Nonaqueous electrolyte and lithium secondary battery containing same

Abstract

The present invention provides a non-aqueous electrolyte comprising a lithium salt, an organic solvent, and an additive, wherein the additive comprises at least one compound selected from the group consisting of compounds represented by the following Chemical Formula 1 and Chemical Formula 2: JPEG2025538743000027.jpg42170JPEG2025538743000028.jpg33170 (In the above Chemical Formula 1, n1 is an integer of 0 to 18, and in the above Chemical Formula 2, n2 is an integer of 0 to 18, and L is an alkylene group having 1 to 10 carbon atoms.)

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0182372, filed December 22, 2022, and all contents disclosed in the documents of this Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a non-aqueous electrolyte and a lithium secondary battery containing the same. [Background technology]

[0003] The development of the information society has led to the development of personal IT devices and computer networks, which has increased society's overall dependence on electrical energy. This has led to a demand for the development of technologies to efficiently store and utilize electrical energy.

[0004] Of the technologies currently being developed, secondary batteries are the most suitable for a variety of applications, and among these secondary batteries, interest is growing in lithium-ion batteries, which not only can be miniaturized to a degree suitable for use in personal IT devices, but also have the highest energy density.

[0005] Generally, a lithium secondary battery is manufactured by injecting or impregnating a non-aqueous electrolyte into an electrode assembly including a positive electrode, a negative electrode, and a porous separator.

[0006] Positive electrode active materials for such lithium secondary batteries that are being considered for use include lithium-containing cobalt oxide, LiMnO2 with a layered crystal structure, LiMn2O4 with a spinel crystal structure, lithium-containing nickel oxide (LiNiO2), lithium nickel-cobalt-manganese transition metal oxide, and lithium iron phosphate (e.g., LiFePO4)-based compounds.

[0007] On the other hand, lithium salts such as LiPF6 contained in non-aqueous electrolytes are converted into PF6 -The anion is thermally decomposed to form a Lewis acid such as PF5, which reacts with water to produce HF. Such substances, such as PF5 or HF, can not only destroy the coating formed on the surface of the electrode, but also potentially cause decomposition of the organic solvent. Furthermore, the HF and PF5 mentioned above can cause the problem of leaching transition metals from the surface of the positive electrode active material, which destabilizes the lattice structure of the positive electrode active material. This can accelerate the decomposition of the organic solvent in the non-aqueous electrolyte, generating active oxygen and accelerating gas generation. Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to solve the above-mentioned problems and to provide a nonaqueous electrolyte that can form a strong and low-resistance SEI coating on a positive electrode and a negative electrode and can scavenge radicals such as active oxygen generated from the positive electrode, thereby improving the output characteristics, life characteristics, and high-temperature storage characteristics of a lithium secondary battery.

[0009] Another object of the present invention is to provide a lithium secondary battery containing the above-mentioned non-aqueous electrolyte. [Means for solving the problem]

[0010] The present invention provides a non-aqueous electrolyte comprising a lithium salt, an organic solvent, and an additive, wherein the additive comprises at least one compound selected from the group consisting of compounds represented by the following Chemical Formula 1 and Chemical Formula 2:

[0011] [ka]

[0012] [ka]

[0013] In the above Chemical Formula 1, n1 is an integer of 0 to 18, In the above chemical formula 2, n2 is an integer of 0 to 18, and L is an alkylene group having 1 to 10 carbon atoms.

[0014] The present invention also provides a lithium secondary battery including a positive electrode, a negative electrode facing the positive electrode, a separator interposed between the positive electrode and the negative electrode, and the non-aqueous electrolyte. [Effects of the Invention]

[0015] The present invention relates to a non-aqueous electrolyte containing, as an additive, at least one compound selected from the group consisting of compounds represented by Chemical Formula 1 and Chemical Formula 2. The compound represented by Chemical Formula 1 contains a propargyl group (—C≡C—) and a fluorine-substituted alkyl group within its structure, and therefore can be reduced prior to organic solvents, forming a strong, low-resistance SEI coating on the surfaces of the positive and negative electrodes. Furthermore, the compounds represented by Chemical Formula 1 and / or Chemical Formula 2 can scavenge radicals such as active oxygen generated from the positive electrode, thereby improving the oxidation resistance and flame retardancy of the positive electrode. As a result, a lithium secondary battery incorporating the non-aqueous electrolyte according to the present invention can exhibit improved output characteristics (specifically, room-temperature output characteristics and low-temperature output characteristics), life characteristics, and high-temperature storage characteristics. DETAILED DESCRIPTION OF THE INVENTION

[0016] First, before describing the present invention, the terms and words used in this specification and claims should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, in accordance with the principle that inventors can appropriately define the concepts of terms in order to best explain their inventions.

[0017] Meanwhile, the terms used in this specification are used only to describe exemplary embodiments and are not intended to limit the present invention. The singular expressions include the plural expressions unless the context clearly indicates otherwise.

[0018] As used herein, the terms "comprises," "comprises," or "having" are intended to specify the presence of embodied features, numbers, steps, components, or combinations thereof, and should be understood as not precluding the presence or possible addition of one or more other features, numbers, steps, components, or combinations thereof.

[0019] In this specification, "%" means % by weight unless expressly indicated otherwise.

[0020] Before describing the present invention, in the description of "number of carbon atoms a to b" in the specification, "a" and "b" refer to the number of carbon atoms contained in a specific functional group. That is, the functional group may contain "a" to "b" carbon atoms.

[0021] In addition, in this specification, unless otherwise defined, the term "substituted" means that at least one hydrogen atom bonded to a carbon atom is substituted with an element other than hydrogen, for example, with an alkyl group having 1 to 5 carbon atoms or a fluorine atom.

[0022] In this specification, the average particle size (D 50 The average particle size (D) can be defined as the particle size corresponding to 50% of the cumulative volume in the particle size distribution curve. 50 ) can be measured by, for example, the laser diffraction method. The laser diffraction method is generally capable of measuring particle sizes from the submicron range to several mm, and can provide results with high reproducibility and high resolution.

[0023] The present invention will now be described in more detail.

[0024] non-aqueous electrolyte The present invention relates to a non-aqueous electrolyte, and more particularly to a non-aqueous electrolyte for a lithium secondary battery.

[0025] The non-aqueous electrolyte according to the present invention comprises a lithium salt, an organic solvent, and an additive, and the additive comprises at least one compound selected from the group consisting of compounds represented by the following Chemical Formula 1 and Chemical Formula 2:

[0026] [ka]

[0027] [ka]

[0028] In the above Chemical Formula 1, n1 is an integer of 0 to 18, In the above chemical formula 2, n2 is an integer of 0 to 18, and L is an alkylene group having 1 to 10 carbon atoms.

[0029] The present invention relates to a non-aqueous electrolyte containing, as an additive, at least one compound selected from the group consisting of compounds represented by Chemical Formula 1 and Chemical Formula 2. The compound represented by Chemical Formula 1 contains a propargyl group (—C≡C—) and a fluorine-substituted alkyl group within its structure, and therefore can be reduced prior to organic solvents, forming a strong, low-resistance SEI coating on the surfaces of the positive and negative electrodes. Furthermore, the compounds represented by Chemical Formula 1 and / or Chemical Formula 2 can scavenge radicals such as active oxygen generated from the positive electrode, thereby improving the oxidation resistance and flame retardancy of the positive electrode. As a result, a lithium secondary battery incorporating the non-aqueous electrolyte according to the present invention can exhibit improved output characteristics (specifically, room-temperature output characteristics and low-temperature output characteristics), life characteristics, and high-temperature storage characteristics.

[0030] 1) Lithium salt First, the lithium salt will be described as follows.

[0031] In the non-aqueous electrolyte for a lithium secondary battery according to one embodiment of the present invention, the lithium salt may be any of those commonly used in electrolytes for lithium secondary batteries, without any limitation. For example, Li + and the anion is F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , AlO4 - , AlCl4 - , PF6 - , SbF6 - , AsF6 - , B 10 Cl 10 - , BF2C2O4 - , BC4O8 - , PF4C2O4 - , PF2C4O8 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , C4F9SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , CH3SO3 - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - , and (CF3CF2SO2)2N - Specifically, the lithium salt may be at least one selected from the group consisting of LiCl, LiBr, LiI, LiBF4, LiClO4, LiAlO4, LiAlCl4, LiPF6, LiSbF6, LiAsF6, LiB 10Cl 10 , LiBOB (LiB(C2O4)2), LiCF3SO3, LiTFSI (LiN(SO2CF3)2), LiFSI (LiN(SO2F)2), LiCH3SO3, LiCF3CO2, LiCH3CO2, and LiBETI (LiN(SO2CF2CF3)2). Specifically, the lithium salt may include a single substance or a mixture of two or more substances 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), and more specifically, may include LiPF6.

[0032] The lithium salt may be varied as appropriate within a range that is normally usable, but in order to obtain the optimum effect of forming a corrosion prevention coating on the electrode surface, it may be contained in the electrolyte at a concentration of 0.8 M to 3.0 M, specifically 1.0 M to 3.0 M.

[0033] When the concentration of the lithium salt satisfies the above range, the viscosity of the nonaqueous electrolyte can be controlled to achieve optimal impregnation, and the mobility of lithium ions can be improved, resulting in improved capacity characteristics and cycle characteristics of the lithium secondary battery.

[0034] 2) Organic solvents The organic solvent is not particularly limited as long as it is a non-aqueous solvent commonly used in lithium secondary batteries and minimizes decomposition due to oxidation reactions during charging and discharging of the secondary battery.

[0035] Specifically, the organic solvent may include a cyclic carbonate organic solvent and a linear carbonate organic solvent.

[0036] The cyclic carbonate organic solvent is a highly viscous organic solvent that has a high dielectric constant and easily dissociates the lithium salt in the electrolyte. Specifically, the cyclic carbonate organic solvent may include at least one organic solvent selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, and vinylene carbonate, and more specifically, may include ethylene carbonate.

[0037] The linear carbonate organic solvent is an organic solvent having low viscosity and low dielectric constant, and may specifically include at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate, and ethyl propyl carbonate. The linear carbonate organic solvent may specifically include ethyl methyl carbonate and dimethyl carbonate, more specifically, ethyl methyl carbonate and dimethyl carbonate in a volume ratio of 60:40 to 90:10.

[0038] The organic solvent may be a mixture of a cyclic carbonate organic solvent and a linear carbonate organic solvent, in which the cyclic carbonate organic solvent and the linear carbonate organic solvent may be mixed in a volume ratio of 10:90 to 50:50, specifically 15:85 to 40:60.

[0039] Meanwhile, the organic solvent may further include, as needed, any organic solvent commonly used in non-aqueous electrolytes, for example, at least one of an ester-based organic solvent, an ether-based organic solvent, a glyme-based solvent, and a nitrile-based organic solvent.

[0040] The ester-based organic solvent may include at least one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone.

[0041] The ether solvent may be any one selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether, ethyl propyl ether, 1,3-dioxolane (DOL), and 2,2-bis(trifluoromethyl)-1,3-dioxolane (TFDOL), or a mixture of two or more of these, but is not limited thereto.

[0042] The glyme-based solvent has a higher dielectric constant and lower surface tension than linear carbonate-based organic solvents and is less reactive with metals, and 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.

[0043] The nitrile solvent may be one or more selected from the group consisting of acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentanecarbonitrile, cyclohexanecarbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile, but is not limited thereto.

[0044] On the other hand, in the non-aqueous electrolyte, the remainder excluding the lithium salt and the additive is an organic solvent unless otherwise specified.

[0045] (3) Additives The non-aqueous electrolyte of the present invention contains an additive.

[0046] The additive includes a compound represented by the following Chemical Formula 1:

[0047] [ka]

[0048] [ka]

[0049] In the above Chemical Formula 1, n1 is an integer of 0 to 18, In the above chemical formula 2, n2 is an integer of 0 to 18, and L is an alkylene group having 1 to 10 carbon atoms.

[0050] Specifically, at least one compound selected from the group consisting of compounds represented by Formula 1 and Formula 2 contains a propargyl functional group within its structure, which allows it to be easily reductively decomposed on the surface of the negative electrode, thereby forming an SEI film with low resistance and high passivation ability. Therefore, when a nonaqueous electrolyte containing the compound represented by Formula 1 as an electrolyte additive is used, it is possible to prevent a self-discharge reaction of the negative electrode due to additional reductive decomposition of the electrolyte caused by the instability of the SEI film.

[0051] Furthermore, at least one compound selected from the group consisting of compounds represented by Chemical Formula 1 and Chemical Formula 2 contains an alkyl group substituted with a fluorine atom at the structural terminal, thereby forming an oxidation-resistant coating on the surface of the positive electrode. This prevents transition metals from leaching from the positive electrode and the leached transition metals from being electrodeposited and precipitated on the negative electrode, thereby preventing internal short circuits. Furthermore, the fluorine-substituted alkyl group, which has excellent flame retardancy and non-flammability, acts as a radical scavenger due to the fluorine atom and can form a passivation coating on the surface of the positive electrode that ensures excellent oxidation resistance. As a result, side reactions between the electrode and the electrolyte are suppressed, and a lithium secondary battery with improved room-temperature and low-temperature life characteristics can be provided.

[0052] In addition, at least one compound selected from the group consisting of compounds represented by Chemical Formula 1 and Chemical Formula 2 contains one or two oxygen atoms in its molecular structure, and therefore has improved oxidation safety, high voltage stability, and electrolyte durability compared to compounds containing three or more oxygen atoms.

[0053] As described above, the compound represented by Chemical Formula 1 contains a fluorine-containing alkyl group and a propargyl group, which have excellent flame retardancy and non-flammability, and therefore forms a low-resistance, strong SEI coating on the negative electrode, which not only suppresses the additional reduction decomposition reaction of the electrolyte but also prevents the self-discharge reaction of the negative electrode, thereby improving the life performance, suppressing an increase in initial resistance, and providing a lithium secondary battery with improved room temperature and low temperature output characteristics.

[0054] In Chemical Formula 1, n1 may be an integer from 0 to 18, specifically an integer from 0 to 10, more specifically an integer from 0 to 5, and even more specifically an integer from 1 to 3. In Chemical Formula 2, n2 may be an integer from 0 to 18, specifically an integer from 0 to 10, more specifically an integer from 0 to 7, and even more specifically an integer from 3 to 7. When n1 or n2 satisfies the above range, the thermal properties of the compound itself can be improved, and the stability of the coating formed therefrom can be expected. In Chemical Formula 1 and Chemical Formula 2, when n1 and n2 each exceed 18, the fluorine element is contained in an excessive amount, which increases the viscosity and non-polarity of the material and reduces its solubility in the electrolyte, potentially resulting in reduced ionic conductivity and deterioration of battery performance.

[0055] In the above chemical formula 2, L may be an alkylene group having 1 to 10 carbon atoms, specifically an alkylene group having 1 to 3 carbon atoms, more specifically an alkylene group selected from a methylene group and an ethylene group, and even more specifically a methylene group.

[0056] The compound represented by Chemical Formula 1 may preferably include at least one selected from the group consisting of compounds represented by Chemical Formula 1-1, Chemical Formula 1-2, and Chemical Formula 1-3 below, more preferably a compound represented by Chemical Formula 1-1 below.

[0057] [ka]

[0058] [ka]

[0059] [ka]

[0060] Furthermore, the compound represented by Chemical Formula 2 may preferably include at least one selected from the group consisting of compounds represented by Chemical Formula 2-1, Chemical Formula 2-2, and Chemical Formula 2-3, and more preferably include a compound represented by Chemical Formula 2-3 below.

[0061] [ka]

[0062] [ka]

[0063] [ka]

[0064] Meanwhile, the additive may be contained in the non-aqueous electrolyte in an amount of 0.01% by weight to 10% by weight.

[0065] When the additive is contained in the non-aqueous electrolyte within the above content range, drawbacks such as additive-induced side reactions, capacity reduction, and resistance increase can be minimized. In addition, a low-resistance SEI coating can be formed on the surface of the negative electrode, improving the lithium migration effect in the coating, suppressing further reduction decomposition reactions of the electrolyte, and preventing self-discharge reactions of the negative electrode.

[0066] Specifically, when the content of the compound represented by Chemical Formula 1 is 0.01 wt % or more, a stable coating is formed during the battery's operating time, forming a low-resistance SEI coating on the surface of the negative electrode, thereby improving battery output performance. Also, when the content of the compound represented by Chemical Formula 1 is 10 wt % or less, the viscosity of the nonaqueous electrolyte can be controlled to achieve optimal impregnation, effectively suppressing an increase in battery resistance due to decomposition of additives, further increasing ionic conductivity within the battery, and preventing a decrease in output characteristics.

[0067] Specifically, the compound represented by Chemical Formula 1 may be contained in the non-aqueous electrolyte solution in an amount of 0.05 wt % to 8 wt %, more specifically 0.1 wt % to 5 wt %, and even more specifically 0.1 wt % to 3 wt %.

[0068] Meanwhile, the non-aqueous electrolyte may further contain an auxiliary additive together with the additive, if necessary, to prevent the non-aqueous electrolyte from being decomposed and causing the collapse of the negative electrode in a high-power environment, or to further improve low-temperature high-rate discharge characteristics, high-temperature stability, overcharge prevention effect, and battery expansion suppression effect at high temperatures.

[0069] Examples of such auxiliary additives include at least one selected from the group consisting of cyclic carbonate compounds, halogen-substituted carbonate compounds, sultone compounds, sulfate compounds, phosphate or phosphite compounds, borate compounds, nitrile compounds, benzene compounds, amine compounds, silane compounds, and lithium salt compounds.

[0070] The cyclic carbonate compound may be, for example, vinylene carbonate (VC) or vinylethylene carbonate.

[0071] The halogen-substituted carbonate compound may be, for example, fluoroethylene carbonate (FEC).

[0072] The sultone compound may be, for example, at least one compound selected from the group consisting of 1,3-propane sultone (PS), 1,4-butane sultone, ethene sultone, 1,3-propene sultone (PRS), 1,4-butene sultone, and 1-methyl-1,3-propene sultone.

[0073] The sulfate compound may be, for example, ethylene sulfate (Esa), trimethylene sulfate (TMS), or methyl trimethylene sulfate (MTMS).

[0074] The phosphate-based or phosphite-based compound may be, for example, one or more compounds selected from the group consisting of lithium difluoro(bisoxalato)phosphate, lithium difluorophosphate, tris(trimethylsilyl)phosphate, tris(trimethylsilyl)phosphite, tris(2,2,2-trifluoroethyl)phosphate, and tris(trifluoroethyl)phosphite.

[0075] Examples of the borate-based compounds include tetraphenylborate, lithium difluoro(oxalato)borate (LiODFB), and lithium bisoxalatoborate (LiB(C2O4)2, LiBOB).

[0076] The nitrile compound may be, for example, at least one compound selected from the group consisting of succinonitrile, adiponitrile, acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentanecarbonitrile, cyclohexanecarbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile.

[0077] The benzene-based compound may be, for example, fluorobenzene, the amine-based compound may be, for example, triethanolamine or ethylenediamine, and the silane-based compound may be, for example, tetravinylsilane.

[0078] The lithium salt-based compound is a compound different from the lithium salt contained in the non-aqueous electrolyte, and examples thereof include lithium difluorophosphate (LiPO2F2) and LiBF4.

[0079] Among these auxiliary additives, when at least one selected from the group consisting of vinylene carbonate, vinylethylene carbonate, 1,3-propane sultone, fluoroethylene carbonate, ethylene sulfate, succinonitrile, and lithium difluoro(oxalato)borate, specifically at least one selected from the group consisting of vinylene carbonate and ethylene sulfate, is used, a stronger SEI coating can be formed on the surface of the negative electrode during the initial activation step of the secondary battery.

[0080] The auxiliary additive may be a combination of two or more compounds, and the total content of the additives and auxiliary additives may be 50 wt % or less, specifically 0.05 wt % to 20 wt %, more specifically 0.05 wt % to 10 wt %, based on the total weight of the non-aqueous electrolyte. When the total content of the additives satisfies the above range, the low-temperature output characteristics of the battery can be improved, and the high-temperature storage characteristics and high-temperature life characteristics can be more effectively improved, and side reactions in the battery due to residual additives after the reaction can be prevented.

[0081] Lithium secondary battery The present invention also provides a lithium secondary battery containing the above-mentioned non-aqueous electrolyte.

[0082] Specifically, the lithium secondary battery according to the present invention includes a positive electrode, a negative electrode facing the positive electrode, a separator interposed between the positive electrode and the negative electrode, and the non-aqueous electrolyte.

[0083] The lithium secondary battery may be manufactured by placing an electrode assembly including the positive electrode, a negative electrode facing the positive electrode, and a separator interposed between the positive electrode and the negative electrode in a battery case, and then injecting a non-aqueous electrolyte therein.

[0084] (1) Positive electrode The positive electrode includes a positive electrode active material.

[0085] The positive electrode active material may include lithium iron phosphate particles. The lithium iron phosphate particles have a problem of leaching Fe when exposed to lithium salt by-products (e.g., HF, PF5). The leached Fe migrates to the negative electrode via the non-aqueous electrolyte and destroys the SEI film formed on the negative electrode surface, accelerating electrolyte side reactions, or generating active oxygen from the positive electrode active material, potentially promoting decomposition of the organic solvent. However, when the non-aqueous electrolyte according to the present invention is used with a positive electrode containing lithium iron phosphate particles, a strong SEI film is formed on the positive electrode surface, preventing Fe leaching. Furthermore, the aforementioned radical scavenging effect removes active oxygen, significantly preventing electrolyte side reactions. This allows for the realization of a lithium secondary battery with significantly improved output characteristics, life characteristics, and high-temperature storage performance.

[0086] The lithium iron phosphate particles may include a compound represented by the following chemical formula A:

[0087] [Chemical formula A] Li 1+a Fe 1-s M s (PO 4-b )X b

[0088] In the chemical formula A, M is one or more elements selected from Co, Ni, Al, Mg, Ti, and V, and X is F, S, or N, where 0≦s≦0.5; −0.5≦a≦+0.5; and 0≦b≦0.1.

[0089] The chemical formula A can be specifically represented as LiFePO4 (a=0, s=0, and b=0).

[0090] The lithium iron phosphate particles may be composed of primary particles, secondary particles formed by agglomeration of two or more primary particles, or a mixture of primary particles and secondary particles formed by agglomeration of two or more primary particles.

[0091] At this time, the primary particles have an average particle size (D 50 ) of 0.2 μm to 3.0 μm, specifically 0.2 μm to 2.0 μm, and more specifically may be 0.3 μm to 1.5 μm. The secondary particles may have an average particle size (D 50 ) of 7 μm to 25 μm, specifically 10 μm to 20 μm.

[0092] The positive electrode active material may further include a carbon coating layer located on the lithium iron phosphate oxide particles. The carbon coating layer can be introduced for the purpose of protecting the lithium iron phosphate oxide particles and improving the electrical conductivity.

[0093] On the other hand, the positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically includes a lithium transition metal composite oxide containing at least one transition metal selected from nickel, cobalt, manganese, and aluminum and lithium, preferably a lithium transition metal composite oxide containing a transition metal containing nickel, cobalt, and manganese and lithium.

[0094] For example, as the lithium transition metal composite oxide, there are lithium-manganese-based oxides (such as LiMnO2, LiMn2O4, etc.), lithium-cobalt-based oxides (such as LiCoO2, etc.), lithium-nickel-based oxides (such as LiNiO2, etc.), lithium-nickel-manganese-based oxides (such as LiNi 1-Y Mn Y O2 (where 0 < Y < 1), LiMn 2-Z Ni Z O4 (where 0 < Z < 2), etc.), lithium-nickel-cobalt-based oxides (such as LiNi 1-Y1 Co Y1 O2 (where 0 < Y1 < 1), etc.), lithium-manganese-cobalt-based oxides (such as LiCo 1-Y2 Mn Y2 O2 (where 0 < Y2 < 1), LiMn 2-Z1 Co Z1O4 (where 0 < Z1 < 2), etc.), lithium-nickel-manganese-cobalt-based oxides (e.g., Li(Ni p Co q Mn r1 )O2 (where 0 < p < 1, 0 < q < 1, 0 < r1 < 1, p + q + r1 = 1) or Li(Ni p1 Co q1 Mn r2 )O4 (where 0 < p1 < 2, 0 < q1 < 2, 0 < r2 < 2, p1 + q1 + r2 = 2), etc.), or lithium-nickel-cobalt-transition metal (M) oxides (e.g., Li(Ni p2 Co q2 Mn r3 M S2 )O2 (where M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, and p2, q2, r3, and s2 are the atomic fractions of independent elements, respectively, where 0 < p2 < 1, 0 < q2 < 1, 0 < r3 < 1, 0 < s2 < 1, and p2 + q2 + r3 + s2 = 1), etc.), and any one or two or more of these compounds may be included. Among them, from the point of view of improving the capacity characteristics and stability of the battery, the lithium transition metal composite oxide is LiCoO2, LiMnO2, LiNiO2, lithium nickel-manganese-cobalt oxide (e.g., Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2, or Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc.), or lithium nickel cobalt aluminum oxide (e.g., Li(Ni 0.8 Co 0.15 Al 0.05 )O2, etc.), and considering the significance of the improvement effect by controlling the types and content ratios of the constituent elements forming the lithium transition metal composite oxide, the lithium transition metal composite oxide is Li(Ni 0.6 Mn 0.2 Co0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2, or Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc., and any one or a mixture of two or more of these can be used.

[0095] More specifically, the positive electrode active material may be a lithium transition metal composite oxide containing 60 mol% or more of nickel, based on the total number of moles of transition metals contained in the lithium transition metal composite oxide. Specifically, the positive electrode active material may be a lithium transition metal composite oxide, the transition metals of which include nickel and at least one selected from manganese, cobalt, and aluminum, and the nickel content may be 60 mol% or more, specifically 60 mol% to 90 mol%, based on the total number of moles of the transition metals. When such a lithium transition metal composite oxide containing a high content of nickel is used together with the nonaqueous electrolyte solution, it is preferable because it can reduce by-products in the gas generated by structural collapse.

[0096] The positive electrode active material may include a lithium composite transition metal oxide represented by the following chemical formula B:

[0097] [Chemical formula B] Li 1+x (Ni a Co b Mn c M d )O2

[0098] In the chemical formula B, 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 atomic fractions of each independent element, and 0≦x≦0.2, 0.50≦a<1, 0 <b≦0.25、0<c≦0.25、0≦d≦0.1、a+b+c+d=1である。

[0099] Preferably, a, b, c, and d may be in the ranges 0.70≦a≦0.95, 0.025≦b≦0.20, 0.025≦c≦0.20, and 0≦d≦0.05, respectively.

[0100] Furthermore, the a, b, c, and d may be in the ranges 0.80≦a≦0.95, 0.025≦b≦0.15, 0.025≦c≦0.15, and 0≦d≦0.05, respectively.

[0101] Furthermore, the a, b, c, and d may be 0.85≦a≦0.90, 0.05≦b≦0.10, 0.05≦c≦0.10, and 0≦d≦0.03, respectively.

[0102] The positive electrode may include a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. In this case, the positive electrode active material layer may include the positive electrode active material described above.

[0103] The positive electrode current collector usually has a thickness of 3 μm to 500 μm.

[0104] The positive electrode current collector may have a surface with fine irregularities to enhance the bonding strength of the positive electrode active material. For example, the positive electrode current collector may be used in various forms such as a film, sheet, foil, mesh, porous material, foam, or nonwoven fabric.

[0105] The positive electrode active material layer may be disposed on at least one surface of the positive electrode current collector. Specifically, the positive electrode active material layer may be disposed on one or both surfaces of the positive electrode current collector.

[0106] The positive electrode active material may be contained in the positive electrode active material layer in an amount of 80% by weight to 99% by weight, taking into consideration the sufficient capacity of the positive electrode active material.

[0107] The positive electrode active material layer may further contain a binder and / or a conductive material in addition to the positive electrode active material.

[0108] The binder is a component that assists in binding the active material and conductive material, etc., and in binding them to the current collector, and specifically may contain at least one selected from the group consisting of polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber, and fluororubber, and preferably polyvinylidene fluoride.

[0109] The binder may be contained in the positive electrode active material layer in an amount of 1 to 20% by weight, preferably 1.2 to 10% by weight, in order to ensure sufficient binding strength between components such as the positive electrode active material.

[0110] The conductive material is used to assist and improve the conductivity of the secondary battery, and is not particularly limited as long as it does not cause chemical changes and is conductive. Specifically, the positive electrode conductive material may include at least one selected from the group consisting of graphite such as natural graphite and artificial graphite; carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; conductive tubes such as carbon nanotubes; fluorocarbons; metal powders such as aluminum and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and polyphenylene derivatives, and preferably includes carbon nanotubes in order to improve conductivity.

[0111] In order to ensure sufficient electrical conductivity, the conductive material may be contained in the positive electrode active material layer in an amount of 1 to 20% by weight, preferably 1.2 to 10% by weight.

[0112] The thickness of the positive electrode active material layer may be 100 μm to 400 μm, and preferably 150 μm to 300 μm.

[0113] The loading amount of the positive electrode active material layer is 2 mAh / cm 2 ~5mAh / cm 2 , preferably 3.5mAh / cm 2 ~4.0mAh / cm 2 It may be.

[0114] The positive electrode may be prepared by coating a positive electrode slurry containing a positive electrode active material, and optionally a binder, a conductive material, and a solvent for forming the positive electrode slurry, on the positive electrode current collector, followed by drying and rolling.

[0115] The solvent for forming the positive electrode slurry may include an organic solvent such as N-methyl-2-pyrrolidone (NMP), and the solid content of the positive electrode slurry may be 40% by weight to 90% by weight, specifically 50% by weight to 80% by weight.

[0116] (2) Negative electrode The negative electrode faces the positive electrode.

[0117] The negative electrode includes a negative electrode active material.

[0118] The negative electrode may include a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material may be contained in the negative electrode active material layer.

[0119] The negative electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and has high conductivity. Specifically, the negative electrode current collector may be made of copper, stainless steel, aluminum, nickel, titanium, baked carbon, copper or stainless steel whose surface is treated with carbon, nickel, titanium, silver, or the like, or an aluminum-cadmium alloy.

[0120] The negative electrode current collector usually has a thickness of 3 μm to 500 μm.

[0121] The negative electrode current collector may have a surface with fine irregularities to enhance the bonding strength of the negative electrode active material. For example, the negative electrode current collector may be used in various forms such as a film, sheet, foil, mesh, porous material, foam, or nonwoven fabric.

[0122] The negative electrode active material layer may be 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.

[0123] The negative electrode active material layer may include a negative electrode active material.

[0124] The negative electrode active material is a material capable of reversibly intercalating / deintercalating lithium ions, and may include at least one selected from the group consisting of a carbon-based active material, a (semi)metal-based active material, and lithium metal, and specifically may include at least one selected from a carbon-based active material and a (semi)metal-based active material.

[0125] 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 includes graphite. The graphite may include at least one selected from the group consisting of artificial graphite and natural graphite.

[0126] The average particle size (D 50) may be 10 μm to 30 μm, preferably 15 μm to 25 μm, in order to ensure structural stability during charge and discharge and reduce side reactions with the electrolyte.

[0127] Specifically, the (semi)metal-based active material may include at least one (semi)metal selected from the group consisting of Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, V, Ti, and Sn; an alloy of lithium with at least one (semi)metal selected from the group consisting of Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, V, Ti, and Sn; an oxide of at least one (semi)metal selected from the group consisting of Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, V, Ti, and Sn; lithium titanium oxide (LTO); lithium vanadium oxide; and the like.

[0128] More specifically, the (semi)metallic active material may include a silicon-based active material.

[0129] The silicon-based active material is SiO x (0≦x<2). SiO2 does not react with lithium ions and therefore cannot store lithium. Therefore, x is preferably within the above range, and more preferably, the silicon-based oxide may be SiO.

[0130] The average particle size (D 50 ) may be 1 μm to 30 μm, preferably 2 μm to 15 μm, from the viewpoint of improving structural stability during charge and discharge and reducing side reactions with the electrolyte.

[0131] The negative electrode active material may be contained in the negative electrode active material layer in an amount of 60% by weight to 99% by weight, preferably 75% by weight to 95% by weight.

[0132] The negative electrode active material layer may further include a binder and / or a conductive material in addition to the negative electrode active material.

[0133] The binder is used to improve the adhesive strength between the negative electrode active material layer and the negative electrode current collector, thereby improving battery performance. For example, the binder may include at least one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, and substances in which hydrogen is substituted with Li, Na, Ca, or the like, or may include various copolymers thereof.

[0134] The binder may be contained in the negative electrode active material layer in an amount of 0.5% by weight to 10% by weight, preferably 1% by weight to 5% by weight.

[0135] The conductive material is not particularly limited as long as it does not cause a chemical change in the battery and is conductive. For example, graphite such as natural graphite and artificial graphite; carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; conductive tubes such as carbon nanotubes; fluorocarbons; metal powders such as aluminum and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives may be used.

[0136] The conductive material may be contained in the negative electrode active material layer in an amount of 0.5% by weight to 10% by weight.

[0137] The thickness of the negative electrode active material layer may be 100 μm to 300 μm, and preferably 150 μm to 200 μm.

[0138] The loading amount of the negative electrode active material layer is 2 mAh / cm 2 ~5mAh / cm 2 , preferably 3.5mAh / cm 2 ~4.0mAh / cm 2 It may be.

[0139] The negative electrode may be prepared by coating at least one surface of a negative electrode current collector with a negative electrode slurry containing a negative electrode active material, a binder, a conductive material, and / or a solvent for forming the negative electrode slurry, followed by drying and rolling.

[0140] The solvent for forming the negative electrode slurry may include, for example, at least one selected from the group consisting of distilled water, N-methyl-2-pyrrolidone (NMP), ethanol, methanol, and isopropyl alcohol, preferably distilled water, in order to facilitate dispersion of the negative electrode active material, binder, and / or conductive material. The solid content of the negative electrode slurry may be 30% by weight to 80% by weight, specifically 40% by weight to 70% by weight.

[0141] (3) Separator The separator may be interposed between the positive electrode and the negative electrode.

[0142] The separator may be a conventional porous polymer film, such as a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer, either alone or in a laminate, or a conventional porous nonwoven fabric, such as a nonwoven fabric made of a high-melting point glass fiber, a polyethylene terephthalate fiber, etc., but is not limited to these. Furthermore, to ensure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymer material may be used, and may be selectively used in a single-layer or multi-layer structure.

[0143] The lithium secondary battery according to the present invention can be usefully used in the fields of portable devices such as mobile phones, notebook computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0144] Therefore, according to another embodiment of the present invention, there is provided a battery module including the lithium secondary battery as a unit cell, and a battery pack including the same.

[0145] The battery module or battery pack can be used as a power source for one or more medium- to large-sized devices, such as power tools; electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); and power storage systems.

[0146] The external shape of the lithium secondary battery of the present invention is not particularly limited, and may be a cylindrical shape using a can, a square shape, a pouch shape, a coin shape, or the like.

[0147] The lithium secondary battery according to the present invention can be used not only as a battery cell used as a power source for small devices, but also as a unit battery in a medium- to large-sized battery module containing a large number of battery cells.

[0148] The present invention will be specifically described below with reference to examples.

[0149] In this regard, the embodiments of the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.

[0150] The present invention will be specifically described below with reference to specific examples.

[0151] Example Example 1 (Production of non-aqueous electrolyte) An organic solvent was prepared by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 30:55:15.

[0152] LiPF6 as a lithium salt was dissolved in the organic solvent to a molar concentration of 1.0M.

[0153] In addition, the compound represented by Formula 1-1, vinylene carbonate, and ethylene sulfate were added to the organic solvent in which the lithium salt was dissolved to prepare a non-aqueous electrolyte.

[0154] The compound represented by Chemical Formula 1-1 was contained in the non-aqueous electrolyte at 0.5 wt %, the vinylene carbonate was contained in the non-aqueous electrolyte at 3 wt %, and the ethylene sulfate was contained in the non-aqueous electrolyte at 1 wt %.

[0155] (Secondary battery manufacturing) Lithium iron phosphate particles (LiFePO4, D50 A positive electrode slurry (solid content 65 wt%) was prepared by adding a 96:1:3 weight ratio of carbon nanotubes as a conductive material and polyvinylidene fluoride as a binder to N-methyl-2-pyrrolidone (NMP) as a solvent. The positive electrode slurry was applied to a 15 μm-thick positive electrode current collector (Al thin film) at 3.7 mAh / cm. 2 After drying, a positive electrode was manufactured by roll pressing (positive electrode active material thickness: 200 μm).

[0156] Anode active material graphite, binder SBR-CMC, and conductive material carbon black were mixed in a weight ratio of 95.5:4.0:0.5 with water as a solvent to prepare anode slurry (solid content: 50 wt%). The anode slurry was applied to an 8 μm-thick copper (Cu) thin film as anode current collector, and the resulting anode slurry provided 3.9 mAh / cm 2 After drying, a negative electrode was manufactured by roll pressing (thickness of negative electrode active material: 160 μm).

[0157] The positive electrode, a polyolefin-based porous separator, and a negative electrode were stacked in this order to prepare an electrode assembly.

[0158] The assembled electrode assembly was placed in a battery case, and the prepared non-aqueous electrolyte was injected into the battery case to manufacture a lithium secondary battery.

[0159] Example 2 A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that the compound represented by Chemical Formula 1-2 was added to the non-aqueous electrolyte in an amount of 0.5 wt % instead of the compound represented by Chemical Formula 1-1.

[0160] Example 3 A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that the compound represented by Chemical Formula 1-3 was added to the non-aqueous electrolyte in an amount of 0.5 wt % instead of the compound represented by Chemical Formula 1-1.

[0161] Example 4 A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that the compound represented by Chemical Formula 2-1 was added to the non-aqueous electrolyte in an amount of 0.5 wt % instead of the compound represented by Chemical Formula 1-1.

[0162] Example 5 A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that the compound represented by Chemical Formula 2-2 was added to the non-aqueous electrolyte in an amount of 0.5 wt % instead of the compound represented by Chemical Formula 1-1.

[0163] Example 6 A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that the compound represented by Chemical Formula 2-3 was added to the non-aqueous electrolyte in an amount of 0.5 wt % instead of the compound represented by Chemical Formula 1-1.

[0164] Comparative Example 1 A non-aqueous electrolyte and a lithium secondary battery were produced in the same manner as in Example 1, except that the compound represented by Chemical Formula 1-1 was not added.

[0165] Comparative Example 2 A non-aqueous electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that a compound represented by the following Chemical Formula 3 (a=20) was added to the non-aqueous electrolyte at a content of 0.5 wt % instead of the compound represented by Chemical Formula 1-1.

[0166] [ka]

[0167] Comparative Example 3 A non-aqueous electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 2, except that a compound represented by the following Chemical Formula 4 (b=20) was added to the non-aqueous electrolyte in an amount of 0.5 wt % instead of the compound represented by Chemical Formula 2-1.

[0168] [ka]

[0169] Comparative Example 4 A non-aqueous electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that a compound represented by the following Chemical Formula 5 (c=2) was added to the non-aqueous electrolyte in an amount of 0.5 wt % instead of the compound represented by Chemical Formula 1-1.

[0170] [ka]

[0171] Comparative Example 5 A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that a compound represented by the following Chemical Formula 6 was added to the non-aqueous electrolyte in an amount of 0.5 wt % instead of the compound represented by Chemical Formula 1-1.

[0172] [ka]

[0173] Experimental example Experimental Example 1: Evaluation of low-temperature cycle capacity retention The lithium secondary batteries of Examples 1 to 6 and Comparative Examples 1 to 5 manufactured as described above were initially charged and discharged at 25°C using an electrochemical charger / discharger under conditions of CC / CV, 1 / 3C to 3.65V, 0.05C, and then discharged under conditions of CC, 1 / 3C to 2.5V.

[0174] Thereafter, using an electrochemical charger / discharger, the battery was charged at -10°C under CC / CV conditions at 0.33C up to 3.65V at 0.05C, and then discharged under CC conditions at 0.33C down to 2.5V, and 100 charge / discharge cycles were performed, and the capacity retention rate was measured using the following formula. The results are shown in Table 1.

[0175] Capacity retention rate (%) = (100 cycle discharge capacity / 1 cycle discharge capacity) x 100

[0176] Experimental example 2: Evaluation of low-temperature cycle resistance increase rate The lithium secondary batteries of Examples 1 to 6 and Comparative Examples 1 to 5 manufactured as above were subjected to 100 charge / discharge cycles in the same manner as in Experimental Example 1.

[0177] After one charge / discharge cycle, the discharge capacity after one cycle was measured using an electrochemical charge / discharge device, and after adjusting the SOC to 50%, a 2.5C pulse was applied for 10 seconds, and the initial resistance was calculated from the difference in voltage before and after the pulse application.

[0178] After 100 cycles of charge and discharge, the resistance after 100 cycles was calculated in the same manner as above, and the results are shown in Table 1 below.

[0179] Resistance increase rate (%) = {(resistance after 100 cycles - initial resistance) / (initial resistance)} x 100

[0180] [Table 1]

[0181] Referring to Table 1, it can be seen that the lithium secondary batteries of Examples 1 to 6 according to the present invention exhibit superior low-temperature life performance and low-temperature output performance compared to Comparative Examples 1 to 5.

Claims

1. a lithium salt, an organic solvent, and an additive; The additive comprises at least one selected from the group consisting of compounds represented by the following Chemical Formula 1 and Chemical Formula 2: 【Chemistry 1】 【Chemistry 2】 (In the above Chemical Formula 1, n1 is an integer of 0 to 18, In the above chemical formula 2, n2 is an integer of 0 to 18, and L is an alkylene group having 1 to 10 carbon atoms.

2. 2. The non-aqueous electrolyte according to claim 1, wherein n1 in Chemical Formula 1 is an integer of 0 to 10.

3. 2. The non-aqueous electrolyte according to claim 1, wherein n2 in Chemical Formula 2 is an integer of 0 to 10.

4. 4. The non-aqueous electrolyte according to claim 1, wherein in Chemical Formula 2, L is an alkylene group having 1 to 3 carbon atoms.

5. The compound represented by Chemical Formula 1 preferably includes at least one selected from the group consisting of compounds represented by the following Chemical Formula 1-1, Chemical Formula 1-2, and Chemical Formula 1-3: 【Transformation 3】 【Chemistry 4】 【Transformation 5】

6. The nonaqueous electrolyte according to claim 1 or 3, wherein the compound represented by Chemical Formula 2 includes at least one selected from the group consisting of compounds represented by Chemical Formula 2-1, Chemical Formula 2-2, and Chemical Formula 2-3. 【Transformation 6】 【Transformation 7】 【Transformation 8】

7. 4. The non-aqueous electrolyte according to claim 1, wherein the additive is contained in the non-aqueous electrolyte in an amount of 0.01% by weight to 10% by weight.

8. 4. The non-aqueous electrolyte according to claim 1, further comprising at least one auxiliary additive selected from the group consisting of halogen-substituted or unsubstituted carbonate-based compounds, sultone-based compounds, sulfate-based compounds, phosphate-based or phosphite-based compounds, borate-based compounds, nitrile-based compounds, amine-based compounds, silane-based compounds, and lithium salt-based compounds.

9. The non-aqueous electrolyte according to claim 1 , wherein the organic solvent includes a cyclic carbonate organic solvent and a linear carbonate organic solvent.

10. the cyclic carbonate organic solvent contains ethylene carbonate, The non-aqueous electrolyte according to claim 9 , wherein the linear carbonate organic solvent includes ethyl methyl carbonate and dimethyl carbonate.

11. A positive electrode and a negative electrode facing the positive electrode; a separator interposed between the positive electrode and the negative electrode; A lithium secondary battery comprising the nonaqueous electrolyte according to claim 1 .

12. the positive electrode includes a positive electrode active material, The lithium secondary battery according to claim 11 , wherein the positive electrode active material comprises lithium iron phosphate particles.

13. The lithium secondary battery according to claim 12 , wherein the lithium iron phosphate particles include a compound represented by the following chemical formula A: [Chemical formula A] Li １＋ａ Fe １－ｓ M ｓ (PO ４－ｂ )X ｂ (In the chemical formula A, M is one or more elements selected from Co, Ni, Al, Mg, Ti, and V, X is F, S, or N, and 0≦s≦0.5; −0.5≦a≦+0.5; and 0≦b≦0.1.)

14. the negative electrode includes a negative electrode active material, The lithium secondary battery according to claim 11 , wherein the negative electrode active material comprises a carbon-based active material.

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