Additive, electrolyte for rechargeable lithium battery and rechargeable lithium battery

Abstract

The invention relates to an additive, an electrolyte for a lithium secondary battery containing the same, and a lithium secondary battery, wherein the additive is represented by the following chemical formula 1: [Chemical Formula 1] (The description of Chemical Formula 1 above is in accordance with the specification.)

Description

Technology Field

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

[0003] With the recent rapid proliferation of battery-powered electronic devices such as mobile phones, laptop computers, and electric vehicles, the demand for high-energy-density, high-capacity rechargeable batteries is increasing rapidly. Accordingly, research and development to improve the performance of lithium-ion batteries is actively underway.

[0004] A lithium secondary battery is a battery comprising a positive electrode and a negative electrode containing an active material capable of lithium ion intercalation and deintercalation, and an electrolyte, and produces electrical energy through oxidation and reduction reactions when lithium ions are intercalated / deintercalated from the positive electrode and the negative electrode.

[0005] One of the recent development directions for lithium-ion batteries is to improve high-temperature performance. Generally, lithium-ion batteries can experience problems such as increased resistance, gas generation, or reduced lifespan at high temperatures. The problem to be solved

[0007] One embodiment provides an electrolyte additive for a lithium secondary battery that improves lifespan characteristics while suppressing the increase in resistance and gas generation of the lithium secondary battery at high temperatures. means of solving the problem

[0009] One embodiment provides an electrolyte additive for a lithium secondary battery represented by the following chemical formula 1:

[0010] [Chemical Formula 1]

[0011]

[0012] In the above chemical formula 1, L 1 is a substituted or unsubstituted C1 to C20 alkylene group; and R 1 to R 4Each is independently a substituted or unsubstituted C6 to C20 aryl group.

[0013] Another embodiment provides an electrolyte containing the above electrolyte additive.

[0014] Another embodiment provides a lithium secondary battery comprising the above electrolyte. Effects of the invention

[0016] An additive according to one embodiment can suppress metal leaching from the positive electrode active material at high temperatures, thereby suppressing the increase in resistance and gas generation of the lithium secondary battery while improving lifespan characteristics. Brief explanation of the drawing

[0018] FIGS. 1 to 4 are schematic diagrams illustrating a lithium secondary battery according to one embodiment. Specific details for implementing the invention

[0019] Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples and are not intended to limit the present invention, and the present invention is defined only by the scope of the claims set forth below.

[0020] Unless otherwise specifically stated in this specification, when a part such as a layer, film, region, plate, etc. is described as being "on" another part, this includes not only cases where it is "immediately on" another part, but also cases where there is another part in between.

[0021] Unless otherwise specified in this specification, a singular form may also include a plural form. Additionally, unless otherwise specified, "A or B" may mean "including A, including B, or including A and B."

[0022] In this specification, "combination of these" may mean a mixture of components, a laminate, a composite, a copolymer, an alloy, a blend, and a reaction product, etc.

[0023] Unless otherwise specifically stated in this specification, "alkyl group" means a C1 to C20 alkyl group, "alkenyl group" means a C2 to C20 alkenyl group, "cycloalkenyl group" means a C3 to C20 cycloalkenyl group, "heterocycloalkenyl group" means a C3 to C20 heterocycloalkenyl group, "aryl group" means a C6 to C20 aryl group, "arylalkyl group" means a C6 to C20 arylalkyl group, "alkylene group" means a C1 to C20 alkylene group, "arylene group" means a C6 to C20 arylene group, "alkylarylene group" means a C6 to C20 alkylarylene group, "heteroarylene group" means a C3 to C20 heteroarylene group, and "alkoxylene group" means a C1 to C20 alkoxylene group It means.

[0024] Unless specifically stated in this specification, "substitution" means that at least one hydrogen atom is a halogen atom (F, Cl, Br, I), a hydroxyl group, a C1 to C20 alkoxy group, a nitro group, a cyano group, an amine group, an imino group, an azido group, an amidino group, a hydrazino group, a hydrazono group, a carbonyl group, a carbamyl 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 or a salt thereof, a C1 to C20 alkyl group, a C2 to C20 alkenyl group, a C2 to C20 alkynyl group, a C6 to C20 aryl group, a C3 to C20 cycloalkyl group, a C3 to C20 cycloalkenyl group, a C3 to C20 cycloalkynyl group, a C2 to C20 heterocycloalkyl group, a C2 to C20 heterocycloalkenyl group, a C2 to C20 It means substituted with a heterocycloalkynyl group, a C3 to C20 heteroaryl group, or a combination thereof.

[0025] Unless otherwise defined in the chemical formulas within this specification, if 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 said position.

[0027] (Additives)

[0028] One embodiment provides an electrolyte additive for a lithium secondary battery represented by the following chemical formula 1:

[0029] [Chemical Formula 1]

[0030]

[0032] An additive according to one embodiment symmetrically contains phosphate and aryl groups, and is oxidatively decomposed on the anode surface to form an SEI film with high stability and heat resistance. The SEI film formed on the anode surface suppresses metal leaching from the anode active material, thereby suppressing the increase in resistance and gas generation of the lithium secondary battery while improving lifespan characteristics.

[0034] The description of Chemical Formula 1 representing the above additive is as follows.

[0035] L 1 is a substituted or unsubstituted C1 to C20 alkylene group.

[0036] For example, L 1 It may be a substituted or unsubstituted C1 to C3 alkylene group.

[0038] R 1 to R 4 Each is independently a substituted or unsubstituted C6 to C20 aryl group.

[0039] For example, R 1 to R 4 All of them can be phenyl groups.

[0041] The above chemical formula 1 can be represented by the following chemical formula 1-1:

[0042] [Chemical Formula 1-1]

[0043]

[0044] In the above chemical formula 1-1, L 1 The definition of is as stated above.

[0046] Representative examples of the above chemical formula 1 are as follows:

[0047] [Chemical Formula 1-1-1]

[0048]

[0049] [Chemical Formula 1-1-2]

[0050]

[0051] [Chemical Formula 1-1-3]

[0052] .

[0054] (Electrolyte)

[0055] Another embodiment provides an electrolyte for a lithium secondary battery comprising a non-aqueous organic solvent; a lithium salt; and an additive represented by the following chemical formula 1.

[0056] [Chemical Formula 1]

[0057]

[0059] An electrolyte according to one embodiment includes the additive. The additive included in the electrolyte suppresses metal leaching from the positive electrode active material at high temperatures, thereby suppressing the increase in resistance and gas generation of the lithium secondary battery while improving lifespan characteristics.

[0061] The above additive may be included in an amount of 0.05 to 3 weight%, 0.05 to 2 weight%, or 0.05 to 1 weight% with respect to 100 weight% of the electrolyte. In this range, the additive is oxidatively decomposed on the anode surface to form an SEI film with high stability and heat resistance.

[0063] Non-aqueous organic solvents

[0064] The above-mentioned non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0065] The above-mentioned non-aqueous organic solvent may be a carbonate-based, ester-based, ether-based, ketone-based, or alcohol-based solvent, an aprotic solvent, or a combination thereof.

[0066] The above carbonate-based solvents may include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc. As ester-based solvents, methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methylpropionate, ethylpropionate, decanolide, mevalonolactone, valerolactone, caprolactone, etc. As ether-based solvents, dibutyl ether, tetraglame, diglame, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. may be used. Additionally, as ketone-based solvents, cyclohexanone, etc. may be used. As alcohol-based solvents, ethyl alcohol, isopropyl alcohol, etc. may be used, and as aprotic solvents, nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double bond, an aromatic ring, or an ether group); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane, 1,4-dioxolane; sulfolanes, etc. may be used.

[0067] The above-mentioned non-aqueous organic solvent can be used alone or in a mixture of two or more types.

[0068] In addition, when using a carbonate-based solvent, a mixture of cyclic carbonates and chain carbonates can be used, and the cyclic carbonates and chain carbonates can be mixed in a volume ratio of 1:1 to 1:9.

[0070] lithium salt

[0071] The above lithium salt is a substance that dissolves in an organic solvent and acts as a source of lithium ions within the battery, enabling the basic operation of a lithium secondary battery and facilitating the movement of lithium ions between the anode and cathode. 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, LiN(C x F 2x+1 SO2)(C y F 2y+1 It may include one or more selected from SO2)(x and y are integers from 1 to 20), lithium trifluoromethane sulfonate, lithium tetrafluoroethane sulfonate, lithium difluorobis(oxalate)phosphate (LiDFOB), and lithium bis(oxalate)borate (LiBOB).

[0073] (Lithium secondary battery)

[0074] Another embodiment provides a lithium secondary battery comprising: a positive electrode comprising a positive active material; a negative electrode comprising a negative active material; and an electrolyte comprising a non-aqueous organic solvent; a lithium salt; and an additive represented by the following chemical formula 1:

[0075] [Chemical Formula 1]

[0076]

[0078] A lithium secondary battery according to one embodiment includes an electrolyte containing the additive. The additive included in the electrolyte suppresses metal leaching from the positive electrode active material at high temperatures, thereby suppressing the increase in resistance and gas generation of the lithium secondary battery while improving lifespan characteristics.

[0080] positive electrode active material

[0081] As a positive electrode active material, a compound capable of reversible intercalation and deintercalation of lithium (a lithated intercalation compound) may be used. Specifically, one or more composite oxides of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof may be used.

[0082] The above composite oxide may be a lithium transition metal composite oxide, and specific examples include a lithium nickel-based oxide, a lithium cobalt-based oxide, a lithium manganese-based oxide, a lithium iron phosphate-based compound, a cobalt-free nickel-manganese-based oxide, or a combination thereof.

[0083] As an example, a compound represented by any one of the following chemical formulas may be used. 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 b O2(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 FePO4(0.90≤a≤1.8).

[0084] 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; L 1 is Mn, Al, or a combination thereof.

[0085] For example, the above-mentioned positive electrode active material may be a high-nickel positive electrode active material in which the nickel content relative to 100 mol% of the metal excluding lithium in the 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. The high-nickel positive electrode active material can achieve high capacity and can be applied to high-capacity, high-density lithium secondary batteries.

[0087] The above positive active material may include a lithium nickel-based composite oxide represented by the following chemical formula 11:

[0088] [Chemical Formula 11]

[0089] Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1

[0090] 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 Each is 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.

[0091] In the above chemical formula 1, 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.

[0092] For example, the above-mentioned positive electrode active material may include a lithium nickel-based complex oxide represented by the following chemical formula 12. The compound represented by the following chemical formula 12 may be described as a lithium nickel cobalt-based complex oxide:

[0093] [Chemical Formula 12]

[0094] Li a2 Ni x2 Co y2 M 3 z2 O 2-b2 X b2

[0095] In the above 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, 및 0≤b2≤0.1이고 M 3 is 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.

[0096] In the above 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.

[0097] For example, the above-mentioned positive active material may 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.

[0098] [Chemical Formula 13]

[0099] Li a3 Ni x3 Co y3 M 4 z3 M5 w3 O 2-b3 X b3

[0100] In the above 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, and 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.

[0101] In the above 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.

[0102] For example, the above-mentioned 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 described as a cobalt-free lithium nickel-manganese-based oxide.

[0103] [Chemical Formula 14]

[0104] Li a4 Ni x4 Mn y4 M 6 z4 O 2-b4 X b4

[0105] In the above 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, 및 0≤b4≤0.1이고 M6 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.

[0106] The above cobalt-free lithium nickel-manganese oxide has strong structural instability, so under high voltage and / or high temperature conditions, its structure collapses, causing transition metals (e.g., Ni) to leach out, and the stability and lifespan of the lithium secondary battery increase rapidly.

[0107] However, even when the additive according to one embodiment is used in combination with a cobalt-free lithium nickel-manganese oxide, it can suppress the structural collapse of the cobalt-free lithium nickel-manganese oxide even under high voltage and / or high temperature conditions, thereby improving the stability and lifespan characteristics of the lithium secondary battery.

[0109] anode

[0110] A positive electrode for a lithium secondary battery may include a current collector and a positive electrode active material layer formed on the current collector. The positive electrode active material layer may include a positive electrode active material and may further include a binder and / or a conductive material.

[0111] For example, the above anode may further include an additive that can serve as a sacrificial anode.

[0112] The content of the positive active material is 90% to 99.5% by weight with respect to 100% by weight of the positive active material layer, and the content of the binder and the conductive material may each be 0.5% to 5% by weight with respect to 100% by weight of the positive active material layer.

[0113] The above binder serves to adhere the positive active material particles well to each other and also to adhere the positive active material well to the current collector. Representative examples of binders include, but are not limited to, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, 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, nylon, etc.

[0114] The above conductive material is used to impart conductivity to the electrode, and any electronically conductive material that does not cause chemical changes can be used in the battery being constructed. Examples of conductive materials include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, carbon nanotube; metal-based materials in the form of metal powder or metal fibers containing copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0115] Al may be used as the current collector mentioned above, but is not limited thereto.

[0117] cathode active material

[0118] The negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

[0119] A material capable of reversibly intercalating / deintercalating the above lithium ions may be a carbon-based negative electrode active material, such as crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as amorphous, plate-like, flake-like, spherical, or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, etc.

[0120] As the above lithium metal alloy, 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 may be used.

[0121] As a material capable of doping and undoping the above lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material may be used. The Si-based negative electrode active material may be silicon, a silicon-carbon composite, SiOx (0 < x < 2), a Si-Q alloy (wherein Q is selected from alkali metals, alkaline earth metals, group 13 elements, group 14 elements (excluding Si), group 15 elements, group 16 elements, transition metals, rare earth elements, 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.

[0122] The silicon-carbon composite may be a composite of silicon and amorphous carbon. According to one embodiment, the silicon-carbon composite may be in the form of silicon particles and amorphous carbon coated on the surface of the silicon particles. For example, it may include a secondary particle (core) assembled from silicon primary particles and an amorphous carbon coating layer (shell) located on the surface of the secondary particle. The amorphous carbon may also be located between the silicon primary particles, so that, for example, the silicon primary particles may be coated with amorphous carbon. The secondary particles may be dispersed in an amorphous carbon matrix.

[0123] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include a core comprising crystalline carbon and silicon particles and an amorphous carbon coating layer located on the surface of the core.

[0124] The above Si-based or Sn-based negative electrode active material can be used in combination with a carbon-based negative electrode active material.

[0126] cathode

[0127] A negative electrode for a lithium secondary battery comprises a current collector and a negative electrode active material layer located on the current collector. The negative electrode active material layer comprises a negative electrode active material and may further comprise a binder and / or a conductive material.

[0128] For example, the negative electrode active material layer may comprise 90% to 99% by weight of negative electrode active material, 0.5% to 5% by weight of binder, and 0% to 5% by weight of conductive material.

[0129] The above binder serves to effectively bond the negative electrode active material particles to each other and also to effectively bond the negative electrode active material to the current collector. As the binder, a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof may be used.

[0130] Examples of the above-mentioned non-aqueous binders 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] The above-mentioned 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, ethylenepropylenediene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0132] When a water-based binder is used as the above-mentioned cathode binder, a cellulose-based compound capable of imparting viscosity may be further included. As this cellulose-based compound, one or more types such as carboxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, or alkali metal salts thereof may be mixed and used. Na, K, or Li may be used as the alkali metal.

[0133] The above dry binder is a polymer material capable of fiberization, and may be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0134] The above conductive material is used to impart conductivity to the electrode, and any electronically conductive material that does not cause chemical changes can be used in the battery being constructed. Specific examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, carbon nanotube; metal-based materials in the form of metal powder or metal fibers including copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0135] As the above-mentioned cathode current collector, a material 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 may be used.

[0137] separator

[0138] Depending on the type of lithium secondary battery, a separator may be present between the positive and negative electrodes. As such a separator, polyethylene, polypropylene, polyvinylidene fluoride, or multilayer films of two or more layers thereof may be used, and of course, mixed multilayer films such as polyethylene / polypropylene two-layer separators, polyethylene / polypropylene / polyethylene three-layer separators, and polypropylene / polyethylene / polypropylene three-layer separators may be used.

[0139] The above separator may 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.

[0140] The porous substrate may be a polymer membrane formed from any one of the following: 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 oxide; cyclic olefin copolymer; polyphenylene sulfide; polyethylene naphthalate; glass fiber; Teflon; and polytetrafluoroethylene, or a copolymer or mixture of two or more of these.

[0141] The above organic material may include a polyvinylidene fluoride-based antibody or a (meth)acrylic-based polymer.

[0142] The above inorganic materials are Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, It may include, but is not limited to, inorganic particles selected from SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof.

[0143] The above organic and inorganic materials may exist mixed in a single coating layer, or may exist in a stacked form with a coating layer containing organic materials and a coating layer containing inorganic materials.

[0145] lithium secondary battery

[0146] Lithium secondary batteries can be classified into cylindrical, prismatic, pouch, coin, etc., depending on their shape. FIGS. 1 to 4 are schematic diagrams illustrating lithium secondary batteries according to one embodiment, where FIG. 1 is a cylindrical battery, FIG. 2 is a prismatic battery, and FIGS. 3 and 4 are pouch-type batteries. Referring to FIGS. 1 to 4, the lithium secondary battery (100) may include an electrode assembly (40) having a separator (30) interposed between a positive electrode (10) and a negative electrode (20), and a case (50) in which the electrode assembly (40) is housed. The positive electrode (10), the negative electrode (20), and the separator (30) may be impregnated with an electrolyte (not shown). The lithium secondary battery (100) may include a sealing member (60) that seals the case (50) as in FIG. 1. In addition, in FIG. 2, the lithium secondary battery (100) may include a positive lead tab (11) and a positive terminal (12), a negative lead tab (21) and a negative terminal (22). As shown in FIG. 3 and FIG. 4, the lithium secondary battery (100) may include an electrode tab (70), namely a positive tab (71) and a negative tab (72), which serve as an electrical path to guide the current formed in the electrode assembly (40) to the outside.

[0148] A lithium secondary battery according to one embodiment of the present invention may be applied to automobiles, mobile phones, and / or various types of electric devices, etc., but the present invention is not limited thereto.

[0150] Examples and comparative examples of the present invention are described below. However, the following examples are merely one example of the present invention, and the present invention is not limited to the following examples.

[0152] Synthesis Example 1: Compound represented by Chemical Formula 1-1-1

[0153] 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. Afterward, the precipitate was filtered, and the resulting compound was dissolved in a small amount of acetone. The solution was slowly added dropwise to 500 ml of methylene chloride using a dropping funnel, and the resulting reaction product was filtered, purified, and vacuum dried to obtain the compound represented by the chemical formula 1-1-1.

[0154] (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))

[0155] [Chemical Formula 1-1-1]

[0156]

[0158] Example 1

[0159] (1) Preparation of electrolyte

[0160] An electrolyte was prepared by dissolving 1.15 M LiPF6 in a non-aqueous organic solvent mixed with 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 the chemical formula 1-1-1.

[0161] (However, in the above electrolyte composition, the “weight%” content of the additive is based on 100 weight% of the total electrolyte (lithium salt + non-aqueous organic solvent + additive).)

[0162] (2) Manufacturing of lithium secondary batteries

[0163] LiNi as a positive electrode active material0.75 Mn 0.23 Al 0.02 O2, polyvinylidene fluoride as a binder, and acetylene black as a conductive material are mixed in a weight ratio of 96:3:1, respectively. N - A positive electrode active material slurry was prepared by dispersing in methylpyrrolidone.

[0164] The above positive active material slurry was coated onto an Al foil with a thickness of 15 μm, dried at 100°C, and then pressed to produce a positive electrode.

[0165] A mixture of artificial graphite and a Si-C composite mixed in a weight ratio of 93:7 was used as the negative electrode active material, and a negative electrode active material slurry was prepared by mixing the negative electrode active material, a styrene-butadiene rubber binder, and carboxymethylcellulose in a weight ratio of 98:1:1, respectively, and dispersing them in distilled water.

[0166] The above Si-C composite used a core containing artificial graphite and silicon particles and a coal-based pitch coated on the surface of the core.

[0167] The above cathode active material slurry was coated onto a 10㎛ thick Cu foil, dried at 100℃, and then pressed to manufacture a cathode.

[0168] An electrode assembly was manufactured by assembling the above positive electrode and the above negative electrode with a separator made of polyethylene material with a thickness of 10 μm, and a lithium secondary battery was manufactured by injecting the above electrolyte.

[0170] Example 2

[0171] An electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1 above, except that the content of the additive was changed to 1 weight%.

[0173] Example 3

[0174] An electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1 above, except that the content of the additive was changed to 2 weight%.

[0176] Example 4

[0177] LiNi as the positive active material 0.9 Co 0.05 Al 0.05 The electrolyte and lithium secondary battery were manufactured in the same manner as in Example 1 above, except that the O2 was changed.

[0179] Example 5

[0180] An electrolyte and a lithium secondary battery were prepared in the same manner as in Example 4 above, except that the content of the additive was changed to 1 weight%.

[0182] Example 6

[0183] An electrolyte and a lithium secondary battery were prepared in the same manner as in Example 4 above, except that the content of the additive was changed to 2 weight%.

[0185] Comparative Example 1

[0186] An electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1 above, except that no additives were added.

[0188] Comparative Example 2

[0189] An electrolyte 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, Aldrich) was used instead of the additive represented by the chemical formula 1-1-1 above.

[0190] [Chemical Formula A]

[0191]

[0193] Comparative Example 3

[0194] An electrolyte 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, Aldrich) was used instead of the additive represented by the chemical formula 1-1-1 above.

[0195] [Chemical Formula B]

[0196]

[0198] Comparative Example 4

[0199] LiNi as the positive active material 0.9 Co 0.05 Al 0.05 The electrolyte and lithium secondary battery were manufactured in the same manner as Comparative Example 1 above, except that the O2 was changed.

[0201] Comparative Example 5

[0202] LiNi as the positive active material 0.9 Co 0.05 Al 0.05 The electrolyte and lithium secondary battery were manufactured in the same manner as Comparative Example 2 above, except that the O2 was changed.

[0204] Comparative Example 6

[0205] LiNi as the positive active material 0.9 Co 0.05 Al 0.05 The electrolyte and lithium secondary battery were manufactured in the same manner as Comparative Example 3 above, except that the O2 was changed.

[0207] Evaluation Example 1: Evaluation of High-Temperature Storage Characteristics

[0208] (1) DCIR growth rate

[0209] For the lithium secondary batteries according to Examples 1 to 6 and Comparative Examples 1 to 6, the initial DC resistance (DCIR) was measured using the △V / △I (change in voltage / change in current) value, the maximum energy state inside the battery was made to a fully charged state (SOC 100%), and after storing it at a high temperature (60℃) for 30 days in this state, the DC resistance was measured, and the DCIR increase rate (%) was calculated according to Equation 1 below, and the results are shown in Table 1 below.

[0210] [Equation 1]

[0211] DCIR growth rate = (DCIR after 30 days / Initial DCIR) * 100

[0213] division Initial DCIR(mΩ) DCIR (mΩ) after high-temperature storage DCIR growth rate (%) after high-temperature storage Comparative Example 1 11.29 13.55 120 Comparative Example 2 11.56 13.64 118 Comparative Example 3 12.30 15.01 122 Comparative Example 4 9.85 12.12 123 Comparative Example 5 9.96 11.95 120 Comparative Example 6 10.12 12.45 123 Example 1 11.15 11.48 103 Example 2 11.18 11.29 101 Example 3 11.60 12.30 106 Example 4 9.86 11.04 112 Example 5 9.95 10.95 110 Example 6 10.23 11.76 115

[0215] (2) Amount of gas generated

[0216] For the lithium secondary batteries according to Examples 1 to 3 and Comparative Examples 1 to 3, the maximum energy state inside the battery was made to a fully charged state (SOC 100%), and after storing them in this state at a high temperature (60°C) for 1 day or 7 days, the amount of gas generated was evaluated and the results are shown in Table 2 below.

[0217] The amount of gas generated was calculated by measuring the volume change before and after high-temperature storage and converting it into a change in mass using Archimedes' method.

[0219] division Gas generation amount (mL) after high-temperature storage 1 day 7 days Comparative Example 1 0.031 0.076 Comparative Example 2 0.025 0.065 Comparative Example 3 0.021 0.070 Example 1 0.023 0.046 Example 2 0.022 0.038 Example 3 0.024 0.049

[0221] Evaluation Example 2: Evaluation of High-Temperature Charge / Discharge Characteristics

[0222] For the lithium secondary batteries according to Examples 1 to 3 and Comparative Examples 1 to 3, the capacity retention rate was expressed according to the following Equation 2 after 200 cycles of charge and discharge under conditions of 45°C, 0.33C charge (CC / CV, 4.45V, 0.025C Cut-off) / 1.0C discharge (CC, 2.5V Cut-off).

[0223] [Equation 2]

[0224] Capacity retention rate = (Discharge capacity after 200 cycles / Discharge capacity after 1 cycle) * 100

[0226] division Dose retention rate (%) Comparative Example 1 85.3 Comparative Example 2 86.5 Comparative Example 3 84.2 Example 1 92.1 Example 2 93.3 Example 3 91.8

[0228] synthesis

[0229] According to Table 1, the lithium secondary batteries of Examples 1 to 6 suppressed the increase in resistance at high temperatures compared to the lithium secondary batteries of Comparative Examples 1 to 6.

[0230] In addition, according to Tables 2 and 3, the lithium secondary batteries of Examples 1 to 3 have improved lifespan characteristics while suppressing gas generation at high temperatures compared to the lithium secondary batteries of Comparative Examples 1 to 3.

[0231] From this, it can be seen that the additive according to one embodiment suppresses metal leaching from the positive electrode active material at high temperatures, thereby suppressing the increase in resistance and gas generation of the lithium secondary battery while improving lifespan characteristics.

[0232] Furthermore, it can be seen that the additive according to one embodiment suppresses structural collapse of the cobalt-free lithium nickel-manganese oxide even when used in combination with the cobalt-free lithium nickel-manganese oxide, even under high voltage and / or high temperature conditions.

[0234] Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto and can be implemented with various modifications within the scope of the claims, the detailed description of the invention, and the attached drawings, and it is obvious that such modifications also fall within the scope of the present invention. Explanation of the symbols

[0236] 100: Lithium secondary battery 10: Positive electrode 11: Positive lead tab 12: Positive terminal 20: Cathode 21: Cathode lead tab 22: Negative terminal 30: Separator 40: Electrode assembly 50: Case 60: Sealing member 70: Electrode tab 71: Positive tab 72: Negative tab

Claims

Claim 1 Electrolyte additive for lithium secondary batteries represented by any one of the following chemical formulas 1-1-1 to 1-1-3: [Chemical Formula 1-1-1] [Chemical Formula 1-1-2] [Chemical Formula 1-1-3] . Claim 2 delete Claim 3 delete Claim 4 delete Claim 5 delete Claim 6 Electrolyte for a lithium secondary battery comprising: 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] [Chemical Formula 1-1-2] [Chemical Formula 1-1-3] . Claim 7 In claim 6, the above additive is an electrolyte for a lithium secondary battery containing 0.05 to 3 weight% with respect to 100 weight% of the electrolyte. Claim 8 A lithium secondary battery comprising: a positive electrode comprising a positive active material; a negative electrode comprising a negative active material; and a non-aqueous organic solvent; a lithium salt; and an electrolyte comprising an additive represented by any one of the following chemical formulas 1-1-1 to 1-1-3: [Chemical Formula 1-1-1] [Chemical Formula 1-1-2] [Chemical Formula 1-1-3] . Claim 9 In claim 8, the positive active material comprises a lithium secondary battery containing a lithium nickel-based composite oxide. Claim 10 In claim 9, the positive electrode active material comprises a lithium secondary battery comprising 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 Each is 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.

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