Method for evaluating quality of positive electrode active material, method for manufacturing positive electrode active material and positive electrode

Abstract

The present invention relates to a method for evaluating the quality of a positive electrode active material, including a step of determining that it is a good product when the Raman shift value of the peak corresponding to the A1g vibration mode of LiNiO2 in the Raman spectrum of the surface of the positive electrode active material (A) satisfies a preset quality evaluation criterion for the positive electrode active material, a positive electrode active material that is determined to be a good product by this method and can further improve the performance of the battery, and a method for manufacturing a positive electrode including a step of evaluating the quality of the positive electrode active material by the method for evaluating the quality of the positive electrode active material.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0122638 filed on September 27, 2022, and all the contents disclosed in the literature of the Korean patent application are incorporated herein by reference in their entirety.

[0002] The present invention relates to a method for evaluating the quality of a positive electrode active material, a positive electrode active material, and a method for manufacturing a positive electrode including a step of evaluating the quality of the positive electrode active material by the method for evaluating the quality of the positive electrode active material.

Background Art

[0003] Recently, with the development of technologies related to mobile devices and electric vehicles and the increasing demand, the demand for secondary batteries as an energy source has been rapidly increasing.

[0004] On the other hand, the positive electrode active material used in a lithium secondary battery generally has a spherical secondary particle form in which several hundred fine primary particles of submicron size are aggregated. However, the positive electrode active material in the form of secondary particles has a problem that when repeatedly charged and discharged, as the aggregated primary particles are separated, the secondary particles are cracked and the characteristics of the battery deteriorate.

[0005] To solve such problems, although the development of positive electrode active materials in the form of single particles is actively underway, when manufacturing positive electrode active materials in the form of single particles, firing at a higher temperature than when manufacturing positive electrode active materials in the form of secondary particles is required, and there is a problem that the ratio of the NiO reduction layer on the particle surface increases. On the other hand, when the ratio of the NiO reduction layer on the surface of the positive electrode active material increases, problems such as an increase in battery resistance, a decrease in capacity, and a decrease in output occur, and therefore, it is necessary to control the NiO reduction layer.

[0006] To control the NiO reduction layer, when surface treatment is performed on the surface of the positive electrode active material using a cobalt-containing substance, the cobalt-containing substance diffuses and the NiO reduction layer is reduced, and a coating layer containing cobalt is formed.

[0007] On the one hand, since the performance of the positive electrode active material changes according to the degree of cobalt diffusion, not only is an evaluation method necessary to more accurately confirm the degree of cobalt diffusion, but there is also a need for development of a positive electrode active material that can further improve the performance of the battery.

Summary of the Invention

Problems to be Solved by the Invention

[0008] The present invention is for solving the above problems, and an object thereof is to provide a quality evaluation method for a positive electrode active material that can easily distinguish a positive electrode active material with poor quality based on the Raman spectrum of the surface of the positive electrode active material, and a positive electrode active material that is thereby determined to be a good product and can further improve the performance of the battery.

[0009] Another object is to provide a method for manufacturing a positive electrode including a step of evaluating the quality of the positive electrode active material by the quality evaluation method of the positive electrode active material.

Means for Solving the Problems

[0010] The present invention provides a quality evaluation method for a positive electrode active material, a positive electrode active material, and a method for manufacturing a positive electrode.

[0011] (1) The present invention provides a quality evaluation method for a positive electrode active material including a first determination step of determining a good product when the Raman shift value of a peak corresponding to the A1g vibration mode of LiNiO2 in the Raman spectrum of the surface of the positive electrode active material satisfies a preset quality evaluation criterion for the positive electrode active material, and determining a defective product when the preset quality evaluation criterion for the positive electrode active material is not satisfied.

[0012] (2) In the above (1), the present invention provides a quality evaluation method for a positive electrode active material including a step of preparing a single-particle-form positive electrode active material including (A’) a single-particle-form lithium transition metal oxide and a coating portion including cobalt formed on the single-particle-form lithium transition metal oxide before the step (A).

[0013] (3) In the present invention, in the above (2), a method for evaluating the quality of a positive electrode active material is provided, wherein the positive electrode active material in the single particle form is produced by heat-treating a mixture obtained by mixing a single particle form lithium transition metal oxide and a cobalt raw material substance.

[0014] (4) In the present invention, in any one of the above (1) to (3), in the step (A), the preset quality evaluation criteria for the positive electrode active material are such that the Raman shift value of the peak corresponding to the A1g vibration mode of LiNiO2 is 560 cm -1 or more, and a method for evaluating the quality of a positive electrode active material is provided.

[0015] (5) In the present invention, in any one of the above (1) to (4), in (B), for the peak (500 cm -1 ~600 cm -1 ) corresponding to the A1g vibration mode of LiNiO2 in the Raman spectrum of the surface of the positive electrode active material determined to be a good product in the step (A), when the ratio of the intensity of the peak (550 cm -1 ~620 cm -1 ) corresponding to the A1g vibration mode of LiCoO2 is 0.3 or less, it is determined to be a good product, and when it exceeds 0.3, a method for evaluating the quality of a positive electrode active material is provided, which further includes a second determination step of determining it to be a defective product.

[0016] (6) The present invention provides a method for manufacturing a positive electrode, including the steps of: (S1) preparing a positive electrode active material in a single particle form, including a single particle form lithium transition metal oxide and a coating portion formed on the single particle form lithium transition metal oxide and containing cobalt; (S2) evaluating the quality of the positive electrode active material by the method according to any one of claims 1 to 5; and (S3) manufacturing a positive electrode using the positive electrode active material determined to be a good product.

[0017] (7) In the present invention, in the above (6), a method for manufacturing a positive electrode is provided, wherein the positive electrode active material in the single particle form is produced by heat-treating a mixture obtained by mixing a single particle form lithium transition metal oxide and a cobalt raw material substance.

[0018] (8) In the above (6), the method for manufacturing a positive electrode provided by the present invention is such that the positive electrode active material in the single-particle form is manufactured by heat-treating a mixture of a single-particle form lithium transition metal oxide and a cobalt raw material at a temperature exceeding 720 °C and less than 780 °C.

[0019] (9) The present invention provides a positive electrode active material in a single-particle form, which includes a single-particle form lithium transition metal oxide and a coating portion containing cobalt formed on the single-particle form lithium transition metal oxide, and the Raman shift value of the peak corresponding to the A1g vibration mode of LiNiO2 in the Raman spectrum of the surface of the positive electrode active material is 560 cm -1 or more.

[0020] (10) In the above (9), the present invention provides a positive electrode active material in a single-particle form, which further includes island-shaped LiCoO2 discontinuously formed on the surface.

[0021] (11) In the above (9) or (10), the present invention provides a positive electrode active material in a single-particle form, in which the ratio of the intensity of the peak (550 cm -1 ~620 cm -1 ) corresponding to the A1g vibration mode of LiCoO2 to the intensity of the peak (500 cm -1 ~600 cm -1 ) corresponding to the A1g vibration mode of LiNiO2 in the Raman spectrum of the surface of the positive electrode active material is 0.3 or less.

[0022] (12) In any one of the above (9) to (11), the present invention provides a positive electrode active material in a single-particle form, in which the average particle size (D 50 ) is 0.1 μm to 10 μm.

[0023] (13) In any one of the above (9) to (12), the present invention provides a positive electrode active material in a single-particle form, in which the primary particles composed of 10 or fewer single crystal grains (grain) are aggregated in a form of 50 or fewer.

[0024] (14) In any one of (9) to (13) above, the present invention provides a positive electrode active material in the form of single particles, wherein the lithium transition metal oxide in the form of single particles is a lithium composite transition metal oxide containing nickel (Ni), cobalt (Co), and manganese (Mn).

[0025] (15) In any one of (9) to (14) above, the present invention provides a positive electrode active material in the form of single particles, wherein the lithium transition metal oxide in the form of single particles has a composition represented by the following Chemical Formula 1. [Chemical Formula 1] Li a Ni b Co c Mn d M 1 e O2 In Chemical Formula 1 above, M 1 is one or more selected from Al, Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, Sn, Y, Zn, F, P, and S, 0.9 ≦ a ≦ 1.1, 0.8 ≦ b < 1.0, 0 < c < 0.2, 0 < d < 0.2, 0 ≦ e ≦ 0.1, and b + c + d + e = 1.

[0026] (16) In any one of (9) to (15) above, the present invention provides a positive electrode active material in the form of single particles, wherein the coating portion is a region from the surface of the positive electrode active material to the center direction with a range of 5 nm to 100 nm.

Advantages of the Invention

[0027] The method for evaluating the quality of the positive electrode active material according to the present invention can easily determine a positive electrode active material with good quality by measuring only the Raman spectrum of the surface of the positive electrode active material.

[0028] The positive electrode active material according to the present invention can improve the resistance performance of a lithium secondary battery.

Modes for Carrying Out the Invention

[0029] In this specification and the claims, terms and words used should not be construed as limited to their ordinary or dictionary meanings. In accordance with the principle that the inventors can appropriately define the concepts of terms in order to best explain their invention, they should be construed in meanings and concepts consistent with the technical idea of the present invention.

[0030] In this specification, terms such as "comprising", "including" or "having" are used to specify the presence of implemented features, numbers, steps, components, or combinations thereof, and should be understood not to preclude in advance the presence or addition possibility of one or more other features, numbers, steps, components, or combinations thereof.

[0031] In this specification, the term "on" means not only when a certain component is formed immediately above another component, but also includes the case where a third component is interposed between these components.

[0032] In this specification, the "positive electrode active material in single particle form" is a concept contrasted with the positive electrode active material in spherical secondary particle form formed by aggregation of hundreds of primary particles produced by conventional methods, and means a positive electrode active material composed of 50 or fewer primary particles. Specifically, in the present invention, the positive electrode active material in single particle form may be a single particle composed of one primary particle, or may be a secondary particle form in which 2 to 50, 2 to 40, 2 to 30, 2 to 20, 2 to 15, 2 to 10, or 2 to 5 primary particles are aggregated. Here, the "primary particle" means the minimum unit of particles recognized when observing the positive electrode active material through a scanning electron microscope.

[0033] On the one hand, the primary particles can consist of 10 or fewer single crystal grains, and the grains can be analyzed using an electron backscatter diffraction (EBSD) analyzer. The single crystal grains are units represented by the same color in the electron backscatter diffraction (EBSD) Euler map data of one positive electrode active material particle, and are grains in which no grain boundaries exist within the grains.

[0034] As used herein, the average particle diameter (D 50 ) means the particle diameter at the 50% standard of the volume cumulative particle size distribution of the positive electrode active material precursor, the positive electrode active material, or the lithium transition metal oxide powder. The average particle diameter (D 50 ) can be measured using the laser diffraction method. For example, after dispersing the positive electrode active material powder in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000), irradiated with ultrasonic waves of about 28 kHz at an output of 60 W, and after obtaining a volume cumulative particle size distribution graph, it can be measured by determining the particle diameter corresponding to 50% of the volume cumulative amount.

[0035] As used herein, the average particle diameter (D EBSD ) of the single crystal grains means the particle diameter at the 50% standard of the volume cumulative particle size distribution of the single crystal grains obtained by EBSD analysis using SEM. The EBSD analysis can acquire an image with an SEM-EBSD equipment (e.g., Quanta200 manufactured by FEI - Velocity super OIM 8 manufactured by EDAX), and this can be analyzed by image analysis software (EDAX OIM Analysis).

[0036] As used herein, the Raman spectrum is obtained by placing the sample in a general-purpose XRD holder, then performing pretreatment by pressing with a slide glass so that the surface height of the sample becomes uniform, and measuring the portion corresponding to an area of 410 μm × 100 μm of the sample located on the XRD holder with a Raman spectrometer (using a 532 nm laser).

[0037] The present invention will be described in more detail below.

[0038] Method for Evaluating Quality of Positive Electrode Active Material The method for evaluating the quality of a positive electrode active material according to the present invention includes a first determination step of determining that it is a non-defective product when the Raman shift value of the peak corresponding to the A1g vibration mode of LiNiO2 in the Raman spectrum of the surface of the positive electrode active material satisfies the preset quality evaluation criteria for the positive electrode active material, and determining that it is a defective product when it does not satisfy the preset quality evaluation criteria for the positive electrode active material.

[0039] The method for evaluating the quality of the positive electrode active material may include, before the step (A), a step of preparing a single-particle form of the positive electrode active material including (A') a single-particle form of a lithium transition metal oxide and a coating portion containing cobalt formed on the single-particle form of the lithium transition metal oxide. Further, after the step (A), (B) the ratio of the intensity of the peak (550 cm -1 ~600 cm -1 ) corresponding to the A1g vibration mode of LiCoO2 to the intensity of the peak (550 cm -1 ~620 cm -1 ) corresponding to the A1g vibration mode of LiCoO2 in the Raman spectrum of the surface of the positive electrode active material determined to be a non-defective product in the step (A) is 0.3 or less, it is determined to be a non-defective product, and when it exceeds 0.3, it may further include a second step of determining that it is a defective product.

[0040] The method for evaluating the quality of a positive electrode active material according to the present invention can easily determine a positive electrode active material with good quality by measuring only the Raman spectrum of the surface of the positive electrode active material. Specifically, when applied to a lithium secondary battery, a positive electrode active material that can improve the resistance characteristics of the battery can be easily confirmed.

[0041] Hereinafter, each step of the method for evaluating the quality of a positive electrode active material according to the present invention will be described in more detail.

[0042] Step (A') The step (A') is a step of preparing a positive electrode active material in a single particle form, which includes a lithium transition metal oxide in a single particle form and a coating portion containing cobalt formed on the lithium transition metal oxide in the single particle form, before the step (A).

[0043] According to the present invention, the positive electrode active material in the single particle form can be manufactured by heat-treating a mixture of a lithium transition metal oxide in a single particle form and a cobalt raw material substance. When the mixture is heat-treated, cobalt ions present in the cobalt raw material substance diffuse from the surface to the center of the lithium transition metal oxide in the single particle form, and a Raman shift of a peak corresponding to the A1g vibration mode of LiNiO2 is confirmed in the Raman spectrum of the surface of the positive electrode active material.

[0044] The heat treatment temperature can be higher than 720 °C and less than 780 °C. Specifically, it can be higher than 720 °C, 730 °C or higher, or 740 °C or higher, 760 °C or lower, 770 °C or lower, or less than 780 °C. When the mixture is heat-treated within the temperature range, a coating portion containing cobalt is formed while being optimized on the surface of the positive electrode active material in the single particle form, and the lithium secondary battery including the positive electrode containing the positive electrode active material can have excellent resistance performance. Specifically, when the mixture is heat-treated within the temperature range, it includes a lithium transition metal oxide in the single particle form and a coating portion containing cobalt formed on the lithium transition metal oxide in the single particle form, and the Raman shift value of the peak corresponding to the A1g vibration mode of LiNiO2 in the Raman spectrum of the surface of the positive electrode active material is 560 cm -1The above-mentioned single-particle form of the positive electrode active material can be manufactured. LiNiO2, which is the main constituent of the lithium transition metal oxide in the single-particle form, and LiCoO2 confirmed in the coating part have the same crystal structure (R3m). The R3m crystal structure has two vibration modes, A1g and Eg, in the Raman spectrum. When the mixture is heat-treated within the above temperature range, cobalt penetrates into the interior of the positive electrode active material, and an appropriate amount of Co penetrates into the interior of the LiNiO2 lattice. As a result, the vibration frequency of the LiNiO2 vibration mode increases. In addition, the positive electrode active material manufactured by heat-treating the mixture within the above temperature range has a peak (500 cm -1 ~600 cm -1 ) corresponding to the A1g vibration mode of LiNiO2 in the Raman spectrum of the surface. The ratio of the intensity of the peak (550 cm -1 ~620 cm -1 ) corresponding to the A1g vibration mode of LiCoO2 to the intensity of the peak can be 0.3 or less. This is because when the mixture is heat-treated within the above temperature range, cobalt penetrates into the interior of the positive electrode active material, and the surface LiCoO2 decreases. In addition, when cobalt penetrates into the interior of the positive electrode active material, NiO that was present on the surface conventionally decreases, the surface is stabilized, and the resistance of the battery can be decreased.

[0045] In the present invention, the coating part is a layer formed while cobalt diffuses from the surface to the center direction of the single-particle form of the lithium transition metal oxide when the single-particle form of the lithium transition metal oxide and the cobalt raw material are mixed and then heat-treated. Therefore, the composition of the coating part is similar to the composition of the single-particle form of the lithium transition metal oxide contained in the positive electrode active material of the present invention, but the ratio of cobalt occupied in all metals other than lithium is higher than that of the single-particle form of the lithium transition metal oxide. On the other hand, cobalt diffuses from the surface to the center direction of the single-particle form of the lithium transition metal oxide, and Ni present in the single-particle form of the lithium transition metal oxide can be replaced by Co. The coating part can have the same structure as the single-particle form of the lithium transition metal oxide, that is, a layered structure.

[0046] In the present invention, the coating part can be a region from the surface of the positive electrode active material to the center direction in the range of 5 nm to 100 nm. Specifically, the coating part can be a region from the surface of the positive electrode active material to the center direction of 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, or 100 nm.

[0047] (A) Step In the step (A), when the Raman shift value of the peak corresponding to the A1g vibration mode of LiNiO2 in the Raman spectrum of the surface of the positive electrode active material satisfies the preset quality evaluation criteria of the positive electrode active material, it is determined as a good product. When the preset quality evaluation criteria of the positive electrode active material are not satisfied, it is the first determination step of determining as a defective product.

[0048] When the Raman shift value of the peak corresponding to the A1g vibration mode of LiNiO2 in the Raman spectrum of the surface of the positive electrode active material satisfies the preset quality evaluation criteria of the positive electrode active material, the resistance performance of the lithium secondary battery including the positive electrode containing such a positive electrode active material can be significantly improved. Specifically, for the lithium secondary battery, the value of the resistance increase rate that appears as the charge and discharge cycles are repeated at a high temperature can be reduced.

[0049] According to the present invention, in the step (A), the preset quality evaluation criteria of the positive electrode active material are that the Raman shift value of the peak corresponding to the A1g vibration mode of LiNiO2 is 560 cm -1 or more. Specifically, the preset quality evaluation criteria of the positive electrode active material are that the Raman shift value of the peak corresponding to the A1g vibration mode of LiNiO2 is 560 cm -1 or more, 570 cm -1 or less, 580 cm -1 or less, 590 cm -1 or less, or less than 597 cm -1 In this case, it is considered that the coating part containing cobalt is formed on the surface of the positive electrode active material in a single particle form so as to optimize the improvement of the resistance performance of the lithium secondary battery.

[0050] (B) Step In the said (B) step, when the ratio of the intensity of the peak (550 cm -1 ~600 cm -1 ) corresponding to the A1g vibration mode of LiCoO2 to the intensity of the peak (500 cm -1 ~620 cm -1 ) corresponding to the A1g vibration mode of LiNiO2 in the Raman spectrum of the surface of the positive electrode active material is 0.30 or less, it is a step of judging as a good product. The ratio of the intensity of the peak (550 cm -1 ~600 cm -1 ) corresponding to the A1g vibration mode of LiCoO2 to the intensity of the peak (500 cm -1 ~620 cm -1 ) corresponding to the A1g vibration mode of LiNiO2 can specifically be more than 0, or 0.10 or more and 0.30 or less.

[0051] When the ratio of the intensity of the peak (550 cm -1 ~600 cm -1 ) corresponding to the A1g vibration mode of LiCoO2 to the intensity of the peak (500 cm -1 ~620 cm -1 ) corresponding to the A1g vibration mode of LiNiO2 in the Raman spectrum of the surface of the positive electrode active material is 0.30 or less, instead of NiO which is electrochemically inactive on the surface, a LiCoO2 crystal structure which is electrochemically active is formed in an appropriate amount, and the resistance decreases.

[0052] Positive Electrode Active Material The present invention includes a lithium transition metal oxide in a single particle form and a coating portion containing cobalt formed on the lithium transition metal oxide in the single particle form, and provides a positive electrode active material in a single particle form in which the Raman shift value of the peak corresponding to the A1g vibration mode of LiNiO2 in the Raman spectrum of the surface of the positive electrode active material is 560 cm -1 or more. The Raman shift value of the peak corresponding to the A1g vibration mode of LiNiO2 is specifically 560 cm -1 or more and 570 cm -1580 cm or less -1 590 cm or less -1 or 597 cm or less -1 It can be less than that.

[0053] The positive electrode active material according to the present invention is a positive electrode active material determined to be a good product by the quality evaluation method of the positive electrode active material according to the present invention.

[0054] The inventors of the present invention have found that the positive electrode active material in the single particle form includes a single particle form of a lithium transition metal oxide and a coating portion containing cobalt formed on the single particle form of the lithium transition metal oxide, and the Raman shift value of the peak corresponding to the A1g vibration mode of LiNiO2 in the Raman spectrum of the surface of the positive electrode active material is 560 cm -1 When it is 560 cm or more, it was confirmed that the resistance performance of the lithium secondary battery including this is improved.

[0055] The positive electrode active material according to the present invention is the same as the positive electrode active material in the step (A'), and can be manufactured as described above.

[0056] When the Raman shift value of the peak corresponding to the A1g vibration mode of LiNiO2 in the Raman spectrum of the surface of the positive electrode active material in the single particle form is less than 560 cm -1 In this case, since cobalt does not diffuse much into the surface layer portion of the positive electrode active material, the surface is not stabilized, and there is a problem that the resistance performance of the lithium secondary battery including this is not improved.

[0057] According to the present invention, the single-particle form cathode active material may further include island-shaped LiCoO2 formed discontinuously on the surface. The island-shaped LiCoO2 is formed discontinuously on the surface of the cathode active material. That is, the island-shaped LiCoO2 does not entirely cover the surface of the cathode active material but is partially dispersed and distributed. The island-shaped LiCoO2 can be formed discontinuously in an area of 5% to 50% of the total surface area of the surface of the cathode active material. In this case, the coating portion and the island-shaped LiCoO2 exist in an appropriate ratio, and the performance of the battery can be further improved.

[0058] According to the present invention, in the Raman spectrum of the surface of the cathode active material, the ratio of the intensity of the peak corresponding to the A1g vibration mode of LiCoO2 (550 cm -1 ~600 cm -1 ) to the intensity of the peak corresponding to the A1g vibration mode of LiCoO2 (550 cm -1 ~620 cm -1 ) can be 0.3 or less. Specifically, the ratio of the intensity of the peak corresponding to the A1g vibration mode of LiCoO2 (550 cm -1 ~600 cm -1 ) to the intensity of the peak corresponding to the A1g vibration mode of LiCoO2 (550 cm -1 ~620 cm -1 ) can be greater than 0, 0.10 or more, and 0.30 or less. In this case, instead of NiO which is electrochemically inactive on the surface of the cathode active material, a LiCoO2 crystal structure that is electrochemically active exists in an appropriate amount, and the resistance performance of the battery including the cathode active material can be further improved. On the other hand, the peak corresponding to the A1g vibration mode of LiCoO2 (550 cm -1 ~620 cm -1 ) can be a peak resulting from the island-shaped LiCoO2.

[0059] According to the present invention, the single-particle form cathode active material can have an average particle size (D 50 ) of 0.1 μm to 10 μm. Specifically, the average particle size (D50 ) can be 0.1 μm or more, 1.0 μm or more, or 2.0 μm or more and 5.0 μm or less, 6.0 μm or less, 7.0 μm or less, 8.0 μm or less, 9.0 μm or less, or 10.0 μm or less. In this case, the rolling rate of the battery containing the single-particle form of the positive electrode active material can be increased, and the performance of the battery can be further improved.

[0060] According to the present invention, the single-particle form of the positive electrode active material can be in a form in which primary particles composed of 10 or fewer single-crystal grains (grains) are aggregated into 50 or fewer, specifically 30 or fewer, 20 or fewer, 10 or fewer, or 5 or fewer. In this case, the capacity and resistance performance of the battery can be improved, and the occurrence of cracks in the particles during the process of repeating charge and discharge can be reduced. Here, the average particle diameter (D EBSD ) of the single-crystal grain can be 0.1 μm to 10 μm. Specifically, the average particle diameter (D EBSD ) of the single-crystal grain can be 0.1 μm or more, 1.0 μm or more, or 2.0 μm or more and 5.0 μm or less, 6.0 μm or less, 7.0 μm or less, 8.0 μm or less, 9.0 μm or less, or 10.0 μm or less.

[0061] According to the present invention, the single-particle form of the lithium transition metal oxide can be a lithium composite transition metal oxide containing nickel (Ni), cobalt (Co), and manganese (Mn). Here, the single-particle form of the lithium transition metal oxide can contain 80 mol% or 85 mol% or more of nickel (Ni) among all metals other than lithium. Specifically, the single-particle form of the lithium transition metal oxide can have a composition represented by the following Chemical Formula 1.

[0062] [Chemical Formula 1] Li a Ni b Co c Mn d M 1 e O2

[0063] In Chemical Formula 1, M1 is at least one selected from Al, Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, Sn, Y, Zn, F, P, and S, 0.9 ≦ a ≦ 1.1, 0.8 ≦ b < 1.0, 0 < c < 0.2, 0 < d < 0.2, 0 ≦ e ≦ 0.1, and b + c + d + e = 1.

[0064] Said b represents the atomic fraction of nickel among the metal elements other than lithium in the lithium transition metal oxide, and can be 0.8 or more, or 0.85 or more, 0.95 or less, or 0.98 or less.

[0065] Said c represents the atomic fraction of cobalt among the metal elements other than lithium in the lithium transition metal oxide, and can be 0.01 or more, 0.1 or less, or 0.2 or less.

[0066] Said d represents the atomic fraction of manganese among the metal elements other than lithium in the lithium transition metal oxide, and can be 0.01 or more, 0.1 or less, or 0.2 or less.

[0067] Said e represents the elemental fraction of element M 1 among the metal elements other than lithium in the lithium transition metal oxide, and can be 0 or more, 0.02 or less, 0.05 or less, or 0.1 or less.

[0068] In the present invention, when the coating portion is formed by mixing single-particle-form lithium transition metal oxide and a cobalt raw material substance and then performing heat treatment, cobalt diffuses from the surface to the center direction of the single-particle-form lithium transition metal oxide to form a layer. Therefore, the composition of the coating portion is the same as that of the single-particle-form lithium transition metal oxide contained in the positive electrode active material of the present invention, but the ratio of cobalt occupied by the total metals other than lithium is higher than that of the single-particle-form lithium transition metal oxide. On the other hand, Ni present in the single-particle-form lithium transition metal oxide can be substituted by Co while cobalt diffuses from the surface to the center direction of the single-particle-form lithium transition metal oxide, and the coating portion can have the same structure as the single-particle-form lithium transition metal oxide, that is, a layered structure.

[0069] According to the present invention, the coating portion can be a region from 5 nm to 100 nm in the center direction from the surface of the positive electrode active material. Specifically, the coating portion can be a region from 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, or 100 nm in the center direction from the surface of the positive electrode active material.

[0070] In this specification, the coating portion is a region up to the point where the Co content measured by TEM-EDX experiment from the surface of the positive electrode active material exceeds 1.1 times the overall average Co content (mol%) of the positive electrode active material. Here, in the TEM-EDX experiment, after manufacturing a thin film sample with a thickness of 100 nm to 200 nm from the positive electrode active material powder using a Helios G4 UX FIB equipment manufactured by FEI Company, the X-ray spectrum of the elements at different positions of the sample is measured using a Titan G2 80-200 ChemiSTEM equipment manufactured by FEI Company and an EDX (in-column super-X Energy Dispersive X-ray spectroscopy) unit (ChemiSTEM technology), and the intensity is compared to obtain the molar ratio (mol%) value for each element.

[0071] Method for Manufacturing Positive Electrode The method for manufacturing a positive electrode according to the present invention includes: (S1) a step of preparing a positive electrode active material in the form of single particles, which includes a lithium transition metal oxide in the form of single particles and a coating portion containing cobalt formed on the lithium transition metal oxide in the form of single particles; (S2) a step of evaluating the quality of the positive electrode active material by the method for evaluating the quality of the positive electrode active material according to the present invention; and (S3) a step of manufacturing a positive electrode using the positive electrode active material determined to be a good product.

[0072] Hereinafter, each step of the method for manufacturing a positive electrode of the present invention will be described in more detail.

[0073] (S1) step The (S1) step is a step of preparing a positive electrode active material in the form of single particles, which includes a lithium transition metal oxide in the form of single particles and a coating portion containing cobalt formed on the lithium transition metal oxide in the form of single particles.

[0074] The (S1) step is the same step as the (A') step in the method for evaluating the quality of the positive electrode active material.

[0075] According to the present invention, the positive electrode active material in the form of single particles can be manufactured by heat-treating a mixture of a lithium transition metal oxide in the form of single particles and a cobalt raw material substance. When the mixture is heat-treated, cobalt ions present in the cobalt raw material substance diffuse from the surface to the center of the lithium transition metal oxide in the form of single particles, and a Raman shift of a peak corresponding to the A1g vibration mode of LiNiO2 is confirmed in the Raman spectrum of the surface of the positive electrode active material.

[0076] The heat treatment temperature can be higher than 720°C and less than 780°C. Specifically, it can be higher than 720°C, 730°C or higher, or 740°C or higher, and 760°C or lower, 770°C or lower, or less than 780°C. When the mixture is heat-treated within the above temperature range, a cobalt-containing coating part is optimally formed on the surface of the single-particle form cathode active material, and the resistance performance of the lithium secondary battery including the cathode containing the cathode active material can be improved. Specifically, when the mixture is heat-treated within the above temperature range, it includes a single-particle form lithium transition metal oxide and a cobalt-containing coating part formed on the single-particle form lithium transition metal oxide, and the Raman shift value of the peak corresponding to the A1g vibration mode of LiNiO2 in the Raman spectrum of the surface of the cathode active material is 560 cm -1 or more, and a single-particle form cathode active material can be manufactured. Further, the cathode active material manufactured by heat-treating the mixture within the above temperature range has a peak (500 cm -1 ~600 cm -1 ) corresponding to the A1g vibration mode of LiNiO2 in the Raman spectrum of the surface, and the ratio of the intensity of the peak (550 cm -1 ~620 cm -1 ) corresponding to the A1g vibration mode of LiCoO2 to the intensity of the peak corresponding to the A1g vibration mode of LiNiO2 can be 0.3 or less.

[0077] (S2) Step The (S2) step is a step of evaluating the quality of the cathode active material by the method for evaluating the quality of the cathode active material according to the present invention.

[0078] That is, for the single-particle form cathode active material with a cobalt-containing coating layer formed thereon, using a Raman spectrometer, the Raman spectrum of the surface of the cathode active material is obtained. When the Raman shift value of the peak corresponding to the A1g vibration mode of LiNiO2 in the Raman spectrum of the surface of the cathode active material meets the preset quality evaluation criteria for the cathode active material, it is determined as a good product. When it does not meet the preset quality evaluation criteria for the cathode active material, it is determined as a defective product. This step is included.

[0079] The specific content is as described above.

[0080] (S3) Step The (S3) step is a step of manufacturing a positive electrode using the positive electrode active material determined to be a good product.

[0081] The positive electrode can be manufactured by applying a composition for forming a positive electrode active material layer (slurry) containing the positive electrode active material determined to be a good product, a conductive material, and a binder on a current collector, and then drying to form an active material layer. The active material layer can be formed on one or both surfaces of the current collector.

[0082] The current collector is not particularly limited as long as it does not cause a chemical change in the battery and has conductivity. In the case of a positive electrode current collector, for example, stainless steel, aluminum, nickel, titanium, fired carbon, or a material obtained by surface treatment with carbon, nickel, titanium, silver, etc. on the surface of aluminum or stainless steel can be used. In the case of a negative electrode current collector, for example, copper, stainless steel, aluminum, nickel, titanium, fired carbon, a material obtained by surface treatment with carbon, nickel, titanium, silver, etc. on the surface of copper or stainless steel, an aluminum-cadmium alloy, etc. can be used.

[0083] The current collector can usually have a thickness of 3 μm to 500 μm, and fine irregularities can be formed on the surface of the current collector to enhance the adhesive force of the positive electrode material or the negative electrode material. For example, it can be used in various forms such as films, sheets, foils, meshes, porous bodies, foams, non-woven fabrics, etc.

[0084] The composition for forming the positive electrode active material layer can be manufactured by dissolving or dispersing the positive electrode active material determined to be a good product, a conductive material, and a binder in a solvent.

[0085] The positive electrode active material determined to be the above-mentioned good product can be a compound capable of reversible intercalation and deintercalation of lithium, specifically, a lithium composite metal oxide containing one or more transition metals such as cobalt, manganese, nickel, or aluminum and lithium. More specifically, the lithium composite metal oxide is a lithium-manganese-based oxide (for example, LiMnO2, LiMn2O4, etc.), a lithium-cobalt-based oxide (for example, LiCoO2, etc.), a lithium-nickel-based oxide (for example, LiNiO2, etc.), a lithium-nickel-manganese-based oxide (for example, LiNi 1-Y Mn Y O2(0 < Y < 1), LiMn 2-z Ni z O4(0 < Z < 2), a lithium-nickel-cobalt-based oxide (for example, LiNi 1-Y1 Co Y1 O2(0 < Y1 < 1), a lithium-manganese-cobalt-based oxide (for example, LiCo 1-Y2 Mn Y2 O2(0 < Y2 < 1), LiMn 2-z1 Co z1 O4(0 < Z1 < 2)), a lithium-nickel-manganese-cobalt-based oxide (for example, Li(Ni p Co q Mn r1 )O2(0 < p < 1, 0 < q < 1, 0 < r1 < 1, p + q + r1 = 1) or Li(Ni p1 Co q1 Mn r2 )O4(0 < p1 < 2, 0 < q1 < 2, 0 < r2 < 2, p1 + q1 + r2 = 2), or a lithium-nickel-cobalt-transition metal (M) oxide (for example, Li(Ni p2 Co q2 Mn R3 M S2 )O2(M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, and p2, q2, r3, and s2 are the atomic fractions of the respective independent elements, 0 < p2 < 1, 0 < q2 < 1, 0 < r3 < 1, 0 < s2 < 1, and p2 + q2 + r3 + s2 = 1), etc.), and any one or two or more of these compounds can be included.

[0086] The positive electrode active material determined to be a good product can be contained in an amount of 80% to 99% by weight, more specifically 85% to 98% by weight, based on the total weight of the active material layer. When the content of the positive electrode active material determined to be a good product is within the above range, excellent capacity characteristics and electrochemical characteristics can be obtained.

[0087] The conductive material is used to impart conductivity to the electrode and can be used without particular limitation as long as it has electron conductivity and does not cause chemical changes in the battery being constructed. Specific examples include graphite such as natural graphite and 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. Among these, one kind alone or a mixture of two or more kinds can be used.

[0088] The conductive material can be contained in an amount of 1% to 30% by weight based on the total weight of the active material layer.

[0089] The binder serves to improve the adhesion between the active material particles and the adhesion force between the active material and the current collector. Specific examples of the binder include polyvinylidene fluoride (PVDF), vinylidene fluoride - hexafluoropropylene copolymer (PVDF - co - HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene - propylene - diene polymer (EPDM), sulfonated - EPDM, styrene - butadiene rubber (SBR), fluororubber, or various copolymers thereof, etc. One of these alone or a mixture of two or more can be used.

[0090] The binder can be contained in an amount of 1% to 30% by weight based on the total weight of the positive electrode active material layer.

[0091] The solvent can be a solvent generally used in the art, and examples include dimethyl sulfoxide (DMSO), isopropyl alcohol, N - methylpyrrolidone (NMP), acetone, or water, etc. One of these alone or a mixture of two or more can be used. The amount of the solvent used can be adjusted so that the composition for forming the positive electrode active material layer has an appropriate viscosity, taking into account factors such as the coating thickness of the composition for forming the positive electrode active material layer, production yield, workability, etc., and is not particularly limited.

[0092] As described above, a positive electrode can be manufactured using the positive electrode active material determined to be a good product by the quality evaluation method of the positive electrode active material of the present invention, and the positive electrode can be used as an electrode of a lithium secondary battery. The lithium secondary battery has improved resistance performance and can be usefully used in portable devices such as mobile phones, notebook computers, digital cameras, and the field of electric vehicles such as hybrid electric vehicles (HEV).

[0093] Hereinafter, the embodiments of the present invention will be described in detail so that those having ordinary knowledge in the technical field to which the present invention pertains can easily implement them. However, the present invention can be realized in various different forms and is not limited to the embodiments described herein.

Embodiment

[0094] Production Example 1 LiNi 0.88 Co 0.03 Mn 0.09 Powdery Co(OH)2 (manufactured by HUAYOU COBALT) was mixed with a single-particle form of lithium transition metal oxide having a composition represented by O2 in a molar ratio of 1:0.02 to prepare a mixture. The mixture was heat-treated at a temperature of 660 °C for 3 hours in an oxygen atmosphere to produce a single-particle form of positive electrode active material (average particle size: 4 μm) having a cobalt-containing coating layer formed thereon.

[0095] Production Example 2 A single-particle form of positive electrode active material (average particle size: 4 μm) having a cobalt-containing coating layer formed thereon was produced in the same manner as in Production Example 1, except that the mixture was heat-treated at a temperature of 680 °C.

[0096] Production Example 3 A single-particle form of positive electrode active material (average particle size: 4 μm) having a cobalt-containing coating layer formed thereon was produced in the same manner as in Production Example 1, except that the mixture was heat-treated at a temperature of 700 °C.

[0097] Production Example 4 A positive electrode active material in the form of single particles (average particle size: 4 μm) having a cobalt-containing coating layer formed in the same manner as in Production Example 1 was produced, except that the mixture was heat-treated at a temperature of 720°C.

[0098] Production Example 5 A positive electrode active material in the form of single particles (average particle size: 4 μm) having a cobalt-containing coating layer formed in the same manner as in Production Example 1 was produced, except that the mixture was heat-treated at a temperature of 740°C.

[0099] Production Example 6 A positive electrode active material in the form of single particles (average particle size: 4 μm) having a cobalt-containing coating layer formed in the same manner as in Production Example 1 was produced, except that the mixture was heat-treated at a temperature of 760°C.

[0100] Production Example 7 A positive electrode active material in the form of single particles (average particle size: 4 μm) having a cobalt-containing coating layer formed in the same manner as in Production Example 1 was produced, except that the mixture was heat-treated at a temperature of 780°C.

[0101] Example: Quality Evaluation of Positive Electrode Active Material After placing samples of each of the positive electrode active materials produced in Production Examples 1 to 7 in a general-purpose XRD holder, they were crimped with a slide glass and pretreated so that the surface height of the samples was uniform. A portion corresponding to an area of 410 μm × 100 μm of the sample located on the XRD holder was measured with a Raman spectrometer (using a 532 nm laser) to obtain the Raman spectrum of the surface of the positive electrode active material.

[0102] The Raman shift value of the peak corresponding to the A1g vibration mode of LiNiO2 and the ratio of the intensity of the peak corresponding to the A1g vibration mode of LiCoO2 (550 cm -1 ~600 cm -1 ) to the intensity of the peak corresponding to the A1g vibration mode of LiNiO2 (500 cm -1 ~620 cm -1 ) in the Raman spectrum (hereinafter, LiNiO2 / LiCoO2) were confirmed, and the results are shown in Table 1 below.

[0103]

Table 1

[0104] Referring to Table 1 above, when the Raman shift value of the peak corresponding to the A1g vibration mode of LiNiO2 in the Raman spectrum is 560 cm -1 or more (a preset value), the cathode active materials of Production Examples 5 and 6 were judged as good products.

[0105] On the other hand, for the cathode active materials of Production Examples 1 to 4 and Production Example 7, in all cases, the Raman shift value of the peak corresponding to the A1g vibration mode of LiNiO2 in the Raman spectrum was less than 560 cm -1 or more, so they were judged as defective products.

[0106] Furthermore, for the cathode active materials of Production Examples 5 and 6, it can be confirmed that the ratio of LiNiO2 / LiCoO2, which is the ratio of the intensity of the peak corresponding to the A1g vibration mode of LiCoO2 (550 cm -1 ~600 cm -1 ) to the intensity of the peak corresponding to the A1g vibration mode of LiNiO2 (500 cm -1 ~620 cm -1 ) in the Raman spectrum, is 0.3 or less.

[0107] Experimental Example: Battery Characteristic Evaluation (Manufacture of Half Cell) Each of the cathode active materials produced in Production Examples 1 to 7, carbon black (Denka Black, manufactured by Denka Co., Ltd.) conductive material, and PVdF (KF1300, manufactured by Kureha Corporation) binder were added to an N-methylpyrrolidone (NMP) (manufactured by DAEJUNG Chemical & Metals Co., Ltd.) solvent at a weight ratio of 95:3:2 to produce a composition for forming a cathode active material layer.

[0108] The composition for forming a positive electrode active material layer was applied to one surface of an aluminum foil current collector with a thickness of 20 μm, and dried at a temperature of 135 °C for 3 hours to form a positive electrode active material layer. Next, after rolling, it was rolled by a roll pressing method so that the porosity of the positive electrode active material layer became 20% by volume to manufacture a positive electrode.

[0109] A half-cell was manufactured using lithium metal as a negative electrode together with the positive electrode.

[0110] (Evaluation of battery cycle characteristics) Each of the half-cells manufactured above was charged at 25 °C with a constant current (CC) of 0.2C until it reached 4.25V, and then charged with a constant voltage (CV) of 4.25V until the charging current reached 0.05 mAh (cut-off current). After being left for 20 minutes, it was discharged at a constant current of 0.2C until it reached 2.5V.

[0111] Thereafter, the cell was transferred to a chamber at 45 °C and charged at a constant current of 0.33C until it reached 4.25V, and then charged with a constant voltage (CV) of 4.25V until the charging current reached 0.05 mAh (cut-off current). After that, discharging at a constant current of 0.33C until it reached 2.5V was defined as one cycle, and charge and discharge were performed 50 cycles. Here, the percentage of the DCIR value of the 50th cycle with respect to the DCIR value of the first cycle was defined as the resistance increase rate and shown in Table 2 below. For reference, the DCIR value of the nth cycle is a value calculated by dividing the difference in voltage between the fully charged state and when 10 seconds have elapsed since the start of discharging by the current while discharging at a constant current of 0.33C until it reaches 2.5V in the nth cycle.

[0112]

Table 2

[0113] As shown in Table 2 above, in the case of the positive electrode active materials of Production Examples 5 and 6 classified as good products by the quality evaluation method of the positive electrode active material of the present invention, the resistance increase rate of the battery containing the positive electrode active material is 140.0% or less, and it can be confirmed that it is significantly lower than the resistance increase rate of the batteries containing the positive electrode active materials of Production Examples 1 to 4 and 7.

[0114] Therefore, according to the present invention, it can be seen that by measuring the Raman spectrum of the surface of the positive electrode active material, it is possible to easily distinguish a positive electrode active material with poor quality. That is, it can be seen that it is possible to more easily select a good quality positive electrode active material that can improve the resistance performance of the lithium secondary battery. Further, it can be seen that the positive electrode active material according to the present invention can improve the resistance performance of the lithium secondary battery.

Claims

1. (A) When the Raman shift value of the peak corresponding to the A1g vibration mode of LiNiO in the Raman spectrum of the surface of the positive electrode active material meets the preset quality evaluation criteria for the positive electrode active material, it is judged as a good product, and when it does not meet the preset quality evaluation criteria for the positive electrode active material, it is judged as a defective product. The quality evaluation method of the positive electrode active material includes a first judgment step. ２ A quality evaluation method for a positive electrode active material, including a first judgment step of judging it as a good product when the Raman shift value of the peak corresponding to the A1g vibration mode of LiNiO in the Raman spectrum of the surface of the positive electrode active material meets the preset quality evaluation criteria for the positive electrode active material, and judging it as a defective product when it does not meet the preset quality evaluation criteria for the positive electrode active material.

2. Before the step (A), the method for evaluating the quality of a positive electrode active material according to claim 1, comprising the step of preparing a positive electrode active material in the form of single particles, the positive electrode active material in the form of single particles including a lithium transition metal oxide in the form of single particles and a coating portion containing cobalt formed on the lithium transition metal oxide in the form of single particles.

3. The method for evaluating the quality of a positive electrode active material according to claim 2, wherein the positive electrode active material in the form of single particles is produced by heat-treating a mixture of a lithium transition metal oxide in the form of single particles and a cobalt raw material.

4. In the step (A), the preset quality evaluation criteria for the positive electrode active material are that the Raman shift value of the peak corresponding to the A1g vibration mode of LiNiO ２ is 560 cm －１ or more. The method for evaluating the quality of the positive electrode active material according to claim 1.

5. (B) In the Raman spectrum of the surface of the positive electrode active material determined to be a good product in the step (A), the peak corresponding to the A1g vibration mode of LiNiO ２ If the ratio of the intensity of the peak (500 cm －１ to 600 cm －１ ) corresponding to the A1g vibration mode of LiCoO ２ to the intensity of the peak (550 cm －１ to 620 cm －１ ) corresponding to the A1g vibration mode is 0.3 or less, it is determined to be a good product, and if it exceeds 0.3, it further includes a second determination step of determining it to be a defective product. The method for evaluating the quality of the positive electrode active material according to claim 1.

6. (S1) A step of preparing a positive electrode active material in the form of single particles, the positive electrode active material in the form of single particles including a lithium transition metal oxide in the form of single particles and a coating portion containing cobalt formed on the lithium transition metal oxide in the form of single particles; (S2) A step of evaluating the quality of the positive electrode active material by the method according to any one of claims 1 to 5; (S3) A method for manufacturing a positive electrode, comprising the step of manufacturing a positive electrode using the positive electrode active material determined to be a good product.

7. The method for manufacturing a positive electrode according to claim 6, wherein the positive electrode active material in the form of single particles is produced by heat-treating a mixture of a lithium transition metal oxide in the form of single particles and a cobalt raw material.

8. The method for manufacturing a positive electrode according to claim 6, wherein the positive electrode active material in the form of single particles is produced by heat-treating a mixture of a lithium transition metal oxide in the form of single particles and a cobalt raw material at a temperature exceeding 720 °C and less than 780 °C.

9. Including a lithium transition metal oxide in the form of single particles and a coating portion containing cobalt formed on the lithium transition metal oxide in the form of single particles, The Raman shift value of the peak corresponding to the A1g vibration mode of LiNiO in the Raman spectrum of the surface of the positive electrode active material is 560 cm ２ or more, and the positive electrode active material is in a single particle form. －１ ​

10. The positive electrode active material in the form of single particles further includes island-shaped LiCoO discontinuously formed on the surface. ２ The positive electrode active material according to claim 9, further comprising ２ .

11. The peak corresponding to the A1g vibration mode of LiNiO in the Raman spectrum of the surface of the positive electrode active material ２ (500 cm －１ to 600 cm －１ ), and the ratio of the intensity of the peak corresponding to the A1g vibration mode of LiCoO ２ (550 cm －１ to 620 cm －１ ) is 0.3 or less. The positive electrode active material in the form of single particles according to claim 9.

12. The positive electrode active material in the single particle form has an average particle size (D ５０ ), which is from 0.1 μm to 10 μm, and is the positive electrode active material in the single particle form according to claim 9.

13. The positive electrode active material in the form of single particles according to claim 9, wherein the primary particles composed of 10 or fewer single crystal grains (grains) are aggregated in a form of 50 or fewer.

14. The positive electrode active material in the form of single particles according to claim 9, wherein the lithium transition metal oxide in the form of single particles is a lithium composite transition metal oxide containing nickel (Ni), cobalt (Co), and manganese (Mn).

15. The positive electrode active material in the form of single particles according to claim 9, wherein the lithium transition metal oxide in the form of single particles has a composition represented by the following Chemical Formula 1. [Chemical Formula 1] Li ａ Ni ｂ Co ｃ Mn ｄ M １ ｅ O ２ In the Chemical Formula 1, M １ is one or more selected from Al, Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, Sn, Y, Zn, F, P, and S, 0.9 ≤ a ≤ 1.1, 0.8 ≤ b < 1.0, 0 < c < 0.2, 0 < d < 0.2, 0 ≤ e ≤ 0.1, and b + c + d + e = 1.

16. The coating portion is a region from 5 nm to 100 nm in the central direction from the surface of the positive electrode active material, and the single-particle-shaped positive electrode active material according to Claim 9.

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