Additive, electrolyte for lithium secondary battery containing the same, and lithium secondary battery

Abstract

To provide an electrolyte additive for a lithium secondary battery that improves the life characteristics while suppressing an increase in resistance and gas generation in the lithium secondary battery at high temperature.SOLUTION: The present invention relates to an additive, an electrolyte for a lithium secondary battery including the additive, and a lithium secondary battery, the additive is represented by the following chemical formula 1. (In chemical formula 1, L1 is a substituted or unsubstituted alkylene group having 1 to 20 carbon atoms, and R1 to R4 are each independently a substituted or unsubstituted aryl group having 6 to 20 carbon atoms.)SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an additive, an electrolyte for a lithium secondary battery containing the additive, and a lithium secondary battery. [Background technology]

[0002] Recently, with the rapid spread of battery-powered electronic devices such as mobile phones, laptops, and electric vehicles, the demand for high-energy-density, high-capacity secondary batteries has been increasing rapidly. This has led to active research and development into improving the performance of lithium secondary batteries.

[0003] A lithium secondary battery is a battery that includes a positive electrode, a negative electrode, and an electrolyte, each containing an active material capable of lithium ion intercalation and deintercalation. Electrical energy is produced through oxidation and reduction reactions that occur when lithium ions are intercalated and deintercalated from the positive and negative electrodes.

[0004] Recently, one of the development directions for lithium secondary batteries is to improve their high-temperature characteristics. Generally, lithium secondary batteries can encounter problems such as increased resistance, gas generation, and reduced lifespan at high temperatures. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-299542 Summary of the Invention [Problem to be solved by the invention]

[0006] An embodiment of the present invention provides an electrolyte additive for a lithium secondary battery that improves the life characteristics while suppressing an increase in resistance and gas generation of the lithium secondary battery at high temperatures. [Means for solving the problem]

[0007] One embodiment of the present invention provides an electrolyte additive for a lithium secondary battery represented by the following Chemical Formula 1:

[0008] [Chemical formula 1] [ka]

[0009] In chemical formula 1, L 1 is a substituted or unsubstituted alkylene group having 1 to 20 carbon atoms, and R 1 ~R 4 are each independently a substituted or unsubstituted aryl group having 6 to 20 carbon atoms.

[0010] An embodiment of the present invention provides an electrolyte for a lithium secondary battery, including the electrolyte additive for a lithium secondary battery.

[0011] An embodiment of the present invention provides a lithium secondary battery including the above-mentioned electrolyte solution for lithium secondary batteries. [Effects of the Invention]

[0012] The electrolyte additive for lithium secondary batteries according to the present invention can suppress metal elution from the positive electrode active material at high temperatures, and can improve the life characteristics of the lithium secondary battery while suppressing an increase in resistance and gas generation. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic diagram illustrating a lithium secondary battery according to an embodiment. [Figure 2] 1 is a schematic diagram illustrating a lithium secondary battery according to an embodiment. [Figure 3] 1 is a schematic diagram illustrating a lithium secondary battery according to an embodiment. [Figure 4] 1 is a schematic diagram illustrating a lithium secondary battery according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] DETAILED DESCRIPTION OF THE INVENTION The following detailed description of the preferred embodiments of the present invention is provided by way of example only and is not intended to limit the scope of the present invention, which is defined solely by the scope of the following claims.

[0015] Unless otherwise specified in this specification, when a layer, film, region, plate, or other part is said to be "on" another part, this includes not only the case where it is "directly on" the other part, but also the case where there is another part in between.

[0016] Unless otherwise specified herein, singular terms can also include plural terms. At the same time, unless otherwise specified, "A or B" means "including A, including B, or including A and B."

[0017] As used herein, "combinations thereof" refers to mixtures, laminates, composites, copolymers, alloys, blends, reaction products, and the like of compositions.

[0018] Unless otherwise specified in this specification, the term "alkyl group" refers to an alkyl group having 1 to 20 carbon atoms, the term "alkenyl group" refers to an alkenyl group having 2 to 20 carbon atoms, the term "cycloalkenyl group" refers to a cycloalkenyl group having 3 to 20 carbon atoms, the term "heterocycloalkenyl group" refers to a heterocycloalkenyl group having 3 to 20 carbon atoms, the term "aryl group" refers to an aryl group having 6 to 20 carbon atoms, the term "arylalkyl group" refers to an arylalkyl group having 6 to 20 carbon atoms, the term "alkylene group" refers to an alkylene group having 1 to 20 carbon atoms, the term "arylene group" refers to an arylene group having 6 to 20 carbon atoms, the term "alkylarylene group" refers to an alkylarylene group having 6 to 20 carbon atoms, the term "heteroarylene group" refers to a heteroarylene group having 3 to 20 carbon atoms, and the term "alkoxylen group" refers to an alkoxylen group having 1 to 20 carbon atoms.

[0019] Unless otherwise specified in this specification, "substituted" means that at least one hydrogen atom has been replaced with a halogen atom (F, Cl, Br, I), a hydroxy group, an alkoxy group having 1 to 20 carbon atoms, a nitro group, a cyano group, an amino group, an imino group, an azide group, an amidino group, a hydrazino group, a hydrazono group, a carbonyl group, a carbamoyl group, a thiol group, an ester group, an ether group, a carboxyl group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, an alkyl group having 1 to 20 carbon atoms, It means being substituted with an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, a cycloalkenyl group having 3 to 20 carbon atoms, a cycloalkynyl group having 3 to 20 carbon atoms, a heterocycloalkyl group having 2 to 20 carbon atoms, a heterocycloalkenyl group having 2 to 20 carbon atoms, a heterocycloalkynyl group having 2 to 20 carbon atoms, a heteroaryl group having 3 to 20 carbon atoms, or a substituent that is a combination thereof.

[0020] Unless otherwise defined in the chemical formulas herein, when a chemical bond is not drawn at a position where a chemical bond should be drawn, it means that a hydrogen atom is bonded at that position.

[0021] (Electrolyte additive for lithium secondary batteries) One embodiment provides an electrolyte additive for lithium secondary batteries (hereinafter, sometimes simply referred to as "additive") represented by the following Chemical Formula 1:

[0022] [Chemical formula 1] [ka]

[0023] The electrolyte additive for a lithium secondary battery according to one embodiment contains a phosphate group and an aryl group symmetrically, and is oxidatively decomposed on the surface of the positive electrode to form a highly stable and heat-resistant SEI coating. The SEI coating formed on the surface of the positive electrode can suppress metal elution from the positive electrode active material, thereby suppressing an increase in resistance and gas generation in the lithium secondary battery and improving its lifespan.

[0024] The explanation for Chemical Formula 1, which represents the additive, is as follows:

[0025] L 1 is a substituted or unsubstituted alkylene group having 1 to 20 carbon atoms.

[0026] For example, L 1 may be a substituted or unsubstituted alkylene group having 1 to 3 carbon atoms.

[0027] R 1 ~R 4 are each independently a substituted or unsubstituted aryl group having 6 to 20 carbon atoms.

[0028] For example, R 1 ~R 4 may all be phenyl groups.

[0029] Chemical Formula 1 may be represented by the following Chemical Formula 1-1:

[0030] [Chemical formula 1-1] [ka]

[0031] In chemical formula 1-1, L 1 The definition of is as described above.

[0032] Representative examples of Chemical Formula 1 are represented by the following Chemical Formulas 1-1-1 to 1-1-3.

[0033] [Chemical formula 1-1-1] [ka]

[0034] [Chemical formula 1-1-2] [ka]

[0035] [Chemical formula 1-1-3] [ka] .

[0036] (Electrolyte for lithium secondary batteries) One embodiment provides an electrolyte solution for a lithium secondary battery (hereinafter, sometimes simply referred to as "electrolyte solution") comprising a non-aqueous organic solvent, a lithium salt, and an additive represented by the following Chemical Formula 1:

[0037] [Chemical formula 1] [ka]

[0038] The electrolyte solution for a lithium secondary battery according to one embodiment includes the additive described above. The additive contained in the electrolyte solution can suppress metal elution from the positive electrode active material at high temperatures, suppress an increase in resistance and gas generation in the lithium secondary battery, and improve the life characteristics.

[0039] The additive may be contained in an amount of 0.05 to 3 wt %, 0.05 to 2 wt %, or 0.05 to 1 wt % relative to 100 wt % of the electrolyte solution. Within these ranges, the additive is oxidatively decomposed on the positive electrode surface to form an SEI coating that is highly stable and heat-resistant.

[0040] (non-aqueous organic solvent) The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can migrate.

[0041] The non-aqueous organic solvent may be a carbonate solvent, an ester solvent, an ether solvent, a ketone solvent, an alcohol solvent, an aprotic solvent, or a combination thereof.

[0042] Examples of carbonate solvents that can be used include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc. Examples of ester solvents that can be used include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, caprolactone, etc. Examples of ether solvents that can be used include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and tetrahydrofuran. Examples of ketone solvents that can be used include cyclohexanone. Examples of alcohol solvents that can be used include ethyl alcohol and isopropyl alcohol. Examples of aprotic solvents that can be used include nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, which may contain a double bond, an aromatic ring, or an ether group), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane and 1,4-dioxolane, and sulfolanes.

[0043] The non-aqueous organic solvents can be used alone or in combination of two or more kinds.

[0044] When a carbonate-based solvent is used, a cyclic carbonate and a chain carbonate can be mixed and used, and the cyclic carbonate and the chain carbonate can be mixed in a volume ratio of 1:1 to 1:9.

[0045] (lithium salts) Lithium salts are substances that dissolve in organic solvents and act as a source of lithium ions within the battery, enabling basic lithium secondary battery operation and facilitating the movement of lithium ions between the positive and negative electrodes. Representative examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide (LiFSI), LiC4F9SO3, and LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2) (x and y are integers of 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalato)phosphate (LiDFOB), and lithium bis(oxalato)borate (LiBOB).

[0046] (lithium secondary battery) One embodiment provides a lithium secondary battery including: a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material; and an electrolyte solution including a non-aqueous organic solvent, a lithium salt, and an additive represented by Chemical Formula 1 below:

[0047] [Chemical formula 1] [ka]

[0048] A lithium secondary battery according to one embodiment includes an electrolyte solution containing the additive described above. The additive contained in the electrolyte solution can suppress metal elution from the positive electrode active material at high temperatures, thereby suppressing an increase in resistance and gas generation in the lithium secondary battery and improving its life characteristics.

[0049] (Cathode active material) The positive electrode active material may be a compound capable of reversibly intercalating and deintercalating lithium (lithiated intercalation compound). Specifically, one or more of composite oxides of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof may be used.

[0050] The composite oxide may be a lithium transition metal composite oxide, and specific examples include lithium nickel-based oxides, lithium cobalt-based oxides, lithium manganese-based oxides, lithium iron phosphate-based compounds, cobalt-free nickel-manganese-based oxides, or combinations thereof.

[0051] As an example, 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 O 2-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 O2 (0.90≦a≦1.8, 0≦b≦0.9, 0≦c≦0.5, 0≦d≦0.5, 0≦e≦0.1), Li a NiG bO2 (0.90≦a≦1.8, 0.001≦b≦0.1), Li a CoG b O2 (0.90≦a≦1.8, 0.001≦b≦0.1), Li a Mn 1-b G b O2 (0.90≦a≦1.8, 0.001≦b≦0.1), Li a Mn2G b O4 (0.90≦a≦1.8, 0.001≦b≦0.1), Li a Mn 1-g G g PO4(0.90≦a≦1.8, 0≦g≦0.5), Li (3-f) Fe2(PO4)3(0≦f≦2);Li a Any one of the compounds represented by the chemical formula FePO4 (0.90≦a≦1.8) can be used.

[0052] In the above chemical formula, A is Ni, Co, Mn, or a combination thereof; X is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth 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.

[0053] For example, the positive electrode active material may be a high-nickel positive electrode active material in which the nickel content relative to 100 mol% of metals excluding lithium in a lithium transition metal composite oxide is 80 mol% or more, 85 mol% or more, 90 mol% or more, 91 mol% or more, or 94 mol% or more and 99 mol% or less. High-nickel positive electrode active materials can achieve high capacity and are applicable to high-capacity, high-density lithium secondary batteries.

[0054] The positive electrode active material can include a lithium nickel-based composite oxide represented by the following chemical formula 11.

[0055] [Chemical formula 11] Li a1 Nix1 M 1 y1 M 2 z1 O 2-b1 X b1

[0056] In Chemical Formula 11, 0.9≦a1≦1.2, 0.7≦x1≦1, 0≦y1≦0.3, 0≦z1≦0.1, 0.9≦x1+y1+z1≦1.1, and 0≦b1≦0.1; M 1 and M 2 are each independently one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

[0057] In Chemical Formula 11, 0.75≦x1≦1, 0≦y1≦0.28, and 0≦z1≦0.08, or 0.85≦x1≦1, 0≦y1≦0.15, and 0≦z1≦0.15, or 0.9≦x1≦1, 0≦y1≦0.1, and 0≦z1≦0.1.

[0058] The positive electrode active material may include a lithium nickel-based composite oxide represented by the following Chemical Formula 12. The compound represented by the following Chemical Formula 12 may be a lithium nickel cobalt-based composite oxide.

[0059] [Chemical formula 12] Li a2 Ni x2 Co y2 M 3 z2 O 2-b2 X b2

[0060] In chemical formula 12, 0.9≦a2≦1.8, 0.7≦x2<1, 0 <y2≦0.2、0≦z2≦0.2、0.9≦x2+y2+z2≦1.1、および0≦b2≦0.1であり、M 3is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Fe, Mg, Mn, Mo, Nb, Si, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

[0061] In Chemical Formula 12, 0.75≦x2≦0.99, 0≦y2≦0.15, and 0≦z2≦0.15, or 0.85≦x2≦0.99, 0.01≦y2≦0.15, and 0.01≦z2≦0.15, or 0.9≦x2≦0.99, 0.01≦y2≦0.1, and 0.01≦z2≦0.1.

[0062] The positive electrode active material may also include a lithium nickel-based composite oxide represented by the following Chemical Formula 13. The compound of the following Chemical Formula 13 may be lithium nickel-cobalt-aluminum oxide or lithium nickel-cobalt-manganese oxide.

[0063] [Chemical formula 13] Li a3 Ni x3 Co y3 M 4 z3 M 5 w3 O 2-b3 X b3

[0064] In chemical formula 13, 0.9≦a3≦1.8, 0.7≦x3≦0.98, 0.01≦y3≦0.19, 0.01≦z3≦0.19, 0≦w3≦0.19, 0.9≦x3+y3+z3+w3≦1.1, and 0≦b3≦0.1; M 4 is one or more elements selected from the group consisting of Al and Mn, and M 5 is one or more elements selected from the group consisting of B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

[0065] In Chemical Formula 13, 0.75≦x3≦0.98, 0≦y3≦0.16, and 0≦z3≦0.16, or 0.85≦x3≦0.98, 0.01≦y3≦0.14, 0.01≦z3≦0.14, and 0≦w3≦0.14, or 0.9≦x3≦0.98, 0.01≦y3≦0.09, 0.01≦z3≦0.09, and 0≦w3≦0.09.

[0066] In addition, the positive electrode active material may include a lithium nickel-based composite oxide represented by the following Chemical Formula 14. The compound of the following Chemical Formula 14 may be a cobalt-free lithium nickel-manganese-based oxide.

[0067] [Chemical formula 14] Li a4 Ni x4 Mn y4 M 6 z4 O 2-b4 X b4

[0068] In chemical formula 14, 0.9≦a2≦1.8, 0.7≦x4<1, 0 <y4≦0.3、0≦z4≦0.1、0.9≦x4+y4+z4≦1.1、および0≦b4≦0.1であり、M 6 is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

[0069] Cobalt-free lithium nickel manganese oxides have a strong structural instability, so under high voltage and / or high temperature conditions, the structure collapses and the transition metal (e.g., Ni) dissolves, dramatically increasing the stability and lifespan of lithium secondary batteries.

[0070] However, even when used in combination with a cobalt-free lithium nickel-manganese oxide, the additive for a lithium secondary battery according to one embodiment can suppress structural collapse of the cobalt-free lithium nickel-manganese oxide under high voltage and / or high temperature conditions, thereby improving the stability and life characteristics of the lithium secondary battery.

[0071] (positive electrode) A positive electrode for a lithium secondary battery can include a current collector and a positive electrode active material layer formed on the current collector. The positive electrode active material layer includes a positive electrode active material and can further include a binder and / or a conductive material.

[0072] As an example, the positive electrode may further include an additive that can act as a sacrificial positive electrode.

[0073] The content of the positive electrode active material may be 90% by weight to 99.5% by weight relative to 100% by weight of the positive electrode active material layer, and the contents of the binder and conductive material may each be 0.5% by weight to 5% by weight relative to 100% by weight of the positive electrode active material layer.

[0074] The binder serves to firmly adhere the positive electrode active material particles to each other and to firmly adhere the positive electrode active material to the current collector. Representative examples of binders include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers 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 nylon.

[0075] The conductive material is used to impart conductivity to the electrode, and any material that is electron-conductive and does not cause a chemical change in the battery that is constructed can be used. Examples of the conductive material include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials in the form of metal powder or metal fiber containing copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; and mixtures thereof.

[0076] The current collector may be made of Al, but is not limited to this.

[0077] (Negative electrode active material) The negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, a lithium metal alloy, a material capable of being doped and dedoped with lithium, or a transition metal oxide.

[0078] The material capable of reversibly intercalating / deintercalating lithium ions may be a carbon-based negative electrode active material, such as crystalline carbon, amorphous carbon, or a combination thereof. Examples of crystalline carbon include graphite, such as amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, and examples of amorphous carbon include soft or hard carbon, mesophase pitch carbide, or calcined coke.

[0079] As the alloy of lithium metal, an alloy of lithium and a metal selected from the group consisting of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al and Sn can be used.

[0080] As the substance capable of being doped and undoped with lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material can be used. The Si-based negative electrode active material may be silicon, a silicon-carbon composite, SiOx (0 < x < 2), a Si-Q alloy (Q is selected from 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, and combinations thereof), or a combination thereof. The Sn-based negative electrode active material may be Sn, SnO2, a Sn-based alloy, or a combination thereof.

[0081] The silicon-carbon composite may be a composite of silicon and amorphous carbon. According to one embodiment, the silicon-carbon composite may be in a form in which silicon particles are coated with amorphous carbon on the surface of the silicon particles. For example, it may include secondary particles (cores) formed by granulating primary silicon particles and an amorphous carbon coating layer (shell) located on the surface of the secondary particles. Amorphous carbon may also be located between the primary silicon particles. For example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed and present in an amorphous carbon matrix.

[0082] The silicon-carbon composite may further contain crystalline carbon. For example, the silicon-carbon composite may include a core containing crystalline carbon and silicon particles and an amorphous carbon coating layer located on the surface of the core.

[0083] The Si-based negative electrode active material or the Sn-based negative electrode active material can be used by being mixed with a carbon-based negative electrode active material.

[0084] (Negative electrode) The negative electrode for a lithium secondary battery includes a current collector and a negative electrode active material layer located on the current collector. The negative electrode active material layer contains a negative electrode active material and may further contain a binder and / or a conductive material.

[0085] For example, the negative electrode active material layer can contain 90% to 99% by weight of the negative electrode active material, 0.5% to 5% by weight of the binder, and 0% to 5% by weight of the conductive material.

[0086] The binder serves to firmly adhere the negative electrode active material particles to each other and to the current collector, and may be a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0087] Non-aqueous binders include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or combinations thereof.

[0088] The water-based binder may be selected from styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0089] When an aqueous binder is used as the negative electrode binder, a cellulose-based compound that can impart viscosity may be further included. The cellulose-based compound may be a mixture of one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, or alkali metal salts thereof. The alkali metal may be sodium, potassium, or lithium.

[0090] The dry binder may be a fiberizable polymeric material such as polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0091] The conductive material is used to impart conductivity to the electrodes, and any material that is electron-conductive and does not cause chemical changes in the battery that is constructed can be used. Specific examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials in the form of metal powder or metal fiber, including copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; and mixtures thereof.

[0092] The negative electrode current collector may be selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof.

[0093] (separator) Depending on the type of lithium secondary battery, a separator may be present between the positive and negative electrodes. Such separators may be made of polyethylene, polypropylene, polyvinylidene fluoride, or multilayer films of two or more of these. Of course, mixed multilayer films such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, or a polypropylene / polyethylene / polypropylene three-layer separator may also be used.

[0094] The separator can include a porous substrate and a coating layer comprising an organic material, an inorganic material, or a combination thereof located on one or both sides of the porous substrate.

[0095] The porous substrate may be a polymer membrane formed from any one polymer selected from polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyacetal, polyamide, polyimide, polycarbonate, polyether ketone, polyaryl ether ketone, polyetherimide, polyamide imide, polybenzimidazole, polyethersulfone, polyphenylene oxide, cyclic olefin copolymers, polyphenylene sulfide, polyethylene naphthalate, glass fiber, Teflon (registered trademark), and polytetrafluoroethylene, or a copolymer or mixture of two or more of these.

[0096] The organic material may include a polyvinylidene fluoride-based polymer or a (meth)acrylic-based polymer.

[0097] The inorganic material may include, but is not limited to, inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof.

[0098] The organic material and the inorganic material may be mixed in one coating layer, or a coating layer containing an organic material and a coating layer containing an inorganic material may be laminated.

[0099] (lithium secondary battery) Lithium secondary batteries can be classified into cylindrical, prismatic, pouch, and coin types depending on their shape. FIGS. 1 to 4 are schematic diagrams showing a lithium secondary battery according to one embodiment, with FIG. 1 representing a cylindrical battery, FIG. 2 representing a prismatic battery, and FIGS. 3 and 4 representing pouch-type batteries. Referring to FIGS. 1 to 4, a lithium secondary battery 100 may include an electrode assembly 40 having a positive electrode 10 and a negative electrode 20 with a separator 30 interposed therebetween, and a case 50 housing the electrode assembly 40. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte (not shown). As shown in FIG. 1, the lithium secondary battery 100 may include a sealing member 60 that seals the case 50. Also, in FIG. 2, the lithium secondary 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 shown in FIGS. 3 and 4, the lithium secondary battery 100 may include electrode tabs 70, i.e., a positive electrode tab 71 and a negative electrode tab 72, which serve as electrical paths for conducting the current generated in the electrode assembly 40 to the outside.

[0100] The lithium secondary battery according to an embodiment of the present invention may be applied to automobiles, mobile phones, and / or various types of electrical devices, but the present invention is not limited thereto.

[0101] Examples of the present invention and comparative examples are described below. However, the examples described below are merely examples of the present invention, and the present invention is not limited to the examples described below. [Example]

[0102] (Synthesis Example 1: Compound represented by chemical formula 1-1-1) 1,2-Bis(diphenylphosphino)ethane (0.5 mmol, 2.5 mg) and hydrogen peroxide (3.0 mmol) were added dropwise to a Schlenk flask containing 100 ml of methylene chloride and stirred at 50°C for 24 hours. The precipitate was then filtered, and the resulting compound was dissolved in a small amount of acetone to obtain a solution. This solution was slowly added dropwise to 500 ml of methylene chloride using a dropping funnel, and the resulting reaction mixture was filtered, purified, and then vacuum dried to obtain the compound represented by chemical formula 1-1-1.

[0103] [Chemical formula 1-1-1] [ka]

[0104] (H NMR(300MHz): δ=2.49, 2.50(4H, CH2P); 7.42(t, 3JHH=7.5Hz, 8H); 7.47(t, 3JHH=7.4Hz, 4H); 7.68(dd, 3JHH=7.5Hz, 3JHP=12.0Hz, 8H))

[0105] Example 1 (1) Electrolyte production An electrolyte solution was prepared by dissolving 1.15 M LiPF6 in a non-aqueous organic solvent prepared by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 2:1:7, and adding 0.5 wt% of an additive represented by chemical formula 1-1-1.

[0106] Here, the content of the additive in the composition of the electrolyte solution in "% by weight" is based on the entire electrolyte solution (lithium salt + non-aqueous organic solvent + additive) being 100% by weight.

[0107] (2) Manufacture of lithium secondary batteries LiNi as the positive electrode active material 0.75 Mn 0.23 Al 0.02 O2, polyvinylidene fluoride as a binder, and acetylene black as a conductive material were mixed in a weight ratio of 96:3:1, and dispersed in N-methylpyrrolidone to prepare a positive electrode active material slurry.

[0108] The positive electrode active material slurry was coated on an aluminum foil having a thickness of 15 μm, dried at 100° C., and then pressed to prepare a positive electrode.

[0109] A mixture of artificial graphite and Si-C composite in a weight ratio of 93:7 was used as the negative electrode active material, and the negative electrode active material was mixed with styrene-butadiene rubber binder and carboxymethyl cellulose in a weight ratio of 98:1:1, respectively, and dispersed in distilled water to prepare a negative electrode active material slurry.

[0110] The Si-C composite used was a core containing artificial graphite and silicon particles, and the surface of the core was coated with coal-based pitch.

[0111] The negative electrode active material slurry was coated on a copper foil having a thickness of 10 μm, dried at 100° C., and then pressed to prepare a negative electrode.

[0112] The prepared positive and negative electrodes were assembled with a 10 μm thick polyethylene separator to prepare an electrode assembly, and an electrolyte was injected to prepare a lithium secondary battery.

[0113] <Example 2> An electrolyte solution and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the content of the additive was changed to 1 wt %.

[0114] Example 3 An electrolyte solution and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the content of the additive was changed to 2 wt %.

[0115] Example 4 The positive electrode active material is LiNi 0.9 Co 0.05 Al 0.05 An electrolyte solution and a lithium secondary battery were manufactured in the same manner as in Example 1, except that O2 was used.

[0116] <Example 5> An electrolyte solution and a lithium secondary battery were manufactured in the same manner as in Example 4, except that the content of the additive was changed to 1 wt %.

[0117] Example 6 An electrolyte solution and a lithium secondary battery were manufactured in the same manner as in Example 4, except that the content of the additive was changed to 2 wt %.

[0118] <Comparative Example 1> An electrolyte solution and a lithium secondary battery were manufactured in the same manner as in Example 1, except that no additives were added.

[0119] <Comparative Example 2> An electrolyte solution and a lithium secondary battery were prepared in the same manner as in Example 1, except that a compound represented by the following chemical formula A (CAS No. 1663-45-2, manufactured by Aldrich) was used instead of the additive represented by chemical formula 1-1-1.

[0120] [Chemical formula A] [ka]

[0121] <Comparative Example 3> An electrolyte solution and a lithium secondary battery were prepared in the same manner as in Example 1, except that a compound represented by the following chemical formula B (CAS No. 23936-60-9, manufactured by Aldrich) was used instead of the additive represented by chemical formula 1-1-1.

[0122] [Chemical formula B] [ka]

[0123] <Comparative Example 4> The positive electrode active material is LiNi 0.9 Co 0.05 Al 0.05 An electrolyte solution and a lithium secondary battery were manufactured in the same manner as in Comparative Example 1, except that O2 was used.

[0124] <Comparative Example 5> The positive electrode active material is LiNi 0.9 Co 0.05 Al 0.05 An electrolyte solution and a lithium secondary battery were manufactured in the same manner as in Comparative Example 2, except that O2 was used instead.

[0125] <Comparative Example 6> The positive electrode active material is LiNi 0.9 Co 0.05 Al 0.05 An electrolyte solution and a lithium secondary battery were manufactured in the same manner as in Comparative Example 3, except that O2 was used instead.

[0126] (Evaluation example 1: High temperature storage characteristics evaluation) (1) DCIR Increase Rate For the lithium secondary batteries of Examples 1 to 6 and Comparative Examples 1 to 6, the initial DC resistance (DCIR) was measured using the ΔV / ΔI (change in voltage / change in current) value. Next, the maximum energy state inside the battery was set to a fully charged state (SOC 100%), and after storing in this state at high temperature (60°C) for 30 days, the DC resistance was measured. The DCIR increase rate (%) was calculated using the following formula 1, and the results are shown in Table 1 below.

[0127] [Formula 1] DCIR increase rate = (DCIR after 30 days / initial DCIR) x 100

[0128] [Table 1]

[0129] (2) Amount of gas generated The lithium secondary batteries of Examples 1 to 3 and Comparative Examples 1 to 3 were set to a fully charged state (SOC 100%) so that the maximum energy state inside the battery was reached. After storing the batteries in this state at a high temperature (60°C) for one day or seven days, the amount of gas generated was evaluated, and the results are shown in Table 2 below.

[0130] The amount of gas generated was determined by measuring the change in volume before and after high-temperature storage, and converting this into a change in mass using Archimedes' method.

[0131] [Table 2]

[0132] (Evaluation example 2: Evaluation of charge / discharge characteristics at high temperatures) The lithium secondary batteries according to Examples 1 to 3 and Comparative Examples 1 to 3 were subjected to 200 charge / discharge cycles at 45°C under the conditions of 0.33C charge (CC / CV, 4.45V, 0.025C cut-off) / 1.0C discharge (CC, 2.5V cut-off), and then the capacity retention rate was calculated using the following formula 2.

[0133] [Formula 2] Capacity retention rate = (discharge capacity after 200 cycles / discharge capacity after 1 cycle) × 100

[0134] [Table 3]

[0135] (General) According to Table 1, the lithium secondary batteries of Examples 1 to 6 exhibited a more suppressed increase in resistance at high temperatures than the lithium secondary batteries of Comparative Examples 1 to 6.

[0136] Furthermore, according to Tables 2 and 3, the lithium secondary batteries of Examples 1 to 3 suppressed gas generation at high temperatures and had improved life characteristics compared to the lithium secondary batteries of Comparative Examples 1 to 3.

[0137] From these findings, it was found that the additive according to one embodiment suppresses metal elution from the positive electrode active material at high temperatures, and improves the life characteristics of the lithium secondary battery while suppressing an increase in resistance and gas generation.

[0138] Furthermore, it has been found that the additive according to one embodiment, when used in combination with a cobalt-free lithium nickel manganese oxide, suppresses structural collapse of the cobalt-free lithium nickel manganese oxide even under high voltage and / or high temperature conditions.

[0139] Although the preferred embodiment of the present invention has been described above, the present invention is not limited thereto, and various modifications can be made within the scope of the claims, the detailed description of the invention, and the accompanying drawings, and it is natural that these also fall within the scope of the present invention. [Explanation of symbols]

[0140] 100 Lithium secondary battery 10 positive electrode 11 Positive electrode lead tab 12 Positive terminal 20 negative electrode 21 Negative electrode lead tab 22 Negative terminal 30 Separator 40 Electrode assembly 50 cases 60 Sealing member 70 Electrode tab 71 Positive electrode tab 72 Negative electrode tab

Claims

1. An electrolyte additive for a lithium secondary battery represented by any one of the following chemical formulas 1-1-1 to 1-1-3: [Chemical formula 1-1-1] 【Chemistry 1】 [Chemical formula 1-1-2] 【Chemistry 2】 [Chemical formula 1-1-3] 【Transformation 3】 。

2. a non-aqueous organic solvent; A lithium salt, An electrolyte solution for a lithium secondary battery, comprising an additive represented by any one of the following chemical formulas 1-1-1 to 1-1-3: [Chemical formula 1-1-1] 【Chemistry 4】 [Chemical formula 1-1-2] 【Transformation 5】 [Chemical formula 1-1-3] 【Transformation 6】 。

3. 3. The electrolyte solution for lithium secondary batteries according to claim 2, wherein the additive is contained in an amount of 0.05 to 3% by weight relative to 100% by weight of the electrolyte solution for lithium secondary batteries.

4. a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material; A lithium secondary battery comprising: an electrolyte solution containing a non-aqueous organic solvent, a lithium salt, and an additive represented by any one of the following chemical formulas 1-1-1 to 1-1-3: [Chemical formula 1-1-1] 【Transformation 7】 [Chemical formula 1-1-2] 【Transformation 8】 [Chemical formula 1-1-3] 【Chemistry 9】 。

5. The lithium secondary battery according to claim 4 , wherein the positive electrode active material includes a lithium nickel-based composite oxide.

6. 6. The lithium secondary battery according to claim 5, wherein the positive electrode active material comprises a lithium nickel-based composite oxide represented by the following chemical formula 11: [Chemical formula 11] Li ａ１ Ni ｘ１ M １ ｙ１ M ２ ｚ１ O ２－ｂ１ X ｂ１ In the above Chemical Formula 11, 0.9≦a1≦1.2, 0.7≦x1≦1, 0≦y1≦0.3, 0≦z1≦0.1, 0.9≦x1+y1+z1≦1.1, and 0≦b1≦0.1; M １ and M ２ are each independently one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sr, Ti, V, W, and Zr; X is one or more elements selected from the group consisting of F, P and S.

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