Electrolyte for rechargeable lithium battery and rechargeable lithium battery including same

Abstract

The invention relates to an electrolyte for a rechargeable lithium battery and a rechargeable lithium battery including the electrolyte. The electrolyte includes a lithium salt, a non-aqueous organic solvent, a first additive represented by Chemical Formula 1, and a second additive represented by Chemical Formula 2. [Chemical Formula 1] [Chemical Formula 2]

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to Korean Patent Application No. 10-2024-0112114, filed on August 21, 2024, with the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] This disclosure relates to electrolytes for rechargeable lithium batteries and rechargeable lithium batteries including electrolytes, and more specifically to electrolytes including lithium salts, non-aqueous organic solvents, a first additive represented by chemical formula 1 and a second additive represented by chemical formula 2, and rechargeable lithium batteries including electrolytes. Background Technology

[0004] Recently, with the rapid proliferation of battery-powered electronic devices such as mobile phones, laptops, and electric vehicles, the demand for rechargeable batteries with high energy density and high capacity has increased rapidly. Therefore, extensive research has been conducted to improve the performance of rechargeable lithium batteries.

[0005] A rechargeable lithium battery includes a positive electrode, a negative electrode, and an electrolyte. The positive and negative electrodes contain active materials in which lithium ions can be inserted and extracted. When lithium ions are inserted and extracted, electrical energy is generated through oxidation and reduction reactions.

[0006] Lithium salts dissolved in non-aqueous organic solvents are used as electrolytes in rechargeable lithium-ion batteries. The characteristics of rechargeable lithium-ion batteries are exhibited through complex reactions between the positive electrode and the electrolyte, and between the negative electrode and the electrolyte. Accordingly, using a suitable electrolyte is one of the important variables for improving rechargeable lithium-ion batteries. Summary of the Invention

[0007] Embodiments of this disclosure provide electrolytes for rechargeable lithium batteries that exhibit improved lifespan characteristics and stability at both room temperature and high temperature.

[0008] Embodiments of this disclosure provide a rechargeable lithium battery including an electrolyte.

[0009] According to embodiments of this disclosure, the electrolyte for a rechargeable lithium battery may include: a lithium salt; a non-aqueous organic solvent; a first additive represented by chemical formula 1; and a second additive represented by chemical formula 2.

[0010] [Chemical Formula 1]

[0011]

[0012] [Chemical Formula 2]

[0013]

[0014] In chemical formula 1 and chemical formula 2,

[0015] R1 to R6 may be the same or different, and each may independently be hydrogen, substituted or unsubstituted C1 to C20 alkyl, substituted or unsubstituted C1 to C20 alkoxy, substituted or unsubstituted C2 to C20 alkenyl, substituted or unsubstituted C2 to C20 alkynyl, substituted or unsubstituted C3 to C20 cycloalkyl, substituted or unsubstituted C6 to C20 aryl, or substituted or unsubstituted C2 to C20 heteroaryl.

[0016] R 101 and R 102 Each can be independently hydrogen or a substituted or unsubstituted C1 to C10 alkyl group.

[0017] R 103 It can be hydrogen, substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C2-C10 alkenyl, or substituted or unsubstituted C6-C20 aryl.

[0018] The subscript n can be an integer from 0 to 10. For example, the subscript n can be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10.

[0019] According to embodiments of this disclosure, a rechargeable lithium battery may include: a positive electrode, including a positive electrode active material; a negative electrode, including a negative electrode active material; and the aforementioned electrolyte for a rechargeable lithium battery. Attached Figure Description

[0020] Figure 1 A conceptual diagram illustrating a rechargeable lithium battery according to an embodiment of the present disclosure is provided.

[0021] Figures 2-5 A diagram illustrating a rechargeable lithium battery according to an embodiment of the present disclosure is provided, wherein... Figure 2 A cylindrical battery is shown. Figure 3 A prismatic battery is shown, and Figure 4 and Figure 5 A pouch-type battery is shown. Detailed Implementation

[0022] To fully understand the configuration and effects of this disclosure, some embodiments of this disclosure will be described with reference to the accompanying drawings. However, it should be noted that this disclosure is not limited to the exemplary embodiments described below and can be implemented in various forms. Rather, exemplary embodiments are provided only to disclose this disclosure and to enable those skilled in the art to fully understand its scope.

[0023] In this specification, it will be understood that when an element is referred to as being on another element, the element may be directly on the other element or an intervening element may be present between them. To effectively explain the technical content, the dimensions (e.g., thickness) of some components are enlarged in the drawings. Throughout the specification, the same reference numerals refer to the same elements.

[0024] Unless otherwise specified in this specification, singular expressions may include plural expressions. Additionally, unless otherwise specified, the phrase "A or B" may indicate "A but not B," "B but not A," and "A and B." The terms "comprises / includes" and / or "comprising / including" as used in this specification do not exclude the presence or addition of one or more other components.

[0025] In this specification, the term "combination thereof" may refer to a mixture, stack, complex, copolymer, alloy, blend, or reaction product of the components.

[0026] In this specification, unless otherwise defined separately, the term "substitution" may mean that at least one hydrogen atom of a substituent or compound is substituted by: deuterium, halogen, hydroxyl, amino, C1-C30 amino, nitro, C1-C40 silyl, C1-C30 alkyl, C1-C10 alkylsilyl, C6-C30 arylsilyl, C3-C30 cycloalkyl, C3-C30 heterocycloalkyl, C6-C30 aryl, C2-C30 heteroaryl, C1-C20 alkoxy, C1-C10 fluoroalkyl, cyano, or a combination thereof.

[0027] For example, the term "substitution" may refer to the substitution of at least one hydrogen atom in a substituent or compound by the following: deuterium, halogroup, C1-C30 alkyl, C1-C10 alkylsilyl, C6-C30 arylsilyl, C3-C30 cycloalkyl, C3-C30 heterocycloalkyl, C6-C30 aryl, C2-C30 heteroaryl, C1-C10 fluoroalkyl, or cyano. Alternatively, the term "substitution" may refer to the substitution of at least one hydrogen atom in a substituent or compound by the following: deuterium, halogroup, C1-C20 alkyl, C6-C30 aryl, C1-C10 fluoroalkyl, or cyano. For example, the term "substitution" can refer to the substitution of at least one hydrogen atom of a substituent or compound by the following: deuterium, cyano, halo, methyl, ethyl, propyl, butyl, phenyl, biphenyl, terphenyl, trifluoromethyl, or naphthyl.

[0028] Figure 1 A conceptual diagram illustrating a rechargeable lithium battery according to an embodiment of the present disclosure is provided. (See reference...) Figure 1 A rechargeable lithium battery may include a positive electrode 10, a negative electrode 20, a separator 30, and an electrolyte ELL.

[0029] The positive electrode 10 and the negative electrode 20 may be spaced apart from each other by a diaphragm 30. The diaphragm 30 may be located between the positive electrode 10 and the negative electrode 20. The positive electrode 10, the negative electrode 20, and the diaphragm 30 may be in contact with the electrolyte ELL. The positive electrode 10, the negative electrode 20, and the diaphragm 30 may be immersed in the electrolyte ELL.

[0030] The electrolyte ELL can serve as a medium for transporting lithium ions between the positive electrode 10 and the negative electrode 20. In the electrolyte ELL, lithium ions can move towards one of the positive electrode 10 and the negative electrode 20 through the membrane 30.

[0031] In recent years, most commercially available lithium-ion batteries have used LiPF6 as the lithium salt in the electrolyte. However, LiPF6 can react with moisture in lithium-ion batteries to form PF5, while simultaneously decomposing into HF. The highly reactive HF can degrade the lifespan and high-temperature storage properties of lithium-ion batteries. Although fluorophosphite additives are used to stabilize PF5 by donating electrons and utilizing its Lewis acid properties, the release of HF from these additives... - Ions can trigger side reactions that degrade the performance of lithium-ion batteries. For example, when the positive electrode active material includes lithium iron phosphate compounds (such as lithium iron phosphate (LFP) or lithium manganese iron phosphate (LMFP)), these side reactions can accelerate the degradation of lithium-ion battery performance.

[0032] Since the electrolyte for rechargeable lithium batteries according to embodiments of this disclosure includes a first additive represented by chemical formula 1 and a second additive represented by chemical formula 2, it can effectively suppress the formation of F - Ion-induced side reactions, and improve lifetime characteristics and stability not only at room temperature, but also at high temperatures.

[0033] Electrolyte for rechargeable lithium batteries

[0034] An electrolyte for a rechargeable lithium battery according to embodiments of the present disclosure may include a lithium salt, a non-aqueous organic solvent, a first additive represented by chemical formula 1, and a second additive represented by chemical formula 2.

[0035] [Chemical Formula 1]

[0036]

[0037] [Chemical Formula 2]

[0038]

[0039] In chemical formula 1 and chemical formula 2,

[0040] R1 to R6 may be the same or different, and each may independently be hydrogen, substituted or unsubstituted C1 to C20 alkyl, substituted or unsubstituted C1 to C20 alkoxy, substituted or unsubstituted C2 to C20 alkenyl, substituted or unsubstituted C2 to C20 alkynyl, substituted or unsubstituted C3 to C20 cycloalkyl, substituted or unsubstituted C6 to C20 aryl, or substituted or unsubstituted C2 to C20 heteroaryl.

[0041] R 101 and R 102 Each can be independently hydrogen or a substituted or unsubstituted C1 to C10 alkyl group.

[0042] R 103 It can be hydrogen, substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C2-C10 alkenyl, or substituted or unsubstituted C6-C20 aryl.

[0043] The subscript n can be an integer from 0 to 10.

[0044] Non-aqueous organic solvents can be used as media for transporting ions that participate in the electrochemical reactions of a battery.

[0045] Non-aqueous organic solvents may include carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, aprotic solvents, or mixtures thereof. Non-aqueous organic solvents may be used alone or in mixtures of two or more substances.

[0046] Carbonate solvents may include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), or butyl carbonate (BC).

[0047] Ester solvents may include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanoic acid lactone, mevalonate lactone, valonate lactone, or caprolactone.

[0048] Ether solvents may include dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, ethylene glycol dimethyl ether, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, or tetrahydrofuran. Ketone solvents may include cyclohexanone. Alcohol solvents may include ethanol or isopropanol. Aprotic solvents may include nitrile solvents (such as R-CN (where R is a hydrocarbon group having a C2-C20 straight-chain, branched, or cyclic structure and may include double bonds, aromatic rings, or ether bonds)); amides (such as dimethylformamide); dioxolane (such as 1,3-dioxolane or 1,4-dioxolane); or sulfolane.

[0049] In addition, when carbonate solvents are used as non-aqueous organic solvents, cyclic carbonates and chain carbonates can be mixed and used, and cyclic carbonates and chain carbonates can be mixed in a volume ratio of about 1:1 to about 1:9.

[0050] For example, non-aqueous organic solvents may include at least one selected from ethylene carbonate (EC), propylene carbonate (PC), propyl propionate (PP), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), and butyl carbonate (BC).

[0051] For example, non-aqueous organic solvents can be mixtures of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC).

[0052] For example, the content of ethylene carbonate (EC) relative to the total volume of non-aqueous organic solvents can be about 10 vol% to about 30 vol%. The content of ethyl methyl carbonate (EMC) relative to the total volume of non-aqueous organic solvents can be about 20 vol% to about 70 vol% or about 35 vol% to about 60 vol%. The content of dimethyl carbonate (DMC) solvent relative to the total volume of non-aqueous organic solvents can be about 5 vol% to about 50 vol% or about 10 vol% to about 40 vol%.

[0053] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) may be present in a volume ratio of 1:a:b, wherein a may be about 1 to about 3 or about 1.5 to about 2.5, and b may be about 0.5 to about 2 or about 0.5 to about 1.5.

[0054] Lithium salts can be dissolved in organic solvents to serve as a source of lithium ions in batteries, and play a role in enabling the basic operation of rechargeable lithium batteries and facilitating the transport of lithium ions between the positive and negative electrodes. Lithium salts may include, for example, those selected from LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide, LiFSI), LiC4F9SO3, LiN(C x F 2x+1 SO2)(C y F 2y+1 At least one of SO2 (where x and y are integers between 1 and 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalate)phosphate (LiDFBOP), and lithium bis(oxalate)borate (LiBOB).

[0055] For example, lithium salts may include one or more of LiPF6, LiClO4, LiBF4, lithium bis(fluorosulfonyl)imide (LiFSI), LiTFSI, LiSO3CF3, LiBOB, LiFOB, LiDFBOP, lithium tetrafluorooxalate phosphate (LiTFOP), LiPO2F2, LiSbF6, LiAsF6, LiAlO2, LiAlCl4, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N, and LiC4F9SO3. For example, lithium salts may include LiPF6.

[0056] Lithium salts can have concentrations from about 0.1 M to about 2.0 M. For example, lithium salts can have concentrations from about 0.5 M to about 1.0 M, equal to or less than about 2.0 M, equal to or less than about 1.7 M, or equal to or less than about 1.5 M. Because the concentration of the lithium salt falls within the above range, the electrolyte can appropriately maintain its conductivity and viscosity.

[0057] According to embodiments of this disclosure, the first additive may be represented by chemical formula 1.

[0058] [Chemical Formula 1]

[0059]

[0060] In chemical formula 1,

[0061] R1 to R6 may be the same or different, and each may independently be hydrogen, substituted or unsubstituted C1 to C20 alkyl, substituted or unsubstituted C1 to C20 alkoxy, substituted or unsubstituted C2 to C20 alkenyl, substituted or unsubstituted C2 to C20 alkynyl, substituted or unsubstituted C3 to C20 cycloalkyl, substituted or unsubstituted C6 to C20 aryl, or substituted or unsubstituted C2 to C20 heteroaryl, and n may be an integer from 0 to 10.

[0062] For example, R1 to R6 may be the same or different, and each may independently be hydrogen, a substituted or unsubstituted C1 to C10 alkyl, a substituted or unsubstituted C1 to C10 alkoxy, a substituted or unsubstituted C2 to C10 alkenyl, a substituted or unsubstituted C2 to C10 alkynyl, a substituted or unsubstituted C3 to C10 cycloalkyl, a substituted or unsubstituted C6 to C10 aryl, or a substituted or unsubstituted C2 to C15 heteroaryl. For example, each of R1 to R6 may be hydrogen, and n may be 0 or 1.

[0063] The first additive may be represented by chemical formula 1-1 or chemical formula 1-2.

[0064] [Chemical Formula 1-1]

[0065]

[0066] [Chemical Formula 1-2]

[0067]

[0068] According to embodiments of this disclosure, the second additive may be represented by chemical formula 2.

[0069] [Chemical Formula 2]

[0070]

[0071] In chemical formula 2,

[0072] R 101 and R 102 Each can be independently hydrogen or a substituted or unsubstituted C1-C10 alkyl group, and R 103 It can be hydrogen, substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C2-C10 alkenyl, or substituted or unsubstituted C6-C20 aryl.

[0073] For example, R 101 and R 102 Each can be independently hydrogen or a substituted or unsubstituted C1-C5 alkyl group, and R 103 It can be hydrogen, substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted C2-C5 alkenyl, or substituted or unsubstituted C6-C15 aryl. For example, R 101 ~R 103 Each can be independently hydrogen or a substituted or unsubstituted C1 to C5 alkyl group.

[0074] The second additive can be represented by one of chemical formulas 2-1 to 2-3.

[0075] [Chemical Formula 2-1]

[0076]

[0077] [Chemical Formula 2-2]

[0078]

[0079] [Chemical Formula 2-3]

[0080]

[0081] For example, the second additive may be at least one selected from acrylonitrile, methacrylonitrile, and 2-pentenonitrile.

[0082] The first additive may be present in an amount of about 0.01 wt% to about 5 wt% relative to the total weight of the electrolyte used in the rechargeable lithium battery. For example, the first additive may be present in an amount of about 0.05 wt% to about 5 wt%, about 0.05 wt% to about 2.5 wt%, about 0.1 wt% to about 2 wt%, about 0.1 wt% to about 1 wt%, or about 0.5 wt% to about 1.5 wt% relative to the total weight of the electrolyte used in the rechargeable lithium battery.

[0083] Furthermore, the second additive may be present in an amount of about 0.01 wt% to about 5 wt% relative to the total weight of the electrolyte used in the rechargeable lithium battery. For example, the second additive may be present in an amount of about 0.05 wt% to about 5 wt%, about 0.05 wt% to about 2.5 wt%, about 0.1 wt% to about 2 wt%, about 0.1 wt% to about 1 wt%, or about 0.5 wt% to about 1.5 wt% relative to the total weight of the electrolyte used in the rechargeable lithium battery.

[0084] The weight ratio of the first additive to the second additive may be in the range of about 1:10 to about 10:1. For example, the weight ratio of the first additive to the second additive may be in the range of about 1:5 to about 5:1, about 1:3 to about 3:1, or about 1:2 to about 2:1.

[0085] Since the amount and weight ratio of the first and second additives fall within the above range, it can effectively realize rechargeable lithium batteries with improved storage and lifespan characteristics at room temperature and high temperature.

[0086] Rechargeable lithium batteries

[0087] The rechargeable lithium battery according to this disclosure may include: a positive electrode, including a positive electrode active material; a negative electrode, including a negative electrode active material; and the aforementioned electrolyte for the rechargeable lithium battery.

[0088] Based on their shape, rechargeable lithium batteries can be classified into cylindrical batteries, prismatic batteries, pouch batteries, and coin-shaped batteries. Figures 2-5 A rechargeable lithium battery according to an embodiment of the present disclosure is illustrated, wherein... Figure 2 A cylindrical battery is shown. Figure 3 A prismatic battery is shown, and Figure 4 and Figure 5 A pouch-type battery is shown. (Reference) Figures 2-5 The rechargeable lithium battery 100 may include an electrode assembly 40 (with a separator 30 inserted between a positive electrode 10 and a negative electrode 20), and may also include a housing 50 (containing the electrode assembly 40). The positive electrode 10, the negative electrode 20, and the separator 30 may be immersed in an electrolyte (not shown). The rechargeable lithium battery 100 may include, as in... Figure 2The sealing member 60 of the sealing housing 50 as described herein. Additionally, as... Figure 3 As explained herein, the rechargeable lithium battery 100 may include a positive electrode lead connector 11, a positive electrode terminal 12, a negative electrode lead connector 21, and a negative electrode terminal 22. For example... Figure 4 and Figure 5 As shown, the rechargeable lithium battery 100 may include electrode terminals 70 or positive electrode terminals 71 and negative electrode terminals 72, which serve as electrical paths for guiding current generated in the electrode assembly 40 to the outside.

[0089] Positive electrode 10

[0090] A rechargeable lithium battery according to embodiments of the present disclosure may include a positive electrode. For example, a rechargeable lithium battery according to embodiments of the present disclosure may include a positive electrode comprising a positive electrode active material.

[0091] The positive electrode 10 for a rechargeable lithium battery may include a positive electrode current collector COL1 and a positive electrode active material layer AML1 formed on the positive electrode current collector COL1. The positive electrode active material layer AML1 may include a positive electrode active material and further include a binder and / or a conductive material.

[0092] The amount of positive electrode active material relative to 100 wt% of the positive electrode active material layer AML1 can be about 90 wt% to about 99.5 wt%. For example, the amount of positive electrode active material in the positive electrode active material layer AML1 relative to 100 wt% can be about 92 wt% to about 99.5 wt% or about 95 wt% to about 99 wt%. For example, the positive electrode active material can be present in an amount of about 90 wt% to about 99.3 wt%, about 92 wt% to about 99.3 wt%, or about 95 wt% to about 99 wt% relative to the total weight of the positive electrode.

[0093] The positive electrode active material in the positive electrode active material layer AML1 may include compounds that can reversibly insert and extract lithium (e.g., lithiation intercalation compounds). For example, the positive electrode active material may include a composite oxide comprising lithium and a metal selected from cobalt, manganese, nickel and combinations thereof.

[0094] Composite oxides may include lithium transition metal composite oxides, such as lithium nickel oxides, lithium cobalt oxides, lithium manganese oxides, lithium iron phosphate oxides, cobalt-free nickel manganese oxides, or combinations thereof.

[0095] The positive electrode active material may include lithium composite oxide represented by chemical formula 3.

[0096] [Chemical Formula 3]

[0097] Li x M1 y M 2 z M 3 1-y-z O 2-a X a

[0098] In Chemical Formula 3,

[0099] the subscripts x, y, z, and a may satisfy the relationships of 0.5 ≤ x ≤ 1.8, 0 < y ≤ 1, 0 ≤ z ≤ 1, 0 ≤ a ≤ 0.05, and 0 < y + z ≤ 1.

[0100] M 1 、M 2 and M 3 may each independently be one or more elements selected from Ni, Co, Mn, Al, B, Ba, Ca, Ce, Cr, Fe, Mo, Nb, Si, Sr, Mg, Ti, V, W, Y, Zr, and La.

[0101] X may be one or more elements selected from F, S, P, and Cl.

[0102] For example, the lithium composite oxide may include a compound represented by one of the following chemical formulas. Li a A 1-b X b O 2-c D c (where 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, and 0 ≤ c ≤ 0.05); Li a Mn 2-b X b O 4-c D c (where 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, and 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b X c O 2-α D α (where 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.5, and 0 < α < 2); Li a Ni 1-b-c Mn b X c O 2-α D α (where 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.5, and 0 < α < 2); Li a Ni b Co c L 1d G e O2 (where 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, and 0 ≤ e ≤ 0.1); Li a NiG b O2 (where 0.90 ≤ a ≤ 1.8 and 0.001 ≤ b ≤ 0.1); Li a CoG b O2 (where 0.90 ≤ a ≤ 1.8 and 0.001 ≤ b ≤ 0.1); Li a Mn 1-b G b O2 (where 0.90 ≤ a ≤ 1.8 and 0.001 ≤ b ≤ 0.1); Li a Mn2G b O4 (where 0.90 ≤ a ≤ 1.8 and 0.001 ≤ b ≤ 0.1); Li a Mn 1-g G g PO4 (where 0.90 ≤ a ≤ 1.8 and 0 ≤ g ≤ 0.5); Li (3-f) Fe2(PO4)3 (where 0≤f≤2); Li a FePO4 (where 0.90≤a≤1.8).

[0103] In the above chemical formulas, A can be Ni, Co, Mn, or a combination thereof; X can be Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, or a combination thereof; D can be O, F, S, P, or a combination thereof; G can be Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; and L 1 It can be Mn, Al, or a combination thereof.

[0104] In lithium complex oxides, nickel may be present in an amount equal to or greater than about 50 mol% relative to 100 mol% of lithium-excluded metal. For example, in lithium complex oxides, nickel may be present in an amount equal to or greater than about 65 mol%, 80 mol%, 85 mol%, 90 mol%, 91 mol%, 94 mol%, or 99 mol% relative to 100 mol% of lithium-excluded metal.

[0105] For example, the positive electrode active material may include one or more of lithium iron phosphate (LFP), lithium manganese iron phosphate (LMFP), lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCM), lithium cobalt oxide (LCO), lithium manganese oxide (LMO), and lithium nickel manganese oxide (LNMO).

[0106] The positive electrode may include a binder. The binder included in the positive electrode can be used to improve the adhesion between the positive electrode active material particles and each other, and also to improve the adhesion between the positive electrode active material and the positive electrode current collector COL1.

[0107] The binder can be used to improve the adhesion between the positive electrode active material particles and also to improve the adhesion between the positive electrode active material and the positive electrode current collector COL1. The binder may include, for example, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylate resin, polyester resin, or nylon, but this disclosure is not limited thereto.

[0108] For example, the positive electrode may include an adhesive comprising one or more of the following: polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, and polypropylene.

[0109] The binder may be present in an amount of about 0.5 wt% to about 5 wt% relative to the total weight of the positive electrode. For example, the binder may be present in an amount of about 1 wt% to about 4.5 wt% or about 1.5 wt% to about 4 wt% relative to the total weight of the positive electrode.

[0110] Conductive materials can be used to provide electrode conductivity, and as conductive materials, any suitable conductive material that will not cause chemical changes in the battery can be used. Conductive materials may include, for example, carbon-based materials (such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes); metal powders or metal fibers containing one or more of copper, nickel, aluminum, and silver; conductive polymers (such as polyphenylene derivatives); or mixtures thereof.

[0111] For example, the positive electrode may include a conductive material comprising carbon-based materials, metallic materials in the form of metal powder or metal fibers, conductive polymers, or mixtures thereof.

[0112] The conductive material may be present in an amount of about 0.5 wt% to about 5 wt% relative to the total weight of the positive electrode. For example, the conductive material included in the positive electrode may be present in an amount of about 0.5 wt% to about 4 wt%, about 0.5 wt% to about 3.5 wt%, or about 0.5 wt% to about 2 wt% relative to the total weight of the positive electrode.

[0113] Aluminum (Al) foil can be used as the positive electrode current collector COL1, but the present disclosure is not limited thereto.

[0114] Negative electrode 20

[0115] A rechargeable lithium battery according to an embodiment of the present disclosure may include a negative electrode. For example, a rechargeable lithium battery according to an embodiment of the present disclosure may include a negative electrode containing a negative electrode active material.

[0116] The negative electrode 20 for a rechargeable lithium battery may include a negative electrode current collector COL2 and a negative electrode active material layer AML2 located on the negative electrode current collector COL2. The negative electrode active material layer AML2 may include a negative electrode active material and may further include one or more of a binder and a conductive material.

[0117] The negative electrode active material in the negative electrode active material layer AML2 may include a material that can reversibly intercalate and deintercalate lithium ions, lithium metal, a lithium metal alloy, a material that can be doped and undoped with lithium, or a transition metal oxide.

[0118] The material that can reversibly intercalate and deintercalate lithium ions may include a carbon-based negative electrode active material. For example, crystalline carbon, amorphous carbon, or a combination thereof. For example, crystalline carbon may include graphite (such as natural graphite or artificial graphite that is amorphous, flaky, lamellar, spherical, or fibrous), and amorphous carbon may include soft carbon, hard carbon, mesophase pitch carbon, or calcined coke.

[0119] The lithium metal alloy may include an alloy of lithium and a metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn.

[0120] The material that can be doped and undoped with lithium may include a Si-based negative electrode active material or a Sn-based negative electrode active material. The Si-based negative electrode active material may include silicon, a silicon-carbon composite, SiO x (where 0 < x ≤ 2), a Si-Q alloy (where Q is an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element (excluding Si), a Group 15 element, a Group 16 element, a transition metal, a rare earth element, or a combination thereof), or a combination thereof. The Sn-based negative electrode active material may include Sn, SnO x (where 0 < x ≤ 2) (for example, SnO2), a Sn-based alloy, or a combination thereof.

[0121] The silicon-carbon composite can be a composite of silicon and amorphous carbon. In an embodiment, the silicon-carbon composite can have a structure in which amorphous carbon is coated on the surface of silicon particles. For example, the silicon-carbon composite can include secondary particles (cores) in which primary silicon particles are concentrated and an amorphous carbon coating (shells) located on the surface of the secondary particles. Amorphous carbon can also be located between the primary silicon particles, and for example, the primary silicon particles can be coated with amorphous carbon. The secondary particles can be dispersed in an amorphous carbon matrix.

[0122] The silicon-carbon composite can further include crystalline carbon. For example, the silicon-carbon composite can include a core containing crystalline carbon and silicon particles and can also include an amorphous carbon coating located on the surface of the core.

[0123] Si-based negative electrode active materials or Sn-based negative electrode active materials can be used in combination with carbon-based negative electrode active materials.

[0124] Relative to the total weight of the negative electrode active material layer AML2, the negative electrode active material in the negative electrode active material layer AML2 can be present in an amount of about 90 wt% to about 99 wt%. For example, relative to the total weight of the negative electrode active material layer AML2, the negative electrode active material can be present in an amount of about 93 wt% to about 99 wt% or about 96 wt% to about 98.5 wt%.

[0125] The negative electrode active material can include at least one selected from graphite and silicon composites.

[0126] When the negative electrode active material includes both a silicon composite and graphite, the silicon composite and graphite can be included in the form of a mixture, and in this case, the silicon composite and graphite can be included in a weight ratio of about 1:99 to about 50:50. For example, the weight ratio of the silicon composite and graphite can be about 3:97 to about 20:80 or about 5:95 to about 20:80.

[0127] The silicon composite can include a core containing silicon-based particles and an amorphous carbon coating, and the silicon-based particles can include at least one selected from silicon particles, silicon-carbon composites, SiO x (where 0 < x < 2) and silicon alloys. For example, the silicon-carbon composite can include a core containing silicon particles and crystalline carbon and can also include an amorphous carbon coating located on the surface of the core.

[0128] The crystalline carbon can include graphite, for example, natural graphite, artificial graphite, or a mixture thereof.

[0129] The negative electrode can include a binder. The binder included in the negative electrode can be used to improve the adhesion between the negative electrode active material particles and also to improve the adhesion between the negative electrode active material and the negative electrode current collector COL2. The binder can include a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0130] Non-aqueous adhesives may include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyimide, or combinations thereof.

[0131] Waterborne adhesives may include styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluoroelastomers, polyethylene oxide, polyvinylpyrrolidone, polyepoxychloropropane, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, or combinations thereof.

[0132] When an aqueous binder is used as a binder included in the negative electrode, it may further include a cellulose compound capable of providing viscosity. The cellulose compound may include one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and their alkali metal salts. The alkali metal may include Na, K, or Li.

[0133] Dry adhesives may include fibrous polymeric materials, such as polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or combinations thereof.

[0134] The binder may be present in an amount of about 0.5 wt% to about 5 wt% relative to the total weight of the negative electrode. For example, the binder may be present in an amount of about 0.5 wt% to about 3.5 wt% or about 0.5 wt% to about 2 wt% relative to the total weight of the negative electrode.

[0135] The negative electrode may include a conductive material. The conductive material may be described as described above.

[0136] The negative electrode current collector COL2 may include copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, or a combination thereof.

[0137] Diaphragm 30

[0138] Depending on the type of rechargeable lithium battery, the separator 30 may be present between the positive electrode 10 and the negative electrode 20. The separator 30 may include one or more of polyethylene separators, polypropylene separators, and polyvinylidene fluoride separators, and may have multiple layers of such separators (such as polyethylene / polypropylene bilayer separators, polyethylene / polypropylene / polyethylene trilayer separators, and polypropylene / polyethylene / polypropylene trilayer separators).

[0139] The diaphragm 30 may include a porous substrate and a coating located on one or the opposite surface of the porous substrate, the coating comprising an organic material, an inorganic material, or a combination thereof.

[0140] The porous substrate may be a polymer layer comprising one selected from polyolefins (such as polyethylene and polypropylene), polyesters (such as polyethylene terephthalate and polybutylene terephthalate), polyacetal, polyamide, polyimide, polycarbonate, polyetherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene ether, cyclic olefin copolymers, polyphenylene sulfide, polyethylene naphthalate, glass fiber, and polytetrafluoroethylene (e.g., Teflon), or the polymer layer may comprise copolymers or mixtures comprising two or more of the materials mentioned above.

[0141] Organic materials may include polyvinylidene fluoride copolymers or (meth)acrylic acid copolymers.

[0142] Inorganic materials may include inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite or combinations thereof, but this disclosure is not limited thereto.

[0143] Organic and inorganic materials can be mixed in a coating, or they can exist in the form of a layer of coatings including organic materials and coatings including inorganic materials.

[0144] Electrolyte ELL

[0145] The rechargeable lithium battery according to embodiments of this disclosure may include the aforementioned electrolyte for a rechargeable lithium battery.

[0146] The electrolyte used in rechargeable lithium batteries can be described as above.

[0147] Some embodiments and comparative examples of this disclosure will be described below. However, the embodiments described below are merely exemplary, and this disclosure is not limited to the embodiments described below.

[0148] [Implementation Method]

[0149] Manufacturing of rechargeable lithium batteries

[0150] Implementation Method 1

[0151] (1) Preparation of electrolyte

[0152] An electrolyte was prepared by dissolving 1.15 M LiPF6 in a non-aqueous organic solvent containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) mixed in a volume ratio of 20:55:20. Then, 0.5 wt% of a first additive represented by chemical formula 1-1 and 1.0 wt% of a second additive represented by chemical formula 2-1 were added to the mixture.

[0153] [Chemical Formula 1-1]

[0154]

[0155] [Chemical Formula 2-1]

[0156]

[0157] (2) Manufacturing of rechargeable lithium batteries

[0158] LiFePO4, used as the positive electrode active material, polyvinylidene fluoride, used as a binder, and acetylene black, used as a conductive material, were mixed in a weight ratio of 96:3:1, and the mixture was dispersed in N-methylpyrrolidone to prepare a positive electrode active material slurry. The positive electrode active material slurry was coated onto a 15 μm thick Al foil, dried at 100 °C, and then pressed to manufacture the positive electrode.

[0159] Artificial graphite and silicon composites, used as the negative electrode active material, were mixed in a weight ratio of 93:7. Styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC), used as binders, were mixed in a weight ratio of 98:1:1. The mixture was then dispersed in distilled water to prepare a negative electrode active material slurry. The negative electrode active material slurry was coated onto a 10 μm thick Cu foil, dried at 100 °C, and then pressed to manufacture the negative electrode.

[0160] The positive electrode, negative electrode and 10 μm thick polyethylene separator are assembled to manufacture an electrode assembly, and the electrolyte prepared in step (1) is introduced to manufacture a rechargeable lithium battery.

[0161] Implementation Method 2

[0162] The rechargeable lithium battery is manufactured according to a method substantially the same as that in Embodiment 1, except that 0.1 wt% of a first additive and 0.5 wt% of a second additive are added in step (1).

[0163] Implementation Method 3

[0164] The rechargeable lithium battery is manufactured according to a method substantially the same as that in Embodiment 1, except that 0.1 wt% of a first additive is added in step (1).

[0165] Implementation Method 4

[0166] The rechargeable lithium battery is manufactured according to a method substantially the same as that in Embodiment 1, except that 0.5 wt% of a second additive is added in step (1).

[0167] Implementation Method 5

[0168] The rechargeable lithium battery is manufactured according to a method substantially the same as that in Embodiment 1, except that 1.0 wt% of a first additive and 0.5 wt% of a second additive are added in step (1).

[0169] Implementation Method 6

[0170] The rechargeable lithium battery is manufactured according to a method substantially the same as that in Embodiment 1, except that 1.0 wt% of a first additive is added in step (1).

[0171] Comparative Example 1

[0172] The rechargeable lithium battery is manufactured according to a method that is essentially the same as that in Embodiment 1, except that neither the first additive nor the second additive is added in step (1).

[0173] Comparative Example 2

[0174] The rechargeable lithium battery is manufactured according to a method that is essentially the same as that in Embodiment 1, except that the first additive is not added in step (1).

[0175] Comparative Example 3

[0176] The rechargeable lithium battery is manufactured according to a method substantially the same as that in Embodiment 1, except that in step (1), a compound represented by chemical formula A is used instead of the first additive.

[0177] [Chemical Formula A]

[0178]

[0179] Comparative Example 4

[0180] The rechargeable lithium battery is manufactured according to a method substantially the same as that in Embodiment 1, except that 0.05 wt% of a first additive and 1.0 wt% of a second additive are added in step (1).

[0181] Comparative Example 5

[0182] The rechargeable lithium battery is manufactured according to a method substantially the same as that in Embodiment 1, except that 1.0 wt% of a first additive and 0.05 wt% of a second additive are added in step (1).

[0183] [Evaluation Example]

[0184] Evaluation 1: Storage characteristics at high temperature (60°C) (capacity retention and DC-IR increase rate)

[0185] The storage characteristics at high temperature (60°C) were evaluated for rechargeable lithium batteries manufactured according to Embodiments 1 to 6 and Comparative Examples 1 to 5.

[0186] For rechargeable lithium batteries, after measuring the initial DC internal resistance (DC-IR) using ΔV / ΔI (voltage change / current change), the battery is charged to its maximum energy state, i.e., fully charged state (SOC 100%), and stored in the charged state at high temperature (60°C) for 60 days. The DC internal resistance (DC-IR after 60 days) is then measured to calculate the DC-IR increase rate (%) according to Equation A below, and the results are listed in Table 1.

[0187] [Equation A]

[0188] DC-IR increase rate (%) = (DC-IR after 60 days / Initial DC-IR) × 100

[0189] In addition, under 0.2C charging (CC / CV, 4.25V, 0.05C cutoff) and 0.2C discharging (CC, 2.75V cutoff) conditions, the rechargeable lithium battery was charged and discharged once at 25°C to measure the charge-discharge capacity (initial capacity). The rechargeable lithium battery was charged to 4.25V at 0.2C (0.05C cutoff), stored at 60°C for 30 days, and then discharged to 2.75V at 0.5C to measure the discharge capacity after high-temperature storage (discharge capacity after 30 days). The measured initial capacity and the discharge capacity after 30 days were substituted into Equation B below to calculate the high-temperature storage capacity retention rate (%).

[0190] [Equation B]

[0191] High-temperature storage capacity retention (%) = {Discharge capacity after 30 days / Initial capacity} × 100

[0192] [Table 1]

[0193]

[0194] Referring to Table 1, the rechargeable lithium batteries of the embodiments exhibit superior storage characteristics at high temperatures (60°C) compared to the rechargeable lithium batteries of Comparative Examples 1 to 5. For example, it can be determined that the rechargeable lithium batteries of Embodiments 1 to 6 (which are manufactured from an electrolyte comprising a first additive represented by Chemical Formula 1 and a second additive represented by Chemical Formula 2) have superior DC-IR increase rate and / or capacity retention rate after high-temperature storage. Therefore, Embodiments 1 to 6 are found to have superior high-temperature storage characteristics compared to Comparative Examples 1 to 5 (which each used additives having structures different from Chemical Formula 1 or Chemical Formula 2).

[0195] Assessment 2: Gas generation after storage at high temperature (60°C)

[0196] For the rechargeable lithium batteries manufactured in Embodiments 1 to 6 and Comparative Examples 1 to 5, the gas generation after storage at high temperature (60°C) was evaluated.

[0197] For example, a rechargeable lithium battery was charged at 25°C at a rate of 0.1C under constant current conditions until the voltage reached 4.3V (vs. Li), and then cut off at 0.05C under constant voltage conditions while maintaining 4.3V (measurement of initial gas generation). Afterwards, the rechargeable lithium battery was disassembled and the positive electrode plate was placed in a bag along with the electrolyte, and then stored in an oven at 60°C for 7 days (measurement of gas generation over 7 days). At this point, gas generation was measured by converting the mass change of the bag into a volume change using the Archimedes method, and the high-temperature gas increase rate (%) was calculated according to the following equation C. The Archimedes method is a method for measuring gas generation by periodically measuring the weight of a bag in a water-filled container and converting the mass change into a volume change.

[0198] [Equation C]

[0199] High-temperature gas increase rate (%) = (7-day gas generation / initial gas generation) × 100

[0200] [Table 2]

[0201]

[0202] Referring to Table 2, since the rechargeable lithium batteries of Embodiments 1 to 6 have a lower gas increase rate at high temperature (60°C) compared with the rechargeable lithium batteries of Comparative Examples 1 to 5, it was found that the rechargeable lithium batteries of Embodiments 1 to 6 have excellent high-temperature storage characteristics.

[0203] Evaluation 3: Room temperature cycling characteristics (capacity retention)

[0204] The charge-discharge cycle characteristics at room temperature were evaluated for the rechargeable lithium batteries manufactured in Embodiments 1 to 6 and Comparative Examples 1 to 5.

[0205] For example, 200 charge-discharge cycles were performed at 25°C, with a charging rate of 0.33C (CC / CV, 4.45V, 0.025C cutoff) and a discharging rate of 1.0C (CC, 2.5V cutoff). The discharge capacity of the rechargeable lithium battery was measured simultaneously, and the room temperature capacity retention rate (%) was calculated according to Equation D below. The rate of change in room temperature capacity retention rate (%) compared to Comparative Example 1 (without the two additives) was also calculated.

[0206] [Equation D]

[0207] Room temperature capacity retention (%) = (Discharge capacity after 200 cycles / Discharge capacity after 1 cycle) × 100

[0208] [Table 3]

[0209]

[0210] Referring to Table 3, compared with the rechargeable lithium batteries of Comparative Examples 1 to 5, the rechargeable lithium batteries of Embodiments 1 to 6 exhibit superior cycle characteristics at room temperature. For example, it was found that the rechargeable lithium batteries of Embodiments 1 to 6 (which are manufactured from an electrolyte comprising a first additive represented by Chemical Formula 1 and a second additive represented by Chemical Formula 2) have superior capacity retention at room temperature compared with the rechargeable lithium batteries of Comparative Examples 1 to 5. For example, the rechargeable lithium batteries of Embodiments 1 to 6 have superior room temperature capacity retention compared with the rechargeable lithium battery of Comparative Example 1 (which does not use the first and second additives).

[0211] Since the electrolyte for rechargeable lithium batteries according to embodiments of the present disclosure includes a first additive represented by chemical formula 1 and a second additive represented by chemical formula 2, it can improve life characteristics and stability not only at room temperature but also at high temperature during the activation of the rechargeable lithium battery.

[0212] Although this disclosure has been described in conjunction with embodiments now regarded as preferred, it should be understood that this disclosure is not limited to the disclosed embodiments and is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the claims. Therefore, the foregoing embodiments should be understood as exemplary and not as limiting this disclosure in any way.

Claims

1. An electrolyte for a rechargeable lithium battery, the electrolyte comprising: Lithium salts; Non-aqueous organic solvents; The first additive represented by chemical formula 1; and The second additive represented by chemical formula 2, Chemical Formula 1 Chemical formula 2 Among them, in chemical formula 1 and chemical formula 2, R1 to R6 may be the same or different, and each is independently hydrogen, a substituted or unsubstituted C1 to C20 alkyl, a substituted or unsubstituted C1 to C20 alkoxy, a substituted or unsubstituted C2 to C20 alkenyl, a substituted or unsubstituted C2 to C20 alkynyl, a substituted or unsubstituted C3 to C20 cycloalkyl, a substituted or unsubstituted C6 to C20 aryl, or a substituted or unsubstituted C2 to C20 heteroaryl. R 101 and R 102 Each is independently hydrogen or a substituted or unsubstituted C1-C10 alkyl group. R 103 It is hydrogen, substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C2-C10 alkenyl, or substituted or unsubstituted C6-C20 aryl, and n is an integer from 0 to 10. The term "substitution" refers to the substitution of at least one hydrogen atom in a substituent or compound by the following: deuterium, halogen, hydroxyl, amino, C1-C30 amino, nitro, C1-C40 silyl, C1-C30 alkyl, C1-C10 alkylsilyl, C6-C30 arylsilyl, C3-C30 cycloalkyl, C3-C30 heterocycloalkyl, C6-C30 aryl, C2-C30 heteroaryl, C1-C20 alkoxy, C1-C10 fluoroalkyl, cyano, or combinations thereof.

2. The electrolyte according to claim 1, wherein the first additive is represented by chemical formula 1-1 or chemical formula 1-2. Chemical Formula 1-1 Chemical formula 1-2 3. The electrolyte according to claim 1, wherein the second additive is represented by chemical formula 2-1, chemical formula 2-2, or chemical formula 2-3. Chemical formula 2-1 Chemical formula 2-2 Chemical formula 2-3 4. The electrolyte according to claim 1, wherein the first additive is present in an amount of 0.05 wt% to 5 wt% relative to the total weight of the electrolyte used in the rechargeable lithium battery.

5. The electrolyte according to claim 1, wherein the second additive is present in an amount of 0.01 wt% to 5 wt% relative to the total weight of the electrolyte used in the rechargeable lithium battery.

6. The electrolyte according to claim 1, wherein the weight ratio of the first additive to the second additive is in the range of 1:10 to 10:

1.

7. The electrolyte according to claim 1, wherein the weight ratio of the first additive to the second additive is in the range of 1:2 to 2:

1.

8. The electrolyte according to claim 1, wherein the lithium salt comprises LiPF6, LiClO4, LiBF4, lithium bis(fluorosulfonyl)imide, LiTFSI, LiSO3CF3, LiBOB, LiFOB, LiDFBOP, LiTFOP, LiPO2F2, LiSbF6, LiAsF6, LiAlO2, LiAlCl4, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N, and LiC4F9SO3.

9. The electrolyte according to claim 1, wherein the concentration of the lithium salt is in the range of 0.1M to 2.0M.

10. The electrolyte according to claim 1, wherein the non-aqueous organic solvent comprises one or more of ethylene carbonate, propylene carbonate, propyl propionate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, and butylene carbonate.

11. The electrolyte according to claim 1, wherein the non-aqueous organic solvent comprises ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate.

12. The electrolyte according to claim 11, wherein the ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate have a volume ratio of 1:a:b, where a is 1 to 3, and where b is 0.5 to 2.

13. A rechargeable lithium battery, comprising: a positive electrode comprising a positive electrode active material; a negative electrode comprising a negative electrode active material; and the electrolyte for a rechargeable lithium battery according to any one of claims 1 to 12.

14. The rechargeable lithium battery according to claim 13, wherein the positive electrode active material comprises a lithium iron phosphate-based compound.

15. The rechargeable lithium battery according to claim 13, wherein the positive electrode active material comprises a lithium composite oxide represented by Chemical Formula 3, Chemical Formula 3 Li x M 1 y M 2 z M 3 1-y-z O 2-a X a in, In Chemical Formula 3, 0.5 ≤ x ≤ 1.8, 0 < y ≤ 1, 0 ≤ z ≤ 1, 0 ≤ a ≤ 0.05, and 0 < y + z ≤ 1, M 1 M 2 and M 3 Each element is independently selected from one or more elements chosen from Ni, Co, Mn, Al, B, Ba, Ca, Ce, Cr, Fe, Mo, Nb, Si, Sr, Mg, Ti, V, W, Y, Zr, and La. X is one or more elements selected from F, S, P, and Cl.

16. The rechargeable lithium battery according to claim 13, wherein the positive electrode active material comprises one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese oxide, lithium cobalt oxide, lithium manganese oxide, and lithium nickel manganese oxide.

17. The rechargeable lithium battery according to claim 13, wherein the negative electrode active material comprises a carbon-based negative electrode active material, a Si-based negative electrode active material, a Sn-based negative electrode active material, or a combination thereof.

18. The rechargeable lithium battery according to claim 13, wherein the positive electrode comprises a binder comprising one or more of the following: polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, poly(ethylene oxide), polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, and polypropylene, where the amount of the binder is in the range of 0.5 wt% to 5 wt% relative to the total weight of the positive electrode.

19. The rechargeable lithium battery according to claim 13, wherein the positive electrode comprises a conductive material comprising a carbon-based material, a metal-based material in the form of metal powder or metal fiber, a conductive polymer, or a mixture thereof, where the amount of the conductive material is in the range of 0.5 wt% to 5 wt% relative to the total weight of the positive electrode.

20. The rechargeable lithium battery according to claim 13, wherein the rechargeable lithium battery is a cylindrical battery, a prismatic battery, a pouch-type battery, or a coin-type battery.

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