Non-aqueous electrolyte and lithium secondary battery comprising the same

Abstract

The present invention relates to a non-aqueous electrolyte and a lithium secondary battery comprising the same. The non-aqueous electrolyte of the present invention comprises a lithium salt, a non-aqueous organic solvent, and an additive, wherein the additive can include a compound represented by Formula 1.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to Korean Patent Application No. 10-2024-0153869, filed November 1, 2024, and Korean Patent Application No. 10-2025-0157235, filed October 27, 2025, the entire contents of which are incorporated herein by reference. Technical Field

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

[0004] With modern society's increasing reliance on electricity, the development of high-capacity energy storage devices capable of providing stable power and increasing output has become a focus of attention. Furthermore, the increasing performance of electronic products, ranging from small devices like mobile phones to medium to large electronic devices such as electric vehicles, has led to a growing demand for high-capacity portable power supplies. Lithium-ion batteries, with their highest potential, meet the requirements for high-capacity energy storage and are therefore already used in various scenarios, from small electronic devices to electric vehicles (EVs) and energy storage devices (ESS).

[0005] A typical lithium-ion secondary battery includes: a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, an electrolyte serving as a lithium-ion transport medium, and a separator. In this case, carbon-based active materials, silicon-based active materials, lithium transition metal oxides, lithium metal, etc., can be used as negative electrode active materials. Furthermore, lithium transition metal oxides (e.g., lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium nickel-cobalt-manganese composite oxide) or lithium iron phosphate can be used as positive electrode active materials.

[0006] When a lithium-ion battery is charged, lithium ions are generated from the positive electrode and can be stacked or alloyed and stored in the negative electrode. The discharge process can occur in the opposite direction. Theoretically, the movement of lithium ions towards the positive and negative electrodes during charging and discharging should be reversible; however, the actual movement of lithium within the battery can be partially irreversible. Specifically, the medium through which lithium ions can be transported is the electrolyte. During charging, most lithium ions are deposited / alloyed within the negative electrode active material, but some are reduced along with the organic and inorganic materials constituting the electrolyte, forming nanoscale organic and inorganic composites on the surface of the negative electrode material. This organic and inorganic film is called the solid electrolyte interphase (SEI) layer. On the surface of the positive electrode active material, the solid electrolyte interphase can also be formed through oxidation reactions of the electrolyte-forming materials.

[0007] Although such a solid-electrolyte interface layer causes irreversible permanent loss of lithium ions supplied by the positive electrode during formation, this irreversible loss is reduced after formation, and the driving potential of the electrolyte is largely ensured, allowing lithium ions to move smoothly and reversibly between the positive and negative electrodes. Depending on its composition, such a solid-electrolyte interface layer can also help lower the energy barrier required for lithium ions to transfer charge to either the positive or negative electrode. Alternatively, the lifespan characteristics and durability of the lithium secondary battery can be determined based on its stability.

[0008] On the other hand, as the application of lithium secondary batteries has expanded to medium-sized power sources, such as medium and large power sources, such as power tools, electric bicycles, hybrid electric vehicles (HEVs) and plug-in hybrid electric vehicles (PHEVs), as well as portable power sources, such as mobile phones, laptops, digital cameras and portable camcorders, high drive voltages are required to achieve high energy density.

[0009] However, when operating continuously at high voltages, not only is the electrolyte consumed due to the oxidative decomposition reaction between the positive electrode and the electrolyte, but the passivation film on the electrode surface also collapses. This leads to problems such as gas generation caused by side reactions in the electrolyte solution and the elution of transition metals from the positive electrode, resulting in a deterioration in the battery's long-life performance. Such problems are exacerbated or accelerated by exothermic reactions that occur during battery operation.

[0010] Therefore, in order to improve the high-voltage driving performance of lithium secondary batteries, enhancing the stability of the solid-electrolyte interface layer formed on the surfaces of the positive and negative electrodes has become an important task. Summary of the Invention

[0011] [Technical Issues]

[0012] The purpose of this invention is to solve the above-mentioned problems and to provide a non-aqueous electrolyte that can improve the stability of the solid-electrolyte interface layer formed on the negative and positive electrodes.

[0013] Furthermore, the present invention provides a lithium secondary battery with improved high-temperature durability comprising the aforementioned non-aqueous electrolyte.

[0014] [Technical Solution]

[0015] [1] This invention provides a non-aqueous electrolyte comprising a lithium salt, a non-aqueous organic solvent, and an additive, wherein the additive comprises a compound represented by Formula 1: [Formula 1]

[0016] In Formula 1, R1 and R2 are each independently hydrogen or an alkyl group having 1 to 5 carbon atoms.

[0017] [2] In the above [1], the present invention provides a non-aqueous electrolyte, wherein, in Formula 1, R1 and R2 are each independently hydrogen or an alkyl group having 1 to 3 carbon atoms.

[0018] [3] In [1] or [2] above, the present invention provides a non-aqueous electrolyte, wherein the compound represented by Formula 1 is at least one selected from the compounds represented by Formulas 1A to 1D. [Formula 1A]

[0019] [Formula 1B]

[0020] [Formula 1C]

[0021] [Formula 1D] .

[0022] [4] In at least one of [1] to [3] above, the present invention provides a non-aqueous electrolyte, wherein the content of the compound represented by Formula 1 is from 0.01% by weight to 13.0% by weight based on the total weight of the non-aqueous electrolyte.

[0023] [5] In at least one of [1] to [4] above, the present invention provides a non-aqueous electrolyte, wherein the content of the compound represented by Formula 1 is from 0.01% by weight to 5.0% by weight based on the total weight of the non-aqueous electrolyte.

[0024] [6] In at least one of [1] to [5] above, the present invention provides a non-aqueous electrolyte, wherein the additive further comprises a lithium salt compound.

[0025] [7] In the above [6], the present invention provides a non-aqueous electrolyte, wherein the lithium salt compound is at least one selected from lithium bis(oxalate)borate (LiB(C2O4)2, LiBOB), lithium difluoro(oxalate)borate (LiDFOB), lithium difluorophosphate (LiPO2F2, LiDFP) and lithium difluoro(bis(oxalate)phosphate (LiDFOP).

[0026] [8] In [6] or [7] above, the present invention provides a non-aqueous electrolyte, wherein the content of the lithium salt compound is from 0.01% by weight to 10.0% by weight based on the total weight of the non-aqueous electrolyte.

[0027] [9] In at least one of [1] to [8] above, the present invention provides a non-aqueous electrolyte, wherein the non-aqueous electrolyte further comprises at least one auxiliary additive selected from cyclic carbonate compounds, halogenated carbonate compounds, sulfonyl lactone compounds, sulfate ester / salt compounds, phosphate ester / salt compounds, borate ester / salt compounds, nitrile compounds, benzene compounds, amine compounds and silane compounds.

[0028]

[10] The present invention provides a lithium secondary battery comprising a positive electrode, a negative electrode facing the positive electrode, a separator disposed between the negative electrode and the positive electrode, and the non-aqueous electrolyte described in [1] above.

[0029] [Beneficial Effects]

[0030] The non-aqueous electrolyte of the present invention can contain selenium-based compounds as additives, thereby forming an inorganic film with excellent durability on the surfaces of the positive and negative electrodes. When this non-aqueous electrolyte of the present invention is applied to a lithium secondary battery, it can improve the structural stability of the positive electrode under high voltage conditions and suppress side reactions between the negative electrode and the electrolyte, thereby improving high-temperature durability. Detailed Implementation

[0031] It should be understood that the words or terms used in the specification and claims are only for describing exemplary embodiments and should not be construed as limited to the meanings defined in common dictionaries. Rather, they should be interpreted as having a concept consistent with the technical concept of the invention, based on the principle that the inventors can appropriately define the concepts of the terms to best interpret the invention.

[0032] For example, it should also be understood that in this specification, the terms “comprising,” “including,” or “having” are intended to specify the presence of the said features, numbers, steps, elements, or combinations thereof, but do not exclude the presence or addition of one or more other features, numbers, steps, elements, or combinations thereof.

[0033] Furthermore, when describing "a to b carbon atoms" in this specification, "a" and "b" each refer to the number of carbon atoms contained in a specific functional group. That is, a functional group may include "a" to "b" carbon atoms. For example, "alkylene with 1 to 5 carbon atoms" refers to an alkylene containing 1 to 5 carbon atoms, namely -CH2-, -CH2CH2-, -CH2CH2CH2-, -CH2(CH3)CH-, -CH2CH2CH2CH2CH2-, and -CH(CH3)CH2CH2-.

[0034] Furthermore, in this specification, the term "alkylene" refers to a branched or unbranched aliphatic hydrocarbon group or a functional group in the form of a group having a hydrogen atom removed from each of the carbon atoms at both ends of the aliphatic hydrocarbon group. In one embodiment, the alkylene group may be substituted or unsubstituted. Alkylene groups include, but are not limited to, methylene, ethylene, propylene, isopropylene, butylene, isobutylene, tert-butylene, pentylene, 3-pentylene, etc., and in other embodiments, they may optionally be substituted.

[0035] Unless otherwise defined in the specification, the term "substitution" means that at least one hydrogen atom bonded to carbon is replaced by another element, such as fluorine.

[0036] Furthermore, unless otherwise stated in this invention, the term " "The connecting part between the ends of the expression."

[0037] Furthermore, in this specification, unless otherwise expressly stated, the expression "%" indicates weight.

[0038] The invention will be described in more detail below.

[0039] The non-aqueous electrolyte and lithium secondary battery of the present invention may include at least one of the following disclosed components, and may include any combination of the following technically possible components.

[0040] Non-aqueous electrolytes

[0041] This invention relates to non-aqueous electrolytes, and more particularly to non-aqueous electrolytes for lithium secondary batteries.

[0042] Specifically, the non-aqueous electrolyte of the present invention comprises a lithium salt, a non-aqueous organic solvent, and an additive, wherein the additive may include a compound represented by Formula 1: [Formula 1]

[0043] In Formula 1, R1 and R2 are each independently hydrogen or an alkyl group having 1 to 5 carbon atoms.

[0044] The non-aqueous electrolyte of the present invention contains a selenium-based compound that replaces nitrogen dioxide (NO2) as an additive, thereby enabling the formation of a highly durable inorganic film on the surfaces of the positive and negative electrodes. Therefore, when the non-aqueous electrolyte of the present invention is applied to lithium secondary batteries, high-voltage and high-temperature durability can be improved.

[0045] (1) Lithium salts

[0046] As the lithium salt used in this invention, various lithium salts commonly used in non-aqueous electrolytes of lithium secondary batteries can be used without limitation. For example, the lithium salt may include Li + As a cation, and may include F - Cl - ,Br - I - NO3 - N(CN)2 - BF4 - ClO4 - B 10 Cl 10 - AlCl4 - AlO4 - PF6 - CF3SO3 - CH3CO2 - CF3CO2 - AsF6 - SbF6 - CH3SO3 - (CF3CF2SO2)2N - (CF3SO2)2N - (FSO2)2N - BF2C2O4 - BC4O8 - PF4C2O4 - PF2C4O8 - (CF3)2PF4 - (CF3)3PF3 - (CF3)4PF2 - (CF3)5PF - (CF3)6P - C4F9SO3 - CF3CF2SO3 - CF3CF2(CF3)2CO - (CF3SO2)2CH - and CF3(CF2)7SO3 - At least one of them is used as an anion.

[0047] Specifically, lithium salts may include a single material selected from the group consisting of: LiCl, LiBr, LiI, LiBF4, LiClO4, LiB 10 Cl 10The lithium salt comprises at least one of the following: LiAlCl4, LiAlO4, LiPF6, LiCF3SO3, LiCH3CO2, LiCF3CO2, LiAsF6, LiSbF6, LiCH3SO3, LiN(SO2F)2 (lithium bis(fluorosulfonyl)imide, LiFSi), LiN(SO2CF2CF3)2 (lithium bis(perethylfluorosulfonyl)imide, LiBETI), and LiN(SO2CF3)2 (lithium bis(trifluoromethanesulfonyl)imide, LiTFSi). Specifically, the lithium salt comprises at least one selected from the group consisting of LiBF4, LiClO4, LiPF6, LiBOB (LiB(C2O4)2), LiCF3SO3, LiTFSI (LiN(SO2CF3)2), LiFSI ((LiN(SO2F)2) and LiBETI (LiN(SO2CF2CF3)2).

[0048] The lithium salts mentioned above can be appropriately varied within the generally available range, but can be included in the electrolyte at a concentration of 0.8 M to 4.0 M, specifically 1.0 M to 3.0 M, to achieve the best effect in forming an anti-corrosion film on the electrode surface.

[0049] When the concentration of lithium salt is within the above range, the viscosity of the non-aqueous electrolyte can be controlled to achieve optimal impregnation and improve the mobility of lithium ions, thereby improving the capacity and cycle characteristics of lithium secondary batteries.

[0050] (2) Non-aqueous organic solvents

[0051] Non-aqueous organic solvents are commonly used in lithium secondary batteries and are not restricted, as long as decomposition caused by oxidation reactions during battery charging and discharging can be minimized.

[0052] Non-aqueous organic solvents may be included in the non-aqueous electrolyte in the remainder, except for, for example, lithium salts and additives.

[0053] Specifically, non-aqueous organic solvents may include carbonate organic solvents. Carbonate organic solvents may specifically include at least one selected from (i) cyclic carbonate organic solvents and (ii) linear carbonate organic solvents, and more specifically may include (iii) mixed solvents of cyclic carbonate organic solvents and linear carbonate organic solvents.

[0054] (i) Cyclic carbonate organic solvents are organic solvents with high viscosity and are organic solvents that can well dissociate lithium salts in electrolytes due to their high dielectric constant. Specific examples may include at least one organic solvent selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentene carbonate, 2,3-pentene carbonate and vinylene carbonate, and specifically may include at least one of ethylene carbonate and propylene carbonate.

[0055] (ii) Linear carbonate organic solvents are organic solvents with low viscosity and low dielectric constant. Typical examples may include at least one organic solvent selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate and ethyl propyl carbonate, and specifically may include at least one of dimethyl carbonate and ethyl methyl carbonate.

[0056] The non-aqueous electrolyte of the present invention may use a mixture of (iii) cyclic carbonate organic solvents and linear carbonate organic solvents to ensure high ionic conductivity, wherein the cyclic carbonate organic solvents and linear carbonate organic solvents may be mixed in a volume ratio of 10:90 to 50:50, specifically 20:80 to 40:60.

[0057] In addition to carbonate organic solvents, the non-aqueous electrolyte of the present invention may further include at least one organic solvent selected from (iv) linear ester organic solvents and (v) cyclic ester organic solvents, which has a lower melting point and higher stability at high temperatures compared with cyclic carbonate organic solvents and / or linear carbonate organic solvents.

[0058] (iv) Common examples of straight-chain ester organic solvents may be at least one organic solvent selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate and butyl propionate, and specifically may include at least one of ethyl propionate and propyl propionate.

[0059] (v) Cyclic ester organic solvents may include at least one organic solvent selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone and ε-caprolactone.

[0060] The organic solvent may consist solely of carbonate-based organic solvents. Even using only carbonate-based organic solvents is preferred because the non-aqueous electrolyte component (e.g., the additives described below) can be readily dissolved, and the mobility of the lithium salt and the appropriate viscosity of the non-aqueous electrolyte can be achieved.

[0061] Furthermore, unless otherwise stated, the remaining portion of the non-aqueous electrolyte of the present invention, excluding lithium salt, electrolyte additives and auxiliary additives as described below, may be entirely organic solvents.

[0062] (3) Additives

[0063] The non-aqueous electrolyte of the present invention may include compounds represented by Formula 1.

[0064] [Formula 1]

[0065] In Formula 1, R1 and R2 are each independently hydrogen or an alkyl group having 1 to 5 carbon atoms.

[0066] The compound represented by Formula 1 is a 1,3,2-dioxane-2-oxide compound with a substituted nitro (-NO2) group. In its heterocyclic structure containing two or more oxygen elements, it contains selenium (Se) elements that strongly interact with metals. Therefore, when the electron density around the selenium element decreases, a ring-opening reaction easily occurs around it. After the ring-opening reaction, a polymer film containing LiSe2 and SeO bonds and a certain degree of oxygen (O) can be formed on the cathode surface through electrochemical reduction and recombination reactions. This improves Li ion transfer characteristics and effectively suppresses the elution of transition metals from the cathode by preventing side reactions between the electrolyte and the cathode. Therefore, compared to selenium compounds without oxygen in their structure (such as selenophene), a film with excellent Li ion transfer characteristics is formed, resulting in improved output characteristics due to reduced interfacial resistance and increased charge / discharge efficiency.

[0067] Furthermore, compared to the nitro-free (-NO2) 1,3,2-dioxane-2-oxide represented by Formula 4 below, or to compounds with a nitro group (-NO2) substituted at the ortho position of selenium, the compound represented by Formula 1 above has a symmetrically positioned electron configuration in its ring structure, thus enabling it to readily participate in film formation. As a result, a more robust nitrogen-containing inorganic film can be formed on the negative electrode surface. Therefore, the stability of the solid-electrolyte interface layer can be further enhanced to prevent side reactions between the negative electrode and the electrolyte, and to prevent the electrodeposition of transition metal ions eluted from the positive electrode onto the negative electrode surface, thereby preparing a lithium secondary battery with excellent high-temperature durability and minimized reversible lithium-ion loss.

[0068] [Formula 4]

[0069] Meanwhile, in Formula 1 above, R1 can be hydrogen or an alkyl group having 1 to 3 carbon atoms, specifically hydrogen or an alkyl group having 1 or 2 carbon atoms.

[0070] Meanwhile, in Formula 1, R2 can be hydrogen or an alkyl group having 1 to 3 carbon atoms, specifically hydrogen or an alkyl group having 1 or 2 carbon atoms.

[0071] Specifically, the compound represented by Formula 1 above can be at least one selected from the compounds represented by Formulas 1A to 1D below.

[0072] [Formula 1A]

[0073] [Formula 1B]

[0074] [Formula 1C]

[0075] [Formula 1D] .

[0076] Specifically, the content of the compound represented by Formula 1 in the non-aqueous electrolyte can be 0.01% by weight or more, 0.02% by weight or more, 0.03% by weight or more, 0.04% by weight or more, 0.05% by weight or more, 0.06% by weight or more, 0.07% by weight or more, 0.08% by weight or more, 0.09% by weight or more, or 1.0% by weight or more. Furthermore, the content of the compound represented by Formula 1 in the non-aqueous electrolyte can be 13% by weight or less, 12% by weight or less, 11% by weight or less, 10% by weight or less, 9% by weight or less, 8% by weight or less, 7% by weight or less, 6% by weight or less, 5% by weight or less, or 4% by weight or less.

[0077] The above ranges can be combined with each other without limitation. For example, the content of the compound represented by Formula 1 above in a non-aqueous electrolyte can be from 0.01 wt% to 13.0 wt%, or from 0.01 wt% to 5.0 wt%, or from 0.1 wt% to 3.0 wt%.

[0078] When the compound represented by Formula 1 satisfies the above numerical range, a strong inorganic film containing lithium-selenium (LiSe2), selenium-oxygen (Se-O), lithium-nitrogen (Li3N) bonds can be uniformly formed on the surfaces of the positive and negative electrodes, while suppressing problems such as side reactions caused by additives, reduced capacity, and increased resistance to the greatest extent possible. As a result, side reactions between the electrolyte and the electrode, the elution of transition metals from the positive electrode, and the electrodeposition of transition metals on the surface of the negative electrode can be effectively suppressed, thereby achieving excellent high voltage and high temperature durability.

[0079] Additives may further include lithium salt compounds.

[0080] When lithium salt compounds and selenium-based compounds are used in combination, Li ions can be supplied smoothly to stably form a lithium-based inorganic film on the negative electrode surface. Specifically, because the anions of the lithium salt compounds, similar to those of the selenium-based compounds, form a strong interaction with the positive electrode surface and participate in the positive electrode film formation reaction together with the selenium-based compounds, a more robust film with improved coverage properties can be formed. Furthermore, when lithium salt compounds are further included as additives, the compound represented by Formula 1 above can be referred to as the first additive, and the lithium salt compound can be referred to as the second additive.

[0081] Such lithium salt compounds are compounds that differ from lithium salts contained in electrolytes, and examples may include at least one selected from lithium bis(oxalate)borate (LiB(C2O4)2, LiBOB), lithium difluoro(oxalate)borate (LiDFOB), lithium difluorophosphate (LiPO2F2, LiDFP), and lithium difluoro(bis(oxalate)phosphate) (LiDFOP). Specifically, lithium salt compounds may include lithium difluorophosphate (LiPO2F2, LiDFP).

[0082] Specifically, based on the total weight of the non-aqueous electrolyte, the content of lithium salt compounds can be 0.01% by weight or more, 0.02% by weight or more, 0.03% by weight or more, 0.04% by weight or more, 0.05% by weight or more, 0.06% by weight or more, 0.07% by weight or more, 0.08% by weight or more, 0.09% by weight or more, or 1.0% by weight or more. Furthermore, based on the total weight of the non-aqueous electrolyte, the content of the compound represented by Formula 1 above can be 10% by weight or less, 9% by weight or less, 8% by weight or less, 7% by weight or less, 6% by weight or less, 5% by weight or less, 4% by weight or less, or 3% by weight or less.

[0083] The above ranges can be combined with each other without limitation. For example, based on the total weight of the non-aqueous electrolyte, the content of lithium salt compounds can be from 0.01 wt% to 10.0 wt%, or from 0.01 wt% to 5.0 wt%, or from 0.1 wt% to 3.0 wt%.

[0084] When the content of lithium salt compounds meets the above range, they can form a stable Li-based inorganic film on the surface of the positive and negative electrodes together with selenium-based compounds. This film effectively inhibits the elution of oxygen or transition metals from the positive electrode and prevents side reactions between the negative electrode and the electrolyte, thereby achieving excellent high voltage and high temperature durability.

[0085] Meanwhile, to prevent the electrolyte from decomposing in a high-output environment and causing the negative electrode to collapse, or to further improve the low-temperature high-rate discharge characteristics, high-temperature stability, overcharge protection, and battery expansion suppression effect at high temperatures, the non-aqueous electrolyte of the present invention may, if necessary, further include other auxiliary additives in the above electrolyte. When auxiliary additives are further included in the non-aqueous electrolyte, the compound represented by Formula 1 above may be called the first additive, and the auxiliary additive may be called the second additive. Furthermore, when both lithium salt compounds and auxiliary additives are included as electrolyte additives, the compound represented by Formula 1 above may be called the first additive, the lithium salt compound may be called the second additive, and the auxiliary additive may be called the third additive.

[0086] The auxiliary additives may include at least one selected from cyclic carbonates, halogenated carbonates, sulfonyl lactones, sulfates / salts, phosphates / salts, borates / salts, nitriles, benzenes, amines, and silanes, and the phosphates / salts and borates / salts may include compounds having a structure different from that of the lithium salts described above.

[0087] Cyclic carbonate compounds may include vinylene carbonate (VC) or vinyl ethylene carbonate.

[0088] Halogenated carbonate compounds can include fluoroethylene carbonate (FEC).

[0089] Sulfolactone compounds may include at least one compound selected from 1,3-propanesulfonyl lactone (PS), 1,4-butanesulfonyl lactone, ethanesulfonyl lactone, 1,3-propenesulfonyl lactone (PRS), 1,4-butenesulfonyl lactone, and 1-methyl-1,3-propenesulfonyl lactone.

[0090] Sulfate / ester compounds may include ethylene sulfate (Esa), trimethylol sulfate (TMS), or methyltrimethylol sulfate (MTMS).

[0091] Phosphate ester / salt compounds may include one or more compounds selected from lithium difluoro(bis(oxalate)phosphate), lithium difluorophosphate, tris(trimethylsilyl)phosphate, tris(2,2,2-trifluoroethyl)phosphate and tris(trifluoroethyl)phosphate.

[0092] Borate / ester compounds may include tetraphenylborate.

[0093] Nitrile compounds may include at least one compound selected from butadionitrile, adiponitrile, acetonitrile, propionitrile, butadionitrile, valerate, octanoic acid, heptanoic acid, cyclopentaneformitrile, cyclohexaneformitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile.

[0094] Benzene compounds can include fluorobenzene, and amine compounds can include triethanolamine, ethylenediamine, etc. Silane compounds can include tetravinylsilane.

[0095] In the presence of vinylene carbonate, vinyl ethylene carbonate, or succinate among these auxiliary additives, a more robust SEI film can be formed on the negative electrode surface during the initial activation process of the secondary battery.

[0096] The auxiliary additives can be used in the form of a mixture of two or more, and their content can be less than 30% by weight, specifically from 0.01% to 10.0% by weight, preferably from 0.05% to 5.0% by weight, based on the total weight of the electrolyte. If the content of the auxiliary additives is less than 0.01% by weight, the effect of improving the low-temperature output, high-temperature storage characteristics, and high-temperature life characteristics of the battery is not significant, and if the content of the auxiliary additives is greater than 30% by weight, excessive side reactions may occur in the electrolyte during the charging and discharging of the battery. In particular, if the additives used to form the SEI film are added in excess, the additives may not decompose sufficiently at high temperatures, so that they may exist in the form of unreacted materials, or may precipitate in the electrolyte at room temperature. Therefore, side reactions that reduce the life or resistivity characteristics of the secondary battery may occur.

[0097] Lithium secondary batteries

[0098] Furthermore, the present invention provides a lithium secondary battery comprising the aforementioned non-aqueous electrolyte.

[0099] Specifically, the lithium secondary battery of the present invention may include a positive electrode, a negative electrode facing the positive electrode, a separator disposed between the negative electrode and the positive electrode, and a non-aqueous electrolyte. The electrolyte may be the electrolyte for the lithium secondary battery of the present invention described above.

[0100] After accommodating an electrode assembly comprising a positive electrode, a negative electrode facing the positive electrode, and a separator disposed between the positive and negative electrodes in a battery case, a lithium secondary battery can be prepared by injecting the aforementioned non-aqueous electrolyte for lithium secondary batteries of the present invention into it.

[0101] Since non-aqueous electrolytes have already been described above, the positive electrode, negative electrode, and membrane will be described below.

[0102] (1) Positive electrode

[0103] The positive electrode can include positive electrode active materials.

[0104] The positive electrode active material is a compound capable of reversible insertion and extraction, and is not particularly limited, as long as it is a positive electrode active material used in the art. Specifically, it can include lithium metal composite oxides. More specifically, lithium metal composite oxides can be: layered compounds, such as lithium cobalt oxide (LiCoO2), 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-c1 O4 (0≤c1≤0.33), LiMnO3, LiMn2O3 and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides, such as LiV3O8, V2O5 and Cu2V2O7; and LiNi 1-c2 M c2 O2 represents nickel-site lithium nickel oxide (where M is selected from at least one of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, and satisfies 0.01 ≤ c2 ≤ 0.3); LiMn 2-c3 M c3 Lithium manganese composite oxides represented by O2 (where M is selected from at least one of Co, Ni, Fe, Cr, Zn and Ta, and satisfies 0.01≤c3≤0.1) or Li2Mn3MO8 (where M is selected from at least one of Fe, Co, Ni, Cu and Zn), etc., but not limited to these. The positive electrode can be a lithium metal positive electrode.

[0105] Specifically, the lithium metal composite oxide may include at least one selected from lithium cobalt oxide (LiCoO2), lithium nickel cobalt manganese oxide, lithium-rich manganese oxide, and lithium iron phosphate, and most preferably may include lithium nickel cobalt manganese oxide.

[0106] Lithium nickel cobalt manganese oxide can be represented by the following formula 2.

[0107] [Equation 2]

[0108] Li 1+a Ni x Co y M 1 z M 2 w O2

[0109] In Equation 2, M 1 It is Mn, Al, or a combination thereof. M 2is at least one selected from the group consisting of Al, Zr, W, Ti, Mg, Ca and Sr, wherein 0≤a≤0.5, 0.55<x<1.0, 0<y≤0.4, 0<z≤0.4, 0≤w≤0.1.

[0110] Here, x+y+z+w may be 1.

[0111] In the above Formula 2, 1+a represents the molar ratio of lithium in the lithium-nickel-cobalt-manganese composite oxide, and may satisfy 0≤a≤0.5, preferably 0≤a≤0.2, more preferably 0≤a≤0.1.

[0112] In the above Formula 2, x represents the molar ratio of nickel among all transition metals excluding lithium in the lithium-nickel-cobalt-manganese composite oxide, and may satisfy 0.55<x<1.0, specifically 0.6≤x≤0.98, more specifically 0.6≤x≤0.95.

[0113] In the above Formula 2, y represents the molar ratio of cobalt among all transition metals excluding lithium in the lithium-nickel-cobalt-manganese composite oxide, and may satisfy 0<y≤0.4, specifically 0<y≤0.3, and more specifically 0.05≤y≤0.3.

[0114] In the above Formula 2, z represents the molar ratio of element M among all transition metals excluding lithium in the lithium-nickel-cobalt-manganese composite oxide 1 , and may satisfy 0<z≤0.4, more preferably 0<z≤0.3, and still more preferably 0.01≤z≤0.3.

[0115] In the above Formula 2, w represents the molar ratio of element M among all transition metals excluding lithium in the lithium-nickel-cobalt-manganese composite oxide 2 , and may satisfy 0<w≤0.1, preferably 0<w≤0.05, more preferably 0<w≤0.02.

[0116] The lithium-nickel-cobalt-manganese composite oxide may be Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2, Li(Ni 0.7 Mn 0.2 Co 0.1 )O2, Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, Li(Ni 0.8 Co 0.15 Al 0.05 )O2, Li(Ni 0.86 Mn 0.07 Co0.05 Al 0.02 O2, Li(Ni) 0.90 Mn 0.05 Co 0.05 O2 or Li(Ni) 0.9 Mn 0.03 Co 0.06 Al 0.01 (O2), with a Ni content of 0.55 atm% or higher, to obtain high-capacity batteries.

[0117] Meanwhile, the positive electrode active material can be in particulate form. Specifically, the average particle size (D) of the positive electrode active material... 50 The diameter can range from 1 μm to 30 μm.

[0118] To improve the capacity of the positive electrode active material layer, the content of the positive electrode active material in the positive electrode active material layer can be from 70% to 99% by weight, specifically from 80% to 98% by weight.

[0119] The positive electrode may include a positive electrode current collector and a layer of positive electrode active material disposed on at least one surface of the positive electrode current collector.

[0120] The positive electrode active material layer may contain the aforementioned positive electrode active material.

[0121] Positive current collectors typically have a thickness of 3 to 500 μm.

[0122] Microscopic irregularities can be formed on the surface of the positive electrode current collector to improve the adhesion of the positive electrode active material. For example, the positive electrode current collector can be used in various shapes, such as membranes, sheets, foils, meshes, porous bodies, foams, non-woven fabrics, etc.

[0123] The positive electrode active material layer can be disposed on at least one surface of the positive electrode current collector. Specifically, the positive electrode active material layer can be disposed on one or both surfaces of the positive electrode current collector.

[0124] To ensure sufficient capacity of the positive electrode active material layer, the content of the positive electrode active material in the positive electrode active material layer can be 70% to 99% by weight, preferably 80% to 98% by weight.

[0125] In addition to the aforementioned positive electrode active material, the positive electrode active material layer may further include an adhesive and / or a conductive material.

[0126] Adhesives improve the adhesion between positive electrode active material particles and between the positive electrode active material and the current collector. Examples of adhesives include any of the following: fluoropolymer adhesives, including polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); rubber adhesives, including styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, or styrene-isoprene rubber; cellulose adhesives, including carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, or regenerated cellulose; polyol adhesives, including polyvinyl alcohol; polyolefin adhesives, including polyethylene or polypropylene; polyimide adhesives; polyester adhesives; silane adhesives, or mixtures of two or more thereof.

[0127] Based on the total weight of the positive electrode active material layer, the content of the binder can be from 0.1% to 15.0% by weight, preferably from 0.1% to 10.0% by weight.

[0128] Conductive materials can be used to assist and improve the conductivity of secondary batteries, and are not particularly limited, as long as they are conductive and do not cause chemical changes. Specifically, positive electrode conductive materials may include: carbon black, such as carbon black, acetylene black (or Denka black), Ketjen black, channel black, furnace black, lamp black, or thermally cracked carbon black; graphite powder, such as natural graphite, artificial graphite, or graphite with a well-developed crystal structure; conductive fibers, such as carbon fibers or metal fibers; conductive powders, such as fluorocarbon powders, aluminum powders, or nickel powders; conductive whiskers, such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides, such as titanium oxide; polyphenylene derivatives, etc., and any one or a mixture of two or more of these may be used.

[0129] Based on the total weight of the positive electrode active material layer, the content of the conductive agent can be from 0.1% to 10.0% by weight, preferably from 0.1% to 5.0% by weight.

[0130] The thickness of the positive electrode active material layer can be from 5 μm to 500 μm, preferably from 20 μm to 200 μm.

[0131] The positive electrode can be manufactured by coating a positive electrode current collector with a positive electrode slurry containing a positive electrode active material and optional binders, conductive materials, and a positive electrode slurry, followed by drying and rolling. Alternatively, the positive electrode can be prepared by laminating the membrane onto the positive electrode current collector after preparing a membrane by mixing the positive electrode active material and optional binders, conductive materials, etc.

[0132] To facilitate the dispersion of the positive electrode active material, binder, and / or conductive material, the solvent for forming the positive electrode slurry may include, for example, at least one selected from distilled water, N-methylpyrrolidone, ethanol, methanol, and isopropanol, preferably N-methylpyrrolidone. Considering the coating thickness, manufacturing yield, and processability of the positive electrode material mixture, the amount of solvent used is sufficient and not particularly limited if the positive electrode material mixture can be adjusted to have an appropriate viscosity.

[0133] (2) Negative electrode

[0134] Next, the negative electrode will be explained.

[0135] The negative electrode may include a negative electrode active material.

[0136] The negative electrode active material is a compound capable of reversibly inserting and deintercalating lithium ions, and may include at least one selected from the group consisting of carbon-based active materials, (semi-)metal active materials and lithium metal, and specifically may include at least one selected from carbon-based active materials and (semi-)metal active materials.

[0137] Carbon-based active materials may include at least one selected from graphite, hard carbon, soft carbon, carbon black, graphene, and fibrous carbon, and preferably may include graphite. Graphite may be, for example, at least one selected from artificial graphite and natural graphite.

[0138] In terms of ensuring structural stability during charging and discharging and reducing side reactions with the electrolyte solution, the average particle size (D) of carbon-based active materials is crucial. 50 The diameter can be from 10 μm to 30 μm, preferably from 15 μm to 25 μm.

[0139] Specifically, the (semi)metal active material may include: at least one selected from Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Fe, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, V, Ti, and Sn; an alloy of lithium and at least one (semi)metal selected from Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Fe, 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, Fe, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, V, Ti, and Sn; lithium titanium oxide (LTO); lithium vanadium oxide; and so on.

[0140] More specifically, (semi)metal active materials may include silicon-based active materials.

[0141] The silicon-based active material may include at least one selected from compounds represented by SiOx (0≤x<2) and silicon-carbon composites. In the case of SiO2, since it does not react with lithium ions and therefore cannot store lithium, x is preferably within the above range. More preferably, the silicon-based active material may be SiO.

[0142] In terms of ensuring structural stability during charging and discharging and reducing side reactions with the electrolyte solution, the average particle size (D) of silicon-based active materials is crucial. 50 The diameter can range from 1 μm to 30 μm, preferably from 2 μm to 15 μm.

[0143] Furthermore, the negative electrode active material of the present invention may include carbon-based negative electrode active materials and silicon-based negative electrode active materials.

[0144] Here, the weight ratio of silicon-based anode active material to carbon-based anode active material can be from 1:99 to 30:70, preferably from 3:97 to 15:85. When the mixing ratio of silicon-based active material to carbon-based active material meets the above range, excellent cycle performance can be ensured because the volume expansion of silicon-based active material is suppressed and the capacity characteristics are improved.

[0145] Meanwhile, the negative electrode 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. The negative electrode active material may be contained within the negative electrode active material layer.

[0146] There are no particular restrictions on the negative electrode current collector, as long as it has high conductivity and does not cause adverse chemical changes in the battery. Specifically, copper, stainless steel, aluminum, nickel, titanium, sintered carbon, copper or stainless steel that has been surface-treated with one of carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloys can be used as negative electrode current collectors.

[0147] Negative current collectors typically have a thickness of 3 to 500 μm.

[0148] Microscopic irregularities can be formed on the surface of the negative electrode current collector to improve the adhesion of the negative electrode active material. For example, the negative electrode current collector can be used in various shapes, such as membranes, sheets, foils, meshes, porous bodies, foams, non-woven fabrics, etc.

[0149] The negative electrode active material layer can be disposed on at least one surface of the negative electrode current collector. Specifically, the negative electrode active material layer can be disposed on one or both surfaces of the negative electrode current collector.

[0150] To achieve sufficient capacity in a secondary battery while minimizing the effects of volume expansion / contraction on the battery, the negative electrode active material can be included in the negative electrode active material layer in an amount of 60% to 99% by weight.

[0151] In addition to the aforementioned negative electrode active material, the negative electrode active material layer may also contain conductive materials and / or adhesives.

[0152] The conductive material is a component used to further improve the conductivity of the negative electrode active material, wherein the conductive material can be added in an amount of less than 10% by weight, preferably less than 5% by weight, and specifically from 0.1% to 5% by weight based on the total weight of the negative electrode active material layer. Any conductive agent can be used without particular limitation, as long as it is conductive and does not cause adverse chemical changes in the battery. Examples include: carbon black, such as carbon black, acetylene black (or Denka black), Ketjen black, channel black, furnace black, lamp black, or thermally cracked carbon black; graphite powder, such as natural graphite, artificial graphite, or graphite with a well-developed crystal structure; conductive fibers, such as carbon fibers or metal fibers; conductive powders, such as fluorocarbon powders, aluminum powders, or nickel powders; conductive whiskers, such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides, such as titanium oxide; or polyphenylene derivatives.

[0153] Adhesives are components that facilitate adhesion between conductive materials, active materials, and current collectors, and examples of adhesives can be: fluoropolymer adhesives, including polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); rubber adhesives, including styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, or styrene-isoprene rubber; cellulose adhesives, including carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, or regenerated cellulose; polyol adhesives, including polyvinyl alcohol; polyolefin adhesives, including polyethylene or polypropylene; polyimide adhesives; polyester adhesives; and silane adhesives.

[0154] Based on the total weight of the negative electrode active material layer, the content of the binder can be from 0.1% to 15.0% by weight, preferably from 0.1% to 10.0% by weight.

[0155] The thickness of the negative electrode active material layer can be from 5 μm to 500 μm, preferably from 5 μm to 100 μm.

[0156] The negative electrode can be prepared by coating a negative electrode current collector with a negative electrode slurry, followed by drying and rolling. The negative electrode slurry comprises a negative electrode active material and optionally a binder, a conductive material, and a solvent for forming the negative electrode slurry. Alternatively, the negative electrode can be prepared by laminating the membrane onto the negative electrode current collector after preparing a membrane by mixing the negative electrode active material and optionally a binder, a conductive material, etc.

[0157] To promote the dispersion of the negative electrode active material, binder and / or conductive material, the solvent for forming the negative electrode slurry may include, for example, at least one selected from distilled water, N-methylpyrrolidone, ethanol, methanol and isopropanol, preferably distilled water.

[0158] (3) Diaphragm

[0159] The separator separates the negative and positive electrodes and provides a path for the movement of lithium ions. Any separator can be used without particular limitation, as long as it is commonly used in lithium secondary batteries. In particular, a separator with high electrolyte retention capacity and low resistance to lithium salt ion transport is preferred.

[0160] Specifically, porous polymer membranes can be used, such as porous polymer membranes prepared from polyolefin polymers (e.g., ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, ethylene / methacrylate copolymers, etc.), or laminated structures of two or more layers thereof. Alternatively, common porous nonwoven fabrics can be used, such as nonwoven fabrics formed from high-melting-point glass fibers or polyethylene terephthalate fibers. Furthermore, coated diaphragms including ceramic components or polymer materials can be used to ensure heat resistance or mechanical strength, and diaphragms with single-layer or multi-layer structures can be selectively used.

[0161] The lithium secondary battery of the present invention, as described above, is suitable for use in portable devices such as mobile phones, laptops and digital cameras, as well as electric vehicles such as hybrid electric vehicles (HEVs).

[0162] The shape of the lithium secondary battery of the present invention is not particularly limited, and it can be cylindrical, prismatic, pouch-shaped or coin-shaped.

[0163] The lithium secondary battery of the present invention can be used not only as a single cell for use as a power source for small devices, but also as a unit cell in medium and large battery modules comprising multiple single cells.

[0164] The invention will now be described in more detail with reference to embodiments. However, the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these exemplary embodiments are provided so that this description will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0165] Example

[0166] Example 1

[0167] (Preparation of non-aqueous electrolytes)

[0168] LiPF6 was dissolved in a non-aqueous organic solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 20:80 to achieve a LiPF6 concentration of 1.2 M. Then, a compound represented by Formula 1A was added as an electrolyte additive to prepare a non-aqueous electrolyte (see Table 1 below). The non-aqueous electrolyte contained 0.01% by weight of the compound represented by Formula 1A.

[0169] (Preparation of secondary batteries)

[0170] The positive electrode active material (Li(Ni) 0.8 Mn 0.1 Co 0.1 O2, 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 (solid content: 60.0 wt%). This positive electrode slurry was then coated onto a 13.5 μm thick positive electrode current collector (Al film), dried, and rolled to prepare the positive electrode.

[0171] A negative electrode slurry (solid content: 60 wt%) was prepared by adding the negative electrode active material (natural graphite), binder (SBR-CMC), and conductive material (carbon black) to water as a solvent in a weight ratio of 97.6:0.8:1.6. This negative electrode slurry was then coated onto a 6 μm thick negative electrode current collector (Cu film), dried, and rolled to prepare the negative electrode.

[0172] A porous polypropylene separator is placed between the positive and negative electrodes to prepare an electrode assembly. Then, the electrode assembly is housed in a battery case, and the non-aqueous electrolyte prepared above is injected into it to prepare a lithium secondary battery.

[0173] Example 2

[0174] (Preparation of non-aqueous electrolytes)

[0175] LiPF6 was dissolved in a non-aqueous organic solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 20:80 to achieve a LiPF6 concentration of 1.2 M. Then, a compound represented by Formula 1A was added as an electrolyte additive to prepare a non-aqueous electrolyte (see Table 1 below). The non-aqueous electrolyte contained 0.5% by weight of the compound represented by Formula 1A.

[0176] (Preparation of secondary batteries)

[0177] A lithium secondary battery was prepared in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0178] Example 3

[0179] (Preparation of non-aqueous electrolytes)

[0180] LiPF6 was dissolved in a non-aqueous organic solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 20:80 to achieve a LiPF6 concentration of 1.2 M. Then, a compound represented by Formula 1A was added as an electrolyte additive to prepare a non-aqueous electrolyte (see Table 1 below). The non-aqueous electrolyte contained 5% by weight of the compound represented by Formula 1A.

[0181] (Preparation of secondary batteries)

[0182] A lithium secondary battery was prepared in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0183] Example 4

[0184] (Preparation of non-aqueous electrolytes)

[0185] LiPF6 was dissolved in a non-aqueous organic solvent containing a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 20:80 to achieve a LiPF6 concentration of 1.2 M. Then, a compound represented by Formula 1A was added as an electrolyte additive to prepare a non-aqueous electrolyte (see Table 1 below). The non-aqueous electrolyte contained 10% by weight of the compound represented by Formula 1A.

[0186] (Preparation of secondary batteries)

[0187] A lithium secondary battery was prepared in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0188] Example 5

[0189] (Preparation of non-aqueous electrolytes)

[0190] LiPF6 was dissolved in a non-aqueous organic solvent containing a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 20:80 to achieve a LiPF6 concentration of 1.2 M. Then, a compound represented by Formula 1B was added as an electrolyte additive to prepare a non-aqueous electrolyte (see Table 1 below). The non-aqueous electrolyte contained 5% by weight of the compound represented by Formula 1B.

[0191] (Preparation of secondary batteries)

[0192] A lithium secondary battery was prepared in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0193] Example 6

[0194] (Preparation of non-aqueous electrolytes)

[0195] LiPF6 was dissolved in a non-aqueous organic solvent containing a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 20:80 to achieve a LiPF6 concentration of 1.2 M. A compound represented by formula 1C was then added as an electrolyte additive to prepare a non-aqueous electrolyte (see Table 1 below). The non-aqueous electrolyte contained 5% by weight of the compound represented by formula 1C.

[0196] (Preparation of secondary batteries)

[0197] A lithium secondary battery was prepared in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0198] Example 7

[0199] (Preparation of non-aqueous electrolytes)

[0200] LiPF6 was dissolved in a non-aqueous organic solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 20:80 to achieve a LiPF6 concentration of 1.2 M. A compound represented by formula 1D was then added as an electrolyte additive to prepare a non-aqueous electrolyte (see Table 1 below). The non-aqueous electrolyte contained 5% by weight of the compound represented by formula 1D.

[0201] (Preparation of secondary batteries)

[0202] A lithium secondary battery was prepared in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0203] Example 8

[0204] (Preparation of non-aqueous electrolytes)

[0205] LiPF6 was dissolved in a non-aqueous organic solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 20:80 to achieve a LiPF6 concentration of 1.2 M. Then, a compound of formula 1A and lithium difluorophosphate (LiDFP) were added as electrolyte additives to prepare a non-aqueous electrolyte. The non-aqueous electrolyte contained 0.01 wt% of the compound of formula 1A and 0.01 wt% of lithium difluorophosphate (LiDFP) (see Table 1 below).

[0206] (Preparation of secondary batteries)

[0207] A lithium secondary battery was prepared in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0208] Example 9

[0209] (Preparation of non-aqueous electrolytes)

[0210] LiPF6 was dissolved in a non-aqueous organic solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 20:80 to achieve a LiPF6 concentration of 1.2 M. Then, a compound of formula 1A and lithium difluorophosphate (LiDFP) were added as electrolyte additives to prepare a non-aqueous electrolyte. The non-aqueous electrolyte contained 10 wt% of the compound of formula 1A and 0.01 wt% of lithium difluorophosphate (LiDFP) (see Table 1 below).

[0211] (Preparation of secondary batteries)

[0212] A lithium secondary battery was prepared in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0213] Example 10

[0214] (Preparation of non-aqueous electrolytes)

[0215] LiPF6 was dissolved in a non-aqueous organic solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 20:80 to achieve a LiPF6 concentration of 1.2 M. Then, a compound of formula 1A and lithium difluorophosphate (LiDFP) were added as electrolyte additives to prepare a non-aqueous electrolyte. The non-aqueous electrolyte contained 0.01 wt% of the compound of formula 1A and 10 wt% of lithium difluorophosphate (LiDFP) (see Table 1 below).

[0216] (Preparation of secondary batteries)

[0217] A lithium secondary battery was prepared in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0218] Example 11

[0219] (Preparation of non-aqueous electrolytes)

[0220] LiPF6 was dissolved in a non-aqueous organic solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 20:80 to achieve a LiPF6 concentration of 1.2 M. Then, a compound of formula 1A and lithium difluorophosphate (LiDFP) were added as electrolyte additives to prepare a non-aqueous electrolyte. The non-aqueous electrolyte contained 10 wt% of the compound of formula 1A and 10 wt% of lithium difluorophosphate (LiDFP) (see Table 1 below).

[0221] (Preparation of secondary batteries)

[0222] A lithium secondary battery was prepared in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0223] Example 12

[0224] (Preparation of non-aqueous electrolytes)

[0225] LiPF6 was dissolved in a non-aqueous organic solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 20:80 to achieve a LiPF6 concentration of 1.2 M. Then, a compound of formula 1A and lithium difluorophosphate (LiDFP) were added as electrolyte additives to prepare a non-aqueous electrolyte. The non-aqueous electrolyte contained 3 wt% of the compound of formula 1A and 1 wt% of lithium difluorophosphate (LiDFP) (see Table 1 below).

[0226] (Preparation of secondary batteries)

[0227] A lithium secondary battery was prepared in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0228] Example 13

[0229] (Preparation of non-aqueous electrolytes)

[0230] LiPF6 was dissolved in a non-aqueous organic solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 20:80 to achieve a LiPF6 concentration of 1.2 M. Then, a compound of formula 1A and lithium bis(oxalate)borate (LiB(C2O4)2, LiBOB) were added as electrolyte additives to prepare a non-aqueous electrolyte. The non-aqueous electrolyte contained 3 wt% of the compound of formula 1A and 1 wt% of lithium bis(oxalate)borate (LiB(C2O4)2, LiBOB) (see Table 1 below).

[0231] (Preparation of secondary batteries)

[0232] A lithium secondary battery was prepared in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0233] Example 14

[0234] (Preparation of non-aqueous electrolytes)

[0235] LiPF6 was dissolved in a non-aqueous organic solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 20:80 to achieve a LiPF6 concentration of 1.2 M. Then, a compound of formula 1A and lithium difluoro(oxalate)borate (LiDFOB) were added as electrolyte additives to prepare a non-aqueous electrolyte. The non-aqueous electrolyte contained 3 wt% of the compound of formula 1A and 1 wt% of lithium difluoro(oxalate)borate (LiDFOB) (see Table 1 below).

[0236] (Preparation of secondary batteries)

[0237] A lithium secondary battery was prepared in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0238] Example 15

[0239] (Preparation of non-aqueous electrolytes)

[0240] LiPF6 was dissolved in a non-aqueous organic solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 20:80 to achieve a LiPF6 concentration of 1.2 M. Then, a compound of formula 1A and lithium difluoro(bis(oxalato)phosphate) (LiDFOP) were added as electrolyte additives to prepare a non-aqueous electrolyte. The non-aqueous electrolyte contained 3 wt% of the compound of formula 1A and 1 wt% of lithium difluoro(bis(oxalato)phosphate) (LiDFOP) (see Table 1 below).

[0241] (Preparation of secondary batteries)

[0242] A lithium secondary battery was prepared in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0243] Example 16

[0244] (Preparation of non-aqueous electrolytes)

[0245] LiPF6 was dissolved in a non-aqueous organic solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 20:80 to achieve a LiPF6 concentration of 1.2 M. Then, a compound represented by Formula 1B and lithium difluorophosphate (LiDFP) were added as electrolyte additives to prepare a non-aqueous electrolyte. The non-aqueous electrolyte contained 3 wt% of the compound represented by Formula 1B and 1 wt% of lithium difluorophosphate (LiDFP) (see Table 1 below).

[0246] (Preparation of secondary batteries)

[0247] A lithium secondary battery was prepared in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0248] Example 17

[0249] (Preparation of non-aqueous electrolytes)

[0250] LiPF6 was dissolved in a non-aqueous organic solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 20:80 to achieve a LiPF6 concentration of 1.2 M. Then, a compound represented by formula 1C and lithium difluorophosphate (LiDFP) were added as electrolyte additives to prepare a non-aqueous electrolyte. The non-aqueous electrolyte contained 3 wt% of the compound represented by formula 1C and 1 wt% of lithium difluorophosphate (LiDFP) (see Table 1 below).

[0251] (Preparation of secondary batteries)

[0252] A lithium secondary battery was prepared in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0253] Example 18

[0254] (Preparation of non-aqueous electrolytes)

[0255] LiPF6 was dissolved in a non-aqueous organic solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 20:80 to achieve a LiPF6 concentration of 1.2 M. Then, a compound represented by Formula 1D and lithium difluorophosphate (LiDFP) were added as electrolyte additives to prepare a non-aqueous electrolyte. The non-aqueous electrolyte contained 3 wt% of the compound represented by Formula 1D and 1 wt% of lithium difluorophosphate (LiDFP) (see Table 1 below).

[0256] (Preparation of secondary batteries)

[0257] A lithium secondary battery was prepared in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0258] Example 19

[0259] (Preparation of non-aqueous electrolytes)

[0260] LiPF6 was dissolved in a non-aqueous organic solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 20:80 to achieve a LiPF6 concentration of 1.2 M. Then, a compound of formula 1A and lithium difluorophosphate (LiDFP) were added as electrolyte additives to prepare a non-aqueous electrolyte. The non-aqueous electrolyte contained 15 wt% of the compound of formula 1A and 0.01 wt% of lithium difluorophosphate (LiDFP) (see Table 1 below).

[0261] (Preparation of secondary batteries)

[0262] A lithium secondary battery was prepared in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0263] Comparative Example 1

[0264] (Preparation of non-aqueous electrolytes)

[0265] LiPF6 was dissolved in a non-aqueous organic solvent to achieve a LiPF6 concentration of 1.2 M, thereby preparing a non-aqueous electrolyte for lithium secondary batteries (see Table 1 below).

[0266] (Preparation of secondary batteries)

[0267] A lithium secondary battery was prepared in the same manner as in Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0268] Comparative Example 2

[0269] (Preparation of non-aqueous electrolytes)

[0270] LiPF6 was dissolved in a non-aqueous organic solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 20:80 to achieve a LiPF6 concentration of 1.2 M. Then, 1% by weight of LiDFP was added as an electrolyte additive to prepare a non-aqueous electrolyte (see Table 1 below).

[0271] (Preparation of secondary batteries)

[0272] A lithium secondary battery was prepared in the same manner as in Comparative Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0273] Comparative Example 3

[0274] (Preparation of non-aqueous electrolytes)

[0275] LiPF6 was dissolved in a non-aqueous organic solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 20:80 to achieve a LiPF6 concentration of 1.2 M. Then, 3% by weight of ethylene carbonate (VC) was added as an electrolyte additive to prepare a non-aqueous electrolyte (see Table 1 below).

[0276] (Preparation of secondary batteries)

[0277] A lithium secondary battery was prepared in the same manner as in Comparative Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0278] Comparative Example 4

[0279] (Preparation of non-aqueous electrolytes)

[0280] LiPF6 was dissolved in a non-aqueous organic solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 20:80 to achieve a LiPF6 concentration of 1.2 M. Then, vinylene carbonate (VC) and LiDFP were added as electrolyte additives to prepare a non-aqueous electrolyte. The non-aqueous electrolyte contained 3% by weight of vinylene carbonate (VC) and 1% by weight of LiDFP (see Table 1 below).

[0281] (Preparation of secondary batteries)

[0282] A lithium secondary battery was prepared in the same manner as in Comparative Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0283] Comparative Example 5

[0284] (Preparation of non-aqueous electrolytes)

[0285] LiPF6 was dissolved in a non-aqueous organic solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 20:80 to achieve a LiPF6 concentration of 1.2 M. Then, vinylene carbonate (VC) and lithium bis(oxalate)borate (LiB(C2O4)2, LiBOB) were added as electrolyte additives to prepare a non-aqueous electrolyte. The non-aqueous electrolyte contained 3 wt% vinylene carbonate (VC) and 1 wt% lithium bis(oxalate)borate (LiB(C2O4)2, LiBOB) (see Table 1 below).

[0286] (Preparation of secondary batteries)

[0287] A lithium secondary battery was prepared in the same manner as in Comparative Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0288] Comparative Example 6

[0289] (Preparation of non-aqueous electrolytes)

[0290] LiPF6 was dissolved in a non-aqueous organic solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 20:80 to achieve a LiPF6 concentration of 1.2 M. Then, vinylene carbonate (VC) and lithium difluoro(oxalate)borate (LiDFOB) were added as electrolyte additives to prepare a non-aqueous electrolyte. The non-aqueous electrolyte contained 3% by weight of vinylene carbonate (VC) and 1% by weight of lithium difluoro(oxalate)borate (LiDFOB) (see Table 1 below).

[0291] (Preparation of secondary batteries)

[0292] A lithium secondary battery was prepared in the same manner as in Comparative Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0293] Comparative Example 7

[0294] (Preparation of non-aqueous electrolytes)

[0295] LiPF6 was dissolved in a non-aqueous organic solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 20:80 to achieve a LiPF6 concentration of 1.2 M. Then, vinylene carbonate (VC) and lithium difluoro(bis(oxalato)phosphate) (LiDFOP) were added as electrolyte additives to prepare a non-aqueous electrolyte. The non-aqueous electrolyte contained 3 wt% vinylene carbonate (VC) and 1 wt% lithium difluoro(bis(oxalato)phosphate) (LiDFOP) (see Table 1 below).

[0296] (Preparation of secondary batteries)

[0297] A lithium secondary battery was prepared in the same manner as in Comparative Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0298] Comparative Example 8

[0299] (Preparation of non-aqueous electrolytes)

[0300] LiPF6 was dissolved in a non-aqueous organic solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 20:80 to achieve a LiPF6 concentration of 1.2 M. Then, a compound represented by Formula 3 and lithium difluorophosphate (LiDFP) were added as electrolyte additives to prepare a non-aqueous electrolyte. The non-aqueous electrolyte contained 3 wt% of the compound represented by Formula 3 and 1 wt% of lithium difluorophosphate (LiDFP) (see Table 1 below).

[0301] [Formula 3]

[0302] (Preparation of secondary batteries)

[0303] A lithium secondary battery was prepared in the same manner as in Comparative Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0304] Comparative Example 9

[0305] (Preparation of non-aqueous electrolytes)

[0306] LiPF6 was dissolved in a non-aqueous organic solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 20:80 to achieve a LiPF6 concentration of 1.2 M. Then, a compound represented by Formula 4 and lithium difluorophosphate (LiDFP) were added as electrolyte additives to prepare a non-aqueous electrolyte. The non-aqueous electrolyte contained 3 wt% of the compound represented by Formula 4 and 1 wt% of lithium difluorophosphate (LiDFP) (see Table 1 below).

[0307] [Formula 4]

[0308] (Preparation of secondary batteries)

[0309] A lithium secondary battery was prepared in the same manner as in Comparative Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0310] Comparative Example 10

[0311] (Preparation of non-aqueous electrolytes)

[0312] LiPF6 was dissolved in a non-aqueous organic solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 20:80 to achieve a LiPF6 concentration of 1.2 M. Then, a compound represented by Formula 5 and lithium difluorophosphate (LiDFP) were added as electrolyte additives to prepare a non-aqueous electrolyte. The non-aqueous electrolyte contained 3 wt% of the compound represented by Formula 5 and 1 wt% of lithium difluorophosphate (LiDFP) (see Table 1 below).

[0313] [Formula 5]

[0314] (Preparation of secondary batteries)

[0315] A lithium secondary battery was prepared in the same manner as in Comparative Example 1, except that the non-aqueous electrolyte prepared above was injected.

[0316] [Table 1]

[0317] The abbreviations for the compounds in Table 1 have the following meanings.

[0318] EC: Ethylene carbonate

[0319] EMC: Ethyl methyl carbonate

[0320] LiDFP: Lithium difluorophosphate

[0321] LiBOB: Lithium bis(oxalate)borate

[0322] LiDFOB: Lithium difluoro(oxalic acid) borate

[0323] LiDFOP: Lithium difluoro(bis(oxalic acid) phosphate)

[0324] VC: Vinylene carbonate

[0325] Experimental Example

[0326] Experimental Example 1. Evaluation of High-Temperature Cycling Characteristics

[0327] The lithium secondary batteries prepared in the examples and comparative examples were subjected to a formation process at a rate of 0.1C for 3 hours. Afterwards, they were charged at 25°C under CC / CV conditions at a rate of 0.33C (0.05C cutoff) to 4.2 V, to fully charge to 100% SOC. The fully charged batteries were then charged to 4.4 V at a rate of 0.33C under CC / CV conditions at a high temperature (45°C), and discharged to 2.5 V under CC conditions at a rate of 0.33C. This was defined as one cycle. After 400 cycles, the capacity retention was measured using Equation 1 below, and the results are shown in Table 2 below. Furthermore, the resistance increase rate after 400 cycles was calculated using Equation 2 below, and the results are shown in Table 2 below.

[0328] [Relation 1]

[0329] Capacity retention (%) = (Capacity after 400 cycles / Capacity after 1 cycle) × 100

[0330] [Relationship 2]

[0331] Resistance increase rate (%) = {(resistance after 400 cycles - initial resistance) / initial resistance} × 100

[0332] [Table 2]

[0333] Referring to Table 2 above, it can be understood that, compared with the lithium secondary battery of the comparative example, the secondary battery of the present invention has an improved resistance increase rate (%) and an improved capacity retention rate (%) after high-temperature cycling.

[0334] Experimental Example 2. Evaluation of High-Temperature Storage Characteristics

[0335] The lithium secondary batteries prepared in the examples and comparative examples were formed at a rate of 0.1C for 3 hours, then charged at 25°C under CC / CV conditions at a rate of 0.33C (0.05C cutoff) to 4.4 V to fully charge to SOC 100%, and stored at high temperature (60°C) for 20 weeks. Subsequently, the batteries were discharged at a rate of 0.33C to 2.5 V under CC conditions, and the capacity retention after high-temperature storage was calculated using the following equation 3. The results are shown in Table 3 below. Additionally, the resistance was measured by transferring the batteries to a charge / discharger at room temperature (25°C), and the increase in resistance after high-temperature storage was calculated using the following equation 4. The results are then shown in Table 3 below.

[0336] [Relationship 3]

[0337] Capacity retention (%) = (Capacity after high-temperature storage / Capacity after one cycle) × 100

[0338] [Relationship 4]

[0339] Resistance increase rate (%) = {(resistance after high-temperature storage - initial resistance) / initial resistance} × 100

[0340] [Table 3]

[0341] Referring to Table 3 above, it can be understood that, compared with the lithium secondary battery of the comparative example, the secondary battery of the present invention has an improved resistance increase rate (%) and an improved capacity retention rate (%) after high-temperature storage.

[0342] Although the invention has been described above with reference to embodiments thereof, those skilled in the art will understand that various modifications and details may be made to the invention without departing from the spirit and scope of the invention as set forth in the following claims. Therefore, the scope of the invention should be defined by the claims and not limited to the description of the exemplary embodiments provided herein.

Claims

1. A non-aqueous electrolyte comprising a lithium salt, a non-aqueous organic solvent, and an additive, wherein, The additives include compounds represented by Formula 1: [Formula 1] In Formula 1, R1 and R2 are each independently hydrogen or an alkyl group having 1 to 5 carbon atoms.

2. The non-aqueous electrolyte as described in claim 1, wherein, In Formula 1, R1 and R2 are each independently hydrogen or an alkyl group having 1 to 3 carbon atoms.

3. The non-aqueous electrolyte as described in claim 1, wherein, The compound represented by Formula 1 is at least one selected from the compounds represented by Formulas 1A to 1D. [Formula 1A] [Formula 1B] [Formula 1C] [Formula 1D] 。 4. The non-aqueous electrolyte as described in claim 1, wherein, Based on the total weight of the non-aqueous electrolyte, the content of the compound represented by Formula 1 is from 0.01% by weight to 13.0% by weight.

5. The non-aqueous electrolyte as described in claim 1, wherein, Based on the total weight of the non-aqueous electrolyte, the content of the compound represented by Formula 1 is from 0.01% by weight to 5.0% by weight.

6. The non-aqueous electrolyte as described in claim 1, wherein, The additives also include lithium salt compounds.

7. The non-aqueous electrolyte as described in claim 6, wherein, The lithium salt compound is selected from at least one of lithium bis(oxalate)borate (LiB(C2O4)2, LiBOB), lithium difluoro(oxalate)borate (LiDFOB), lithium difluorophosphate (LiPO2F2, LiDFP), and lithium difluoro(bis(oxalate)phosphate (LiDFOP).

8. The non-aqueous electrolyte as described in claim 6, wherein, Based on the total weight of the non-aqueous electrolyte, the content of the lithium salt compound is from 0.01% by weight to 10.0% by weight.

9. The non-aqueous electrolyte as described in claim 1, wherein, The non-aqueous electrolyte further comprises at least one auxiliary additive selected from cyclic carbonates, halogenated carbonates, sulcolepsy compounds, sulfates / salts, phosphates / salts, borates / salts, nitriles, benzenes, amines, and silanes.

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

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