Lithium secondary battery

Abstract

A lithium secondary battery includes: a positive electrode; a negative electrode; a separator interposed between the positive electrode and the negative electrode; and a nonaqueous electrolyte. The positive electrode includes a positive electrode active material including a lithium transition metal oxide represented by a specific chemical formula, and the non-aqueous electrolyte includes a lithium salt, an organic solvent, and additives including a first additive including a phosphoric acid ester-based additive having a silyl group, and a second additive including a phosphoric acid ester-based additive having a silyl group. The second additive contains a compound represented by a specific chemical formula.

Description

[0001] Cross - reference to related applications

[0002] This application is based on and claims priority to Korean Patent Application No. 10-2023-0046337, filed on April 7, 2023, and Korean Patent Application No. 10-2023-0183780, filed on December 15, 2023, in the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] The present invention relates to a lithium secondary battery. Background Art

[0004] In recent years, the applications of lithium secondary batteries have rapidly expanded from powering electronic devices such as power, electronics, communication, and computers to energy storage and power supply for large-scale devices such as automobiles and energy storage systems. Therefore, the demand for secondary batteries with high capacity, high power, and high stability is increasing day by day.

[0005] A lithium secondary battery generally includes a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, an electrolyte as a lithium ion transport medium, and a separator. In this case, the negative electrode active material can be a carbon-based active material or a silicon-based active material. In addition, the positive electrode active material can be a lithium transition metal oxide, such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or lithium nickel cobalt manganese composite oxide.

[0006] Meanwhile, efforts are being made to improve the characteristics of each of the positive electrode, negative electrode, electrolyte, and separator to construct a high-capacity secondary battery. Summary of the Invention

[0007] Technical problem

[0008] The present invention provides a lithium secondary battery using a lithium transition metal oxide in which the content of nickel as a positive electrode active material is reduced to a certain level, thereby providing a lithium secondary battery having improved life performance and storage performance during high-voltage operation.

[0009] Technical solution

[0010] The present invention provides a lithium secondary battery, comprising: a positive electrode; a negative electrode; a separator interposed between the positive electrode and the negative electrode; and a non-aqueous electrolyte, wherein the positive electrode includes a positive electrode active material, the positive electrode active material includes a lithium transition metal oxide represented by the following Chemical Formula X, the non-aqueous electrolyte includes a lithium salt, an organic solvent, and an additive, the additive includes a first additive and a second additive, the first additive includes a phosphoric acid ester additive having a silyl group, and the second additive includes a compound represented by the following Chemical Formula 1:

[0011] (Chemical formula X)

[0012] Li 1+x [Ni a Co b Mn c M 1 d O 2+w

[0013] In chemical formula X, x, a, b, c, d, and w satisfy 0 ≤ x ≤ 0.5, a + b + c + d = 1, 0.5 ≤ a ≤ 0.7, 0 ≤ b ≤ 0.15, c = 1 - a - b - d, 0 ≤ d ≤ 0.1, 0 ≤ b / a ≤ 0.2, 1 ≤ a / c ≤ 3, 0 ≤ w ≤ 1; 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,

[0014] (Chemical formula 1)

[0015]

[0016] In chemical formula 1, 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 selected from the substituents represented by chemical formula 2:

[0017] (Chemical formula 2)

[0018]

[0019] In chemical formula 2, 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 and X2 is -O-; R 31 to R 36Each independently is hydrogen, an alkyl group having 1 to 6 carbon atoms, -C(=O)-R4 or -R5-O-C(=O)-R6; R4 and R6 each independently are 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; Each substituent of L1, L2, R4, R5 and R6 is independently selected from at least one of the group consisting of deuterium, -F, -Cl, -Br, -I, -CN, -NO2 and -SO3; * is the bonding position with L1 or L2; When L1 and L2 are both direct bonds, then R1 and R2 are not simultaneously the following CS-7; When L1 and L2 are both methylene groups and n is 2, then R1 and R2 are not simultaneously the following CS-2:

[0020]

[0021] Advantageous effect

[0022] The lithium secondary battery of the present invention uses a lithium transition metal oxide in which nickel, cobalt and manganese are adjusted to a specific range as a positive electrode active material, and includes a first additive (for example, tris(trimethylsilyl) phosphate) and a second additive (containing a cyclic sulfoxide represented by a specific chemical formula) as additives for a non-aqueous electrolyte. According to the present invention, the organic action of the first additive and the second additive can form a film with reduced resistance and excellent durability on the positive electrode, thereby reducing the resistance while improving the life performance and storage performance of a lithium secondary battery that requires the use of a high voltage. Detailed Description

[0023] In the following detailed description, reference will be made to the accompanying drawings which form a part thereof. The illustrative embodiments described in the detailed description, the drawings and the claims are not intended to be limiting. Other embodiments may be utilized and other changes may be made without departing from the spirit or scope of the subject matter presented herein.

[0024] In this specification, terms such as "comprising", "disposed" or "having" are intended to specify the presence of the stated features, numbers, steps, operations, components, parts or combinations thereof, but should not be construed as precluding the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof.

[0025] Meanwhile, unless otherwise specified herein, "*" refers to the connecting portion (bonding site) between the end portions of the same or different atoms or chemical formulas.

[0026] In addition, when "a to b carbon atoms" are mentioned in the specification, "a" and "b" refer to the number of carbon atoms contained in a specific functional group. That is, the functional group may contain "a" to "b" carbon atoms. For example, "an 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.

[0027] In addition, in the description herein, all alkyl or aryl groups may be substituted or unsubstituted. Unless otherwise defined, the term "substituted" means that at least one hydrogen bonded to carbon is substituted by an element other than hydrogen (for example, 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, an aryloxy group having 6 to 12 carbon atoms, a halogen atom, a fluoroalkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, a heteroaryl group having 2 to 20 carbon atoms, or a haloaryl group having 6 to 20 carbon atoms).

[0028] The terms "about", "approximately", and "substantially" as used herein are used to denote a range or approximation of a numerical value or degree in view of the inherent manufacturing and material tolerances, and are used to prevent an infringer from improperly taking advantage of the present disclosure in cases where exact or absolute numerical values are provided to aid in understanding the present disclosure.

[0029] In order to increase the energy density of the positive electrode of a lithium secondary battery, lithium nickel cobalt manganese composite transition metal oxides having a nickel content of 80 mol% or more relative to the transition metal have been studied. However, increasing the nickel content in the lithium nickel cobalt manganese composite transition metal oxide has been shown to reduce the thermal stability of the positive electrode.

[0030] To avoid this problem, reducing the nickel content in the lithium nickel cobalt manganese composite transition metal oxide requires increasing the driving voltage to achieve the desired energy density. The present invention provides a lithium secondary battery in which, by using a lithium transition metal oxide as a positive electrode active material and containing a specific additive in a non-aqueous electrolyte, nickel, cobalt, and manganese are controlled within a certain range, so that even when driven at a high voltage, the electrolyte side reaction at the positive electrode can be reduced.

[0031] Hereinafter, the present invention will be described in more detail.

[0032] Lithium secondary battery

[0033] The present invention relates to a lithium secondary battery.

[0034] The lithium secondary battery of the present invention includes: a positive electrode; a negative electrode; a separator interposed 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 transition metal oxide represented by the following Chemical Formula X, the non-aqueous electrolyte includes a lithium salt, an organic solvent, and an additive, the additive includes a first additive and a second additive, the first additive includes a phosphoric acid ester additive having a silyl group, and the second additive includes a compound represented by the following Chemical Formula 1:

[0035] (Chemical Formula X)

[0036] Li 1+x [Ni a Co b Mn c M 1 d O 2+w

[0037] In Chemical Formula X, x, a, b, c, d, and w satisfy 0 ≤ x ≤ 0.5, a + b + c + d = 1, 0.5 ≤ a ≤ 0.7, 0 ≤ b ≤ 0.15, c = 1 - a - b - d, 0 ≤ d ≤ 0.1, 0 ≤ b / a ≤ 0.2, 1 ≤ a / c ≤ 3, 0 ≤ w ≤ 1; 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,

[0038] (Chemical Formula 1)

[0039]

[0040] In Chemical Formula 1, 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 selected from the substituents represented by Chemical Formula 2:

[0041] (Chemical Formula 2)

[0042]

[0043] In Chemical Formula 2, 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 and X2 is -O-; R 31 to R 36Each is independently hydrogen, an alkyl group having 1 to 6 carbon atoms, -C(=O)-R4 or -R5-O-C(=O)-R6, where 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; each substituent of L1, L2, R4, R5, and R6 is independently selected from at least one of the group consisting of deuterium, -F, -Cl, -Br, -I, -CN, -NO2, and -SO3; * is the bonding position with L1 or L2; when both L1 and L2 are direct bonds, then R1 and R2 are not simultaneously the following CS-7; when both L1 and L2 are methylene groups and n is 2, then R1 and R2 are not simultaneously the following CS-2:

[0044]

[0045] The lithium secondary battery includes a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte. For example, the lithium secondary battery includes a positive electrode, a negative electrode, a separator inserted between the positive electrode and the negative electrode, and a non-aqueous electrolyte. A lithium secondary battery can be manufactured by accommodating an electrode assembly including a positive electrode, a negative electrode, and a separator inserted between the positive electrode and the negative electrode in a battery case and injecting a non-aqueous electrolyte into the battery case.

[0046] (1) Positive electrode

[0047] The positive electrode includes a positive electrode active material.

[0048] The positive electrode active material of the embodiment includes a lithium transition metal oxide represented by Chemical Formula X:

[0049] (Chemical Formula X)

[0050] Li 1+x [Ni a Co b Mn c M 1 d O 2+w

[0051] In Chemical Formula X, x, a, b, c, d, and w satisfy 0 ≤ x ≤ 0.5, a + b + c + d = 1, 0.5 ≤ a ≤ 0.7, 0 ≤ b ≤ 0.15, c = 1 - a - b - d, 0 ≤ d ≤ 0.1, 0 ≤ b / a ≤ 0.2, 1 ≤ a / c ≤ 3, 0 ≤ w ≤ 1; and M 1is 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.

[0052] The lithium transition metal oxide represented by Chemical Formula X is different from, for example, a high-nickel lithium transition metal oxide having a Ni content greater than 70 mol% with respect to a metal other than lithium. The disadvantage of the high-nickel lithium transition metal oxide is that it contains a large amount of nickel, resulting in deteriorated thermal stability, especially at high voltages, and degenerates into a rock salt form due to changes in the structure within the lattice, leading to a decrease in lithium mobility and performance degradation.

[0053] At the same time, compared with the high-nickel lithium transition metal oxide, the compound represented by Chemical Formula X has a relatively small nickel content, and thus needs to be driven at a high voltage (for example, above 4.35 V) to increase the energy density of the positive electrode. However, when driven at such a high voltage, for example, oxygen is removed due to changes in the oxidation numbers of nickel and cobalt, thereby exacerbating the electrolyte side reaction, resulting in a significant reduction in life performance and storage performance.

[0054] In order to balance high energy density with excellent life performance and storage performance, the lithium secondary battery of the present invention uses the lithium transition metal oxide represented by Chemical Formula X as a positive electrode active material, and uses a combination of a first additive (containing tris(trimethylsilyl) phosphate) and a second additive (containing a cyclic sulfoxide represented by Chemical Formula 1) as an additive for the non-aqueous electrolyte. The lithium secondary battery of the present invention can form a film with reduced resistance and excellent durability on the positive electrode through the organic action of the first additive and the second additive added to the non-aqueous electrolyte, and can improve the life performance and storage performance of the lithium secondary battery, especially when a high voltage needs to be used.

[0055] At the same time, in the case of high-nickel lithium transition metal oxides such as Li[Ni 0.8 Co 0.1 Mn 0.1 O2, the ratio of Ni in the transition metal or the molar ratio of Ni / Mn is relatively high, and the axial change of the lattice due to the increase and decrease of the Ni oxidation number during the charge and discharge process is relatively large. Thus, Ni, which is unstable in terms of energy, exacerbates the surface side reaction. Therefore, it is difficult to exhibit the effect of improving the performance by forming a positive electrode film through the additive. Moreover, in high-nickel lithium transition metal oxides such as Li[Ni 0.8 Co 0.1 Mn 0.1 O2, the molar ratio of Ni / Mn is relatively high, and there is a large amount of rock salt structure on the surface due to the phase change during high-voltage operation, which is not conducive to the insertion and extraction of lithium ions and the formation of a positive electrode film through the combination of additives. In addition, in the case of Li[Ni0.6 Co 0.2 Mn 0.2 In the case of lithium transition metal oxides such as Co, Mn, etc. that do not satisfy the chemical formula X, the ratio of Co in the transition metal is relatively high, which increases the irreversibility of the structure. Therefore, it is not easy to achieve the performance improvement effect by forming a positive electrode film through additives. At the same time, in the case of the compound represented by the chemical formula X, even when the first and second additives are used in combination, it is easy to achieve the desired improvement in life performance and storage performance.

[0056] In the chemical formula X, x can be about 0 ≤ x ≤ 0.5, for example, about 0 ≤ x ≤ 0.2.

[0057] In the chemical formula X, a can be about 0 ≤ a ≤ 0.7, for example, about 0.55 ≤ a ≤ 0.65.

[0058] In the chemical formula X, b is about 0 ≤ b ≤ 0.15. b corresponds to the molar percentage of Co in the metals other than lithium in the lithium transition metal oxide represented by the chemical formula X. According to the present invention, reducing the Co content has a cost advantage, and the structural stability of the positive electrode active material can be improved by increasing the relative proportion of Mn. For example, in the chemical formula X, b can be about 0 ≤ b ≤ 0.1.

[0059] In the chemical formula X, b / a is about 0 ≤ b / a ≤ 0.2. When b / a exceeds 0.2, the ratio of Co in the transition metal is relatively high, increasing the irreversibility within the structure. Therefore, the performance improvement effect by forming a positive electrode film through additives may be limited. For example, in the chemical formula X, b / a can be about 0.05 ≤ b ≤ 0.2.

[0060] In the chemical formula X, c = 1 - a - b - d, and a / c is about 1 ≤ a / c ≤ 3. c corresponds to the molar percentage of Mn in the metals other than lithium in the lithium transition metal oxide represented by the chemical formula X. According to the present invention, the structural stability of the positive electrode active material can be improved by adjusting the molar ratio of Ni to Mn to about 1 ≤ a / c ≤ 3. For example, a / c can be about 1.5 ≤ a / c ≤ 2.5.

[0061] In the chemical formula X, M 1 can be understood as a doping element of the lithium transition metal oxide, and can be, for example, 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 be about 0 ≤ d ≤ 0.1, for example, about 0 ≤ d ≤ 0.05.

[0062] In chemical formula X, a / (b×c) can be about 18 to 50, such as about 18 to 40, or about 20 to 35. Within the above range, the contents of nickel, cobalt and manganese in chemical formula A are coordinately adjusted, thereby improving the performance improvement effect of forming a positive electrode film through an additive, and at the same time improving the structural stability of the positive electrode active material.

[0063] The positive electrode active material can be in the form of particles. For example, the positive electrode active material can be a single particle composed of one nodule or a quasi-single particle form composed of a complex of 30 or fewer nodules. Alternatively, the positive electrode active material can be a quasi-single particle that is a complex of 2 to 20 nodules, such as 2 to 10 nodules, or can be in a form including the complex. In this case, cracking of the particles of the positive electrode active material during electrode manufacturing can be prevented, and internal cracking due to volume expansion / contraction of the nodules during charge and discharge can be prevented, thereby improving the high-temperature life characteristics and high-temperature storage characteristics.

[0064] The average particle size (D 50 ) of the positive electrode active material can be about 1 μm to 10 μm, such as about 2 μm to 8 μm, about 3 μm to 7 μm, about 3 μm to 5 μm, or about 3.5 μm to 4.5 μm. When the above range is satisfied, the processability during electrode manufacturing becomes excellent, the electrochemical performance is improved due to high electrolyte impregnation, the resistance is reduced, and the output characteristics are improved.

[0065] The specific surface area of the positive electrode active material is about 0.1 m 2 / g to 3.0 m 2 / g, such as about 0.3 m 2 / g to 2.5 m 2 / g, about 0.4 m 2 / g to 1.8 m 2 / g, about 0.5 m 2 / g to 1.0 m 2 / g, or about 0.7 m 2 / g to 0.9 m 2 / g. When the above range is satisfied, the calendering characteristics of the electrode are improved, particle breakage is reduced, and side reactions with the electrolyte are suppressed.

[0066] The positive electrode can 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. At this time, the positive electrode active material can be included in the positive electrode active material layer.

[0067] The positive electrode current collector is not particularly limited, and can be any positive electrode current collector having high conductivity and not causing chemical changes in the battery. For example, the positive electrode current collector can include at least one selected from the group consisting of copper, stainless steel, aluminum, nickel, titanium, fired carbon, and aluminum cadmium alloy. According to one embodiment, the positive electrode current collector can include aluminum.

[0068] The thickness of the positive electrode current collector can generally be about 3 μm to 500 μm.

[0069] The positive electrode current collector may have fine irregularities formed on its surface to enhance the bonding force of the positive electrode active material. For example, the positive electrode current collector can be used in various forms such as a film, sheet, foil, net, porous body, foam, and non-woven fabric body.

[0070] The positive electrode active material layer can be provided on at least one surface of the positive electrode current collector, for example, on one or both surfaces of the positive electrode current collector.

[0071] Considering the sufficient capacity of the positive electrode active material, the content of the positive electrode active material in the positive electrode active material layer can be about 80% by weight to 99% by weight, for example, about 92% by weight to 98.5% by weight.

[0072] Since the positive electrode active material has been described above, other descriptions will be omitted.

[0073] The positive electrode active material layer may further contain a binder and / or a conductive material together with the positive electrode active material.

[0074] The binder is a component that aids in the bonding of the active material and the conductive material and the bonding to the current collector. For example, it may 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. According to one embodiment, the binder may include polyvinylidene fluoride.

[0075] To ensure sufficient bonding force between components such as the positive electrode active material, the content of the binder in the positive electrode active material layer can be about 1% by weight to 20% by weight, for example, about 1.2% by weight to 10% by weight.

[0076] The conductive material can be used to assist and improve the conductivity of the secondary battery and is not particularly limited, and can be any material having conductivity and not causing chemical changes. For example, the positive electrode conductive material may include at least one selected from the group consisting of: graphite, such as natural graphite or artificial graphite; carbon black, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal cracking carbon black; conductive fibers, such as carbon fibers and metal fibers; conductive tubes, such as carbon nanotubes; fluorocarbons; metal powders, such as aluminum and nickel powders; conductive whiskers, such as zinc oxide and potassium titanate; conductive metal oxides, such as titanium dioxide; polyphenylene derivatives. According to one embodiment, in terms of improving conductivity, the positive electrode conductive material may include carbon nanotubes.

[0077] In terms of ensuring sufficient conductivity, the content of the conductive material in the positive electrode active material layer can be about 1 wt% to 20 wt%, for example, about 1.2 wt% to 10 wt%.

[0078] The thickness of the positive electrode active material layer can be about 30 μm to 400 μm, for example, about 40 μm to 200 μm.

[0079] The positive electrode can be manufactured by the following method: coating a positive electrode paste containing a positive electrode active material, and optionally a binder, a conductive material, and a solvent for forming the positive electrode paste on a positive electrode current collector, and then drying and calendaring.

[0080] The solvent for forming the positive electrode paste can include an organic solvent such as N-methyl-2-pyrrolidone (NMP). The solid content of the positive electrode paste can be about 40 wt% to 90 wt%, for example, about 50 wt% to 80 wt%.

[0081] (2) Negative electrode

[0082] The negative electrode can be opposite to the positive electrode.

[0083] The negative electrode contains a negative electrode active material.

[0084] The negative electrode active material is a material capable of reversibly inserting / extracting lithium ions, and can include at least one selected from the group consisting of carbonaceous active materials, (quasi) metallic active materials, and lithium metal. For example, the negative electrode active material can contain at least one selected from carbonaceous active materials and (quasi) metallic active materials.

[0085] The carbonaceous active material can contain at least one selected from the group consisting of artificial graphite, natural graphite, hard carbon, soft carbon, carbon black, graphene, and fibrous carbon. For example, the carbonaceous active material can include at least one selected from the group consisting of artificial graphite and natural graphite.

[0086] In terms of ensuring the structural stability during charge and discharge processes and reducing side reactions with the electrolyte, the average particle size (D 50 ) of the carbonaceous active material can be about 10 μm to 30 μm, for example, about 15 μm to 25 μm.

[0087] For example, the (semi) metallic active material may include at least one semi-metal selected from the group consisting of Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, V, Ti, and Sn; an alloy of lithium and at least one (semi) metal selected from the group consisting of Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, V, Ti, and Sn; an oxide of at least one (semi) metal selected from the group consisting of Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, V, Ti, and Sn; lithium titanium oxide (LTO); and lithium vanadium oxide.

[0088] According to one embodiment, the (semi) metallic active material may include a silicon-based active material.

[0089] The silicon-based active material may include SiO x a compound represented by (0 ≤ x < 2). For SiO2, since it does not react with lithium ions, it cannot store lithium, so x is selected within the above range other than 2. According to one embodiment, the silicon-based active material may be SiO.

[0090] In terms of ensuring the structural stability during charge and discharge and reducing side reactions with the electrolyte, the average particle size (D 50 ) of the silicon-based active material may be about 1 μm to 30 μm, for example, about 2 μm to 15 μm.

[0091] The negative electrode may include a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector. At this time, the negative electrode active material may be included in the negative electrode active material layer.

[0092] The negative electrode current collector is not particularly limited and may be any negative electrode current collector having high conductivity and not causing chemical changes in the battery. For example, the negative electrode current collector may be copper, stainless steel, aluminum, nickel, titanium, fired carbon, carbon, copper or stainless steel surface-treated with nickel, titanium or silver, and an aluminum-cadmium alloy.

[0093] The thickness of the negative electrode current collector may generally be about 3 μm to 500 μm.

[0094] The negative electrode current collector may be formed with fine irregularities on its surface to enhance the binding force of the negative electrode active material. For example, the negative electrode current collector may be used in various forms such as a film, sheet, foil, net, porous body, foam, and non-woven fabric body.

[0095] The negative electrode active material layer can be provided on at least one surface of the negative electrode current collector, for example, on one or both surfaces of the negative electrode current collector.

[0096] The content of the negative electrode active material in the negative electrode active material layer can be about 60% by weight to 99% by weight, for example, about 75% by weight to 95% by weight.

[0097] Since the positive electrode active material has been described above, other descriptions will be omitted.

[0098] The negative electrode active material layer can further contain a binder and / or a conductive material together with the negative electrode active material.

[0099] The binder is used to improve the battery performance by improving the adhesion between the negative electrode active material layer and the negative electrode current collector, thereby improving the battery performance. It can include, for example, at least one selected from the group consisting of polyvinylidene fluoride - hexafluoropropylene copolymer (PVDF - co - HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene - propylene - diene monomer (EPDM), sulfonated EPDM, styrene - butadiene rubber (SBR), fluororubber, and substances in which hydrogen is replaced by Li, Na, or Ca, and can also include various copolymers thereof.

[0100] The content of the binder in the negative electrode active material layer can be about 0.5% by weight to 10% by weight, for example, about 1% by weight to 5% by weight.

[0101] The conductive material is not particularly limited and can be any material having conductivity and not causing chemical changes in the battery. Examples thereof include: graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal cracking carbon black; conductive fibers such as carbon fibers and metal fibers; conductive tubes such as carbon nanotubes; fluorocarbons; metal powders such as aluminum and nickel powders; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium dioxide; and conductive materials such as polyphenylene derivatives.

[0102] The content of the conductive material in the negative electrode active material layer can be about 0.5% by weight to 10% by weight, for example, about 1% by weight to 5% by weight.

[0103] The thickness of the negative electrode active material layer can be about 10 μm to 200 μm, for example, about 20 μm to 150 μm.

[0104] The negative electrode can be manufactured by coating a negative electrode slurry containing a negative electrode active material, a binder, a conductive material, and a solvent for forming the negative electrode slurry on at least one surface of the negative electrode current collector, and then drying and calendering.

[0105] In terms of promoting the dispersion of the negative electrode active material, binder, and / or conductive material, the solvent for forming the negative electrode paste may include, for example, at least one selected from the group consisting of distilled water, N-methyl-2-pyrrolidone (NMP), ethanol, methanol, and isopropyl alcohol. According to one embodiment, the solvent may include distilled water. The solid content of the negative electrode paste may be about 30% by weight to 80% by weight, for example, about 40% by weight to 70% by weight.

[0106] (3) Separator

[0107] The separator may be inserted between the positive electrode and the negative electrode.

[0108] In addition, the separator that can be used may be any porous polymer film commonly used as a separator. For example, a porous polymer film made of polyolefin polymers (such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer) may be used alone or in a laminated form. Alternatively, the separator that can be used here may be any porous non-woven fabric, such as a non-woven fabric made of high melting point glass fiber or polyethylene terephthalate fiber, etc., but is not limited thereto. In addition, a coated separator containing a ceramic component or a polymer material may be used to ensure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0109] (4) Non-aqueous electrolyte

[0110] The non-aqueous electrolyte contains a lithium salt, an organic solvent, and an additive.

[0111] 1) Lithium salt

[0112] For the lithium salt used here, various lithium salts commonly used in non-aqueous electrolytes for lithium secondary batteries can be used without limitation. For example, the lithium salt contains Li as a cation + , and as an anion, 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 at least one selected from the group consisting of (CF3CF2SO2)2N - .

[0113] For example, 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 , LiBOB (LiB(C2O4)2), LiCF3SO3, LiFSI (LiN(SO2F)2), LiCH3SO3, LiCF3CO2, LiCH3CO2, and LiBETI (LiN(SO2CF2CF3)2). For example, the lithium salt may include at least one selected from the group consisting of LiBF4, LiClO4, LiPF6, LiBOB (LiB(C2O4)2), LiCF3SO3, LiTFSI (LiN(SO2CF3)2), LiFSI ((LiN(SO2F)2), and LiBETI (LiN(SO2CF2CF3)2).

[0114] The concentration of the lithium salt contained in the non-aqueous electrolyte may be about 0.5 M to 5 M, for example, about 0.8 M to 4 M, or about 0.8 M to 2.0 M. When the concentration of the lithium salt satisfies the above range, the lithium ion yield (Li + transference number) and the dissociation degree of lithium ions are improved, thereby improving the output characteristics of the battery.

[0115] 2) Organic solvent

[0116] The organic solvent is a commonly used non-aqueous solvent in lithium secondary batteries and is not particularly limited as long as it can minimize the decomposition caused by the oxidation reaction during the charge and discharge process of the secondary battery.

[0117] For example, 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.

[0118] For example, the organic solvent may include cyclic carbonate organic solvents, linear carbonate organic solvents, or a mixture thereof.

[0119] The cyclic carbonate organic solvent is a high-viscosity organic solvent having a high dielectric constant and capable of easily dissociating the lithium salt in the electrolyte, and may include, for example, at least one organic solvent selected from the group consisting of ethylene carbonate (EC), fluoroethylene carbonate (FEC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, and vinylene carbonate. Alternatively, the cyclic carbonate organic solvent may include at least one selected from the group consisting of ethylene carbonate (EC) and fluoroethylene carbonate (FEC). According to one embodiment, the cyclic carbonate organic solvent may include ethylene carbonate (EC).

[0120] In addition, the linear carbonate organic solvent is an organic solvent having a low viscosity and a low dielectric constant, and may include, for example, at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate, and ethyl propyl carbonate. Alternatively, the linear carbonate organic solvent may include at least one selected from the group consisting of ethyl methyl carbonate (EMC) and diethyl carbonate (DEC). According to one embodiment, the linear carbonate organic solvent may include ethyl methyl carbonate (EMC).

[0121] The organic solvent may include 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 may be mixed in a volume ratio of 5:95 to 40:60, for example, 8:92 to 35:65, or 10:90 to 25:75. When the mixing ratio of the cyclic carbonate organic solvent to the linear carbonate organic solvent satisfies the above range, the high dielectric constant and low viscosity characteristics can be satisfied simultaneously, and excellent ionic conductivity characteristics can be achieved.

[0122] In addition, in order to prepare an electrolyte with high ionic conductivity, the organic solvent may include at least one carbonate organic solvent selected from the group consisting of cyclic carbonate organic solvents and linear carbonate organic solvents, and may also include at least one ester organic solvent selected from the group consisting of linear ester organic solvents and cyclic ester organic solvents.

[0123] Examples of the linear ester organic solvent 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.

[0124] In addition, examples of the cyclic ester organic solvent include at least one selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone.

[0125] Meanwhile, if necessary, the organic solvent may also include the organic solvents commonly used in non-aqueous electrolytes without limitation. For example, the organic solvent may also include at least one organic solvent selected from the group consisting of ether organic solvents, glycol ether solvents, and nitrile organic solvents.

[0126] The ether solvent used herein may be any one selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether, ethyl propyl ether, 1,3-dioxolane (DOL), and 2,2-bis(trifluoromethyl)-1,3-dioxolane (TFDOL), or a mixture of two or more of them, but is not limited thereto.

[0127] The glycol ether solvent has a high dielectric constant and a low surface tension compared with the linear carbonate organic solvent, and has a low reactivity with metals, and may include at least one selected from the group consisting of dimethoxyethane (glycol dimethyl ether, DME), diethoxyethane, diethylene glycol ether, triethylene glycol ether, and tetraethylene glycol dimethyl ether (TEGDME), but is not limited thereto.

[0128] The nitrile solvent may include at least one selected from the group consisting of acetonitrile, propionitrile, butyronitrile, valeronitrile, octanenitrile, heptanenitrile, cyclopentanecarbonitrile, cyclohexanecarbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile, but is not limited thereto.

[0129] 3) Additive

[0130] The non-aqueous electrolyte contains an additive.

[0131] The additive includes a first additive and a second additive.

[0132] The first additive is a phosphate additive having a silyl group, and examples thereof include tris(trimethylsilyl) phosphate (TMSPa).

[0133] Tris(trimethylsilyl) phosphate can decompose to form P-O radicals, which can be used to form a P-O-based film on the positive electrode. Tris(trimethylsilyl) phosphate can also act as an HF scavenger to remove decomposition products (PF5, HF, etc.) of lithium salts generated during charge and discharge of the lithium secondary battery.

[0134] Meanwhile, tris(trimethylsilyl) phosphate is used as the first additive, but not limited thereto. For example, any other material can also be used as long as the material can decompose to form PO radicals, can be used to form a PO-based film on the positive electrode, or the material can act as an HF scavenger to remove decomposition products (PF5, HF, etc.) of lithium salts generated during charge and discharge of the lithium secondary battery.

[0135] Meanwhile, since the reaction rate of the P-O radicals generated by tris(trimethylsilyl) phosphate is relatively fast, a monomolecular film is formed instead of a polymeric film formed by a chain reaction. Therefore, when tris(trimethylsilyl) phosphate is used alone, there is a problem that a film with sufficient coverage cannot be expected to be formed on the positive electrode. However, in the present invention, the first additive and the second additive are used in combination. As a result, a film with excellent lithium transfer characteristics, excellent coverage, and improved durability can be formed on the positive electrode, and the life performance and high-temperature storage performance of the lithium secondary battery can be improved.

[0136] The content of the first additive in the non-aqueous electrolyte can be about 0.01% by weight to 10% by weight, for example, about 0.05% by weight to 7% by weight, about 0.1% by weight to 5% by weight, or about 1% by weight to 4% by weight. When the first additive is used within the above content range, the above effects of improving the life performance and high-temperature storage performance can be achieved, while avoiding the possibility of increasing the resistance when adding excessively.

[0137] The second additive may include a compound represented by Chemical Formula 1:

[0138] (Chemical Formula 1)

[0139]

[0140] In Chemical Formula 1, 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 selected from the substituents represented by Chemical Formula 2:

[0141] (Chemical Formula 2)

[0142]

[0143] In Chemical Formula 2, 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 and X2 is -O-; R 31 to R 36 are each independently hydrogen, an alkyl group having 1 to 6 carbon atoms, -C(=O)-R4, or -R5-O-C(=O)-R6, and 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; each substituent of L1, L2, R4, R5, and R6 is independently selected from at least one of the group consisting of deuterium, -F, -Cl, -Br, -I, -CN, -NO2, and -SO3; * is the bonding position to L1 or L2; when both L1 and L2 are direct bonds, then R1 and R2 are not simultaneously the following CS-7; when both L1 and L2 are methylene groups and n is 2, then R1 and R2 are not simultaneously the following CS-2:

[0144]

[0145] The compound represented by Chemical Formula 1 has a sulfoxide structure at the center and cyclic sulfoxide structures at both ends. By adopting such a chemical structure, when the compound is used as an additive for a non-aqueous electrolyte, it can induce the stable formation of anions and can further ensure the formation of a stable solid electrolyte interface (SEI) layer.

[0146] Meanwhile, although the compound represented by Chemical Formula 1 forms a film on the positive electrode through the ring-opening reaction of the cyclic sulfoxide, due to steric hindrance, there is a problem of low reaction participation rate. Therefore, when the compound represented by Chemical Formula 1 is used alone, it is difficult to form a desired positive electrode film due to the low reaction participation rate. However, in the present invention, since the first additive is used together with the second additive, P-O radicals are formed by the first additive, and the P-O radicals can promote the ring-opening reaction of the compound represented by Chemical Formula 1, resulting in the formation of an oxygen (O)-rich positive electrode film based on sulfur (S) and phosphorus (P), thereby achieving a lithium secondary battery having excellent lithium transport characteristics, excellent life performance, and storage performance. In addition, when the first additive and the second additive are used in combination, since the first additive forms P-O radicals and the radicals promote the ring-opening reaction of the second additive, a film with excellent coverage and improved durability can be formed on the positive electrode.

[0147] Meanwhile, in addition to the above-mentioned second additive, any other additive can be used as the second additive in combination with the first additive, for example, as long as the additive can promote the ring-opening reaction of free radicals or the like.

[0148] The effects of improving the life performance and storage performance due to the organic actions of the first and second additives are more obvious when used at high voltages, and are particularly effective when using the lithium transition metal oxide represented by the above chemical formula X as the positive electrode active material.

[0149] For example, in the compound represented by Chemical Formula 1, R1 and R2 can each independently be selected from the group consisting of CS-1 to CS-15:

[0150]

[0151]

[0152] The above substituent structures CS-1 to CS-15 are preferred examples of R1 and R2 in Chemical Formula 1. When the substituents shown by CS-1 to CS-15 are used as R1 and R2 in Chemical Formula 1, the entire compound has good structural stability and can be used well as an additive for non-aqueous electrolytes. For example, R1 and R2 can each independently be selected from the group consisting of CS-1, CS-2, CS-5, CS-8, CS-10, and CS-11, which may be preferred in terms of structural stability and ease of synthesis.

[0153] Meanwhile, in the compound represented by Chemical Formula 1 of the present invention, when both L1 and L2 are direct bonds and R1 and R2 are CS-7, or when both L1 and L2 are methylene groups, n is 2, and R1 and R2 are simultaneously CS-2, the compound itself may be easily decomposed due to low structural stability, and thus the synthesis of the compound itself may be relatively difficult. Specifically, the compound satisfying the above conditions has the disadvantages that the cyclic R1 and R2 structures are easily decomposed during the synthesis process, and even if the compound is finally synthesized, it is easily decomposed during storage, and the synthesis yield is significantly low. Therefore, the present invention excludes the compounds in which both L1 and L2 are direct bonds and R1 and R2 are CS-7, and the compounds in which n is 2 and R1 and R2 are simultaneously CS-2.

[0154] In the compound represented by Chemical Formula 1, L1 and L2 can each independently be a direct bond, a methylene group, or an ethylene group. In particular, according to one embodiment, it can be a methylene group. When L1 and L2 are methylene groups, it is beneficial to the synthesis of the compound and can inhibit the decomposition of the compound after synthesis.

[0155] For example, the compound represented by Chemical Formula 1 can be any one selected from the group consisting of Compounds A to R:

[0156]

[0157]

[0158]

[0159] When the compound represented by Chemical Formula 1 has the above structure, compared with common additives, this compound has the advantage that even a small amount can form a stable SEI layer with low resistance.

[0160] The content of the compound represented by Chemical Formula 1 in the non-aqueous electrolyte can be about 0.01% by weight to 10% by weight, such as about 0.05% by weight to 7% by weight, about 0.1% by weight to 5% by weight, or about 1% by weight to 4% by weight. When within the above range, it is desirable to prevent an increase in resistance caused by excessive use of additives while achieving the above effects of improving the life performance and storage performance of the secondary battery.

[0161] Meanwhile, in addition to the above second additive, any other type of compound can be used as the second additive as long as the compound can achieve similar functions and effects.

[0162] The weight ratio of the first additive to the second additive can be about 1:99 to 99:1, such as about 30:70 to 70:30, or 40:60 to 60:40. When the weight ratio is as described above, the effects of the first additive and the second additive used in combination are coordinated. As a result, it is more preferably to exhibit the effects of improving the high-temperature life performance and high-temperature storage performance of the lithium secondary battery.

[0163] The additive can further contain a supplementary additive in combination with the first additive or with the first additive and the second additive. The non-aqueous electrolyte can contain the supplementary additive to prevent the non-aqueous electrolyte from decomposing and causing negative electrode breakdown in a high-power environment, or for low-temperature high-rate discharge characteristics, high-temperature stability, overcharge protection, and suppression of battery swelling at high temperatures.

[0164] For example, the supplementary additive can contain at least one selected from the group consisting of vinylene carbonate, ethyl vinyl carbonate, fluoroethylene carbonate, propane sultone, propene sultone, 1,4-butane sultone, succinonitrile, adiponitrile, ethylene sulfite, lithium difluorophosphate (LiDFP), lithium tetrafluoroborate (LiBF4), lithium difluorooxalate borate (LiODFB), and tris(trimethylsilyl) phosphite (TMSPi):

[0165] The content of the supplementary additive in the non-aqueous electrolyte can be about 0.1% by weight to 15% by weight.

[0166] The driving voltage of the lithium secondary battery of the present invention can be about 4.35 V or more, for example, about 4.4 V or more. Through the combination of the above-mentioned positive electrode and non-aqueous electrolyte, the lithium secondary battery of the present invention can achieve excellent energy density, improved life performance, and storage performance at a high driving voltage.

[0167] The shape of the lithium secondary battery of the present invention is not particularly limited and can be cylindrical, square, pouch-type, or coin-type using a can.

[0168] Hereinafter, the present invention will be described through examples. However, the following examples are intended to illustrate the present invention and are not intended to limit the scope of the present invention. It will be obvious to those skilled in the art that various changes and modifications can be made within the scope of the present specification and technical idea, and such changes and modifications fall within the scope of the appended claims.

[0169] Examples and comparative examples

[0170] Example 1

[0171] (Preparation of non-aqueous electrolyte)

[0172] A mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) with a volume ratio of 20:80 was used as the organic solvent.

[0173] A non-aqueous electrolyte was prepared by adding LiPF6 as a lithium salt, tris(trimethylsilyl) phosphate (TMSPa) as a first additive, and compound A as a second additive to the organic solvent.

[0174] LiPF6 was contained in the non-aqueous electrolyte at a molar concentration of 1.2 M.

[0175] The content of the first additive in the non-aqueous electrolyte was 0.1 wt%, and the content of the second additive in the non-aqueous electrolyte was 0.1 wt%.

[0176] (Preparation of lithium secondary battery)

[0177] The positive electrode active material (Li[Ni 0.60 Co 0.05 Mn 0.35 O2), a conductive material (carbon nanotubes), and a binder (polyvinylidene fluoride) were added to the solvent N-methyl-2-pyrrolidone (NMP) at a weight ratio of 97.74:0.70:1.56 to prepare a positive electrode slurry (75.5 wt% solids). The positive electrode slurry was coated on one side of a positive electrode current collector (Al film) with a thickness of 15 μm, dried, and calendered to prepare a positive electrode. The positive electrode active material was in the form of single particles or quasi-single particles.

[0178] The negative electrode active material (natural graphite), the conductive material (carbon black), and the binder (styrene-butadiene rubber and carboxymethyl cellulose) were added to distilled water as a solvent at a weight ratio of 96.15:1.55:2.30 to prepare a negative electrode paste (26 wt% solids). The negative electrode paste was coated on one side of a negative electrode current collector (Cu film) with a thickness of 15 μm, dried, and calendered to prepare a negative electrode.

[0179] In a drying chamber, a separator made of a porous polyethylene film was inserted between the prepared positive electrode and negative electrode, and then the prepared non-aqueous electrolyte was injected to prepare a secondary battery.

[0180] Example 2

[0181] A lithium secondary battery was prepared in the same manner as in Example 1, except that the content of the second additive added to the non-aqueous electrolyte was 5 wt% instead of 0.1 wt% in Example 1.

[0182] Example 3

[0183] A lithium secondary battery was prepared in the same manner as in Example 1, except that the content of the first additive added to the non-aqueous electrolyte was 3 wt% instead of 0.1 wt% in Example 1, and the content of the second additive added to the non-aqueous electrolyte was 3 wt% instead of 0.1 wt% in Example 1.

[0184] Example 4

[0185] A lithium secondary battery was prepared in the same manner as in Example 1, except that the content of the first additive added to the non-aqueous electrolyte was 5 wt% instead of 0.1 wt% in Example 1.

[0186] Example 5

[0187] A lithium secondary battery was prepared in the same manner as in Example 1, except that the content of the first additive added to the non-aqueous electrolyte was 5 wt% instead of 0.1 wt% in Example 1, and the content of the second additive added to the non-aqueous electrolyte was 5 wt% instead of 0.1 wt% in Example 1.

[0188] Example 6

[0189] A lithium secondary battery was prepared in the same manner as in Example 3, except that compound F with a content of 3 wt% was included in the non-aqueous electrolyte instead of compound A in Example 1 as the second additive.

[0190] Example 7

[0191] A lithium secondary battery was prepared in the same manner as in Example 3, except that 3 wt% of Compound J was included in the non-aqueous electrolyte instead of Compound A in Example 1 as the second additive.

[0192] Comparative Example 1

[0193] A lithium secondary battery was prepared in the same manner as in Example 1, except that no second additive was added to the non-aqueous electrolyte.

[0194] Comparative Example 2

[0195] A lithium secondary battery was prepared in the same manner as in Example 1, except that the content of the first additive added to the non-aqueous electrolyte was 5 wt% instead of 0.1 wt% in Example 1, and no second additive was added to the non-aqueous electrolyte.

[0196] Comparative Example 3

[0197] A lithium secondary battery was prepared in the same manner as in Example 1, except that no first additive was added to the non-aqueous electrolyte.

[0198] Comparative Example 4

[0199] A lithium secondary battery was prepared in the same manner as in Example 1, except that no first additive was added to the non-aqueous electrolyte, and the content of the second additive added to the non-aqueous electrolyte was 5 wt% instead of 0.1 wt%.

[0200] Comparative Example 5

[0201] A lithium secondary battery was prepared in the same manner as in Example 3, except that 3 wt% of a comparative compound was included in the non-aqueous electrolyte instead of Compound A in Example 1 as the second additive.

[0202] [Comparative Compound]

[0203]

[0204] Table 1

[0205]

[0206] Experimental examples

[0207] Experimental Example 1: Evaluation of High-Temperature Cycling Performance

[0208] Using an electrochemical charge-discharge device, the lithium secondary batteries of Examples 1 to 7 and Comparative Examples 1 to 5 prepared above were each subjected to 300 cycles of charge and discharge, each cycle including charging to 4.4 V at 45 °C under constant current / constant voltage (CC / CV) and 0.33 C and 0.05 C, and discharging to 2.5 V under constant current (CC) and 0.33 C.

[0209] Capacity retention rate

[0210] The capacity retention rate was calculated using the following mathematical formula, and the results are shown in Table 2 below.

[0211] Capacity retention rate (%) = {(discharge capacity after 300 cycles / discharge capacity after 1 cycle)} × 100

[0212] Resistance increase rate

[0213] 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%, a pulse of 2.5 C was applied for 10 seconds, and the initial resistance was calculated from the difference between the voltage before the pulse application and the voltage after the pulse application.

[0214] After 300 charge-discharge cycles, the resistance after 300 cycles was calculated in the same manner as above, and the resistance increase rate was calculated using the following mathematical formula, and the results are shown in Table 2 below.

[0215] Resistance increase rate (%) = (resistance after 300 cycles - initial resistance) / initial resistance × 100

[0216] Table 2

[0217] Capacity retention rate (%) Resistance increase rate (%) Example 1 96 10 Example 2 95 9 Example 3 96 8 Example 4 96 11 Example 5 95 10 Example 6 96 8 Example 7 97 9 Comparative example 1 75 27 Comparative example 2 81 26 Comparative example 3 70 25 Comparative example 4 82 18 Comparative example 5 80 34

[0218] Referring to Table 2, it can be seen that the lithium secondary batteries of Examples 1 to 7 including the combination of a positive electrode containing a lithium transition metal oxide represented by Chemical Formula X and a non-aqueous electrolyte of the present invention containing a first additive and a second additive as additives have a higher capacity retention rate and a lower resistance increase rate during high-temperature cyclic charge and discharge at high voltages compared to the cases of Comparative Examples 1 to 5 where the present invention was not applied.

[0219] Experimental Example 2: Evaluation of high-temperature storage performance

[0220] The lithium secondary batteries of Examples 1 to 7 and Comparative Examples 1 to 5 prepared above were each initially charged and discharged using an electrochemical charge-discharge device, including charging to 4.4 V and 0.05 C at 25 °C under CC / CV and 0.33 C conditions, and then discharging to 2.5 V under CC and 0.33 C conditions. Then, the lithium secondary batteries were charged to 4.4 V and 0.05 C at 25 °C under CC / CV and 0.33 C conditions, and then stored at 60 °C for 12 weeks.

[0221] Capacity retention rate

[0222] After storing for 12 weeks, the lithium secondary batteries were charged to 4.4 V, 0.05 C at 25 °C under CC / CV and 0.33 C conditions using an electrochemical charge-discharge device, and discharged to 2.5 V under CC and 0.33 C conditions to measure the capacity during the discharge process.

[0223] The capacity retention rate was calculated according to the following mathematical formula, and the results are shown in Table 3 below.

[0224] Capacity retention rate (%) = (Discharge capacity after 12-week storage / Initial discharge capacity) × 100

[0225] Resistance increase rate

[0226] After the initial charge and discharge, the capacity was checked at room temperature. Then, the lithium secondary battery was charged to 50% SOC based on the discharge capacity and discharged at a current of 2.5 C for 10 seconds. Then, the resistance was measured using the voltage drop difference at this time and used as the initial resistance. After storing at 60 °C for 12 weeks, the resistance was measured in the same manner and used as the final resistance. Then, the resistance increase rate was calculated using the following mathematical formula. The results are shown in Table 3 below.

[0227] Resistance increase rate (%) = (Final resistance - Initial resistance) / Initial resistance × 100

[0228] Table 3

[0229] Capacity retention rate (%) Resistance increase rate (%) Example 1 95 9 Example 2 95 8 Example 3 96 6 Example 4 94 7 Example 5 95 8 Example 6 97 7 Example 7 96 6 Comparative example 1 85 24 Comparative example 2 86 22 Comparative example 3 75 19 Comparative example 4 72 16 Comparative example 5 76 28

[0230] Referring to Table 3, it can be seen that the lithium secondary batteries of Examples 1 to 7, which include the combination of a positive electrode containing a lithium transition metal oxide represented by Chemical Formula X and a non-aqueous electrolyte of the present invention containing a first additive and a second additive as additives, have a higher capacity retention rate and a lower resistance increase rate during high-temperature storage compared to the cases of Comparative Examples 1 to 5 where the present invention is not applied.

[0231] Reference Example A: The case of using Li[Ni 0.8 Co 0.1 Mn 0.1 O2 as the positive electrode active material

[0232] Reference example 1A

[0233] Preparation of non-aqueous electrolyte

[0234] A mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) with a volume ratio of 20:80 is used as the organic solvent.

[0235] The non-aqueous electrolyte is prepared by adding LiPF6 as the lithium salt, tris(trimethylsilyl) phosphate (TMSPa) as the first additive, and compound A as the second additive to the organic solvent.

[0236] LiPF6 is contained in the non-aqueous electrolyte at a molar concentration of 1.2 M.

[0237] The content of the first additive in the non-aqueous electrolyte is 5 wt%, and the content of the second additive in the non-aqueous electrolyte is 5 wt%.

[0238] Preparation of lithium secondary battery

[0239] The positive electrode active material (Li[Ni 0.8 Co 0.1 Mn 0.1 O2), the conductive material (carbon nanotubes), and the binder (PVDF) are added to the solvent N-methyl-2-pyrrolidone (NMP) at a weight ratio of 96.78:1.20:2.02 to prepare a positive electrode mixture slurry (75.5 wt% solids). The positive electrode mixture slurry is coated on one side of a positive electrode current collector (Al film) with a thickness of 15 μm, dried, and calendered to prepare a positive electrode.

[0240] The negative electrode active material (natural graphite), the conductive material (carbon black), and the binder (styrene-butadiene rubber and carboxymethyl cellulose) are added to distilled water as the solvent at a weight ratio of 96.15:0.50:3.35 to prepare a negative electrode mixture slurry (26 wt% solids). The negative electrode mixture slurry is coated on one side of a negative electrode current collector (Cu film) with a thickness of 15 μm, dried, and calendered to prepare a negative electrode.

[0241] A separator made of a porous polyethylene film is inserted between the prepared positive electrode and negative electrode in a drying chamber, and then the prepared non-aqueous electrolyte is injected to prepare a secondary battery.

[0242] Reference example 2A

[0243] A lithium secondary battery is prepared in the same manner as in Reference Example 1A except that the second additive is not added to the non-aqueous electrolyte.

[0244] Reference example 3A

[0245] A lithium secondary battery was prepared in the same manner as in Reference Example 1A, except that the first additive was not added to the non-aqueous electrolyte.

[0246] Reference Experimental Example A-1

[0247] Using an electrochemical charge-discharge device, each of the lithium secondary batteries prepared in Reference Examples 1A to 3A above was charged and discharged 300 times, each cycle including charging to 4.2 V at 45 °C under constant current / constant voltage (CC / CV) and 0.33 C and 1 / 40 C, and discharging to 2.5 V under constant current (CC) and 0.33 C.

[0248] Capacity retention rate

[0249] The capacity retention rate was calculated using the following mathematical formula, and the results are shown in Table 4 below.

[0250] Capacity retention rate (%) = {(discharge capacity after 300 cycles / discharge capacity after 1 cycle)} × 100

[0251] Resistance increase rate

[0252] After one charge-discharge cycle, the discharge capacity after one cycle was measured using an electrochemical charge-discharge device. The SOC was adjusted to 50% SOC, a pulse of 2.5 C was applied for 10 seconds, and the initial resistance was calculated from the difference between the voltage before applying the pulse and the voltage after applying the pulse.

[0253] After 300 charge-discharge cycles, the resistance after 300 cycles was calculated in the same manner as above. The resistance increase rate was calculated using the following mathematical formula, and the results are shown in Table 4 below.

[0254] Resistance increase rate (%) = (resistance after 300 cycles - initial resistance) / initial resistance × 100

[0255] Reference Experimental Example A-2

[0256] Each of the lithium secondary batteries prepared in Reference Examples 1A to 3A above was initially charged and discharged, including charging to 4.2 V at 25 °C under CC / CV and 0.33 C and 1 / 40 C, and then discharging to 2.5 V under CC and 0.33 C. Then, the lithium secondary battery was charged to 4.2 V at 25 °C under CC / CV and 0.33 C and 1 / 40 C, and then stored at 60 °C for 12 weeks.

[0257] Capacity retention rate

[0258] After 12 weeks of storage, the lithium secondary battery was charged to 4.2 V at 1 / 40 C under CC / CV conditions at 25 °C and then discharged to 2.5 V at 0.33 C to measure the capacity during the discharge process.

[0259] The capacity retention rate was calculated according to the following mathematical formula, and the results are shown in Table 4 below.

[0260] Capacity retention rate (%) = (Discharge capacity after 12 weeks of storage / Initial discharge capacity) × 100

[0261] Rate of increase in resistance

[0262] After the initial charge and discharge, the capacity was checked at room temperature. Then, the lithium secondary battery was charged to 50% SOC based on the discharge capacity and discharged at a current of 2.5 C for 10 seconds. Then, the resistance was measured using the voltage drop difference at this time and used as the initial resistance. After 12 weeks of storage at 60 °C, the resistance was measured in the same manner and used as the final resistance. Then, the rate of increase in resistance was calculated using the following mathematical formula. The results are shown in Table 4 below.

[0263] Rate of increase in resistance (%) = (Final resistance - Initial resistance) / Initial resistance × 100

[0264] Table 4

[0265]

[0266] Referring to Table 4, it can be seen that although the first additive and the second additive are used as additives in the non-aqueous electrolyte, the improvement in the effect of the lithium secondary battery of Reference Example 1A is relatively small compared to Reference Examples 2A and 3A. For example, in the case of Reference Examples 1A to 3A using high-nickel lithium transition metal oxide (Li[Ni 0.8 Co 0.1 Mn 0.1 O2) as the positive electrode active material, even when the first additive and the second additive are used in combination, the effect is not improved at all. On the contrary, compared with Reference Examples 2A and 3A, the capacity retention rate of Reference Example 1A during charge-discharge cycling or high-temperature storage is equal to or lower.

[0267] Reference Example B: Case of using Li[Ni 0.6 Co 0.2 Mn 0.2 O2 as the positive electrode active material

[0268] Reference example 1B

[0269] Preparation of non-aqueous electrolyte

[0270] A mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) with a volume ratio of 20:80 was used as the organic solvent.

[0271] A non-aqueous electrolyte was prepared by adding LiPF6 as a lithium salt, tris(trimethylsilyl) phosphate (TMSPa) as a first additive, and compound A as a second additive to the organic solvent.

[0272] LiPF6 was contained in the non-aqueous electrolyte at a molar concentration of 1.2 M.

[0273] The content of the first additive in the non-aqueous electrolyte was 5 wt%, and the content of the second additive in the non-aqueous electrolyte was 5 wt%.

[0274] Preparation of Lithium Secondary Battery

[0275] The positive electrode active material (Li[Ni 0.6 Co 0.2 Mn 0.2 O2), a conductive material (carbon nanotubes), and a binder (PVDF) were added to the solvent N-methyl-2-pyrrolidone (NMP) at a weight ratio of 97.74:0.70:1.56 to prepare a positive electrode mixture slurry (75.5 wt% solids). The positive electrode mixture slurry was coated on one side of a positive electrode current collector (Al film) with a thickness of 15 μm, dried, and calendered to prepare a positive electrode.

[0276] The negative electrode active material (natural graphite), a conductive material (carbon black), and a binder (styrene-butadiene rubber and carboxymethyl cellulose) were added to distilled water as a solvent at a weight ratio of 96.15:1.55:2.30 to prepare a negative electrode mixture slurry (26 wt% solids). The negative electrode mixture slurry was coated on one side of a negative electrode current collector (Cu film) with a thickness of 15 μm, dried, and calendered to prepare a negative electrode.

[0277] A separator made of a porous polyethylene film was inserted between the prepared positive electrode and negative electrode in a drying chamber, and then the prepared non-aqueous electrolyte was injected to prepare a secondary battery.

[0278] Reference example 2B

[0279] A lithium secondary battery was prepared in the same manner as in Reference Example 1B, except that the second additive was not added to the non-aqueous electrolyte.

[0280] Reference example 3B

[0281] A lithium secondary battery was prepared in the same manner as in Reference Example 1B, except that the first additive was not added to the non-aqueous electrolyte.

[0282] Reference Experimental Example B-1

[0283] Using an electrochemical charge-discharge device, each of the lithium secondary batteries prepared in Reference Examples 1B to 3B above was charged and discharged 300 times. Each cycle included charging to 4.4 V at 45 °C under constant current / constant voltage (CC / CV) and 0.33 C and 0.05 C, and discharging to 2.5 V under constant current (CC) and 0.33 C.

[0284] Capacity retention rate

[0285] The capacity retention rate was calculated using the following mathematical formula, and the results are shown in Table 5 below.

[0286] Capacity retention rate (%) = {(discharge capacity after 300 cycles / discharge capacity after 1 cycle)} × 100

[0287] Resistance increase rate

[0288] After one charge-discharge cycle, the discharge capacity after one cycle was measured using an electrochemical charge-discharge device. The SOC was adjusted to 50% SOC, a pulse of 2.5 C was applied for 10 seconds, and the initial resistance was calculated from the difference between the voltage before applying the pulse and the voltage after applying the pulse.

[0289] After 300 charge-discharge cycles, the resistance after 300 cycles was calculated in the same manner as above. The resistance increase rate was calculated using the following mathematical formula, and the results are shown in Table 5.

[0290] Resistance increase rate (%) = (resistance after 300 cycles - initial resistance) / initial resistance × 100

[0291] Reference Experimental Example B-2

[0292] Each of the lithium secondary batteries prepared in Reference Examples 1B to 3B above was initially charged and discharged, including charging to 4.4 V at 25 °C under CC / CV and 0.33 C and 0.05 C, and then discharging to 2.5 V under CC and 0.33 C. Then, the lithium secondary battery was charged to 4.4 V and 40 C at 25 °C under CC / CV and 0.33 C, and then stored at 60 °C for 12 weeks.

[0293] Capacity retention rate

[0294] After storing for 12 weeks, the lithium secondary battery was charged to 4.4 V, 0.05 C at 25 °C under CC / CV and 0.33 C, and discharged to 2.5 V under 0.33 C to measure the capacity during discharge.

[0295] The capacity retention rate was calculated according to the following mathematical formula, and the results are shown in Table 5 below.

[0296] Capacity retention rate (%) = (Discharge capacity after 12 - week storage / Initial discharge capacity) × 100

[0297] Rate of increase in resistance

[0298] After initial charge and discharge, the capacity is checked at room temperature. Thereafter, the lithium secondary battery is charged to 50% SOC based on the discharge capacity and discharged at a current of 2.5C for 10 seconds. Then, the resistance is measured using the voltage drop difference at this time and used as the initial resistance. After storing at 60 °C for 12 weeks, the resistance is measured in the same manner and used as the final resistance. Then, the rate of increase in resistance is calculated using the following mathematical formula. The results are shown in Table 4 below.

[0299] Rate of increase in resistance (%) = (Final resistance - Initial resistance) / Initial resistance × 100

[0300] Table 5

[0301]

[0302] Referring to Table 5, it can be seen that although the first additive and the second additive are used as additives for the non - aqueous electrolyte, the improvement in the lithium secondary battery of Reference Example 1B is relatively small compared to Reference Examples 2B and 3B. For example, in the case of Reference Examples 1B to 3B where Li[Ni 0.6 Co 0.2 Mn 0.2 O2 is used as the positive electrode active material, even when the first additive and the second additive are used in combination, the effect is not improved. On the contrary, compared with Reference Examples 2B and 3B, the capacity retention rate of Reference Example 1B during charge - discharge cycling or high - temperature storage is equal to or lower.

[0303] In addition, referring to Tables 1, 2, and 5, it can be seen that the high - temperature life performance and high - temperature storage performance of Reference Example 1B are significantly lower than those of Examples 1 to 5. From this, it can be known that when using the lithium transition metal oxide represented by Chemical Formula X as the positive electrode active material, the effect of using the combination of the first additive and the second additive of the present invention can be uniquely exerted.

[0304] As can be seen from the above, various embodiments of the present invention have been described for illustrative purposes, and various modifications can be made without departing from the scope and spirit of the present invention. Therefore, the various embodiments disclosed herein are not intended to be limiting, and its true scope and spirit are shown by the appended claims.

Claims

1. A lithium secondary battery comprising: positive electrode; negative electrode; a separator interposed between the positive electrode and the negative electrode; and Non-aqueous electrolytes, in, The positive electrode comprises a positive electrode active material, The positive electrode active material comprises a lithium transition metal oxide represented by the following chemical formula X: The non-aqueous electrolyte comprises a lithium salt, an organic solvent and an additive, The additives include a first additive and a second additive, The first additive includes a phosphate-based additive having a silyl group, and The second additive includes a compound represented by the following Chemical Formula 1: (Chemical formula X) Li 1+x [Ni a Co b Mr c M 1 d ]O 2+w Wherein, x, a, b, c, d and w satisfy 0≤x≤0.5, a+b+c+d=1, 0.5≤a≤0.7, 0≤b≤0.15, c=1-abd, 0≤d≤0.1, 0≤b / a≤0.2, 1≤a / c≤3, 0≤w≤1, 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, (Chemical formula 1) in, n is 1 or 2, L1 and L2 are each independently a direct bond or a substituted or unsubstituted alkylene group having 1 to 6 carbon atoms, R1 and R2 are each independently selected from substituents represented by Chemical Formula 2: (Chemical formula 2) in, 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 and X2 is -O-, R 31 To R 36 are each independently hydrogen, an alkyl group having 1 to 6 carbon atoms, -C(=O)-R4 or -R5-OC(=O)-R6, R4 and R6 are each independently a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 20 carbon atoms, R5 is a substituted or unsubstituted alkylene group having 1 to 6 carbon atoms, Each substituent of L1, L2, R4, R5 and R6 is at least one independently selected from the group consisting of deuterium, -F, -Cl, -Br, -I, -CN, -NO2 and -SO3, * is the binding site with L1 or L2, When L1 and L2 are both directly bonded, then R1 and R2 are not both CS-7 below, and When L1 and L2 are both methylene and n is 2, R1 and R2 are not the following CS-2 at the same time 2. The lithium secondary battery according to claim 1, wherein The first additive is tris(trimethylsilyl) phosphate.

3. The lithium secondary battery according to claim 1, wherein The content of the first additive in the non-aqueous electrolyte is 0.01 wt % to 10 wt %.

4. The lithium secondary battery according to claim 1, wherein The content of the second additive in the non-aqueous electrolyte is 0.01 wt % to 10 wt %.

5. The lithium secondary battery according to claim 1, wherein R1 and R2 are each independently selected from the group consisting of CS-1 to CS-15:

6. The lithium secondary battery according to claim 5, wherein: 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.

7. The lithium secondary battery according to claim 1, wherein L1 and L2 are methylene groups.

8. The lithium secondary battery according to claim 1, wherein The compound represented by Chemical Formula 1 includes at least one compound selected from the group consisting of compounds A to R:

9. The lithium secondary battery according to claim 1, wherein: The lithium salt includes a salt selected from the group consisting of LiCl, LiBr, LiI, LiBF4, LiClO4, LiAlO4, LiAlCl4, LiPF6, LiSbF6, LiAsF6, LiB 10 Cl 10 , LiBOB (LiB (C2O4) 2), LiCF3SO3, LiFSI (LiN (SO2F) 2), LiCH3SO3, LiCF3CO2, LiCH3CO2 and LiBETI (LiN (SO2CF2CF3) 2) At least one of the group consisting of.

10. The lithium secondary battery according to claim 1, wherein The lithium salt is included in the non-aqueous electrolyte at a molar concentration of 0.5M to 5.0M.

11. The lithium secondary battery according to claim 1, wherein The organic solvent includes at least one selected from the group consisting of a cyclic carbonate organic solvent, a linear carbonate organic solvent, a linear ester organic solvent, and a cyclic ester organic solvent.

12. A method for manufacturing a lithium secondary battery, the method comprising: housing an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode in a battery case; and injecting a non-aqueous electrolyte into the battery case containing the electrode assembly, Wherein, the positive electrode comprises a positive electrode active material, The positive electrode active material comprises a lithium transition metal oxide represented by the following chemical formula X: The non-aqueous electrolyte comprises a lithium salt, an organic solvent and an additive, The additives include a first additive and a second additive, The first additive includes a phosphate-based additive having a silyl group, and The second additive includes a compound represented by the following Chemical Formula 1: (Chemical formula X) Li 1+x [Ni a Co b Mr c M 1 d ]O 2+w Wherein, x, a, b, c, d and w satisfy 0≤x≤0.5, a+b+c+d=1, 0.5≤a≤0.7, 0≤b≤0.15, c=1-abd, 0≤d≤0.1, 0≤b / a≤0.2, 1≤a / c≤3, 0≤w≤1, 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, (Chemical formula 1) in, n is 1 or 2, L1 and L2 are each independently a direct bond or a substituted or unsubstituted alkylene group having 1 to 6 carbon atoms, R1 and R2 are each independently selected from substituents represented by Chemical Formula 2: (Chemical formula 2) in, 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 and X2 is -O-, R 31 To R 36 are each independently hydrogen, an alkyl group having 1 to 6 carbon atoms, -C(=O)-R4 or -R5-OC(=O)-R6, R4 and R6 are each independently a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 20 carbon atoms, R5 is a substituted or unsubstituted alkylene group having 1 to 6 carbon atoms, Each substituent of L1, L2, R4, R5 and R6 is at least one independently selected from the group consisting of deuterium, -F, -Cl, -Br, -I, -CN, -NO2 and -SO3, * is the binding site with L1 or L2, When L1 and L2 are both directly bonded, then R1 and R2 are not both CS-7 below, and When L1 and L2 are both methylene and n is 2, R1 and R2 are not the following CS-2 at the same time 13. The method of claim 12, wherein: The first additive is tris(trimethylsilyl) phosphate.

14. The method of claim 12, wherein: The content of the first additive in the non-aqueous electrolyte is 0.01 wt % to 10 wt %.

15. The method of claim 12, wherein: The content of the second additive in the non-aqueous electrolyte is 0.01 wt % to 10 wt %.

16. The method of claim 12, wherein: R1 and R2 are each independently selected from the group consisting of CS-1 to CS-15:

17. The method of claim 16, wherein: 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.

18. The method of claim 12, wherein: L1 and L2 are methylene groups.

19. The method of claim 12, wherein: The compound represented by Chemical Formula 1 includes at least one compound selected from the group consisting of compounds A to R:

20. The method of claim 12, wherein: The lithium salt includes a salt selected from the group consisting of LiCl, LiBr, LiI, LiBF4, LiClO4, LiAlO4, LiAlCl4, LiPF6, LiSbF6, LiAsF6, LiB 10 Cl 10 , LiBOB (LiB (C2O4) 2), LiCF3SO3, LiFSI (LiN (SO2F) 2), LiCH3SO3, LiCF3CO2, LiCH3CO2 and LiBETI (LiN (SO2CF2CF3) 2) At least one of the group consisting of.

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