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

Abstract

The present invention provides a positive electrode active material and a method for manufacturing the same, a positive electrode containing the same, and a lithium secondary battery, which can exhibit high initial charge / discharge capacity and efficiency even under high voltage driving conditions and achieve long-life characteristics under high voltage and high temperature conditions. [Solution] The positive electrode active material according to one embodiment includes core particles containing a lithium nickel-based composite oxide in which the nickel content is 80 mol% or more relative to 100 mol% of the total metal excluding lithium, and a coating layer containing aluminum located on the surface of the core particles, wherein the core particles are in a secondary particle form in which a plurality of primary particles are aggregated, and 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 is 10 at% to 15 at%.

Description

Technical Field

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

Background Art

[0002] Lithium secondary batteries having a high energy density and being easy to carry are mainly used as driving power sources for mobile information terminals such as mobile phones, notebook computers, and smart phones. Recently, research has been actively conducted on using lithium secondary batteries having a high energy density as driving power sources or power storage power sources for hybrid automobiles and electric automobiles.

[0003] In order to realize a lithium secondary battery suitable for such applications, various positive electrode active materials have been studied. Among them, lithium nickel-based oxides, lithium nickel manganese cobalt composite oxides, lithium nickel cobalt aluminum composite oxides, lithium cobalt oxides, etc. are mainly used as positive electrode active materials. Recently, in a situation where the demand for large-sized, high-capacity, or high-energy density lithium secondary batteries has increased rapidly, there is a need for the development of a positive electrode active material that simultaneously improves stability and performance.

Summary of the Invention

Problems to be Solved by the Invention

[0004] A positive electrode active material containing a lithium nickel-based composite oxide, which improves the performance of a lithium secondary battery at high temperature and high voltage by introducing an optimal coating layer, and improves the capacity characteristics, initial charge-discharge efficiency, and high-temperature life characteristics.

Means for Solving the Problems

[0005] In one embodiment, a positive electrode active material is provided which includes core particles containing a lithium nickel-based composite oxide in which the nickel content is 80 mol% or more relative to 100 mol% of the total metal excluding lithium, and a coating layer containing aluminum located on the surface of the core particles, wherein the core particles are in a secondary particle form in which a plurality of primary particles are aggregated, and the aluminum content is 10 at% to 15 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.

[0006] In another embodiment, a method for producing a positive electrode active material is provided, which includes the steps of (i) preparing core particles containing a lithium nickel composite oxide, (ii) adding the core particles to an aqueous solvent and mixing them to produce a first mixed solution from which the aqueous solvent is removed to produce a primary dried product, (iii) adding the primary dried product to an aqueous solvent, then adding an aluminum raw material and mixing it to produce a second mixed solution, and (iv) removing the aqueous solvent from the second mixed solution to produce a secondary dried product, and heat-treating the secondary dried product to form a coated product in which a coating layer is formed on the surface of the core particles.

[0007] In another embodiment, the present invention includes a current collector and a positive electrode active material layer located on the 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 lithium secondary battery using a positive electrode active material 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 figure schematically shows a lithium secondary battery according to one embodiment. [Figure 2] This figure schematically shows a lithium secondary battery according to one embodiment. [Figure 3] This figure schematically shows a lithium secondary battery according to one embodiment. [Figure 4] This figure schematically shows a lithium secondary battery according to one embodiment. [Figure 5] This is a scanning electron microscope (SEM) image of the surface of the positive electrode active material manufactured in Example 2-1. [Figure 6] This is an SEM image of the surface of the positive electrode active material manufactured in Comparative Example 2-2. [Figure 7] This is an SEM image of the surface of the positive electrode active material produced in Comparative Example 2-5. [Figure 8] This is an SEM image of the surface of the positive electrode active material produced in Comparative Example 2-6. [Figure 9] This is a transmission electron microscope-energy dispersive spectroscopy (TEM-EDS) image showing aluminum in a cross-section of the positive electrode active material manufactured in Example 2-1. [Figure 10] This is a scanning electron microscope-energy dispersive spectroscopy (SEM-EDS) image showing aluminum in a cross-section of the positive electrode active material manufactured in Comparative Example 2-2. [Modes for carrying out the invention]

[0011] The following describes specific embodiments in detail so that they can be easily implemented by those with ordinary skill in the art. However, the present invention can be realized in a variety of different forms and is not limited to the embodiments described herein.

[0012] The terms used herein are for illustrative purposes only and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0013] Here, "these combinations" refers to mixtures of components, laminates, composites, copolymers, alloys, blends, reaction products, etc.

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

[0015] To clearly represent various layers and regions in the drawings, thicknesses are shown enlarged, 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 on top of" another part, but also when there is another part in between. Conversely, when a part is said to be "directly on top of" 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 a part of the surface.

[0017] The average particle size can be measured by methods widely 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 the average particle size value can be calculated after counting the number of particles for each particle size range through data analysis. Unless otherwise defined, the average particle size is the diameter (D) of the particle whose cumulative volume in the particle size distribution is 50% by volume. 50 ) can mean. Also, unless otherwise defined, the average particle size is the diameter (D) of the particle whose cumulative volume in the particle size distribution is 50% by volume, obtained by measuring the size (diameter or length of the long axis) of more than 20 randomly selected particles in a scanning electron microscope image. 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 metalloids.

[0020] positive electrode active material In one embodiment, a positive electrode active material is provided which includes core particles containing a lithium-nickel composite oxide in which the nickel content is 80 mol% or more relative to 100 mol% of the total metal excluding lithium, and a coating layer containing aluminum located on the surface of the core particles, wherein the core particles are in a secondary particle form in which a plurality of primary particles are aggregated, and 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 is 10 at% to 15 at%.

[0021] In one embodiment, a method is proposed in which a coating layer containing aluminum at a specific content is introduced on the surface of core particles containing lithium nickel-based composite oxide, thereby maintaining a stable structure even at high voltages, achieving high capacity, long lifespan characteristics, and improving high-temperature storage characteristics.

[0022] When coating aluminum to strengthen the particle surface of the positive electrode active material, since aluminum has a strong tendency to diffuse into the interior of the particles, it is actually difficult to uniformly coat the particle surface with aluminum in a shell form. In one embodiment, conditions are proposed under which aluminum can be uniformly coated on the particle surface without increasing the resistance. As a result, the aluminum concentration on the particle surface, that is, the ratio of Al / (Ni + Co + Al), is confirmed to be 10 at% to 15 at%, and a method for actually achieving such a concentration is proposed. A lithium secondary battery applying the positive electrode active material according to one embodiment is confirmed to have improved initial charge-discharge capacity and efficiency under high voltage conditions, and at the same time, the high-temperature life characteristics are improved, and the high-temperature storage characteristics are also improved.

[0023] core particles The core particles contain a lithium nickel-based composite oxide in which the nickel content is 80 mol% or more based on 100 mol% of the total metal excluding lithium. Specifically, the lithium nickel-based composite oxide can be represented by the following Chemical Formula 1. [Chemical Formula 1] Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1

[0024] In Chemical Formula 1, 0.9 ≤ a1 ≤ 1.8, 0.8 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 0.2, 0 ≤ z1 ≤ 0.2, 0.9 ≤ x1 + y1 + z1 ≤ 1.1, and 0 ≤ b1 ≤ 0.1, and M 1 and M <​​​​​​​ 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。

[0026] The lithium-nickel composite oxide may be a high-nickel positive electrode active material in which the nickel content is 80 mol% or more relative to 100 mol% of the total metal excluding lithium, and may be 85 mol% or more, 90 mol% or more, 91 mol% or more, or 94 mol% or more, or 99 mol% or less. High-nickel positive electrode active materials can achieve high capacity and can be applied to high-capacity, high-density lithium secondary batteries. Although nickel is contained in the core particles, some can move to the coating layer during the coating process, and therefore the nickel content can refer to the nickel content contained in the entire positive electrode active material.

[0027] In the lithium nickel-based composite oxide, the cobalt content may be 8 mol% or less relative to 100 mol% of the total metal excluding lithium, 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, a stable structure can be maintained, the problem of structural collapse due to charging and discharging can be suppressed, and the long-life characteristics of the positive electrode active material can be realized.

[0028] The lithium nickel-based composite oxide may, as an example, be a lithium nickel-aluminum composite oxide further containing aluminum in addition to nickel. When aluminum is included in the composite oxide, it is advantageous for maintaining a stable structure. In the lithium nickel-based composite oxide, the aluminum content relative to 100 mol% of the total metal excluding lithium may be 0.1 mol% or more, 0.5 mol% or more, or 1.0 mol% or more, for example, 1.0 mol% to 3.0 mol%, 1.0 mol% to 2.5 mol%, 1.0 mol% to 2.0 mol%, or 1.0 mol% to 1.5 mol%. Here, the aluminum content refers to the aluminum content present in the core particles. When the aluminum content satisfies the above range, a stable structure can be maintained, the problem of structural collapse due to charging and discharging can be suppressed, and the long-life characteristics of the positive electrode active material can be realized.

[0029] According to one embodiment, the concentration of aluminum within the core particles may be uniform. That is, the aluminum concentration within the core particles does not have a concentration gradient from the center to the surface, nor is the aluminum concentration higher or lower outside the core particles than inside, meaning that the aluminum is uniformly dispersed within the core particles. This can be said to be a structure obtained by synthesizing a composite oxide using nickel-aluminum hydroxide as a precursor by using aluminum raw materials during precursor production, without additional aluminum doping during the core particle synthesis process. The core particles are in a secondary particle form in which multiple primary particles are aggregated, and the aluminum content inside the primary particles can be said to be the same or similar regardless of the position of the primary particles. That is, if a primary particle is selected at any position in the cross-section of the secondary particle and the aluminum content inside the primary particle, not at the interface, can be expressed as the same / similar / uniform regardless of the position of the primary particle, i.e., whether the primary particle is close to the center or the surface of the secondary particle. With such a structure, a stable structure can be maintained, no aluminum byproducts or aluminum aggregates are generated, and the capacity, efficiency, and lifetime characteristics of the positive electrode active material can be improved simultaneously.

[0030] The core particle is a secondary particle morphology formed by the aggregation of multiple primary particles. The secondary particle may be spherical, ellipsoidal, polyhedronal, or irregular in shape, and the primary particle may be spherical, ellipsoidal, plate-shaped, or a combination thereof.

[0031] 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 in a scanning electron microscope image of the positive electrode active material to obtain a particle size distribution, and taking the diameter of the particle whose cumulative volume is 50% by volume in the particle size distribution as the average particle size. If the average particle size of the core particles satisfies the above range, high capacity and long life can be achieved, which may be advantageous for forming a coating layer according to one embodiment.

[0032] 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, which can lead to numerous side reactions with the electrolyte. This can result in increased gas generation, reducing battery life and safety. However, this problem can be resolved by introducing a coating layer according to one embodiment described later.

[0033] coating layer The positive electrode active material according to one embodiment is located on the surface of the core particles and includes a coating layer containing aluminum. The aluminum content is characterized by being 10 at% to 15 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, for example, 10.5 at% to 14.5 at% or 11 at% to 14 at%.

[0034] The aluminum content in the coating layer relative to 100 mol% of the total metal excluding lithium in the positive electrode active material may be 0.1 mol% to 2.0 mol%, for example, 0.5 mol% to 2.0 mol%, 0.5 mol% to 1.5 mol%, or 1.0 mol% to 1.5 mol%. The aluminum content in the coating layer can refer only to the aluminum content in the coating layer, regardless of the aluminum contained in the core particles. When the aluminum content satisfies the above range, a stable structure can be maintained, the problem of structural collapse due to charging and discharging can be suppressed, and the long-life characteristics of the positive electrode active material can be realized.

[0035] Furthermore, the ratio of cobalt molar content to aluminum molar content (Co / Al) in the entire positive electrode active material may be 1.1 to 5.0, for example, 1.2 to 4.5, 1.3 to 4.0, 1.4 to 4.0, or 1.5 to 3.0. The ratio (Co / Al) can mean, for example, the ratio of cobalt content (mol%) to 100 mol% of the entire metal excluding lithium in the entire positive electrode active material to the aluminum content (mol%) to 100 mol% of the entire metal excluding lithium in the entire positive electrode active material. The entire metal excluding lithium in the entire positive electrode active material that serves as the basis for the content range can mean the entire metal excluding lithium present in the entire positive electrode active material particles that are not on the positive electrode active material surface, the aluminum content can mean the entire aluminum content contained in or potentially contained in the core particles and contained in the coating layer, and the cobalt content can mean the entire cobalt content contained in or potentially contained in the core particles and contained in the coating layer.

[0036] The aluminum and cobalt content can be measured, for example, by SEM-EDS analysis of the surface or cross-section of the positive electrode active material. When the ratio of cobalt content to aluminum content in the entire positive electrode active material satisfies the aforementioned range, the resistance of the positive electrode active material does not increase, side reactions with the electrolyte are effectively suppressed, and the life characteristics, initial charge / discharge capacity, and initial charge / discharge efficiency of the lithium secondary battery can be improved under high voltage and high temperature conditions.

[0037] The coating layer in one embodiment may be in the form of a film that continuously surrounds the surface of the core particles, or it may be in the form of a shell that surrounds 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 can be formed to surround 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 an increase in resistance or a decrease in capacity, effectively suppressing side reactions with the electrolyte, reducing gas generation under high voltage and high temperature conditions, and achieving long-life characteristics.

[0038] The thickness of the coating layer in one embodiment 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 can improve the structural stability of the positive electrode active material and effectively suppress side reactions with the electrolyte without increasing resistance or decreasing capacitance. 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.

[0039] One embodiment of the coating layer is characterized by its thinness, ranging from a few nanometers to several hundred nanometers, while maintaining 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 expressed, for example, by measuring the thickness at more than 10 points in an electron microscope image of the cross-section of a single positive electrode active material particle, calculating the arithmetic mean, then dividing the absolute value of the difference between one data point and the arithmetic mean by the arithmetic mean and 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.

[0040] 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 present in the core particles and may have entered during the coating layer formation process, and their content is not particularly limited. One embodiment of the coating layer selectively contains nickel and cobalt while essentially containing aluminum, and can be formed with a thin and uniform thickness to improve the high-voltage characteristics of the positive electrode active material and enhance its lifespan.

[0041] Furthermore, the coating layer may contain sulfur in addition to aluminum. The sulfur may be introduced during the process of adding aluminum sulfate, which is one of the aluminum raw materials used to form the coating layer, and its content is not particularly limited. The coating layer according to one embodiment selectively contains sulfur while essentially containing aluminum, and can improve the high-voltage characteristics of the positive electrode active material and enhance its lifespan.

[0042] On the other hand, during the aluminum coating layer formation process, aluminum is diffused into the secondary particles. As a result, the positive electrode active material in one embodiment is located on the surface of primary particles located inside the secondary particles and can further include a grain boundary coating portion containing aluminum. The interior of the secondary particle can mean the entire interior excluding the surface of the secondary particle, or it can mean the region from the surface of the secondary particle to approximately 60% of the radius in the direction toward the center of the secondary particle. The grain boundary coating portion is a concept distinct from the coating layer on the surface of the secondary particle and refers to the coating portion formed on the surface of primary particles located inside the secondary particle. The presence of the grain boundary coating portion can be confirmed by SEM-EDS analysis of the cross-section of the positive electrode active material. The formation of the aluminum grain boundary coating portion further stabilizes the positive electrode active material structurally and improves its lifetime characteristics.

[0043] The aluminum content of the grain boundary coating is not particularly limited; for example, the aluminum content of the grain boundary coating may be less than the aluminum content in the coating layer.

[0044] The grain boundary coating portion may contain no cobalt or only a very small amount of cobalt. The cobalt content relative to 100 mol% of the total metal excluding lithium may be 0.01 mol% or less, 0.005 mol% or less, or 0.001 mol% or less, for example, 0 mol% to 0.01 mol%, 0 mol% to 0.005 mol%, or 0 mol% to 0.001 mol%. When the cobalt content of the grain boundary coating portion satisfies the above range, side reactions with the electrolyte can be effectively suppressed, and the amount of gas generated can be effectively reduced under high voltage and high temperature conditions.

[0045] The primary particles may be polycrystalline primary particles, in which case the crystal size of the primary particles measured by the X-ray diffraction analysis method may be 10 nm to 300 nm, for example, 15 nm to 250 nm, 30 nm to 200 nm, 45 nm to 150 nm, or 60 nm to 100 nm. The smaller the crystal size of the primary particles, the smaller the volume change may be, approximately proportional to the square root of 3. When the crystal size is adjusted to the above range, the volume change of the particles during charging and discharging can be minimized, which has the advantage of minimizing cracks and improving lifespan, as well as improving high-temperature storage characteristics.

[0046] The crystal size of the primary particles may be measured by X-ray diffraction analysis, for example, by calculating it using the following formula 1 in the 2θ range of 10° to 70° using Cu-Kα line (wavelength 1.54 Å) in an X-ray diffraction spectrum with an accelerating voltage of 40 kV / 40 mA and a scan speed of 0.01° / sec. [Formula 1] Crystal size (nm) = Kλ / βcosθ

[0047] In Equation 1, K is 0.9, λ is 1.54 Å, β is the full width at half maximum at the peak fitted with the Lorentzian function, and θ is the Bragg angle at the peak fitted with the Lorentzian function.

[0048] The crystal size of the primary particles can be said to represent the crystal size calculated using peaks fitted with a Lorentzian function that satisfies Bragg's law within the range of 10° to 90°.

[0049] Furthermore, the positive electrode active material according to one embodiment does not need to contain sodium. Generally, sodium ions can be used in the manufacturing process of positive electrode active materials, but according to the manufacturing method described later, core particles with a stable structure and a coating layer of uniform thickness can be formed without using sodium ions.

[0050] Method for manufacturing positive electrode active material In one embodiment, a method for producing a positive electrode active material is provided, which includes the steps of (i) preparing core particles containing a lithium nickel composite oxide, (ii) adding the core particles to an aqueous solvent and mixing them to produce a first mixed solution from which the aqueous solvent is removed to produce a primary dried product, (iii) adding the primary dried product to an aqueous solvent, then adding an aluminum raw material and mixing it to produce a second mixed solution, and (iv) removing the aqueous solvent from the second mixed solution to produce a secondary dried product, and heat-treating the secondary dried product to form a coated product in which a coating layer is formed on the surface of the core particles.

[0051] 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 includes 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.

[0052] In the nickel-based composite hydroxide, the nickel content relative to 100 mol% of the total metal may be 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 stability can be enhanced.

[0053] 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 stability of the positive electrode active material while achieving high capacity.

[0054] Furthermore, if the nickel-based composite hydroxide further contains aluminum, the aluminum content relative to 100 mol% of the total metal may be 0.1 mol% or more, 0.5 mol% or more, or 1.0 mol% or more, for example, 1.0 mol% to 3.0 mol%, 1.0 mol% to 2.5 mol%, 1.0 mol% to 2.0 mol%, or 1.0 mol% to 1.5 mol%. When the aluminum content satisfies the above range, it is possible to improve the structural stability of the positive electrode active material while achieving high capacity, thereby lowering production costs and improving economic efficiency.

[0055] In one embodiment of the method for producing a positive electrode active material, aluminum may be used as the precursor by using an aluminum raw material during precursor production, thereby uniformly dispersing aluminum within the structure of a nickel-aluminum composite hydroxide, without additional aluminum doping during core particle production. When such a precursor is used, a positive electrode active material can be produced in which the structure is stably maintained even after repeated charge and discharge cycles, and the capacity, efficiency, and lifespan characteristics of the positive electrode active material can be improved without the formation of aluminum by-products or aluminum aggregates.

[0056] The aforementioned nickel-based composite hydroxide can be represented, for example, by the following chemical formula 2. [Chemical formula 2] Ni x2 M 3 y2 M 4 z2 (OH)2

[0057] In chemical formula 2, 0.8 ≤ x² ≤ 1, 0 ≤ y² ≤ 0.2, 0 ≤ z² ≤ 0.2, and 0.9 ≤ x² + y² + z² ≤ 1.1, and M 3 and M 4 Each is 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, V, W, Zn, Y, and Zr, M 3 and M 4 These are elements that are different from each other.

[0058] 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。

[0059] The nickel-based composite hydroxide is in particulate form, and the average particle size (D 50 The size of the ) may be 10 μm to 25 μm, for example, 11 μm to 20 μm, or 12 μm to 18 μm.

[0060] The nickel-based composite hydroxide and lithium raw material can be mixed in a molar ratio of 1:0.9 to 1:1.8, for example, in 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 750°C to 900°C, or 750°C to 890°C, for 2 to 20 hours, or 4 to 16 hours.

[0061] A lithium nickel-based composite oxide can be obtained through a first heat treatment. In the obtained lithium nickel-based composite oxide, the nickel content relative to 100 mol% of the total metal excluding lithium may be 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. The cobalt content 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%, and the aluminum content may be 1.0 mol% to 3.0 mol%. In one embodiment, a method is proposed in which the particle surface of the lithium nickel-based composite oxide can be coated with aluminum to a very uniform thickness.

[0062] In one embodiment, the process of first adding the core particles to an aqueous solvent and mixing to produce a first mixed solution, then removing the aqueous solvent to produce a primary dried product with reduced residual lithium content on the core particle surface, is carried out first. Subsequently, the primary dried product is added to the aqueous solvent, and then aluminum raw material is added and mixed to produce a second mixed solution. After that, the aqueous solvent is removed from the second mixed solution to produce a secondary dried product, and the secondary dried product can be heat-treated to form a coating layer according to one embodiment. 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 reduces the residual lithium content on the surface by washing the high-nickel positive electrode active material twice using an aqueous solvent, and then applies an aluminum coating, thereby applying the optimal conditions for forming a uniform aluminum coating layer on the lithium nickel composite oxide.

[0063] The aqueous solvent may include distilled water, an alcoholic solvent, or a combination thereof. The aluminum raw material may be aluminum sulfate, aluminum nitride, or a combination thereof, and may be aluminum sulfate as an example. Aluminum sulfate is an optimal raw material for forming a uniform aluminum coating layer on a lithium nickel composite oxide.

[0064] In the core particles, the aluminum content in the aluminum raw material may be 0.1 mol% to 2.0 mol% relative to the total metal excluding lithium and the total aluminum in the aluminum raw material (100 mol%), for example, it can be designed to be 0.5 mol% to 2.0 mol%, 0.5 mol% to 1.5 mol%, or 1.0 mol% to 1.5 mol%. By designing the aluminum coating content within this range, a thin and uniform coating layer with a thickness 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 and improving high capacity and long life characteristics.

[0065] The time required to add the primary dried product to the aqueous solvent may be 30 seconds / 500g to 2 minutes / 500g, or for example, 30 seconds / 500g to 1.5 minutes / 500g. By appropriately adjusting the rate at which the primary dried product is added, the pH of the supernatant after coating is complete can be appropriately adjusted, thereby effectively leading to the formation of a uniform coating layer according to one embodiment. If the rate at which the primary dried product is added is excessively slow, the reaction rate for each particle will change, and a uniform coating layer may not be formed. Also, if the rate at which the primary dried product is added is excessively fast, the rate of pH change will be too fast, and a uniform coating layer may not be formed.

[0066] The stirring time after adding all of the primary dried product and aluminum raw material to the aqueous solvent may be approximately 15 to 60 minutes, for example, 20 to 50 minutes, or 30 to 45 minutes. The time from the start of adding the primary dried product and aluminum raw material to the aqueous solvent until stirring is completed, i.e., the coating reaction time, can be appropriately adjusted to within approximately 1 hour. Through these mixing conditions, the aluminum raw material is completely dissolved in the aqueous solvent to produce a colorless and transparent coating solution, and by using such a coating solution, a uniform coating layer according to one embodiment can be effectively formed.

[0067] In one embodiment, when the primary dried product and aluminum raw material are added to the aqueous solvent and mixing is stopped, that is, when the pH range of the supernatant of the second mixed solution may be 5.5 to 8.5, for example, 5.5 to 7.5, 6.0 to 8.0, or 6.5 to 7.5. If the pH of the supernatant is less than 5.5, it may become too acidic and a uniform coating layer may not be formed, and if the pH is greater than 8.5, it may become too basic and in this case it may also be difficult to form a uniform aluminum coating layer.

[0068] After removing the aqueous solvent from the second mixed solution, the secondary dried product can be manufactured at temperatures such as 40°C to 240°C, 100°C to 220°C, or 150°C to 200°C, and can also be carried out under vacuum conditions, which can yield a good coated product.

[0069] The coated product comprises core particles and a coating layer containing aluminum located on the surface of the core particles. For example, the coating layer may have a fibrous structure, such as a mesh or spiderweb pattern. Such a mesh may be continuously formed across the entire surface of the core particles. The mesh-like coating layer can surround the core particles with a very thin and uniform thickness, thereby strengthening the surface of the positive electrode active material, improving structural stability, and improving high-temperature and high-voltage characteristics.

[0070] If the process of first mixing nickel-based composite hydroxide and lithium raw material and heat-treating it is referred to as the first heat treatment, then the heat treatment of the secondary dried product can be called the second heat treatment. The second heat treatment can be understood as the process of forming a coating layer, and can be carried out, for example, in an oxygen atmosphere at a temperature range of 700°C to 850°C, 700°C to 840°C, or 700°C to 830°C for 2 to 20 hours, or 3 to 15 hours. When the second heat treatment temperature is set within the above range, the tendency of aluminum to diffuse into the secondary particles decreases and it mainly remains on the surface of the secondary particles, and at the same time, a very thin, uniformly thick shell-like coating is formed on the surface of the secondary particles.

[0071] positive electrode In one embodiment, the device includes a current collector and a positive electrode active material layer located on the 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.

[0072] According to one embodiment, the loading level of the positive electrode active material layer is 10 mg / cm³. 2 ~40 mg / cm³ 2 It may be 10 mg / cm³, for example. 2 ~30 mg / cm³ 2 or 10 mg / cm³ 2 ~20 mg / cm³ 2 It may also be the case that the density of the positive electrode active material layer in the rolled final positive electrode is 3.2 g / cc to 3.6 g / cc, for example, 3.3 g / cc to 3.6 g / cc or 3.4 g / cc to 3.58 g / cc. When applying the positive electrode active material according to one embodiment, it is advantageous to achieve such a loading level and positive electrode density, and a positive electrode satisfying the above range of loading level and positive electrode density is suitable for realizing a high-capacity, high-energy-density lithium secondary battery.

[0073] 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.

[0074] conductive material Conductive materials are used to impart conductivity to electrodes, and any electronically conductive material that does not cause chemical changes can be used in the battery that is constructed. 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.

[0075] 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.

[0076] Al can be used as the positive electrode current collector, but it is not limited to this.

[0077] Lithium-ion rechargeable 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 and negative electrodes, and an electrolyte.

[0078] Lithium-ion 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-ion battery according to one embodiment, where Figure 1 is cylindrical, Figure 2 is prismatic, and Figures 3 and 4 are pouch-type batteries. Referring to Figures 1 to 4, the lithium-ion battery 100 can 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 may be impregnated with an electrolyte (not shown). The lithium-ion battery 100 can include a sealing member 60 that seals the case 50, as shown in Figure 1. Also, in Figure 2, the lithium-ion battery 100 can 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 generated in the electrode assembly 40 to the outside.

[0079] A lithium secondary battery according to one embodiment may be capable of being charged at a high voltage or suitable for being driven at a high voltage. For example, the upper limit charging voltage of the lithium secondary battery may be 4.45V or higher, and may be, for example, 4.25V to 4.7V, 4.25V to 4.6V, or 4.25V to 4.55V. By applying the positive electrode active material according to one embodiment, the amount of gas generated can be significantly reduced even when charged at a high voltage, and high capacity and long life characteristics can be achieved.

[0080] 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.

[0081] negative electrode active material The negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and undoping lithium, or a transition metal oxide.

[0082] Examples of the material capable of reversibly intercalating / deintercalating the lithium ions include carbon-based negative electrode active materials, which may include, for example, crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as amorphous, plate-like, flaky, spherical or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, etc.

[0083] As the alloy of 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 can be used.

[0084] As the material capable of doping and undoping lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material can be used. The Si-based negative electrode active material may be 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. The Sn-based negative electrode active material may be Sn, SnO2, a Sn alloy, or a combination thereof.

[0085] The silicon-carbon composite may be a composite of silicon and amorphous carbon. The average particle size (D) of the silicon-carbon composite particles. 50 The particle size may be, for example, 0.5 μm to 20 μm. According to one embodiment, the silicon-carbon composite may be in the form of silicon particles and amorphous carbon coated on the surface of the silicon particles. For example, it may include secondary particles (core) formed by granulating primary silicon particles, and an amorphous carbon coating layer (shell) located on the surface of these secondary particles. The amorphous carbon may also be located between the primary silicon particles, for example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed in the amorphous carbon matrix.

[0086] 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 this core. The crystalline carbon may be artificial graphite, natural graphite, or a combination thereof. The amorphous carbon may be soft carbon or hard carbon, mesophase pitch carbide, calcined coke, etc.

[0087] When the silicon-carbon composite contains silicon and amorphous carbon, the silicon content may be 10% to 50% by weight relative to 100% by weight of the silicon-carbon composite, and the amorphous carbon content may be 50% to 90% by weight. Furthermore, when the composite contains silicon, amorphous carbon, and crystalline carbon, the silicon content may be 10% to 50% by weight relative to 100% by weight of the silicon-carbon composite, the crystalline carbon content may be 10% to 70% by weight, and the amorphous carbon content may be 20% to 40% by weight.

[0088] Furthermore, the thickness of the amorphous carbon coating layer may be 5 nm to 100 nm. The average particle size (D) of the silicon particles (primary particles) 50) may be 10 nm to 1 μm, or 10 nm to 200 nm. The silicon particles may exist alone as silicon, or in the form of a silicon alloy, or in an oxidized form. The oxidized form of silicon is SiO x (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.

[0089] 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 ratio.

[0090] binder The binder serves to make the negative electrode active material particles adhere well to each other and make the negative electrode active material adhere 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.

[0091] Examples of the non-aqueous binder include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

[0092] 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.

[0093] When an aqueous binder is used 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.

[0094] 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.

[0095] conductive material Conductive materials are used to impart conductivity to electrodes, and any electronically conductive material that does not cause chemical changes can be used in the battery that is constructed. 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 in the form of metal powders or metal fibers containing copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0096] 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.

[0097] 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.

[0098] electrolyte The electrolyte for lithium secondary batteries may be, for example, an electrolyte solution, which may contain a non-aqueous organic solvent and a lithium salt.

[0099] Non-aqueous organic solvents serve 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.

[0100] Examples of carbonate-based solvents that can be used include 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). Examples of ester-based solvents that can be used include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, and caprolactone. As ether-based solvents, dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and tetrahydrofuran can be used. As ketone-based solvents, cyclohexanone can be used. As alcohol-based 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 with 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.

[0101] 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 should be widely understood by those working in this field.

[0102] 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.

[0103] The non-aqueous organic solvent may further contain an aromatic hydrocarbon organic solvent. For example, the carbonate solvent and the aromatic hydrocarbon organic solvent can be mixed and used in a volume ratio of 1:1 to 30:1.

[0104] The electrolyte may further contain vinyl ethyl carbonate, vinylene carbonate, or ethylene carbonate compounds to improve battery life.

[0105] 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.

[0106] 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 F 2y+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(oxalato)phosphate (LiDFOB), and lithium bis(oxalato)borate (LiBOB).

[0107] It is desirable to use lithium salts within a concentration 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.

[0108] 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.

[0109] 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.

[0110] 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, Teflon®, and polytetrafluoroethylene, or from a copolymer or mixture of two or more of these polymers.

[0111] 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.

[0112] 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.

[0113] 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 50 The wavelength can be 1 nm to 2000 nm, for example, 100 nm to 1000 nm or 100 nm to 700 nm.

[0114] The organic and inorganic materials may exist mixed in a single coating layer, or they may exist in a form in which a coating layer containing organic materials and a coating layer containing inorganic materials are laminated together.

[0115] 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.

[0116] The following describes examples and comparative examples of the present invention. The following examples are merely illustrative of the present invention, and the present invention is not limited to the following examples. [Examples]

[0117] Example 1-1 1. Manufacturing of positive electrode active material 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 O2 and average particle size (D 50 A lithium nickel-based composite oxide in secondary particle form with a particle size of approximately 14 μm was fabricated.

[0118] 600 g of distilled water and 500 g of the prepared lithium nickel-based composite oxide were added to a 1 L reactor and stirred for about 30 minutes. The solvent was removed using an aspirator and filter press, and the product was vacuum-dried at 190°C to obtain a dried product. Then, 600 g of distilled water and aluminum sulfate were added to a 1 L reactor and stirred at approximately 350 rpm for about 5 minutes to prepare a coating solution for salt dissolution. It was confirmed that the salt was completely dissolved in the coating solution and that it was colorless and transparent. 500 g of the prepared dried product was added to the coating solution while it was being continuously stirred for 1.5 minutes and stirred for about 60 minutes. At this time, the aluminum content in the aluminum sulfate was designed to be 1.0 mol% relative to 100 mol% of the total metal excluding lithium in the final cathode active material. The pH of the supernatant after stirring was confirmed to be 7.

[0119] The solvent was removed from the mixed solution using an aspirator and a filter press, and the coated product was obtained by vacuum drying at 190°C.

[0120] The aforementioned coated product was subjected to a second heat treatment at 710°C for 13 hours in an oxygen atmosphere to produce the final cathode active material.

[0121] 2. Manufacturing of lithium-ion batteries A slurry of 97.7% by weight of the manufactured positive electrode active material, 1.0% by weight of polyvinylidene fluoride binder, and 1.3% by weight of carbon nanotube conductive material was mixed to produce a positive electrode active material layer slurry. This slurry was then coated onto an aluminum foil current collector, dried, and rolled to produce the positive electrode. At this time, the loading level of the positive electrode active material layer was 20 mg / cm². 2 Therefore, the density of the rolled final positive electrode is approximately 3.4 g / cc.

[0122] A negative electrode active material slurry was prepared by mixing 97.5% by weight of graphite negative electrode active material, 1.5% by weight of carboxymethylcellulose, and 1% by weight of styrene-butadiene rubber in an aqueous solvent. The negative electrode was prepared by coating a copper foil current collector with the negative electrode active material slurry, drying, and rolling.

[0123] A lithium secondary battery was manufactured using a conventional method with a polytetrafluoroethylene separator and an electrolyte solution prepared by dissolving 1M LiPF6 in a solvent containing a 3:7 volume ratio mixture of ethylene carbonate and dimethyl carbonate.

[0124] Examples 1-2 The positive electrode active material and lithium secondary battery were manufactured in substantially the same manner as in Example 1-1, except that the aluminum content in the aluminum sulfate was designed and mixed so that it was 1.5 mol% relative to 100 mol% of the total metals excluding lithium in the final positive electrode active material.

[0125] Example 2-1 Ni 0.95 Co 0.04 Al 0.01 (OH)2 and LiOH are mixed in a molar ratio of 1:1.03 and subjected to a first heat treatment at 750°C for 15 hours in an oxygen atmosphere, resulting in a composition of Li 1.03 Ni 0.95 Co 0.04 Al 0.01 O2 and average particle size (D 50 The cathode active material and lithium secondary battery were manufactured in substantially the same manner as in Example 1-1, except that a lithium nickel-based composite oxide in the form of secondary particles with a diameter of approximately 14 μm was used.

[0126] Example 2-2 The positive electrode active material and lithium secondary battery were manufactured in substantially the same manner as in Example 2-1, except that the aluminum content in the aluminum sulfate was designed and mixed so that it was 1.5 mol% relative to 100 mol% of the total metals excluding lithium in the final positive electrode active material.

[0127] Comparative Example 1-1 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 O2 and average particle size (D 50 A lithium nickel-based composite oxide in secondary particle form with a particle size of approximately 14 μm was fabricated.

[0128] The lithium nickel-based composite oxide and aluminum oxide produced above were mixed and heat-treated at 710°C for 13 hours to produce the final cathode active material. At this time, the aluminum content in the aluminum oxide was designed to be 0.5 mol% relative to 100 mol% of the total metal excluding lithium in the final cathode active material.

[0129] The lithium secondary battery was manufactured in substantially the same manner as in Example 1-1.

[0130] Comparative Example 1-2 The positive electrode active material and lithium secondary battery were manufactured in substantially the same manner as in Comparative Example 1-1, except that the aluminum content in the aluminum oxide was designed and mixed so that it was 1.0 mol% relative to 100 mol% of the total metals excluding lithium in the final positive electrode active material.

[0131] Comparative Examples 1-3 The positive electrode active material and lithium secondary battery were manufactured in substantially the same manner as in Example 1-1, except that the aluminum content in the aluminum sulfate was designed and mixed so that it was 0.5 mol% relative to 100 mol% of the total metal excluding lithium in the final positive electrode active material.

[0132] Comparative Example 1-4 The positive electrode active material and lithium secondary battery were manufactured in substantially the same manner as in Example 1-1, except that the aluminum content in the aluminum sulfate was designed and mixed so that it was 2.0 mol% relative to 100 mol% of the total metals excluding lithium in the final positive electrode active material.

[0133] Comparative Example 2-1 Ni 0.95 Co 0.04 Al 0.01 (OH)2 and LiOH are mixed in a molar ratio of 1:1.03 and subjected to a first heat treatment at 750°C for 15 hours in an oxygen atmosphere, resulting in a composition of Li 1.03 Ni 0.95 Co 0.04 Al 0.01 O2 and average particle size (D 50 A lithium nickel-based composite oxide in secondary particle form with a particle size of approximately 14 μm was fabricated.

[0134] The lithium nickel-based composite oxide and aluminum oxide produced above were mixed and heat-treated at 710°C for 13 hours to produce the final cathode active material. At this time, the aluminum content in the aluminum oxide was designed to be 0.5 mol% relative to 100 mol% of the total metal excluding lithium in the final cathode active material.

[0135] The lithium secondary battery was manufactured in substantially the same manner as in Example 1-1.

[0136] Comparative Example 2-2 The positive electrode active material and lithium secondary battery were manufactured in substantially the same manner as in Comparative Example 2-1, except that the aluminum content in the aluminum oxide was designed and mixed so that it was 1.0 mol% relative to 100 mol% of the total metals excluding lithium in the final positive electrode active material.

[0137] Comparative Example 2-3 The positive electrode active material and lithium secondary battery were manufactured in substantially the same manner as in Example 2-1, except that the aluminum content in the aluminum sulfate was designed and mixed so that it was 0.5 mol% relative to 100 mol% of the total metals excluding lithium in the final positive electrode active material.

[0138] Comparative Example 2-4 The positive electrode active material and lithium secondary battery were manufactured in substantially the same manner as in Example 2-1, except that the aluminum content in the aluminum sulfate was designed and mixed so that it was 2.0 mol% relative to 100 mol% of the total metals excluding lithium in the final positive electrode active material.

[0139] Comparative Example 2-5 The positive electrode active material and lithium secondary battery were manufactured in substantially the same manner as in Example 2-1, except that the aluminum content in the aluminum sulfate was designed and mixed so that it was 3.0 mol% relative to 100 mol% of the total metals excluding lithium in the final positive electrode active material.

[0140] Comparative Example 2-6 The positive electrode active material and lithium secondary battery were manufactured in substantially the same manner as in Example 1-1, except that aluminum coating was not performed in the manufacturing of the positive electrode active material.

[0141] Evaluation Example 1: Surface Analysis of Cathode Active Material The cathode active materials prepared 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.

[0142] Figure 5 is an SEM image of the surface of the final cathode active material produced in Example 2-1. Figure 6 is an SEM image of the surface of the final cathode active material produced in Comparative Example 2-2. Figure 7 is an SEM image of the surface of the final cathode active material produced in Comparative Example 2-5. Figure 8 is an SEM image of the surface of the final cathode active material produced in Comparative Example 2-6.

[0143] Referring to Figures 5 to 8, a uniform aluminum coating layer can be observed on the surface of the final cathode active material produced in Example 2-1. On the other hand, although the aluminum content in the coating layer is the same as in Example 2-1, it can be confirmed that the coating layer was formed unevenly on the surface of the final cathode active material produced in Comparative Example 2-2, which was dry-coated. Furthermore, an excessive aluminum coating layer was formed on the surface of the final cathode active material produced in Comparative Example 2-5, while the surface of the final cathode active material produced in Comparative Example 2-6 was smooth with no coating layer formed.

[0144] Evaluation Example 2: Cross-sectional Analysis of Cathode Active Material The aluminum coating state was confirmed on the cross-section of the positive electrode active material manufactured in the example, which was cut with a focused ion beam (FIB), by SEM-EDS mapping and TEM. SEM-EDS was performed using an IM4000PLUS with a polishing treatment at 6kV for 40 minutes, followed by confirmation using a Helios G4 HX under the conditions of HT:3kV, current:0.8nA, and live time:90s. TEM-EDS was performed using a Helios G4 HX with an accelerating voltage of 15 kV, followed by a Spectra 300 with an accelerating voltage of 200 kV.

[0145] Figure 9 is a TEM-EDS image showing aluminum in a cross-section of the positive electrode active material produced in Example 2-1, and Figure 10 is a SEM-EDS image showing aluminum in a cross-section of the positive electrode active material produced in Comparative Example 2-2.

[0146] Referring to Figures 9 and 10, it can be seen that a clear aluminum coating layer was formed on the surface (grain boundaries) of the primary particles that make up the secondary particles through a cross-section of the positive electrode active material produced in Example 2-1, which was wet-coated. In contrast, it can be seen that the aluminum coating layer was formed unevenly through a cross-section of the positive electrode active material produced in Comparative Example 2-1, which was dry-coated, and that the grain boundaries were not coated.

[0147] Evaluation Example 3: Aluminum content analysis on the surface of the positive electrode active material The aluminum content on the surface of the positive electrode active material 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 performed at Ultim (100 mm). 2 The test was performed using a detector under the conditions of HT: 3kV, current: 0.8nA, and live time: 90s.

[0148] [Table 1]

[0149] 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 positive electrode active material produced in the Examples is 10 at% to 15 at%. Conversely, it can be confirmed that the aluminum content relative to 100 at% of the total nickel, cobalt, and aluminum on the surface of the positive electrode active material produced in the Comparative Example is less than 10 at% or more than 15 at%.

[0150] Evaluation Example 4: Initial Charge / Discharge Capacity and Efficiency Evaluation The lithium secondary batteries manufactured in the examples and comparative examples were charged at 25°C with a constant current of 0.2C up to an upper voltage limit of 4.25V, then with a constant voltage down to 0.05C, and finally discharged at 0.2C down to a cutoff voltage of 3.0V to perform initial charge and discharge. Table 2 below shows the initial charge capacity, initial discharge capacity, and the ratio of the latter to the former, calculated as efficiency.

[0151] Evaluation Example 5: High-Temperature Life Characteristics Following the initial charge and discharge cycle in Evaluation Example 4, the charge and discharge cycles were repeated more than 50 times at 45°C in a voltage range of 3.0V to 4.3V at 1.0C. The ratio of the discharge capacity after 50 cycles to the initial discharge capacity was calculated and is shown in Table 2 below.

[0152] Evaluation Example 6: High-Temperature Storage Characteristics Following the initial charge and discharge in Evaluation Example 4, the batteries were charged at 0.2C in a voltage range of 3.0V to 4.3V at 75°C. The ratio of the discharge capacity after 10 days of storage at a high temperature (75°C) to the initial discharge capacity was calculated and is shown in Table 2 below.

[0153] [Table 2]

[0154] Referring to Table 2 above, it can be confirmed that in the example, high initial charge / discharge capacity and initial charge / discharge efficiency, excellent high-temperature life characteristics, and excellent high-temperature storage characteristics can be achieved simultaneously.

[0155] More specifically, in the case of Examples 1-1 and 1-2, it can be confirmed that higher initial charge / discharge capacity and initial charge / discharge efficiency, excellent high-temperature life characteristics, and excellent high-temperature storage characteristics are simultaneously achieved compared to Comparative Examples 1-1 to 1-3. However, it can be confirmed that the high-temperature life characteristics and high-temperature storage characteristics are not as good compared to Comparative Example 1-4, but Li 1.03 Ni 0.91 Co 0.075 Al 0.015When using O2 as the positive electrode active material, battery design is only possible if it exhibits a 0.2C discharge capacity of 200 mAh / g or more. However, the 0.2C discharge capacities of Comparative Examples 1-4 were found to be less than 200 mAh / g, confirming that battery design is impossible.

[0156] Additionally, in the case of Examples 2-1 and 2-2, it can be confirmed that higher initial charge / discharge capacity and initial charge / discharge efficiency, excellent high-temperature life characteristics, and excellent high-temperature storage characteristics are simultaneously achieved compared to Comparative Examples 2-1 to 2-3 and 2-6. However, it can be confirmed that the high-temperature life characteristics and high-temperature storage characteristics are not as good compared to Comparative Examples 2-4 and 2-5. 1.03 Ni 0.95 Co 0.04 Al 0.01 When using O2 as the positive electrode active material, battery design is only possible if it exhibits a 0.2C discharge capacity of 205 mAh / g or more. However, the 0.2C discharge capacities of Comparative Examples 2-4 and 2-5 were found to be less than 205 mAh / g, confirming that battery design is impossible.

[0157] Although preferred embodiments have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concepts defined in the claims also fall within the scope of the present invention. [Explanation of Symbols]

[0158] 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. Core particles containing a lithium-nickel composite oxide in which the nickel content is 80 mol% or more relative to 100 mol% of the total metal excluding lithium, and A coating layer containing aluminum is located on the surface of the core particles. It is a positive electrode active material that contains, The aforementioned core particle is a secondary particle form in which multiple primary particles are aggregated. A positive electrode active material having an aluminum content of 10 at% to 15 at% relative to a total of 100 at% nickel, cobalt, and aluminum, as measured by energy profiling energy dispersive spectroscopy (EP-EDS) on the surface of the positive electrode active material.

2. The lithium nickel-based composite oxide is represented by the following chemical formula 1, and is the positive electrode active material according to claim 1: [Chemical formula 1] Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1 In Chemical Formula 1, 0.9 ≦ a1 ≦ 1.8, 0.8 ≦ x1 ≦ 1, 0 ≦ y1 ≦ 0.2, 0 ≦ z1 ≦ 0.2, 0.9 ≦ x1 + y1 + z1 ≦ 1.1, and 0 ≦ b1 ≦ 0.1, and M 1 and M 2 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, V, W, Zn, Y, and Zr, and M 1 and M 2 are different elements from each other, and X is one or more elements selected from the group consisting of F, P, and S.

3. The positive electrode active material according to claim 1, wherein the lithium nickel-based composite oxide has a cobalt content of 8 mol% or less relative to 100 mol% of the total metal excluding lithium.

4. The aforementioned lithium nickel-based composite oxide further contains aluminum, The positive electrode active material according to claim 1, wherein the lithium nickel-based composite oxide has an aluminum content of 1.0 mol% to 3.0 mol% relative to 100 mol% of the total metal excluding lithium.

5. The average particle size (D) of the core particles 50 The positive electrode active material according to claim 1, wherein the diameter is 10 μm to 25 μm.

6. The positive electrode active material according to claim 1, wherein the aluminum content in the coating layer is 1.0 mol% to 1.5 mol% relative to 100 mol% of the total metal excluding lithium in the positive electrode active material.

7. The positive electrode active material according to claim 1, wherein the ratio of cobalt molar content to aluminum molar content (Co / Al) in the entire positive electrode active material is 1.5 to 3.

0.

8. The positive electrode active material according to claim 1, further comprising a grain boundary coating portion containing aluminum, located on the surface of a primary particle located inside the secondary particle.

9. The positive electrode active material according to claim 8, wherein the cobalt content in the grain boundary coating portion is 0.01 mol% or less relative to 100 mol% of the total metal excluding lithium.

10. The positive electrode active material according to claim 1, wherein the crystal size of the primary particles measured by X-ray diffraction analysis is 10 nm to 300 nm.

11. (i) The step of preparing core particles containing lithium nickel-based composite oxide; (ii) A step of producing a primary dried product by adding the core particles to an aqueous solvent and mixing them to obtain a first mixed solution, and then removing the aqueous solvent from the mixed solution. (iii) A step of adding the primary dried product to an aqueous solvent, then adding and mixing aluminum raw material to produce a second mixed solution, and (iv) The step of removing the aqueous solvent from the second mixed solution to produce a secondary dried product, and then heat-treating the secondary dried product to form a coated product in which a coating layer is formed on the surface of the core particles. A method for producing a positive electrode active material containing the active material.

12. The method for producing a positive electrode active material according to claim 11, wherein the aluminum raw material is aluminum sulfate, aluminum nitride, or a combination thereof.

13. The method for producing a positive electrode active material according to claim 11, wherein the pH of the supernatant of the second mixed solution is 5.5 to 7.

5.

14. 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 any one of claims 1 to 10.

15. The loading level of the positive electrode active material layer is 10 mg / cm². 2 ~30 mg / cm³ 2 The positive electrode according to claim 14.

16. The positive electrode according to claim 14, wherein the density of the positive electrode active material layer is 3.2 g / cc to 3.6 g / cc.

17. Positive electrode according to claim 14, Negative electrode, and electrolyte Lithium-ion secondary batteries, including lithium-ion batteries.

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