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 comprising a positive electrode active material; a negative electrode comprising 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 total metals excluding lithium, the negative electrode active material comprises primary-particle-type artificial graphite in which A defined by formula (1) is 0.8 or more, and the product of A defined by formula (1) and the porosity of the negative electrode is 30 or more.

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. 10-2024-0196377 filed on December 24, 2024 and Korean Patent Application No. 10-2025-0208534 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 having excellent high-rate charge / discharge performance and output characteristics, 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 field of electric vehicles, there is a demand for cells with high energy density to extend the driving range on a single charge. Accordingly, lithium secondary batteries containing high-nickel (High-Ni) cathode active materials, which improve capacity by increasing the Ni content of the cathode active material, have been developed. However, because high-nickel (High-Ni) cathode active materials have a high unit cost, their application increases the production costs of secondary batteries and electric vehicles, which is hindering the widespread adoption of electric vehicles.

[0005] Since the manufacturing cost of lithium secondary batteries is influenced by the price of raw materials that make up the lithium secondary battery, particularly the positive and negative active materials, attempts are being made to use low-cost raw materials for the positive and negative active materials. For example, a plan is being considered to apply a positive active material with a relatively low Ni content compared to high-nickel (High-Ni) positive active materials as the positive active material, and to apply a relatively low-cost primary particle form of artificial graphite instead of the expensive secondary particle form of artificial graphite as the negative active material.

[0006] However, when using low-cost raw materials, the battery performance is degraded compared to lithium secondary batteries using high-cost raw materials, making it difficult to meet market demands. Specifically, when using a cathode active material with low Ni content, the energy density decreases, and when using artificial graphite in the form of primary particles, there are problems such as reduced capacity characteristics and high-rate charging performance.

[0007] Therefore, there is a need to develop lithium secondary batteries with excellent electrochemical performance while using low-cost active material raw materials.

[0008] The present invention aims to solve the above-mentioned problems by applying a single-particle lithium nickel-based oxide having a Ni content of 50 mol% to 70 mol% as the positive electrode active material, and as the negative electrode active material having an orientation index and average particle size D 50 By applying primary particle-type artificial graphite that satisfies this specific condition, we aim to provide a lithium secondary battery with excellent price competitiveness and electrochemical performance.

[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 negative electrode active material comprises primary-particle artificial graphite having an A defined by the following formula (1) of 0.8 or more, and the product of A defined by the following formula (1) and the porosity of the negative electrode is 30 or more.

[0010] Equation (1): A = OI / D 50

[0011] In the above equation (1), OI is an orientation index of artificial graphite defined by the following equation (2), and D 50 This is the particle size (unit: μm) when the cumulative volume is 50% in the volume cumulative particle size distribution of the primary particle-type artificial graphite measured by laser diffraction.

[0012] Equation (2): OI = I 004 / I 110

[0013] In the above equation (2), I 004 is the peak area (Integrated intensity) of the (004) plane in the spectrum obtained by X-ray diffraction analysis of the above primary particulate artificial graphite, and I 110 is the peak area (Integrated intensity) of the (110) plane in the spectrum obtained by X-ray diffraction analysis of the above primary particle-type artificial graphite.

[0014] [2] The present invention, in [1] above, has an average particle size D of the primary particle-type artificial graphite. 50 This provides a lithium secondary battery with a thickness of 9㎛ to 15㎛.

[0015] [3] The present invention provides a lithium secondary battery in which the orientation index OI of the primary particulate artificial graphite is 12 to 36, in accordance with [1] or [2].

[0016] [4] The present invention provides a lithium secondary battery in which, in at least one of [1] to [3], the negative electrode active material further comprises natural graphite.

[0017] [5] The present invention provides a lithium secondary battery in which the porosity of the negative electrode is 25% to 50% in at least one of [1] to [4].

[0018] [6] The present invention provides a lithium secondary battery comprising, in at least one of [1] to [5], a negative electrode having a negative electrode current collector; a first negative electrode active material layer formed on the 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.

[0019] [7] The present invention provides a lithium secondary battery in which, in at least one of [1] to [6], the single-particle lithium nickel-based oxide comprises 30 or fewer nodules.

[0020] [8] The present invention provides a lithium secondary battery in which, in at least one of [1] to [7], the single-particle lithium nickel-based oxide is represented by the following [Chemical Formula 1].

[0021] [Chemical Formula 1]

[0022] Li 1+x [Ni a Co b Mn c M 1 d ]O2

[0023] 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.

[0024] [9] The present invention provides a lithium secondary battery in which, in at least one of [1] to [8], the positive 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 single-particle lithium nickel-based oxide.

[0025]

[0010] The present invention provides a lithium secondary battery in which, in at least one of [1] to [9], the electrolyte comprises an organic solvent comprising dimethylsulfamoyl fluoride and a lithium salt.

[0026]

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

[0010] the dimethylsulfamoyl fluoride is included in an amount of 30 volume% or less based on the total volume of the organic solvent.

[0027]

[0012] The present invention provides a lithium secondary battery according to

[0010] , wherein the dimethylsulfamoyl fluoride is included in an amount of 10 volume% to 30 volume% based on the total volume of the electrolyte.

[0028]

[0013] The present invention provides a lithium secondary battery having a nominal voltage of 3.68V or higher in at least one of [1] to

[0012] .

[0029]

[0014] 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

[0013] .

[0030]

[0015] The present invention provides a battery module comprising at least one of the lithium secondary batteries [1] to

[0014] as a unit cell.

[0031]

[0016] The present invention provides a battery module according to

[0015] , wherein the battery module comprises 10 to 50 unit cells.

[0032]

[0017] The present invention provides a battery pack comprising at least one of the lithium secondary batteries [1] to

[0014] as a unit cell.

[0033]

[0018] The present invention provides a battery pack according to

[0017] , wherein the battery pack comprises 10 to 1,000 unit cells.

[0034]

[0019] The present invention provides a battery pack comprising the battery module of

[0015] .

[0035] The lithium secondary battery according to the present invention uses a mid-nickel (Mid-Ni) lithium nickel-based oxide with a relatively low Ni content, which is expensive, as the positive electrode active material, and uses primary particulate artificial graphite, which is relatively inexpensive, as the negative electrode active material, so the manufacturing cost is low.

[0036] 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 70 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. Accordingly, since the lithium secondary battery according to the present invention can operate at a higher voltage than conventional batteries, it can achieve a relatively high energy density despite having a low Ni content in the positive active material.

[0037] The lithium secondary battery according to the present invention has an orientation index (OI) and an average particle size (D) as negative electrode active materials. 50 By using primary particle-type artificial graphite that satisfies specific conditions and controlling the cathode porosity, it is possible to achieve a discharge capacity equal to or greater than that of a secondary particle-type artificial graphite and high-rate charge / discharge characteristics of an equivalent level.

[0038] In addition, 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 side reactions with the electrolyte during high temperature and / or high voltage operation and improving lifespan characteristics. Specifically, using dimethylsulfamoyl fluoride as an electrolyte solvent minimizes the use of solvents that induce gas generation, and oxidation stability is improved due to a change 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, a highly durable film-forming effect can be obtained by participating in the film-forming reaction to suppress additional decomposition reactions.

[0039] Figure 1 is a scanning electron microscope image of a single-particle positive electrode active material.

[0040] Figure 2 is a scanning electron microscope image of a pseudo-single particle cathode active material.

[0041] Figure 3 is a scanning electron microscope image of a secondary particle positive electrode active material.

[0042] 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.

[0043] In the present invention, "single particle type" refers to an aggregate composed of 30 or fewer sub-particles, and each sub-particle unit constituting the single particle type is called a "nodule." The "single particle type" 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.

[0044] 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.

[0045] In the present invention, "secondary particle" refers to an aggregate composed of more than 30 sub-particles, and each sub-particle unit forming the secondary particle is called a "primary particle." Figure 3 shows a scanning electron microscope (SEM) image of a positive electrode active material in the form of a secondary particle.

[0046] 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.

[0047] In the present invention, the average particle size (D) of the nodule or primary particle mean ) refers to the arithmetic mean value calculated after measuring the particle sizes of nodules or primary particles observed in scanning electron microscope images.

[0048] 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.

[0049] In the present invention, “orientation index OI” is the peak intensity (I) of the (110) plane appearing in the spectrum obtained by X-ray diffraction analysis of primary particle-type artificial graphite powder. 110 Peak intensity of the (004) plane for ) (I 004 The ratio of )(I 004 / I 110 ...is. At this time, the X-ray diffraction analysis can be performed by the following method. After filling the holder within the XRD measuring instrument (Bruker D8 Endeavor) with primary particulate synthetic graphite powder to be measured and flattening the surface, X-ray diffraction analysis is performed on the regions of FDS 0.5°, 2θ=53°~56° ((004) plane) and 2θ=76°~79° ((110) plane) using a Bruker D8 Endeavor (light source: Cu Kα, λ=1.54Å) equipped with a LynxEye XE-T position-sensitive detector, under conditions of a step size of 0.014°. The measured data is fitted to a single peak using an analytical function to obtain the (110) plane peak area (I 110 ) and (004) plane peak area (I 004 Measures ).

[0050]

[0051] In the present invention, the “porosity (%)” can be calculated as (1 - electrode composite layer density / electrode composite layer true density) × 100. The electrode composite layer density can be measured by dividing the weight of the electrode composite layer by its volume after measuring the weight and volume of the electrode composite layer, and the electrode composite layer true density can be measured using a Gas Pycnometer. A Gas Pycnometer is a device capable of measuring density by placing a sample of known weight into a sample chamber and injecting helium or nitrogen gas to determine the volume occupied by the sample excluding pores. Specifically, the volume of the sample can be measured from the pressure change between the sample chamber containing the sample and a reference chamber with a known volume, and then the density value of the sample can be calculated by applying the ideal gas state equation (PV=nRT).

[0052] In the present invention, the “BET specific surface area” is measured by the BET method, and specifically, can be calculated from the amount of nitrogen gas adsorbed at a liquid nitrogen temperature (77K) using BEL Japan’s BELSORP-mini II.

[0053]

[0054] As a result of repeated research to develop a lithium secondary battery with relatively low manufacturing costs and excellent electrochemical performance, the inventors applied a single-particle lithium nickel-based oxide having a Ni content of 50 mol% to 70 mol% as the positive electrode active material, and as the negative electrode active material, an average particle size (D 50 It was discovered that by applying primary particle-type artificial graphite in which the ratio of the orientation index (OI) to ) satisfies a specific range, a lithium secondary battery with low manufacturing cost and excellent electrochemical performance can be realized, and the present invention was completed.

[0055]

[0056] A lithium secondary battery according to the present invention comprises a positive electrode including a positive active material; a negative electrode including a negative active material; and an electrolyte, wherein the positive 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 negative active material comprises primary-particle artificial graphite having an A value of 0.8 or higher as defined by the following formula (1), and the product of the A and the porosity of the negative electrode is 30 or higher.

[0057] Equation (1): A = OI / D 50

[0058] In the above equation (1), OI is an orientation index of artificial graphite defined by the following equation (2), and D 50 This is the particle size (unit: μm) when the cumulative volume is 50% in the volume cumulative particle size distribution of the primary particle-type artificial graphite measured by laser diffraction.

[0059] Equation (2): Orientation index OI = I 004 / I 110

[0060] In the above equation (2), I 004 is the peak area of ​​the (004) plane in the spectrum obtained by X-ray diffraction analysis of the above primary particle-type artificial graphite, and I 110 is the peak area of ​​the (110) plane in the spectrum obtained by X-ray diffraction analysis of the above primary particle-type artificial graphite.

[0061] Artificial graphite is manufactured by crushing carbon materials such as petroleum coke and / or coal coke, molding them into a desired shape, carbonizing them through heat treatment, and then graphitizing them through ultra-high temperature heat treatment of 2700°C to 3000°C. The artificial graphite produced through the graphitization process has a single particle (primary particle) form. Since the lithium ion diffusion path of the single-particle artificial graphite is long and the crystal orientation is non-uniform, if it is used directly as an active material for secondary batteries, high-rate charge / discharge characteristics or capacity characteristics are not sufficiently exhibited. Therefore, to date, secondary particle artificial graphite, which is formed by mixing the above primary particle artificial graphite with a binder, etc., and then heat-treating it, is mainly used as a negative electrode active material for secondary batteries. Secondary particle-type artificial graphite has the advantage of improved high-rate charge / discharge characteristics and discharge capacity characteristics compared to primary particle-type artificial graphite because crystal orientation, structural stability, and lithium ion mobility are increased as the particle arrangement is adjusted and densified during the aggregation process. However, there is a problem that the unit cost is high because an additional aggregation process is required to manufacture secondary particle-type artificial graphite.

[0062] However, the average particle size (D) defined by the above equation (1) 50 When using primary particle-type artificial graphite in which the ratio (A) of the orientation index (OI) to ) is 0.8 or higher, discharge capacity and high-rate charge / discharge characteristics equivalent to or greater than those of secondary particle-type artificial graphite can be achieved. In the case of secondary particle-type artificial graphite, OI / D 50The ratio is 0.7 or less. In the case of secondary particle-type artificial graphite, the degree of orientation becomes relatively uniform during the aggregation process, so excellent discharge capacity and high-rate charge / discharge performance are exhibited even when the particle size is relatively large. However, in the case of primary particle-type artificial graphite, the degree of orientation appears non-uniform because it does not undergo an aggregation process. Consequently, as the particle size increases, the discharge capacity and high-rate charge / discharge performance drop sharply, so it is necessary to control the particle size according to the degree of orientation.

[0063] Preferably, A may be 0.8 to 3.0, 1.0 to 3.0, 1.0 to 2.5, 1.1 to 2.5, 1.2 to 2.5, or 1.25 to 2.5. When primary particulate artificial graphite satisfying the above range is used, excellent discharge capacity and high-rate charge / discharge characteristics are exhibited.

[0064] According to the inventors' research, when an electrode is manufactured using primary particulate artificial graphite having an appropriate A range and controlling the porosity of the cathode, the interface between the electrolyte and the electrode and the degradation within the electrode are reduced, thereby enabling the realization of discharge capacity and high-rate charge / discharge characteristics.

[0065] Preferably, the lithium secondary battery according to the present invention can be designed such that the product of the porosity of A and the negative electrode is 30 or more, 30 to 80, or 30 to 70. When the product of A and the porosity of the negative electrode satisfies the above range, it is possible to achieve discharge capacity and high-rate charge / discharge characteristics equivalent to or greater than those of using secondary particle-type artificial graphite, even when using inexpensive primary particle-type artificial graphite.

[0066]

[0067] Single-particle lithium nickel-based oxides with a nickel content of 50 mol% to 70 mol% are cheaper and have excellent 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 rapid degradation of the cathode active material even when operated at high voltages of 4.35 V or higher. Therefore, if a single-particle lithium nickel-based oxide with a nickel content of 50 mol% to 70 mol% is used as the cathode active material, the battery can be operated at higher voltages compared to conventional methods, thereby improving energy density.

[0068]

[0069] The components of the lithium secondary battery according to the present invention will be described in more detail below.

[0070]

[0071] anode

[0072] 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.

[0073] 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.

[0074]

[0075] The above positive active material may include a single-particle 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%.

[0076] As the nickel content in lithium nickel-based oxides increases, the reactivity of Ni increases. +4 As 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%.

[0077] Specifically, the lithium nickel-based oxide may be a lithium transition metal oxide containing nickel, manganese and cobalt, and may be represented by, for example, the following [Chemical Formula 1].

[0078] [Chemical Formula 1]

[0079] Li 1+x [Ni a Co b Mn c M 1 d ]O2

[0080] 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. 1When 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.

[0081] 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.

[0082] 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.

[0083] When a satisfies the above range, it can be stably driven at high voltage to realize high capacity and long lifespan characteristics.

[0084] 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.

[0085] 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.

[0086] 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 1When the molar ratio of the elements satisfies the above range, both the structural stability and capacity of the positive active material can be excellent.

[0087] 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.

[0088] 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.

[0089]

[0090] The above lithium nickel-based oxide may be a single-particle lithium nickel-based oxide containing 30 or fewer nodules.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] The above lithium nickel-based oxide is D 50This 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.

[0095]

[0096] 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.

[0097]

[0098] 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 70 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.

[0099] 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.

[0100]

[0101] 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.

[0102] 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.

[0103]

[0104] 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.

[0105] 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.

[0106]

[0107] 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.

[0108] 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.

[0109]

[0110] cathode

[0111] 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.

[0112] 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.

[0113]

[0114] In the present invention, the negative electrode active material comprises primary particulate artificial graphite having an A value defined by the following formula (1) of 0.8 or higher, 0.8 to 3.0, 1 to 3.0, 1 to 2.5, 1.1 to 2.5, 1.2 to 2.5, or 1.25 to 2.5.

[0115] As described above, primary particulate artificial graphite with an A value satisfying the above range is inexpensive and exhibits discharge capacity and high-rate charge / discharge characteristics equivalent to those of secondary particulate artificial graphite. Therefore, by applying primary particulate artificial graphite with an A value of 0.8 or higher, it is possible to achieve excellent electrochemical performance while reducing the manufacturing cost of the secondary battery.

[0116] The above primary particulate artificial graphite has an average particle size D 50 This can be 9㎛ to 15㎛, preferably 10㎛ to 15㎛, more preferably 10㎛ to 13㎛. Average particle size D 50 When the above range is satisfied, excellent lithium ion mobility is exhibited within the artificial graphite particles, and a cathode with an appropriate porosity can be manufactured. If the average particle size of the primary particle-type artificial graphite is too large, lithium ion mobility within the artificial graphite particles may be reduced, and if it is too small, the cathode porosity decreases, which may lead to reduced electrolyte impregnation and increased electrode resistance.

[0117] The above primary particulate artificial graphite may have an orientation index (OI) of 12 to 36, 12 to 30, 15 to 25, 12 to 20, or 12 to 18. When the orientation index (OI) satisfies the above range, high-rate charge / discharge efficiency is excellent. If the orientation index is too high, it becomes difficult to insert and extract lithium within the artificial graphite, which reduces high-rate charge / discharge efficiency. On the other hand, as the orientation index decreases, the structure becomes easier for lithium ions to insert and extract, thus increasing high-rate charge / discharge performance; however, it is practically difficult to form the orientation index of the primary particulate artificial graphite to be less than 12.

[0118] The above primary particulate artificial graphite has a BET specific surface area of ​​0.9 to 1.2 m² 2 / g, preferably 0.95 to 1.15m 2 / g, more preferably 0.9 to 1.1m 2 It can be / g. If the BET specific surface area is too small or too large, problems with dispersion may occur during the slurry preparation process.

[0119] The above primary particulate artificial graphite may have a tap density of 0.8 g / cc to 2.0 g / cc, preferably 0.8 g / cc to 1.8 g / cc, and more preferably 0.9 g / cc to 1.6 g / cc. When the tap density satisfies the above range, good dispersion is achieved during slurry preparation, and a uniform coating can be achieved during electrode composite layer formation.

[0120]

[0121] The above cathode active material may further include a carbon-based cathode active material other than the above primary particulate artificial graphite as needed, for example, may further include natural graphite. When natural graphite is further included, the weight ratio of natural graphite to artificial graphite may be 1:9 to 9:1, preferably 2:8 to 8:2.

[0122] The above natural graphite has an average particle size D50 This can be 2㎛ to 30㎛, preferably 5㎛ to 30㎛, more preferably 15㎛ to 25㎛.

[0123] 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.

[0124]

[0125] 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.

[0126] 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.

[0127] 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.

[0128] 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.

[0129]

[0130] 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. At this time, at least one of the first negative electrode active material and the second negative electrode active material comprises primary particulate artificial graphite having the above-described A of 0.8 or more, and may further comprise natural graphite as needed.

[0131]

[0132] Meanwhile, if the negative electrode active material layer is a multilayer structure composed of two or more layers, the types and / or contents of the negative electrode active material, binder and / or conductive material in each layer may differ from one another.

[0133] 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.

[0134] 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).

[0135] 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 high-rate charge / discharge characteristics of the negative electrode can be further improved.

[0136]

[0137] The above-mentioned cathode may have a porosity of 25% to 35%, 27% to 35%, or 27% to 32%. When the porosity of the cathode satisfies the above range, improvements in high-speed charging performance and energy density can be obtained. If the cathode porosity is too small, the capacity may be lower than the designed capacity, or contact with the electrolyte may become difficult, causing cell resistance to increase; if it is too large, the cell thickness may increase, lowering energy density, or the distance between active materials within the cathode may increase, causing electrode resistance to increase.

[0138]

[0139] 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.

[0140] 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.

[0141]

[0142] electrolytes

[0143] A lithium secondary battery according to the present invention comprises an electrolyte comprising an organic solvent and a lithium salt.

[0144] It is preferable that the above organic solvent includes dimethylsulfamoyl fluoride (N,N-DiMethyl Sulfamoyl Fluoride, DMSF).

[0145] Conventional electrolytes for lithium secondary batteries have generally used 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, since dimethylsulfamoyl fluoride (N,N-Dimethylsulfamoyl fluoride, DMSF) exhibits relatively high oxidation stability even at high potentials of 4.35V or higher, it is possible to minimize the generation of gas and side reactions caused by electrolyte decomposition. Therefore, when an organic solvent containing dimethylsulfamoyl fluoride is used as the organic solvent for the electrolyte, the effect of improving lifespan characteristics during high-voltage operation can be obtained.

[0146] The above dimethylsulfamoyl fluoride may be included in an amount of 30 volume% or less, preferably 10 volume% to 30 volume%, and more preferably 15 volume% to 25 volume% based on the total volume of the organic solvent. When the content of dimethylsulfamoyl fluoride satisfies the above range, the effect of improving high-temperature durability is more excellent when driven at a high voltage of 4.35V or higher. If the content of dimethylsulfamoyl fluoride is too low, the effect of improving high-temperature durability is negligible, and if it is too high, the initial resistance increases, and accordingly, the high-speed charging performance and / or output characteristics may be degraded.

[0147] Meanwhile, the above organic solvent may further include organic solvents other than dimethylsulfamoyl fluoride.

[0148] 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.

[0149] 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.

[0150] 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.

[0151] 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.

[0152]

[0153] 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.

[0154] 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.

[0155] 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.

[0156] 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.

[0157]

[0158] Separator

[0159] 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.

[0160] 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.

[0161] 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.

[0162]

[0163] 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.

[0164] 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.

[0165]

[0166] 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.

[0167] 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.

[0168] 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.

[0169] In addition, the present invention provides a pack cell assembly.

[0170] 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.

[0171] 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.

[0172]

[0173] 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.

[0174]

[0175] Example 1

[0176] <Anode Manufacturing>

[0177] 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 0.3O2 was used, and carbon nanotubes were used as the positive electrode conductive material.

[0178] The above anode slurry was applied onto an aluminum current collector, dried, and then rolled to produce an anode with a porosity of 22%.

[0179]

[0180] Cathode Manufacturing

[0181] 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 at a weight ratio of 96.65:0.5:1.8:1.05. As the cathode active material, a mixture of primary particulate artificial graphite and natural graphite at a weight ratio of 8:2 was used, and the primary particulate artificial graphite was D 50 The thickness was 11.6 μm, and the orientation index OI was 15. Carbon black was used as the cathode conductive material.

[0182] The above cathode slurry was applied onto a copper current collector, dried, and then rolled to produce a cathode with a porosity of 32%.

[0183]

[0184] Electrolyte Preparation

[0185] 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.

[0186]

[0187] Lithium secondary battery manufacturing

[0188] 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.

[0189]

[0190] Example 2

[0191] D as primary particulate artificial graphite during cathode manufacturing 50 A positive electrode, a negative electrode, and a lithium secondary battery were manufactured in the same manner as in Example 1, except that artificial graphite with a thickness of 11.4 μm and an orientation index OI of 24 was used.

[0192]

[0193] Example 3

[0194] D as primary particulate artificial graphite during cathode manufacturing 50 A positive electrode, a negative electrode, and a lithium secondary battery were manufactured in the same manner as in Example 1, except that artificial graphite with a thickness of 12.8 μm and an orientation index OI of 17 was used.

[0195]

[0196] Example 4

[0197] A positive electrode, a negative electrode, and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the negative electrode was manufactured such that the porosity was 36%.

[0198]

[0199] Comparative Example 1

[0200] When manufacturing the cathode, D instead of primary particulate artificial graphite 50 A positive electrode, a negative electrode, and a lithium secondary battery were manufactured in the same manner as in Example 1, except that a secondary particle-type artificial graphite with a diameter of 18 μm and an orientation index OI of 8 was used, and a mixed solvent of ethylene carbonate (EC): ethyl methyl carbonate (EMC): diethyl carbonate (DEC) in a volume ratio of 20:70:10 was used when manufacturing the electrolyte.

[0201]

[0202] Comparative Example 2

[0203] When manufacturing the cathode, single-particle Li[Ni] is used as the cathode active material. 0.75 Co 0.10 Mn 0.15A lithium secondary battery was manufactured in the same manner as in Example 1, except that O2 was used.

[0204]

[0205] Comparative Example 3

[0206] A positive electrode, a negative electrode, and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the negative electrode was manufactured such that the porosity was 23%.

[0207] Positive active material artificial graphite negative electrode porosity A×porosity type OID 50A Example 1 single particle type Li[Ni 0.6 Co 0.1 Mn 0.3 ]O2 1st stage particle type 1511.61.2931033241.37931 Example 2-stage particle type Li[Ni 0.6 Co 0.1 Mn 0.3 ]O21st stage particle type 2411.42.1052633267.36842 Example 3-stage particle type Li[Ni 0.6 Co 0.1 Mn 0.3 ]O21st stage particle type 1712.81.3281253242.5 Example 4th stage particle type Li[Ni 0.6 Co 0.1 Mn 0.3 ]O2 1st stage particle type 1511.61.2931033646.55171 Comparative Example 1st stage particle type Li[Ni 0.6 Co 0.1 Mn 0.3 ]O2 2nd stage particle type 8180.4444443214.22222 Comparative Example 2nd stage particle type Li[Ni 0.75 Co 0.10 Mn 0.15 ]O2 1st stage particle type 1511.61.2931033241.37931 Comparative Example 3-stage particle type Li[Ni 0.6 Co 0.1 Mn 0.3 ]O21st particulate type1511.61.2931032329.74138

[0208] Experimental Example 1: Measurement of High-Temperature Cycle Characteristics

[0209] Each lithium secondary battery prepared in the above examples and comparative examples was charged and discharged for up to 200 cycles at 0.33C at 45°C 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 2] below.

[0210] 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 97.46 107.694.5 1113.892.07 120.9 Example 3 97.76 108.595.02 113.292.47 118.6 Example 4 97.64 105.8995.5 111.992.5 117.4 Comparative Example 196.86 102.294.90 111.792.15 116.1 Comparative Example 297.21108.293.78118.390.77127.2 Comparative Example 395.12110.8791.03117.4387.49124.10

[0211] Through [Table 2] above, it can be confirmed that the lithium secondary batteries of Examples 1 to 4, which contain a single-particle lithium nickel-based oxide with a Ni content of 50 mol% to 70 mol% and primary-particle artificial graphite with an A value of 0.8 or higher, and in which the product of A and the negative electrode porosity is 30 or higher, exhibit superior high-temperature cycle characteristics compared to the lithium secondary battery of Comparative Example 2, which uses a secondary-particle lithium nickel-based oxide, and show high-temperature cycle characteristics similar to those of the lithium secondary battery of Comparative Example 1, which uses secondary-particle artificial graphite. In addition, it can be confirmed that in the case of the lithium secondary battery of Comparative Example 3, in which the product of A and the negative electrode porosity is less than 30, the high-temperature cycle characteristics are significantly degraded.

[0212] Experimental Example 2: Measurement of High-Temperature Storage Performance

[0213] 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 3] below.

[0214] 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 9 105.8 96.5 4 108.5 95.6 3 113.3 Example 2 97.5 4 108.6 96.5 5 108.7 95.6 4 114.5 Example 3 96.9 7 105.9 95.9 8 108.7 95.0 8 114.4 Example 4 97.8 104.8 96.4 0 108.6 95.5 116.7 Comparative Example 1 97.7 7 102.4 96.9 1107.6 95.1 4 112.1 Comparative Example 297.12112.496.66123.994.59136.0 Comparative Example 396.23108.1393.06112.6290.27119.64

[0215] Through [Table 3] above, it can be confirmed that the lithium secondary batteries of Examples 1 to 4, which contain a single-particle lithium nickel-based oxide with a Ni content of 50 mol% to 70 mol% and primary-particle artificial graphite with an A value of 0.8 or higher, and in which the product of A and the negative electrode porosity is 30 or higher, exhibit superior high-temperature storage characteristics compared to the lithium secondary battery of Comparative Example 2, which uses a secondary-particle lithium nickel-based oxide, and show high-temperature storage performance similar to that of the lithium secondary battery of Comparative Example 1, which uses secondary-particle artificial graphite. In addition, it can be confirmed that the lithium secondary battery of Comparative Example 3, in which the product of A and the negative electrode porosity is less than 30, has inferior capacity and resistance characteristics during high-temperature storage.

[0216] Experimental Example 3: Evaluation of Initial Discharge Capacity

[0217] A coin cell was manufactured by interposing an electrode assembly with a separator between the respective negative electrode and lithium metal counter electrode prepared in Examples 1 to 3 and Comparative Example 1, housing it in a coin cell case, and injecting an electrolyte. The manufactured coin cell was charged to 1.5V and discharged to 0.005V, with each cycle comprising three charge-discharge cycles, after which the discharge capacity was measured. The measurement results are listed in [Table 4] below.

[0218] Discharge Capacity (mAh / g) Example 1 350 Example 2 352 Example 3 353 Comparative Example 1 350

[0219] Through Table 4 above, it can be confirmed that in the case of Examples 1 to 3, which use primary particle-type artificial graphite with an A value of 0.8 or higher, even though low-cost primary particle-type artificial graphite was used, discharge capacity characteristics equivalent to or greater than those of Comparative Example 1, which uses secondary particle-type artificial graphite, are observed.

[0220] Experimental Example 4: Evaluation of Rapid Charging Performance

[0221] An electrode assembly was prepared by interposing a separator between each negative electrode and a lithium metal counter electrode prepared in Example 1 and Comparative Example 1, housing it in a coin cell case, and then injecting an electrolyte to produce a coin cell.

[0222] The above coin cell was charged in 3.0C, CC mode to obtain a charging profile according to SOC, and the inflection point in the charging profile was evaluated as the point at which lithium precipitation occurs to measure the SOC value at which lithium precipitation occurs. The measurement results are shown in [Table 5] below.

[0223] 3C Li-plating SOC Example 131 Comparative Example 134

[0224] Through Table 5 above, it can be confirmed that when the cathode of Example 1 is applied, it has a rapid charging performance equivalent to that of Comparative Example 1, which uses secondary particle-type artificial graphite.

[0225]

Claims

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, The above-mentioned positive electrode active material comprises a single-particle lithium nickel-based oxide having a Ni content of 50 mol% to 70 mol% among the total metals excluding lithium, and The above-mentioned negative electrode active material comprises primary particulate artificial graphite having an A of 0.8 or more as defined by the following formula (1), and A lithium secondary battery in which the product of A, defined by the following formula (1), and the porosity of the negative electrode is 30 or more. (1): A = OI / D 50 In the above equation (1), OI is an orientation index of artificial graphite defined by the following equation (2), and D 50 This is the particle size (unit: μm) at 50% of the cumulative volume in the volume cumulative particle size distribution of the primary particle-type artificial graphite measured by laser diffraction. (2): OI = I 004 / I 110 In the above equation (2), I 004 is the peak area of ​​the (004) plane in the spectrum obtained by X-ray diffraction analysis of the above primary particle-type artificial graphite, and I 110 is the peak area of ​​the (110) plane in the spectrum obtained by X-ray diffraction analysis of the above primary particle-type artificial graphite. In paragraph 1, Average particle size D of the above primary particulate artificial graphite 50 A lithium secondary battery having a size of 9㎛ to 15㎛. In paragraph 1, A lithium secondary battery having an orientation index OI of the above primary particulate artificial graphite of 12 to 36. In paragraph 1, A lithium secondary battery in which the above-mentioned negative electrode active material further comprises natural graphite. In paragraph 1, The above-mentioned negative electrode is a lithium secondary battery having a porosity of 25% to 35%. In paragraph 1, A lithium secondary battery comprising: a negative electrode current collector; a first negative electrode active material layer formed on the 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 paragraph 1, A lithium secondary battery in which the above-mentioned single-particle lithium nickel-based oxide comprises 30 or fewer nodules. In paragraph 1, A lithium secondary battery in which the above-mentioned single-particle 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. In paragraph 1, A lithium secondary battery wherein the above positive active material further comprises a coating layer containing 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 above single-particle lithium nickel-based oxide. In paragraph 1, A lithium secondary battery in which the above electrolyte comprises an organic solvent containing dimethylsulfamoyl fluoride and a lithium salt. In Paragraph 10, A lithium secondary battery in which the above dimethylsulfamoyl fluoride is included in an amount of 30 volume% or less based on the total volume of the organic solvent. In Paragraph 10, A lithium secondary battery in which the above dimethylsulfamoyl fluoride is included in an amount of 10 volume% to 30 volume% based on the total volume of the electrolyte. In paragraph 1, The above lithium secondary battery is a lithium secondary battery with a nominal voltage of 3.68V or higher. In paragraph 1, The above lithium secondary battery is a lithium secondary battery having a charge cut-off voltage of 4.35V or higher. A battery module comprising a lithium secondary battery of any one of claims 1 to 14 as a unit cell. In paragraph 15, The above battery module is a battery module comprising 10 to 50 unit cells. A battery pack comprising a lithium secondary battery of any one of claims 1 to 14 as a unit cell. In Paragraph 17, The above battery pack is a battery pack comprising 10 to 1,000 unit cells. A battery pack comprising the battery module of claim 15.

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