Positive electrode active material, method for preparing positive electrode active material, positive electrode, and rechargeable lithium battery

Abstract

The present application provides a positive electrode active material, a method of preparing the same, a positive electrode, and a rechargeable lithium battery. A positive electrode active material for a rechargeable lithium battery includes: a core particle including a layered lithium nickel manganese-based composite oxide and in the form of secondary particles, in which the secondary particles are each an aggregate of a plurality of primary particles; an aluminum coating on a surface of the core particle; and a grain boundary coated portion on the surface of the primary particle and including cobalt. For a rechargeable lithium battery including a positive electrode active material, the positive electrode active material can achieve characteristics of high density, high capacity, and long cycle life, and can reduce the amount of high temperature storage gas generation.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of Korean Patent Application No. 10-2024-0028309 filed in the Korean Intellectual Property Office on February 27, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] One or more embodiments of the present disclosure relate to a positive electrode active material, a method of preparing the positive electrode active material, a positive electrode including the positive electrode active material, and a rechargeable lithium battery including the positive electrode. Background Art

[0004] Portable information devices (such as cellular phones, laptop computers, smart phones, etc.) and / or electric vehicles have used rechargeable lithium batteries with relatively high energy density and portability as driving power sources. Recently, research has been actively conducted to use rechargeable lithium batteries with high energy density as driving power sources for hybrid or electric vehicles or as energy storage power sources for energy storage systems (ESS) or power walls.

[0005] Various positive electrode active materials have been studied to realize rechargeable lithium batteries for such purposes. Among them, lithium nickel oxide, lithium nickel manganese cobalt composite oxide, lithium nickel cobalt aluminum composite oxide and / or lithium cobalt oxide are mainly used as positive electrode active materials. However, with the recent increase in demand for large-scale, high-capacity and / or high-energy-density rechargeable lithium batteries, the supply of positive electrode active materials containing the rare metal cobalt is expected to be in serious shortage. For example, since cobalt is expensive and there are not many remaining reserves, it is necessary to develop positive electrode active materials that do not contain cobalt or reduce the cobalt content (for example, significantly reduce its amount). That is, lithium-based positive electrode active materials are being actively developed due to their relatively high capacity and energy density. However, in view of the high price of cobalt and its limited reserves, it is necessary or there is a demand to develop positive electrode active materials that do not use cobalt or significantly reduce the presence of cobalt in these materials. Summary of the Invention

[0006] One or more aspects of the embodiments of the present disclosure relate to a positive electrode active material that can achieve high density, high capacity, and long cycle life and reduce the amount of high-temperature storage gas generated, a method for preparing the positive electrode active material, and a positive electrode and a rechargeable lithium battery using the positive electrode active material.

[0007] Additional aspects will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the presented embodiments.

[0008] In one or more embodiments, the positive electrode active material may include: a core particle (i.e., a plurality of core particles) comprising a lithium nickel manganese composite oxide (i.e., a layered lithium nickel manganese composite oxide) and in the form of a secondary particle, wherein each secondary particle is an aggregate of a plurality of primary particles (e.g., in the form of secondary particles in which a plurality of primary particles are aggregated); an aluminum coating located on the surface of the core particle; and a grain boundary coating portion located on the surface of the primary particle and comprising cobalt.

[0009] In one or more embodiments, a method for preparing a positive electrode active material may include: (i) preparing core particles comprising a lithium nickel manganese composite oxide and in the form of secondary particles, wherein the secondary particles are formed (e.g., composed) by aggregating a plurality of primary particles (e.g., in the form of secondary particles in which a plurality of primary particles are aggregated); (ii) preparing an aluminum coating solution comprising an aqueous solvent and an aluminum raw material; (iii) adding the core particles to the aluminum coating solution, mixing them, and then drying them to prepare a coating product; and (iv) dry-mixing the coating product and a cobalt raw material and heat-treating them to obtain a positive electrode active material.

[0010] In one or more embodiments, a rechargeable lithium battery may include a positive electrode, a negative electrode, and an electrolyte.

[0011] The positive electrode active material according to one or more embodiments of the present disclosure may achieve high density, high capacity, and long cycle life characteristics, and further reduce the amount of high-temperature stored gas generated. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The above and other aspects, features and advantages of certain embodiments of the present disclosure will become more apparent from the following description taken in conjunction with the accompanying drawings.

[0013] Figures 1 to 4 Each is a schematic diagram illustrating a rechargeable lithium battery according to one or more embodiments of the present disclosure.

[0014] Figure 5 and Figure 6 Each is a scanning electron microscope (SEM)-energy dispersive x-ray spectroscopy (EDS) image of a cross section of a positive electrode active material prepared in Example 1.

[0015] Figure 7 This is a SEM-EDS analysis image of the cobalt element mapped on the cross section of the positive electrode active material in Example 1.

[0016] Reference numerals

[0017] 100: Rechargeable lithium battery 10: Positive electrode

[0018] 11: Positive electrode lead lug 12: Positive electrode terminal

[0019] 20: Negative electrode 21: Negative electrode lead lug

[0020] 22: Negative electrode terminal 30: Separator

[0021] 40: Electrode assembly 50: Shell

[0022] 60: Sealing member 70: Electrode terminal tab

[0023] 71: Positive electrode terminal tab 72: Negative electrode terminal tab DETAILED DESCRIPTION

[0024] The following will describe example embodiments in more detail so that those skilled in the art can more easily implement them. However, the present disclosure may be embodied in many different forms and is not to be construed as limited to the example embodiments set forth herein.

[0025] The terms used herein are intended only to describe embodiments and are not intended to limit the present disclosure. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. In addition, when describing embodiments of the present disclosure, the use of "may" refers to "one or more embodiments of the present disclosure."

[0026] As used herein, "combinations thereof" refers to mixtures, laminates, composites, copolymers, alloys, blends, reaction products, and the like, of the components.

[0027] In this document, it should be understood that terms such as “comprise(s) / comprising”, “include(s) / including” or “have(has) / having” are intended to indicate the presence of specified features, quantities, steps (e.g., actions or tasks), elements and / or their (e.g., any appropriate) combination, but do not exclude the possibility of the presence or addition of one or more other features, quantities, steps (e.g., actions or tasks), elements and / or their (e.g., any appropriate) combination.

[0028] In the accompanying drawings, the size (e.g., thickness) of layers, films, panels, regions, etc. are exaggerated for clarity, and in the present disclosure, the same reference numerals represent the same elements, and for the sake of brevity, their repeated description may not be provided. It should be understood that if (for example, when) an element (such as a layer, film, region, or substrate) is referred to as being "on" another element (such as a layer, film, region, or substrate), it can be directly on the other element (such as a layer, film, region, or substrate) or intervening elements may be present therebetween. In contrast, if (for example, when) an element (such as a layer, film, region, or substrate) is referred to as being "directly on" another element (such as a layer, film, region, or substrate), there are no intervening elements.

[0029] In addition, the “layer” as used herein may include not only a shape or layer formed on the entire surface if (for example, when) viewed from a plan view but also a shape or layer formed on a partial surface.

[0030] In one or more embodiments, the average particle size can be measured by methods well known to those skilled in the art, for example, by a particle size analyzer (e.g., HORIBA's LA-950 laser particle size analyzer) or by a transmission electron microscope (TEM) or a scanning electron microscope (SEM). In one or more embodiments, it can be measured by using a dynamic light scattering method, performing data analysis, counting the number of particles in each particle size range, and calculating the average particle size value accordingly. Unless otherwise specified, the average particle size (D 50 ) may refer to the diameter of particles that account for 50% by volume of the cumulative volume in the particle size distribution. 50 Refers to the average diameter (or size) of particles corresponding to 50% by volume of the cumulative volume in a particle size distribution (e.g., cumulative distribution), and refers to the value of the particle size corresponding to 50% from the smallest particle when the total number of particles is 100% in a distribution curve accumulated in the order of the smallest particle size to the largest particle size. In one or more embodiments, as used herein, if (e.g., when) no definition is otherwise provided, the average particle diameter (D 50 ) refers to the diameter of particles accounting for 50% by volume of the cumulative volume in a particle size distribution obtained by randomly measuring the size (diameter or major axis length) of about 20 particles in a scanning electron microscope image. In the present disclosure, when the particles are spherical, "diameter" indicates the average particle size, and when the particles are non-spherical, "diameter" indicates the major axis length.

[0031] In this document, "or" is not interpreted as being exclusive, for example, "A or B" is interpreted as including A, B, A+B, etc. In addition, as used in this document, the term "and / or" includes any and all combinations of one or more related listed items. Expressions such as "at least one of...", "one of...", and "selected from...", when before / after a list of elements, modify the entire list of elements without modifying the individual elements of the list. For example, "at least one of a, b, and c", "at least one selected from a, b, and c", "at least one selected from a to c", etc. may represent only a, only b, only c, both a and b (for example, at the same time), both a and c (for example, at the same time), both b and c (for example, at the same time), all a, b, and c, or variations thereof. The " / " used in this document may be interpreted as "and" or "or" depending on the circumstances.

[0032] As used herein, the term "metal" is interpreted as a concept including common metals, transition metals and metalloids (semimetals). The term "group" used herein refers to a group of the periodic table of the elements according to the 1 to 18 grouping system of the International Union of Pure and Applied Chemistry ("IUPAC").

[0033] Method for preparing positive electrode active material

[0034] According to one or more embodiments of the present disclosure, the positive electrode active material may include: a core particle comprising a lithium nickel manganese composite oxide and in the form of a secondary particle, wherein the secondary particle is formed (e.g., composed) by aggregating a plurality of primary particles (e.g., in the form of secondary particles in which a plurality of primary particles are aggregated); an aluminum coating located on the surface of the core particle; and a grain boundary coating portion located on the surface of the primary particle and comprising cobalt.

[0035] Due to the sharp rise in the price of rare metal cobalt in recent years, it is necessary to develop positive electrode active materials that do not contain cobalt or reduce the cobalt content (e.g., amount). Among the positive electrode active materials that do not contain cobalt or reduce (e.g., significantly reduce) the cobalt content, the positive electrode active materials having an olivine crystal structure (such as lithium iron phosphate (LFP), lithium manganese phosphate (LMP), lithium manganese iron phosphate (LMFP), etc.) or a spinel crystal structure (such as lithium manganese oxide (LMO), etc.) are limited in achieving high capacity due to the small amount of available lithium in the structure (e.g., olivine crystal structure and spinel crystal structure). Layered lithium nickel manganese positive electrode active materials have excellent or appropriate capacity and efficiency characteristics due to the high amount of available lithium in the structure, making them suitable as materials for high-capacity batteries. However, when the cobalt that plays a key role in the layered structure is removed, the structural stability of the layered structure is reduced, the resistance of the layered structure increases, and it becomes difficult to ensure long cycle life characteristics. In addition, layered lithium nickel manganese positive electrode active materials that do not contain cobalt may have the problem of accelerated side reactions with the electrolyte under high voltage and / or high temperature conditions. Therefore, a positive electrode active material that does not contain cobalt may suffer from characteristics of increased gas generation and deteriorated cycle life.

[0036] Therefore, in one or more embodiments of the present disclosure, an aluminum coating is introduced on the surface of a core particle comprising a layered lithium nickel manganese composite oxide, and a grain boundary coating portion is introduced, the grain boundary coating portion containing cobalt and located on the surface of a primary particle formed (e.g., formed or to be formed) in the form of a secondary particle, to enhance the ion surface and simultaneously (e.g., synchronously) form a strong internal structure, thereby improving the initial charge and discharge efficiency and the amount of gas generated during high temperature storage, as well as high voltage and high temperature cycle life characteristics. That is, some embodiments of the present disclosure provide a method for applying an aluminum coating to the surface of (e.g., each) core particle. These particles include a layered lithium nickel manganese composite oxide (e.g., formed by a layered lithium nickel manganese composite oxide). The method also includes adding a grain boundary coating portion containing cobalt to the surface of the primary particles. These primary particles constitute the core particles as secondary particles, and the coating enhances the surface strength, thereby forming a durable internal structure. Therefore, the method improves the efficiency of the initial charge and discharge cycle, minimizes or reduces gas generation during high temperature storage, and improves the characteristics of high voltage and high temperature cycle life.

[0037] nuclear particles

[0038] The core particle according to one or more embodiments of the present disclosure may include a layered lithium nickel manganese-based composite oxide.

[0039] In the layered lithium nickel manganese composite oxide, the nickel content (e.g., amount) may be greater than or equal to 60 mol%, such as about 60 mol% to about 80 mol%, about 65 mol% to about 80 mol%, about 70 mol% to about 80 mol%, about 60 mol% to about 79 mol%, about 60 mol% to about 78 mol%, or about 60 mol% to about 75 mol%, based on 100 mol% of the total metal excluding lithium. In one embodiment, when the nickel content (e.g., amount) satisfies the above range, even if the cobalt content (e.g., amount) is reduced, high capacity can be achieved and structural stability can be increased.

[0040] In the layered lithium nickel manganese composite oxide, the manganese content (e.g., amount) may be greater than or equal to about 10 mol%, greater than or equal to 15 mol%, based on 100 mol% of the total metal excluding lithium, for example, from about 15 mol% to about 40 mol%, from about 15 mol% to about 35 mol%, from about 15 mol% to about 30 mol%, or from about 20 mol% to about 30 mol%. In one embodiment, when the manganese content (e.g., amount) satisfies the above range, the positive electrode active material can improve structural stability while achieving high capacity.

[0041] The layered lithium nickel manganese composite oxide may be a lithium nickel manganese aluminum composite oxide further including aluminum in addition to nickel and manganese. When the layered lithium nickel manganese composite oxide contains aluminum, even if the cobalt element is excluded from the structure, it is beneficial to maintain a stable layered structure. That is, when the layered lithium nickel manganese composite oxide contains aluminum, even if cobalt is not present in its structure, it is beneficial to maintain a stable layered structure. Based on 100 mol% of the total metal without lithium in the lithium nickel manganese aluminum composite oxide, the aluminum content (e.g., amount) may be greater than or equal to 0 mol% and less than or equal to about 3 mol%, greater than or equal to about 0.1 mol%, greater than or equal to 0.5 mol%, greater than or equal to 1 mol%, for example, it may be about 1 mol% to about 3 mol%, about 1 mol% to about 2.5 mol%, about 1 mol% to about 2 mol% or about 1.5 mol% to about 2.5 mol%. As used herein, the term "aluminum content" (e.g., amount) refers to the content (e.g., amount) of aluminum present in the core particles. In one embodiment, when the aluminum content satisfies the above range, a stable layered structure can be maintained even if cobalt is not contained in the core particles, the problem of structural collapse due to charging and discharging can be suppressed or reduced, and a long cycle life characteristic of the positive electrode active material can be achieved.

[0042] According to one or more embodiments of the present disclosure, the aluminum concentration in the core particles may be substantially uniformly distributed. For example, this refers to the fact that within the core particles, there is no (e.g., substantially no) aluminum concentration gradient from the center of each core particle to the surface of the core particle, and / or the aluminum concentration outside each core particle is neither higher than nor lower than the aluminum concentration inside, and the aluminum within each core particle is uniformly distributed. This may be a structure obtained by synthesizing a composite oxide using nickel-manganese-aluminum hydroxide as a precursor. For example, a uniform concentration of aluminum in the core particles may be achieved by using an aluminum raw material during precursor generation rather than additionally doping aluminum during the synthesis of the core particles. In one or more embodiments, the core particles may be in the form of secondary particles, wherein each of the secondary particles is formed by aggregating a plurality of primary particles (e.g., each secondary particle is an aggregate of a plurality of primary particles or is in the form of a secondary particle, with a plurality of primary particles aggregated in each secondary particle), and regardless of the position of the primary particles, the aluminum content (e.g., amount) inside the primary particles may be the same or similar. For example, if a primary particle is selected at a random position in the cross section of the secondary particle and the aluminum content (e.g., amount) is measured inside the primary particle rather than at its interface, then the aluminum content (e.g., amount) can be the same / similar / substantially the same regardless of the position of the primary particle, for example, whether the primary particle is near the center of the secondary particle or near the surface of the secondary particle. In this structure, a stable layered structure can be maintained even if cobalt is absent or present in very small amounts. In addition, aluminum byproducts or aluminum aggregates can be avoided, thereby simultaneously improving the capacity, efficiency, and cycle life characteristics of the positive electrode active material.

[0043] The layered lithium nickel manganese-based composite oxide may be specifically represented by Chemical Formula 1.

[0044] Chemical formula 1

[0045] Li a1 Ni x1 Mn y1 Al z1 M 1 w1 O 2-b1 X b1

[0046] In Chemical Formula 1, 0.9≤a1≤1.8, 0.6≤x1≤0.8, 0.1≤y1≤0.4, 0≤z1≤0.03, 0≤w1≤0.3, 0.9≤x1+y1+z1+w1≤1.1, and 0≤b1≤0.1, M 1may be one or more elements selected from boron (B), barium (Ba), calcium (Ca), cerium (Ce), chromium (Cr), iron (Fe), magnesium (Mg), molybdenum (Mo), niobium (Nb), silicon (Si), tin (Sn), strontium (Sr), titanium (Ti), vanadium (V), tungsten (W), yttrium (Y), zirconium (Zr), and zinc (Zn), and X is one or more elements selected from fluorine (F), phosphorus (P), and sulfur (S).

[0047] In one or more embodiments, in Chemical Formula 1, 0.9 ≤ a1 ≤ 1.5, or 0.9 ≤ a1 ≤ 1.2. Additionally, Chemical Formula 1 may include aluminum, in which case, 0.6 ≤ x1 ≤ 0.8, 0.1 ≤ y1 ≤ 0.39, 0.01 ≤ z1 ≤ 0.03, and 0 ≤ w1 ≤ 0.29 may be satisfied, or for example, 0.6 ≤ x1 ≤ 0.8, 0.1 ≤ y1 ≤ 0.39, 0.01 < z1 ≤ 0.03, and 0 ≤ w1 ≤ 0.29 may be satisfied.

[0048] In Chemical Formula 1, for example, 0.6 ≤ x1 ≤ 0.79, 0.6 ≤ x1 ≤ 0.78, 0.6 ≤ x1 ≤ 0.75, 0.65 ≤ x1 ≤ 0.8, or 0.7 ≤ x1 ≤ 0.79, 0.1 ≤ y1 ≤ 0.35, 0.1 ≤ y1 ≤ 0.30, 0.1 ≤ y1 ≤ 0.29, 0.15 ≤ y1 ≤ 0.39, or 0.2 ≤ y1 ≤ 0.3, 0.01 ≤ z1 ≤ 0.025, 0.01 < z1 ≤ 0.02, or 0.01 < z1 ≤ 0.019, 0 ≤ w1 ≤ 0.28, 0 ≤ w1 ≤ 0.27, 0 ≤ w1 ≤ 0.26, 0 ≤ w1 ≤ 0.25, 0 ≤ w1 ≤ 0.24, 0 ≤ w1 ≤ 0.23, 0 ≤ w1 ≤ 0.22, 0 ≤ w1 ≤ 0.21, 0 ≤ w1 ≤ 0.2, 0 ≤ w1 ≤ 0.15, 0 ≤ w1 ≤ 0.1, or 0 ≤ w1 ≤ 0.09.

[0049] The layered lithium nickel manganese composite oxide may be a cobalt-free compound. For example, a cobalt-free compound may refer to a compound that does not include cobalt or includes a very small amount of cobalt. That is, in the context of the present disclosure, unless otherwise indicated, the term "cobalt-free" means that cobalt is not deliberately added, selected, or used as an element in a formula, composition, or compound. However, due to the influence of impurities or external factors, trace amounts of cobalt may still be present, as long as its content is below an appropriate level. In one or more embodiments, based on 100 mol% of the total metal excluding lithium, the cobalt content (e.g., amount) of the layered lithium nickel manganese composite oxide may be less than or equal to about 0.01 mol%, less than or equal to about 0.005 mol%, less than or equal to about 0.001 mol%, for example, about 0 mol% to about 0.01 mol%, about 0 mol% to about 0.005 mol%, or about 0 mol% to about 0.001 mol%.

[0050] The core particles may be secondary particles formed by aggregating a plurality of primary particles. The secondary particles may be spherical, ellipsoidal, polyhedral and / or irregular in shape, and the primary particles constituting the secondary particles may be spherical, ellipsoidal, plate-shaped and / or (e.g., any appropriate) combination thereof.

[0051] coating

[0052] According to one or more embodiments of the present disclosure, the positive electrode active material may include an aluminum coating layer on the surface of the core particle and a grain boundary coating portion on the surface of the primary particle and including cobalt.

[0053] Layered lithium nickel manganese composite oxides may be susceptible to chemical attack by components in the electrolyte. For example, if (e.g., when) the battery is operated under high voltage or high temperature conditions (which may produce many side reactions with the electrolyte), it may lead to increased gas generation, thereby deteriorating the battery cycle life and safety. These problems can be solved by introducing a coating according to one or more embodiments of the present disclosure.

[0054] The coating layer of the positive electrode active material may include aluminum and may optionally further include a zirconium coating layer on the aluminum coating layer. In this regard, the content (e.g., amount) of the coating element may vary depending on the type or species of the coating element, based on 100 mol% of the total metal excluding lithium in the entire positive electrode active material. For example, the content (e.g., amount) of the coating element may be about 0.01 mol% to about 5 mol%, about 0.05 mol% to about 3 mol%, or about 0.1 mol% to about 2 mol%.

[0055] For example, if (e.g., when) an aluminum coating is introduced, the aluminum content (e.g., amount) of the aluminum coating may be about 0.1 mol% to about 3.0 mol%, about 0.1 mol% to about 2.0 mol%, about 0.5 mol% to about 1.5 mol%, or about 0.7 mol% to about 1.3 mol%, based on 100 mol% of the total metal excluding lithium in the positive electrode active material. In one or more embodiments, the aluminum content (e.g., amount) of the aluminum coating may refer only to the content (e.g., amount) of aluminum in the aluminum coating, without regard to the aluminum included in the core particle. In one or more embodiments, if (e.g., when) an aluminum coating is introduced, the aluminum coating may include a layered aluminum compound, such as aluminum oxide, lithium aluminum oxide, and / or (e.g., any suitable) combination thereof, for example, the aluminum coating may include LiAlO2.

[0056] For example, if (e.g., when) a zirconium coating is introduced on an aluminum coating, the zirconium content (e.g., amount) of the zirconium coating may be about 0.1 mol% to about 1.5 mol%, about 0.1 mol% to about 1.0 mol%, about 0.1 mol% to about 0.5 mol%, or about 0.1 mol% to about 0.4 mol%, based on 100 mol% of the total metal excluding lithium in the positive electrode active material. When the content of aluminum and / or zirconium in the coating satisfies the above ranges, the positive electrode active material can form a good or appropriate coating without reducing capacity or increasing resistance, effectively inhibiting or reducing side reactions with the electrolyte, and effectively reducing the amount of gas generated under high voltage or high temperature conditions.

[0057] According to one or more embodiments of the present invention, the aluminum coating may be in the form of a film that continuously surrounds the surface of the core particle, for example, in the form of a shell surrounding the entire surface of the core particle. This is different from a coating structure in which a portion of the surface of the core particle is coated. According to one or more embodiments, the aluminum coating may be formed to completely cover the surface of the core particle and have a very thin and substantially uniform thickness, which improves the structural stability of the positive electrode active material without increasing resistance or degrading capacity, while still effectively suppressing or reducing its side reactions with the electrolyte and reducing the amount of gas generated. That is, in some embodiments, an aluminum coating that completely wraps the core particle with a uniform thin layer can be manufactured. This enhances the structural integrity of the positive electrode active material without increasing resistance or reducing its capacity. In addition, it successfully minimizes side reactions with the electrolyte, resulting in a reduction in gas generation. Therefore, the aluminum coating can achieve long cycle life characteristics of the positive electrode active material under high voltage and high temperature conditions.

[0058] According to one or more embodiments of the present disclosure, the thickness of the aluminum coating layer may be about 10 nm to about 500 nm, about 10 nm to about 450 nm, about 10 nm to about 400 nm, about 10 nm to about 350 nm, about 10 nm to about 300 nm, about 10 nm to about 250 nm, about 10 nm to about 200 nm, about 10 nm to about 150 nm, about 10 nm to about 100 nm, about 10 nm to about 50 nm, about 20 nm to about 500 nm, about 30 nm to about 500 nm, or about 40 nm to about 500 nm. For example, the thickness of the aluminum coating layer may be less than or equal to 40 nm. If (for example, when) the thickness of the aluminum coating layer meets the above-mentioned thickness range (when), the coating layer neither increases resistance nor reduces capacity, but can improve the structural stability of the positive electrode active material and inhibit or reduce its side reaction with the electrolyte. In one or more embodiments, the thickness of the aluminum coating can be measured, for example, using SEM, TEM, time-of-flight secondary ion mass spectrometry (TOF-SIMS), x-ray photoelectron spectroscopy (XPS), or energy dispersive x-ray spectroscopy (EDS), and the thickness range of the aluminum coating can be measured by TEM-EDS line profile.

[0059] According to one or more embodiments of the present disclosure, the aluminum coating layer may be thin and substantially uniform in thickness, at the level of tens to hundreds of nanometers. For example, the deviation of the aluminum coating layer thickness in one positive electrode active material particle may be less than or equal to about 20%, less than or equal to about 18%, or less than or equal to about 15%. As used herein, the deviation of the aluminum coating layer thickness may refer to the deviation of the coating layer thickness within one positive electrode active material particle. For example, the deviation of the aluminum coating layer thickness may be calculated by measuring the thickness of about 10 points in an electron microscope image of a cross section of a single positive electrode active material particle to calculate the arithmetic mean of the thickness, then dividing the absolute value of the difference between one measurement data and the arithmetic mean by the arithmetic mean and multiplying by 100%. When the deviation or standard deviation of the aluminum coating layer thickness meets the above range, it may mean that a coating layer with substantially uniform thickness can be formed in the form of a good or appropriate film on the surface of the positive electrode active material particle. Therefore, the structural stability of the positive electrode active material can be improved, side reactions with the electrolyte can be effectively suppressed or reduced, and the resistance increase or capacity reduction caused by the coating layer can be minimized or reduced.

[0060] According to one or more embodiments of the present disclosure, in addition to aluminum, the aluminum coating may further include nickel, manganese and / or a combination thereof (e.g., any suitable combination). In the process of forming the aluminum coating, the nickel and manganese already contained in the core particles may flow into the aluminum coating, and each of the nickel content and the manganese content (e.g., amount) is not particularly limited. According to one or more embodiments of the present invention, the aluminum coating, which must contain aluminum and may optionally contain nickel and manganese, can be formed to have a thin and substantially uniform thickness, and improves the high voltage characteristics and cycle life characteristics of the positive electrode active material.

[0061] In addition, according to one or more embodiments of the present disclosure, the aluminum coating may further contain sulfur in addition to aluminum. Sulfur may be introduced during the addition of aluminum sulfate as an aluminum raw material to form the aluminum coating, and the sulfur content (e.g., amount) is not particularly limited. According to one or more embodiments, the aluminum coating, which necessarily contains aluminum and may optionally contain sulfur, can improve the high-voltage characteristics of the positive electrode active material and enhance cycle life characteristics.

[0062] In contrast, in the process of forming the aluminum coating, aluminum can diffuse into the secondary particles. Therefore, in one or more embodiments, the positive electrode active material may include a grain boundary coating portion, which contains aluminum and is located on the surface of the (e.g., each) primary particle inside the (e.g., each) secondary particle. The interior of the (e.g., each) secondary particle may refer to the entire interior of the (e.g., corresponding one) secondary particle, but the surface of the secondary particle or in the center direction from the surface of the (e.g., corresponding one) secondary particle to the radius of the (e.g., corresponding one) secondary particle. Except for the region of about 60% of the length. For example, the positive electrode active material may include a grain boundary coating portion consisting of aluminum. The grain boundary coating portion is present on the surface of each primary particle inside each secondary particle. It extends to the entire internal area of ​​each secondary particle, excluding the outer surface, and about 60% of the length from the surface to the center radius. The grain boundary coating portion is different from the coating on the surface of the secondary particle, and refers to the coating portion formed on the surface of the primary particle inside the secondary particle. For example, the grain boundary coating portion is different from the outer coating of the secondary particle. Specifically, it refers to a coating on the surface of the primary particles located inside the secondary particles. The grain boundary coating portion can be examined on a cross section of the positive electrode active material by SEM-EDS analysis, etc. The aluminum grain boundary coating portion can be formed to further structurally stabilize the positive electrode active material and improve cycle life characteristics.

[0063] The aluminum content (eg, amount) in the grain boundary coating portion may not be particularly limited, and for example, the aluminum content (eg, amount) of the grain boundary coating portion may be smaller than the aluminum content (eg, amount) of the coating layer.

[0064] According to one or more embodiments of the present disclosure, the positive electrode active material may include core particles in the form of secondary particles, wherein the secondary particles are formed by aggregating a plurality of primary particles (e.g., in the form of secondary particles, a plurality of primary particles are aggregated in each secondary particle), and the grain boundary coating portion of the primary particles is located on the surface of the primary particles and contains cobalt. Because the positive electrode active material is prepared by coating aluminum on the surface of the core particles and then dry-coating cobalt on the surface of the core particles, in the positive electrode active material, cobalt may be rarely present on the surface of the core particles, but diffuses into the interior of the core particles. If (e.g., when) cobalt is doped, cobalt may be uniformly (e.g., substantially uniformly) present in the interior of the primary particles, but in one or more embodiments, the positive electrode active material may have the characteristic that cobalt is not coated on the interior of the primary particles but is coated on the grain boundaries of the primary particles. For example, after LiAlO2 is formed on the surface of the core particles by aluminum coating and cobalt dry coating, cobalt may diffuse into the interior of the core particles and be coated on the grain boundaries of the primary particles. Through these, cobalt can be coated on the surface of the primary particles, and aluminum can be coated on the surface of the secondary particles and the surface of the secondary particles can be modified, thereby improving capacity and cycle life characteristics and reducing the amount of gas generated during high temperature storage. As used herein, based on 100 mol% of the total metal excluding lithium in the positive electrode active material, the cobalt content (e.g., amount) of the grain boundary coating portion can be about 0.1 mol% to about 5.0 mol%, about 0.5 mol% to about 4.0 mol%, about 1.0 mol% to about 3.0 mol%, or 2.0 mol% to about 3.0 mol%. If (e.g., when) the cobalt content (e.g., amount) of the grain boundary coating portion meets these ranges, cobalt can diffuse into the interior of the core particle to form a coating portion at the grain boundary of the primary particle, which can effectively inhibit or reduce side reactions with the electrolyte and effectively reduce gas generation under high voltage or high temperature conditions.

[0065] The surface of the core particle may not include (e.g., may exclude any) cobalt or may include a very small amount of cobalt, and the cobalt content (e.g., amount) may be less than or equal to 0.01 mol%, less than or equal to 0.005 mol%, less than or equal to 0.001 mol%, for example, from about 0 mol% to about 0.01 mol%, from about 0 mol% to about 0.005 mol%, or from about 0 mol% to about 0.001 mol%, based on about 100 mol% of the total metal excluding lithium in the positive electrode active material. For example, the coating on the surface of the core particle may not include (e.g., may exclude any) cobalt, or may include a very small amount of cobalt, and the cobalt may diffuse into the interior of the core particle and coat the grain boundaries of the primary particles.

[0066] According to one or more embodiments of the present disclosure, the average particle size (D 50) may not be particularly limited, but may be, for example, about 10 micrometers (μm) to about 25 μm, about 11 μm to about 20 μm, or about 12 μm to about 18 μm. As used herein, if (for example, when) no definition is otherwise provided, the average particle size (D 50 ) may refer to the diameter of particles accounting for 50% by volume of the cumulative volume in a particle size distribution obtained by randomly measuring the size (diameter or major axis length) of approximately 20 particles in a scanning electron microscope image of the positive electrode active material. When the average particle size of the positive electrode active material satisfies the above range, high capacity and long cycle life can be achieved, and it can be beneficial to form a coating according to one or more embodiments.

[0067] Method for preparing positive electrode active material

[0068] In one or more embodiments, a method for preparing a positive electrode active material may include (i) preparing core particles comprising a lithium nickel manganese composite oxide and in the form of secondary particles, wherein the secondary particles are formed by aggregating a plurality of primary particles (e.g., in the form of secondary particles in which a plurality of primary particles are aggregated); (ii) preparing an aluminum coating solution comprising an aqueous solvent and an aluminum raw material; (iii) adding the core particles to the aluminum coating solution, mixing them, and then drying them to prepare a coating product; and (iv) dry-mixing the coating product and a cobalt raw material and performing a heat treatment to obtain a positive electrode active material.

[0069] According to one or more embodiments of the present disclosure, in a method for preparing a positive electrode active material, step (e.g., action or task) (i) may include (a) mixing a nickel-manganese composite hydroxide and a lithium raw material; and (b) performing a first heat treatment. The nickel-manganese composite hydroxide as a core particle precursor may not contain cobalt or contain a very small amount of cobalt, and may be, for example, a cobalt-free nickel-manganese composite hydroxide. The nickel-manganese composite hydroxide may be prepared by a conventional coprecipitation method.

[0070] Based on about 100mol% of the total metal in the nickel-manganese composite hydroxide, the nickel-manganese composite hydroxide can have a nickel content (e.g., amount) of about 60mol% to about 80mol%, about 65mol% to about 80mol%, about 70mol% to about 80mol%, about 60mol% to about 79mol%, about 60mol% to about 78mol% or about 60mol% to about 75mol%. If (e.g., when) nickel content (e.g., amount) meets this range (when), high capacity can be achieved, and even if cobalt content (e.g., amount) is reduced, structural stability can be increased.

[0071] Based on about 100mol% of the total metal in the nickel-manganese composite hydroxide, the nickel-manganese composite hydroxide may have a manganese content of about 10mol%, about 10mol% to about 40mol%, about 15mol% to about 35mol%, about 15mol% to about 30mol%, or about 20mol% to about 30mol%. If (for example, when) the manganese content (for example, amount) satisfies this range (when), not only high capacity can be achieved, but also the structural stability of the positive electrode active material can be increased, and production costs can also be reduced, which can further improve economic feasibility.

[0072] In addition, if (for example, when) the nickel-manganese composite hydroxide may further include aluminum (when), the aluminum content (for example, amount) may be greater than or equal to 0 mol% and less than or equal to about 3 mol%, greater than or equal to 0.1 mol%, greater than or equal to 0.5 mol%, or greater than or equal to 1 mol%, based on about 100 mol% of the total metal in the nickel-manganese composite hydroxide, for example, about 1 mol% to about 3 mol%, about 1 mol% to about 2.5 mol%, about 1 mol% to about 2 mol%, or about 1 mol% to about 1.9 mol%. In the nickel-manganese composite hydroxide, if (for example, when) the aluminum content (for example, amount) satisfies this range (when), not only high capacity can be achieved, but also the structural stability of the positive electrode active material can be increased, and the production cost can be reduced, which can further improve economic feasibility.

[0073] According to one or more embodiments of the present disclosure, the method for preparing a positive electrode active material may not additionally dope aluminum when manufacturing core particles, but rather use an aluminum raw material when preparing a precursor, thereby using a nickel-manganese-aluminum composite hydroxide in which aluminum is uniformly dispersed within the structure as a precursor. If (for example, when) such a precursor is used, a positive electrode active material that can stably maintain a layered structure even when repeatedly charged and discharged in the absence of cobalt can be manufactured. In such a process for preparing a positive electrode active material, aluminum byproducts or aluminum aggregates may not be formed, thereby improving the capacity and efficiency characteristics of the positive electrode active material and the cycle life characteristics of a lithium battery including the positive electrode active material.

[0074] In the nickel-manganese composite hydroxide, the cobalt content (e.g., amount) based on 100 mol% of total metal may be less than or equal to 0.01 mol%, less than or equal to 0.005 mol%, or less than or equal to 0.001 mol%, for example, may be from about 0 mol% to about 0.01 mol%, from about 0 mol% to about 0.005 mol%, or from about 0 mol% to about 0.001 mol%. The nickel-manganese composite hydroxide may be economical because it avoids the increase in unit cost caused by cobalt, maximizes capacity, and improves structural stability.

[0075] For example, the nickel-manganese-based composite hydroxide can be represented by Chemical Formula 2.

[0076] Chemical formula 2

[0077] Ni x2 Mn y2 Al z2 M 2 w2 (OH)2

[0078] In Chemical Formula 2, 0.6≤x2≤0.8, 0.1≤y2≤0.4, 0≤z2≤0.03, 0≤w2≤0.3, and 0.9≤x2+y2+z2+w2≤1.1, M 2 It may be one or more elements selected from B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zr and Zn.

[0079] In Chemical Formula 2, for example, 0.6≤x2≤0.8, 0.1≤y2≤0.39, 0.01≤z2≤0.03, and 0≤w2≤0.29.

[0080] The nickel-manganese composite hydroxide is in the form of particles, and the average particle size (D 50 ) may be from about 10 μm to about 25 μm, for example, from about 11 μm to about 20 μm or from about 12 μm to about 18 μm.

[0081] The nickel-manganese composite hydroxide and the lithium raw material may be mixed in a molar ratio of about 1:0.9 to about 1:1.8 (eg, about 1:0.9 to about 1:1.5 or about 1:1 to about 1:1.2).

[0082] The first heat treatment may be performed in an oxygen atmosphere, for example, at a temperature range of about 750°C to about 950°C, about 780°C to about 900°C, or about 810°C to about 890°C for about 2 hours to about 20 hours, or about 4 hours to about 12 hours.

[0083] By the first heat treatment, a lithium nickel manganese composite oxide can be obtained. Based on about 100 mol% of the total metal without lithium, the obtained lithium nickel manganese composite oxide may have a nickel content (e.g., amount) of about 60 mol% to 80 mol%, a manganese content (e.g., amount) greater than or equal to about 10 mol%, an aluminum content (e.g., amount) of about 0 mol% to about 3 mol%, and a very small amount of cobalt content (e.g., amount) of about 0 mol% to about 0.01 mol%. Because this composite oxide and oxides with different compositions (e.g., lithium nickel cobalt manganese composite oxides, lithium nickel cobalt aluminum composite oxides, lithium cobalt composite oxides, etc.) may have significantly different residual lithium contents and different one or more appropriate properties on the surface of the core particles, it is impossible to form a satisfactory coating in the form of a substantially uniform film using existing coating methods.

[0084] Therefore, in the method for preparing a positive electrode active material according to one or more embodiments, steps (e.g., actions or tasks) (ii) and (iii) can introduce a substantially uniform coating onto the positive electrode active material by mixing an aqueous solvent and an aluminum raw material to prepare an aluminum coating solution (in which the salt is completely dissolved by a salting method), adding core particles to the aluminum coating solution and mixing them, and drying the core particles for coating.

[0085] The salt dissolution method is a salt dissolution wet coating method, and is a pre-addition method in which the salt of the coating raw material (e.g., the salt of the aluminum raw material) is first dissolved, and then the active material particles (i.e., core particles) are added to a mixture of the salt of the coating raw material and an aqueous solvent (e.g., an aluminum coating solution). By the salt dissolution method, a coating can be successfully formed on the surface of the layered lithium nickel manganese composite oxide in the form of a substantially uniform and thin film. Compared to a general dry method or a post-addition wet method, the coating method according to one or more embodiments of the present disclosure can further increase the coating element content (e.g., amount) on the surface of the active material particles.

[0086] The aqueous solvent may include distilled water, an alcoholic solvent, and / or any suitable combination thereof. The aluminum raw material may be, for example, aluminum sulfate. Aluminum sulfate may be an optimal or suitable raw material for forming a substantially uniform aluminum coating on the layered lithium nickel manganese composite oxide.

[0087] In the core particles, the aluminum content (e.g., amount) of the aluminum raw material can be designed to be about 0.1 mol% to about 3.0 mol%, for example, about 0.1 mol% to about 2.0 mol%, about 0.5 mol% to about 1.5 mol%, or about 0.7 mol% to about 1.3 mol%, based on about 100 mol% of the total metal excluding lithium and the aluminum of the aluminum raw material. The aluminum coating content (e.g., amount) can be designed within these ranges to form a coating having a substantially uniform thickness of tens to hundreds of nanometers, thereby reducing gas generation and achieving high capacity, and improving the long cycle life characteristics of rechargeable lithium batteries manufactured under high voltage or high temperature driving conditions.

[0088] The mixing of the aluminum raw material and the aqueous solvent (e.g., preparing an aluminum coating solution) can be carried out for about 1 minute to about 60 minutes, for example, about 3 minutes to about 30 minutes or about 5 minutes to about 10 minutes. In addition, the mixing of the aluminum raw material and the aqueous solvent can be carried out at a speed of about 100rpm to about 800rpm (e.g., about 200rpm to about 600rpm or about 250rpm to about 500rpm). Through this mixing condition, the aluminum raw material can be completely dissolved in the aqueous solvent to obtain a colorless and transparent coating solution (i.e., an aluminum coating solution), and the coating solution can be used to effectively form a substantially uniform coating according to one or more embodiments. The mixed coating solution has a pH value of about 1.5 to about 4 (e.g., about 2.0 to about 3.5, about 2.5 to about 3.3, about 2.7 to about 3.3, or about 2.9 to about 3.2).

[0089] The addition of the core particles can be performed while stirring the coating solution to increase the coating quality.

[0090] In addition, the time used for adding core particles to the coating solution can be about 30 seconds to add about 500 grams (g) of core particles to about 2 minutes to add about 500g of core particles, for example, about 30 seconds to add about 500g of core particles to about 1.5 minutes to add about 500g of core particles, etc. The speed of adding core particles can be appropriately or suitably adjusted to appropriately or suitably control the pH value of the supernatant after coating is completed, thereby effectively inducing the formation of a substantially uniform coating according to one or more embodiments. For example, if (for example, when) the speed of adding core particles is too slow (for example, slower than the above-mentioned time range) (time), the reaction speed of each particle can vary, which can result in a substantially uniform coating being unable to be formed. In addition, if the speed of adding core particles is too fast (for example, faster than the above-mentioned time range), the pH value will be caused to change too fast, which can also result in a substantially uniform coating being unable to be formed.

[0091] After all the core particles are added to the coating solution, the mixture (e.g., a mixture of core particles and coating solution) can be stirred for about 15 minutes to about 60 minutes, for example, about 20 minutes to about 50 minutes or about 30 minutes to 45 minutes, and the time taken to add the core particles to the coating solution to complete the stirring (e.g., the coating reaction time) can be appropriately or suitably adjusted within about 1 hour.

[0092] In one or more embodiments of the present disclosure, if (e.g., when) stirring is stopped after adding the core particles to the coating solution (e.g., mixing of the core particles with the coating solution is completed), or if (e.g., when) coating is completed (e.g., a coating is formed on the core particles), the pH of the supernatant may be in the range of about 5.5 to about 8.5. If (e.g., when) the pH of the supernatant is less than about 5.5, the acidity may become too strong to form a substantially uniform coating, but if the pH is greater than about 8.5, the alkalinity may also become too strong to form a substantially uniform coating.

[0093] After removing the aqueous solvent from the mixed solution (e.g., the mixture of the core particles and the coating solution after the stirring step (action)), the obtained product can be dried, for example, under vacuum conditions at a temperature of, for example, about 40° C. to about 240° C., about 100° C. to about 220° C., or about 150° C. to about 200° C. Under such conditions, a satisfactory coating product can be obtained.

[0094] After removing the aqueous solvent from the mixed solution, the product obtained (e.g., the coating product after the drying step (action) is completed) is called a coating product. The coating product may include core particles and a coating layer located on the surface of the core particles and containing aluminum. That is, once the aqueous solvent is removed from the mixed solution and the resulting product is completely dried, it is called a coating product. The product includes core particles coated with a coating layer comprising aluminum on its surface. For example, the coating layer may be fibrous (e.g., in the form of fibers), grid-like and / or spider-web-like. Such a grid may be formed continuously over the entire surface of the core particles. A grid-like coating layer having a very thin and substantially uniform thickness may surround (e.g., surround) the core particles, thereby strengthening the surface of the positive electrode active material and enhancing structural stability, thereby improving its high temperature and high voltage characteristics.

[0095] According to one or more embodiments of the present disclosure, step (e.g., action or task) (iv) in the method for preparing a positive electrode active material may be dry mixing the coated product with a cobalt raw material and performing a heat treatment to obtain a positive electrode active material (e.g., a product obtained after the step of dry mixing). In the process of preparing the positive electrode active material, LiAlO2 is formed on the core particles by an aluminum coating, cobalt is diffused into the interior of the core particles by dry coating, and a coating is formed at the grain boundaries of the primary particles. Therefore, since cobalt can be coated on the surface of the primary particles and aluminum can be coated on the surface of the secondary particles to modify the surface, in the process of preparing the positive electrode active material, there may be an effect of improving the capacity and cycle life characteristics of the positive electrode active material and reducing the amount of gas generated during high temperature storage. For example, as a result, by coating cobalt on the surface of the primary particles and aluminum on the surface of the secondary particles to change their characteristics, it can be observed that the capacity and cycle life performance are enhanced, and the amount of gas generated during high temperature storage is reduced.

[0096] The cobalt raw material may be, for example, cobalt hydroxide (Co(OH)2), cobalt oxide and / or (e.g., any suitable) combination thereof, which may be additionally mixed with a lithium raw material in the step of dry mixing the coated product with the cobalt raw material, wherein the lithium raw material may be, for example, lithium hydroxide (LiOH).

[0097] In the core particles, the cobalt content (e.g., amount) of the cobalt raw material can be designed to be about 0.1 mol% to about 5.0 mol%, for example, about 0.5 mol% to about 4.0 mol%, about 1.0 mol% to about 3.0 mol%, or about 2.0 mol% to 3.0 mol%, based on about 100 mol% of the total metal excluding lithium in the core particles and the sum of the cobalt of the cobalt raw material. The cobalt content (e.g., amount) can be designed within the above range so that cobalt can diffuse into the interior of the core particles and coat the grain boundaries of the primary particles, thereby improving the cycle life characteristics of the lithium battery including the positive electrode active material under high voltage or high temperature driving conditions and simultaneously (e.g., synchronously) increasing the initial charge and discharge efficiency of the lithium battery including the positive electrode active material.

[0098] In step (e.g., action or task) (iv) of the method for preparing a positive electrode active material, during the step (action) of dry mixing the coated product and the cobalt raw material, a lithium raw material and a zirconium raw material may be mixed together to perform zirconium coating. The zirconium raw material may be, for example, zirconium oxide.

[0099] The zirconium content (e.g., amount) of the zirconium raw material can be designed to be about 0.01 mol% to about 1.5 mol%, for example, about 0.05 mol% to about 1.0 mol%, about 0.1 mol% to about 1.0 mol%, about 0.1 mol% to about 0.5 mol%, or about 0.1 mol% to about 0.4 mol%, based on about 100 mol% of the total metal excluding lithium in the positive electrode active material. The zirconium coating content (e.g., amount) can be designed within the above range to form a coating having a substantially uniform thickness of tens to hundreds of nanometers, thereby improving the cycle life characteristics of a lithium battery including the positive electrode active material under high voltage or high temperature driving conditions and simultaneously (e.g., synchronously) increasing the charge and discharge efficiency of the lithium battery including the positive electrode active material.

[0100] In one or more embodiments of the present disclosure, the heat treatment performed after the aforementioned nickel-manganese composite hydroxide is mixed with the lithium raw material can be expressed as a first heat treatment, and the heat treatment of the coated product can be expressed as a second heat treatment. The second heat treatment can be understood as, for example, in an oxygen atmosphere, at about 700°C to 850°C, about 750°C to about 840°C or about 800°C to 830°C for about 2 hours to about 20 hours or about 3 hours to about 10 hours to form a coating. If (for example, when) the second heat treatment temperature is set within the above range (when), aluminum tends to diffuse less into the interior of the secondary particles and mainly remain on the surface of the secondary particles, and at the same time (for example, synchronously) coated on the surface of the secondary particles in the form of a shell having a very thin and substantially uniform thickness.

[0101] positive electrode

[0102] In one or more embodiments of the present disclosure, the positive electrode may include 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 includes the aforementioned positive electrode active material. In addition to the aforementioned positive electrode active material, the positive electrode active material layer may further include other types (kinds) of positive electrode active materials. In addition, the positive electrode active material layer may optionally further include a binder, a conductive material (e.g., an electronic conductor) and / or a combination thereof (e.g., any suitable combination).

[0103] According to one or more embodiments, the loading level of the positive electrode active material layer may be about 10 mg / cm 2 ~about 40mg / cm 2 , for example, about 10 mg / cm 2 ~about 30mg / cm 2 or about 10 mg / cm 2 ~about 20mg / cm 2. In addition, the density of the positive electrode active material layer in the final pressed positive electrode may be about 3.3 g / cc to about 3.7 g / cc, for example, 3.3 g / cc to 3.6 g / cc or about 3.4 g / cc to about 3.58 g / cc. When the positive electrode active material according to one or more embodiments is applied, it is beneficial to achieve such a loading level and density of the positive electrode active material layer, and the positive electrode that satisfies the loading level and density of the positive electrode active material layer within the above range is suitable for realizing a high-capacity, high-energy-density rechargeable lithium battery.

[0104] adhesive

[0105] The binder can improve the bonding properties between the positive electrode active material particles and the bonding properties between the positive electrode active material particles and the positive electrode current collector. Examples of the binder may include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, and / or nylon, but are not limited thereto.

[0106] Conductive materials

[0107] A conductive material (e.g., an electron conductor) may be included to provide electrode (e.g., electron) conductivity, and any conductive material can be used as the conductive material unless it causes a chemical change. Examples of the conductive material may include carbon-based materials (such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, carbon nanotubes, etc.), metal-based materials including metal powders or metal fibers of copper, nickel, aluminum, silver, etc., conductive polymers (such as polyphenylene derivatives), and / or (e.g., any suitable) mixtures thereof.

[0108] Each content (eg, amount) of the binder and the conductive material may be about 0.5 wt % to about 5 wt % based on 100 wt % of the positive electrode active material layer.

[0109] The positive electrode current collector may include Al foil, etc., but the present disclosure is not limited thereto.

[0110] Rechargeable lithium battery

[0111] Some embodiments provide a rechargeable lithium battery comprising: the aforementioned positive electrode, negative electrode, and electrolyte. As an example, the rechargeable lithium battery may include a positive electrode, a negative electrode, a separator between the positive electrode and the negative electrode, and an electrolyte solution (i.e., electrolyte).

[0112] Rechargeable lithium batteries may be classified according to shape into cylindrical, prismatic, pouch, coin, etc. Figures 1 to 4 is a schematic diagram illustrating a rechargeable lithium battery according to one or more embodiments, wherein Figure 1 For cylindrical batteries, Figure 2 It is a prismatic battery, and Figure 3 and Figure 4 It is a pouch-shaped battery. Figures 1 to 4 , the rechargeable lithium battery 100 includes an electrode assembly 40 (which has 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, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte solution. Figure 1 As shown in FIG, the rechargeable lithium battery 100 may include a sealing member 60 that seals the housing 50. Figure 2 In the embodiment, the rechargeable lithium battery 100 may include a positive electrode lead tab 11, a positive electrode terminal 12, a negative electrode lead tab 21, and a negative electrode terminal 22. Figure 3 and Figure 4 As shown in FIG, the rechargeable lithium battery 100 includes electrode tabs 70, ie, a positive electrode tab 71 and a negative electrode tab 72, serving as an electrical path for guiding current formed in the electrode assembly 40 to the outside.

[0113] The rechargeable lithium battery according to one or more embodiments may be properly or appropriately charged or driven at a high voltage and exhibit improved characteristics under the high voltage condition.

[0114] For example, the upper limit voltage for charging the rechargeable lithium battery may be greater than or equal to about 4.45 V, for example, about 4.45 V to about 4.6 V, about 4.45 V to about 4.55 V, or about 4.45 V to about 4.5 V. A rechargeable lithium battery using the positive electrode active material of one or more embodiments can significantly reduce gas generation and achieve high capacity and long cycle life characteristics when charged at a high voltage.

[0115] negative electrode

[0116] The negative electrode may include a negative electrode current collector and a negative electrode active material layer on the negative electrode current collector, and the negative electrode active material layer may further include a negative electrode active material, a binder, a conductive material (e.g., an electron conductor) and / or a combination thereof (e.g., any appropriate combination).

[0117] Negative electrode active material

[0118] The negative electrode active material may include a material that reversibly intercalates / deintercalates lithium ions, lithium metal, a lithium metal alloy, a material capable of doping / dedoping lithium, or a transition metal oxide.

[0119] Materials capable of reversibly embedding / desorbing lithium ions may include crystalline carbon, amorphous carbon, and / or its (e.g., any suitable) combination as carbonaceous negative electrode active materials. The crystalline carbon may be natural graphite or artificial graphite that is amorphous or in the form of flakes, sheets, spheres, or fibers (e.g., in the form of fibers). The amorphous carbon may be soft carbon, hard carbon, mesophase pitch carbonized product, calcined coke, etc.

[0120] Lithium metal alloys include alloys of lithium and metals selected from sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), beryllium (Be), Mg, Ca, Sr, Si, antimony (Sb), lead (Pb), indium (In), Zn, Ba, radium (Ra), germanium (Ge), Al, and Sn.

[0121] Materials capable of doping / undoping lithium may be Si-based negative electrode active materials or Sn-based negative electrode active materials. The Si-based negative electrode active materials may include silicon, silicon-carbon composites, SiO x (0 < x ≤ 2), Si-Q alloys (where Q is an element selected from alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements (except Si), Group 15 elements, Group 16 elements, transition metals, rare earth elements, and / or its (e.g., any suitable) combination, such as Mg, Ca, Sr, Ba, Ra, scandium (Sc), yttrium (Y), Ti, Zr, hafnium (Hf), (Rf), V, Nb, tantalum (Ta), dubnium (Db), Cr, Mo, W, (Sg), technetium (Tc), rhenium (Re), (Bh), Fe, Pb, ruthenium (Ru), osmium (Os), (Hs), rhodium (Rh), iridium (Ir), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), cadmium (Cd), B, Al, gallium (Ga), Sn, In, thallium (Tl), Ge, P, arsenic (As), Sb, bismuth (Bi), S, selenium (Se), tellurium (Te), polonium (Po), and / or its (e.g., any suitable) combination) and / or its (e.g., any suitable) combination. The Sn-based negative electrode active materials may be Sn, SnO x (0 < x ≤ 2) (e.g., SnO2), Sn alloys, and / or its (e.g., any suitable) combination.

[0122] 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)It can be, for example, about 0.5 to about 20 μm. According to one or more embodiments, the silicon-carbon composite can be in the form of silicon particles and amorphous carbon coated on the surface of the silicon particles. The silicon-carbon composite can include secondary particles (cores) in which silicon primary particles are aggregated and an amorphous carbon coating (shell) on the surface of the secondary particles. Amorphous carbon can also be present between the silicon primary particles. For example, the silicon primary particles can be coated with amorphous carbon. The secondary particles can be dispersed in an amorphous carbon matrix.

[0123] The silicon-carbon composite can further include crystalline carbon. For example, the silicon-carbon composite can include a core containing crystalline carbon and silicon particles and an amorphous carbon coating on the surface of the core. The crystalline carbon can be artificial graphite, natural graphite, and / or a combination thereof (e.g., any suitable combination). The amorphous carbon can include soft carbon or hard carbon, mesophase pitch carbonized products, and / or calcined coke.

[0124] In one or more embodiments, when the silicon-carbon composite includes silicon and amorphous carbon, based on 100 wt% of the silicon-carbon composite, the content (e.g., amount) of silicon can be about 10 wt% to about 50 wt%, and based on 100 wt% of the silicon-carbon composite, the content (e.g., amount) of amorphous carbon can be about 50 wt% to about 90 wt%. Additionally, if (e.g., when) the silicon-carbon composite includes silicon, amorphous carbon, and crystalline carbon, based on 100 wt% of the silicon-carbon composite, the content (e.g., amount) of silicon can be about 10 wt% to about 50 wt%, based on 100 wt% of the silicon-carbon composite, the content (e.g., amount) of crystalline carbon can be about 10 wt% to about 70 wt%, and based on 100 wt% of the silicon-carbon composite, the content (e.g., amount) of amorphous carbon can be about 20 wt% to about 40 wt%.

[0125] Additionally, the thickness of the amorphous carbon coating can be about 5 nm to about 100 nm. The average particle size (D 50 ) of the silicon particles (primary particles) can be about 10 nm to about 1 μm or about 10 nm to about 200 nm. The silicon particles can exist in the form of elemental silicon, silicon alloys, and / or oxidized forms of silicon. The oxidized form of silicon can be represented by SiO x (0 < x ≤ 2) (e.g., SiO2). In this regard, the atomic content (e.g., amount) ratio of Si:O that can indicate the degree of oxidation of the oxidized form of silicon can be about 99:1 to about 33:67. As used herein, if (e.g., when) no other definition is provided, the average particle size (D 50 ) can indicate the diameter of the particles in the particle size distribution of the silicon particles in which the cumulative volume is about 50 volume%.

[0126] The Si-based negative electrode active material or the Sn-based negative electrode active material may be mixed with the carbon-based negative electrode active material. In one or more embodiments, 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 mixed and used, the mixing ratio may be about 1:99 to about 90:10 by weight.

[0127] adhesive

[0128] The binder is used to bind the negative electrode active material particles well to each other and also to bind the negative electrode active material to the negative electrode current collector. The binder can be a non-aqueous binder, an aqueous binder, a dry binder, and / or any suitable combination thereof.

[0129] The non-aqueous binder may include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, and / or (eg, any suitable) combinations thereof.

[0130] The aqueous binder may include styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinyl pyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinyl pyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol and / or (e.g., any suitable) combination thereof.

[0131] In one or more embodiments, when an aqueous binder is used as a binder in the negative electrode active material layer, a cellulose compound capable of imparting viscosity may be further included. As the cellulose compound, one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and alkali metal salts thereof may be mixed and used. The alkali metal may be Na, K, or lithium (Li).

[0132] The dry binder may be a polymer material capable of becoming fibers, and may be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, and / or (eg, any suitable) combinations thereof.

[0133] Conductive materials

[0134] A conductive material may be included to provide conductivity to the electrode, and any electrically conductive material may be used as the conductive material unless it undergoes chemical changes. Examples of the conductive material may include carbon-based materials (such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, carbon nanotubes, etc.), metal-based materials including metal powders or metal fibers of copper, nickel, aluminum, silver, etc., conductive polymers (such as polyphenylene derivatives), and / or (e.g., any suitable) mixtures thereof.

[0135] Based on 100 wt % of the negative electrode active material layer, the content (e.g., amount) of the negative electrode active material may be about 95 wt % to about 99.5 wt %, and based on 100 wt % of the negative electrode active material layer, the content (e.g., amount) of the binder may be about 0.5 wt % to about 5 wt %. For example, based on 100 wt % of the negative electrode active material layer, the negative electrode active material layer may include about 90 wt % to about 99 wt % of the negative electrode active material, about 0.5 wt % to about 5 wt % of the binder, and about 0.5 wt % to about 5 wt % of the conductive material.

[0136] current collector

[0137] 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), and / or alloys thereof, and may be in the form of foil, sheet, and / or foam. The thickness of the negative electrode current collector may be, for example, about 1 μm to about 20 μm, about 5 μm to about 15 μm, or about 7 μm to about 10 μm.

[0138] electrolyte

[0139] For example, the electrolyte for a rechargeable lithium battery may be an electrolyte solution that may include a non-aqueous organic solvent and a lithium salt.

[0140] The non-aqueous organic solvent is used as a medium for transporting ions participating in the electrochemical reaction of the battery. The non-aqueous organic solvent may include carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, aprotic solvents and / or (for example, any appropriate) combinations thereof.

[0141] Carbonate solvents may include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), ethyl methyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc. Ester solvents may include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanoic acid lactone, mevalonolactone, valerolactone, caprolactone, etc. Ether solvents may include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. In addition, ketone solvents may include cyclohexanone, etc. Alcohol solvents may include ethanol, isopropanol, etc., and aprotic solvents may include nitriles (such as R-CN, wherein R is a C2-C20 straight chain, branched and / or cyclic hydrocarbon group, and may include double bonds, aromatic rings and / or ether bonds, etc.), amides (such as dimethylformamide), dioxolanes (such as 1,3-dioxolane, 1,4-dioxolane), etc. and / or cyclopentane, etc.

[0142] The non-aqueous organic solvent can be used alone or in a mixture of two or more types (species), and if (for example, when) two or more types (species) are used in a mixture, the mixing ratio can be suitably or appropriately adjusted according to the desired or appropriate battery performance, which is widely applicable to those skilled in the art.

[0143] When the carbonate-based solvent is used, cyclic carbonate and chain carbonate may be mixed and used, and the cyclic carbonate and chain carbonate may be mixed in a volume ratio of about 1:1 to about 1:9.

[0144] The non-aqueous organic solvent may further include an aromatic hydrocarbon organic solvent. For example, a carbonate-based solvent and an aromatic hydrocarbon organic solvent may be mixed and used in a volume ratio of about 1:1 to about 30:1.

[0145] The electrolyte solution may further include vinyl ethylene carbonate, vinylene carbonate and / or ethylene carbonate-based compounds to improve battery cycle life.

[0146] Examples of the ethylene carbonate-based compound may include fluoroethylene carbonate, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, and / or cyanoethylene carbonate.

[0147] The lithium salt dissolved in the non-aqueous organic solvent supplies lithium ions in the battery, ensures the basic operation of the rechargeable lithium battery, and improves the transport of lithium ions between the positive electrode and the negative electrode. Examples of the lithium salt may include those selected from LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide; LiFSI), LiC4F9SO3, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2) (wherein x and y are integers of 1 to 20), at least one of lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalato)phosphate (LiDFBOP) and lithium bis(oxalato)borate (LiBOB).

[0148] The concentration of the lithium salt may be in the range of about 0.1 M to about 2.0 M. In one or more embodiments, when the concentration of the lithium salt is within the above range, the electrolyte solution has suitable or appropriate ion conductivity and viscosity, and thus excellent or appropriate performance may be achieved, and lithium ions may be efficiently moved.

[0149] diaphragm

[0150] Depending on the type or kind of rechargeable lithium battery, a separator may be present between the positive electrode and the negative electrode. The separator may include a polyethylene separator, a polypropylene separator, a polyvinylidene fluoride separator, or a multilayer film of two or more layers thereof, such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, a polypropylene / polyethylene / polypropylene three-layer separator, etc.

[0151] The separator may include a porous substrate and a coating on a surface (eg, one or both surfaces (eg, two opposing surfaces)) of the porous substrate, the coating including an organic material, an inorganic material, and / or (eg, any suitable) combination thereof.

[0152] The porous substrate may be a polymer film formed from any one of the following polymers and / or copolymers or mixtures of two or more thereof: polyolefins (such as polyethylene and polypropylene), polyesters (such as polyethylene terephthalate and polybutylene terephthalate), polyacetals, polyamides, polyimides, polycarbonates, polyetherketones, polyaryletherketones, polyetherimides, polyamideimides, polybenzimidazoles, polyethersulfones, polyphenylene oxides, cyclic olefin copolymers, polyphenylene sulfide, polyethylene naphthalate, glass fibers, and polytetrafluoroethylene (e.g., ).

[0153] The porous substrate may have a thickness of about 1 μm to about 40 μm (eg, about 1 μm to about 30 μm, about 1 μm to about 20 μm, about 5 μm to about 15 μm, or about 10 μm to about 15 μm).

[0154] The organic material may include a (meth)acrylic copolymer including a first structural unit derived from (meth)acrylamide and a second structural unit including at least one of a structural unit derived from (meth)acrylic acid or (meth)acrylate and a structural unit derived from (meth)acrylamidesulfonic acid or a salt thereof.

[0155] The inorganic material may include inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, and boehmite, but the present disclosure is not limited thereto. The average particle size (D 50 ) may be from about 1 nm to about 2000 nm, for example, from about 100 nm to about 1000 nm or from about 100 nm to about 700 nm.

[0156] The organic material and the inorganic material may be mixed in one coating layer, or a coating layer including an organic material and a coating layer including an inorganic material may be stacked.

[0157] The coating layer may have a thickness of about 0.5 μm to about 20 μm, for example, about 1 μm to about 10 μm or about 1 μm to about 5 μm.

[0158] The embodiments and comparative examples of the present disclosure are described in more detail. However, the following examples are merely examples of the present disclosure, and the present disclosure is not limited to the following embodiments.

[0159] Example 1

[0160] 1. Preparation of positive electrode active material

[0161] Ni 0.75 Mn 0.23 Al 0.02 (OH)2 and LiOH were mixed in a molar ratio of 1:1.05 and then subjected to a preliminary heat treatment at 845°C for 8 hours in an oxygen atmosphere to prepare a lithium nickel manganese based composite oxide in the form of secondary particles having Li 1.05 Ni 0.75 Mn 0.23 Al 0.02 The composition of O2 and the average particle size of about 14 μm (D 50 ).

[0162] A coating solution is prepared by adding aluminum sulfate to a distilled water solvent and then stirring the mixture at about 350 rpm for about 5 minutes. Confirm that the salt is completely dissolved in the coating solution that appears colorless and transparent. While the coating solution is continuously stirred, 500 g of lithium nickel manganese composite oxide is added thereto for 1.5 minutes and then stirred for 25 minutes. In this article, the aluminum content (e.g., amount) in aluminum sulfate is designed to be 1.0 mol% based on 100 mol% of the total metal without lithium in the positive electrode active material. After stirring, the pH value of its supernatant is 5.5. After removing the solvent from the mixed solution by using an aspirator and a filter press, a coating product is obtained by vacuum drying at 190 ° C.

[0163] The coated product was mixed with cobalt hydroxide (Co(OH)2) and LiOH, and then subjected to a secondary heat treatment at 825°C for 8 hours under an oxygen atmosphere to prepare a positive electrode active material. Here, the cobalt content (e.g., amount) of the cobalt hydroxide was designed to be 2.0 mol% based on 100 mol% of the total metal excluding lithium in the positive electrode active material.

[0164] 2. Manufacturing of rechargeable lithium battery cells

[0165] 98.5 wt % of a positive electrode active material, 1.0 wt % of a polyvinylidene fluoride binder, and 0.5 wt % of a carbon nanotube conductive material were mixed to prepare a positive electrode active material layer slurry, and the positive electrode active material layer slurry was coated on an aluminum foil current collector, and then dried and pressed to manufacture a positive electrode.

[0166] A half-cell was fabricated using a conventional method using a positive electrode, a lithium metal counter electrode, and an electrolyte. Polytetrafluoroethylene was used as the separator, and the electrolyte was prepared by dissolving 1M LiPF6 in a mixed solvent of ethylene carbonate and dimethyl carbonate in a volume ratio of 3:7.

[0167] Example 2

[0168] A positive electrode active material and a rechargeable lithium battery cell were manufactured in substantially the same manner as in Example 1, except that zirconium oxide (the zirconium content (e.g., amount) of which was designed to be 0.2 mol% based on 100 mol% of the total metal excluding lithium in the positive electrode active material) was mixed with the coated product, cobalt hydroxide (Co(OH)2), and LiOH, wherein the cobalt content (e.g., amount) of the cobalt hydroxide was designed to be 1.0 mol% based on 100 mol% of the total metal excluding lithium in the positive electrode active material.

[0169] Example 3

[0170] A positive electrode active material and a rechargeable lithium battery cell were manufactured in substantially the same manner as in Example 2, except that the cobalt content (e.g., amount) of cobalt hydroxide was designed to be 2.0 mol % based on 100 mol % of total metal excluding lithium in the positive electrode active material.

[0171] Example 4

[0172] A positive electrode active material and a rechargeable lithium battery cell were manufactured in substantially the same manner as in Example 2, except that the cobalt content (e.g., amount) of cobalt hydroxide was designed to be 3.0 mol % based on 100 mol % of total metal excluding lithium in the positive electrode active material.

[0173] Comparative Example 1

[0174] A positive electrode active material and a rechargeable lithium battery cell were manufactured in substantially the same manner as in Example 2, except that, in preparing the positive electrode active material, the coated product and zirconium oxide were subjected to a secondary heat treatment without adding cobalt hydroxide (Co(OH)2) and LiOH.

[0175] Comparative Example 2

[0176] A positive electrode active material and a rechargeable lithium battery cell were manufactured in substantially the same manner as in Example 1, except that cobalt hydroxide (Co(OH)2) and LiOH were not added in the preparation of the positive electrode active material, only the coated product was subjected to a secondary heat treatment, and after adding aluminum oxide to the lithium nickel manganese composite oxide, dry coating with heat treatment at 600°C for 5 hours was adopted for aluminum coating, rather than wet coating using a distilled water solvent and aluminum sulfate.

[0177] Comparative Example 3

[0178] A positive electrode active material and a rechargeable lithium battery cell were manufactured in substantially the same manner as in Comparative Example 2, except that, in preparing the positive electrode active material, a rechargeable lithium battery cell was prepared by using a rechargeable lithium battery cell having a Ni 0.75 Mn 0.25 (OH)2)Li 1.05 Ni 0.75 Mn 0.25 The lithium nickel manganese composite oxide composed of O2 and further doped with aluminum is designed to have an aluminum content (eg, amount) of 2.0 mol% (based on 100 mol% of total metal excluding lithium in the positive electrode active material).

[0179] Comparative Example 4

[0180] A positive electrode active material and a rechargeable lithium battery cell were manufactured in substantially the same manner as in Comparative Example 3, except that the positive electrode active material was prepared without aluminum coating.

[0181] Comparative Example 5

[0182] A positive electrode active material and a rechargeable lithium battery cell were manufactured in substantially the same manner as in Comparative Example 4, except that the positive electrode active material was prepared without additionally doping with aluminum.

[0183] The production methods of Examples 1 to 4 and Comparative Examples 1 to 5 are summarized and shown in Table 1.

[0184] Table 1

[0185]

[0186] Evaluation Example 1: Cross-sectional observation of positive electrode active material

[0187] The coating states of aluminum and cobalt of the positive electrode active material of Example 1 were examined by performing SEM-EDS mapping on a cross section cut by a focused ion beam (FIB). Figure 5 and Figure 6 The SEM-EDS image shows aluminum on the cross section of the positive electrode active material of Example 1. Figure 5 and Figure 6 , the aluminum coating layer was formed as a substantially uniform film having a thickness of about 40 nm on the surface of the positive electrode active material, and aluminum was partially coated on the grain boundaries of the primary particles (which were boundaries of the primary particles inside the secondary particles).

[0188] in addition, Figure 7 The SEM-EDS analysis image of the cobalt element mapped on the cross section of the positive electrode active material of Example 1 is shown. Figure 7 , cobalt does not form a coating on the surface of the positive electrode active material, but diffuses into the interior of the secondary particles and coats the grain boundaries of the primary particles (which are the boundaries of the primary particles).

[0189] Evaluation Example 2: Evaluation of initial charge / discharge capacity and efficiency

[0190] The rechargeable lithium battery cells of Examples 1 to 4 and Comparative Examples 1 to 5 were initially charged and discharged at 25°C at a constant current of 0.2C to an upper voltage limit of 4.45V, charged at a constant voltage of 0.05C, and then discharged at 0.2C to a cutoff voltage of 3.0V. Table 2 shows the initial charge capacity, initial discharge capacity, and the ratio of the latter to the former (as efficiency).

[0191] Evaluation Example 3: Cycle Life Characteristics

[0192] After the initial charge and discharge of Evaluation Example 2 was completed, the rechargeable lithium battery cell was charged 50 times or more at 1.0C in the voltage range of 3.0V to 4.5V at 45°C, and discharged 50 times or more at 1.0C to calculate the ratio of the 50th cycle discharge capacity to the initial discharge capacity, and the results are shown in Table 2.

[0193] Evaluation Example 4: Evaluation of gas generation during storage at 80°C

[0194] The rechargeable lithium battery cells of Examples 1 to 4 and Comparative Examples 1 to 5 were made into 4.4V 30mAh battery cells, and then allowed to stand at 80°C for 30 days, and then the gas generation amount (mL / g) on ​​the 30th day was measured by using a gas analyzer (refinery gas analysis, RGA), and the results are shown in Table 2.

[0195] Table 2

[0196]

[0197] Referring to Table 2, Examples 1 to 4 (in each of which aluminum wet coating was followed by cobalt dry coating) exhibited improved efficiency and cycle life characteristics, as well as reduced gas generation during high-temperature storage, compared to Comparative Examples 1 to 5 (in each of which aluminum wet coating and / or cobalt dry coating were not performed). In particular, Examples 3 and 4 (each of which had a cobalt content (e.g., amount) of 2 mol% to 3 mol%) exhibited the highest degree of positive (e.g., most excellent or most appropriate) effects on cycle life characteristics and gas generation during high-temperature storage.

[0198] In addition, compared with Comparative Example 1 in which aluminum coating was performed by wet coating, Comparative Example 2 and Comparative Example 3 (in each of Comparative Example 2 and Comparative Example 3, aluminum coating was performed by dry coating) showed poorer effects in terms of cycle life characteristics and gas generation during high-temperature storage, and compared with Comparative Examples 1 to Comparative Examples 3 (in each of Comparative Examples 1 to Comparative Examples 3, aluminum coating was performed), Comparative Examples 4 and Comparative Examples 5 (in each of Comparative Examples 4 and Comparative Examples 5, aluminum coating was not performed) showed poorer effects in terms of cycle life characteristics and gas generation during high-temperature storage.

[0199] As used herein, the terms "substantially," "about," and similar terms are used as terms of approximation and not as terms of degree, and are intended to account for the inherent deviations in measured or calculated values ​​that would be recognized by one of ordinary skill in the art. As used herein, "about" or "approximately" also encompasses the stated value and means within an acceptable range of deviation of the particular value as determined by one of ordinary skill in the art, taking into account the measurement in question and the errors associated with the measurement of the particular quantity (i.e., the limitations of the measurement system). For example, "about" can mean within one or more standard deviations of the stated value, or within ±30%, ±20%, ±10%, or ±5% of the stated value.

[0200] In the context of this disclosure, and unless otherwise defined, the terms "use," "using," and "used" may be considered synonymous with the terms "utilize," "utilizing," and "utilized," respectively.

[0201] Any numerical range set forth in this article is intended to include all subranges of the same numerical precision included in the range set forth. For example, the range of "1.0 to 10.0" is intended to include all subranges between the minimum value 1.0 set forth and the maximum value 10.0 set forth (and including 1.0 and 10.0), that is, all subranges with a minimum value equal to or greater than 1.0 and a maximum value equal to or less than 10.0, such as, for example, all subranges of 2.4 to 7.6. Any maximum numerical limit set forth in this article is intended to include all lower numerical limits contained therein, and any minimum numerical limit set forth in this specification is intended to include all higher numerical limits contained therein. Therefore, the applicant reserves the right to amend this specification (including claims) to explicitly set forth any subrange contained in the range explicitly set forth in this article.

[0202] The device for preparing the positive electrode active material according to the embodiment of the present invention described herein, the battery management system (BMS) device and / or any other related device or component can be implemented using any appropriate hardware, firmware (e.g., a dedicated integrated circuit), software, or a combination of software, firmware, and hardware. For example, the various components of the device can be formed on an integrated circuit (IC) chip or on a separate IC chip. In addition, the various components of the device can be implemented on a flexible printed circuit film, a tape carrier package (TCP), or a printed circuit board (PCB), or formed on a substrate. In addition, the various components of the device can be processes or threads running on one or more processors in one or more computing devices, executing computer program instructions and interacting with other system components to perform the various functions described herein. The computer program instructions are stored in a memory that can be implemented in a computing device using a standard memory device (such as, for example, a random access memory (RAM)). The computer program instructions can also be stored in other non-transitory computer-readable media (such as, for example, a CD-ROM, a flash drive, etc.). Moreover, those skilled in the art will recognize that, without departing from the scope of this disclosure, the functions of various computing devices can be combined or integrated into a single computing device, or the functions of a dedicated computing device can be distributed on one or more other computing devices.

[0203] In view of the overall content of the present disclosure, those skilled in the art will recognize that each appropriate feature of the various embodiments of the present disclosure can be partially or completely combined or combined with each other, and can be technically interlocked and operated in various appropriate ways, and unless otherwise described or implied, the various embodiments can be implemented independently of each other or in combination with each other in any appropriate manner.

[0204] While the present disclosure has been described in conjunction with what are presently considered to be practical example embodiments, it is to be understood that the present disclosure is not limited to the disclosed embodiments, but is intended to cover one or more suitable modifications and equivalent arrangements included within the spirit and scope of the claims and their equivalents.

Claims

1. A positive electrode active material comprising: a plurality of core particles comprising a lithium nickel manganese-based composite oxide and in the form of secondary particles, wherein each of the secondary particles comprises an aggregate of a plurality of primary particles; an aluminum coating on the surface of the core particle, and A grain boundary coating portion is located on the surface of the primary particle and includes cobalt.

2. The positive electrode active material according to claim 1, wherein The lithium nickel manganese-based composite oxide includes 60 mol% to 80 mol% of nickel based on 100 mol% of total metal excluding lithium and 10 mol% or more of manganese based on 100 mol% of total metal excluding lithium.

3. The positive electrode active material according to claim 1, wherein The lithium nickel manganese-based composite oxide further includes aluminum, and the aluminum content is greater than or equal to 0 mol % and less than or equal to 3 mol % based on 100 mol % of total metals excluding lithium in the lithium nickel manganese-based composite oxide.

4. The positive electrode active material according to claim 3, wherein The concentration of aluminum is uniform in the lithium nickel manganese-based composite oxide.

5. The positive electrode active material according to claim 1, wherein The cobalt content is at most 0.01 mol% based on 100 mol% of total metals excluding lithium in the lithium nickel manganese-based composite oxide.

6. The positive electrode active material according to claim 1, wherein The lithium nickel manganese composite oxide is represented by Chemical Formula 1: Chemical formula 1 Li a1 Ni x1 Mr y1 Al z1 M 1 w1 O 2-b1 X b1 In chemical formula 1, 0.9≤a1≤1.8, 0.6≤x1≤0.8, 0.1≤y1≤0.4, 0≤z1≤0.03, 0≤w1≤0.3, 0.9≤x1+y1+z1+w1≤1.1, and 0≤b1≤0.1, M 1 is one or more elements selected from B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zr and Zn, and X is one or more elements selected from F, P and S.

7. The positive electrode active material according to claim 1, wherein The aluminum coating layer may have an aluminum content of 0.1 mol% to 3.0 mol% based on 100 mol% of total metal excluding lithium in the positive electrode active material.

8. The positive electrode active material according to claim 1, wherein The positive electrode active material further includes a zirconium coating on the aluminum coating.

9. The positive electrode active material according to claim 8, wherein The zirconium coating layer has a zirconium content of 0.1 mol % to 1.5 mol % based on 100 mol % of total metal excluding lithium in the positive electrode active material.

10. The positive electrode active material according to claim 1, wherein The aluminum coating is in the form of a shell continuously surrounding the surface of the core particle.

11. The positive electrode active material according to claim 1, wherein The aluminum coating layer has a thickness of 10 nm to 500 nm.

12. The positive electrode active material according to claim 1, wherein The cobalt content of the grain boundary coating portion is 0.1 mol% to 5.0 mol% based on 100 mol% of total metal excluding lithium in the positive electrode active material.

13. The positive electrode active material according to claim 1, wherein The cobalt content on the surface of each of the core particles is less than or equal to 0.01 mol % based on 100 mol % of total metal excluding lithium in the positive electrode active material.

14. The positive electrode active material according to claim 1, wherein The positive electrode active material has an average particle size of 10 μm to 25 μm.

15. A method for preparing a positive electrode active material, comprising: (i) preparing a core particle comprising a lithium nickel manganese-based composite oxide and in the form of a secondary particle, wherein the secondary particle is formed by aggregating a plurality of primary particles; (ii) preparing an aluminum coating solution comprising an aqueous solvent and an aluminum raw material; (iii) adding the core particles to the aluminum coating solution, mixing the core particles and the aluminum coating solution, and drying the core particles and the aluminum coating solution to prepare a coated product; as well as (iv) dry-mixing the coated product and a cobalt raw material, and heat-treating the coated product and the cobalt raw material to obtain a positive electrode active material.

16. The method of claim 15, wherein The aluminum raw material has an aluminum content of 0.1 mol% to 3.0 mol% based on 100 mol% of the total metal excluding lithium in the core particles and the aluminum of the aluminum raw material, and the cobalt raw material has a cobalt content of 0.1 mol% to 5.0 mol% based on 100 mol% of the total metal excluding lithium in the core particles and the aluminum of the aluminum raw material.

17. The method of claim 15, wherein In step (iv), the heat treatment is performed at a temperature ranging from 700°C to 850°C.

18. The method of claim 15, wherein In step (iv), when dry-mixing the coated product and the cobalt raw material, a lithium raw material and a zirconium raw material are mixed together.

19. A positive electrode comprising: a positive electrode current collector, and a positive electrode active material layer, the positive electrode active material layer being located on the positive electrode current collector, The positive electrode active material layer comprises the positive electrode active material according to any one of claims 1 to 14 or the positive electrode active material prepared by the method according to claims 15 to 18.

20. A rechargeable lithium battery comprising: The positive electrode according to claim 19, negative electrode, and electrolyte.

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