Lithium secondary battery

Abstract

The present invention provides a lithium secondary battery comprising: a negative electrode; a positive electrode facing the negative electrode; a separator interposed between the negative electrode and the positive electrode; and a non-aqueous electrolyte, wherein the separator includes a porous substrate and a coating layer located on at least one surface of the porous substrate, the coating layer includes polyacrylonitrile, the non-aqueous electrolyte includes a lithium salt, an organic solvent, and an additive, and the additive includes at least one selected from the group consisting of a cyclic carbonate-based compound in which an unsaturated hydrocarbon group is present outside a ring and a linear carbonate-based compound in which an unsaturated hydrocarbon group is present.

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] Generally, a lithium secondary battery consists of a positive electrode containing a positive active material, a negative electrode containing a negative active material, an electrolyte serving as a medium for transporting lithium ions, and a separator. In this case, carbon-based active materials, silicon-based active materials, etc., may be used as the negative electrode active material. Additionally, lithium transition metal oxides such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), and lithium nickel-cobalt-manganese composite transition metal oxides may be used as the positive electrode active material.

[0004] In the case of the aforementioned lithium secondary battery, a solid electrolyte interface layer (SEI film) is formed on the anode and / or cathode during the initial activation process. This protects the anode and cathode during battery operation and prevents electrolyte consumption caused by side reactions. However, if the SEI film is destroyed or collapses due to volume expansion / contraction of the cathode during charging and discharging or the leaching of anode transition metals, problems such as electrolyte consumption and gas generation resulting from continuous side reactions may arise. Additionally, if the cathode active material has a large specific surface area, the induction of unnecessary side reactions can also be an issue. If a robust electrode film is not formed on the anode and / or cathode during this initial activation process, it may lead to problems such as capacity degradation and reduced lifespan.

[0005] The present invention provides a lithium secondary battery capable of reducing electrolyte side reactions by forming a flexible yet highly durable film on the electrode and improving the adhesion between the electrode and the separator, thereby improving the room temperature and high temperature durability and lifespan performance of the lithium secondary battery.

[0006] [1] The present invention provides a lithium secondary battery comprising a cathode; an anode facing the cathode; a separator interposed between the cathode and the anode; and a non-aqueous electrolyte, wherein the separator comprises a porous substrate and a coating layer located on at least one surface of the porous substrate, the coating layer comprises polyacrylonitrile, the non-aqueous electrolyte comprises a lithium salt, an organic solvent and an additive, and the additive comprises at least one selected from the group consisting of a cyclic carbonate compound having unsaturated hydrocarbon groups on the outside of the ring and a linear carbonate compound having unsaturated hydrocarbon groups.

[0007] [2] The present invention provides a lithium secondary battery in which the unsaturated hydrocarbon group is a vinyl group or a proparzil group, in accordance with [1].

[0008] [3] The present invention provides a lithium secondary battery comprising at least one cyclic carbonate compound having an unsaturated hydrocarbon group outside the ring in at least one of [1] and [2], selected from the group consisting of 4-ethenyl-1,3-dioxolane-2-one, 4-ethenyl-4-methyl-1,3-dioxolane-2-one, 4-ethenyl-4-ethyl-1,3-dioxolane-2-one, 4-ethenyl-4-n-propyl-1,3-dioxolane-2-one, 4-ethenyl-5-methyl-1,3-dioxolane-2-one, 4-ethenyl-5-ethyl-1,3-dioxolane-2-one and 4-ethenyl-5-n-propyl-1,3-dioxolane-2-one.

[0009] [4] The present invention provides a lithium secondary battery comprising, in at least one of [1] to [3] above, a linear carbonate compound having an unsaturated hydrocarbon group, selected from the group consisting of proparzyl methyl carbonate, proparzyl ethyl carbonate, proparzyl propyl carbonate, ethenyl methyl carbonate, ethenyl ethyl carbonate, and ethenyl propyl carbonate.

[0010] [5] The present invention provides a lithium secondary battery in which, in at least one of [1] to [4], at least one selected from the group consisting of a cyclic carbonate compound having unsaturated hydrocarbon groups on the outside of the ring and a linear carbonate compound having unsaturated hydrocarbon groups is included in the non-aqueous electrolyte in an amount of 0.1% to 10% by weight.

[0011] [6] The present invention provides a lithium secondary battery in which, in at least one of [1] to [5], the coating layer comprises 0.001% by weight or more of polyacrylonitrile.

[0012] [7] The present invention provides a lithium secondary battery in which, in at least one of [1] to [6], the coating layer may further comprise a polymer of an acrylic acid ester-based monomer, and the acrylic acid ester-based monomer is at least one selected from the group consisting of methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, butyl acrylate, isononyl acrylate and 2-ethylhexyl acrylate.

[0013]

[0014] [8] The present invention is a lithium secondary battery according to [7], wherein the polymer of the acrylic acid ester monomer is included in the coating layer in an amount of 0.1% to 10% by weight.

[0015] [9] The present invention relates to a lithium secondary battery in which, in at least one of [7] and [8], the weight ratio of the polymer of the polyacrylonitrile and the acrylic acid ester monomer is 0.1:99.9 to 20:80.

[0016]

[0010] The present invention provides a lithium secondary battery in which, in at least one of [1] to [9], the coating layer comprises an inorganic oxide, and the inorganic oxide comprises one or more elements selected from the group consisting of Si, Al, Ti, Zr, Sn, Ce, Mg, Ca, Zn, Y, Pb, Ba, Hf, and Sr.

[0017]

[0011] The present invention provides a lithium secondary battery in which, in

[0010] the inorganic oxide is included in the coating layer in an amount of 10% to 99% by weight.

[0018]

[0012] The present invention provides a lithium secondary battery in which, in at least one of [1] to

[0011] , the negative electrode comprises a negative electrode active material, and the negative electrode active material comprises at least one selected from the group consisting of a carbon-based active material and a silicon-based active material.

[0019] The lithium secondary battery of the present invention is characterized by comprising polyacrylonitrile as a coating layer of the separator, and at the same time, the additive of the non-aqueous electrolyte comprises at least one selected from the group consisting of cyclic carbonate compounds having unsaturated hydrocarbon groups on the outside of the ring and linear carbonate compounds having unsaturated hydrocarbon groups. The polyacrylonitrile and the aforementioned unsaturated hydrocarbon group-containing carbonate compounds can be copolymerized with each other, which can improve the adhesion between the electrode and the separator, thereby improving the operating performance of the battery, and at the same time, provide an SEI film component on the electrode surface that is durable, flexible, and capable of preventing side reactions of the electrolyte. Accordingly, the lithium secondary battery according to the present invention can improve room temperature and high temperature durability and lifespan performance.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] In this specification, the average particle size (D 50) can be defined as the particle size corresponding to 50% of the cumulative volume in the particle size distribution curve. The above average particle size (D 50 ) can be measured, for example, using the laser diffraction method. The laser diffraction method generally enables the measurement of particle sizes ranging from the submicron range to several millimeters, and can obtain results with high reproducibility and high resolution.

[0024] In this specification, the BET specific surface area is measured by the BET method, and specifically, it may be calculated by determining the amount of nitrogen gas adsorbed at a liquid nitrogen temperature (77K) using BEL Japan's BELSORP-mini II.

[0025]

[0026] The present invention will be described in more detail below.

[0027]

[0028] lithium secondary battery

[0029] The present invention provides a lithium secondary battery.

[0030] Specifically, the lithium secondary battery according to the present invention comprises a negative electrode; a positive electrode facing the negative electrode; a separator interposed between the negative electrode and the positive electrode; and a non-aqueous electrolyte, wherein the separator comprises a porous substrate and a coating layer located on at least one surface of the porous substrate, the coating layer comprises polyacrylonitrile, the non-aqueous electrolyte comprises a lithium salt, an organic solvent, and an additive, and wherein the additive comprises at least one selected from the group consisting of a cyclic carbonate compound having an unsaturated hydrocarbon group on the outside of the ring and a linear carbonate compound having an unsaturated hydrocarbon group.

[0031] The lithium secondary battery of the present invention is characterized by comprising polyacrylonitrile as a coating layer of the separator, and at the same time, the additive of the non-aqueous electrolyte comprises at least one selected from the group consisting of cyclic carbonate compounds having unsaturated hydrocarbon groups on the outside of the ring and linear carbonate compounds having unsaturated hydrocarbon groups. The polyacrylonitrile and the aforementioned unsaturated hydrocarbon group-containing carbonate compounds can be copolymerized with each other, which can improve the adhesion between the electrode and the separator, thereby improving the operating performance of the battery, and at the same time, provide an SEI film component on the electrode surface that is durable, flexible, and capable of preventing side reactions of the electrolyte. Accordingly, the lithium secondary battery according to the present invention can improve room temperature and high temperature durability and lifespan performance.

[0032] (1) Cathode

[0033] The above cathode may include a cathode active material.

[0034] The above-mentioned negative electrode active material may be any material used as a negative electrode active material in the field without limitation. Specifically, the above-mentioned negative electrode active material may include at least one selected from silicon-based active materials and carbon-based active materials.

[0035] As described below, the lithium secondary battery according to the present invention can form a flexible and highly durable SEI film component on the electrode surface by copolymerizing a separator coating layer component and a non-aqueous electrolyte additive, thereby increasing the adhesion between the electrode and the separator. For example, according to the present invention, the destruction of the SEI film due to volume expansion and contraction of the negative electrode caused by the insertion and extraction of lithium ions can be prevented, and problems such as electrolyte depletion and gas generation caused by continuous electrolyte side reactions can be prevented to a significant degree.

[0036] The above silicon-based active material is silicon (Si) and silicon oxide (SiO₂). xIt may include at least one core particle selected from , 0 < x < 2) and silicon-carbon composite.

[0037] Average particle size (D) of the above silicon-based active material 50 ) can be 1㎛ to 20㎛.

[0038] The above carbon-based active material may include at least one selected from the group consisting of graphite, hard carbon, soft carbon, carbon black, graphene, and fibrous carbon, and preferably may include graphite. The above graphite may include at least one selected from the group consisting of artificial graphite and natural graphite, and specifically may include natural graphite. For example, natural graphite is known to be a material with a large number of pores compared to artificially manufactured artificial graphite, and thus exhibits significant side reactions in the electrolyte; however, the lithium secondary battery according to the present invention can prevent side reactions in the electrolyte to a significant degree, thereby enabling desirable battery operating performance.

[0039] 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.

[0040] In addition, the cathode of the present invention may use a mixture of the carbon-based active material and the silicon-based active material as needed.

[0041] At this time, the weight ratio of the silicon-based active material and the carbon-based active material may be 1:99 to 30:70, specifically 3:97 to 15:85. When the mixing ratio of the silicon-based active material and the carbon-based active material satisfies the above range, excellent cycle performance can be secured by suppressing the volume expansion of the silicon-based active material while improving capacity characteristics.

[0042]

[0043] 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.

[0044] 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.

[0045] The above-mentioned cathode current collector can typically have a thickness of 3 to 500 μm.

[0046] 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.

[0047] The above-mentioned negative electrode active material layer is disposed on at least one surface of the negative electrode current collector. Specifically, the negative electrode active material layer may be disposed on one or both surfaces of the negative electrode current collector.

[0048] The above negative electrode active material may be included in the negative electrode active material layer in an amount of 60% to 99% by weight to minimize the effect of volume expansion / contraction on the battery while sufficiently expressing capacity in the secondary battery.

[0049] The above negative electrode active material layer may further include a conductive material and / or a binder together with the silicon-based active material.

[0050] The above binder can be used to improve the adhesion between the above negative electrode active material layer and the negative electrode current collector to be described later, or to improve the bonding strength between silicon-based active materials.

[0051] Specifically, the binder may include at least one selected from the group consisting of styrene butadiene rubber (SBR), nitrile butadiene rubber (NBR), acrylonitrile butadiene rubber, acrylic rubber, butyl rubber, fluoro rubber, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinyl alcohol (PVA), polyacrylic acid (PAA), polyethylene glycol (PEG), polyacrylonitrile (PAN), and polyacryl amide (PAM), in order to further improve electrode adhesion and provide sufficient resistance to volume expansion / contraction of the silicone-based active material.

[0052] The binder may be included in the cathode active material layer in an amount of 1% to 30% by weight. When within this range, the cathode active material can be better bound to minimize the volume expansion problem of the active material, and at the same time, the binder can be easily dispersed during the preparation of a slurry for forming the cathode active material layer, and the coating properties and phase stability of the slurry can be improved.

[0053] The above conductive material may be used to assist and improve conductivity in a secondary battery, and is not particularly limited as long as it is conductive without causing chemical changes. Specifically, the above 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 fiber such as carbon fiber or metal fiber; conductive tube such as carbon nanotube; metal powder such as fluorocarbon, aluminum, or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and polyphenylene derivatives.

[0054] The above conductive material may be included in the above cathode active material layer in an amount of 1% to 20% by weight, and when in this range, it is desirable in that it can form an excellent conductive network while mitigating the increase in resistance caused by the binder.

[0055] The thickness of the above negative electrode active material layer may be 5㎛ to 500㎛, preferably 5㎛ to 100㎛.

[0056] The above cathode can be manufactured by coating a cathode slurry comprising a cathode active material and optionally a binder, a conductive material, and a solvent for forming a cathode slurry onto the cathode current collector, and then drying and rolling.

[0057] The solvent for forming the above cathode slurry may include, for example, at least one selected from the group consisting of distilled water, ethanol, methanol, and isopropyl alcohol, preferably distilled water, in order to facilitate the dispersion of the cathode active material, binder, and / or conductive material.

[0058]

[0059] (2) bipolar

[0060] The above positive electrode faces the above negative electrode.

[0061] The above anode may include an anode active material.

[0062] 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, it may include a lithium metal composite oxide. More specifically, the lithium metal composite oxide 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 Mn 2-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. The anode may also be a Li-metal anode.

[0063] More specifically, the lithium metal composite oxide may include at least one selected from the group consisting of lithium cobalt oxide (LiCoO2), lithium nickel-cobalt-manganese oxide, lithium-manganese-rich oxide, and lithium iron phosphate.

[0064] The above lithium nickel-cobalt-manganese oxide may be at least one of the compounds represented by the following chemical formulas P-1 and P-2.

[0065] [Chemical Formula P-1]

[0066] Li 1+x (Ni a Co b Mn c M d )O2

[0067] In the above chemical formula P-1, 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≤0.25, 0<c≤0.25, 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.

[0068] [Chemical Formula P-2]

[0069] Li 1+y [Ni e Co f Mn g M 1 h ]O2+w

[0070] In the above chemical formula P-2, 0≤y≤0.5, e+f+g+h = 1, 0.5≤e≤0.7, 0≤f≤0.15, g=1-efh, 0≤h≤0.1, 0≤f / e≤0.2, 1≤g / e≤3, 0≤w≤1, and M 1 It 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.

[0071] In the above chemical formula P-2, y may be 0 ≤ y ≤ 0.5, specifically 0 ≤ y ≤ 0.2. In the above chemical formula P-2, 0.5 ≤ e ≤ 0.7, specifically 0.55 ≤ e ≤ 0.65. In the above chemical formula P-2, 0 ≤ f ≤ 0.15, specifically 0 ≤ f ≤ 0.1. In the above chemical formula P-2, 0 ≤ f / e ≤ 0.2, specifically 0.05 ≤ f / e ≤ 0.2. In the above chemical formula P-2, g = 1 - efh. Also, 1 ≤ g / e ≤ 3, specifically 1.5 ≤ g / e ≤ 2.5. In the above chemical formula P-2, M 1 It can be understood as an element doped into a lithium transition metal oxide, and specifically, it may be 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. In this case, h may be 0≤h≤0.1, specifically 0≤h≤0.05.

[0072] The above-mentioned lithium manganese-rich oxide may include a compound represented by the following chemical formula P-3.

[0073] [Chemical Formula P-3]

[0074] Li 1+s [Ni t Co u Mn v M 2 w ]O2+z

[0075] In the above chemical formula P-3, M 2 ... 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 0.05≤s≤1, 0≤t≤0.5, 0≤u≤0.3, 0.5≤v<1.0, 0≤w≤0.2, 0≤z≤1. Preferably, in the above formula P-3, 0.05≤s≤1.0, 0.1≤t≤0.5, 0≤u≤0.1, 0.5≤v<1.0, 0≤w≤0.2, and 0≤z≤1. More preferably, in the above formula P-3, 0.10≤s≤0.50, 0.1≤t≤0.5, 0≤u≤0.1, 0.6≤v<1.0, 0≤w≤0.1, and 0≤z≤0.50.

[0076] The above lithium iron phosphate may include a compound represented by the following chemical formula P-4.

[0077] [Chemical Formula P-4]

[0078] Li 1+z Fe 1-m M 2 m (PO 4-n )X n

[0079] In the above chemical formula P-4, M 2 is one or more elements selected from Co, Ni, Mn, Al, Mg, Ti, and V, X is F, S, or N, and 0≤m≤0.5; -0.5≤z≤+0.5; 0≤n≤0.1. The above chemical formula P-4 can be specifically represented as LiFePO4 (z=0, m=0, and n=0).

[0080]

[0081] The above positive active material may be in the form of particles. Specifically, the average particle size (D) of the above positive active material 50 ) can be 1㎛ to 30㎛.

[0082] The above positive active material may be included in the positive active material layer in an amount of 70% to 99% by weight, specifically 80% to 98% by weight, for capacity enhancement.

[0083]

[0084] 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. In this case, the positive active material layer may include the aforementioned positive active material.

[0085] The thickness of the above positive current collector can typically be 3 to 500 μm.

[0086] 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.

[0087] The positive active material layer is 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.

[0088] The above positive active material may be included in the positive active material layer in an amount of 80% to 99% by weight, taking into consideration the sufficient capacity exertion of the positive active material.

[0089] The above positive active material layer may further include a binder and / or a conductive material together with the aforementioned positive active material.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] The above conductive material 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 ensure electrical conductivity.

[0094] The thickness of the above positive active material layer may be 5㎛ to 500㎛, preferably 20㎛ to 200㎛.

[0095] 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.

[0096]

[0097] (3) Separator

[0098] The above separator is interposed between the cathode and the anode.

[0099] The above separation membrane may include a porous substrate and a coating layer located on at least one surface of the porous substrate.

[0100] The porous substrate is not particularly limited as long as it is typically used as a separator for a secondary battery. Specifically, it is desirable that the porous substrate has low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention capacity. More specifically, the porous substrate (131) may include at least one selected from the group consisting of polyolefin-based resins such as polyethylene, polypropylene, polybutylene, and polypentene; fluorine-based resins such as polyvinylidene fluoride and polytetrafluoroethylene; polyester-based resins such as polyethylene terephthalate and polybutylene terephthalate; and cellulose-based resins, and may be a porous film or nonwoven fabric comprising one or more copolymers or mixtures of these, or a laminated structure of two or more layers thereof. The porous substrate may be a porous film, nonwoven fabric, or a laminated structure of two or more layers thereof comprising the polyolefin-based resin.

[0101] The pore size and porosity present in the porous substrate are not particularly limited. Specifically, the porous substrate may be a porous substrate containing pores with an average pore diameter of 0.01 μm to 1 μm, specifically 20 nm to 60 nm, with a porosity of 10 vol% to 90 vol%, specifically 30 vol% to 60 vol%. In this case, it is desirable in that it improves the mechanical strength of the porous substrate and allows ionic substances to move more smoothly between the anode and the cathode. The average pore diameter and porosity may be measured by analysis using a focused ion beam (FIB), gas adsorption, or mercury intrusion.

[0102] The thickness of the porous substrate is not particularly limited, but considering the appropriate mechanical strength as a separation membrane and the ease of movement of ionic substances, it may be specifically 1 μm to 100 μm, or specifically 2 μm to 15 μm.

[0103] The coating layer may be located on one or both sides of the porous substrate.

[0104] The above coating layer contains polyacrylonitrile.

[0105] The above-mentioned polyacrylonitrile can be copolymerized with additives contained in the non-aqueous electrolyte (including cyclic carbonate compounds in which unsaturated hydrocarbon groups exist outside the ring), and such copolymerized products can improve the adhesion between the electrode and the separator while simultaneously functioning as a component of the SEI film on the electrode surface. In particular, since acrylonitrile contains both nitrile groups and carbon-carbon double bonds within its structure, polymerization occurs at various sites, which has an advantage in that it enables the realization of a film with wide coverage on the electrode.

[0106] The above polyacrylonitrile may be included in the coating layer in an amount of 0.001% by weight or more, specifically 0.005% by weight or more, more specifically 0.01% by weight or more. Meanwhile, the above polyacrylonitrile may be included in the coating layer in an amount of 100% by weight or less, specifically 5% by weight or less, more specifically 1% by weight or less, more specifically 0.1% by weight or less.

[0107] The coating layer may further comprise a polymer of an acrylic acid ester-based monomer together with the polyacrylonitrile. The polymer of the acrylic acid ester-based monomer can be used as a support for the polyacrylonitrile within the coating layer and can be utilized in terms of improving the transportability of lithium ions.

[0108] The above acrylic acid ester-based monomer may be at least one selected from the group consisting of methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, butyl acrylate, isononyl acrylate, and 2-ethylhexyl acrylate, and more specifically, may be butyl acrylate. More specifically, the polymer of the above acrylic acid ester-based monomer may be polybutyl acrylate.

[0109] If the coating layer further comprises a polymer of an acrylic acid ester-based monomer, the polymer of the acrylic acid ester-based monomer may be included in the coating layer in an amount of 0.1% to 10% by weight, specifically 0.2% to 2% by weight.

[0110] When the coating layer further comprises a polymer of an acrylic acid ester-based monomer, the weight ratio of the polyacrylonitrile and the polymer of the acrylic acid ester-based monomer may be 0.1:99.9 to 20:80, and specifically 1:99 to 10:90. Being within this range is preferable in that the supporting role of the polyacrylonitrile and the transportability of lithium ions can be further improved.

[0111] The coating layer may further include an inorganic oxide together with the polyacrylonitrile. The inorganic oxide may be included to improve the mechanical strength of the separator as well as to improve heat resistance.

[0112] Specifically, for example, the inorganic oxide may include at least one element selected from the group consisting of Si, Al, Ti, Zr, Sn, Ce, Mg, Ca, Zn, Y, Pb, Ba, Hf, and Sr, and preferably may include at least one element selected from the group consisting of Si, Al, Ti, and Zr.

[0113] More specifically, the inorganic oxides are SiO2, Al2O3, TiO2, ZrO2, SnO2, CeO2, MgO, CaO, ZnO, Y2O3, 　 Pb(Zr,Ti)O3 (PZT), Pb (1-a1) La a1 Zr (1-b1) Ti b1 O3 (0≤a1≤1, 0≤b1≤1, PLZT), PB(Mg3Nb 2 / 3 )O3-PbTiO 3　 (PMN-PT), BaTiO3, HfO2(hafnia), SrTiO 3　 These include, and the inorganic oxides listed above generally have the characteristic that their physical properties do not change even when the temperature reaches 200°C or higher. More preferably, the inorganic oxide may include at least one selected from the group consisting of SiO2, Al2O3, TiO2, and ZrO2.

[0114] The above inorganic oxide may be in the form of particles, and the average particle size (D) of the inorganic particles 50 ) can be 0.1㎛ to 1㎛, specifically 0.2㎛ to 0.7㎛.

[0115] When the above inorganic oxide is included in the coating layer, the above inorganic oxide may be included in the coating layer in an amount of 10% to 99% by weight, specifically 70% to 95% by weight, and the durability of the separator may be further improved when in this range.

[0116] In addition to the aforementioned components, the coating layer may include other additives used in the field, such as wetting agents and dispersants.

[0117] For example, the dispersant may be one or more selected from the group consisting of polyacrylic acid, polyacrylamide, polymethyl acrylate, polyethyl acrylate, polyisopropyl acrylate, polybutyl acrylate, polyisobutyl acrylate, polyethylhexyl acrylate, polymethyl methacrylate, polyvinylidene fluoride, styrene-butadiene rubber, nitrile-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, and copolymers comprising one or more of these. The dispersant may be included in the coating layer in an amount of 0.005 weight% or more, specifically 0.01 weight% or more, more specifically 0.02 weight% or more. The dispersant may be included in the coating layer in an amount of 10 weight% or less, more specifically 2 weight% or less, more specifically 1 weight% or less.

[0118] In addition, the wetting agent may include at least one selected from the group consisting of polyethylene, polyethylene glycol, and polypropylene glycol. The wetting agent may be included in the coating layer in an amount of 0.001% by weight or more, specifically 0.005% by weight or more, specifically 0.01% by weight or more. The wetting agent may be included in the coating layer in an amount of 10% by weight or less, specifically 5% by weight or less, more specifically 2% by weight or less, and more specifically 1% by weight or less.

[0119] The thickness of the coating layer may be 0.1㎛ to 10㎛, specifically 0.5㎛ to 5㎛.

[0120]

[0121] (4) Non-aqueous electrolyte

[0122] The above-mentioned non-aqueous electrolyte may include a lithium salt, an organic solvent, and an additive.

[0123]

[0124] 1) Lithium salt

[0125] 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

[0126] 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).

[0127] 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.

[0128]

[0129] 2) Organic solvent

[0130] The above organic solvent is a non-aqueous solvent commonly used in lithium secondary batteries, and is not particularly limited as long as it minimizes decomposition due to oxidation reactions, etc., during the charging and discharging process of the secondary battery.

[0131] Specifically, the organic solvent may include at least one selected from the group consisting of cyclic carbonate-based organic solvents, linear carbonate-based organic solvents, linear ester-based organic solvents, and cyclic ester-based organic solvents.

[0132] The above-mentioned cyclic carbonate-based organic solvent is a high-viscosity organic solvent that has a high dielectric constant and can effectively dissociate lithium salts in the electrolyte. Specifically, it may include at least one organic solvent selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, and vinylene carbonate, and more specifically, it may include ethylene carbonate.

[0133] In addition, the linear carbonate-based organic 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, ethylmethyl carbonate (EMC), methylpropyl carbonate, and ethylpropyl carbonate, and more specifically may include ethylmethyl carbonate (EMC).

[0134] The above organic solvent may be a mixture of a cyclic carbonate-based organic solvent and a linear carbonate-based organic solvent. In this case, the cyclic carbonate-based organic solvent and the linear carbonate-based organic solvent may be mixed in a volume ratio of 10:90 to 40:60, specifically a volume ratio of 10:90 to 30:70, and more specifically a volume ratio of 15:85 to 30:70. When the mixing ratio of the cyclic carbonate-based organic solvent and the linear carbonate-based organic solvent satisfies the above range, high dielectric constant and low viscosity characteristics are simultaneously satisfied, and excellent ionic conductivity characteristics can be achieved.

[0135] In addition, to produce an electrolyte having high ionic conductivity, the organic solvent may further include at least one ester-based organic solvent selected from the group consisting of a linear ester-based organic solvent and a cyclic ester-based organic solvent in addition to at least one carbonate-based organic solvent selected from the group consisting of a cyclic carbonate-based organic solvent and a linear carbonate-based organic solvent.

[0136] The above linear ester-based organic 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.

[0137] In addition, the above-mentioned cyclic ester-based organic solvent may specifically include at least one selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone.

[0138] Meanwhile, the above organic solvent may be used without limitation by adding organic solvents commonly used in non-aqueous electrolytes as needed. For example, it may additionally include at least one organic solvent among ether-based organic solvents, glyme-based solvents, and nitrile-based organic solvents.

[0139] 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.

[0140] The above-mentioned glyme-based solvent has a high dielectric constant and low surface tension compared to linear carbonate-based organic solvents and is a solvent with low reactivity with metals. It 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.

[0141] 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.

[0142]

[0143] 3) Additives

[0144] The above additive may include at least one selected from the group consisting of cyclic carbonate compounds having unsaturated hydrocarbon groups on the outside of the ring and linear carbonate compounds having unsaturated hydrocarbon groups.

[0145] At least one compound selected from the group consisting of cyclic carbonate compounds having or being substituted with unsaturated hydrocarbon groups on the outside of the ring and linear carbonate compounds having or being substituted with unsaturated hydrocarbon groups can be copolymerized with polyacrylonitrile included in the separator, and such copolymerized reaction products can improve the adhesion between the electrode and the separator while simultaneously functioning as a SEI film component on the electrode surface. Specifically, cyclic carbonate compounds having unsaturated hydrocarbon groups on the outside of the ring have an advantage in that the unsaturated hydrocarbon groups are located on the outside rather than the inside of the ring, allowing for a smooth copolymerization reaction with polyacrylonitrile within the separator.

[0146] The above unsaturated hydrocarbon group may be a vinyl group or a proparzyl group, and specifically, may be a vinyl group.

[0147] A cyclic carbonate compound having an unsaturated hydrocarbon group on the outside of the ring may include at least one selected from the group consisting of 4-ethenyl-1,3-dioxoran-2-one, 4-ethenyl-4-methyl-1,3-dioxoran-2-one, 4-ethenyl-4-ethyl-1,3-dioxoran-2-one, 4-ethenyl-4-n-propyl-1,3-dioxoran-2-one, 4-ethenyl-5-methyl-1,3-dioxoran-2-one, 4-ethenyl-5-ethyl-1,3-dioxoran-2-one, and 4-ethenyl-5-n-propyl-1,3-dioxoran-2-one, and preferably may include 4-ethenyl-1,3-dioxoran-2-one.

[0148] A linear carbonate compound having an unsaturated hydrocarbon group may include at least one selected from the group consisting of proparzyl methyl carbonate, proparzyl ethyl carbonate, proparzyl propyl carbonate, ethenyl methyl carbonate, ethenyl ethyl carbonate, and ethenyl propyl carbonate, and preferably may include proparzyl methyl carbonate.

[0149] At least one selected from the group consisting of cyclic carbonate compounds having unsaturated hydrocarbon groups on the outside of the ring and linear carbonate compounds having unsaturated hydrocarbon groups may be included in the non-aqueous electrolyte in an amount of 0.1% to 10% by weight, specifically 0.15% to 5% by weight, more specifically 0.2% to 1% by weight.

[0150]

[0151] The above additive may include an additional additive along with at least one selected from the group consisting of a cyclic carbonate compound having an unsaturated hydrocarbon group outside the ring and a linear carbonate compound having an unsaturated hydrocarbon group. If the above additive further includes an additional additive, at least one selected from the group consisting of a cyclic carbonate compound having an unsaturated hydrocarbon group outside the ring and a linear carbonate compound having an unsaturated hydrocarbon group may be named as the first additive, and the additional additive may be named as the second additive.

[0152] The above additional additive may be additionally included in the electrolyte as needed to prevent the electrolyte from decomposing and causing cathode breakdown in a high-power environment, or to further improve low-temperature high-rate discharge characteristics, high-temperature stability, prevention of overcharging, and suppression of battery expansion at high temperatures.

[0153] The above additive may include at least one selected from the group consisting of cyclic carbonate compounds, sulfate compounds, sulfone compounds, nitrile compounds, benzene compounds, lithium salt compounds, amine compounds, and silane compounds.

[0154] The above-mentioned cyclic carbonate compound may be vinylene carbonate (VC). In this case, since vinylene carbonate has unsaturated hydrocarbon groups inside the ring, in order to achieve the effect intended by the present invention, it is necessary to use at least one selected from the group consisting of a cyclic carbonate compound having unsaturated hydrocarbon groups outside the ring and a linear carbonate compound having unsaturated hydrocarbon groups, together with vinylene carbonate.

[0155] The above sulfate-based compound may be at least one selected from ethylene sulfate (Esa), trimethylene sulfate (TMS), and methyl trimethylene sulfate (MTMS).

[0156] The above sulfone-based compound may be at least one selected from the group consisting of 1,3-propane sulfone (PS), 1,4-butane sulfone, ethen sulfone, 1,3-propene sulfone (PRS), 1,4-butene sulfone, and 1-methyl-1,3-propene sulfone.

[0157] The above benzene-based compound may be fluorobenzene. The above amine-based compound may be at least one selected from triethanolamine and ethylenediamine. The above silane-based compound may be at least one selected from tetravinylsilane, tris(trimethylsilyl)phosphate (TMSPa), and tris(trimethylsilyl)phosphite (TMSPi).

[0158] The above lithium salt-based additive may be at least one selected from lithium bis-(oxalato)borate (LiBOB), lithium difluorooxalatoborate (LiODFB), and lithium difluorophosphate (LiDFP).

[0159] The above nitrile compound may be at least one selected from the group consisting of succinonitrile, adiponitrile, acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanitrile, cyclopentane carbonitrile, cyclohexane carbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile.

[0160] Meanwhile, the above additive may be used by mixing one or more of the aforementioned components, and may be included in an amount of less than 10% by weight based on the total weight of the non-aqueous electrolyte, specifically 0.01% by weight or more and less than 8.0% by weight, and preferably 0.05% by weight to 5.0% by weight.

[0161]

[0162] The above lithium secondary battery can be manufactured by housing an electrode assembly comprising at least one of the above negative electrode, the above positive electrode, and the above separator, and the above non-aqueous electrolyte in a battery case and sealing it.

[0163] The above lithium secondary battery can be manufactured by housing an electrode assembly and a non-aqueous electrolyte in the battery case and then sealing it. The structure, material, etc. of the battery case may be used without limitation as those known in the art.

[0164]

[0165] 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.

[0166]

[0167] Examples and Comparative Examples

[0168] Example 1

[0169] (Preparation of non-aqueous electrolytes)

[0170] As an organic solvent, a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 30:70 was used.

[0171] LiPF6 was added to the above organic solvent at a concentration of 1.0 M as a lithium salt, and vinylethylene carbonate (4-ethenyl-1,3-dioxoran-2-one) and vinylene carbonate were added as additives.

[0172] Vinylethylene carbonate (4-ethenyl-1,3-dioxoran-2-one) and vinylene carbonate were included in the non-aqueous electrolyte at 0.5 wt% and 0.5 wt%, respectively.

[0173]

[0174] (Manufacturing of electrode assemblies)

[0175] Cathode active material (Li[Ni 0.6 Co 0.1 Mn 0.3 An anode slurry was prepared by adding a conductive material (a mixture of carbon nanotubes and carbon black) and a binder (polyvinylidene fluoride) to the solvent N-methyl-2-pyrrolidone (NMP) in a weight ratio of 97.0:1.2:1.8. At this time, the weight ratio of the carbon nanotubes and carbon black was 1:0.2. The anode slurry was applied to one surface of an anode current collector (Al thin film) with a thickness of 12 μm, and a positive electrode active material layer (thickness: 150.5 μm) was formed by drying and roll pressing, and this was used as the anode.

[0176] A cathode slurry was prepared by adding a cathode active material (graphite), a conductive material (carbon black), a binder (SBR), and a thickener (CMC) to distilled water in a weight ratio of 96.5:0.5:1.9:1.1. The cathode slurry was applied to one surface of a cathode current collector (Cu thin film) with a thickness of 8 μm, and a cathode active material layer (thickness: 196.5 μm) was formed by drying and roll pressing, and this was used as the cathode.

[0177] Next, a separator was manufactured by forming coating layers on both sides of a porous substrate made of polyethylene (thickness: 9 μm). The coating layers contained polyacrylonitrile, polybutyl acrylate, polyvinylidene fluoride, polyacrylic acid, polyethylene glycol, and Al2O3 as an inorganic oxide in a weight ratio of 0.06:1.14:10.50:0.24:0.06:88.00. The thickness of each coating layer located on both sides of the porous substrate was 2.5 μm. The coating layers were manufactured by applying a dispersion containing polyacrylonitrile, polybutyl acrylate, polyvinylidene fluoride, polyacrylic acid, polyethylene glycol, and Al2O3 as an inorganic oxide in the above weight ratios to the porous substrate and then drying it.

[0178] An electrode assembly was manufactured in a dry room by interposing a polyethylene porous film separator between the anode and cathode manufactured above.

[0179]

[0180] (Manufacturing of lithium secondary batteries)

[0181] A lithium secondary battery was manufactured by housing the above electrode assembly in a pouch-type battery case, injecting the above-mentioned non-aqueous electrolyte, and sealing it.

[0182]

[0183] Example 2

[0184] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that vinylethylene carbonate was included in the non-aqueous electrolyte at 0.01 wt% instead of 0.5 wt%.

[0185]

[0186] Example 3

[0187] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that vinylethylene carbonate was included in the non-aqueous electrolyte at 5% by weight instead of 0.5% by weight.

[0188]

[0189] Example 4

[0190] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that proparzyl methyl carbonate was included in the non-aqueous electrolyte at a content of 0.5 wt% instead of vinylethylene carbonate as an additive.

[0191]

[0192] Comparative Example 1

[0193] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that vinylethylene carbonate was not included in the non-aqueous electrolyte.

[0194]

[0195] Comparative Example 2

[0196] A non-aqueous electrolyte and a lithium secondary battery were prepared in the same manner as in Example 1, except that vinylethylene carbonate was not included in the non-aqueous electrolyte and vinylene carbonate was included in the non-aqueous electrolyte at a content of 1% by weight instead of 0.5% by weight.

[0197]

[0198] Comparative Example 3

[0199] A separator was manufactured by forming coating layers on both sides of a porous substrate made of polyethylene (thickness: 9 μm). The coating layers contained polybutyl acrylate, polyvinylidene fluoride, polyacrylic acid, polyethylene glycol, and Al2O3 as an inorganic oxide in a weight ratio of 1.20:10.50:0.24:0.06:88.00. The thickness of each coating layer located on both sides of the porous substrate was 2.5 μm.

[0200] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the separator prepared above was used instead of the separator of Example 1.

[0201]

[0202] Comparative Example 4

[0203] A separator was manufactured by forming coating layers on both sides of a porous substrate made of polyethylene (thickness: 9 μm). The coating layers contained polyvinylidene fluoride, polyacrylic acid, polyethylene glycol, and Al2O3 as an inorganic oxide in a weight ratio of 11.7:0.24:0.06:88.00. The thickness of each coating layer located on both sides of the porous substrate was 2.5 μm.

[0204] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the separator prepared above was used instead of the separator of Example 1.

[0205]

[0206] Experimental Example

[0207] Experimental Example 1: Lifespan Performance

[0208] The lithium secondary batteries of Examples 1 to 4 and Comparative Examples 1 to 4 prepared above were charged to 4.35V and 1 / 20V 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 300 charge / discharge cycles performed as one cycle.

[0209]

[0210] (1) Capacity retention rate

[0211] The capacity retention rate was calculated using the formula below, and the results are shown in Table 2 below.

[0212]

[0213] Capacity Retention Rate (%) = {(Discharge Capacity after 300 Cycles) / (Discharge Capacity after 1 Cycle)} × 100

[0214]

[0215] (2) Resistance increase rate

[0216] 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 using the difference between the voltage before and after the pulse application.

[0217] After 300 charge-discharge cycles, the resistance after 300 cycles was calculated using the same method as above, and the resistance increase rate was calculated using the formula below. The results are shown in Table 1 below.

[0218]

[0219] Capacitance Retention Rate (%) Resistance Increase Rate (%) Example 196.5 13.8 Example 283.1 37.4 Example 383.5 37.1 Example 493.7 17.1 Comparative Example 170.3 50.9 Comparative Example 278.1 45.6 Comparative Example 338.2 90.4 Comparative Example 440.6 88.1

[0220]

[0221] Referring to Table 1 above, it is confirmed that the lithium secondary battery combined with the separator and non-aqueous electrolyte of the present invention has significantly improved lifespan and resistance characteristics during cycle charging and discharging compared to a comparative example that does not.

[0222]

[0223] Experimental Example 2: High Temperature Durability

[0224] The lithium secondary batteries of Examples 1 to 4 and Comparative Examples 1 to 4 prepared above were charged to 4.35V and 1 / 20C at 25℃ under CC / CV and 0.33C conditions, and discharged to 2.5V at 0.33C to perform initial charge and discharge, and then charged to 4.35V and 1 / 20C at 25℃ under CC / CV and 0.33C conditions, and then stored at 60℃ for 12 weeks.

[0225]

[0226] (1) Capacity retention rate

[0227] The capacity retention rate was calculated using the formula below, and the results are shown in Table 2 below.

[0228]

[0229] Capacity Retention Rate (%) = (Discharge Capacity after 12 Weeks of Storage / Initial Discharge Capacity) × 100

[0230]

[0231] (2) Resistance increase rate

[0232] During the initial charge / discharge, the capacity was checked at room temperature, then charged to SOC 50 based on the discharge capacity, and discharged for 10 seconds with a current of 3C. The resistance was measured using the difference in voltage drop at that time and set as the initial resistance. After storing at 60℃ for 12 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 4 below.

[0233]

[0234] Resistance Increase Rate (%) = (Final Resistance - Initial Resistance) / (Initial Resistance) × 100

[0235]

[0236] Capacitance Retention Rate (%) Resistance Increase Rate (%) Example 192.8 20.9 Example 280.5 43.4 Example 380.8 43.8 Example 489.4 25.5 Comparative Example 167.0 60.7 Comparative Example 273.1 50.8 Comparative Example 332.2 100.3 Comparative Example 437.6 95.1

[0237]

[0238] Referring to Table 2 above, it can be seen that the lithium secondary battery combined with the separator and non-aqueous electrolyte of the present invention can have significantly improved high-temperature storage performance compared to a comparative example that does not.

Claims

1. Cathode; An anode facing the above cathode; A separator interposed between the above cathode and the above anode; and Contains non-aqueous electrolytes, The above separator comprises a porous substrate and a coating layer located on at least one surface of the porous substrate, and The above coating layer comprises polyacrylonitrile, and The above-mentioned non-aqueous electrolyte comprises a lithium salt, an organic solvent, and an additive, and A lithium secondary battery comprising at least one additive selected from the group consisting of cyclic carbonate compounds having unsaturated hydrocarbon groups on the outside of the ring and linear carbonate compounds having unsaturated hydrocarbon groups.

2. In Claim 1, A lithium secondary battery in which the above-mentioned unsaturated hydrocarbon group is a vinyl group or a proparzyl group.

3. In Claim 1, A lithium secondary battery comprising at least one cyclic carbonate compound having an unsaturated hydrocarbon group on the outside of the ring, selected from the group consisting of 4-ethenyl-1,3-dioxolane-2-one, 4-ethenyl-4-methyl-1,3-dioxolane-2-one, 4-ethenyl-4-ethyl-1,3-dioxolane-2-one, 4-ethenyl-4-n-propyl-1,3-dioxolane-2-one, 4-ethenyl-5-methyl-1,3-dioxolane-2-one, 4-ethenyl-5-ethyl-1,3-dioxolane-2-one, and 4-ethenyl-5-n-propyl-1,3-dioxolane-2-one.

4. In Claim 1, A lithium secondary battery comprising at least one linear carbonate compound having an unsaturated hydrocarbon group selected from the group consisting of proparzyl methyl carbonate, proparzyl ethyl carbonate, proparzyl propyl carbonate, ethenyl methyl carbonate, ethenyl ethyl carbonate, and ethenyl propyl carbonate.

5. In Claim 1, A lithium secondary battery comprising at least one selected from the group consisting of cyclic carbonate compounds having unsaturated hydrocarbon groups on the outside of the ring and linear carbonate compounds having unsaturated hydrocarbon groups, wherein the non-aqueous electrolyte contains 0.1% to 10% by weight.

6. In Claim 1, The above coating layer is a lithium secondary battery containing 0.001% by weight or more of polyacrylonitrile.

7. In Claim 1, The above coating layer may further include a polymer of an acrylic acid ester-based monomer, and A lithium secondary battery in which the above acrylic acid ester monomer is at least one selected from the group consisting of methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, butyl acrylate, isononyl acrylate, and 2-ethylhexyl acrylate.

8. In Claim 7, A lithium secondary battery in which the polymer of the above acrylic acid ester-based monomer is included in the coating layer at a concentration of 0.1% to 10% by weight.

9. In Claim 7, A lithium secondary battery in which the weight ratio of the polymer of the polyacrylonitrile and the acrylic acid ester-based monomer is 0.1:99.9 to 20:

80.

10. In Claim 1, The above coating layer includes inorganic oxides, and The above-mentioned inorganic oxide is a lithium secondary battery comprising one or more elements selected from the group consisting of Si, Al, Ti, Zr, Sn, Ce, Mg, Ca, Zn, Y, Pb, Ba, Hf, and Sr.

11. In Claim 10, A lithium secondary battery in which the above-mentioned inorganic oxide is included in the coating layer in an amount of 10% to 99% by weight.

12. In Claim 1, The above cathode includes a cathode active material, and A lithium secondary battery comprising at least one type selected from the group consisting of carbon-based active materials and silicon-based active materials, wherein the above-mentioned negative electrode active material.