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

Abstract

Disclosed herein is a positive electrode active material including: a core particle including a layered lithium nickel manganese-based composite oxide; and an yttrium-containing coating on a surface of the core particle; wherein the content (e.g., amount) of yttrium on the surface of the positive electrode active material measured by energy-mapped energy dispersion spectroscopy (EP-EDS) is about 0.1 at% to about 5.0 at% based on 100 at% of the total metal other than lithium, and the positive electrode active material according to some example embodiments may maximize or increase capacity while minimizing or reducing production costs, and can be applied to the field of lithium ion batteries, such as lithium ion batteries, lithium ion batteries, lithium ion batteries, lithium ion batteries, lithium ion batteries, lithium ion batteries, lithium ion batteries, lithium ion batteries, lithium ion batteries, lithium ion batteries, lithium ion batteries, lithium ion batteries, lithium ion batteries, lithium ion batteries, and lithium ion batteries. Thus, long cycle life characteristics are ensured, and high-voltage characteristics and high-temperature characteristics are improved. The rechargeable lithium battery using the positive electrode active material may exhibit high initial charge / discharge capacity and efficiency even under high voltage driving conditions, may achieve long cycle life characteristics, and may effectively suppress or reduce gas generation problems due to high voltage driving and high temperatures.

Description

TECHNICAL FIELD

[0001] Disclosed are a positive electrode active material, a method of preparing the same, a positive electrode including the same, and a rechargeable lithium battery. BACKGROUND

[0002] Portable information devices such as cellular phones, laptop computers, smart phones, etc., or electric vehicles have used rechargeable lithium batteries having high energy density and portability as a driving power source. Recently, research has been actively conducted to use rechargeable lithium batteries having high energy density as a driving power source and / or an energy storage power source for hybrid and / or electric vehicles.

[0003] To realize rechargeable lithium batteries suitable for the aforementioned uses, various positive electrode active materials have been researched. Among them, 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 mainly used as positive electrode active materials. However, although the demand for rechargeable lithium batteries of large size, high capacity, and / or high energy density has recently increased, the supply of positive electrode active materials including the rare metal cobalt is expected to be severely short. Since cobalt is expensive and lacks remaining reserves, there is interest in developing positive electrode active materials that exclude cobalt or use cobalt in a reduced amount. SUMMARY

[0004] Some example embodiments of the present disclosure provide a positive electrode active material, a method of preparing a positive electrode active material, and a positive electrode and a rechargeable lithium battery including the same, the positive electrode active material including a layered lithium nickel-manganese-based composite oxide (hereinafter, can be simply referred to as "lithium nickel-manganese-based composite oxide") that ensures economic feasibility, high capacity, and long cycle life characteristics and exhibits improved high-voltage characteristics and high-temperature characteristics.

[0005] In some example embodiments, the positive electrode active material includes: core particles including a lithium nickel-manganese-based composite oxide; and a yttrium-containing coating (hereinafter, can be simply referred to as "coating") on a surface of the core particles; wherein a content (e.g., amount) of yttrium on the surface of the positive electrode active material, as measured by energy profiling energy dispersive spectroscopy (EP-EDS), based on 100 at% of total metals excluding lithium, is about 0.1 at% to about 5.0 at%.

[0006] In some example embodiments, the method for preparing a positive electrode active material includes: (i) preparing core particles comprising layered lithium nickel manganese composite oxides; (ii) adding and mixing a yttrium feedstock into an aqueous solvent to prepare a coating solution; (iii) adding and mixing the core particles into the coating solution to prepare a mixed solution; and (iv) removing the aqueous solvent from the mixed solution, then drying and heat-treating the obtained product to obtain the positive electrode active material.

[0007] In some example embodiments, the positive electrode includes a positive electrode current collector and a layer of positive electrode active material on the positive electrode current collector, wherein the layer of positive electrode active material includes the aforementioned positive electrode active material.

[0008] In some example implementations, a rechargeable lithium battery includes a positive electrode, a negative electrode, and an electrolyte.

[0009] Positive electrode active materials according to some example embodiments can maximize or increase capacity while minimizing or reducing production costs, ensuring long cycle life characteristics and improving high-voltage and high-temperature characteristics. If (for example, 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 realized. Attached Figure Description

[0010] The accompanying drawings, together with the specification, illustrate embodiments of the subject matter of this disclosure and, together with the description, serve to explain the principles of embodiments of the subject matter of this disclosure.

[0011] Figures 1-4 A schematic diagram of a rechargeable lithium battery according to some example embodiments is shown for illustrative purposes.

[0012] Figure 5 and Figure 6 Scanning electron microscope (SEM) image of the positive electrode active material of Comparative Example 1.

[0013] Figure 7 and Figure 8 SEM image of the positive electrode active material for Comparative Example 2.

[0014] Figure 9 and Figure 10 This is a SEM image of the positive electrode active material of Example 3.

[0015] Explanation of reference numerals in the attached figures

[0016] 100: Rechargeable lithium battery; 10: Positive electrode

[0017] 11: Positive electrode lead connector 12: Positive electrode terminal

[0018] 20: Negative electrode 21: Negative electrode lead connector

[0019] 22: Negative electrode terminal; 30: Diaphragm

[0020] 40: Electrode assembly; 50: Housing

[0021] 60: Sealing component; 70: Electrode terminal piece

[0022] 71: Positive electrode connector; 72: Negative electrode connector Detailed Implementation

[0023] The following describes example implementations in more detail, enabling those skilled in the art to readily implement them. However, the subject matter of this disclosure can be implemented in many different forms and should not be construed as limited to the example implementations set forth herein.

[0024] The terminology used herein is for descriptive purposes only and is not intended to limit this disclosure. Unless the context clearly indicates otherwise, singular expressions include plural expressions.

[0025] As used herein, “combinations thereof” refers to mixtures, laminates, complexes, copolymers, alloys, blends, reaction products, etc. of the components.

[0026] In this document, it should be understood that terms such as “comprising,” “including,” or “having” are intended to indicate the presence of a specific feature, quantity, step, element, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, quantities, steps, elements, or combinations thereof.

[0027] In the accompanying drawings, for clarity, the dimensions (e.g., thickness) of layers, films, panels, areas, etc., may be enlarged, and throughout the specification, the same reference numerals label the same elements. It will be understood that if (e.g., when) an element (such as a layer, film, area, or substrate) is referred to as being "on" another element, it may be directly on the other element or an intervening element may be present. In embodiments, if (e.g., when) an element is referred to as being "directly on" another element, no intervening element is present.

[0028] Here, “layer” in this article includes not only shapes that form across the entire surface when viewed from a plan view, but also shapes that form on a portion of the surface.

[0029] In embodiments, the average particle size can be measured by any suitable method commonly used in the art, for example, by a particle size analyzer and / or by transmission electron microscopy images and / or scanning electron microscopy images. In embodiments, the average particle size can be obtained by measuring using dynamic light scattering, performing data analysis, counting the number of particles for each particle size range, and calculating therefrom. Unless otherwise defined, the average particle size (D) is... 50 The term "average particle size" can refer to the diameter of particles that constitute 50% of the total volume in the particle size distribution. As used herein, if (e.g., when) no other definition is provided, the average particle size (D) is... 50 This refers to the diameter of particles that constitute 50% of the total volume in a particle size distribution obtained by randomly measuring the size (diameter or major axis length) of approximately 20 particles in a scanning electron microscope image.

[0030] In the implementation, "or" is not interpreted as exclusive; for example, "A or B" is interpreted as including A, B, A+B, etc.

[0031] In the implementation, "metal" is interpreted as including the concepts of common metals, transition metals, and / or quasi-metals (semi-metals).

[0032] Positive electrode active material

[0033] In some example embodiments, the positive electrode active material includes: core particles comprising a lithium-nickel-manganese composite oxide; and a yttrium-containing coating on the surface of the core particles; wherein the yttrium content (e.g., amount) on the surface of the positive electrode active material, measured by energy-mapping energy dispersive spectroscopy (EP-EDS) based on 100 at% of total metals excluding lithium, is about 0.1 at% to about 5.0 at%.

[0034] Due to the recent sharp rise in the price of the rare metal cobalt, there is a need to develop positive electrode active materials that exclude or reduce its content (e.g., amount). Positive electrode active materials with olivine crystal structures (such as lithium iron phosphate (LFP), lithium manganese phosphate (LMP), lithium manganese iron phosphate (LMFP), etc.) and / or positive electrode active materials with spinel crystal structures (such as lithium manganese oxide (LMO), etc.) are limited in achieving high capacities due to the small amount of lithium available within their structure. Layered lithium nickel manganese positive electrode active materials exhibit excellent capacity and efficiency characteristics due to the large amount of lithium available within their structure, making them suitable as materials for high-capacity batteries. However, with the removal of cobalt, which plays a role in the layered structure, structural stability decreases, impedance (e.g., resistance) increases, and it becomes difficult to ensure long cycle life characteristics. Furthermore, excluding cobalt leads to the problem of accelerated side reactions between the positive electrode active material and the electrolyte under high voltage and high temperature conditions, increasing the amount of generated gas and degrading cycle life characteristics.

[0035] In some example implementations, a positive electrode active material is provided that maximizes or increases capacity and efficiency by coating a uniform (e.g., substantially uniform) coating with a set or specific amount of yttrium, and achieves long cycle life characteristics by reducing gas generation even under high voltage and / or high temperature conditions.

[0036] nuclear particles

[0037] The core particles include layered lithium-nickel-manganese composite oxides.

[0038] Based on 100 mol% of total metals other than lithium in lithium-nickel-manganese composite oxides, the nickel content (e.g., amount) can be greater than or equal to about 60 mol%, 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) meets the above ranges, high capacity and improved structural stability can be achieved even if the cobalt content (e.g., amount) is reduced. Nickel is included in the core particles, but can migrate to some coatings during the coating process, so the nickel content (e.g., amount) can refer to the nickel content (e.g., amount) included in the entire positive electrode active material.

[0039] Based on 100 mol% of total metals other than lithium in lithium-nickel-manganese composite oxides, the manganese content (e.g., amount) can 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 mol%. If (e.g., when) the manganese content (e.g., amount) meets the above ranges, the positive electrode active material can improve structural stability while achieving high capacity. Manganese is included in the core particles, but can migrate to some coatings during the coating process, so the manganese content (e.g., amount) can refer to the manganese content (e.g., amount) included throughout the positive electrode active material.

[0040] Lithium-nickel-manganese composite oxides can be, for example, lithium-nickel-manganese-aluminum composite oxides that further include aluminum in addition to nickel and manganese. If (for example, when) the lithium-nickel-manganese composite oxide includes aluminum, a stable layered structure is maintained even when cobalt is excluded from the structure. Based on 100 mol% of the total metals other than lithium in the lithium-nickel-manganese composite oxide, 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%, for example, greater than 0 mol% and less than or equal to 3 mol%, for example, about 1 mol% to about 3 mol%, about 1 mol% to about 2.5 mol%, about 1 mol% to about 2 mol%, or about 1 mol% to about 1.9 mol%. If (for example, when) the aluminum content (e.g., amount) meets the above ranges, a stable layered structure is maintained even when cobalt is excluded from the core particles, which can suppress or reduce structural collapse problems due to charging and discharging, and can achieve or improve the long cycle life characteristics of the positive electrode active material.

[0041] According to some exemplary embodiments, the aluminum concentration within the core particle can be uniform (e.g., substantially uniform). In embodiments, this means that there may be no aluminum concentration gradient from the center to the surface within the core particle, or that the aluminum concentration within the inner portion of the core particle is neither higher nor lower than the aluminum concentration in the outer portion, and that the aluminum is uniformly distributed within the core particle. In embodiments, the difference in aluminum concentration gradient within the core particle may be less than or equal to about 0.05 mol%, for example, from about 0.01 mol% to about 0.05 mol%. This can be a structure obtained by using an aluminum feedstock during precursor generation and not additionally doping aluminum during core particle synthesis, thereby using a nickel-manganese-aluminum composite hydroxide as a precursor to synthesize lithium nickel-manganese-aluminum composite oxides. The core particle may take the form of a secondary particle in which multiple primary particles aggregate, and the aluminum content (e.g., amount) within the primary particles may be the same or similar, regardless of the position of the primary particles. In this implementation, if primary particles are selected at random locations within the cross-section of secondary particles and the aluminum content (e.g., amount) is measured inside the primary particles rather than at their interfaces, the aluminum content (e.g., amount) can be the same / similar / uniform, independent of the location of the primary particles (e.g., whether the primary particles are near the center or surface of the secondary particles). In this structure, a stable layered structure is maintained even if cobalt is absent or present in very small amounts, and no aluminum byproducts or aluminum aggregates are generated, allowing for simultaneous improvement in the capacity, efficiency, and cycle life characteristics of the positive electrode active material.

[0042] Layered lithium-nickel-manganese composite oxides can be represented, for example, by chemical formula 1.

[0043] Chemical Formula 1

[0044] Lia1 Ni x1 Mn y1 Al z1 M 1 w1 O 2-b1 X b1

[0045] 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, and Zr, and X is one or more elements selected from F, P, and S.

[0046] In Chemical Formula 1, for example, 0.9 ≤ a1 ≤ 1.5 or 0.9 ≤ a1 ≤ 1.2. Chemical Formula may include aluminum, in which case 0.6 ≤ x1 ≤ 0.8, 0.1 ≤ y1 ≤ 0.39, 0.01 ≤ z1 ≤ 0.03, and 0 ≤ w1 ≤ 0.29 may be satisfied, and 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.

[0047] 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.

[0048] The layered lithium nickel manganese - based composite oxide of the core particles may be, for example, a cobalt - free compound that does not include cobalt or includes a very small amount of cobalt, and based on the total metals other than lithium in 100 mol% of the lithium nickel manganese - based composite oxide, the cobalt content (for example, amount) may be from about 0 mol% to about 1 mol%, for example, from about 0 mol% to about 0.1 mol%, from about 0 mol% to about 0.01 mol%.

[0049] Nuclear particles can take the form of secondary particles formed by the aggregation of multiple primary particles. Secondary particles can be spherical (e.g., approximately spherical), ellipsoidal (e.g., approximately ellipsoidal), polyhedral, or irregular in shape, and primary particles can be spherical (e.g., approximately spherical), ellipsoidal (e.g., approximately ellipsoidal), plate-like, or a combination thereof.

[0050] If (for example, when) a battery operates under high voltage or high temperature conditions, the core particles are susceptible to chemical corrosion by components in the electrolyte, leading to frequent side reactions with the electrolyte. This results in the generation of large amounts of gas, which reduces battery cycle life and safety. However, these problems can be addressed by introducing coatings according to some example embodiments described below.

[0051] coating

[0052] According to some exemplary embodiments, the positive electrode active material is characterized by a yttrium content (e.g., amount) of 100 at% of total metals other than lithium on the surface of the positive electrode active material, as measured by EP-EDS, of about 0.1 at% to about 5.0 at%, for example about 0.2 at% to about 4.5 at%, about 0.3 at% to about 4.0 at%, or about 0.4 at% to about 3.6 at%. This may refer only to the yttrium content (e.g., amount) included in the coating. If (e.g., when) the yttrium content (e.g., amount) on the surface of the positive electrode active material particles meets the above range, the coating can have a uniform (e.g., substantially uniform) and thin thickness, which can not increase the impedance (e.g., resistance) of the positive electrode active material and effectively suppress or reduce side reactions with the electrolyte, thereby improving the cycle life characteristics of the rechargeable lithium battery under high voltage and high temperature conditions.

[0053] Based on 100 mol% of total metals other than lithium in the positive electrode active material, the yttrium content (e.g., amount) in the coating can be from about 0.1 mol% to about 3.0 mol%, for example, from about 0.1 mol% to about 2.8 mol%, from about 0.1 mol% to about 2.6 mol%, from about 0.1 mol% to about 2.4 mol%, from about 0.1 mol% to about 2.2 mol%, or from about 0.2 mol% to about 2.0 mol%. If (e.g., when) the yttrium content (e.g., amount) meets the above range, the positive electrode active material can effectively suppress or reduce side reactions with the electrolyte and effectively reduce the amount of gas generated under high voltage or high temperature conditions by forming a good coating, without reducing capacity or increasing impedance (e.g., resistance).

[0054] According to some exemplary embodiments, the coating can be in the form of a film continuously surrounding the surface of the nucleus particle, for example, it can be in the form of a shell surrounding the entire surface of the nucleus particle. This differs from a structure in which only a portion of the surface of the nucleus particle is coated. According to some exemplary embodiments, the coating can be formed to completely cover the surface of the nucleus particle and can be formed to be very thin and uniform (e.g., substantially uniform) in thickness, so that the positive electrode active material does not increase impedance (e.g., resistance) or reduce capacity, improves structural stability, effectively suppresses or reduces side reactions with the electrolyte, reduces the amount of gas generated under high voltage and high temperature conditions, and achieves long cycle life characteristics.

[0055] The thickness of the coating according to some example embodiments can be from about 30 nm to about 500 nm, for example, about 30 nm to about 450 nm, about 30 nm to about 400 nm, about 30 nm to about 350 nm, about 30 nm to about 300 nm, about 30 nm to about 250 nm, about 30 nm to about 200 nm, about 30 nm to about 150 nm, about 50 nm to about 500 nm, about 80 nm to about 500 nm, or about 100 nm to about 500 nm. If (for example, when) the coating meets the above thickness range, the structural stability of the positive electrode active material can be improved without increasing impedance (e.g., resistance) or reducing 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, time-of-flight secondary ion mass spectrometry (TOF-SIMS), X-ray photoelectron spectroscopy (XPS), or energy-dispersive X-ray spectroscopy (EDS), and the thickness range of the coating can be measured by transmission electron microscopy-energy-dispersive X-ray spectroscopy (TEM-EDS) line scan analysis.

[0056] According to some exemplary embodiments, the coating may be thin and uniform in thickness (e.g., substantially uniform), at the level of tens to hundreds of nanometers. For example, the deviation in 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%. In embodiments, the deviation in coating thickness refers to the deviation in coating thickness within a single positive electrode active material particle. For example, the deviation in coating thickness can be calculated by measuring the thickness at about 10 points in an electron microscope image of a cross-section of a single positive electrode active material particle to calculate the arithmetic mean, and then dividing the absolute value of the difference between a measurement and the arithmetic mean by the arithmetic mean and multiplying by 100%. The fact that the deviation or standard deviation of coating thickness meets the above range means that a coating of uniform thickness (e.g., substantially uniform) is well formed in the form of a film on the surface of the core particle of the positive electrode active material. Accordingly, the structural stability of the positive electrode active material is improved, side reactions with the electrolyte are effectively suppressed or reduced, and the increase in impedance (e.g., resistance) or reduction in capacity due to the coating can be minimized or reduced.

[0057] In embodiments, the coating may further include nickel, manganese, or a combination thereof in addition to yttrium. Nickel and manganese may be included in the core particles and introduced during the coating formation process, and their content (e.g., amount) is not particularly limited. The coating according to some example embodiments primarily includes yttrium and optionally includes nickel and manganese, and is formed to have a thin and uniform (e.g., substantially uniform) thickness, thereby improving the high-voltage characteristics of the positive electrode active material and enhancing cycle life characteristics.

[0058] According to some example embodiments, the average particle size (D) of the positive electrode active material is... 50 There are no particular restrictions. The positive electrode active material can be, for example, large particles in the form of secondary granules, and its average particle size (D) is... 50 The average particle size (D) can be, for example, about 2 μm to about 18 μm, about 11 μm to about 16 μm, or about 12 μm to about 15 μm. As used herein, if (e.g., when) no other definition is provided, the average particle size (D) 50 This refers to the diameter of particles that constitute 50% of the total volume in the particle size distribution obtained by randomly measuring the size (diameter or major axis length) of approximately 20 particles in a scanning electron microscope image of the positive electrode active material. If the average particle size of the positive electrode active material meets the above range, high capacity and long cycle life can be achieved, and it is beneficial to form coatings according to some example embodiments.

[0059] According to some example embodiments, the cobalt content (e.g., amount) in the positive electrode active material, based on 100 mol% of total metals excluding lithium, may be, for example, less than or equal to about 1 mol%, less than or equal to about 0.1 mol%, 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 1 mol%, about 0 mol% to about 0.1 mol%, about 0 mol% to about 0.01 mol%, about 0 mol% to about 0.005 mol%, or about 0 mol% to about 0.011 mol%.

[0060] In some exemplary embodiments, the positive electrode active material may not include sodium. Generally, sodium ions can be used in the preparation process of the positive electrode active material; however, according to the preparation methods described herein, core particles with a stable structure and a uniform (e.g., substantially uniform) thickness of coating can be formed without the use of sodium ions.

[0061] Method for preparing positive electrode active materials

[0062] In some example embodiments, the method for preparing a positive electrode active material includes: (i) preparing core particles comprising layered lithium nickel manganese composite oxides; (ii) adding and mixing a yttrium feedstock into an aqueous solvent to prepare a coating solution; (iii) adding and mixing the core particles into the coating solution to prepare a mixed solution; and (iv) removing the aqueous solvent from the mixed solution, then drying and heat-treating the obtained product to obtain the positive electrode active material.

[0063] In an embodiment, based on 100 mol% of total metals other than lithium in the positive electrode active material, the yttrium content (e.g., amount) in the yttrium raw material can be from about 0.1 mol% to about 3.0 mol%, for example, from about 0.1 mol% to about 2.8 mol%, from about 0.1 mol% to about 2.6 mol%, from about 0.1 mol% to about 2.4 mol%, from about 0.1 mol% to about 2.2 mol%, or from about 0.2 mol% to about 2.0 mol%. The aforementioned positive electrode active material can be prepared by the above method.

[0064] In a method for preparing a positive electrode active material according to some exemplary embodiments, the preparation of core particles comprising layered lithium nickel-manganese composite oxides includes mixing a nickel-manganese composite hydroxide with a lithium raw material and performing a first heat treatment. The layered nickel-manganese composite hydroxide (nickel-manganese composite hydroxide), as a precursor to the core particles, may take the form of secondary particles in which multiple primary particles aggregate, and may be cobalt-free or may include a very small amount of cobalt; for example, it may be a cobalt-free nickel-manganese composite hydroxide. The nickel-manganese composite hydroxide can be prepared by conventional co-precipitation methods.

[0065] In the above nickel-manganese composite hydroxides, based on 100 mol% of total metal, the nickel content (e.g., amount) can be about 60 mol% to about 80 mol%, for example, 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 (e.g., when) the nickel content (e.g., amount) meets the above range, even if (e.g., when) the cobalt content (e.g., amount) is reduced, high capacity can be achieved and structural stability can be improved.

[0066] In the above nickel-manganese composite hydroxides, based on 100 mol% of total metal, the manganese content (e.g., amount) can 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 (e.g., when) the manganese content (e.g., amount) meets the above range, high capacity can be achieved while improving the structural stability of the positive electrode active material, and the production price can be reduced to improve economic feasibility.

[0067] In embodiments, if (for example, when) the nickel-manganese composite hydroxide further comprises aluminum, the aluminum content (e.g., amount) based on a total of 100 mol% of metal can be 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%, for example, about 1 mol% to about 3 mol%, about 1 mol% to about 2.5 mol%, about 1 mol% to about 2 mol%, or about 1 mol% to about 1.9 mol%. If (for example, when) the aluminum content (e.g., amount) in the above nickel-manganese composite hydroxide meets the above range, high capacity can be achieved while improving the structural stability of the positive electrode active material, and production costs can be reduced to improve economic feasibility.

[0068] In a method for preparing a positive electrode active material according to some exemplary embodiments, aluminum is not additionally doped during the preparation of the core particles; however, an aluminum raw material can be used to prepare a 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 a precursor. If, for example, such a precursor is used, the positive electrode active material can stably maintain a layered structure without cobalt, even with repeated charging and discharging, and aluminum byproducts and / or aluminum aggregates can be avoided, thereby improving the capacity and efficiency characteristics and cycle life characteristics of the positive electrode active material.

[0069] In nickel-manganese complex hydroxides, based on 100 mol% of total metals, the cobalt content (e.g., amount) may be less than or equal to about 1 mol%, less than or equal to about 0.1 mol%, 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, from about 0 mol% to about 1 mol%, from about 0 mol% to about 0.1 mol%, from about 0 mol% to about 0.01 mol%, from about 0 mol% to about 0.005 mol%, or from about 0 mol% to about 0.001 mol%. In layered nickel-manganese complex hydroxides, based on 100 mol% of total metals, the cobalt content (e.g., amount) may 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%.

[0070] Nickel-manganese complex hydroxides can be represented, for example, by chemical formula 2.

[0071] Chemical formula 2

[0072] Ni x2 Mn y2 Al z2 M 2 w2 (OH)2

[0073] 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 It is one or more elements selected from B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W and Zr.

[0074] In chemical formula 2, for example, 0.6≤x2≤0.8, 0.1≤y2≤0.39, 0.01≤z2≤0.03, 0≤w2≤0.29.

[0075] Nickel-manganese composite hydroxides can exist in particulate form, and the average particle size (D) of the particles is... 50 The size can be approximately 10 μm to approximately 18 μm, approximately 11 μm to approximately 16 μm, or approximately 12 μm to approximately 15 μm.

[0076] Nickel-manganese composite hydroxides and lithium feedstocks can be mixed in a molar ratio of about 1:0.9 to about 1:1.8 (e.g., about 1:0.9 to about 1:1.5 or about 1:1 to about 1:1.2).

[0077] The first heat treatment may be carried out in an oxygen atmosphere (e.g., in a temperature range of about 750°C to about 950°C, about 780°C to about 900°C, or about 810°C to about 890°C) for about 2 hours to about 20 hours or about 4 hours to about 12 hours.

[0078] Lithium-nickel-manganese composite oxides can be obtained through a first heat treatment. In the obtained lithium-nickel-manganese composite oxide, based on 100 mol% of total metals excluding lithium, the nickel content (e.g., amount) can be from 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 from about 0 mol% to about 3 mol% (e.g., greater than 0 mol% and less than or equal to 3 mol%), and cobalt can be included in a very small amount from about 0 mol% to about 1 mol%. This lithium-nickel-manganese composite oxide has a significantly different residual lithium content (e.g., amount) and different surface characteristics compared to oxides with other compositions (e.g., other nickel oxides, such as lithium-nickel-cobalt-manganese composite oxides, lithium-nickel-cobalt-aluminum composite oxides, etc.), on which other coating methods may not be able to successfully form a good coating in the form of a uniform (e.g., substantially uniform) film. In some example implementations, a method is applied to improve high voltage and high temperature characteristics by uniformly (e.g., substantially uniformly) forming a coating of very thin thickness on the surface of a lithium nickel manganese composite oxide having a very small amount of cobalt and a nickel content greater than or equal to about 60 mol% (e.g., amount).

[0079] In some example embodiments, the coating can be formed by adding and mixing a yttrium raw material into an aqueous solvent to prepare a coating solution, adding and mixing core particles comprising a lithium-nickel-manganese composite oxide obtained through a first heat treatment, followed by drying and a second heat treatment. This is a wet salt coating method and can be a pre-addition method, wherein the salt, which serves as the coating raw material, is first completely dissolved and then the active material particles (i.e., core particles) are added.

[0080] Aqueous solvents may include distilled water, alcoholic solvents, or combinations thereof. Yttrium feedstocks may include, for example, yttrium nitrate, yttrium sulfate, yttrium carbonate, yttrium hydroxide, or combinations thereof. The yttrium feedstock is used to form the coating, and based on 100 mol% of the total metals excluding lithium in the final obtained positive electrode active material, the yttrium content (e.g., amount) in the yttrium feedstock can be designed to be from about 0.1 mol% to about 3.0 mol%, for example, from about 0.1 mol% to about 2.8 mol%, from about 0.1 mol% to about 2.6 mol%, from about 0.1 mol% to about 2.4 mol%, from about 0.1 mol% to about 2.2 mol%, or from about 0.2 mol% to about 2.0 mol%. If the content (e.g., amount) of the coating material is designed to have the above range, the coating can be formed to have a thin and uniform (e.g., substantially uniform) thickness of tens or hundreds of nanometers, which can reduce the amount of gas generated in rechargeable lithium batteries under high voltage and / or high temperature operating conditions and improve high capacity and long cycle life characteristics.

[0081] The coating solution in which yttrium raw material is added and mixed into the above-mentioned aqueous solvent may have a pH of about 1.5 to about 3.5 (e.g., about 2.0 to about 3.4, about 2.5 to about 3.3, about 2.7 to about 3.3 or about 2.9 to about 3.2).

[0082] The nuclei are added to the coating solution and mixed for approximately 5 to 80 minutes, or approximately 5 to 60 minutes, or approximately 5 to 40 minutes. After mixing, the mixture may have a pH of approximately 4.5 to approximately 8.5 (e.g., approximately 5.0 to approximately 8.0, approximately 5.5 to approximately 7.5, or approximately 6.0 to approximately 7.0). If these conditions are met, it is beneficial to form a coating with a uniform (e.g., substantially uniform) thickness.

[0083] The drying process following the above mixing process can be understood as a solvent removal process, and can be carried out at, for example, about 40°C to about 240°C, about 100°C to about 220°C, or about 150°C to about 200°C.

[0084] If the heat treatment of the nickel-manganese composite hydroxide and lithium raw material is described as the first heat treatment, then the heat treatment of the obtained product after removing the solvent from the mixed solution and drying the product can be referred to as the second heat treatment. The second heat treatment can be understood as a coating formation process, and can be carried out, for example, in an oxygen atmosphere at a temperature range of about 700°C to about 850°C or about 750°C to about 840°C for about 2 hours to about 20 hours or about 3 hours to about 10 hours. In embodiments, the second heat treatment temperature may be lower than the first heat treatment temperature, and the second heat treatment time may be the same as or shorter than the first heat treatment time. A suitable or desired coating can be obtained by performing the second heat treatment under these conditions.

[0085] positive electrode

[0086] In some example embodiments, the positive electrode includes a positive electrode current collector and a layer of positive electrode active material on the positive electrode current collector, wherein the positive electrode active material layer includes the aforementioned positive electrode active material. In addition to the aforementioned positive electrode active material, the positive electrode active material layer may further include other types (or categories) of positive electrode active materials. In embodiments, the positive electrode active material layer may optionally further include a binder, a conductive material (e.g., an electrically conductive material), or a combination thereof.

[0087] According to some exemplary embodiments, the loading level of the positive electrode active material layer can be approximately 10 g / cm³. 2 ~ Approximately 40 mg / cm 2 For example, about 10 mg / cm 2 ~ Approximately 30 mg / cm³ 2 or about 10mg / cm 2 ~ Approximately 20 mg / cm2 Implementing such a loading level is advantageous if (for example, when) a positive electrode active material according to some example embodiments is applied, and a positive electrode in which the loading level of the positive electrode active material layer is within the above range is suitable for implementing a high-capacity, high-energy-density rechargeable lithium battery.

[0088] The loading level refers to the ratio of the weight to the area of ​​the electrode active material layer (e.g., the positive electrode active material layer). In an embodiment, the electrode can be prepared by coating a slurry comprising the electrode active material onto a current collector, drying, and pressing. The loading level can refer to one of the conditions designed in the process of coating the electrode active material slurry (e.g., the positive electrode active material slurry) onto the current collector (e.g., the positive electrode current collector). For example, the loading level can be calculated as the ratio of the weight to the cross-sectional area of ​​the electrode active material layer (e.g., the positive electrode active material layer) if (e.g., when) the electrode active material slurry is coated onto the current collector before drying and pressing the electrode plate. It is understood that a higher loading level results in more electrode active material slurry being coated and a thicker electrode active material layer. In an embodiment, the electrode active material slurry comprises the electrode active material and a solvent, and may optionally include a binder and / or a conductive material (e.g., an electrically conductive material). Electrode plates can also be prepared by a dry process, in which an electrode active material layer is formed on the current collector without the use of solvents and then pressed to prepare a positive electrode, and the load level can refer to the ratio of the weight to the area of ​​the electrode active material layer before pressing.

[0089] In this embodiment, the density of the positive electrode active material layer in the finally pressed positive electrode can be about 3.3 g / cc to about 3.7 g / cc, for example, about 3.3 g / cc to about 3.6 g / cc or about 3.4 g / cc to about 3.58 g / cc. This density of the positive electrode active material layer is advantageous when (for example, when) a positive electrode active material according to some example embodiments is applied, and a positive electrode with a positive electrode active material layer density within the above range is suitable for implementing high-capacity, high-energy-density rechargeable lithium batteries.

[0090] The density of the positive electrode active material layer refers to the weight-to-volume ratio of the positive electrode active material layer in a pressed positive electrode, and can be expressed as a mixture density or electrode plate density. The density of the positive electrode active material layer can be measured by: coating a positive electrode active material slurry onto a positive electrode current collector, drying and pressing to prepare the positive electrode; cutting the positive electrode to approximately 30 mm × 30 mm dimensions; measuring the thickness and weight of the positive electrode active material layer excluding the positive electrode current collector; multiplying the cross-sectional area of ​​the positive electrode active material layer by the thickness to calculate the volume; and dividing the weight by the volume. In embodiments, the positive electrode active material slurry includes a positive electrode active material and a solvent, and optionally includes a binder and / or a conductive material (e.g., an electrically conductive material). After coating the positive electrode active material slurry, drying and pressing can be performed, for example, by drying at 80°C and pressing for 3 seconds at a pressure of approximately 50 MPa. The electrode plate (positive electrode active material layer) can also be prepared by a dry process, in embodiments where the positive electrode active material layer is formed on a positive electrode current collector without the use of a solvent, and then pressed to prepare the positive electrode. It can measure the area, thickness, and weight of the positive electrode active material layer under pressed conditions, and can divide the weight by the volume to measure the electrode plate density. Dry pressing of the electrode plate can involve, for example, pressing for 30 seconds under a pressure of about 3 tons.

[0091] adhesive

[0092] The binder improves the adhesion properties between the active material particles of the positive electrode and with the positive electrode current collector. Examples of binders may include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylate resin, polyester resin, or nylon.

[0093] conductive materials

[0094] Conductive materials are included to provide or increase electrode conductivity (e.g., electrical conductivity), and any suitable conductive material may be used as a conductive material unless it causes a chemical change (e.g., an undesirable chemical change in a rechargeable lithium battery). Examples of conductive materials may include: carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, carbon nanotubes, etc.; metallic materials including metal powders and / or metal fibers of copper, nickel, aluminum, silver, etc.; conductive polymers (e.g., electrically conductive polymers), such as polyphenylene derivatives; or mixtures thereof.

[0095] Based on a 100wt% positive electrode active material layer, the respective contents (e.g., amounts) of the binder and conductive material can be from about 0.5wt% to about 5wt%.

[0096] The positive electrode current collector may include, but is not limited to, Al foil.

[0097] Rechargeable lithium batteries

[0098] Some example embodiments provide a rechargeable lithium battery including the aforementioned positive electrode, negative electrode, and electrolyte. As an example, a rechargeable lithium battery may include a positive electrode, a negative electrode, a separator between the positive and negative electrodes, and an electrolyte.

[0099] Rechargeable lithium batteries can be classified according to their shape as cylindrical batteries, prismatic batteries, pouch batteries, coin-shaped batteries, etc. Figures 1-4 To illustrate a schematic diagram of a rechargeable lithium battery according to some example embodiments, wherein Figure 1 It is a cylindrical battery. Figure 2 It is a prismatic battery, and Figure 3 and Figure 4 Each is a pouch-shaped battery. (Reference) Figures 1-4 The rechargeable lithium battery 100 includes an electrode assembly 40 (having a separator 30 between a positive electrode 10 and a negative electrode 20) and a housing 50 (containing the electrode assembly 40). The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte. Figure 1 As shown, the rechargeable lithium battery 100 may include a sealing member 60 of a sealed housing 50. Figure 2 In this context, the rechargeable lithium battery 100 may include a positive electrode lead connector 11, a positive electrode terminal 12, a negative electrode lead connector 21, and a negative electrode terminal 22. For example... Figure 3 and Figure 4 As shown, the rechargeable lithium battery 100 includes electrode terminals 70 that serve as an electrical path to guide the current generated in the electrode assembly 40 to the outside. Figure 4 For example, positive electrode terminal 71 and negative electrode terminal 72. Figure 3 ).

[0100] Rechargeable lithium batteries according to some example embodiments can be charged at high voltages and / or are suitable for driving at high voltages. For example, the charging voltage of a rechargeable lithium battery can be greater than or equal to about 4.45V, and can be about 4.45V to about 4.7V, about 4.45V to about 4.6V, or about 4.45V to about 4.55V. By applying the positive electrode active material according to some example embodiments, even when charged at high voltages, rechargeable lithium batteries can significantly reduce gas generation and achieve high capacity and long cycle life characteristics.

[0101] negative electrode

[0102] The negative electrode may include a negative electrode current collector and a negative electrode active material layer on the negative electrode current collector, and may further include a negative electrode active material, a binder, a conductive material (e.g., a conductive material), or a combination thereof.

[0103] Negative electrode active material

[0104] The negative electrode active material may include a material that reversibly intercalates / deintercalates lithium ions, lithium metal, a lithium metal alloy, a material capable of doping / dedoping lithium, and / or a transition metal oxide.

[0105] The material that reversibly intercalates / deintercalates lithium ions may include, for example, crystalline carbon, amorphous carbon, or a combination thereof as a carbon-based negative electrode active material. The crystalline carbon may be amorphous and / or flaky, sheet-like, spherical, and / or fibrous natural graphite and / or artificial graphite. The amorphous carbon may be soft carbon, hard carbon, mesophase pitch carbonization product, calcined coke, etc.

[0106] 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.

[0107] The material capable of doping / dedoping lithium may be a Si-based negative electrode active material and / or a Sn-based negative electrode active material. The Si-based negative electrode active material may include silicon, a silicon-carbon composite, SiO x (0 < x ≤ 2, for example, SiO2), a Si-Q alloy (where Q is an element selected from alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements (excluding Si), Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof, for example, Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof) or a combination thereof. The Sn-based negative electrode active material may be Sn, SnO k (0 < k ≤ 2, for example, SnO2), a Sn alloy, or a combination thereof.

[0108] The silicon-carbon composite may be a composite of silicon and amorphous carbon. The average particle size (D 50)It can be, for example, from about 0.5 μm to about 20 μm. According to some exemplary embodiments, the silicon-carbon composite can be in the form of silicon particles and amorphous carbon coated on the surface of the silicon particles. For example, the silicon-carbon composite can include secondary particles (cores) in which silicon primary particles are aggregated and an amorphous carbon coating (shell) on the surface of the secondary particles. Amorphous carbon can also be present between the silicon primary particles. For example, the silicon primary particles can be coated with amorphous carbon. The secondary particles can be dispersed in an amorphous carbon matrix.

[0109] The silicon-carbon composite can further include crystalline carbon. For example, the silicon-carbon composite can include: a core including crystalline carbon and silicon particles, and an amorphous carbon coating on the surface of the core. The crystalline carbon can be artificial graphite, natural graphite, or a combination thereof. The amorphous carbon can include soft carbon and / or hard carbon, mesophase pitch carbonized products, and / or calcined coke.

[0110] If the silicon-carbon composite includes silicon and amorphous carbon, based on 100 wt% of the silicon-carbon composite, the content (e.g., amount) of silicon can be from about 10 wt% to about 50 wt%, and the content (e.g., amount) of amorphous carbon can be from about 50 wt% to about 90 wt%. In an embodiment, if (e.g., when) the silicon-carbon composite includes silicon, amorphous carbon, and crystalline carbon, based on 100 wt% of the silicon-carbon composite, the content (e.g., amount) of silicon can be from about 10 wt% to about 50 wt%, the content (e.g., amount) of crystalline carbon can be from about 10 wt% to about 70 wt%, and the content (e.g., amount) of amorphous carbon can be from about 20 wt% to about 40 wt%.

[0111] In an embodiment, the thickness of the amorphous carbon coating can be from about 5 nm to about 100 nm. The average particle size (D 50 ) of the silicon particles (primary particles) can be from about 10 nm to about 1 μm or from about 10 nm to about 200 nm. The silicon particles can exist as separate silicon, can be in the form of a silicon alloy, and / or in the oxidized form of silicon. The oxidized form of silicon can be represented by SiO x (0 < x ≤ 2). In an embodiment, the atomic content (e.g., amount) ratio Si:O indicating the degree of oxidation can be from about 99:1 to about 33:67. As used herein, if (e.g., when) no definition is otherwise provided, the average particle size (D 50 ) indicates the diameter of the particles in which the cumulative volume in the particle size distribution is about 50% by volume.

[0112] Si-based negative electrode active materials and / or Sn-based negative electrode active materials can be mixed with carbon-based negative electrode active materials. If (e.g., when) the Si-based negative electrode active materials and / or Sn-based negative electrode active materials are mixed and used with the carbon-based negative electrode active materials, the mixing ratio can be a weight ratio of from about 1:99 to about 90:10.

[0113] adhesive

[0114] The binder is used to bond the active material particles of the negative electrode to each other and to the negative electrode current collector. The binder can be a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0115] Non-aqueous adhesives may include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyimide, or combinations thereof.

[0116] Waterborne adhesives may include styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepoxychloropropane, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, or combinations thereof.

[0117] If (for example, when) an aqueous binder is used as a binder in the negative electrode active material layer, it may further include a cellulose compound capable of imparting or increasing viscosity. As a cellulose compound, one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and their alkali metal salts may be mixed and used. The alkali metal may be Na, K, and / or Li.

[0118] Dry adhesives can be polymeric materials that can be turned into fibers (e.g., can be fibrous), and can be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or combinations thereof.

[0119] conductive materials

[0120] Conductive materials are included to provide or increase electrode conductivity (e.g., electrical conductivity), and any suitable conductive material may be used as a conductive material unless it causes a chemical change (e.g., an undesirable chemical change in a rechargeable lithium battery). Examples of conductive materials may include: carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, carbon nanotubes, etc.; metallic materials including metal powders and / or metal fibers of copper, nickel, aluminum, silver, etc.; conductive polymers (e.g., electrically conductive polymers), such as polyphenylene derivatives; or mixtures thereof.

[0121] Based on a 100wt% negative electrode active material layer, the content (e.g., amount) of the negative electrode active material can be from about 95wt% to about 99.5wt%, and based on the 100wt% negative electrode active material layer, the content (e.g., amount) of the binder can be from about 0.5wt% to about 5wt%. For example, based on a 100wt% negative electrode active material layer, the negative electrode active material layer may include about 90wt% to about 99.5wt% of the negative electrode active material, about 0.5wt% to about 5wt% of the binder, and about 0wt% to about 5wt% of the conductive material.

[0122] current collector

[0123] The negative electrode current collector may include, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), and / or alloys thereof, and may be in the form of foil, sheet, 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.

[0124] For example, the electrolyte used in rechargeable lithium batteries may be an electrolyte solution, which may include non-aqueous organic solvents and lithium salts.

[0125] Non-aqueous organic solvents are used as media for transporting ions that participate in the electrochemical reactions of a battery. Non-aqueous organic solvents may include carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, aprotic solvents, or combinations thereof.

[0126] 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), butyl carbonate (BC), etc. Ester solvents may include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolactone, mevalonolactone, valproic acid lactone, caprolactone, etc. Ether solvents may include dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, ethylene glycol dimethyl ether, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. In embodiments, ketone solvents may include cyclohexanone, etc. Alcohol solvents may include ethanol, isopropanol, etc., and aprotic solvents may include nitriles (such as R-CN, where R is a C2 to C20 straight-chain, branched or cyclic hydrocarbon group, and may include double bonds, aromatic rings, ether bonds, etc.); amides, such as dimethylformamide; dioxolane, such as 1,3-dioxolane, 1,4-dioxolane, etc.; sulfolane, etc.

[0127] Non-aqueous organic solvents may be used alone or in mixtures of two or more types (or kinds), and if (for example, when) two or more types (or kinds) are used in mixtures, the mixing ratio may be appropriately or suitably adjusted according to suitable or desired battery performance, as will be apparent to those skilled in the art upon reading this disclosure.

[0128] If (for example, when) a carbonate solvent is used, cyclic carbonates and chain carbonates can be mixed and used, and cyclic carbonates and chain carbonates can be mixed in a volume ratio of about 1:1 to about 1:9.

[0129] Non-aqueous organic solvents may further include aromatic hydrocarbon organic solvents. For example, carbonate solvents and aromatic hydrocarbon organic solvents can be mixed and used in a volume ratio of about 1:1 to about 30:1.

[0130] The electrolyte may further include ethylene carbonate, vinylene carbonate and / or ethylene carbonate compounds to improve battery cycle life.

[0131] Examples of ethylene carbonate compounds may include fluoroethylene carbonate, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, etc.

[0132] Lithium salts dissolved in non-aqueous organic solvents supply lithium ions in batteries, ensuring basic operation of rechargeable lithium batteries and improving lithium ion transport between the positive and negative electrodes. Examples of lithium salts may include those selected from LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide, LiFSI), LiC4F9SO3, and LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2 (where x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalate)phosphate (LiDFBOP), and lithium bis(oxalate)borate (LiBOB).

[0133] The concentration of lithium salt can be in the range of about 0.1 M to about 2.0 M. If the concentration of lithium salt is within this range, the electrolyte has appropriate or suitable ionic conductivity and viscosity, and thus excellent performance can be achieved and lithium ions can move efficiently.

[0134] diaphragm

[0135] Depending on the type (or category) of the rechargeable lithium battery, a separator may be present between the positive and negative electrodes. The separator may include a polyethylene separator, a polypropylene separator, a polyvinylidene fluoride separator, or a multilayer film of two or more layers thereof (such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polypropylene three-layer separator, a polypropylene / polypropylene / polypropylene three-layer separator, etc.).

[0136] The diaphragm may include a porous substrate and a coating on one or both (e.g., two opposite) surfaces of the porous substrate, the coating comprising an organic material, an inorganic material, or a combination thereof.

[0137] The porous substrate may be a polymer film formed from any one or a copolymer or mixture of two or more of the following polymers: polyolefins (such as polyethylene and polypropylene), polyesters (such as polyethylene terephthalate and polybutylene terephthalate), polyacetal, polyamide, polyimide, polycarbonate, polyetherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene ether, cyclic olefin copolymers, polyphenylene sulfide, polyethylene naphthalate, glass fiber, and polytetrafluoroethylene (e.g., Teflon).

[0138] 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.

[0139] Organic materials may include (meth)acrylic acid copolymers, which include a first structural unit derived from (meth)acrylamide and a second structural unit including at least one of structural units derived from (meth)acrylic acid or (meth)acrylate and structural units derived from (meth)acrylamide sulfonic acid or a salt thereof.

[0140] Inorganic materials may include, but are not limited to, inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof. The average particle size (D) of the inorganic particles... 50 The range can be approximately 1 nm to approximately 2000 nm, for example, approximately 100 nm to approximately 1000 nm or approximately 100 nm to approximately 700 nm.

[0141] Organic and inorganic materials can be mixed in a coating, or coatings containing organic materials and coatings containing inorganic materials can be stacked.

[0142] The thickness of the coating can 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.

[0143] The following describes embodiments and comparative examples of this disclosure. However, the following embodiments are merely examples of this disclosure, and this disclosure is not limited to the following embodiments.

[0144] Example 1

[0145] 1. Preparation of positive electrode active material

[0146] Ni 0.75 Mn 0.24 Al 0.01 (OH)₂ and LiOH were mixed in a molar ratio of 1:1.05, and then subjected to a first heat treatment at 845°C under an oxygen atmosphere for 8 hours to prepare a product exhibiting Li 1.05 Ni 0.75 Mn 0.24 Al 0.01 The composition of O2 and its average particle size of approximately 14 μm (D 50 Lithium-nickel-manganese composite oxides in the form of secondary particles.

[0147] The coating solution was prepared by pouring 600 g of distilled water and yttrium nitrate into a 1 L reactor and stirring it at approximately 350 rpm for about 5 minutes to dissolve the salt (yttrium nitrate). The salt was confirmed to be completely dissolved in the colorless and transparent coating solution. While continuously stirring the coating solution, 500 g of lithium-nickel-manganese composite oxide was added over 1.5 minutes, followed by stirring for 30 minutes to prepare a mixed solution. In this paper, based on 100 wt% of total metals other than lithium in the final positive electrode active material, the yttrium content (e.g., amount) in yttrium nitrate was designed to be 0.2 mol%.

[0148] Subsequently, the solvent was removed from the mixed solution using a vacuum filter and a filter press, and the residue was dried under vacuum at 190°C to obtain the coated product.

[0149] The coated product was subjected to a second heat treatment at 750°C for 8 hours in an oxygen atmosphere to prepare the final positive electrode active material.

[0150] 2. Preparation of rechargeable lithium battery cells

[0151] Based on the total weight of the positive electrode active material layer slurry, 98.5 wt% of the prepared positive electrode active material, 1.0 wt% of polyvinylidene fluoride binder, and 0.5 wt% of carbon nanotube conductive material were mixed to prepare the positive electrode active material layer slurry (positive electrode active material slurry). The positive electrode active material layer slurry was then coated onto an aluminum foil current collector, followed by drying and pressing to prepare the positive electrode. In this paper, the positive electrode active material layer has a content of 20 mg / cm³. 2 The loading level, and the final pressed positive electrode has a density of about 3.4 g / cc.

[0152] Based on the total weight of the negative electrode active material layer slurry, a negative electrode active material layer slurry was prepared by mixing 97.5 wt% graphite negative electrode active material, 1.5 wt% carboxymethyl cellulose, and 1 wt% styrene-butadiene rubber in an aqueous solvent. The negative electrode active material layer slurry was coated onto a copper foil current collector, then dried and pressed to prepare the negative electrode.

[0153] Rechargeable lithium-ion battery cells were prepared using conventional methods with a polytetrafluoroethylene separator and an electrolyte prepared by mixing ethylene carbonate and dimethyl carbonate in a volume ratio of 3:7 and dissolving 1M LiPF6 in the mixed solvent.

[0154] Example 2

[0155] The positive electrode active material and rechargeable lithium battery cell were prepared in essentially the same manner as in Example 1, except that the yttrium content (e.g., amount) in yttrium nitrate was changed to 0.5 mol% of the total metals other than lithium in the final positive electrode active material, based on 100 mol% of the total metals in the final positive electrode active material.

[0156] Example 3

[0157] The positive electrode active material and rechargeable lithium battery cell were prepared in essentially the same manner as in Example 1, except that the yttrium content (e.g., amount) in yttrium nitrate was changed to 1.0 mol of 100 mol% of total metals other than lithium in the final positive electrode active material during preparation.

[0158] Example 4

[0159] The positive electrode active material and rechargeable lithium battery cell were prepared in essentially the same manner as in Example 1, except that the yttrium content (e.g., amount) in yttrium nitrate was changed to 2.0 mol% of the total metals other than lithium in the final positive electrode active material, based on 100 mol% of the total metals in the final positive electrode active material.

[0160] Comparative Example 1

[0161] The positive electrode active material and rechargeable lithium battery cell were prepared in essentially the same manner as in Example 1, except that during the preparation of the positive electrode active material, a lithium nickel manganese composite oxide Li was used. 1.05 Ni 0.75 Mn 0.24 Al 0.01 O2 itself is used as the active material for the positive electrode without undergoing a yttrium coating process.

[0162] Comparative Example 2

[0163] The positive electrode active material and rechargeable lithium battery cell were prepared in essentially the same manner as in Example 1, except that aluminum sulfate was added to the distilled water solvent instead of yttrium nitrate when preparing the positive electrode active material, wherein the aluminum content (e.g., amount) of the aluminum sulfate was designed to be based on 1.0 mol of 100 mol% of the total metals other than lithium in the final positive electrode active material.

[0164] Evaluation Example 1: Surface Analysis of Positive Electrode Active Material

[0165] Images of the positive electrode active materials of Example 3, Comparative Example 1, and Comparative Example 2 were captured using a scanning electron microscope for comparison. Figure 5 and Figure 6 For comparison, the SEM image of the particle surface of the uncoated positive electrode active material in Example 1, Figure 7 and Figure 8 For comparison, SEM images of the particle surface of the positive electrode active material with only aluminum coating in Example 2 are shown. Figure 9 and Figure 10 This is a SEM image of the particle surface of the positive electrode active material in Example 3. (Reference) Figures 5-10 It was confirmed that the positive electrode active material of Example 3 has a surface shape that is different from the surface shape of the positive electrode active materials of Comparative Example 1 and Comparative Example 2.

[0166] Evaluation Example 2: Analysis of Yttrium Content on the Surface of the Positive Electrode Active Material

[0167] The yttrium content (e.g., amount) on the surface of the positive electrode active materials of Examples 1 to 4, and Comparative Examples 1 and 2 was analyzed by energy-mapping energy-dispersive spectroscopy (EP-EDS), and the results are shown in Table 1. EP-EDS (AMETEK Octane Elite) was performed under the following conditions: EDS vacc: 15 kV, current: 10 μA, live time: 90 s.

[0168] Table 1

[0169]

[0170] Referring to Table 1, it was confirmed that the positive electrode active materials of Examples 1 to 4 have a yttrium content (e.g., amount) on the surface of the positive electrode active material within an appropriate or suitable range.

[0171] Evaluation Example 3: Initial Charge / Discharge Capacity and Efficiency Evaluation

[0172] For the initial charging and discharging, at 25°C, the rechargeable lithium batteries (cells) according to Examples 1 to 4, Comparative Examples 1 and 2 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 cutoff voltage of 3.0V. Table 2 shows the initial charging capacity, the initial discharging capacity, and the ratio of the initial discharging capacity to the initial charging capacity as efficiency (initial charging / discharging efficiency (%)).

[0173] Evaluation Example 4: High Temperature Cyclic Life Characteristics

[0174] After the initial charge and discharge of Example 3, the battery cells were charged at 1.0C (0.05C cutoff) and discharged for 50 or more cycles at 45°C within a voltage range of 3.0V to 4.45V to calculate the ratio of the discharge capacity at the 50th cycle to the initial discharge capacity (capacity retention rate at the 50th cycle (%)) (i.e., high-temperature cycle life), and the results are shown in Table 2.

[0175] Table 2

[0176]

[0177] Referring to Table 2, the rechargeable lithium battery cells of Examples 1 to 4 not only achieve higher or comparable initial charge capacity, initial discharge capacity, and efficiency characteristics compared to the comparative examples, but also improve or maintain high-temperature cycle life characteristics.

[0178] Conversely, it was confirmed that Comparative Example 1, which was not coated, exhibited worse cycle life characteristics under high voltage and high temperature conditions compared to the cycle life characteristics of Examples 1 to 4. Furthermore, Comparative Example 2, which was only coated with aluminum, exhibited insufficient initial charge / discharge efficiency and poor cycle life characteristics under high voltage and high temperature conditions compared to Examples 1 to 4.

[0179] While the subject matter of this disclosure has been described in conjunction with exemplary embodiments now regarded as practice, it should be understood that this disclosure is not limited to the disclosed embodiments. Rather, it is intended to cover various 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 including a layered lithium nickel manganese-based complex oxide; and a yttrium-containing coating layer on a surface of the core particle; wherein a yttrium content on the surface of the positive electrode active material is 0.1 at% to 5.0 at% as measured by energy mapping energy dispersive spectroscopy based on 100 at% of total metals other than lithium.

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

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

4. The positive electrode active material according to claim 3, wherein: a concentration gradient difference of aluminum within the core particle is less than or equal to 0.05 mol%.

5. The positive electrode active material according to claim 1, wherein: in the layered lithium nickel manganese-based complex oxide, a cobalt content is 0 mol% to 1 mol% based on 100 mol% of total metals other than lithium.

6. The positive electrode active material according to claim 1, wherein: the layered lithium nickel manganese-based complex oxide is represented by Chemical Formula 1: Chemical Formula 1 Li a1 Ni x1 Mn y1 Al z1 M 1 w1 O 2-b1 X b1 wherein, 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 the group consisting of B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

7. The positive electrode active material according to claim 1, wherein: the yttrium-containing coating layer is in the form of a film that continuously surrounds the surface of the core particle.

8. The positive electrode active material according to claim 1, wherein: a thickness of the yttrium-containing coating layer is 30 nm to 500 nm.

9. The positive electrode active material according to claim 1, wherein: a deviation in the thickness of the yttrium-containing coating layer within a single positive electrode active material particle is less than or equal to 20%.

10. The positive electrode active material according to claim 1, wherein: The average particle diameter D of the positive electrode active material is 2 μm to 18 μm. 50 is 2 μm to 18 μm.

11. A method for producing a positive electrode active material, comprising: (i) preparing a core particle including a layered lithium nickel manganese-based complex oxide; (ii) adding and mixing a yttrium raw material into an aqueous solvent to prepare a coating solution; (iii) adding and mixing the core particle into the coating solution to prepare a mixed solution; and (iv) removing the aqueous solvent from the mixed solution, and then drying and heat-treating the obtained product to obtain a positive electrode active material.

12. The method for producing a positive electrode active material according to claim 11, wherein: in the layered lithium nickel manganese-based complex oxide, a nickel content is 60 mol% to 80 mol%, a manganese content is greater than or equal to 10 mol%, an aluminum content is greater than 0 mol% and less than or equal to 3 mol%, and a cobalt content is 0 mol% to 0.01 mol% based on 100 mol% of total metals other than lithium.

13. The method for producing a positive electrode active material according to claim 11, wherein: The yttrium content in the yttrium raw material is 0.1 mol% to 3.0 mol% based on 100 mol% of total metals other than lithium in the positive electrode active material.

14. The method for producing a positive electrode active material according to claim 11, wherein: The pH of the coating solution including the yttrium raw material mixed into the aqueous solvent is 1.5 to 3.5, and The pH of the mixed solution in which the core particles are added and mixed into the coating solution is 4.5 to 8.

5.

15. The method for producing a positive electrode active material according to claim 11, wherein: The heat treatment is performed at 700°C to 850°C.

16. A positive electrode comprising: 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 positive electrode active material according to any one of claims 1 to 10 or produced by the method according to any one of claims 11 to 15.

17. The positive electrode according to claim 16, wherein: The positive electrode active material layer has a loading level of 10 mg / cm 2 ~ 40 mg / cm 2 .

18. The positive electrode according to claim 16, wherein: The density of the positive electrode active material layer is 3.3 g / cc to 3.7 g / cc.

19. A rechargeable lithium battery comprising: the positive electrode according to any one of claims 16 to 18; a negative electrode; and an electrolyte.

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

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