Lithium secondary battery

Abstract

The present invention provides a lithium secondary battery comprising: a positive electrode; a negative electrode facing the positive electrode; a separator interposed between the positive electrode and the negative electrode; and a non-aqueous electrolyte, wherein the positive electrode includes a positive electrode active material, the positive electrode active material comprising a lithium transition metal oxide, an organic solvent includes ethylene carbonate and a compound represented by chemical formula 1 below, and the ratio of the volume of the compound represented by chemical formula 1 to the volume of the ethylene carbonate is 0.2 to 2.5. [Chemical formula 1] In chemical formula 1, R1 is a fluorine atom, an alkyl group having 1 to 10 carbon atoms substituted with at least one fluorine, or an alkoxy group having 1 to 10 carbon atoms substituted with at least one fluorine, and R2 and R3 are each independently hydrogen, an alkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms.

Description

lithium secondary battery

[0001] The present invention relates to a lithium secondary battery.

[0002] Recently, as the application areas of lithium-ion batteries have rapidly expanded to include not only power supply for electronic devices such as electrical, electronic, telecommunications, and computers, but also power storage for large-area devices such as automobiles and power storage systems, there is a growing demand for high-capacity, high-output, and high-stability secondary batteries.

[0003] In particular, with the growing interest in solving environmental problems and realizing a sustainable circular society, research on energy storage devices such as lithium-ion batteries and electric double-layer capacitors is being conducted extensively. Among these, lithium-ion batteries are receiving attention as battery systems that theoretically have the highest energy density within battery technology.

[0004] The aforementioned lithium secondary battery is largely composed of a positive electrode made of a transition metal oxide containing lithium, a negative electrode capable of storing lithium, an electrolyte that acts as a medium for transporting lithium ions, and a separator. Among these components, the electrolyte is known to have a significant impact on the battery's stability and safety, and as such, extensive research is being conducted on it.

[0005] In this regard, the electrolyte of a lithium secondary battery is generally a non-aqueous electrolyte containing a lithium salt, an organic solvent, etc., and the organic solvent used is a carbonate-based organic solvent. At this time, for example, LiPF6 can be used as the lithium salt, PF6 -In the case of anions, they are very susceptible to heat, so when the battery is exposed to high temperatures, there is a problem in that Lewis acids such as HF and PF5 are generated due to the thermal decomposition of lithium salts. Lewis acids such as HF and PF5 cause the decomposition of the organic solvent itself and destroy the solid electrolyte interface layer (SEI layer) formed on the surface of the negative electrode active material, which leads to increased resistance, reduced lifespan, and problems with storage performance in lithium secondary batteries.

[0006] Furthermore, in the case of lithium transition metal oxides used as cathode active materials, structural instability can be caused by internal transition metal content and high-voltage operation, leading to the generation of large amounts of carbon dioxide (CO2). This results in problems such as increased resistance and reduced high-temperature durability in lithium secondary batteries.

[0007] One objective of the present invention is to solve the above-mentioned problems by providing a lithium secondary battery capable of minimizing gas generation that may occur during operation, effectively protecting the positive and negative electrodes, and improving the lifespan, resistance reduction, and durability of the secondary battery.

[0008] [1] The present invention provides a lithium secondary battery comprising: a positive electrode; a negative electrode facing the positive electrode; a separator interposed between the positive electrode and the negative electrode; and a non-aqueous electrolyte; wherein the positive electrode comprises a positive active material, the positive active material comprises a lithium transition metal oxide, the organic solvent comprises ethylene carbonate and a compound represented by the following chemical formula 1, and the ratio of the volume of the compound represented by the following chemical formula 1 to the volume of the ethylene carbonate is 0.2 to 2.5.

[0009] [Chemical Formula 1]

[0010]

[0011] In the above chemical formula 1, R1 is a fluorine atom, a carbon-1 to carbon-10 alkyl group substituted with one or more fluorines, or a carbon-1 to carbon-10 alkoxy group substituted with one or more fluorines, and R2 and R3 are independently hydrogen, a carbon-1 to carbon-10 alkyl group, or a carbon-6 to carbon-20 aryl group.

[0012] [2] The present invention provides a lithium secondary battery according to [1], wherein the organic solvent comprises 10 volume% to 40 volume% of the ethylene carbonate.

[0013] [3] The present invention provides a lithium secondary battery in which, in at least one of [1] and [2], the organic solvent comprises 5 volume% to 40 volume% of a compound represented by the chemical formula 1.

[0014] [4] The present invention provides a lithium secondary battery comprising, in at least one of [1] to [3], a compound represented by Formula 1, which is selected from the group consisting of compounds represented by Formulas 1-1 to 1-5.

[0015] [Chemical Formula 1-1]

[0016]

[0017] [Chemical Formula 1-2]

[0018]

[0019] [Chemical Formula 1-3]

[0020]

[0021] [Chemical Formula 1-4]

[0022]

[0023] [Chemical Formula 1-5]

[0024]

[0025] In the above chemical formulas 1-1 to 1-5, R2 and R3 are as defined in the above chemical formula 1.

[0026] [5] The present invention provides a lithium secondary battery comprising, in at least one of [1] to [4], a compound represented by Formula 1 selected from the group consisting of the following compounds represented by Formula 1-A, Formula 1-B, Formula 1-C, Formula 1-D and Formula 1-E.

[0027] [Chemical Formula 1-A]

[0028]

[0029] [Chemical Formula 1-B]

[0030]

[0031] [Chemical Formula 1-C]

[0032]

[0033] [Chemical Formula 1-D]

[0034]

[0035] [Chemical Formula 1-E]

[0036]

[0037] [6] The present invention provides a lithium secondary battery in which, in at least one of [1] to [5], the organic solvent further comprises a linear carbonate-based solvent.

[0038] [7] The present invention provides a lithium secondary battery according to [6], wherein the linear carbonate-based solvent comprises at least one selected from the group consisting of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethylmethyl carbonate (EMC), methylpropyl carbonate and ethylpropyl carbonate.

[0039] [8] The present invention provides a lithium secondary battery in which, in at least one of [6] and [7], the organic solvent comprises 20 volume% to 85 volume% of the linear carbonate-based solvent.

[0040] [9] The present invention provides a lithium secondary battery in which, in at least one of [6] to [8], the ratio of the volume of the compound represented by Formula 1 to the volume of the linear carbonate-based solvent is 0.05 to 1.5.

[0041]

[0010] The present invention provides a lithium secondary battery in which, in at least one of [1] to [9], the lithium transition metal oxide contains nickel in an amount of 50 mol% or more of the metals excluding lithium.

[0042]

[0011] The present invention provides a lithium secondary battery in which, in at least one of [1] to

[0010] , the lithium transition metal oxide is a compound represented by the following chemical formula A.

[0043] [Chemical Formula A]

[0044] Li 1+x (Ni a Co b Mn c M d )O2

[0045] In the above chemical formula A, M is one or more selected from W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, and 0≤x≤0.2, 0.50≤a<1, 0 <b≤0.2, 0<c≤0.3, 0≤d≤0.1, a+b+c+d=1이다.

[0046] A lithium secondary battery using a lithium transition metal oxide as the positive electrode active material of the present invention is characterized by combining a non-aqueous electrolyte of specific components. The non-aqueous electrolyte comprises ethylene carbonate as an organic solvent and a sulfonamide-based compound having a specific structural formula. According to the present invention, the combination of these organic solvent components can minimize gas generation due to the decomposition of the cyclic carbonate-based solvent, prevent the destruction of the SEI film on the surface of the negative electrode active material, and improve the oxidation stability, chemical stability, and electrochemical stability of the non-aqueous electrolyte. Furthermore, the lithium transition metal oxide used as the positive electrode active material has problems such as structural instability caused by the content of the transition metal contained therein and high-voltage operation, which leads to increased carbon dioxide gas generation and causes an increase in cell resistance and lithium precipitation. However, when using the combination of the aforementioned sulfonamide-based compound and ethylene carbonate, the carbon dioxide generated at the positive electrode is reduced at the negative electrode, thereby significantly reducing the amount of gas generated within the cell. Therefore, a lithium secondary battery to which the above-mentioned non-aqueous electrolyte is applied is desirable as it prevents an increase in resistance, improves lifespan performance, and can have excellent durability.

[0047] Terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0048] In this specification, terms such as “comprising,” “comprising,” or “having” are intended to specify the existence of the implemented features, numbers, steps, components, or combinations thereof, and should be understood as not excluding in advance the existence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0049] Meanwhile, prior to describing the present invention, unless otherwise specifically stated in the present invention, "*" refers to a connected portion (bonding site) between identical or different atoms or terminal portions of a chemical formula.

[0050] In addition, in the description of "a to b carbon atoms" within this specification, "a" and "b" refer to the number of carbon atoms included in a specific functional group. That is, the functional group may include "a" to "b" carbon atoms. For example, "alkyl group having 1 to 5 carbon atoms" refers to an alkyl group containing 1 to 5 carbon atoms, namely CH3-, CH3CH2-, CH3CH2CH2-, (CH3)2CH-, CH3CH2CH2CH2-, (CH3)2CHCH2-, CH3CH2CH2CH2CH2-, (CH3)2CHCH2CH2-, etc.

[0051] In addition, in this specification, alkyl groups or aryl groups may all be substituted or unsubstituted. Unless otherwise defined, the term "substitution" above means that at least one hydrogen bonded to a carbon is substituted with an element other than hydrogen, for example, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a cycloalkenyl group having 3 to 12 carbon atoms, a cycloalkynyl group having 3 to 12 carbon atoms, a heterocycloalkyl group having 3 to 12 carbon atoms, a heterocycloalkynyl group having 2 to 12 carbon atoms, an aryloxy group having 6 to 12 carbon atoms, a halogen atom, a fluoroalkyl group having 1 to 20 carbon atoms, a nitro group, an aryl group having 6 to 20 carbon atoms, and a group having 2 to It means that it is substituted with a heteroaryl group of 20 carbon atoms, a haloaryl group having 6 to 20 carbon atoms, etc.

[0052]

[0053] The present invention will be described in more detail below.

[0054]

[0055] lithium secondary battery

[0056] The present invention relates to a lithium secondary battery.

[0057] Specifically, the lithium secondary battery according to the present invention comprises a positive electrode; a negative electrode facing the positive electrode; a separator interposed between the positive electrode and the negative electrode; and a non-aqueous electrolyte; wherein the positive electrode comprises a positive active material, the positive active material comprises a lithium transition metal oxide, the organic solvent comprises ethylene carbonate and a compound represented by the following chemical formula 1, and the ratio of the volume of the compound represented by the following chemical formula 1 to the volume of the ethylene carbonate is 0.2 to 2.5.

[0058] [Chemical Formula 1]

[0059]

[0060] In the above chemical formula 1, R1 is a fluorine atom, a carbon-1 to carbon-10 alkyl group substituted with one or more fluorines, or a carbon-1 to carbon-10 alkoxy group substituted with one or more fluorines, and R2 and R3 are independently hydrogen, a carbon-1 to carbon-10 alkyl group, or a carbon-6 to carbon-20 aryl group.

[0061] A lithium secondary battery using a lithium transition metal oxide as the positive electrode active material of the present invention is characterized by combining a non-aqueous electrolyte of specific components. The non-aqueous electrolyte comprises ethylene carbonate as an organic solvent and a sulfonamide-based compound having a specific structural formula. According to the present invention, the combination of these organic solvent components can minimize gas generation due to the decomposition of the cyclic carbonate-based solvent, prevent the destruction of the SEI film on the surface of the negative electrode active material, and improve the oxidation stability, chemical stability, and electrochemical stability of the non-aqueous electrolyte. Furthermore, the lithium transition metal oxide used as the positive electrode active material has problems such as structural instability caused by the content of the transition metal contained therein and high-voltage operation, which leads to increased carbon dioxide gas generation and causes an increase in cell resistance and lithium precipitation. However, when using the combination of the aforementioned sulfonamide-based compound and ethylene carbonate, the carbon dioxide generated at the positive electrode is reduced at the negative electrode, thereby significantly reducing the amount of gas generated within the cell. Therefore, a lithium secondary battery to which the above-mentioned non-aqueous electrolyte is applied is desirable as it prevents an increase in resistance, improves lifespan performance, and can have excellent durability.

[0062]

[0063] (1) positive electrode

[0064] The above lithium secondary battery includes a positive electrode.

[0065] The above anode includes an anode active material.

[0066] The above-mentioned cathode active material is a compound capable of reversible intercalation and deintercalation, and is not particularly limited as long as it is a cathode active material used in the field. Specifically, the above-mentioned cathode active material is a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; lithium iron oxide such as LiFe3O4; lithium iron phosphate such as LiFePO4; and a compound with the chemical formula Li 1+c1 Mn2-c1 Lithium manganese oxides such as O4 (0≤c1≤0.33), LiMnO3, LiMn2O3, LiMnO2, etc.; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, Cu2V2O7, etc.; chemical formula LiNi 1-c2 M c2 Ni-site type lithium nickel oxide represented by O2 (wherein M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, satisfying 0.01≤c2≤0.3); chemical formula LiMn 2-c3 M c3 Lithium manganese composite oxides represented by O2 (wherein M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn and Ta, satisfying 0.01≤c3≤0.1) or Li2Mn3MO8 (wherein M is at least one selected from the group consisting of Fe, Co, Ni, Cu and Zn); etc., but are not limited to these.

[0067] The above-mentioned positive electrode active material may include a lithium transition metal oxide. Lithium transition metal oxides may experience structural instability due to factors such as the content of internally contained transition metals (e.g., Ni) or high-voltage operation, which can lead to problems such as accelerated generation of gases like CO2. To solve these problems, the present invention utilizes a non-aqueous electrolyte composed of specific components, thereby enabling the realization of a lithium secondary battery with minimized gas generation within the cell and excellent durability.

[0068] Specifically, the lithium transition metal oxide may contain nickel in an amount of 50 mol% or more among the metals excluding lithium. According to the present invention, even when using a high-nickel lithium transition metal oxide containing nickel in an amount of 50 mol% or more, 70 mol% or more, or 80 mol% or more among the metals excluding lithium, the amount of gas generated within the cell can be minimized and the stability of the lithium secondary battery can be improved.

[0069] Specifically, the lithium transition metal oxide may be a compound represented by the following chemical formula A.

[0070] [Chemical Formula A]

[0071] Li 1+x (Ni a Co b Mn c M d )O2

[0072] In the above chemical formula A, M is one or more selected from W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, and 1+x, a, b, c, and d are each atomic fractions of independent elements, where 0≤x≤0.2, 0.50≤a<1, 0 <b≤0.2, 0<c≤0.3, 0≤d≤0.1, a+b+c+d=1이다. 바람직하게는, 상기 a, b, c 및 d는 각각 0.70≤a≤0.95, 0.025≤b≤0.20, 0.025≤c≤0.20, 0≤d≤0.05일 수 있다. 또한, 상기 a, b, c 및 d는 각각 0.80≤a≤0.95, 0.025≤b≤0.15, 0.025≤c≤0.15, 0≤d≤0.05일 수 있다. 또한, 상기 a, b, c 및 d는 각각 0.85≤a≤0.90, 0.05≤b≤0.10, 0.05≤c≤0.10, 0≤d≤0.03일 수 있다.

[0073] The above positive electrode may include a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector.

[0074] The above positive current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. Specifically, the above positive current collector may include at least one selected from the group consisting of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, and aluminum-cadmium alloy, preferably aluminum.

[0075] The thickness of the above positive current collector can typically be 3 to 500 μm.

[0076] The above positive current collector may form fine irregularities on its surface to strengthen the bonding force of the positive active material. For example, the above positive current collector can be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0077] The positive active material layer may be disposed on at least one surface of the positive current collector. Specifically, the positive active material layer may be disposed on one or both surfaces of the positive current collector.

[0078] The above positive active material layer may include the aforementioned positive active material.

[0079] The above positive active material may be included in the above positive active material layer in an amount of 80% to 99% by weight, specifically 85% to 98% by weight.

[0080] The above positive active material layer may optionally further include a binder and / or a conductive material together with the aforementioned positive active material.

[0081] The above binder is a component that assists in the binding of active materials and conductive materials, and in binding to current collectors, and specifically may include at least one selected from the group consisting of polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene ter polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, and fluororubber, preferably polyvinylidene fluoride.

[0082] The above binder may be included in the positive active material layer in an amount of 1% to 20% by weight, preferably 1.2% to 10% by weight, in order to sufficiently secure binding strength between components such as the positive active material.

[0083] The above conductive material can be used to assist and enhance conductivity in a secondary battery, and is not particularly limited as long as it is conductive without causing chemical changes. Specifically, the above cathode conductive material may include at least one selected from the group consisting of graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, channel black, Farnes black, lamp black, thermal black; conductive fibers such as carbon fibers or metal fibers; conductive tubes such as carbon nanotubes; fluorocarbons; metal powders such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and polyphenylene derivatives, and preferably may include carbon nanotubes for the purpose of enhancing conductivity.

[0084] The above conductive material may be included in the above positive active material layer in an amount of 1% to 20% by weight, preferably 1.2% to 10% by weight, in order to sufficiently ensure electrical conductivity.

[0085] The thickness of the above positive active material layer may be 5㎛ to 500㎛, preferably 20㎛ to 200㎛.

[0086] The above anode can be manufactured by coating an anode slurry comprising an anode active material and optionally a binder, a conductive material, and a solvent for forming an anode slurry onto the above anode current collector, and then drying and rolling.

[0087]

[0088] (2) Cathode

[0089] The above cathode can be opposite to the above anode.

[0090] The above cathode includes a cathode active material.

[0091] The above-mentioned negative electrode active material is a material capable of reversibly inserting / extracting lithium ions, and may include at least one selected from the group consisting of carbon-based active materials, (quasi)metal-based active materials, and lithium metal, and specifically may include at least one selected from carbon-based active materials and (quasi)metal-based active materials. The above-mentioned negative electrode active material may include at least one selected from the group consisting of carbon-based active materials and silicon-based active materials.

[0092] The above carbon-based active material may include at least one selected from the group consisting of artificial graphite, natural graphite, hard carbon, soft carbon, carbon black, graphene, and fibrous carbon, and preferably may include at least one selected from the group consisting of artificial graphite and natural graphite.

[0093] Average particle size (D of the above carbon-based active material) 50 ) can be 10㎛ to 30㎛, preferably 15㎛ to 25㎛, in terms of ensuring structural stability during charging and discharging and reducing adverse reactions with the electrolyte.

[0094] Specifically, the above (quasi)metallic active material may include at least one (quasi)metal selected from the group consisting of Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, V, Ti, and Sn; an alloy of lithium with at least one (quasi)metal selected from the group consisting of Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, V, Ti, and Sn; an oxide of at least one (quasi)metal selected from the group consisting of Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, V, Ti, and Sn; lithium titanium oxide (LTO); lithium vanadium oxide; etc.

[0095] More specifically, the above (quasi)metallic active material may include a silicon-based active material.

[0096] The above silicon-based active material is silicon (Si) and silicon oxide (SiO₂). x (0 <x<2)로 표시될 수 있음) 및 실리콘-탄소 복합체(Si / C Composite)로 이루어진 군에서 선택된 적어도 1종을 포함할 수 있다.

[0097] Average particle size (D) of the above silicon-based active material 50 ) can be 1㎛ to 30㎛, preferably 2㎛ to 15㎛, in terms of reducing adverse reactions with the electrolyte while ensuring structural stability during charging and discharging.

[0098]

[0099] The above cathode may include a cathode current collector; and a cathode active material layer disposed on at least one surface of the cathode current collector. In this case, the cathode active material may be included in the cathode active material layer.

[0100] The above-mentioned negative current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. Specifically, the above-mentioned negative current collector may be copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface treated with carbon, nickel, titanium, silver, etc., or aluminum-cadmium alloy.

[0101] The above-mentioned cathode current collector can typically have a thickness of 3 to 500 μm.

[0102] The above-mentioned negative current collector may form fine irregularities on its surface to strengthen the bonding force of the negative active material. For example, the above-mentioned negative current collector can be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0103]

[0104] The above negative electrode active material layer may be disposed on at least one surface of the negative electrode current collector, specifically on one or both surfaces of the negative electrode current collector.

[0105] The above-mentioned negative electrode active material may be included in the negative electrode active material layer in an amount of 60% to 99% by weight, preferably 75% to 95% by weight.

[0106] The description of other cathode active materials has been previously explained, so it will be omitted.

[0107] The above cathode active material layer may further include a binder and / or a conductive material together with the cathode active material.

[0108] The binder is used to improve the performance of the battery by enhancing the adhesion between the negative electrode active material layer and the negative electrode current collector, and may include, for example, at least one selected from the group consisting of polyvinylidenefluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidenefluoride (PVDF), polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber, and materials in which hydrogens thereof are substituted with Li, Na, or Ca, etc., and may also include various copolymers thereof. there is.

[0109] The above binder may be included in the cathode active material layer in an amount of 0.5% to 10% by weight, preferably 1% to 5% by weight.

[0110] The above conductive material is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, channel black, Farnes black, lamp black, thermal black; conductive fibers such as carbon fibers or metal fibers; conductive tubes such as carbon nanotubes; fluorocarbons; metal powders such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives may be used.

[0111] The above conductive material may be included in the above negative electrode active material layer in an amount of 0.5% to 10% by weight, preferably 1% to 5% by weight.

[0112] The thickness of the above negative electrode active material layer may be 10㎛ to 200㎛, preferably 20㎛ to 150㎛.

[0113] The above cathode can be manufactured by coating a cathode slurry comprising a cathode active material, a binder, a conductive material, and / or a solvent for forming a cathode slurry on at least one surface of a cathode current collector, and then drying and rolling.

[0114] The solvent for forming the cathode slurry may include, for example, at least one selected from the group consisting of distilled water, NMP (N-methyl-2-pyrrolidone), ethanol, methanol, and isopropyl alcohol, preferably distilled water, in order to facilitate the dispersion of the cathode active material, binder, and / or conductive material. The solid content of the cathode slurry may be 30% to 80% by weight, specifically 40% to 70% by weight.

[0115]

[0116] (3) Separator

[0117] The above separator may be interposed between the anode and the cathode.

[0118] As the above separator, a conventional porous polymer film used as a separator, such as a polyolefin-based polymer film made of ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, may be used alone or in a laminate thereof, or a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc., may be used, but is not limited thereto. In addition, a coated separator containing a ceramic component or a polymer material may be used to ensure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0119]

[0120] (4) Non-aqueous electrolyte

[0121] The above-mentioned non-aqueous electrolyte includes a lithium salt and an organic solvent.

[0122]

[0123] 1) Lithium salt

[0124] As the lithium salt used in the present invention, various lithium salts commonly used in non-aqueous electrolytes for lithium secondary batteries may be used without limitation. For example, the lithium salt is Li as a cation. + It includes, and as anion, F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , AlO4 - , AlCl4 - , PF6 - , SbF6 - , AsF6 - , B 10 Cl 10 - , BF2C2O4 -, BC4O8 - , PF4C2O4 - , PF2C4O8 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , C4F9SO3 - , CF3CF2SO3 - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , CH3SO3 - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - It may include at least one selected from a group consisting of

[0125] Specifically, the lithium salt is LiCl, LiBr, LiI, LiBF4, LiClO4, LiAlO4, LiAlCl4, LiPF6, LiSbF6, LiAsF6, LiB 10 Cl 10 It may include at least one selected from the group consisting of LiBOB (LiB(C2O4)2), LiCF3SO3, LiFSI (LiN(SO2F)2), LiCH3SO3, LiCF3CO2, LiCH3CO2, and LiBETI (LiN(SO2CF2CF3)2). Specifically, the lithium salt may include at least one selected from the group consisting of LiBF4, LiClO4, LiPF6, LiBOB (LiB(C2O4)2), LiCF3SO3, LiTFSI (LiN(SO2CF3)2), LiFSI (LiN(SO2F)2), and LiBETI (LiN(SO2CF2CF3)2).

[0126] The above lithium salt may be included in the above-mentioned non-aqueous electrolyte at a concentration of 0.5M to 5M, specifically 0.8M to 4M, and more specifically 0.8M to 2.0M. When the concentration of the above-mentioned lithium salt satisfies the above range, the lithium ion yield (Li + The transference number and the degree of dissociation of lithium ions are improved, which can enhance the output characteristics of the battery.

[0127]

[0128] (2) Organic solvent

[0129] The above organic solvent includes ethylene carbonate and a compound represented by the following chemical formula 1.

[0130] [Chemical Formula 1]

[0131]

[0132] In the above chemical formula 1, R1 is a fluorine atom, a carbon-1 to carbon-10 alkyl group substituted with one or more fluorines, or a carbon-1 to carbon-10 alkoxy group substituted with one or more fluorines, and R2 and R3 are independently hydrogen, a carbon-1 to carbon-10 alkyl group, or a carbon-6 to carbon-20 aryl group.

[0133] A lithium secondary battery using a lithium transition metal oxide as the positive electrode active material of the present invention is characterized by combining a non-aqueous electrolyte of specific components. The non-aqueous electrolyte comprises ethylene carbonate as an organic solvent and a sulfonamide-based compound having a specific structural formula. According to the present invention, the combination of these organic solvent components can minimize gas generation due to the decomposition of the cyclic carbonate-based solvent, prevent the destruction of the SEI film on the surface of the negative electrode active material, and improve the oxidation stability, chemical stability, and electrochemical stability of the non-aqueous electrolyte. Furthermore, the lithium transition metal oxide used as the positive electrode active material has problems such as structural instability caused by the content of the transition metal contained therein and high-voltage operation, which leads to increased carbon dioxide gas generation and causes an increase in cell resistance and lithium precipitation. However, when using the combination of the aforementioned sulfonamide-based compound and ethylene carbonate, the carbon dioxide generated at the positive electrode is reduced at the negative electrode, thereby significantly reducing the amount of gas generated within the cell. Therefore, a lithium secondary battery to which the above-mentioned non-aqueous electrolyte is applied is desirable as it prevents an increase in resistance, improves lifespan performance, and can have excellent durability.

[0134]

[0135] The above ethylene carbonate can prevent decomposition according to the compound represented by Chemical Formula 1, thereby further improving the mobility characteristics of lithium. Meanwhile, the above ethylene carbonate is also desirable in that it does not impede the CO2 gas generation prevention effect of the lithium transition metal oxide resulting from the application of the compound represented by Chemical Formula 1.

[0136] If cyclic carbonates other than ethylene carbonate, specifically fluorine-substituted ethylene carbonates (fluoroethylene carbonates, etc.), are used, F in high voltage and high temperature environments -Defluoronation reactions in which fluoride is released are easily induced, and the acidity of the non-aqueous electrolyte increases due to acidic byproducts such as HF generated during this process. This can intensify metal leaching from the surface of the anode and promote the destruction of the coatings on the anode and cathode, thereby accelerating the degradation of the lithium secondary battery. In addition, fluorine-substituted ethylene carbonates may induce the generation of gases such as CO2, CO, and fluorinated hydrocarbons by accompanying irreversible decomposition reactions of CO or CF bonds during reduction or oxidative decomposition processes. Consequently, this can lead to pressure increase and expansion inside the cell during battery operation, thereby reducing stability. In this regard, it may be desirable for fluorine-substituted ethylene carbonates, such as fluoroethylene carbonates, not to be included in the non-aqueous electrolyte, or at least to be added in small amounts (e.g., 5% by weight or less of the non-aqueous electrolyte).

[0137] The organic solvent may contain the cyclic carbonate-based solvent in an amount of 10 volume% or more, 12 volume% or more, 15 volume% or more, 18 volume% or more, 20 volume% or more, 22 volume% or more, or 24 volume% or more. The organic solvent may contain the cyclic carbonate-based solvent in an amount of 50 volume% or less, 48 ​​volume% or less, 45 volume% or less, 42 volume% or less, 40 volume% or less, 38 volume% or less, 35 volume% or less, or 30 volume% or less. The above numerical ranges may be combined without limitation. Specifically, the organic solvent may contain the cyclic carbonate-based solvent in an amount of 10 volume% to 40 volume%, specifically 15 volume% to 35 volume%, and when within this range, the viscosity of the organic solvent is appropriately controlled, and the dissociation, migration, and transport of the lithium salt can be carried out smoothly.

[0138] The compound represented by Chemical Formula 1 above does not generate gases such as CO2 or CH4 due to its structural characteristics, yet exhibits excellent electrochemical and chemical stability, and does not reduce the degree of dissociation of the lithium salt when used in the aforementioned content or content ratio. Furthermore, the compound represented by Chemical Formula 1 above is also desirable in that it can reduce the amount of gas generated within the cell by promoting the reduction of CO2 gas derived from the lithium transition metal compound used as the positive electrode active material at the negative electrode.

[0139] The compound represented by the above chemical formula 1 has a structure in which a fluorine or fluorine-containing functional group and N(R2)(R3) are combined via a sulfonate group (-SO2-). In particular, the sulfonate group is different from the carbonate functional group, which is the cause of gas generation, and is therefore particularly desirable for gas reduction effects.

[0140] In addition, the compound represented by Chemical Formula 1 above possesses structural stability of its own, and at the same time, has the characteristic of being less affinity for the lithium cation of the lithium salt but more affinity for the corresponding anion. This promotes the formation of a solvation structure between the lithium cation and ethylene carbonate, which can further enhance oxidation stability.

[0141] Meanwhile, the compound represented by Chemical Formula 1 has high structural stability, so decomposition reactions during initial activation or battery operation are minimized, but a very small amount may decompose during the initial activation process to form an SEI film. At this time, the SEI film derived from the compound represented by Chemical Formula 1 contains a Li2SO4-based compound, so it has excellent durability and can prevent rapid decomposition of the additive during initial activation, thereby preventing an increase in the resistance of the negative electrode film.

[0142] In the compound represented by the above chemical formula 1, R1 may be a fluorine atom (F), an alkyl group having 1 to 10 carbon atoms substituted with one or more fluorines, or an alkoxy group having 1 to 10 carbon atoms substituted with one or more fluorines; specifically, it may be a fluorine atom, an alkyl group having 1 to 5 carbon atoms substituted with one or more fluorines, or an alkoxy group having 1 to 5 carbon atoms substituted with one or more fluorines; more specifically, it may be a fluorine atom, an alkyl group having 1 to 3 carbon atoms substituted with one or more fluorines, or an alkoxy group having 1 to 3 carbon atoms substituted with one or more fluorines; more specifically, it may be a fluorine atom, CF3-*, CF3CF2-*, CF3O-*, or CF3CF2O-*; more specifically, it may be a fluorine atom, CF3-*, or CF3O-*; more specifically, it may be a fluorine atom or CF3-*; and more specifically, it may be a fluorine atom. In the above, "*" may indicate a connection site.

[0143] Additionally, R2 and R3 may independently be hydrogen, an alkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms; specifically, they may independently be an alkyl group having 1 to 10 carbon atoms; more specifically, they may independently be an alkyl group having 1 to 5 carbon atoms; even more specifically, they may independently be an alkyl group having 1 to 3 carbon atoms; even more specifically, they may independently be a methyl group or an ethyl group; and even more specifically, they may each be a methyl group.

[0144] The compound represented by the above chemical formula 1 may include at least one selected from the group consisting of compounds represented by the following chemical formulas 1-1 to 1-5, more specifically may include at least one selected from the group consisting of compounds represented by the following chemical formulas 1-1 to 1-3, and even more specifically may include the compound represented by the following chemical formula 1-1.

[0145] [Chemical Formula 1-1]

[0146]

[0147] [Chemical Formula 1-2]

[0148]

[0149] [Chemical Formula 1-3]

[0150]

[0151] [Chemical Formula 1-4]

[0152]

[0153] [Chemical Formula 1-5]

[0154]

[0155] At this time, in the above chemical formulas 1-1 to 1-5, R2 and R3 are as defined in the above chemical formula 1.

[0156] The compound represented by the above chemical formula 1 may include at least one selected from the group consisting of compounds represented by the following chemical formulas 1-A, 1-B, 1-C, 1-D, and 1-E, specifically, it may include at least one selected from the group consisting of compounds represented by the following chemical formulas 1-A, 1-B, and 1-C, and more specifically, it may include the compound represented by the following chemical formula 1-A.

[0157] [Chemical Formula 1-A]

[0158]

[0159] [Chemical Formula 1-B]

[0160]

[0161] [Chemical Formula 1-C]

[0162]

[0163] [Chemical Formula 1-D]

[0164]

[0165] [Chemical Formula 1-E]

[0166]

[0167] The organic solvent may contain the compound represented by Chemical Formula 1 in an amount of 5 volume% or more, 7 volume% or more, 8 volume% or more, 10 volume% or more, 12 volume% or more, or 15 volume% or more. The organic solvent may contain the compound represented by Chemical Formula 1 in an amount of 50 volume% or less, 45 volume% or less, 42 volume% or less, 40 volume% or less, 38 volume% or less, 35 volume% or less, 32 volume% or less, 30 volume% or less, 28 volume% or less, or 25 volume% or less. The above numerical ranges may be combined with one another without limitation. The organic solvent may contain the compound represented by Chemical Formula 1 in an amount of 5 to 50 volume%, specifically 5 to 40 volume%, more specifically 5 to 30 volume%, more specifically 7 to 25 volume%, and more specifically 10 to 22 volume%. When within this range, the effect of preventing gas generation due to the decomposition of the organic solvent can be maximized without reducing the degree of dissociation of the lithium salt.

[0168] The ratio of the volume of the compound represented by the following chemical formula 1 to the volume of the above ethylene carbonate may be 0.2 to 2.5. When within this range, the viscosity of the organic solvent is controlled to an appropriate level, and the degree of dissociation of the lithium salt is improved, thereby improving ionic conductivity.

[0169] If the ratio of the volume of the compound represented by Chemical Formula 1 below to the volume of the above-mentioned ethylene carbonate is less than 0.2, not only is the viscosity of the organic solvent excessively high, but gas generation due to the decomposition of ethylene carbonate is also intensified, which is undesirable. In addition, if the ratio of the volume of the compound represented by Chemical Formula 1 below to the volume of ethylene carbonate exceeds 2.5, the degree of dissociation of the lithium salt decreases, and there is a problem that the ionic conductivity decreases rapidly.

[0170] Specifically, the ratio of the volume of the compound represented by the following chemical formula 1 to the volume of the ethylene carbonate may be 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, or 0.9 or more. The ratio of the volume of the compound represented by the following chemical formula 1 to the volume of the ethylene carbonate may be 2.5 or less, 2 or less, 1.9 or less, 1.8 or less, 1.7 or less, 1.6 or less, 1.5 or less, 1.4 or less, 1.3 or less, 1.2 or less, 1.1 or less, 1.0 or less, or 0.8 or less. The above numerical ranges may be combined with one another without limitation. Specifically, the ratio of the volume of the compound represented by the following chemical formula 1 to the volume of the ethylene carbonate may be 0.3 to 1.5, specifically 0.4 to 1.2, and more specifically 0.7 to 1. When within the above range, the viscosity of the organic solvent is adequately secured and the ionic conductivity of the lithium salt can be improved, and furthermore, through the combination of these organic solvent components, gas generation due to the decomposition of ethylene carbonate can be minimized, the destruction of the SEI film on the surface of the negative electrode active material can be prevented, and the oxidation stability, chemical stability, and electrochemical stability of the non-aqueous electrolyte can be improved.

[0171]

[0172] The above organic solvent may further include a linear carbonate-based solvent.

[0173] In addition, the linear carbonate-based solvent is an organic solvent having low viscosity and low dielectric constant, and specifically may include at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethylmethyl carbonate (EMC), methylpropyl carbonate (MPC), and ethylpropyl carbonate (EPC); more specifically, in terms of further improving the oxidation stability of the organic solvent, it may include at least one selected from the group consisting of ethylmethyl carbonate (EMC), dimethyl carbonate (DMC), and diethyl carbonate (DEC); and more specifically, it may include ethylmethyl carbonate (EMC) and diethyl carbonate (DEC).

[0174] The above organic solvent may contain the above linear carbonate-based solvent in an amount of 20 to 85 volume%, specifically 40 to 78 volume%, more specifically 50 to 70 volume%, and even more specifically 54 to 66 volume%. Within this range, it is possible to implement a non-aqueous electrolyte with excellent oxidation stability while appropriately controlling the viscosity of the organic solvent. The above linear carbonate-based solvent may be included, for example, as the remainder after excluding the volume of the above cyclic carbonate-based solvent and the compound represented by Chemical Formula 1 from the above organic solvent.

[0175] When the above organic solvent further includes the above linear carbonate-based solvent, the ratio of the volume of the compound represented by Formula 1 to the volume of the above linear carbonate-based solvent may be 0.05 or more, 0.06 or more, 0.08 or more, 0.1 or more, 0.15 or more, 0.2 or more, 0.25 or more, 0.27 or more, 0.3 or more, 0.35 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, 0.9 or more, 1.0 or more, 1.1 or more, or 1.2 or more. The ratio of the volume of the compound represented by Formula 1 to the volume of the linear carbonate-based solvent may be 2.5 or less, 2.0 or less, 1.8 or less, 1.7 or less, 1.5 or less, 1.4 or less, 1.3 or less, 1.2 or less, 1.0 or less, 0.8 or less, 0.6 or less, or 0.5 or less. The above numerical ranges may be combined with one another without limitation. For example, the ratio of the volume of the compound represented by Formula 1 to the volume of the linear carbonate-based solvent may be 0.05 to 2, preferably 0.05 to 1.5. When within this range, it is possible to implement a non-aqueous electrolyte with excellent oxidation stability while appropriately controlling the viscosity of the organic solvent.

[0176]

[0177] If the above organic solvent further comprises the above linear carbonate-based solvent, the ratio of the total volume of the ethylene carbonate and the compound represented by Formula 1 to the volume of the above linear carbonate-based solvent may be 0.3 or more, 0.35 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, 0.9 or more, 0.95 or more, or 1.0 or more. The ratio of the total volume of the ethylene carbonate and the compound represented by Formula 1 to the volume of the above linear carbonate-based solvent may be 2.5 or less, 2.4 or less, 2.3 or less, 1.7 or less, 1.6 or less, 1.5 or less, 1.4 or less, 1.3 or less, 1.25 or less, or 1.2 or less. When within the above ranges, it is possible to realize a non-aqueous electrolyte having excellent oxidation stability while appropriately controlling the viscosity of the organic solvent.

[0178]

[0179] Meanwhile, the above organic solvent may be used without limitation by adding organic solvents commonly used in non-aqueous electrolytes as needed. For example, the above organic solvent may additionally include at least one organic solvent selected from linear ester-based solvents, cyclic ester-based solvents, ether-based solvents, glycine-based solvents, and nitrile-based solvents.

[0180] The above linear ester-based solvent may specifically include at least one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate.

[0181] In addition, the cyclic ester-based solvent may specifically include at least one selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone.

[0182] As the above ether-based solvent, any one selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methylpropyl ether, ethyl propyl ether, 1,3-dioxolane (DOL), and 2,2-bis(trifluoromethyl)-1,3-dioxolane (TFDOL), or a mixture of two or more of these may be used, but is not limited thereto.

[0183] The above-mentioned glyme solvent has a high dielectric constant and low surface tension compared to linear carbonate solvents and is a solvent with low reactivity with metal, and may include at least one selected from the group consisting of dimethoxyethane (glyme, DME), diethoxyethane, diglyme, triglyme, and tetraglyme (TEGDME), but is not limited thereto.

[0184] The above nitrile-based solvent may be one or more selected from the group consisting of acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanitrile, cyclopentane carbonitrile, cyclohexane carbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile, but is not limited thereto.

[0185]

[0186] (3) Additives

[0187] The above-mentioned non-aqueous electrolyte further comprises additives along with the lithium salt and organic solvent.

[0188] The above additive may be included in the non-aqueous electrolyte to prevent the decomposition of the non-aqueous electrolyte in a high-power environment from causing cathode collapse, or to provide low-temperature high-rate discharge characteristics, high-temperature stability, prevention of overcharging, and suppression of battery expansion at high temperatures.

[0189] Specifically, the above additive may include at least one selected from the group consisting of lithium difluorophosphate (LiDFP), vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, propane sultone, propene sultone, succinonitrile, adiponitrile, ethylene sulfate, LiBOB (Lithium bis-(oxalato)borate), LiBF4 (Lithium tetrafluoroborate), LiDFOB (Lithium difluoro(oxalato)borate), LiDFOP (Lithium difluoro bis(oxalato) phosphate), TMSPa (Tris(trimethylsilyl) Phosphate), TMSPi (Tris(trimethylsilyl) Phosphite), and compounds represented by the following chemical formula 3.

[0190] [Chemical Formula 3]

[0191]

[0192]

[0193] The above additive may be included in the above non-aqueous electrolyte in an amount of 0.1% to 15% by weight, more specifically 0.3% to 5% by weight.

[0194]

[0195] The external shape of the lithium secondary battery of the present invention is not particularly limited, but can be a cylindrical shape using a can, a prismatic shape, a pouch shape, or a coin shape.

[0196]

[0197] The present invention will be explained in more detail below through specific embodiments. However, the following embodiments are merely examples to aid in understanding the invention and do not limit the scope of the invention. It is obvious to those skilled in the art that various changes and modifications are possible within the scope and spirit of this description, and it is natural that such variations and modifications fall within the scope of the appended claims.

[0198]

[0199] Examples and Comparative Examples

[0200] Example 1

[0201] (Manufacture of non-aqueous electrolytes for lithium secondary batteries)

[0202] A non-aqueous electrolyte was prepared by dissolving LiPF6 to a volume ratio of 1.0 M in an organic solvent mixed with ethylene carbonate, ethylmethyl carbonate, and a compound represented by the chemical formula 1-A in a volume ratio of 20:70:10, and then adding vinylene carbonate, 1,3-propanesulfone, and ethylene sulfate as additives. Vinylene carbonate, 1,3-propanesulfone, and ethylene sulfate were each included in the non-aqueous electrolyte at a weight of 0.5%.

[0203]

[0204] (Secondary battery manufacturing)

[0205] Anode active material (Li[Ni 0.6 Co 0.1 Mn 0.3 An anode slurry (solid content 75.5 wt%) was prepared by adding [O2], a conductive material (carbon black), and a binder (polyvinylidene fluoride) in a weight ratio of 97.74:0.70:1.56. The anode slurry was applied to an anode current collector (Al thin film) and dried, then a roll press was performed to produce an anode.

[0206] A cathode slurry (solid content: 60 wt%) was prepared by adding a cathode active material (a mixture of graphite and a silicon-carbon composite in a weight ratio of 92:8), a binder (SBR-CMC), and a conductive material (carbon black) to water, a solvent, in a weight ratio of 97.6:0.8:1.5. The cathode slurry was coated onto a copper (Cu) thin film serving as a cathode current collector and dried, after which a roll press was performed to manufacture the cathode.

[0207] An electrode assembly was manufactured by interposing a porous separator polypropylene between the anode and cathode manufactured above, then housing it in a battery case, and a lithium secondary battery was manufactured by injecting the non-aqueous electrolyte manufactured above.

[0208]

[0209] Example 2

[0210] (Manufacture of non-aqueous electrolytes for lithium secondary batteries)

[0211] A non-aqueous electrolyte was prepared in the same manner as in Example 1, except that as an organic solvent, a mixture of ethylene carbonate, ethylmethyl carbonate, and a compound represented by the chemical formula 1-A was used in a volume ratio of 20:60:20.

[0212]

[0213] (Secondary battery manufacturing)

[0214] A lithium secondary battery was manufactured using the same method as in Example 1, except that the non-aqueous electrolyte for a lithium secondary battery manufactured above was used.

[0215]

[0216] Example 3

[0217] (Manufacture of non-aqueous electrolytes for lithium secondary batteries)

[0218] A non-aqueous electrolyte was prepared in the same manner as in Example 1, except that as an organic solvent, a mixture of ethylene carbonate, ethylmethyl carbonate, and a compound represented by the chemical formula 1-A was used in a volume ratio of 20:50:30.

[0219]

[0220] (Secondary battery manufacturing)

[0221] A lithium secondary battery was manufactured using the same method as in Example 1, except that the non-aqueous electrolyte for a lithium secondary battery manufactured above was used.

[0222]

[0223] Example 4

[0224] (Manufacture of non-aqueous electrolytes for lithium secondary batteries)

[0225] A non-aqueous electrolyte was prepared using the same method as in Example 1.

[0226]

[0227] (Secondary battery manufacturing)

[0228] Anode active material (Li[Ni 0.8 Co 0.1 Mn 0.1 An anode slurry (solid content 60 wt%) was prepared by adding [O2], a conductive material (carbon black), and a binder (polyvinylidene fluoride) in a weight ratio of 97.6:0.8:1.6. The anode slurry was applied to an anode current collector (Al thin film) and dried, then a roll press was performed to produce an anode.

[0229] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the anode manufactured above was used.

[0230]

[0231] Example 5

[0232] (Manufacture of non-aqueous electrolytes for lithium secondary batteries)

[0233] A non-aqueous electrolyte was prepared using the same method as in Example 2.

[0234]

[0235] (Secondary battery manufacturing)

[0236] A lithium secondary battery was manufactured in the same manner as in Example 4, except that the non-aqueous electrolyte prepared above was used.

[0237]

[0238] Example 6

[0239] (Manufacture of non-aqueous electrolytes for lithium secondary batteries)

[0240] A non-aqueous electrolyte was prepared using the same method as in Example 3.

[0241]

[0242] (Secondary battery manufacturing)

[0243] A lithium secondary battery was manufactured in the same manner as in Example 4, except that the non-aqueous electrolyte prepared above was used.

[0244]

[0245] Comparative Example 1

[0246] (Manufacture of non-aqueous electrolytes for lithium secondary batteries)

[0247] A non-aqueous electrolyte was prepared in the same manner as in Example 1, except that a mixture of ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a volume ratio of 20:70:10 was used as the organic solvent.

[0248]

[0249] (Secondary battery manufacturing)

[0250] A lithium secondary battery was manufactured using the same method as in Example 4, except that the non-aqueous electrolyte for a lithium secondary battery manufactured above was used.

[0251]

[0252] Comparative Example 2

[0253] (Manufacture of non-aqueous electrolytes for lithium secondary batteries)

[0254] A non-aqueous electrolyte was prepared in the same manner as in Example 1, except that as an organic solvent, a mixture of ethylene carbonate, ethylmethyl carbonate, and a compound represented by the chemical formula 1-A was used in a volume ratio of 20:77:3.

[0255]

[0256] (Secondary battery manufacturing)

[0257] A lithium secondary battery was manufactured using the same method as in Example 1, except that the non-aqueous electrolyte for a lithium secondary battery manufactured above was used.

[0258]

[0259] Comparative Example 3

[0260] (Manufacture of non-aqueous electrolytes for lithium secondary batteries)

[0261] A non-aqueous electrolyte was prepared in the same manner as in Example 1, except that as an organic solvent, a mixture of ethylene carbonate, ethylmethyl carbonate, and a compound represented by the chemical formula 1-A was used in a volume ratio of 20:20:60.

[0262]

[0263] (Secondary battery manufacturing)

[0264] A lithium secondary battery was manufactured using the same method as in Example 1, except that the non-aqueous electrolyte for a lithium secondary battery manufactured above was used.

[0265]

[0266] Comparative Example 4

[0267] (Manufacture of non-aqueous electrolytes for lithium secondary batteries)

[0268] A non-aqueous electrolyte was prepared in the same manner as in Example 1, except that as an organic solvent, a mixture of fluoroethylene carbonate, ethylmethyl carbonate, and a compound represented by the chemical formula 1-A was used in a volume ratio of 20:70:10.

[0269]

[0270] (Secondary battery manufacturing)

[0271] A lithium secondary battery was manufactured using the same method as in Example 1, except that the non-aqueous electrolyte for a lithium secondary battery manufactured above was used.

[0272]

[0273] Comparative Example 5

[0274] (Manufacture of non-aqueous electrolytes for lithium secondary batteries)

[0275] A non-aqueous electrolyte was prepared using the same method as Comparative Example 2.

[0276]

[0277] (Secondary battery manufacturing)

[0278] A lithium secondary battery was manufactured using the same method as in Example 4, except that the non-aqueous electrolyte for a lithium secondary battery manufactured above was used.

[0279]

[0280] Comparative Example 6

[0281] (Manufacture of non-aqueous electrolytes for lithium secondary batteries)

[0282] A non-aqueous electrolyte was prepared using the same method as Comparative Example 3.

[0283]

[0284] (Secondary battery manufacturing)

[0285] A lithium secondary battery was manufactured using the same method as in Example 4, except that the non-aqueous electrolyte for a lithium secondary battery manufactured above was used.

[0286]

[0287] Comparative Example 7

[0288] (Manufacture of non-aqueous electrolytes for lithium secondary batteries)

[0289] A non-aqueous electrolyte was prepared using the same method as Comparative Example 4.

[0290]

[0291] (Secondary battery manufacturing)

[0292] A lithium secondary battery was manufactured using the same method as in Example 4, except that the non-aqueous electrolyte for a lithium secondary battery manufactured above was used.

[0293]

[0294] Experimental Example 1. Evaluation of High-Temperature Cycle Characteristics

[0295] The lithium secondary batteries of the examples and comparative examples prepared above were charged to 4.3V and 0.05C at 45℃ under CC / CV and 0.33C conditions using an electrochemical charge / discharger, and then discharged to 2.5V under CC and 0.33C conditions, with 400 charge / discharge cycles performed as one cycle.

[0296]

[0297] (1) Evaluation of capacity retention rate

[0298] The capacity retention rate was calculated using the formula below, and the results are shown in Table 1 below.

[0299]

[0300] Capacity Retention Rate (%) = {(Discharge Capacity after 400 cycles / Discharge Capacity after 1 cycle)} × 100

[0301]

[0302] (2) Evaluation of resistance growth rate

[0303] After one cycle of charging and discharging, the discharge capacity after one cycle was measured using an electrochemical charge / discharger, and the SOC was adjusted to 50%. Then, a pulse of 2.5C was applied for 10 seconds, and the initial resistance was calculated through the difference between the voltage before and after the pulse application.

[0304] After 400 cycles of charging and discharging, the resistance after 400 cycles was calculated using the same method as above, and the resistance increase rate was calculated. The results are shown in Table 1 below.

[0305]

[0306] Resistance increase rate (%) = {(Resistance after 400 cycles - Resistance after 1 cycle) / Resistance after 1 cycle)} × 100

[0307]

[0308] (3) Evaluation of gas generation amount

[0309] After 400 cycles of charge and discharge, the amount of gas generated was measured using gas chromatography-mass spectrometry (GC-MS).

[0310]

[0311] Capacity Retention Rate (%) Resistance Increase Rate (%) Gas Generation Amount (mL / Ah) Example 191.5 21.7 1.32 Example 289.6 22.11.28 Example 387.9 24.71.23 Example 491.4 20.6 2.21 Example 592.3 18.11.76 Example 691.6 19.9 1.69 Comparative Example 190.8 21.3 2.55 Comparative Example 285.2 27.3 1.59 Comparative Example 382.7 30.9 0.89 Comparative Example 484.0 29.6 3.38 Comparative Example 586.5 23.3 2.69 Comparative Example 683.9 28.71.31 Comparative Example 781.4 33.8 5.19

[0312]

[0313] Referring to Table 1, it can be seen that the lithium secondary batteries of the embodiments using the non-aqueous electrolyte according to the present invention have significantly improved cycle charge / discharge performance at high temperatures compared to the comparative example.

[0314]

[0315] Experimental Example 2. Evaluation of High-Temperature Storage Characteristics

[0316] The lithium secondary batteries of the examples and comparative examples prepared above were charged to 4.3V and 0.05C at 25℃ under CC / CV and 0.33C conditions, and discharged to 2.5V at CC and 0.33C conditions to perform initial charge and discharge, and then charged to 4.3V and 0.05C at 25℃ under CC / CV and 0.33C conditions, and then stored at 60℃ for 16 weeks.

[0317]

[0318] (1) Evaluation of capacity retention rate

[0319] After storage, the above secondary batteries were charged to 4.3V and 0.05C at 25℃ under CC / CV and 0.33C conditions, and discharged to 2.5V at 0.33C. The capacity retention rate was evaluated according to the following formula, and the results are shown in Table 2 below.

[0320]

[0321] Capacity Retention Rate (%) = (Discharge Capacity after 16 Weeks of Storage / Initial Discharge Capacity) × 100

[0322]

[0323] (2) Evaluation of resistance growth rate

[0324] During the initial charge / discharge, the capacity was checked at room temperature, charged to SOC 50 based on the discharge capacity, and discharged for 10 seconds with a current of 2.5C. The resistance was measured using the difference in voltage drop at that time and set as the initial resistance. After storing at 60℃ for 16 weeks, the resistance was measured in the same way and set as the final resistance. The resistance increase rate was then calculated using the following formula. The results are shown in Table 2 below.

[0325]

[0326] Resistance Increase Rate (%) = (Final Resistance - Initial Resistance) / (Initial Resistance) × 100

[0327]

[0328] (3) Evaluation of gas generation amount

[0329] After storage under the above conditions, the amount of gas generated was measured using gas chromatography-mass spectrometry (GC-MS). The results are shown in Table 2 below.

[0330]

[0331] Capacity Retention Rate (%) Resistance Increase Rate (%) Gas Generation Amount (mL / Ah) Example 187.8 23.6 1.94 Example 288.1 23.8 1.86 Example 387.3 24.7 1.79 Example 488.7 22.8 3.26 Example 589.6 21.4 2.58 Example 689.0 22.3 2.43 Comparative Example 188.0 23.7 3.82 Comparative Example 283.3 29.5 2.09 Comparative Example 384.1 28.4 1.45 Comparative Example 482.9 31.7 4.28 Comparative Example 587.5 27.0 3.77 Comparative Example 685.3 30.6 1.89 Comparative Example 779.7 35.16.80

[0332]

[0333] Referring to Table 2, it can be seen that the lithium secondary batteries of the embodiments using the non-aqueous electrolyte according to the present invention have significantly improved storage performance at high temperatures compared to the comparative example.

Claims

1. A positive electrode; a negative electrode facing the positive electrode; a separator interposed between the positive electrode and the negative electrode; and a non-aqueous electrolyte; comprising, The above-mentioned positive electrode includes a positive electrode active material, and The above positive active material comprises a lithium transition metal oxide, and The above organic solvent comprises ethylene carbonate and a compound represented by the following chemical formula 1, and A lithium secondary battery in which the ratio of the volume of a compound represented by the following chemical formula 1 to the volume of the above ethylene carbonate is 0.2 to 2.5: [Chemical Formula 1] In the above chemical formula 1, R1 is a fluorine atom, a carbon-1 to carbon-10 alkyl group substituted with one or more fluorines, or a carbon-1 to carbon-10 alkoxy group substituted with one or more fluorines, and R2 and R3 are independently hydrogen, a carbon-1 to carbon-10 alkyl group, or a carbon-6 to carbon-20 aryl group.

2. In Claim 1, The above organic solvent is a lithium secondary battery containing 10 volume% to 40 volume% of the ethylene carbonate.

3. In Claim 1, A lithium secondary battery comprising 5 volume% to 40 volume% of a compound represented by the above chemical formula 1 in the above organic solvent.

4. In Claim 1, A lithium secondary battery comprising at least one compound selected from the group consisting of compounds represented by the following chemical formulas 1-1 to 1-5, represented by the compound represented by the above chemical formula 1: [Chemical Formula 1-1] [Chemical Formula 1-2] [Chemical Formula 1-3] [Chemical Formula 1-4] [Chemical Formula 1-5] In the above chemical formulas 1-1 to 1-5, R2 and R3 are as defined in the above chemical formula 1.

5. In Claim 1, A lithium secondary battery comprising at least one compound selected from the group consisting of compounds represented by the above chemical formula 1, chemical formula 1-A, chemical formula 1-B, chemical formula 1-C, chemical formula 1-D, and chemical formula 1-E: [Chemical Formula 1-A] [Chemical Formula 1-B] [Chemical Formula 1-C] [Chemical Formula 1-D] [Chemical Formula 1-E] .

6. In Claim 1, The above organic solvent is a lithium secondary battery further comprising a linear carbonate-based solvent.

7. In Claim 6, A lithium secondary battery comprising at least one linear carbonate-based solvent selected from the group consisting of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethylmethyl carbonate (EMC), methylpropyl carbonate, and ethylpropyl carbonate.

8. In Claim 6, The above organic solvent is a lithium secondary battery comprising 20 volume% to 85 volume% of the above linear carbonate-based solvent.

9. In Claim 6, A lithium secondary battery in which the ratio of the volume of the compound represented by Chemical Formula 1 to the volume of the linear carbonate-based solvent is 0.05 to 1.

5.

10. In Claim 1, The above lithium transition metal oxide is a lithium secondary battery containing nickel in an amount of 50 mol% or more of the metals excluding lithium.

11. In Claim 1, The above lithium transition metal oxide is a lithium secondary battery that is a compound represented by the following chemical formula A: [Chemical Formula A] Li 1+x (Ni a Co b Mr c M d )O2 In the above chemical formula A, M is one or more selected from W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, and 0≤x≤0.2, 0.50≤a<1, 0 <b≤0.2, 0<c≤0.3, 0≤d≤0.1, a+b+c+d=1이다.

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