Non-aqueous electrolyte and lithium secondary battery comprising same

Abstract

The present invention relates to a non-aqueous electrolyte and lithium secondary battery comprising same. The non-aqueous electrolyte comprises a lithium salt, an organic solvent, and an additive. The organic solvent includes a carbonate-based organic solvent and a cyclic lactone compound. The additive includes a first additive and a second additive. The first additive is a lithium nitrate (LiNO3), and the second additive may include a compound represented by chemical formula 1.

Description

Non-aqueous electrolyte and lithium secondary battery containing the same

[0001] Cross-citation with related application(s)

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0154766 filed November 4, 2024 and Korean Patent Application No. 10-2025-0158433 filed October 28, 2025, and all contents disclosed in the documents of said Korean patent applications are incorporated herein as part of this specification.

[0003]

[0004] Technology field

[0005] The present invention relates to a non-aqueous electrolyte and a lithium secondary battery containing the same.

[0006] Recently, as the application areas of lithium-ion batteries have rapidly expanded to include not only power supply for electronic devices such as electrical, electronic, telecommunications, and computers, but also power storage for large-area devices such as automobiles and power storage systems, there is a growing demand for high-capacity, high-output, and high-stability secondary batteries.

[0007] The above lithium secondary battery generally consists of a positive electrode containing a positive active material, a negative electrode containing a negative active material, an electrolyte serving as a medium for transporting lithium ions, and a separator. In this case, carbon-based active materials, silicon-based active materials, lithium transition metal oxides, lithium metal, etc., may be used as the negative electrode active material. Additionally, lithium transition metal oxides such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium nickel-cobalt-manganese composite oxide, and lithium iron phosphate may be used as the positive electrode active material.

[0008] During the charging of a lithium secondary battery, lithium ions are generated from the positive electrode and can be converted into stacked or alloyed forms for storage on the negative electrode, while discharge proceeds in the opposite direction. Theoretically, the movement of lithium ions to the positive and negative electrodes during charging and discharging should be reversible; however, in reality, the movement of lithium within the battery may be partially irreversible. Specifically, the medium through which lithium ions can move is the electrolyte. During charging, most lithium ions are stacked or alloyed within the negative electrode active material; however, some may be reduced along with the organic and inorganic materials constituting the electrolyte to form nano-sized organic-inorganic composites on the surface of the negative electrode material. This represents an irreversible, permanent loss of lithium ions provided by the positive electrode, and the organic-inorganic film formed in this way is called the solid electrolyte interface layer (SEI layer). On the surface of the positive electrode active material, a solid electrolyte interface layer can be formed through the oxidation reaction of the materials constituting the electrolyte. When the above solid electrolyte interface layer is formed, irreversible loss of lithium ions is reduced, and a wide driving potential of the electrolyte is secured, enabling smooth reversible movement of lithium ions between the anode and the cathode. Since this solid electrolyte interface layer can contribute to lowering the energy barrier required for charge transfer of lithium ions to the cathode or anode depending on its internal components, the proper design of the solid-electrolyte interface layer has been a research task for improving the performance of lithium secondary batteries.

[0009] Specifically, the lifespan characteristics and durability of lithium secondary batteries can be determined by the stability of the solid-electrolyte interface layer. For example, as charging and discharging progresses, the instability of the initially formed solid-electrolyte interface layer can lead to additional reduction of lithium ions on the surface of the anode material, resulting in the formation of a film thicker than the initially formed interface layer. Due to the loss of additional lithium ions, an additional interface layer thicker than the initially formed one may develop on the surface of the cathode material, or structural degradation of the cathode material may occur. This can be one of the causes of increased resistance in lithium secondary batteries. When lithium secondary batteries are exposed to high temperatures, the materials constituting the electrolyte undergo decomposition; the resulting by-products can degrade the performance of the electrolyte and increase the resistance of the lithium secondary battery. Furthermore, when lithium secondary batteries are exposed to low temperatures, the increasing resistance with repeated charging and discharging can cause the anode and cathode to operate at voltages lower than their initial lifespan. This accelerates oxidation and reduction reactions of the electrolyte at the anode and cathode, which can degrade the performance of the lithium secondary battery. Additionally, instability in the solid-electrolyte interface layer can lead to continuous oxidation and reduction reactions of the electrolyte, resulting in gas generation within the lithium secondary battery. In other words, strengthening the stability of the solid-electrolyte interface layer is a critical task for ensuring stable operation and securing battery performance characteristics such as long lifespan, low-temperature output characteristics, and reduced gas generation.

[0010] The present invention aims to solve the aforementioned problems by providing a non-aqueous electrolyte that improves electrolyte impregnation while simultaneously increasing the stability of the solid-electrolyte interface layer formed on the cathode and anode and enhancing charge transfer phenomena, thereby ensuring excellent output characteristics and stability at low and room temperatures.

[0011] In addition, the present invention provides a lithium secondary battery with improved overall performance by including the above-mentioned non-aqueous electrolyte, thereby enabling the maintenance of cycle capacity at low and room temperatures.

[0012] [1] The present invention provides a non-aqueous electrolyte comprising a lithium salt; an organic solvent; and an additive, wherein the organic solvent comprises a carbonate-based organic solvent and a cyclic lactone compound, and the additive comprises a first additive and a second additive, wherein the first additive is lithium nitrate (LiNO3) and the second additive is a compound represented by the following chemical formula 1:

[0013] [Chemical Formula 1]

[0014]

[0015] In the above chemical formula 1,

[0016] R1 is -O-NO2, and

[0017] L1 is an alkyleneoxy group having 1 to 5 carbon atoms, and

[0018] M is a metal cation or an organic cation, and

[0019] a is the valence of M when M is a metal cation, 1 when M is an organic cation, and a=b.

[0020] [2] The present invention provides a non-aqueous electrolyte comprising a cyclic carbonate organic solvent and a linear carbonate organic solvent, wherein the carbonate organic solvent in [1] is a cyclic carbonate organic solvent and a linear carbonate organic solvent.

[0021] [3] The present invention provides a non-aqueous electrolyte comprising gamma-butyrolactone, wherein the cyclic lactone compound in [1] or [2] is gamma-butyrolactone.

[0022] [4] The present invention provides a non-aqueous electrolyte in which, in at least one of [1] to [3], the first additive is included in an amount of 0.2% to 5% by weight based on the total weight of the non-aqueous electrolyte.

[0023] [5] The present invention provides a non-aqueous electrolyte in at least one of [1] to [4], wherein in Formula 1, M is a metal cation and M is selected from the group consisting of Li, K, Ca, Mg and Cs.

[0024] [6] The present invention provides a non-aqueous electrolyte in which, in at least one of [1] to [5], M in Formula 1 is an organic cation and M is selected from the group consisting of compounds represented by the following Formulas M-1 to M-6.

[0025] [Chemical Formula M-1]

[0026]

[0027] In the above chemical formula M-1, X M1 is -N(R M15 )- or -S- and, R M11 , R M12 , R M13 , R M14 and R M15 The groups are independently hydrogen, an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, an alkynyl group having 2 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a cyanoalkyl group having 2 to 12 carbon atoms, an alkoxyalkyl group having 2 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms.

[0028] [Chemical Formula M-2]

[0029]

[0030] In the above chemical formula M-2, X M2 is -N(R M25 )- or -S- and, R M21 , R M22 , R M23 , R M24 and R M25The groups are independently hydrogen, an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, an alkynyl group having 2 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a cyanoethyl group having 1 to 12 carbon atoms, an alkoxyalkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms.

[0031] [Chemical Formula M-3]

[0032]

[0033] In the above chemical formula M-3, R M31 , R M32 , R M33 , R M34 , R M35 and R M36 The groups are independently hydrogen, an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, an alkynyl group having 2 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a cyanoethyl group having 1 to 12 carbon atoms, an alkoxyalkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms.

[0034] [Chemical Formula M-4]

[0035]

[0036] In the above chemical formula M-4, R M41 , R M42 , R M43 and R M44 is independently hydrogen, an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, an alkynyl group having 2 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a cyanoethyl group having 1 to 12 carbon atoms, an alkoxyalkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms, and R M41 , R M42 , R M43 and R M44 At least two of these can be combined to form an aliphatic hydrocarbon ring.

[0037] [Chemical Formula M-5]

[0038]

[0039] In the above chemical formula M-5, R M51 , R M52 , R M53 and R M54 is independently hydrogen, an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, an alkynyl group having 2 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a cyanoethyl group having 1 to 12 carbon atoms, an alkoxyalkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms, and R M51 , R M52 , R M53 and R M54 At least two of these can be combined to form an aliphatic hydrocarbon ring.

[0040] [Chemical Formula M-6]

[0041]

[0042] In the above chemical formula M-6, R M61 , R M62 and R M63 is independently hydrogen, an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, an alkynyl group having 2 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a cyanoethyl group having 1 to 12 carbon atoms, an alkoxyalkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms, and R M61 , R M62 and R M63 At least two of these can be combined to form an aliphatic hydrocarbon ring.

[0043] [7] The present invention provides a non-aqueous electrolyte comprising, in at least one of [1] to [6], a compound represented by Formula 1, a compound represented by Formula 1-A.

[0044] [Chemical Formula 1-A]

[0045]

[0046] In the above chemical formula 1-A, each of M, a, b, and R1 is as defined in the above chemical formula 1.

[0047] [8] The present invention provides a non-aqueous electrolyte comprising, in at least one of [1] to [7], a compound represented by Formula 1, a compound represented by Formula 1-A-1.

[0048] [Chemical Formula 1-A-1]

[0049]

[0050] In the above chemical formula 1-A-1, each of M, a, and b is as defined in the above chemical formula 1.

[0051] [9] The present invention provides a non-aqueous electrolyte comprising, in at least one of [1] to [8], a compound represented by Formula 1, a compound represented by Formula 1-a-1.

[0052] [Chemical Formula 1-a-1]

[0053] .

[0054]

[0010] The present invention provides a non-aqueous electrolyte in which, in at least one of [1] to [9], the compound represented by Formula 1 is included in an amount of 0.1% to 3% by weight based on the total weight of the non-aqueous electrolyte.

[0055]

[0011] The present invention provides a lithium secondary battery comprising: a positive electrode; a negative electrode facing the positive electrode; a separator interposed between the negative electrode and the positive electrode; and a non-aqueous electrolyte according to [1].

[0056]

[0012] The present invention provides a lithium secondary battery according to

[0011] , wherein the positive electrode comprises a positive electrode active material, and the positive electrode active material comprises a lithium iron phosphate.

[0057]

[0013] The present invention provides a lithium secondary battery comprising, in

[0012] above, a compound represented by the following chemical formula P-1, the lithium iron phosphate.

[0058] [Chemical Formula P-1]

[0059] Li 1+e Fe 1-g M 2 g (PO 4-f )X f

[0060] In the above chemical formula P-1,

[0061] M 2 is one or more elements selected from Co, Ni, Mn, Al, Mg, Ti, and V, X is F, S, or N, and 0≤g≤0.5; -0.5≤e≤+0.5; 0≤f≤0.1.

[0062]

[0014] The present invention is such that, in

[0012] or

[0013] above, the lithium iron phosphate is LiFePO4, LiMn 0.5 Fe 0.5 PO4 or LiMn 0.6 Fe 0.4 A lithium secondary battery containing PO4 is provided.

[0063]

[0015] The present invention provides a lithium secondary battery in which, in at least one of

[0011] to

[0014] , the negative electrode comprises a negative electrode active material, and the negative electrode active material comprises at least one selected from a carbon-based active material and a silicon-based active material.

[0064] The non-aqueous electrolyte according to the present invention comprises an organic solvent containing a cyclic lactone compound and, as an additive, a compound in the form of a salt containing an organosulfonyl group represented by Formula 1 and nitrogen and / or oxygen, thereby forming a film on the positive / negative electrode surface that is highly durable and capable of reducing resistance. In particular, it can improve the electrolyte impregnation properties of a cathode containing a high-loading lithium iron phosphate-based cathode active material and form a solid-electrolyte interface layer on the high-loading cathode surface that is highly durable and capable of reducing resistance. Therefore, when the non-aqueous electrolyte of the present invention is applied to a lithium secondary battery, excellent lifespan performance and storage performance can be achieved even under conditions such as high voltage, while output performance at low temperatures can be improved.

[0065] Figure 1 shows the XIC results for a compound represented by the chemical formula 1-a-1.

[0066] Figure 2 is the MS spectrum for the compound represented by the chemical formula 1-a-1.

[0067] Figure 3 shows the results of MS / MS analysis (Tandem MS, dual mass spectrometry) for a compound represented by chemical formula 1-a-1.

[0068] Figure 4 is the ¹H-NMR spectrum for a preparation solution of the compound represented by chemical formula 1-a-1.

[0069] Figure 5 is a graph showing the low-temperature cycle performance evaluation results for lithium secondary batteries manufactured in the examples and comparative examples.

[0070] The terms and words used in this specification and claims are used merely to describe exemplary embodiments and should not be interpreted as being limited to their ordinary or dictionary meanings, and should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0071] For example, in this specification, terms such as “comprising,” “having,” or “having” are intended to specify the existence of the implemented features, numbers, steps, components, or combinations thereof, and should be understood as not excluding in advance the existence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0072] In addition, in the description of “carbon number a to b” within this 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, “alkylene group having 1 to 5 carbon atoms” refers to an alkylene group containing carbon atoms having 1 to 5 carbon atoms, namely -CH2-, -CH2CH2-, -CH2CH2CH2-, -CH2(CH3)CH-, -CH2CH2CH2CH2CH2-, and -CH(CH3)CH2CH2-, etc.

[0073] Additionally, in this specification, the term “alkylene group” means a branched or unbranched aliphatic hydrocarbon group or a functional group in which one hydrogen atom is removed from each carbon atom located at both ends of the aliphatic hydrocarbon group. In one embodiment, the alkylene group may be substituted or unsubstituted. The alkylene group includes, but is not limited to, methylene groups, ethylene groups, propylene groups, isopropylene groups, butylene groups, isobutylene groups, tert-butylene groups, pentylene groups, 3-pentylene groups, etc., and each of these may be optionally substituted in other embodiments.

[0074] Additionally, in this specification, “substitution” means that at least one hydrogen bonded to carbon is substituted with another element, such as fluorine, unless otherwise defined.

[0075] Additionally, in this specification, “*” refers to a bonding site in a chemical formula unless otherwise defined.

[0076] In addition, in this specification, “loading amount” refers to the amount of active material per unit area of ​​a positive electrode active material layer comprising a lithium iron phosphate-based positive electrode active material formed on a current collector, and “g / cm²” 2” It is indicated as such. In this specification, “loading amount of the anode” means the total sum of the loading amounts of both anodes.

[0077] The present invention will be described in more detail below.

[0078] The non-aqueous electrolyte according to the present invention and the lithium secondary battery including the same comprise at least one of the configurations disclosed below, and may comprise any combination of technically feasible configurations among the configurations below.

[0079] Non-aqueous electrolytes

[0080] The present invention relates to a non-aqueous electrolyte, and more specifically, to a non-aqueous electrolyte for a lithium secondary battery.

[0081] Specifically, the non-aqueous electrolyte of the present invention may comprise a lithium salt; an organic solvent; and an additive.

[0082] The above organic solvent may include carbonate-based organic solvents and cyclic lactone compounds.

[0083] The above additive may include a first additive and a second additive.

[0084] The first additive above may be lithium nitrate (LiNO3).

[0085] The above second additive may be a compound represented by the following chemical formula 1.

[0086] [Chemical Formula 1]

[0087]

[0088] In the above chemical formula 1,

[0089] R1 is -O-NO2, L1 is an alkyleneoxy group having 1 to 5 carbon atoms, M is a metal cation or an organic cation, a is the valence of M when M is a metal cation, 1 when M is an organic cation, and a=b.

[0090] The non-aqueous electrolyte according to the present invention is characterized by including an additive, wherein the additive comprises a salt-type compound containing an organosulfonyl group, nitrogen, and oxygen (a compound represented by Chemical Formula 1) and lithium nitrate (LiNO3). When having such an additive composition, a film capable of reducing resistance while maintaining strong durability can be formed on the surface of the positive and negative electrodes. Therefore, when the non-aqueous electrolyte of the present invention is applied to a lithium secondary battery, excellent lifespan and storage performance can be achieved even under conditions such as high voltage, while output performance at low temperatures can be improved.

[0091]

[0092] (1) Lithium salt

[0093] As the lithium salt used in the present invention, various lithium salts commonly used in non-aqueous electrolytes for lithium secondary batteries may be used without limitation. For example, the lithium salt is Li as a cation. + It includes, and as anion, F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , AlO2 - , 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 a group consisting of

[0094] Specifically, the lithium salt is LiCl, LiBr, LiI, LiBF4, LiClO4, LiAlO2, LiAlCl4, LiPF6, LiSbF6, LiAsF6, LiB 10 Cl 10 It may include at least one selected from the group consisting of LiBOB (LiB(C2O4)2), LiCF3SO3, LiFSI (LiN(SO2F)2), LiCH3SO3, LiCF3CO2, LiCH3CO2, and LiBETI (LiN(SO2CF2CF3)2). Specifically, the lithium salt may include 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).

[0095] The above lithium salt may be included in the above-mentioned non-aqueous electrolyte at a concentration of 0.5M to 5M, specifically 0.8M to 4M, and more specifically 0.8M to 2.5M. When the concentration of the above-mentioned lithium salt satisfies the above range, the lithium ion yield (Li + The transference number and the degree of dissociation of lithium ions are improved, which can enhance the output characteristics of the battery.

[0096] Alternatively, the above lithium salt may be included in the non-aqueous electrolyte in the remainder excluding, for example, the organic solvent and additives described below.

[0097]

[0098] (2) Organic solvent

[0099] The above organic solvent is a non-aqueous solvent commonly used in lithium secondary batteries, and is not particularly limited as long as it minimizes decomposition due to oxidation reactions, etc., during the charging and discharging process of the secondary battery.

[0100] The above organic solvent may be included in the non-aqueous electrolyte in the remainder excluding lithium salts and additives, for example.

[0101] Specifically, the organic solvent may include a carbonate-based organic solvent. Specifically, the carbonate-based organic solvent may include at least one selected from a cyclic carbonate-based organic solvent and a linear carbonate-based organic solvent, and more specifically, may include a cyclic carbonate-based organic solvent and a linear carbonate-based organic solvent.

[0102] The above-mentioned cyclic carbonate-based organic solvent is a high-viscosity organic solvent that has a high dielectric constant and can effectively dissociate lithium salts in an electrolyte. Specifically, it may include at least one organic solvent selected from the group consisting of 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. More specifically, it may include at least one selected from the group consisting of ethylene carbonate (EC) and fluoroethylene carbonate (FEC), and even more specifically, it may include ethylene carbonate (EC).

[0103] In addition, the linear carbonate-based organic solvent is an organic solvent having low viscosity and low dielectric constant, and specifically may include at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethylmethyl carbonate (EMC), methylpropyl carbonate (MPC), and ethylpropyl carbonate (EPC); more specifically, may include at least one selected from the group consisting of ethylmethyl carbonate and dimethyl carbonate; and even more specifically, may include ethylmethyl carbonate and dimethyl carbonate.

[0104] Meanwhile, when a mixture of a cyclic carbonate-based organic solvent and a linear carbonate-based organic solvent is used as the carbonate-based organic solvent, it is preferable that the linear carbonate-based organic solvent be included in the carbonate-based organic solvent in an amount of 70 volume% or less, 65 volume% or less, 60 volume% or less, 55 volume% or less, 50 volume% or less, 45 volume% or less, 40 volume% or less, 35 volume% or less, or 30 volume% or less. Additionally, it is preferable that the linear carbonate-based organic solvent be included in the carbonate-based organic solvent in an amount of 5 volume% or more, 6 volume% or more, 7 volume% or more, 8 volume% or more, 9 volume% or more, or 10 volume% or more. When the content ratio of the linear carbonate-based organic solvent satisfies the above ranges, the control of viscosity and electrolyte impregnation of the non-aqueous electrolyte for a lithium secondary battery may be easier.

[0105] In addition, the organic solvent of the present invention may further include a cyclic lactone compound.

[0106] The above-mentioned cyclic lactone compound has a high dielectric constant and excellent solubility for lithium salts, allowing for stable dissolution of the electrolyte salt to secure high ionic conductivity. In addition, the cyclic lactone compound has a high boiling point (approx. 204°C) and high thermal and oxidation stability, which can suppress electrolyte decomposition at high temperatures, thereby improving the cycle life and low-temperature output characteristics of the battery. In particular, the above-mentioned cyclic lactone compound can be easily mixed with carbonate-based solvents, allowing for easy control of the electrolyte viscosity. Furthermore, compared to a non-aqueous electrolyte composed solely of carbonate-based organic solvents, it can secure excellent solubility for the first and second additives described later. Consequently, the additives described later can undergo reduction decomposition in large quantities on the surfaces of the anode and cathode before the solvent, thereby forming a denser inorganic film. This increases the insulating properties of the film and prevents further decomposition of the solvent. Furthermore, as side reactions between the electrode and the electrolyte are reduced by the formed organic / inorganic film components, and as the solvent containing the cyclic lactone compound is preserved, the lithium salt can be further hydrated to secure high ionic conductivity and oxidation stability, thereby achieving a more significant improvement in battery cycle characteristics and low-temperature characteristics compared to the case where only a carbonate solvent is included as the electrolyte solvent.

[0107] In the non-aqueous electrolyte of the present invention, the carbonate-based organic solvent and the cyclic lactone compound may be included in a volume ratio of 1:99 to 40:60, and specifically, in a volume ratio of 5:95 to 40:60, 10:90 to 40:60, 10:90 to 30:70, or 20:80 to 30:70.

[0108] When the mixing ratio of the carbonate-based organic solvent and the cyclic lactone compound satisfies the above range, a high ion transfer characteristic effect can be achieved, and battery performance with low resistance characteristics can be secured. Specifically, when the cyclic lactone compound is included in a volume ratio of 60 or more, the lithium ion transfer characteristic can be improved to enhance the resistance reduction effect, and the viscosity of the electrolyte can be easily controlled while ensuring excellent solubility for the second additive described later, thereby forming a more stable SEI film. In addition, when the cyclic lactone compound is included in a volume ratio of 99 or less, a stable film can be formed to further improve battery life characteristics.

[0109] The above organic solvent may additionally include at least one of an ester-based organic solvent, an ether-based organic solvent, a glycine-based solvent, and a nitrile-based organic solvent, together with the carbonate-based organic solvent and the cyclic lactone compound, as needed.

[0110] The above ester-based organic solvent may include a linear ester-based organic solvent. Specifically, the linear ester-based organic solvent may include at least one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate.

[0111] As the above ether-based solvent, any one selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methylpropyl ether, ethyl propyl ether, 1,3-dioxolane (DOL), and 2,2-bis(trifluoromethyl)-1,3-dioxolane (TFDOL), or a mixture of two or more of these may be used, but is not limited thereto.

[0112] The above-mentioned 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. It may include at least one selected from the group consisting of dimethoxyethane (glyme, DME), diethoxyethane, diglyme, triglyme, and tetraglyme (TEGDME), but is not limited thereto.

[0113] The above nitrile-based solvent may be one or more selected from the group consisting of acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanitrile, cyclopentane carbonitrile, cyclohexane carbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile, but is not limited thereto.

[0114] The above organic solvent may consist solely of the carbonate-based organic solvent. Even if only the carbonate-based organic solvent is used as the organic solvent, it is preferable in that it facilitates the dissolution of non-aqueous electrolyte components, such as the additives described later, and enables the realization of appropriate mobility of the lithium salt and viscosity of the non-aqueous electrolyte.

[0115]

[0116] (3) Additives

[0117] The electrolyte of the present invention may include three or more additives to form a stable film with low resistance that can improve electrolyte impregnation on the electrode surface and simultaneously improve charge mobility.

[0118] 3-1) First Additive

[0119] The electrolyte of the present invention may include lithium nitrate (LiNO3) as a first additive.

[0120] The lithium nitrate (LiNO3) included as the first additive described above can form an inorganic film containing lithium-nitrogen and lithium-oxygen bonds, which can function as an ion carrier capable of uniformly transferring lithium ions to the surfaces of the anode and cathode through an electrochemical reduction reaction during the activation step, thereby inducing a more effective charge transfer reaction. In particular, since the lithium nitrate (LiNO3) possesses a Lowest Unoccupied Molecular Orbital (LIMO) energy similar to that of the second additive described later, reductive decomposition occurs at a similar time to that of the first additive, thereby forming a dense composite inorganic film containing nitrogen, sulfur, and oxygen as a result of sequential or simultaneous reactions between the two materials. Due to this composite inorganic film, lithium ion diffusivity can be improved to lower internal resistance and minimize reversible lithium ion loss, and side reactions between the electrolyte and the anode can be prevented, thereby more effectively suppressing the leaching of transition metals from the anode.

[0121] The first additive may be included in the non-aqueous electrolyte in a specific amount. Specifically, the first additive may be included in an amount of 0.2 wt% or more, 0.25 wt% or more, 0.3 wt% or more, 0.35 wt% or more, 0.4 wt% or more, 0.45 wt% or more, or 0.5 wt% or more, based on the total weight of the non-aqueous electrolyte. Additionally, the first additive may be included in an amount of 5 wt% or less, 4 wt% or less, 3.5 wt% or less, 3 wt% or less, 2.5 wt% or less, or 2 wt% or less, based on the total weight of the non-aqueous electrolyte. The above numerical ranges may be appropriately combined, and specifically, may be included in an amount of 0.2 wt% to 5 wt%, 0.2 wt% to 4 wt%, or 0.25 wt% to 3 wt%.

[0122] When the content of the first additive of the present invention satisfies the above range, a robust inorganic film containing lithium-nitrogen and lithium-oxygen bonds can be formed on the surfaces of the anode and cathode. That is, when the first additive is included in 0.2 weight% or more, it is possible to form an electrode film having low resistance, thereby suppressing the increase in battery resistance and preventing the induction of battery performance degradation, and when included in 5 weight% or less, it is possible to suppress the increase in resistance caused by side reactions or excessive film formation caused by an excess amount of additive, thereby preventing the deterioration of low-temperature output characteristics.

[0123]

[0124] (3-2) Second additive

[0125] In addition, the present invention may include a compound represented by the following chemical formula 1 as a second additive.

[0126] [Chemical Formula 1]

[0127]

[0128] In the above chemical formula 1,

[0129] R1 is -O-NO2, and

[0130] L1 is an alkyleneoxy group having 1 to 5 carbon atoms, and

[0131] M is a metal cation or an organic cation, a is the valence of M if M is a metal cation, 1 if M is an organic cation, and a=b.

[0132] The compound represented by the above chemical formula 1 includes a salt-type compound containing an organosulfonyl group, nitrogen, and oxygen, thereby forming a film on the positive / negative electrode surface that is highly durable and capable of reducing resistance.

[0133] Specifically, the compound represented by Chemical Formula 1 contains an organosulfonyl group in its structure, and by undergoing reductive decomposition before the organic solvent during charging and discharging, it can uniformly form a solid-electrolyte interface layer containing lithium sulfide or lithium sulfate, which is excellent in terms of ion conductivity, on the surface of the cathode. Since the formed solid-electrolyte interface layer can function as an effective ion carrier, it can suppress the degradation of the cathode and anode. Furthermore, the solid-electrolyte interface layer derived from the functional group has excellent durability, so it can improve the degradation of the solid-electrolyte interface layer and the problem of transition metal leaching from the anode caused therefrom. Additionally, the compound represented by Chemical Formula 1 contains nitrogen as an anionic terminal group in its structure, so it can form a solid-electrolyte interface layer containing lithium nitride, lithium nitrate, lithium oxide, etc., on the surface of the cathode. Since this interface layer can lower resistance by improving lithium ion diffusion, it is possible to minimize reversible lithium ion loss and improve low-temperature output performance, while simultaneously preventing side reactions between the electrolyte and the anode, thereby effectively suppressing the leaching of transition metals from the anode.

[0134] In addition, the compound represented by the above chemical formula 1 is a salt-type compound containing an organosulfonyl group and nitrogen, which enables the formation of a uniform solid-electrolyte interface layer, can suppress the reduction reaction of the organic solvent, and can form an electrode film with low resistance, and in particular, can improve output performance even under low temperature conditions where the mobility characteristics of lithium ions are problematic.

[0135] In particular, when a compound represented by Chemical Formula 1 above is used as an electrolyte additive, the uniform formation of the solid-electrolyte interface layer is achieved by simultaneously including an organosulfonyl group and nitrogen within a single compound structure. If a substance that does not simultaneously include an organosulfonyl group and nitrogen within a single compound, such as lithium nitrate or cyclic sulfur oxide, is used as an electrolyte additive, a solid-electrolyte interface layer is formed in a particulate or non-uniform form, and thus effects such as preventing the reduction decomposition of organic solvents, forming a low-resistance film, suppressing the leaching of transition metals from the anode, and preventing the reduction reaction of transition metal ions cannot be achieved.

[0136] In other words, in the case of the compound represented by Chemical Formula 1 above, it is possible to realize a robust and highly durable electrode film without degrading the lithium ion mobility characteristics or output performance. Accordingly, in the case of a non-aqueous electrolyte containing the compound represented by Chemical Formula 1 above, the electrode can be effectively protected in environments where side reactions of the electrolyte, anode decay, or destruction of the SEI film of the cathode are likely to occur, such as at high voltage; as a result, the lifespan and storage performance of the lithium secondary battery, particularly the lifespan and storage performance of the lithium secondary battery under high voltage, can be significantly improved. That is, the compound represented by Chemical Formula 1 above is highly desirable in that it can achieve the effect of improving the output performance, lifespan performance, and storage performance of the lithium secondary battery.

[0137] The compound represented by Chemical Formula 1 above may be included in an amount of 0.1 wt% or more, 0.2 wt% or more, 0.3 wt% or more, 0.4 wt% or more, 0.5 wt% or more, 0.6 wt% or more, or 0.7 wt% or more, based on the total weight of the non-aqueous electrolyte. Additionally, the compound represented by Chemical Formula 1 above may be included in the non-aqueous electrolyte in an amount of 3 wt% or less, 2.8 wt% or less, 2.5 wt% or less, 2.3 wt% or less, 2 wt% or less, 1.9 wt% or less, 1.8 wt% or less, 1.6 wt% or less, 1.5 wt% or less, 1.3 wt% or less, or 1 wt% or less. The above ranges may be combined with each other without limitation. Specifically, the compound represented by Chemical Formula 1 may be included in an amount of 0.1% to 3% by weight, 0.5% to 2.5% by weight, 0.5% to 2% by weight, or 0.6% to 1.6% by weight based on the total weight of the non-aqueous electrolyte. When the content of the compound represented by Chemical Formula 1 satisfies the above numerical range, a robust inorganic film containing lithium-nitrogen, lithium-oxygen, and lithium-sulfur bonds can be formed on the surfaces of the anode and cathode while preventing problems such as side reactions caused by the additive, capacity reduction, and increased resistance. Accordingly, in order to exhibit the effects of applying the compound represented by Chemical Formula 1 in the present invention, it is preferable to use it within the range described above. Through this, while minimizing disadvantages such as side reactions caused by additives, capacity reduction, and increased resistance, a robust inorganic film containing lithium-nitrogen, lithium-oxygen, and lithium-sulfur bonds is uniformly formed on the surfaces of the anode and cathode, thereby enabling it to function as an ion carrier while effectively suppressing the leaching of transition metals from the anode and effectively suppressing side reactions between the electrolyte and the electrode, thereby enabling excellent low-temperature output performance.

[0138] In the above chemical formula 1, M can be a metal cation or an organic cation.

[0139] Specifically, when M is a metal cation, M may be any one selected from the group consisting of Li, K, Ca, Mg, and Cs, and, for example, may be Li.

[0140] In addition, if M is an organic cation (i.e., a cation in the form of an organic compound), M may be any one selected from the group consisting of compounds represented by the following chemical formulas M-1 to M-6.

[0141] [Chemical Formula M-1]

[0142]

[0143] In the above chemical formula M-1, X M1 is -N(R M15 )- or -S- and, R M11 , R M12 , R M13 , R M14 and R M15 may independently be hydrogen, an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, an alkynyl group having 2 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a cyanoalkyl group having 2 to 12 carbon atoms, an alkoxyalkyl group having 2 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms. Specifically, R M11 , R M12 , R M13 , R M14 and R M15 s⁻¹ may independently be hydrogen, an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, an alkynyl group having 2 to 5 carbon atoms, an aryl group having 6 to 12 carbon atoms, a cyanoalkyl group having 2 to 5 carbon atoms, an alkoxyalkyl group having 2 to 10 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms. More specifically, in the above formula M-1, R⁻¹ M11 , R M12 , R M13 , R M14 and R M15The groups may independently be hydrogen, methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, allyl group (*-CH2CH=CH2), phenyl group, cyanomethyl group, 2-cyanoethyl group, 3-cyanopropyl group, 4-cyanobutyl group, methoxymethyl group, 2-methoxyethyl group, 3-methoxypropyl group, methoxy group, or ethoxy group.

[0144] [Chemical Formula M-2]

[0145]

[0146] In the above chemical formula M-2, X M2 is -N(R M25 )- or -S- is. R M21 , R M22 , R M23 , R M24 and R M25 may independently be hydrogen, an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, an alkynyl group having 2 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a cyanoalkyl group having 2 to 12 carbon atoms, an alkoxyalkyl group having 2 to 12 carbon atoms, or an alkoxy group having 2 to 12 carbon atoms. Specifically, R M21 , R M22 , R M23 , R M24 and R M25 may independently be hydrogen, an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, an alkynyl group having 2 to 5 carbon atoms, an aryl group having 6 to 12 carbon atoms, a cyanoalkyl group having 2 to 5 carbon atoms, an alkoxyalkyl group having 2 to 10 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms. More specifically, in the above formula M-2, R M21 , R M22 , R M23 , R M24 and R M25The groups may independently be hydrogen, methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, allyl group (*-CH2CH=CH2), phenyl group, cyanomethyl group, 2-cyanoethyl group, 3-cyanopropyl group, 4-cyanobutyl group, methoxymethyl group, 2-methoxyethyl group, 3-methoxypropyl group, ethoxymethyl group, 2-ethoxyethyl group, 3-ethoxypropyl group, methoxy group, or ethoxy group.

[0147] [Chemical Formula M-3]

[0148]

[0149] In the above chemical formula M-3, R M31 , R M32 , R M33 , R M34 , R M35 and R M36 may independently be hydrogen, an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, an alkynyl group having 2 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a cyanoalkyl group having 2 to 12 carbon atoms, an alkoxyalkyl group having 2 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms. Specifically, R M31 , R M32 , R M33 , R M34 , R M35 and R M36 may independently be hydrogen, an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, an alkynyl group having 2 to 5 carbon atoms, an aryl group having 6 to 12 carbon atoms, a cyanoalkyl group having 2 to 5 carbon atoms, an alkoxyalkyl group having 2 to 10 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms. More specifically, R M31 , R M32 , R M33 , R M34 , R M35 and R M36The groups may independently be hydrogen, methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, allyl group (*-CH2CH=CH2), phenyl group, cyanomethyl group, 2-cyanoethyl group, 3-cyanopropyl group, 4-cyanobutyl group, methoxymethyl group, 2-methoxyethyl group, 3-methoxypropyl group, ethoxymethyl group, 2-ethoxyethyl group, 3-ethoxypropyl group, methoxy group, or ethoxy group.

[0150] [Chemical Formula M-4]

[0151]

[0152] In the above chemical formula M-4, R M41 , R M42 , R M43 and R M44 may independently be hydrogen, an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, an alkynyl group having 2 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a cyanoalkyl group having 2 to 12 carbon atoms, an alkoxyalkyl group having 2 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms. Specifically, R M41 , R M42 , R M43 and R M44 may independently be hydrogen, an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, an alkynyl group having 2 to 5 carbon atoms, an aryl group having 6 to 12 carbon atoms, a cyanoalkyl group having 2 to 5 carbon atoms, an alkoxyalkyl group having 2 to 10 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms. More specifically, R M41 , R M42 , R M43 and R M44may independently be hydrogen, methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, allyl group (*-CH2CH=CH2), phenyl group, cyanomethyl group, 2-cyanoethyl group, 3-cyanopropyl group, 4-cyanobutyl group, methoxymethyl group, 2-methoxyethyl group, 3-methoxypropyl group, ethoxymethyl group, 2-ethoxyethyl group, 3-ethoxypropyl group, methoxy group, or ethoxy group. Additionally, R M41 , R M42 , R M43 and R M44 At least two of these types may combine to form an aliphatic ring, specifically R M41 , R M42 , R M43 and R M44 At least two of them are alkyl groups having 1 to 5 carbon atoms or alkyl groups having 2 to 3 carbon atoms, and they can be bonded together to form an aliphatic hydrocarbon ring.

[0153] [Chemical Formula M-5]

[0154]

[0155] In the above chemical formula M-5, R M51 , R M52 , R M53 and R M54 may independently be hydrogen, an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, an alkynyl group having 2 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a cyanoalkyl group having 2 to 12 carbon atoms, an alkoxyalkyl group having 2 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms. Specifically, R M51 , R M52 , R M53 and R M54may independently be hydrogen, an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, an alkynyl group having 2 to 5 carbon atoms, an aryl group having 6 to 12 carbon atoms, a cyanoalkyl group having 2 to 5 carbon atoms, an alkoxyalkyl group having 2 to 10 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms. More specifically, R M51 , R M52 , R M53 and R M54 may independently be hydrogen, methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, allyl group (*-CH2CH=CH2), phenyl group, cyanomethyl group, 2-cyanoethyl group, 3-cyanopropyl group, 4-cyanobutyl group, methoxymethyl group, 2-methoxyethyl group, 3-methoxypropyl group, ethoxymethyl group, 2-ethoxyethyl group, 3-ethoxypropyl group, methoxy group, or ethoxy group. Additionally, R M51 , R M52 , R M53 and R M54 At least two of these types may combine to form an aliphatic ring, specifically R M51 , R M52 , R M53 and R M54 At least two of them are alkyl groups having 1 to 5 carbon atoms or alkyl groups having 2 to 3 carbon atoms, and they can be bonded together to form an aliphatic hydrocarbon ring.

[0156] [Chemical Formula M-6]

[0157]

[0158] In the above chemical formula M-6, R M61 , R M62 and R M63may independently be hydrogen, an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, an alkynyl group having 2 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a cyanoalkyl group having 2 to 12 carbon atoms, an alkoxyalkyl group having 2 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms. Specifically, R M61 , R M62 and R M63 is independently hydrogen, an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, an alkynyl group having 2 to 5 carbon atoms, an aryl group having 6 to 12 carbon atoms, a cyanoalkyl group having 2 to 5 carbon atoms, an alkoxyalkyl group having 2 to 10 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms. More specifically, R M61 , R M62 and R M63 may independently be hydrogen, methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, allyl group (*-CH2CH=CH2), phenyl group, cyanomethyl group, 2-cyanoethyl group, 3-cyanopropyl group, 4-cyanobutyl group, methoxymethyl group, 2-methoxyethyl group, 3-methoxypropyl group, ethoxymethyl group, 2-ethoxyethyl group, 3-ethoxypropyl group, methoxy group, or ethoxy group. Additionally, R M61 , R M62 and R M63 At least two of these types may combine to form an aliphatic ring, specifically R M61 , R M62 and R M63 At least two of them are alkyl groups having 1 to 5 carbon atoms or alkyl groups having 2 to 3 carbon atoms, and they can be bonded together to form an aliphatic hydrocarbon ring.

[0159] At this time, in the above chemical formulas M-1 to M-6, the alkoxyalkyl group having 2 to 10 carbon atoms is, for example, R j2 -OR j1 It can be indicated as -*(* is the connection site). In this case, Rj1 and R j2 The groups may independently be alkyl groups having 1 to 5 carbon atoms, and specifically, may independently be methyl groups, ethyl groups, propyl groups, butyl groups, or pentyl groups.

[0160] At this time, in the above chemical formulas M-1 to M-6, the alkoxyalkyl group having 2 to 10 carbon atoms is, for example, R j2 -OR j1 It can be indicated as -*(* is the connection site). In this case, R j1 and R j2 The groups may independently be alkyl groups having 1 to 5 carbon atoms, and specifically, may independently be methyl groups, ethyl groups, propyl groups, butyl groups, or pentyl groups.

[0161] For example, the compound represented by the above formula M-1 may include at least one selected from the group consisting of compounds represented by the following formulas M-1-1 to M-1-10.

[0162]

[0163] The compound represented by the above chemical formula M-2 may be at least one selected from the group consisting of compounds represented by the following chemical formulas M-2-1 to M-2-3.

[0164]

[0165] The compound represented by the above chemical formula M-3 may be at least one selected from the group consisting of compounds represented by the following chemical formulas M-3-1 to M-3-6.

[0166]

[0167] The compound represented by the above chemical formula M-4 may be at least one selected from the group consisting of compounds represented by the following chemical formulas M-4-1 to M-4-17.

[0168]

[0169]

[0170]

[0171] The compound represented by the above chemical formula M-5 may be at least one selected from the group consisting of compounds represented by the following chemical formulas M-5-1 to M-5-14.

[0172]

[0173]

[0174]

[0175] The compound represented by the above chemical formula M-6 may be at least one selected from the group consisting of compounds represented by the following chemical formulas M-6-1 to M-6-11.

[0176]

[0177]

[0178] In the above chemical formula 1, if M is a metal cation, a is the valence of M. For example, in the case of the alkali metal Li, a is 1, and in the case of the alkaline earth metal Ca, a is 2. If M is an organic cation, a is 1. In the above chemical formula 1, a=b.

[0179] For example, the compound represented by the above chemical formula 1 may include the compound represented by the following chemical formula 1-1.

[0180] [Chemical Formula 1-1]

[0181]

[0182] In the above chemical formula 1-1, M, a, b, and L1 are as defined in the above chemical formula 1.

[0183] In the above Chemical Formula 1, L1 may be an alkyleneoxy group having 1 to 5 carbon atoms. For example, L1 is -OR L1 -It could be, R L1... may be an alkylene group having 1 to 5 carbon atoms. In this case, L1 is an alkyleneoxy group (e.g., -OR L1 In the case of -), oxygen (O) may be bonded to sulfur (S). L1 may specifically be an alkyleneoxy group having 2 to 3 carbon atoms, more specifically an ethyleneoxy group or a propyleneoxy group, and even more specifically an ethyleneoxy group.

[0184] Specifically, the compound represented by the above chemical formula 1 may include the compound represented by the following chemical formula 1-A.

[0185] [Chemical Formula 1-A]

[0186]

[0187] In the above chemical formula 1-A, each of M, a, b, and R1 is as defined in the above chemical formula 1.

[0188] More specifically, the compound represented by the above chemical formula 1 may include the compound represented by the following chemical formula 1-A-1.

[0189] [Chemical Formula 1-A-1]

[0190]

[0191] In the above chemical formula 1-A-1, each of M, a, and b is as defined in the above chemical formula 1.

[0192] More specifically, the compound represented by the above chemical formula 1 may include the compound represented by the following chemical formula 1-a-1.

[0193] [Chemical Formula 1-a-1]

[0194]

[0195] The compound represented by the above chemical formula 1 may be formed, for example, by reacting a sulfur oxide (e.g., a cyclic sulfur oxide containing a sulfate group (-OS(=O)2-O-) within the ring) with a metal nitrate (e.g., lithium nitrate, lithium nitrite, etc.), but is not particularly limited thereto. This reaction may be carried out in advance before the manufacture of the non-aqueous electrolyte, or the aforementioned sulfur oxide and metal nitrate may be introduced into an organic solvent during the manufacture of the non-aqueous electrolyte.

[0196] The presence of the compound represented by the above Chemical Formula 1 is determined by HR-LS / MS (High Resolution Liquid Chromatography-Mass Spectrometry) and / or 1 It can be confirmed via H-NMR (H-Nuclear Magnetic Resonance Spectroscopy), but is not specifically limited to this.

[0197] The non-aqueous electrolyte according to the present invention can improve the electrolyte impregnation properties of a cathode containing a high-loading lithium iron phosphate-based cathode active material by using an organic solvent containing a cyclic lactone compound and, as an additive, a lithium nitrate (LiNO3) and a salt-type compound containing an organosulfonyl group represented by Formula 1 and nitrogen and / or oxygen, and can form a film on the positive / negative electrode surface that is highly durable and capable of reducing resistance. Therefore, when the non-aqueous electrolyte of the present invention is applied to a lithium secondary battery, excellent lifespan and storage performance can be achieved even under high voltage conditions, while output performance at low temperatures can be improved.

[0198]

[0199] (3-3) Auxiliary Additives

[0200] Meanwhile, the above additive may additionally include auxiliary additives in the electrolyte as needed to prevent the electrolyte from decomposing and causing cathode collapse in a high-power environment, or to further improve low-temperature high-rate discharge characteristics, low-temperature stability, and overcharge prevention effects. If an auxiliary additive is additionally included in the above non-aqueous electrolyte, the auxiliary additive may be named as a third additive.

[0201] The above auxiliary additive may include at least one selected from the group consisting of cyclic carbonate compounds, sulfate compounds, sulfone compounds, nitrile compounds, benzene compounds, lithium salt compounds, amine compounds, and silane compounds.

[0202] The above cyclic carbonate compound may be at least one selected from vinylene carbonate (VC) and vinylethylene carbonate (VEC).

[0203] The above sulfate-based compound may be at least one selected from ethylene sulfate (Esa), trimethylene sulfate (TMS), and methyl trimethylene sulfate (MTMS).

[0204] The above sulfone-based compound may be at least one selected from the group consisting of 1,3-propane sulfone (PS), 1,4-butane sulfone, ethen sulfone, 1,3-propene sulfone (PRS), 1,4-butene sulfone, and 1-methyl-1,3-propene sulfone.

[0205] The above benzene-based compound may be fluorobenzene. The above amine-based compound may be at least one selected from triethanolamine and ethylenediamine. The above silane-based compound may be at least one selected from tetravinylsilane, tris(trimethylsilyl)phosphate (TMSPa), and tris(trimethylsilyl)phosphite (TMSPi). The above lithium salt-based additive may be at least one selected from lithium bis-(oxalato)borate (LiBOB), lithium difluorooxalatoborate (LiODFB), and lithium difluorophosphate (LiDFP).

[0206] The above nitrile compound may be at least one selected from the group consisting of succinonitrile, adiponitrile, acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanitrile, cyclopentane carbonitrile, cyclohexane carbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile.

[0207] Meanwhile, the above auxiliary additives may be used in a mixture of two or more types, and may be included in an amount of less than 10% by weight based on the total weight of the non-aqueous electrolyte, specifically 0.01% by weight or more and less than 8.0% by weight, and preferably 0.05% by weight to 5.0% by weight.

[0208]

[0209] lithium secondary battery

[0210] In addition, the present invention provides a lithium secondary battery comprising the aforementioned non-aqueous electrolyte.

[0211] Specifically, a lithium secondary battery according to the present invention may comprise a positive electrode; a negative electrode facing the positive electrode; a separator interposed between the negative electrode and the positive electrode; and a non-aqueous electrolyte. The non-aqueous electrolyte may be the non-aqueous electrolyte described above.

[0212] The above lithium secondary battery can be manufactured by housing an electrode assembly comprising the above positive electrode; a negative electrode facing the above positive electrode; and a separator interposed between the above positive electrode and the above negative electrode in a battery case, and then injecting the aforementioned non-aqueous electrolyte.

[0213] At this point, since the explanation regarding the non-aqueous electrolyte has been provided above, the cathode, anode, and separator will be explained below.

[0214] (1) positive electrode

[0215] The above anode may include an anode active material.

[0216] The above-mentioned 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 field, and specifically may include lithium iron phosphate, and the lithium iron phosphate may include a compound represented by the following chemical formula P-1.

[0217] [Chemical Formula P-1]

[0218] Li 1+e Fe 1-g M 2 g (PO 4-f )X f

[0219] In the above chemical formula P-1, M 2 is one or more elements selected from Co, Ni, Mn, Al, Mg, Ti and V, X is F, S, or N, and 0≤g≤0.5; -0.5≤e≤+0.5; 0≤f≤0.1.

[0220] The above lithium iron phosphate is specifically LiFePO4(LFP) (g=0, e=0, and f=0), LiMn0.5 Fe 0.5 PO4(g=0.5, e=0, and f=0) or LiMn 0.6 Fe 0.4 It may include PO4 (g=0.4, e=0, and f=0).

[0221] The above lithium iron phosphate may use primary particles of nanometer size for high lithium ion input / output, or it is possible to use secondary particles formed by assembling these primary particles. For example, when primary particles are used as the above lithium iron phosphate, the particle size may be 50 nm to 2000 nm, more specifically 200 nm to 1100 nm. In addition, when secondary particles formed by assembling these primary particles are used, the average particle size (D50) of the secondary particles may be 0.5 μm to 30 μm.

[0222] Meanwhile, the above lithium iron phosphate-based cathode active material may have an amorphous layer of carbon or metal oxide coated on its surface. In this case, since the amorphous layer of carbon or metal oxide coated on the surface is not crystalline, the insertion and extraction of lithium ions into and out of the lithium iron phosphate-based cathode active material in the core portion occurs through the amorphous layer of the shell. The amorphous layer of carbon or metal oxide coated on the surface allows lithium ions to pass through while also possessing excellent electronic conductivity, so it can act as a current path to the core of the lithium iron phosphate-based cathode active material, which is the active material, thereby enabling charging and discharging at a high rate. When the surface of the above lithium iron phosphate-based cathode active material is coated with the amorphous layer of carbon or metal oxide, safety can be further increased in that unnecessary reactions between the core material and the electrolyte can be controlled.

[0223] In addition, in order to increase electrical conductivity and energy density by reducing the movement of lithium ions and the flow of electrons, the lithium nickel-cobalt-manganese oxide represented by the following chemical formula P-2, which has significantly higher electrical conductivity, can be used together with the lithium iron phosphate.

[0224] The above lithium nickel-cobalt-manganese oxide can be represented by the following chemical formula P-2.

[0225] [Chemical Formula P-2]

[0226] Li 1+x (Ni a Co b Mn c M d )O2

[0227] In the above chemical formula P-2, M is one or more 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 1+x, a, b, c, and d are each atomic fractions of independent elements, where 0≤x≤0.2, 0.50≤a<1, 0 <b≤0.25, 0<c≤0.25, 0≤d≤0.1, a+b+c+d=1이다.

[0228] Preferably, a, b, c, and d may each be 0.70≤a≤0.95, 0.025≤b≤0.20, 0.025≤c≤0.20, and 0≤d≤0.05. Additionally, a, b, c, and d may each be 0.80≤a≤0.95, 0.025≤b≤0.15, 0.025≤c≤0.15, and 0≤d≤0.05. Additionally, a, b, c, and d may each be 0.85≤a≤0.90, 0.05≤b≤0.10, 0.05≤c≤0.10, and 0≤d≤0.03.

[0229] These lithium nickel-cobalt-manganese oxides are Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni) 0.7 Mn 0.2Co 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 Co 0.05 Al 0.02 )O2 and Li(Ni 0.90 Mn 0.05 Co 0.05 It can be any one selected from the group consisting of )O2.

[0230] In the positive electrode active material of the present invention, the lithium iron phosphate and lithium nickel-cobalt-manganese oxide may be included in a weight ratio of 70:30 to 80:20, and specifically in a weight ratio of 70:30 to 50:50.

[0231] When the mixing ratio of the lithium iron phosphate and lithium nickel-cobalt-manganese oxide satisfies the above range, low-temperature and high-voltage safety of the battery can be secured while simultaneously further improving electrical conductivity.

[0232] Specifically, when the content ratio of lithium iron phosphate to the lithium nickel-cobalt-manganese oxide is less than 80 weight percent, excellent capacity characteristics and electrical conductivity can be secured, and when the content ratio of lithium iron phosphate to the lithium nickel-cobalt-manganese oxide is 70 weight percent or more, low temperature and high voltage stability can be secured.

[0233] In addition, the above-mentioned positive active material may include lithium-rich manganese oxide.

[0234] The above-mentioned lithium manganese-rich oxide may include a compound represented by the following chemical formula P-3.

[0235] [Chemical Formula P-3]

[0236] Li 1+s [Ni t Co u Mn v M1 w ]O 2+z

[0237] In the above chemical formula P-3, M 1 is one or more 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 0.05≤s≤1, 0≤t≤0.5, 0≤u≤0.3, 0.5≤v<1.0, 0≤w≤0.2, 0≤z≤1.

[0238] Preferably, in the above formula P-3, 0.05≤s≤1.0, 0.1≤t≤0.5, 0≤u≤0.1, 0.5≤v<1.0, 0≤w≤0.2, and 0≤z≤1. More preferably, in the above formula P-3, 0.10≤s≤0.50, 0.1≤t≤0.5, 0≤u≤0.1, 0.6≤v<1.0, 0≤w≤0.1, and 0≤z≤0.50.

[0239] The above positive active material may be in the form of particles. Specifically, the average particle size (D) of the above positive active material 50 ) can be 1㎛ to 30㎛.

[0240] The above positive electrode may include a positive current collector; and a positive active material layer disposed on at least one surface of the positive current collector. In this case, the positive active material layer may include the aforementioned positive active material.

[0241] The thickness of the above positive current collector can typically be 3 to 500 μm.

[0242] The above positive current collector may form fine irregularities on its surface to strengthen the bonding force of the positive active material. For example, the above positive current collector can be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0243] The positive active material layer is disposed on at least one surface of the positive current collector. Specifically, the positive active material layer may be disposed on one or both surfaces of the positive current collector.

[0244] The above positive active material may be included in the positive active material layer in an amount of 80% to 99% by weight, taking into consideration the sufficient capacity exertion of the positive active material.

[0245] The above positive active material layer may further include a binder and / or a conductive material together with the aforementioned positive active material.

[0246] The above binder serves to improve adhesion between positive active material particles and adhesion between the positive active material and the current collector. Examples of such binders include fluoropolymer-based binders such as polyvinylidene fluoride (PVDF); rubber-based binders including styrene butadiene rubber (SBR), acrylonitrile-butadiene rubber, and styrene-isoprene rubber; cellulose-based binders including carboxyl methyl cellulose (CMC), starch, hydroxypropyl cellulose, and regenerated cellulose; polyalcohol-based binders including polyvinyl alcohol; polyolefin-based binders including polyethylene and polypropylene; polyimidazole-based binders; polyester-based binders; and silane-based binders, either alone or as a mixture of two or more types, and preferably may include polyvinylidene fluoride.

[0247] The above binder may be included in the positive active material layer in an amount of 1% to 20% by weight, preferably 1.2% to 10% by weight, in order to sufficiently secure binding strength between components such as the positive active material.

[0248] The above conductive material can be used to assist and enhance conductivity in a secondary battery, and is not particularly limited as long as it is conductive without causing chemical changes. Specifically, the above cathode conductive material may include at least one selected from the group consisting of graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, ketjen black, channel black, Farnes black, lamp black, thermal black; conductive fibers such as carbon fibers or metal fibers; conductive tubes such as carbon nanotubes; fluorocarbons; metal powders such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and polyphenylene derivatives, and preferably may include carbon nanotubes for the purpose of enhancing conductivity.

[0249] The above conductive material may be included in the above positive active material layer in an amount of 1% to 20% by weight, preferably 1.2% to 10% by weight, in order to sufficiently ensure electrical conductivity.

[0250] The thickness of the above positive active material layer may be 5㎛ to 500㎛, preferably 20㎛ to 200㎛.

[0251] The anode may be manufactured by coating an anode slurry comprising an anode active material and optionally a binder, a conductive material, and a solvent for forming an anode slurry onto the anode current collector, and then drying and rolling. Alternatively, the anode may be manufactured by mixing an anode active material and optionally a binder, a conductive material, etc. to produce a film, and then laminating it onto an anode current collector.

[0252] The solvent for forming the anode slurry may include, for example, at least one selected from the group consisting of distilled water, N-methylpyrrolidone, ethanol, methanol, and isopropyl alcohol, preferably N-methylpyrrolidone, in order to facilitate the dispersion of the anode active material, binder, and / or conductive material.

[0253] Meanwhile, for the design of a high-capacity electrode, the loading amount of the cathode containing the lithium iron phosphate-based cathode active material is 12 mg / cm² 2 Above (6 mg / cm² based on cross-sectional area) 2 (above), specifically 18 mg / cm² 2 to 36 mg / cm² 2 , more specifically 20 mg / cm² 2 to 32 mg / cm² 2 , preferably 24 mg / cm² 2 to 30 mg / cm² 2 It is possible. If the loading amount of the above positive active material satisfies the above range, a high-energy-density battery design is possible.

[0254]

[0255] (2) Cathode

[0256] The above cathode may include a cathode active material.

[0257] The above-mentioned negative electrode active material is a material capable of reversibly inserting / extracting lithium ions and may include at least one selected from the group consisting of carbon-based active materials, (quasi)metal-based active materials, and lithium metal, and specifically may include at least one selected from carbon-based active materials and (quasi)metal-based active materials. More specifically, the above-mentioned negative electrode active material may include at least one selected from carbon-based active materials and silicon-based active materials.

[0258] The carbon-based active material may include at least one selected from the group consisting of graphite, hard carbon, soft carbon, carbon black, graphene, and fibrous carbon, and preferably may include graphite. The graphite may be, for example, at least one of artificial graphite and natural graphite.

[0259] Average particle size (D) of the above carbon-based active material 50) can be 10㎛ to 30㎛, preferably 15㎛ to 25㎛, in terms of ensuring structural stability during charging and discharging and reducing adverse reactions with the electrolyte.

[0260] Specifically, the (quasi)metallic active material comprises: at least one (quasi)metal selected from the group consisting of 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 (quasi)metal selected from the group consisting of 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 (quasi)metal selected from the group consisting of 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); and lithium vanadium oxide. It may include the back.

[0261] More specifically, the above (quasi)metallic active material may include a silicon-based active material.

[0262] The above silicon-based active material is SiO x It may include at least one selected from the group consisting of compounds represented by (0≤x<2) and silicon-carbon composites. Since SiO2 does not react with lithium ions and therefore cannot store lithium, it is preferable that x be within the above range, and more preferably, the silicon-based active material may be SiO.

[0263] Average particle size (D) of the above silicon-based active material 50) can be 1㎛ to 30㎛, preferably 2㎛ to 15㎛, in terms of reducing adverse reactions with the electrolyte while ensuring structural stability during charging and discharging.

[0264] In addition, the cathode of the present invention may include at least one selected from the carbon-based active material and the silicon-based active material.

[0265] Specifically, the cathode of the present invention may include the carbon-based active material and the silicon-based active material.

[0266] At this time, the weight ratio of the silicon-based active material and the carbon-based active material may be 1:99 to 30:70, specifically 3:97 to 15:85. When the mixing ratio of the silicon-based active material and the carbon-based active material satisfies the above range, excellent cycle performance can be secured by suppressing the volume expansion of the silicon-based active material while improving capacity characteristics.

[0267] The above cathode may include a cathode current collector; and a cathode active material layer disposed on at least one surface of the cathode current collector. In this case, the cathode active material may be included in the cathode active material layer.

[0268] The above-mentioned negative current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. Specifically, the above-mentioned negative current collector may be copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface treated with carbon, nickel, titanium, silver, etc., or aluminum-cadmium alloy.

[0269] The above-mentioned cathode current collector can typically have a thickness of 3 to 500 μm.

[0270] The above-mentioned negative current collector may form fine irregularities on its surface to strengthen the bonding force of the negative active material. For example, the above-mentioned negative current collector can be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0271] The above-mentioned negative electrode active material layer is disposed on at least one surface of the negative electrode current collector. Specifically, the negative electrode active material layer may be disposed on one or both surfaces of the negative electrode current collector.

[0272] The above negative electrode active material may be included in the negative electrode active material layer in an amount of 60% to 99% by weight in order to sufficiently express capacity in the secondary battery while minimizing the effect of volume expansion / contraction on the battery.

[0273] The above negative electrode active material layer may further include a conductive material and / or a binder together with the silicon-based active material.

[0274] The above binder can be used to improve the adhesion between the above negative electrode active material layer and the negative electrode current collector to be described later, or to improve the bonding strength between silicon-based active materials.

[0275] Specifically, in terms of the fact that the binder can further improve electrode adhesion and provide sufficient resistance to volume expansion / contraction of silicon-based active materials, styrene butadiene rubber (SBR), nitrile butadiene rubber (NBR), acrylonitrile butadiene rubber, acrylic rubber, butyl rubber, fluoro rubber, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinyl alcohol (PVA), polyacrylic acid (PAA), polyethylene glycol (PEG), polyacrylonitrile (PAN), polyacryl amide (PAM), polyvinylidene fluoride, polytetrafluoroethylene, It may include at least one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene.

[0276] The binder may be included in the cathode active material layer in an amount of 1% to 30% by weight. When within this range, the cathode active material can be better bound to minimize the volume expansion problem of the active material, and at the same time, the binder can be easily dispersed during the preparation of a slurry for forming the cathode active material layer, and the coating properties and phase stability of the slurry can be improved.

[0277] The above conductive material may be used to assist and improve conductivity in a secondary battery, and is not particularly limited as long as it is conductive without causing chemical changes. Specifically, the above conductive material may include at least one selected from the group consisting of graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, ketjen black, channel black, Farnes black, lamp black, thermal black; conductive fibers such as carbon fibers or metal fibers; conductive tubes such as carbon nanotubes; metal powders such as fluorocarbon, aluminum, or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and polyphenylene derivatives.

[0278] The above conductive material may be included in the above cathode active material layer in an amount of 1% to 20% by weight, and when in this range, it is desirable in that it can form an excellent conductive network while mitigating the increase in resistance caused by the binder.

[0279] The thickness of the above negative electrode active material layer may be 5㎛ to 500㎛, preferably 5㎛ to 100㎛.

[0280] The above cathode may be manufactured by coating a cathode slurry comprising a cathode active material and optionally a binder, a conductive material, and a solvent for forming a cathode slurry onto the cathode current collector, and then drying and rolling. Alternatively, the cathode may be manufactured by mixing a cathode active material and optionally a binder, a conductive material, etc. to produce a film, and then laminating it onto a cathode current collector.

[0281] The solvent for forming the above cathode slurry may include, for example, at least one selected from the group consisting of distilled water, N-methylpyrrolidone, ethanol, methanol, and isopropyl alcohol, preferably distilled water, in order to facilitate the dispersion of the cathode active material, binder, and / or conductive material.

[0282] Meanwhile, for a balanced design with the anode, the cathode loading amount is 20 mg / cm²2 Above (10 mg / cm² based on cross-sectional area) 2 It may be above 20 mg / cm², specifically 20 mg / cm² 2 to 32 mg / cm² 2 It may be possible. If the loading amount of the above negative electrode satisfies the above range, long-term life characteristics of the battery can be secured.

[0283]

[0284] (3) Separator

[0285] The above separator separates the negative and positive electrodes and provides a pathway for the movement of lithium ions. It can be used without any specific restrictions as long as it is typically used as a separator in a lithium secondary battery, and it is particularly desirable that it has low resistance to the movement of ions in a non-aqueous electrolyte and excellent moisture retention capacity for the non-aqueous electrolyte.

[0286] Specifically, as a separator, a porous polymer film made of a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof may be used. In addition, a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fibers or polyethylene terephthalate fibers, may be used. Furthermore, a coated separator containing a ceramic component or a polymer material may be used to ensure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0287]

[0288] Meanwhile, the external shape of the lithium secondary battery of the present invention is not particularly limited and can be cylindrical, prismatic, pouch-type, or coin-type.

[0289] In addition, the lithium secondary battery of the present invention can be usefully applied in portable devices such as mobile phones, laptop computers, and digital cameras, as well as in the field of electric vehicles such as hybrid electric vehicles (HEVs).

[0290] In addition, the lithium secondary battery according to the present invention can be applied not only as a battery cell used as a power source for a small device, but also as a unit cell of a medium-to-large battery module comprising a plurality of battery cells. Specifically, the lithium secondary battery of the present invention can be applied to a battery cell for a small device having a volume of width (38 mm) × height (96 mm) × thickness (3.0 mm to 4.5 mm) and a capacity of 1,000 mAh to 3,000 mAh.

[0291]

[0292] Hereinafter, the present invention will be described in detail with reference to examples in order to specifically explain the invention. However, the embodiments according to the present invention may be modified in various different forms, and the scope of the present invention should not be interpreted as being limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the invention to those with average knowledge in the art.

[0293] Examples and Comparative Examples

[0294] Example 1

[0295] (1) Preparation of a compound represented by Chemical Formula 1

[0296] Ethylene sulfate and LiNO3 were dissolved in ethyl acetate (EA) solvent at a ratio of 10 wt% with an equivalent ratio of 1.2:1, and then mixed at room temperature (15-25°C) to proceed with a reaction to form a compound represented by Chemical Formula 1-a-1. Through the above reaction to form a compound, the compound represented by Chemical Formula 1 that was not dissolved in the ethyl acetate (EA) solvent was precipitated in powder form. The solution after the above reaction was filtered to obtain powder. Subsequently, the ethyl acetate solvent remaining in the powder was evaporated, thereby obtaining the compound represented by Chemical Formula 1-a-1.

[0297] The presence of the compound represented by the above chemical formula 1-a-1 is determined by HR-LC / MS (High Resolution Liquid Chromatography-Mass Spectrometry) and 1 It was confirmed using the H-NMR (H-Nuclear Magnetic Resonance Spectroscopy) method.

[0298] First, the compound (powder) represented by the above chemical formula 1-a-1 was added to an organic solvent mixed with ethylene carbonate, ethylmethyl carbonate, and dimethyl carbonate in a volume ratio of 30:50:20, and this was diluted in acetone D6 solvent to prepare a sample solution. Using the above sample solution, HR-LC / MS and 1 H-NMR was measured.

[0299] The HR-LC / MS instrument used was the ThermoFisher Orbitrap IQ-X Tribrid. Under the measurement conditions, CapcellPak C18 was used as the column, acetonitrile and trifluoroacetate (volume ratio 100:0.02) as eluent A, and distilled water and trifluoroacetate (volume ratio 100:0.02) as eluent B. Measurements were performed with a flow rate of 1 mL / min, a UV detector of 220 nm, and the ionization mode set to Electron Spray Ionization (ESI) anionization mode. The 1H-NMR instrument used was the Bruker Advance Neo.

[0300] The presence of the compound represented by chemical formula 1-a-1 was confirmed through Figures 1 to 4. Specifically, the Extracted Ion Chromatogram (XIC) for m / z 185.97140 according to Figure 1 showed a single peak at 1.35 min, confirming that the compound represented by chemical formula 1-a-1 is present in the sample and separated on the LC.

[0301] In the MS spectrum according to Fig. 2, 185.97140 was observed, corresponding to the anion of the compound represented by chemical formula 1-a-1, which corresponds to the molecular formula C2H4NO7S of the compound represented by chemical formula 1-a-1. - It matched.

[0302] Through additional MS / MS analysis (Tandem MS, dual mass spectrometry) according to Fig. 3, fragment ions such as m / z 61.98818 (O3N) and 79.95725 (O3S) were detected, which are consistent with the expected structural decomposition pattern. These results support the presence and structural identity of the compound represented by Chemical Formula 1-a-1.

[0303] The characteristic chemical shifts of 4.76 (t,2) and 4.18 (t,2) observed in the ¹H-NMR spectrum according to Fig. 4 support the presence of a compound represented by the chemical formula 1-a-1.

[0304]

[0305] (2) Preparation of non-aqueous electrolytes

[0306] A non-aqueous electrolyte was prepared by dissolving LiPF6 to a concentration of 1.0 M in an organic solvent mixed with ethylene carbonate (EC) and gamma-butyrolactone in a volume ratio of 20:80, and then adding lithium nitrate (LiNO3), the compound represented by the chemical formula 1-a-1, 1,3-propanesulfone (PS), vinylene carbonate (VC), and fluoroethylene carbonate (FEC) as additives. The lithium nitrate (LiNO3), the compound represented by the chemical formula 1-a-1, vinylene carbonate (VC), fluoroethylene carbonate (FEC), and 1,3-propanesulfone (PS) were included in the non-aqueous electrolyte at concentrations of 0.5 wt%, 0.75 wt%, 0.5 wt%, 3 wt%, and 1 wt%, respectively.

[0307]

[0308] (3) Lithium secondary battery manufacturing

[0309] A cathode active material slurry (solid content 63 wt%) was prepared by mixing a cathode active material (LiFePO4), a conductive material (carbon nanotubes, CNT), and a binder (polyvinylidene fluoride, PVDF) in a weight ratio of 96.0:0.5:3.5. The cathode active material slurry was applied to a cathode current collector (Al thin film) with a thickness of 13 μm, and a cathode was manufactured by performing a roll press. The cathode loading amount was 24 mg / cm² 2 (Anode loading amount based on cross-section: 12 g / cm² 2 )am.

[0310] A cathode active material slurry (solid content: 53 wt%) was prepared by adding a cathode active material (a mixture of artificial graphite and natural graphite mixed in a weight ratio of 80:20), styrene-butadiene rubber and carboxymethylcellulose as binders, and carbon black as a conductive material to distilled water as a solvent in a weight ratio of 96.7:2.8:0.5. The cathode active material slurry was coated onto a cathode current collector (Cu thin film) with a thickness of 6 μm, dried, and rolled to produce a cathode.

[0311] An electrode assembly was manufactured by sequentially laminating the above-manufactured positive and negative electrodes together with a polyethylene porous film using a conventional method, and then the assembly was housed in a secondary battery case, and a lithium secondary battery was manufactured by injecting the above-manufactured non-aqueous electrolyte for a lithium secondary battery.

[0312]

[0313] Example 2

[0314] (1) Preparation of non-aqueous electrolytes

[0315] LiPF6 was dissolved to a concentration of 1.0 M in an organic solvent mixed with ethylene carbonate (EC) and gamma-butyrolactone in a volume ratio of 20:80, and then the lithium nitrate (LiNO3), the compound represented by Formula 1-a-1 prepared in Example 1, vinylene carbonate (VC), fluoroethylene carbonate (FEC), ethylene sulfate (ESa), and 1,3-propanesulfone (PS) were added as additives to prepare a non-aqueous electrolyte. The lithium nitrate (LiNO3), the compound represented by Formula 1-a-1, ethylene sulfate (ESa), 1,3-propanesulfone (PS), vinylene carbonate (VC), and fluoroethylene carbonate (FEC) were included in the non-aqueous electrolyte at concentrations of 2 wt%, 0.75 wt%, 0.5 wt%, 0.5 wt%, 3 wt%, and 1 wt%, respectively.

[0316]

[0317] (2) Manufacturing of lithium secondary batteries

[0318] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the above-mentioned non-aqueous electrolyte was used.

[0319]

[0320] Example 3

[0321] (1) Preparation of non-aqueous electrolytes

[0322] A non-aqueous electrolyte was prepared by dissolving LiPF6 to a concentration of 1.0 M in an organic solvent mixed with ethylene carbonate (EC) and gamma-butyrolactone in a volume ratio of 20:80, and then adding the lithium nitrate (LiNO3), the compound represented by Formula 1-a-1 prepared in Example 1, vinylene carbonate (VC), fluoroethylene carbonate (FEC), and 1,3-propanesulfone (PS) as additives. The lithium nitrate (LiNO3), the compound represented by Formula 1-a-1, ethylene sulfate (ESa), 1,3-propanesulfone (PS), vinylene carbonate (VC), and fluoroethylene carbonate (FEC) were included in the non-aqueous electrolyte at concentrations of 0.25 wt%, 0.75 wt%, 1.5 wt%, 0.5 wt%, 3 wt%, and 1 wt%, respectively.

[0323]

[0324] (2) Manufacturing of lithium secondary batteries

[0325] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the above-mentioned non-aqueous electrolyte was used.

[0326]

[0327] Example 4

[0328] (1) Preparation of non-aqueous electrolytes

[0329] A non-aqueous electrolyte was prepared by dissolving LiPF6 to a concentration of 1.0 M in an organic solvent mixed with ethylene carbonate (EC) and gamma-butyrolactone in a volume ratio of 20:80, and then adding the lithium nitrate (LiNO3), vinylene carbonate (VC) prepared in Example 1, and fluoroethylene carbonate (FEC) as additives. The lithium nitrate, the compound represented by chemical formula 1-a-1, ethylene sulfate (ESa), 1,3-propanesulfone (PS), vinylene carbonate (VC), and fluoroethylene carbonate (FEC) were included in the non-aqueous electrolyte at concentrations of 0.25 wt%, 1.5 wt%, 0.5 wt%, 3 wt%, and 1 wt%, respectively.

[0330]

[0331] (2) Manufacturing of lithium secondary batteries

[0332] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the above-mentioned non-aqueous electrolyte was used.

[0333]

[0334] Example 5

[0335] (1) Preparation of non-aqueous electrolytes

[0336] LiPF6 was dissolved to a concentration of 1.0 M in an organic solvent mixed with ethylene carbonate (EC) and gamma-butyrolactone in a volume ratio of 20:80, and then the lithium nitrate (LiNO3), vinylene carbonate (VC) prepared in Example 1, and fluoroethylene carbonate (FEC) were added as additives to prepare a non-aqueous electrolyte. The lithium nitrate, the compound represented by chemical formula 1-a-1, ethylene sulfate (ESa), 1,3-propanesulfone (PS), vinylene carbonate (VC), and fluoroethylene carbonate (FEC) were included in the non-aqueous electrolyte in amounts of 1.5 wt%, 1.5 wt%, 0.5 wt%, 0.5 wt%, 3 wt%, and 1 wt%, respectively.

[0337]

[0338] (2) Manufacturing of lithium secondary batteries

[0339] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the above-mentioned non-aqueous electrolyte was used.

[0340]

[0341] Comparative Example 1

[0342] (1) Preparation of non-aqueous electrolytes

[0343] A non-aqueous electrolyte was prepared by dissolving LiPF6 to a concentration of 1.0 M in an organic solvent mixed with ethylene carbonate (EC) and gamma-butyrolactone in a 20:80 volume ratio, and then adding vinylene carbonate (VC), fluoroethylene carbonate (FEC), and 1,3-propane sulfone (PS). The non-aqueous electrolyte contained vinylene carbonate (VC), fluoroethylene carbonate (FEC), and 1,3-propane sulfone (PS) in amounts of 3 wt%, 1 wt%, and 0.5 wt%, respectively.

[0344]

[0345] (2) Manufacturing of lithium secondary batteries

[0346] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the above-mentioned non-aqueous electrolyte was used.

[0347]

[0348] Comparative Example 2

[0349] (1) Preparation of non-aqueous electrolytes

[0350] A non-aqueous electrolyte was prepared by dissolving LiPF6 to a concentration of 1.0 M in an organic solvent mixed with ethylene carbonate (EC) and gamma-butyrolactone in a 20:80 volume ratio, and then adding LiNO3, 1,3-propanesulfone (PS), vinylene carbonate (VC), and fluoroethylene carbonate (FEC). The non-aqueous electrolyte contained LiNO3, 1,3-propanesulfone (PS), vinylene carbonate (VC), and fluoroethylene carbonate (FEC) in amounts of 0.2 wt%, 0.5 wt%, 3 wt%, and 1 wt%, respectively.

[0351]

[0352] (2) Manufacturing of lithium secondary batteries

[0353] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the above-mentioned non-aqueous electrolyte was used.

[0354]

[0355] Comparative Example 3

[0356] (1) Preparation of non-aqueous electrolytes

[0357] A non-aqueous electrolyte was prepared by dissolving LiPF6 to a concentration of 1.0 M in an organic solvent mixed with ethylene carbonate (EC) and gamma-butyrolactone in a 20:80 volume ratio, and then adding the compound represented by Formula 1-a-1 prepared in Example 1, ethylene sulfate (ESa), vinylene carbonate (VC), fluoroethylene carbonate (FEC), and 1,3-propanesulfone (PS). The compound represented by Formula 1-a-1, ethylene sulfate (ESa), vinylene carbonate (VC), fluoroethylene carbonate (FEC), and 1,3-propanesulfone (PS) were included in amounts of 0.75 wt%, 0.5 wt%, 3 wt%, 1 wt%, and 0.5 wt%, respectively.

[0358]

[0359] (2) Manufacturing of lithium secondary batteries

[0360] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the above-mentioned non-aqueous electrolyte was used.

[0361]

[0362] Comparative Example 4

[0363] (1) Preparation of non-aqueous electrolytes

[0364] A non-aqueous electrolyte was prepared by dissolving LiPF6 to a concentration of 1.0 M in an organic solvent mixed with ethylene carbonate (EC), ethylmethyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 30:50:20, and then adding LiNO3, the compound represented by Formula 1-a-1 prepared in Example 1, vinylene carbonate (VC), fluoroethylene carbonate (FEC), ethylene sulfate (ESa), and 1,3-propanesulfone (PS) as additives. The LiNO3, the compound represented by Formula 1-a-1, ethylene sulfate (ESa), 1,3-propanesulfone (PS), vinylene carbonate (VC), and fluoroethylene carbonate (FEC) were included in the non-aqueous electrolyte at concentrations of 0.25 wt%, 0.75 wt%, 0.5 wt%, 0.5 wt%, 3 wt%, and 1 wt%, respectively.

[0365]

[0366] (2) Manufacturing of lithium secondary batteries

[0367] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the above-mentioned non-aqueous electrolyte was used.

[0368] Additives (Weight %, based on weight of non-aqueous electrolyte) 1st Additive 2nd Additive Auxiliary Additive Type Weight % Chemical Formula 1-a-1ESaPSVCFEC Example 1 ○LiNO3 0.5 0.75 -0.531 Example 2 ○LiNO3 20.75 0.5 0.531 Example 3 ○LiNO3 0.25 0.75 1.5 0.531 Example 4 ○LiNO3 0.25 1.5 0.5 0.531 Example 5 ○LiNO3 1.5 1.5 0.5 0.531 Comparative Example 1 ○----0.531 Comparative Example 2 ○LiNO3 0.2 --0.531 Comparative Example 3 ○--0.75 0.5 0.531 Comparative Example 4 ×LiNO3 0.25 0.75 0.5 0.531

[0369] In Table 1 above, the abbreviations of the compounds each have the following meanings.

[0370] ESa: Ethylene sulfate

[0371] PS: 1,3-propanesulfonate

[0372] VC: Vinylene carbonate

[0373] FEC: Fluoroethylene carbonate

[0374]

[0375] Experimental Example: Low-temperature cycle performance evaluation

[0376] Low-temperature cycle performance evaluation was performed on the lithium secondary batteries of the examples and comparative examples manufactured above.

[0377] Specifically, the lithium secondary batteries of the examples and comparative examples are charged to 3.65V at -10℃ under 0.2C conditions using constant current / constant voltage (CC / CV) (0.05C cut-off), and discharged to 2.0V at 0.33C using constant current (CC), with 200 as one cycle. th After performing the cycle, 200 th The discharge capacity in the cycle was measured. 200 th The discharge capacity measured in the cycle is shown in Table 2 below. In addition, 200 th The change in discharge capacity up to the cycle is shown in Figure 5.

[0378] 200 th Discharge capacity per cycle (mAh) Example 1968.890 Example 2975.189 Example 3959.866 Example 4882.714 Example 5851.890 Comparative Example 1353.910 Comparative Example 2466.189 Comparative Example 3603.297 Comparative Example 4348.991 (47 th Cycle)

[0379]

[0380] Referring to Table 2 and FIG. 5 above, in the case of the lithium secondary batteries of the examples comprising gamma-butyrolactone as an organic solvent and lithium nitrate and a compound represented by Formula 1-a-1 as additives, compared to the lithium secondary batteries of Comparative Examples 1 to 3, 200 th It can be confirmed that it exhibits significantly superior discharge capacity during the cycle.

[0381] Meanwhile, in the case of the lithium secondary battery of Comparative Example 4, which does not contain gamma-butyrolactone as a non-aqueous electrolyte solvent, 47 th It can be predicted that the discharge capacity deteriorated significantly during the cycle, making subsequent operation difficult.

[0382]

[0383] Although the present invention has been described above with reference to preferred embodiments, those skilled in the art or those with ordinary knowledge in the relevant technical field will understand that various modifications and changes can be made to the invention without departing from the spirit and technical scope of the invention as set forth in the claims below. Accordingly, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be determined by the claims.

Claims

1. A non-aqueous electrolyte comprising a lithium salt; an organic solvent; and an additive, The above organic solvent includes a carbonate-based organic solvent and a cyclic lactone compound, and The above additive includes a first additive and a second additive, and The first additive mentioned above is lithium nitrate (LiNO3), and The above second additive is a non-aqueous electrolyte that is a compound represented by the following chemical formula 1: [Chemical Formula 1] In the above chemical formula 1, R1 is -O-NO2, and L1 is an alkyleneoxy group having 1 to 5 carbon atoms, and M is a metal cation or an organic cation, and a is the valence of M when M is a metal cation, 1 when M is an organic cation, and a=b.

2. In Paragraph 1, The above carbonate-based organic solvent is a non-aqueous electrolyte comprising a cyclic carbonate-based organic solvent and a linear carbonate-based organic solvent.

3. In Paragraph 1, The above-mentioned cyclic lactone compound is a non-aqueous electrolyte containing gamma-butyrolactone.

4. In Paragraph 1, The first additive is a non-aqueous electrolyte included in an amount of 0.2% to 5% by weight based on the total weight of the non-aqueous electrolyte.

5. In Paragraph 1, In the above chemical formula 1, M is a metal cation, and The above M is a non-aqueous electrolyte selected from the group consisting of Li, K, Ca, Mg and Cs.

6. In Paragraph 1, In the above chemical formula 1, M is an organic cation, and The above M is a non-aqueous electrolyte selected from the group consisting of compounds represented by the following chemical formulas M-1 to M-6: [Chemical Formula M-1] In the above chemical formula M-1, X M1 is -N(R M15 )- or -S- and, R M11 , R M12 , R M13 , R M14 and R M15 The groups are independently hydrogen, an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, an alkynyl group having 2 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a cyanoalkyl group having 2 to 12 carbon atoms, an alkoxyalkyl group having 2 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms. [Chemical Formula M-2] In the above chemical formula M-2, X M2 is -N(R M25 )- or -S- and, R M21 , R M22 , R M23 , R M24 and R M25 The groups are independently hydrogen, an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, an alkynyl group having 2 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a cyanoethyl group having 1 to 12 carbon atoms, an alkoxyalkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms. [Chemical Formula M-3] In the above chemical formula M-3, R M31 , R M32 , R M33 , R M34 , R M35 and R M36 The groups are independently hydrogen, an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, an alkynyl group having 2 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a cyanoethyl group having 1 to 12 carbon atoms, an alkoxyalkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms. [Chemical Formula M-4] In the above chemical formula M-4, R M41 , R M42 , R M43 and R M44 is independently hydrogen, an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, an alkynyl group having 2 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a cyanoethyl group having 1 to 12 carbon atoms, an alkoxyalkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms, and R M41 , R M42 , R M43 and R M44 At least two of these can be combined to form an aliphatic hydrocarbon ring. [Chemical Formula M-5] In the above chemical formula M-5, R M51 , R M52 , R M53 and R M54 is independently hydrogen, an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, an alkynyl group having 2 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a cyanoethyl group having 1 to 12 carbon atoms, an alkoxyalkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms, and R M51 , R M52 , R M53 and R M54 At least two of these can be combined to form an aliphatic hydrocarbon ring. [Chemical Formula M-6] In the above chemical formula M-6, R M61 , R M62 and R M63 is independently hydrogen, an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, an alkynyl group having 2 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a cyanoethyl group having 1 to 12 carbon atoms, an alkoxyalkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms, and R M61 , R M62 and R M63 At least two of these can be combined to form an aliphatic hydrocarbon ring.

7. In Paragraph 1, The compound represented by the above chemical formula 1 is a non-aqueous electrolyte comprising the compound represented by the following chemical formula 1-A: [Chemical Formula 1-A] In the above chemical formula 1-A, each of M, a, b, and R1 is as defined in the above chemical formula 1.

8. In Paragraph 1, The compound represented by the above chemical formula 1 is a non-aqueous electrolyte comprising the compound represented by the following chemical formula 1-A-1: [Chemical Formula 1-A-1] In the above chemical formula 1-A-1, each of M, a, and b is as defined in the above chemical formula 1.

9. In Paragraph 1, The compound represented by the above chemical formula 1 is a non-aqueous electrolyte comprising the compound represented by the following chemical formula 1-a-1: [Chemical Formula 1-a-1] .

10. In Paragraph 1, The compound represented by the above chemical formula 1 is a non-aqueous electrolyte included in an amount of 0.1% to 3% by weight based on the total weight of the non-aqueous electrolyte.

11. Anode; A cathode facing the anode above; A separator interposed between the above cathode and the above anode; and A lithium secondary battery comprising a non-aqueous electrolyte according to claim 1.

12. In Paragraph 11, The above-mentioned positive electrode includes a positive electrode active material, and The above positive active material is a lithium secondary battery containing lithium iron phosphate.

13. In Paragraph 12, The above lithium iron phosphate is a lithium secondary battery comprising a compound represented by the following chemical formula P-1: [Chemical Formula P-1] Li 1+e Fe 1-g M 2 g (PO 4-f )X f In the above chemical formula P-1, M 2 is one or more elements selected from Co, Ni, Mn, Al, Mg, Ti and V, X is F, S, or N, and 0≤g≤0.5; -0.5≤e≤+0.5; 0≤f≤0.

1.

14. In Paragraph 13, The above lithium iron phosphate is LiFePO4, LiMn 0.5 Fe 0.5 PO4 or LiMn 0.6 Fe 0.4 Lithium secondary battery containing PO4.

15. In Paragraph 11, The above cathode includes a cathode active material, and The above negative electrode active material comprises at least one selected from carbon-based active materials and silicon-based active materials, forming a lithium secondary battery.

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