Method for manufacturing a positive electrode active material, a positive electrode active material, a positive electrode containing the same, and a lithium secondary battery

Abstract

A method for producing a positive electrode active material containing a lithium nickel-based composite oxide, wherein the performance of a lithium secondary battery at high temperature and high voltage is improved by introducing an optimal coating layer, thereby enhancing capacity characteristics, initial charge / discharge efficiency, and high-temperature life characteristics. [Solution] In one embodiment, a method for producing a positive electrode active material is provided, comprising the steps of (i) preparing core particles containing a lithium nickel composite oxide; (ii) adding the core particles to an aqueous solvent and mixing to adjust the pH of a first mixed solution to 5.5 to 7.5; (iii) adding an aluminum raw material to the first mixed solution and mixing to produce a second mixed solution; and (iv) removing the aqueous solvent from the second mixed solution to produce a dried product. A positive electrode active material and a lithium secondary battery to which the method for producing a positive electrode active material according to one embodiment is applied can exhibit high initial charge / discharge capacity and efficiency even under high voltage driving conditions, and can achieve long-life characteristics under high voltage and high temperature conditions.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a positive electrode active material, a positive electrode active material, a positive electrode containing the same, and a lithium secondary battery. [Background technology]

[0002] Lithium-ion batteries, which offer high energy density while being easily portable, are primarily used as power sources for mobile information terminals such as mobile phones, laptops, and smartphones. Recently, research has been actively conducted on using high-energy-density lithium-ion batteries as power sources or energy storage sources for hybrid and electric vehicles.

[0003] To realize lithium secondary batteries suitable for such applications, various cathode active materials are being investigated. Among these, lithium nickel-based oxides, lithium nickel manganese cobalt composite oxides, lithium nickel cobalt aluminum composite oxides, and lithium cobalt oxides are mainly used as cathode active materials. In recent years, with the rapid increase in demand for large, high-capacity, or high-energy-density lithium secondary batteries, there is a need to develop cathode active materials that simultaneously improve stability and performance. [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] A method for producing a positive electrode active material containing a lithium nickel-based composite oxide, wherein by introducing an optimal coating layer, the performance of lithium secondary batteries at high temperatures and high voltages is improved, and the capacity characteristics, initial charge-discharge efficiency, and high-temperature life characteristics are enhanced. [Means for solving the problem]

[0005] In one embodiment, a method for producing a positive electrode active material is provided, comprising the steps of (i) preparing core particles containing a lithium nickel-based composite oxide; (ii) adding the core particles to an aqueous solvent and mixing to adjust the pH of the first mixed solution to 5.5-7.5; (iii) adding an aluminum raw material to the first mixed solution and mixing to produce a second mixed solution; and (iv) removing the aqueous solvent from the second mixed solution to produce a dried product.

[0006] In another embodiment, a positive electrode active material produced by the above-described manufacturing method is provided.

[0007] In another embodiment, the positive electrode includes a positive electrode current collector and a positive electrode active material layer located on the positive electrode current collector, wherein the positive electrode active material layer provides a positive electrode containing the positive electrode active material.

[0008] In another embodiment, a lithium secondary battery comprising the positive electrode; negative electrode; and electrolyte is provided. [Effects of the Invention]

[0009] A positive electrode active material and a lithium secondary battery obtained by applying the positive electrode active material manufacturing method according to one embodiment can exhibit high initial charge / discharge capacity and efficiency even under high voltage driving conditions, and can achieve long-life characteristics under high voltage and high temperature conditions. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram showing a lithium secondary battery according to one embodiment. [Figure 2] This is a schematic diagram showing a lithium secondary battery according to one embodiment. [Figure 3] This is a schematic diagram showing a lithium secondary battery according to one embodiment. [Figure 4] This is a schematic diagram showing a lithium secondary battery according to one embodiment. [Figure 5]It is a scanning electron microscopy (SEM) image of the surface of the dried product manufactured in Example 1. [Figure 6] It is an SEM image of the surface of the dried product manufactured in Comparative Example 1. [Figure 7] It is an SEM image of the surface of the dried product manufactured in Comparative Example 2. [Figure 8] It is an SEM image of the surface of the dried product manufactured in Comparative Example 3. [Figure 9] It is an SEM image of the surface of the lithium nickel-based composite oxide manufactured in Comparative Example 4. [Figure 10] It is an SEM-EDS image showing aluminum in the cross-section of the dried product manufactured in Example 1. [[ID=十六]] [[ID=十七]] [Figure 11] It is an SEM-EDS image showing aluminum in the cross-section of the dried product manufactured in Comparative Example 1.

Mode for Carrying Out the Invention

[0011] Hereinafter, specific embodiments will be described in detail so that those having ordinary knowledge in this technical field can easily implement them. However, the present invention can be implemented in various different forms and is not limited to the embodiments described herein.

[0012] The terms used here are for the purpose of merely explaining exemplary embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates a different meaning.

[0013] Here, "these combinations" means a mixture, laminate, composite, copolymer, alloy, blend, reaction product, etc. of components.

[0014] Here, terms such as “include,” “equip,” or “possess” should be understood as intending to specify the existence of the implemented features, figures, stages, components, or combinations thereof, and not preemptively excluding the possibility of the existence or addition of one or more other features, figures, stages, components, or combinations thereof.

[0015] In the drawings, thickness is shown enlarged to clearly represent various layers and regions, and similar parts are given the same drawing reference numerals throughout the specification. When a layer, film, region, plate, or other part is said to be "on top of" or "on" another part, this includes not only when it is "directly above" the other part, but also when there is another part in between. Conversely, when a part is said to be "directly above" another part, it means that there is no other part in between.

[0016] Here, "layer" includes not only the shapes formed on the entire surface when observed in a plan view, but also the shapes formed on some of the surfaces.

[0017] The average particle size can be measured by methods known to those skilled in the art, for example, by a particle size analyzer, or by transmission electron microscope images or scanning electron microscope images. Alternatively, it can be measured using dynamic light scattering, and after performing data analysis to count the number of particles for each particle size range, the average particle size value can be calculated from there. Unless otherwise defined, the average particle size is the diameter (D) of the particle with a cumulative volume of 50% in the particle size distribution. 50 ) can mean. Also, unless otherwise defined, the average particle size is obtained by measuring the size (diameter or length of the long axis) of more than 20 random particles in a scanning electron microscope image to obtain a particle size distribution, and the diameter (D) of the particle whose cumulative volume is 50% in the said particle size distribution is the diameter of the particle (D 50 ) may be used as the average particle size.

[0018] Here, "or" is not interpreted as having an exclusive meaning; for example, "A or B" is interpreted as including A, B, A+B, etc.

[0019] Here, "metal" is interpreted as a concept that includes general metals, transition metals, and semimetals.

[0020] Method for manufacturing positive electrode active material In one embodiment, a method for producing a positive electrode active material is provided, comprising the steps of (i) preparing core particles containing a lithium nickel-based composite oxide; (ii) adding the core particles to an aqueous solvent and mixing to adjust the pH of the first mixed solution to 5.5-7.5; (iii) adding an aluminum raw material to the first mixed solution and mixing to produce a second mixed solution; and (iv) removing the aqueous solvent from the second mixed solution to produce a dried product.

[0021] When coating the particle surface of a positive electrode active material with aluminum to strengthen it, it is not easy to achieve a uniform coating of aluminum in a shell form on the particle surface because aluminum tends to diffuse into the interior of the particle. In one embodiment, we propose conditions under which aluminum can be uniformly coated on the particle surface without increasing resistance. A lithium secondary battery to which a positive electrode active material manufactured by the manufacturing method of the positive electrode active material according to one embodiment is applied has been confirmed to have improved initial charge / discharge capacity and efficiency under high voltage conditions, as well as improved high-temperature life characteristics, and also improved high-temperature storage characteristics.

[0022] The dried product can be described as a positive electrode active material in which aluminum is coated on the surface of the core particles. The method for producing the positive electrode active material may optionally further include a step of heat-treating the dried product after step (iv).

[0023] In a method for producing a positive electrode active material according to one embodiment, the step of preparing core particles containing a lithium nickel-based composite oxide may include the step of mixing a nickel-based composite hydroxide and a lithium raw material and performing a first heat treatment. The nickel-based composite hydroxide is a precursor of the core particles and may be in the form of secondary particles in which a plurality of primary particles are aggregated. The nickel-based composite hydroxide can be produced by a general coprecipitation method.

[0024] In the nickel-based composite hydroxide, the nickel content relative to 100 mol% of the total metal is 80 mol% or more, 85 mol% or more, 90 mol% or more, 91 mol% or more, or 94 mol% or more, and may be 99 mol% or less. When the nickel content satisfies the above range, high capacity can be achieved and structural safety can be enhanced.

[0025] In the nickel-based composite hydroxide, the cobalt content relative to 100 mol% of the total metal may be 8 mol% or less, for example, 0.1 mol% to 8 mol%, 1 mol% to 8 mol%, 3 mol% to 8 mol%, 3 mol% to 6 mol%, or 6 mol% to 8 mol%. When the cobalt content satisfies the above range, it is possible to improve the structural safety of the positive electrode active material while achieving high capacity.

[0026] The aforementioned nickel-based composite hydroxide can be represented, for example, by the following chemical formula 1. [Chemical formula 1] Ni x1 M1 y1 M2 z1 (OH)2

[0027] In chemical formula 1, 0.8 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 0.2, 0 ≤ z1 ≤ 0.2, and 0.9 ≤ x1 + y1 + z1 ≤ 1.1, and M1 and M2 are each independently one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, Y, V, W, Zn, and Zr, and M1 and M2 may be different elements from each other.

[0028] In chemical formula 1, 0.9≦x1<1, 0 <y1≦0.1、および0≦z1≦0.1であってもよい。

[0029] The nickel-based composite hydroxide is in particulate form, and the average particle size (D 50 The particle size may be 10 μm to 25 μm, for example, 11 μm to 20 μm, or 12 μm to 18 μm.

[0030] The nickel-based composite hydroxide and the lithium raw material can be mixed at a molar ratio of 1:0.9 to 1:1.8, for example, at a molar ratio of 1:0.9 to 1:1.5 or 1:1 to 1:1.2. The first heat treatment can be carried out in an oxygen atmosphere, for example, in a temperature range of 750°C to 950°C, or 780°C to 900°C, or 810°C to 890°C, and can be carried out for 2 hours to 20 hours, or 4 hours to 12 hours.

[0031] By the first heat treatment, a lithium nickel-based composite oxide can be obtained. The content of nickel with respect to 100 mol% of the total metal excluding lithium in the obtained lithium nickel-based composite oxide is 80 mol% or more, 85 mol% or more, 90 mol% or more, 91 mol% or more, or 94 mol% or more, and may be 99 mol% or less. When the content of nickel satisfies the above range, high capacity can be realized and the structural safety can be enhanced.

[0032] The content of cobalt with respect to 100 mol% of the total metal excluding lithium in the obtained lithium nickel-based composite oxide may be 8 mol% or less, for example, 0.1 mol% to 8 mol%, 1 mol% to 8 mol%, 3 mol% to 8 mol%, 3 mol% to 6 mol%, or 6 mol% to 8 mol%. When the content of cobalt satisfies the above range, the structural safety of the positive electrode active material can be enhanced while realizing high capacity.

[0033] The lithium nickel-based composite oxide is represented by the following Chemical Formula 2. [Chemical Formula 2] Li a2 Ni x2 M3 y2 M4 z2 O 2-b2 X b2

[0034] In chemical formula 2, 0.9 ≤ a² ≤ 1.8, 0.8 ≤ x² ≤ 1, 0 ≤ y² ≤ 0.2, 0 ≤ z² ≤ 0.2, 0.9 ≤ x² + y² + z² ≤ 1.1, and 0 ≤ b² ≤ 0.1. M3 and M4 are each independently one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, Y, V, W, Zn, and Zr. M3 and M4 may be different elements from each other, and X is one or more elements selected from the group consisting of F, P, and S.

[0035] In chemical formula 2, 0.9≦x2<1, 0 <y2≦0.1、および0≦z2≦0.1であってもよい。

[0036] In one embodiment, the lithium content remaining on the surface of the core particles relative to 100% by weight of the entire core particle may be 0.4% by weight or more, for example, 0.4% to 0.8% by weight. Specifically, the LiOH content remaining on the surface of the core particles relative to 100% by weight of the entire core particle may be 1.0% by weight or more, for example, 1.0% to 2.0% by weight, and the Li2CO3 content remaining on the surface of the core particles relative to 100% by weight of the entire core particle may be 0.6% by weight or more, for example, 0.6% to 1.0% by weight. The residual lithium content, LiOH content, and Li2CO3 content may be measured by HCl titration.

[0037] The aforementioned lithium nickel-based composite oxide differs significantly from oxides of other compositions, such as lithium nickel-cobalt-manganese composite oxides, lithium nickel-cobalt-aluminum composite oxides, and lithium cobalt-based oxides, in terms of residual lithium content on the particle surface. As a result, various surface properties differ, making it impossible to form a good coating layer with a uniform film morphology using conventional coating methods. In one embodiment, we propose a method for very uniformly coating the particle surface of a lithium nickel-based composite oxide having the aforementioned residual lithium content with aluminum.

[0038] In one embodiment, the core particles are first added to an aqueous solvent and mixed to produce a first mixed solution. The pH of the first mixed solution is then adjusted to 5.5-7.5 to appropriately adjust the residual lithium content on the surface of the core particles. Subsequently, an aluminum raw material is added to the first mixed solution and mixed to produce a second mixed solution. After that, the aqueous solvent is removed from the second mixed solution to produce a dried product, and the dried product can be heat-treated to form a coating layer on the surface of the core particles. Unlike the pre-addition method, in which the salt, which is the coating raw material, is completely dissolved first before adding the positive electrode active material particles, this method applies optimal conditions for forming a uniform aluminum coating layer on the lithium nickel composite oxide by washing the high-nickel positive electrode active material with an aqueous solvent whose pH has been adjusted to neutral, thereby lowering the residual lithium content on the surface, and then performing an aluminum coating.

[0039] The aqueous solvent may include distilled water, an alcoholic solvent, or a combination thereof. The aluminum raw material may be aluminum sulfate, aluminum nitrate, or a combination thereof, and for example, aluminum sulfate. Aluminum sulfate is an optimal raw material for forming a uniform aluminum coating layer on a lithium nickel composite oxide.

[0040] The aluminum content in the aluminum raw material can be set to 0.1 mol% to 2.0 mol%, relative to 100 mol% of the total metal (excluding lithium) from the core particles and the total aluminum in the aluminum raw material. For example, it can be set to 0.5 mol% to 2.0 mol%, 0.5 mol% to 1.5 mol%, or 1.0 mol% to 1.5 mol%. By setting the aluminum content within this range, a thin coating layer with a uniform thickness at the level of tens to hundreds of nanometers can be formed, reducing the amount of gas generated in the lithium secondary battery under high voltage or high temperature operating conditions, thereby improving high capacity and long life characteristics.

[0041] The time required to add the core particles to the aqueous solvent may be 1 second / 500g to 2 minutes / 500g, or for example, 1 second / 500g to 1.5 minutes / 500g. By appropriately adjusting the rate at which the core particles are added, the pH of the supernatant after coating is complete can be appropriately adjusted, thereby enabling the effective formation of the aluminum coating layer according to one embodiment. If the rate at which the core particles are added is too fast, the pH of the supernatant after coating is complete will rise and become basic, which may prevent the formation of a uniform coating layer. Conversely, if the rate at which the core particles are added is too slow, the pH of the supernatant will become low and acidic, which may also prevent the formation of a uniform coating layer. The time for stirring after all the core particles have been added to the aqueous solvent may be about 15 minutes to 60 minutes, or for example, 20 minutes to 50 minutes, or 30 minutes to 45 minutes. The time from the start of adding the core particles to the aqueous solvent to the completion of stirring can be appropriately adjusted to within about 1 hour.

[0042] Step (ii) of adjusting the pH of the first mixed solution, obtained by adding and mixing core particles in an aqueous solvent, to 5.5 to 7.5 is performed by adding an acidic aqueous solution. For example, after adding and mixing the core particles in the aqueous solvent, an acidic aqueous solution can be added and mixed. As the acidic aqueous solution, for example, hydrochloric acid aqueous solution, sulfuric acid aqueous solution, or nitric acid aqueous solution can be used, but hydrochloric acid aqueous solution is most preferred. The pH of the first mixed solution can be adjusted to 5.5 to 7.5 using an acidic aqueous solution, for example, to 6.0 to 7.5 or 6.5 to 7.5. When the pH of the first mixed solution is adjusted to the above range, it is easy to form a uniform aluminum coating layer on the lithium nickel composite oxide by lowering the residual lithium content on the surface and then performing an aluminum coating.

[0043] After adding the aluminum raw material to the pH-adjusted first mixed solution, the stirring time is 1 to 60 minutes, for example, 3 to 30 minutes or 5 to 10 minutes. The mixing speed may be 100 rpm to 800 rpm, for example, 200 rpm to 600 rpm or 250 rpm to 500 rpm. Under these mixing conditions, the aluminum raw material can be completely dissolved in the aqueous solvent, and a uniform aluminum coating layer according to one embodiment can be effectively formed.

[0044] In one embodiment, when the aluminum raw material is added to the first mixed solution and mixing is stopped, the pH range of the supernatant of the second mixed solution is 5.5 to 7.5, for example, 6.0 to 7.5 or 6.5 to 7.5. If the pH of the supernatant is less than 5.5, it becomes too acidic, and a uniform coating layer may not be formed. If the pH exceeds 7.5, it becomes too basic, and in this case as well, it becomes difficult to form a uniform aluminum coating layer.

[0045] After removing the aqueous solvent from the second mixed solution, the drying process can be carried out at temperatures such as 40°C to 240°C, 100°C to 220°C, or 150°C to 200°C, and can also be performed under vacuum conditions, which can yield a good quality dried product.

[0046] The dried product comprises core particles and a coating layer located on the surface of the core particles, which contains aluminum. For example, the coating layer may have a fibrous structure, such as a spiderweb or mesh structure. Such a mesh may be formed continuously across the entire surface of the core particles. The mesh-shaped coating layer can encase the core particles with a very thin and uniform thickness, thereby strengthening the surface of the positive electrode active material, improving structural stability, and enhancing high-temperature and high-voltage characteristics.

[0047] In one embodiment, the aluminum content relative to 100 at% of the total of nickel, cobalt, and aluminum, as measured by energy profiling energy-dispersive spectroscopy (EP-EDS) on the surface of the dried product, may be 35 at% to 45 at%. The method for producing the positive electrode active material according to one embodiment may further include a step of heat-treating the dried product. If the mixing of the aforementioned nickel-based composite hydroxide and lithium raw material and heat treatment is referred to as the first heat treatment, then the heat treatment of the dried product can be referred to as the second heat treatment. The second heat treatment is performed, for example, in an oxygen atmosphere at a temperature range of 700°C to 850°C, 750°C to 840°C, or 800°C to 830°C for 2 to 20 hours, or 3 to 10 hours. When the second heat treatment temperature is set within the above range, the tendency of aluminum to diffuse into the interior of secondary particles decreases, and it mainly remains on the surface of the secondary particles, and at the same time, it is coated on the surface of the secondary particles in a very thin and uniform shell form.

[0048] In one embodiment, the coating layer may be in the form of a film that continuously encloses the surface of the core particles, or it may be in the form of a shell that encloses the entire surface of the core particles. This is distinct from a structure in which only a part of the surface of the core particles is partially coated. According to one embodiment, the coating layer is formed to enclose the entire surface of the core particles with a very thin and uniform thickness, thereby improving the structural stability of the positive electrode active material without increasing resistance or decreasing capacity, effectively suppressing side reactions with the electrolyte, and reducing gas generation under high voltage and high temperature conditions, thereby achieving long-life characteristics.

[0049] In one embodiment, the thickness of the coating layer may be 5 nm to 200 nm, for example, 5 nm to 150 nm, 5 nm to 100 nm, 5 nm to 80 nm, 5 nm to 50 nm, or 10 nm to 50 nm. When the coating layer satisfies the above thickness range, the coating does not increase resistance or decrease capacitance, improving the structural stability of the positive electrode active material and effectively suppressing side reactions with the electrolyte. The thickness of the coating layer can be measured by, for example, SEM, TEM, TOF-SIMS, XPS, or EDS analysis, and as an example, it can be measured by EDS line profile analysis of the cross-section of the positive electrode active material.

[0050] One embodiment of the coating layer is characterized by being thin, at the level of tens to hundreds of nanometers, and having a uniform thickness. For example, the thickness deviation of the coating layer within a single positive electrode active material particle may be 20% or less, 18% or less, or 15% or less. Here, the thickness deviation of the coating layer refers to the thickness of the coating layer within a single positive electrode active material particle. The thickness deviation of the coating layer can be, for example, calculated by measuring the thickness of more than 10 points from an electron microscope image of the cross-section of a single positive electrode active material particle, calculating the arithmetic mean, dividing the absolute value of the difference between one data point and the arithmetic mean by the arithmetic mean, and then multiplying by 100. When the thickness deviation or standard deviation of the coating layer satisfies the above range, it means that a coating layer of uniform thickness is formed in a good form on the surface of the positive electrode active material particle, thereby improving the structural stability of the positive electrode active material, effectively suppressing side reactions with the electrolyte, and minimizing resistance increase and capacity decrease due to the coating.

[0051] On the other hand, the coating layer may further contain nickel, cobalt, or a combination thereof, in addition to aluminum. The nickel and cobalt may be those that were contained in the core particles and flowed in during the coating layer formation process, and their content is not particularly limited. A coating layer according to one embodiment contains aluminum as an essential component and selectively contains nickel and cobalt, is formed to a thin and uniform thickness, and can improve the high-voltage characteristics of the positive electrode active material and enhance its lifespan.

[0052] Furthermore, the coating layer may contain chlorine in addition to aluminum. The chlorine may be introduced during the process of adding hydrochloric acid aqueous solution to the acidic aqueous solution used to form the coating layer, and the chlorine content may be 0.1% by weight or more relative to 100% by weight of the total positive electrode active material, for example, 0.1% to 0.3% by weight. That is, the chlorine content relative to the total weight of the positive electrode active material may be 1000 ppm or more, for example, 1000 ppm to 3000 ppm. The coating layer according to one embodiment contains aluminum as an essential component and selectively contains chlorine, which can improve the high-voltage characteristics of the positive electrode active material and enhance its lifespan. The chlorine content may be measured by inductively coupled plasma spectroscopy (ICP) of the positive electrode active material.

[0053] The resulting positive electrode active material can be described as comprising core particles containing a lithium nickel-based composite oxide, and a coating layer located on the surface of the core particles that contains aluminum oxide, lithium-aluminum oxide, or a combination thereof.

[0054] positive electrode active material In one embodiment, a positive electrode active material produced by the method for producing the positive electrode active material described above is provided. By introducing a coating layer containing aluminum in a specific amount on the surface of core particles containing lithium nickel-based composite oxide, a stable structure can be maintained even at high voltages, achieving high capacity, long lifespan characteristics, and improved high-temperature storage characteristics.

[0055] core particle The core particles contain a lithium nickel-based composite oxide, which is represented by the chemical formula 2.

[0056] The nickel content of the lithium-nickel composite oxide, relative to 100 mol% of the total metal excluding lithium, is 80 mol% or more, 85 mol% or more, 90 mol% or more, 91 mol% or more, or 94 mol% or more, and may be 99 mol% or less. When the nickel content satisfies the above range, high capacity can be achieved and structural safety can be enhanced.

[0057] The cobalt content in the lithium nickel-based composite oxide, relative to 100 mol% of the total metal excluding lithium, may be 8 mol% or less, for example, 0.1 mol% to 8 mol%, 1 mol% to 8 mol%, 3 mol% to 8 mol%, 3 mol% to 6 mol%, or 6 mol% to 8 mol%. When the cobalt content satisfies the above range, the structural safety of the positive electrode active material can be enhanced while achieving high capacity.

[0058] The core particles may be in the form of secondary particles formed by the aggregation of multiple primary particles. The secondary particles may be spherical, ellipsoidal, polyhedronal, or irregular in shape, and the primary particles may be spherical, ellipsoidal, plate-shaped, or a combination thereof.

[0059] Average particle size of core particles (D 50 The particle size (D) may be 10 μm to 25 μm, for example, 11 μm to 20 μm, or 12 μm to 18 μm. Here, the average particle size (D) 50 The particle size may be obtained by randomly measuring the size (diameter or length of the major axis) of more than 20 particles from scanning electron microscope images of the positive electrode active material to obtain a particle size distribution, and then taking the diameter of the particle with a cumulative volume of 50% from the particle size distribution as the average particle size. When the average particle size of the core particles satisfies the above range, high capacity and long life can be achieved, which is advantageous for forming a coating layer according to one embodiment.

[0060] The aforementioned core particles are susceptible to chemical attack from components within the electrolyte when the battery is operated under high voltage or high temperature conditions, leading to numerous side reactions with the electrolyte. This results in increased gas generation, which reduces battery life and safety. However, this problem can be resolved by introducing a coating layer according to one embodiment described later.

[0061] coating layer In one embodiment, the positive electrode active material is located on the surface of the core particles and includes a coating layer containing aluminum. The aluminum content may be 35 at% to 45 at% relative to 100 at% of the total nickel, cobalt, and aluminum measured by energy profiling energy dispersive spectroscopy (EP-EDS) on the surface of the positive electrode active material. Furthermore, the chlorine content may be 0.1% by weight or more relative to 100% by weight of the entire positive electrode active material.

[0062] As explained above, a detailed explanation of the coating layer will be omitted.

[0063] positive electrode In one embodiment, the positive electrode includes a positive electrode current collector and a positive electrode active material layer located on the positive electrode current collector, wherein the positive electrode active material layer provides a positive electrode containing the aforementioned positive electrode active material. The positive electrode active material layer may further contain other types of positive electrode active materials in addition to the aforementioned positive electrode active material. The positive electrode active material layer may also selectively further contain a binder, a conductive material, or a combination thereof.

[0064] binder The binder plays a role in ensuring that the positive electrode active material particles adhere well to each other and that the positive electrode active material adheres well to the current collector. Typical examples of binders include, but are not limited to, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, and nylon.

[0065] conductive material Conductive materials are used to impart conductivity to electrodes, and any electronically conductive material that does not undergo chemical changes can be used in the battery that is constructed from them. Examples of conductive materials include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjenblack, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic materials containing copper, nickel, aluminum, silver, etc., in the form of metal powders or metal fibers; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0066] The content of the binder and conductive material may be 0.5% to 5% by weight, respectively, based on 100% by weight of the positive electrode active material layer.

[0067] Al can be used as the positive electrode current collector, but it is not limited to this.

[0068] Lithium-ion battery In one embodiment, a lithium secondary battery is provided that includes the positive electrode, negative electrode, and electrolyte described above. As an example, the lithium secondary battery may include a positive electrode, a negative electrode, a separator located between the positive electrode and the negative electrode, and an electrolyte.

[0069] Lithium secondary batteries can be classified into cylindrical, prismatic, pouch-type, coin-type, and other types depending on their form. Figures 1 to 4 are schematic diagrams showing a lithium secondary battery according to one embodiment, with Figure 1 being cylindrical, Figure 2 being prismatic, and Figures 3 and 4 being pouch-type batteries. Referring to Figures 1 to 4, the lithium secondary battery 100 may include an electrode assembly 40 with a separator 30 interposed between a positive electrode 10 and a negative electrode 20, and a case 50 in which the electrode assembly 40 is housed. The positive electrode 10, negative electrode 20, and separator 30 are impregnated with an electrolyte (not shown). The lithium secondary battery 100 may include a sealing member 60 that seals the case 50, as shown in Figure 1. Also, in Figure 2, the lithium secondary battery 100 may include a positive electrode lead tab 11 and a positive electrode terminal 12, a negative electrode lead tab 21, and a negative electrode terminal 22. As shown in Figures 3 and 4, the lithium secondary battery 100 may include electrode tabs 70, namely a positive electrode tab 71 and a negative electrode tab 72, which serve as electrical pathways for guiding the current formed in the electrode assembly 40 to the outside.

[0070] negative electrode The negative electrode may include a current collector and a negative electrode active material layer located on the current collector, the negative electrode active material layer including a negative electrode active material and may further include a binder, a conductive material, or a combination thereof.

[0071] negative electrode active material The negative electrode active material includes a substance capable of reversibly inserting / de-inserting lithium ions, lithium metal, an alloy of lithium metal, a lithium-doped and de-doped substance, or a transition metal oxide.

[0072] The material capable of reversibly inserting / deinserting lithium ions is a carbon-based anode active material, which may include, for example, crystalline carbon, amorphous carbon, or a combination thereof. Examples of crystalline carbon include graphite such as amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, while examples of amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, and calcined coke.

[0073] As the alloy of the lithium metal, an alloy of lithium and a metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn is used.

[0074] As the substance capable of doping and undoping lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material can be used. As the Si-based negative electrode active material, silicon, a silicon-carbon composite, SiOx (0 < x ≦ 2), a Si-Q alloy (where Q is an element selected from alkali metals, alkaline earth metals, group 13 elements, group 14 elements (excluding Si), group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof, for example, Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof), or a combination thereof may be used. As the Sn-based negative electrode active material, Sn, SnO2, a Sn alloy, or a combination thereof may be used.

[0075] The silicon-carbon composite may be a composite of silicon and amorphous carbon. The average particle diameter (D 50 ) of the silicon-carbon composite particles may be, for example, 0.5 μm to 20 μm. According to one embodiment, the silicon-carbon composite may be in a form in which silicon particles are coated with amorphous carbon on the surface of the silicon particles. For example, it may include secondary particles (cores) formed by granulating primary silicon particles and an amorphous carbon coating layer (shell) located on the surface of the secondary particles. The amorphous carbon may also be located between the primary silicon particles, and for example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be present dispersed in an amorphous carbon matrix.

[0076] The silicon-carbon composite may further contain crystalline carbon. For example, the silicon-carbon composite may include a core containing crystalline carbon and silicon particles and an amorphous carbon coating layer located on the surface of the core. The crystalline carbon may be artificial graphite, natural graphite, or a combination thereof. Examples of the amorphous carbon include soft carbon, hard carbon, mesophase pitch carbide, and calcined coke.

[0077] When the silicon-carbon composite contains silicon and amorphous carbon, the content of silicon may be 10% to 50% by weight based on 100% by weight of the silicon-carbon composite, and the content of amorphous carbon may be 50% to 90% by weight. When the composite contains silicon, amorphous carbon, and crystalline carbon, the content of silicon may be 10% to 50% by weight based on 100% by weight of the silicon-carbon composite, the content of crystalline carbon may be 10% to 70% by weight, and the content of amorphous carbon may be 20% to 40% by weight.

[0078] In addition, the thickness of the amorphous carbon coating layer may be 5 nm to 100 nm. The average particle size (D 50 ) of the silicon particles (primary particles) may be 10 nm to 1 μm, or 10 nm to 200 nm. The silicon particles may exist alone as silicon, in the form of a silicon alloy, or in an oxidized form. The oxidized form of silicon is represented by SiOx (0 < x ≤ 2). At this time, the atomic content ratio of Si:O indicating the degree of oxidation may be 99:1 to 33:67. In this specification, unless otherwise defined, the average particle size (D 50 ) means the diameter of the particle with a cumulative volume of 50% by volume in the particle size distribution.

[0079] The Si-based negative electrode active material or the Sn-based negative electrode active material can be used by mixing with a carbon-based negative electrode active material. When the Si-based negative electrode active material or the Sn-based negative electrode active material and the carbon-based negative electrode active material are used in combination, the mixing ratio may be 1:99 to 90:10 by weight.

[0080] binder The binder plays a role in ensuring that the negative electrode active material particles adhere well to each other and that the negative electrode active material adheres well to the current collector. As the binder, a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof can be used.

[0081] Examples of non-aqueous binders include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyimide, or combinations thereof.

[0082] The water-based binder may be selected from styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0083] When using an aqueous binder as the negative electrode binder, it may further contain a cellulosic compound that can impart viscosity. This cellulosic compound can be a mixture of one or more carboxymethylcellulose, hydroxypropylmethylcellulose, methylcellulose, or alkali metal salts thereof. The alkali metal can be Na, K, or Li.

[0084] The dry binder is a polymeric substance that can be formed into fibers, and may be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0085] conductive material Conductive materials are used to impart conductivity to electrodes, and any electronically conductive material that does not undergo chemical changes in the battery that is constructed can be used. Specific examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjenblack, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic materials containing copper, nickel, aluminum, silver, etc., in the form of metal powders or metal fibers; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0086] The content of the negative electrode active material may be 95% to 99.5% by weight relative to 100% by weight of the negative electrode active material layer, and the content of the binder may be 0.5% to 5% by weight relative to 100% by weight of the negative electrode active material layer. For example, the negative electrode active material layer may contain 90% to 99% by weight of the negative electrode active material, 0.5% to 5% by weight of the binder, and 0.5% to 5% by weight of the conductive material.

[0087] Current collector The negative electrode current collector may include, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or alloys thereof, and may be in the form of foil, sheet, or foam. The thickness of the negative electrode current collector may be, for example, 1 μm to 20 μm, 5 μm to 15 μm, or 7 μm to 10 μm.

[0088] electrolyte The electrolyte for lithium secondary batteries may, for example, be an electrolyte solution, which may contain a non-aqueous organic solvent and a lithium salt.

[0089] Non-aqueous organic solvents act as a medium through which ions involved in the electrochemical reactions of the battery can move. Non-aqueous organic solvents may be carbonate-based, ester-based, ether-based, ketone-based, or alcohol-based solvents, aprotic solvents, or combinations thereof.

[0090] As carbonate-based solvents, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC) can be used. As ester-based solvents, methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, and caprolactone can be used. As ether-based solvents, dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and tetrahydrofuran can be used. Furthermore, ketone solvents such as cyclohexanone can be used. As alcoholic solvents, ethyl alcohol and isopropyl alcohol can be used, and as aprotic solvents, nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, and can include double bonds, aromatic rings, or ether groups); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane and 1,4-dioxolane; and sulfolanes can be used.

[0091] Non-aqueous organic solvents can be used alone or in combination of two or more, and the mixing ratio when using two or more can be appropriately adjusted according to the desired battery performance, which is widely understood by those working in the field.

[0092] When using carbonate-based solvents, cyclic carbonates and linear carbonates can be mixed, and the cyclic carbonates and linear carbonates can be mixed in a volume ratio of 1:1 to 1:9.

[0093] Non-aqueous organic solvents may further include aromatic hydrocarbon organic solvents. For example, carbonate solvents and aromatic hydrocarbon organic solvents can be mixed and used in a volume ratio of 1:1 to 30:1.

[0094] The electrolyte may further contain vinyl ethyl carbonate, vinylene carbonate, or ethylene carbonate compounds to improve battery life.

[0095] Typical examples of the aforementioned ethylene carbonate compounds include fluoroethylene carbonate, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, and cyanoethylene carbonate.

[0096] Lithium salts are substances that dissolve in organic solvents and act as a source of lithium ions in batteries, enabling the operation of basic lithium secondary batteries and facilitating the movement of lithium ions between the positive and negative electrodes. Typical examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide; LiFSI), LiC4F9SO3, and LiN(C x F 2x+1 SO2)(C y F2y+1 It may contain one or more selected from SO2) (where x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalate)phosphate (LiDFBOP), and lithium bis(oxalate) borate (LiBOB).

[0097] The lithium salt concentration is preferably used within the range of 0.1 M to 2.0 M. When the lithium salt concentration falls within this range, the electrolyte has appropriate ionic conductivity and viscosity, resulting in excellent performance and effective lithium ion movement.

[0098] Separator Depending on the type of lithium secondary battery, a separator may be present between the positive and negative electrodes. Such separators can be made of polyethylene, polypropylene, polyvinylidene fluoride, or multilayer films of two or more layers of these materials. Mixed multilayer films such as polyethylene / polypropylene two-layer separators, polyethylene / polypropylene / polyethylene three-layer separators, and polypropylene / polyethylene / polypropylene three-layer separators can also be used.

[0099] The separator may include a porous substrate and a coating layer comprising organic, inorganic, or a combination thereof located on one or both sides of the porous substrate.

[0100] The porous substrate may be a polymer film formed from one polymer selected from polyethylene, polyolefins such as polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyacetal, polyamide, polyimide, polycarbonate, polyetherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene oxide, cyclic olefin copolymer, polyphenylene sulfide, polyethylene naphthalate, glass fiber, and polytetrafluoroethylene (e.g., Teflon®), or from a copolymer or mixture of two or more of these polymers.

[0101] The porous substrate can have a thickness of approximately 1 μm to 40 μm, for example, 1 μm to 30 μm, 1 μm to 20 μm, 5 μm to 15 μm, or 10 μm to 15 μm.

[0102] The organic material may include a (meth)acrylic copolymer comprising a first structural unit derived from (meth)acrylamide, and a second structural unit comprising at least one of a structural unit derived from (meth)acrylic acid or (meth)acrylate and a structural unit derived from (meth)acrylamide sulfonic acid or a salt thereof.

[0103] The inorganic material may include, but is not limited to, inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof. The average particle size (D) of the inorganic particles is 50 The wavelength range may be 1 nm to 2000 nm, for example, 100 nm to 1000 nm or 100 nm to 700 nm.

[0104] The organic and inorganic materials can exist mixed together in a single coating layer, or in a form where a coating layer containing organic materials and a coating layer containing inorganic materials are stacked on top of each other.

[0105] The thickness of the coating layer may be 0.5 μm to 20 μm, for example, 1 μm to 10 μm, or 1 μm to 5 μm.

[0106] Examples and comparative examples of the present invention are described below. However, the following examples are merely illustrative examples of the present invention, and the present invention is not limited to the following examples.

[0107] Example 1 Ni 0.91 Co 0.075 Al 0.015 (OH)2 and LiOH are mixed in a molar ratio of 1:1.03 and subjected to a first heat treatment at 775°C for 15 hours in an oxygen atmosphere, resulting in a composition of Li 1.03 Ni 0.91 Co 0.075 Al 0.015 It is O2 and the average particle size (D 50 ) manufactured lithium nickel-based composite oxides in the form of secondary particles approximately 14 μm in size.

[0108] The residual lithium in the manufactured lithium nickel-based composite oxide was measured by HCl titration. The content of Li2CO3 and LiOH was calculated from EP1 (Equivalence Point 1) and EP2 (Equivalence Point 2) obtained by HCl injection, and the total residual lithium was calculated from EP2. As a result, the content of LiOH was confirmed to be 16370 ppm, Li2CO3 8500 ppm, and the residual lithium content was confirmed to be 6350 ppm.

[0109] 600 g of distilled water and 500 g of the prepared lithium nickel-based composite oxide were added to a 1 L reactor over 10 seconds, and the mixture was stirred for about 30 minutes to produce the first mixed solution. The pH of the first mixed solution was measured to be 13, and HCl was added to the first mixed solution to adjust its pH to 7.0. Then, aluminum sulfate was added to the first mixed solution, and the mixture was stirred at approximately 350 rpm for about 5 minutes to dissolve the salt and produce the second mixed solution. At this time, the aluminum content in the aluminum sulfate was set to 1.0 mol% relative to 100 mol% of the total metal excluding lithium from the final cathode active material. The pH of the supernatant after stirring was confirmed to be 7. Subsequently, the solvent was removed from the second mixed solution using an aspirator and a filter press, and the dried product was obtained by vacuum drying at 190°C.

[0110] Comparative Example 1 The dried product was prepared in substantially the same manner as in Example 1, except that the step of adding HCl to the first mixed solution to adjust the pH of the first mixed solution to 7.0 was omitted.

[0111] Comparative Example 2 The dried product was manufactured in substantially the same manner as in Example 1, except that the lithium nickel-based composite oxide produced in Example 1 was used and a dry coating method using aluminum oxide was applied.

[0112] More specifically, the lithium nickel-based composite oxide produced in Example 1 was mixed with aluminum oxide, and the mixture was heat-treated in an oxygen atmosphere at 710°C for 13 hours to produce an aluminum coating. At this time, the aluminum content in the aluminum oxide was designed to be 1.0 mol% relative to 100 mol% of the total metal content excluding lithium from the dry product.

[0113] Comparative Example 3 The dried product was produced in substantially the same manner as in Example 1, except that the lithium nickel-based composite oxide produced in Example 1 was used to prepare an aluminum sulfate solution, and then the lithium nickel-based composite oxide was added to the aluminum sulfate solution and the dried product was produced by applying a pre-addition-wet coating method.

[0114] More specifically, 600g of distilled water and aluminum sulfate were added to a 1L reactor, and the mixture was stirred at approximately 350 rpm for about 5 minutes to dissolve the salt and produce a coating solution. It was confirmed that the salt was completely dissolved in the coating solution and that it was colorless and transparent. 500g of the prepared lithium nickel-based composite oxide was added to the coating solution over 1.5 minutes while it was being continuously stirred, and the mixture was stirred for about 30 minutes. At this time, the aluminum content in the aluminum sulfate was set to 1.0 mol% relative to 100 mol% of the total metal content excluding lithium from the dry product. The pH of the supernatant after stirring was confirmed to be 12.

[0115] The solvent was removed from the mixed solution using an aspirator and filter press, and the coated product was obtained by vacuum drying at 190°C.

[0116] Comparative Example 4 The lithium nickel-based composite oxide produced in Example 1 was used.

[0117] Evaluation Example 1: Surface Analysis of Cathode Active Material The dried products produced in the examples and comparative examples were compared using a scanning electron microscope (SEM). The SEM was performed using a Helios G4 HX under the conditions of HT: 3kV, current: 0.8nA, and live time: 90s. Figure 5 is an SEM image of the surface of the dried product according to Example 1. Figure 6 is an SEM image of the surface of the dried product according to Comparative Example 1. Figure 7 is an SEM image of the surface of the dried product according to Comparative Example 2. Figure 8 is an SEM image of the surface of the dried product according to Comparative Example 3. Figure 9 is an SEM image of the surface of the lithium nickel-based composite oxide according to Comparative Example 4.

[0118] Referring to Figures 5 to 9, a uniform mesh-like or spiderweb-like aluminum coating layer can be observed on the surface of the dried product according to Example 1, while the coating layer on the surface of the dried product according to Comparative Example 1, in which the pH of the first mixed solution was not adjusted, was found to be unevenly formed. Furthermore, the coating layers on the surface of the dried product according to Comparative Example 2, which underwent dry coating, the surface of the dried product according to Comparative Example 3, which underwent pre-added-wet coating, and the surface of the lithium nickel-based composite oxide according to Comparative Example 4, in which no coating layer was formed, were also found to be unevenly formed.

[0119] Evaluation Example 2: Cross-sectional Analysis of Cathode Active Material The aluminum coating state was confirmed using SEM-EDS mapping on cross-sections obtained by cutting the dried products prepared in the examples and comparative examples with a focused ion beam (FIB). SEM-EDS was performed using a Helios G4 HX under the conditions of HT: 3kV, current: 0.8nA, and live time: 90s.

[0120] Figure 10 is an SEM-EDS image showing aluminum in a cross-section of the dried product manufactured in Example 1, and Figure 11 is an SEM-EDS image showing aluminum in a cross-section of the dried product manufactured in Comparative Example 1.

[0121] Referring to Figures 10 and 11, it can be seen from the cross-section of the dried product produced in Example 1, where the aluminum post-addition wet coating was performed with pH adjustment, that a clear aluminum coating layer was formed on the surface of the particles. In contrast, it can be seen from the cross-section of the dried product produced in Comparative Example 1, where the aluminum post-addition wet coating was performed without pH adjustment, that the aluminum coating layer was formed unevenly.

[0122] Evaluation Example 3: Analysis of aluminum content on the surface of the positive electrode active material The aluminum content on the surface of the dried products prepared in the examples and comparative examples was analyzed by energy profiling energy-dispersive spectroscopy (EP-EDS), and the results are shown in Table 1 below. EP-EDS was confirmed using an Ultim (100mm2 Detector) under the conditions of HT: 3kV, current: 0.8nA, and live time: 90s.

[0123] Evaluation Example 4: ICP Composition The Cl, Na, and S content of the dried products prepared in the examples and comparative examples was measured by inductively coupled plasma (ICP) spectroscopy, and the results are shown in Table 1 below.

[0124] [Table 1]

[0125] Referring to Table 1, it can be confirmed that the aluminum content relative to 100 at% of the total nickel, cobalt, and aluminum on the surface of the dried product in Example 1, where aluminum post-addition wet coating was performed with pH adjustment, is higher than the aluminum content relative to 100 at% of the total nickel, cobalt, and aluminum on the surface in Comparative Example 1, where aluminum post-addition wet coating was performed without pH adjustment; Comparative Example 2, where dry coating was performed; Comparative Example 3, where aluminum pre-addition wet coating was performed; and Comparative Example 4, where no coating was performed.

[0126] Furthermore, while the chlorine content in Example 1, where aluminum post-addition wet coating was performed with pH adjustment, was 0.1% by weight of the total dry product (100% by weight), it can be confirmed that the chlorine content in Comparative Example 1, where aluminum post-addition wet coating was performed without pH adjustment, Comparative Example 2, where dry coating was performed, Comparative Example 3, where aluminum pre-addition wet coating was performed, and Comparative Example 4, where no coating was performed, was less than 0.1% by weight of the total coated product or lithium nickel-based composite oxide (100% by weight).

[0127] Although preferred embodiments have been described in detail above, the scope of the present invention is not limited thereto. Various modifications and improvements by those skilled in the art, utilizing the basic concepts defined in the claims, also fall within the scope of the present invention. [Explanation of Symbols]

[0128] 100: Lithium-ion rechargeable battery 10: Positive electrode 11: Positive lead tab 12: Positive terminal 20: Negative electrode 21: Negative lead tab 22: Negative terminal 30: Separator 40: Electrode Assembly 50: Case 60: Sealing member 70: Electrode Tab 71: Positive Tab 72: Negative electrode tab

Claims

1. (i) A step of preparing core particles containing a lithium nickel-based composite oxide; (ii) Adding the core particles to an aqueous solvent and mixing them to adjust the pH of the first mixed solution to 5.5 to 7.5; (iii) The step of adding aluminum raw material to the first mixed solution and mixing to produce a second mixed solution; and (iv) A step of removing the aqueous solvent from the second mixed solution to produce a dry product; A method for producing a positive electrode active material containing the active material.

2. The lithium nickel-based composite oxide is represented by the following chemical formula 2, and is a method for producing a positive electrode active material according to claim 1: [Chemical formula 2] Li a2 ii x2 73 y2 74 z2 9 2-b2 8 b2 In chemical formula 2, 0.9 ≤ a² ≤ 1.8, 0.8 ≤ x² ≤ 1, 0 ≤ y² ≤ 0.2, 0 ≤ z² ≤ 0.2, 0.9 ≤ x² + y² + z² ≤ 1.1, and 0 ≤ b² ≤ 0.

1. M3 and M4 are each independently one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, Y, V, W, Zn, and Zr. M3 and M4 are different elements from each other, and X is one or more elements selected from the group consisting of F, P, and S.

3. A method for producing a positive electrode active material according to claim 1, wherein the nickel content in the lithium nickel-based composite oxide is 80 mol% or more relative to 100 mol% of the total metal excluding lithium.

4. A method for producing a positive electrode active material according to claim 1, wherein the cobalt content in the lithium nickel-based composite oxide is 8 mol% or less relative to 100 mol% of the total metal excluding lithium.

5. The amount of LiOH remaining on the surface of the core particles is 1.0% to 2.0% by weight relative to 100% by weight of the entire core particle composition. 2 CO 3 A method for producing a positive electrode active material according to claim 1, wherein the content of is 0.6% by weight to 1.0% by weight.

6. The method for producing a positive electrode active material according to claim 1, wherein in step (ii) above, an acidic aqueous solution is used to adjust the pH of the first mixed solution to 5.5 to 7.

5.

7. The method for producing a positive electrode active material according to claim 6, wherein the acidic aqueous solution is an aqueous hydrochloric acid solution.

8. The method for producing a positive electrode active material according to claim 1, wherein the aluminum raw material is aluminum sulfate, aluminum nitrate, or a combination thereof.

9. The method for producing a positive electrode active material according to claim 1, wherein the pH of the supernatant liquid of the second mixed solution is 5.5 to 7.

5.

10. The method for producing a positive electrode active material according to claim 1, wherein the surface of the dried product has a spiderweb or mesh-like structure.

11. A method for producing a positive electrode active material according to claim 1, wherein the aluminum content relative to 100 at% of the total of nickel, cobalt, and aluminum, as measured by energy profiling energy dispersive spectroscopy (EP-EDS) on the surface of the dried product, is 35 at% to 45 at%.

12. The method for producing a positive electrode active material according to claim 1, wherein the chlorine content is 0.1% by weight or more relative to 100% by weight of the entire dried product.

13. A method for producing a positive electrode active material according to claim 1, further comprising the step of heat-treating the dried product after step (iv).

14. A positive electrode active material manufactured by the manufacturing method described in any one of claims 1 to 13.

15. Core particles containing lithium nickel-based composite oxides; and A coating layer containing aluminum, located on the surface of the core particles; A positive electrode active material containing, The aluminum content relative to 100 at% of the total nickel, cobalt, and aluminum measured by energy profiling energy-dispersive spectroscopy (EP-EDS) on the surface of the positive electrode active material was 35 at% to 45 at%. A positive electrode active material having a chlorine content of 0.1% by weight or more relative to 100% by weight of the total positive electrode active material.

16. The lithium nickel-based composite oxide is the positive electrode active material according to claim 15, represented by the following chemical formula 2: [Chemical formula 2] Li a2 ii x2 73 y2 74 z2 9 2-b2 8 b2 In chemical formula 2, 0.9 ≤ a² ≤ 1.8, 0.8 ≤ x² ≤ 1, 0 ≤ y² ≤ 0.2, 0 ≤ z² ≤ 0.2, 0.9 ≤ x² + y² + z² ≤ 1.1, and 0 ≤ b² ≤ 0.

1. M3 and M4 are each independently one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, Y, V, W, Zn, and Zr. M3 and M4 are different elements from each other, and X is one or more elements selected from the group consisting of F, P, and S.

17. The positive electrode active material according to claim 15, wherein the nickel content in the lithium nickel-based composite oxide is 80 mol% or more relative to 100 mol% of the total metal excluding lithium.

18. The positive electrode active material according to claim 15, wherein the cobalt content in the lithium nickel-based composite oxide is 8 mol% or less relative to 100 mol% of the total metal excluding lithium.

19. Current collector, and Positive electrode active material layer located on the current collector Includes, The positive electrode active material layer comprises the positive electrode active material described in claim 14.

20. The positive electrode according to claim 19; Negative electrode; and Electrolyte; Lithium-ion secondary batteries, including lithium-ion batteries.

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