Lithium secondary battery, and battery module and battery pack comprising same

Abstract

The present invention relates to a lithium secondary battery, and a battery module and a battery pack comprising same, the lithium secondary battery comprising: a positive electrode containing a positive electrode active material; a negative electrode containing a negative electrode active material; and an electrolyte, wherein the positive electrode active material comprises a single-particle-type lithium nickel-based oxide having a Ni content of 50 mol% to 70 mol% among all metals excluding lithium, the electrolyte contains N,N-dimethylsulfamoyl fluoride (DMSF), and the N,N-dimethylsulfamoyl fluoride is contained in an amount of less than 30 vol% on the basis of the total volume of the electrolyte.

Description

Lithium secondary battery, battery module including the same, and battery pack

[0001] The present application claims the benefit of priority based on Korean Patent Application No. 10-2024-0196378 filed on December 24, 2024 and Korean Patent Application No. 10-2025-0208535 filed on December 23, 2025, and all contents disclosed in said Korean patent application documents are incorporated herein as part of the specification.

[0002] The present invention relates to a lithium secondary battery, and more specifically, to a lithium secondary battery with improved high-temperature durability, and to a battery module and a battery pack including the same.

[0003] With the advancement of technologies such as electric vehicles, energy storage systems (ESS), and portable electronic devices, the demand for lithium secondary batteries as an energy source is rapidly increasing.

[0004] Recently, in the electric vehicle sector, there has been a demand for cells with high energy density to extend driving range on a single charge. Accordingly, lithium-ion batteries containing high-nickel (High-Ni) cathode active materials, which improve capacity by increasing the nickel content, have been developed. However, because high-nickel cathode active materials have a high unit cost, their application increases the production costs of both secondary batteries and electric vehicles, acting as an obstacle to the widespread adoption of electric vehicles. Furthermore, while increasing the nickel content in the cathode active material improves initial capacity characteristics, the highly reactive nickel... +4 There is a problem in that the excessive generation of ions causes structural collapse of the cathode active material, which increases the degradation rate of the cathode active material, leading to reduced lifespan characteristics and decreased battery safety.

[0005] To reduce the manufacturing costs of electric vehicles, technologies are being developed to secure energy density by applying cathode active materials with a relatively lower nickel content compared to high-nickel (High-Ni) materials and operating at higher voltages than conventional methods. However, operating lithium-ion batteries at high voltages presents a problem in that side reactions with the electrolyte increase, leading to increased gas generation and cell degradation, which in turn degrades lifespan characteristics.

[0006] To address these issues, various additives capable of suppressing gas generation in the electrolyte are being attempted; however, this approach has drawbacks, such as increased costs due to additive addition, reduced gas suppression efficacy as the additives are consumed during cycles, and insufficient improvement in lifespan. Additionally, there is a problem in that cell degradation is further accelerated when exposed to high temperatures.

[0007] Therefore, there is a need to develop lithium secondary batteries that have high energy density, excellent lifespan characteristics, and low manufacturing costs.

[0008] The present invention aims to solve the above-mentioned problems by applying a single-particle lithium nickel-based oxide with a Ni content of 50 mol% to 70 mol% as the positive electrode active material, and by replacing part of the electrolyte solvent with dimethylsulfamoyl fluoride, thereby providing a lithium secondary battery having excellent high-temperature durability even at high voltage.

[0009] [1] The present invention provides a lithium secondary battery comprising a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material; and an electrolyte, wherein the positive electrode active material comprises a single-particle lithium nickel-based oxide having a Ni content of 50 mol% to 70 mol% among all metals excluding lithium, and the electrolyte comprises dimethylsulfamoyl fluoride (N,N-DiMethyl Sulfamoyl Fluoride, DMSF), wherein the dimethylsulfamoyl fluoride is included in an amount of less than 30 volume% based on the total volume of the electrolyte.

[0010] [2] The present invention provides a lithium secondary battery according to [1], wherein the lithium nickel-based oxide comprises 30 or fewer nodules.

[0011] [3] The present invention provides a lithium secondary battery in which, in [1] or [2], the lithium nickel-based oxide is represented by the following [Chemical Formula 1].

[0012] [Chemical Formula 1]

[0013] Li 1+x [Ni a Co b Mn c M 1 d ]O2

[0014] In the above [Chemical Formula 1], M 1 It contains one or more elements selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, Ca, Sr, W, Ta, Nb, and Mo, and -0.1≤x≤0.1, 0.5≤a≤0.70, 0 <b<0.5, 0<c<0.5, 0≤d≤0.2이다.

[0015] [4] The present invention provides a lithium secondary battery in which, in at least one of [1] to [3], the positive electrode active material further comprises a coating layer comprising one or more elements selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, Ca, Sr, W, Ta, Nb, and Mo on the surface of the lithium nickel-based oxide.

[0016] [5] The present invention provides a lithium secondary battery in which, in at least one of [1] to [4], the dimethylsulfamoyl fluoride is included in an amount of 5 volume% or more and less than 30 volume% based on the total volume of the electrolyte.

[0017] [6] The present invention provides a lithium secondary battery in which, in at least one of [1] to [5], the dimethylsulfamoyl fluoride is included in an amount of 5% to 25% by volume based on the total volume of the electrolyte.

[0018] [7] The present invention provides a lithium secondary battery in which, in at least one of [1] to [6], the electrolyte further comprises a lithium salt, a cyclic carbonate-based organic solvent, and a linear carbonate-based organic solvent.

[0019] [8] The present invention provides a lithium secondary battery in which, in at least one of [1] to [7], the negative electrode comprises a carbon-based negative electrode active material.

[0020] [9] The present invention provides a lithium secondary battery in which, in at least one of [1] to [8], the cathode comprises: a cathode current collector; a first cathode active material layer formed on the cathode current collector and comprising a first cathode active material; and a second cathode active material layer formed on the first cathode active material layer and comprising a second cathode active material, wherein the first cathode active material and the second cathode active material are made of carbon-based cathode active materials.

[0021]

[0010] The present invention provides a lithium secondary battery in which, in [9] above, the first negative electrode active material and the second negative electrode active material are each independently natural graphite, artificial graphite, or a combination thereof.

[0022]

[0011] The present invention provides a lithium secondary battery having a nominal voltage of 3.68V or higher in at least one of [1] to

[0010] .

[0023]

[0012] The present invention provides a lithium secondary battery having a charge cut-off voltage of 4.35V or higher in at least one of [1] to

[0011] .

[0024]

[0013] The present invention provides a lithium secondary battery having a capacity retention rate of 95% or more after charging and discharging the lithium secondary battery 200 cycles at 0.33C at 45°C in a voltage range of 2.5V to 4.35V, in at least one of [1] to

[0012] .

[0025]

[0014] The present invention provides a lithium secondary battery in which, in at least one of [1] to

[0013] , the resistance increase rate is 115% or less after charging and discharging the lithium secondary battery for 200 cycles at 0.33C at 45°C in a voltage range of 2.5V to 4.35V.

[0026]

[0015] The present invention provides a lithium secondary battery in which the resistance increase rate measured after charging the lithium secondary battery to 4.35V and then storing it at 60°C for 12 weeks is 120% or less.

[0027]

[0016] The present invention provides a battery module comprising at least one lithium secondary battery among [1] to

[0015] as a unit cell.

[0028]

[0017] The present invention provides a battery module according to

[0016] , wherein the battery module comprises 10 to 50 unit cells.

[0029]

[0018] The present invention provides a battery pack comprising at least one of the lithium secondary batteries [1] to

[0015] as a unit cell.

[0030]

[0019] The present invention provides a battery pack according to

[0018] , wherein the battery pack comprises 10 to 1,000 unit cells.

[0031]

[0020] The present invention provides a battery pack comprising the secondary battery module of

[0016] .

[0032] The lithium secondary battery according to the present invention uses a single-particle lithium nickel-based oxide having a nickel content of 50 mol% to 75 mol% as the positive active material, thereby preventing the positive active material from rapidly degrading at a high voltage of 4.35 V or higher.

[0033] The lithium secondary battery according to the present invention includes dimethylsulfamoyl fluoride, which has excellent oxidation stability and structural stability, as an electrolyte solvent, thereby minimizing adverse reactions with the electrolyte when operating at high temperature and / or high voltage, and thus improving lifespan characteristics.

[0034] Specifically, using dimethylsulfamoyl fluoride as an electrolyte solvent minimizes the use of gas-generating solvents and improves oxidation stability due to changes in the solvation structure. Furthermore, dimethylsulfamoyl fluoride contains electron-withdrawing groups in its chemical structure, which enhances oxidation stability, and improves structural stability through a uniform electron distribution. Additionally, it can achieve a highly durable film-forming effect by participating in film-forming reactions to suppress further decomposition reactions.

[0035] Figure 1 is a scanning electron microscope image of a single-particle positive electrode active material.

[0036] Figure 2 is a scanning electron microscope image of a pseudo-single particle cathode active material.

[0037] Figure 3 is a scanning electron microscope image of a secondary particle positive electrode active material.

[0038] Figure 4 is a graph showing the resistance characteristics of lithium secondary batteries of Examples 2 to 3 and Comparative Examples 1 and 3.

[0039] 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.

[0040] In the present invention, "single particle type" refers to a particle composed of 30 or fewer nodules, and is a concept that includes a single particle composed of one nodule and a pseudo-single particle which is a composite of 2 to 30 nodules. Fig. 1 shows a scanning electron microscope image of a positive electrode active material in a single particle form, and Fig. 2 shows a scanning electron microscope image of a positive electrode active material in a pseudo-single particle form.

[0041] The above “nodule” is a sub-grain unit constituting a single particle and a pseudo-single particle, and may be a single crystal that does not have crystalline grain boundaries, or a polycrystalline one in which no grain boundaries appear to exist when observed at a field of view of 5,000 to 20,000 times using a scanning electron microscope.

[0042] In the present invention, "secondary particle" refers to a particle formed by the aggregation of a plurality of primary particles, for example, tens to hundreds of primary particles. Specifically, the secondary particle may be an aggregate of more than 30 primary particles. FIG. 3 shows a scanning electron microscope (SEM) image of a positive electrode active material in the form of a secondary particle.

[0043] In the present invention, the term “particle” is a concept that includes any one or all of a single particle, a pseudo-single particle, a primary particle, a nodule, and a secondary particle.

[0044] In the present invention, the average particle size (Dmean) of nodules or primary particles refers to the arithmetic mean value calculated after measuring the particle sizes of nodules or primary particles observed in scanning electron microscope images.

[0045] In the present invention, "average particle size D50" refers to a particle size corresponding to 50% of the volume cumulative amount of the volume cumulative particle size distribution of the powder to be measured, and can be measured using a laser diffraction method. For example, the powder to be measured can be measured by dispersing it in a dispersion medium, introducing it into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000), irradiating it with ultrasound of about 28 kHz at an output of 60 W, obtaining a volume cumulative particle size distribution graph, and then determining the particle size corresponding to 50% of the volume cumulative amount.

[0046]

[0047] As a result of repeated research to develop a lithium secondary battery that has relatively low manufacturing costs and excellent high-temperature durability even at high voltages, the inventors discovered that by applying a single-particle lithium nickel-based oxide with a Ni content of 50 mol% to 70 mol% as the positive electrode active material and including dimethylsulfamoyl fluoride in a specific amount as the electrolyte solvent, excellent high-temperature life characteristics and high-temperature storage characteristics can be achieved even when operating at high voltages, and thus completed the present invention.

[0048]

[0049] A lithium secondary battery according to the present invention comprises a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material; and an electrolyte, wherein the positive electrode active material comprises a single-particle lithium nickel-based oxide having a Ni content of 50 mol% to 70 mol% among all metals excluding lithium, and the electrolyte comprises dimethylsulfamoyl fluoride (N,N-DiMethyl Sulfamoyl Fluoride, DMSF).

[0050] Single-particle lithium nickel-based oxides with a nickel content of 50 mol% to 70 mol% have superior structural stability compared to high-nickel (High-Ni) lithium transition metal oxides with a nickel content of 80 mol% or more, so they can prevent the rapid degradation of the cathode active material even when operated at high voltages of 4.35 V or higher.

[0051] Dimethylsulfamoyl fluoride (N,N-DiMethyl Sulfamoyl Fluoride, DMSF) exhibits superior oxidation stability at high potential compared to conventional carbonate-based organic solvents used as electrolyte solvents. Therefore, its application minimizes side reactions caused by the decomposition of organic solvents within the electrolyte, thereby suppressing gas generation and active material degradation resulting from side reactions with the electrolyte. Conventionally, combinations of cyclic carbonates such as ethylene carbonate and linear carbonates such as methyl ethyl carbonate and diethyl carbonate have been primarily used as electrolyte solvents. However, these carbonate-based solvents decompose rapidly at high potentials of 4.35V or higher, generating large amounts of gas and side reactions. In contrast, since N,N-DiMethyl Sulfamoyl Fluoride (DMSF) has relatively high oxidation stability even at high potentials of 4.35V or higher, it can minimize the generation of gases and side reactions caused by electrolyte decomposition. However, if the content of N,N-DiMethyl Sulfamoyl Fluoride is too high, the initial resistance increases, which may degrade fast charging performance and / or output performance. Therefore, it is preferable to include the N,N-DiMethyl Sulfamoyl Fluoride (DMSF) in an amount of less than 30 volume% based on the total volume of the electrolyte.

[0052]

[0053] The components of the lithium secondary battery according to the present invention will be described in more detail below.

[0054]

[0055] anode

[0056] A lithium secondary battery according to the present invention comprises a positive electrode comprising a positive electrode active material. Specifically, the positive electrode comprises a positive electrode current collector and a positive electrode active material layer formed on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer comprises a positive electrode active material. In addition, the positive electrode active material layer may further comprise a positive electrode conductive material and a positive electrode binder in addition to the positive electrode active material.

[0057] The above positive current collector is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the above positive current collector may typically have a thickness of 3 to 500 μm, and fine irregularities may be formed on the surface of the positive current collector to increase the adhesion of the positive active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0058]

[0059] The above positive active material may include a lithium nickel-based oxide having a Ni content of 50 mol% to 70 mol%, preferably 55 mol% to 70 mol%, more preferably 55 mol% to 65 mol%.

[0060] As the nickel content in lithium nickel-based oxides increases, the reactivity of Ni increases. +4As the number of ions increases, the structural stability of the positive electrode active material decreases during charging and discharging, leading to rapid degradation of the positive electrode. This phenomenon is further exacerbated during high-voltage operation. In contrast, lithium nickel-based oxides with a Ni content of 50 mol% to 70 mol% have higher structural stability at high voltage compared to lithium nickel-based oxides with a nickel content of 80 mol% or more, thereby minimizing the degradation of lifespan characteristics during high-voltage operation. However, since capacity characteristics deteriorate if the Ni content is too low, it is preferable that the Ni content of the lithium nickel-based oxide be approximately 50 mol% to 70 mol%.

[0061] Specifically, the lithium nickel-based oxide may be a lithium transition metal oxide containing nickel, manganese and cobalt, and, for example, may be represented by the following [Chemical Formula 1].

[0062] [Chemical Formula 1]

[0063] Li 1+x [Ni a Co b Mn c M 1 d ]O2

[0064] In the above [Chemical Formula 1], M 1 It may contain one or more elements selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, Ca, Sr, W, Ta, Nb, and Mo. 1 When the element is included, the structural stability of the lithium nickel-based oxide particles is improved, enabling superior lifespan characteristics during high-voltage operation. Preferably, the above M 1 The elements may include one or more selected from the group consisting of Ti, Mg, Al, Zr, and Y, and more preferably, may include two or more selected from the group consisting of Ti, Mg, Al, Zr, and Y.

[0065] The above 1+x represents the lithium molar ratio in the lithium nickel-based oxide, and may be -0.1≤x≤0.1, 0≤x≤0.1, or 0≤x≤0.07. When 1+x satisfies the above range, a stable layered crystal structure can be formed.

[0066] The above a represents the molar ratio of nickel among the total metals excluding lithium in the lithium nickel-based oxide, and may be 0.50≤a≤0.70, 0.55≤a≤0.70, or 0.55≤a≤0.65.

[0067] When a satisfies the above range, it can be stably driven at high voltage to realize high capacity and long lifespan characteristics.

[0068] The above b represents the molar ratio of cobalt among the total metals excluding lithium in the lithium nickel-based oxide, where 0 <b<0.50, 0.05≤b≤0.40 또는 0.05≤b≤0.30일 수 있다.

[0069] The above c represents the molar ratio of manganese among the total metals excluding lithium in the lithium nickel-based oxide, where 0 <c<0.50, 0.05≤c≤0.40 또는 0.10≤c≤0.40일 수 있다.

[0070] The above d is M among the total metals excluding lithium in the lithium nickel-based oxide. 1 Representing the molar ratio of elements, 0 ≤ d ≤ 0.20, 0 ≤ d ≤ 0.10, or 0 <d≤0.10일 수 있다. M 1 When the molar ratio of the elements satisfies the above range, both the structural stability and capacity of the positive active material can be excellent.

[0071] The above lithium nickel-based oxide may further include a coating layer on its surface comprising one or more elements selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, Ca, Sr, W, Ta, Nb, and Mo.

[0072] When a coating layer is present on the surface of a lithium nickel-based oxide, contact between the electrolyte and the lithium nickel-based oxide is suppressed by the coating layer. This reduces the leaching of transition metals or gas generation caused by side reactions with the electrolyte, thereby further improving stability during thermal runaway. Preferably, the coating layer may include two or more elements selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, Ca, Sr, W, Ta, Nb, and Mo, and more preferably, may include two or more elements selected from the group consisting of Ti, Mg, Al, Zr, Y, and W.

[0073]

[0074] The above lithium nickel-based oxide may be a single-particle lithium nickel-based oxide containing 30 or fewer nodules.

[0075] In the case of lithium nickel-based oxides in the form of secondary particles aggregated from more than 30 to hundreds of primary particles, the contact area with the electrolyte is large, resulting in significant side reactions with the electrolyte and the generation of gas during these side reactions. Under high temperature and / or high voltage conditions, the amount of gas generated and the side reactions with the electrolyte increase further, causing the performance of the lithium secondary battery to degrade rapidly. In contrast, single-particle lithium nickel-based oxides have a small number of nodules constituting the particles, and consequently, fewer interfaces within the particles, resulting in a smaller contact area with the electrolyte. Consequently, compared to secondary particles, they exhibit fewer side reactions with the electrolyte and generate significantly less gas. Therefore, when single-particle lithium nickel-based oxides are applied as cathode active materials, the degradation of lifespan characteristics under high temperature and / or high voltage conditions can be minimized.

[0076] The above single-particle lithium nickel-based oxide preferably comprises 30 or fewer nodules, preferably 1 to 25, and more preferably 1 to 15 nodules. If the number of nodules constituting the lithium nickel-based oxide exceeds 30, particle breakage increases during electrode manufacturing, and the occurrence of internal cracks due to volume expansion / contraction of nodules during charging and discharging increases, which may reduce the effect of improving high-temperature life characteristics and high-temperature storage characteristics.

[0077] The above nodules may have an average particle size of 0.8㎛ to 4.0㎛, preferably 0.8㎛ to 3㎛, and more preferably 1.0㎛ to 3.0㎛. When the average particle size of the nodules satisfies the above range, particle breakage during electrode manufacturing is minimized, and the increase in resistance can be suppressed more effectively. At this time, the average particle size of the nodules refers to a value obtained by measuring the particle sizes of the nodules observed in the SEM image obtained by analyzing the positive electrode active material powder with a scanning electron microscope, and then calculating the arithmetic mean of the measured values.

[0078] The above lithium nickel-based oxide is D 50 This can be 2.0㎛ to 10.0㎛, preferably 2.0㎛ to 8.0㎛. More preferably, it is about 3.0㎛ to 7.0㎛. D of lithium nickel-based oxide 50 If this is too small, processability during electrode manufacturing decreases, and electrolyte impregnation decreases, which may increase electrochemical properties, and D 50 If this is too large, there is a problem in that resistance increases and output characteristics deteriorate.

[0079]

[0080] The single-particle lithium nickel-based oxide having a nickel content of 50 mol% to 70 mol% may be included in the total positive active material layer in an amount of more than 50 weight%, preferably 55 weight% or more, more preferably 60 weight% or more, even more preferably 70 weight% or more, and even more preferably 100 weight% of the total positive active material. When the proportion of the single-particle lithium nickel-based oxide having a nickel content of 50 mol% to 70 mol% of the total weight of the positive active material satisfies the above range, excellent lifespan characteristics can be obtained even when operating at high voltage.

[0081]

[0082] The above positive active material layer may include a positive active material other than a single-particle lithium nickel-based oxide with a nickel content of 50 mol% to 70 mol%, that is, a lithium nickel-based oxide with a nickel content exceeding 75 mol% or a secondary-particle lithium nickel-based oxide, but if the proportion of the lithium nickel-based oxide with a nickel content exceeding 70 mol% or the secondary-particle lithium nickel-based oxide is 50 weight% or more of the total positive active material, the lifespan characteristics may be degraded when operating at high voltage.

[0083] The above positive active material may be included in an amount of 80% to 98% by weight, preferably 90% to 98% by weight, and more preferably 93% to 98% by weight, based on the total weight of the positive active material layer. When the content of the positive active material satisfies the above range, excellent energy density can be achieved.

[0084]

[0085] Next, the above-mentioned positive electrode conductive material is used to impart conductivity to the positive electrode, and in the battery being constructed, any material that possesses electronic conductivity without causing chemical changes can be used without any particular limitations. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, carbon nanotube; metal powder or metal fiber such as copper, nickel, aluminum, or silver; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and one of these alone or a mixture of two or more of these may be used.

[0086] The above-mentioned positive conductive material may typically be included in an amount of 0.1 to 10 weight%, preferably 0.5 to 8 weight%, and more preferably 0.5 to 5 weight% based on the total weight of the positive active material layer.

[0087]

[0088] Next, the anode binder serves to improve adhesion between anode active material particles and adhesion between the anode active material and the anode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one of these alone or a mixture of two or more may be used.

[0089] The above anode binder may be included in an amount of 1 to 10 weight%, preferably 1 to 8 weight%, more preferably 1 to 5 weight% based on the total weight of the anode active material layer.

[0090]

[0091] The above anode may be manufactured according to a conventional anode manufacturing method. For example, the above anode may be manufactured by mixing an anode active material, an anode binder, and / or an anode conductive material in a solvent to prepare an anode slurry, applying the anode slurry onto an anode current collector, and then drying and rolling, or by casting the anode slurry onto a separate support and then laminating the film obtained by peeling it off from the support onto an anode current collector.

[0092] Meanwhile, solvents commonly used in the relevant technical field may be used as solvents for the anode slurry; for example, dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, water, etc., may be used individually or as a mixture of two or more. The amount of the solvent used is sufficient if it is sufficient to dissolve or disperse the anode active material, conductive material, and binder, taking into account the coating thickness and manufacturing yield of the slurry, and to have a viscosity that exhibits excellent thickness uniformity when coated for anode manufacturing thereafter.

[0093]

[0094] cathode

[0095] A lithium secondary battery according to the present invention comprises a negative electrode comprising a negative electrode active material. Specifically, the negative electrode comprises a negative electrode current collector and a negative electrode active material layer formed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer comprises a negative electrode active material. In addition, the negative electrode active material layer may further comprise a negative electrode conductive material and a negative electrode binder in addition to the negative electrode active material.

[0096] The above-mentioned negative current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. In addition, the above-mentioned negative current collector may typically have a thickness of 3 to 500 μm, and, similar to the positive current collector, fine irregularities may be formed on the surface of the current collector to strengthen the bonding strength of the negative active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0097]

[0098] The above-mentioned cathode active material may include a carbon-based cathode active material, and preferably may be composed of a carbon-based cathode active material. The above-mentioned carbon-based cathode active material may include, for example, natural graphite, artificial graphite, graphitized carbon fiber, amorphous carbon, soft carbon, hard carbon, or a combination thereof. For example, the above-mentioned carbon-based cathode active material may include natural graphite and artificial graphite, in which case the weight ratio of natural graphite to artificial graphite may be 1:9 to 9:1, preferably 2:8 to 8:2.

[0099] The above carbon-based negative electrode active material has an average particle size D 50 This can be 2㎛ to 30㎛, preferably 5㎛ to 30㎛.

[0100] The above-mentioned negative electrode active material may be included in an amount of 80% to 98% by weight, preferably 90% to 98% by weight, and more preferably 93% to 98% by weight, based on the total weight of the negative electrode active material layer. When the content of the negative electrode active material satisfies the above range, excellent energy density can be achieved.

[0101]

[0102] Next, the above-mentioned cathode conductive material is used to impart conductivity to the cathode, and in the battery being constructed, it may be used without special limitations as long as it has electronic conductivity without causing chemical changes. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, carbon nanotube; metal powder or metal fiber such as copper, nickel, aluminum, or silver; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and one of these alone or a mixture of two or more may be used.

[0103] The above-mentioned cathode conductive material may typically be included in an amount of 0.1 to 10 weight%, preferably 0.25 to 8 weight%, and more preferably 0.25 to 5 weight% based on the total weight of the cathode active material layer.

[0104] The above-mentioned cathode binder serves to improve adhesion between cathode active material particles and adhesion between the cathode active material and the cathode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one of these alone or a mixture of two or more may be used.

[0105] The above-mentioned cathode binder may be included in an amount of 1 to 10 weight%, preferably 1 to 8 weight%, more preferably 1 to 5 weight% based on the total weight of the positive active material layer.

[0106]

[0107] Meanwhile, in the lithium secondary battery according to the present invention, the negative electrode active material layer may have a single-layer structure or a multi-layer structure of two or more layers. For example, the negative electrode may include a first negative electrode active material layer formed on at least one surface of a negative electrode current collector and comprising a first negative electrode active material; and a second negative electrode active material layer formed on the first negative electrode active material layer and comprising a second negative electrode active material. In this case, the first negative electrode active material and the second negative electrode active material may be composed of carbon-based negative electrode active materials, for example, natural graphite, artificial graphite, or a combination thereof.

[0108]

[0109] Meanwhile, if the cathode active material layer is a multilayer structure composed of two or more layers, the types and / or contents of the cathode active material, binder and / or conductive material in each layer may differ from one another.

[0110] For example, the weight ratio of natural graphite to the total weight of the cathode active material in the first cathode active material layer (lower layer) can be formed higher than the weight ratio of natural graphite to the total weight of the cathode active material in the second cathode active material layer (upper layer), and the weight ratio of artificial graphite to the total weight of the cathode active material in the second cathode active material layer can be formed higher than the weight ratio of artificial graphite to the total weight of the cathode active material in the first cathode active material layer.

[0111] Alternatively, the weight ratio of the conductive material to the total weight of the second cathode active material layer (upper layer) can be formed to be higher than the weight ratio of the conductive material to the total weight of the first cathode active material layer (upper layer).

[0112] In this way, the negative electrode active material layer can be formed into a multilayer structure, and the performance characteristics of the battery can be improved by varying the composition of each layer. For example, if the first negative electrode active material layer has a high proportion of natural graphite and the second negative electrode active material layer has a high proportion of artificial graphite, the effect of reducing explosive pressure during thermal runaway can be further improved.

[0113]

[0114] The above cathode may be manufactured according to a conventional cathode manufacturing method. For example, the above cathode may be manufactured by mixing a cathode active material, a cathode binder, and / or a cathode conductive material in a solvent to prepare a cathode slurry, applying the cathode slurry onto a cathode current collector, and then drying and rolling, or by casting the cathode slurry onto a separate support and then laminating a film obtained by peeling off from the support onto a cathode current collector.

[0115] As solvents for the cathode slurry, solvents commonly used in the relevant technical field may be used; for example, dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, water, etc., may be used individually or as a mixture of two or more. The amount of the solvent used is sufficient if it is sufficient to dissolve or disperse the cathode active material, conductive material, and binder, taking into account the coating thickness and manufacturing yield of the slurry, and to have a viscosity that provides excellent thickness uniformity when coated for subsequent anode manufacturing.

[0116]

[0117] electrolytes

[0118] The lithium secondary battery according to the present invention comprises an electrolyte comprising dimethylsulfamoyl fluoride (N,N-DiMethyl Sulfamoyl Fluoride, DMSF).

[0119] Conventional electrolytes for lithium secondary batteries typically use carbonate-based solvents as organic solvents. However, carbonate-based solvents decompose rapidly at high potentials of 4.35V or higher, generating a large amount of gas and side reactions. In contrast, dimethylsulfamoyl fluoride (N,N-DiMethyl Sulfamoyl Fluoride, DMSF) exhibits relatively high oxidation stability even at high potentials of 4.35V or higher, thereby minimizing the generation of gas and side reactions caused by electrolyte decomposition.

[0120] The above dimethylsulfamoyl fluoride may be included in an amount of less than 30 volume% based on the total volume of the electrolyte, preferably 5 volume% or more and less than 30 volume%, and more preferably 5 volume% to 25 volume%. When the content of dimethylsulfamoyl fluoride satisfies the above range, the effect of improving high-temperature durability is more excellent when operating at a high voltage of 4.35V or higher. If the content of dimethylsulfamoyl fluoride is 30 volume% or more, the initial resistance increases, which may degrade fast charging performance and / or output performance.

[0121] The above electrolyte may further include an organic solvent other than dimethylsulfamoyl fluoride and a lithium salt.

[0122] The above organic solvent may be used without special restrictions as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0123] Specifically, the above organic solvents include ester-based solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether-based solvents such as dibutyl ether or tetrahydrofuran; ketone-based solvents such as cyclohexanone; aromatic hydrocarbon-based solvents such as benzene and fluorobenzene; linear carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methylethyl carbonate (MEC), and ethylmethyl carbonate (EMC); and cyclic carbonate-based solvents such as ethylene carbonate (EC) and propylene carbonate (PC). Alcohol-based solvents such as ethyl alcohol, isopropyl alcohol, etc.; R-CN (R is C2 to C 20 Nitriles such as straight-chain, branched, or ring-shaped hydrocarbon groups, which may include double bond-directing rings or ether bonds; amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used.

[0124] Preferably, the electrolyte may include a carbonate-based organic solvent, and more preferably, may include a cyclic carbonate-based organic solvent and a linear carbonate-based organic solvent. Since the cyclic carbonate-based organic solvent (e.g., ethylene carbonate or propylene carbonate, etc.) has high ionic conductivity and high dielectric constant, it can improve the charge and discharge performance of the battery.

[0125] Linear carbonate-based organic solvents (e.g., ethylmethyl carbonate, dimethyl carbonate, or diethyl carbonate) can improve lithium ion mobility by lowering the concentration of the electrolyte.

[0126]

[0127] The above lithium salt can be used without special limitations as long as it is a compound capable of providing lithium ions used in lithium secondary batteries. Specifically, the above lithium salt may include one or more selected from the group consisting of LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2(LiFSI), LiCl, LiI, and LiB(C2O4)2. Preferably, the above lithium salt may include a phosphate-based lithium salt such as LiPF6, an imide-based lithium salt such as LiN(C2F5SO3)2, LiN(C2F5SO2)2, and LiN(CF3SO2)2, or a combination thereof.

[0128] For example, the lithium salt may be used alone as a phosphate-based lithium salt such as LiPF6, or a mixture of the phosphate-based lithium salt and the imide-based lithium salt.

[0129] It is preferable to use the above lithium salt within a concentration range of 0.1 to 3.0 M, preferably 0.1 to 2.0 M, and more preferably 0.5 to 1.5 M. When the concentration of the lithium salt falls within the above range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and lithium ions can move effectively.

[0130] In addition to the above electrolyte components, the above electrolyte may additionally include additives for the purpose of improving the lifespan characteristics of the battery, suppressing the reduction of battery capacity, and improving the discharge capacity of the battery. For example, the above additives may include various additives used in the relevant technical field, for example, fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinylethylene carbonate (VEC), ethylene sulfate (ESa), lithium difluorophosphate (LiPO2F2), lithium bisoxalatetoborate (LiBOB), lithium tetrafluoroborate (LiBF4), lithium difluorooxalatetoborate (LiDFOB), lithium difluorobisoxalatetophosphate (LiDFBP), lithium tetrafluorooxalatetophosphate (LiTFOP), lithium methyl sulfate (LiMS), lithium ethyl sulfate (LiES), propanesulfone (PS), propensulfone (PRS), succinonitrile (SN), adiponitrile (AND), 1,3,6-hexanedricarbonitrile (HTCN), 1,4-disyano-2-butene (DCB), fluorobenzene (FB). Ethyl di(pro-2-i-1-nyl) phosphate (EDP), 5-methyl-5-propazyloxylcarbonyl-1,3-dioxane-2-one (MPOD), etc. may be used alone or in combination, but are not limited thereto. The above additives may be included in an amount of 0.1 to 10 weight%, preferably 0.1 to 5 weight%, based on the total weight of the electrolyte.

[0131]

[0132] Separator

[0133] The lithium secondary battery according to the present invention may further include a separator between the positive electrode and the negative electrode as needed. The separator separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions. Any separator commonly used as a separator in a lithium secondary battery may be used without special limitations, and it is particularly desirable that it has low resistance to the movement of electrolyte ions and excellent electrolyte moisture retention capacity.

[0134] For example, the above separator may include a porous polymer film made of a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof; or a porous nonwoven fabric made of a high melting point glass fiber, a polyethylene terephthalate fiber, etc. as a substrate.

[0135] In addition, a coating layer containing ceramic components and / or polymer materials may be formed on at least one surface of the above substrate to ensure heat resistance or mechanical strength.

[0136]

[0137] The lithium secondary battery according to the present invention may have a nominal voltage of 3.68V or higher, preferably 3.68V to 3.80V, and more preferably 3.69V to 3.75V. In this case, the nominal voltage refers to the average voltage value during discharge of the lithium secondary battery. Since the energy density of the lithium secondary battery is calculated as the product of the average voltage and average current during discharge, the energy density increases when the nominal voltage is high. Conventional lithium secondary batteries using lithium nickel-cobalt-manganese oxide as the positive electrode active material generally had a charge cut-off voltage of 4.25V, in which case the nominal voltage was 3.6V. In contrast, the present invention enables the realization of high energy density by raising the charge cut-off voltage to 4.35V or higher so that the nominal voltage becomes 3.68V or higher. Specifically, the lithium secondary battery according to the present invention may have an energy density of 500 Wh / L or more, 500 Wh / L to 800 Wh / L, 550 Wh / L to 800 Wh / L, or 600 Wh / L to 750 Wh / L.

[0138] In the lithium secondary battery according to the present invention, it is preferable that the charge cut-off voltage (full charge voltage) be 4.35V or higher, preferably 4.35V to 5V, and more preferably 4.35V to 4.5V. When the charge cut-off voltage satisfies the above range, the capacity of the positive electrode active material increases, and the nominal voltage increases, thereby enabling the realization of high energy density. Generally, as the charge cut-off voltage increases, the capacity of the positive electrode active material increases. However, there is a problem in that if the driving voltage increases, side reactions with the electrolyte during charging and discharging increase, and structural collapse of the positive electrode active material occurs rapidly, causing the lifespan characteristics to deteriorate rapidly. Such problems are more pronounced in high-nickel lithium nickel-cobalt-manganese oxides with a high nickel content. Therefore, conventionally, when lithium nickel-cobalt-manganese oxides were used as positive electrode active materials, the charge cut-off voltage was generally around 4.25V. However, in the present invention, by applying a single-particle lithium nickel-based oxide with a Ni content of 50 mol% to 70 mol% as the positive electrode active material, excellent lifespan characteristics can be maintained even when the charge cut-off voltage is 4.35V or higher.

[0139]

[0140] The lithium secondary battery according to the present invention is capable of realizing excellent high-temperature life characteristics and high-temperature storage characteristics even when the charge cut-off voltage is high at 4.35V or higher by using a specific positive active material and an electrolyte solvent.

[0141] The lithium secondary battery according to the present invention may have a capacity retention rate of 95% or more after 200 cycles of charging and discharging at 0.33C at 45℃ in a voltage range of 2.5V to 4.35V.

[0142] The lithium secondary battery according to the present invention may have a resistance increase rate of 115% or less after 200 cycles of charging and discharging at 0.33C at 45℃ in a voltage range of 2.5V to 4.35V.

[0143] The lithium secondary battery according to the present invention may have a resistance increase rate of 120% or less when measured after charging to 4.35V and then storing at 60℃ for 12 weeks.

[0144]

[0145] The lithium secondary battery according to the present invention can be usefully applied to portable devices such as mobile phones, laptop computers, and digital cameras, as well as electric vehicles such as hybrid electric vehicles (HEVs). The lithium secondary battery according to the present invention can achieve high energy density by operating at high voltage and can be particularly useful in the electric vehicle field because it exhibits excellent safety in the event of thermal runaway.

[0146] According to another embodiment of the present invention, a battery module comprising a lithium secondary battery according to the present invention as a unit cell and a battery pack comprising a plurality of battery modules are provided.

[0147] According to another embodiment of the present invention, a battery pack comprising a plurality of lithium secondary batteries according to the present invention as unit cells is provided. The battery pack may not include a battery module.

[0148] In addition, the present invention provides a pack cell assembly.

[0149] According to one embodiment, the battery module may include 10 to 50, preferably 16 to 36 unit cells. The battery pack may include 10 to 1,000, preferably 10 to 500 unit cells.

[0150] The above battery module or battery pack can be used as a power source for one or more medium-to-large devices, including a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0151]

[0152] Hereinafter, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0153]

[0154] Example 1

[0155] <Anode Manufacturing>

[0156] A cathode slurry was prepared by mixing a cathode active material, a cathode conductive material, and a PVDF binder in a weight ratio of 97:1.2:1.8 in N-methylpyrrolidone (NMP). At this time, the cathode active material was single-particle Li[Ni 0.6 Co 0.1 Mn 0.3 O2 was used, and carbon nanotubes were used as the positive electrode conductive material.

[0157] The above anode slurry was applied onto an aluminum current collector, dried, and then rolled to manufacture an anode.

[0158] Cathode Manufacturing

[0159] A cathode slurry was prepared by mixing a cathode active material, a cathode conductive material, styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) in water in a weight ratio of 96.65:0.5:1.8:1.05. As the cathode active material, a mixture of artificial graphite and natural graphite in a weight ratio of 8:2 was used, and carbon black was used as the cathode conductive material.

[0160] The above cathode slurry was applied onto a copper current collector, dried, and then rolled to manufacture a cathode.

[0161] Electrolyte Preparation

[0162] An electrolyte was prepared by dissolving a lithium salt (LiPF6) to a concentration of 1.0 M in a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl sulfamoyl fluoride (DMSF) in a volume ratio of 20:65:15.

[0163] Lithium secondary battery manufacturing

[0164] An electrode assembly was manufactured by placing a polyethylene separator between the anode and cathode manufactured above, and after inserting the electrode assembly into a battery case, the electrolyte manufactured above was injected and sealed to manufacture a lithium secondary battery.

[0165]

[0166] Example 2

[0167] A lithium secondary battery was manufactured in the same manner as in Example 1, except that a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl sulfamoyl fluoride (DMSF) in a volume ratio of 20:70:10 was used when manufacturing the electrolyte.

[0168]

[0169] Example 3

[0170] A lithium secondary battery was manufactured in the same manner as in Example 1, except that a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl sulfamoyl fluoride (DMSF) in a volume ratio of 20:60:20 was used when manufacturing the electrolyte.

[0171]

[0172] Comparative Example 1

[0173] A lithium secondary battery was manufactured in the same manner as in Example 1, except that a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 20:70:10 was used when manufacturing the electrolyte.

[0174]

[0175] Comparative Example 2

[0176] When manufacturing the cathode, single-particle Li[Ni] is used as the cathode active material. 0.75 Co 0.10 Mn 0.15 A lithium secondary battery was manufactured in the same manner as in Example 1, except that O2 was used.

[0177]

[0178] Comparative Example 3

[0179] A lithium secondary battery was manufactured in the same manner as in Example 1, except that a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl sulfamoyl fluoride (DMSF) in a volume ratio of 20:50:30 was used when manufacturing the electrolyte.

[0180]

[0181] Experimental Example 1: Measurement of High-Temperature Cycle Characteristics

[0182] Each lithium secondary battery prepared in the above examples and comparative examples was charged and discharged for up to 300 cycles at 45°C at 0.33C in a voltage range of 2.5V to 4.35V, and the capacity retention rate and resistance increase rate were measured after 100, 200, and 300 cycles. The measurement results are shown in [Table 1] below. At this time, the capacity retention rate is a value calculated by multiplying the ratio of the discharge capacity after 100, 200, or 300 cycles to the discharge capacity after 1 cycle by 100, and the resistance increase rate is a value calculated by multiplying the ratio of the resistance after 100, 200, or 300 cycles to the resistance after 1 cycle by 100.

[0183] After 100 cycles After 200 cycles After 300 cycles Capacitance retention rate (%) Resistance increase rate (%) Capacitance retention rate (%) Resistance increase rate (%) Capacitance retention rate (%) Resistance increase rate (%) Example 1 97.56 106.495.12 112.792.68 119.1 Example 2 97.65 104.495.2 1113.192.83 118.9 Example 3 96.99 108.594.9 1113.292.43 118.6 Comparative Example 197.34 108.194.49 117.191.86 125.1 Comparative Example 297.2 1108.293.78 118.390.77 127.2

[0184]

[0185] Experimental Example 2: Measurement of High-Temperature Storage Performance

[0186] Each lithium secondary battery prepared in the above examples and comparative examples was charged to 4.35V and then stored at 60°C for 4, 8, and 12 weeks, after which the capacity retention rate and resistance increase rate were measured. The measurement results are shown in [Table 2] below. In this case, the capacity retention rate is a value calculated by multiplying the ratio of the discharge capacity after high-temperature storage to the initial discharge capacity before high-temperature storage by 100, and the resistance increase rate is a value calculated by multiplying the ratio of the resistance after high-temperature storage to the initial resistance before high-temperature storage by 100.

[0187] 4 Weeks 8 Weeks 12 Weeks Capacity Retention Rate (%) Resistance Increase Rate (%) Capacity Retention Rate (%) Resistance Increase Rate (%) Capacity Retention Rate (%) Resistance Increase Rate (%) Example 1 97.8 9100.7 96.5 4108.5 95.6 3111.6 Example 2 97.7 2104.9 96.7 4110.3 95.8 4115.3 Example 3 97.3 6106.2 95.90 110.4 95.00 114.3 Comparative Example 197.5 7103.7 96.7 8110.3 95.10 120.7 Comparative Example 2 97.1 2112.4 96.6 6123.9 94.5 9136.0

[0188] Through Tables 1 and 2 above, it can be confirmed that the lithium secondary batteries of Examples 1 to 3, which contain a lithium nickel-based oxide with a Ni content of 50 mol% to 70 mol% and dimethylsulfamoyl fluoride, have superior high-temperature life characteristics and high-temperature storage performance compared to Comparative Example 1, which does not use dimethylsulfamoyl fluoride, and Comparative Example 2, which uses a lithium nickel-based oxide with a Ni content exceeding 70 mol%.

[0189]

[0190] Experimental Example 3: Measurement of Resistance Characteristics

[0191] Each lithium secondary battery prepared in Examples 2 and 3 and Comparative Examples 1 and 3 was charged to SOC 50 at 0.33C at 25℃, then a pulse was applied at 3.5C for 120 seconds, and the resistance was measured. The measurement results are shown in [Table 3] and Figure 4 below.

[0192] Resistance (Ω) after 120-second pulse application Example 20.0090 Example 30.0098 Comparative Example 10.133 Comparative Example 30.113

[0193] Through Table 3 and Figure 4 above, it can be confirmed that the lithium secondary batteries of Examples 2 and 3, containing less than 30 volume% of dimethylsulfamoyl fluoride, have significantly lower resistance compared to the lithium secondary battery of Comparative Example 1, which does not contain dimethylsulfamoyl fluoride. In addition, it can be confirmed that the resistance increases in the case of the lithium secondary battery of Comparative Example 3, which contains 30 volume% of dimethylsulfamoyl fluoride.

Claims

1. A lithium secondary battery comprising a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material; and an electrolyte, and The above-mentioned positive electrode active material comprises a lithium nickel-based oxide having a Ni content of 50 mol% to 70 mol% among the total metals excluding lithium, and The above electrolyte includes dimethylsulfamoyl fluoride (N,N-DiMethyl Sulfamoyl Fluoride, DMSF), and A lithium secondary battery in which the above dimethylsulfamoyl fluoride is included in an amount of less than 30 volume% based on the total volume of the electrolyte.

2. In Paragraph 1, The above lithium nickel-based oxide is a lithium secondary battery that is a single-particle lithium nickel-based oxide containing 30 or fewer nodules.

3. In Paragraph 1, A lithium secondary battery in which the above lithium nickel-based oxide is represented by the following [Chemical Formula 1]. [Chemical Formula 1] Li 1+x [Ni a Co b Mr c M 1 d ]O2 In the above [Chemical Formula 1], M 1 It contains one or more elements selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, Ca, Sr, W, Ta, Nb, and Mo, and -0.1≤x≤0.1, 0.5≤a≤0.70, 0 <b<0.5, 0<c<0.5, 0≤d≤0.2임.

4. In Paragraph 1, A lithium secondary battery wherein the above positive active material further comprises a coating layer on the surface of the lithium nickel-based oxide containing one or more elements selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, Ca, Sr, W, Ta, Nb, and Mo.

5. In Paragraph 1, A lithium secondary battery in which the above dimethylsulfamoyl fluoride is included in an amount of 5% or more and less than 30% by volume based on the total volume of the electrolyte.

6. In Paragraph 1, A lithium secondary battery in which the above dimethylsulfamoyl fluoride is included in an amount of 5% to 25% by volume based on the total volume of the electrolyte.

7. In Paragraph 1, A lithium secondary battery in which the above electrolyte further comprises a lithium salt, a cyclic carbonate-based organic solvent, and a linear carbonate-based organic solvent.

8. In Paragraph 1, The above-mentioned negative electrode is a lithium secondary battery comprising a carbon-based negative electrode active material.

9. In Paragraph 1, The above cathode comprises a cathode current collector; a first cathode active material layer formed on the cathode current collector and comprising a first cathode active material; and a second cathode active material layer formed on the first cathode active material layer and comprising a second cathode active material. A lithium secondary battery in which the first negative electrode active material and the second negative electrode active material are composed of carbon-based negative electrode active materials.

10. In Paragraph 9, A lithium secondary battery in which the first negative electrode active material and the second negative electrode active material are each independently natural graphite, artificial graphite, or a combination thereof.

11. In Paragraph 1, The above lithium secondary battery is a lithium secondary battery with a nominal voltage of 3.68V or higher.

12. In Paragraph 1, The above lithium secondary battery is a lithium secondary battery having a charge cut-off voltage of 4.35V or higher.

13. In Paragraph 1, A lithium secondary battery having a capacity retention rate of 95% or more after 200 charge-discharge cycles at 45°C and 0.33C in a voltage range of 2.5V to 4.35V.

14. In Paragraph 1, A lithium secondary battery having a resistance increase rate of 115% or less after charging and discharging the above lithium secondary battery for 200 cycles at 45°C at 0.33C in a voltage range of 2.5V to 4.35V.

15. In Paragraph 1, A lithium secondary battery having a resistance increase rate of 120% or less, measured after charging the above lithium secondary battery to 4.35V and then storing it at 60℃ for 12 weeks.

16. A battery module comprising a lithium secondary battery of any one of claims 1 to 15 as a unit cell.

17. In Paragraph 16, The above battery module is a battery module comprising 10 to 50 unit cells.

18. A battery pack comprising a lithium secondary battery of any one of claims 1 to 15 as a unit cell.

19. In Paragraph 18, The above battery pack is a battery pack comprising 10 to 1,000 unit cells.

20. A battery pack comprising the secondary battery module of claim 16.

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