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

Abstract

The invention relates to a positive electrode active material, a method of preparing the same, a positive electrode, and a rechargeable lithium battery including the same. The positive electrode active material includes: a core particle including a layered lithium nickel manganese-based composite oxide; and a coating layer on the surface of the core particle and containing aluminum and zinc.

Description

Technical Field

[0001] Embodiments of the present disclosure described herein 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

[0002] Rechargeable lithium batteries having a relatively high energy density and portability have been used as a driving power source for portable information devices (such as cellular phones, laptop computers, smart phones, and / or electric vehicles). Recently, research has been explored or conducted to use rechargeable lithium batteries having a high energy density as a driving power source for hybrid vehicles or electric vehicles or as a power storage source for a power storage system or a power wall.

[0003] Various positive electrode active materials have been used in rechargeable lithium batteries. For example, lithium nickel-based oxides, lithium nickel manganese cobalt-based composite oxides, lithium nickel cobalt aluminum-based composite oxides, and lithium cobalt-based oxides have been used as positive electrode active materials. However, despite the increasing demand for large-sized, high-capacity, or high-energy density rechargeable lithium batteries, the supply of positive electrode active materials containing the rare metal cobalt is expected to be severely insufficient. For example, because cobalt is expensive and the remaining reserves are not much, it is necessary or desirable to develop positive electrode active materials that do not contain cobalt or reduce its content (e.g., amount). Summary of the Invention

[0004] Aspects according to one or more embodiments relate to a positive electrode active material including a layered lithium nickel manganese-based composite oxide, the positive electrode active material including an optimal or appropriate coating to improve the performance, capacity characteristics, initial charge / discharge efficiency (hereinafter, also written as "initial charge and discharge efficiency", or simply referred to as "efficiency"), and high-temperature cycle life characteristics of a rechargeable lithium battery at high temperature and high voltage.

[0005] Aspects according to one or more embodiments relate to a positive electrode active material that can maximize or increase the capacity while minimizing or reducing the production cost to ensure long cycle life characteristics and improve high-voltage characteristics and high-temperature characteristics. When the positive electrode active material is applied to a rechargeable lithium battery, high initial charge / discharge capacity and efficiency can be achieved under high-voltage operating conditions, and long cycle life characteristics can be achieved under high-voltage and high-temperature conditions.

[0006] Additional aspects will be set forth in part in the following description, and in part will be obvious from the description, or may be learned by practice of the presented embodiments of the present disclosure.

[0007] In one or more embodiments, the positive electrode active material includes: core particles including a layered lithium nickel manganese-based composite oxide; and a coating located on the surface of the core particles and containing aluminum and zinc.

[0008] In one or more embodiments, a method for preparing a positive electrode active material includes: preparing core particles including a layered lithium nickel manganese composite oxide; adding an aluminum raw material and a zinc raw material to an aqueous solvent and mixing to prepare a coating solution; adding the core particles to the coating solution and mixing to prepare a mixed solution; removing the aqueous solvent from the mixed solution; drying the resulting product; and performing a heat treatment to obtain the positive electrode active material.

[0009] In one or more embodiments, a positive electrode includes a positive electrode current collector and a positive electrode active material layer on the positive electrode current collector, wherein the positive electrode active material layer includes the aforementioned positive electrode active material.

[0010] In one or more embodiments, a rechargeable lithium battery includes the aforementioned positive electrode, negative electrode, and electrolyte. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figures 1 to 4 are schematic diagrams each showing a rechargeable lithium battery according to one or more embodiments.

[0012] Figure 5 and Figure 6 is a scanning electron microscope (SEM) image of the surface of the final positive electrode active material prepared in Example 1.

[0013] Figure 7 and Figure 8 is an SEM image of the surface of the final positive electrode active material prepared in Example 2.

[0014] Figure 9 and Figure 10 is an SEM image of the surface of the final positive electrode active material prepared in Comparative Example 1.

[0015] Figure 11 and Figure 12 is an SEM image of the surface of the final positive electrode active material prepared in Comparative Example 2.

[0016] Figure 13 and Figure 14 is an SEM image of the surface of the final positive electrode active material prepared in Comparative Example 3.

[0017] Figure 15 and Figure 16 is the XPS analysis result of the final positive electrode active material prepared in Example 1.

[0018] Figure 17 and Figure 18 shows the XPS analysis result of the positive electrode active material before the second heat treatment in Example 1.

[0019] Description of Reference Numerals

[0020] 100: Rechargeable lithium battery 10: Positive electrode

[0021] 11: Positive electrode lead lug 12: Positive electrode terminal

[0022] 20: Negative electrode 21: Negative electrode lead lug

[0023] 22: Negative electrode terminal 30: Separator

[0024] 40: electrode assembly 50: shell

[0025] 60: Sealing member 70: Electrode terminal piece

[0026] 71: Positive electrode terminal tab 72: Negative electrode terminal tab DETAILED DESCRIPTION

[0027] Hereinafter, specific embodiments will be described in more detail so that those skilled in the art can easily implement them. However, the present disclosure may be implemented in many different forms and is not to be construed as limited to the example embodiments set forth herein.

[0028] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. As used herein, expressions such as "at least one of," "one of," and "selected from," when preceding or following a list of elements, modify the entire list of elements and do not modify 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," and the like may indicate only a, only b, only c, both a and b (e.g., simultaneously), both a and c (e.g., simultaneously), both b and c (e.g., simultaneously), all of a, b, and c, or variations thereof.

[0029] The terms used herein are for describing the embodiments only and are not intended to limit the present disclosure. A singular expression includes a plural expression unless the context clearly indicates otherwise.

[0030] As used herein, "combinations thereof" refers to mixtures, laminates, composites, copolymers, alloys, blends, reaction products, and the like, of the components.

[0031] In this document, it should be understood that terms such as "comprising", "including" or "having" are intended to indicate the presence of implemented aspects, features, quantities, steps (e.g., actions or tasks), elements and / or their (e.g., any appropriate) combinations thereof, but they do not exclude the possibility of the presence or addition of one or more other aspects, features, quantities, steps (e.g., actions or tasks), elements and / or their (e.g., any appropriate) combinations thereof.

[0032] In the drawings, for clarity, the thicknesses of layers, films, panels, regions, etc. are exaggerated, and like reference numerals throughout the drawings denote like elements, and repeated description thereof may not be provided in the specification. It will be understood that if (e.g., 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 an intervening element may also be present. In contrast, if (e.g., 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 is no intervening element.

[0033] A “layer” herein, if (e.g., when) viewed in a plan view, includes not only a shape formed on the entire surface but also a shape formed on a partial surface.

[0034] The average particle diameter can be measured by methods well known to those skilled in the art (e.g., by a particle size analyzer, or by a transmission electron microscope image or a scanning electron microscope image. In one or more embodiments, the dynamic light scattering method is used, data analysis is performed, the number of particles in each particle size range is counted, and calculations are thereby made to obtain the average particle diameter value. Unless otherwise defined, the average particle diameter (D 50 ) may refer to the diameter of the particle having a cumulative volume of 50% by volume in the particle size distribution. If (e.g., when) no other definition is provided, the average particle diameter (D 50 ) as used herein refers to the diameter of the particle having a cumulative volume of 50% by volume in the particle size distribution obtained by randomly measuring the sizes (diameter or major axis length) of about 20 particles in a scanning electron microscope image.

[0035] In this document, “or” is not interpreted in an exclusive sense. For example, “A or B” is interpreted to include A, B, A + B, etc.

[0036] “Metal” is interpreted to include the concepts of ordinary metals, transition metals, and metalloids (semi-metals).

[0037] As used herein, the terms "substantially" and like terms are used as approximate terms and not as terms of degree, and are intended to account for the inherent variations in measured or calculated values as would be recognized by a person of ordinary skill in the art. Also, the terms "about" and like terms when used in conjunction with a numerical value or numerical range herein include the recited value and values within the acceptable variation range of the specific value determined by a person of ordinary skill in the art in view of the measurements discussed and the errors associated with the measurement of a particular quantity (e.g., limitations of the measurement system). For example, "about" can mean within one or more standard deviations, or within ±30%, ±20%, ±10%, or ±5% of the recited value.

[0038] Also, any numerical range recited herein is intended to include all sub-ranges of the same numerical precision falling within the recited range. For example, a range of "1.0 to 10.0" is intended to include all sub-ranges between the recited minimum value of 1.0 and the recited maximum value of 10.0 (and including 1.0 and 10.0), that is, all sub-ranges having a minimum value equal to or greater than 1.0 and a maximum value equal to or less than 10.0, such as, by way of example, 2.4 to 7.6. Any maximum numerical limit recited herein is intended to include all lower numerical limits falling therein, and any minimum numerical limit recited in this specification is intended to include all higher numerical limits falling therein. Accordingly, the applicant reserves the right to amend this specification (including the claims) to expressly recite any sub-ranges that fall within the ranges expressly recited herein.

[0039] In the context of this application, unless otherwise defined, the terms "use", "using", and "used" may each be regarded as synonymous with the terms "utilize", "utilizing", and "utilized", respectively. Additionally, when describing embodiments of the present invention, the use of "may" refers to "one or more embodiments of the present invention".

[0040] The positive electrode active material for a rechargeable lithium battery, the rechargeable lithium battery including the positive electrode active material, and the method for preparing the positive electrode active material for a rechargeable lithium battery according to one or more embodiments will be described in more detail below.

[0041] Positive electrode active material

[0042] In one or more embodiments, the positive electrode active material includes: core particles including a layered lithium nickel manganese composite oxide; and a coating located on the surface of the core particles and containing aluminum and zinc.

[0043] As the price of the rare metal cobalt has increased, there is a need or desire to develop a positive electrode active material that does not contain cobalt or has a reduced content thereof (e.g., amount). 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.) have limitations in achieving high capacity due to the small amount of lithium available in the structure. Layered lithium nickel manganese-based 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, as cobalt, which plays a key role in the layered structure, is removed, the structural stability decreases, the resistance increases, and it becomes more difficult to ensure long cycle life characteristics. In addition, cobalt-free layered lithium nickel manganese-based positive electrode active materials may have problems in that side reactions with the electrolyte accelerate under high voltage and high temperature conditions, resulting in an increase in gas generation amount and deterioration of cycle life characteristics.

[0044] In one or more embodiments, a coating including both aluminum and zinc (e.g., including aluminum and zinc simultaneously) is introduced onto the surface of the layered lithium nickel manganese-based positive electrode active material, thereby strengthening the particle surface and forming a coating having a 3D lithium channel structure, thereby improving high voltage, high temperature cycle life characteristics, and initial charge and discharge efficiency.

[0045] Core particle

[0046] The core particle includes a layered lithium nickel manganese-based composite oxide.

[0047] Based on the total metals other than lithium in the layered lithium nickel manganese-based composite oxide of 100 mol%, the nickel content (e.g., amount) may be greater than or equal to about 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%. If the nickel content (e.g., amount) satisfies the above range, high capacity can be achieved even if the cobalt content (e.g., amount) is reduced, and the structural stability can be increased. Nickel is included in the core particle, but may move to some coatings during the coating process, so the nickel content (e.g., amount) may refer to the nickel content (e.g., amount) included in the entire positive electrode active material.

[0048] Based on the total metals other than lithium in the layered lithium nickel manganese composite oxide of 100 mol%, the manganese content (e.g., amount) can be, for example, greater than or equal to about 10 mol%, such as about 10 mol% to about 40 mol%, about 15 mol% to about 35 mol%, about 15 mol% to about 30 mol%, or about 20 mol% to about 30%. If the manganese content (e.g., amount) satisfies the above range, high capacity can be achieved while the structural stability of the positive electrode active material can be increased. Manganese is contained in the core particles, but may move to some coatings during the coating process. Therefore, the manganese content (e.g., amount) can refer to the manganese content (e.g., amount) contained in the entire positive electrode active material.

[0049] The layered lithium nickel manganese composite oxide can be a layered lithium nickel manganese aluminum composite oxide that further includes aluminum in addition to nickel and manganese. If the layered lithium nickel manganese composite oxide contains aluminum, it is beneficial to maintain a stable layered structure even when the cobalt element is excluded from the structure. Based on the total metals other than lithium in the layered lithium nickel manganese composite oxide of 100 mol%, the aluminum content (e.g., amount) can be greater than about 0 mol%, greater than or equal to about 0.1 mol%, greater than or equal to about 0.5 mol%, or greater than or equal to about 1 mol% (e.g., greater than about 0 mol% and less than or equal to about 3 mol%, 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%). Here, the aluminum content (e.g., amount) refers to the content (e.g., amount) of aluminum present in the core particles. If the aluminum content (e.g., amount) satisfies the above range, a stable layered structure can be maintained even when cobalt is excluded from the core particles, the problem of structural collapse caused by charging and discharging can be suppressed or reduced, and the long cycle life characteristics of the positive electrode active material can be achieved.

[0050] According to one or more embodiments, the concentration of aluminum within the core particles may be substantially uniform. For example, there may be a concentration gradient of aluminum from the center to the surface within the core particles, or the aluminum concentration in the outer portion of the core particles is neither higher nor lower than that in the inner portion of the core particles, and the aluminum within the core particles may be uniformly distributed. This may be a structure obtained by using aluminum raw materials during precursor production without additional doping of aluminum during the synthesis of the core particles, so that nickel manganese aluminum hydroxide is used as a precursor to synthesize a composite oxide. The core particles may include secondary particles in which a plurality of primary particles are aggregated (e.g., may be in the form of secondary particles in which a plurality of primary particles are aggregated), and regardless of the position of the primary particles, the aluminum content (e.g., amount) within the primary particles may be the same or similar. For example, if primary particles are selected at random positions in the cross-section of the secondary particles and the aluminum content (e.g., amount) is measured inside the primary particles rather than at their interfaces, then regardless of the position of the primary particles (i.e., whether the primary particles are close to the center or the surface of the secondary particles), the aluminum content (e.g., amount) may be the same / similar / substantially uniform. In this structure, even if cobalt is absent or present in a very small amount, a stable layered structure can be maintained, and no aluminum by-products or aluminum aggregates are generated, thereby simultaneously improving the capacity, efficiency, and cycle life characteristics of the positive electrode active material.

[0051] The layered lithium nickel manganese composite oxide may be represented by Chemical Formula 1.

[0052] Chemical Formula 1

[0053] Li a1 Ni x1 Mn y1 Al z1 M 1 w1 O 2-b1 X b1

[0054] 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, Zr, and Zn, and X is one or more elements selected from F, P, and S.

[0055] In Chemical Formula 1, 0.9 ≤ a1 ≤ 1.5 or 0.9 ≤ a1 ≤ 1.2. Additionally, Chemical Formula 1 may contain 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.

[0056] 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, and 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.

[0057] For example, the layered lithium nickel manganese - type composite oxide of the core particles may be a cobalt - free compound that does not contain cobalt or contains a very small amount of cobalt, and based on the total metals other than lithium in 100 mol% of the layered lithium nickel manganese - type composite oxide, the cobalt content (e.g., amount) is about 0 mol% to about 0.01 mol%.

[0058] The core particles may include secondary particles made by aggregating a plurality of primary particles (e.g., may be in the form of secondary particles made by aggregating a plurality of primary particles). The secondary particles may be spherical, elliptical, polyhedral, or irregular in shape, and the primary particles may be spherical, elliptical, plate - shaped, and / or any appropriate combination thereof.

[0059] If (e.g., when) the battery operates under high - voltage or high - temperature conditions, the core particles are vulnerable to chemical erosion by the components in the electrolyte, and thus may undergo many side reactions with the electrolyte, resulting in an increased gas generation amount, thereby deteriorating the battery cycle life and safety. However, these problems can be solved by introducing a coating according to one or more embodiments, and the coating according to one or more embodiments will be described in more detail later.

[0060] Coating

[0061] The positive electrode active material according to one or more embodiments includes a coating located on the surface of the core particles and containing aluminum and zinc.

[0062] By XPS (X-ray photoelectron spectroscopy) measurement, based on 100 at% of the total components on the surface of the positive electrode active material, the aluminum content (e.g., amount) of the positive electrode active material according to one or more embodiments may be about 5 at% to about 35 at%, e.g., about 5 at% to about 30 at%, about 5 at% to about 25 at%, or about 10 at% to about 20 at%. Additionally, by XPS measurement, based on 100 at% of the total components on the surface of the positive electrode active material, the zinc content (e.g., amount) may be about 0.1 at% to about 3.0 at%, e.g., about 0.3 at% to about 2.5 at% or about 0.5 at% to about 2.0 at%. These may refer only to the contents of aluminum and zinc contained in the coating. If the aluminum and zinc contents on the surface of the positive electrode active material particles satisfy the above ranges, a substantially uniform and thin coating can be formed, the resistance of the positive electrode active material will not increase, and the side reactions with the electrolyte can be effectively suppressed or reduced, thereby improving the cycle life characteristics of the rechargeable lithium battery under high voltage and high temperature conditions.

[0063] Based on 100 mol% of the total metals other than lithium in the positive electrode active material, the aluminum content (e.g., amount) in the coating may be about 0.5 mol% to about 1.5 mol%, e.g., about 0.5 mol% to about 1.4 mol%, about 0.6 mol% to about 1.4 mol%, or about 0.7 mol% to about 1.3 mol%. The aluminum content (e.g., amount) in the coating may refer only to the content (e.g., amount) of aluminum contained in the coating and is independent of the aluminum contained in the core particles.

[0064] Additionally, based on 100 mol% of the total metals other than lithium in the positive electrode active material, the zinc content (e.g., amount) in the coating may be about 0.01 mol% to about 1.5 mol%, e.g., about 0.05 mol% to about 1.5 mol%, 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%. The zinc content (e.g., amount) in the coating may refer only to the content (e.g., amount) of zinc contained in the coating and is independent of the zinc contained in the core particles.

[0065] In addition, based on the total metals other than lithium in 100 mol% of the positive electrode active material, the total amount of aluminum and zinc in the coating may be from about 0.51 mol% to about 3.0 mol%, for example, from about 0.51 mol% to about 1.5 mol%. These may refer only to the content of aluminum and zinc contained in the coating and are independent of the aluminum and zinc contained in or possibly contained in the core particles. The total metals other than lithium in the positive electrode active material, which serve as the basis for the above content (e.g., amount) range, may refer to the content (e.g., amount) of the total metals other than lithium present in the entire positive electrode active material particles, rather than the content (e.g., amount) of the total metals other than lithium on the surface of the positive electrode active material.

[0066] The aluminum and zinc contents in the coating of the entire positive electrode active material can be measured, for example, by SEM-EDS analysis of the surface or cross-section of the positive electrode active material. If the aluminum and zinc contents in the coating satisfy the above range, the coating can have a substantially uniform and thin thickness, which does not increase the resistance of the positive electrode active material and effectively suppresses or reduces side reactions with the electrolyte, thereby improving the cycle life characteristics of the rechargeable lithium battery under high voltage and high temperature conditions. For example, if the aluminum and zinc contents in the coating are excessive, a substantially uniform coating may not be formed, or the resistance may increase, which may reduce the charge / discharge efficiency and cycle life characteristics. And if the aluminum and zinc contents in the coating are too low, a coating with a suitable or appropriate thickness may not be formed, and the effect of suppressing or reducing side reactions with the electrolyte may be reduced.

[0067] On the surface of the positive electrode active material, the molar ratio (Al / Zn) of the aluminum content (e.g., amount) to the zinc content (e.g., amount) may satisfy greater than or equal to about 2, for example, about 2 to about 50, about 2 to about 40, about 2 to about 30, about 2 to about 20, about 2 to about 10, or about 3 to about 7. If the above ratio is satisfied, the initial charge / discharge capacity, initial charge / discharge efficiency, and cycle life characteristics of the rechargeable lithium battery under high temperature and high voltage can be improved simultaneously.

[0068] The coating according to one or more embodiments may include a film continuously surrounding the surface of the core particles or be in the form of a film continuously surrounding the surface of the core particles, or include a shell surrounding the entire surface of the core particles or be in the form of a shell surrounding the entire surface of the core particles. This is different from a structure that only partially coats a part of the surface of the core particles. According to one or more embodiments, the coating can be formed to completely cover the surface of the core particles and can be formed to have a very thin and substantially uniform thickness, so that the positive electrode active material does not increase resistance or reduce capacity, improves structural stability, effectively suppresses side reactions with the electrolyte, reduces the gas generation amount under high voltage and high temperature conditions, and realizes long cycle life characteristics.

[0069] In a coating according to one or more embodiments, aluminum and zinc may be mixed together, and zinc may be distributed in some or all of the regions where aluminum is distributed.

[0070] The thickness of a coating according to one or more embodiments may be from about 5 nm to about 200 nm, such as from about 5 nm to about 150 nm, from about 5 nm to about 100 nm, from about 5 nm to about 80 nm, from about 5 nm to about 50 nm, or from about 10 nm to about 50 nm. If the coating meets the above thickness range, the structural stability of the positive electrode active material can be improved without increasing the resistance or reducing the capacity due to the coating, and side reactions with the electrolyte can be effectively suppressed or reduced. The thickness of the coating can be measured by, for example, SEM, transmission electron microscopy (TEM), time-of-flight secondary ion mass spectrometry (TOF-SIMS), XPS, or energy dispersive spectrometer (EDS) analysis, and can be measured, for example, by EDS line profile analysis of the cross-section of the positive electrode active material.

[0071] A coating according to one or more embodiments is characterized by being thin and having a substantially uniform thickness at the level of several nanometers to several hundred nanometers. For example, the deviation of the coating thickness within a single 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%. Herein, the deviation of the coating thickness refers to the deviation of the coating thickness within a single positive electrode active material particle. For example, the deviation of the coating thickness can be calculated by measuring the thickness at about 10 points in the electron microscope image of the cross-section of a single positive electrode active material particle to calculate the arithmetic mean, then dividing the absolute value of the difference between a measurement data and the arithmetic mean by the arithmetic mean, and multiplying by 100%. If the deviation or standard deviation of the coating thickness meets the above range, a coating with a substantially uniform thickness can be formed on the surface of the core particle of the positive electrode active material in a good or appropriate film form. Accordingly, the structural stability of the positive electrode active material is improved, side reactions with the electrolyte can be effectively suppressed or reduced, and an increase in resistance or a decrease in capacity due to the coating can be minimized or reduced.

[0072] In one or more embodiments, in addition to aluminum and zinc, the coating may further contain nickel, manganese, and / or a combination thereof (e.g., any suitable combination). Nickel and manganese may already be included in the core particle and may have been introduced during the coating formation process, and their contents are not particularly limited. A coating according to one or more embodiments mainly contains aluminum and zinc, optionally contains nickel and manganese, and is formed to be thin and have a substantially uniform thickness, thereby improving the high-voltage characteristics of the positive electrode active material and improving the cycle life characteristics.

[0073] In addition, in addition to aluminum and zinc, the coating may further contain sulfur. Sulfur can be introduced during the process of adding aluminum raw material aluminum sulfate or zinc raw material zinc sulfate to form the coating, and its content (e.g., amount) is not particularly limited. The coating according to one or more embodiments mainly contains aluminum and zinc, and optionally contains sulfur, and can improve the high-voltage characteristics and cycle life characteristics of the positive electrode active material.

[0074] The average particle diameter (D 50 ) of the positive electrode active material (in the form of particles) according to one or more embodiments is not particularly limited, but can be, for example, about 10 μm to about 18 μm, about 11 μm to about 16 μm, or about 12 μm to about 15 μm. If no definition is provided otherwise (e.g., when), the average particle diameter (D 50 ) as used herein refers to the diameter of the particle with a cumulative volume of 50% by volume in the particle size distribution obtained by randomly measuring the sizes (diameter or major axis length) of about 20 particles in the scanning electron microscope image of the positive electrode active material. If the average particle diameter of the positive electrode active material satisfies the above range, high capacity and long cycle life can be achieved, and it can be beneficial for forming the coating according to one or more embodiments. Also, in the present disclosure, when the particle is spherical, "diameter" indicates the particle diameter or average particle diameter, and when the particle is non-spherical, "diameter" indicates the major axis length or average major axis length.

[0075] Based on the total metals other than lithium in 100 mol% of the layered lithium nickel manganese composite oxide, the cobalt content (e.g., amount) in the positive electrode active material according to one or more embodiments can be, for example, less than or equal to about 0.01 mol%, less than or equal to about 0.005 mol%, or 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%.

[0076] In addition, in one or more embodiments, the positive electrode active material may not contain sodium. Generally, sodium ions can be used in the preparation process of the positive electrode active material, but according to the preparation method described in more detail later, a core particle with a stable structure and a coating with a substantially uniform thickness can be formed without using sodium ions.

[0077] Method for preparing positive electrode active material

[0078] In one or more embodiments, a method for preparing a positive electrode active material includes (i) preparing core particles including a layered lithium nickel manganese composite oxide; (ii) adding an aluminum raw material and a zinc raw material to an aqueous solvent and mixing to prepare a coating solution; (iii) adding the core particles to the coating solution and mixing to prepare a mixed solution; and (iv) removing the aqueous solvent from the mixed solution, drying the resulting product, and performing a heat treatment to obtain the positive electrode active material.

[0079] In the method for preparing a positive electrode active material according to one or more embodiments, preparing the core particles including a layered lithium nickel manganese composite oxide includes: mixing a nickel manganese composite hydroxide and a lithium raw material; and performing a first heat treatment. The nickel manganese composite hydroxide may be a precursor of the core particles, may include secondary particles in which a plurality of primary particles are aggregated (e.g., may be in the form of secondary particles in which a plurality of primary particles are aggregated), may not contain cobalt or may 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 general coprecipitation method.

[0080] Based on the total metal in 100 mol% of the nickel manganese composite hydroxide, the nickel content (e.g., amount) may be greater than or equal to about 60 mol%, and for example, 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%. If the nickel content (e.g., amount) satisfies the above range, high capacity can be achieved and the structural stability can be increased even when the cobalt content (e.g., amount) is reduced.

[0081] Based on the total metal in 100 mol% of the nickel manganese composite hydroxide, the manganese content (e.g., amount) may be greater than or equal to about 10 mol%, for example, about 10 mol% to about 40 mol%, about 15 mol% to about 35 mol%, about 15 mol% to about 30 mol%, or about 20 mol% to about 30%. If the manganese content (e.g., amount) of the nickel manganese composite hydroxide satisfies the above range, high capacity can be achieved, the structural stability of the positive electrode active material can be increased, and the production price can be reduced to increase economic efficiency.

[0082] Alternatively, if (e.g., when) the nickel-manganese composite hydroxide further contains aluminum, based on the total metals in 100 mol% of the nickel-manganese composite hydroxide, the aluminum content (e.g., amount) can be greater than 0 mol%, greater than or equal to about 0.1 mol%, greater than or equal to about 0.5 mol%, or greater than or equal to about 1 mol% (e.g., greater than 0 mol% and less than or equal to 3 mol%, 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%).

[0083] If the aluminum content (e.g., amount) of the nickel-manganese composite hydroxide satisfies the above range, high capacity can be achieved, while the structural stability of the positive electrode active material can be increased, and the production price can be reduced to increase economic benefits.

[0084] In a method for preparing a positive electrode active material according to one or more embodiments, in the preparation of the core particles, aluminum is not doped additionally, but an aluminum raw material can be used to prepare the precursor, such that a nickel-manganese-aluminum composite hydroxide in which aluminum is uniformly (e.g., substantially uniformly) dispersed in the structure can be used as the precursor. When using such a precursor, even without cobalt, even after repeated charging and discharging, the positive electrode active material can stably maintain a layered structure, and no aluminum by-products or aluminum aggregates are formed, so as to improve the capacity and efficiency characteristics and the cycle life characteristics of the positive electrode active material.

[0085] Based on the total metals in 100 mol% of the nickel-manganese composite hydroxide, the cobalt content (e.g., amount) can be less than or equal to about 0.01 mol%, less than or equal to about 0.005 mol%, or less than or equal to about 0.001 mol%, e.g., 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%. This nickel-manganese composite hydroxide can be said to be economical because it avoids the increase in unit cost caused by cobalt, maximizes the capacity, and improves the structural stability.

[0086] For example, the nickel-manganese composite hydroxide can be represented by Chemical Formula 2.

[0087] Chemical Formula 2

[0088] Ni x2 Mn y2 Al z2 M 2 w2 (OH) 2

[0089] 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, and M 2 is one or more elements selected from B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Zr, and Zn.

[0090] 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.

[0091] The nickel-manganese composite hydroxide is in the form of particles, and the average particle size (D 50 ) can be about 10 μm to about 18 μm, about 11 μm to about 16 μm, or about 12 μm to about 15 μm.

[0092] The nickel-manganese composite hydroxide and the lithium raw material can be mixed at a molar ratio of about 1:0.9 to about 1:1.8, for example, about 1:0.9 to about 1:1.5 or about 1:1 to about 1:1.2.

[0093] The first heat treatment can be carried out in an oxygen atmosphere, for example, at a temperature in the 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.

[0094] The layered lithium nickel manganese composite oxide can be obtained by the first heat treatment. In the obtained layered lithium nickel manganese composite oxide, based on the total metals other than lithium in 100 mol% of the layered lithium nickel manganese composite oxide, the nickel content (e.g., amount) can be about 60 mol% to about 80 mol%, the manganese content (e.g., amount) can be greater than or equal to about 10 mol%, the aluminum content (e.g., amount) can be about 0 mol% to about 3 mol%, and can contain a very small amount of about 0 mol% to about 0.01 mol% of cobalt. Because the layered lithium nickel manganese composite oxide can have significantly different residual lithium contents on the particle surface and has different one or more suitable properties from oxides with different compositions (e.g., lithium nickel cobalt manganese composite oxides, lithium nickel cobalt aluminum composite oxides, lithium cobalt oxides, etc.), it is impossible to form a satisfactory coating in the form of a substantially uniform film in the coating methods used in the prior art. In one or more embodiments, a method of coating the surface of the layered lithium nickel manganese composite oxide particles with aluminum and zinc with a very (e.g., substantially) uniform thickness is proposed.

[0095] In one or more embodiments, a coating solution is first prepared by adding aluminum raw material and zinc raw material to an aqueous solvent, adding core particles including layered lithium nickel manganese composite oxide obtained by a first heat treatment and mixing, then drying, and performing a second heat treatment to form a coating according to one or more embodiments. This is a salt dissolution wet coating method and can be called a pre-addition method, in which salts as coating raw materials are first completely dissolved and then core particles of a positive electrode active material are added.

[0096] The aqueous solvent may include distilled water, alcohol solvents, and / or a combination thereof (e.g., any suitable combination). For example, the aluminum raw material may be aluminum sulfate. Aluminum sulfate can be called the optimal or suitable raw material for forming a substantially uniform aluminum-containing coating on the layered lithium nickel manganese composite oxide. The zinc raw material may be zinc sulfate, zinc nitrate, and / or a combination thereof (e.g., any suitable combination).

[0097] Based on the total metal other than lithium in 100 mol% of the core particles, aluminum in the aluminum raw material, and zinc in the zinc raw material, the aluminum content (e.g., amount) in the aluminum raw material can be designed to be about 0.5 mol% to about 1.5 mol%, such as about 0.5 mol% to about 1.4 mol%, about 0.6 mol% to about 1.4 mol%, or about 0.7 mol% to about 1.3 mol%. If the aluminum content (e.g., amount) of the coating is designed within the above range, the coating can be formed to have a thin and substantially uniform thickness of several nanometers to several hundred nanometers, so as to reduce the amount of gas generated by the rechargeable lithium battery under high voltage or high temperature operating conditions, and improve the high-capacity and long cycle life characteristics.

[0098] Based on the total metal other than lithium in 100 mol% of the core particles, aluminum in the aluminum raw material, and zinc in the zinc raw material, the zinc content (e.g., amount) in the zinc raw material can be designed to be about 0.01 mol% to about 1.5 mol%, such as 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%. If the zinc content (e.g., amount) of the coating is designed within the above range, the coating can be formed to have a thin and substantially uniform thickness of several nanometers to several hundred nanometers, so as to improve the cycle life characteristics under high voltage or high temperature operating conditions, and increase the initial charge and discharge efficiency.

[0099] The addition of aluminum raw material and zinc raw material to an aqueous solvent and mixing 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. Additionally, the mixing speed can be about 100 rpm to about 800 rpm, for example, about 200 rpm to about 600 rpm or about 250 rpm to about 500 rpm. Under these conditions, the aluminum raw material and zinc raw material are dissolved (e.g., completely dissolved) in the aqueous solvent to obtain a colorless and transparent coating solution, and this coating solution can be used to effectively form a substantially uniform coating according to one or more embodiments. The pH of the mixed coating solution can be, for example, 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).

[0100] When adding the core particles to the prepared coating solution, while stirring (i.e., mixing) the coating solution, add the core particles to it to increase the coating quality.

[0101] In addition, the time taken to add the core particles to the coating solution can be about 30 seconds / 500 g to about 2 minutes / 500 g, for example, about 30 seconds / 500 g to about 1.5 minutes / 500 g, etc. The speed of adding the core particles can be appropriately adjusted to control the pH of the supernatant after coating is completed to induce the effective formation of a substantially uniform coating according to one or more embodiments. If the speed of adding the core particles is too low, the reaction rate of each particle will vary, and a substantially uniform coating may not be formed. Additionally, if the speed of adding the core particles is too fast, the pH may change rapidly, and a substantially uniform coating may not be formed.

[0102] After all the core particles are added to the coating solution, stirring can be carried out for about 15 minutes to about 60 minutes, for example, about 20 minutes to about 50 minutes or about 30 minutes to about 45 minutes. The time taken from the start of adding the core particles to the coating solution to the completion of stirring (i.e., the coating reaction time) can be adjusted within about 1 hour.

[0103] In one or more embodiments, if (e.g., when) the addition of core particles to the coating solution is stopped and mixed, then, for example, the pH range of the supernatant after mixing is about 5.5 to about 8.5. If the pH of the supernatant is less than 5.5, the acidity may become stronger, and a substantially uniform coating may not be formed, and if the pH is greater than 8.5, the alkalinity may become stronger, making it difficult to form a substantially uniform Al-containing coating.

[0104] After removing the aqueous solvent from the mixed solution, the resulting product can be dried, for example, at about 40 °C to about 240 °C, about 100 °C to about 220 °C, or about 150 °C to about 200 °C and, for example, under vacuum conditions, and a satisfactory coated product can be obtained under these conditions.

[0105] The dried product after removing the aqueous solvent from the mixed solution can be referred to as a coated product. The coated product includes core particles and a coating located on the surface of the core particles and containing aluminum and zinc. For example, the coating containing aluminum and zinc can have a fibrous shape (e.g., in the form of fibers), for example, a mesh shape or a spiderweb shape. Such a mesh can be continuously formed over the entire surface of the core particles. The mesh-shaped coating can surround (e.g., encircle) the core particles with a very thin and substantially uniform thickness to strengthen the surface of the positive electrode active material and improve the structural stability, thereby enhancing the high-temperature and high-voltage characteristics.

[0106] After mixing nickel-manganese-based composite hydroxide and lithium raw materials, the heat treatment of the mixture can be referred to as the first heat treatment, and the heat treatment of the coated product can be referred to as the second heat treatment. The second heat treatment can be a process for forming the coating, for example, carried out in an oxygen atmosphere at a temperature range of about 700 °C to about 850 °C, about 750 °C to about 840 °C, or about 800 °C to about 830 °C for about 2 hours to about 20 hours or about 3 hours to about 10 hours. If the second heat treatment temperature is set within the above range, the tendency of aluminum to diffuse into the secondary particles can be reduced, and aluminum is mainly retained on the surface of the secondary particles, and at the same time, the surface of the secondary particles can be coated in the form of a shell with a very thin and uniform (e.g., substantially uniform) thickness, and zinc can also be well coated on the surface of the secondary particles.

[0107] Positive electrode

[0108] In one or more embodiments, the positive electrode includes a positive electrode current collector and a positive electrode active material layer 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 can further include other types (kinds) of positive electrode active materials. Additionally, the positive electrode active material layer can optionally further include a binder, a conductive material, and / or a combination thereof (e.g., any suitable combination).

[0109] According to one or more embodiments, the loading level of the positive electrode active material layer can be about 10 mg / cm 2 ~ about 40 mg / cm 2 , for example, about 10 mg / cm 2 ~ about 30 mg / cm 2 or about 10 mg / cm 2 ~ about 20 mg / cm2 In addition, the density of the positive electrode active material layer in the final pressed positive electrode can be about 3.3 g / cc to about 3.7 g / cc, such as about 3.3 g / cc to about 3.6 g / cc or about 3.4 g / cc to about 3.58 g / cc. When applying the positive electrode active material according to one or more embodiments, it is beneficial to achieve such a loading level and the density of the positive electrode active material layer, and a positive electrode that satisfies the loading level and the density of the positive electrode active material layer within the above range is suitable for achieving a rechargeable lithium battery with high capacity and high energy density.

[0110] Binder

[0111] The binder improves the bonding characteristics between the positive electrode active material particles and 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, a polymer containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylic acid esterified styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin or nylon, but are not limited thereto.

[0112] Conductive material

[0113] A conductive material is included to provide electrode 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 fiber, carbon nanofiber, carbon nanotube, etc.); metal-based materials including metal powders or metal fibers such as copper, nickel, aluminum, silver, etc.; conductive polymers (such as polyphenylene derivatives); and / or a mixture thereof (for example, any suitable one).

[0114] Based on 100 wt% of the positive electrode active material layer, the respective contents (for example, amounts) of the binder and the conductive material can be about 0.5 wt% to about 5 wt%.

[0115] The positive electrode current collector may include Al foil, but the present disclosure is not limited thereto.

[0116] Rechargeable lithium battery

[0117] One or more embodiments include a rechargeable lithium battery, which includes 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.

[0118] According to the shape, the rechargeable lithium battery can be classified into a cylindrical battery, a prismatic battery, a pouch battery, a coin-shaped battery, etc.Figures 1 to 4 Schematic diagrams each showing a rechargeable lithium battery according to one or more embodiments, where Figure 1 is a cylindrical battery, Figure 2 is a prismatic battery, and Figure 3 and Figure 4 are pouch batteries. Referring to Figures 1 to 4 , the rechargeable lithium battery 100 includes: an electrode assembly 40 having a separator 30 inserted between a positive electrode 10 and a negative electrode 20; and a housing 50 in which the electrode assembly 40 is accommodated. The positive electrode 10, the negative electrode 20, and the separator 30 can be impregnated with an electrolyte. As Figure 1 shown, the rechargeable lithium battery 100 can include a sealing member 60 that seals the housing 50. Additionally, in Figure 2 , the rechargeable lithium battery 100 can include a positive electrode lead tab 11, a positive electrode terminal 12, a negative electrode lead tab 21, and a negative electrode terminal 22. As Figure 3 and Figure 4 shown, the rechargeable lithium battery 100 includes electrode tabs 70, that is, a positive electrode tab 71 and a negative electrode tab 72 that serve as a circuit path for guiding the current formed in the electrode assembly 40 to the outside.

[0119] The rechargeable lithium battery according to one or more embodiments can be rechargeable at a high voltage or can be suitable for driving at a high voltage. For example, the charging voltage of the rechargeable lithium battery can be greater than or equal to about 4.45 V, about 4.45 V to about 4.7 V, about 4.45 V to about 4.6 V, or about 4.45 V to about 4.55 V, etc. By applying the positive electrode active material according to one or more embodiments, even when (e.g., when) charging at a high voltage, the rechargeable lithium battery can significantly reduce the amount of gas generation and can achieve high capacity and long cycle life characteristics.

[0120] Negative electrode

[0121] The negative electrode can 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 can include a negative electrode active material and can further include a binder, a conductive material, and / or a combination thereof (e.g., any suitable combination).

[0122] Negative electrode active material

[0123] The negative electrode active material can 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.

[0124] Materials capable of reversibly embedding / desorbing lithium ions may include, for example, crystalline carbon, amorphous carbon, and / or any suitable combination thereof as carbonaceous negative electrode active materials. The crystalline carbon may be amorphous, or natural graphite or artificial graphite in the form of flakes, platelets, spheres, or fibers (e.g., in fiber form). The amorphous carbon may be soft carbon, hard carbon, mesophase pitch carbonized product, calcined coke, etc.

[0125] The lithium metal alloy includes an alloy of lithium and a metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn.

[0126] Materials capable of doping / dedoping 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 (excluding Si), Group 15 elements, Group 16 elements, transition metals, rare earth elements, and / or any suitable combination thereof, such as Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, and / or any suitable combination thereof) and / or any suitable combination thereof. The Sn-based negative electrode active materials may be Sn, SnO x (0 < x ≤ 2) (e.g., SnO 2 ), Sn alloys, and / or any suitable combination thereof.

[0127] The silicon-carbon composite may be a composite of silicon and amorphous carbon. The average particle size (D 50 ) of the silicon-carbon composite particles may be, for example, about 0.5 μm to about 20 μm. According to one or more embodiments, the silicon-carbon composite may include silicon particles and amorphous carbon coated on the surface of the silicon particles (e.g., may be in the form of silicon particles and amorphous carbon coated on the surface of the silicon particles). For example, it may include secondary particles (cores) in which silicon primary particles are aggregated and an amorphous carbon coating (shell) on the surface of the secondary particles. The amorphous carbon may also be present between the silicon primary particles. For example, the silicon primary particles may be coated with amorphous carbon. The secondary particles may be present in a dispersed state in the amorphous carbon matrix.

[0128] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include: a core including crystalline carbon and silicon particles; and an amorphous carbon coating on the surface of the core. The crystalline carbon may be artificial graphite, natural graphite, and / or a combination thereof (e.g., any suitable combination). The amorphous carbon may include soft carbon, hard carbon, mesophase pitch carbonization products, calcined coke, and the like.

[0129] 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 may be about 10 wt% to about 50 wt% and the content (e.g., amount) of amorphous carbon may be about 50 wt% to about 90 wt%. Additionally, if (e.g., when) the silicon-carbon composite includes silicon, amorphous carbon, and crystalline carbon, then based on 100 wt% of the silicon-carbon composite, the content (e.g., amount) of silicon may be about 10 wt% to about 50 wt%, the content (e.g., amount) of crystalline carbon may be about 10 wt% to about 70 wt%, and the content (e.g., amount) of amorphous carbon may be about 20 wt% to about 40 wt%.

[0130] Additionally, the thickness of the amorphous carbon coating may be about 5 nm to about 100 nm. The average particle diameter (D 50 ) of the silicon particles (primary particles) may be about 10 nm to about 1 μm or about 10 nm to about 200 nm. The silicon particles may exist alone as silicon, in the form of a silicon alloy, or in the form of an oxide of silicon. The oxide form of silicon may be represented by SiO x (0 < x ≤ 2). The atomic content (e.g., amount) ratio of Si:O (which indicates the degree of oxidation) may be about 99:1 to about 33:67. If (e.g., when) no other definition is provided, then as used herein, the average particle diameter (D 50 ) indicates the diameter of the particles in which the cumulative volume in the particle size distribution is about 50 volume%.

[0131] 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. When the Si-based negative electrode active material or the Sn-based negative electrode active material is mixed with the carbon-based negative electrode active material, the mixing ratio may be a weight ratio of about 1:99 to about 90:10.

[0132] Binder

[0133] The binder is used to bond the negative electrode active material particles well to each other and is also used to bond the negative electrode active material to the negative electrode current collector. The binder may be a non-aqueous binder, an aqueous binder, a dry binder, and / or a combination thereof (e.g., any suitable combination).

[0134] 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 a combination thereof (e.g., any suitable combination).

[0135] 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, polyvinylpyrrolidone, epichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene-propylene-diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and / or a combination thereof (e.g., any suitable combination).

[0136] When the 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 their alkali metal salts may be used in combination. The alkali metal may be Na, K, or Li.

[0137] The dry binder may be a polymer material capable of fibrillation and may be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, and / or a combination thereof (e.g., any suitable combination).

[0138] Conductive material

[0139] A conductive material is included to provide electrode conductivity, and any conductive material may be used as the conductive material unless it causes a chemical change. Examples of the conductive material include: Examples of the conductive material include: carbonaceous materials (such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, carbon nanotube, etc.); metallic materials including metal powders or metal fibers such as copper, nickel, aluminum silver, etc.; conductive polymers (such as polyphenylene derivatives); and / or a mixture thereof (e.g., any suitable mixture).

[0140] 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, 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.

[0141] Negative electrode current collector

[0142] The negative electrode current collector may include, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof, and may be in the form of a foil, sheet, 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.

[0143] Electrolyte

[0144] For example, the electrolyte for a rechargeable lithium battery may be an electrolyte that may include a non-aqueous organic solvent and a lithium salt.

[0145] The non-aqueous organic solvent serves 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 a combination thereof (e.g., any suitable combination).

[0146] The carbonate solvents may include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc. The ester solvents may include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, caprolactone, etc. The ether solvents may include dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. In addition, the ketone solvents may include cyclohexanone, etc. The alcohol solvents may include ethanol, isopropanol, etc., and the aprotic solvents may include nitriles (such as R-CN (where R is a C2 - C20 straight-chain, branched-chain, or cycloalkyl group, and may include double bonds, aromatic rings, or bonds, etc.)); amides (such as dimethylformamide); dioxolanes (such as 1,3-dioxolane, 1,4-dioxolane, etc.); sulfolane, etc.

[0147] The non-aqueous organic solvent may be used alone or in the form of a mixture of two or more types (species), and if (e.g., when) two or more types (species) are used in a mixture, the mixing ratio may be appropriately or suitably adjusted according to the desired or appropriate battery performance, which is well-known to those skilled in the art.

[0148] When using carbonate solvents, cyclic carbonates and chain carbonates may be used in combination, and the cyclic carbonate and the chain carbonate may be mixed in a volume ratio of about 1:1 to about 1:9.

[0149] The non-aqueous organic solvent may further include an aromatic hydrocarbon organic solvent. For example, a carbonate solvent and an aromatic hydrocarbon organic solvent may be mixed and used in a volume ratio of about 1:1 to about 30:1.

[0150] The electrolyte may further include vinylene carbonate, ethylene carbonate or a compound of ethylene carbonate to improve the battery cycle life.

[0151] Examples of the compound of ethylene carbonate may include fluoroethylene carbonate, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate or cyanoethylene carbonate.

[0152] 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 LiPF 6 , LiBF 4 , LiSbF 6 , LiAsF 6 , LiClO 4 , LiAlO 2 , LiAlCl 4 , LiPO 2 F 2 , LiCl, LiI, LiN(SO 3 C 2 F 5 ), 2 , Li(FSO 2 ), 2 N (lithium bis(fluorosulfonyl)imide; LiFSI), LiC 4 F 9 SO 3 , LiN(C x F 2x+1 SO 2 )(C y F 2y+1 SO 2 )(where x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluoro bis(oxalate) phosphate (LiDFBOP) and lithium bis(oxalate) borate (LiBOB), at least one of them.

[0153] The concentration of the lithium salt may be in the range of about 0.1 M to about 2.0 M. If the concentration of the lithium salt is within the above range, the electrolyte has appropriate or proper ionic conductivity and viscosity, so excellent or proper performance can be achieved, and lithium ions can move effectively.

[0154] Separator

[0155] 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 mixed multi-layer film (such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, a polypropylene / polyethylene / polypropylene three-layer separator, etc.).

[0156] The separator may include a porous substrate and a coating on the surface (e.g., one or two surfaces (e.g., opposite surfaces)) of the porous substrate, and the coating includes an organic material, an inorganic material, and / or a combination thereof (e.g., any suitable combination).

[0157] The porous substrate may be a polymer film formed of any one of polyolefins (such as polyethylene and / or polypropylene), polyesters (such as polyethylene terephthalate and / or polybutylene terephthalate), polyacetals, polyamides, polyimides, polycarbonates, polyether ketones, polyarylether ketones, polyetherimides, polyamideimides, polybenzimidazoles, polyethersulfones, polyphenylene ethers, cycloolefin copolymers, polyphenylene sulfides, polyethylene naphthalate, glass fibers, and polytetrafluoroethylene (e.g., Teflon), or may be a polymer film formed of a copolymer or mixture of two or more of them.

[0158] The porous substrate may have a thickness of about 1 μm to about 40 μm, for example, 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.

[0159] The organic material may include a (meth)acryloyl copolymer, and the (meth)acryloyl copolymer includes: 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)acrylamidosulfonic acid and / or its salt.

[0160] The inorganic material may include selected from Al 2 O 3 、SiO 2 、TiO 2 、SnO 2 、CeO 2 、MgO、NiO、CaO、GaO、ZnO、ZrO 2 、Y 2 O 3 、SrTiO 3 、BaTiO 3 、Mg(OH) 2 、boehmite and inorganic particles in a combination thereof (e.g., any suitable combination), but the present disclosure is not limited thereto. The average particle size (D 50)It 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.

[0161] The organic material and the inorganic material may be mixed in one coating, or may exist in the form of a stack of a coating including the organic material and a coating including the inorganic material.

[0162] The thickness of the coating may be from about 0.5 μm to about 20 μm, for example, from about 1 μm to about 10 μm or from about 1 μm to about 5 μm.

[0163] Examples and comparative examples of the present disclosure are described herein. However, the following examples are only examples of the present disclosure, and the present disclosure is not limited to the following examples.

[0164] Example 1

[0165] 1. Preparation of the positive electrode active material

[0166] Ni 0.75 Mn 0.23 Al 0.02 (OH) 2 and LiOH are mixed at a molar ratio of 1:1.05, and then, a first heat treatment is performed at 845 °C for 8 hours in an oxygen atmosphere to prepare a layered lithium nickel manganese composite oxide in the form of secondary particles, which secondary particles have a composition of LiNi 0.75 Mn 0.23 Al 0.02 O 2 and an average particle diameter (D 50 ) of about 14 μm.

[0167] A coating solution is prepared by adding aluminum sulfate and titanium sulfate and 600 g of distilled water to a 1 L reactor, and then stirring the mixture at about 350 rpm for about 5 minutes to dissolve the salts. When the salts are completely dissolved, it is confirmed that the coating solution is colorless and transparent. Subsequently, 500 g of the layered lithium nickel manganese composite oxide is added to the stirring coating solution for 1.5 minutes, and then continuously stirred for about 30 minutes. Here, based on the total metal other than lithium in 100 mol% of the final positive electrode active material (i.e., the total metal other than lithium in 100 mol% of the core particles, the aluminum of the aluminum raw material, and the zinc of the zinc raw material), aluminum sulfate is designed to have an aluminum content (e.g., amount) of 1.0 mol%, and based on the total metal other than lithium in 100 mol% of the final positive electrode active material, zinc sulfate is designed to have a zinc content (e.g., amount) of 0.1 mol%. After completion of stirring, the pH of the supernatant is 8.

[0168] The solvent is removed from the mixed solution by using a suction device and a filter press, and then a coated product is obtained by vacuum drying at 190 °C.

[0169] The coated product is subjected to a second heat treatment at 750 °C for 8 hours in an oxygen atmosphere to obtain the final positive electrode active material.

[0170] 2. Manufacture of rechargeable lithium battery cells

[0171] 98.5 wt% of the positive electrode active material, 1.0 wt% of the polyvinylidene fluoride binder, and 0.5 wt% of the carbon nanotube conductive material are mixed to prepare a positive electrode active material layer slurry, and the positive electrode active material layer slurry is coated on an aluminum foil current collector, and then dried and pressed to manufacture a positive electrode. Here, the loading level of the positive electrode active material layer is 10 mg / cm 2 , and the density of the positive electrode active material layer in the finally pressed positive electrode is about 3.4 g / cc.

[0172] 97.5 wt% of the graphite negative electrode active material, 1.5 wt% of carboxymethyl cellulose, and 1 wt% of styrene-butadiene rubber are mixed in an aqueous solvent to prepare a negative electrode active material layer slurry. The negative electrode active material layer slurry is coated on a copper foil current collector, dried and pressed to manufacture a negative electrode.

[0173] Subsequently, a positive electrode, lithium metal as a counter electrode, and a polytetrafluoroethylene separator are used, and additionally an electrolyte (the electrolyte is prepared by dissolving 1 M LiPF 6 in a mixed solvent of ethylene carbonate and dimethyl carbonate with a volume ratio of 3:7) is used to manufacture a rechargeable lithium battery cell by a conventional method.

[0174] Example 2

[0175] The positive electrode active material and the rechargeable lithium battery cell are manufactured in substantially the same manner as in Example 1, except that, based on the total metal content (e.g., amount) other than lithium in 100 mol% of the final positive electrode active material, zinc sulfate is designed to have a zinc content (e.g., amount) of 0.25 mol%.

[0176] Example 3

[0177] The positive electrode active material and the rechargeable lithium battery cell are manufactured in substantially the same manner as in Example 1, except that, based on the total metal content (e.g., amount) other than lithium in 100 mol% of the final positive electrode active material, zinc sulfate is designed to have a zinc content (e.g., amount) of 0.05 mol%.

[0178] Example 4

[0179] The positive electrode active material and the rechargeable lithium battery cell were produced in substantially the same manner as in Example 1, except that zinc sulfate was designed to have a zinc content (e.g., amount) of 0.5 mol% based on the total metal content (e.g., amount) other than lithium in 100 mol% of the final positive electrode active material.

[0180] Comparative Example 1

[0181] The positive electrode active material and the rechargeable lithium battery cell were produced in substantially the same manner as in Example 1, except that by not adding aluminum sulfate and zinc sulfate, i.e., without performing aluminum and zinc coating, LiNi 0.75 Mn 0.23 Al 0.02 O 2 the composite oxide itself was used as the positive electrode active material.

[0182] Comparative Example 2

[0183] The positive electrode active material and the rechargeable lithium battery cell were produced in substantially the same manner as in Example 1, except that by not adding zinc sulfate, i.e., without performing zinc coating, by using LiNi coated with 1 mol% of aluminum (based on the total metal content (e.g., amount) other than lithium in 100 mol% of the final positive electrode active material) 0.75 Mn 0.23 Al 0.02 O 2 the composite oxide to prepare the positive electrode active material.

[0184] Comparative Example 3

[0185] The positive electrode active material and the rechargeable lithium battery cell were produced in substantially the same manner as in Example 1, except that by not adding aluminum sulfate, i.e., without performing aluminum coating, by using LiNi coated with 1 mol% of zinc (based on the total metal content (e.g., amount) other than lithium in 100 mol% of the final positive electrode active material) 0.75 Mn 0.23 Al 0.02 O 2 the composite oxide to prepare the positive electrode active material.

[0186] Evaluation Example 1: Surface Analysis of Positive Electrode Active Material

[0187] The positive electrode active materials according to Example 1, 2 and Comparative Examples 1 to 3 were imaged using a scanning electron microscope (SEM). Figure 5 is an SEM image of the surface of the final positive electrode active material prepared in Example 1, and Figure 6 is an enlarged image thereof. Figure 7SEM image of the surface of the final positive electrode active material prepared in Example 2, and Figure 8 is its enlarged image. Figure 9 SEM image of the surface of the final positive electrode active material manufactured in Comparative Example 1, and Figure 10 is its enlarged image. Figure 11 SEM image of the surface of the final positive electrode active material prepared in Comparative Example 2, and Figure 12 is its enlarged image. Figure 13 SEM image of the surface of the final positive electrode active material prepared in Comparative Example 3, and Figure 14 is its enlarged image. Refer to Figures 9 to 14 , Comparative Examples 1 to 3 show a smooth surface of the secondary particles, but refer to Figures 5 to 8 , Examples 1 and 2 show a coating containing aluminum and zinc formed on the surface of the secondary particles.

[0188] Evaluation Example 2: Analysis of the aluminum and zinc contents on the surface of the positive electrode active material

[0189] The aluminum and zinc contents on the surface of the positive electrode active material were confirmed by depth profiling and peak quantification using XPS (X-ray photoelectron spectroscopy), and the results are as shown in Figure 15 and Figure 16 . In addition, the aluminum and zinc contents on the surface of the positive electrode active material before the second heat treatment were also confirmed, and the results are as shown in Figure 17 and Figure 18 . XPS analysis was performed using an ESCALAB 250Xi instrument manufactured by Thermo Fisher Scientific Inc. Here, the aluminum and zinc contents are based on a value where the sum of the atomic percentages (at%) of all components is 100. Figure 15 and Figure 17 show the Al element distribution, Figure 16 and Figure 18 show the Zn element distribution.

[0190] -X-ray: Al Ka 1486.6 eV

[0191] -Charge neutralization: Low-energy ions and electrons

[0192] -Ar + Gun: 4000 eV

[0193] -Ar + Single atom gun

[0194] Refer to Figure 15 and Figure 16, by XPS, the aluminum concentration decreases in the range of 5 at% to 35 at% from the surface to the bulk, which confirms that the coating in the form of a film is distributed on the outside. This can be confirmed by the decrease in aluminum concentration with the increase in sputter etching time. In addition, the zinc concentration is formed in the range of 0.1 at% to 3.0 at%.

[0195] In addition, referring to Figure 17 and Figure 18 , even if (for example, when) the positive electrode active material before the second heat treatment is confirmed by XPS, the aluminum concentration decreases in the range of 5 at% to 35 at% from the surface to the bulk, which also confirms that the coating in the form of a thin film is distributed on the outside. This can be confirmed by the decrease in aluminum concentration with the increase in sputter etching time. In addition, the zinc concentration is formed in the range of 0.1 at% to 3.0 at%.

[0196] Evaluation Example 3: Evaluation of Initial Charge / Discharge Capacity and Efficiency

[0197] At 25 °C, the rechargeable lithium battery cells of Examples 1 to 4 and Comparative Examples 1 to 3 were charged at a constant current of 0.2C to an upper limit voltage of 4.45V, and then charged at a constant voltage to 0.05C, and then discharged at 0.2C to a cut-off voltage of 3.0V to perform initial charge and discharge. In Table 1, the initial charge capacity (i.e., "0.2C charge" in Table 1), the initial discharge capacity (i.e., "0.2C discharge" in Table 1), and the ratio of the initial discharge capacity to the initial charge capacity as the efficiency (i.e., "efficiency" in Table 1) are provided.

[0198] Evaluation Example 4: High Temperature Cycle Life Characteristics

[0199] After the initial charge and discharge in Evaluation Example 3, at 45 °C, in the voltage range of 3.0V to 4.45V, the battery cells were charged at 1.0C and discharged at 1.0C for 50 or more cycles, and the ratio of the 50th cycle discharge capacity to the initial discharge capacity was calculated as the high temperature cycle life, and the results are shown in Table 1.

[0200] Table 1

[0201]

[0202] Referring to Table 1, Examples 1 and 2 each exhibit high initial charge and discharge capacities, high initial charge and discharge efficiencies, and excellent or suitable high-temperature cycle life characteristics simultaneously (e.g., synchronously). Compared with Comparative Example 2 in which only 1.0 mol% of aluminum is coated, Example 1 shows improvements in the initial discharge capacity, initial charge and discharge efficiencies, and high-temperature cycle life characteristics. And compared with Comparative Example 2, Example 2 shows improvements in the initial discharge capacity, initial charge and discharge efficiencies, and high-temperature cycle life characteristics. Additionally, compared with Comparative Example 3 in which only 1.0 mol% of zinc is coated, Example 1 shows improved initial discharge capacity and initial charge / discharge efficiency, and compared with Comparative Example 3, Example 2 shows improved initial discharge capacity and initial charge / discharge efficiency.

[0203] Comparative Example 1 without introducing a coating containing aluminum and zinc exhibits inferior high-temperature cycle life characteristics to Examples 1 to 4, and the initial discharge capacity and initial charge / discharge efficiency characteristics are slightly deteriorated compared with Examples 1 to 3.

[0204] In contrast, each of Examples 1 to 3 in which the zinc content (e.g., amount) of the coating is in the range of 0.05 mol% to 1.5 mol% shows improved initial discharge capacity, initial charge / discharge efficiency, and high-temperature cycle life characteristics compared with Example 4 in which the zinc content (e.g., amount) is outside the range of 0.1 mol% to 0.4 mol%, thereby improving the battery performance.

[0205] The battery management system (BMS) device and / or any other relevant device or component according to the embodiments of the present disclosure described herein can be implemented using any suitable hardware, firmware (e.g., application-specific integrated circuit), software, or a combination of software, firmware, and hardware. For example, various components of the device can be formed on one integrated circuit (IC) chip or on separate IC chips. Additionally, various components of the device can be implemented on a flexible printed circuit film, tape carrier package (TCP), or printed circuit board (PCB), or formed on a substrate. Moreover, 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, which can be implemented using a standard memory device (such as, for example, random access memory (RAM)) in the computing device. The computer program instructions can also be stored in other non-transitory computer-readable media, such as, for example, a CD-ROM or a flash drive, etc. Also, those skilled in the art should recognize that, without departing from the scope of the present disclosure, the functions of various computing devices can be combined or integrated into a single computing device, or the functions of a particular computing device can be distributed over one or more other computing devices.

[0206] Although the present invention has been described in connection with what are presently considered to be practical example embodiments, it is to be understood that the disclosure is not limited to the disclosed embodiments. On the contrary, it 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 core particle comprising a layered lithium nickel manganese composite oxide; and A coating is disposed on the surface of the core particle and contains aluminum and zinc.

2. The positive electrode active material according to claim 1, wherein The nickel content of the layered lithium nickel manganese-based composite oxide is 60 mol% to 80 mol% based on 100 mol% of total metals except lithium in the layered lithium nickel manganese-based composite oxide and the manganese content of the layered lithium nickel manganese-based composite oxide is greater than or equal to 10 mol%.

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

4. The positive electrode active material according to claim 3, wherein The concentration of aluminum in the core particles is uniform.

5. The positive electrode active material according to claim 1, wherein The layered lithium nickel manganese-based composite oxide has a cobalt content of 0 mol % to 0.01 mol % based on 100 mol % of total metals except lithium in the layered lithium nickel manganese-based composite oxide.

6. The positive electrode active material according to claim 1, wherein The layered 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, 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, 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 content is 5 at % to 35 at % based on 100 at % of the total components on the surface of the positive electrode active material as measured by X-ray photoelectron spectroscopy, and the zinc content is 0.1 at % to 3.0 at % based on 100 at % of the total components on the surface of the positive electrode active material as measured by X-ray photoelectron spectroscopy.

8. The positive electrode active material according to claim 1, wherein The coating has an aluminum content of 0.5 mol% to 1.5 mol% based on 100 mol% of the total metals excluding lithium in the positive electrode active material, and a zinc content of 0.01 mol% to 1.5 mol% based on 100 mol% of the total metals excluding lithium in the positive electrode active material.

9. The positive electrode active material according to claim 1, wherein A molar ratio Al / Zn of the aluminum content to the zinc content on the surface of the positive electrode active material is 2 to 50.

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

11. The positive electrode active material according to claim 1, wherein The thickness of the coating is 5nm-200nm.

12. The positive electrode active material according to claim 1, wherein The coating layer has a thickness variation of less than or equal to 20% within one positive electrode active material particle.

13. A method for preparing a positive electrode active material, comprising: preparing core particles including layered lithium nickel manganese composite oxides; adding an aluminum raw material and a zinc raw material to an aqueous solvent and mixing them to prepare a coating solution; adding the core particles to the coating solution and mixing to prepare a mixed solution; removing the aqueous solvent from the mixed solution; drying the obtained product; as well as Heat treatment is performed to obtain a positive electrode active material.

14. The method of claim 13, wherein The aluminum content of the aluminum raw material is 0.5 mol% to 1.5 mol%, and the zinc content of the zinc raw material is 0.05 mol% to 1.5 mol%, based on 100 mol% of the total metals except lithium in the core particles, the aluminum of the aluminum raw material, and the zinc of the zinc raw material.

15. The method of claim 13, wherein The aluminum raw material is aluminum sulfate, and The zinc raw material is zinc sulfate, zinc nitrate or a combination thereof.

16. The method of claim 13, wherein The heat treatment is performed in a temperature range of 700°C to 850°C.

17. A positive electrode comprising a positive electrode current collector, and a positive electrode active material layer 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 12 or a positive electrode active material prepared by the method according to any one of claims 13 to 16.

18. The positive electrode according to claim 17, wherein The loading level of the positive electrode active material layer is 10 mg / cm 2 ~40mg / cm 2 ,and The positive electrode active material layer has a density of 3.3 g / cc to 3.7 g / cc.

19. A rechargeable lithium battery comprising The positive electrode according to any one of claims 17 and 18; a negative electrode; and Electrolyte.

20. The rechargeable lithium battery of claim 19, wherein The charging voltage of the rechargeable lithium battery is greater than or equal to 4.45V.

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