Positive electrode active material, method for manufacturing the same, and positive electrode and lithium secondary battery containing the same

Abstract

The present invention relates to a positive electrode active material that can improve the performance of a lithium secondary battery, comprising a lithium composite transition metal oxide in single-particle form and a coating portion formed on the lithium composite transition metal oxide, wherein the coating portion comprises a first coating portion and a second coating portion, the first coating portion being discontinuously formed island-like, and the second coating portion being continuously formed coating layer-like, the first coating portion comprising boron (B) and selectively comprising one or more coating elements selected from the group consisting of 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, the second coating portion comprising a compound having a composition represented by chemical formula 1 or 2 as described herein, and the content of boron (B) among the total metals other than lithium in the positive electrode active material being 0.1 mol% or more and 1.25 mol% or less, the present invention relates to a positive electrode active material, a method for producing the same, and a positive electrode and a lithium secondary battery containing the same.

Description

[Technical Field]

[0001] This application claims priority under Korean Patent Application No. 10-2023-0071873 dated June 2, 2023, and all content disclosed in the said Korean Patent Application is incorporated herein by reference.

[0002] This invention relates to a positive electrode active material, a method for producing the same, and a positive electrode and lithium secondary battery containing the same. [Background technology]

[0003] Recently, with the advancement of technologies such as electric vehicles, the demand for high-capacity secondary batteries has increased, and consequently, research on cathodes using high-nickel (High Ni) cathode active materials with excellent capacity characteristics is being actively conducted.

[0004] High-nickel cathode active materials are manufactured using a co-precipitation method, resulting in a secondary particle form formed by the aggregation of primary particles. However, active materials with a secondary particle form have disadvantages: fine cracks can develop in the secondary particles during long-term charge-discharge processes, causing side reactions; and if the electrode density is increased to improve energy density, the secondary particles undergo structural breakdown, leading to a decrease in energy density and reduced lifetime characteristics due to a reduction in active material and electrolyte.

[0005] To address the problems associated with secondary particle-type high-nickel cathode active materials, single-particle nickel-based cathode active materials have recently been developed. Single-particle nickel-based cathode active materials have the advantage of not causing particle breakdown even when increasing electrode density due to their high energy density. However, because single-particle nickel-based cathode active materials require relatively high firing temperatures to manufacture, the R-3m layered structure is not properly maintained, lithium detaches from the crystal structure, and a phase change occurs to an Fm-3m rock-salt structure like NiO. This reduces the crystallinity of the cathode active material, increasing the proportion of NiO on the surface of the manufactured single-particle particles. As NiO increases, resistance increases, leading to problems such as a decrease in energy density and power output.

[0006] Furthermore, in order to manufacture a positive electrode using a positive electrode active material, it is essential to mix the positive electrode active material with a conductive material, binder, additives, and solvent to form a slurry. During this process, Li by-products located on the surface base the solvent, and the based solvent mixes with the binder to gel the slurry. Using such a gelled slurry makes it difficult to uniformly coat the slurry for the manufacture of the positive electrode.

[0007] Therefore, there is a need to develop a method that introduces an additional process during the manufacturing of the positive electrode active material to suppress the reaction of Li by-products present on the surface of the positive electrode active material with external substances, thereby preventing performance degradation of the positive electrode active material and gelation of the slurry. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] KR10-2019-0094529 [Patent Document 2] KR10-2022-0048191 A [Patent Document 3] KR10-2022-0048192 A [Overview of the project] [Problems that the invention aims to solve]

[0009] The problem that this invention aims to solve is to provide a positive electrode active material that reduces gelation during the manufacturing of the positive electrode slurry and improves the capacity characteristics, resistance characteristics, and life characteristics of the battery.

[0010] Another problem that the present invention aims to solve is to provide a method for producing the positive electrode active material.

[0011] Another problem that the present invention aims to solve is to provide a positive electrode with improved performance and a lithium secondary battery containing the positive electrode active material. [Means for solving the problem]

[0012] To solve the above problems, the present invention provides a positive electrode active material, a method for producing the same, and a positive electrode and a lithium secondary battery containing the same.

[0013] (1) The present invention provides a positive electrode active material comprising a lithium composite transition metal oxide in single-particle form and a coating portion formed on the lithium composite transition metal oxide, wherein the coating portion comprises a first coating portion and a second coating portion, the first coating portion being discontinuously formed island-like, and the second coating portion being continuously formed coating layer-like, the first coating portion comprising boron (B) and selectively comprising one or more coating elements selected from the group consisting of 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, and the second coating portion comprising a compound having a composition represented by the following chemical formula 1 or 2, wherein the content of boron (B) among the total metals other than lithium in the positive electrode active material is 0.1 mol% or more and 1.25 mol% or less. [Chemical formula 1] Li a Cob B c M 1 d M 2 e O f In the above Chemical Formula 1, M 1 is one or more selected from the group consisting of Ni and Mn, M 2 is one or more selected from the group consisting of H, Al, Ba, Ce, Cr, F, Mg, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, S, Sr, Ta, and Hf, 1 ≦ a ≦ 2, 1 ≦ b ≦ 4, 1 ≦ c ≦ 2, 0 ≦ d ≦ 1, 0 ≦ e ≦ 1, 2 ≦ f ≦ 8, [Chemical Formula 2] Co g B h M 3 i M 4 j O k In the above Chemical Formula 2, M 3 is one or more selected from the group consisting of Ni and Mn, M 4 is one or more selected from the group consisting of H, Al, Ba, Ce, Cr, F, Mg, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, S, Sr, Ta, and Hf, 1 ≦ g ≦ 4, 1 ≦ h ≦ 2, 0 ≦ i ≦ 1, 0 ≦ j ≦ 1, 2 ≦ k ≦ 8.

[0014] (2) The present invention provides a positive electrode active material in which, in the above (1), the first coating portion is dispersed and distributed on one or more of the surface of the lithium composite transition metal oxide and the surface of the second coating portion.

[0015] (3) The present invention provides a positive electrode active material in which, in the above (1) or (2), the content of boron (B) is 0.13 mol% or more and 1.1 mol% or less.

[0016] (4) The present invention relates to any one of (1) to (3) above, in which the average particle size (D 50 The invention provides a positive electrode active material having a size of 3 μm or more and 20 μm or less.

[0017] (5) In any one of (1) to (4) above, the present invention provides a positive electrode active material in which the lithium composite transition metal oxide has a composition represented by the following chemical formula 3. [Chemical formula 3] Li l Ni m Co n Mn o M 5 p O2 In the aforementioned chemical formula 3, M 5 This is one or more elements 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. 0.9≦l≦1.1, 0.6≦m<1, 0 <n<0.4、0<o<0.4、0≦p<0.1である。

[0018] (6) In any one of (1) to (5) above, the present invention provides a positive electrode active material in which the first coating portion comprises a compound having a composition represented by the following chemical formula 4. [Chemical formula 4] Li q B r M 6 s M 7 t O u In the aforementioned chemical formula 4, M 6 is one or more elements selected from the group consisting of Ni, Co, and Mn. M 7 This is one or more elements selected from the group consisting of 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. 0≦q≦4, 1≦r≦4, 0≦s≦1, 0≦t≦1, 1≦u≦8.

[0019] (7) The present invention provides a positive electrode active material in any one of (1) to (6) above, wherein the total area of ​​the coating portion is 10% or more and 100% or less of the total surface area of ​​the lithium composite transition metal oxide.

[0020] (8) The present invention provides a method for producing a positive electrode active material comprising (1) mixing a lithium composite transition metal oxide in single-particle form with a cobalt-containing raw material and selectively mixing with a coating element-containing raw material to produce a mixture; (2) firing the mixture to produce a fired product; and (3) mixing the fired product with a boron-containing raw material and heat-treating it to form a coating portion containing cobalt (Co) and boron (B) on the lithium composite transition metal oxide, wherein the coating element is one or more selected from the group consisting of 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, and the firing is performed at a temperature of 600°C to 800°C.

[0021] (9) The present invention provides a method for producing a positive electrode active material, wherein the lithium composite transition metal oxide in single-particle form is produced by a method comprising: (A) mixing a composite transition metal hydroxide containing nickel, cobalt, and manganese with a first lithium-containing raw material and performing primary calcination at a temperature of 800°C to 950°C to produce a primary calcined product; and (B) mixing the primary calcined product with a second lithium-containing raw material and performing secondary calcination at a temperature of 680°C to 850°C to produce a secondary calcined product.

[0022] (10) The present invention provides a method for producing a positive electrode active material, further comprising the step (A1) of crushing the primary calcined product immediately after step (A) in (8) or (9).

[0023] (11) The present invention provides a method for producing a positive electrode active material, further comprising the step of grinding the secondary calcined product immediately after step (B) in any one of the above steps (8) to (10).

[0024] (12) The present invention provides a positive electrode comprising a positive electrode active material according to any one of (1) to (7) above.

[0025] (13) The present invention provides a lithium secondary battery comprising a positive electrode according to (12), a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte. [Effects of the Invention]

[0026] The positive electrode active material of the present invention comprises a lithium composite transition metal oxide in single-particle form and a coating portion formed on the lithium composite transition metal oxide, wherein the coating portion comprises a first coating portion and a second coating portion, the first coating portion having a discontinuous form and the second coating portion having a continuous form, the first coating portion containing boron (B) and selectively containing one or more coating elements selected from the group consisting of 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, the second coating portion containing a compound having a composition represented by chemical formula 1 or 2 as described herein, and satisfying the condition that the content of boron (B) among the total metals other than lithium in the positive electrode active material is 0.1 mol% or more and 1.25 mol% or less, gelation is reduced during slurry production, and the battery containing the positive electrode active material has the effect of improving capacity characteristics, resistance characteristics and life characteristics. [Brief explanation of the drawing]

[0027] [Figure 1] (A) is an EPMA analysis image of the positive electrode active material produced in Example 1, (B) is an EPMA analysis image of the positive electrode active material produced in Example 2, and (C) is an EPMA analysis image of the positive electrode active material produced in Example 3. [Figure 2] (A) is an SEM image of the positive electrode active material produced in Example 1, (B) is an SEM image of the positive electrode active material produced in Example 2, and (C) is an SEM image of the positive electrode active material produced in Example 3. [Figure 3] The data shown are related to the Li2CoBO3 peak in the surface analysis results of the cathode active materials produced in the examples and comparative examples. [Figure 4] The CoBO3 peak-related data are from the surface analysis results of the cathode active materials produced in the examples and comparative examples. [Figure 5] (A) is a segmentation image of the positive electrode active material produced in Example 1, (B) is a segmentation image of the positive electrode active material produced in Example 2, and (C) is a segmentation image of the positive electrode active material produced in Example 3. [Figure 6] (A) is a segmentation image of the positive electrode active material produced in Comparative Example 1, (B) is a segmentation image of the positive electrode active material produced in Comparative Example 2, (C) is a segmentation image of the positive electrode active material produced in Comparative Example 3, (D) is a segmentation image of the positive electrode active material produced in Comparative Example 4, and (E) is a segmentation image of the positive electrode active material produced in Comparative Example 5. [Figure 7] This is a temperature graph of the positive electrode slurry containing the respective positive electrode active materials produced in the examples and comparative examples, over time. [Figure 8] This is a viscosity graph of the positive electrode slurry containing the respective positive electrode active materials produced in the examples and comparative examples, measured over time. [Modes for carrying out the invention]

[0028] The present invention will be described in more detail below to facilitate understanding of it.

[0029] The terms and words used in the description and claims of this invention should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather should be interpreted in a manner consistent with the technical idea of ​​this invention, in accordance with the principle that inventors may define the concepts of terms as appropriate to best describe their invention.

[0030] In the present invention, the term "primary particle" refers to the smallest particle unit that can be distinguished as a single mass when a cross-section of the positive electrode active material is observed using a scanning electron microscope (SEM), and can consist of one crystal grain or multiple crystal grains.

[0031] In this invention, the term "secondary particle" refers to a secondary structure formed by the aggregation of multiple primary particles. The average particle size of the secondary particle can be measured using a particle size analyzer.

[0032] In this specification, "single particle form" is a concept contrasted with the form of spherical secondary particles formed by the aggregation of tens to hundreds of primary particles manufactured by conventional methods, and refers to a form consisting of 50 or fewer primary particles. Specifically, in the present invention, the single particle form may be a single particle consisting of one primary particle, or it may be a form of secondary particles formed by the aggregation of 2 or more, 3 or more, 4 or more, 5 or more, 10 or more, and 30 or fewer, 35 or fewer, 40 or fewer, 45 or fewer, or 50 or fewer primary particles.

[0033] In this specification, the term "average particle size (D)" is used. 50 )" refers to the particle size at the 50% point of the cumulative volume distribution by particle size. The average particle size is calculated by dispersing the powder to be measured in a dispersion medium, introducing it into a commercially available laser diffraction particle size analyzer (for example, Microtrac's S3500), measuring the difference in diffraction patterns due to particle size as the particles pass through the laser beam to calculate the particle size distribution, and then calculating the particle size at the point where the cumulative volume distribution by particle size in the measuring device reaches 50%. 50 It can be measured.

[0034] In the present invention, the term "segmentation image" refers to an image segmented at the individual positive electrode active material particle level, and can be obtained by a method comprising: a first step of analyzing the positive electrode active material powder with a scanning electron microscope to obtain an SEM image; and a second step of using computer image processing techniques to remove the boundaries (edges) of the individual positive electrode active material particles from the SEM image, then detecting the seeds or contours of the individual positive electrode active material particles, and using these to obtain an image segmented at the individual positive electrode active material particle level. Specifically, the segmentation image can be obtained by the method described in KR10-2022-0048191 A and KR10-2022-0048192 A.

[0035] In the present invention, the term "island-like" may mean a form formed with an area greater than 0%, 1% or less, 5% or less, 10% or less, 20% or less, 30% or less, 50% or less, 60% or less, 70% or less, 80% or less, 90% or less, or less than 100% of the total surface area of ​​the lithium composite transition metal oxide.

[0036] positive electrode active material The positive electrode active material of the present invention will be described below.

[0037] The positive electrode active material of the present invention comprises a lithium composite transition metal oxide in single-particle form and a coating portion formed on the lithium composite transition metal oxide, wherein the coating portion comprises a first coating portion and a second coating portion, the first coating portion being discontinuously formed island-like, and the second coating portion being continuously formed coating layer-like, the first coating portion containing boron (B) and selectively containing one or more coating elements selected from the group consisting of 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, and the second coating portion containing a compound having a composition represented by the following chemical formula 1 or 2, and the content of boron (B) among the total metals other than lithium in the positive electrode active material is 0.1 mol% or more and 1.25 mol% or less.

[0038] [Chemical formula 1] Li a Co b B c M 1 d M 2 e O f In the above chemical formula 1, M 1 is one or more elements selected from the group consisting of Ni and Mn. M 2 is one or more elements selected from the group consisting of H, Al, Ba, Ce, Cr, F, Mg, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, S, Sr, Ta, and Hf. 1≦a≦2, 1≦b≦4, 1≦c≦2, 0≦d≦1, 0≦e≦1, 2≦f≦8, [Chemical formula 2] Co g B h M 3 i M 4 j O k In the aforementioned chemical formula 2, M 3is one or more elements selected from the group consisting of Ni and Mn. M 4 is one or more elements selected from the group consisting of H, Al, Ba, Ce, Cr, F, Mg, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, S, Sr, Ta, and Hf. 1≦g≦4, 1≦h≦2, 0≦i≦1, 0≦j≦1, 2≦k≦8.

[0039] The lithium composite transition metal oxide is in the form of a single particle consisting of 50 or fewer primary particles. That is, the lithium composite transition metal oxide is in the form of a single particle or a single particle formed by the aggregation of 2 to 50 particles. Specifically, it may be in the form of 2 to 40, 2 to 30, 2 to 20, or 2 to 10 primary particles, and preferably 2 to 10. The single particle form is distinguished from secondary particles formed by the aggregation of more than 50 primary particles.

[0040] When the lithium composite transition metal oxide is in the form of a single particle, it exhibits excellent stability, and even when the positive electrode active material containing it is rolled, the positive electrode active material either cracks or develops fewer cracks, thus reducing side reactions between the positive electrode active material and the electrolyte. This improves the battery's resistance to volume changes during charging and discharging, and thus improves its lifespan. On the other hand, lithium composite transition metal oxides, which are secondary particles, are prone to particle cracking during the electrode rolling process. This increases the surface area of ​​the positive electrode active material, leading to a significant decrease in storage performance at high temperatures and a reduced lifespan. In particular, lithium composite transition metal oxides containing a high nickel content are susceptible to particle cracking during rolling for the manufacture of the positive electrode. In this case, side reactions between the lithium composite transition metal oxide and the electrolyte may increase, potentially resulting in inferior battery properties.

[0041] The lithium composite transition metal oxide may have a layered (R-3m) structure and may have a high NiO content before the coating is formed on the lithium composite transition metal oxide. Since the formation of NiO is induced by the high firing temperature required during the manufacture of the lithium composite transition metal oxide, the lithium composite transition metal oxide may have a high NiO content on its surface, and this NiO has the problem of lowering the energy density of the battery and degrading its resistance and output characteristics.

[0042] The positive electrode active material of the present invention includes a coating portion formed on the lithium composite transition metal oxide, the coating portion comprising a first coating portion and a second coating portion, the first coating portion being discontinuously formed island-like, the second coating portion being continuously formed coating layer-like, the first coating portion comprising boron (B) and selectively comprising one or more coating elements selected from the group consisting of 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, and the second coating portion comprising a compound having a composition represented by chemical formula 1 or 2 as described herein.

[0043] The present invention, by including a coating portion, reduces side reactions between the positive electrode active material and the electrolyte, and has the effect of reducing the NiO content in the positive electrode active material. Furthermore, by including boron (B) in the first coating portion, the density of the positive electrode active material is reduced, improving the dispersibility of the positive electrode active material during the production of the positive electrode slurry. During storage of the produced positive electrode slurry, the precipitation of positive electrode active material particles in the slurry over time is reduced, and gelation, that is, the phenomenon in which positive electrode active material particles settle to the bottom in the positive electrode slurry while aggregation occurs between particles, can be reduced. In addition, the sphericity of the positive electrode active material can be increased, and consequently, the collision between particles and friction between the agitator and particles can be reduced during the production of the positive electrode slurry. On the other hand, if the lithium composite transition metal oxide does not include a coating portion, there is a problem of poor lifetime characteristics due to side reactions between the positive electrode active material and the electrolyte. If the first coating portion does not contain boron, the dispersibility of the positive electrode active material is poor, and there is a problem of excessive gelation occurring during the manufacturing of the positive electrode slurry.

[0044] On the other hand, in the above chemical formula 1, M 1 is one or more selected from the group consisting of Ni and Mn, and M 2 is one or more selected from the group consisting of H, Al, Ba, Ce, Cr, F, Mg, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, S, Sr, Ta, and Hf. 2 While not a mandatory component, it can improve capacity and lifespan characteristics.

[0045] The aforementioned value a may be 1 or more, 1.5 or more, or 2 or less.

[0046] The aforementioned b may be 1 or more, or it may be 2 or less, 3 or less, or 4 or less.

[0047] The aforementioned c may be 1 or more, 1.5 or less, or 2 or less.

[0048] The aforementioned d may be 0 or greater, 0.5 or less, or 1 or less.

[0049] The aforementioned e may be 0 or greater, 0.5 or less, or 1 or less.

[0050] The aforementioned f may be 2 or more, or 3 or more, and may be 4 or less, 5 or less, 6 or less, 7 or less, or 8 or less.

[0051] When a, b, c, d, e, and f are within the specified range, the capacity characteristics and lifespan characteristics of the manufactured battery can be improved. In particular, in the case of Li2CoBO3, there is an effect of suppressing the gelation of the positive electrode slurry.

[0052] In the above chemical formula 2, M 3 is one or more selected from the group consisting of Ni and Mn, and M 4 This is one or more elements selected from the group consisting of H, Al, Ba, Ce, Cr, F, Mg, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, S, Sr, Ta, and Hf.

[0053] The aforementioned g may be 1 or more, or it may be 2 or less, 3 or less, or 4 or less.

[0054] The aforementioned h may be 1 or greater, 1.5 or less, or 2 or less.

[0055] The aforementioned i may be 0 or greater, 0.5 or less, or 1 or less.

[0056] The aforementioned j may be 0 or greater, 0.5 or less, or 1 or less.

[0057] The aforementioned k may be 2 or more, or 3 or more, and may be 4 or less, 5 or less, 6 or less, 7 or less, or 8 or less.

[0058] When g, h, i, j, and k are within the specified range, the capacity characteristics and lifespan characteristics of the manufactured battery can be improved. In particular, in the case of CoBO3, it has the effect of suppressing the gelation of the positive electrode slurry.

[0059] Furthermore, according to the present invention, the content of boron (B) among the total metals other than lithium in the positive electrode active material is 0.1 mol% or more and 1.25 mol% or less. Specifically, the content of boron (B) may be 0.1 mol% or more, or 0.2 mol% or more, or 1.1 mol% or less, 1.2 mol% or less, or 1.25 mol% or less. When the content of boron (B) is within the above range, there is an effect of reducing gelation of the positive electrode slurry due to a decrease in the density of the positive electrode active material, improvement in the dispersibility of the positive electrode active material, and an increase in sphericity. In particular, when the content of boron (B) is 0.13 mol% or more and 1.1 mol% or less, there is an effect of improving the capacity characteristics. On the other hand, when the content of boron (B) is less than 0.1 mol%, there is a problem that it is difficult to increase the dispersibility of the positive electrode active material or improve the sphericity, and when it is greater than 1.25 mol%, there is a problem that the resistance characteristics are inferior.

[0060] According to one embodiment of the present invention, the first coating portion may be dispersed on one or more of the surfaces of the lithium composite transition metal oxide and the second coating portion. "Dispersed distribution" means that the coating portions are not formed in a continuous, connected manner, but rather dispersed as dots. In this case, the first coating portion does not act as a resistor and has the effect of improving capacitance characteristics and lifetime characteristics.

[0061] According to one embodiment of the present invention, the average particle size (D 50 The average particle size (D) may be 3 μm or more and 20 μm or less. Specifically, the average particle size (D) 50The particle size may be 3 μm or larger, or 3.5 μm or larger, and may be 5 μm or smaller, 6 μm or smaller, 7 μm or smaller, 8 μm or smaller, 9 μm or smaller, 10 μm or smaller, 11 μm or smaller, 12 μm or smaller, 13 μm or smaller, 14 μm or smaller, 15 μm or smaller, 16 μm or smaller, 17 μm or smaller, 18 μm or smaller, 19 μm or smaller, or 20 μm or smaller. When the average particle size is within the above range, excellent electrode density can be achieved and capacitance characteristics can be improved.

[0062] According to one embodiment of the present invention, the lithium composite transition metal oxide may have a composition represented by the following chemical formula 3.

[0063] [Chemical formula 3] Li l Ni m Co n Mn o M 5 p O2

[0064] In the aforementioned chemical formula 3, M 5 This is one or more elements 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. 0.9≦l≦1.1, 0.6≦m<1, 0 <n<0.4、0<o<0.4、0≦p<0.1である。

[0065] In the aforementioned chemical formula 3, Said M 5 This is a doping element, specifically, the aforementioned M 5 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. 5 While not a mandatory component, it can improve capacity and lifespan characteristics.

[0066] The value l may be 0.9 or greater, 1.0 or greater, or 1.1 or less. When l satisfies the above range, high safety and high energy density per unit volume can be achieved.

[0067] The aforementioned m is the molar ratio of nickel (Ni) among all metals other than lithium in the lithium composite transition metal compound, and may be 0.6 or more, 0.7 or more, 0.8 or more, or 0.9 or more, and may be 0.96 or less, 0.97 or less, 0.98 or less, 0.99 or less, or less than 1. When m satisfies the above range, high energy characteristics can be achieved.

[0068] The aforementioned n is the molar ratio of cobalt (Co) among all metals other than lithium in the lithium composite transition metal compound, and may be greater than 0, 0.01 or more, or 0.02 or more, and may be 0.03 or less, 0.04 or less, 0.05 or less, 0.06 or less, 0.07 or less, 0.08 or less, 0.09 or less, 0.1 or less, 0.11 or less, 0.12 or less, 0.13 or less, 0.14 or less, 0.15 or less, 0.16 or less, It may be 0.17 or less, 0.18 or less, 0.19 or less, 0.2 or less, 0.21 or less, 0.22 or less, 0.23 or less, 0.24 or less, 0.25 or less, 0.26 or less, 0.27 or less, 0.28 or less, 0.29 or less, 0.3 or less, 0.31 or less, 0.32 or less, 0.33 or less, 0.34 or less, 0.35 or less, 0.36 or less, 0.37 or less, 0.38 or less, 0.39 or less, or less than 0.4. When n satisfies the above range, stability can be improved during the charge-discharge process and rate characteristics can be improved.

[0069] The above o is the molar ratio of manganese (Mn) among all metals other than lithium in the lithium composite transition metal compound, and may be greater than 0, 0.01 or more, or 0.02 or more, and may be 0.03 or less, 0.04 or less, 0.05 or less, 0.06 or less, 0.07 or less, 0.08 or less, 0.09 or less, 0.1 or less, 0.11 or less, 0.12 or less, 0.13 or less, 0.14 or less, 0.15 or less, 0.16 or less, It may be 0.17 or less, 0.18 or less, 0.19 or less, 0.2 or less, 0.21 or less, 0.22 or less, 0.23 or less, 0.24 or less, 0.25 or less, 0.26 or less, 0.27 or less, 0.28 or less, 0.29 or less, 0.3 or less, 0.31 or less, 0.32 or less, 0.33 or less, 0.34 or less, 0.35 or less, 0.36 or less, 0.37 or less, 0.38 or less, 0.39 or less, or less than 0.4. When o satisfies the above range, high-temperature stability can be increased and side reactions with the electrolyte can be relatively reduced.

[0070] The aforementioned p is M, which is the total amount of metals other than lithium in the lithium composite transition metal compound. 5 The molar ratio of p is such that p may be 0 or greater, 0.01 or greater, 0.02 or greater, 0.03 or greater, 0.04 or greater, or 0.05 or greater, and may be 0.06 or less, 0.07 or less, 0.08 or less, 0.09 or less, or less than 1. When p satisfies the above range, the stability of the positive electrode active material crystal structure is improved and the grain shape can be improved.

[0071] According to one embodiment of the present invention, the first coating portion may contain a compound having a composition represented by the following chemical formula 4.

[0072] [Chemical formula 4] Li q B r M 6 s M 7 t O u

[0073] In the aforementioned chemical formula 4, M 6 is one or more elements selected from the group consisting of Ni, Co, and Mn. M 7 This is one or more elements selected from the group consisting of 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. 0≦q≦4, 1≦r≦4, 0≦s≦1, 0≦t≦1, 1≦u≦8.

[0074] In the aforementioned chemical formula 4, M 6 is one or more selected from the group consisting of Ni, Co, and Mn, and M 7 This is one or more elements selected from the group consisting of 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.

[0075] The aforementioned q may be 0 or greater, and may be 1 or less, 2 or less, 3 or less, or 4 or less.

[0076] The aforementioned r may be 1 or more, or it may be 2 or less, 3 or less, or 4 or less.

[0077] The aforementioned s may be 0 or greater, 0.5 or less, or 1 or less.

[0078] The aforementioned t may be 0 or greater, 0.5 or less, or 1 or less.

[0079] The aforementioned u may be 1 or more, 2 or more, or 3 or more, and may be 4 or less, 5 or less, 6 or less, 7 or less, or 8 or less.

[0080] When q, r, s, t, and u are within the aforementioned ranges, the capacity characteristics and lifespan characteristics of the manufactured battery can be improved. In particular, in the case of Li2CoBO3 and CoBO3, there is an effect of suppressing the gelation of the positive electrode slurry.

[0081] According to one embodiment of the present invention, the first coating portion is made of B2O3, Li2BO3, Li2B4O7, Li3BO3, Lix B y O z (1 ≦ x ≦ 3, 1 ≦ y ≦ 4, 2 ≦ z ≦ 7), LiCoBO3, and LiAl 0.1 Co 0.9 It may be one or more selected from the group consisting of BO3.

[0082] In the present specification, the surface means the outermost edge of the lithium composite transition metal oxide. Also, a region having a predetermined thickness in the direction from the outermost edge of the lithium composite transition metal oxide toward the center can be shown as the surface portion. The surface portion may be a region with a depth of 1 nm to 50 nm, specifically 5 nm to 30 nm, in the direction from the outermost edge of the lithium composite transition metal oxide toward the center. With respect to the surface portion, in the lithium composite transition metal oxide, the inside other than the surface portion can be referred to as the core.

[0083] The surface portion of the lithium composite transition metal oxide may be doped with cobalt, boron, or cobalt and boron diffused from the coating portion.

[0084] The coating portion may be formed on the surface which is the outermost edge of the lithium composite transition metal oxide, and the coating portion may be formed on a part or all of the outer edge of the surface.

[0085] According to an embodiment of the present invention, the total area of the coating portion may be 10% or more and 100% or less with respect to the total surface area of the lithium composite transition metal oxide. Specifically, the total area of the coating portion may be 10% or more, 15% or more, 20% or more, 25% or more, 30% or more, 35% or more, 40% or more, 45% or more, or 50% or more with respect to the total surface area of the lithium composite transition metal oxide, and may be 55% or less, 60% or less, 65% or less, 70% or less, 75% or less, 80% or less, 90% or less, 95% or less, or 100% or less. When the total area of the coating portion is within the above range, it does not act as a resistance, prevents side reactions between the positive electrode active material and the electrolyte, and has the effect of improving the life characteristics and capacity characteristics of the battery.

[0086] According to one embodiment of the present invention, the first coating portion and the second coating portion may have the same or different compositions. The content may be a comparison of the content of the first coating portion and the content of the second coating portion located in a region twice the diameter of the first coating portion, centered on the first coating portion. If the compositions differ, the content of coating elements other than B and Co may differ, and the content of coating elements other than B and Co in the first coating portion may be higher than the content of coating elements other than B and Co in the second coating portion.

[0087] Method for manufacturing positive electrode active material Next, the method for producing the positive electrode active material of the present invention will be described. The method for producing the positive electrode active material of the present invention is the method for producing the positive electrode active material according to the present invention.

[0088] The method for producing a positive electrode active material according to the present invention includes the steps of: (1) mixing a lithium composite transition metal oxide in single-particle form with a cobalt-containing raw material, selectively mixing in a coating element-containing raw material to produce a mixture; (2) firing the mixture to produce a fired product; and (3) mixing the fired product with a boron-containing raw material and heat-treating it to form a coating portion containing cobalt (Co) and boron (B) on the lithium composite transition metal oxide, wherein the coating element is one or more selected from the group consisting of 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, and the firing may be carried out at a temperature of 600°C to 800°C.

[0089] The positive electrode active material according to the present invention described above can be manufactured by appropriately adjusting the type of raw material, the mixing ratio of the raw material, the heat treatment step, the heat treatment temperature, the heat treatment heating rate, the heat treatment atmosphere, and so on.

[0090] The steps of the present invention will be described in detail below.

[0091] (1) Step The present invention comprises the step of (1) mixing a lithium composite transition metal oxide in single-particle form with a cobalt-containing raw material and selectively mixing with a coating element-containing raw material to produce a mixture.

[0092] The mixture of the present invention, specifically the lithium composite transition metal oxide, is mixed using a dry mixing method with a solid-phase raw material mixture. This dry mixing method has the advantage of enabling mass production through a relatively simple synthesis process.

[0093] According to one embodiment of the present invention, the cobalt-containing raw material can be mixed with the lithium composite transition metal oxide in an amount of 0.1 mol% to 10 mol%, specifically 0.5 mol% to 5 mol%, and more specifically 1 mol% to 3 mol%. When the cobalt raw material is mixed within this range, no unreacted cobalt compound remains on the surface of the particles, and a cobalt-containing coating can be sufficiently formed on the lithium composite transition metal oxide.

[0094] The cobalt-containing raw material may be an oxide, hydroxide, oxyhydroxide, carbonate, sulfate, halide, sulfide, acetate, nitrate, carboxylate, or combination thereof, and examples include Co(OH)2, CoOOH, Co(OCOCH3)2·4H2O, Co(NO3)2·6H2O, or Co(SO4)2·7H2O, and one or more of these can be used, and specifically, Co(OH)2 can be used.

[0095] The coating element is one or more selected from the group consisting of 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. The raw material containing the coating element may be, for example, an oxide, hydroxide, oxyhydroxide, carbonate, sulfate, halide, sulfide, acetate, nitrate, carboxylate, or a combination thereof, specifically Co(OH)2, ZrO2, Zr(OH)4, ZnO, TiO2, WO3, Al2O3, Al(OH)3, Al2(SO4)3, ·xH2O, AlCl3, C2H5O4Al, Al-isopropoxide, Al(NO3)3, AlF, Li3WO4, (NH4) 10 W 12 O 41 Examples include, but are not limited to, 5H2O or NH4H2PO4.

[0096] According to one embodiment of the present invention, the coating element-containing raw material can be used in an amount such that the coating element is 0.001 mol% to 10 mol%, specifically 0.005 mol% to 5 mol%, based on the total number of metal moles of the lithium composite transition metal oxide. When the amount of the coating element-containing raw material is within this range, it can be expected that side reactions with the electrolyte will be effectively suppressed, and the electrochemical properties can be further improved.

[0097] According to one embodiment of the present invention, the lithium composite transition metal oxide in single-particle form can be produced by a method comprising the steps of (A) mixing a composite transition metal hydroxide containing nickel, cobalt, and manganese with a first lithium-containing raw material and performing primary firing at a temperature of 800°C to 950°C to produce a primary fired product, and (B) mixing the primary fired product with a second lithium-containing raw material and performing secondary firing at a temperature of 680°C to 850°C to produce a secondary fired product. The first lithium-containing raw material and the second lithium-containing raw material may be the same or different.

[0098] The lithium-composite transition metal oxide can be manufactured by a process in which lithium-containing raw materials are added in two stages. That is, the lithium-containing raw materials can be added before the primary calcination and before the secondary calcination. In this case, lithium is inserted into the rock salt structure that may form on the surface, which has the advantage of favoring the recovery to a layered structure.

[0099] Specifically, the primary firing may be performed at temperatures of 800°C or higher, or 820°C or higher, and 850°C or lower, 900°C or lower, or 950°C or lower, and the secondary firing may be performed at temperatures of 680°C or higher, 700°C or higher, or 720°C or higher, and 750°C or lower, 760°C or lower, 770°C or lower, 780°C or lower, 790°C or lower, 800°C or lower, 810°C or lower, 820°C or lower, 830°C or lower, 840°C or lower, or 850°C or lower. When the primary firing is performed within the above temperature range, sufficient energy necessary for the formation of single particles can be supplied, and when the secondary firing is performed within the above range, lithium in the lithium composite transition metal oxide can be replenished and the NiO phase can be minimized.

[0100] When the lithium-containing raw material is added in two separate steps, in step (A), the first lithium-containing raw material can be mixed such that the ratio (M:Li) of the total number of moles of transition metal (M) contained in the composite transition metal hydroxide to the number of moles of lithium (Li) contained in the first lithium-containing raw material is 1:0.98 or higher, 0.99 or higher, 1.00 or higher, 1.01 or higher, or 1.02 or higher, and 1:1.04 or lower, or 1.05 or lower. In step (B), the second lithium-containing raw material can be mixed such that the ratio (M':Li) of the total number of moles of transition metal (M') contained in the primary calcined product from step (A) to the total number of moles of lithium (Li) is 1:1.01 or higher, or 1.05 or higher, and 1.06 or lower, 1.07 or lower, 1.08 or lower, 1.09 or lower, or 1.10 or lower.

[0101] The aforementioned primary calcination may be carried out under an oxygen atmosphere in order to prevent the lithium composite transition metal oxide from degrading into a rock salt structure.

[0102] The aforementioned primary firing may be carried out for 3 hours or more, 4 hours or more, 5 hours or more, or 6 hours or more, and 9 hours or less, 10 hours or less, 11 hours or less, or 12 hours or less, in order to aggregate the primary particles and improve the crystallinity of the primary fired product.

[0103] The aforementioned secondary calcination may be carried out under an oxygen atmosphere in order to prevent the lithium composite transition metal oxide from degrading into a rock salt structure.

[0104] The aforementioned secondary firing may be performed for 3 hours or more, and for 4 hours or less, 5 hours or less, 6 hours or less, 7 hours or less, 8 hours or less, 9 hours or less, 10 hours or less, 11 hours or less, or 12 hours or less, in order to increase the degree of crystallinity of the internal crystal structure of the positive electrode active material.

[0105] According to one embodiment of the present invention, immediately after step (A), a step (A1) of grinding the primary calcined product may be further included. In this case, the particle size can be adjusted to improve process efficiency and the quality of the positive electrode active material. In terms of preventing high initial resistance, the primary calcined product may be given an average particle size (D 50 The particles may be ground to a size of 3 μm to 20 μm.

[0106] According to one embodiment of the present invention, immediately after step (B), the process may further include a step (B1) of grinding the secondary calcined product. In this case, the particle size can be adjusted to improve process efficiency and the quality of the positive electrode active material. In terms of preventing high initial resistance, the secondary calcined product may be given an average particle size (D 50 The particles may be ground to a size of 3 μm to 20 μm.

[0107] The pulverization in the steps (A1) and (B1) may be carried out using a pin mill, ACM, jet mill, etc. On the other hand, for a pin mill, under the condition of 18,000 rpm, for ACM, using equipment manufactured by Hosokawa, under the conditions of classification at 6,000 rpm and pulverization at 12,000 rpm, and for a jet mill, using equipment manufactured by ZM solution, it may be carried out under the conditions of a pulverization pressure of 6 bar and classification at 3,500 rpm. In this case, a positive electrode active material having a desired average particle size (D 50 ) can be easily obtained.

[0108] (2) Step Next, it includes the step (2) of firing the mixture to produce a fired product.

[0109] The firing is carried out at a temperature of 600 °C or higher and 800 °C or lower. Specifically, the firing is carried out at a temperature of 600 °C or higher, 650 °C or higher, or 700 °C or higher, and 750 °C or lower, or 800 °C or lower. When the firing temperature satisfies the above range, in the temperature rising process for firing, a coating part containing cobalt on the lithium composite transition metal oxide, specifically, cobalt that was present as a LiCoO2 phase formed discontinuously in an island shape on the surface of the lithium composite transition metal oxide, penetrates into the lithium composite transition metal oxide to an appropriate depth, and the NiO layer which is a degradation layer can be appropriately changed into a layered structure of nickel cobalt manganese (NCM) oxide. Along with this, the surface part of the lithium composite transition metal oxide has a layered (R-3m) structure, and an oxidation number gradient layer in which the oxidation number of nickel increases in the outermost edge direction is included in the surface part, so that excellent effects in cell performance such as charge-discharge capacity, initial efficiency, and initial resistance can be exerted. On the other hand, when the firing temperature is less than 600 °C, the thickness of the coating part becomes thick, and too much of the coating part is formed, making it difficult to exert the merits due to the formation of the coating part as described above. When the firing temperature exceeds 800 °C, cobalt may be deeply doped into the lithium composite transition metal oxide, and there is a possibility that the coating part may not be appropriately formed on the surface part.

[0110] The firing can be carried out for a period of 2 hours or more, and 6 hours or less, 9 hours or less, or 12 hours or less. When the firing is carried out within the above time range, excellent productivity can be achieved and uniform firing can be ensured.

[0111] According to one embodiment of the present invention, by performing step (2), a coating portion containing Co can be formed on a lithium composite transition metal oxide, specifically, a second coating portion represented by chemical formula 1 or 2 as described herein can be formed.

[0112] (3) Step The process includes (3) mixing the calcined product with a boron-containing raw material and heat-treating it to form a coating portion containing cobalt (Co) and boron (B) on the lithium composite transition metal oxide.

[0113] The boron-containing raw material may be an oxide, hydroxide, oxyhydroxide, carbonate, sulfate, halide, sulfide, acetate, nitrate, carboxylate, or combination thereof, and examples include, but are not limited to, B(OH)3, H2BO3, HBO2, H3BO3, H2B4O7, B2O3, C6H5B(OH)2, (C6H5O)3B, (CH3(CH2)3O)3B, C3H9B3O6, (C3H7O3)B, etc.

[0114] According to one embodiment of the present invention, the boron-containing raw material can be mixed with the calcined product in an amount of 0.15 mol% to 1.25 mol%, specifically 0.20 mol% to 1.10 mol%, and more specifically 0.25 to 1.05 mol%. When the amount of the boron-containing raw material mixed is within the above range, the boron content of the formed coating can satisfy the appropriate range.

[0115] According to one embodiment of the present invention, the heat treatment may be performed at temperatures of 200°C or higher, 250°C or higher, or 300°C or higher, and 350°C or lower, 400°C or lower, 420°C or lower, 440°C or lower, 460°C or lower, 480°C or lower, or 500°C or lower. When the heat treatment temperature is within the above range, the boron-containing raw material can appropriately form an amorphous boron coating rather than a boron oxide. If the heat treatment temperature is too high, boron oxide may be formed on the surface of the lithium composite transition metal oxide, potentially impairing its properties as a positive electrode active material.

[0116] The heat treatment may be carried out for 3 hours or more, and for 6 hours or less, 7 hours or less, 8 hours or less, 9 hours or less, 10 hours or less, 11 hours or less, or 12 hours or less. When the heat treatment is carried out within the above time range, excellent productivity can be achieved and uniform firing can be ensured.

[0117] According to one embodiment of the present invention, by performing step (3), a coating portion containing B can be formed on a lithium composite transition metal oxide, specifically, a first coating portion represented by chemical formula 4 as described herein or a second coating portion represented by chemical formula 1 or 2 can be formed.

[0118] According to one embodiment of the present invention, in steps (1) to (3) above, a coating can be formed by the diffusion of cobalt, boron, or cobalt and boron from the surface toward the center of the lithium composite transition metal oxide.

[0119] According to yet another embodiment of the present invention, a positive electrode comprising the positive electrode active material described above is provided. Specifically, the positive electrode comprises a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector and comprising the positive electrode active material described above.

[0120] The positive electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and is conductive. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with surface treatment using carbon, nickel, titanium, silver, etc., can be used. The positive electrode current collector can usually have a thickness of 3 to 500 μm, and fine irregularities can be formed on the surface of the current collector to enhance the adhesion of the positive electrode active material. For example, it may be used in various forms such as film, sheet, foil, mesh, porous material, foam, or nonwoven fabric.

[0121] The positive electrode active material layer may include a conductive material and a binder, along with the positive electrode active material described above.

[0122] Here, the conductive material is used to impart conductivity to the electrodes and can be used without particular limitations as long as it does not cause chemical changes and has electronic conductivity in the battery it is used in. 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 powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. Of these, one or more can be used. The conductive material can usually be included in an amount of 1 to 30% by weight relative to the total weight of the positive electrode active material layer.

[0123] The binder plays a role in improving the adhesion between positive electrode active material particles and the adhesion between the positive electrode 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, of which one or more can be used. The binder can be contained in an amount of 1 to 30% by weight relative to the total weight of the positive electrode active material layer.

[0124] The positive electrode can be manufactured according to a conventional method for manufacturing a positive electrode, except that the positive electrode active material described above is used. Specifically, it can be manufactured by coating a positive electrode active material layer-forming composition, prepared by dissolving or dispersing the positive electrode active material and, selectively, a binder and a conductive material in a solvent, onto a positive electrode current collector, followed by drying and rolling. Here, the types and contents of the positive electrode active material, binder, and conductive material are as described above.

[0125] The solvent may be any solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and one or more of these can be used individually or in mixtures of two or more. The amount of solvent used should be sufficient to dissolve or disperse the positive electrode active material, conductive material, and binder, taking into consideration the coating thickness of the slurry and the manufacturing yield, and to have a viscosity that allows for excellent thickness uniformity when applied for the manufacture of the positive electrode.

[0126] Alternatively, the positive electrode may be manufactured by casting the positive electrode active material layer forming composition onto another support, peeling it off the support, and then laminating the resulting film onto the positive electrode current collector.

[0127] According to yet another example of the present invention, an electrochemical element including the positive electrode is provided. Specifically, the electrochemical element may be a battery, a capacitor, and more specifically, a lithium secondary battery.

[0128] The lithium secondary battery specifically includes a positive electrode, a negative electrode positioned opposite the positive electrode, and a separator and electrolyte interposed between the positive and negative electrodes, the positive electrode being as previously described. The lithium secondary battery may also selectively further include a battery container housing the electrode assembly of the positive electrode, negative electrode, and separator, and a sealing member for sealing the battery container.

[0129] In the lithium secondary battery, the negative electrode includes a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector.

[0130] The negative electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel with surface treatment using carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloys can be used. The negative electrode current collector can usually have a thickness of 3 to 500 μm, and, similar to the positive electrode current collector, fine irregularities can be formed on the surface of the current collector to strengthen the bonding force of the negative electrode active material. For example, it can be used in various forms such as film, sheet, foil, mesh, porous material, foam, and nonwoven fabric.

[0131] The negative electrode active material layer selectively includes a binder and a conductive material together with the negative electrode active material.

[0132] As the negative electrode active material, compounds capable of reversible intercalation and deintercalation of lithium can be used. 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 Examples include metallic oxides that can be doped and dedoped with lithium, such as (0<β<2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites containing the metallic compound and carbonaceous material, such as Si-C composites or Sn-C composites; and any one or more mixtures thereof can be used. A metallic lithium thin film can also be used as the negative electrode active material. Furthermore, both low-crystallinity carbon and high-crystallinity carbon can be used as the carbon material. Examples of low-crystalline carbon include soft carbon and hard carbon, while examples of high-crystalline carbon include amorphous, plate-like, flaky, 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.

[0133] Furthermore, the binder and conductive material are as described above in the section on the positive electrode.

[0134] The negative electrode active material layer may be manufactured, for example, by coating a negative electrode forming composition, which is prepared by dispersing a negative electrode active material and a binder and conductive material selectively in a solvent, onto a negative electrode current collector and drying it, or by casting the negative electrode forming composition onto another support, peeling it off the support, and then laminating the resulting film onto the negative electrode current collector.

[0135] On the other hand, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without particular limitations, but those with low resistance to ion movement of the electrolyte and excellent electrolyte impregnation ability are particularly preferred. Specifically, porous polymer films, such as porous polymer films made from polyolefin polymers like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or laminated structures of two or more layers thereof, can be used. Alternatively, ordinary porous nonwoven fabrics, such as nonwoven fabrics made from high-melting-point glass fibers or polyethylene terephthalate fibers, may be used. Furthermore, coated separators containing ceramic components or polymeric substances can be used to ensure heat resistance or mechanical strength, and can be selectively used as single-layer or multi-layer structures.

[0136] Furthermore, the electrolytes used in the present invention include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0137] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0138] The organic solvent can be used without particular limitations, as long as it can act as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvents include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (propylene Carbonate solvents such as carbonate (PC); alcoholic solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a C2-C20 linear, branched, or cyclic hydrocarbon group, which can include a double-bonded aromatic ring or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. Among these, carbonate solvents are preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant that can improve the charge and discharge performance of the battery, and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more preferred. In this case, mixing the cyclic carbonate and linear carbonate in a volume ratio of about 1:1 to about 1:9 can produce an electrolyte with excellent performance.

[0139] The lithium salt can be any compound capable of providing lithium ions for use in lithium secondary batteries, without any particular limitations. Specifically, the lithium salt can 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, etc. The concentration of the lithium salt is preferably within the range of 0.1 to 2.0 M. When the concentration of the lithium salt falls within this range, the electrolyte has appropriate conductivity and viscosity, exhibiting excellent electrolyte performance and allowing lithium ions to move effectively.

[0140] In addition to the components of the electrolyte, the electrolyte may further contain one or more additives for purposes such as improving battery life characteristics, suppressing battery capacity reduction, and improving battery discharge capacity. These additives may include, for example, haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphate triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride. Here, the additives may be present in an amount of 0.1 to 5% by weight relative to the total weight of the electrolyte.

[0141] As described above, the lithium secondary battery containing the positive electrode active material according to the present invention exhibits excellent discharge capacity, output characteristics, and capacity retention rate stably, making it useful in portable devices such as mobile phones, notebook computers, and digital cameras, as well as in the field of electric vehicles such as hybrid electric vehicles (HEVs).

[0142] Accordingly, according to another embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

[0143] The aforementioned battery module or battery pack can be used as a power source for one or more medium-to-large devices, including power tools; electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or power storage systems.

[0144] The external shape of the lithium secondary battery of the present invention is not particularly limited, but may be cylindrical, rectangular, pouch-type, or coin-type using a can.

[0145] In addition to being usable as a battery cell for powering small devices, the lithium secondary battery according to the present invention can also be preferably used as a unit battery in medium- and large-sized battery modules containing a large number of battery cells.

[0146] Hereinafter, embodiments of the present invention will be described in detail so that they can be easily implemented by a person with ordinary skill in the art to which the present invention pertains. However, the present invention can be realized in various different forms and is not limited to the embodiments described herein.

[0147] Manufacturing example Manufacturing Example 1 Composite transition metal hydroxide [composition: Ni 0.95 Co 0.03 Mn 0.02 (OH)2, average particle size (D 50 A mixture of 3.5 μm of [material] and LiOH was mixed so that the molar ratio of (Ni+Co+Mn):Li was 1:1.00. The mixture was then subjected to primary calcination at 820°C for 6 hours under an oxygen atmosphere to produce a primary calcined product, which was then pulverized.

[0148] Subsequently, the primary calcined product and LiOH were mixed so that the molar ratio of (Ni+Co+Mn):total Li was 1:1.05, and secondary calcination was performed at 740°C for 12 hours under an oxygen atmosphere to obtain LiNi in single-particle form. 0.95 Co 0.03 Mn 0.02 A lithium composite transition metal oxide (secondary calcined product) having a composition represented by O2 was manufactured.

[0149] The lithium complex transition metal oxide and powdered Co(OH)2 (manufactured by HUAYOU Cobalt Co., Ltd.) were added to a reactor in a molar ratio of 98:2. Al(OH)3 was then added to a concentration of 500 ppm relative to the total weight of the lithium complex transition metal oxide, and the mixture was dry-mixed using an acoustic mixer to produce a mixture. The mixture was baked at 700°C for 3 hours to obtain a baked cake, which was then pulverized to produce a baked powder.

[0150] Examples and Comparative Examples Example 1 In Manufacturing Example 1, the calcined product and B(OH)3 were dry-mixed so that the molar ratio of the calcined product to B(OH)3 was 99.75:0.25. The mixture was then heat-treated at 330°C for 5 hours to obtain a cake-like positive electrode active material, which was then pulverized to produce a powder-like positive electrode active material. The positive electrode active material has a coating portion containing cobalt and boron formed on a lithium composite transition metal oxide, with an average particle size (D 50 The thickness is 3.8 μm.

[0151] Example 2 The positive electrode active material was manufactured in the same manner as in Example 1, except that the calcined product manufactured in Manufacturing Example 1 and B(OH)3 were dry-mixed so that the molar ratio of the calcined product to B(OH)3 was 99.5:0.5.

[0152] Example 3 The positive electrode active material was produced in the same manner as in Example 1, except that the calcined product produced in Production Example 1 and B(OH)3 were dry-mixed so that the molar ratio of the calcined product to B(OH)3 was 99.0:1.0.

[0153] Comparative Example 1 The powdered calcined product produced in Manufacturing Example 1 was used as the positive electrode active material in Comparative Example 1.

[0154] Comparative Example 2 The positive electrode active material was produced in the same manner as in Example 1, except that the calcined product produced in Production Example 1 and B(OH)3 were dry-mixed so that the molar ratio of the calcined product to B(OH)3 was 99.9:0.1.

[0155] Comparative Example 3 The positive electrode active material was produced in the same manner as in Example 1, except that the calcined product produced in Production Example 1 and B(OH)3 were dry-mixed so that the molar ratio of the calcined product to B(OH)3 was 98.5:1.5.

[0156] Comparative Example 4 Composite transition metal hydroxide [composition: Ni 0.95 Co 0.03 Mn 0.02 (OH)2, average particle size (D 50 Mixing 3.5 μm of [material] and LiOH so that the molar ratio of (Ni+Co+Mn):Li was 1:1.00, and the mixture was subjected to primary calcination at 650°C for 3 hours under an oxygen atmosphere to produce a primary calcined product, after which the primary calcined product was pulverized.

[0157] Subsequently, the primary calcined product and LiOH were mixed so that the molar ratio of (Ni+Co+Mn):total Li was 1:1.05, and secondary calcination was performed at 690°C for 4 hours under an oxygen atmosphere to obtain LiNi in secondary particle form. 0.95 Co 0.03 Mn 0.02 A lithium-compound transition metal oxide having a composition represented by O2 was fabricated.

[0158] The lithium complex transition metal oxide and powdered Co(OH)2 (manufactured by HUAYOU Cobalt Co., Ltd.) were added to a reactor in a molar ratio of 98:2. Al(OH)3 was then added to a concentration of 500 ppm relative to the total weight of the lithium complex transition metal oxide, and the mixture was dry-mixed using an acoustic mixer to produce a mixture. The mixture was baked at 700°C for 3 hours to obtain a baked cake, which was then pulverized to produce a baked powder.

[0159] The aforementioned calcined product and B(OH)3 were dry-mixed so that the molar ratio of the calcined product to B(OH)3 was 99.5:0.5, and the mixture was heat-treated at 330°C for 5 hours to obtain a cake-like positive electrode active material. This cake was then pulverized to produce a powder-like positive electrode active material. The positive electrode active material has a coating portion containing cobalt and boron formed on a lithium composite transition metal oxide, with an average particle size (D 50 The thickness is 3.8 μm.

[0160] Comparative Example 5 The lithium composite transition metal oxide (secondary calcined product) produced in Production Example 1 and B(OH)3 were dry-mixed so that the molar ratio of lithium composite transition metal oxide to B(OH)3 was 99.5:0.5, and the mixture was heat-treated at 330°C for 5 hours to obtain a cake-like positive electrode active material. This cake was then pulverized to produce a powder-like positive electrode active material. In addition, the positive electrode active material was produced in the same manner as in Example 1.

[0161] [Table 1]

[0162] Experimental example Experimental Example 1: Analysis of the coating layer EPMA image analysis EPMA cross-sectional analysis was performed on the positive electrode active materials manufactured in the examples to confirm their surface coating properties. First, the positive electrode active materials, carbon black conductive material, and PVDF binder manufactured in Examples 1-3 were mixed in N-methylpyrrolidone (NMP) solvent in a weight ratio of 95:2:3 to produce positive electrode slurries. The produced positive electrode slurry was applied to one surface of an aluminum current collector, dried at 130°C, and then rolled to an electrode porosity of 20% to produce a positive electrode. To obtain a flat surface for EPMA cross-sectional analysis, the positive electrode was subjected to Ar-ion milling using a HITACHI Ar Blade 5000 instrument at an acceleration voltage of 5.5kV to obtain a cross-section of the positive electrode sample. Then, using a JEOL JXA-iHP200F instrument, a cross-sectional image of the positive electrode sample was observed at an acceleration voltage of 15kV and a probe current of 50nA, and is shown in Figure 1.

[0163] Figure 1(A) is an EPMA analysis image of the positive electrode active material produced in Example 1, (B) is an EPMA analysis image of the positive electrode active material produced in Example 2, and (C) is an EPMA analysis image of the positive electrode active material produced in Example 3.

[0164] In Figure 1, the green areas represent regions where a coating layer containing Co exists. Referring to Figure 1, it was confirmed that the green areas are continuous, and that a second coating region exists, which is a coating layer continuously formed on a lithium composite transition metal oxide.

[0165] SEM Image Analysis 1 SEM images of the cathode active materials produced in the examples and comparative examples were obtained using a scanning electron microscope (JEOL, JSM-7610F) and are shown in Figure 2.

[0166] Figure 2(A) is an SEM image of the positive electrode active material produced in Example 1, (B) is an SEM image of the positive electrode active material produced in Example 2, and (C) is an SEM image of the positive electrode active material produced in Example 3.

[0167] Referring to Figure 2, it was confirmed that the positive electrode active material produced in the example was in the form of single particles.

[0168] In Figure 2, the uneven, bumpy areas, i.e., the irregularities, are the areas where the first coating exists. Referring to Figure 2, it was confirmed that discontinuously formed, island-like first coating areas exist.

[0169] Experimental Example 2: TOF-SIMS Analysis Using TOF-SIMS (IonTOF (Germany), TOF-SIMS 5-100), surface analysis was performed on each of the positive electrode active materials produced in the examples and comparative examples. The types of Co-B solid solutions contained in the coating portion of the positive electrode active material were identified and are shown in Figures 1 and 2. The content (mol%) of boron (B) among the total metals other than lithium in the positive electrode active material is shown in Table 3.

[0170] Specifically, the surface analysis of the cathode active material was performed using secondary ion mass spectrometry (SIMS), and the conditions under which the analysis was performed are shown in Table 2 below.

[0171] Figure 3 shows the surface analysis results for the positive electrode active materials produced in the examples and comparative examples, and the data is related to the Li2CoBO3 peak. Specifically, A* represents data for Example 1, B* for Example 2, C* for Example 3, D* for Comparative Example 1, E* for Comparative Example 2, and F* for Comparative Example 3.

[0172] Figure 4 shows the surface analysis results for the positive electrode active materials produced in the examples and comparative examples, and the data is related to the CoBO3 peak. Specifically, A* represents data for Example 1, B* for Example 2, C* for Example 3, D* for Comparative Example 1, E* for Comparative Example 2, and F* for Comparative Example 3.

[0173] [Table 2]

[0174] Referring to Figures 1 and 2, it was confirmed that the positive electrode active material produced in the example contained Li2CoBO3 and CoBO3 in the coating portion.

[0175] Experimental Example 3: XPS Etching Analysis The distribution of boron (B) in the coating on the surface of each positive electrode active material produced in the above examples and comparative examples was analyzed using ESCA (K-Alpha, Thermo Fisher Scientific Inc.). The depth profiling conditions involved etching at a rate of 0.3 nm / 10 s using an Ar ion source, and the boron (B) content (mol%) in the coating layer with a thickness of 0 to 100 nm was measured and is shown in Table 3 below.

[0176] For reference, a range of 0.1 mol% or less corresponds to the error range during XPS etching analysis.

[0177] [Table 3]

[0178] Referring to Table 3, it was confirmed that the content of boron (B) among the total metals other than lithium in the positive electrode active material produced in the examples was between 0.1 mol% and 1.25 mol%.

[0179] Experimental Example 4: SEM Image Analysis 2 Using a scanning electron microscope (JEOL, JSM-7610F), SEM images of the cathode active materials produced in the examples and comparative examples were acquired. Then, segmentation images were obtained using the DX program (see KR10-2022-0048191 A), which are shown in Figures 5 and 6.

[0180] Figure 5(A) is a segmentation image of the positive electrode active material produced in Example 1, (B) is a segmentation image of the positive electrode active material produced in Example 2, and (C) is a segmentation image of the positive electrode active material produced in Example 3.

[0181] Figure 6(A) is a segmentation image of the positive electrode active material produced in Comparative Example 1, (B) is a segmentation image of the positive electrode active material produced in Comparative Example 2, (C) is a segmentation image of the positive electrode active material produced in Comparative Example 3, (D) is a segmentation image of the positive electrode active material produced in Comparative Example 4, and (E) is a segmentation image of the positive electrode active material produced in Comparative Example 5.

[0182] Furthermore, the sphericity of the positive electrode active material was evaluated from the segmentation image. Sphericity is an element that can be evaluated by circularity and kurtosis. Circularity is an index that evaluates the degree to which a particle is round, and kurtosis is an index that evaluates the degree to which a curve is gentle. The closer the circularity and kurtosis are to 1, the more ideal the spherical shape is. The area and perimeter of the particle were measured and the circularity was calculated, which is shown in Table 4 below. The convex perimeter and contour perimeter were also measured and the kurtosis was calculated, which is also shown in Table 4 below.

[0183] Specifically, the circularity is calculated as 4π (area of ​​the particle / circumference of the particle). 2 This value is calculated as the area of ​​the particle, and the smaller the difference between the square of the particle's circumference and the particle's area, the closer it is to a circle. The area of ​​the particle may be calculated using the number of pixels corresponding to each of the n particles present in the segmentation image, and the circumference of the particle may be calculated using the length of the outermost boundary corresponding to each of the n particles present in the segmentation image.

[0184] Furthermore, the kurtosis is a value calculated by comparing the perimeter of the convex surface with the perimeter of the contour. The smaller the difference between the perimeter of the convex surface and the perimeter of the contour, the smoother the contour is compared to a bumpy one. The perimeter of the convex surface refers to the perimeter of a virtual polygon created by converting an SEM image into a binary image using the DX program and connecting the vertices of particles recognized from the binary image, while the perimeter of the contour refers to the perimeter of the particles actually recognized.

[0185] [Table 4]

[0186] Referring to Figures 5 and 6 and Table 4, it was confirmed that the positive electrode active materials produced in Examples 1 to 3, i.e., positive electrode active materials comprising a discontinuous first coating portion containing boron(B) on a single-particle lithium composite transition metal oxide and a continuous second coating portion containing a compound having a composition represented by chemical formula 1 or 2 as described herein, wherein the boron(B) content of the total metals other than lithium in the positive electrode active material is 0.1 mol% or more and 1.25 mol% or less, have a circularity of 0.680 or more and a kurtosis of 0.930 or more.

[0187] On the other hand, in the case of the positive electrode active materials produced in Comparative Examples 1 and 2, i.e., positive electrode active materials in which the boron (B) content among the total metals other than lithium in the positive electrode active material is 0 mol% or less than 0.1 mol%, it was confirmed that the circularity was less than 0.680 and the kurtosis was less than 0.930. In the case of the positive electrode active material produced in Comparative Example 3, i.e., positive electrode active material in which the boron (B) content among the total metals other than lithium in the positive electrode active material is greater than 1.25 mol%, it was confirmed that the circularity was less than 0.680. Furthermore, in the case of the positive electrode active material produced in Comparative Example 4, i.e., lithium composite transition metal oxide in secondary particle form, it was confirmed that the kurtosis was less than 0.930. In the case of the positive electrode active material produced in Comparative Example 5, i.e., positive electrode active material in which the coating portion does not include a first coating portion and a second coating portion, it was confirmed that the circularity was less than 0.680.

[0188] Therefore, it was confirmed that the positive electrode active material produced in the example had superior roundness and kurtosis compared to the positive electrode active material produced in the comparative example, indicating an improvement in sphericity.

[0189] Experimental Example 5: Analysis of Rolling Density Using an automatic pellet press (Carver, 3887.4), the zero point was adjusted using a cylindrical mold on a circular pellet holder.

[0190] After placing the respective positive electrode active materials produced in the above examples and comparative examples into the circular pellet holder, the thickness of the formed pellets was measured by applying force until a force equivalent to 9,000 kgf was reached.

[0191] Based on this, the volume of the pellets and the rolling density were calculated. The results are shown in Table 5 below.

[0192] Pellet volume (cm³) 3 ) = π (radius of the circular pellet holder) 2 × Pellet thickness

[0193] Rolling density (g / cm³)3 ) = Weight of positive electrode active material (g) / Volume of pellet (cm³) 3 )

[0194] Referring to Table 5, the positive electrode active material produced in the example had a rolling density of 3.50 g / cm³. 3 The following conditions were confirmed, and the positive electrode active materials produced in Comparative Examples 1 and 2 had a rolling density of 3.50 g / cm³. 3 I confirmed that it is super.

[0195] This means that the density of the positive electrode active material decreases due to the inclusion of boron in the coating, which improves the dispersibility of the positive electrode active material during the manufacturing of the positive electrode slurry.

[0196] Experimental Example 6: Analysis of the viscosity of the positive electrode slurry Manufacturing of positive electrode slurry The cathode active materials produced in the above examples and comparative examples, carbon black (DENKA, FX35), and binders PVdF (Kureha, KF9709) and BM740H (Zeon) were added to a solvent (N-methylpyrrolidone (NMP)) in a weight ratio of 96.25:1.5:2.1:0.15. The mixture was then stirred at 1,500 rpm for 95 minutes using a homogenizing disper model 2.5 (primix) to produce a cathode slurry.

[0197] Measurement of positive electrode slurry temperature During the production of the positive electrode slurry, the temperature of the slurry was measured every 10 minutes after stirring, and the results are shown in Figure 7.

[0198] Figure 7 is a temperature graph of the measurement time for the positive electrode slurry containing the respective positive electrode active material produced in the examples and comparative examples.

[0199] Referring to Figure 7, the temperature of the positive electrode slurry containing the positive electrode active material produced in Examples 1 to 3 increased gradually compared to the positive electrode slurry containing the positive electrode active material produced in Comparative Examples 1, 2, and 4. Specifically, A* is Example 1, B* is Example 2, C* is Example 3, D* is Comparative Example 1, E* is Comparative Example 2, F* is Comparative Example 3, G* is Comparative Example 4, and H* is Comparative Example 5.

[0200] Measurement of positive electrode slurry viscosity After collecting each of the manufactured cathode slurries, their viscosity was measured using a viscometer (DV2T viscometer, Brookfield Ametek) by shearing at 16 rpm for 1 minute. The change in viscosity over time was measured for up to 7 days after the manufacture of the cathode slurry, and the results are shown in Table 5 and Figure 8 below.

[0201] Figure 8 shows viscosity graphs of the positive electrode slurries containing the respective positive electrode active materials produced in the examples and comparative examples, with respect to measurement time.

[0202] Slurry viscosity (cP) = Shear stress (g / cm·s) / Shear coefficient (1 / s)

[0203] [Table 5]

[0204] Referring to Table 5 and Figure 8, it was confirmed that the cathode slurries containing the cathode active material produced in Examples 1-3 had lower initial viscosity and a lower viscosity increase rate compared to the cathode slurries containing the cathode active material produced in Comparative Examples 1, 2, and 4.

[0205] Experimental Example 7: Evaluation of Electrochemical Properties The positive electrode slurry produced in Experimental Example 5 was coated onto one surface of an aluminum foil current collector, dried at 130°C for 3 hours, and then rolled using a roll persing method. After rolling, a positive electrode with a positive electrode layer porosity of 20% was produced.

[0206] After manufacturing an electrode assembly by interposing a separator between the positive electrode and the lithium metal disk negative electrode, the assembly was placed inside a battery case, and then an electrolyte solution of 1M LiPF6 dissolved in an EC / EME / DMC (3:3:4, volume ratio) organic solvent was injected to manufacture a lithium secondary battery.

[0207] The lithium secondary battery was charged in CC / CV mode at 25°C with a constant current (CC) of 0.2C until it reached 4.25V (end current 0.005C). After leaving it for 20 minutes, it was discharged in CC mode with a constant current (CC) of 0.2C until it reached 2.5V. The charge capacity (mAh / g) and discharge capacity (mAh / g) were measured, and the percentage of discharge capacity to charge capacity (efficiency (%)) was calculated and is shown in Table 6 below. The DC internal resistance (DCIR) (Ω) was also calculated and is shown in Table 6 below. The DCIR is calculated by dividing the difference between the voltage at 60 seconds while discharging with a constant current of 0.2C during the initial charge / discharge by the applied current. For reference, 1C = 200mA / g.

[0208] On the other hand, the lithium secondary battery was charged in CC / CV mode at 45°C with a constant current (CC) of 0.5C until it reached 4.25V (termination current 0.005C), and then, after being left for 20 minutes, it was discharged in CC mode with a constant current (CC) of 1.0C until it reached 2.5V. Each of these charging and discharging cycles was considered one cycle, and the charging and discharging cycles were repeated for a total of 50 cycles. The discharge capacity (mAh) and DC internal resistance (DCIR) were measured for the first and 50th cycles. The percentage of the discharge capacity in the 50th cycle relative to the discharge capacity in the first cycle (capacity retention rate (%)) and the percentage of the DC internal resistance in the 50th cycle relative to the DC internal resistance (initial resistance (Ω)) in the first cycle (resistance increase rate (%)) were calculated and are shown in Table 6 below.

[0209] [Table 6]

[0210] Referring to Table 6, it was confirmed that the batteries containing the positive electrode active materials manufactured in Examples 1 to 3 had an efficiency of 87% or higher, a DCIR of 26Ω or less, a capacity retention rate of 95.2% or higher, an initial resistance of 14.7Ω or less, and a resistance increase rate of 169% or less.

[0211] On the other hand, it was confirmed that the battery containing the positive electrode active material manufactured in Comparative Example 1 had an efficiency of less than 87% and a capacity retention rate of less than 95.2%, the battery containing the positive electrode active material manufactured in Comparative Example 2 had an efficiency of less than 89.2%, the battery containing the positive electrode active material manufactured in Comparative Example 3 had a DCIR of more than 26 Ω, an initial resistance of more than 14.7 Ω, and a resistance increase rate of more than 169%, the battery containing the positive electrode active material manufactured in Comparative Example 4 had a capacity retention rate of less than 95.2%, and the battery containing the positive electrode active material manufactured in Comparative Example 5 had a DCIR of more than 26 Ω, a capacity retention rate of less than 95.2%, an initial resistance of more than 14.7 Ω, and a resistance increase rate of more than 169%.

[0212] In other words, when a positive electrode active material, which includes a coating portion containing a first coating portion and a second coating portion on a single-particle lithium composite transition metal oxide, contains boron in a specific amount within the positive electrode active material, it was confirmed that gelation is reduced during the production of the positive electrode slurry containing the positive electrode active material, improving the capacity characteristics of the produced battery, as well as the resistance characteristics and life characteristics.

Claims

1. Lithium composite transition metal oxides in single-particle form, The lithium composite transition metal oxide includes a coating portion formed on the lithium composite transition metal oxide, The coating portion includes a first coating portion and a second coating portion, The first coating portion is formed discontinuously in the form of islands, and the second coating portion is formed continuously in the form of a coating layer. The first coating portion contains boron (B) and selectively includes one or more coating elements selected from the group consisting of 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. The second coating portion contains a compound having a composition represented by the following chemical formula 1 or 2, A positive electrode active material in which the content of boron (B) among all metals other than lithium is 0.1 mol% or more and 1.25 mol% or less. [Chemical formula 1] Li ａ Co ｂ B ｃ M １ ｄ M ２ ｅ O ｆ In the aforementioned chemical formula 1, M １ is one or more selected from the group consisting of Ni and Mn, M ２ is one or more selected from the group consisting of Al, Ba, Ce, Cr, F, Mg, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, S, Sr, Ta, and Hf. 1≦a≦2, 1≦b≦4, 1≦c≦2, 0≦d≦1, 0≦e≦1, 2≦f≦8, [Chemical formula 2] Co ｇ B ｈ M ３ ｉ M ４ ｊ O ｋ In the aforementioned chemical formula 2, M ３ is one or more selected from the group consisting of Ni and Mn, M ４ is one or more selected from the group consisting of Al, Ba, Ce, Cr, F, Mg, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, S, Sr, Ta, and Hf. 1 ≤ g ≤ 4, 1 ≤ h ≤ 2, 0 ≤ i ≤ 1, 0 ≤ j ≤ 1, 2 ≤ k ≤ 8.

2. The positive electrode active material according to claim 1, wherein the first coating portion is dispersed and distributed on one or more of the surfaces of the lithium composite transition metal oxide and the second coating portion.

3. The positive electrode active material according to claim 1, wherein the content of boron (B) is 0.13 mol% or more and 1.1 mol% or less.

4. Average particle size (D ５０ The positive electrode active material according to claim 1, wherein the particle size is 3 μm or more and 20 μm or less.

5. The positive electrode active material according to claim 1, wherein the lithium composite transition metal oxide has a composition represented by the following chemical formula 3. [Chemical formula 3] Li ｌ Ni ｍ Co ｎ Mn ｏ M ５ ｐ O ２ In the aforementioned chemical formula 3, M ５ 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. 0.9 ≤ l ≤ 1.1, 0.6 ≤ m < 1, 0 < n < 0.4, 0 < o < 0.4, 0 ≤ p < 0.

1.

6. The positive electrode active material according to claim 1, wherein the first coating portion contains a compound having a composition represented by the following chemical formula 4. [Chemical formula 4] Li ｑ B ｒ M ６ ｓ M ７ ｔ O ｕ In the aforementioned chemical formula 4, M ６ is one or more elements selected from the group consisting of Ni, Co, and Mn. M ７ is one or more selected from the group consisting of 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. 0 ≤ q ≤ 4, 1 ≤ r ≤ 4, 0 ≤ s ≤ 1, 0 ≤ t ≤ 1, 1 ≤ u ≤ 8.

7. The positive electrode active material according to claim 1, wherein the total area of ​​the coating portion is 10% or more and 100% or less of the total surface area of ​​the lithium composite transition metal oxide.

8. (1) A step of mixing a lithium composite transition metal oxide in single-particle form with a cobalt-containing raw material, and selectively mixing in a coating element-containing raw material to produce a mixture, (2) A step of firing the mixture to produce a fired product, (3) The process includes the step of mixing the calcined product with a boron-containing raw material and heat-treating it to form a coating portion containing cobalt (Co) and boron (B) on the lithium composite transition metal oxide, The coating element is one or more selected from the group consisting of 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. The method for producing a positive electrode active material involves firing at a temperature of 600°C or higher and 800°C or lower.

9. The lithium composite transition metal oxide in single-particle form is produced by (A) mixing a composite transition metal hydroxide containing nickel, cobalt, and manganese with a first lithium-containing raw material, and performing primary calcination at a temperature of 800°C to 950°C to produce a primary calcined product. (B) A method for producing a positive electrode active material according to claim 8, comprising the step of mixing the primary calcined product with a second lithium-containing raw material and performing secondary calcination at a temperature of 680°C to 850°C to produce a secondary calcined product.

10. The method for producing a positive electrode active material according to claim 8, further comprising the step of grinding the primary calcined product (A1) immediately after step (A).

11. The method for producing a positive electrode active material according to claim 8, further comprising the step of grinding the secondary calcined product (B1) immediately after step (B).

12. A positive electrode comprising the positive electrode active material according to any one of claims 1 to 7.

13. The positive electrode according to claim 12, The negative electrode and, A separator interposed between the positive electrode and the negative electrode, A lithium secondary battery containing an electrolyte.

Images