75% to 95% by weight.

[0154] Other descriptions of the positive electrode active material have already been described above, and will therefore be omitted.

[0155] In addition to the negative electrode active material, the negative electrode active material layer may further include an adhesive and / or a conductive material.

[0156] Adhesives are used to improve the adhesion between the negative electrode active material layer and the negative electrode current collector, and to improve battery performance. Adhesives may include, for example, at least one selected from the following: polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, and materials obtained by substituting hydrogen with Li, Na, or Ca, and may also include various copolymers thereof.

[0157] The amount of binder in the negative electrode active material layer can be from about 0.5% to 10% by weight, for example, from about 1% to 5% by weight.

[0158] There are no particular restrictions on conductive materials, as long as they are conductive and do not cause chemical changes in the corresponding battery. Examples include: graphite, such as natural or artificial graphite; carbon black, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermally cracked carbon black; conductive fibers, such as carbon fibers or metal fibers; conductive tubes, such as carbon nanotubes; fluorocarbons; metal powders, such as aluminum or nickel powder; conductive whiskers, such as zinc oxide or potassium titanate; conductive metal oxides, such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0159] The content of conductive material in the negative electrode active material layer can be from about 0.5% to 10% by weight, for example, from about 1% to 5% by weight.

[0160] The thickness of the negative electrode active material layer can be from about 10 μm to 200 μm, for example, from about 20 μm to 150 μm.

[0161] The negative electrode 120 can be manufactured by coating a negative electrode slurry onto at least one surface of a negative electrode current collector and then drying and rolling it. The negative electrode slurry includes a negative electrode active material, a binder, a conductive material, and / or a solvent for forming the negative electrode slurry.

[0162] For promoting the dispersion of, for example, negative electrode active materials, binders and / or conductive materials, the solvent for forming the negative electrode slurry may include at least one selected from distilled water, N-methyl-2-pyrrolidone (NMP), ethanol, methanol and isopropanol, such as distilled water. The solids content of the negative electrode slurry may be from about 30% to 80% by weight, for example from 40% to 70% by weight.

[0163] (3) Diaphragm

[0164] The diaphragm 130 can be placed between the positive and negative electrodes.

[0165] Furthermore, for the diaphragm 130, a general porous polymer membrane commonly used as a diaphragm can be used alone or in a laminated manner. This includes porous polymer membranes made of polyolefin polymers (e.g., ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers), or conventional porous nonwoven fabrics can be used, such as nonwoven fabrics made of high-melting-point glass fibers, polyethylene terephthalate fibers, etc., but the invention is not limited thereto. Additionally, coated diaphragms containing ceramic components or polymer materials can be used to ensure heat resistance or mechanical strength, and can optionally be used in single-layer or multi-layer structures.

[0166] The external shape of the lithium secondary battery 100 of the present invention is not particularly limited, but it can be cylindrical, prismatic, pouch-shaped or coin-shaped.

[0167] The invention will be described below by way of examples. However, the following examples are merely illustrative of the invention and do not limit its scope. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of this specification and the technical concept, and such changes and modifications obviously fall within the scope of the appended claims.

[0168] Examples and Comparative Examples

[0169] Example 1

[0170] (Manufacturing of non-aqueous electrolytes)

[0171] For the organic solvent, a mixture obtained by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 20:80 was used.

[0172] A non-aqueous electrolyte is produced by adding LiPF6 as a lithium salt, and compounds represented by Formula 1-1 and Formula 2 as additives to the organic solvent.

[0173] LiPF6 was contained in a non-aqueous electrolyte at a molar concentration of 1.2 M.

[0174] The compound represented by Formula 1-1 has a content of 0.5% by weight in the non-aqueous electrolyte, and the compound represented by Formula 2 has a content of 0.2% by weight in the non-aqueous electrolyte.

[0175] (Manufacturing of lithium secondary batteries)

[0176] The positive electrode active material (Li[Ni) 0.6 Co 0.1 Mn 0.3O2, conductive material (carbon black), and binder (polyvinylidene fluoride) were added to N-methyl-2-pyrrolidone (NMP) as a solvent in a weight ratio of 97.6:0.8:1.6 to prepare a positive electrode slurry (60% by weight solids). The positive electrode slurry was coated on one surface of a 15 µm thick positive electrode current collector (Al film) and dried, then rolled to form a positive electrode active material layer (136.6 μm thick). This was used as the positive electrode. The positive electrode active material exists in the form of single particles or quasi-single particles.

[0177] A negative electrode slurry (60% by weight) was prepared by adding a negative electrode active material (graphite), a conductive material (carbon black), and a binder (styrene-butadiene rubber and carboxymethyl cellulose) to distilled water as a solvent in a weight ratio of 96.75:0.50:2.75. The negative electrode slurry was coated onto one surface of a 6 µm thick negative electrode current collector (Cu film) and dried, then rolled to form a negative electrode active material layer (179.8 μm thick). This was used as the negative electrode.

[0178] In a drying chamber, a porous polyethylene membrane is placed between the manufactured positive and negative electrodes. Then, the prepared non-aqueous electrolyte is injected to manufacture a lithium secondary battery.

[0179] Example 2

[0180] The non-aqueous electrolyte and lithium secondary battery were manufactured in the same manner as in Example 1, except that, when preparing the non-aqueous electrolyte, the content of the compound represented by Formula 1-1 in the non-aqueous electrolyte was 1% by weight instead of 0.5% by weight relative to the total weight of the non-aqueous electrolyte.

[0181] Example 3

[0182] The non-aqueous electrolyte and lithium secondary battery were manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte did not contain the compound represented by Formula 1-1, and the content of the compound represented by Formula 1-2 in the non-aqueous electrolyte was 0.5 by weight relative to the total weight of the non-aqueous electrolyte.

[0183] Example 4

[0184] The non-aqueous electrolyte and lithium secondary battery were manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte did not contain the compound represented by Formula 1-1, and the content of the compound represented by Formula 1-3 in the non-aqueous electrolyte was 0.5 by weight relative to the total weight of the non-aqueous electrolyte.

[0185] Comparative Example 1

[0186] The non-aqueous electrolyte and lithium secondary battery were manufactured in the same manner as in Example 1, except that the compound represented by Formula 1-1 was not added to the non-aqueous electrolyte.

[0187] Comparative Example 2

[0188] The non-aqueous electrolyte and lithium secondary battery were manufactured in the same manner as in Example 1, except that the compound represented by Formula 1-1 was not added, and the content of compound A in the non-aqueous electrolyte was 0.5 by weight relative to the total weight of the non-aqueous electrolyte.

[0189] [Compare compound A]

[0190] Comparative Example 3

[0191] The non-aqueous electrolyte and lithium secondary battery were manufactured in the same manner as in Example 1, except that the compound represented by Formula 1-1 was not added, and the content of compound B in the non-aqueous electrolyte was 0.5 by weight relative to the total weight of the non-aqueous electrolyte.

[0192] [Compare compound B]

[0193] Comparative Example 4

[0194] The non-aqueous electrolyte and lithium secondary battery were manufactured in the same manner as in Example 1, except that the compound represented by Formula 1-1 was not added, and the content of compound C in the non-aqueous electrolyte was 0.5 by weight relative to the total weight of the non-aqueous electrolyte.

[0195] [Compare compound C]

[0196] Comparative Example 5

[0197] The non-aqueous electrolyte and lithium secondary battery were manufactured in the same manner as in Example 1, except that the compound represented by Formula 1-1 was not added, and the content of compound D in the non-aqueous electrolyte was 0.5 by weight relative to the total weight of the non-aqueous electrolyte.

[0198] [Compare compound D]

[0199] Comparative Example 6

[0200] The non-aqueous electrolyte and lithium secondary battery were manufactured in the same manner as in Example 1, except that the compound represented by Formula 1-1 was not added, and the content of compound E in the non-aqueous electrolyte was 0.5 by weight relative to the total weight of the non-aqueous electrolyte.

[0201] [Compare compound E]

[0202] Experimental Example

[0203] Experimental Example 1: High-Temperature Cycling Performance Evaluation

[0204] Using an electrochemical charger / discharger, the lithium secondary batteries of Examples 1 to 4 and Comparative Examples 1 to 6 manufactured above were charged to 4.4 V and 0.05 C at 45°C under CC / CV and 0.33 C conditions, and then discharged to 2.5 V under CC and 0.33 C conditions. This was set as one cycle, and 200 charge / discharge cycles were performed.

[0205] (1) Capacity retention rate

[0206] The capacity retention rate is calculated using the following equation, and the results are recorded in Table 1 below.

[0207] Capacity retention (%) = {(Discharge capacity after 200 cycles / Discharge capacity after one cycle)} × 100

[0208] (2) Rate of increase in resistance

[0209] After one charge / discharge cycle, the discharge capacity after one cycle was measured using an electrochemical charger / discharger, and the SOC (State of Charge) was adjusted to 50%. Then, a 2.5 C pulse was applied for 10 seconds, and the initial resistance was calculated by the difference between the voltage before and after the pulse.

[0210] After 200 charge / discharge cycles, the resistance after 200 cycles was calculated in the same manner as described above, and the rate of increase in resistance was calculated using the following equation. The results are recorded in Table 1 below.

[0211] Resistance increase rate (%) = (Resistance after 200 cycles - Initial resistance) / Initial resistance × 100

[0212] [Table 1]

[0213] Referring to Table 1, it can be seen that, compared with Comparative Examples 1 to 6, Examples 1 to 4 using the non-aqueous electrolyte of the present invention exhibit significantly superior high-temperature cycle charge / discharge performance.

[0214] Experiment Example 2: High-Temperature Storage Performance Evaluation

[0215] Using an electrochemical charger / discharger, the lithium secondary batteries of Examples 1 to 4 and Comparative Examples 1 to 6 manufactured above were charged to 4.4 V and 0.05 C at 25°C under CC / CV and 0.33 C conditions, and then discharged to 2.5 V under CC and 0.33 C conditions. After this initial charge / discharge, these batteries were charged to 4.4 V and 0.05 C at 25°C under CC / CV and 0.33 C conditions, and then stored at 60°C for 8 weeks.

[0216] (1) Capacity retention rate

[0217] After 8 weeks of storage, the lithium secondary batteries were charged to 4.4 V and 0.05 C at 25°C under CC / CV and 0.33 C conditions using an electrochemical charger / discharger, and then discharged to 2.5 V at CC and 0.33 C. The capacity during discharge was then measured.

[0218] The capacity retention rate was evaluated using the following equation, and the results are recorded in Table 2 below.

[0219] Capacity retention (%) = (Discharge capacity after 8 weeks of storage / Initial discharge capacity) × 100

[0220] (2) Rate of increase in resistance

[0221] After the initial charge / discharge, the capacity was measured at room temperature. The battery was then charged to 50% of its SOC based on the discharge capacity and discharged at 2.5 C for 10 seconds. The resistance was measured by the difference in voltage drop at this point and set as the initial resistance. After storage at 60°C for 8 weeks, the resistance was measured using the same method and set as the final resistance. The rate of increase in resistance was then calculated using the following equation. The results are recorded in Table 2 below.

[0222] Resistance increase rate (%) = (final resistance - initial resistance) / (initial resistance) × 100

[0223] [Table 2]

[0224] Referring to Table 2, it can be seen that, compared with Comparative Examples 1 to 6, Examples 1 to 4 using the non-aqueous electrolyte of the present invention exhibit significantly superior high-temperature storage characteristics.

[0225] Figure 2 It is used to explain including by Figure 1 The image shows a vehicle 300 consisting of a battery pack 200 composed of 100 lithium secondary batteries.

[0226] refer to Figure 2 The vehicle 300 of one embodiment of the present invention may be, for example, an electric vehicle, a hybrid vehicle, or a plug-in hybrid vehicle, and includes a battery pack 200 composed of a lithium secondary battery 100 according to one embodiment of the present invention. The vehicle 300 includes four-wheeled and two-wheeled vehicles. The vehicle 300 operates when electricity is supplied by the battery pack 200 according to one embodiment of the present invention.

[0227] Based on the foregoing, it should be understood that various embodiments of the invention have been described herein for illustrative purposes, and various modifications can be made without departing from the scope and spirit of the invention. Therefore, the various embodiments disclosed herein are not intended to be limiting, and the true scope and spirit are indicated by the following claims.

Claims

1. A non-aqueous electrolyte comprising a lithium salt, an organic solvent, and additives. in, The additives include compounds represented by Formula 1: [Formula 1] In Formula 1, L1 is an alkylene group having 1 to 10 carbon atoms, and L2 is a directly bonded or -C(R 25 (R) 26 )- And L3 is directly bonded or -C(R 35 (R) 36 )- , R1 is an unsaturated hydrocarbon group having 2 to 10 carbon atoms, and R 21 R 22 R 23 R 24 R 25 R 26 R 31 R 32 R 33 R 34 R 35 R 36 R4 and R4 are each independently hydrogen or alkyl groups having 1 to 5 carbon atoms, and It is a bonding site.

2. The non-aqueous electrolyte as described in claim 1, wherein, R1 is a substituent selected from formulas 1-a and 1-b: [Equation 1-a] [Equation 1-b] In Equation 1-a, R a It is hydrogen or an alkyl group having 1 to 5 carbon atoms, and It is a bonding site.

3. The non-aqueous electrolyte as described in claim 1, wherein, The compound represented by Formula 1 includes at least one selected from the compounds represented by Formulas 1-1 to 1-8: [Equation 1-1] [Equation 1-2] [Equation 1-3] [Equations 1-4] [Equations 1-5] [Equations 1-6] [Equations 1-7] [Equations 1-8] 。 4. The non-aqueous electrolyte as described in claim 1, wherein, The amount of the compound represented by Formula 1 included in the additive is from 0.01% to 10% by weight relative to the weight of the non-aqueous electrolyte.

5. The non-aqueous electrolyte as described in claim 1, wherein, The additives also include at least one additional additive selected from coumarin, fluoroethylene carbonate, propane sulpholactone, propene sulpholactone, succinate, adiponitrile, ethylene sulfate, lithium difluorophosphate (LiDFP), lithium tetrafluoroborate (LiBF4), lithium bis(oxalate)borate (LiBOB), 3-trimethoxysilyl-propyl-N-aniline (TMSPa), tris(trimethylsilyl)phosphite (TMSPi), compounds represented by Formula 2, and compounds represented by Formula 3: [Equation 2] [Formula 3] In Formula 3, R5 includes halogen, nitrile, propargyl, ester, ether, ketone, carboxyl, alkyl, alkenyl, substituted or unsubstituted alkynyl, alkoxy, boron, borate ester, isocyanate, isothiocyanate, silyl, siloxane, sulfone, sulfonate, sulfate ester, or a combination of two or more thereof, and n is an integer selected from 0 to 6.

6. The non-aqueous electrolyte as described in claim 1, wherein, The lithium salt includes those selected from LiCl, LiBr, LiI, LiBF4, LiClO4, LiAlO4, LiAlCl4, LiPF6, LiSbF6, LiAsF6, and LiB. 10 Cl 10 At least one of LiBOB (LiB(C2O4)2), LiCF3SO3, LiFSI (LiN(SO2F)2), LiCH3SO3, LiCF3CO2, LiCH3CO2 and LiBETI (LiN(SO2CF2CF3)2).

7. The non-aqueous electrolyte as described in claim 1, wherein, The non-aqueous electrolyte contains lithium salts with a molar concentration of 0.5 M to 5.0 M.

8. The non-aqueous electrolyte as described in claim 1, wherein, The organic solvent includes at least one selected from cyclic carbonate organic solvents, linear carbonate organic solvents, linear ester organic solvents, and cyclic ester organic solvents.

9. A lithium secondary battery, comprising: positive electrode; The negative electrode facing the positive electrode; A diaphragm is disposed between the positive electrode and the negative electrode; as well as The non-aqueous electrolyte according to claim 1.

10. The lithium secondary battery as described in claim 9, wherein, The positive electrode includes a positive electrode active material, and the positive electrode active material contains a lithium transition metal oxide represented by formula A: [Formula A] Li 1+x [Ni a Co b Mr c M d ]O2 In equation A, 0 ≤ x ≤ 0.5, a + b + c + d = 1, 0.5 ≤ a ≤ 0.7, 0 ≤ b ≤ 0.15, c = 1 - abd, 0 ≤ d ≤ 0.1, 0 ≤ b / a ≤ 0.2, 1 ≤ a / c ≤ 3, and... M is selected from at least one of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo.

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