Electrolyte for lithium secondary battery and lithium secondary battery comprising same

Abstract

The present invention relates to an electrolyte for a lithium secondary battery and a lithium secondary battery comprising same. The electrolyte may include: a non-aqueous organic solvent; a lithium salt; and an additive, wherein the additive may be represented by chemical formula 1 or chemical formula 2. The details of chemical formula 1 and chemical formula 2 are as described in the specification.

Description

Electrolyte for lithium secondary batteries and lithium secondary batteries containing the same

[0001] The present invention relates to an electrolyte for a lithium secondary battery and a lithium secondary battery including the same.

[0002]

[0003] The recent rapid proliferation of battery-powered electronic devices, such as mobile phones, laptops, and electric vehicles, has led to a rapid increase in demand for high-energy density, high-capacity secondary batteries. Accordingly, active research and development is underway to improve the performance of lithium secondary batteries.

[0004] A lithium secondary battery is a battery that includes a positive electrode and a negative electrode that contain active materials capable of intercalating and deintercalating lithium ions, and an electrolyte, and produces electrical energy through oxidation and reduction reactions when lithium ions are intercalated / deintercalated from the positive electrode and negative electrode.

[0005] The electrolyte of these lithium secondary batteries consists of a lithium salt dissolved in a non-aqueous organic solvent. The characteristics of a lithium secondary battery are determined by complex reactions between the positive electrode and electrolyte, and the negative electrode and electrolyte. Therefore, the use of an appropriate electrolyte is a critical factor in improving lithium secondary battery performance.

[0006]

[0007] One embodiment provides an electrolyte for a lithium secondary battery having an excellent cathode stabilization effect. The effect may be even more excellent at high temperatures.

[0008] Another embodiment provides a lithium secondary battery comprising the electrolyte.

[0009]

[0010] One embodiment provides an electrolyte for a lithium secondary battery, comprising a non-aqueous organic solvent; a lithium salt; and an additive. The additive may be represented by the following chemical formula 1 or the following chemical formula 2:

[0011] [Chemical Formula 1]

[0012]

[0013] [Chemical Formula 2]

[0014]

[0015] In the above chemical formulas 1 and 2,

[0016] The above R1 to R8 may each independently be hydrogen, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C2 to C10 alkenyl group, or a substituted or unsubstituted C2 to C10 alkynyl group or a hydroxy group,

[0017] At least one of the above R1 to R4 may be a hydroxy group,

[0018] At least one of the above R5 to R8 may be a hydroxy group,

[0019] The above n can be 1 or 2.

[0020] Another embodiment provides a lithium secondary battery comprising: a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material; and an electrolyte for the lithium secondary battery.

[0021]

[0022] An electrolyte for a lithium secondary battery according to one embodiment may have an excellent positive electrode stabilization effect. The effect may be even more excellent at high temperatures.

[0023]

[0024] FIG. 1 is a schematic diagram illustrating a lithium secondary battery according to embodiments of the present invention.

[0025] FIGS. 2 to 5 are schematic diagrams illustrating a lithium secondary battery according to one embodiment. FIG. 2 can be said to be a cylindrical battery, FIG. 3 a square battery, and FIGS. 4 and 5 a pouch battery.

[0026]

[0027] To fully understand the structure and effects of the present invention, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various forms and subject to various modifications. However, the description of these embodiments is provided solely to ensure a complete disclosure of the present invention and to fully inform those skilled in the art of the invention of the scope of the invention.

[0028] In this specification, when a component is referred to as being on another component, it means that it can be formed directly on the other component, or a third component may be interposed between them. Furthermore, in the drawings, the thicknesses of the components are exaggerated for the sake of clarity. Parts designated by the same reference numerals throughout the specification represent the same components.

[0029] Unless otherwise specified herein, the singular may also include the plural. Furthermore, unless otherwise specified, "A or B" may mean "including A, including B, or including A and B." As used herein, "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components.

[0030] As used herein, “combination thereof” may mean mixtures, laminates, composites, copolymers, alloys, blends, and reaction products of the components.

[0031] Unless otherwise defined herein, the particle size may be the average particle size. In addition, the particle size refers to the average particle size (D50), which means the diameter of particles with a cumulative volume of 50% by volume in a particle size distribution. The average particle size (D50) can be measured by a method well known to those skilled in the art, for example, by measuring with a particle size analyzer, or by measuring with a transmission electron microscope (TEM) photograph or a scanning electron microscope (SEM) photograph. Alternatively, the average particle size (D50) value can be obtained by measuring with a measuring device that utilizes dynamic light-scattering, performing data analysis to count the number of particles for each particle size range, and calculating from the counted number. Alternatively, the average particle size (D50) value can be obtained by measuring with a laser diffraction method. When measuring by laser diffraction, more specifically, after the particles to be measured are dispersed in a dispersion medium, they are introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000) and irradiated with ultrasonic waves of approximately 28 kHz at an output of 60 W, and the average particle size (D50) based on 50% of the particle size distribution in the measuring device can be calculated.

[0032] As used herein, “substituted” means, unless otherwise defined, that at least one hydrogen in a substituent or compound is substituted with deuterium, a halogen group, a hydroxyl group, an amino group, a C1 to C30 amine group, a nitro group, a C1 to C40 silyl group, a C1 to C30 alkyl group, a C1 to C10 alkylsilyl group, a C6 to C30 arylsilyl group, a C3 to C30 cycloalkyl group, a C3 to C30 heterocycloalkyl group, a C6 to C30 aryl group, a C2 to C30 heteroaryl group, a C1 to C20 alkoxy group, a C1 to C10 fluoroalkyl group, a cyano group, or a combination thereof.

[0033] Specifically, "substituted" may mean that at least one hydrogen in a substituent or compound is replaced by a deuterium, a halogen group, a C1 to C30 alkyl group, a C1 to C10 alkylsilyl group, a C6 to C30 arylsilyl group, a C3 to C30 cycloalkyl group, a C3 to C30 heterocycloalkyl group, a C6 to C30 aryl group, a C2 to C30 heteroaryl group, a C1 to C10 fluoroalkyl group, or a cyano group. For example, "substituted" may mean that at least one hydrogen in a substituent or compound is replaced by a deuterium, a halogen group, a C1 to C20 alkyl group, a C6 to C30 aryl group, a C1 to C10 fluoroalkyl group, or a cyano group. Alternatively, "substituted" may mean that at least one hydrogen in the substituent or compound is replaced with a deuterium atom, a halogen group, a C1 to C5 alkyl group, a C6 to C18 aryl group, a C1 to C5 fluoroalkyl group, or a cyano group. As an example, "substituted" may mean that at least one hydrogen in the substituent or compound is replaced with a deuterium atom, a cyano group, a halogen group, a methyl group, an ethyl group, a propyl group, a butyl group, a phenyl group, a biphenyl group, a terphenyl group, a trifluoromethyl group, or a naphthyl group.

[0034]

[0035] Figure 1 is a schematic conceptual diagram illustrating a lithium secondary battery according to embodiments of the present invention. Referring to Figure 1, the lithium secondary battery may include a positive electrode (10), a negative electrode (20), a separator (30), and an electrolyte (ELL).

[0036] The positive electrode (10) and the negative electrode (20) may be spaced apart from each other with a separator (30) therebetween. The separator (30) may be placed 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).

[0037] The electrolyte (ELL) may be a medium for transferring lithium ions between the positive electrode (10) and the negative electrode (20). Within the electrolyte (ELL), the lithium ions may pass through the separator (30) and move toward the positive electrode (10) or the negative electrode (20).

[0038]

[0039] Bipolar (10)

[0040] A positive electrode (10) for a lithium secondary battery may include a current collector (COL1) and a positive electrode active material layer (AML1) formed on the current collector (COL1). The positive electrode active material layer (AML1) includes a positive electrode active material and may further include a binder and / or a conductive material.

[0041] For example, the anode (10) may further include an additive that can act as a sacrificial anode.

[0042] The content of the positive electrode active material in the positive electrode active material layer (AML1) may be 90 wt% to 99.5 wt% with respect to 100 wt% of the positive electrode active material layer (AML1). The contents of the binder and the conductive material may each be 0.5 wt% to 5 wt% with respect to 100 wt% of the positive electrode active material layer (AML1).

[0043] The above binder serves to adhere the positive electrode active material particles well to each other and also to adhere the positive electrode active material well to the current collector (COL1). Representative examples of the binder 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, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, nylon, etc.

[0044] The conductive material is used to provide conductivity to the electrode, and any material that does not cause chemical changes and is electronically conductive can be used in the battery. 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 containing copper, nickel, aluminum, silver, etc. in the form of metal powder or metal fiber; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0045] Al can be used as the current collector (COL1), but is not limited thereto.

[0046]

[0047] positive electrode active material

[0048] As the cathode active material in the cathode active material layer (AML1), a compound capable of reversible intercalation and deintercalation of lithium (lithiated intercalation compound) can be used. Specifically, one or more of a composite oxide of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof can be used.

[0049] The above composite oxide may be a lithium transition metal composite oxide, and specific examples thereof include lithium nickel-based oxide, lithium cobalt-based oxide, lithium manganese-based oxide, lithium iron phosphate-based compound, cobalt-free nickel-manganese-based oxide, or a combination thereof.

[0050] 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); Lia 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).

[0051] In the 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 L1 is Mn, Al, or a combination thereof.

[0052] For example, the cathode active material may be a high-nickel cathode active material in which the nickel content 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, based on 100 mol% of metals excluding lithium in the lithium transition metal composite oxide. The high-nickel cathode active material can realize high capacity and thus can be applied to high-capacity, high-density lithium secondary batteries.

[0053]

[0054] Cathode (20)

[0055] A negative electrode (20) for a lithium secondary battery includes a current collector (COL2) and a negative electrode active material layer (AML2) positioned on the current collector (COL2). The negative electrode active material layer (AML2) includes a negative electrode active material and may further include a binder and / or a conductive material.

[0056] For example, the negative active material layer (AML2) may include 90 to 99 wt% of the negative active material, 0.5 to 5 wt% of the binder, and 0 to 5 wt% of the conductive material.

[0057] The above binder serves to adhere the negative electrode active material particles well to each other and also to adhere the negative electrode active material well to the current collector (COL2). The binder may be a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0058] Examples of the non-aqueous binder include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or combinations thereof.

[0059] The above-mentioned aqueous binder may be selected from styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluoroelastomer, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0060] When using an aqueous binder as the above-mentioned negative electrode binder, a cellulose-based compound capable of imparting viscosity may be further included. The cellulose-based compound may be a mixture of one or more of carboxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, or an alkali metal salt thereof. The alkali metal may be Na, K, or Li.

[0061] The above dry binder is a polymeric material capable of being fiberized, and may be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0062] The conductive material is used to provide conductivity to the electrode, and any material that does not cause chemical changes and is electronically conductive can be used in the battery. Specific examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes; metal-based materials in the form of metal powder or metal fibers, including copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0063] The current collector (COL2) may be selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrate coated with a conductive metal, and combinations thereof.

[0064]

[0065] Negative active material

[0066] The negative active material in the negative active material layer (AML2) 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.

[0067] The material capable of reversibly intercalating / deintercalating the lithium ions may include a carbon-based negative electrode active material, for example, crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as natural graphite or artificial graphite in an amorphous, plate-like, flake-like, spherical, or fibrous form, and examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, and the like.

[0068] 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 can be used.

[0069] As the material capable of doping and dedoping the 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.

[0070] 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, the composite may include secondary particles (cores) in which silicon primary particles are assembled and an amorphous carbon coating layer (shell) positioned on the surface of the secondary particles. The amorphous carbon may also be positioned between the silicon primary particles, such that, for example, the silicon primary particles may be coated with amorphous carbon. The secondary particles may be dispersed and present in an amorphous carbon matrix.

[0071] The silicon-carbon composite may further comprise crystalline carbon. For example, the silicon-carbon composite may comprise a core comprising crystalline carbon and silicon particles and an amorphous carbon coating layer positioned on the surface of the core.

[0072] The above Si-based negative electrode active material or Sn-based negative electrode active material can be used in a mixture with a carbon-based negative electrode active material.

[0073]

[0074] Separator (30)

[0075] Depending on the type of lithium secondary battery, a separator (30) may be present between the positive electrode (10) and the negative electrode (20). As the separator (30), a multilayer film of two or more layers of polyethylene, polypropylene, polyvinylidene fluoride, or these may be used, and of course, a mixed multilayer film such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, or a polypropylene / polyethylene / polypropylene three-layer separator may be used.

[0076] The separator (30) may include a porous substrate and a coating layer including an organic material, an inorganic material, or a combination thereof located on one or both sides of the porous substrate.

[0077] The above porous substrate may be a polymer film formed of 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, polyarylether ketone, 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 thereof.

[0078] The organic material may include a polyvinylidene fluoride polymer or a (meth)acrylic polymer.

[0079] The above inorganic materials are Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, It may include inorganic particles selected from, but not limited to, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof.

[0080] The organic and inorganic substances may be mixed and present in one coating layer, or a coating layer including an organic substance and a coating layer including an inorganic substance may be present in a laminated form.

[0081]

[0082] Electrolyte (ELL)

[0083] The electrolyte (ELL) for a lithium secondary battery contains a non-aqueous organic solvent and a lithium salt.

[0084] The above non-aqueous organic solvent acts as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0085] The above 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.

[0086] Examples of the above carbonate solvents that can be used include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC).

[0087] Ester solvents that can be used include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, caprolactone, and propyl propionate (PP).

[0088] Examples of ether solvents that can be used include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and tetrahydrofuran. In addition, examples of ketone solvents that can be used include cyclohexanone. Examples of alcohol solvents that can be used include ethyl alcohol and isopropyl alcohol, and 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 and may include 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.

[0089] The above non-aqueous organic solvents can be used alone or in combination of two or more.

[0090] In addition, when using a carbonate solvent, 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.

[0091] The above lithium salt is a substance that dissolves in an organic solvent and acts as a source of lithium ions in the battery, enabling the basic operation of a lithium secondary battery and promoting 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, LiN(C x F 2x+1 SO2)(C y F 2y+1SO2) (x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluoro(oxalato)borate (LiDFOB), lithium difluorobis(oxalato)phosphate (LiDFBOP), and lithium bis(oxalato)borate (LiBOB).

[0092] Hereinafter, the electrolyte of a lithium secondary battery according to embodiments of the present invention will be described in more detail.

[0093] An electrolyte for a lithium secondary battery according to one embodiment may include a non-aqueous organic solvent; a lithium salt; and an additive. The additive may be represented by the following chemical formula 1 or the following chemical formula 2:

[0094] [Chemical Formula 1]

[0095]

[0096] [Chemical Formula 2]

[0097]

[0098] In the above chemical formulas 1 and 2,

[0099] The above R1 to R8 may each independently be hydrogen, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C2 to C10 alkenyl group, or a substituted or unsubstituted C2 to C10 alkynyl group or a hydroxy group,

[0100] At least one of the above R1 to R4 may be a hydroxy group,

[0101] At least one of the above R5 to R8 may be a hydroxy group,

[0102] The above n can be 1 or 2.

[0103] A detailed description of the above additives will be provided separately later.

[0104] The above electrolyte can be manufactured through a mixing process by dissolving a lithium salt in a non-aqueous organic solvent and adding an additive represented by Chemical Formula 1 or Chemical Formula 2. The process of mixing the electrolyte is widely known in the field of electrolyte manufacturing, and those skilled in the art will be able to select and use it appropriately.

[0105] In one embodiment, the non-aqueous organic solvent may include an ester solvent and a carbonate solvent.

[0106] In one embodiment, the non-aqueous organic solvent may be a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC).

[0107] In one embodiment, the ethylene carbonate (EC) may be included in an amount of 10% to 30% by volume based on the total amount of the non-aqueous organic solvent. The ethyl methyl carbonate (EMC) may be included in an amount of 30% to 50% by volume based on the total amount of the non-aqueous organic solvent. The dimethyl carbonate (DMC) may be included in an amount of 30% to 50% by volume based on the total amount of the non-aqueous organic solvent. In another embodiment, the ethylene carbonate (EC) may be included in an amount of 15% to 25% by volume based on the total amount of the non-aqueous organic solvent. The ethyl methyl carbonate (EMC) may be included in an amount of 35% to 45% by volume based on the total amount of the non-aqueous organic solvent. The above dimethyl carbonate (DMC) may be included in an amount of 35% to 45% by volume based on the total amount of the non-aqueous organic solvent.

[0108] The above ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) may have a volume ratio of 1:a:b. The a may be 1 to 3, and the b may be 1 to 3.

[0109] In one embodiment, the lithium salt is 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 SO2) (x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluoro(oxalato)borate (LiDFOB), lithium difluorobis(oxalato)phosphate (LiDFBOP), and lithium bis(oxalato)borate (LiBOB).

[0110] In one embodiment, the lithium salt may be LiPF6.

[0111] The concentration of the lithium salt may be 0.1 M to 2.0 M. Specifically, the concentration of the lithium salt may be 0.5 M or more, or 1.0 M or more. The concentration of the lithium salt may be 2.0 M or less, 1.7 M or less, or 1.5 M or less. In the present invention, when the concentration is 0.1 M to 2.0 M, the conductivity of the electrolyte and the viscosity of the electrolyte can be appropriately maintained.

[0112]

[0113] additives

[0114] The additive according to the present invention may be represented by the following chemical formula 1 or the following chemical formula 2:

[0115] [Chemical Formula 1]

[0116]

[0117] [Chemical Formula 2]

[0118]

[0119] In the above chemical formulas 1 and 2,

[0120] The above R1 to R8 may each independently be hydrogen, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C2 to C10 alkenyl group, or a substituted or unsubstituted C2 to C10 alkynyl group or a hydroxy group,

[0121] At least one of the above R1 to R4 may be a hydroxy group,

[0122] At least one of the above R5 to R8 may be a hydroxy group,

[0123] The above n can be 1 or 2.

[0124] In one embodiment, R1 to R8 may each independently be hydrogen, a substituted or unsubstituted C1 to C5 alkyl group, a substituted or unsubstituted C2 to C5 alkenyl group, or a substituted or unsubstituted C2 to C5 alkynyl group or a hydroxy group.

[0125] In one embodiment, at least one of R2 and R3 may be a hydroxyl group, and at least one of R6 and R7 may be a hydroxyl group.

[0126] In one embodiment, R2 may be a hydroxyl group and R6 may be a hydroxyl group.

[0127] In one embodiment, the additive may be represented by the following chemical formula 1A.

[0128] [Chemical Formula 1A]

[0129]

[0130] The above R 1A Inland R 4A may each independently be hydrogen, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C2 to C10 alkenyl group, or a substituted or unsubstituted C2 to C10 alkynyl group or a hydroxy group,

[0131] The above R1A Inland R 4A At least one of which may be a hydroxyl group.

[0132] In one embodiment, the R 2A and R 3A At least one of which may be a hydroxyl group.

[0133] In one embodiment, the R 2A may be a hydroxyl group.

[0134] In one embodiment, the additive may be one selected from the group consisting of the following chemical formulae 1B to 2A:

[0135] [Chemical Formula 1B]

[0136]

[0137] [Chemical Formula 1C]

[0138]

[0139] [Chemical Formula 1D]

[0140]

[0141] [Chemical Formula 1E]

[0142]

[0143] [Chemical Formula 2A]

[0144] .

[0145] The additive according to the present invention may include a phenol moiety and a dioxolane derivative moiety. The dioxolane derivative moiety may be, for example, a dioxolane moiety, a dioxane moiety, or a dioxolan-2-one moiety.

[0146] The phenol moiety can stabilize the positive electrode by removing unstable oxygen (e.g., active oxygen) generated due to positive electrode deterioration. As lithium ion batteries are repeatedly charged and discharged, unstable oxygen may be generated internally. The unstable oxygen may attack the positive electrode surface and cause the positive electrode to deteriorate. The phenol moiety can effectively remove such unstable oxygen, thereby significantly improving positive electrode deterioration. Through this, the additive according to the present invention can improve the performance of the battery. The above-described positive electrode stabilizing effect of the phenol moiety can be more excellent at high voltage and / or high temperature. Specifically, the high voltage may be 4.25 V or higher or 4.5 V or higher. The high temperature may be 150°C or higher or 200°C or higher.

[0147] The above dioxolane derivative moiety can stabilize the positive electrode by contributing to the formation of a robust CEI (Cathode Electrolyte Interphase) on the positive electrode surface. In addition, it can stabilize the positive electrode by removing unstable oxygen (e.g., active oxygen) generated due to positive electrode deterioration. Through this, the additive according to the present invention can improve the performance of the battery. The above-described positive electrode stabilizing effect of the dioxolane derivative moiety can be more excellent at high voltage and / or high temperature. Specifically, the high voltage can be 4.25 V or higher or 4.5 V or higher. The high temperature can be 150°C or higher or 200°C or higher.

[0148] The additive according to the present invention may have an excellent function of suppressing thermal runaway.

[0149] Since the additive according to the present invention includes a phenol moiety and a dioxolane derivative moiety in a covalently bonded form, the above-described effects can be more effectively expressed. Due to the structural characteristics described above, the additive according to the present invention can exhibit a significantly superior anode stabilization effect compared to an additive containing pure phenol.

[0150] The content of the additive according to the present invention may be 0.01 to 10 parts by weight based on 100 parts by weight of the electrolyte for a lithium secondary battery. Specifically, the content of the additive may be 0.01 to 5 parts by weight based on 100 parts by weight of the electrolyte for a lithium secondary battery, or may be 0.01 to 3 parts by weight, or may be 0.1 to 3 parts by weight. The content of the additive may refer to the weight of the additive included in the electrolyte with respect to the total weight of the electrolyte. When the content of the additive satisfies the above range, the positive electrode stabilization effect may be maximized. The effect may be more excellent at high temperatures.

[0151] If the content of the above additive is below the above content range, the additive may not sufficiently perform its function of removing unstable oxygen, resulting in a lack of anode stabilization effect. If the content of the above additive exceeds the above content range, the additive itself may act as a resistance-inducing substance, resulting in a lack of anode stabilization effect.

[0152]

[0153] lithium secondary battery

[0154] Lithium secondary batteries can be classified into cylindrical, square, pouch, coin, etc. types according to their shapes. FIGS. 2 to 5 are schematic diagrams illustrating lithium secondary batteries according to one embodiment, wherein FIG. 2 can be said to be a cylindrical battery, FIG. 3 a square battery, and FIGS. 4 and 5 a pouch battery. Referring to FIGS. 2 to 4, a 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 built. 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 shown in FIG. 2. In addition, in FIG. 3, the lithium secondary battery (100) may include a positive lead tab (11), a positive terminal (12), a negative lead tab (21), and a negative terminal (22). As in FIGS. 4 and 5, the lithium secondary battery (100) may include electrode tabs (70), i.e., a positive tab (71) and a negative tab (72), which serve as electrical paths for inducing current formed in the electrode assembly (40) to the outside.

[0155] A lithium secondary battery according to one embodiment of the present invention can be applied to automobiles, mobile phones, and / or various types of electrical devices, but the present invention is not limited thereto.

[0156] A lithium secondary battery according to the present invention may include a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material; and an electrolyte for a lithium secondary battery as described above.

[0157] The above positive electrode active material may include a lithium composite oxide represented by the following chemical formula 3:

[0158] [Chemical Formula 3]

[0159] Li x M 1 y M 2 z M3 1-y-z O 2-a X a

[0160] 0.5≤x≤1.8, 0≤a≤0.05, 0 <y≤1, 0≤z≤1, 및 0≤y+z≤1이고,

[0161] M 1 , M 2 and M 3 Each may independently include one or more elements selected from metals such as Ni, Co, Mn, Al, B, Ba, Ca, Ce, Cr, Fe, Mo, Nb, Si, Sr, Mg, Ti, V, W, Zr or La and combinations thereof,

[0162] X may contain one or more elements selected from F, S, P or Cl.

[0163] In one embodiment, in the chemical formula 3, M 1 can be Ni. Or, in the above chemical formula 3, M 1 is Ni, and M 2 is Co, and M 3 can be Al.

[0164] The above negative electrode active material may be a carbon-based negative electrode active material, a Si-based negative electrode active material, a Sn-based negative electrode active material, or a combination thereof.

[0165] In one embodiment, the negative electrode active material may be a Si-based negative electrode active material.

[0166] Lithium secondary batteries can generate reactive oxygen species (ROS) within the battery due to irreversible structural changes in the positive and negative electrodes during repeated charging and discharging. These ROS can attack internal materials and accelerate battery deterioration. This ROS-induced deterioration can be particularly problematic at high voltages and / or high temperatures.

[0167] Lithium secondary batteries may experience problems with the anode and cathode films deteriorating due to acid attack generated inside the battery. When the non-aqueous electrolyte is decomposed during the initial charge and discharge of lithium secondary batteries, a film with passive ability is formed on the surfaces of the anode and cathode, which can improve high-temperature storage characteristics. The film is formed by HF generated by the thermal decomposition of lithium salts (such as LiPF6) widely used in lithium ion batteries. - Wow PF5 - , etc., may be degraded by acids such as . Alternatively, the film may increase the surface resistance of the electrode due to changes in the surface structure as transition metal elements are eluted from the anode by such acid attack. Since the theoretical capacity decreases as the metal elements that are redox centers are lost, the expressed capacity may decrease. In addition, the eluted transition metal ions may be deposited on the cathode where they react in the strong reduction potential band. As the transition metal ions are deposited on the cathode, they may consume electrons and destroy the film, exposing the cathode surface. This may cause additional electrolyte decomposition reactions. As a result, the resistance of the cathode increases, and there may be a problem in which the irreversible capacity increases and the capacity of the cell continuously decreases.

[0168] The lithium secondary battery according to the present invention can exhibit the effects of removing active oxygen and strengthening the positive electrode film because the additives described above include a phenol moiety and a dioxolane derivative moiety. Accordingly, the positive electrode deterioration can be effectively prevented. As a result, the lithium secondary battery according to the present invention can exhibit excellent electrochemical performance. The above effects can be further enhanced at high voltages and / or high temperatures.

[0169]

[0170] Hereinafter, examples and comparative examples of the present invention will be described. However, the following examples are merely examples of the present invention, and the present invention is not limited to the following examples.

[0171] Example 1

[0172] (1) Preparation of electrolyte

[0173] An electrolyte was prepared by dissolving 1.15 M LiPF6 in a non-aqueous organic solvent containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 20:40:40, and adding an additive represented by the following chemical formula 1B.

[0174] The content of the above additive was 1.0 part by weight based on 100 parts by weight of the above electrolyte.

[0175] [Chemical Formula 1B]

[0176]

[0177] (2) Manufacturing of lithium secondary batteries

[0178] LiNi as a cathode active material 0.91 Co 0.08 Al 0.01 O2, polyvinylidene fluoride as a binder, and Ketjen Black as a conductive material were mixed in a weight ratio of 97:2:1, and dispersed in N-methyl pyrrolidone to prepare a positive electrode active material slurry.

[0179] The above slurry was coated on an aluminum current collector having a thickness of 14 μm, dried at 110°C, and pressed to manufacture a positive electrode.

[0180] A slurry of negative active material was prepared by mixing artificial graphite and silicon nanoparticles as a negative active material in a weight ratio of 93:7, mixing styrene-butadiene rubber (SBR) as a binder, and mixing carboxymethyl cellulose (CMC) as a thickener in a weight ratio of 97:1:2, and dispersing the mixture in distilled water.

[0181] The above negative electrode active material slurry was coated on a 10 μm thick copper current collector, dried at 100°C, and then pressed to manufacture a negative electrode.

[0182] An electrode assembly was manufactured by assembling the positive electrode and the negative electrode and a separator made of polyethylene material having a thickness of 25 ㎛, and an electrolyte was injected to manufacture a lithium secondary battery.

[0183]

[0184] Example 2

[0185] An electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the content of the additive was 0.5 parts by weight based on 100 parts by weight of the electrolyte.

[0186]

[0187] Example 3

[0188] An electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the content of the additive was 3.0 parts by weight based on 100 parts by weight of the electrolyte.

[0189]

[0190] Comparative Example 1

[0191] An electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that an additive represented by the following chemical formula 4 was added; and the content of the additive was 1.0 part by weight based on 100 parts by weight of the electrolyte.

[0192] [Chemical Formula 4]

[0193] .

[0194]

[0195] Comparative Example 2

[0196] An electrolyte and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the electrolyte did not contain the additive represented by the chemical formula 1B.

[0197]

[0198] Evaluation Example 1: Evaluation of resistance increase rate during high-temperature storage

[0199] The lithium secondary batteries manufactured in the examples and comparative examples were charged at 25°C with a current of 0.33 C-rate and a voltage of 4.25 V, and the initial resistance value of the battery and the resistance value of the battery after being left at 60°C for 28 days were measured. The resistance increase rate was calculated, and the results are shown in Table 1 below. The resistance was measured using electrochemical impedance spectroscopy (EIS).

[0200] The above resistance increase rate was calculated according to Equation 1 below.

[0201] [Formula 1]

[0202] Resistance increase rate (%) = [Battery resistance value after 28 days / Initial battery resistance value] * 100

[0203]

[0204] Evaluation Example 2: Evaluation of gas generation during high-temperature storage

[0205] The lithium secondary batteries manufactured in the examples and comparative examples were charged to a voltage of 4.25 V at 25°C, then left at 60°C for 28 days, and the amount of gas generated was measured. The amount of gas generated was measured by a buoyancy measurement method using water. The results are shown in Table 1 below.

[0206] Content evaluation results Chemical formula 1B (weight %) Chemical formula 4 (weight %) Resistance increase rate (%) Gas generation amount (mg) Example 11.0-92.134.4 Example 20.5-88.437.2 Example 33.0-99.430.1 Comparative example 1-1.010541.6 Comparative example 2--11242.6

[0207] Referring to Table 1, when comparing examples using an electrolyte containing an additive according to the present invention with comparative examples that do not, it can be confirmed that the resistance increase rate is low at high temperatures (60°C) and the amount of gas generated is low at high temperatures (60°C). This confirms the excellent anode stabilization effect.

Claims

1. Non-aqueous organic solvent; lithium salt; and Additives; including, The above additive is represented by the following chemical formula 1 or the following chemical formula 2, Electrolyte for lithium secondary batteries: [Chemical Formula 1] [Chemical Formula 2] In the above chemical formulas 1 and 2, The above R1 to R8 are each independently hydrogen, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C2 to C10 alkenyl group, or a substituted or unsubstituted C2 to C10 alkynyl group or a hydroxy group, At least one of the above R1 to R4 is a hydroxy group, At least one of the above R5 to R8 is a hydroxy group, The above n is 1 or 2.

2. In paragraph 1, The above R1 to R8 are each independently hydrogen, a substituted or unsubstituted C1 to C5 alkyl group, a substituted or unsubstituted C2 to C5 alkenyl group, or a substituted or unsubstituted C2 to C5 alkynyl group or hydroxy group. Electrolyte for lithium secondary batteries.

3. In paragraph 1, At least one of the above R2 and R3 is a hydroxy group, At least one of the above R6 and R7 is a hydroxy group, Electrolyte for lithium secondary batteries.

4. In paragraph 1, The above R2 is a hydroxyl group, The above R6 is a hydroxy group, Electrolyte for lithium secondary batteries.

5. In paragraph 1, The above additive is represented by the following chemical formula 1A: Electrolyte for lithium secondary batteries: [Chemical Formula 1A] The above R 1A Inland R 4A are each independently hydrogen, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C2 to C10 alkenyl group, or a substituted or unsubstituted C2 to C10 alkynyl group or a hydroxy group, The above R 1A Inland R 4A At least one of them is a hydroxyl group.

6. In paragraph 5, The above R 2A and R 3A At least one of which is a hydroxyl group, Electrolyte for lithium secondary batteries.

7. In paragraph 5, The above R 2A is a hydroxyl group, Electrolyte for lithium secondary batteries 8. In paragraph 1, The above additive is one selected from the group consisting of the following chemical formulas 1B to 2A: Electrolyte for lithium secondary batteries: [Chemical Formula 1B] [Chemical Formula 1C] [Chemical Formula 1D] [Chemical Formula 1E] [Chemical Formula 2A] .

9. In paragraph 1, An electrolyte for a lithium secondary battery, wherein the content of the additive is 0.01 to 10 parts by weight based on 100 parts by weight of the electrolyte for a lithium secondary battery.

10. In paragraph 1, The above non-aqueous organic solvent includes an ester solvent and a carbonate solvent. Electrolyte for lithium secondary batteries.

11. In paragraph 1, The above non-aqueous organic solvent includes ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC). Electrolyte for lithium secondary batteries.

12. In paragraph 11, The above ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) have a volume ratio of 1:a:b, The above a is 1 to 3, The above b is 1 to 3, Electrolyte for lithium secondary batteries.

13. In paragraph 1, The above lithium salt is, 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 SO2) (x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluoro(oxalato)borate (LiDFOB), lithium difluorobis(oxalato)phosphate (LiDFBOP), and lithium bis(oxalato)borate (LiBOB), at least one selected from the group consisting of Electrolyte for lithium secondary batteries.

14. In paragraph 1, The above lithium salt is LiPF6, Electrolyte for lithium secondary batteries.

15. In paragraph 1, The concentration of the lithium salt is 0.1 M to 2.0 M, Electrolyte for lithium secondary batteries.

16. A cathode containing a cathode active material; A negative electrode comprising a negative active material; and Comprising an electrolyte for a lithium secondary battery according to any one of claims 1 to 15, Lithium secondary battery.

17. In paragraph 16, The above positive electrode active material comprises a lithium composite oxide represented by the following chemical formula 3. Lithium secondary battery: [Chemical Formula 3] Li x M 1 y M 2 z M 3 1-y-z O 2-a X a 0.5≤x≤1.8, 0≤a≤0.05, 0 <y≤1, 0≤z≤1, 및 0≤y+z≤1이고, M 1 , M 2 and M 3 Each independently contains at least one element selected from metals such as Ni, Co, Mn, Al, B, Ba, Ca, Ce, Cr, Fe, Mo, Nb, Si, Sr, Mg, Ti, V, W, Zr or La and combinations thereof, X contains one or more elements selected from F, S, P or Cl.

18. In paragraph 17, Above M 1 is Ni, Lithium secondary battery.

19. In paragraph 16, The above negative electrode active material includes a carbon-based negative electrode active material, a Si-based negative electrode active material, a Sn-based negative electrode active material, or a combination thereof. Lithium secondary battery.

20. In paragraph 16, The above negative electrode active material is a Si-based negative electrode active material. Lithium secondary battery.

Images