Non-aqueous electrolyte for lithium secondary batteries and lithium secondary batteries containing the same

Abstract

The present invention provides a non-aqueous electrolyte for a lithium secondary battery and a lithium secondary battery including the same. Specifically, the non-aqueous electrolyte for a lithium secondary battery may include a lithium salt, a non-aqueous organic solvent, a first additive including a compound represented by Chemical Formula 1, at least one second additive selected from the group consisting of vinyl ethylene carbonate (VEC) and ethyl di(prop-2-yn-1-yl)phosphate (EDP), and at least one third additive selected from the group consisting of a cyclic carbonate compound and a compound represented by Chemical Formula 2.

Description

[Technical Field]

[0001] This application claims priority rights under Korean Patent Application No. 10-2021-0180099 dated December 15, 2021, and Korean Patent Application No. 10-2022-0169868 dated December 7, 2022, and all content disclosed in the documents of said Korean Patent Applications is incorporated herein by reference.

[0002] The present invention relates to a non-aqueous electrolyte for lithium secondary batteries containing an additive that has excellent decomposition product removal and SEI enhancement effects from lithium salts, and to a lithium secondary battery in which high-temperature durability is improved by containing the same. [Background technology]

[0003] In recent years, with the development of personal IT devices and computer networks due to the advancement of the information society, society as a whole has become more dependent on electrical energy, and there is a growing need for technological development to efficiently store and utilize electrical energy.

[0004] In particular, as interest in solving environmental problems and realizing a sustainable, circular society has grown, research on lithium-ion secondary batteries, which are attracting attention as a clean energy source with low carbon dioxide emissions, is being conducted extensively.

[0005] Lithium-ion rechargeable batteries can be miniaturized to a degree suitable for personal IT devices, and they have the advantages of high energy density and operating voltage. They are used not only as power sources for laptops and mobile phones, but also as power sources for energy storage and electric vehicles.

[0006] On the other hand, a lithium-ion secondary battery comprises a positive electrode mainly composed of a lithium-containing transition metal oxide, a negative electrode using a carbonaceous material such as a lithium alloy or graphite, a separator interposed between the positive and negative electrodes, and a non-aqueous electrolyte. The non-aqueous electrolyte is a medium through which Li ions move, and is typically a solution in which an electrolyte such as lithium hexafluoride phosphate (LiPF6) is dissolved in a high dielectric constant organic solvent such as ethylene carbonate or dimethyl carbonate.

[0007] However, electrolytes such as lithium hexafluoride phosphate (LiPF6) are susceptible to heat and moisture, and therefore react with moisture present in the cell or undergo thermal decomposition to generate Lewis acids such as PF5. Such Lewis acids not only cause the decomposition of organic solvents such as ethylene carbonate, but can also erode the passivation film formed at the electrode-electrolyte interface, inducing further electrolyte decomposition and the elution of transition metal ions from the positive electrode.

[0008] The eluted transition metal ions either accelerate gas generation by promoting the decomposition of the electrolyte, or re-deposition onto the positive electrode, increasing its resistance. They also move to the negative electrode via the electrolyte and then electrodeposit onto it, causing self-discharge of the negative electrode, destruction and regeneration of the SEI (solid electrolyte interphase) film, and resulting in additional lithium ion consumption and increased resistance.

[0009] Therefore, there is a need for a non-aqueous electrolyte composition that can improve not only safety but also battery performance, such as high-rate charge-discharge characteristics, by removing by-products (such as HF and PF5) generated by the thermal decomposition of lithium salts, forming a stable film on the electrode surface to suppress the dissolution of transition metals, or suppressing the electrodeposition of dissolved transition metal ions onto the negative electrode. [Overview of the project] [Problems that the invention aims to solve]

[0010] The present invention aims to solve the above-mentioned problems and to provide a non-aqueous electrolyte for lithium secondary batteries that includes an additive that can improve the removal effect of decomposition products generated from lithium salts and the SEI enhancement effect.

[0011] Furthermore, the present invention aims to provide a lithium secondary battery with improved high-temperature durability by including the non-aqueous electrolyte for lithium secondary batteries. [Means for solving the problem]

[0012] According to one embodiment, the present invention is Lithium salts and Non-aqueous organic solvents, A first additive containing the compound represented by the following chemical formula 1, A second additive comprising vinyl ethylene carbonate (VEC), ethyl di(propa-2-in-1-yl) phosphate (EDP), or a mixture thereof, The present invention provides a non-aqueous electrolyte for lithium secondary batteries comprising a third additive containing a cyclic carbonate compound excluding vinylethylene carbonate (VEC), a compound represented by the following chemical formula 2, or a mixture thereof.

[0013] [Chemical formula 1] [ka]

[0014] In the aforementioned chemical formula 1, R is a substituted or unsubstituted alkylene group having 1 to 3 carbon atoms. R1 to R3 are each independently hydrogen, an alkyl group having 1 to 3 carbon atoms, or -CN.

[0015] [Chemical formula 2] [ka]

[0016] In the aforementioned chemical formula 2, n is an integer, either 1 or 2.

[0017] According to other embodiments, the present invention is A negative electrode, a positive electrode, a separator interposed between the negative electrode and the positive electrode, and The present invention provides a lithium secondary battery containing a non-aqueous electrolyte for lithium secondary batteries. [Effects of the Invention]

[0018] The compound represented by chemical formula 1 contained in the non-aqueous electrolyte for lithium secondary batteries of the present invention is a Lewis base compound containing a propargyl group (-C≡C-) and a nitrogen element having a lone pair of electrons in its structure. It can easily remove Lewis acids generated as electrolyte decomposition products inside the battery during charging and discharging, and can form a solid film on the surface of the positive electrode to suppress side reactions between the positive electrode and the electrolyte at high temperatures.

[0019] Furthermore, the non-aqueous electrolyte of the present invention contains both a first additive and second and third additives capable of forming a stable film on the electrode surface. This allows for the formation of an even more robust passive film on the electrode surface, preventing side reactions between the electrode and the electrolyte, and thus achieving an effect of suppressing resistance increase. By including such a non-aqueous electrolyte of the present invention, a lithium secondary battery with improved high-temperature durability can be realized. [Modes for carrying out the invention]

[0020] The present invention will be described in more detail below. The terms and words used in this specification and in the claims should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather should be interpreted in a manner consistent with the technical idea of ​​the present invention, in accordance with the principle that inventors may appropriately define the concepts of terms in order to best describe their invention.

[0021] In this specification, when words such as "includes," "composes," "consists of," or "has" are used, other parts may be added unless "only" is used. When a component is expressed singularly, it includes cases where it includes multiple components unless otherwise explicitly stated. In this specification, "%" means weight percent unless otherwise explicitly indicated.

[0022] Furthermore, in this specification, the term "alkylene group" means a branched or unbranched divalent unsaturated hydrocarbon group. In one embodiment, the alkylene group may be substituted or unsubstituted. The alkylene group includes, but is not limited to, a methylene group, an ethylene group, a propylene group, an isopropylene group, a butylene group, an isobutylene group, a tert-butylene group, a pentylene group, a 3-pentylene group, and the like, and each of these may be selectively substituted in other embodiments.

[0023] Generally, lithium secondary batteries ensure high-temperature storage characteristics by forming a passivation film on the surfaces of the positive and negative electrodes through the decomposition of the non-aqueous electrolyte during initial charging and discharging. However, this film can be degraded by Lewis acid substances such as HF and PF5, which are produced by the thermal decomposition of lithium salts (such as LiPF6) widely used in lithium-ion secondary batteries. Specifically, when transition metal elements are leached from the positive electrode due to attack by Lewis acid substances, the surface resistance of the electrode increases due to changes in the surface structure, the theoretical capacity decreases as the metal elements, which are redox centers, disappear, and the actual capacity may decrease. Furthermore, these leached transition metal ions electrodeposit onto the negative electrode, which reacts in a strong reduction potential band, not only consuming electrons but also destroying the film during electrodeposition, exposing the surface of the negative electrode and potentially triggering additional electrolyte decomposition reactions. As a result, the negative electrode resistance and irreversible capacity increase, leading to a problem of a sustained decrease in cell capacity.

[0024] Therefore, the present invention aims to provide a non-aqueous electrolyte containing an additive that is excellent in removing decomposition products generated from lithium salts and in enhancing SEI, and a lithium secondary battery containing the same.

[0025] Nonaqueous electrolyte for lithium secondary batteries According to one embodiment, the present invention is Lithium salts and Non-aqueous organic solvents, A first additive containing the compound represented by the following chemical formula 1, A second additive comprising vinyl ethylene carbonate (VEC), ethyl di(propa-2-in-1-yl) phosphate (EDP), or a mixture thereof, The present invention provides a non-aqueous electrolyte for lithium secondary batteries comprising a third additive containing a cyclic carbonate compound excluding vinylethylene carbonate (VEC), a compound represented by the following chemical formula 2, or a mixture thereof.

[0026] [Chemical formula 1] [ka]

[0027] In the aforementioned chemical formula 1, R is a substituted or unsubstituted alkylene group having 1 to 3 carbon atoms. R1 to R3 are each independently hydrogen, an alkyl group having 1 to 3 carbon atoms, or -CN.

[0028] [Chemical formula 2] [ka]

[0029] In the aforementioned chemical formula 2, n is an integer, either 1 or 2.

[0030] (1) Lithium salt First, let me explain the lithium salts mentioned above. The lithium salt may be used without limitation as long as it is commonly used in electrolytic solutions for lithium secondary batteries. For example, as the cation, Li + is included, and as the anion, F - 、Cl - 、Br - 、I - 、NO3 - 、N(CN)2 - 、BF4 - 、ClO4 - 、B 10 Cl 10 - 、AlCl4 - 、AlO4 - 、PF6 - 、CF3SO3 - 、CH3CO2 - 、CF3CO2 - 、AsF6 - 、SbF6 - 、CH3SO3 - 、(CF3CF2SO2)2N - 、(CF3SO2)2N - 、(FSO2)2N - 、BF2C2O4 - BC4O8 - 、PF4C2O4 - 、PF2C4O8 - 、(CF3)2PF4 - 、(CF3)3PF3 - 、(CF3)4PF2 - 、(CF3)5PF - 、(CF3)6P - 、C4F9SO3 - 、CF3CF2SO3 - 、CF3CF2(CF3)2CO - 、(CF3SO2)2CH - 、CF3(CF2)7SO3 - 、and at least any one selected from the group consisting of SCN - is included.

[0031] Specifically, the lithium salt is LiCl, LiBr, LiI, LiBF4, LiClO4, LiB 10 Cl 10The material may include a single substance or a mixture of two or more substances selected from the group consisting of LiAlCl4, LiAlO4, LiPF6, LiCF3SO3, LiCH3CO2, LiCF3CO2, LiAsF6, LiSbF6, LiCH3SO3, LiN(SO2F)2 (Lithium bis(fluorosulfonyl)imide, LiFSI), LiN(SO2CF2CF3)2 (Lithium bis(perfluoroethanesulfonyl)imide, LiBETI), and LiN(SO2CF3)2 (Lithium bis(trifluoromethanesulfonyl)imide, LiTFSI), and in particular, LiPF6 or LiBF4, which have high ionic conductivity, may be used.

[0032] On the other hand, when the organic solvent of a non-aqueous electrolyte decomposes under high-temperature environmental conditions, the decomposition products of the organic solvent react with the anions of the lithium salt to generate Lewis acid byproducts. For example, as shown in the reaction equation below, when LiPF6 is used as the lithium salt, Lewis acid byproducts such as PF5 are produced. Such Lewis acid byproducts generate byproducts including HF through a chain reaction as shown below, promoting the spontaneous decomposition reaction of the organic solvent and leading to side reactions that cause the SEI film formed on the electrode interface to break down.

[0033] [Reaction Equation] [ka]

[0034] On the other hand, the content of the lithium salt may be appropriately changed within the range of normal use, but in order to obtain the optimal film formation effect for preventing corrosion of the electrode surface, it may be included in the electrolyte at a concentration of 0.8 M to 3.0 M, specifically at a concentration of 1.0 M to 3.0 M.

[0035] When the concentration of the lithium salt satisfies the aforementioned range, the viscosity of the non-aqueous electrolyte can be controlled to achieve optimal impregnation, thereby improving the mobility of lithium ions and obtaining improvements in the capacity characteristics and cycle characteristics of the lithium secondary battery.

[0036] (2) Non-aqueous organic solvents Furthermore, the explanation regarding non-aqueous organic solvents is as follows: As the non-aqueous organic solvent, a variety of organic solvents commonly used in non-aqueous electrolytes may be used without limitation. However, there are no restrictions on the type of organic solvent as long as it can minimize decomposition due to oxidation reactions during the charging and discharging process of the secondary battery and can exhibit the desired properties together with the additives.

[0037] Specifically, the non-aqueous organic solvent may include a cyclic carbonate organic solvent, a linear carbonate organic solvent, a linear ester organic solvent, or a mixture thereof.

[0038] The cyclic carbonate-based organic solvent is a high-viscosity organic solvent with a high dielectric constant that readily dissociates lithium salts in a non-aqueous electrolyte. Specific examples of such organic solvents 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 among these, ethylene carbonate may be included.

[0039] The linear carbonate-based organic solvent is an organic solvent having low viscosity and low dielectric constant, and may include, as a specific example, at least one organic solvent selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate, and ethyl propyl carbonate, and may specifically include ethyl methyl carbonate (EMC).

[0040] The aforementioned linear ester-based organic solvent is a solvent that is relatively more stable under high-temperature and high-voltage driving conditions compared to cyclic carbonate-based organic solvents. It improves upon the disadvantages of cyclic carbonate-based organic solvents, which cause gas generation under high-temperature driving conditions, and can achieve high ionic conductivity.

[0041] The linear ester-based organic solvent may include, as a specific example, at least one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate, and more specifically, at least one of ethyl propionate and propyl propionate.

[0042] The non-aqueous electrolyte of the present invention may further contain a cyclic ester organic solvent, if necessary. Furthermore, the cyclic ester organic solvent may contain at least one selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone. On the other hand, the remainder of the non-aqueous electrolyte of the present invention, excluding the lithium salt and the first to third additives, may all be non-aqueous organic solvents unless otherwise specified.

[0043] (3) First additive The non-aqueous electrolyte for lithium secondary batteries of the present invention may contain a compound represented by the following chemical formula 1 as a first additive.

[0044] [Chemical formula 1] [ka]

[0045] In the aforementioned chemical formula 1, R is a substituted or unsubstituted alkylene group having 1 to 3 carbon atoms. R1 to R3 are each independently hydrogen, an alkyl group having 1 to 3 carbon atoms, or -CN.

[0046] Specifically, the lone pair of electrons of the nitrogen element contained in the compound represented by chemical formula 1 stabilizes the anion of the lithium salt, suppressing the generation of Lewis acids such as HF and PF5, which are decomposition products of the anion. Furthermore, the nitrogen element acts as a Lewis base to remove Lewis acids generated in the electrolyte. As a result, the degradation behavior of the coating on the surface of the positive or negative electrode caused by Lewis acids can be suppressed, and the resulting decomposition of the electrolyte can be prevented. Consequently, the self-discharge of the secondary battery can be mitigated and its high-temperature storage characteristics can be improved.

[0047] Furthermore, the compound represented by chemical formula 1 contains propargyl functional groups in its structure that are easily reduced on the surface of the negative electrode. By forming a highly passivated SEI film on the surface of the negative electrode, it is possible to prevent additional reductive decomposition reactions of the electrolyte caused by the instability of the SEI film, thereby improving the high-temperature durability of the negative electrode itself and suppressing the self-discharge reaction of the negative electrode. In particular, the propargyl groups contained in the compound represented by chemical formula 1 can adsorb onto the surface of metallic impurities contained in the positive electrode, suppressing the elution of impurities. This suppresses the electrodeposition of metal ions on the surface of the negative electrode and prevents internal short circuits.

[0048] Specifically, in the above chemical formula 1, R is a substituted or unsubstituted alkylene group having 1 or 2 carbon atoms, and R1 to R3 may each independently be hydrogen or an alkyl group having 1 or 2 carbon atoms. Furthermore, in the above chemical formula 1, R is a substituted or unsubstituted alkylene group having 1 or 2 carbon atoms, and R1 to R3 may each be hydrogen.

[0049] Preferably, the compound represented by chemical formula 1 may be the compound represented by the following chemical formula 1a.

[0050] [Chemical formula 1a] [ka]

[0051] The first additive may be present in an amount of 0.05% to 5% by weight based on the total weight of the non-aqueous electrolyte. When the first additive is included within the specified content range, it is possible to manufacture a secondary battery that is excellent at removing lithium salt decomposition products and has further improved performance, while minimizing disadvantages such as side reactions, capacity reduction, and resistance increase caused by the additive.

[0052] Specifically, when the first additive is present in an amount of 0.05% by weight or more, the HF or PF5 removal effect can be maintained during repeated charge and discharge cycles. Furthermore, when the first additive is present in an amount of 5.0% by weight or less, side reactions caused by the additive can be prevented, as can an increase in the viscosity of the electrolyte, thereby suppressing the decrease in ionic conductivity. This prevents a deterioration in rate characteristics during high-temperature storage and low-temperature life characteristics. Specifically, the first additive may be included in an amount of 0.05% to 3% by weight based on the total weight of the non-aqueous electrolyte.

[0053] (4) Second additive The non-aqueous electrolyte for lithium secondary batteries of the present invention may further contain a second additive.

[0054] The second additive may include at least one selected from vinyl ethylene carbonate (VEC) represented by the following chemical formula 3, ethyl di(prop-2-yn-1-yl) phosphate (EDP) represented by the following chemical formula 4, or a mixture thereof.

[0055] [Chemical formula 3] [ka]

[0056] [Chemical formula 4] [ka]

[0057] The vinylethylene carbonate (VEC) represented by chemical formula 3 can be reductively decomposed on the surface of the negative electrode to form a robust SEI film containing inorganic components such as Li2CO3. In particular, vinylethylene carbonate is more thermally stable than vinylene carbonate (VC), and therefore has the advantage of undergoing relatively less chemical decomposition even when exposed to high temperatures. Consequently, when used in combination with vinylene carbonate or the like as an additional additive, it can be oxidatively decomposed on the surface of the positive electrode to form a stable polymer-like film (such as CEI), further enhancing the stabilization of the positive electrode interface. This effect is even more evident when using a high-Ni material with a Ni content of 80 atm% or more as the positive electrode material.

[0058] Furthermore, ethyl di(propa-2-in-1-yl) phosphate (EDP), represented by chemical formula 4, which contains two or more propargyl functional groups and phosphate functional groups in its structure, is easily reductively decomposed by radicalization of the functional groups, allowing it to form a high-density, stable film on the surface of the negative electrode. It also forms a stable PO-based film with excellent Li-ion permeability on the surface of the positive electrode, thereby suppressing an increase in interfacial resistance.

[0059] Specifically, the second additive of the present invention may contain vinylethylene carbonate (VEC) or ethyl di(propa-2-in-1-yl) phosphate (EDP) represented by the chemical formula 4, or it may contain both vinylethylene carbonate (VEC) and ethyl di(propa-2-in-1-yl) phosphate (EDP).

[0060] When the second additive contains both vinyl ethylene carbonate (VEC) and ethyl di(propa-2-in-1-yl) phosphate (EDP), the vinyl ethylene carbonate (VEC) and ethyl di(propa-2-in-1-yl) phosphate (EDP) may be present in a weight ratio of 1:1 or 1:3.

[0061] When vinyl ethylene carbonate (VEC) and ethyl di(propa-2-in-1-yl) phosphate (EDP) are included in the aforementioned ratio, the initial film formation effect can be further improved compared to when each additive is used alone. The reduction potential difference causes the SEI film to be formed sequentially according to the voltage, and an even more stable and robust multilayer film can be formed.

[0062] Furthermore, in the non-aqueous electrolyte of the present invention, the first additive and the second additive may be included in a weight ratio of 1:0.5 to 1:60. When the first and second additives are included in the aforementioned ratios, the surface tension can be lowered, improving the wettability of the electrolyte, and a stable SEI film can be formed without increasing resistance, thereby suppressing side reactions between the electrode and the electrolyte during high-temperature charging. Specifically, when the second additive is included in a ratio of 0.5 by weight or more to the first additive, a stable SEI film can be formed, suppressing side reactions between the electrode and the electrolyte and reducing the volume increase rate. When the ratio of the second additive to the first additive is 60 by weight or less, it is possible to prevent the formation of an excessively thick film on the electrode surface, effectively suppressing the increase in initial interfacial resistance and preventing a decrease in output. Specifically, the first and second additives may be mixed and used in a weight ratio of 1:0.5 to 1:30, preferably 1:0.5 to 1:15, and more preferably 1:1 to 1:10.

[0063] (5) Third additive Furthermore, the non-aqueous electrolyte for lithium secondary batteries of the present invention may further contain a third additive in order to provide an even more stable film-forming effect on the electrode surface.

[0064] The third additive may include a cyclic carbonate compound excluding vinylethylene carbonate, a compound represented by the following chemical formula 2, or a mixture thereof.

[0065] [Chemical formula 2] [ka]

[0066] In the aforementioned chemical formula 2, n is an integer, either 1 or 2.

[0067] Examples of the aforementioned cyclic carbonate compound include vinylene carbonate (VC). The vinylene carbonate can react with the propargyl group, which is a substituent of the first additive, when it forms a radical, to form a stable polymer-based coating. Therefore, when the third additive is used together, an even more stable coating effect can be provided on the surface of the negative electrode.

[0068] Furthermore, in the above chemical formula 2, n may be 1. Specifically, the compound represented by chemical formula 2 may be 1,3-propane sultone (PS) or 1,4-butanesultone, and preferably 1,3-propanesultone.

[0069] The inclusion of the third additive improves the stabilization of the bulk properties of the electrolyte and the film formation effect at the electrode interface, further strengthening the film components and achieving an effect of suppressing lithium deposition. Therefore, when the third additive is used together with the first and second additives, the durability of the film can be effectively improved.

[0070] The third additive may be included in an amount of 0.01 to 15% by weight, specifically 0.1 to 10% by weight, based on the total weight of the non-aqueous electrolyte. When the third additive is included within the range described above, secondary batteries with further improved performance can be manufactured. For example, when the third additive is included in an amount of 0.01% by weight or more, it has the effect of improving the durability of the SEI film within a range that suppresses the increase in resistance to the greatest extent possible. Also, when the third additive is 1 5 When included in amounts below weight percent, it can provide long-term maintenance effects for the SEI film, prevent excessive side reactions in the electrolyte during battery charging and discharging, and prevent the presence of unreacted material in the electrolyte, thereby suppressing the increase in resistance caused by unreacted material.

[0071] (6) Fourth Additive Furthermore, the non-aqueous electrolyte of the present invention may further contain a fourth additive as needed in order to prevent the decomposition of the non-aqueous electrolyte in high-power environments, which can induce negative electrode collapse, and to further improve low-temperature high-rate discharge characteristics, high-temperature stability, overcharging prevention, and the effect of suppressing battery swelling at high temperatures.

[0072] Examples of the fourth additive include at least one selected from the group consisting of halogen-substituted carbonate compounds, sulfate compounds, phosphate or phosphite compounds, borate compounds, benzene compounds, amine compounds, silane compounds, and lithium salt compounds.

[0073] Examples of the halogen-substituted carbonate compounds include fluoroethylene carbonate (FEC). The sulfate compound may be, for example, ethylene sulfate (Esa), trimethylene sulfate (TMS), or methyl trimethylene sulfate (MTMS).

[0074] The phosphate or phosphite 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 tetraphenyl borate, lithium oxalyl difluoroborate (LiODFB) which can form a film on the surface of the negative electrode, or lithium bisoxalate borate (LiB(C2O4)2, LiBOB).

[0076] The benzene-based compound may be fluorobenzene or the like, the amine-based compound may be triethanolamine or ethylenediamine or the like, and the silane-based compound may be tetravinylsilane or the like.

[0077] The lithium salt compound is a compound different from the lithium salt contained in the non-aqueous electrolyte, and examples include lithium difluorophosphate (LiPO2F2, LiDFP) or LiBF4.

[0078] Among these other additives, in order to form an even more robust SEI film on the surface of the negative electrode during the initial activation process, at least one selected from the group consisting of ethylene sulfate, fluoroethylene carbonate (FEC), LiBF4, and lithium oxalyl difluoroborate (LiODFB), which have excellent film-forming effects on the surface of the negative electrode, may be included.

[0079] The fourth additive may be a mixture of two or more compounds, and may be included in an amount of 10% by weight or less based on the total weight of the non-aqueous electrolyte in order to prevent side reactions caused by an excessive amount of additive.

[0080] Lithium-ion battery Furthermore, in another embodiment of the present invention, a lithium secondary battery is provided, comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and the non-aqueous electrolyte of the present invention described above.

[0081] The lithium secondary battery of the present invention can be manufactured by first forming an electrode assembly in which a positive electrode, a negative electrode, and a separator between the positive and negative electrodes are sequentially stacked, then housing the assembly in a battery case, and finally adding the non-aqueous electrolyte of the present invention.

[0082] The method for manufacturing such a lithium secondary battery of the present invention may be any conventional method for manufacturing lithium secondary batteries that is well known in the art, and the specifics will be described below.

[0083] (1) Positive electrode The positive electrode according to the present invention may include a positive electrode active material layer containing a positive electrode active material, and optionally the positive electrode active material layer may further include a conductive material and / or a binder.

[0084] The positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and may specifically include a lithium composite metal oxide containing lithium and one or more metals such as cobalt, manganese, nickel, and aluminum.

[0085] Specifically, the positive electrode active material may include at least one of lithium-cobalt oxides, lithium-manganese oxides (e.g., LiMnO2, LiMn2O4, etc.), and lithium-nickel-manganese-cobalt oxides, which have high capacity characteristics and safety for batteries. Specifically, the positive electrode active material may include lithium-cobalt oxides or lithium-nickel-manganese-cobalt oxides or lithium-nickel-cobalt-transition metal (M) oxides represented by the following chemical formula 5.

[0086] [Chemical formula 5] Li x [Ni y Co z Mnw M 1 v ]O2

[0087] In the aforementioned chemical formula 5, Said M 1 is a doping element substituted at a transition metal site, and may be one or more elements selected from the group consisting of 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.

[0088] The aforementioned x represents the atomic ratio of lithium to the total transition metal in the lithium nickel cobalt manganese oxide, and may be 0.8 to 1.2, preferably 1 to 1.2.

[0089] The above y represents the atomic ratio of nickel among the transition metals in the lithium nickel cobalt manganese oxide, and is 0.5 or more and less than 1, preferably 0.7 to less than 1, and more preferably 0.75 to 0.98. Since a higher nickel content among the transition metals allows for the realization of even higher capacities, a nickel content of 0.5 or more is even more advantageous for achieving high capacities.

[0090] The value of z represents the atomic ratio of cobalt among the transition metals in the lithium nickel cobalt manganese oxide, and is greater than 0 and less than 0.5, preferably 0.01 to 0.3, and more preferably 0.01 to 0.25.

[0091] The aforementioned w represents the atomic ratio of manganese among the transition metals in the lithium nickel cobalt manganese oxide, and is greater than 0 and less than 0.5, preferably 0.01 to 0.3, and more preferably 0.01 to 0.25.

[0092] The aforementioned v is a doping element M doped at the transition metal site in lithium nickel cobalt manganese oxide. 1This represents the atomic ratio, which may be 0 to 0.2, preferably 0 to 0.1. That is, doping element M 1 When added, it has the effect of improving the structural stability of lithium nickel cobalt manganese oxides, but as the content of the doping element increases, the volume may decrease, so it is preferable that v is included in a content of 0.2 or less. On the other hand, in the above chemical formula 1, y + z + w + v = 1 is also acceptable.

[0093] A specific example of the aforementioned lithium-nickel-manganese-cobalt oxide is Li(Ni) 0.5 Co 0.2 Mn 0.3 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.7 Mn 0.1 Co 0.2 )O2, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2, Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, or Li(Ni 0.86 Mn 0.05 Co 0.07 Al 0.02 Examples include O2, and more specifically, Li(Ni) with a nickel content of 70 atm% or more. 0.7 Mn 0.1 Co 0.2 )O2, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2, Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, or Li(Ni 0.86 Mn 0.05 Co 0.07 Al 0.02 It is more preferable that it be O2.

[0094] The positive electrode active material may be present in an amount of 80% to 99% by weight, specifically 90% to 99% by weight, based on the total weight of solids in the positive electrode slurry. In this case, if the content of the positive electrode active material is 80% by weight or less, the energy density will be low and the capacity may decrease.

[0095] Furthermore, the conductive material is not particularly limited as long as it does not induce a chemical change in the battery and is conductive. For example, carbon powders such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powders such as natural graphite, artificial graphite, or graphite with a highly developed crystalline structure; conductive fibers such as carbon fibers or metal fibers; conductive powders such as fluorinated carbon powder, aluminum powder, or 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. The conductive material is usually added in an amount of 1 to 30% by weight, based on the total weight of the solid content in the positive electrode active material layer.

[0096] Furthermore, the binder is a component that plays a role in improving the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the current collector, and is usually added at a concentration of 1 to 30% by weight based on the total weight of solids in the positive electrode active material layer. Examples of such binders include fluororesin binders containing polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); rubber binders containing styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, and styrene-isoprene rubber; cellulose binders containing carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, and regenerated cellulose; polyalcohol binders containing polyvinyl alcohol; polyolefin binders containing polyethylene and polypropylene; polyimide binders; polyester binders; and silane binders.

[0097] The positive electrode of the present invention as described above may be manufactured by a method for manufacturing a positive electrode that is well known in the art. For example, the positive electrode may be manufactured by a method in which a positive electrode slurry prepared by dissolving or dispersing a positive electrode active material, a binder, and / or a conductive material in a solvent is applied to a positive electrode current collector, and then dried and rolled to form a positive electrode active material layer, or by a method in which the positive electrode active material layer is cast onto another support, and then the support is peeled off to obtain a film which is then laminated onto the positive electrode current collector.

[0098] The positive electrode current collector is not particularly limited as long as it does not induce a chemical change in the battery and is conductive. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc. may be used.

[0099] The solvent may contain an organic solvent such as N-methyl-2-pyrrolidone (NMP), and may be used in an amount that results in a preferable viscosity when the positive electrode active material, and optionally a binder, a conductive material, etc. are included. For example, it may be included such that the solid content concentration in the active material slurry containing the positive electrode active material, and optionally a binder and a conductive material, is 10% to 90% by weight, preferably 30% to 80% by weight.

[0100] (2) Negative electrode Next, the negative electrode will be described. The negative electrode according to the present invention includes a negative electrode active material layer containing a negative electrode active material, and the negative electrode active material layer may further contain a conductive material and / or a binder as required.

[0101] The negative electrode active material may include a silicon-based active material capable of doping and undoping lithium. Typical examples of the silicon-based active material include Si, SiO x (0 < x < 2), Si-Y alloy (where Y is an element selected from the group consisting of an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, a rare earth element, and combinations thereof, and is not Si), etc. Examples of the element Y may be selected from the group consisting of Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof. The Si-Y alloy is an alloy in which the content of silicon is the highest among all metal elements with respect to the total amount of the alloy.

[0102] Further, the silicon-based active material may be used as a mixture with a carbon material capable of reversibly intercalating / deintercalating lithium ions.

[0103] As the carbon material capable of reversibly intercalating / deintercalating the lithium ions, any carbon-based negative electrode active material generally used in lithium ion secondary batteries may be used without particular limitation. Representative examples thereof include crystalline carbon, amorphous carbon, or a combination of these. Examples of the crystalline carbon include graphite such as amorphous, plate-like, flaky, spherical, or fibrous natural graphite or artificial graphite. Examples of the amorphous carbon include soft carbon (low-temperature calcined carbon), hard carbon, mesophase pitch carbide, calcined coke, and the like.

[0104] In addition to this, the negative electrode active material may contain at least one or more selected from the group consisting of lithium metal, a metal or an alloy of these metals and lithium, and a metal composite oxide.

[0105] As the metal, a 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, and Sn or an alloy of these metals and lithium may be used.

[0106] Examples of the metal composite oxide include PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5, Li x Fe2O3(0≦x≦1), Li x WO2(0≦x≦1), and Sn x Me 1-x Me’ y O z (Me: Mn, Fe, Pb, Ge; Me’: Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen; 0<x≦1; 1≦y≦3; 1≦z≦8) may be used. The negative electrode active material may be contained at 80% to 99% by weight based on the total weight of the solid content in the negative electrode slurry.

[0107] The conductive material is a component for further improving the conductivity of the negative electrode active material and may be added in an amount of 1 to 20% by weight based on the total weight of the solid content in the negative electrode active material layer. Such a conductive material is not particularly limited as long as it does not induce a chemical change in the battery and is conductive, and may be used, for example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; conductive fibers such as carbon fibers or metal fibers; conductive powders such as fluorinated carbon powder, aluminum powder, or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0108] The binder is a component that assists in bonding between the conductive material, active material, and current collector, and is usually added at a concentration of 1 to 30% by weight based on the total weight of solids in the negative electrode active material layer. Examples of such binders include fluoropolymer binders containing polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); rubber binders containing styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, and styrene-isoprene rubber; cellulose binders containing carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, and regenerated cellulose; polyalcohol binders containing polyvinyl alcohol; polyolefin binders containing polyethylene and polypropylene; polyimide binders; polyester binders; and silane binders.

[0109] The negative electrode may be manufactured by a method for manufacturing a negative electrode that is well known in the art. For example, the negative electrode may be manufactured by applying a negative electrode active material slurry, which is prepared by selectively dissolving or dispersing a negative electrode active material, a binder, and a conductive material in a solvent, onto a negative electrode current collector, and then rolling and drying it to form a negative electrode active material layer, or by casting the negative electrode active material layer onto another support, peeling off the support, and then laminating the resulting film onto the negative electrode current collector.

[0110] The negative electrode current collector generally has a thickness of 3 to 500 μm. Such a negative electrode current collector is not particularly limited as long as it does not induce chemical changes in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. Also, similar to the positive electrode current collector, fine irregularities may be formed on the surface to strengthen the bonding force of the negative electrode active material, and it may be used in various forms such as film, sheet, foil, mesh, porous material, foam, and nonwoven fabric.

[0111] The solvent may include water or an organic solvent such as NMP or alcohol, and may be used in an amount that results in a desirable viscosity when the negative electrode active material and selectively include a binder and conductive material. For example, the solvent may be included such that the solid content concentration in the active material slurry containing the negative electrode active material and selectively including a binder and conductive material is 50% to 75% by weight, preferably 40% to 70% by weight.

[0112] (3) Separator The separator included in the lithium secondary battery of the present invention may be a porous polymer film made from a commonly used, ordinary porous polymer film, such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, either alone or in a laminated manner, or an ordinary porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fibers or polyethylene terephthalate fibers, may be used, but is not limited thereto.

[0113] The external shape of the lithium secondary battery of the present invention is not particularly limited, but it may be cylindrical, rectangular, pouch-type, or coin-type, using a can.

[0114] The present invention will be described in detail below with reference to examples. However, the examples of the present invention may be modified into various different forms, and the scope of the present invention should not be construed as being limited to the examples described below. The examples of the present invention are provided to give a more complete explanation of the present invention to a person of average knowledge in the industry.

[0115] Examples Example 1. (Manufacturing of non-aqueous electrolytes for lithium secondary batteries) A non-aqueous electrolyte was prepared by dissolving LiPF6 in a non-aqueous organic solvent prepared by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 30:70 to a concentration of 1.0 M. Then, 0.1% by weight of the compound represented by chemical formula 1a was added as the first additive, 0.3% by weight of vinylethylene carbonate (hereinafter referred to as "VEC") as the second additive, 3.0% by weight of vinylene carbonate (hereinafter referred to as "VC") and 0.5% by weight of 1,3-propanesultone (hereinafter referred to as "PS") as the third additive, and 1.0% by weight of ethylene sulfate (hereinafter referred to as "Esa") as the fourth additive (see Table 1 below).

[0116] (Manufacturing of secondary batteries) N-methyl-2-pyrrolidone (NMP) and positive electrode active material Li(Ni 0.86 Mn 0.05 Co 0.07 Al 0.02 O2, a conductive material (carbon black), and a binder (polyvinylidene fluoride) were added in a weight ratio of 97.5:1:1.5 to produce a positive electrode slurry (solid content: 50% by weight). The positive electrode slurry was applied to a 12 μm thick aluminum (Al) thin film, which was a positive electrode current collector, and dried. After that, a roll press was performed to produce the positive electrode.

[0117] A negative electrode slurry (solid content: 60% by weight) was prepared by adding a negative electrode active material (graphite), a binder (SBR-CMC), and a conductive material (carbon black) in a weight ratio of 97.5:1.5:1.0 to water, which was used as a solvent. The negative electrode slurry was then applied to a 6 μm thick copper (Cu) thin film, which was a negative electrode current collector, and dried. Finally, the negative electrode was manufactured by roll pressing.

[0118] After sequentially stacking the positive electrode, a polyolefin-based porous separator coated with inorganic particles (Al2O3), and a negative electrode to manufacture an electrode assembly, the assembly was wound into a jelly-roll shape, housed in a cylindrical battery case, and the non-aqueous electrolyte for lithium secondary batteries was poured in to manufacture a cylindrical lithium secondary battery with a driving voltage of 4.2V or higher.

[0119] Example 2. A lithium secondary battery was manufactured in the same manner as in Example 1, except that LiPF6 was dissolved in a non-aqueous organic solvent prepared by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 30:70 to a concentration of 1.0 M, and then 0.1% by weight of the compound represented by chemical formula 1a was added as the first additive, 0.3% by weight of ethyl di(propa-2-in-1-yl) phosphate (hereinafter referred to as "EDP") as the second additive, 3.0% by weight of VC and 0.5% by weight of PS as the third additive, and 1.0% by weight of Esa as the fourth additive to produce a non-aqueous electrolyte (see Table 1 below).

[0120] Example 3. A lithium secondary battery was manufactured in the same manner as in Example 1, except that LiPF6 was dissolved in a non-aqueous organic solvent prepared by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 30:70 to a concentration of 1.0 M, and then 0.1% by weight of the compound represented by chemical formula 1a as the first additive, 0.1% by weight of EDP as the second additive, 3.0% by weight of VC and 0.5% by weight of PS as the third additive, and 1.0% by weight of Esa as the fourth additive to produce a non-aqueous electrolyte (see Table 1 below).

[0121] Example 4. A lithium secondary battery was manufactured in the same manner as in Example 1, except that LiPF6 was dissolved in a non-aqueous organic solvent prepared by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 30:70 to a concentration of 1.0 M, and then 0.1% by weight of the compound represented by chemical formula 1a as the first additive, 0.5% by weight of EDP as the second additive, 3.0% by weight of VC and 0.5% by weight of PS as the third additive, and 1.0% by weight of Esa as the fourth additive to produce a non-aqueous electrolyte (see Table 1 below).

[0122] Example 5. A lithium secondary battery was manufactured in the same manner as in Example 1, except that LiPF6 was dissolved in a non-aqueous organic solvent prepared by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 30:70 to a concentration of 1.0 M, and then 0.1% by weight of the compound represented by chemical formula 1a was added as the first additive, 1.0% by weight of EDP as the second additive, 3.0% by weight of VC and 0.5% by weight of PS as the third additive, and 1.0% by weight of Esa as the fourth additive to produce a non-aqueous electrolyte (see Table 1 below).

[0123] Example 6. A lithium secondary battery was manufactured in the same manner as in Example 1, except that LiPF6 was dissolved in a non-aqueous organic solvent prepared by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 30:70 to a concentration of 1.0 M, and then 0.1% by weight of the compound represented by chemical formula 1a was added as the first additive, 3.0% by weight of EDP as the second additive, 3.0% by weight of VC and 0.5% by weight of PS as the third additive, and 1.0% by weight of Esa as the fourth additive to produce a non-aqueous electrolyte (see Table 1 below).

[0124] Example 7. A non-aqueous organic solvent obtained by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 30:70 was dissolved with LiPF6 to a concentration of 1.0 M. Then, except for adding 0.1 wt% of the compound represented by Chemical Formula 1a as the first additive, 6.0 wt% of EDP as the second additive, 3.0 wt% of VC and 0.5 wt% of PS as the third additive, and 1.0 wt% of Esa as the fourth additive to produce a non-aqueous electrolyte, a lithium secondary battery was manufactured in the same manner as in Example 1 (see Table 1 below).

[0125] Example 8. A non-aqueous organic solvent obtained by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 30:70 was dissolved with LiPF6 to a concentration of 1.0 M. Then, except for adding 0.1 wt% of the compound represented by Chemical Formula 1a as the first additive, 0.04 wt% of EDP as the second additive, 3.0 wt% of VC and 0.5 wt% of PS as the third additive, and 1.0 wt% of Esa as the fourth additive to produce a non-aqueous electrolyte, a lithium secondary battery was manufactured in the same manner as in Example 1 (see Table 1 below).

[0126] Example 9. Li(Ni 0.7 Mn 0.1 Co 0.2 A lithium secondary battery was manufactured in the same manner as in Example 1 (see Table 1 below), except that Li(Ni

[0127] Example 10. Li(Ni 0.6 Mn 0.2 Co 0.2 A lithium secondary battery was manufactured in the same manner as in Example 1 (see Table 1 below), except that Li(Ni

[0128] Comparative Example 1. A lithium secondary battery was manufactured in the same manner as in Example 1, except that LiPF6 was dissolved in a non-aqueous organic solvent prepared by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 30:70 to a concentration of 1.0 M, and then 0.3 wt% VEC, 3.0 wt% VC, 0.5 wt% PS, and 1.0 wt% Esa were added to produce a non-aqueous electrolyte (see Table 2 below).

[0129] Comparative Example 2. A lithium secondary battery was manufactured in the same manner as in Example 1, except that LiPF6 was dissolved in a non-aqueous organic solvent prepared by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 30:70 to a concentration of 1.0 M, and then 0.3 wt% EDP, 3.0 wt% VC, 0.5 wt% PS, and 1.0 wt% Esa were added to produce a non-aqueous electrolyte (see Table 2 below).

[0130] Comparative Example 3. A lithium secondary battery was manufactured in the same manner as in Example 1, except that LiPF6 was dissolved in a non-aqueous organic solvent prepared by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 30:70 to a concentration of 1.0 M, and then 0.1% by weight of the compound represented by chemical formula 1a, 3.0% by weight of VC, 0.5% by weight of PS, and 1.0% by weight of Esa as a fourth additive were added to produce a non-aqueous electrolyte (see Table 2 below).

[0131] Comparative Example 4. A lithium secondary battery was manufactured in the same manner as in Example 1, except that LiPF6 was dissolved in a non-aqueous organic solvent prepared by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 30:70 to a concentration of 1.0 M, and then VC 3.0% by weight, PS 0.5% by weight, and Esa 1.0% by weight were added to produce a non-aqueous electrolyte (see Table 2 below).

[0132] Comparative Example 5. A lithium secondary battery was manufactured in the same manner as in Example 1, except that LiPF6 was dissolved in a non-aqueous organic solvent prepared by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 30:70 to a concentration of 1.0 M, and then 3.0 wt% VC, 0.5 wt% PS, 1.0 wt% Esa, and 1.0 wt% lithium difluorophosphate (LiDFP) were added to produce a non-aqueous electrolyte (see Table 2 below).

[0133] Comparative Example 6. A lithium secondary battery was manufactured in the same manner as in Example 1, except that LiPF6 was dissolved in a non-aqueous organic solvent prepared by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 30:70 to a concentration of 1.0 M, and then 3.0 wt% VC, 0.5 wt% PS, 1.0 wt% Esa, and 5.0 wt% fluoroethylene carbonate (FEC) were added to produce a non-aqueous electrolyte (see Table 2 below).

[0134] Comparative Example 7. Li(Ni) 0.7 Mn 0.1 Co 0.2 A lithium secondary battery was manufactured in the same manner as in Comparative Example 1, except that O2 was used as the positive electrode active material (see Table 2 below).

[0135] Comparative Example 8. Li(Ni) 0.6 Mn 0.2 Co 0.2 A lithium secondary battery was manufactured in the same manner as in Comparative Example 1, except that O2 was used as the positive electrode active material (see Table 2 below).

[0136] [Table 1] [Table 1]

[0137] [Table 2] [Table 2]

[0138] In Tables 1 and 2 above, the abbreviations for each compound mean the following: VEC: Vinyl ethylene carbonate EDP: Ethyldi(propa-2-in-1-yl)phosphate VC: Vinylen carbonate PS: 1,3-propanethultone Esa: Ethylene sulfate LiDFP: Lithium difluorophosphate FEC: Fluoroethylene carbonate NCM 712: Li(Ni 0.7 Mn 0.1 Co 0.2 )O2 NCM 622: Li(Ni 0.6 Mn 0.2 Co 0.2 )O2

[0139] Experimental example Experiment Example 1: Evaluation experiment of volume increase rate The lithium secondary batteries produced in Examples 1 to 10 and the lithium secondary batteries produced in Comparative Examples 1 to 8 were each charged to 4.2V at 0.33C. After charging was complete, the initial volume was measured using the Archimedes method with distilled water.

[0140] Next, each of the lithium secondary batteries was stored at 60°C with a State of Charge (SOC) of 100% for 12 weeks. The percentage increase in volume of the lithium secondary battery after high-temperature storage relative to its initial volume was measured using the Archimedes method, and the measured volume change was calculated as a percentage (%) and is shown in Table 3 below.

[0141] [Table 3] [Table 3]

[0142] Referring to Table 3 above, it can be seen that the volume increase rate after high-temperature storage of the lithium secondary batteries produced in Examples 1 to 10 using the non-aqueous electrolyte of the present invention was 3.5% or less, which is significantly lower than that of the lithium secondary batteries in Comparative Examples 1 to 8.

[0143] On the other hand, the volume increase rate after high-temperature storage of the lithium secondary battery of Example 8, which contained a slightly lower amount of the second additive, was 3.5%, which is a slight increase compared to the lithium secondary batteries manufactured in Examples 1 to 7.

[0144] On the other hand, referring to Table 3 above, Li(Ni) is used as the positive electrode active material. 0.7 Mn 0.1 Co 0.2 In the case of the lithium secondary battery of Example 9, which includes a positive electrode containing O2 and the non-aqueous electrolyte of the present invention, the volume increase rate after high-temperature storage is reduced by approximately 65% ​​compared to the lithium secondary battery of Comparative Example 7, and Li(Ni) is used as the positive electrode active material. 0.6 Mn 0.2 Co 0.2 In the case of the lithium secondary battery of Example 10, which includes a positive electrode containing O2 and the non-aqueous electrolyte of the present invention, it was found that the volume increase rate after high-temperature storage was reduced by approximately 75% compared to the lithium secondary battery of Comparative Example 8, and Li(Ni) was used as the positive electrode active material. 0.86 Mn 0.05 Co 0.07 Al 0.02 In the case of the lithium secondary battery of Example 1, which uses a positive electrode containing O2 and the non-aqueous electrolyte of the present invention in combination, the second additive is used in addition to the first additive. 、 Third Coating and fourth additive Compared to the lithium secondary battery of Comparative Example 1, which had a non-aqueous electrolyte containing only [the specified substance], the volume increase rate after high-temperature storage was reduced by approximately 80% or more. Referring to these results, it can be confirmed that the effect of suppressing the volume increase rate is further improved when a positive electrode containing a positive electrode active material with a nickel content of 80 atm% or more is applied in combination with the non-aqueous electrolyte of the present invention.

[0145] Experimental Example 2. Resistivity increase rate during high-temperature storage. The secondary batteries produced in Examples 1-7, 9, and 10, and the secondary batteries produced in Comparative Examples 1-8, were activated at 0.1 C CC, and then degassed.

[0146] Next, at 25°C, the battery was charged to 4.20V with a constant current-constant voltage (CC-CV) charge at 0.33C CC. Then, under a 50% state of charge (SOC) condition, it was pulse-discharged at a rate of 2.5C, and the voltage drop over 10 seconds was measured to determine the initial resistance.

[0147] Next, after storing the batteries at a high temperature of 60°C for 12 weeks, the batteries were charged to a State of Charge (SOC) of 50%. Then, the voltage drop was measured over 10 seconds during pulse discharge under a 2.5C rate condition to determine the resistance value after high-temperature storage. The percentage increase in resistance relative to the initial resistance was then calculated and is shown in Table 4 below. The voltage drop was measured using a PNE-0506 charger / discharger (manufacturer: PNE solution Co., Ltd., 5V, 6A).

[0148] [Table 4] [Table 4]

[0149] Referring to Table 4 above, the resistance increase rate after high-temperature storage of lithium secondary batteries manufactured in Examples 1 to 7, 9, and 10 using the non-aqueous electrolyte of the present invention is approximately 7.5 The result is less than %, which is a significant improvement compared to the lithium secondary batteries of Comparative Examples 1 to 8. In other words, the secondary battery of the embodiment of the present invention equipped with the non-aqueous electrolyte forms a stable SEI film on the electrode surface, and can suppress film breakdown at high temperatures even when the battery is exposed to high temperatures. Therefore, because there is less additional electrolyte decomposition due to film breakdown, it is expected to provide an excellent effect of suppressing resistance increase even after high-temperature storage.

[0150] On the other hand, referring to Table 4 above, Li(Ni 0.7 Mn 0.1 Co 0.2In the case of the lithium secondary battery of Example 9, which includes a positive electrode containing O2 and the non-aqueous electrolyte of the present invention, the resistance increase rate is reduced by approximately 54% compared to the lithium secondary battery of Comparative Example 7, and Li(Ni) is used as the positive electrode active material. 0.6 Mn 0.2 Co 0.2 In the case of the lithium secondary battery of Example 10, which includes a positive electrode containing O2 and the non-aqueous electrolyte of the present invention, it was found that the resistance increase rate was reduced by approximately 58% compared to the lithium secondary battery of Comparative Example 8, and Li(Ni) was used as the positive electrode active material. 0.86 Mn 0.05 Co 0.07 Al 0.02 In the case of the lithium secondary battery of Example 1, which uses a positive electrode containing O2 and the non-aqueous electrolyte of the present invention in combination, the second additive is used in addition to the first additive. 、 Third Coating and fourth additive Compared to the lithium secondary battery of Comparative Example 1, which had a non-aqueous electrolyte containing only [the specified substance], the resistance increase rate was reduced by approximately 59% or more. Referring to these results, it can be seen that the effect of suppressing the resistance increase rate is further improved when a positive electrode containing a positive electrode active material with a nickel content of 80 atm% or more is applied in combination with the non-aqueous electrolyte of the present invention.

[0151] Experimental Example 3. Evaluation of Initial Resistance The lithium secondary batteries produced in Examples 1 to 7 and the lithium secondary battery produced in Comparative Example 6 were each activated at 0.1 C CC, and then degassed.

[0152] Next, the battery was charged to 4.20V at 25°C under constant current-constant voltage (CC-CV) charging conditions using 0.33C CC. Then, under a 50% state of charge (SOC) condition, it was pulse-discharged at a rate of 2.5C, and the voltage drop over 10 seconds was measured to determine the initial resistance. The measured initial resistance values ​​are shown in Table 5 below.

[0153] [Table 5] [Table 5]

[0154] Referring to Table 5 above, the initial resistance value of the lithium secondary batteries manufactured in Examples 1 to 5 using the non-aqueous electrolyte of the present invention is 17.5 mohm It can be seen that the following is true. In contrast, the initial resistance value of the lithium secondary battery of Comparative Example 6, which does not contain either the first or second additive of the present invention, is 21.4. mohm This indicates a significant increase compared to the lithium secondary batteries manufactured in Examples 1-5.

[0155] On the other hand, the initial resistance values ​​of the lithium secondary batteries in Examples 6 and 7, which contained a slightly higher amount of the second additive, were 20.3, respectively. mohm and 27.7 mohm This indicates a significant increase compared to the lithium secondary batteries manufactured in Examples 1-5.

Claims

1. Lithium salts and Non-aqueous organic solvents, A first additive containing a compound represented by the following chemical formula 1, A second additive containing ethyldi(propa-2-in-1-yl)phosphate (EDP), A third additive comprising a cyclic carbonate compound excluding vinylethylene carbonate (VEC), a compound represented by the following chemical formula 2, or a mixture thereof, Includes, The first and second additives are present in a weight ratio of 1:5 to 1:30 in a non-aqueous electrolyte for lithium secondary batteries: [Chemical formula 1] 【Chemistry 1】 In the aforementioned chemical formula 1, R is a substituted or unsubstituted alkylene group having 1 to 3 carbon atoms. R １ ~R ３ Each of these is independently hydrogen, an alkyl group having 1 to 3 carbon atoms, or -CN. [Chemical formula 2] 【Chemistry 2】 In the aforementioned chemical formula 2, n is an integer, either 1 or 2.

2. The R is a substituted or unsubstituted alkylene group having 1 or 2 carbon atoms. R １ ~R ３ The non-aqueous electrolyte for lithium secondary batteries according to claim 1, wherein each is independently hydrogen or an alkyl group having 1 or 2 carbon atoms.

3. The compound represented by the aforementioned chemical formula 1 is the compound represented by the following chemical formula 1a, the non-aqueous electrolyte for lithium secondary batteries according to claim 1: [Chemical formula 1a] 【Transformation 3】

4. The non-aqueous electrolyte for lithium secondary batteries according to claim 1, wherein the first additive is contained in an amount of 0.05% to 5% by weight based on the total weight of the non-aqueous electrolyte.

5. The non-aqueous electrolyte for lithium secondary batteries according to claim 1, wherein the first additive and the second additive are included in a weight ratio of 1:5 to 1:

15.

6. The non-aqueous electrolyte for lithium secondary batteries according to claim 1, wherein the second additive further comprises vinyl ethylene carbonate (VEC).

7. The non-aqueous electrolyte for lithium secondary batteries according to claim 1, wherein the cyclic carbonate compound is vinylene carbonate (VC).

8. The non-aqueous electrolyte for lithium secondary batteries according to claim 1, wherein the compound represented by chemical formula 2 is 1,3-propane sultone (PS) or 1,4-butane sultone.

9. The non-aqueous electrolyte for lithium secondary batteries according to claim 1, wherein the third additive is a mixture containing vinylene carbonate (VC) and a compound represented by chemical formula 2.

10. The non-aqueous electrolyte for lithium secondary batteries according to claim 1, further comprising at least one fourth additive selected from the group consisting of halogen-substituted carbonate compounds, sulfate compounds, phosphate or phosphite compounds, borate compounds, benzene compounds, amine compounds, silane compounds, and lithium salt compounds.

11. A negative electrode, a positive electrode, a separator interposed between the negative electrode and the positive electrode, and Non-aqueous electrolyte for lithium secondary battery according to any one of claims 1 to 10 Lithium-ion batteries, including lithium-ion batteries.

12. The lithium secondary battery according to claim 11, wherein the positive electrode comprises a positive electrode active material consisting of a lithium transition metal oxide containing lithium and one or more metals selected from cobalt, manganese, nickel, and aluminum.

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