Lithium secondary battery

Abstract

The present invention relates to a lithium secondary battery comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte, in which the positive electrode comprises a positive electrode active material comprising a lithium nickel-based oxide represented by a specific chemical formula, the non-aqueous electrolyte includes a lithium salt, an organic solvent, a first additive, and a second additive, the first additive including a compound represented by a specific chemical formula, and the second additive including a compound represented by a specific chemical formula.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to Korean Patent Application No. 10-2023-0131252, filed on September 27, 2023, and Korean Patent Application No. 10-2024-0118849, filed on September 2, 2024, the disclosures of which are incorporated herein by reference. Technical Field

[0003] This invention relates to lithium secondary batteries, and more specifically to lithium secondary batteries exhibiting excellent high-temperature life characteristics, high-temperature storage characteristics, and thermal stability. Background Technology

[0004] Recently, the application of lithium-ion batteries in energy storage and supply for large-area devices such as automobiles and energy storage devices, as well as in energy supply for electronic devices such as electrical, electronic, communication and computer equipment, has expanded rapidly, leading to increased demand for high-capacity, high-output and high-stability rechargeable batteries.

[0005] A typical lithium-ion secondary battery comprises: a positive electrode containing a positive active material, a negative electrode containing a negative active material, an electrolyte that acts as a medium for delivering lithium ions, and a separator. In this case, carbon-based active materials, silicon-based active materials, etc., can be used as the negative active material. Furthermore, lithium transition metal oxides, such as lithium cobalt oxide, lithium nickel oxide (LiNiO2), and lithium nickel cobalt manganese composite transition metal oxides, can be used as the positive active material.

[0006] Meanwhile, current research mainly focuses on lithium-nickel-cobalt-manganese composite transition metal oxides with a nickel content of at least 70 mol% to improve the energy density of the cathode. However, as the nickel content in the lithium-nickel-cobalt-manganese composite transition metal oxides increases, the thermal stability of the cathode deteriorates.

[0007] To prevent this problem, reducing the nickel content in lithium-nickel-cobalt-manganese composite transition metal oxides requires increasing the driving voltage to achieve the desired energy density. However, during these high-voltage conditions, side reactions caused by electrolyte degradation during charging and discharging can lead to the deterioration of the films or electrode surface structures formed on the positive and negative electrodes, causing transition metal ions to dissolve from the positive electrode surface. Consequently, these dissolved transition metal ions electrodeposit on the negative electrode, degrading the passivation capability of the SEI (Sediment Electrode Ion), thus leading to negative electrode degradation.

[0008] The degradation of secondary batteries tends to be accelerated by increasing the potential of the positive electrode or by exposing the battery to high temperatures.

[0009] Therefore, in order to solve these problems, research and development work is being carried out to develop a method of forming a durable film on the surfaces of the positive and negative electrodes during the initial activation process, thereby suppressing electrolyte side reactions and the dissolution of metal ions from the positive electrode, and improving the high-temperature life characteristics and stability. Summary of the Invention

[0010] Technical Problem

[0011] The present invention aims to overcome the above limitations. Therefore, one aspect of the present invention provides a lithium secondary battery that uses a lithium transition metal oxide with a reduced nickel content to a certain level as a positive electrode active material, and exhibits improved high-temperature life performance, storage performance, and thermal stability when driven at a high voltage.

[0012] Technical Solution

[0013] [1] According to one aspect of the present invention, there is provided a lithium secondary battery comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte. Among them, the positive electrode includes a positive electrode active material, the positive electrode active material includes a lithium nickel-based oxide represented by Formula 1 below, the non-aqueous electrolyte includes a lithium salt, an organic solvent, a first additive, and a second additive, the first additive includes a compound represented by Formula A below, and the second additive includes a compound represented by Formula C below.

[0014] [Formula 1]

[0015] Li

[0017] , d , c ,

[0016] , , a , ,

[0018] , , 1 , 1 , , b , , ,

[0019] [Ni a Co b Mn c M 1 d O2

[0016] In Formula 1 above, x, a, b, c, and d satisfy 0 ≤ x ≤ 0.5, a + b + c + d = 1, 0.5 ≤ a ≤ 0.7, 0 < b < 0.2, 0 < c ≤ 0.4, and 0 ≤ d ≤ 0.2, and M 1 is at least one 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.

[0017] [Formula A]

[0018]

[0019] In Formula A above, n is 1 or 2, L1 and L2 are each independently a direct connection, or an alkylene group having 1 to 6 carbon atoms with or without substituents, and R1 and R2 are each independently a substituent represented by Formula B below.

[0020] [Formula B]

[0021]

[0022] In equation B above, m is 1 or 2, and X1 and X2 are each independently -O- or -C(R). 31 (R) 32 -, provided that at least one of X1 or X2 is -O-, R 31 To R 36 Each of the following is independently hydrogen, an alkyl group having 1 to 6 carbon atoms, -C(=O)-R4 or -R5-OC(=O)-R6, wherein R4 and R6 are independently alkyl groups having 1 to 6 carbon atoms with or without substituents, alkenyl groups having 2 to 20 carbon atoms, alkynyl groups having 2 to 20 carbon atoms, or aryl groups having 6 to 20 carbon atoms with or without substituents, and R5 is an alkyl group having 1 to 6 carbon atoms with or without substituents. An alkylene group of one carbon atom, wherein the substituents of L1, L2, R4, R5 and R6 are each independently selected from at least one group consisting of deuterium, -F, -Cl, -Br, -I, -CN, -NO2 and -SO3, * is a site bonded to L1 or L2, wherein when L1 and L2 are both directly linked, R1 and R2 are not both CS-7, and when L1 and L2 are both methylene and n is 2, R1 and R2 are not both CS-2.

[0023]

[0024] [Formula C]

[0025]

[0026] In formula C above, R7 includes halogen, nitrile, propargyl, ester, ether, ketone, carboxyl, alkyl with or without a substituent, alkenyl with or without a substituent, alkynyl with or without a substituent, alkoxy with or without a substituent, boron, borate, isocyanate, isothiocyanate, silyl, siloxane, sulfone, sulfonate, sulfate, or a combination of two or more of these, and p is an integer selected from 0 to 6.

[0027] [2] The present invention provides a lithium secondary battery according to [1] above, wherein, in Formula 1 above, a / b is 3.2 to 9.0.

[0028] [3] The present invention provides a lithium secondary battery according to [1] or [2] above, wherein, in Formula 1 above, a / c is 1.5 to 2.8.

[0029] [4] The present invention provides a lithium secondary battery according to any one of [1] to [3] above, wherein, in Formula 1, x, a, b, c, and d satisfy 0 ≤ x ≤ 0.2, a + b + c + d = 1, 0.55 ≤ a ≤ 0.65, 0 < b ≤ 0.15, 0.2 ≤ c ≤ 0.4, 0 ≤ d ≤ 0.1, 4.0 ≤ a / b ≤ 8.5, and 1.6 ≤ a / c ≤ 2.6.

[0030] [5] The present invention provides a lithium secondary battery according to any one of [1] to [4] above, wherein, in Formula A, R1 and R2 are each independently a substituent selected from the group consisting of the following CS-1 to CS-15.

[0031]

[0032] [6] The present invention provides a lithium secondary battery according to any one of [1] to [5] above, wherein R1 and R2 are each independently a substituent selected from the group consisting of CS-1, CS-2, CS-5, CS-8, CS-10, and CS-11.

[0033] [7] The present invention provides a lithium secondary battery according to any one of [1] to [6] above, wherein L1 and L2 are methylene groups.

[0034] [8] The present invention provides a lithium secondary battery according to any one of [1] to [7] above, wherein the compound represented by Formula A includes at least one selected from the group consisting of the following compounds A-1 to A-18.

[0035] _

[0036] [9] The present invention provides a lithium secondary battery according to any one of [1] to [8] above, wherein the compound represented by Formula C includes at least one selected from the group consisting of the compound represented by Formula C-1 and the compound represented by Formula C-2.

[0037] [Formula C-1]

[0038]

[0039] [Formula C-2]

[0040]

[0041] In equations C-1 and C-2 above, R7 is the same as that defined in equation C above.

[0042]

[11] The present invention provides a lithium secondary battery according to any one of [1] to

[10] above, wherein the weight ratio of the first additive to the second additive is 12:1 to 0.5:1.

[0043]

[12] The present invention provides a lithium secondary battery according to any one of [1] to

[11] above, wherein the content of the first additive is from 0.01% by weight to 12% by weight relative to the total weight of the non-aqueous electrolyte.

[0044]

[13] The present invention provides a lithium secondary battery according to any one of [1] to

[12] above, wherein the content of the second additive is from 0.01% by weight to 6% by weight relative to the total weight of the non-aqueous electrolyte.

[0045]

[14] The present invention provides a lithium secondary battery according to any one of [1] to

[13] above, wherein the lithium secondary battery has a charging cut-off voltage of 4.3 V or higher when driven.

[0046]

[15] The present invention provides a lithium secondary battery according to any one of [1] to

[14] above, wherein the nominal voltage of the lithium secondary battery is 3.68 V or higher.

[0047] Beneficial effects

[0048] The lithium secondary battery of the present invention comprises a positive electrode containing a lithium nickel oxide satisfying a specific chemical formula as the positive electrode active material, a first additive (a cyclic sulfur oxide represented by a specific chemical formula) and a second additive (a coumarin compound represented by a specific chemical formula). Therefore, during the activation process of the lithium secondary battery, the second additive can decompose rapidly to form free radicals, which can promote the ring-opening reaction of the first additive with a large volume structure and can rapidly and stably form a durable film on the positive / negative electrode surface from the initial activation process.

[0049] Therefore, this lithium secondary battery can have improved high-temperature life characteristics and high-temperature storage characteristics when driven at high voltage, as well as reduced resistance and improved thermal stability. Detailed Implementation

[0050] The present invention will be described in detail below.

[0051] It will be understood that the words or terms used herein and in the claims of this invention should not be construed as having the meanings defined in commonly used dictionaries. It will also be understood that, based on the principle that inventors may appropriately define the meanings of words or terms to best describe the invention, the words or terms should be interpreted as having meanings consistent with their meanings in the context of the relevant field and in the technical spirit of the invention.

[0052] The terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to limit the invention. The singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0053] It will also be understood that the terms “comprising,” “including,” or “having” as used herein specify the presence of the said feature, quantity, step, element, or combination thereof, but do not exclude the presence or addition of more than one other feature, quantity, step, element, or combination thereof.

[0054] Furthermore, prior to the description of this invention, unless otherwise specified herein, "*" indicates a portion connecting the ends of the same or different atoms or chemical formulas.

[0055] Furthermore, as used herein, in the description of “a0 to b0 carbon atoms,” “a0” and “b0” represent the number of carbon atoms contained in a particular functional group. That is, the functional group can include “a0” to “b0” carbon atoms. For example, the term “alkyl group having 1 to 5 carbon atoms” refers to an alkyl group containing 1 to 5 carbon atoms, namely, CH3-, CH3CH2-, CH3CH2CH2-, (CH3)2CH-, CH3CH2CH2CH2-, (CH3)2CHCH2-, CH3CH2CH2CH2CH2-, (CH3)2CHCH2CH2-, etc.

[0056] Furthermore, as used herein, alkyl or aryl groups may be substituented or unsubstituented. Unless otherwise defined, the term "substituented" means that at least one hydrogen atom bonded to a carbon atom is substituted by an element other than hydrogen, for example, it means substituted with an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a cycloalkenyl group having 3 to 12 carbon atoms, a heterocycloalkyl group having 3 to 12 carbon atoms, a heterocycloalkenyl group having 3 to 12 carbon atoms, a heterocycloalkynyl group having 2 to 12 carbon atoms, an aryloxy group having 6 to 12 carbon atoms, a halogen atom, a fluoroalkyl group having 1 to 20 carbon atoms, a nitro group, an aryl group having 6 to 20 carbon atoms, a heteroaryl group having 2 to 20 carbon atoms, a haloaryl group having 6 to 20 carbon atoms, etc.

[0057] The inventors of the present invention have conducted repeated studies to solve the problem of deterioration of the high-temperature life and storage characteristics of a lithium secondary battery caused by electrolyte side reactions and positive electrode transition metal dissolution when a lithium secondary battery using a lithium nickel-based oxide represented by a specific chemical formula as a positive electrode active material is driven at a high voltage. It has been found that when both a first additive and a second additive represented by specific chemical formulas are included in a non-aqueous electrolyte, a durable film can be stably and rapidly formed on the positive electrode / negative electrode during the initial activation process. Therefore, a lithium secondary battery exhibiting excellent high-temperature life characteristics, storage characteristics, and thermal stability at high voltages can be realized, thus completing the present invention.

[0058] Hereinafter, the present invention will be described in detail.

[0059] The lithium secondary battery of the present invention may include at least one of the following components and may include any combination of technically feasible components among the following components.

[0060] Lithium secondary batteries

[0061] The lithium secondary battery of the present invention includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte. Among them, the positive electrode includes a positive electrode active material, the positive electrode active material includes a lithium nickel-based oxide represented by the following formula 1, the non-aqueous electrolyte includes a lithium salt, an organic solvent, a first additive, and a second additive, the first additive includes a compound represented by the following formula A, and the second additive includes a compound represented by the following formula C.

[0062] [Formula 1]

[0063] Li 1+x [Ni a Co b Mn c M 1 d O2

[0064] In the above formula 1, x, a, b, c, and d satisfy 0 ≤ x ≤ 0.5, a + b + c + d = 1, 0.5 ≤ a ≤ 0.7, 0 < b < 0.2, 0 < c ≤ 0.4, and 0 ≤ d ≤ 0.2, and

[0065] M 1 is at least one 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.

[0066] [Formula A]

[0067]

[0068] In formula A above, n is 1 or 2, L1 and L2 are each independently directly connected, or alkylene groups with 1 to 6 carbon atoms with or without substituents, and R1 and R2 are each independently substituents represented by formula B below.

[0069] [Formula B]

[0070]

[0071] In equation B above, m is 1 or 2, and X1 and X2 are each independently -O- or -C(R). 31 (R) 32 -, provided that at least one of X1 or X2 is -O-, R 31 To R 36 Each of the following is independently hydrogen, an alkyl group having 1 to 6 carbon atoms, -C(=O)-R4 or -R5-OC(=O)-R6, wherein R4 and R6 are independently alkyl groups having 1 to 6 carbon atoms with or without substituents, alkenyl groups having 2 to 20 carbon atoms, alkynyl groups having 2 to 20 carbon atoms, or aryl groups having 6 to 20 carbon atoms with or without substituents, and R5 is an alkyl group having 1 to 6 carbon atoms with or without substituents. An alkylene group of one carbon atom, wherein the substituents of L1, L2, R4, R5 and R6 are each independently selected from at least one group consisting of deuterium, -F, -Cl, -Br, -I, -CN, -NO2 and -SO3, * is a site bonded to L1 or L2, wherein when L1 and L2 are both directly linked, R1 and R2 are not both CS-7, and when L1 and L2 are both methylene and n is 2, R1 and R2 are not both CS-2.

[0072]

[0073] [Formula C]

[0074]

[0075] In formula C above, R7 includes halogen, nitrile, propargyl, ester, ether, ketone, carboxyl, alkyl with or without a substituent, alkenyl with or without a substituent, alkynyl with or without a substituent, alkoxy with or without a substituent, boron, borate, isocyanate, isothiocyanate, silyl, siloxane, sulfone, sulfonate, sulfate, or a combination of two or more of these, and p is an integer selected from 0 to 6.

[0076] The lithium secondary battery includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte. Specifically, the lithium secondary battery includes a positive electrode, a negative electrode facing the positive electrode, a separator disposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte.

[0077] The lithium secondary battery can be manufactured according to methods generally known in the art. For example, the positive electrode, the negative electrode, and the separator disposed between the positive electrode and the negative electrode are sequentially laminated to form an electrode assembly, and then the electrode assembly is inserted into a battery case, and the non-aqueous electrolyte is injected into the battery case to manufacture the lithium secondary battery of the present invention.

[0078] (1) Positive electrode

[0079] The positive electrode includes a positive electrode active material. Specifically, the positive electrode may include a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector, and the positive electrode active material may be included in the positive electrode active material layer.

[0080] The positive electrode current collector is not particularly limited as long as it has conductivity and does not cause chemical changes in the battery. Specifically, the positive electrode current collector includes at least one selected from the group consisting of copper, stainless steel, aluminum, nickel, titanium, fired carbon, and aluminum cadmium alloy, and may preferably include aluminum.

[0081] The thickness of the positive electrode current collector is generally 3 μm to 500 μm.

[0082] The positive electrode current collector may have fine concavo-convex on its surface to improve 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, a sheet, a foil, a net, a porous body, a foam body, and a non-woven fabric body.

[0083] The positive electrode active material may be provided on at least one surface of the positive electrode current collector, specifically, on one surface or two surfaces of the positive electrode current collector. The positive electrode active material layer may have a single-layer structure or a multi-layer structure of two or more layers.

[0084] The positive electrode active material contains a lithium nickel-based oxide represented by the following formula 1.

[0085] [Formula 1]

[0086] Li 1+x [Ni a Co b Mn c M 1 d O2

[0087] In the above formula 1, x, a, b, c, and d satisfy 0 ≤ x ≤ 0.5, a + b + c + d = 1, 0.5 ≤ a ≤ 0.7, 0 < b < 0.2, 0 < c ≤ 0.4, and 0 ≤ d ≤ 0.2, and M1 It is selected from at least one 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 lithium-nickel oxides mentioned above are distinct from, for example, high-nickel lithium transition metal oxides containing more than 70 mol% nickel in all metals other than lithium. The disadvantage of high-nickel lithium transition metal oxides is that the high nickel content leads to deteriorated thermal stability, particularly under high voltage conditions. These oxides degenerate into rock salt form due to structural changes within the crystal lattice, resulting in reduced lithium mobility and impaired performance.

[0089] Meanwhile, lithium nickel oxides with lower nickel content than high-nickel lithium transition metal oxides require high voltage (e.g., above 4.3V) to improve cathode energy density. However, when lithium nickel oxides are driven at such high voltages, changes in the oxidation numbers of nickel and cobalt lead to oxygen desorption, thereby exacerbating electrolyte side reactions and causing significant degradation in lifetime and storage performance.

[0090] The lithium secondary battery of the present invention, using lithium nickel oxide represented by Formula 1 above as the positive electrode active material, achieves high energy density and excellent lifespan and storage performance through the use of the combination of the first and second additives described below. By promoting the ring-opening reaction of the first additive by the second additive, the lithium secondary battery of the present invention can rapidly and stably form a film with reduced resistance and excellent durability on the positive electrode, especially providing improved high-temperature lifespan performance, high-temperature storage performance, and thermal stability when high voltage is required.

[0091] Meanwhile, lithium nickel oxides containing less than 50 mol% nickel (Ni) in all metals other than lithium are difficult to achieve high capacities. Furthermore, lithium nickel oxides such as Li[Ni]... 0.8 Co 0.1 Mn 0.1 ]O2 and Li[Ni 0.86 Co 0.05 Mn 0.07 Al 0.02 High-nickel lithium transition metal oxides such as O2 have a high Ni ratio or a high Ni / Mn molar ratio in the transition metal, and exhibit significant axial changes in the lattice due to the increase or decrease in Ni oxidation number during charge and discharge. Therefore, the energy-unstable Ni exacerbates surface side reactions, making it difficult to achieve the performance improvement effect of forming positive / negative electrode films through first and second additives. Furthermore, materials such as Li[Ni] 0.8 Co 0.1 Mn 0.1 ]O2 and Li[Ni 0.86 Co 0.05 Mn0.07 Al 0.02 O2 and other high-nickel lithium transition metal oxides have a high Ni / Mn molar ratio. Therefore, when driven at high voltage, a phase transformation occurs, resulting in the formation of a large amount of rock salt structure on the surface. This hinders the intercalation / deintercalation of lithium ions and the formation of a positive electrode film through the combination of additives. In addition, transition metals in lithium cobalt-based oxides such as Li[Ni 0.6 Co 0.2 Mn 0.2 O2 and LiCoO2 contain a relatively large amount of cobalt (Co), and the Co ratio in the transition metals is high, which increases the irreversibility of the structure. Therefore, it is difficult to have the effect of improving the performance of forming a positive electrode film through additives. Therefore, if it is not the lithium nickel-based oxide represented by the above formula 1, even if the combination of the first and second additives is used, it is difficult to achieve the improvement of the required life performance and storage performance.

[0092] In the above formula 1, x can satisfy 0 ≤ x ≤ 0.5, specifically satisfy 0 ≤ x ≤ 0.2, and more specifically satisfy 0 ≤ x ≤ 0.1. x represents the lithium molar ratio in the lithium nickel-based oxide particles. When the above range is satisfied, the positive electrode active material can form a stable layered crystal structure.

[0093] In the above formula 1, a can satisfy 0.5 ≤ a ≤ 0.7, specifically satisfy 0.52 ≤ a ≤ 0.68, more specifically satisfy 0.55 ≤ a ≤ 0.65. a represents the nickel molar ratio in all metals other than lithium in the lithium nickel-based oxide particles. When the above range is satisfied, as described above, when driven at high voltage, it can have excellent high-temperature storage characteristics, high-temperature life characteristics, and thermal stability.

[0094] In the above formula 1, b can satisfy 0 < b < 0.2, specifically satisfy 0 < b ≤ 0.18, more specifically satisfy 0 < b ≤ 0.16, and even more specifically satisfy 0 < b ≤ 0.15. b represents the Co molar ratio in all metals other than lithium in the lithium nickel-based oxide represented by the above formula 1. When the above range is satisfied, reducing the Co content can provide cost-effectiveness and satisfactory resistance and output characteristics, and increasing the Mn ratio can enhance the structural stability of the positive electrode active material.

[0095] In the above formula 1, c can satisfy 0 < c ≤ 0.4, specifically satisfy 0.1 ≤ c ≤ 0.4, more specifically satisfy 0.15 ≤ c ≤ 0.4, and even more specifically satisfy 0.2 ≤ c ≤ 0.4. c represents the Mn molar ratio in all metals other than lithium in the lithium nickel-based oxide represented by the above formula 1. When the above range is satisfied, the structural stability of the positive electrode active material can be enhanced.

[0096] In the above formula 1, M 1 can be regarded as a doping element of the lithium nickel-based oxide. Specifically, M 1It can be at least one 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. In this case, d can satisfy 0 ≤ d ≤ 0.2, specifically 0 ≤ d ≤ 0.15, and more specifically 0 ≤ d ≤ 0.10. d represents M among all metals other than lithium in the lithium-nickel oxides represented by Equation 1 above. 1 When the elemental molar ratio meets the above range, it can promote particle growth or improve the stability of crystal structure during the sintering process of positive electrode active material.

[0097] Meanwhile, in Equation 1 above, a / b can be from 3.2 to 9.0, specifically from 4.0 to 8.5, more specifically from 5.0 to 8.0, and even more specifically from 5.5 to 7.0. When the above range is met, high capacity can be achieved by including a high content of nickel (Ni), and after achieving high capacity, the crystal structure of the positive electrode will not collapse, thus exhibiting excellent lifetime characteristics. Furthermore, when the cobalt (Co) content is high, the irreversible film formed on the surface of the positive / negative electrode is thicker, but when the above a / b range is met, the thickness of the irreversible film decreases, thus allowing the film to be stably formed by the first and second additives, enabling the battery to have excellent electrochemical characteristics.

[0098] In Equation 1 above, a / c can be from 1.5 to 2.8, specifically from 1.6 to 2.6, more specifically from 1.7 to 2.4, more specifically from 1.8 to 2.3, and even more specifically from 1.9 to 2.1. When the above ranges are met, manganese (Mn) effectively suppresses the variability in the c-axis direction within the layered structure during charging and discharging, while nickel (Ni) enables a stable capacity, giving the battery excellent electrochemical properties.

[0099] Considering that the positive electrode active material exhibits sufficient capacity, the content of the positive electrode active material can be 80% to 99% by weight, preferably 92% to 98.5% by weight, relative to the total weight of the positive electrode active material layer.

[0100] The positive electrode active material layer may also include a binder and a conductive material together with the positive electrode active material.

[0101] The adhesive is a component that helps to bond the active material to the conductive material and to the current collector, and may specifically include 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 may preferably include polyvinylidene fluoride.

[0102] To ensure sufficient adhesion strength between components such as positive electrode active materials, the adhesive content in the positive electrode active material layer can be from 1% to 20% by weight, preferably from 1.2% to 10% by weight.

[0103] Conductive materials can be used to aid and improve the conductivity of secondary batteries, and there are no particular limitations, as long as they are conductive and do not cause chemical changes in the battery. Specifically, the positive electrode conductive material may include at least one selected from the group consisting of: graphite, such as natural or artificial graphite; carbon black, such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermally cracked carbon black; conductive fibers, such as carbon fibers and metal fibers; conductive tubes, such as carbon nanotubes; fluorocarbons; metal powders, such as aluminum powder and nickel powder; conductive whiskers, such as zinc oxide and potassium titanate; conductive metal oxides, such as titanium oxide; and polyphenylene derivatives, which may preferably include carbon nanotubes for the purpose of improving conductivity.

[0104] In the positive electrode active material layer, the content of conductive material can be from 0.1% to 20% by weight, preferably from 0.1% to 10% by weight, and more specifically from 0.3% to 5% by weight, in order to fully ensure conductivity.

[0105] The thickness of the positive electrode active material layer can be from 30 μm to 400 μm, preferably from 40 μm to 200 μm.

[0106] The positive electrode can be manufactured according to conventional positive electrode manufacturing methods. For example, the positive electrode active material, positive electrode binder and / or positive electrode conductive material can be mixed in a positive electrode solvent to prepare a positive electrode slurry, the positive electrode slurry can be applied to a positive electrode current collector, and then dried and rolled to prepare the positive electrode.

[0107] The cathode solvent can be any solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropanol, N-methylpyrrolidone (NMP), acetone, or water, and any one or a mixture of two or more of these can be used. The amount of solvent used is sufficient if it can dissolve or disperse the cathode active material, conductive material, and binder when considering the applied slurry thickness and preparation yield, and subsequently has a viscosity that exhibits excellent thickness uniformity during the application to the cathode preparation process.

[0108] The solid content of the cathode slurry can be from 40% to 90% by weight, specifically from 50% to 80% by weight.

[0109] In other methods, the positive electrode can be prepared by casting a positive electrode slurry onto a separate carrier and then stacking the membrane separated from the carrier onto the positive electrode current collector.

[0110] (2) Negative electrode

[0111] The negative electrode can face the positive electrode.

[0112] The negative electrode contains a negative electrode active material. Specifically, the negative electrode may include a negative electrode current collector and a layer of negative electrode active material disposed on at least one surface of the negative electrode current collector, and the negative electrode active material layer may contain the negative electrode active material.

[0113] There are no particular restrictions on the negative electrode current collector, as long as it has high conductivity and does not cause chemical changes in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, sintered carbon, or copper or stainless steel, aluminum-cadmium alloys with one of the following surface treatments: carbon, nickel, titanium, silver, etc.

[0114] The thickness of the negative electrode current collector can typically range from 3 μm to 500 μm.

[0115] Furthermore, similar to positive electrode current collectors, negative electrode current collectors can have fine irregularities formed on their surface to improve the bonding strength of the negative electrode active material. For example, negative electrode current collectors can be used in various forms, such as membranes, sheets, foils, meshes, porous bodies, foams, and nonwoven fabrics.

[0116] The negative electrode active material can be placed on the negative electrode current collector, and specifically on one or both surfaces of the negative electrode current collector. The negative electrode active material layer can have a single-layer structure or a multi-layer structure with two or more layers.

[0117] Compounds capable of reversibly inserting and de-intercalating lithium can be used as anode active materials. Specific examples of anode active materials can be: carbon-based materials, such as artificial graphite, natural graphite, graphitized carbon fibers, and amorphous carbon; metal compounds that can be alloyed with lithium, such as silicon (Si), aluminum (Al), tin (Sn), lead (Pb), zinc (Zn), bismuth (Bi), indium (In), magnesium (Mg), gallium (Ga), cadmium (Cd), Si alloys, Sn alloys, or Al alloys; and (quasi)metal oxides that can be doped and de-doped with lithium, such as SiO2. β (0<β<2), SnO2, vanadium oxide and lithium vanadium oxide; or a composite containing (quasi)metal oxide and carbon materials, such as Si-C composite or Sn-C composite, any one or a mixture of two or more of them may be used.

[0118] Furthermore, lithium metal films can be used as anode active materials. Additionally, as carbon materials, both low-crystallinity carbon and high-crystallinity carbon can be used. Typical examples of low-crystallinity carbon include soft carbon and hard carbon, while typical examples of high-crystallinity carbon include irregularly shaped, planar, sheet-like, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fibers, mesophase carbon microspheres, mesophase pitch, and high-temperature calcined carbons such as coke derived from petroleum or coal tar pitch.

[0119] The content of negative electrode active material in the negative electrode active material layer can be from 60% to 99% by weight, preferably from 75% to 95% by weight.

[0120] In addition to the negative electrode active material, the negative electrode active material layer may optionally contain conductive materials and adhesives.

[0121] Conductive materials are used to impart conductivity to the electrodes. Any conductive material can be used without particular limitation, as long as it is electronically conductive and does not cause chemical changes in the battery to be constructed. Specific examples may include: graphite, such as natural or artificial graphite; carbon materials, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermally cracked carbon black, carbon fibers, and carbon nanotubes; metal powders or fibers, such as copper, nickel, aluminum, and silver; conductive whiskers, such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides, such as titanium oxide; or conductive polymers, such as polyphenylene derivatives, and any one or a mixture of two or more of these can be used. The content of the conductive material relative to the total weight of the negative electrode active material layer can be from 1% to 30% by weight, preferably from 1% to 20% by weight, and more preferably from 1% to 10% by weight.

[0122] The adhesive serves to improve the bonding between the negative electrode active material particles and the adhesion between the negative electrode active material and the negative electrode current collector. Specific examples may include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene propylene diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, and any one or a mixture of two or more thereof may be used. The adhesive content relative to the total weight of the negative electrode active material layer may be from 1% to 30% by weight, preferably from 1% to 20% by weight, and more preferably from 1% to 10% by weight.

[0123] The thickness of the negative electrode active material layer can be from 10 μm to 200 μm, preferably from 20 μm to 150 μm.

[0124] The negative electrode can be manufactured according to conventional negative electrode manufacturing methods. For example, the negative electrode active material, negative electrode conductive material and / or negative electrode conductive material can be mixed in a negative electrode solvent to prepare a negative electrode slurry, and the negative electrode slurry can be applied to a negative electrode current collector, and then dried and rolled to prepare the negative electrode.

[0125] Regarding the components that help disperse the negative electrode slurry, the negative electrode solvent may include at least one selected from the group consisting of distilled water, ethanol, methanol and isopropanol, preferably distilled water.

[0126] The solids content of the negative electrode slurry can be from 30% to 80% by weight, specifically from 40% to 70% by weight.

[0127] The negative electrode can be prepared by casting a negative electrode slurry onto another carrier and then stacking the membrane layer separated from the carrier onto the negative electrode current collector.

[0128] (3) Diaphragm

[0129] The diaphragm can be placed between the positive and negative electrodes.

[0130] Furthermore, commonly used porous polymer membranes, such as those made of polyolefin polymers (e.g., ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers), can be used alone or in layers as separators. Alternatively, conventional porous nonwoven fabrics, such as those formed from high-melting-point glass fibers or polyethylene terephthalate, can be used, but the invention is not limited thereto. Furthermore, coated separators containing ceramic or polymer components can be used to ensure heat resistance or mechanical strength, and single-layer or multi-layer separators can be used.

[0131] (4) Non-aqueous electrolytes

[0132] Non-aqueous electrolytes contain lithium salts, organic solvents, a first additive, and a second additive.

[0133] 1) Lithium salts

[0134] As the lithium salt used in this invention, various lithium salts commonly used in non-aqueous electrolytes for lithium secondary batteries can be used without limitation. For example, the lithium salt may include Li + As a cation, and may include at least any one selected from the group consisting of: 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 - (FSO2)2N - CF3CF2(CF3)2CO - (CF3SO2)2CH - CH3SO3 - CF3(CF2)7SO3 - CF3CO2 - CH3CO2 - SCN - and (CF3CF2SO2)2N - .

[0135] Specifically, the lithium salt may include at least one selected from the group consisting of: LiCl, LiBr, LiI, LiBF4, LiClO4, LiAlO4, LiAlCl4, LiPF6, LiSbF6, LiAsF6, LiB 10 Cl 10 LiBF4, LiClO4, LiPF6, LiBOB (LiB(C2O4)2), LiCF3SO3, LiFSI (LiN(SO2F)2), LiCH3SO3, LiCF3CO2, LiCH3CO2, and LiBETI (LiN(SO2CF2CF3)2). Specifically, lithium salts may include at least one selected from the group consisting of: LiBF4, LiClO4, LiPF6, LiBOB (LiB(C2O4)2), LiCF3SO3, LiTFSI (LiN(SO2CF3)2), LiFSI (LiN(SO2F)2), and LiBETI (LiN(SO2CF2CF3)2).

[0136] The concentration of the lithium salt in the non-aqueous electrolyte can be from 0.5 M to 5 M, specifically from 0.8 M to 4 M, and more specifically from 0.8 M to 2.0 M. When the concentration of the lithium salt meets the above range, the lithium-ion yield is improved (Li... +The transference number and the degree of lithium-ion dissociation can be used to improve the battery's output characteristics.

[0137] 2) Organic solvents

[0138] Organic solvents are generally non-aqueous solvents used in secondary batteries, and there are no particular restrictions, as long as their decomposition caused by oxidation reactions during the charging and discharging process of the secondary battery can be minimized.

[0139] Specifically, the organic solvent may include at least one selected from the group consisting of cyclic carbonate organic solvents, linear carbonate organic solvents, linear ester organic solvents, and cyclic ester organic solvents.

[0140] Specifically, organic solvents may include cyclic carbonate organic solvents, linear carbonate organic solvents, or mixtures thereof.

[0141] Cyclic carbonate organic solvents, due to their high viscosity and high dielectric constant, are suitable for the good dissociation of lithium salts in electrolytes. Specifically, they may include at least one organic solvent selected from the group consisting of ethylene carbonate (EC), fluoroethylene carbonate (FEC), propylene carbonate (PC), 1,2-butyl carbonate, 2,3-butyl carbonate, 1,2-pentane carbonate, 2,3-pentane carbonate, and vinylene carbonate. More specifically, they may include at least one selected from the group consisting of ethylene carbonate (EC) and fluoroethylene carbonate (FEC), and even more specifically, they may include ethylene carbonate (EC).

[0142] Linear carbonate organic solvents are organic solvents with 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, methyl ethyl carbonate (EMC), methyl propyl carbonate and ethyl propyl carbonate, and may more specifically include at least one selected from the group consisting of methyl ethyl carbonate (EMC) and dimethyl carbonate (DEC), and may more specifically include methyl ethyl carbonate (EMC).

[0143] The organic solvent can be a mixture of cyclic carbonate organic solvents and linear carbonate organic solvents. In this case, the cyclic carbonate organic solvent and the linear carbonate organic solvent can be mixed in a volume ratio of 5:95 to 40:60, specifically 10:90 to 25:75. When the mixing ratio of the cyclic carbonate organic solvent and the linear carbonate organic solvent meets the above range, high dielectric constant and low viscosity can be achieved, and excellent ionic conductivity can be obtained.

[0144] In addition, in order to prepare an electrolyte with high ionic conductivity, the organic solvent may also include at least one ester organic solvent selected from the group consisting of straight-chain ester organic solvents and cyclic ester organic solvents, together with at least one carbonate organic solvent selected from the group consisting of cyclic carbonate organic solvents and straight-chain carbonate organic solvents.

[0145] Straight-chain ester organic solvents may specifically include at least one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate.

[0146] In addition, cyclic ester organic solvents may specifically include at least one selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone and ε-caprolactone.

[0147] Furthermore, when necessary, organic solvents can be used by adding organic solvents commonly used in non-aqueous electrolytes, without limitation. For example, it may also contain at least one organic solvent selected from ether organic solvents, glycol ether solvents, and nitrile organic solvents.

[0148] As an ether-based organic solvent, 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 thereof, may be used, but the invention is not limited thereto.

[0149] Glycol ether solvents, which have higher dielectric constants, lower surface tensions, and lower reactivity with metals compared to straight-chain carbonate organic solvents, may include at least one selected from the group consisting of dimethoxyethane (glycol dimethyl ether, DME), diethoxyethane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether (TEGDME), but are not limited thereto.

[0150] Nitrile solvents may include, but are not limited to, at least one selected from the group consisting of acetonitrile, propionitrile, butyronitrile, valerate, octanoic acid, heptanonitrile, cyclopentanoic acid, cyclohexanoic acid, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile.

[0151] 3) First additive

[0152] The first additive includes compounds represented by formula A.

[0153] [Formula A]

[0154]

[0155] In formula A above, n is 1 or 2, L1 and L2 are each independently directly connected, or alkylene groups with 1 to 6 carbon atoms with or without substituents, and R1 and R2 are each independently substituents represented by formula B below.

[0156] [Formula B]

[0157]

[0158] In equation B above, m is 1 or 2, and X1 and X2 are each independently -O- or -C(R). 31 (R) 32 -, provided that at least one of X1 or X2 is -O-, R 31 To R 36 Each of the following is independently hydrogen, an alkyl group having 1 to 6 carbon atoms, -C(=O)-R4 or -R5-OC(=O)-R6, wherein R4 and R6 are independently alkyl groups having 1 to 6 carbon atoms with or without substituents, alkenyl groups having 2 to 20 carbon atoms, alkynyl groups having 2 to 20 carbon atoms, or aryl groups having 6 to 20 carbon atoms with or without substituents, and R5 is an alkyl group having 1 to 6 carbon atoms with or without substituents. The alkylene group has 6 carbon atoms, and the substituents of L1, L2, R4, R5 and R6 are each independently selected from at least one of the group consisting of deuterium, -F, -Cl, -Br, -I, -CN, -NO2 and -SO3, * is the site bonded to L1 or L2, and when L1 and L2 are both directly linked, R1 and R2 are not both CS-7, and when L1 and L2 are both methylene and n is 2, R1 and R2 are not both CS-2.

[0159]

[0160] The compound represented by formula A above has a sulfur oxide structure at the center and cyclic sulfur oxide structures at both ends.

[0161] By employing this chemical structure, the compound represented by Formula A can induce the stable formation of anions when used as a non-aqueous electrolyte additive, and further promotes the formation of a stable SEI layer. In particular, cyclic sulfur oxide additives (e.g., 1,3-propanesulfonyl lactone) commonly used as electrolyte additives are structurally unstable, leading to undesirable side reactions and potentially generating toxic substances. However, the compound represented by Formula A improves chemical reaction stability by linking chemically unstable reactive sites with linking groups, while maintaining a cyclic structure, reducing adverse side reactions, and allowing the additive to fully participate in the SEI film formation reaction. Furthermore, the compound represented by Formula A exhibits enhanced reactive surface coverage due to the increased unit size, enabling effective SEI film formation even in smaller quantities. Therefore, using the compound represented by Formula A as an electrolyte additive can lead to the formation of a more stable SEI layer compared to conventional additives.

[0162] Specifically, in the compound represented by formula A above, R1 and R2 can each be independently substituents selected from the group consisting of CS-1 to CS-15:

[0163]

[0164] The substituent structures CS-1 to CS-15 listed above are preferred examples of R1 and R2 of Formula A. When substituents CS-1 to CS-15 are used as R1 and R2 of Formula A, the compound can exhibit excellent structural stability as a whole and effectively act as a non-aqueous electrolyte additive. In particular, it is preferred that R1 and R2 are each independently selected from the group consisting of CS-1, CS-2, CS-5, CS-8, CS-10, and CS-11 to ensure structural stability and ease of synthesis.

[0165] Furthermore, in the compounds represented by formula A of the present invention, when L1 and L2 are both directly linked and R1 and R2 are CS-7, or when L1 and L2 are both methylene groups and n is 2 and R1 and R2 are both CS-2, the compounds themselves exhibit low structural stability and may easily decompose, thus making the synthesis of the compounds themselves difficult. In particular, compounds satisfying the above conditions may have cyclic R1 and R2 structures that are easily decomposed during synthesis, and even if finally synthesized, they may easily decompose during storage, resulting in significantly lower synthesis yields. Therefore, the present invention excludes compounds where L1 and L2 are both directly linked and R1 and R2 are CS-7, and compounds where n is 2 and R1 and R2 are both CS-2.

[0166] In the compound represented by formula A above, L1 and L2 can each be independently directly linked, methylene, or ethylene, and in particular, methylene is preferred. When L1 and L2 are methylene, the compound can be readily synthesized, and post-synthesis decomposition can be prevented.

[0167] More specifically, compounds represented by formula A are particularly preferred, including at least one selected from the group consisting of compounds A-1 to A-18:

[0168]

[0169] When the compound represented by formula A has the preferred structure as described above, it can form a stable SEI layer with low resistance even when the content is less than that of commonly used additives.

[0170] In the non-aqueous electrolyte, the content of the first additive can be 0.1% by weight or more, 0.5% by weight or more, 1% by weight or more, 1.5% by weight or more, 2% by weight or more, 2.5% by weight or more, 3% by weight or more, 3.5% by weight or more, 4% by weight or more, 4.5% by weight or more, and the content can be less than 12% by weight, less than 11.5% by weight, less than 11% by weight, less than 10.5% by weight, less than 10% by weight, less than 9.5% by weight, less than 9% by weight, less than 8.5% by weight, less than 8% by weight, less than 7.5% by weight, less than 7% by weight, less than 6.5% by weight, less than 6% by weight, and less than 5.5% by weight. For example, relative to the total weight of the non-aqueous electrolyte, the content of the first additive can be from 0.01% by weight to 12% by weight, specifically from 1% by weight to 11% by weight, more specifically from 2% by weight to 10% by weight, more specifically from 3% by weight to 7% by weight, and more specifically from 4% by weight to 6% by weight. Ideally, when the above range is met, the lifespan and storage performance of the secondary battery are achieved, and the increase in resistance caused by excessive use of additives is prevented.

[0171] 4) Second additive

[0172] The second additive includes compounds represented by the formula C.

[0173] [Formula C]

[0174]

[0175] In formula C above, R7 includes halogen, nitrile, propargyl, ester, ether, ketone, carboxyl, alkyl with or without a substituent, alkenyl with or without a substituent, alkynyl with or without a substituent, alkoxy with or without a substituent, boron, borate, isocyanate, isothiocyanate, silyl, siloxane, sulfone, sulfonate, sulfate, or a combination of two or more of these, and p is an integer selected from 0 to 6.

[0176] The compound represented by formula C (a coumarin compound) included in the second additive exhibits strong reducibility at the negative electrode, thus enabling a rapid ring-opening reaction during the initial formation of the SEI film, thereby forming a PEO-based polymeric SEI film. This polymeric SEI film exhibits excellent flexibility and recoverability.

[0177] However, when the second additive is used alone, the film formed on the positive / negative electrode may suffer from deterioration in thermal stability, chemical and electrochemical stability, and durability. For example, when the second additive is used alone, it is difficult to form an SEI exhibiting excellent durability for negative electrode active materials (e.g., silicon-based active materials) that undergo volume expansion during charging and discharging. Furthermore, when the second additive is used alone, it can be reduced to form free radicals, which subsequently attack carbonate solvents, leading to undesirable additional reduction reactions. In this regard, the non-aqueous electrolyte of the present invention uses a first additive containing cyclic sulfur oxides at both ends in combination with a second additive. The free radicals formed by the second additive promote the ring-opening reaction of the first additive, thereby forming a flexible, resilient, and durable (e.g., thermally stable) film on the positive / negative electrode.

[0178] Specifically, the compound represented by Formula A forms a film on the positive / negative electrode via a ring-opening reaction of cyclic sulfur oxides, but exhibits low participation in the reaction due to steric hindrance. Therefore, when using the compound represented by Formula A alone, it is difficult to achieve the desired positive / negative electrode film due to its low reaction participation. However, according to the present invention, by utilizing a combination of a first additive and a second additive, free radicals are formed by the first additive during the initial activation stage of the lithium secondary battery, and these free radicals can promote the ring-opening reaction of the compound represented by Formula A. Therefore, a sulfur (S)-based oxygen-rich (O) positive / negative electrode film is rapidly and stably formed, resulting in a lithium secondary battery exhibiting excellent lithium migration characteristics, as well as excellent high-temperature lifetime performance and high-temperature storage performance. Furthermore, by utilizing the combination of the first additive and the second additive, since free radicals are formed by the second additive and the ring-opening reaction of the first additive is promoted by the free radicals, a film with excellent coverage and improved durability can be formed on the positive / negative electrode, which is preferred.

[0179] The combined effect of the first and second additives in enhancing high-temperature life performance and high-temperature storage performance is particularly evident at higher voltages, especially when the lithium nickel oxide represented by Formula 1 above is used as the positive electrode active material, the active material exhibits this effect.

[0180] In formula C above, R7 is specifically a halogen (the halogen can be selected from F, C, Br and I, and can specifically be F), nitrile, propargyl, ester, ether or a combination of two or more of them. These substituents exhibit excellent reducibility, which is beneficial for forming a polymeric SEI layer, and exhibit excellent lithium-ion transport performance, and are therefore preferred.

[0181] In the above equation C, p can be an integer selected from 0 to 6, specifically, an integer selected from 1 to 6, and more specifically, p can be 1. In the above equation C, when p is 2 or more, R7 can be the same or different from each other.

[0182] Specifically, the compound represented by formula C above may include at least one selected from the group consisting of the compound represented by formula C-1 and the compound represented by formula C-2.

[0183] [Formula C-1]

[0184]

[0185] [Formula C-2]

[0186]

[0187] In equations C-1 and C-2 above, R7 is the same as that defined in equation C above.

[0188] The compounds represented by formulas C-1 and C-2 each have substituents at the 3 and 7 positions (according to IUPAC nomenclature) of the cyclic structure. In this case, it is preferable that the compound is synthesized at the aforementioned positions compared to other substitution positions. In particular, in the case of the compound represented by formula C-1 with a substituent at the 3 position, it is more preferable to improve the uniformity of the reaction during reduction at the negative electrode.

[0189] Specifically, the compound represented by formula C above may include at least one selected from the group consisting of compounds represented by formulas C-3 to C-11 below. For smoother reduction at the negative electrode and more favorable formation of a polymeric SEI layer, the compound represented by formula C above may specifically include at least one selected from the group consisting of compounds represented by formulas C-3 to C-11 below, and more specifically, at least one selected from the group consisting of compounds represented by formulas C-3, C-4, and C-6 below. For high reducibility and excellent effect in inhibiting transition metal dissolution, as well as the aforementioned effects, the compound represented by formula C above may further specifically include the compound represented by formula C-3 below.

[0190] [Formula C-3]

[0191]

[0192] [Formula C-4]

[0193]

[0194] [Formula C-5]

[0195]

[0196] [Formula C-6]

[0197]

[0198] [Formula C-7]

[0199]

[0200] [Formula C-8]

[0201]

[0202] [Formula C-9]

[0203]

[0204] [Formula C-10]

[0205]

[0206] [Formula C-11]

[0207]

[0208] The content of the second additive relative to the total weight of the non-aqueous electrolyte can be 0.01% by weight or more, 0.1% by weight or more, 0.2% by weight or more, 0.3% by weight or more, 0.4% by weight or more, 0.5% by weight or more, 0.6% by weight or more, 0.7% by weight or more, 0.8% by weight or more, 0.9% by weight or more, and the content can be less than 6% by weight, less than 5.5% by weight, less than 5% by weight, less than 4.5% by weight, less than 4% by weight, less than 3.5% by weight, less than 3% by weight, less than 2.5% by weight, less than 2% by weight, less than 1.5% by weight, or less than 1.3% by weight. For example, relative to the total weight of the non-aqueous electrolyte, the content of the second additive can be from 0.01% by weight to 6% by weight, specifically from 0.5% by weight to 5% by weight, more specifically from 0.6% by weight to 3% by weight, more specifically from 0.7% by weight to 2% by weight, and even more specifically from 0.8% by weight to 1.3% by weight. When the content of the second additive meets the above range, it is preferred for providing sufficient flexibility and recoverability to the SEI film and for preventing the increase in resistance of the lithium secondary battery and subsequent degradation of its life performance caused by excessive addition.

[0209] Meanwhile, the weight ratio of the first additive to the second additive can be from 12:1 to 0.5:1, specifically from 10:1 to 1:1, more specifically from 7:1 to 3:1, and even more specifically from 6:1 to 4:1. When the above ranges are met, an appropriate amount of positive / negative electrode film can be formed, and an appropriate amount of free radicals can be formed to promote the ring-opening reaction of the first additive, thereby accelerating the formation of the film, which can improve high-temperature storage and high-temperature lifetime characteristics.

[0210] The non-aqueous electrolyte may also contain a third additive along with the first and second additives. The inclusion of this third additive in the non-aqueous electrolyte can prevent negative electrode disintegration caused by the decomposition of the non-aqueous electrolyte under high-power conditions, achieving low-temperature high-rate discharge characteristics, high-temperature stability, preventing overcharging, and suppressing battery expansion at high temperatures.

[0211] Specifically, the third additive may include at least one selected from the group consisting of: vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, propane sulpholactone, propene sulpholactone, 1,4-butane sulpholactone, ethane sulpholactone, succinic acid, adiponitrile, ethylene sulpholactone, lithium difluorophosphate (LiDFP), lithium tetrafluoroborate (LiBF4), lithium difluorooxalate borate (LiODFB), lithium dioxalate borate (LiBOB), and trimethylsilyl phosphite (TMSPi).

[0212] The content of the third additive for non-aqueous electrolytes can be from 0.1% by weight to 15% by weight.

[0213] The lithium secondary battery of the present invention can have a charging cut-off voltage of 4.3 V or higher during operation, specifically 4.35 V or higher, and more specifically 4.4 V or higher. Through the combination of the above-described positive electrode and non-aqueous electrolyte, the lithium secondary battery of the present invention can achieve excellent energy density at high driving voltages, as well as improved high-temperature lifespan and high-temperature storage performance.

[0214] Meanwhile, the nominal voltage of the lithium secondary battery can be 3.68 V or higher, preferably 3.68 V to 3.80 V, and more preferably 3.69 V to 3.75 V. In this case, the nominal voltage represents the average voltage value of the lithium secondary battery during discharge. Since the energy density of the lithium secondary battery is calculated by multiplying the average voltage during discharge by the average current, the energy density increases when the nominal voltage is high. The nominal voltage of a lithium secondary battery using conventional lithium nickel cobalt manganese oxides as the positive electrode active material is 3.6 V, but in this invention, the charging cut-off voltage is increased to set the nominal voltage to 3.68 V or higher in order to achieve a high energy density. Specifically, the energy density of the lithium secondary battery of this invention can be 500 Wh / L or higher, 550 Wh / L or higher, or 500 Wh / L to 800 Wh / L.

[0215] The shape of the lithium secondary battery of the present invention is not particularly limited, but it can be cylindrical, prismatic, pouch-shaped or coin-shaped.

[0216] Furthermore, the lithium secondary battery of the present invention, as described above, stably exhibits excellent discharge capacity, output properties, and capacity retention, and therefore can be used in portable devices such as mobile phones, laptops, and digital cameras, as well as in electric vehicles such as hybrid electric vehicles (HEVs).

[0217] Therefore, according to another embodiment of the present invention, a battery module comprising the lithium secondary battery as a unit cell and a battery pack comprising the same are provided.

[0218] Battery modules or battery packs can be used as a power source for at least any of the following medium to large-sized devices: power tools; electric vehicles, including electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or energy storage systems.

[0219] The invention will be described in more detail below through specific embodiments. However, the embodiments shown below are for illustrative purposes only, and the scope of the invention is not limited thereto. It will be apparent to those skilled in the art that various modifications and variations can be made within the scope and technical range of the invention, and such modifications and variations fall within the scope of the claims contained herein.

[0220] Examples and Comparative Examples

[0221] Example 1

[0222] <Preparation of Non-Aqueous Electrolytes>

[0223] As an organic solvent, a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 20:80 is used.

[0224] A non-aqueous electrolyte is prepared by adding LiPF6 as a lithium salt, compound A-1 as a first additive, and a compound represented by formula C-3 as a second additive to an organic solvent.

[0225] [Compound A-1]

[0226]

[0227] [Compound C-3]

[0228]

[0229] In the non-aqueous electrolyte, the molar concentration of LiPF6 is 1.2 M.

[0230] The first additive is present in the non-aqueous electrolyte at a content of 5.0% by weight, and the second additive is present in the non-aqueous electrolyte at a content of 1.0% by weight.

[0231] <Manufacturing of Lithium Secondary Batteries>

[0232] A positive electrode active material (Li[Ni)) was added to N-methyl-2-pyrrolidone (NMP) as a solvent in a weight ratio of 97.74:0.70:1.56. 0.6 Co 0.1 Mn 0.3 O2), conductive material (carbon nanotubes), and binder (polyvinylidene fluoride) were used to prepare a positive electrode slurry (solids content: 75.5 wt%). The positive electrode slurry was applied to one surface of a 15 μm thick positive electrode current collector (Al film), then dried and rolled to form a positive electrode active material layer (thickness: 136.6 μm), which was used as the positive electrode.

[0233] A negative electrode slurry (solids content: 26 wt%) was prepared by adding a negative electrode active material (natural graphite), a conductive material (carbon black), and a binder (styrene-butadiene rubber (SBR)-carboxymethyl cellulose (CMC)) in a weight ratio of 96.15:1.55:2.30 to distilled water as a solvent. The negative electrode slurry was applied to the surface of a 15 μm thick negative electrode current collector (Cu film), then dried and rolled to form a negative electrode active material layer (thickness: 179.8 μm), which was used as the negative electrode.

[0234] In a drying chamber, a polyethylene porous membrane separator is placed between the prepared positive and negative electrodes, and then the prepared non-aqueous electrolyte is injected to manufacture a secondary battery.

[0235] Example 2

[0236] The lithium secondary battery was manufactured in the same manner as in Example 1, except that 10% by weight of the first additive was added to the non-aqueous electrolyte in place of 5.0% by weight of the first additive.

[0237] Example 3

[0238] The lithium secondary battery was manufactured in the same manner as in Example 1, except that 1.0% by weight of the first additive was added to the non-aqueous electrolyte in place of 5.0% by weight of the first additive.

[0239] Example 4

[0240] The lithium secondary battery was manufactured in the same manner as in Example 1, except that 0.5% by weight of the second additive was added to the non-aqueous electrolyte in place of 1.0% by weight of the second additive.

[0241] Example 5

[0242] The lithium secondary battery was manufactured in the same manner as in Example 1, except that 5.0% by weight of the second additive was added to the non-aqueous electrolyte in place of 1.0% by weight of the second additive.

[0243] Example 6

[0244] The lithium secondary battery was manufactured in the same manner as in Example 1, except that compound A-4 was used as the first additive.

[0245] [Compound A-4]

[0246]

[0247] Example 7

[0248] The lithium secondary battery was manufactured in the same manner as in Example 1, except that the compound represented by the following formula C-4-1 was used as a second additive.

[0249] [Formula C-4-1]

[0250]

[0251] Example 8

[0252] The lithium secondary battery was manufactured in the same manner as in Example 1, except that compound A-4 was used as the first additive and the compound represented by formula C-4-1 was used as the second additive.

[0253] Comparative Example 1

[0254] The lithium secondary battery was manufactured in the same manner as in Example 1, except that the first and second additives were not added to the non-aqueous electrolyte.

[0255] Comparative Example 2

[0256] The lithium secondary battery was manufactured in the same manner as in Example 1, except that no second additive was added to the non-aqueous electrolyte.

[0257] Comparative Example 3

[0258] The lithium secondary battery was manufactured in the same manner as in Example 1, except that the first additive was not added to the non-aqueous electrolyte.

[0259] Comparative Example 4

[0260] In addition to Li[Ni 0.8 Co 0.1 Mn 0.1 O2 replaces Li[Ni 0.6 Co 0.1 Mn 0.3 In addition to using O2 as the positive electrode active material, a lithium secondary battery was manufactured in the same manner as in Example 1.

[0261] Comparative Example 5

[0262] In addition to Li[Ni 0.8 Co 0.1 Mn 0.1 O2 replaces Li[Ni 0.6 Co 0.1 Mn 0.3 The lithium secondary battery was manufactured in the same manner as in Example 1, except that O2 was used as the positive electrode active material and no second additive was added to the non-aqueous electrolyte.

[0263] Comparative Example 6

[0264] In addition to Li[Ni 0.8 Co 0.1 Mn 0.1 O2 replaces Li[Ni 0.6 Co 0.1 Mn 0.3 The lithium secondary battery was manufactured in the same manner as in Example 1, except that O2 was used as the positive electrode active material and no first additive was added to the non-aqueous electrolyte.

[0265] Comparative Example 7

[0266] In addition to Li[Ni 0.86 Co 0.05 Mn 0.08 Al 0.01 O2 replaces Li[Ni 0.6 Co 0.1 Mn 0.3 In addition to using O2 as the positive electrode active material, a lithium secondary battery was manufactured in the same manner as in Example 1.

[0267] Comparative Example 8

[0268] In addition to Li[Ni 0.86 Co 0.05 Mn 0.08 Al 0.01 O2 replaces Li[Ni 0.6 Co 0.1 Mn 0.3 The lithium secondary battery was manufactured in the same manner as in Example 1, except that O2 was used as the positive electrode active material and no second additive was added to the non-aqueous electrolyte.

[0269] Comparative Example 9

[0270] In addition to Li[Ni 0.86 Co 0.05 Mn 0.08 Al 0.01 O2 replaces Li[Ni 0.6 Co 0.1 Mn 0.3 The lithium secondary battery was manufactured in the same manner as in Example 1, except that O2 was used as the positive electrode active material and no first additive was added to the non-aqueous electrolyte.

[0271] Comparative Example 10

[0272] Besides replacing Li[Ni] with LiCoO2 0.6 Co 0.1 Mn 0.3 In addition to using O2 as the positive electrode active material, a lithium secondary battery was manufactured in the same manner as in Example 1.

[0273] Comparative Example 11

[0274] Besides replacing Li[Ni] with LiCoO2 0.6 Co 0.1 Mn 0.3 The lithium secondary battery was manufactured in the same manner as in Example 1, except that O2 was used as the positive electrode active material and no second additive was added to the non-aqueous electrolyte.

[0275] Comparative Example 12

[0276] Besides replacing Li[Ni] with LiCoO2 0.6 Co 0.1 Mn 0.3 The lithium secondary battery was manufactured in the same manner as in Example 1, except that O2 was used as the positive electrode active material and no first additive was added to the non-aqueous electrolyte.

[0277] Comparative Example 13

[0278] In addition to Li[Ni 0.6 Co 0.2 Mn 0.2 O2 replaces Li[Ni 0.6 Co 0.1 Mn 0.3 In addition to using O2 as the positive electrode active material, a lithium secondary battery was manufactured in the same manner as in Example 1.

[0279] Comparative Example 14

[0280] In addition to Li[Ni 0.6 Co 0.2 Mn 0.2 O2 replaces Li[Ni 0.6 Co 0.1 Mn 0.3 The lithium secondary battery was manufactured in the same manner as in Example 1, except that O2 was used as the positive electrode active material and no second additive was added to the non-aqueous electrolyte.

[0281] Comparative Example 15

[0282] In addition to Li[Ni 0.6 Co 0.2 Mn 0.2 O2 replaces Li[Ni 0.6 Co 0.1 Mn 0.3 The lithium secondary battery was manufactured in the same manner as in Example 1, except that O2 was used as the positive electrode active material and no first additive was added to the non-aqueous electrolyte.

[0283] Comparative Example 16

[0284] The lithium secondary battery was manufactured in the same manner as in Example 1, except that 1,3-propanesulfonyl lactone was used as the first additive.

[0285] [Table 1]

[0286]

[0287] Experiment Example 1: High-Temperature Cycling Performance Test

[0288] As one cycle, the lithium secondary batteries of Examples 1 to 8 and Comparative Examples 1 to 16 prepared above were charged to 4.4 V and 0.05 C under CC / CV and 0.33C conditions using an electrochemical charge-discharge device at 45°C, and then discharged to 2.5 V under CC and 0.33C conditions. This was considered as one cycle, and 400 charge-discharge cycles were performed.

[0289] (1) Capacity retention rate

[0290] The capacity retention rate is calculated using the following mathematical formula, and the results are shown in Table 2 below.

[0291] Capacity retention (%) = {(Discharge capacity after 400 cycles) / (Discharge capacity after 1 cycle)} × 100

[0292] (2) Rate of increase in resistance

[0293] After one charge-discharge cycle, the discharge capacity after one cycle was measured using an electrochemical charge-discharge device. The state of charge (SOC) was adjusted to 50%, and then a 2.5 C pulse was applied for 10 seconds. The initial resistance was calculated by the difference between the voltage before and after the pulse.

[0294] After 400 charge-discharge cycles, the resistance after 400 cycles was calculated in the same manner as described above. The rate of increase in resistance was calculated using the following mathematical formula, and the results are shown in Table 2 below.

[0295] Resistance increase rate (%) = (Resistance after 400 cycles - Initial resistance) / Initial resistance × 100

[0296] [Table 2]

[0297]

[0298] Referring to Table 2 above, it is confirmed that Li[Ni] will be included. 0.6 Co 0.1 Mn 0.3 The lithium secondary batteries of Examples 1 to 8, which combine an O2-based positive electrode and a non-aqueous electrolyte containing a first additive and a second additive, exhibit higher capacity retention and lower resistance increase during high-voltage, high-temperature cycle charging and discharging compared to Comparative Examples 1 to 16. Specifically, Li[Ni] 0.8 Co 0.1 Mn 0.1 O2, Li[Ni 0.86 Co 0.05 Mn 0.08 Al 0.01 O2, LiCoO2 and Li[Ni 0.6 Co0.2 Mn 0.2 O2 replaces Li[Ni 0.6 Co 0.1 Mn 0.3 Comparative Examples 4 to 6, 7 to 9, 10 to 12, and 13 to 15, which used O2 as the positive electrode active material, did not show any improvement in high-temperature cycling characteristics even when the first additive and the second additive were used in combination. In particular, Comparative Examples 7 and 13, which used a positive electrode with the same positive electrode active material but used a combination of the first additive and the second additive, were found to have lower capacity retention rates compared to Comparative Examples 8 and 9 and 14 and 15, which used either the first additive or the second additive alone. Furthermore, Comparative Example 16, which used 1,3-propanesulfonyl lactone as the first additive, was found to have reduced high-temperature cycling performance.

[0299] Experiment Example 2: High-Temperature Storage Performance Test

[0300] The lithium secondary batteries of Examples 1 to 8 and Comparative Examples 1 to 16 prepared above were charged to 4.4 V and 0.05 C under CC / CV and 0.33 C conditions at 25°C, and discharged to 2.5 V under CC and 0.33 C conditions for initial charge / discharge. Then they were charged to 4.4 V and 0.05 C under CC / CV and 0.33 C conditions at 25°C, and then stored at 60°C for 20 weeks.

[0301] (1) Capacity retention rate

[0302] After 20 weeks of storage, the lithium secondary battery was charged to 4.4 V and 0.05 C at 25°C under CC / CV and 0.33 C conditions, and discharged to 2.5 V under CC and 0.33 C conditions to measure the capacity during the discharge process.

[0303] The capacity retention rate was evaluated using the following formula, and the results are shown in Table 3 below.

[0304] Capacity retention (%) = (Discharge capacity after 20 weeks of storage / Initial discharge capacity) × 100

[0305] (2) Rate of increase in resistance

[0306] After the initial charge and discharge, the capacity was measured at room temperature. The lithium secondary battery was charged to 50% of its state of charge (SOC) and discharged at 2.5 C for 10 seconds. The voltage drop difference at this point was used to measure the resistance as the initial resistance. The battery was stored at 60°C for 20 weeks, and the resistance was measured in the same manner as the final resistance. The rate of increase in resistance was then calculated using the following mathematical formula. The results are shown in Table 3 below.

[0307] Resistance increase rate (%) = (final resistance - initial resistance) / initial resistance × 100

[0308] [Table 3]

[0309]

[0310] Referring to Table 3 above, it is confirmed that Li[Ni] will be included. 0.6 Co 0.1 Mn 0.3 The lithium secondary batteries of Examples 1 to 8, which combine an O2-based positive electrode and a non-aqueous electrolyte containing a first additive and a second additive as additives, exhibited higher capacity retention and lower resistance increase during high-temperature storage compared to Comparative Examples 1 to 16. Specifically, Li[Ni] 0.8 Co 0.1 Mn 0.1 O2, Li[Ni 0.86 Co 0.05 Mn 0.08 Al 0.01 O2, LiCoO2, Li[Ni 0.6 Co 0.2 Mn 0.2 ]O2 and Li[Ni 0.6 Co 0.2 Mn 0.2 O2 replaces Li[Ni 0.6 Co 0.1 Mn 0.3 Comparative Examples 4 to 6, 7 to 9, 10 to 12, and 13 to 15, which used O2 as the positive electrode active material, did not show any improvement in high-temperature cycling characteristics even when the first additive and the second additive were used in combination. In particular, it was confirmed that Comparative Examples 4 and 13, which used positive electrodes with the same positive electrode active material and used a combination of the first additive and the second additive, showed a significantly reduced effect compared to Comparative Examples 5 and 6 and 14 and 15, which added the first additive or the second additive alone. Furthermore, it was confirmed that Comparative Example 16, which used 1,3-propanesulfonyl lactone as the first additive, showed reduced high-temperature storage performance.

[0311] Experiment Example 3: Hot Box Test

[0312] The lithium secondary batteries of Examples 1 to 8 and Comparative Examples 1 to 16 prepared above were charged to 4.4 V and 0.05 C under CC / CV and 0.1 C conditions using an electrochemical charge-discharge apparatus at 45°C under a pressure of 50 kgf, and then discharged to 2.5 V under CC and 0.1 C conditions to activate them. Subsequently, the activated lithium secondary batteries of Examples 1 to 8 and Comparative Examples 1 to 16 were charged to 4.4 V and 0.05 C under CC / CV and 0.33 C conditions at 25°C to fully charge to 100% SOC. Each fully charged lithium secondary battery was placed in a room temperature hot chamber and heated to 140°C at a heating rate of 5°C / min, and left to stand for 1 hour to measure the battery temperature change. A test was marked as passed when no thermal runaway or fire occurred during the test, and marked as a failure when thermal runaway and / or fire occurred. The results are shown in Table 4 below.

[0313] [Table 4]

[0314]

[0315] Referring to Table 4 above, it is confirmed that Li[Ni] will be included. 0.6 Co 0.1 Mn 0.3 The lithium secondary batteries of Examples 1 to 8, which use O2 as the positive electrode active material and a non-aqueous electrolyte containing a first additive and a second additive as additives, did not exhibit fire according to the hot box test results, while the lithium secondary batteries of Comparative Examples 1 to 16 exhibited fire according to the hot box test results.

Claims

1. A lithium secondary battery, comprising: a positive electrode; a negative electrode; a separator disposed between the positive electrode and the negative electrode; and a non-aqueous electrolyte; in, the positive electrode includes a positive electrode active material, the positive electrode active material includes a lithium nickel-based oxide represented by Formula 1 below, the non-aqueous electrolyte includes a lithium salt, an organic solvent, a first additive, and a second additive, the first additive includes a compound represented by Formula A below, and the second additive includes a compound represented by Formula C below, [Formula 1] Li 1+x [Ni a Co b Mr c M 1 d ]O2 wherein, in Formula 1 above, x, a, b, c, and d satisfy 0 ≤ x ≤ 0.5, a + b + c + d = 1, 0.5 ≤ a ≤ 0.7, 0 < b < 0.2, 0 < c ≤ 0.4, 0 ≤ d ≤ 0.2, and M 1 It is selected from at least one 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. [Formula A] wherein, in Formula A above, n is 1 or 2, L1 and L2 are each independently a direct bond, or an alkylene group having 1 to 6 carbon atoms with or without substituents, R1 and R2 are each independently a substituent represented by Formula B below: [Formula B] wherein, in Formula B above, m is 1 or 2, X1 and X2 are each independently -O- or -C(R) 31 (R) 32 -, provided that at least one of X1 or X2 is -O-, R 31 To R 36 Each is independently hydrogen, an alkyl group having 1 to 6 carbon atoms, or a group of -C(=O)-R4 or -R5-OC(=O)-R6. R4 and R6 are each independently an alkyl group having 1 to 6 carbon atoms with or without substituents, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms with or without substituents, R5 is an alkylene group having 1 to 6 carbon atoms with or without substituents, the substituents of L1, L2, R4, R5, and R6 are each independently at least one selected from the group consisting of deuterium, -F, -Cl, -Br, -I, -CN, -NO2, and -SO3, * is the site bonded to L1 or L2, when L1 and L2 are both direct bonds, R1 and R2 are not simultaneously CS-7 below, and when L1 and L2 are both methylene groups and n is 2, R1 and R2 are not simultaneously CS-2 below, [Formula C] wherein, in Formula C above, R7 includes a halogen, a nitrile group, a propargyl group, an ester group, an ether group, a ketone group, a carboxyl group, an alkyl group with or without substituents, an alkenyl group with or without substituents, an alkynyl group with or without substituents, an alkoxy group with or without substituents, a boron group, a borate group, an isocyanate group, an isothiocyanate group, a silyl group, a siloxanyl group, a sulfone group, a sulfonate group, a sulfate group, or a combination of two or more thereof, and p is an integer selected from 0 to 6.

2. The lithium secondary battery as described in claim 1, wherein, In Formula 1 above, a / b is 3.2 to 9.

0.

3. The lithium secondary battery as described in claim 1, wherein, In Formula 1 above, a / c is 1.5 to 2.

8.

4. The lithium secondary battery as described in claim 1, wherein, In Formula 1 above, x, a, b, c, and d satisfy 0 ≤ x ≤ 0.2, a + b + c + d = 1, 0.55 ≤ a ≤ 0.65, 0 < b ≤ 0.15, 0.2 ≤ c ≤ 0.4, 0 ≤ d ≤ 0.1, 4.0 ≤ a / b ≤ 8.5, 1.6 ≤ a / c ≤ 2.

6.

5. The lithium secondary battery as described in claim 1, wherein, In Formula A above, R1 and R2 are each independently a substituent selected from the group consisting of the following CS-1 to CS-15: 。 6. The lithium secondary battery as described in claim 5, wherein, R1 and R2 are each independently substituents selected from the group consisting of CS-1, CS-2, CS-5, CS-8, CS-10, and CS-11.

7. The lithium secondary battery as described in claim 1, wherein, L1 and L2 are methylene groups.

8. The lithium secondary battery as described in claim 1, wherein, The compound represented by formula A above includes at least one selected from the group consisting of compounds A-1 to A-18: 。 9. The lithium secondary battery as described in claim 1, wherein, The compound represented by formula C above includes at least one selected from the group consisting of the compound represented by formula C-1 and the compound represented by formula C-2: [Formula C-1] [Formula C-2] In equations C-1 and C-2 above, R7 is the same as that defined in equation C above.

10. The lithium secondary battery as described in claim 1, wherein, The compound represented by formula C above includes at least one selected from the group consisting of compounds represented by formulas C-3 to C-11: [Formula C-3] [Formula C-4] [Formula C-5] [Formula C-6] [Formula C-7] [Formula C-8] [Formula C-9] [Formula C-10] [Formula C-11] 。 11. The lithium secondary battery as described in claim 1, wherein, The weight ratio of the first additive to the second additive is from 12:1 to 0.5:

1.

12. The lithium secondary battery as described in claim 1, wherein, The content of the first additive is from 0.01% to 12% by weight relative to the total weight of the non-aqueous electrolyte.

13. The lithium secondary battery as described in claim 1, wherein, The content of the second additive is from 0.01% to 6% by weight relative to the total weight of the non-aqueous electrolyte.

14. The lithium secondary battery as described in claim 1, wherein the charging cutoff voltage of the lithium secondary battery during driving is 4.3V or higher.

15. The lithium secondary battery as described in claim 1, wherein the nominal voltage of the lithium secondary battery is 3.68 V or higher.

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