Positive electrode active material for lithium secondary battery and manufacturing method therefor

Abstract

A positive electrode active material comprising lithium transition metal composite oxide particles is provided. The lithium transition metal composite oxide comprises nickel in an amount of 50 mol% or more relative to the total number of moles of transition metals. The lithium transition metal composite oxide particles have a quasi-consolidation ratio of 0.2 (inclusive) to 0.4 (exclusive), wherein the quasi-consolidation ratio is the volume% of particles having a particle size of 4 to 5 μm with respect to the volume% of particles having a particle size of 2 to 3 μm, on the basis of a total volume of the particles. The rolling density of the positive electrode active material is significantly improved due to the particle characteristics. In addition, when the positive electrode active material having the particle characteristics is applied to a lithium secondary battery, the performance of the battery can be improved in terms of an increased initial discharge capacity and a decreased internal resistance.

Description

Cathode active material for lithium secondary batteries and method for manufacturing the same

[0001] The present invention relates to a positive electrode active material for a lithium secondary battery and a method for manufacturing the same. Specifically, the invention relates to a positive electrode active material for a lithium secondary battery comprising lithium transition metal composite oxide particles having a semi-heavy particle size ratio of 0.2 or more and less than 0.4, and a method for manufacturing the same.

[0002] The present application claims the benefit of priority based on Korean Patent Application No. 10-2024-0176995 filed December 3, 2024 and Korean Patent Application No. 10-2025-0178297 filed November 21, 2025, and includes all contents disclosed in the documents of said Korean patent applications as part of this specification.

[0003] Recently, with the advancement of technology such as electric vehicles, the demand for high-capacity secondary batteries is increasing. In these secondary batteries, the cathode active material directly affects the performance of the secondary battery and is a key component accounting for about 40% of the total battery price. Research on nickel-based lithium oxide, which has excellent capacity characteristics, has been actively conducted as the cathode active material. However, since cathode active materials such as nickel-based lithium oxide have high manufacturing costs, measures to lower the cost of cathode active materials must be sought to achieve price competitiveness in the secondary battery market.

[0004] Among cathode active materials, multi-particle cathode active materials, in which multiple particles are clustered into small clusters, have a higher battery capacity compared to single-particle cathode active materials; therefore, active development of multi-particle cathode active materials has been actively pursued in the relevant technology field. However, secondary batteries containing multi-particle cathode active materials have a problem in that cracks between cathode active material particles are prone to occurring during the rolling process in cathode manufacturing and during the charging and discharging process of the secondary battery. Due to this problem, gas generation within the battery increases, and the charge / discharge cycle of the secondary battery decreases, which can lead to a reduction in the lifespan of the secondary battery. Due to the aforementioned problems with multi-particle cathode active materials, the need for the development of single-particle cathode active materials is growing. Furthermore, in batteries that use a mixture of large and small particles, attempts are being made to replace the small particles with single-particle cathode active materials. However, single-particle cathode active materials with a particle size of 3㎛ to 4㎛ have the disadvantage of having high initial resistance and low battery capacity compared to multi-particle cathode active materials.

[0005] Accordingly, the inventors of the present invention have researched a method for manufacturing a new single-particle cathode active material and have completed the present invention by obtaining a cathode active material capable of improving conventional problems by controlling significant particle characteristics in the single-particle cathode active material.

[0006] [Prior Art Literature]

[0007] [Patent Literature]

[0008] (Patent Document 1) Korean Published Patent Application No. 10-2022-0132491

[0009] The present invention aims to provide a positive electrode active material for a lithium secondary battery comprising lithium transition metal composite oxide particles, which improves upon the problems of conventional positive electrode active materials by controlling particle characteristics, and a method for manufacturing the same.

[0010] According to the first aspect of the present invention,

[0011] The present invention provides a positive electrode active material comprising lithium transition metal composite oxide particles.

[0012] In one embodiment of the present invention, the lithium transition metal composite oxide contains 50 mol% or more of nickel based on the total molar amount of transition metal.

[0013] In one embodiment of the present invention, the lithium transition metal composite oxide particles have a semi-heavy particle size ratio of 0.2 or more and less than 0.4, which is the volume percentage of particles with a particle size of 4 to 5 μm relative to the volume percentage of particles with a particle size of 2 μm to 3 μm based on the total volume of particles.

[0014] In one embodiment of the present invention, the lithium transition metal composite oxide comprises 5 mol% to 40 mol% of manganese based on the total molar amount of transition metal.

[0015] In one embodiment of the present invention, the lithium transition metal composite oxide comprises 0.5 mol% to 10 mol% of cobalt based on the total molar amount of transition metal.

[0016] In one embodiment of the present invention, the lithium transition metal composite oxide has a mole of lithium per 1 mole of total transition metal greater than 1.02 and less than 1.07.

[0017] In one embodiment of the present invention, the lithium transition metal composite oxide particles have an average particle size (D) of 2 μm to 5 μm. 50 has ).

[0018] In one embodiment of the present invention, the lithium transition metal composite oxide particles are in the form of single particles.

[0019] In one embodiment of the present invention, the positive active material is 2 tonf / cm 2 It has a rolled density of 2.75 g / cc to 3.2 g / cc under pressure.

[0020] According to a second aspect of the present invention,

[0021] The present invention provides a method for manufacturing an anode active material comprising lithium transition metal composite oxide particles.

[0022] According to one embodiment of the present invention, the manufacturing method comprises: (1) a step of mixing a transition metal raw material and a lithium raw material and performing a first calcination; and (2) a step of mixing a first calcined product and a lithium raw material and performing a second calcination.

[0023] According to one embodiment of the present invention, in step (1), the lithium raw material is controlled such that the number of moles of lithium relative to the total number of moles of transition metals is greater than 1.02 and less than or equal to 1.04.

[0024] According to one embodiment of the present invention, in step (2), the lithium raw material is adjusted so that the number of moles of lithium relative to the total number of moles of transition metal is 1.05 or more and less than 1.07.

[0025] In one embodiment of the present invention, the first firing is performed at 800°C to 1100°C, and the second firing is performed at 700°C to 1000°C.

[0026] In one embodiment of the present invention, in step (2), the primary calcined product is crushed before being mixed with the lithium raw material.

[0027] According to the third aspect of the present invention,

[0028] The present invention provides a positive electrode for a lithium secondary battery comprising the positive electrode active material described above.

[0029] According to the fourth aspect of the present invention,

[0030] The present invention provides a lithium secondary battery comprising the anode, cathode, separator interposed between the anode and cathode, and electrolyte as described above.

[0031] A positive electrode active material according to one embodiment of the present invention is a nickel-based layered positive electrode active material comprising lithium transition metal composite oxide particles containing 50 mol% or more of nickel based on the total molar amount of transition metals, wherein the particles have particle characteristics in which the quasi-graining ratio, which is the volume% of particles with a particle size of 4 μm to 5 μm relative to the volume% of particles with a particle size of 2 μm to 3 μm, is controlled to be 0.2 or more and less than 0.4. Due to the above particle characteristics, the rolling density of the positive electrode active material is significantly improved. In addition, when the positive electrode active material having the above particle characteristics is applied to a lithium secondary battery, the performance of the battery can be improved, such as by increasing the initial discharge capacity and lowering the internal resistance.

[0032] All embodiments provided according to the present invention can be achieved by the following description. It should be understood that the following description describes preferred embodiments of the present invention and that the present invention is not necessarily limited thereto.

[0033] Where measurement conditions and methods are not specifically described for the physical properties described in this specification, said physical properties are measured according to measurement conditions and methods generally used by a person skilled in the art.

[0034]

[0035] <Cathode Active Material>

[0036]

[0037] In the case of nickel-based lithium oxide cathode active materials, multi-particle cathode active materials, in which multiple particles are clustered into small clusters, have advantages such as higher electrical capacity compared to single-particle cathode active materials; however, they have the problem that cracks between cathode active material particles are prone to occur during the rolling process in cathode manufacturing and during the charging / discharging process of the secondary battery. Due to this problem, gas generation within the battery increases, and the charging / discharging cycle of the secondary battery decreases, which may lead to a reduction in the lifespan of the secondary battery. In contrast, while single-particle cathode active materials can resolve the problems associated with multi-particle cathode active materials to some extent, they have the disadvantages of higher initial resistance and lower battery capacity compared to multi-particle cathode active materials. The present invention provides a cathode active material of nickel-based lithium oxide in the form of a single particle, which compensates for the disadvantages of existing single-particle cathode active materials by controlling particle characteristics.

[0038] The present invention provides a positive electrode active material comprising lithium transition metal composite oxide particles. The positive electrode active material may be a nickel-based layered positive electrode active material. Here, a nickel-based layered positive electrode active material means that the molar content of nickel among the transition metals included in the lithium transition metal composite oxide constituting the positive electrode active material is the largest. According to one embodiment of the present invention, the lithium transition metal composite oxide comprises lithium, nickel, cobalt, and manganese, and the molar content of nickel is greater than the sum of the molar content of cobalt and the molar content of manganese. Based on the total molar content of the transition metals in the lithium transition metal composite oxide, the molar content of nickel may be greater than 50 mol%, 52 mol% or more, 54 mol% or more, 56 mol% or more, 58 mol% or more, 60 mol% or more, and 95 mol% or less, 90 mol% or less, or 85 mol% or less.

[0039] The content of lithium, nickel, cobalt, manganese, oxygen, etc., constituting the above lithium transition metal composite oxide can be appropriately controlled within the range generally used in the relevant technical field.

[0040] The ratio of lithium to transition metal in the above lithium transition metal composite oxide can be appropriately adjusted within a range generally used in the relevant technical field. For example, the lithium transition metal composite oxide may have a mole of lithium to a total mole of transition metal of 0.7 to 1.3, 0.8 to 1.2, or 0.9 to 1.1. The above ratio may be adjusted more specifically as needed. According to one embodiment of the present invention, the lithium transition metal composite oxide has a mole of lithium to a total mole of transition metal of greater than 1.02 and less than 1.07. Specifically, the lithium content relative to the transition metal may be greater than 1.02, 1.025 or more, 1.03 or more, 1.035 or more, 1.04 or more, 1.045 or more, 1.05 or more, less than 1.07, 1.065 or less, greater than 1.02 and less than 1.07, 1.04 or more and less than 1.07, and 1.05 or more and less than 1.07. In the lithium transition metal composite oxide, the lithium content relative to the transition metal may affect not only the electrochemical properties of the cathode active material but also the physical properties described below.

[0041] According to one embodiment of the present invention, the lithium transition metal composite oxide comprises 5 mol% to 40 mol% of manganese based on the total molar amount of transition metals. Specifically, the manganese content may be 5 mol% or more, 6 mol% or more, 7 mol% or more, 8 mol% or more, 9 mol% or more, 10 mol% or more, 40 mol% or less, 35 mol% or less, 30 mol% or less, 25 mol% or less, or 5 mol% to 40 mol%, 8 mol% to 35 mol%, and 10 mol% to 30 mol% based on the total molar amount of transition metals. The content of lithium relative to the transition metals in the lithium transition metal composite oxide may affect not only the electrochemical properties of the cathode active material but also the physical properties described below.

[0042] According to one embodiment of the present invention, the lithium transition metal composite oxide comprises 0.5 mol% to 10 mol% of cobalt based on the total molar amount of transition metal. Specifically, the content of cobalt is 10 mol% or less, 9.5 mol% or less, 9 mol% or less, 8.5 mol% or less, 8 mol% or less, 7.5 mol% or less, 7 mol% or less, 0.5 mol% or more, 1 mol% or more, 1.5 mol% or more, 2 mol% or more, and may be 0.5 mol% to 10 mol%, 1 mol% to 9 mol%, 2 mol% to 8 mol%. In the lithium transition metal composite oxide, the content of lithium relative to the transition metal may affect not only the electrochemical properties of the cathode active material but also the physical properties described below. When the above lithium transition metal composite oxide includes nickel, cobalt, and manganese as transition metals, the content of cobalt among the transition metals may be the lowest.

[0043] The lithium transition metal composite oxide particles included in the positive electrode active material according to one embodiment of the present invention have specific particle size characteristics. Although not described in a plurality of forms in this specification, the positive electrode active material comprises a plurality of lithium transition metal composite oxide particles. Accordingly, the particle size characteristics described below are based on a set of a plurality of lithium transition metal composite oxide particles included in the positive electrode active material.

[0044] According to one embodiment of the present invention, the lithium transition metal composite oxide particles have an average particle size (D) of 2 μm to 5 μm. 50 It has ). In this specification, particle size (D 50 ) is a particle size corresponding to 50% of the volume accumulation in the particle size measuring device, which can also be interpreted as an average value of the particle size. Specifically, the average particle size (D) of the lithium transition metal composite oxide particles 50) is 2㎛ or more, 2.5㎛ or more, 3㎛ or more, 3.5㎛ or more, 5㎛ or less, 4.5㎛ or less, 4㎛ or less, and may be 2㎛ to 5㎛, 2.5㎛ to 4.5㎛, or 3㎛ to 4㎛. The average particle size (D) of the lithium transition metal composite oxide particles is 50 If ) is adjusted within the aforementioned range, it can help improve the performance of the battery when a positive electrode active material containing it is applied to a battery.

[0045] In the present invention, among the characteristics related to the particle size of lithium transition metal composite oxide particles, the characteristic that can directly affect the performance of a battery is represented as the semi-heavy particle ratio. The semi-heavy particle ratio represents the ratio of particles that are small but have a particle size close to that of heavy particles, and it means that as this value increases, the small particles become heavy particles. The semi-heavy particle ratio is calculated as the volume percentage of particles with a particle size of 4㎛ to 5㎛ relative to the volume percentage of particles with a particle size of 2㎛ to 3㎛, as (volume% of 4㎛ to 5㎛ particles) / (volume% of 2㎛ to 3㎛ particles). Lithium transition metal composite oxide particles having a semi-heavy particle ratio within a specific range can have excellent rolling density and, when applied to a battery, can have excellent discharge capacity and internal resistance. According to one embodiment of the present invention, the semi-heavy particle ratio of the lithium transition metal composite oxide particles is 0.2 or higher and less than 0.4. Specifically, the quasi-graining rate of the lithium transition metal composite oxide particles may be 0.2 or more, 0.21 or more, 0.22 or more, 0.23 or more, 0.24 or more, 0.25 or more, 0.26 or more, 0.27 or more, 0.28 or more, 0.29 or more, 0.3 or more, less than 0.4, 0.39 or less, 0.38 or less, 0.37 or less, 0.36 or less, 0.35 or less, 0.2 or more, less than 0.4, 0.25 to 0.38, and 0.3 to 0.35.

[0046] According to one embodiment of the present invention, the lithium transition metal composite oxide particles are in the form of single particles. This is distinguished from the multi-particle form, in which several particles are clustered together in a small manner. The multi-particle form has a relatively regular shape due to the aggregation of particles. On the other hand, the single-particle form is not defined by a specific shape, as the particles are not completely unaggregated, but even if they are partially aggregated, the aggregation is not regular. Considering the partially aggregated form, the single-particle form may be a form in which 1 to 30, 1 to 20, or 1 to 10 particles are clustered together.

[0047] According to one embodiment of the present invention, the positive active material is 2 tonf / cm 2 It has a rolled density of 2.75 g / cc to 3.2 g / cc under pressure. Specifically, the rolled density of the anode active material is 2 tonf / cm² 2 Under pressure, it may be 2.75 g / cc or more, 2.8 g / cc or more, 2.85 g / cc or more, 3.2 g / cc or less, 3.15 g / cc or less, 3.1 g / cc or less, 3.05 g / cc or less, 3.0 g / cc or less, and may be 2.75 g / cc to 3.2 g / cc, 2.8 g / cc to 3.1 g / cc, or 2.85 g / cc to 3.0 g / cc. The above rolled density maintains a high level compared to other single-particle type cathode active materials due to the particulate characteristics of the cathode active material according to one embodiment of the present invention.

[0048] The lithium transition metal composite oxide particles may further include a coating layer on the outside. The coating material included in the coating layer is not particularly limited as long as it is a material commonly used in the relevant technical field. For example, the coating material may include one or more elements selected from the group consisting of Al, Ti, Mg, Zr, Y, Sr, W, V, Cr, Nb, Mo, and B. By coating the lithium transition metal composite oxide particles with a functional coating material, the functionality of the cathode active material may be further enhanced. The coating layer may be included in an amount of 0.01 wt% to 5 wt%, 0.05 wt% to 3 wt%, or 0.1 wt% to 1 wt% based on the total weight of the lithium transition metal composite oxide particles.

[0049] The characteristics of the aforementioned positive electrode active material may be attributed to the manufacturing method of the positive electrode active material described below.

[0050]

[0051] Method for manufacturing positive electrode active material

[0052]

[0053] The present invention provides a method for manufacturing the anode active material described above. According to one embodiment of the present invention, the manufacturing method comprises (1) a step of mixing a transition metal raw material and a lithium raw material and performing a first calcination, and (2) a step of mixing the first calcined product and a lithium raw material and performing a second calcination. In the present invention, by dividing and introducing the lithium raw material, the particulate characteristics of the anode active material described above can be realized.

[0054] In step (1) above, the transition metal raw material may include a nickel raw material, a cobalt raw material, and a manganese raw material. The nickel raw material, the cobalt raw material, and the manganese raw material may include acetates, nitrates, sulfates, carbonates, halides, sulfides, hydroxides, oxides, or oxyhydroxides of each transition metal. As a specific example, the nickel raw material may be Ni(OH)2, NiO, NiOOH, NiCO3·2Ni(OH)2·4H2O, NiC2O2·2H2O, Ni(NO3)2·6H2O, NiSO4, NiSO4·6H2O, fatty acid nickel salts, or nickel halides, and any one or more of these may be used. The above cobalt raw material may be Co(OH)2, CoOOH, Co(OCOCH3)2ㆍ4H2O, Co(NO3)2ㆍ6H2O, or Co(SO4)2ㆍ7H2O, etc., and any one or more of these may be used. The above manganese raw material may be manganese oxides such as Mn2O3, MnO2, and Mn3O4; manganese salts such as MnCO3, Mn(NO3)2, MnSO4, manganese acetate, manganese dicarboxylate, manganese citrate, and manganese fatty acid salts; oxyhydroxide or manganese chloride, etc., and any one or more of these may be used.

[0055] The above lithium raw material may be a lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide, or oxyhydroxide, etc., and for example, Li2CO3, LiNO3, LiNO2, LiOH, LiOH·H2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, Li3C6H5O7, or a mixture thereof may be used.

[0056] In step (1) above, the mixing of raw materials is not particularly limited as long as it is a method commonly used in the relevant technical field. The mixing is intended to uniformly disperse various raw materials, and a milling device (e.g., a ball mill) may be utilized.

[0057] In one embodiment of the present invention, by dividing and introducing the lithium raw material, the content of the lithium raw material introduced before the first calcination can be controlled to a specific level. According to one embodiment of the present invention, in step (1), the lithium raw material is controlled so that the number of moles of lithium relative to the total number of moles of transition metals is greater than 1.02 and less than or equal to 1.04. Specifically, the content of the lithium raw material is greater than 1.02, greater than 1.021, greater than 1.022, greater than 1.023, greater than 1.024, greater than 1.025, less than 1.04, less than 1.039, less than 1.038, less than 1.037, less than 1.036, less than 1.035, and may be greater than 1.02 and less than 1.04, 1.025 to 1.04, and 1.025 to 1.035.

[0058] According to one embodiment of the present invention, in step (1), the first firing is performed under temperature conditions of 800°C to 1100°C. Specifically, the temperature of the first firing may be 800°C or higher, 850°C or higher, 900°C or higher, 1100°C or lower, 1050°C or lower, 1000°C or lower, 800°C to 1100°C, 850°C to 1050°C, 900°C to 1000°C. The first firing may be performed for 5 to 10 hours.

[0059] The primary sintered product, which is sintered in step (1) above, is further mixed with a lithium raw material in step (2). The mixing of the raw material in step (2) above is not particularly limited as long as it is a method generally used in the relevant technical field. The mixing is intended to uniformly disperse various raw materials, and a milling device (e.g., a ball mill) may be utilized. The primary sintered product may be crushed before being mixed with the lithium raw material. Through this crushing, particles aggregated by sintering may be broken down.

[0060] According to one embodiment of the present invention, in step (2), the lithium raw material is controlled such that the number of moles of lithium relative to the total number of moles of transition metal is 1.05 or more and less than 1.07. Specifically, the content of the lithium raw material is 1.05 or more, 1.051 or more, 1.052 or more, 1.053 or more, 1.054 or more, 1.055 or more, less than 1.07, 1.069 or less, 1.068 or less, 1.067 or less, 1.066 or less, 1.065 or less, and may be 1.05 or more and less than 1.07, 1.055 or more and less than 1.07, and 1.055 to 1.065. By specifically controlling and dividing the lithium raw material, it helps to closely control the particulate characteristics of the cathode active material.

[0061] According to one embodiment of the present invention, in step (2), the secondary firing is performed under temperature conditions of 700°C to 1000°C. Specifically, the temperature of the secondary firing may be 700°C or higher, 750°C or higher, 800°C or higher, 1000°C or lower, 950°C or lower, 900°C or lower, 700°C to 1000°C, 750°C to 950°C, 800°C to 900°C. The secondary firing may be performed for 5 to 10 hours.

[0062] The secondary sintered product obtained by the above step (2) can be obtained through processing such as grinding and used as an anode active material. In addition, if additional functionality is required through particle coating, the secondary sintered product and the coating raw material can be mixed and tertiarily sintered to obtain an anode active material.

[0063] The positive active material manufactured according to the above method for manufacturing the positive active material has the particulate characteristics of the positive active material described above.

[0064]

[0065] <Polar>

[0066]

[0067] The present invention provides a positive electrode comprising the positive electrode active material described above.

[0068] According to one embodiment of the present invention, the positive electrode comprises a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, and the positive electrode active material layer comprises the positive electrode active material described above.

[0069] According to one embodiment of the present invention, the positive current collector may include a highly conductive metal, and is not particularly limited as long as it allows the positive active material layer to adhere easily and is non-reactive within the voltage range of the battery. The positive current collector may be, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum, and may be used as a stainless steel surface treated with carbon, nickel, titanium, silver, etc. Additionally, the positive current collector may typically have a thickness of 3 μm to 500 μm, and may form fine irregularities on the surface of the current collector to increase the adhesion of the positive active material. The positive current collector may be used in various forms, such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0070] According to one embodiment of the present invention, the positive active material layer may include, together with the positive active material, a conductive material and a binder optionally as needed. In this case, the positive active material may be included in the positive active material layer in an amount of 80% to 99% by weight, more specifically 85% to 98.5% by weight, based on the total weight of the positive active material layer, and may exhibit excellent capacity characteristics within this range.

[0071] According to one embodiment of the present invention, the conductive material is used to impart conductivity to the electrode, 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, or carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, or silver; conductive tubes such as carbon nanotubes; 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. The conductive material may be included in the positive electrode active material layer in an amount of 0.1% to 15% by weight relative to the total weight of the positive electrode active material layer.

[0072] According to one embodiment of the present invention, the binder serves to improve adhesion between positive active material particles and adhesion between the positive active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, polymethyl methacrylate, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, polyacrylic acid, and polymers in which hydrogens thereof are substituted with Li, Na, or Ca, or various copolymers thereof, and one of these alone or a mixture of two or more may be used. The above binder may be included in the positive active material layer in an amount of 0.1% to 15% by weight relative to the total weight of the positive active material layer.

[0073] According to one embodiment of the present invention, the anode may be manufactured according to a conventional anode manufacturing method, except for using the anode active material described above. Specifically, the anode may be manufactured by applying a composition for forming an anode active material layer, prepared by dissolving or dispersing the anode active material described above and optionally a binder, a conductive material, and a dispersant in a solvent, onto an anode current collector, followed by drying and rolling, or by casting the composition for forming an anode active material layer onto a separate support and then laminating the film obtained by peeling from the support onto an anode current collector.

[0074] According to one embodiment of the present invention, the solvent may be a solvent generally used in the relevant technical field, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), dimethylformamide (DMF), acetone, or water, and one of these alone or a mixture of two or more may be used. The amount of solvent used is sufficient to dissolve or disperse the cathode active material, conductive material, binder, and dispersant, taking into account the coating thickness of the slurry and the manufacturing yield, and to have a viscosity that can exhibit excellent thickness uniformity when coated for cathode manufacturing thereafter.

[0075]

[0076] Lithium secondary battery

[0077]

[0078] The present invention provides a lithium secondary battery comprising the anode described above.

[0079] According to one embodiment of the present invention, the lithium secondary battery comprises the anode described above; a cathode; a separator interposed between the anode and the cathode; and an electrolyte. Additionally, the lithium secondary battery may optionally further comprise a battery container housing an electrode assembly of the anode, cathode, and separator described above, and a sealing member sealing the battery container.

[0080] According to one embodiment of the present invention, the cathode may comprise a cathode current collector and a cathode active material layer located on the cathode current collector.

[0081] According to one embodiment of the present invention, the negative current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. The negative current collector may be, for example, copper, stainless steel, aluminum, nickel, titanium, or calcined carbon, and may be a copper or stainless steel surface treated with carbon, nickel, titanium, silver, etc., or an aluminum-cadmium alloy. In addition, the negative current collector may typically have a thickness of 3 μm to 500 μm, and, similar to the positive current collector, fine irregularities may be formed on the surface of the current collector to increase the adhesion of the negative active material. The negative current collector may be used in various forms, such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0082] According to one embodiment of the present invention, the negative electrode active material layer may optionally include a binder and a conductive material together with the negative electrode active material.

[0083] According to one embodiment of the present invention, the negative electrode active material may be a compound capable of reversible intercalation and deintercalation of lithium. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; and SiO₂ β(0<β<2), SnO2, 바나듐 산화물, 리튬 바나듐 산화물과 같이 리튬을 도프 및 탈도프할 수 있는 금속산화물; 또는 Si-C 복합체 또는 Sn-C 복합체과 같이 상기 금속질 화합물과 탄소질 재료를 포함하는 복합물 등을 들 수 있으며, 이들 중 어느 하나 또는 둘 이상의 혼합물이 사용될 수 있다. 또한, 상기 음극 활물질로서 금속 리튬 박막이 사용될 수도 있다. 또한, 탄소 재료는 저결정성 탄소 및 고결정성 탄소 등이 모두 사용될 수 있다. 상기 저결정성 탄소로는 연화 탄소(soft carbon) 및 경화 탄소(hard carbon)가 대표적이며, 상기 고결정성 탄소로는 무정형, 판상, 인편상, 구형 또는 섬유형의 천연 흑연 또는 인조 흑연, 키시 흑연(Kish graphite), 열분해 탄소(pyrolytic carbon), 액정 피치계 탄소섬유(mesophase pitch based carbonfiber), 탄소 미소구체(meso-carbon microbeads), 액정피치(Mesophase pitches) 및 석유와 석탄계 코크스(petroleum or coal tar pitch derived cokes) 등의 고온 소성 탄소가 대표적이다. 상기 음극 활물질은 음극 활물질층의 전체 중량을 기준으로 80 중량% 내지 99 중량%의 함량으로 음극 활물질층에 포함될 수 있다.

[0084] According to one embodiment of the present invention, the binder of the negative electrode active material layer is a component that assists in the bonding between the conductive material, the active material, and the current collector, and can typically be added to the negative electrode active material layer in an amount of 0.1% to 10% by weight based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0085] According to one embodiment of the present invention, the conductive material of the negative electrode active material layer may be added to the negative electrode active material layer in an amount of 10% by weight or less, preferably 5% by weight or less, based on the total weight of the negative electrode active material layer, as a component for further improving the conductivity of the negative electrode active material. Such a conductive material is not particularly limited as long as it possesses conductivity without causing chemical changes in the battery. For example, the conductive material may be graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black; conductive fibers such as carbon fibers or metal fibers; fluorinated carbon; metal powders such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives.

[0086] According to one embodiment of the present invention, the cathode may be manufactured by applying and drying a composition for forming a cathode active material layer, prepared by dissolving or dispersing a cathode active material and optionally a binder and a conductive material in a solvent, on a cathode current collector, or by casting the composition for forming a cathode active material layer onto a separate support and then laminating the film obtained by peeling from the support onto a cathode current collector.

[0087] According to one embodiment of the present invention, the separator separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions. It can be used without special limitations as long as it is typically used as a separator in a lithium secondary battery, and it is particularly desirable that it has low resistance to the movement of electrolyte ions and excellent electrolyte moisture retention capacity. Specifically, a porous polymer film, such as a porous polymer film made of a polyolefin-based polymer like 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 may be used. In addition, a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fibers or polyethylene terephthalate fibers, may be used. Furthermore, a coated separator containing a ceramic component or a polymer material may be used to ensure heat resistance or mechanical strength, and it may optionally be used in a single-layer or multi-layer structure.

[0088] According to one embodiment of the present invention, the electrolyte may be an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, etc., which are usable in the manufacture of a lithium secondary battery, but is not limited thereto. As a specific example, the electrolyte may include an organic solvent and a lithium salt.

[0089] According to one embodiment of the present invention, the organic solvent may be used without particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may 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; and aromatic hydrocarbon-based solvents such as benzene and fluorobenzene. Carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double bond, a directional ring, or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used. Among these, a carbonate-based solvent is preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery, and a low-viscosity linear carbonate-based compound (e.g., ethylmethyl carbonate, dimethyl carbonate or diethyl carbonate, etc.) is more preferred.

[0090] According to one embodiment of the present invention, the lithium salt may be used without particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, as the anion of the lithium salt, F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - The lithium salt may be at least one selected from the group consisting of LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2, etc. It is preferable to use the lithium salt within the range of 0.1 M to 2.0 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.

[0091] According to one embodiment of the present invention, in addition to the electrolyte components, the electrolyte may further include one or more additives for the purpose of improving the lifespan characteristics of the battery, suppressing the decrease in battery capacity, and improving the discharge capacity of the battery, such as, for example, a haloalkylene carbonate-based compound such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, triamide hexaphosphate, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the additive may be included in the electrolyte in an amount of 0.1% to 5% by weight relative to the total weight of the electrolyte.

[0092] A lithium secondary battery comprising a positive electrode active material according to one embodiment of the present invention stably exhibits excellent capacity characteristics, output characteristics, and lifespan characteristics, and is therefore useful in fields such as portable devices like mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs) and electric vehicles (EVs).

[0093] There are no specific restrictions on the external shape of the above lithium secondary battery, but it may be a cylindrical type using a can, a prismatic type, a pouch type, or a coin type.

[0094] A lithium secondary battery according to one embodiment of the present invention can be used not only as a battery cell used as a power source for a small device, but can also preferably be used as a unit cell in a medium-to-large battery module comprising a plurality of battery cells.

[0095] Accordingly, according to one embodiment of the present invention, a battery module comprising the lithium secondary battery as a unit cell and a battery pack comprising the same are provided.

[0096] According to one embodiment of the present invention, the battery module or battery pack may 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.

[0097] Preferred embodiments are presented below to aid in understanding the present invention, but the following embodiments are provided merely to facilitate a better understanding of the invention and do not limit the invention thereto.

[0098]

[0099] Example (Preparation of positive electrode active material)

[0100]

[0101] Example 1

[0102] Lithium, nickel, cobalt, and manganese raw materials were prepared separately so that the molar ratio of Li:Ni:Co:Mn was 1.03:0.70:0.07:0.23 (Li / Me (transition metal) = 1.03), and then mixed in a mixing device (Manufacturer: Resodyn, Product Name: Acoustic Mixer). The mixed powder was placed in an alumina crucible and subjected to primary calcination at 955°C for 7 hours under an oxygen (O2) atmosphere. The primary calcined product was ground in a grinding device (Manufacturer: Isaac E&C, Product Name: Air Jet Mill), and then Li2CO3, a lithium raw material, was added to achieve a Li / Me ratio of 1.06 and mixed in a mixing device. The mixed powder was placed in an alumina crucible and subjected to secondary calcination at 850°C for 7 hours under an oxygen (O2) atmosphere. After grinding the secondary calcined product in a grinding device, Al2O3 (Al content: 1500 ppm based on the total weight of the calcined product) and WO3 (W content: 3000 ppm based on the total weight of the calcined product) were added as coating raw materials and mixed in a mixing device. The mixed powder was placed in an alumina crucible and subjected to a tertiary calcination at 450°C for 6 hours under an air atmosphere to finally produce the cathode active material (average particle size (D 50 ): 3.69㎛) was obtained.

[0103]

[0104] Example 2

[0105] Except for adding the lithium source material Li2CO3 so that the Li / Me ratio becomes 1.065 before the second calcination, the cathode active material (average particle size (D)) is the same as in Example 1. 50 ): 3.68㎛) was manufactured.

[0106]

[0107] Comparative Example 1

[0108] Except for preparing the lithium raw material Li2CO3 so that the Li / Me ratio is 1.02 before the first calcination, the cathode active material (average particle size (D)) is the same as in Example 1. 50 ): 3.66㎛) was manufactured.

[0109]

[0110] Comparative Example 2

[0111] Except for preparing the lithium source material Li2CO3 so that the Li / Me ratio becomes 1.02 before the first calcination and adding the lithium source material Li2CO3 so that the Li / Me ratio becomes 1.065 before the second calcination, the cathode active material (average particle size (D)) is the same as in Example 1 50 ): 3.66㎛) was manufactured.

[0112]

[0113] Comparative Example 3

[0114] Except for preparing the lithium source material Li2CO3 so that the Li / Me ratio becomes 1.02 before the first calcination and adding the lithium source material Li2CO3 so that the Li / Me ratio becomes 1.07 before the second calcination, the cathode active material (average particle size (D)) is the same as in Example 1 50 ): 3.74㎛) was manufactured.

[0115]

[0116] Experimental Example (Evaluation of Anode Active Material)

[0117]

[0118] Experimental Example 1: Evaluation of particle size of cathode active material

[0119] The particle size of the cathode active materials prepared in Examples 1 and 2 and Comparative Examples 1 to 3 was measured and is shown in Table 1 below. The particle size was determined by introducing the material into a laser diffraction particle size measuring device (e.g., Microtrac MT 3000), irradiating it with ultrasound of approximately 28 kHz at an output of 60 W, and then calculating the volume ratio according to the particle size in the measuring device. Specifically, after calculating the volume percentage of particles with a particle size of 2 µm to 3 µm and the volume percentage of particles with a particle size of 4 µm to 5 µm, the volume percentage of particles with a particle size of 4 µm to 5 µm was divided by the volume percentage of particles with a particle size of 2 µm to 3 µm to calculate the semi-heavy particle size ratio.

[0120]

[0121] 2㎛-3㎛ Volume % 4㎛-5㎛ Volume % Semi-heavy Grain Rate Example 1 34% 11% 0.33 Example 2 36% 11% 0.32 Comparative Example 138% 7% 0.18 Comparative Example 239% 7% 0.17 Comparative Example 3 33% 14% 0.44

[0122]

[0123] According to Table 1 above, it was confirmed that the cathode active materials prepared in Examples 1 and 2 have a semi-heavy grain ratio of 0.2 or higher and less than 0.4, which corresponds to an intermediate value when compared to the semi-heavy grain ratio of the cathode active materials prepared in Comparative Examples 1 to 3.

[0124]

[0125] Experimental Example 2: Evaluation of Rolled Density of Anode Active Material

[0126] The rolled density of the cathode active materials prepared in Examples 1 and 2 and Comparative Examples 1 to 3 was measured and is shown in Table 2 below. The rolled density (P / D) was 2 tonf / cm² using a rolled density meter (HPRM-A1, manufactured by Hantech). 2 The rolling density under pressure was measured.

[0127]

[0128] Rolled Density (g / cc) Example 12.91 Example 22.87 Comparative Example 12.72 Comparative Example 22.71 Comparative Example 32.74

[0129]

[0130] According to Table 2 above, it was confirmed that the cathode active materials prepared in Examples 1 and 2 have a rolled density of 2.75 g / cc or higher, which corresponds to a significantly improved value compared to the rolled density of the cathode active materials prepared in Comparative Examples 1 to 3.

[0131]

[0132] Experimental Example 3: Battery Capacity and Resistance Characteristics

[0133] An anode slurry was prepared by mixing 92.5 wt% of the anode active material prepared in Example 1 and Comparative Examples 1 and 2, 3.0 wt% of Super P as a conductive material, and 4.5 wt% of polyvinylidene fluoride (PVDF) as a binder in an N-methylpyrrolidone (NMP) solvent. The anode slurry prepared above was coated on one side of an aluminum current collector, dried at 130°C, and then rolled to produce an anode.

[0134] An electrode assembly was manufactured by using a lithium metal electrode as the negative electrode and interposing a porous polyethylene separator between the positive and negative electrodes. This was placed inside a battery case, and a coin-type half-cell was manufactured by injecting an electrolyte solution in which 1M LiPF6 was dissolved in an organic solvent mixed with ethylene carbonate (EC):ethyl methyl carbonate (EMC):diethyl carbonate (DEC) in a volume ratio of 3:4:3.

[0135] Each manufactured coin-type half-cell was charged to 4.45 V at 25°C with a constant current of 0.1C, and then discharged to 2.0 V at 0.1C to perform the formation process. Subsequently, the initial discharge capacity and internal resistance were measured by charging to 4.45 V at 25°C with a constant current of 0.33C, and then discharging to 2.5 V at 0.33C. The results are shown in Table 3 below.

[0136]

[0137] Initial Discharge Capacity (mAh / g) Internal Resistance (DCIR) (Ω) Example 1 216.5 10.8 Example 2 216.9 11.5 Comparative Example 1 214.2 23.5 Comparative Example 2 214.3 24.7 Comparative Example 3 214.6 25.6

[0138]

[0139] According to Table 3 above, when the positive active material prepared in Examples 1 and 2 was used as the positive active material of the battery, the initial discharge capacity was significantly improved compared to when the positive active material prepared in Comparative Examples 1 to 3 was used. Furthermore, when the positive active material prepared in Examples 1 and 2 was used as the positive active material of the battery, the internal resistance was reduced to a level of 50% or less compared to when the positive active material prepared in Comparative Examples 1 to 3 was used.

[0140]

[0141] All simple variations or modifications of the present invention fall within the scope of the present invention, and the specific scope of protection of the present invention will be clarified by the appended claims.

Claims

1. As a positive electrode active material comprising lithium transition metal complex oxide particles, The above lithium transition metal composite oxide contains 50 mol% or more of nickel based on the total molar amount of transition metals, and The above lithium transition metal composite oxide particles are a positive electrode active material for a lithium secondary battery having a semi-heavy particle ratio of 0.2 or more and less than 0.4, where the volume percentage of particles with a particle size of 4㎛ to 5㎛ is relative to the volume percentage of particles with a particle size of 2㎛ to 3㎛ based on the total particle volume.

2. In Claim 1, A positive electrode active material for a lithium secondary battery, characterized in that the above lithium transition metal composite oxide contains 5 mol% to 40 mol% of manganese based on the total molar amount of transition metals.

3. In Claim 1, A positive electrode active material for a lithium secondary battery, characterized in that the above lithium transition metal composite oxide contains 0.5 mol% to 10 mol% of cobalt based on the total molar amount of transition metal.

4. In Claim 1, The above lithium transition metal composite oxide is a positive electrode active material for a lithium secondary battery characterized by having a mole of lithium per 1 mole of total transition metal of greater than 1.02 and less than 1.

07.

5. In Claim 1, The above lithium transition metal composite oxide particles have an average particle size (D) of 2㎛ to 5㎛. 50 A positive electrode active material for a lithium secondary battery characterized by having ).

6. In Claim 1, A positive electrode active material for a lithium secondary battery, characterized in that the above lithium transition metal composite oxide particles are in the form of single particles.

7. In Claim 1, The above positive active material is 2 tonf / cm 2 A positive electrode active material for a lithium secondary battery characterized by having a rolled density of 2.75 g / cc to 3.2 g / cc under pressure.

8. A method for manufacturing an anode active material comprising lithium transition metal composite oxide particles, wherein The above lithium transition metal composite oxide contains 50 mol% or more of nickel based on the total molar amount of transition metals, and The above lithium transition metal composite oxide particles have a semi-heavy particle ratio of 0.2 or more and less than 0.4, which is the volume percentage of particles with a particle size of 4㎛ to 5㎛ relative to the volume percentage of particles with a particle size of 2㎛ to 3㎛ based on the total particle volume, and The above manufacturing method is, (1) A step of mixing a transition metal raw material and a lithium raw material and performing a first calcination; and (2) A method for manufacturing a positive electrode active material for a lithium secondary battery, comprising the step of mixing a primary calcined product and a lithium raw material and performing a secondary calcination.

9. In Claim 8, A method for manufacturing a positive electrode active material for a lithium secondary battery, characterized in that, in step (1) above, the lithium raw material is controlled such that the number of moles of lithium relative to the total number of moles of transition metals is greater than 1.02 and less than or equal to 1.

04.

10. In Claim 8, A method for manufacturing a positive electrode active material for a lithium secondary battery, characterized in that, in step (2) above, the lithium raw material is controlled such that the number of moles of lithium relative to the total number of moles of transition metals is 1.05 or more and less than 1.

07.

11. In Claim 8, A method for manufacturing a positive electrode active material for a lithium secondary battery, characterized in that the first calcination is performed at 800°C to 1100°C and the second calcination is performed at 700°C to 1000°C.

12. In claim 8, A method for manufacturing a positive electrode active material for a lithium secondary battery, characterized in that the primary calcined product in step (2) above is crushed before being mixed with the lithium raw material.

13. A positive electrode for a lithium secondary battery comprising a positive electrode active material according to Claim 1.

14. A lithium secondary battery comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte according to claim 13.