Positive electrode material, positive electrode comprising same, and lithium secondary battery

Abstract

The present invention relates to a positive electrode material comprising lithium transition metal oxide particles having a single particle form, wherein the coefficient of variation of the cobalt content (mol%) relative to the total transition metals measured for the lithium transition metal oxide particles having a particle diameter of D10 or smaller is 0.30 to 0.75, the particle diameter meaning the diameter of a circle having the same area as a lithium transition metal oxide particle separated on the basis of a particle boundary in a SEM image (equivalent circular diameter (ECD)), and D10 being the particle diameter corresponding to the cumulative volume of 10% on a volume cumulative particle size distribution graph obtained on the basis of the particle diameter.

Description

Cathode material, a cathode including the same, and a lithium secondary battery

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2025-0049610 filed April 16, 2025, and all contents disclosed in the document of said Korean Patent Application are incorporated herein as part of this specification.

[0003] Technology field

[0004] The present invention relates to a cathode material, a cathode including the same, and a lithium secondary battery.

[0005]

[0006] Lithium secondary batteries capable of repeated charging and discharging are gaining attention as an alternative to fossil energy. Lithium secondary batteries have primarily been used in traditional handheld devices such as mobile phones, video cameras, and power tools. However, recently, their application fields are gradually increasing to include electric vehicles (EVs, HEVs, PHEVs), large-capacity energy storage systems (ESS), and uninterruptible power supply systems (UPS). A lithium secondary battery comprises an electrode assembly comprising unit cells having a structure in which a positive electrode plate coated with an active material on a current collector and a negative electrode plate are arranged with a separator in between, and an outer casing, namely a battery case, that seals and houses this electrode assembly together with an electrolyte.

[0007] Lithium transition metal oxides are utilized as cathode active materials for lithium secondary batteries; among these, lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMnO2 or LiMn2O4, etc.), lithium iron phosphate compounds (LiFePO4), or LiNiO2 are primarily used. Furthermore, as a method to improve the low thermal stability of LiNiO2 while maintaining its excellent reversible capacity, nickel-manganese lithium composite metal oxides in which a portion of the nickel is substituted with manganese, which has excellent thermal stability, as well as NCM (substituted with manganese and cobalt) or NCMA (which adds Al to NCM to improve battery output and stability), are being used.

[0008] Conventionally, a method involving mixing Al raw materials with an NCM precursor synthesized by the co-precipitation method and heat-treating it has been proposed as a synthesis method for NCMA single-particle cathode active materials. However, this synthesis method had the disadvantage of incurring additional manufacturing costs and environmental issues due to the involvement of precursor processing and washing / drying processes. Therefore, there is a need to develop a new manufacturing method for cathode active materials to enhance price competitiveness and comply with environmental regulations.

[0009] Meanwhile, conventional cathode active material particles are polycrystalline multi-particle materials that have the form of secondary particles formed by the aggregation of primary particles. When small units, called primary particles, aggregate to form large particles that can be physically distinguished, they are referred to as secondary particles. Conventional cathode active material particles have a large specific surface area and low particle strength. In particular, due to the high contact area with the electrolyte in this form, thermal property degradation caused by repeated charge-discharge cycles is severe, and cracks occur, exposing new surfaces and leading to serious gas generation due to side reactions. Consequently, there has been a demand from the industry for single-particle cathode active materials.

[0010]

[0011] [Prior Art Literature]

[0012] [Patent Literature]

[0013] (Patent Document 1) KR 10-1937926 B1

[0014]

[0015] The problem to be solved by the present invention is to provide a cathode material with improved lifespan characteristics and stability.

[0016]

[0017] (1) The present invention comprises lithium transition metal oxide particles in the form of single particles, and the particle size is D 10 The coefficient of variation of the cobalt content (mol%) relative to the total transition metal, measured for lithium transition metal oxide particles below, is 0.30 to 0.75, and the particle diameter refers to the equivalent circular diameter (ECD) of a circle having the same area as the lithium transition metal oxide particle separated based on the particle boundary in the SEM image, and the above D 10 The provides a cathode material having a particle size corresponding to 10% of the volume accumulation in the volume accumulation particle size distribution graph obtained with the above particle size.

[0018] (2) In the present invention, in (1) above, the anode material has a particle size D 10 The present invention provides a cathode material having a coefficient of variation of 0.10 to 0.21 for the cobalt content (mol%) relative to the total transition metal, measured for excess lithium transition metal oxide particles.

[0019] (3) The present invention provides a cathode material according to (1) or (2), wherein the coefficient of variation of the cobalt content (mol%) relative to the total transition metal, measured on lithium transition metal oxide particles having a particle size of D5 or less, is 0.36 to 0.82.

[0020] (4) The present invention provides a cathode material in which, in any one of (1) to (3), the lithium transition metal oxide has a nickel content of 50 mol% or more relative to the total transition metal.

[0021] (5) The present invention provides a cathode material in any one of (1) to (4), wherein the cathode material further comprises a coating layer located on the surface of a lithium transition metal oxide.

[0022] (6) The present invention provides a cathode material in which, in any one of (1) to (5), the lithium transition metal oxide is a compound represented by the following chemical formula 1.

[0023] [Chemical Formula 1]

[0024] Li a Ni b Co c Mn d M 1 e O2

[0025] In the above chemical formula 1,

[0026] M 1 It is one or more selected from the group consisting of Al, B, Ba, Ce, Cr, F, Mg, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, S, Sr, Ta, La, and Hf, and

[0027] 0.8≤a≤1.2, 0.5≤b<1.0, 0 <c<0.4, 0<d<0.4, 0≤e<0.1이다.

[0028] (7) In any one of (1) to (6) above, the present invention is such that the anode material has an average particle size (D 50 ) provides a cathode material having a thickness of 2㎛ to 10㎛.

[0029] (8) The present invention provides an anode comprising an anode material according to any one of (1) to (7).

[0030] (9) The present invention provides a lithium secondary battery comprising a positive electrode according to (8).

[0031]

[0032] When using the cathode material of the present invention, the lifespan characteristics and stability of the lithium secondary battery are improved.

[0033]

[0034] Figure 1 shows SEM-EDS data of the cathode material prepared in Example 1.

[0035] Figure 2 shows an SEM image of the cathode material prepared in Example 1.

[0036]

[0037] Hereinafter, the present invention will be described in more detail to aid in understanding the invention.

[0038]

[0039] Terms and words used in the description and claims of the present invention shall not be interpreted as being limited to their ordinary or dictionary meanings, and shall be interpreted in a meaning and concept consistent with the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0040]

[0041] In the present invention, "primary particle" refers to a minimum particle unit that is distinguished as a single mass when the cross-section of the positive active material is observed through a scanning electron microscope (SEM), and may consist of multiple crystal grains.

[0042] In the present invention, "secondary particle" refers to a secondary structure formed by the aggregation of a plurality of primary particles.

[0043] In the present invention, "single particle form" may be used as a substitute for the term "single particle type," and refers to a form contrasted with the secondary particle form formed by the aggregation of hundreds of primary particles manufactured by conventional methods. In the present invention, "single particle lithium transition metal oxide" refers to a cathode active material or lithium transition metal active material composed of one or more particles, 50 or fewer particles, 40 or fewer particles, 30 or fewer particles, 20 or fewer particles, 10 or fewer particles, or 5 or fewer particles, as a concept contrasted with the cathode active material in the form of a secondary particle formed by the aggregation of hundreds of primary particles manufactured by conventional methods. The above "single particle" refers to the smallest unit of a particle recognized when the cathode active material is observed through a scanning electron microscope.

[0044] In the present invention, "D 10 " represents the particle size at the 10% point of the volume cumulative distribution according to particle size. At this time, the particle size is the equivalent circular diameter (ECD) value of a circle having the same area as the lithium transition metal oxide particle separated based on the particle boundary in the SEM image. The ECD can be measured from a segmentation image partitioned by lithium transition metal oxide particle unit, obtained by image processing of the SEM image using an artificial intelligence model. Specifically, the segmentation image can be obtained by acquiring an SEM image of the cathode material to be measured, inputting the acquired SEM image into a U-NET structure to generate a binary image, converting the binary image into a distance-converted image based on a distance-converted algorithm, filtering the binary image using a threshold set based on the distance-converted image, identifying multiple objects included in the filtered binary image, and then segmenting the SEM image into particle units based on the multiple objects.

[0045] In the present invention, "average particle size (D 50"" refers to the particle size at the 50% point of the cumulative volume distribution according to particle size. The above average particle size is determined by dispersing the powder to be measured in a dispersion medium, introducing it into a commercially available laser diffraction particle size analyzer (e.g., Microtrac S3500), measuring the difference in diffraction patterns according to particle size as the particles pass through a laser beam to calculate the particle size distribution, and calculating the particle diameter at the point where the cumulative volume distribution according to particle size in the measuring device reaches 50%, thereby D 50 It can measure.

[0046] In the present invention, "coefficient of variation" refers to (standard deviation / mean). The coefficient of variation is calculated by performing SEM-EDS analysis on the cathode material. Specifically, SEM (JEOL, JSM-IT800) is measured at an acceleration voltage of 12 kV, and EDS (Bruker, QUANTAX FlatQUAD) is measured at an acceleration voltage of 2.5 kV to detect X-ray signals emitted from the surface of the particles. After measuring the Co content for each lithium transition metal oxide particle through SEM-EDS analysis, the coefficient of variation value is calculated based on this.

[0047]

[0048] cathode material

[0049] The cathode material of the present invention comprises lithium transition metal oxide particles in the form of single particles, and the particle size is D 10 The coefficient of variation of the cobalt content (mol%) relative to the total transition metal, measured for lithium transition metal oxide particles below, is 0.30 to 0.75, and the particle diameter refers to the equivalent circular diameter (ECD) of a circle having the same area as the lithium transition metal oxide particle separated based on the particle boundary in the SEM image, and the above D 10 It is characterized by being a particle size that corresponds to a volume accumulation of 10% in the volume accumulation particle size distribution graph obtained with the above particle size.

[0050]

[0051] The inventors [have] among the lithium transition metal oxides included in the cathode material, the particle size is D 10 The present invention was completed by confirming that when the coefficient of variation of the cobalt content (mol%) relative to the total transition metal in particles below is 0.30 to 0.75, a concentration gradient and a compositional deviation are formed in the lithium transition metal oxide particles of the cathode material, thereby enabling excellent high-temperature life and resistance in a lithium secondary battery.

[0052] In the present invention, the lithium transition metal oxide particles are in the form of single particles composed of 50 or fewer primary particles. That is, the lithium transition metal oxide particles are in the form of a single particle or a single particle formed by aggregating two or more and 50 or fewer particles. Specifically, they may be in the form of primary particles composed of 2 or more and 50 or fewer, 2 or more and 40 or fewer, 2 or more and 30 or fewer, 2 or more and 20 or fewer, 2 or more and 10 or fewer, or 2 or more and 5 or fewer. The single particle form is distinguished from secondary particles formed by aggregating more than 50 primary particles.

[0053] When the lithium transition metal oxide is in the form of a single particle, it exhibits excellent stability, so even when the cathode active material containing it is rolled, the cathode active material is less prone to breakage or cracking, and side reactions between the cathode active material and the electrolyte can be reduced. As a result, durability against volume changes during charging and discharging of the battery is improved, which can enhance lifespan characteristics. Meanwhile, lithium transition metal oxides, which are secondary particles, are prone to particle breakage during the electrode rolling process. Consequently, the surface area of ​​the cathode active material increases, leading to a worsening of storage and lifespan performance degradation at high temperatures. In particular, in the case of lithium transition metal oxides containing a high amount of nickel, the problem of particle breakage occurring during rolling for cathode manufacturing is exacerbated; in this case, side reactions between the lithium transition metal oxide and the electrolyte may increase, and the physical properties of the battery may deteriorate.

[0054]

[0055] In the present invention, the particle size is D 10 The coefficient of variation of the cobalt content (mol%) relative to the total transition metal, measured for lithium transition metal oxide particles of the following magnitude, is 0.30 to 0.75. Specifically, the coefficient of variation may be 0.31 or higher, 0.32 or higher, 0.33 or higher, 0.34 or higher, or 0.35 or higher, 0.74 or lower, 0.73 or lower, 0.72 or lower, or 0.71 or lower.

[0056] The above coefficient of variation refers to the standard deviation divided by the mean value (Coefficient of Variation = Standard Deviation / Mean). Specifically, values ​​for the cobalt content (mol%) relative to the total transition metal are collected via SEM / EDS targeting the lithium transition metal oxide in the cathode material, and the coefficient can be calculated based on the standard deviation and mean value.

[0057]

[0058] In the present invention, when the coefficient of variation is within the above range, the capacity development in the lithium secondary battery is excellent, and the growth of primary particles is promoted, so the degree of single particle formation can be high.

[0059]

[0060] If the coefficient of variation is less than 0.30, the growth of primary particles is low, resulting in a low degree of single particle size and inferior high-temperature performance of the lithium secondary battery, and if it exceeds 0.75, a problem arises in which the capacity of the lithium secondary battery is reduced due to excessive compositional non-uniformity.

[0061] As described above, the cathode material of the present invention is characterized by a large variation in cobalt content among lithium transition metal oxide particles with small particle sizes.

[0062]

[0063] In the present invention, the anode material has a particle size D 10The coefficient of variation of the cobalt content (mol%) relative to the total transition metal, measured for excess lithium transition metal oxide particles, may be 0.10 to 0.21. Specifically, it may be 0.11 or more, 0.12 or more, 0.13 or more, 0.14 or more, 0.15 or more, or 0.16 or more, 0.20 or less, 0.19 or less, or 0.18 or less.

[0064] When the coefficient of variation is within the above range, the capacity development in the lithium secondary battery is excellent, and the growth of primary particles is promoted, so the degree of single particle formation can be high.

[0065]

[0066] In the present invention, the coefficient of variation of the cobalt content (mol%) relative to the total transition metal, measured on lithium transition metal oxide particles with a particle size of D5 or less, may be 0.36 to 0.82. Specifically, it may be 0.36 or more, 0.37 or more, 0.38 or more, 0.39 or more, 0.81 or less, 0.80 or less, 0.79 or less, or 0.78 or less. When the coefficient of variation is within the above range, excellent capacity development is exhibited in the lithium secondary battery, and the growth of primary particles is promoted, resulting in a high degree of single particle formation.

[0067]

[0068] In the present invention, the anode material has a particle size D 10 The average value of the cobalt content (mol%) relative to the total transition metal, measured for excess lithium transition metal oxide particles, may be 3.0 mol% or more and 10.0 mol% or less. Specifically, it may be 3.5 mol% or more, 4.0 mol% or more, 4.5 mol% or more, 5.0 mol% or more, 5.5 mol% or more, or 6.0 mol% or more, 9.5 mol% or less, 9.0 mol% or less, 8.5 mol% or less, 8.0 mol% or less, 7.5 mol% or less, 7.0 mol% or less, or 6.5 mol% or less.

[0069]

[0070] In the present invention, the anode material has a particle size D 10 The average value of the cobalt content (mol%) relative to the total transition metal, measured for lithium transition metal oxide particles of the following magnitude, may be 5.0 mol% or more and 20.0 mol% or less. Specifically, it may be 5.5 mol% or more, 6.0 mol% or more, 6.5 mol% or more, 7.0 mol% or more, 7.5 mol% or more, 8.0 mol% or more, 8.5 mol% or more, 9.0 mol% or more, 9.5 mol% or more, 10.0 mol% or more, or 10.5 mol% or more, 19.5 mol% or less, 19.0 mol% or less, 18.5 mol% or less, 18.0 mol% or less, 17.5 mol% or less, or 17.0 mol% or less.

[0071]

[0072] In the present invention, the average value of the cobalt content (mol%) relative to the total transition metal, measured on lithium transition metal oxide particles with a particle size of D5 or less, may be 5.0 mol% or more and 20.0 mol% or less. Specifically, it may be 5.5 mol% or more, 6.0 mol% or more, 6.5 mol% or more, 7.0 mol% or more, 7.5 mol% or more, 8.0 mol% or more, 8.5 mol% or more, 9.0 mol% or more, 9.5 mol% or more, 10.0 mol% or more, 10.5 mol% or more, 19.5 mol% or less, 19.0 mol% or less, 18.5 mol% or less, 18.0 mol% or less, 17.5 mol% or less, or 17.0 mol% or less.

[0073]

[0074] As described above, the cathode material of the present invention may exhibit a tendency for higher cobalt content as the particle size of the lithium transition metal oxide particles becomes smaller.

[0075]

[0076] In the present invention, the lithium transition metal oxide may have a nickel content of 50 mol% or more relative to the total transition metal. Specifically, it may be 60 mol% or more, 65 mol% or more, 70 mol% or more, 75 mol% or more, 80 mol% or more, or 85 mol% or more, and may be less than 100 mol%, 99 mol% or less, 98 mol% or less, 97 mol% or less, 96 mol% or less, or 95 mol% or less.

[0077] Specifically, the lithium transition metal oxide may be a compound represented by the following chemical formula 1.

[0078] [Chemical Formula 1]

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

[0080] In the above chemical formula 1,

[0081] M 1 It is one or more selected from the group consisting of Al, B, Ba, Ce, Cr, F, Mg, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, S, Sr, Ta, La, and Hf, and

[0082] 0.8≤a≤1.2, 0.5≤b<1.0, 0 <c<0.4, 0<d<0.4, 0≤e<0.1이다.

[0083] The above 'a' represents the molar ratio of lithium and may be 0.8 or more and 1.2 or less. Specifically, it may be 0.84 or more, 0.88 or more, 0.92 or more, 0.96 or more, or 1.00 or more, and may also be 1.18 or less, 1.16 or less, 1.14 or less, 1.12 or less, 1.10 or less, 1.08 or less, 1.06 or less, or 1.04 or less.

[0084] The above b represents the molar ratio of nickel and may be 0.5 or more and less than 1.0, 0.55 or more, 0.60 or more, 0.65 or more, 0.70 or more, or 0.75 or more, and may also be 0.98 or less, 0.96 or less, 0.94 or less, 0.92 or less, 0.90 or less, or 0.88 or less. When b satisfies the above range, high energy characteristics can be realized.

[0085] The above c represents the molar ratio of cobalt and may be greater than 0 and less than 0.4. Specifically, it may be 0.001 or more, 0.005 or more, 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, or 0.05 or more, and may be less than 0.40, 0.35 or less, 0.30 or less, 0.25 or less, 0.20 or less, 0.15 or less, 0.10 or less, or 0.05 or less. When c satisfies the above range, stability can be improved during the charging and discharging process.

[0086] The above d represents the molar ratio of manganese and may be greater than 0 and less than 0.4. Specifically, it may be 0.001 or more, 0.005 or more, 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, or 0.05 or more, and less than 0.40, 0.35 or less, 0.30 or less, 0.25 or less, 0.20 or less, 0.15 or less, 0.10 or less, or 0.05 or less. When d satisfies the above range, high-temperature stability may be increased and side reactions with the electrolyte may be relatively reduced.

[0087] The above e is a molar ratio of M1, which may be 0 or more and less than 0.10, specifically, 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, or 0.05 or more, and may be less than 0.10, 0.09 or less, 0.08 or less, 0.07 or less, or 0.06 or less. When e satisfies the above range, the stability of the crystal structure of the positive active material can be improved and the particle shape can be improved.

[0088]

[0089] In the present invention, the cathode material may further include a coating layer located on the surface of a lithium transition metal oxide. The coating layer may include one or more coating elements selected from the group consisting of B, Co, Al, Ba, Ce, Cr, F, Mg, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, S, Sr, Ta, La, and Hf. More specifically, the coating layer may include B, Co, or both, and specifically may include Co.

[0090]

[0091] In the present invention, the average particle size (D of the anode material) 50 The particle size may be 2㎛ to 10㎛. Specifically, it may be 2.3㎛ or more, 2.5㎛ or more, 2.7㎛ or more, 3.0㎛ or more, 3.3㎛ or more, 3.5㎛ or more, or 3.6㎛ or more, and may be 9.0㎛ or less, 8.0㎛ or less, 7.0㎛ or less, 6.0㎛ or less, 5.0㎛ or less, or 4.5㎛ or less. The above average particle size may be calculated using a laser diffraction particle size analyzer.

[0092] Within the above range, the discharge capacity and electrode density of a lithium secondary battery using a positive electrode active material can be excellently realized.

[0093]

[0094] The cathode material of the present invention may be manufactured by a manufacturing method comprising: (S1) a step of preparing a mixture by dry mixing a lithium-containing raw material, a nickel-containing raw material, a cobalt-containing raw material, and a manganese-containing raw material; (S2) a step of preparing a sintered product by first sintering the mixture; and (S3) a step of mixing the sintered product with a coating raw material and secondarily sintering it.

[0095]

[0096] In the present invention, the method for manufacturing the cathode material is based on a solid-phase synthesis method in which solid raw materials of each element constituting the cathode material are mixed and calcined to vaporize and remove inorganic substances contained in the raw materials and form oxides. Accordingly, compared to the conventional method for manufacturing precursor-based single-particle cathode materials synthesized by the co-precipitation method, it is possible to prevent additional manufacturing costs and environmental problems associated with precursor processing and washing / drying.

[0097] In addition, since the manufacturing process is carried out by separately inputting and mixing the raw materials of the transition metals constituting the cathode material, variations in composition, such as transition metal content, appear in the lithium transition metal oxide particles depending on their particle size.

[0098]

[0099] In the present invention, the lithium raw material may be one or more selected from the group consisting of lithium hydroxide (LiOH), lithium hydroxide hydrate (LiOH·H2O), and lithium carbonate (Li2CO3).

[0100] In the present invention, the nickel-containing raw material, the cobalt-containing raw material, and the manganese-containing raw material refer to the solid raw materials of nickel, cobalt, and manganese, respectively. This differs from the conventional precursor synthesized by the co-precipitation method, in which nickel, cobalt, and manganese are all included in a single compound. Specifically, the nickel-containing raw material, the cobalt-containing raw material, and the manganese-containing raw material may each be at least one of the forms of nickel, cobalt, and manganese, such as metal, hydroxyoxide, oxide, carbonate, sulfate, sulfide, phosphate, nitrate, chloride, and acetate.

[0101] In the present invention, the nickel-containing raw material, the cobalt-containing raw material, and the manganese-containing raw material have an average particle size (D) of 0.1㎛ or more and 15㎛ or less based on volume. 50It may have ), specifically, 0.12㎛ or more, 0.14㎛ or more, 0.16㎛ or more, 0.18㎛ or more, or 0.20㎛ or more, 14.0㎛ or less, 13.0㎛ or less, 12.0㎛ or less, 11.0㎛ or less, or 10.0㎛ or less.

[0102] When using a material having the above average particle size, particle growth is excellent, so the cathode material of the present invention can be effectively manufactured.

[0103]

[0104] In the present invention, a doping element raw material can be additionally added and mixed in step (S1).

[0105] In this case, the doping element raw material is M of Chemical Formula 1. 1 Referring to the raw material of, the above M 1 It may be at least one of the forms of metal, hydroxyoxide, oxide, carbonate, sulfate, sulfide, phosphate, nitrate, chloride, and acetate.

[0106]

[0107] In the present invention, the mixing of step (S1) can be performed using a vertical mixer, for example, an FM mixer, a Henschel mixer, etc.

[0108] When using the above device, uniform mixing of raw materials is possible, and an anode material having the characteristics of the present invention can be manufactured.

[0109]

[0110] In the present invention, in step (S2), the mixture mixed in step (S1) is first fired to produce a fired product.

[0111] The above first firing can be performed in an oxygen atmosphere at a temperature of 800°C or higher and 1,000°C or lower. Specifically, the first firing can be performed at 800°C or higher, 810°C or higher, 820°C or higher, 830°C or higher, 840°C or higher, 850°C or higher, 860°C or higher, 870°C or higher, 880°C or higher, or 890°C or higher, 1,000°C or lower, 995°C or lower, 990°C or lower, 985°C or lower, 980°C or lower, 975°C or lower, 970°C or lower, 965°C or lower, 960°C or lower, 955°C or lower, 950°C or lower, 945°C or lower, 940°C or lower, 935°C or lower, 930°C or lower, 925°C or lower, 920°C or lower, 915°C or lower, 910°C or lower, 905°C or lower, 900°C or lower, 895°C or lower, or 890°C or lower.

[0112] By performing the first calcination under an oxygen atmosphere, sufficient oxygen required for the reaction can be supplied, and by performing it within the above temperature range, a calcined product in the form of a single particle can be formed. On the other hand, if the first calcination is not performed under an oxygen atmosphere, there is a problem that sufficient oxygen required for the reaction is not supplied, and if the first calcination is performed at a temperature below 800°C, there is a problem that sufficient thermal energy required to form a single particle is not supplied, and if the first calcination is performed at a temperature above 1,000°C, there is a problem that over-calcination occurs and the cathode active material deteriorates.

[0113]

[0114] In the present invention, in step (S3), the sintered product prepared in step (S2) is mixed with a coating raw material and sintered a second time.

[0115] The above coating raw material may be at least one selected from the group consisting of oxides, carbonates, nitrates, hydroxides, oxyhydroxides, and halides containing a coating element. Here, the coating element may be one or more selected from the group consisting of B, Co, Al, Ba, Ce, Cr, F, Mg, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, S, Sr, Ta, La, and Hf.

[0116] The above coating raw material may be mixed such that the coating element has a content of 10,000 ppm or more and 15,000 ppm or less relative to the total weight of the positive electrode active material. Specifically, the coating raw material comprises, with respect to the total weight of the cathode active material, a coating element of 10,000 ppm or more, 10,100 ppm or more, 10,200 ppm or more, 10,300 ppm or more, 10,400 ppm or more, 10,500 ppm or more, 10,600 ppm or more, 10,700 ppm or more, 10,800 ppm or more, 10,900 ppm or more, 11,000 ppm or more, 11,100 ppm or more, 11,200 ppm or more, 11,300 ppm or more, 11,400 ppm or more, 11,500 ppm or more, 11,600 ppm or more, 11,700 ppm or more, 11,800 ppm or more, 11,900 ppm or more, 12,000ppm or more, 12,100ppm or more, 12,300ppm or more, 12,400ppm or more, 12,500ppm or more, 12,600ppm or more, 12,700ppm or more, 12,800ppm or more, 12,900ppm or more, 13,000ppm or more, 13,100ppm or more, 13,200ppm or more, 13,300ppm or more, 13,400ppm or more, or 13,500ppm or more, 15,000ppm or less, 14,900ppm or less, 14,800ppm or less, 14,700ppm or less, 14,600ppm or less, 14,500ppm or less, 14,400ppm or less, It may be 14,300 ppm or less, 14,200 ppm or less, 14,100 ppm or less, 14,000 ppm or less, 13,900 ppm or less, 13,800 ppm or less, 13,700 ppm or less, or 13,600 ppm or less.

[0117] When the coating raw material is within the above range, it has the effect of improving output characteristics without degrading the resistance characteristics of the battery.

[0118] The above secondary firing can be performed at a temperature of 200°C or higher and 900°C or lower. Specifically, the fired product can be fired at a temperature of 200°C or higher, 300°C or higher, 400°C or higher, 500°C or higher, 600°C or higher, or 700°C or higher, and 800°C or lower or 900°C or lower. In this case, the coating raw material can be effectively melted to form a coating portion containing a coating element on a lithium transition metal oxide.

[0119]

[0120] anode

[0121] The anode of the present invention is characterized by comprising the aforementioned anode material.

[0122] Specifically, the anode comprises an anode current collector and an anode active material layer formed on the anode current collector and comprising the anode active material described above.

[0123] In the present invention, the 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 positive current collector may typically have a thickness of 3 to 500 μm, and fine irregularities may be formed on the surface of the 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.

[0124] In the present invention, the positive active material layer may include a conductive material and a binder together with the positive active material described above.

[0125] In the present invention, the conductive material is used to impart conductivity to the electrode, and can be used without special limitations as long as it has electronic conductivity without causing chemical changes in the battery being constructed. 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, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, or silver; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxide 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 typically be included in an amount of 0.3 to 30 weight% relative to the total weight of the positive electrode active material layer.

[0126] In 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), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), 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. The binder may be included in an amount of 0.3 to 30 weight% based on the total weight of the positive active material layer.

[0127] In 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, it may be manufactured by applying a composition for forming an anode active material layer, prepared by mixing or dispersing the anode active material and, optionally, a binder and a conductive material in a solvent, onto an anode current collector, followed by drying and rolling. At this time, the types and contents of the anode active material, binder, and conductive material are as described above.

[0128] In the present invention, the solvent may be a solvent generally used in the relevant technical field, and may include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), 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 if it has a viscosity that dissolves or disperses the anode active material, conductive material, and binder, taking into account the coating thickness of the slurry and the manufacturing yield, and subsequently provides excellent thickness uniformity when coated for anode manufacturing.

[0129] In addition, the anode may also be manufactured by casting the composition for forming the anode active material layer onto a separate support and then laminating the film obtained by peeling from the support onto an anode current collector.

[0130]

[0131] lithium secondary battery

[0132] In the present invention, an electrochemical device comprising the anode is provided. Specifically, the electrochemical device may be a battery, a capacitor, etc., and more specifically, may be a lithium secondary battery.

[0133] In the present invention, the lithium secondary battery specifically comprises a positive electrode, a negative electrode positioned opposite to the positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode is as described above. Additionally, the lithium secondary battery may optionally further comprise a battery container housing an electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member sealing the battery container.

[0134] In the present invention, the lithium secondary battery comprises, wherein the negative electrode includes a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector.

[0135] In the present invention, the negative electrode 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 negative electrode current collector may typically have a thickness of 3 to 500 μm, and, similar to the positive electrode current collector, fine irregularities may be formed on the surface of the current collector to strengthen the bonding strength of the negative electrode active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0136] In the present invention, the negative electrode active material layer optionally includes a binder and a conductive material together with the negative electrode active material.

[0137] In 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 xExamples include metal oxides capable of doping and dedoping lithium, such as (0 < x < 2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the metal compound and carbonaceous material, such as Si-C composites or Sn-C composites, and any one or more of these may be used. Additionally, a metallic lithium thin film may be used as the negative electrode active material. Furthermore, the carbon material may include low-crystallinity carbon and high-crystallinity carbon. Representative examples of low-crystallinity carbon include soft carbon and hard carbon, while representative examples of high-crystallinity carbon include amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch-derived cokes.

[0138] In addition, the binder and conductive material mentioned above may be the same as those described above for the anode.

[0139] In the present invention, the negative electrode active material layer may be manufactured by, for example, applying a negative electrode forming composition prepared by dispersing a negative electrode active material and optionally a binder and a conductive material in a solvent onto a negative electrode current collector and drying it, or by casting the negative electrode forming composition onto a separate support and then laminating the film obtained by peeling from the support onto a negative electrode current collector.

[0140] Meanwhile, in the above-mentioned lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions. Any separator typically used in lithium secondary batteries may be used without special restrictions, and it is particularly desirable that it has low resistance to the movement of electrolyte ions and excellent electrolyte wettability. Specifically, a porous polymer film, such as a porous polymer film made of a polyolefin-based polymer like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and 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 fiber or polyethylene terephthalate fiber, may be used. Furthermore, a coated separator containing ceramic components or polymer materials may be used to ensure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0141] In addition, the electrolytes used in the present invention may include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc., which are usable when manufacturing lithium secondary batteries, but are not limited to these.

[0142] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0143] In the present invention, the organic solvent may be used without special limitations 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 be an ester-based solvent such as methyl acetate, ethyl acetate, γ-butyrolactone, or ε-caprolactone; an ether-based solvent such as dibutyl ether or tetrahydrofuran; a ketone-based solvent such as cyclohexanone; or an aromatic hydrocarbon-based solvent such as benzene or fluorobenzene. Carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl 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 C2 to C20 structures 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.In this case, using a mixture of cyclic carbonate and chain carbonate in a volume ratio of about 1:1 to about 1:9 can result in excellent performance of the electrolyte.

[0144] In the present invention, the lithium salt can be used without special limitations as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. The lithium salt may be used within the range of 0.1 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 allow lithium ions to move effectively.

[0145] In 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 an amount of 0.1 to 5 weight% based on the total weight of the electrolyte.

[0146] In the present invention, since the lithium secondary battery comprising the positive electrode active material according to the present invention as described above stably exhibits excellent discharge capacity, output characteristics, and capacity retention rate, it is useful in fields such as portable devices like mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0147]

[0148] Examples

[0149] The present invention will be explained in more detail below through examples. However, the following examples are intended to illustrate the present invention and do not limit the scope of the present invention.

[0150]

[0151] Example 1

[0152] Ni(OH)2 (average particle size (D 50 ): 4.0㎛), Co(OH)2(average particle size (D 50 ): 0.2㎛), Mn3O4(average particle size (D 50 ): 1.0㎛, maximum particle size (D max ): 6.0㎛), Al(OH)3(average particle size (D 50 A mixture was prepared by mixing (1.0㎛) with an FM mixer, and then dry mixing with LiOH so that the molar ratio of Li:(Ni+Co+Mn+Al) was 1.02:1 to 1.04:1. The above mixture was first calcined in an oxygen atmosphere at a temperature of 890℃ to produce a calcined product.

[0153] The above lithium transition metal oxide was mixed with Co(OH)2 and Al(OH)3, and a secondary calcination was performed at a temperature of 710°C to produce a cathode material comprising the above lithium transition metal oxide and a coating portion containing Co and Al. At this time, the above Co(OH)2 was mixed such that the cobalt (Co) content was 13,000 ppm relative to the total weight of the cathode material, and the above Al(OH)3 was mixed such that the aluminum (Al) content was 500 ppm relative to the total weight of the cathode material.

[0154]

[0155] Example 2

[0156] Mn3O4 (average particle size (D 50 ): 1.0㎛, maximum particle size (D max ): 6.0㎛) instead of Mn3O4(average particle size (D 50 ): 1.0㎛, maximum particle size (D max The cathode material was prepared in the same manner as in Example 1, except that ): 12.0㎛) was used.

[0157]

[0158] Comparative Example 1

[0159] Complex transition metal hydroxide [Composition: Ni 0.885 Co 0.035 Mn 0.075 Al 0.005 (OH)2, average particle size (D 50 ) 4㎛] and LiOH are mixed so that the molar ratio of (Ni+Co+Mn):Li is 1:1.05, and a first calcined product is prepared by first calcination at 850°C for 6 hours under an oxygen atmosphere; then, the first calcined product is disassembled and second calcined at 750°C for 9 hours under an oxygen atmosphere, thereby producing Li Ni 0.885 Co 0.035 Mn 0.075 Al 0.005 A cathode material having a composition represented by O2 and an average particle size of 4㎛ was manufactured.

[0160]

[0161] Comparative Example 2

[0162] The cathode material was prepared in the same manner as in Example 1, except that a shovel mixer was used instead of an FM mixer.

[0163]

[0164] Experimental Example 1

[0165] SEM-EDS analysis was performed on the cathode materials prepared in the above examples and comparative examples to calculate the coefficient of variation of Co.

[0166] n SEM (JEOL, JSM-IT800) images (at least 10) were obtained for the cathode materials prepared in the examples and comparative examples. The area of ​​each particle was calculated using the number of pixels corresponding to each single-particle lithium transition metal oxide particle present in the SEM images, and the particle diameter of each lithium transition metal oxide particle was calculated using the equivalent circular diameter (ECD) of a circle having the same area as each particle. From this, a volume cumulative particle size distribution graph was derived, and the particle diameter at the point where the volume cumulative reaches 10% was D 10 It was defined as such, and the particle size at the point where the volume accumulation corresponds to 5% was defined as D5.

[0167] In addition, the cobalt content was measured by performing EDS (Bruker, QUANTAX FlatQUAD) analysis on the lithium transition metal oxide particles. As shown in Fig. 2, the cobalt content of each particle was analyzed by allocating a particle-specific area to each lithium transition metal oxide particle. Based on this, the above D 10 The standard deviation and arithmetic mean were calculated based on D5, respectively, and the coefficient of variation was calculated by dividing the standard deviation by the arithmetic mean.

[0168] The above process was carried out on at least 100 lithium transition metal oxide particles by obtaining at least 10 SEM images. In addition, SEM-EDS data of the cathode material of Example 1 is shown in Fig. 1.

[0169] Particle Size Range Mean Standard Deviation Coefficient of Variation Example 1D 10 Excess 6.071.110.18D 10 Below 16.61 11.8 30.71D5 Below 16.68 12.9 60.78 Example 2D 10 Excess 6.371.000.16D 10 Below 10.6 13.7 30.35D5 Below 10.6 24.1 50.39 Comparative Example 1D 10 Excess 5.410.840.16D 10 Below 6.70 1.8 40.27D5 Below 6.99 2.4 30.35 Comparative Example 2D 10 Excess 6.271.380.22D 10 Below 8.546.640.78D5 Below 8.617.170.83

[0170] As shown in Table 1 above, the cathode materials of Examples 1 and 2 according to the present invention have a particle size of D 10 It was confirmed that the coefficient of variation of the cobalt content (mol%) relative to the total transition metal, measured for the lithium transition metal oxide particles below, was 0.30 to 0.75. In addition, as can be seen in Figure 1, it was found that the cobalt content was high in lithium transition metal oxide particles with small particle sizes.

[0171]

[0172] Experimental Example 2

[0173] Using the cathode materials prepared in Examples 1 and 2 and Comparative Examples 1 and 2 above, carbon black (Denka, DenkaBlack) as a conductive material and PVdF (Kureha, KF1300) as a binder were added to a solvent (Daejeong Hwakum Co., N-methylpyrrolidone (NMP)) in a weight ratio of 95:3:2 (cathode material:conductive material:binder) to prepare a composition for forming a cathode active material layer.

[0174] The above-described composition for forming an anode active material layer was coated on one side of an aluminum foil current collector with a thickness of 20 μm and dried at 135°C for 3 hours to form an anode active material layer. Subsequently, the anode active material layer was rolled using a roll pressing method, and an anode having a porosity of 20% of the anode active material layer was manufactured after rolling.

[0175] A coin-shaped half-cell was manufactured using lithium metal as the cathode along with the above-mentioned anode.

[0176] The electrochemical properties were evaluated as follows using the half-cell prepared above.

[0177] Each of the manufactured coin half cells was charged at 25°C with a constant current (CC) of 0.1 C until it reached 4.25 V, and then charged with a constant voltage (CV) of 4.25 V until the charging current reached 0.05 mAh, thereby measuring the charging capacity. After leaving them for 20 minutes, they were discharged with a constant current of 0.1 C until they reached 2.5 V, and the discharge capacity of the first cycle was measured. The charge / discharge efficiency of the first cycle was evaluated, and the initial resistance (DCIR) was measured by dividing the difference in voltage between immediately before and after 60 seconds of current application during the 0.1 C discharge by the current.

[0178] Charging Capacity (mAh / g) Discharging Capacity (mAh / g) Example 1 23.20 207.60 Example 2 23.00 207.80 Comparative Example 1 23.00 206.77 Comparative Example 2 22.8.30 205.60

[0179] As shown in Table 2 above, it was confirmed that the capacity characteristics of the lithium secondary battery are excellent when the cathode materials of Examples 1 and 2 according to the present invention are applied.

[0180]

[0181] Experimental Example 3

[0182] A composition for forming an anode active material layer was prepared by adding the anode material prepared in Examples 1 and 2 and Comparative Examples 1 and 2, carbon black (Denka, DenkaBlack) conductive material, dispersant (BM 730H), and PVDF (Kureha, KF1300) binder to an N-methylpyrrolidone (NMP) (Daejeong Chemical Co.) solvent in a weight ratio of 95:2:0.2:2.8. The composition for forming an anode active material layer was applied to one side of an aluminum foil current collector with a thickness of 20 μm, and the anode active material layer was formed by drying at a temperature of 130°C for 1 hour. Subsequently, an anode was manufactured by rolling using a roll pressing method so that the porosity of the anode active material layer after rolling was 20 volume%.

[0183] A cathode was prepared in which a cathode active material layer containing graphite was formed on one side of a Cu foil current collector with a thickness of 10 μm.

[0184] An electrode assembly was manufactured by interposing a porous polyethylene separator between the anode and the cathode. This was placed inside a battery case, and a pouch-type monocell was manufactured by injecting an electrolyte solution in which 1.0 M LiPF6 was dissolved in an organic solvent mixed with ethylene carbonate (EC):ethyl methyl carbonate (EMC):diethyl carbonate (DEC) in a volume ratio of 3:3:4.

[0185] Each of the manufactured monocells was charged at 25°C with a constant current (CC) of 0.3C until it reached 4.2V, then charged with a constant voltage (CV) of 4.2V until the charging current reached 0.05mAh (cut-off current), left for 20 minutes, and then discharged with a constant current of 0.3C until it reached 2.5V. This charge-discharge process was repeated twice. Afterward, the cells were fully charged again with a constant current of 0.3C from a discharged state, and after the measurement of the room temperature output by SOC using the HPCC (Hybrid Pulse Power Characterization) protocol was completed, they were charged in a 45°C oven with a constant current (CC) of 0.3C until it reached 4.2V, and then charged with a constant voltage (CV) of 4.2V until the charging current reached 0.05mA (cut-off current). Subsequently, after leaving it for 20 minutes, one charge-discharge cycle was performed by discharging at a constant current of 0.3C until the voltage reached 2.5V. Afterward, the charge-discharge cycle was repeated 300 times by charging at a constant current of 0.5C until the voltage reached 4.2V, then charging at a constant voltage of 4.2V until the charging current reached 0.05mA (cut-off current), leaving it for 20 minutes, and then discharging at a constant current of 1.0C until the voltage reached 2.5V. At this time, the percentage of the discharge capacity of the 300th cycle relative to the discharge capacity of the first cycle was defined as the capacity retention rate (%). Additionally, the percentage of the DCIR value of the 300th cycle relative to the DCIR value of the first cycle was defined as the resistance increase rate (%).

[0186] Capacitance Retention Rate (%) Resistance Increase Rate (%) Example 1 90.9 45.5 Example 2 90.8 59.1 Comparative Example 190.6 83.0 Comparative Example 289.6 91.8

[0187] As shown in Table 3 above, it was confirmed that the lithium secondary battery containing the positive active material of Examples 1 and 2 exhibited superior lifespan characteristics compared to the lithium secondary battery using the positive active material of Comparative Examples 1 and 2.

Claims

1. Includes lithium transition metal oxide particles in the form of single particles, and Particle size is D 10 The coefficient of variation of the cobalt content (mol%) relative to the total transition metal, measured for lithium transition metal oxide particles below this level, is 0.30 to 0.75, and The above particle diameter refers to the equivalent circular diameter (ECD) of a circle having the same area as the lithium transition metal oxide particles separated based on particle boundaries in the SEM image, and The above D 10 The anode material having a particle size corresponding to 10% of the volume accumulation in the volume accumulation particle size distribution graph obtained with the above particle size.

2. In Claim 1, The above cathode material has a particle size of D 10 A cathode material having a coefficient of variation of 0.10 to 0.21 for the cobalt content (mol%) relative to the total transition metal, measured for excess lithium transition metal oxide particles.

3. In Claim 1, The above-mentioned cathode material is a cathode material having a coefficient of variation of 0.36 to 0.82 for the cobalt content (mol%) relative to the total transition metal, measured on lithium transition metal oxide particles with a particle size of D5 or less.

4. In Claim 1, The above lithium transition metal oxide is a cathode material having a nickel content of 50 mol% or more relative to the total transition metal.

5. In Claim 1, The above-mentioned cathode material is a cathode material further comprising a coating layer located on the surface of a lithium transition metal oxide.

6. In Claim 1, The above lithium transition metal oxide is a cathode material that is a compound represented by the following chemical formula 1: [Chemical Formula 1] Li a Ni b Co c Mr d M 1 e O2 In the above chemical formula 1, M 1 It is one or more selected from the group consisting of Al, B, Ba, Ce, Cr, F, Mg, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, S, Sr, Ta, La, and Hf, and 0.8≤a≤1.2, 0.5≤b<1.0, 0 <c<0.4, 0<d<0.4, 0≤e<0.1이다.

7. In Claim 1, The above cathode material has an average particle size (D 50 A cathode material having a thickness of 2㎛ to 10㎛.

8. A cathode comprising the cathode material according to claims 1 to 7.

9. A lithium secondary battery comprising a positive electrode according to claim 8.

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