Non-aqueous electrolyte and lithium secondary battery comprising same

Abstract

The present invention provides a non-aqueous electrolyte and a lithium secondary battery comprising same. The non-aqueous electrolyte of the present invention comprises a lithium salt, an organic solvent, and an additive, wherein the additive comprises a cyclic borate-based compound, thereby preventing decomposition of the non-aqueous electrolyte of the lithium secondary battery in a high-output environment that causes negative electrode collapse, or further improving low-temperature high-rate discharge characteristics, high-temperature stability, overcharge prevention, battery expansion suppression effects at high temperatures, and the like.

Description

Non-aqueous electrolyte and lithium secondary battery containing the same

[0001] Related applications

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2024-0073345, filed June 4, 2024, the entire contents of which are incorporated herein by reference.

[0003] Technology field

[0004] The present invention relates to a non-aqueous electrolyte and a lithium secondary battery including the same.

[0005] Recently, as the application areas of lithium secondary batteries have rapidly expanded to include not only power supply for electronic devices such as electric, electronic, communication, and computer devices, but also power storage 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.

[0006] For example, as lithium secondary batteries are developed to have high capacity and high output, the probability of abnormal temperature rises due to various reasons during the charging and discharging process is increasing, which can lead to the so-called thermal runaway phenomenon in which sparks explode at high temperatures, and in case of thermal runaway, the fire is not easily extinguished, etc. Safety issues are recognized as one of the more important issues to be resolved in high capacity and high output lithium secondary batteries.

[0007] The present invention provides a non-aqueous electrolyte that can improve the life performance and storage performance of a lithium secondary battery when driven at high temperature and high voltage, and significantly prevent an increase in resistance.

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

[0009] The present invention provides a non-aqueous electrolyte comprising a lithium salt, an organic solvent, and an additive, wherein the additive comprises a compound represented by the following chemical formula 1.

[0010] [Chemical Formula 1]

[0011]

[0012] In the above chemical formula 1, L1 is an alkylene group having 1 to 10 carbon atoms, and L2 is a direct bond or *-C(R 25 )(R 26 )-*, and L3 is a direct bond 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 , and R4 are each independently hydrogen or an alkyl group having 1 to 5 carbon atoms, and * is a bonding site.

[0013] In addition, the present invention provides a lithium secondary battery including: a positive electrode; a negative electrode opposite to the positive electrode; a separator interposed between the positive electrode and the negative electrode; and the non-aqueous electrolyte described above.

[0014] The non-aqueous electrolyte of the present invention is characterized by including a cyclic borate compound (compound represented by Chemical Formula 1) having a structure comprising two cyclic borate groups and an unsaturated hydrocarbon group as an additive. The cyclic borate group can form a dense and highly durable SEI film while promoting lithium transport characteristics on the electrode surface, but has a problem of reduced reactivity due to steric hindrance. The cyclic borate compound included in the non-aqueous electrolyte of the present invention includes an unsaturated hydrocarbon group, thereby facilitating the access of the cyclic borate group to the electrode and improving reactivity, thereby further facilitating the formation of the SEI film derived from the above-described cyclic borate compound. In addition, since the cyclic borate compound includes two cyclic borate groups, it can provide a film component beneficial for improving durability at an abundant level on the electrode surface, and has an excellent stabilizing effect on the lithium salt due to the presence of a large number of boron sites.

[0015] Accordingly, a lithium secondary battery including a non-aqueous electrolyte according to the present invention may be capable of improving life performance and storage performance, for example, improving life performance and storage performance at high temperatures and high voltages.

[0016] The following drawings attached to this specification illustrate embodiments of the present invention and, together with the detailed description of the invention described below, serve to further understand the technical idea of ​​the present invention, and therefore, the present invention should not be interpreted as being limited to matters described in such drawings.

[0017] Figure 1 shows the structure of a lithium secondary battery according to one embodiment of the present invention.

[0018] FIG. 2 is a drawing for explaining an automobile including a battery pack composed of the lithium secondary battery of FIG. 1.

[0019] In some of the accompanying drawings, corresponding components are designated by the same reference numerals. Those skilled in the art will appreciate that the drawings illustrate elements simply and clearly and are not necessarily drawn to scale. For example, to facilitate understanding of various embodiments, the dimensions of some elements depicted in the drawings may be exaggerated relative to other elements. Furthermore, elements of known technology that are useful or essential in commercially feasible embodiments may often not be depicted so as not to obscure the spirit of various embodiments of the present invention.

[0020] Terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best possible manner.

[0021] It should be understood that the terms “include,” “comprising,” or “having” used in this specification 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.

[0022] Meanwhile, before explaining the present invention, unless otherwise specified, “*” in the present invention means a connected portion (bonding site) between terminals of the same or different atoms or chemical formulas.

[0023] In addition, in the description of "carbon atoms a to b" in the present specification, "a" and "b" refer to the number of carbon atoms included in a specific functional group. That is, the functional group may include "a" to "b" carbon atoms. For example, "an alkyl group having 1 to 5 carbon atoms" refers to an alkyl group including 1 to 5 carbon atoms, i.e., CH3-, CH3CH2-, CH3CH2CH2-, (CH3)2CH-, CH3CH2CH2CH2-, (CH3)2CHCH2-, CH3CH2CH2CH2CH2-, (CH3)2CHCH2CH2CH2-, (CH3)2CHCH2CH2CH2-, etc.

[0024] Additionally, in this specification, any alkyl group, alkenyl group, silyl group, siloxane group, or aryl group may be substituted or unsubstituted. The above "substitution" means, unless otherwise defined, that at least one hydrogen bonded to carbon is replaced by an element other than hydrogen, for example, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a cycloalkenyl group having 3 to 12 carbon atoms, a cycloalkynyl group having 3 to 12 carbon atoms, a heterocycloalkyl group having 3 to 12 carbon atoms, a 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, an aryl group having 2 to 20 carbon atoms, an alkyl ... It means substituted with a heteroaryl group having 20 carbon atoms, a haloaryl group having 6 to 20 carbon atoms, etc.

[0025] A lithium secondary battery generally consists 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 that serves as a medium for transferring lithium ions through the separator. In one embodiment, a carbon-based active material, a silicon-based active material, etc. may be used as the negative electrode active material, and a lithium transition metal oxide such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a lithium nickel-cobalt-manganese composite transition metal oxide may be used as the positive electrode active material.

[0026] Recently, 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 to increase the energy density of lithium secondary battery cathodes. However, increasing the nickel content of these lithium nickel-cobalt-manganese composite transition metal oxides can lead to a decrease in the thermal stability of the cathode.

[0027] To avoid these problems, when the nickel content in the lithium nickel-cobalt-manganese composite transition metal oxide is lowered, the operating voltage must be increased to achieve the required energy density. However, this high-voltage operation may exacerbate the problems of electrolyte side reactions at the anode, reduced high-temperature durability, and / or increased resistance.

[0028] The present invention takes these points into consideration and provides a non-aqueous electrolyte that can improve the life performance and storage performance of a lithium secondary battery when driven at high temperature and high voltage, and can suppress or prevent an increase in resistance to a significant level.

[0029] Hereinafter, the present invention will be described in more detail.

[0030] Referring to FIG. 1, a lithium secondary battery (100) according to one embodiment of the present invention includes an electrode assembly comprising a positive electrode (110), a negative electrode (120) facing the positive electrode (110), a separator (130) interposed between the positive electrode (110) and the negative electrode (120), a non-aqueous electrolyte (140), and a battery case (150) that accommodates the electrode assembly and the non-aqueous electrolyte (140).

[0031] The above lithium secondary battery (100) can be manufactured by housing the electrode assembly in a battery case (150) and then injecting the non-aqueous electrolyte (140) described above.

[0032] A lithium secondary battery (100) according to one embodiment of the present invention may be manufactured in, for example, a prismatic type, a pouch type, a coin type, and a cylindrical type, depending on the manufacturing form.

[0033]

[0034] non-aqueous electrolyte

[0035] A non-aqueous electrolyte (140) according to one embodiment of the present invention includes a lithium salt, an organic solvent, and an additive, wherein the additive includes a compound represented by the following chemical formula 1.

[0036] [Chemical Formula 1]

[0037]

[0038] In the above chemical formula 1, L1 is an alkylene group having 1 to 10 carbon atoms, and L2 is a direct bond or *-C(R 25 )(R 26 )-*, and L3 is a direct bond 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 , R26 , R 31 , R 32 , R 33 , R 34 , R 35 , R 36 , and R4 are each independently hydrogen or an alkyl group having 1 to 5 carbon atoms, and * is a bonding site.

[0039]

[0040] (1) Lithium salt

[0041] As the lithium salt used in the present invention, various lithium salts commonly used in non-aqueous electrolytes (140) for lithium secondary batteries (100) can be used without limitation. For example, the lithium salt may be Li as a cation. + , and the anion is 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 - It may include at least one selected from.

[0042] For example, the lithium salts include LiCl, LiBr, LiI, LiBF4, LiClO4, LiAlO4, LiAlCl4, LiPF6, LiSbF6, LiAsF6, LiB 10 Cl 10 , LiBOB (LiB(C2O4)2), LiCF3SO3, LiFSI (LiN(SO2F)2), LiCH3SO3, LiCF3CO2, LiCH3CO2, and LiBETI (LiN(SO2CF2CF3)2). In 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).

[0043] The lithium salt may be included in the non-aqueous electrolyte at a concentration of about 0.5 M to 5 M, for example, a concentration of about 0.8 M to 4 M, or a concentration of 0.8 M to 2.0 M. When the concentration of the lithium salt satisfies the above range, the lithium ion yield (Li + The output characteristics of the battery can be improved by improving the transference number and the degree of dissociation of lithium ions.

[0044]

[0045] (2) Organic solvent

[0046] The organic solvent mentioned above is a non-aqueous solvent commonly used in lithium secondary batteries (100), and is not particularly limited as long as it can minimize decomposition due to oxidation reactions, etc. during the charging and discharging process of the secondary battery.

[0047]

[0048] For example, the organic solvent may include at least one selected from a cyclic carbonate-based organic solvent, a linear carbonate-based organic solvent, a linear ester-based organic solvent, and a cyclic ester-based organic solvent.

[0049] In one embodiment, the organic solvent may include a cyclic carbonate-based organic solvent, a linear carbonate-based organic solvent, or a mixture thereof.

[0050] The above cyclic carbonate-based organic solvent is a high-viscosity organic solvent with a high dielectric constant that can easily dissociate a lithium salt in an electrolyte, and may include at least one organic solvent selected from, for example, ethylene carbonate (EC), fluoroethylene carbonate (FEC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, and vinylene carbonate, and according to one embodiment, may include at least one selected from ethylene carbonate (EC) and fluoroethylene carbonate (FEC).

[0051] The linear carbonate-based organic solvent is an organic solvent having low viscosity and low dielectric constant, and may include, for example, at least one selected from dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethylmethyl carbonate (EMC), methylpropyl carbonate, and ethylpropyl carbonate, and according to one embodiment, may include at least one selected from ethylmethyl carbonate (EMC) and diethyl carbonate (DEC).

[0052] The above organic solvent may be a mixture of a cyclic carbonate-based organic solvent and a linear carbonate-based organic solvent. The cyclic carbonate-based organic solvent and the linear carbonate-based organic solvent may be mixed in a volume ratio of about 5:95 to 40:60, for example, a volume ratio of 7:93 to 25:75. When the mixing ratio of the cyclic carbonate-based organic solvent and the linear carbonate-based organic solvent satisfies the above range, both high dielectric constant and low viscosity characteristics can be satisfied, and excellent ionic conductivity characteristics can be realized.

[0053] The organic solvent may further include at least one carbonate organic solvent selected from the cyclic carbonate organic solvent and the linear carbonate organic solvent, and at least one ester organic solvent selected from the linear ester organic solvent and the cyclic ester organic solvent, in order to produce an electrolyte having high ionic conductivity.

[0054] The linear ester organic solvent may include at least one selected from, for example, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate.

[0055] In addition, the cyclic ester organic solvent may include at least one selected from, for example, γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone.

[0056]

[0057] The above organic solvent may be used without limitation by adding organic solvents commonly used in non-aqueous electrolytes as needed. For example, at least one organic solvent from among an ether-based organic solvent, a glyme-based solvent, and a nitrile-based organic solvent may be additionally included.

[0058] As the above ether solvent, any one selected from 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) or a mixture of two or more thereof may be used, but is not limited thereto.

[0059] The above glyme-based solvent has a high dielectric constant and low surface tension compared to linear carbonate-based organic solvents, and is a solvent with low reactivity with metals, and may include at least one selected from dimethoxyethane (glyme, DME), diethoxyethane, diglyme, tri-glyme, and tetra-glyme (TEGDME), but is not limited thereto.

[0060] The above nitrile solvent may be at least one selected from acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentane carbonitrile, cyclohexane carbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile, but is not limited thereto.

[0061]

[0062] (3) Additives

[0063] The above non-aqueous electrolyte (140) further includes an additive along with the above-described lithium salt and organic solvent.

[0064] The above additive may include an additive that can additionally form an SEI (Solid Electrolyte Interphase) film within the non-aqueous electrolyte (140) as needed, for example, to prevent the non-aqueous electrolyte of a lithium secondary battery from being decomposed and causing cathode collapse in a high-power environment, or to further improve low-temperature high-rate discharge characteristics, high-temperature stability, overcharge prevention, and high-temperature battery expansion suppression effects.

[0065] The above additive includes a compound represented by the following chemical formula 1.

[0066] [Chemical Formula 1]

[0067]

[0068] In the above chemical formula 1, L1 is an alkylene group having 1 to 10 carbon atoms, and L2 is a direct bond or *-C(R 25 )(R 26 )-*, and L3 is a direct bond 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 , and R4 are each independently hydrogen or an alkyl group having 1 to 5 carbon atoms, and * is a bonding site.

[0069] In general, in the case of cyclic borates, they can form a dense and durable SEI film while promoting lithium transport characteristics at the electrode (positive electrode and / or negative electrode), but after being solvated with an organic solvent, they are too bulky and have difficulty in accessing the negative electrode, and this reduced accessibility becomes a factor in reduced reactivity. In this regard, the compound represented by the above chemical formula 1 according to the present invention contains an unsaturated hydrocarbon group in its structure, and this unsaturated hydrocarbon group has high reactivity and easy access to the electrode due to its LUMO (Lowest Unoccupied Molecular Orbital) characteristic, and therefore, the cyclic borate group present together with the unsaturated hydrocarbon group also becomes easy to access the electrode, and thus the reactivity of the cyclic borate at the electrode can be promoted. This effect cannot be realized from a substituent other than an unsaturated hydrocarbon group such as an allyl group or a propargyl group (for example, an alkyl group, etc.).

[0070] In addition, the cyclic borate compound contains two cyclic borate groups, which can provide a film component beneficial for improving durability at an abundant level on the electrode surface, and has an excellent stabilizing effect on the lithium salt due to the presence of a large number of boron sites. For example, when only one cyclic borate group exists in the compound, the durability improving effect of the SEI film is minimal, and the life performance improving effect of the lithium secondary battery at high voltage and high temperature is not sufficient. On the other hand, when three or more cyclic borate groups exist in the compound, it is difficult to protect the electrode through the SEI film due to reduced reactivity caused by excessive steric hindrance.

[0071] In the above chemical formula 1, R1 may be an unsaturated hydrocarbon group having 2 to 10 carbon atoms. At this time, the unsaturated hydrocarbon group may mean a hydrocarbon group containing a carbon-carbon double bond or a hydrocarbon group containing a carbon-carbon triple bond. The R1 may be a substituent selected from the following chemical formulas 1-a and 1-b. Specifically, the R1 may be a substituent represented by the following chemical formula 1-a.

[0072] [Chemical Formula 1-a]

[0073]

[0074] [Chemical Formula 1-b]

[0075]

[0076] In the above chemical formula 1-a, R a may be hydrogen or an alkyl group having 1 to 5 carbon atoms. * is a bonding site.

[0077] In the above chemical formula 1, L1 may be an alkylene group having 1 to 10 carbon atoms, for example, an alkylene group having 1 to 5 carbon atoms, a methylene group, or an ethylene group, and in one embodiment, may be a methylene group, in terms of properly implementing the effect of enhancing the reactivity of a cyclic borate group through an unsaturated hydrocarbon group.

[0078] In the above chemical formula 1, R 21 , R 22 , R 23 , R 24 , R 31 , R 32 , R 33 , R 34And R4 can be independently hydrogen or an alkyl group having 1 to 5 carbon atoms, for example, can be independently hydrogen or an alkyl group having 1 to 3 carbon atoms, or can be independently hydrogen or a methyl group, or can each be hydrogen. In the above range according to one embodiment, a stable SEI film formation reaction is possible without decreasing the reactivity of the cyclic borate group and the unsaturated hydrocarbon group.

[0079] L2 is a direct bond or *-C(R 25 )(R 26 )-*, and L3 is a direct bond or *-C(R 35 )(R 36 )-* may be. In this case, *-C(R 25 )(R 26 )-* and *-C(R 35 )(R 36 )-*, C represents a carbon atom. Also, * represents a bonding site. For example, L2 and L3 can each be a direct bond. Also, L2 and L3 can each be *-C(R 25 )(R 26 )-* or *-C(R 35 )(R 36 )-*, R 25 , R 26 , R 35 and R 36 can be independently hydrogen or an alkyl group having 1 to 5 carbon atoms, can be independently hydrogen or an alkyl group having 1 to 3 carbon atoms, or can be independently hydrogen or a methyl group. Within the above range, a stable SEI film formation reaction is possible without decreasing the reactivity of the cyclic borate group and the unsaturated hydrocarbon group.

[0080] The compound represented by the above chemical formula 1 may include at least one selected from compounds represented by the following chemical formulas 1-1 to 1-8, for example, may include at least one selected from compounds represented by the following chemical formulas 1-1 to 1-4, or may include at least one selected from compounds represented by the following chemical formulas 1-1 and 1-3.

[0081] [Chemical Formula 1-1]

[0082]

[0083] [Chemical Formula 1-2]

[0084]

[0085] [Chemical Formula 1-3]

[0086]

[0087] [Chemical Formula 1-4]

[0088]

[0089] [Chemical Formula 1-5]

[0090]

[0091] [Chemical Formula 1-6]

[0092]

[0093] [Chemical Formula 1-7]

[0094]

[0095] [Chemical Formula 1-8]

[0096]

[0097] The compound represented by the above chemical formula 1 may be included in an amount of about 0.01 wt% to 10 wt%, for example, about 0.05 wt% to 5 wt%, about 0.1 wt% to 3 wt%, about 0.3 wt% to 1.5 wt%, or about 0.5 wt% to 1 wt%, based on the weight of the non-aqueous electrolyte (140), and in one embodiment, may be included in an amount of 0.5 wt% to 0.8 wt%. When the compound represented by the above chemical formula 1 is used in the above-described content range, a flexible and durable SEI film can be formed on the negative electrode while suppressing or preventing an increase in resistance.

[0098]

[0099] The above additive may further include an additional additive together with the compound represented by Chemical Formula 1. The additional additive may be included in the non-aqueous electrolyte (140) to suppress or prevent the non-aqueous electrolyte from decomposing and causing cathode collapse in a high-power environment, or to provide low-temperature high-rate discharge characteristics, high-temperature stability, overcharge prevention, and high-temperature battery expansion suppression effects. When an additional additive is included, the compound represented by Chemical Formula 1 may be represented as a first additive, and the additional additive may be represented as a second additive.

[0100] For example, the additional additive may be at least one selected from lithium difluorophosphate (LiDFP), vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, propane sultone, propene sultone, succinonitrile, adiponitrile, ethylene sulfate, lithium bis-(oxalato)borate (LiBOB), tris(trimethylsilyl) phosphate (TMSPi), and tris(trimethylsilyl) phosphate (TMSPi), a compound represented by the following chemical formula 2, and a compound represented by the following chemical formula 3.

[0101] [Chemical Formula 2]

[0102]

[0103] [Chemical Formula 3]

[0104]

[0105] In the above chemical formula 3, R5 includes a halogen, a nitrile group, a propargyl group, an ester group, an ether group, a ketone group, a carboxyl group, an alkyl group, an alkenyl group, a substituted or unsubstituted alkynyl group, an alkoxy group, a boron group, a borate group, an isocyanate group, an isothiocyanate group, a silyl group, a siloxane group, a sulfone group, a sulfonate group, a sulfate group, or a combination of two or more thereof, and n is an integer selected from 0 to 6.

[0106] The compound represented by the above chemical formula 3 may be, for example, at least one selected from compounds represented by the following chemical formulas 3-1 to 3-9.

[0107] [Chemical Formula 3-1]

[0108]

[0109] [Chemical Formula 3-2]

[0110]

[0111] [Chemical Formula 3-3]

[0112]

[0113] [Chemical Formula 3-4]

[0114]

[0115] [Chemical Formula 3-5]

[0116]

[0117] [Chemical Formula 3-6]

[0118]

[0119] [Chemical Formula 3-7]

[0120]

[0121] [Chemical Formula 3-8]

[0122]

[0123] [Chemical Formula 3-9]

[0124]

[0125]

[0126] The above additional additive may be included in the non-aqueous electrolyte in an amount of about 0.1 wt% to 15 wt%, for example, about 0.3 wt% to 3 wt%.

[0127]

[0128] lithium secondary battery

[0129] According to one embodiment, the present invention provides a lithium secondary battery (100) including the aforementioned non-aqueous electrolyte (140).

[0130] A lithium secondary battery (100) according to the present invention includes a positive electrode (110); a negative electrode (120) facing the positive electrode (110); a separator (130) interposed between the positive electrode (110) and the negative electrode (120); and the non-aqueous electrolyte (140) described above.

[0131] According to one embodiment, the lithium secondary battery (100) may be manufactured by housing an electrode assembly including the positive electrode (110); a negative electrode (120) facing the positive electrode (110); and a separator (130) interposed between the positive electrode (110) and the negative electrode (120) in a battery case (150), and then injecting the non-aqueous electrolyte (140) described above. At this time, as described above, the lithium secondary battery (100) according to one embodiment of the present invention may be manufactured in a prismatic type, a pouch type, a coin type, and a cylindrical type, for example, depending on the manufacturing form.

[0132] Following the aforementioned non-aqueous electrolyte, the cathode, anode, and separator are described below.

[0133]

[0134] (1) Bipolar

[0135] The above positive electrode (110) may include a positive electrode active material.

[0136] The above positive electrode active material is a compound capable of reversible intercalation and deintercalation, and is not particularly limited as long as it is a positive electrode active material used in the relevant field. For example, the positive electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; lithium iron oxide such as LiFe3O4; lithium iron phosphate such as LiFePO4; or a compound having the chemical formula Li 1+c1 Mn 2-c1Lithium manganese oxides such as O4(0≤c1≤0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, Cu2V2O7; chemical formula LiNi 1-c2 M c2 Ni-site type lithium nickel oxide represented by O2 (wherein, M is at least one selected from Co, Mn, Al, Cu, Fe, Mg, B, and Ga, and satisfies about 0.01≤c2≤0.3); chemical formula LiMn 2-c3 M c3 Lithium manganese composite oxide represented by O2 (wherein, M is at least one selected from Co, Ni, Fe, Cr, Zn, and Ta, and satisfies about 0.01≤c3≤0.1) or Li2Mn3MO8 (wherein, M is at least one selected from Fe, Co, Ni, Cu, and Zn); etc., but are not limited thereto. The positive electrode may be a Li-metal positive electrode.

[0137] In one embodiment, the positive electrode active material may include at least one selected from lithium cobalt oxide (LiCoO2), lithium nickel cobalt manganese oxide, lithium manganese-rich oxide, and lithium iron phosphate.

[0138] The above nickel-containing lithium nickel cobalt manganese oxide may be represented by the following chemical formula A. The above cathode active material may include a lithium transition metal oxide represented by the following chemical formula A.

[0139] [Chemical Formula A]

[0140] Li 1+x (Ni a Co b Mn c M d )O2

[0141] In the above chemical 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 atomic fractions of independent elements, x is about 0≤x≤0.2, a is about 0 <a<1, b는 약 0<b<1, c는 약 0<c<1, d는 약 0≤d≤0.1, 그리고 a+b+c+d=1이다.

[0142] In one embodiment, in the formula A, x may be about 0≤x≤0.5, for example, about 0≤x≤0.2.

[0143] In the above chemical formula A, a may be about 0.5≤a≤0.7, for example, about 0.55≤a≤0.65.

[0144] In the above chemical formula A, b is about 0 <b≤0.15일 수 있다. b는 상기 화학식 A로 표시되는 리튬 전이금속 산화물에 있어서, 리튬을 제외한 금속 중 Co가 차지하는 몰 백분율에 해당하며, 본 발명에 따르면 Co 함량을 낮춤으로써 비용적인 이점을 가지며, 상대적으로 Mn의 비율을 높여 양극 활물질의 구조적 안정성을 향상시킬 수 있다. 예를 들면, 상기 화학식 A에서, b는 약 0<b≤0.1일 수 있다.

[0145] In the above chemical formula A, b / a is approximately 0

[0146] ​In the above chemical formula A, c=1-abd, and a / c is about 1≤a / c≤3. c corresponds to the molar percentage of Mn among the metals other than lithium in the lithium transition metal oxide represented by the above chemical formula A, and according to the present invention, the molar ratio of Ni to Mn is adjusted to 1≤a / c≤3, thereby improving the structural stability of the positive electrode active material. In one embodiment, a / c may be about 1.5≤a / c≤2.5.

[0147] In the above chemical formula A, M can be understood as a doping element of a lithium transition metal oxide, and may be, for example, at least one selected from among 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. At this time, d may be 0≤d≤0.1, for example, 0≤d≤0.05.

[0148] In the above chemical formula A, a / (b × c) may be about 18 to 50, for example, about 18 to 40, or about 20 to 35. When within the above range, the contents of nickel, cobalt, and manganese in the chemical formula A are harmoniously controlled, thereby enhancing the performance improvement effect by forming a positive electrode film through an additive and simultaneously improving the structural stability of the positive electrode active material.

[0149] The above lithium manganese-rich oxide may include a compound represented by the following chemical formula B.

[0150] [Chemical Formula B]

[0151] Li 1+s [Ni t Co u Mn v M 1 w ]O 2+z

[0152] In the above chemical formula B, M 1is 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, and s is about 0.05≤s≤1, t is about 0≤t≤0.5, u is about 0≤u≤0.3, v is about 0.5≤v<1.0, w is about 0≤w≤0.2, 0≤z≤1. For example, in the chemical formula B, s may be about 0.05≤s≤1.0, t may be about 0.1≤t≤0.5, u may be about 0≤u≤0.1, v may be about 0.5≤v<1.0, 0≤w≤0.2, 0≤z≤1. Alternatively, in the chemical formula B, 0.10≤s≤0.50, t may be about 0.1≤t≤0.5, u may be about 0≤u≤0.1, v may be about 0.6≤v<1.0, w may be about 0≤w≤0.1, and z may be about 0≤z≤0.50.

[0153] The above lithium iron phosphate may include a compound represented by the following chemical formula C.

[0154] [Chemical Formula C]

[0155] Li 1+e Fe 1-g M 2 g (PO 4-f )X f

[0156] In the above chemical formula C, M 2 is one or more elements selected from Co, Ni, Mn, Al, Mg, Ti, and V, X is F, S, or N, g is about 0≤g≤0.5; e is about -0.5≤e≤+0.5; and f is about 0≤f≤0.1. The above chemical formula C can be represented by, for example, LiFePO4 (g=0, e=0, and f=0).

[0157] The above 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.

[0158] The positive electrode current collector is not particularly limited as long as it has high conductivity without causing 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 an aluminum-cadmium alloy, for example, aluminum.

[0159] The thickness of the above positive electrode collector may typically have a thickness of about 3 ㎛ to 500 ㎛.

[0160] The above-described positive electrode current collector may also form fine irregularities on its surface to enhance the bonding strength of the positive electrode active material. For example, the above-described positive electrode current collector may be used in various forms, such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0161] The positive electrode active material layer may be disposed on at least one surface of the positive electrode current collector. For example, the positive electrode active material layer may be disposed on one or both surfaces of the positive electrode current collector.

[0162] The above positive electrode active material layer may include the above-described positive electrode active material.

[0163] The above-described positive electrode active material layer may optionally further include a binder and / or a conductive material together with the above-described positive electrode active material.

[0164] The above binder is a component that assists in the binding of the active material and the conductive material and the binding to the current collector, and may include at least one selected from, for example, 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, for example, polyvinylidene fluoride.

[0165] The above binder may be included in the positive electrode active material layer at about 1 wt% to 20 wt%, for example, about 1.2 wt% to 10 wt%, in order to sufficiently secure binding force between components such as the positive electrode active material.

[0166] The conductive material may be used to assist and improve conductivity in a secondary battery, and is not particularly limited as long as it has conductivity without causing chemical changes. For example, the positive electrode conductive material may include at least one selected from graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, channel black, paneth black, lamp black, thermal black, etc.; 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 example, in terms of improving conductivity, it may include carbon nanotubes.

[0167] The above-mentioned conductive material may be included in the positive electrode active material layer in an amount of about 1 wt% to 20 wt%, for example, about 1.2 wt% to 10 wt%, in order to sufficiently secure electrical conductivity.

[0168] The thickness of the positive electrode active material layer may be about 5 ㎛ to 500 ㎛, for example, about 20 ㎛ to 200 ㎛.

[0169] The above positive electrode can be manufactured by coating a positive electrode slurry containing a positive electrode active material and optionally a binder, a conductive material, and a solvent for forming a positive electrode slurry on the positive electrode current collector, and then drying and rolling.

[0170]

[0171] (2) Cathode

[0172] The above cathode (120) may face the above anode (110).

[0173] The above negative electrode (120) may include a negative electrode active material.

[0174] The above negative electrode active material is a material capable of reversibly inserting / de-inserting lithium ions, and may include at least one selected from a carbon-based active material, a (semi-)metal-based active material, and lithium metal, and may include, for example, at least one selected from a carbon-based active material and a (semi-)metal-based active material.

[0175] The above carbon-based active material may include at least one selected from graphite, hard carbon, soft carbon, carbon black, graphene, and fibrous carbon, and may include graphite according to one embodiment. The graphite may be, for example, at least one selected from artificial graphite and natural graphite.

[0176] The average particle diameter (D) of the above carbon-based active material 50 ) may be about 10㎛ to 30㎛, for example, about 15㎛ to 25㎛, in order to ensure structural stability during charging and discharging and reduce side reactions with the electrolyte.

[0177] According to one embodiment, the (semi)metal-based 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); lithium vanadium oxide; and the like.

[0178] In one embodiment, the (quasi)metal-based active material may include a silicon-based active material.

[0179] The above silicon-based active material is SiO x It may include a compound represented by (0≤x<2). In the case of SiO2, since it does not react with lithium ions and thus cannot store lithium, x may be within the above range, and in one embodiment, the silicon-based active material may be SiO.

[0180] The average particle diameter (D) of the above silicon-based active material 50 ) may be about 1 ㎛ to 30 ㎛, for example, about 2 ㎛ to 15 ㎛, in order to reduce side reactions with the electrolyte while ensuring structural stability during charge and discharge.

[0181]

[0182] The above 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. In this case, the negative electrode active material may be included in the negative electrode active material layer.

[0183] The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. For example, the negative electrode current collector may be made of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., or an aluminum-cadmium alloy.

[0184] The above negative electrode current collector may typically have a thickness of about 3 μm to 500 μm.

[0185] The negative electrode current collector, like the positive electrode current collector, may have fine irregularities formed on its surface to enhance the bonding strength of the negative electrode active material. For example, the negative electrode current collector may be used in various forms, such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0186]

[0187] The negative electrode active material layer may be disposed on at least one side of the negative electrode current collector, for example, one side or both sides of the negative electrode current collector.

[0188] The above negative active material may be included in the negative active material layer at about 60 wt% to 99 wt%, for example, about 75 wt% to 95 wt%.

[0189] Description of other positive electrode active materials is omitted as it has been described above.

[0190] The above negative electrode active material layer may further include a binder and / or a conductive material together with the negative electrode active material.

[0191] The above binder is used to improve the performance of the battery by improving the adhesion between the negative electrode active material layer and the negative electrode current collector, and may include, for example, at least one selected from polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethylmethacrylate, 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 in which hydrogens of these are substituted with Li, Na, Ca, etc., and may also include various copolymers thereof. there is.

[0192] The above binder may be included in the negative electrode active material layer in an amount of about 0.5 wt% to 10 wt%, for example, about 1 wt% to 5 wt%.

[0193] The conductive material is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, channel black, paneth black, lamp black, thermal black, and the like; 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.

[0194] The above conductive material may be included in the negative electrode active material layer in an amount of about 0.5 wt% to 10 wt%, for example, about 1 wt% to 5 wt%.

[0195] The thickness of the negative electrode active material layer may be about 10 ㎛ to 200 ㎛, for example, about 20 ㎛ to 150 ㎛.

[0196] The above negative electrode (120) can be manufactured by coating a negative electrode slurry containing a negative electrode active material, a binder, a conductive material, and / or a solvent for forming a negative electrode slurry on at least one surface of a negative electrode current collector, and then drying and rolling.

[0197] The solvent for forming the negative electrode slurry may include at least one selected from distilled water, NMP (N-methyl-2-pyrrolidone), ethanol, methanol, and isopropyl alcohol, for example, distilled water, in order to facilitate dispersion of the negative electrode active material, binder, and / or conductive agent. The solid content of the negative electrode slurry may be about 30 wt% to 80 wt%, for example, 40 wt% to 70 wt%.

[0198]

[0199] (3) Membrane

[0200] The above separator (130) may be interposed between the anode and the cathode.

[0201] In addition, as the separator (130), a conventional porous polymer film used as a conventional separator, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, may be used alone or in a laminated manner, or a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. may be used, but is not limited thereto. In addition, a coated separator containing a ceramic component or a polymer material may be used to secure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0202]

[0203] There is no particular limitation on the external shape of the lithium secondary battery (100) of the present invention, but it may be a cylindrical shape using a can, a square shape, a pouch shape, or a coin shape.

[0204]

[0205] Hereinafter, the present invention will be described through examples. However, the following examples are merely illustrative and serve to aid understanding of the present invention and do not limit its scope. It will be apparent to those skilled in the art that various modifications and variations are possible within the scope and technical spirit of this disclosure, and such modifications and variations are naturally within the scope of the appended claims.

[0206]

[0207] Examples and Comparative Examples

[0208] Example 1

[0209] (Manufacture of non-aqueous electrolyte)

[0210] As an organic solvent, a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 20:80 was used.

[0211] A non-aqueous electrolyte was prepared by adding LiPF6 as a lithium salt to the above organic solvent, and a compound represented by the above chemical formula 1-1 and a compound represented by the chemical formula 2 as additives.

[0212] The above LiPF6 was included in the non-aqueous electrolyte at a molar concentration of 1.2 M.

[0213] The compound represented by the above chemical formula 1-1 was included in the non-aqueous electrolyte at 0.5 wt%, and the compound represented by the above chemical formula 2 was included in the non-aqueous electrolyte at 0.2 wt%.

[0214]

[0215] (Lithium secondary battery manufacturing)

[0216] Cathode active material (Li[Ni 0.6 Co 0.1 Mn 0.3 ]O2): Conductive agent (carbon black): Binder (polyvinylidene fluoride) was 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 (solid content 60 wt%). The positive electrode slurry was applied to one surface of a positive electrode current collector (Al thin film) having a thickness of 15 μm, dried, and roll pressed to form a positive electrode active material layer (thickness: 136.6 μm), which was used as a positive electrode. The positive electrode active material was in the form of a single particle or a pseudo-single particle.

[0217] A negative electrode slurry (solid content 60 wt%) was prepared by adding a negative electrode active material (graphite): conductive agent (carbon black): 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 applied to one surface of a 6 μm thick negative electrode current collector (Cu thin film), dried, and roll pressed to form a negative electrode active material layer (thickness: 179.8 μm), which was used as a negative electrode.

[0218] A polyethylene porous film separator was interposed between the positive and negative electrodes manufactured above in a dry room, and then the non-aqueous electrolyte manufactured above was injected to manufacture a lithium secondary battery.

[0219]

[0220] Example 2

[0221] A non-aqueous electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte was manufactured by including the compound represented by the above chemical formula 1-1 in the non-aqueous electrolyte at 1 wt% instead of 0.5 wt% based on the total weight of the non-aqueous electrolyte.

[0222]

[0223] Example 3

[0224] A non-aqueous electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the compound represented by the above chemical formula 1-1 was not included in the non-aqueous electrolyte, and the compound represented by the above chemical formula 1-2 was included in the non-aqueous electrolyte in an amount of 0.5 wt% based on the total weight of the non-aqueous electrolyte.

[0225]

[0226] Example 4

[0227] A non-aqueous electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the compound represented by the above chemical formula 1-1 was not included in the non-aqueous electrolyte, and the compound represented by the above chemical formula 1-3 was included in the non-aqueous electrolyte in an amount of 0.5 wt% based on the total weight of the non-aqueous electrolyte.

[0228]

[0229] Comparative Example 1

[0230] A non-aqueous electrolyte and a lithium secondary battery were manufactured in the same manner as Example 1, except that the compound represented by the above chemical formula 1-1 was not added to the non-aqueous electrolyte.

[0231]

[0232] Comparative Example 2

[0233] A non-aqueous electrolyte and a lithium secondary battery were manufactured in the same manner as Example 1, except that the compound represented by the above chemical formula 1-1 was not added and the comparative compound A below was included in the non-aqueous electrolyte at 0.5 wt% based on the total weight of the non-aqueous electrolyte.

[0234] [Comparative Compound A]

[0235]

[0236]

[0237] Comparative Example 3

[0238] A non-aqueous electrolyte and a lithium secondary battery were manufactured in the same manner as Example 1, except that the compound represented by the above chemical formula 1-1 was not added and the comparative compound B below was included in the non-aqueous electrolyte at 0.5 wt% based on the total weight of the non-aqueous electrolyte.

[0239] [Comparative Compound B]

[0240]

[0241]

[0242] Comparative Example 4

[0243] A non-aqueous electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the compound represented by the above chemical formula 1-1 was not added and the comparative compound C below was included in the non-aqueous electrolyte at 0.5 wt% based on the total weight of the non-aqueous electrolyte.

[0244] [Comparative Compound C]

[0245]

[0246]

[0247] Comparative Example 5

[0248] A non-aqueous electrolyte and a lithium secondary battery were manufactured in the same manner as Example 1, except that the compound represented by the above chemical formula 1-1 was not added and the comparative compound D below was included in the non-aqueous electrolyte at 0.5 wt% based on the total weight of the non-aqueous electrolyte.

[0249] [Comparative Compound D]

[0250]

[0251]

[0252] Comparative Example 6

[0253] A non-aqueous electrolyte and a lithium secondary battery were manufactured in the same manner as Example 1, except that the compound represented by the above chemical formula 1-1 was not added and the comparative compound E below was included in the non-aqueous electrolyte at 0.5 wt% based on the total weight of the non-aqueous electrolyte.

[0254] [Comparative Compound E]

[0255]

[0256]

[0257] Experimental example

[0258] Experimental Example 1: High-Temperature Cycle Performance Evaluation

[0259] The lithium secondary batteries manufactured in Examples 1 to 4 and Comparative Examples 1 to 6 above were charged to 4.4 V, 0.05 C at 45°C using an electrochemical charger / discharger under CC / CV, 0.33 C conditions, and then discharged to 2.5 V under CC, 0.33 C conditions, which constituted one cycle, and 200 cycles of charge and discharge were performed.

[0260]

[0261] (1) Capacity retention rate

[0262] The capacity retention rate is calculated using the formula below, and the results are shown in Table 1 below.

[0263]

[0264] Capacity retention rate (%) = {(discharge capacity after 200 cycles / discharge capacity after 1 cycle)} × 100

[0265]

[0266] (2) Resistance increase rate

[0267] After one cycle of charge and discharge, the discharge capacity after one cycle was measured using an electrochemical charger and discharger, the SOC (State of Charge) was adjusted to 50%, and then a 2.5C pulse was applied for 10 seconds, and the initial resistance was calculated through the difference between the voltage before and after the pulse was applied.

[0268] After 200 cycles of charge and discharge, the resistance after 200 cycles was calculated using the same method as above, and the resistance increase rate was calculated using the equation below, and the results are shown in Table 1 below.

[0269]

[0270] Resistance increase rate (%) = (Resistance after 200 cycles - Initial resistance) / Initial resistance × 100

[0271]

[0272] Capacity retention rate (%) Resistance increase rate (%) Example 19318 Example 29020 Example 39220 Example 48917 Comparative example 17433 Comparative example 28423 Comparative example 37631 Comparative example 48324 Comparative example 58121 Comparative example 68627

[0273]

[0274] Referring to Table 1 above, it can be confirmed that Examples 1 to 4 using the non-aqueous electrolyte according to the present invention exhibited a high-temperature cycle charge / discharge performance that was significantly superior to that of Comparative Examples 1 to 6.

[0275]

[0276] Experimental Example 2: Evaluation of High-Temperature Storage Performance

[0277] The lithium secondary batteries manufactured in Examples 1 to 4 and Comparative Examples 1 to 6 above were charged to 4.4 V, 0.05 C using an electrochemical charger / discharger at 25°C under CC / CV, 0.33 C conditions and discharged to 2.5 V under CC, 0.33 C conditions to perform initial charging / discharging. Afterwards, they were charged to 4.4 V, 0.05 C under CC / CV, 0.33 C conditions at 25°C and stored at 60°C for 8 weeks.

[0278]

[0279] (1) Capacity retention rate

[0280] After 8 weeks of storage, the lithium secondary battery was charged to 4.4 V, 0.05 C using an electrochemical charger / discharger at 25°C under CC / CV, 0.33 C conditions, and discharged to 2.5 V under CC, 0.33 C to measure the capacity during discharge.

[0281] The capacity retention rate was evaluated according to the following formula, and the results are shown in Table 2 below.

[0282]

[0283] Capacity retention rate (%) = (Discharge capacity after 8 weeks of storage / Initial discharge capacity) × 100

[0284]

[0285] (2) Resistance increase rate

[0286] After the initial charge and discharge above, the capacity was checked at room temperature, and then charged to 50% of SOC based on the discharge capacity, discharged for 10 seconds with a current of 2.5 C, and the resistance was measured based on the difference in voltage drop at this time, which was used as the initial resistance. After 8 weeks of storage at 60°C, the resistance was measured using the same method, which was used as the final resistance, and the resistance increase rate was calculated using the following formula. The results are shown in Table 2 below.

[0287]

[0288] Resistance increase rate (%) = (final resistance - initial resistance) / (initial resistance) × 100

[0289]

[0290] Capacity retention rate (%) Resistance increase rate (%) Example 19219 Example 28921 Example 38922 Example 49017 Comparative example 17336 Comparative example 28426 Comparative example 37832 Comparative example 48026 Comparative example 58324 Comparative example 68428

[0291]

[0292] Referring to Table 2 above, it can be confirmed that Examples 1 to 4 using the non-aqueous electrolyte according to the present invention exhibited significantly superior high-temperature storage characteristics compared to Comparative Examples 1 to 6.

[0293] FIG. 2 is a drawing for explaining an automobile (300) including a battery pack (200) composed of the lithium secondary battery (100) of FIG. 1.

[0294] Referring to FIG. 2, a vehicle (300) according to 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 a four-wheeled vehicle and a two-wheeled vehicle. The vehicle (300) operates by receiving power from the battery pack (200) according to one embodiment of the present invention.

[0295] Although the present disclosure has been described above with reference to embodiments thereof, it will be understood by those skilled in the art or having ordinary knowledge in the art that various modifications and changes to the various embodiments of the present disclosure may be made without departing from the technical scope of the various embodiments of the present disclosure as set forth in the claims below. Accordingly, the technical scope of the various embodiments of the present disclosure should not be limited to the contents described in the detailed description of the specification, but should be defined by the claims.

Claims

1. Contains lithium salt, organic solvent and additives, The above additive is a non-aqueous electrolyte containing a compound represented by the following chemical formula 1: [Chemical Formula 1] In the above chemical formula 1, L1 is an alkylene group having 1 to 10 carbon atoms, and L2 is a direct bond or *-C(R 25 )(R 26 )-*, and L3 is a direct bond or *-C(R 35 )(R 36 )-* and, R1 is an unsaturated hydrocarbon group having 2 to 10 carbon atoms, R 21 , R 22 , R 23 , R 24 , R 25 , R 26 , R 31 , R 32 , R 33 , R 34 , R 35 , R 36 , and R4 are each independently hydrogen or an alkyl group having 1 to 5 carbon atoms, and * is a bonding site.

2. In claim 1, The above R1 is a non-aqueous electrolyte which is a substituent selected from the following chemical formulas 1-a and 1-b: [Chemical Formula 1-a] [Chemical Formula 1-b] In the above chemical formula 1-a, R a is hydrogen or an alkyl group having 1 to 5 carbon atoms, and * is a bonding site.

3. In claim 1, The compound represented by the above chemical formula 1 is a non-aqueous electrolyte comprising at least one compound selected from the compounds represented by the following chemical formulas 1-1 to 1-8: [Chemical Formula 1-1] [Chemical Formula 1-2] [Chemical Formula 1-3] [Chemical Formula 1-4] [Chemical Formula 1-5] [Chemical Formula 1-6] [Chemical Formula 1-7] [Chemical Formula 1-8] .

4. In claim 1, The above additive is a non-aqueous electrolyte containing a compound represented by the above chemical formula 1 in an amount of 0.01% to 10% by weight based on the weight of the non-aqueous electrolyte.

5. In claim 1, The additive further comprises at least one additional additive selected from the group consisting of coumarine, fluoroethylene carbonate, propane sultone, propene sultone, succinonitrile, adiponitrile, ethylene sulfate, LiDFP (Lithium difluoro phosphate), LiBF4 (Lithium tetrafluoroborate), LiBOB (Lithium bis-(oxalato)borate), TMSPa (Tris(trimethylsilyl) Phosphate), TMSPi (Tris(trimethylsilyl) Phosphite), a compound represented by the following chemical formula 2, and a compound represented by the following chemical formula 3: [Chemical Formula 2] [Chemical Formula 3] In the above chemical formula 3, R5 comprises a halogen, a nitrile group, a propargyl group, an ester group, an ether group, a ketone group, a carboxyl group, an alkyl group, an alkenyl group, a substituted or unsubstituted alkynyl group, an alkoxy group, a boron group, a borate group, an isocyanate group, an isothiocyanate group, a silyl group, a siloxane group, a sulfone group, a sulfonate group, a sulfate group, or a combination of two or more thereof, and n is an integer selected from 0 to 6.

6. In claim 1, The above lithium salts are LiCl, LiBr, LiI, LiBF4, LiClO4, LiAlO4, LiAlCl4, LiPF6, LiSbF6, LiAsF6, LiB 10 Cl 10 , a non-aqueous electrolyte comprising at least one selected from LiBOB (LiB(C2O4)2), LiCF3SO3, LiFSI (LiN(SO2F)2), LiCH3SO3, LiCF3CO2, LiCH3CO2, and LiBETI (LiN(SO2CF2CF3)2).

7. In claim 1, A non-aqueous electrolyte wherein the lithium salt is included in the non-aqueous electrolyte at a molar concentration of 0.5 M to 5.0 M.

8. In claim 1, A non-aqueous electrolyte comprising at least one organic solvent selected from a cyclic carbonate organic solvent, a linear carbonate organic solvent, a linear ester organic solvent, and a cyclic ester organic solvent.

9. Bipolar; A cathode opposite to the anode; A separator interposed between the positive electrode and the negative electrode; and A lithium secondary battery comprising a non-aqueous electrolyte according to claim 1.

10. In claim 9, The above positive electrode includes a positive electrode active material, The above positive electrode active material is a lithium secondary battery including a lithium transition metal oxide represented by the following chemical formula A: [Chemical Formula A] Li 1+x [Ni a Co b Mr c M d ]O2 In the above chemical formula 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, 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.

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