Electrolyte for rechargeable lithium battery and rechargeable lithium battery including same

Abstract

The invention discloses an electrolyte and a rechargeable lithium battery including the same. The electrolyte comprises a non-aqueous organic solvent, a lithium salt and an additive. The additive includes a compound 1 represented by Chemical Formula 1 and a compound 2 represented by Chemical Formula 2. [Chemical Formula 1] # imgabs0 # [Chemical Formula 2] # imgabs1 #

Description

[0001] Cross - reference to related applications

[0002] This application claims priority and the benefit of Korean Patent Application No. 10 - 2023 - 0160944, filed with the Korean Intellectual Property Office on November 20, 2023, the entire content of which is incorporated herein by reference. Technical field

[0003] Embodiments of the present disclosure relate to an electrolyte for a rechargeable lithium battery and a rechargeable lithium battery including the same. Background art

[0004] Recently, with the rapid popularization of electronic devices (such as mobile phones, laptop computers, and electric vehicles) using batteries, the interest in rechargeable lithium batteries with high energy density and high capacity has increased rapidly. Accordingly, in - depth 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 include active materials capable of intercalating and de - intercalating, and if lithium ions are intercalated and de - intercalated, the rechargeable lithium battery generates electrical energy caused by oxidation and reduction reactions.

[0006] A lithium salt dissolved in a non - aqueous organic solvent is used as the electrolyte of a rechargeable lithium battery. The characteristics of a rechargeable lithium battery are exhibited through complex reactions between the positive electrode and the electrolyte and between the negative electrode and the electrolyte. Accordingly, using an appropriate or suitable electrolyte is a variable factor for improving a rechargeable lithium battery. Summary of the invention

[0007] Embodiments of the present disclosure provide an electrolyte for a rechargeable lithium battery having improved high - temperature life characteristics.

[0008] Embodiments of the present disclosure provide a rechargeable lithium battery including the electrolyte.

[0009] According to an embodiment of the present disclosure, an electrolyte for a rechargeable lithium battery may include: a non - aqueous organic solvent; a lithium salt; and an additive. The additive may include Compound 1 represented by Chemical Formula 1 and Compound 2 represented by Chemical Formula 2.

[0010] [Chemical Formula 1]

[0011]

[0012] [Chemical Formula 2]

[0013]

[0014] According to an embodiment of the present 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 an electrolyte solution discussed above. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings, together with the specification, illustrate embodiments of the subject matter of the present disclosure and, together with the description, are used to explain the principles of embodiments of the subject matter of the present disclosure.

[0016] Figure 1 FIG. is a simplified conceptual diagram showing a rechargeable lithium battery according to an embodiment of the present disclosure.

[0017] Figure 2 FIG. is a simplified perspective view showing a cross-section of a rechargeable lithium battery according to an embodiment of the present disclosure.

[0018] Figure 3 FIG. is a simplified cross-sectional view showing a rechargeable lithium battery according to an embodiment of the present disclosure.

[0019] Figures 4 - 5 FIG. is a simplified perspective view showing a rechargeable lithium battery according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0020] To fully understand the layout and effects of the subject matter of the present disclosure, some embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be noted that the present disclosure is not limited to the following exemplary embodiments and can be implemented in various suitable forms. Instead, the exemplary embodiments are provided only to illustrate the embodiments of the present disclosure and to fully inform those skilled in the art of the scope of the present disclosure.

[0021] In this description, it will be understood that if an element is referred to as being on another element, the element can be directly on the other element or there can be an intervening element between the two. In the drawings, to effectively explain the technical content, the dimensions of some components (e.g., thickness) may be enlarged. Throughout the specification, the same reference numerals refer to the same elements.

[0022] Unless otherwise specifically stated in this description, expressions in the singular form may include the plural form. In an embodiment, unless otherwise specifically stated, 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" used in this description do not exclude the presence or addition of one or more other components.

[0023] As used herein, the term "a combination thereof" may refer to a mixture, stack, composite, copolymer, alloy, blend, and / or reaction product of components.

[0024] Figure 1 A simplified conceptual diagram showing a rechargeable lithium battery according to an embodiment of the present disclosure. Refer to Figure 1 , the rechargeable lithium battery may include a positive electrode 10, a negative electrode 20, a separator 30, and an electrolyte ELL.

[0025] The positive electrode 10 and the negative electrode 20 may be spaced apart from each other across the separator 30. The separator 30 may be between the positive electrode 10 and the negative electrode 20. The positive electrode 10, the negative electrode 20, and the separator 30 may be in contact with the electrolyte ELL. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated in the electrolyte ELL.

[0026] The electrolyte ELL may be a medium for the transfer of lithium ions between the positive electrode 10 and the negative electrode 20. In the electrolyte ELL, lithium ions may move through the separator 30 toward one selected from the positive electrode 10 and the negative electrode 20.

[0027] Positive electrode 10

[0028] 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 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 (e.g., a conductive material).

[0029] For example, the positive electrode 10 may further include an additive that can be used as a sacrificial positive electrode.

[0030] Based on 100 wt% of the positive electrode active material layer AML1, the amount of the positive electrode active material may range from about 90 wt% to about 99 wt%. Based on 100 wt% of the positive electrode active material layer AML1, the amounts of the binder and the conductive material may each be from about 0.5 wt% to about 5 wt%.

[0031] The binder may be used to improve the adhesion of the positive electrode active material particles to each other and also improve the adhesion of the positive electrode active material to 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, a polymer containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, and / or nylon, but the present invention is not limited thereto.

[0032] A conductive material can be used to provide conductivity (e.g., electrical conductivity) to an electrode, and any suitable conductive material that does not cause chemical changes in a rechargeable lithium battery (e.g., does not cause undesired chemical changes in a rechargeable lithium battery) can be used as the conductive material constituting the rechargeable lithium battery. The conductive material can include, for example, carbonaceous materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, and / or carbon nanotube; metal powders and / or metal fibers containing one or more selected from copper, nickel, aluminum, and silver; conductive polymers (e.g., electrically conductive polymers) such as polyphenylene derivatives; or mixtures thereof.

[0033] Al foil can be used as the positive electrode current collector COL1, but the present disclosure is not limited thereto.

[0034] Positive electrode active material

[0035] The positive electrode active material in the positive electrode active material layer AML1 can include a compound that can reversibly intercalate and deintercalate lithium (e.g., a lithiated intercalation compound). For example, the positive electrode active material can include at least one kind of composite oxide containing lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof.

[0036] The composite oxide can include lithium transition metal composite oxides, such as lithium-nickel-based oxides (e.g., lithium-nickel-cobalt-aluminum (NCA) based composite oxides), lithium-cobalt-based oxides, lithium-manganese-based oxides, lithium-iron-phosphate-based compounds, cobalt-free nickel-manganese-based oxides, or combinations thereof.

[0037] For example, the positive electrode active material can include a compound represented by one of the following chemical formulas. Li a A 1-b X b O 2- c D c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05), Li a Mn 2-b X b O 4-c D c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05), Li a Ni 1-b-c Co b X c O 2-α D α (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.5, 0 ≤ α < 2), Li a Ni 1-b-c Mn b X c O2-α D α (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.5, 0 < α < 2), Li a Ni b Co c L 1 d G e O 2 (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0 ≤ e ≤ 0.1), Li a NiG b O 2 (0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1), Li a CoG b O 2 (0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1), Li a Mn 1-b G b O 2 (0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1), Li a Mn 2 G b O 4 (0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1), Li a Mn 1-g G g PO 4 (0.90 ≤ a ≤ 1.8, 0 ≤ g ≤ 0.5), Li (3-f) Fe 2 (PO 4 ) 3 (0 ≤ f ≤ 2) and Li a FePO 4 (0.90 ≤ a ≤ 1.8).

[0038] In the above chemical formulas, A is Ni, Co, Mn, or a combination thereof, X is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare element, or a combination thereof, D is O, F, S, P, or a combination thereof, G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof, and L 1 is Mn, Al, or a combination thereof.

[0039] For example, based on the metal excluding lithium in 100 mol% of the lithium transition metal composite oxide, the positive electrode active material can be a high-nickel type positive electrode active material with a nickel content equal to or greater than about 80 mol%, equal to or greater than about 85 mol%, equal to or greater than about 90 mol%, equal to or greater than about 91 mol%, or equal to or greater than about 94 mol% and equal to or less than about 99 mol%. The high-nickel type positive electrode active material can achieve high capacity, and thus can be applied to high-capacity and high-density rechargeable lithium batteries.

[0040] Negative electrode 20

[0041] 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 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 a binder and / or a conductive material (e.g., a conductive material).

[0042] For example, the negative electrode active material layer AML2 may include about 90 wt% to about 99 wt% of the negative electrode active material, about 0.5 wt% to about 5 wt% of the binder, and about 0 wt% to about 5 wt% of the conductive material (e.g., a conductive material).

[0043] The binder can be used to improve the adhesion between the negative electrode active material particles and also improve the adhesion between the negative electrode active material and the negative electrode current collector COL2. The binder may include a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0044] The non-aqueous binder may include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

[0045] The aqueous binder may include styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluoroelastomer, polyethylene oxide, polyvinylpyrrolidone, epichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene-propylene-diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, or a combination thereof.

[0046] If an aqueous binder is used as the binder in the negative electrode active material layer AML2, a cellulose compound capable of providing or increasing viscosity may be further included. The cellulose compound may include one or more selected from carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and their alkali metal salts. The alkali metal may include Na, K, and / or Li.

[0047] The dry binder may include a fibrillated polymer material such as polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride - hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0048] The conductive material can be used to provide conductivity (e.g., electrical conductivity) to the electrode, and any suitable conductive material that does not cause chemical changes in the rechargeable lithium battery (e.g., does not cause unwanted chemical changes in the rechargeable lithium battery) can be used as the conductive material constituting the rechargeable lithium battery. For example, the conductive material may include carbonaceous materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, and / or carbon nanotube; metal powder and / or metal fiber, which includes one or more selected from copper, nickel, aluminum, and silver; conductive polymers (e.g., electrically conductive polymers) such as polyphenylene derivatives; or a mixture thereof.

[0049] The negative electrode current collector COL2 may include a copper foil, a nickel foil, a stainless - steel foil, a titanium foil, a nickel foam, a copper foam, a polymer substrate coated with a conductive metal (e.g., electrically conductive metal), or a combination thereof.

[0050] Negative electrode active material

[0051] 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, and / or a transition metal oxide.

[0052] The material that can reversibly intercalate and deintercalate lithium ions may include carbonaceous negative electrode active materials such as crystalline carbon, amorphous carbon, or a combination thereof. For example, crystalline carbon may include graphite, such as amorphous, flaky, scaly, spherical, and / or fibrous natural and / or artificial graphite, and amorphous carbon may include soft carbon, hard carbon, mesophase pitch carbon, and / or calcined coke.

[0053] 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.

[0054] The material that can be doped and undoped with lithium may include Si - based negative electrode active materials and / or Sn - based negative electrode active materials. The Si - based negative electrode active materials may include silicon, a silicon - carbon composite, SiO x (0 < x ≤ 2), an Si - Q alloy (where Q is an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element (except 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 materials may include Sn, SnO 2 , an Sn - based alloy, or a combination thereof.

[0055] The silicon-carbon composite can be a composite of silicon and amorphous carbon. According to 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 aggregated and an amorphous carbon coating (shell) on the surface of the secondary particles. Amorphous carbon can also be between the primary silicon particles. For example, the primary silicon particles can be coated with amorphous carbon. The secondary particles can be dispersed in an amorphous carbon matrix.

[0056] 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 on the surface of the core.

[0057] Si-based negative electrode active materials and / or Sn-based negative electrode active materials can be used in combination with carbon-based negative electrode active materials.

[0058] Separator 30

[0059] Based on the type (or kind) of the rechargeable lithium battery, the separator 30 can be between the positive electrode 10 and the negative electrode 20. The separator 30 can include one or more selected from a polyethylene separator, a polypropylene separator, and a polyvinylidene fluoride separator, and can be a multilayer separator thereof, such as a polyethylene / polypropylene bilayer separator, a polyethylene / polypropylene / polyethylene trilayer separator, and / or a polypropylene / polyethylene / polypropylene trilayer separator.

[0060] The separator 30 can include a porous substrate and a coating on one surface or the opposite surface of the porous substrate, where the coating includes an organic material, an inorganic material, or a combination thereof.

[0061] The porous substrate can be a polymer layer, which includes one selected from polyolefins (such as polyethylene and polypropylene), polyesters (such as polyethylene terephthalate and polybutylene terephthalate), polyacetals, polyamides, polyimides, polycarbonates, polyether ketones, polyaryl ether ketones, polyether imides, polyamide imides, polybenzimidazoles, polyether sulfones, polyphenylene ethers, cycloolefin copolymers, polyphenylene sulfides, polyethylene naphthalate, glass fiber, and polytetrafluoroethylene (e.g., Teflon), or can include a copolymer or mixture of two or more of the above-mentioned materials.

[0062] The organic material can include polyvinylidene fluoride copolymers and / or (meth)acrylic acid copolymers.

[0063] The inorganic material can include selected from Al 2 O 3 、SiO 2 、TiO 2 、SnO 2 、CeO 2, MgO, NiO, CaO, GaO, ZnO, ZrO 2 , Y 2 O 3 , SrTiO 3 , BaTiO 3 , Mg(OH) 2 , boehmite, and inorganic particles in combinations thereof, but the present disclosure is not limited thereto.

[0064] The organic material and the inorganic material may be mixed and present together in one coating, or may be present as a stack of a coating including the organic material and a coating including the inorganic material.

[0065] Electrolyte ELL

[0066] The electrolyte ELL for a rechargeable lithium battery may include a non-aqueous organic solvent and a lithium salt.

[0067] The non-aqueous organic solvent can be used as a medium for transporting ions participating in the electrochemical reaction of the rechargeable lithium battery.

[0068] The non-aqueous organic solvent may include carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, aprotic solvents, or combinations thereof.

[0069] The 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), and / or butylene carbonate (BC).

[0070] The ester solvents may include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, propyl propionate, decanolide, mevalonolactone, valerolactone, and / or caprolactone.

[0071] The ether solvents may include dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, ethylene glycol dimethyl ether, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and / or tetrahydrofuran. The ketone solvents may include cyclohexanone. The aprotic solvents may include nitriles such as R-CN (where R is a hydrocarbon group having a C2-C20 straight-chain, branched-chain, or cyclic structure and may include double bonds, aromatic rings, and / or ether groups); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane and / or 1,4-dioxolane; and / or sulfolane.

[0072] The non-aqueous organic solvent can be used alone or as a mixture of two or more substances.

[0073] In an embodiment, if a carbonate solvent is used, a cyclic carbonate and a linear carbonate may be mixed together and used, and the cyclic carbonate and the linear carbonate may be mixed together at a volume ratio of about 1:1 to about 1:9.

[0074] The lithium salt may be a material dissolved in a non-aqueous organic solvent to serve as a source of lithium ions in a rechargeable lithium battery, and plays a role in achieving the basic operation of the rechargeable lithium battery and promoting the movement of lithium ions between the positive electrode and the negative electrode. The lithium salt may include, for example, those selected from LiPF 6 , LiBF 4 , LiSbF 6 , LiAsF 6 , LiClO 4 , LiAlO 2 , LiAlCl 4 , LiPO 2 F 2 , LiCl, LiI, LiN(SO 3 C 2 F 5 ), 2 , Li(FSO 2 ), 2 N, lithium bis(fluorosulfonyl)imide (LiFSI), LiC 4 F 9 SO 3 , LiN(C x F 2x+1 SO 2 )(C y F 2y+1 SO 2 )(where x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluoro(oxalato)borate (LiDFOB), lithium difluoro bis(oxalato)phosphate (LiDFBOP), and lithium bis(oxalato)borate (LiBOB), and at least one of them.

[0075] The lithium salt may include LiPF 6 .

[0076] The lithium salt may be present at a concentration of about 0.1 M to about 2.0 M.

[0077] The additive may include Compound 2 represented by Chemical Formula 2 below.

[0078] [Chemical Formula 2]

[0079]

[0080] Compound 2 may form a stable film on the electrode surface of the rechargeable lithium battery to improve the cycle characteristics of the rechargeable lithium battery.

[0081] Based on the total weight of the electrolyte, the amount of Compound 2 present can be from about 0.01 wt% to about 10 wt%. For example, based on the total weight of the electrolyte, the amount of Compound 2 present can be equal to or greater than about 0.05 wt%, equal to or greater than about 0.1 wt%, equal to or greater than about 0.5 wt%, or equal to or greater than about 1 wt%. Based on the total weight of the electrolyte, the amount of Compound 2 present can be equal to or less than about 7 wt%, equal to or less than about 5 wt%, equal to or less than about 2 wt%, or equal to or less than about 1 wt%. If Compound 2 is present in the aforementioned concentration range, the impedance (e.g., resistance) of the electrode surface of the rechargeable lithium battery can be moderately reduced to improve the battery output performance.

[0082] The additive may further include Compound 1 represented by the following Chemical Formula 1.

[0083] [Chemical Formula 1]

[0084]

[0085] By combining with Compound 2, Compound 1 can act as a crosslinking agent on the film formed on the electrode surface of the rechargeable lithium battery, such that a film with increased denseness can be formed on the electrode.

[0086] Based on the total weight of the electrolyte, the amount of Compound 1 present can be from about 0.01 wt% to about 1 wt%. For example, based on the total weight of the electrolyte, the amount of Compound 1 present can be equal to or greater than about 0.05 wt%, equal to or greater than about 0.1 wt%, or equal to or greater than about 0.2 wt%. Based on the total weight of the electrolyte, the amount of Compound 1 present can be from about 0.5 wt% to about 0.75 wt%. If the amount of Compound 1 is within the aforementioned range, Compound 1 can not only be used to fully act as a crosslinking agent to impart rigidity to the film, but also moderately reduce the impedance (e.g., resistance) of the electrode surface of the rechargeable lithium battery to improve the battery output performance.

[0087] The amount of Compound 1 can be less than the amount of Compound 2.

[0088] Relative to 1 part by weight of Compound 1, the amount of Compound 2 present may be from about 1 part by weight to about 10 parts by weight. For example, relative to 1 part by weight of Compound 1, the amount of Compound 2 present may be from about 1 part by weight to about 5 parts by weight, from about 1 part by weight to about 2.5 parts by weight, or from about 1 part by weight to about 2 parts by weight. For example, relative to 1 part by weight of Compound 1, the amount of Compound 2 present may be from about 2 parts by weight to about 5 parts by weight, from about 2 parts by weight to about 2.5 parts by weight, or from about 2 parts by weight to about 2 parts by weight. If the amounts of Compound 1 and Compound 2 are within the aforementioned ratio ranges, Compound 1 can not only be used sufficiently as a crosslinking agent to impart rigidity to the film, but also can moderately reduce the impedance (e.g., resistance) of the electrode surface of the rechargeable lithium battery to improve the battery output performance.

[0089] Relative to the total weight of the electrolyte, the amount of the additive present may be from about 0.1 wt% to about 2 wt%. For example, relative to the total weight of the electrolyte, the amount of the additive present may be from about 0.1 wt% to about 1.5 wt%, from about 0.6 wt% to about 1.5 wt%, or from about 0.7 wt% to about 1.5 wt%. If the additive included exceeds the above range, the viscosity of the electrolyte including the additive will increase excessively, and the wettability to the positive electrode and the negative electrode will be reduced. If the amount of the additive included is less than the above range, the above-mentioned effects will not be significant.

[0090] Rechargeable lithium battery

[0091] Based on the shape of the rechargeable lithium battery, the rechargeable lithium battery can be classified into a cylindrical shape, a prismatic shape, a pouch type, and / or a coin type (or kind). Figures 2 - 5 A simplified diagram showing a rechargeable lithium battery according to an embodiment. Figure 2 Showing a cylindrical rechargeable lithium battery, Figure 3 Showing a prismatic rechargeable lithium battery, and Figures 4 - 5 Showing a pouch-type rechargeable lithium battery. Refer to Figures 2 - 4 , the rechargeable lithium battery 100 may include an electrode assembly 40, where a separator 30 is between a positive electrode 10 and a negative electrode 20, and may also include a housing 50, where the electrode assembly 40 is accommodated. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte. The rechargeable lithium battery 100 may include a sealing member 60 for sealing the housing 50, as Figure 2 explained in. In an embodiment, as Figure 3 explained in, the rechargeable lithium battery 100 may include a positive electrode lead tab 11, a positive electrode terminal 12, a negative electrode lead tab 21, and a negative electrode terminal 22. As Figures 4 - 5 shown in, the rechargeable lithium battery 100 may include an electrode tab 70 ([[]] Figure 5)(i.e., the positive electrode tab 71 and the negative electrode tab 72) Figure 4 ).

[0092] The rechargeable lithium battery according to an embodiment of the present disclosure can be applied to an automobile, a mobile phone, and / or any other suitable electric device, but the present disclosure is not limited thereto.

[0093] Examples and comparative examples of the present disclosure will be described below. The following examples are only embodiments of the present disclosure, and the present disclosure is not limited to the following examples.

[0094] Examples and Comparative Examples

[0095] Example 1

[0096] (1) Preparation of electrolyte

[0097] About 1.0 M of LiPF 6 was dissolved in a non-aqueous organic solvent (where ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed together in a volume ratio of about 20:20:60), and an additive was added to prepare an electrolyte.

[0098] As the additive, Compound 1 represented by the following Chemical Formula 1 was added in an amount of 0.2 wt% based on the total amount of the electrolyte, and Compound 2 represented by Chemical Formula 2 was added in an amount of 1 wt% based on the total amount of the electrolyte.

[0099] [Chemical Formula 1]

[0100]

[0101] [Chemical Formula 2]

[0102]

[0103] (2) Manufacture of rechargeable lithium battery

[0104] LiNi 0.91 Co 0.08 Al 0.01 O 2 as the positive electrode active material, polyvinylidene fluoride as the binder, and acetylene black as the conductive material were mixed together in a weight ratio of 96:3:1, and the resulting mixture was dispersed in N-methylpyrrolidone to prepare a positive electrode active material slurry.

[0105] The positive electrode active material slurry was coated on an Al foil with a thickness of 15 μm, dried at a temperature of 100 °C, and then pressed to manufacture a positive electrode.

[0106] Mix the silicon negative electrode active material, styrene-butadiene rubber binder, and carboxymethyl cellulose together in a weight ratio of 98:1:1, and disperse them in distilled water to prepare the negative electrode active material slurry.

[0107] Coat the negative electrode active material slurry on a copper (Cu) foil with a thickness of 10 μm, dry it at 100 °C, and then press it to fabricate the negative electrode.

[0108] Assemble the positive electrode, negative electrode, and a 10-μm-thick polyethylene separator to fabricate the electrode assembly, and introduce the electrolyte to fabricate the rechargeable lithium battery.

[0109] Example 2

[0110] Fabricate the rechargeable lithium battery in a method substantially the same as that of Example 1, except that, as an additive, Compound 1 represented by Chemical Formula 1 is added in an amount of 0.5 wt% relative to the total amount of the electrolyte, and Compound 2 represented by Chemical Formula 2 is added in an amount of 1 wt% relative to the total amount of the electrolyte.

[0111] Example 3

[0112] Fabricate the rechargeable lithium battery in a method substantially the same as that of Example 1, except that, as an additive, Compound 1 represented by Chemical Formula 1 is added in an amount of 0.2 wt% relative to the total amount of the electrolyte, and Compound 2 represented by Chemical Formula 2 is added in an amount of 0.5 wt% relative to the total amount of the electrolyte.

[0113] Example 4

[0114] Fabricate the rechargeable lithium battery in a method substantially the same as that of Example 1, except that, as an additive, Compound 1 represented by Chemical Formula 1 is added in an amount of 0.1 wt% relative to the total amount of the electrolyte, and Compound 2 represented by Chemical Formula 2 is added in an amount of 0.5 wt% relative to the total amount of the electrolyte.

[0115] Comparative Example 1

[0116] Fabricate the rechargeable lithium battery in a method substantially the same as that of Example 1, except that no additive is added.

[0117] Comparative Example 2

[0118] Fabricate the rechargeable lithium battery in a method substantially the same as that of Example 1, except that, as an additive, Compound 4 represented by the following Chemical Formula 4 is added in an amount of 0.2 wt% relative to the total amount of the electrolyte, and Compound 2 represented by Chemical Formula 2 is added in an amount of 1 wt% relative to the total amount of the electrolyte.

[0119] [Chemical Formula 4]

[0120]

[0121] Comparative Example 3

[0122] A rechargeable lithium battery was manufactured in substantially the same manner as in Example 1, except that, as an additive, Compound 4 represented by Chemical Formula 4 was added in an amount of 0.5 wt% based on the total amount of the electrolyte, and Compound 2 represented by Chemical Formula 2 was added in an amount of 1 wt% based on the total amount of the electrolyte.

[0123] Comparative Example 4

[0124] A rechargeable lithium battery was manufactured in substantially the same manner as in Example 1, except that, as an additive, Compound 5 represented by the following Chemical Formula 5 was added in an amount of 0.2 wt% based on the total amount of the electrolyte, and Compound 2 represented by Chemical Formula 2 was added in an amount of 1 wt% based on the total amount of the electrolyte.

[0125] [Chemical Formula 5]

[0126]

[0127] Comparative Example 5

[0128] A rechargeable lithium battery was manufactured in substantially the same manner as in Example 1, except that, as an additive, Compound 5 represented by Chemical Formula 5 was added in an amount of 0.5 wt% based on the total amount of the electrolyte, and Compound 2 represented by Chemical Formula 2 was added in an amount of 1 wt% based on the total amount of the electrolyte.

[0129] Comparative Examples 6, 7 and 8

[0130] A rechargeable lithium battery was manufactured in substantially the same manner as in Example 1, except that, as an additive, Compound 1 represented by Chemical Formula 1 was added in amounts of 0.2 wt%, 0.5 wt% and 1 wt% respectively based on the total amount of the electrolyte, and Compound 2 was not added.

[0131] Comparative Examples 9, 10 and 11

[0132] A rechargeable lithium battery was manufactured in substantially the same manner as in Example 1, except that, as an additive, Compound 1 was not added, and Compound 2 represented by Chemical Formula 2 was added in amounts of 0.2 wt%, 0.5 wt% and 1 wt% respectively based on the total amount of the electrolyte.

[0133] Comparative Examples 12, 13, 14 and 15

[0134] A rechargeable lithium battery was fabricated in substantially the same manner as in Example 1, except that Compound 1 represented by Chemical Formula 1 and Compound 2 represented by Chemical Formula 2 were added in amounts at a weight ratio of substantially 1:1. In these cases, each of Compound 1 and Compound 2 was added in an amount of 0.2 wt%, 0.5 wt%, 1 wt%, and 2 wt% relative to the total amount of the electrolyte solution.

[0135] Comparative Example 16, Comparative Example 17, and Comparative Example 18

[0136] A rechargeable lithium battery was fabricated in substantially the same manner as in Example 1, except that the amount of Compound 1 represented by Chemical Formula 1 was greater than the amount of Compound 2 represented by Chemical Formula 2. In these cases, Compound 1 was added in an amount of 2 wt%, 1 wt%, and 1 wt% relative to the total amount of the electrolyte solution, and Compound 2 was added in an amount of 1 wt%, 0.5 wt%, and 0.2 wt% relative to the total amount of the electrolyte solution, respectively.

[0137] Comparative Example 19

[0138] A rechargeable lithium battery was fabricated in substantially the same manner as in Example 1, except that as an additive, Compound 1 represented by Chemical Formula 1 was added in an amount of 1 wt% relative to the total amount of the electrolyte solution, and Compound 2 represented by Chemical Formula 2 was added in an amount of 2 wt% relative to the total amount of the electrolyte solution.

[0139] The amounts of the compounds included in the electrolyte additives according to each of the Examples and Comparative Examples are listed in Table 1 below.

[0140] Table 1

[0141]

[0142]

[0143] Evaluation Example

[0144] The rechargeable lithium battery was evaluated by the following method.

[0145] Evaluation 1: Storage effect at high temperature (60 °C)

[0146] After measuring the initial discharge capacity (charged at 0.33C to 4.25V / 350mA under constant current and constant voltage (CC-CV), then discharged at 0.33C until its voltage reaches 2.8V), initial recovery capacity (charged at 0.33C to 4.25V / 350mA under constant current and constant voltage (CC-CV), then discharged at 0.33C until its voltage reaches 2.8V), and ΔV / ΔI (voltage change / current change) as the initial direct current internal resistance (DCIR) for rechargeable lithium batteries according to the examples and comparative examples, the maximum energy state inside the rechargeable lithium battery is changed to the fully charged state (SOC 100%). Store the rechargeable lithium battery in a chamber at 60°C in this state for 80 days, then measure the discharge capacity after 80 days of high-temperature storage, the recovery capacity after 80 days of high-temperature storage, and the DCIR after 80 days of high-temperature storage. Then, calculate the remaining capacity (%), recovery capacity (%), and DCIR increase rate (%) according to Equation 1 below, and Table 2 lists the following results.

[0147] Equation 1

[0148] Remaining capacity (%) = (Discharge capacity after 80 days of high-temperature storage / Initial discharge capacity) × 100

[0149] Recovery capacity (%) = (Recovery capacity after 80 days of high-temperature storage / Initial recovery capacity) × 100

[0150] DCIR increase rate (%) = { (DCIR after 80 days of high-temperature storage / Initial DCIR) - 1} × 100

[0151] Table 2

[0152] Category Remaining Capacity (%) Recovery Capacity (%) DCIR Increase Rate (%) Example 1 90.4 90.4 32.5 Example 2 90.9 92.5 25.8 Example 3 91.4 91.5 24.8 Example 4 90.4 90.5 22.8 Comparative Example 1 66.1 70.2 88.3 Comparative Example 2 88.4 87.4 41.5 Comparative Example 3 85.4 85.5 45.5 Comparative Example 4 89.4 87.4 40.5 Comparative Example 5 87.4 80.5 50.5 Comparative Example 6 84.5 86.5 54.4 Comparative Example 7 86.4 87.0 52.5 Comparative Example 8 85.4 84.0 62.5 Comparative Example 9 69.1 72.2 85.3 Comparative Example 10 76.1 80.2 84.3 Comparative Example 11 82.5 86.0 54.8 Comparative Example 12 82.0 83.0 54.9 Comparative Example 13 86.9 84.0 53.5 Comparative Example 14 84.4 83.0 63.0 Comparative Example 15 77.4 78.2 57.4 Comparative Example 16 64.5 67.2 91.3 Comparative Example 17 69.5 71.2 87.3 Comparative Example 18 60.5 64.2 82.3 Comparative Example 19 87.9 85.0 58.5

[0153] Evaluation 2: Life effect at high temperature (45°C)

[0154] Charge and discharge the rechargeable lithium batteries according to the examples and comparative examples 300 times in a chamber at 45°C under the conditions of charging at 0.5C to 1.0C (CC / CV, 4.25V, cutoff at 0.025C) and discharging at 1.0C (CC, cutoff at 2.75V) as one cycle. Then measure and calculate the remaining capacity (%) and DCIR increase rate (%) according to Equation 2 below, and Table 3 lists the following results.

[0155] Equation 2

[0156] Remaining capacity (%) = (Discharge capacity after 300 cycles / Initial discharge capacity) × 100

[0157] DCIR increase rate (%) = {((DCIR after 300 cycles) / (initial DCIR)) - 1} × 100

[0158] Table 3

[0159] Category Remaining Capacity (%) DCIR Increase Rate (%) Example 1 88.1 5.6 Example 2 88.2 3.5 Example 3 88.3 4.5 Example 4 88.3 5.0 Comparative Example 1 86.2 25.5 Comparative Example 2 83.1 11.6 Comparative Example 3 81.2 16.6 Comparative Example 4 81.1 14.6 Comparative Example 5 77.2 18.6 Comparative Example 6 87.1 8.2 Comparative Example 7 87.6 7.6 Comparative Example 8 86.6 10.6 Comparative Example 9 87.3 20.5 Comparative Example 10 87.6 19.5 Comparative Example 11 87.8 10.8 Comparative Example 12 84.1 10.2 Comparative Example 13 81.6 10.6 Comparative Example 14 85.6 12.3 Comparative Example 15 77.3 28.5 Comparative Example 16 66.2 30.5 Comparative Example 17 68.2 26.5 Comparative Example 18 63.2 30.5 Comparative Example 19 82.6 12.1

[0160] Evaluation 3: Fast charging effect

[0161] The rechargeable lithium batteries according to the examples and comparative examples were charged at 0.33C to 2.75C (CC / CV, 4.25V, cutoff at 0.025C) and discharged at 0.33C (CC, cutoff at 2.75V) as the conditions for one cycle, charged and discharged 300 times in a chamber at 35°C, and then the remaining capacity (%) and DCIR increase rate (%) were measured and calculated according to Equation 2 above, and the results are listed in Table 4 below.

[0162] Table 4

[0163] Category Remaining Capacity (%) DCIR Increase Rate (%) Example 1 85.10 24.29 Example 2 85.40 24.00 Example 3 84.30 20.30 Example 4 84.00 19.50 Comparative Example 1 74.61 58.00 Comparative Example 2 55.30 45.30 Comparative Example 3 54.60 47.10 Comparative Example 4 61.30 55.36 Comparative Example 5 61.00 56.10 Comparative Example 6 80.96 35.00 Comparative Example 7 80.02 35.20 Comparative Example 8 77.00 45.30 Comparative Example 9 70.05 51.20 Comparative Example 10 71.20 48.00 Comparative Example 11 79.59 44.00 Comparative Example 12 66.50 58.60 Comparative Example 13 64.30 59.10 Comparative Example 14 61.50 66.00 Comparative Example 15 60.10 75.00 Comparative Example 16 59.50 50.01 Comparative Example 17 60.10 45.30 Comparative Example 18 61.50 43.00 Comparative Example 19 83.20 30.30

[0164] Comprehensive evaluation

[0165] In Comparative Examples 2 to 5, instead of Compound 1, Compound 4 or Compound 5 (whose structure is partially similar to that of Compound 1 and whose function is different from that of Compound 1) was used for the experiment according to the evaluation example. As a result, a high increase rate of the direct current internal resistance (DCIR) was measured, and the high-temperature storage effect, high-temperature life effect, and fast charging effect were reduced.

[0166] In addition, in Comparative Examples 6 to 11, only one of Compound 1 and Compound 2 was added. Thus, it was determined that, compared with the examples and Comparative Examples 2 to 5, a high increase rate of DCIR was measured, and the high-temperature storage effect, high-temperature life effect, and fast charging effect were reduced.

[0167] Moreover, as a result of comparing Comparative Examples 12 to 19 with the examples, it was determined that the content ratio and total content of Compound 1 and Compound 2 have an impact on the DCIR increase rate.

[0168] The electrolyte according to the embodiment for the rechargeable lithium battery can achieve the suppression or reduction of the increase in the stability and impedance (e.g., resistance) of the electrode. Thus, it can have the effect of improving the high-temperature life characteristics.

[0169] Although the subject matter of the present invention has been described in connection with example embodiments that are presently considered to be practical, it should be understood that the present disclosure is not limited to the disclosed embodiments, but is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims and their equivalents. Therefore, the foregoing embodiments should be understood as examples and should not limit the present disclosure in any way.

Claims

1. An electrolyte for a rechargeable lithium battery, the electrolyte comprising: Non-aqueous organic solvents; Lithium salts; and additive, wherein the additive comprises a compound 1 represented by chemical formula 1 and a compound 2 represented by chemical formula 2, [Chemical formula 1] [Chemical formula 2] 2. The electrolyte according to claim 1, wherein the amount of compound 1 present is 0.01 wt% to 1 wt% relative to the total weight of the electrolyte.

3. The electrolyte of claim 1, wherein the additive is present in an amount of 0.1 wt% to 2 wt% relative to the total weight of the electrolyte. The electrolyte according to claim 1 , wherein the amount of the compound 1 is less than the amount of the compound 2. 5 . The electrolyte according to claim 4 , wherein the amount of the compound 2 present is 1 to 10 parts by weight relative to 1 part by weight of the compound 1.

6. The electrolyte of claim 1, wherein the nonaqueous organic solvent comprises at least one selected from the group consisting 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.

7. The electrolyte of claim 6, wherein the nonaqueous organic solvent comprises ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate.

8. The electrolyte of claim 1, wherein the lithium salt comprises a salt selected from the group consisting of LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N, lithium bis(fluorosulfonyl)imide, LiC4F9SO3, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2), at least one of lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluoro(oxalate)borate, lithium difluorobis(oxalate)phosphate and lithium bis(oxalate)borate, wherein x and y are integers of 1 to 20.

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. A rechargeable lithium battery comprising: a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material; and The electrolyte according to any one of claims 1 to 9.

11. The rechargeable lithium battery according to claim 10, wherein the positive electrode active material comprises a lithium metal oxide represented by Chemical Formula 3, [Chemical formula 3] Li a Ni 1-b-c Co b X c O 2-α D α Wherein in chemical formula 3, X is Al, Mn, Cr, Fe, Mg, Sr, V, a rare earth element or a combination thereof, D is F, S, P or a combination thereof, 0.90≤a≤1.8， 0≤b≤0.5， 0≤c≤0.5, and 0≤α<2。 12 . The rechargeable lithium battery of claim 10 , wherein the negative electrode active material comprises a carbon-based negative electrode active material, a silicon-based negative electrode active material, a tin-based negative electrode active material, or a combination thereof.

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