Non-aqueous electrolyte and lithium secondary battery comprising same

Abstract

The present invention relates to a non-aqueous electrolyte and a lithium secondary battery comprising same, the 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, the first additive being a fluorine-based compound, and the second additive being 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] The present application claims the benefit of priority based on Korean Patent Application No. 10-2024-0131182 dated September 26, 2024, Korean Patent Application No. 10-2024-0131183 dated September 26, 2024, Korean Patent Application No. 10-2024-0131184 dated September 26, 2024, and Korean Patent Application No. 10-2025-0138532 dated September 24, 2025, and all contents disclosed in the documents of said Korean patent applications are incorporated herein as part of the specification.

[0003]

[0004] Technology field

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

[0006] As dependence on electrical energy gradually increases in modern society, the development of large-capacity power storage devices capable of stably supplying power while simultaneously increasing production is emerging. Furthermore, the need for high-capacity portable power is growing due to the performance improvements of electronic products, ranging from small devices such as mobile phones to medium-to-large devices such as electric vehicles. Lithium-ion batteries, which possess the highest potential, satisfy high-capacity power storage performance requirements and are therefore utilized in a wide range of applications, from small electronic devices to electric vehicles (EVs) and energy storage systems (ESS).

[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 alloy 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 of such lithium secondary batteries 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 are reduced together 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). Meanwhile, 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. As lithium secondary batteries are exposed to high temperatures and undergo repeated charging and discharging cycles, the increase in resistance can cause the anode and cathode to operate at voltages higher or lower than their initial lifespan. Consequently, the oxidation and reduction reactions of the electrolyte at the anode and cathode are accelerated, 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, high-temperature durability, and reduced gas generation.

[0010] The present invention aims to solve the above-mentioned problems by providing a non-aqueous electrolyte that can secure excellent durability and stability at low, room, and high temperatures by increasing the stability of the solid-electrolyte interface layer formed on the cathode and anode, suppressing lithium loss from the anode to increase the structural stability of the anode, and including a component having low resistance.

[0011] In addition, the present invention provides a lithium secondary battery with improved overall performance by including the above-mentioned non-aqueous electrolyte, thereby improving low-temperature life, low-temperature output, fast charging, room-temperature life, high-temperature storage characteristics, and high-temperature life characteristics.

[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 a fluorine-based compound 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, 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.

[0017] [2] The present invention provides a non-aqueous electrolyte comprising a cyclic carbonate-based organic solvent, wherein the carbonate-based organic solvent in [1] is a cyclic carbonate-based organic solvent.

[0018] [3] The present invention provides a non-aqueous electrolyte in which the cyclic lactone compound in [1] or [2] is gamma-butyrolactone.

[0019] [4] The present invention provides a non-aqueous electrolyte in which, in at least one of [1] to [3], the fluorine compound is at least one of a fluorine phosphate compound, a fluorine acrylate compound, and a fluorine proparzyl compound.

[0020] [5] The present invention provides a non-aqueous electrolyte in which, in at least one of [1] to [4], the fluorine-based phosphate compound is lithium difluorophosphate.

[0021] [6] The present invention provides a non-aqueous electrolyte comprising, in at least one of [1] to [5], a fluorinated acrylate compound represented by the following chemical formula 2.

[0022] [Chemical Formula 2]

[0023]

[0024] In the above chemical formula 2,

[0025] Ra is hydrogen or an alkyl group having 1 to 3 carbon atoms, and

[0026] Rb is an alkyl group having 1 to 20 carbon atoms substituted with at least one fluorine.

[0027] [7] The present invention provides a non-aqueous electrolyte in which, in at least one of [1] to [6], in Formula 2, Ra is hydrogen and Rb is an alkyl group having 3 to 15 carbon atoms substituted with at least one fluorine.

[0028] [8] The present invention provides a non-aqueous electrolyte comprising, in at least one of [1] to [7], at least one fluorinated acrylate compound selected from the group consisting of compounds represented by the following formulas 2A to 2C.

[0029] [Chemical Formula 2A]

[0030]

[0031] [Chemical Formula 2B]

[0032]

[0033] [Chemical Formula 2C]

[0034]

[0035] [9] The present invention provides a non-aqueous electrolyte comprising, in at least one of [1] to [8], a fluorinated proparzyl compound represented by the following chemical formula 3.

[0036] [Chemical Formula 3]

[0037]

[0038] In the above chemical formula 3, A is -C(O)- or -CH2-, and R is an alkyl group having 1 to 20 carbon atoms substituted with at least one fluorine.

[0039]

[0010] 본 발명은, 상기 [1] 내지 [9] 중 적어도 하나 이상에 있어서, 상기 화학식 3에서, R은 적어도 하나의 불소가 치환된 탄소수 3 내지 15의 알킬기인 비수 전해질을 제공한다.

[0040]

[0011] The present invention provides a non-aqueous electrolyte comprising, in at least one of [1] to

[0010] , a fluorinated proparzyl compound selected from the group consisting of compounds represented by the following chemical formulas 3A to 3D.

[0041] [Chemical Formula 3A]

[0042]

[0043] [Chemical Formula 3B]

[0044]

[0045] [Chemical Formula 3C]

[0046]

[0047] [Chemical Formula 3D]

[0048]

[0049]

[0012] The present invention provides a non-aqueous electrolyte in which, in at least one of [1] to

[0011] , the first additive is included in an amount of 0.01% to 10% by weight based on the total weight of the non-aqueous electrolyte.

[0050]

[0013] The present invention provides a non-aqueous electrolyte in which, in at least one of [1] to

[0012] , in the formula 1, M is a metal cation and M is selected from the group consisting of Li, K, Ca, Mg and Cs.

[0051]

[0014] The present invention provides a non-aqueous electrolyte in which, in at least one of [1] to

[0013] , 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.

[0052] [Chemical Formula M-1]

[0053]

[0054] 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.

[0055] [Chemical Formula M-2]

[0056]

[0057] In the above chemical formula M-2, X M2 is -N(R M25 )- or -S- and, RM21 , 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.

[0058] [Chemical Formula M-3]

[0059]

[0060] 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.

[0061] [Chemical Formula M-4]

[0062]

[0063] 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 M44At least two of these can be combined to form an aliphatic hydrocarbon ring.

[0064] [Chemical Formula M-5]

[0065]

[0066] 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.

[0067] [Chemical Formula M-6]

[0068]

[0069] 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.

[0070]

[0015] The present invention provides a non-aqueous electrolyte comprising, in one or more of [1] to

[0014] , a compound represented by Formula 1, a compound represented by Formula 1-A below.

[0071] [Chemical Formula 1-A]

[0072]

[0073] In the above chemical formula 1-A, each of M, a, b, and R1 is as defined in the above chemical formula 1.

[0074]

[0016] The present invention provides a non-aqueous electrolyte comprising, in at least one of [1] to

[0015] , a compound represented by Formula 1, a compound represented by Formula 1-A-1.

[0075] [Chemical Formula 1-A-1]

[0076]

[0077] In the above chemical formula 1-A-1, each of M, a, and b is as defined in the above chemical formula 1.

[0078]

[0017] The present invention provides a non-aqueous electrolyte comprising, in at least one of [1] to

[0016] , a compound represented by Formula 1, a compound represented by Formula 1-a-1 below.

[0079] [Chemical Formula 1-a-1]

[0080]

[0081]

[0018] The present invention provides a non-aqueous electrolyte in which, in at least one of [1] to

[0017] , the compound represented by Formula 1 is included in the non-aqueous electrolyte in an amount of 0.1% to 3.0% by weight.

[0082]

[0019] The present invention provides a non-aqueous electrolyte comprising a third additive, wherein the third additive comprises at least one of ethylene sulfate and 1,3-propane sulfone, in at least one of [1] to

[0018] .

[0083]

[0020] The present invention provides a non-aqueous electrolyte in which, in at least one of [1] to

[0019] , the total content of the ethylene sulfate and 1,3-propane sulfone is 0.1% to 2.0% by weight based on the total weight of the non-aqueous electrolyte.

[0084]

[0021] 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].

[0085]

[0022] The present invention provides a lithium secondary battery according to

[0021] , wherein 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.

[0086]

[0023] The present invention provides a lithium secondary battery in which, in at least one of

[0021] or

[0022] , the positive electrode comprises a positive electrode active material, and the positive electrode active material comprises a lithium iron phosphate.

[0087] The non-aqueous electrolyte according to the present invention can form a film on the surface of the positive and negative electrodes that is highly durable and capable of reducing resistance by using an organic solvent containing a cyclic lactone compound and, as an additive, a fluorine-based compound and a salt-type compound containing an organosulfonyl group represented by Formula 1 and nitrogen and / or oxygen. In particular, it can improve the electrolyte impregnation properties of a positive electrode containing a high-loading lithium iron phosphate-based positive electrode active material and can form a film on the surface of the high-loading positive electrode 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 exhibited even under conditions such as high temperature and high voltage, while output performance at low temperatures can be improved.

[0088] Figure 1 shows the XIC results for a compound represented by the chemical formula 1-a-1.

[0089] Figure 2 is the MS spectrum for the compound represented by the chemical formula 1-a-1.

[0090] Figure 3 shows the results of MS / MS analysis (Tandem MS, dual mass spectrometry) for a compound represented by chemical formula 1-a-1.

[0091] Figure 4 is the ¹H-NMR spectrum for a preparation solution of the compound represented by chemical formula 1-a-1.

[0092] 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.

[0093] 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.

[0094] In addition, in the description of "a to b carbon atoms" 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 1 to 5 carbon atoms, namely -CH2-, -CH2CH2-, -CH2CH2CH2-, -CH2(CH3)CH-, -CH2CH2CH2CH2CH2-, and -CH(CH3)CH2CH2-, etc.

[0095] Additionally, in this specification, the term "alkylene group" refers to 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.

[0096] 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.

[0097] Additionally, in this specification, "*" refers to a bonding site in a chemical formula unless otherwise defined.

[0098] 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 an olivine-structured lithium iron phosphate-based positive electrode active material formed on a current collector, and "g / cm²" 2 It is indicated as ". In this specification, "loading amount of the anode" refers to the total sum of the loading amounts of both anodes.

[0099]

[0100] The present invention will be described in more detail below.

[0101] 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.

[0102]

[0103] Non-aqueous electrolytes

[0104] The present invention relates to a non-aqueous electrolyte, more specifically, a non-aqueous electrolyte for a lithium secondary battery.

[0105] Specifically, the non-aqueous electrolyte of the present invention may comprise a lithium salt; an organic solvent; and an additive.

[0106] The above organic solvent may include carbonate-based organic solvents and cyclic lactone compounds.

[0107] The above additive may include a first additive and a second additive.

[0108] The first additive mentioned above may be a fluorine-based compound.

[0109] The above second additive may be a compound represented by the following chemical formula 1.

[0110] [Chemical Formula 1]

[0111]

[0112] In the above chemical formula 1,

[0113] 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.

[0114]

[0115] 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 a fluorine-based compound. 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 temperature and high voltage, while output performance at low temperatures can be improved.

[0116]

[0117] (1) Lithium salt

[0118] 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 - , AlO4 - , AlCl4 - , PF6 - , SbF6 - , AsF6 - , B 10 Cl 10 - , BF2C2O4 -, BC4O8 - , PF4C2O4 - , PF2C4O8 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , C4F9SO3 - , CF3CF2SO3 - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , CH3SO3 - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - It may include at least one selected from a group consisting of

[0119] Specifically, the lithium salt is LiCl, LiBr, LiI, LiBF4, LiClO4, LiAlO2, LiAlO4, 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).

[0120] 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.

[0121] 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.

[0122]

[0123] (2) Organic solvent

[0124] 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.

[0125] The above organic solvent may be included in the non-aqueous electrolyte in the remainder excluding lithium salts and additives, for example.

[0126] Specifically, the organic solvent may include a carbonate-based organic solvent. Specifically, the carbonate-based organic solvent may include a cyclic carbonate-based organic solvent.

[0127] 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).

[0128] The above carbonate-based organic solvent may further include a linear carbonate-based organic solvent.

[0129] The above 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.

[0130] It is preferable that the above linear carbonate-based organic solvent be included in the carbonate-based organic solvent in an amount of 40 volume% or less, 30 volume% or less, 20 volume% or less, or 10 volume% or less. When the linear carbonate-based organic solvent is included in the above carbonate-based organic solvent in an amount of 40 volume% or less, the viscosity of the electrolyte can be lowered without deterioration of battery durability, thereby ensuring the effect of improving the ionic conductivity and electrical output of the electrolyte.

[0131]

[0132] In addition, the organic solvent of the present invention may further include a cyclic lactone compound.

[0133] 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 even in high-temperature environments, thereby improving the cycle life and high-temperature stability 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 viscosity of the electrolyte. Furthermore, because it has excellent solubility for the second additive described later, the second additive acts to decompose before the organic solvent on the surfaces of the anode and cathode to form a stable organic / inorganic film, thereby further improving the film formation effect. Furthermore, by the organic / inorganic film formed from the second additive, side reactions between the electrode and the electrolyte are reduced, and as a result, the electrochemical stability of the cyclic lactone compound is increased, allowing the electrolyte salt to dissolve more stably and secure high ionic conductivity. Therefore, since a more stable SEI film can be formed compared to the case where only a carbonate solvent is included as the electrolyte solvent, significant improvements in battery cycle characteristics and high-temperature characteristics can be obtained.

[0134]

[0135] In addition, the carbonate-based organic solvent and the cyclic lactone compound in the non-aqueous electrolyte of the present invention may be included in a volume ratio of 1:99 to 40:60, specifically in a volume ratio of 10:90 to 40:60, and in a volume ratio of 20:80 to 40:60.

[0136] 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.

[0137]

[0138] Meanwhile, 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.

[0139] 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.

[0140] 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.

[0141] 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.

[0142] 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.

[0143]

[0144] (3) Additives

[0145] The electrolyte of the present invention may include two or more additives to improve electrolyte impregnation on the electrode surface, have low resistance to improve charge mobility, and form a stable film that can suppress film degradation during high-temperature operation.

[0146] 3-1) First Additive

[0147] The present invention may include a fluorine-based compound as a first additive.

[0148] When the above fluorine-based compound is reduced or oxidized, F - As a compound that emits ions or fluorine-containing radicals and these components can form a LiF (Lithium fluoride)-based fluorine-containing inorganic film of excellent durability on the electrode surface, it can improve the ion conductivity of the film and, at the same time, suppress electrolyte decomposition caused by side reactions between the electrode and the electrolyte at high temperatures, thereby suppressing metal leaching from the anode.

[0149] These fluorine-based compounds electrochemically decompose at the anode and cathode surfaces during the initial activation process, F - It is preferable that the compound be in the form of a salt to facilitate the release / desorption of ions or fluorine-containing radicals, or have at least one double bond or upper bond functional group within the structure.

[0150] Specifically, the fluorine-based compound may include at least one selected from the group consisting of fluorine-based phosphate compounds, fluorine-based acrylate compounds, and fluorine-based proparzyl compounds.

[0151] The above fluorine-based phosphate compound may include lithium difluorophosphate in the form of a lithium salt.

[0152] In addition, the above fluorinated acrylate compound may include a compound represented by the following chemical formula 2.

[0153] [Chemical Formula 2]

[0154]

[0155] In the above chemical formula 2,

[0156] Ra is hydrogen or an alkyl group having 1 to 3 carbon atoms, and

[0157] Rb is an alkyl group having 1 to 20 carbon atoms substituted with at least one fluorine.

[0158] The above fluorine-based acrylate compound induces radicals as the double bond (C=C) functional group contained within its molecular structure undergoes reductive decomposition, and these radicals promote the decomposition reaction of additives, thereby electrochemically decomposing on the anode and cathode surfaces during the initial activation process, which can form a fluorine-containing film with improved flame retardancy.

[0159]

[0160] Specifically, in the above formula 2, Ra is hydrogen, and Rb may be an alkyl group having 3 to 15 carbon atoms substituted with at least one fluorine, or an alkyl group having 3 to 7 carbon atoms substituted with at least one fluorine. That is, in the above formula 2, when the number of carbon atoms of Rb is 3 or more, the content of the fluorine element increases, thereby further improving flame retardancy and forming a film with improved high-temperature durability. On the other hand, in the above formula 2, when the number of carbon atoms of Rb exceeds 20, the material viscosity and non-polarity increase due to the excessive content of the fluorine element, and since the solubility in the electrolyte decreases, the electrolyte impregnation ability is reduced, which may lead to inferior battery performance. In particular, in the above formula 2, Rb may include a perfluoro structure.

[0161] Specifically, the fluorinated acrylate compound may be at least one selected from the group consisting of compounds represented by the following chemical formulas 2A to 2C.

[0162] [Chemical Formula 2A]

[0163]

[0164] [Chemical Formula 2B]

[0165]

[0166] [Chemical Formula 2C]

[0167]

[0168]

[0169] In addition, the above-mentioned fluorinated proparzyl compound may include a compound represented by the following chemical formula 3.

[0170] [Chemical Formula 3]

[0171]

[0172] In the above chemical formula 3, A is -C(O)- or -CH2-, and R is an alkyl group having 1 to 20 carbon atoms substituted with at least one fluorine.

[0173] The fluorine-based proparzyl compound represented by the above chemical formula 3 can form a flame-retardant, rigid fluorine-containing film by electrochemically decomposing radicals at the anode and cathode surfaces during the initial activation process, through the triple bond (-C≡C-), i.e., the proparzyl functional group and the ether group (-0), or the propiolate group (HC≡C(=O)-O-R') included at the end of the molecular structure, and promoting the decomposition reaction of additives by these radicals.

[0174]

[0175] Meanwhile, in the above chemical formula 3, R may be an alkyl group having 3 to 15 carbon atoms substituted with at least one fluorine, or an alkyl group having 3 to 7 carbon atoms substituted with at least one fluorine. Specifically, R may include a perfluoro structure.

[0176] In the above chemical formula 3, when the number of carbon atoms of R is 3 or more, the content of the fluorine element increases, thereby further improving flame retardancy and forming a film with improved high-temperature durability. However, in the above chemical formula 3, when the number of carbon atoms of R exceeds 20, the excessive content of the fluorine element increases material viscosity and non-polarity, which reduces solubility in the electrolyte and may lead to inferior battery performance.

[0177] Specifically, the fluorinated proparzyl compound may be at least one selected from the group consisting of compounds represented by the following chemical formulas 3A to 3D.

[0178] [Chemical Formula 3A]

[0179]

[0180] [Chemical Formula 3B]

[0181]

[0182] [Chemical Formula 3C]

[0183]

[0184] [Chemical Formula 3D]

[0185]

[0186]

[0187] 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 0.01 wt% or more, 0.03 wt% or more, 0.05 wt% or more, 0.07 wt% or more, 0.1 wt% or more, 0.15 wt% or more, 0.2 wt% or more, 0.25 wt% or more, 0.3 wt% or more, 0.35 wt% or more, 0.5 wt% or more, 0.7 wt% or more, or 0.9 wt% or more, based on the total weight of the non-aqueous electrolyte. Additionally, the first additive may be included in an amount of 10 wt% or less, 8 wt% or less, 6 wt% or less, 5 wt% or less, 4 wt% or less, 3 wt% or less, or 2 wt% or less, based on the total weight of the non-aqueous electrolyte. The above numerical ranges can be appropriately combined and, specifically, may be included in 0.01% to 10% by weight, 0.05% to 5% by weight, or preferably 0.1% to 3% by weight.

[0188] When the content of the first additive of the present invention satisfies the above range, it can function as an effective ion carrier on the anode and cathode surfaces without acting as a resistor. That is, when the first additive is included in an amount of 0.01% by weight or more, a film can be effectively formed evenly, and when included in an amount of 10% by weight or less, an increase in resistance due to side reactions or excessive film formation can be suppressed.

[0189] Meanwhile, when the above-mentioned fluorine-based compound is mixed with the second additive described later, a film containing not only positive and negative fluorine components but also nitrogen and oxygen can be formed. The film containing these components is not only robust and stable enough to withstand repeated charging and discharging, but the components present in the film also act as catalysts to lower the resistance of lithium ions transferred from the electrolyte to the electrode, thereby resulting in significantly lower activation energy. Consequently, lithium ion conductivity is significantly improved, allowing for an effective reduction in cell resistance, which in turn enables improved high-temperature and low-temperature storage characteristics and long-term cycle performance of the secondary battery.

[0190]

[0191] (3-2) Second additive

[0192] In addition, the present invention may include a compound represented by the following chemical formula 1 as a second additive.

[0193] [Chemical Formula 1]

[0194]

[0195] In the above chemical formula 1,

[0196] 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.

[0197]

[0198] 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.

[0199] Specifically, the compound represented by Chemical Formula 1 contains an organosulfonyl group within its structure, and thus undergoes reductive decomposition before the organic solvent during charging and discharging, thereby enabling the uniform formation of a solid-electrolyte interface layer containing lithium sulfide and 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, since the solid-electrolyte interface layer derived from the functional group has excellent durability, the deterioration of the solid-electrolyte interface layer and the resulting problem of transition metal leaching from the anode can be prevented. In addition, the compound represented by Chemical Formula 1 included as the additive contains nitrogen as an anionic terminal group in its structure, and can form a solid-electrolyte interface layer containing lithium nitride, lithium nitrate, lithium oxide, etc. on the surface of the cathode, which can improve the lithium ion diffusion within the solid-electrolyte interface layer, thereby reducing resistance and minimizing reversible lithium ion loss due to excellent high-temperature durability, and effectively suppressing the leaching of transition metals from the cathode by preventing side reactions between the electrolyte and the anode.

[0200] Meanwhile, in the case of conventional lithium nitrate-based additives (e.g., LiNO3), when introduced as an electrode film component, the non-uniform growth of the solid-electrolyte interface layer induces a reduction reaction of the organic solvent, which leads to increased resistance and reduced output performance. In addition, lithium nitrate-based additives also have the problem of not dissolving well in carbonate-based organic solvents. On the other hand, the compound represented by Chemical Formula 1 according to the present invention is a salt-type compound containing an organosulfonyl group and nitrogen, which enables the formation of a uniform solid-electrolyte interface layer, suppresses the reduction reaction of the organic solvent, enables the formation of an electrode film with low resistance, and particularly enables improved output performance even under low-temperature conditions where lithium ion mobility characteristics are problematic.

[0201] 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.

[0202] 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 high temperature and high voltage. Consequently, the lifespan and storage performance of the lithium secondary battery, particularly under high temperature and 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.

[0203] The compound represented by Chemical Formula 1 above may be included in the non-aqueous electrolyte in an amount of 0.1% to 3.0% by weight. 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 additives, capacity reduction, and increased resistance. Therefore, 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 above-described range. Through this, a robust inorganic film containing lithium-nitrogen, lithium-oxygen, and lithium-sulfur bonds is uniformly formed on the surfaces of the anode and cathode while suppressing disadvantages such as side reactions caused by additives, capacity reduction, and increased resistance as much as possible. This allows the compound 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 high-temperature durability and low-temperature output performance.

[0204] Specifically, the compound represented by Formula 1 may be included in the non-aqueous electrolyte 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, 0.7 wt% or more, 0.8 wt% or more, 0.9 wt% or more, 1 wt% or more, 1.2 wt% or more, 1.3 wt% or more, 1.4 wt% or more, or 1.4 wt% or more. The compound represented by Formula 1 may be included in the non-aqueous electrolyte in an amount of 3.0 wt% or less, 2.9 wt% or less, 2.8 wt% or less, 2.7 wt% or less, 2.6 wt% or less, 2.5 wt% or less, 2.4 wt% or less, 2.3 wt% or less, 2.2 wt% or less, 2.1 wt% or less, or 2.0 wt% or less. The above ranges may be combined with each other without limitation.

[0205]

[0206] In the above chemical formula 1, M can be a metal cation or an organic cation.

[0207] 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.

[0208] 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.

[0209] [Chemical Formula M-1]

[0210]

[0211] 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 M15may 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 M15 The 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.

[0212] [Chemical Formula M-2]

[0213]

[0214] 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 M25may 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 M25 The 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.

[0215] [Chemical Formula M-3]

[0216]

[0217] In the above chemical formula M-3, R M31 , R M32 , R M33 , R M34 , R M35 and R M36may 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 M36 The 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.

[0218] [Chemical Formula M-4]

[0219]

[0220] In the above chemical formula M-4, R M41 , R M42 , R M43 and R M44may 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 M44 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 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.

[0221] [Chemical Formula M-5]

[0222]

[0223] 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 M54 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 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 M54At 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.

[0224] [Chemical Formula M-6]

[0225]

[0226] In the above chemical formula M-6, R M61 , R M62 and R M63 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 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 M62and 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.

[0227] 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.

[0228] 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.

[0229] 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.

[0230]

[0231]

[0232] 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.

[0233]

[0234] 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.

[0235]

[0236] 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.

[0237]

[0238]

[0239]

[0240]

[0241] 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.

[0242]

[0243]

[0244]

[0245] 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.

[0246]

[0247]

[0248] 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.

[0249] For example, the compound represented by the above chemical formula 1 may include the compound represented by the following chemical formula 1-1.

[0250] [Chemical Formula 1-1]

[0251]

[0252] In the above chemical formula 1-1, M, a, b, and L1 are as defined in the above chemical formula 1.

[0253] 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.

[0254]

[0255] Specifically, the compound represented by the above chemical formula 1 may include the compound represented by the following chemical formula 1-A.

[0256] [Chemical Formula 1-A]

[0257]

[0258] In the above chemical formula 1-A, each of M, a, b, and R1 is as defined in the above chemical formula 1.

[0259] More specifically, the compound represented by the above chemical formula 1 may include the compound represented by the following chemical formula 1-A-1.

[0260] [Chemical Formula 1-A-1]

[0261]

[0262] In the above chemical formula 1-A-1, each of M, a, and b is as defined in the above chemical formula 1.

[0263]

[0264] More specifically, the compound represented by the above chemical formula 1 may include the compound represented by the following chemical formula 1-a-1.

[0265] [Chemical Formula 1-a-1]

[0266]

[0267]

[0268] 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.

[0269] 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.

[0270]

[0271] Meanwhile, the first additive and the second additive may be included in a weight ratio of 1:0.05 to 20, 1:0.1 to 10, 1:0.5 to 5, or 1:0.5 to 1:3. When the content ratio of the first additive and the second additive satisfies the above numerical range, a film in which components derived from each additive are uniformly distributed can be formed, and the increase in resistance caused by unnecessary film formation can be minimized. Accordingly, a film with significantly improved lithium ion conductivity and excellent durability can be formed.

[0272]

[0273] (3-3) Third additive

[0274] In addition, the non-aqueous electrolyte of the present invention may include a third additive, and the third additive may further include at least one of ethylene sulfate and 1,3-propane sulfone. The ethylene sulfate and / or 1,3-propane sulfone may be applied as an auxiliary additive for forming a sulfur (S)-containing SEI film.

[0275] The total content of the ethylene sulfate and 1,3-propane sulfone may be 0.1% to 2.0% by weight based on the total weight of the non-aqueous electrolyte. When the total content of the ethylene sulfate and 1,3-propane sulfone satisfies the above numerical range, the film formation effect can be improved to improve the degradation of lifespan performance and / or storage performance, and the increase in resistance of the battery caused by the electrode film becoming thicker can be prevented. Furthermore, adverse effects on charge transfer phenomena such as polarization can be prevented, the generation of gaseous by-products at the area where the positive and negative electrodes face each other can be suppressed to enhance the diffusion effect of lithium ions, and irreversible capacity loss can be improved by preventing the electrodeposition of lithium metal.

[0276] In the present invention, the total content of the ethylene sulfate and 1,3-propanesulfone may mean, for example, the total content of 1,3-propanesulfone in the non-aqueous electrolyte when the non-aqueous electrolyte does not contain ethylene sulfate, and the total content of ethylene sulfate in the non-aqueous electrolyte when the non-aqueous electrolyte does not contain 1,3-propanesulfone.

[0277] Specifically, the total content of the ethylene sulfate and 1,3-propane sulfone may be 0.1% to 2.0% by weight, 0.3% to 1.7% by weight, or 0.5% to 1.5% by weight based on the total weight of the non-aqueous electrolyte. Being within the aforementioned range is desirable in that it not only improves the uniformity of the electrode film but also enables stable battery performance through smooth diffusion of lithium ions.

[0278]

[0279] (3-4) Auxiliary additives

[0280] The above additive may additionally include auxiliary additives in the electrolyte as needed to prevent the decomposition of the electrolyte in a high-power environment from causing cathode collapse, or to further improve low-temperature high-rate discharge characteristics, high-temperature stability, prevention of overcharging, and suppression of battery expansion at high temperatures. If the above auxiliary additive is included, the above auxiliary additive may be named as the fourth additive.

[0281] The above auxiliary additive may include at least one selected from the group consisting of nitrate compounds, cyclic carbonate compounds, nitrile compounds, benzene compounds, lithium salt compounds, amine compounds, and silane compounds.

[0282] The above nitrate-based compound may include lithium nitrate (LiNO3).

[0283] The above cyclic carbonate compound may be at least one selected from vinylene carbonate (VC) and vinylethylene carbonate (VEC).

[0284] 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).

[0285] The above lithium salt-based compound may be at least one selected from lithium bis-(oxalato)borate (LiBOB) and lithium difluorooxalatoborate (LiODFB).

[0286] 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.

[0287] Specifically, the auxiliary additive may include at least one selected from vinylene carbonate and fluoroethylene carbonate, and specifically may include vinylene carbonate and fluoroethylene carbonate.

[0288] 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, more specifically 0.05% by weight to 5.0% by weight, and even more specifically 3% by weight to 5% by weight.

[0289]

[0290] lithium secondary battery

[0291] In addition, the present invention provides a lithium secondary battery comprising the aforementioned non-aqueous electrolyte.

[0292] 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.

[0293] 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.

[0294]

[0295] As the non-aqueous electrolyte has been described above, the cathode, anode, and separator will be described below.

[0296]

[0297] (1) positive electrode

[0298] The above anode may include an anode active material.

[0299] The above-mentioned cathode active material is a compound capable of reversible intercalation and deintercalation, and is not particularly limited as long as it is a cathode active material used in the field; specifically, it may include a lithium metal composite oxide. More specifically, the lithium metal composite oxide is a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; lithium iron oxide such as LiFe3O4; lithium iron phosphate such as LiFePO4; and a compound with the chemical formula Li 1+c1 Mn 2-c1 Lithium manganese oxides such as O4 (0≤c1≤0.33), LiMnO3, LiMn2O3, LiMnO2, etc.; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, Cu2V2O7, etc.; chemical formula LiNi 1-c2 M c2 Ni-site type lithium nickel oxide represented by O2 (wherein M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, satisfying 0.01≤c2≤0.3); chemical formula LiMn 2-c3 M c3 Lithium manganese composite oxides represented by O2 (wherein M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn and Ta, satisfying 0.01≤c3≤0.1) or Li2Mn3MO8 (wherein M is at least one selected from the group consisting of Fe, Co, Ni, Cu and Zn); etc., but are not limited to these. The anode may also be a Li-metal anode.

[0300] More specifically, the positive electrode active material may include lithium iron phosphate.

[0301] The above lithium iron phosphate may include a compound represented by the following chemical formula P-1.

[0302] [Chemical Formula P-1]

[0303] Li 1+e Fe 1-g M 2 g (PO 4-f )X f

[0304] 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.

[0305] Specifically, representative examples of compounds represented by the above chemical formula P-1 include LiFePO4(LFP) (g=0, e=0, and f=0) and LiMn 0.5 Fe 0.5 PO4 (g=0.5, e=0, and f=0) and LiMn 0.6 Fe 0.4 It may include PO4 (g=0.4, e=0, and f=0).

[0306]

[0307] 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.

[0308] Meanwhile, the lithium iron phosphate 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 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 lithium iron phosphate core, which is the active material, thereby enabling charging and discharging at a high rate. Furthermore, when the surface of the lithium iron phosphate is coated with the amorphous layer of carbon or metal oxide, safety can be further enhanced in that unnecessary reactions between the core material and the electrolyte can be controlled.

[0309]

[0310] In addition, in the present invention, the electrical conductivity of the anode can be further improved by using lithium nickel-cobalt-manganese oxide represented by the following chemical formula P-2, which has significantly higher electrical conductivity, together with the lithium iron phosphate.

[0311] The above lithium nickel-cobalt-manganese oxide can be represented by the following chemical formula P-2.

[0312] [Chemical Formula P-2]

[0313] Li 1+x (Ni a Co b Mn c M d )O2

[0314] 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. 바람직하게는, 상기 a, b, c 및 d는 각각 0.70≤a≤0.95, 0.025≤b≤0.20, 0.025≤c≤0.20, 0≤d≤0.05일 수 있다. 또한, 상기 a, b, c 및 d는 각각 0.80≤a≤0.95, 0.025≤b≤0.15, 0.025≤c≤0.15, 0≤d≤0.05일 수 있다. 또한, 상기 a, b, c 및 d는 각각 0.85≤a≤0.90, 0.05≤b≤0.10, 0.05≤c≤0.10, 0≤d≤0.03일 수 있다.

[0315] These lithium nickel-cobalt-manganese oxides are Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni) 0.7 Mn 0.2 Co 0.1 )O2, Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, Li(Ni 0.8 Co 0.15 Al 0.05 )O2, Li(Ni 0.86 Mn 0.07 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.

[0316] 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.

[0317] When the mixing ratio of the lithium iron phosphate and lithium nickel-cobalt-manganese oxide satisfies the above range, high temperature and high voltage safety of the battery can be secured while simultaneously further improving electrical conductivity.

[0318] 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, high temperature and high voltage stability can be secured.

[0319]

[0320] In addition, the above-mentioned positive active material may include lithium-rich manganese oxide.

[0321] The above-mentioned lithium manganese-rich oxide may include a compound represented by the following chemical formula P-3.

[0322] [Chemical Formula P-3]

[0323] Li 1+s [Ni t Co u Mn v M 1 w ]O 2+z

[0324] 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. Preferably, in the above formula B, 0.05≤s≤1.0, 0.1≤t≤0.5, 0≤u≤0.1, 0.5≤v<1.0, 0≤w≤0.2, 0≤z≤1. More preferably, in the above formula P-2, 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.

[0325]

[0326] 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㎛.

[0327] The above positive active material may be included in the positive active material layer in an amount of 70% to 99% by weight, specifically 80% to 98% by weight, for capacity enhancement.

[0328]

[0329] 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.

[0330] The thickness of the above positive current collector can typically be 3 to 500 μm.

[0331] 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.

[0332] 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.

[0333] 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.

[0334] The above positive active material layer may further include a binder and / or a conductive material together with the aforementioned positive active material.

[0335] 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.

[0336] 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.

[0337] 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.

[0338] 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.

[0339] The thickness of the above positive active material layer may be 5㎛ to 500㎛, preferably 20㎛ to 200㎛.

[0340] 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.

[0341] 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.

[0342] Meanwhile, in the present invention, for the design of a high-capacity electrode, the loading amount of the anode containing the lithium iron phosphate is 0.032 g / cm³ 2 Above (Anode loading amount based on cross-section: 0.016 g / cm² 2 It can be formed as (above), specifically 0.032 g / cm³ 2 Up to 0.060 g / cm³ 2 It can be formed to be such that, more preferably 0.040 g / cm³ 2 Up to 0.060 g / cm³ 2 It can be formed to this extent. If the loading amount of the positive electrode active material satisfies the above range, a high-energy-density battery design is possible.

[0343]

[0344] (2) Cathode

[0345] Next, the cathode is explained.

[0346] The above cathode may include a cathode active material.

[0347] 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.

[0348] 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.

[0349] 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.

[0350] 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.

[0351] More specifically, the above (quasi)metallic active material may include a silicon-based active material.

[0352] 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.

[0353] 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.

[0354] 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.

[0355] Specifically, the cathode of the present invention may include the carbon-based active material and the silicon-based active material.

[0356] 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.

[0357]

[0358] 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.

[0359] 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.

[0360] The above-mentioned cathode current collector can typically have a thickness of 3 to 500 μm.

[0361] 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.

[0362] 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.

[0363] 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 to minimize the effect of volume expansion / contraction on the battery while sufficiently expressing capacity in the secondary battery.

[0364] The above negative electrode active material layer may further include a conductive material and / or a binder together with the silicon-based active material.

[0365] 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.

[0366] 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.

[0367] 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.

[0368] 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.

[0369] 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.

[0370] The thickness of the above negative electrode active material layer may be 5㎛ to 500㎛, preferably 5㎛ to 100㎛.

[0371] 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.

[0372] 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.

[0373]

[0374] (3) Separator

[0375] 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 of a non-aqueous electrolyte and excellent moisture retention capacity for the non-aqueous electrolyte.

[0376] 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.

[0377]

[0378] 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.

[0379] In addition, the lithium secondary battery of the present invention can be usefully applied to 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) and energy storage systems (ESS).

[0380]

[0381] 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.

[0382]

[0383] Examples and Comparative Examples

[0384] Example 1

[0385] (1) Preparation of a compound represented by Chemical Formula 1

[0386] 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.

[0387]

[0388] 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.

[0389] 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.

[0390] 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.

[0391] 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.

[0392] 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.

[0393] 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.

[0394] 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.

[0395]

[0396] (2) Preparation of non-aqueous electrolytes

[0397] 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 30:70, and then adding lithium difluorophosphate, 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 difluorophosphate, the compound represented by the chemical formula 1-a-1, 1,3-propanesulfone (PS), vinylene carbonate (VC), and fluoroethylene carbonate (FEC) were included in the non-aqueous electrolyte in amounts of 0.5 wt%, 0.5 wt%, 0.5 wt%, 3 wt%, and 1 wt%, respectively.

[0398]

[0399] (3) Manufacturing of lithium secondary batteries

[0400] A positive electrode active material slurry (solid content 100 wt%) was prepared by mixing a positive electrode active material (LiFePO4), a conductive material (carbon nanotubes, CNT), and a binder (polytetrafluoroethylene, PTFE) in a weight ratio of 96.0:0.5:3.5. The positive electrode active material slurry was applied to a positive electrode current collector (Al thin film) with a thickness of 13 μm, and a positive electrode was manufactured by performing a roll press. The positive electrode loading amount was 0.040 g / cm³. 2 (Anode loading amount based on cross-section: 0.020 g / cm² 2 )am.

[0401] 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.

[0402] 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, then housing it in a secondary battery case, and injecting the above-manufactured non-aqueous electrolyte to manufacture a lithium secondary battery.

[0403]

[0404] Example 2

[0405] (1) Preparation of non-aqueous electrolytes

[0406] 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 30:70, and then the lithium difluorophosphate, the compound represented by Formula 1-a-1 prepared in Example 1, ethylene sulfate (ESa), 1,3-propanesulfone (PS), vinylene carbonate (VC), and fluoroethylene carbonate (FEC) were added as additives to prepare a non-aqueous electrolyte. The lithium difluorophosphate, 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 in amounts of 0.5 wt%, 0.5 wt%, 0.25 wt%, 0.5 wt%, 3 wt%, and 1 wt%, respectively.

[0407]

[0408] (2) Manufacturing of lithium secondary batteries

[0409] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the above-mentioned non-aqueous electrolyte was used.

[0410]

[0411] Example 3

[0412] (1) Preparation of non-aqueous electrolytes

[0413] 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 30:70, and then the lithium difluorophosphate, the compound represented by Formula 1-a-1 prepared in Example 1, vinylene carbonate (VC), and fluoroethylene carbonate (FEC) were added as additives to prepare a non-aqueous electrolyte. The lithium difluorophosphate, the compound represented by Formula 1-a-1, vinylene carbonate (VC), and fluoroethylene carbonate (FEC) were included in the non-aqueous electrolyte at concentrations of 0.5 wt%, 1 wt%, 3 wt%, and 1 wt%, respectively.

[0414]

[0415] (2) Manufacturing of lithium secondary batteries

[0416] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the above-mentioned non-aqueous electrolyte was used.

[0417]

[0418] Example 4

[0419] (1) Preparation of non-aqueous electrolytes

[0420] 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 30:70, and then adding as additives a compound represented by Formula 2A, a compound represented by Formula 1-a-1 prepared in Example 1, 1,3-propanesulfone (PS), vinylene carbonate (VC), and fluoroethylene carbonate (FEC). The compound represented by Formula 2A, the compound represented by Formula 1-a-1, 1,3-propanesulfone (PS), vinylene carbonate (VC), and fluoroethylene carbonate (FEC) were included in the non-aqueous electrolyte at concentrations of 0.5 wt%, 0.5 wt%, 0.5 wt%, 3 wt%, and 1 wt%, respectively.

[0421]

[0422] (2) Manufacturing of lithium secondary batteries

[0423] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the above-mentioned non-aqueous electrolyte was used.

[0424]

[0425] Example 5

[0426] (1) Preparation of non-aqueous electrolytes

[0427] 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 30:70, and then a non-aqueous electrolyte was prepared by adding as additives the compound represented by Chemical Formula 2A, the compound represented by Chemical Formula 1-a-1 prepared in Example 1, ethylene sulfate (ESa), 1,3-propanesulfone (PS), vinylene carbonate (VC), and fluoroethylene carbonate (FEC). The compound represented by Chemical Formula 2A, 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 0.5 wt%, 0.5 wt%, 0.25 wt%, 0.5 wt%, 3 wt%, and 1 wt%, respectively.

[0428]

[0429] (2) Manufacturing of lithium secondary batteries

[0430] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the above-mentioned non-aqueous electrolyte was used.

[0431]

[0432] Example 6

[0433] (1) Preparation of non-aqueous electrolytes

[0434] 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 30:70, and then a non-aqueous electrolyte was prepared by adding as additives the compound represented by Chemical Formula 2A, the compound represented by Chemical Formula 1-a-1 prepared in Example 1, vinylene carbonate (VC), and fluoroethylene carbonate (FEC). The compound represented by Chemical Formula 2A, the compound represented by Chemical Formula 1-a-1, vinylene carbonate (VC), and fluoroethylene carbonate (FEC) were included in the non-aqueous electrolyte at concentrations of 0.5 wt%, 1 wt%, 3 wt%, and 1 wt%, respectively.

[0435]

[0436] (2) Manufacturing of lithium secondary batteries

[0437] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the above-mentioned non-aqueous electrolyte was used.

[0438]

[0439] Example 7

[0440] (1) Preparation of non-aqueous electrolytes

[0441] 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 30:70, and then adding as additives a compound represented by Formula 3A, a compound represented by Formula 1-a-1 prepared in Example 1, 1,3-propanesulfone (PS), vinylene carbonate (VC), and fluoroethylene carbonate (FEC). The compound represented by Formula 3A, the compound represented by Formula 1-a-1, 1,3-propanesulfone (PS), vinylene carbonate (VC), and fluoroethylene carbonate (FEC) were included in the non-aqueous electrolyte at concentrations of 0.5 wt%, 0.5 wt%, 0.5 wt%, 3 wt%, and 1 wt%, respectively.

[0442]

[0443] (2) Manufacturing of lithium secondary batteries

[0444] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the above-mentioned non-aqueous electrolyte was used.

[0445]

[0446] Example 8

[0447] (1) Preparation of non-aqueous electrolytes

[0448] 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 30:70, and then a non-aqueous electrolyte was prepared by adding as additives the compound represented by Chemical Formula 3A, the compound represented by Chemical Formula 1-a-1 prepared in Example 1, ethylene sulfate (ESa), 1,3-propanesulfone (PS), vinylene carbonate (VC), and fluoroethylene carbonate (FEC). The compound represented by Chemical Formula 3A, 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 0.5 wt%, 0.5 wt%, 0.25 wt%, 0.5 wt%, 3 wt%, and 1 wt%, respectively.

[0449]

[0450] (2) Manufacturing of lithium secondary batteries

[0451] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the above-mentioned non-aqueous electrolyte was used.

[0452]

[0453] Example 9

[0454] (1) Preparation of non-aqueous electrolytes

[0455] 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 30:70, and then a non-aqueous electrolyte was prepared by adding as additives the compound represented by Chemical Formula 3A, the compound represented by Chemical Formula 1-a-1 prepared in Example 1, vinylene carbonate (VC), and fluoroethylene carbonate (FEC). The compound represented by Chemical Formula 3A, the compound represented by Chemical Formula 1-a-1, vinylene carbonate (VC), and fluoroethylene carbonate (FEC) were included in the non-aqueous electrolyte at concentrations of 0.5 wt%, 1 wt%, 3 wt%, and 1 wt%, respectively.

[0456]

[0457] (2) Manufacturing of lithium secondary batteries

[0458] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the above-mentioned non-aqueous electrolyte was used.

[0459]

[0460] Comparative Example 1

[0461] (1) Preparation of non-aqueous electrolytes

[0462] 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 30:70 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.

[0463]

[0464] (2) Manufacturing of lithium secondary batteries

[0465] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the above-mentioned non-aqueous electrolyte was used.

[0466]

[0467] Comparative Example 2

[0468] (1) Preparation of non-aqueous electrolytes

[0469] 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 30:70 volume ratio, and then adding LiNO3, vinylene carbonate (VC), and fluoroethylene carbonate (FEC). The non-aqueous electrolyte contained LiNO3, vinylene carbonate (VC), and fluoroethylene carbonate (FEC) in amounts of 0.25 wt%, 3 wt%, and 1 wt%, respectively.

[0470]

[0471] (2) Manufacturing of lithium secondary batteries

[0472] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the above-mentioned non-aqueous electrolyte was used.

[0473]

[0474] Comparative Example 3

[0475] (1) Preparation of non-aqueous electrolytes

[0476] 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 30:70 volume ratio, and then adding lithium difluorophosphate, ethylene sulfate (ESa), vinylene carbonate (VC), and fluoroethylene carbonate (FEC). The non-aqueous electrolyte contained lithium difluorophosphate, ethylene sulfate (ESa), vinylene carbonate (VC), and fluoroethylene carbonate (FEC) in amounts of 0.5 wt%, 0.5 wt%, 3 wt%, and 1 wt%, respectively.

[0477]

[0478] (2) Manufacturing of lithium secondary batteries

[0479] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the above-mentioned non-aqueous electrolyte was used.

[0480]

[0481] Comparative Example 4

[0482] (1) Preparation of non-aqueous electrolytes

[0483] 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 30:70, and then adding the compound represented by Formula 1-a-1 prepared in Example 1, ethylene sulfate (ESa), 1,3-propanesulfone (PS), vinylene carbonate (VC), and fluoroethylene carbonate (FEC). 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 amounts of 0.5 wt%, 0.5 wt%, 0.5 wt%, 3 wt%, and 1 wt%, respectively.

[0484]

[0485] (2) Manufacturing of lithium secondary batteries

[0486] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the above-mentioned non-aqueous electrolyte was used.

[0487]

[0488] Comparative Example 5

[0489] (1) Preparation of non-aqueous electrolytes

[0490] 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 30:70, and then lithium bis(oxalato)borate (LiBOB), the compound represented by Formula 1-a-1 prepared in Example 1, ethylene sulfate (ESa), 1,3-propanesulfone (PS), vinylene carbonate (VC), and fluoroethylene carbonate (FEC) were added as additives to prepare a non-aqueous electrolyte. The LiBOB, 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 0.5 wt%, 0.5 wt%, 0.5 wt%, 3 wt%, and 1 wt%, respectively.

[0491]

[0492] (2) Manufacturing of lithium secondary batteries

[0493] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the above-mentioned non-aqueous electrolyte was used.

[0494]

[0495] Comparative Example 6

[0496] (1) Preparation of non-aqueous electrolytes

[0497] 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 ethylmethyl carbonate (EMC) in a volume ratio of 30:70, and then adding lithium difluorophosphate, the compound represented by Formula 1-a-1 prepared in Example 1, ethylene sulfate (ESa), 1,3-propanesulfone (PS), vinylene carbonate (VC), and fluoroethylene carbonate (FEC) as additives. The lithium difluorophosphate, 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 in amounts of 0.5 wt%, 0.5 wt%, 0.5 wt%, 3 wt%, and 1 wt%, respectively.

[0498]

[0499] (2) Manufacturing of lithium secondary batteries

[0500] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the above-mentioned non-aqueous electrolyte was used.

[0501]

[0502] Comparative Example 7

[0503] (1) Preparation of non-aqueous electrolytes

[0504] LiPF6 was dissolved to a concentration of 1.0 M in an organic solvent mixed with ethylene carbonate (EC) and ethylmethyl carbonate (EMC) in a volume ratio of 30:70, and then a non-aqueous electrolyte was prepared by adding as additives a compound represented by Formula 2A, a compound represented by Formula 1-a-1 prepared in Example 1, ethylene sulfate (ESa), 1,3-propanesulfone (PS), vinylene carbonate (VC), and fluoroethylene carbonate (FEC). The compound represented by Formula 2A, 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 0.5 wt%, 0.5 wt%, 0.5 wt%, 3 wt%, and 1 wt%, respectively.

[0505]

[0506] (2) Manufacturing of lithium secondary batteries

[0507] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the above-mentioned non-aqueous electrolyte was used.

[0508]

[0509] Comparative Example 8

[0510] (1) Preparation of non-aqueous electrolytes

[0511] LiPF6 was dissolved to a concentration of 1.0 M in an organic solvent mixed with ethylene carbonate (EC) and ethylmethyl carbonate (EMC) in a volume ratio of 30:70, and then a non-aqueous electrolyte was prepared by adding as additives a compound represented by Formula 3A, a compound represented by Formula 1-a-1 prepared in Example 1, ethylene sulfate (ESa), 1,3-propanesulfone (PS), vinylene carbonate (VC), and fluoroethylene carbonate (FEC). The compound represented by Formula 3A, 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 0.5 wt%, 0.5 wt%, 0.5 wt%, 3 wt%, and 1 wt%, respectively.

[0512]

[0513] (2) Manufacturing of lithium secondary batteries

[0514] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the above-mentioned non-aqueous electrolyte was used.

[0515]

[0516]

[0517] In Table 1 above, the abbreviations of the compounds mean the following.

[0518] LiDFP: Lithium difluorophosphate

[0519] ESa: Ethylene sulfate

[0520] 1,3-PS: 1,3-propanesulfon

[0521] VC: Vinylene carbonate

[0522] FEC: Fluoroethylene carbonate

[0523] LiBOB: Lithium bis(oxalato)borate

[0524]

[0525] Experimental Example

[0526] Experimental Example 1: Evaluation of Low-Temperature Initial Dose Expression Rate

[0527] The lithium secondary batteries of the examples and comparative examples were charged to 3.8V at room temperature (25℃) under 0.33C conditions using constant current / constant voltage (CC / CV) (0.05C cut-off), discharged to 2.5V at 0.33C using constant current (CC), and the initial discharge capacity was measured using a PNE-0506 charger / discharger (manufacturer: PNE solution).

[0528] Then, at a low temperature (-10℃), constant current / constant voltage (CC / CV) charging was performed up to 3.8V under conditions of 0.33C (0.05C cut-off), and constant current (CC) discharging was performed down to 2.5V under conditions of 0.33C to measure the discharge capacity.

[0529] The low-temperature initial capacity development rate (%) was calculated using the initial capacity obtained at room temperature (25℃) and the discharge capacity obtained at low temperature, and the results are shown in Table 2 below.

[0530]

[0531] Experimental Example 2. Evaluation of Low-Temperature Cycle Performance

[0532] Low-temperature cycle performance evaluation was performed on the lithium secondary batteries of the examples and comparative examples manufactured above.

[0533] Specifically, the lithium secondary batteries of the examples and comparative examples were charged to 3.8V at a constant current / constant voltage (CC / CV) condition at 0.33C at a low temperature (-10℃) (0.05C cut-off), and discharged to 2.5V at a constant current (CC) condition at 0.33C, with the discharge capacity after one cycle being measured.

[0534] Then, after performing 100 charge-discharge cycles under the charge-discharge conditions described above, the capacity retention rate (%) was measured. The capacity retention rate (%) was calculated according to Equation 1 below. The results are shown in Table 2 below.

[0535] [Equation 1]

[0536] Capacity Retention Rate (%) = (Discharge Capacity after 10 Cycles / Discharge Capacity after 1 Cycle) × 100

[0537]

[0538] Experimental Example 3: High-temperature cycle performance evaluation

[0539] High-temperature cycle performance evaluation was performed on the lithium secondary batteries of the examples and comparative examples manufactured above.

[0540] Specifically, the lithium secondary batteries of the examples and comparative examples were charged to 3.8V at 0.33C at 45℃ using a constant current / constant voltage (CC / CV) method (0.05C cut-off), and discharged to 2.5V at 0.33C using a constant current (CC) method, with the discharge capacity after one cycle being measured.

[0541] Then, after performing 300 charge-discharge cycles under the charge-discharge conditions described above, the capacity retention rate (%) was measured. The capacity retention rate (%) was calculated according to Equation 2 below. The results are shown in Table 2 below.

[0542] [Equation 2]

[0543] Capacity Retention Rate (%) = (Discharge Capacity after 300 cycles / Discharge Capacity after 1 cycle) × 100

[0544]

[0545] Experimental Example 4. Evaluation of High-Temperature Storage Characteristics

[0546] The lithium secondary batteries of the examples and comparative examples were charged to 3.8V at room temperature (25℃) under 0.33C conditions using constant current / constant voltage (CC / CV) (0.05C cut-off), discharged to 2.5V at 0.33C using constant current (CC), and the initial discharge capacity was measured using a PNE-0506 charger / discharger (manufacturer: PNE solution).

[0547] Then, after storing at a high temperature (60℃) for 16 weeks, the discharge capacity was measured by charging to 3.8V with a constant current / constant voltage (CC / CV) under conditions of 0.33C (0.05C cut-off) and discharging to 2.5V with a constant current (CC) at 0.33C.

[0548] The capacity retention rate (%) was calculated using the initial capacity obtained at room temperature (25℃) and the discharge capacity obtained after high-temperature storage, and the results are shown in Table 2 below.

[0549]

[0550] Low-temperature capacity development rate (%) Capacity retention rate after low-temperature cycle (%) Capacity retention rate after high-temperature cycle (%) Capacity retention rate after high-temperature storage (%) Example 1 68.6 99.5 94.0 90.2 Example 2 70.4 99.2 93.4 89.6 Example 3 70.3 99.7 94.5 89.5 Example 4 71.8 99.9 3.9 90.0 Example 5 69.9 99.3 93.1 89.5 Example 6 71.1 99.8 94.4 89.8 Example 7 69.9 99.3 93.2 90.4 Example 8 69.0 99.5 94.1 90.5 Example 9 69.9 99.5 93.3 89.6 Comparative Example 168.690.589.658.9 Comparative Example 269.089.790.487.9 Comparative Example 368.887.891.386.7 Comparative Example 467.697.591.086.7 Comparative Example 569.597.290.488.0 Comparative Example 660.314.390.388.0 Comparative Example 758.921.192.689.6 Comparative Example 859.811.393.589.6

[0551]

[0552] Referring to Table 2 above, it can be seen that the lithium secondary batteries of Examples 1 to 9 and Comparative Examples 1 to 5, which contain a cyclic lactone compound as an organic solvent, have a low-temperature initial capacity development rate of 67.6% or higher, which is an improvement compared to the lithium secondary batteries of Comparative Examples 6 to 8, which do not contain a cyclic lactone compound as an organic solvent.

[0553] In particular, in the case of a lithium secondary battery manufactured in the embodiments of the present invention including the first additive and the second additive as additives, it can be confirmed that it exhibits significantly superior performance in terms of capacity retention rate after low-temperature cycle, capacity retention rate after high-temperature cycle, and capacity retention rate after high-temperature storage compared to the lithium secondary batteries of Comparative Examples 1 to 5 that do not include the additives of the present invention.

Claims

As 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 a fluorine-based compound, 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. In paragraph 1, The above carbonate-based organic solvent is a non-aqueous electrolyte comprising a cyclic carbonate-based organic solvent. In paragraph 1, The above-mentioned cyclic lactone compound is a non-aqueous electrolyte, gamma-butyrolactone. In paragraph 1, The above-mentioned fluorine-based compound is a non-aqueous electrolyte comprising at least one of a fluorine-based phosphate compound, a fluorine-based acrylate compound, and a fluorine-based proparzyl compound. In claim 4, The above-mentioned fluorine-based phosphate compound is a non-aqueous electrolyte, which is lithium difluorophosphate. In claim 4, The above fluorinated acrylate compound is a non-aqueous electrolyte comprising a compound represented by the following chemical formula 2: [Chemical Formula 2] In the above chemical formula 2, Ra is hydrogen or an alkyl group having 1 to 3 carbon atoms, and Rb is an alkyl group having 1 to 20 carbon atoms substituted with at least one fluorine. In paragraph 6, In the above chemical formula 2, Ra is hydrogen and Rb is a non-aqueous electrolyte having 3 to 15 carbon atoms substituted with at least one fluorine. In paragraph 6, The above-mentioned fluorinated acrylate compound is a non-aqueous electrolyte comprising at least one selected from the group consisting of compounds represented by the following chemical formulas 2A to 2C: [Chemical Formula 2A] [Chemical Formula 2B] [Chemical Formula 2C] . In paragraph 4, The above-mentioned fluorinated proparzyl compound is a non-aqueous electrolyte comprising a compound represented by the following chemical formula 3: [Chemical Formula 3] In the above chemical formula 3, A is -C(O)- or -CH2-, and R is an alkyl group having 1 to 20 carbon atoms substituted with at least one fluorine. In Paragraph 9, In the above chemical formula 3, R is a non-aqueous electrolyte having 3 to 15 carbon atoms substituted with at least one fluorine. In Paragraph 9, The above-mentioned fluorinated proparzyl compound is a non-aqueous electrolyte comprising at least one selected from the group consisting of compounds represented by the following chemical formulas 3A to 3D: [Chemical Formula 3A] [Chemical Formula 3B] [Chemical Formula 3C] [Chemical Formula 3D] . In paragraph 1, The above-mentioned first additive is a non-aqueous electrolyte included in an amount of 0.01% to 10% by weight based on the total weight of the non-aqueous electrolyte. 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. 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 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 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 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. there is. 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. 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. 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 paragraph 1, The compound represented by the above chemical formula 1 is a non-aqueous electrolyte included in an amount of 0.1% to 3.0% by weight based on the total weight of the non-aqueous electrolyte. In paragraph 1, The above-mentioned non-aqueous electrolyte includes a third additive, The above third additive is a non-aqueous electrolyte comprising at least one of ethylene sulfate and 1,3-propane sulfone. In Paragraph 19, A non-aqueous electrolyte in which the total content of the above ethylene sulfate and 1,3-propane sulfone is 0.1% to 2.0% by weight based on the total weight of the above non-aqueous electrolyte. 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. In claim 21, 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. In claim 21, 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.

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