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

Abstract

The invention relates to a positive electrode active material, a method for preparing the same, a positive electrode, and a rechargeable lithium battery. The positive electrode active material includes: a first positive electrode active material including a first lithium nickel-based composite oxide and in the form of secondary particles having an average particle diameter of about 10 [mu] m to about 25 [mu] m; a second positive electrode active material including a second lithium nickel-based composite oxide and in the form of secondary particles having an average particle diameter of about 0.5 [mu] m to about 8 [mu] m; and a third positive electrode active material including a third lithium nickel-based composite oxide and in the form of secondary particles including a plurality of primary particles, the secondary particles having an average particle diameter of about 0.5 [mu] m to about 8 [mu] m, and the primary particles constituting the secondary particles of the third positive electrode active material being needle-shaped. The nickel content of the third lithium nickel-based composite oxide based on 100 mol% of the total metal other than lithium in the third lithium nickel-based composite oxide is higher than the nickel content of the second lithium nickel-based composite oxide based on 100 mol% of the total metal other than lithium in the second lithium nickel-based composite oxide.

Description

Technical Field

[0001] One or more embodiments of the present disclosure relate to a positive electrode active material, a method for preparing the same, a positive electrode including the positive electrode active material, and a rechargeable lithium battery including the positive electrode. Background Art

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

[0003] Various positive electrode active materials have been studied to obtain or implement rechargeable lithium batteries for these uses. Among them, lithium nickel-based oxides, lithium nickel manganese cobalt-based composite oxides, lithium nickel cobalt aluminum-based composite oxides, and / or lithium cobalt-based oxides are mainly used as positive electrode active materials. Nickel-based positive electrode active materials are materials that are being actively developed because they can achieve a relatively high capacity and a relatively high energy density; however, their synthesis process is relatively simple, and thus there are limitations in improving the characteristics of the positive electrode active material through this process. That is, since nickel-based positive electrode materials can obtain a relatively high capacity and energy density, nickel-based positive electrode materials are being actively developed. However, the simplicity of their synthesis process has certain limitations in further enhancing the characteristics of these materials. Summary of the Invention

[0004] One or more aspects of embodiments of the present disclosure relate to a positive electrode active material and a method for preparing the same, the positive electrode active material having a high initial discharge capacity and a high initial charge / discharge efficiency (hereinafter, "initial charge / discharge efficiency" is also referred to as "initial charge and discharge efficiency", or simply "efficiency") and capable of achieving its long cycle life characteristics.

[0005] 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.

[0006] In one or more embodiments, the positive electrode active material includes: a first positive electrode active material, including a first lithium nickel-based composite oxide and in the form of secondary particles formed by aggregating a plurality of primary particles, wherein the average particle diameter (D 50 ) is about 10 micrometers (μm) to about 25 μm; a second positive electrode active material, including a second lithium nickel-based composite oxide and in the form of secondary particles formed by aggregating a plurality of primary particles, wherein the average particle diameter (D50 ) is from about 0.5 μm to about 8 μm; and a third positive electrode active material, including a third lithium nickel composite oxide and in the form of secondary particles formed by aggregating a plurality of primary particles, wherein the average particle size (D 50 ) is from about 0.5 μm to about 8 μm, and wherein the primary particles of the secondary particles constituting the third positive electrode active material are needle-shaped (e.g., in the form of needles), and the nickel content (e.g., amount) of the third lithium nickel composite oxide based on the total metal other than lithium in 100 mol% of the third lithium nickel composite oxide is higher than the nickel content (e.g., amount) of the second lithium nickel composite oxide based on the total metal other than lithium in 100 mol% of the second lithium nickel composite oxide.

[0007] In one or more embodiments, a method for preparing a positive electrode active material includes: mixing a first nickel hydroxide having an average particle size (D 50 ) of from about 10 μm to about 25 μm and a first lithium raw material such that the molar ratio of lithium in the first lithium raw material to the total metal of the first nickel hydroxide is greater than or equal to about 1.09, and performing a first heat treatment to obtain a first heat treatment product, and mixing the first heat treatment product, a second nickel hydroxide having an average particle size (D 50 ) of from about 0.5 μm to about 8 μm and a second lithium raw material, and performing a second heat treatment.

[0008] In one or more embodiments, a positive electrode for a rechargeable lithium battery includes the aforementioned positive electrode active material.

[0009] In one or more embodiments, a rechargeable lithium battery includes the aforementioned positive electrode, negative electrode, and electrolyte.

[0010] The positive electrode active material prepared according to one or more embodiments of the present disclosure has high initial charge and discharge efficiency and can achieve long cycle life characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The above and other aspects, features, and advantages of certain embodiments of the present disclosure will become more apparent from the following description in conjunction with the accompanying drawings.

[0012] Figures 1 to 4 Each is a schematic diagram showing a rechargeable lithium battery according to one or more embodiments of the present disclosure.

[0013] Figure 5 is a scanning electron microscope (SEM) image of the positive electrode active material prepared in Example 1.

[0014] Figure 6 is an SEM image of a cross section of the positive electrode active material prepared in Example 1.

[0015] Description of Reference Numerals

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

[0017] 11: Positive electrode lead tab; 12: Positive electrode terminal

[0018] 20: Negative electrode; 21: Negative electrode lead tab

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

[0020] 40: Electrode assembly; 50: Housing

[0021] 60: Sealing member; 70: Electrode tab

[0022] 71: Positive electrode tab; 72: Negative electrode tab Detailed Embodiments

[0023] In the following, example embodiments will be described in more detail so that those of ordinary skill in the art can easily implement them. However, the present disclosure can be implemented in many different forms and is not construed as being limited to the example embodiments set forth herein.

[0024] The terms used herein are only for describing embodiments and are not intended to limit the present disclosure. As used herein, the singular forms "a", "an", and "the" are also intended to include the plural forms unless the context clearly indicates otherwise. Further, when describing embodiments of the present disclosure, the use of "may" refers to "one or more embodiments of the present disclosure".

[0025] As used herein, "a combination thereof" refers to a mixture, laminate, composite, copolymer, alloy, blend, reaction product, etc. of components.

[0026] In this document, it should be understood that terms such as "comprise(s) / comprising", "include(s) / including", or "have(has) / having" are intended to indicate the presence of the implemented features, quantities, steps (e.g., actions or tasks), elements, and / or a combination thereof (e.g., any suitable one), but do not exclude the possibility of the presence or addition of one or more other features, quantities, steps (e.g., actions or tasks), elements, and / or a combination thereof (e.g., any suitable one).

[0027] In the drawings, for clarity, the thickness of layers, films, panels, regions, etc. may be exaggerated, and throughout the present disclosure, like reference numerals denote like elements and their repeated description may not be provided for brevity. It should 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 intervening elements may also be present therebetween. 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 are no intervening elements.

[0028] In addition, as used herein, a “layer” may include not only a shape or layer formed over an entire surface when viewed in plan view, but also a shape or layer formed over a partial surface.

[0029] In one or more embodiments, the average particle size can be measured by methods well known to those skilled in the art, e.g., by a particle size analyzer (e.g., HORIBA, LA-950 laser particle size analyzer) or by a transmission electron microscope (TEM) or a scanning electron microscope (SEM). In one or more embodiments, it can be measured by using the dynamic light scattering method, performing data analysis, counting the number of particles in each particle size range, and calculating from the data to obtain the average particle size value. Unless otherwise defined, the average particle size (D 50 ) may refer to the diameter of the particle at which the cumulative volume in the particle size distribution is 50 volume %. D 50 refers to the average diameter (or size) of the particles at which the cumulative volume in the particle size distribution (e.g., cumulative distribution) corresponds to 50 volume %, and refers to the value of the particle size corresponding to 50% starting from the smallest particle in the distribution curve cumulated in the order of the smallest particle size to the largest particle size when the total number of particles is 100%. In one or more embodiments, if (e.g., when) no other definition is provided, the average particle size (D 50 ) as used herein refers to the diameter of the particle at which the cumulative volume in the particle size distribution is 50 volume % obtained by randomly measuring the sizes (diameter or major axis length) of about 20 particles in a scanning electron microscope image. In the present disclosure, when the particle is spherical, “diameter” indicates the average particle size, and when the particle is non-spherical, “diameter” indicates the major axis length.

[0030] In this document, "or" is not construed in an exclusive sense. For example, "A or B" should be construed to include A, B, A + B, etc. Further, as used in this document, the term "and / or" includes any and all combinations of one or more of the associated listed items. Expressions such as "at least one of...", "one of...", and "selected from..." when before or after a list of elements modify the entire list of elements and not a single element of the list. For example, "at least one of a, b, and c", "at least one selected from a, b, and c", "at least one selected from a to c", etc. may 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. " / " used in this document may be construed as "and" or "or" depending on the circumstances.

[0031] As used in this document, the term "metal" is construed to include the concepts of common metals, transition metals, and metalloids (semi-metals). And as used in this document, the term "group" refers to the groups of the periodic table according to the 1 - 18 grouping system of the International Union of Pure and Applied Chemistry ("IUPAC").

[0032] Positive electrode active material

[0033] According to one or more embodiments of the present disclosure, the positive electrode active material for a rechargeable lithium battery may include a first positive electrode active material, a second positive electrode active material, and a third positive electrode active material. The first positive electrode active material includes a first lithium nickel-based composite oxide and is in the form of secondary particles formed by aggregating a plurality of primary particles, wherein the average particle diameter (D 50 ) is about 10 μm to about 25 μm. The second positive electrode active material includes a second lithium nickel-based composite oxide and is in the form of secondary particles formed by aggregating a plurality of primary particles, wherein the average particle diameter (D 50 ) is about 0.5 μm to about 8 μm. The third positive electrode active material includes a third lithium nickel-based composite oxide and is in the form of secondary particles formed by aggregating a plurality of primary particles, wherein the average particle diameter (D 50 ) is about 0.5 μm to about 8 μm. The shape of the primary particles in the secondary particles of the third positive electrode active material is needle-like (e.g., in the form of a needle). In this document, the nickel content (e.g., amount) of the third lithium nickel-based composite oxide based on the total metal other than lithium in 100 mol% of the third lithium nickel-based composite oxide is higher than the nickel content (e.g., amount) of the second lithium nickel-based composite oxide based on the total metal other than lithium in 100 mol% of the second lithium nickel-based composite oxide. For this reason, the positive electrode active material can achieve relatively high efficiency and long cycle life characteristics.

[0034] Nickel-based positive electrode active materials (which are a mixture of large secondary particles and small secondary particles) are typically prepared by synchronously (e.g., simultaneously) heat-treating (e.g., firing) large particle precursors, small particle precursors, and lithium raw materials, and then optionally coating them. In contrast, in one or more embodiments of the present disclosure described in more detail later, a stepwise (e.g., actions or tasks) synthesis method is provided, in which first the large particle precursor and the lithium raw material are mixed and subjected to a first heat treatment, and then the small particle precursor and the lithium raw material are added thereto and subjected to a second heat treatment. In an embodiment, when the lithium raw material is mixed with the large particle precursor, the lithium is mixed in excess to a certain level to synthesize lithium-rich large particles, and then the small particle precursor is added to cause a reaction such that the lithium-rich large particles come into contact with a part of the small particle precursor. Accordingly, since nickel diffuses from the large particles, the small particle precursor that reacts with the lithium-rich large particles is formed into small particles having a nickel content (e.g., amount) higher than the nickel content (e.g., amount) of the small particle precursor. As a result, the primary particles of the secondary particles constituting the small particles are needle-shaped. As the nickel content (e.g., amount) increases, the small particles including needle-shaped primary particles are called the third positive electrode active material.

[0035] Since a part of the small particle precursor does not react directly with the lithium-rich large particles, there are also small particles having the same nickel content (e.g., amount) as the nickel content (e.g., amount) of the small particle precursor and not including needle-shaped primary particles, which are called the second positive electrode active material. The large particles (i.e., lithium-rich large particles) correspond to the first positive electrode active material. That is, some of the small particle precursors do not react directly with the lithium-rich large particles. Accordingly, there are additional small particles having the same nickel content (e.g., amount) as the nickel content (e.g., amount) of the small particle precursor but not having needle-shaped primary particles. These additional small particles are called the second positive electrode active material. The large particles (i.e., lithium-rich large particles) correspond to the first positive electrode active material.

[0036] According to the synthesis method of one or more embodiments, the reactivity between the positive electrode active material precursor and the lithium raw material is further improved, thereby improving the processability, and the positive electrode active material synthesized by this method has a higher initial discharge capacity, significantly improved initial charge and discharge efficiency, and improved cycle life characteristics compared with the positive electrode active material prepared by the existing methods in the art.

[0037] The nickel content (e.g., amount) of the third lithium nickel-based composite oxide based on the total metal other than lithium in 100 mol% of the third lithium nickel-based composite oxide can be, for example, about 1 mol% to about 5 mol% (e.g., about 1 mol% to about 4 mol% or about 2 mol% to about 3 mol%) higher than the nickel content (e.g., amount) of the second lithium nickel-based composite oxide based on the total metal other than lithium in 100 mol% of the second lithium nickel-based composite oxide.

[0038] As the nickel content (e.g., amount) of the third positive electrode active material increases compared to the nickel content (e.g., amount) of its precursor, the content (e.g., amount) of metal components other than lithium and nickel decreases. For example, in one or more embodiments, the second lithium nickel composite oxide and the third lithium nickel composite oxide may further include a metal (M) other than lithium and nickel. In an embodiment, the content (e.g., amount) of metal (M) in the third lithium nickel composite oxide based on the total metal other than lithium in 100 mol% of the third lithium nickel composite oxide may be lower than the content (e.g., amount) of metal (M) in the second lithium nickel composite oxide based on the total metal other than lithium in 100 mol% of the second lithium nickel composite oxide, and for example, it may be about 1 mol% to about 5 mol%, about 1 mol% to about 4 mol%, or about 2 mol% to about 3 mol% lower.

[0039] Hereinafter, each positive electrode active material will be described in more detail.

[0040] The first positive electrode active material

[0041] The first positive electrode active material includes a first lithium nickel composite oxide and is in the form of secondary particles formed by aggregating a plurality of primary particles, where the average particle diameter (D 50 ) of the secondary particles is about 10 μm to about 25 μm. The first positive electrode active material may be in the form of large particles. The average particle diameter (D 50 ) of the secondary particles of the first positive electrode active material may be, for example, about 10 μm to about 20 μm, about 10 μm to about 18 μm, or about 12 μm to about 16 μm.

[0042] The shape of the secondary particles of the first positive electrode active material may be, for example, a spherical shape, an ellipsoidal shape, a polygonal shape, an irregular shape, or a combination thereof (e.g., any suitable combination), but for example, it may not be needle-shaped. Herein, the polygonal shape refers to a three-dimensional shape having a plurality of angles, such as a prism, a pyramid, and a polyhedron. The irregular shape is a three-dimensional shape. The shape of the primary particles constituting the secondary particles of the first positive electrode active material may be, for example, a spherical shape, an ellipsoidal shape, a polygonal shape, a plate shape (e.g., in the form of a plate), an irregular shape, or a combination thereof (e.g., any suitable combination), but for example, it may not be needle-shaped. Different from the third positive electrode active material, the first positive electrode active material may not include (e.g., may exclude) needle-shaped primary particles.

[0043] Based on the total metals other than lithium in the first lithium nickel-based composite oxide of 100 mol%, the nickel content (e.g., amount) can be, for example, about 50 mol% to about 99 mol% (e.g., about 50 mol% to about 90 mol%, about 50 mol% to about 80 mol%, about 50 mol% to about 70 mol%, about 55 mol% to about 70 mol% or about 55 mol% to about 65 mol%). For example, in one or more embodiments, the first positive electrode active material can be a medium-nickel positive electrode active material containing about 55 mol% to about 70 mol% of nickel based on the total metals other than lithium in the first lithium nickel-based composite oxide of 100 mol%.

[0044] The first lithium nickel-based composite oxide and the second lithium nickel-based composite oxide can have the same or different compositions. Similarly, the first lithium nickel-based composite oxide and the third lithium nickel-based composite oxide can have the same or different compositions. However, the second lithium nickel-based composite oxide and the third lithium nickel-based composite oxide can have different compositions because the nickel content (e.g., amount) is different.

[0045] The first lithium nickel-based composite oxide can be represented by Chemical Formula 1, and for example, as a specific example, it can be represented by Chemical Formula 2.

[0046] Chemical Formula 1

[0047] Li a1 Ni x1 M 1 y1 O 2-b1 X b1

[0048] In Chemical Formula 1, 0.9 ≤ a1 ≤ 1.2, 0.5 ≤ x1 < 1, 0 < y1 ≤ 0.5, 0.9 ≤ x1 + y1 ≤ 1.1, and 0 ≤ b1 ≤ 0.1, M 1 can be one or more elements selected from aluminum (Al), boron (B), barium (Ba), calcium (Ca), cerium (Ce), cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), magnesium (Mg), manganese (Mn), molybdenum (Mo), niobium (Nb), silicon (Si), tin (Sn), strontium (Sr), titanium (Ti), vanadium (V), tungsten (W), yttrium (Y), zinc (Zn), and zirconium (Zr), and X can be one or more elements selected from fluorine (F), phosphorus (P), and sulfur (S).

[0049] In one or more embodiments, in Chemical Formula 1, 0.5 ≤ x1 ≤ 0.9 and 0.1 ≤ y1 ≤ 0.5, 0.5 ≤ x1 ≤ 0.8 and 0.2 ≤ y1 ≤ 0.5, 0.5 ≤ x1 ≤ 0.7 and 0.3 ≤ y1 ≤ 0.5, or 0.55 ≤ x1 ≤ 0.7 and 0.3 ≤ y1 ≤ 0.45.

[0050] Chemical formula 2

[0051] Li a2 Ni x2 Co y2 M 2 z2 M 3 w2 O 2-b2 X b2

[0052] In Chemical formula 2, 0.9 ≤ a2 ≤ 1.2, 0.5 ≤ x2 < 1, 0 < y2 ≤ 0.5, 0 < z2 ≤ 0.5, 0 ≤ w2 ≤ 0.1, 0.9 ≤ x2 + y2 + z2 + w2 ≤ 1.1, and 0 ≤ b2 ≤ 0.1, M 2 may be Al, Mn, and / or a combination thereof (e.g., any suitable combination), M 3 may be one or more elements selected from B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X may be one or more elements selected from F, P, and S.

[0053] In one or more embodiments, in Chemical formula 2, 0.5 ≤ x2 ≤ 0.8, 0.1 ≤ y2 ≤ 0.4, 0.1 ≤ z2 ≤ 0.4, and 0 ≤ w2 ≤ 0.1, 0.5 ≤ x2 ≤ 0.7, 0.2 ≤ y2 ≤ 0.4, 0.1 ≤ z2 ≤ 0.3, and 0 ≤ w2 ≤ 0.1, 0.5 ≤ x2 ≤ 0.7, 0.1 ≤ y2 ≤ 0.3, 0.2 ≤ z2 ≤ 0.4, and 0 ≤ w2 ≤ 0.1, or 0.5 ≤ x2 ≤ 0.6, 0.2 ≤ y2 ≤ 0.3, 0.2 ≤ z2 ≤ 0.3, and 0 ≤ w2 ≤ 0.1.

[0054] In one or more embodiments, the first positive electrode active material may include: core particles including a first lithium nickel-based composite oxide; and a coating located on the surface of each core particle. The coating may include coating elements such as Al, B, Co, Mg, Si, Ti, V, W, Zn, Zr, and / or a combination thereof (e.g., any suitable combination), for example, in one or more embodiments, may include aluminum as a coating element. Based on the total metal other than lithium in 100 wt% of the first positive electrode active material, the content (e.g., amount) of the coating element may be about 0.1 wt% to about 5 wt%, about 0.1 wt% to about 3 wt%, about 0.1 wt% to about 2 wt%, about 0.1 wt% to about 1 wt%, or about 0.1 wt% to about 0.9 wt%.

[0055] The second positive electrode active material

[0056] The second positive electrode active material includes a second lithium nickel-based composite oxide and is in the form of secondary particles formed by aggregating a plurality of primary particles, and the average particle diameter (D 50 ) is from about 0.5 μm to about 8 μm. The second positive electrode active material may be in the form of small particles or may be in the form of some small particles. The average particle diameter (D 50 ) of the secondary particles of the second positive electrode active material may be, for example, from about 0.5 μm to about 6 μm, from about 1 μm to about 5 μm, or from about 2 μm to about 4 μm.

[0057] This may mean that the second positive electrode active material maintains a composition substantially the same as that of the small particle precursor, and the primary particles do not form needle-like shapes. For example, unlike the third positive electrode active material, the secondary particles of the second positive electrode active material may not include (for example, may exclude) needle-like primary particles. The shape of the primary particles of the second positive electrode active material may be, for example, spherical shape, ellipsoidal shape, polygonal shape, plate shape (for example, in the form of a plate), irregular shape, or a combination thereof (for example, any suitable combination). The shape of the secondary particles of the second positive electrode active material may be, for example, spherical shape, ellipsoidal shape, polygonal shape, irregular shape, or a combination thereof (for example, any suitable combination), but may not be needle-like, for example.

[0058] Based on the total metal other than lithium in 100 mol% of the second lithium nickel-based composite oxide, the nickel content (for example, amount) may be, for example, from about 50 mol% to about 99 mol% (for example, from about 50 mol% to about 90 mol%, from about 50 mol% to about 80 mol%, from about 50 mol% to about 70 mol%, from about 55 mol% to about 70 mol%, or from about 55 mol% to about 65 mol%). For example, in one or more embodiments, the second positive electrode active material may be a medium-nickel positive electrode active material containing from about 55 mol% to about 70 mol% of nickel based on the total metal other than lithium in 100 mol% of the second lithium nickel-based composite oxide.

[0059] The second lithium nickel-based composite oxide may be represented by the exemplary chemical formula 3 or may be represented by the specific exemplary chemical formula 4.

[0060] Chemical formula 3

[0061] Li a3 Ni x3 M 4 y3 O 2-b3 X b3

[0062] In Chemical Formula 3, 0.9 ≤ a3 ≤ 1.2, 0.5 ≤ x3 < 1, 0 < y3 ≤ 0.5, 0.9 ≤ x3 + y3 ≤ 1.1, and 0 ≤ b3 ≤ 0.1, M 4 may be one or more elements selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X may be one or more elements selected from F, P, and S.

[0063] In one or more embodiments, in Chemical Formula 3, 0.5 ≤ x3 ≤ 0.9 and 0.1 ≤ y3 ≤ 0.5, 0.5 ≤ x3 ≤ 0.8 and 0.2 ≤ y3 ≤ 0.5, 0.5 ≤ x3 ≤ 0.7 and 0.3 ≤ y3 ≤ 0.5, or 0.55 ≤ x3 ≤ 0.7 and 0.3 ≤ y3 ≤ 0.45.

[0064] Chemical Formula 4

[0065] Li a4 Ni x4 Co y4 M 5 z4 M 6 w4 O 2-b4 X b4

[0066] In Chemical Formula 4, 0.9 ≤ a4 ≤ 1.2, 0.5 ≤ x4 < 1, 0 < y4 ≤ 0.5, 0 < z4 ≤ 0.5, 0 ≤ w4 ≤ 0.1, 0.9 ≤ x4 + y4 + z4 + w4 ≤ 1.1, and 0 ≤ b4 ≤ 0.1, M 5 may be Al, Mn, or a combination thereof (e.g., any suitable combination), M 6 may be one or more elements selected from B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X may be one or more elements selected from F, P, and S.

[0067] In one or more embodiments, in Chemical Formula 4, 0.5 ≤ x4 ≤ 0.8, 0.1 ≤ y4 ≤ 0.4, 0.1 ≤ z4 ≤ 0.4, and 0 ≤ w4 ≤ 0.1, 0.5 ≤ x4 ≤ 0.7, 0.2 ≤ y4 ≤ 0.4, 0.1 ≤ z4 ≤ 0.3, and 0 ≤ w4 ≤ 0.1, 0.5 ≤ x4 ≤ 0.7, 0.1 ≤ y4 ≤ 0.3, 0.2 ≤ z4 ≤ 0.4, and 0 ≤ w4 ≤ 0.1, or 0.5 ≤ x4 ≤ 0.6, 0.2 ≤ y4 ≤ 0.3, 0.2 ≤ z4 ≤ 0.3, and 0 ≤ w4 ≤ 0.1.

[0068] In one or more embodiments, the second positive electrode active material may include: core particles including a second lithium nickel-based composite oxide; and a coating on the surface of each core particle. The coating may include coating elements such as Al, B, Co, Mg, Si, Ti, V, W, Zn, Zr, and / or combinations thereof (e.g., any suitable combination), for example, in one or more embodiments, may include aluminum as a coating element. Based on the total metal other than lithium in 100 wt% of the second positive electrode active material, the content (e.g., amount) of the coating element may be about 0.1 wt% to about 5 wt%, about 0.1 wt% to about 3 wt%, about 0.1 wt% to about 2 wt%, about 0.1 wt% to about 1 wt%, or about 0.1 wt% to about 0.9 wt%.

[0069] The third positive electrode active material

[0070] The third positive electrode active material includes a third lithium nickel-based composite oxide and is in the form of secondary particles formed by aggregating a plurality of primary particles, where the average particle size (D 50 ) of the secondary particles is about 0.5 μm to about 8 μm and the secondary particles include acicular primary particles. The third positive electrode active material may appear as small particles or may appear as a portion of small particles. The average particle size (D 50 ) of the secondary particles of the third positive electrode active material may be, for example, about 0.5 μm to about 6 μm, about 1 μm to about 5 μm, or about 2 μm to about 4 μm.

[0071] The third positive electrode active material may be small particles formed by contacting and reacting a lithium-rich large particle and a small particle precursor with each other in the method for preparing the positive electrode active material described in more detail later. By receiving nickel from the large particle, its nickel content (e.g., amount) is higher than the nickel content (e.g., amount) of the small particle precursor, and the shape of the primary particle is acicular (e.g., like a needle). However, the secondary particles of the third positive electrode active material are not acicular and may have, for example, a spherical shape, an ellipsoidal shape, a polygonal shape, an irregular shape, and / or combinations thereof (e.g., any suitable combination).

[0072] Based on the total metal other than lithium in 100 mol% of the third lithium nickel-based composite oxide, the nickel content (e.g., amount) may be, for example, about 50 mol% to about 99 mol% (e.g., about 50 mol% to about 90 mol%, about 50 mol% to about 80 mol%, about 50 mol% to about 70 mol%, about 55 mol% to about 70 mol%, or about 55 mol% to about 65 mol%). For example, in one or more embodiments, the third positive electrode active material may be a medium-nickel positive electrode active material containing about 55 mol% to about 70 mol% of nickel based on the total metal other than lithium in 100 mol% of the third lithium nickel-based composite oxide.

[0073] , the third lithium nickel-based composite oxide can be represented by Chemical Formula 5. For example, as a specific example, it can be represented by Chemical Formula 6.

[0074] Chemical Formula 5

[0075] Li a5 Ni x5 M 7 y5 O 2-b5 X b5

[0076] In Chemical Formula 5, 0.9 ≤ a5 ≤ 1.2, 0.5 ≤ x5 < 1, 0 < y5 ≤ 0.5, 0.9 ≤ x5 + y5 ≤ 1.1, and 0 ≤ b5 ≤ 0.1, M 7 can be one or more elements selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X can be one or more elements selected from F, P, and S.

[0077] In one or more embodiments, in Chemical Formula 5, 0.5 ≤ x5 ≤ 0.9 and 0.1 ≤ y5 ≤ 0.5, 0.5 ≤ x5 ≤ 0.8 and 0.2 ≤ y5 ≤ 0.5, 0.5 ≤ x5 ≤ 0.7 and 0.3 ≤ y5 ≤ 0.5, or 0.55 ≤ x5 ≤ 0.7 and 0.3 ≤ y5 ≤ 0.45.

[0078] Chemical Formula 6

[0079] Li a6 Ni x6 Co y6 M 8 z6 M 9 w6 O 2-b6 X b6

[0080] In Chemical Formula 6, 0.9 ≤ a6 ≤ 1.2, 0.5 ≤ x6 < 1, 0 < y6 ≤ 0.5, 0 < z6 ≤ 0.5, 0 ≤ w6 ≤ 0.1, 0.9 ≤ x6 + y6 + z6 + w6 ≤ 1.1, and 0 ≤ b6 ≤ 0.1, M 8 can be Al, Mn, and / or a combination thereof (e.g., any suitable combination), M 9 can be one or more elements selected from B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X can be one or more elements selected from F, P, and S.

[0081] In one or more embodiments, in Chemical Formula 6, 0.5 ≤ x6 ≤ 0.8, 0.1 ≤ y6 ≤ 0.4, 0.1 ≤ z6 ≤ 0.4, and 0 ≤ w6 ≤ 0.1; 0.5 ≤ x6 ≤ 0.7, 0.2 ≤ y6 ≤ 0.4, 0.1 ≤ z6 ≤ 0.3, and 0 ≤ w6 ≤ 0.1; 0.5 ≤ x6 ≤ 0.7, 0.1 ≤ y6 ≤ 0.3, 0.2 ≤ z6 ≤ 0.4, and 0 ≤ w6 ≤ 0.1; or 0.5 ≤ x6 ≤ 0.6, 0.2 ≤ y6 ≤ 0.3, 0.2 ≤ z6 ≤ 0.3, and 0 ≤ w6 ≤ 0.1.

[0082] In one or more embodiments, the third positive electrode active material may include: core particles including a third lithium nickel-based composite oxide; and a coating located on the surface of each core particle. The coating may include coating elements such as Al, B, Co, Mg, Si, Ti, V, W, Zn, Zr, and / or a combination thereof (e.g., any suitable combination). For example, in one or more embodiments, it may include aluminum as a coating element. Based on the total metals other than lithium in 100 wt% of the third positive electrode active material, the content (e.g., amount) of the coating element may be about 0.1 wt% to about 5 wt%, about 0.1 wt% to about 3 wt%, about 0.1 wt% to about 2 wt%, about 0.1 wt% to about 1 wt%, or about 0.1 wt% to about 0.9 wt%.

[0083] Based on the total weight of 100 wt% of the first positive electrode active material, the second positive electrode active material, and the third positive electrode active material, the content of the first positive electrode active material may be about 60 wt% to about 85 wt% or about 70 wt% to about 80 wt%, and the total amount of the second positive electrode active material and the third positive electrode active material may be about 15 wt% to about 40 wt% or about 20 wt% to about 30 wt%. For example, the content (e.g., amount) of the large particles may be about 60 wt% to about 85 wt% or about 70 wt% to about 80 wt%, and the content (e.g., amount) of the small particles may be about 15 wt% to about 40 wt% or about 20 wt% to about 30 wt%. When the contents of the large particles and the small particles satisfy the above ranges, it is beneficial to prepare a positive electrode active material with high efficiency and long cycle life according to the preparation method of one or more embodiments of the present disclosure.

[0084] The ratio of the second positive electrode active material and the third positive electrode active material is not particularly limited. However, for example, based on the total weight of 100 wt% of the second positive electrode active material and the third positive electrode active material, the content of the second positive electrode active material may be about 10 wt% to about 90 wt% and the content of the third positive electrode active material may be about 10 wt% to about 90 wt%. In one or more embodiments, based on the total weight of 100 wt% of the second positive electrode active material and the third positive electrode active material, the content of the second positive electrode active material may be about 20 wt% to about 80 wt% or about 30 wt% to about 70 wt%, and the content of the third positive electrode active material may be about 20 wt% to about 80 wt% or about 30 wt% to about 70 wt%. When the second positive electrode active material and the third positive electrode active material are mixed in a suitable or appropriate ratio, both the initial charge and discharge efficiency and the cycle life characteristics can be improved (e.g., simultaneously).

[0085] Method for preparing positive electrode active material

[0086] In one or more embodiments, the method for preparing the positive electrode active material comprises (i) mixing a first nickel hydroxide having an average particle diameter (D 50 ) of about 10 μm to about 25 μm with a first lithium raw material such that the molar ratio of lithium in the first lithium raw material to the total metal of the first nickel hydroxide is greater than or equal to about 1.09, and performing a first heat treatment to obtain a first heat-treated product, and (ii) mixing the first heat-treated product, a second nickel hydroxide having an average particle diameter (D 50 ) of about 0.5 μm to about 8 μm with a second lithium raw material, and performing a second heat treatment.

[0087] The first nickel hydroxide may be a large particle precursor, and the second nickel hydroxide may be a small particle precursor. According to this method, if (for example, when) the large particle precursor and the first lithium raw material are mixed, the molar ratio of lithium in the first lithium raw material to the metal in the first nickel hydroxide is designed to be about 1.09 or more to form lithium-rich large particles containing a set or predetermined excessive amount (for example, an excess) of lithium during the first heat treatment. After adding the small particle precursor and the second lithium raw material to these lithium-rich large particles, a second heat treatment is performed on these lithium-rich large particles, such that a part of the small particle precursor can directly contact and react with the lithium-rich large particles, where lithium diffuses into them from the lithium-rich large particles to form small particles of lithium nickel oxide. These small particles have a nickel content (for example, amount) higher than that of the small particle precursor and have acicular primary particles. It should be understood that when lithium diffuses from the surface of the lithium-rich large particles into the small particle precursor, nickel diffuses together with lithium, and this diffusion mechanism can result in the primary particles being acicular. This third positive electrode active material can further achieve a higher capacity, and the acicular primary particles can further promote the movement of lithium ions, thus improving the initial charge and discharge efficiency and output characteristics.

[0088] Generally, when preparing a nickel-based positive electrode active material by mixing a positive electrode active material precursor and a lithium raw material and subjecting them to heat treatment, if the lithium raw material is added by designing the molar ratio of lithium to the metal of the positive electrode active material precursor to be less than about 1, secondary particles including acicular primary particles can be synthesized, where there is a problem or concern of deterioration in the initial charge / discharge capacity due to the low available amount of lithium. In contrast, the third positive electrode active material according to one or more embodiments of the present disclosure receives lithium from the lithium-rich large particles during the synthesis process and supplies lithium from the second lithium raw material, thereby achieving a high capacity without reducing the available amount of lithium.

[0089] In the method for preparing the positive electrode active material of the present disclosure, different from the synthesis method in the prior art, a second lithium raw material is additionally added during the second heat treatment, further improving the reactivity. In addition, the small particle precursor can use the lithium from the lithium-rich large particles, thereby improving the reaction efficiency.

[0090] The molar ratio of lithium in the first lithium raw material to the total metal of the first nickel hydroxide can be designed to be greater than or equal to about 1.09, for example, about 1.09 to about 1.2, about 1.09 to about 1.19, about 1.09 to about 1.15, or about 1.09 to about 1.12. If (for example, when) the lithium molar ratio satisfies the above range, lithium-rich large particles can be effectively formed during the synthesis process, thereby preparing a positive electrode active material with high efficiency and long cycle life.

[0091] For example, in one or more embodiments, the first nickel hydroxide may be represented by Chemical Formula 11 or may be represented by Chemical Formula 12.

[0092] Chemical Formula 11

[0093] Ni x11 M 11 y11 (OH)2

[0094] In Chemical Formula 11, 0.5 ≤ x11 < 1, 0 < y11 ≤ 0.5, and 0.9 ≤ x11 + y11 ≤ 1.1, where M 11 may be one or more elements selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr.

[0095] In one or more embodiments, in Chemical Formula 11, 0.5 ≤ x11 ≤ 0.9 and 0.1 ≤ y11 ≤ 0.5, 0.5 ≤ x11 ≤ 0.8 and 0.2 ≤ y11 ≤ 0.5, 0.5 ≤ x11 ≤ 0.7 and 0.3 ≤ y11 ≤ 0.5, or 0.55 ≤ x11 ≤ 0.7 and 0.3 ≤ y11 ≤ 0.45.

[0096] Chemical Formula 12

[0097] Ni x12 Co y12 M 12 z12 M 13 w12 (OH)2

[0098] In Chemical Formula 12, 0.5 ≤ x12 < 1, 0 < y12 ≤ 0.5, 0 < z12 ≤ 0.5, 0 ≤ w12 ≤ 0.1, and 0.9 ≤ x12 + y12 + z12 + w12 ≤ 1.1, where M 12 may be Al, Mn, or a combination thereof (e.g., any suitable combination), and M 13 may be one or more elements selected from B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr.

[0099] In one or more embodiments, in Chemical Formula 12, 0.5 ≤ x12 ≤ 0.8, 0.1 ≤ y12 ≤ 0.4, 0.1 ≤ z12 ≤ 0.4, and 0 ≤ w12 ≤ 0.1; 0.5 ≤ x12 ≤ 0.7, 0.2 ≤ y12 ≤ 0.4, 0.1 ≤ z12 ≤ 0.3, and 0 ≤ w12 ≤ 0.1; 0.5 ≤ x12 ≤ 0.7, 0.1 ≤ y12 ≤ 0.3, 0.2 ≤ z12 ≤ 0.4, and 0 ≤ w12 ≤ 0.1; or 0.5 ≤ x12 ≤ 0.6, 0.2 ≤ y12 ≤ 0.3, 0.2 ≤ z12 ≤ 0.3, and 0 ≤ w12 ≤ 0.1.

[0100] Based on the total metals in 100 mol% of the first nickel hydroxide, the nickel content (e.g., amount) can be, for example, about 50 mol% to about 99 mol% (e.g., about 50 mol% to about 90 mol%, about 50 mol% to about 80 mol%, about 50 mol% to about 70 mol%, about 55 mol% to about 70 mol%, or about 55 mol% to about 65 mol%).

[0101] The first nickel hydroxide and the second nickel hydroxide can have the same or different compositions. The first nickel hydroxide and the second nickel hydroxide can each be prepared by a general co-precipitation method.

[0102] The first nickel hydroxide can be a secondary particle formed by aggregating a plurality of primary particles, and the average particle diameter (D 50 ) can be about 10 μm to about 25 μm, for example, about 10 μm to about 20 μm, about 10 μm to about 18 μm, or about 12 μm to about 16 μm.

[0103] The first lithium raw material can include lithium carbonate, lithium hydroxide hydrate, anhydrous lithium hydroxide, and / or a combination thereof (e.g., any suitable combination).

[0104] In one or more embodiments, when the first nickel hydroxide is mixed with the first lithium raw material, a doping element raw material can be optionally added to perform a first heat treatment together.

[0105] The first heat treatment can be carried out in an oxygen atmosphere, for example, at 750 °C to 1000 °C, 750 °C to 900 °C, or 800 °C to 900 °C for 4 hours to 24 hours.

[0106] The product of the first heat treatment (e.g., the first heat treatment product) can be large particles containing a lithium nickel composite oxide, wherein the large particles include a set or predetermined excessive content (e.g., an excess) of lithium.

[0107] The molar ratio of lithium in the second lithium raw material to the total metal in the second nickel hydroxide may be less than about 1, for example, about 0.2 to about 0.99, about 0.4 to about 0.9, or about 0.6 to about 0.8. The second lithium raw material can be controlled or selected to have a lithium molar ratio within the above range to further improve the reactivity of the second heat treatment and obtain a final positive electrode active material in which the lithium content (e.g., amount) is appropriately or suitably adjusted.

[0108] The second nickel hydroxide can be represented by Formula 13 as an example, or can be represented by Formula 14 as a specific example.

[0109] Formula 13

[0110] Ni x13 M 14 y13 (OH)2

[0111] In Formula 13, 0.5 ≤ x13 < 1, 0 < y13 ≤ 0.5, and 0.9 ≤ x13 + y13 ≤ 1.1, where M 14 can be one or more elements selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr.

[0112] In one or more embodiments, in Formula 13, 0.5 ≤ x13 ≤ 0.9 and 0.1 ≤ y13 ≤ 0.5, 0.5 ≤ x13 ≤ 0.8 and 0.2 ≤ y13 ≤ 0.5, 0.5 ≤ x13 ≤ 0.7 and 0.3 ≤ y13 ≤ 0.5, or 0.55 ≤ x13 ≤ 0.7 and 0.3 ≤ y13 ≤ 0.45.

[0113] Formula 14

[0114] Ni x14 Co y14 M 15 z14 M 16 w14 (OH)2

[0115] In Formula 14, 0.5 ≤ x14 < 1, 0 < y14 ≤ 0.5, 0 < z14 ≤ 0.5, 0 ≤ w14 ≤ 0.1, and 0.9 ≤ x14 + y14 + z14 + w14 ≤ 1.1, where M 15 can be Al, Mn, or a combination thereof (e.g., any suitable combination), and M 16 can be one or more elements selected from B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr.

[0116] In one or more embodiments, in Chemical Formula 14, 0.5 ≤ x14 ≤ 0.8, 0.1 ≤ y14 ≤ 0.4, 0.1 ≤ z14 ≤ 0.4, and 0 ≤ w14 ≤ 0.1; 0.5 ≤ x14 ≤ 0.7, 0.2 ≤ y14 ≤ 0.4, 0.1 ≤ z14 ≤ 0.3, and 0 ≤ w14 ≤ 0.1; 0.5 ≤ x14 ≤ 0.7, 0.1 ≤ y14 ≤ 0.3, 0.2 ≤ z14 ≤ 0.4, and 0 ≤ w14 ≤ 0.1; or 0.5 ≤ x14 ≤ 0.6, 0.2 ≤ y14 ≤ 0.3, 0.2 ≤ z14 ≤ 0.3, and 0 ≤ w14 ≤ 0.1.

[0117] Based on the total metals in 100 mol% of the second nickel-based hydroxide, the nickel content (e.g., amount) can be, for example, about 50 mol% to about 99 mol% (e.g., about 50 mol% to about 90 mol%, about 50 mol% to about 80 mol%, about 50 mol% to about 70 mol%, about 55 mol% to about 70 mol%, or about 55 mol% to about 65 mol%).

[0118] The second nickel-based hydroxide can be a secondary particle formed by aggregating a plurality of primary particles, and the secondary particle can have an average particle diameter (D 50 ) of, for example, about 0.5 μm to about 8 μm, about 0.5 μm to about 6 μm, about 1 μm to about 5 μm, or about 2 μm to about 4 μm. The primary particles forming the secondary particles of the second nickel-based hydroxide may not be acicular. The acicular primary particles of the third positive electrode active material can be formed during the second heat treatment process.

[0119] The second lithium raw material can include lithium carbonate, lithium hydroxide hydrate, anhydrous lithium hydroxide, and / or a combination thereof (e.g., any suitable combination).

[0120] The second heat treatment can be performed in an oxygen atmosphere, for example, at about 700 °C to about 900 °C or about 750 °C to about 850 °C for about 4 hours to about 24 hours.

[0121] For example, in one or more embodiments, the first heat treatment temperature can be higher than the second heat treatment temperature. The first heat treatment temperature and the second heat treatment temperature can be appropriately or suitably adjusted respectively to effectively prepare a positive electrode active material with high efficiency and long cycle life.

[0122] The ratio of the first nickel hydroxide to the second nickel hydroxide corresponds to the ratio of large particles to small particles. For example, a weight ratio of about 60:40 to about 85:15 or about 70:30 to about 80:20 can be used. If (e.g., when) the first nickel hydroxide and the second nickel hydroxide are mixed within this ratio, a positive electrode active material with high efficiency and long cycle life according to one or more embodiments can be effectively prepared.

[0123] In one or more embodiments, for coating the positive electrode active material, if (e.g., when) the first heat treatment product, the second nickel hydroxide, and the second lithium raw material are mixed, a coating raw material is added thereto together for a second heat treatment.

[0124] The coating raw material may include coating elements Al, B, Co, Mg, Si, Ti, V, W, Zn, Zr, and / or a combination thereof (e.g., any suitable combination), and may be in the form of one or more suitable compounds (such as oxides, hydroxides, nitrates, sulfates, etc.). Based on the total metal other than lithium in the final positive electrode active material of 100 wt%, the content (e.g., amount) of the coating element may be about 0.1 wt% to about 5 wt% or about 0.1 wt% to about 3 wt%.

[0125] For example, in one or more embodiments, the coating raw material may include aluminum, such as alumina particles. Here, the aluminum raw material is mixed such that based on 100 parts by weight of the total metal other than lithium in the first heat treatment product and the second nickel hydroxide, the aluminum content (e.g., amount) of the first heat treatment product and the second nickel hydroxide may be about 0.1 part by weight to about 2 parts by weight (e.g., about 0.1 part by weight to about 1 part by weight or about 0.1 part by weight to about 0.8 part by weight). If (e.g., when) the aluminum coating is carried out within the above range, the initial discharge capacity, the initial charge / discharge efficiency, and the cycle life characteristics can all be improved.

[0126] The method for preparing the positive electrode active material may further include a pulverization process after the first heat treatment and / or the second heat treatment.

[0127] Positive electrode

[0128] In one or more embodiments, a positive electrode for a rechargeable lithium battery including the positive electrode active material of the present disclosure is provided. For example, in one or more embodiments, the positive electrode may include a positive electrode current collector and a positive electrode active material layer on the positive electrode current collector, and the positive electrode active material layer includes the positive electrode active material of the present disclosure and optionally includes a binder, a conductive material (e.g., an electrical conductor), and / or a combination thereof (e.g., any suitable combination).

[0129] Binder

[0130] The binder improves the binding 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)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, or nylon, but embodiments of the present disclosure are not limited thereto.

[0131] Conductive material

[0132] Conductive materials may be included to provide electrode conductivity, and any conductive material may be used as the conductive material unless it causes a chemical change. Non-limiting 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 mixtures thereof (e.g., any suitable mixture).

[0133] Based on the total weight of 100 wt% of the positive electrode active material layer, the respective contents (e.g., amounts) of the binder and the conductive material may be about 0.5 wt% to about 5 wt%.

[0134] The positive electrode current collector may include aluminum (Al) foil, but embodiments of the present disclosure are not limited thereto.

[0135] Rechargeable lithium battery

[0136] According to one or more embodiments of the present disclosure, the rechargeable lithium battery may include the aforementioned positive electrode, negative electrode, and electrolyte. In one or more embodiments, 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.

[0137] The rechargeable lithium battery may be classified into a cylindrical battery, a prismatic battery, a pouch battery, a coin-shaped battery, etc. according to its shape. Figures 1 to 4 Each is a schematic diagram showing a rechargeable lithium battery according to one or more embodiments, wherein Figure 1 shows a cylindrical battery, Figure 2 shows a prismatic battery, and Figure 3 and Figure 4 each shows a pouch battery. Refer to Figures 1 to 4, a rechargeable lithium battery 100 may include: an electrode assembly 40 having a separator 30 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 may be impregnated with an electrolyte. In some embodiments, as Figure 1 shown, the rechargeable lithium battery 100 may include a sealing member 60 that seals the housing 50. In some embodiments, as Figure 2 shown, the rechargeable lithium battery 100 may include a positive electrode lead tab 11, a positive electrode terminal 12, a negative electrode lead tab 21, and a negative electrode terminal 22. In some embodiments, as Figure 3 and Figure 4 shown, the rechargeable lithium battery 100 includes electrode tabs 70, namely a positive electrode tab 71 and a negative electrode tab 72, which serve as a circuit path for guiding the current formed in the electrode assembly 40 to the outside.

[0138] Negative electrode

[0139] The negative electrode may include a negative electrode current collector and a negative electrode active material layer on the negative electrode current collector, and the negative electrode active material layer may include a negative electrode active material and may further include a binder, a conductive material (e.g., an electrical conductor), and / or a combination thereof (e.g., any suitable combination).

[0140] Negative electrode active material

[0141] 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.

[0142] The material that reversibly intercalates / deintercalates lithium ions may include, for example, crystalline carbon, amorphous carbon, and / or a combination thereof (e.g., any suitable combination) as a carbon-based negative electrode active material. The crystalline carbon may be amorphous, flaky, lamellar, spherical, or fibrous natural graphite or artificial graphite. The amorphous carbon may be soft carbon, hard carbon, mesophase pitch carbonized product, calcined coke, etc.

[0143] The lithium metal alloy may include an alloy of lithium and one or more metals selected from sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), silicon (Si), antimony (Sb), lead (Pb), indium (In), zinc (Zn), barium (Ba), radium (Ra), germanium (Ge), aluminum (Al), and tin (Sn).

[0144] The material capable of doping / dedoping lithium may be a Si-based negative electrode active material 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), 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, or a combination thereof (e.g., any suitable combination), such as magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), scandium (Sc), yttrium (Y), titanium (Ti), zirconium (Zr), hafnium (Hf), rutherfordium (Rf), vanadium (V), niobium (Nb), tantalum (Ta), dubnium (Db), chromium (Cr), molybdenum (Mo), tungsten (W), seaborgium (Sg), technetium (Tc), rhenium (Re), bohrium (Bh), iron (Fe), lead (Pb), ruthenium (Ru), osmium (Os), hassium (Hs), rhodium (Rh), iridium (Ir), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), cadmium (Cd), boron (B), aluminum (Al), gallium (Ga), tin (Sn), indium (In), thallium (Tl), germanium (Ge), phosphorus (P), arsenic (As), antimony (Sb), bismuth (Bi), sulfur (S), selenium (Se), tellurium (Te), polonium (Po), and / or a combination thereof (e.g., any suitable combination)). The Sn-based negative electrode active material can be Sn, SnO x (0 < x ≤ 2) (e.g., SnO2), Sn alloy, and / or a combination thereof (e.g., any suitable combination).

[0145] The silicon-carbon composite can be a composite of silicon and amorphous carbon in the form of particles. The average particle size (D 50 ) can be, for example, from about 0.5 μm to about 20 μm. According to one or more embodiments, the silicon-carbon composite can be in the form of silicon particles and an amorphous carbon coating on the surface of each silicon particle. For example, in one or more embodiments, the silicon-carbon composite can include secondary particles (cores) in which silicon primary particles are assembled (e.g., aggregated) and an amorphous carbon coating (shell) on the surface of the secondary particles. In one or more embodiments, amorphous carbon can also be present between the silicon primary particles, e.g., the silicon primary particles can be coated with amorphous carbon. The secondary particles can be dispersed in the amorphous carbon matrix.

[0146] In one or more embodiments, 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, and / or a combination thereof (e.g., any suitable combination). The amorphous carbon can include soft carbon, hard carbon, mesophase pitch carbonization products, calcined coke, etc.

[0147] If (e.g., when) the silicon-carbon composite includes silicon and amorphous carbon, then based on the total weight of 100 wt% of the silicon-carbon composite, the content (e.g., amount) of silicon can be about 10 wt% to about 50 wt% and the content (e.g., amount) of amorphous carbon can be about 50 wt% to about 90 wt%. Additionally, if (e.g., when) the silicon-carbon composite includes silicon, amorphous carbon, and crystalline carbon, then based on the total weight of 100 wt% of the silicon-carbon composite, the content (e.g., amount) of silicon can be about 10 wt% to about 50 wt%, the content (e.g., amount) of crystalline carbon can be about 10 wt% to about 70 wt%, and the content (e.g., amount) of amorphous carbon can be about 20 wt% to about 40 wt%.

[0148] In one or more embodiments, the thickness of the amorphous carbon coating can be about 5 nanometers (nm) to about 100 nm. The average particle size (D 50 ) of the silicon particles (primary particles) can be about 10 nm to about 1 μm or about 10 nm to about 200 nm. The silicon particles can exist as silicon alone, in the form of a silicon alloy, or in the oxidized form of silicon. The oxidized form of silicon can be represented by SiO x (0 < x ≤ 2). In this regard, the atomic content (e.g., amount) ratio of Si:O indicating the degree of oxidation can be about 99:1 to about 33:67. If (e.g., when) no other definition is provided, then as used herein, the average particle size (D 50 ) indicates the diameter of the particles in the particle size distribution with a cumulative volume of about 50 volume%.

[0149] In one or more embodiments, the Si-based negative electrode active material or the Sn-based negative electrode active material can be mixed with the carbon-based negative electrode active material. If (e.g., when) the Si-based negative electrode active material or the Sn-based negative electrode active material and the carbon-based negative electrode active material are used in combination, then their mixing ratio can be about 1:99 to about 90:10 by weight ratio.

[0150] Binder

[0151] The binder is used to appropriately and / or well bond the negative electrode active material particles to each other and also bond the negative electrode active material to the negative electrode current collector. The binder can be a non-aqueous binder (e.g., a water-insoluble binder), an aqueous binder (e.g., a water-soluble binder), a dry binder, and / or a combination thereof (e.g., any suitable combination).

[0152] The non-aqueous binder can 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).

[0153] 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 polymer, 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 any suitable combination thereof.

[0154] If (e.g., when) the aqueous binder is used as a binder for the negative electrode, 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.

[0155] 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 any suitable combination thereof.

[0156] Conductive material

[0157] A conductive material may be included to provide electrode conductivity, and any conductive material may be used as the conductive material unless it causes a chemical change. Non-limiting examples of the conductive material include: carbon materials (such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, carbon nanotube, etc.); metal materials including metal powders or metal fibers such as copper, nickel, aluminum, silver, etc.; conductive polymers (such as polyphenylene derivatives); and / or any suitable mixture thereof.

[0158] In one or more embodiments, based on the total weight of the negative electrode active material layer of 100 wt%, the content (e.g., amount) of the negative electrode active material may be about 95 wt% to about 99.5 wt%, and based on the total weight of the negative electrode active material layer of 100 wt%, the content (e.g., amount) of the binder may be about 0.5 wt% to about 5 wt%. For example, in one or more embodiments, based on the total weight of the negative electrode active material layer of 100 wt%, 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.

[0159] Negative electrode current collector

[0160] 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.

[0161] Electrolyte

[0162] In one or more embodiments, the electrolyte for a rechargeable lithium battery may be an electrolyte that may include a non-aqueous organic solvent and a lithium salt.

[0163] The non-aqueous organic solvent serves as a medium for transporting ions participating in the electrochemical reaction of the rechargeable lithium battery. The non-aqueous organic solvent may include carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, aprotic solvents, or a combination thereof (e.g., any suitable combination).

[0164] 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. Ester solvents may include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, caprolactone, etc. Ether solvents may include dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. Additionally, 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 - C20 straight-chain, branched-chain, or cycloalkyl group and may include double bonds, aromatic rings, or ether bonds, etc.); amides (such as dimethylformamide); dioxolanes (such as 1,3-dioxolane, 1,4-dioxolane, etc.); sulfolane, etc.

[0165] The non-aqueous organic solvent may be used alone or two or more types (species) may be used in combination. And if (e.g., when) two or more types (species) are used in combination, the mixing ratio may be appropriately or suitably adjusted according to the desired or appropriate battery performance, which is widely understood by those skilled in the art.

[0166] If (e.g., when) carbonate solvents are used, cyclic carbonates and chain carbonates may be used in combination, and the cyclic carbonates and chain carbonates may be mixed in a volume ratio of about 1:1 to about 1:9.

[0167] In one or more embodiments, the non-aqueous organic solvent may further include an aromatic hydrocarbon organic solvent. For example, in some embodiments, the carbonate solvent and the aromatic hydrocarbon organic solvent may be mixed and used in a volume ratio of about 1:1 to about 30:1.

[0168] In one or more embodiments, the electrolyte may further include vinylene carbonate, ethylene carbonate or ethylene carbonate compounds to improve the battery cycle life.

[0169] Non-limiting examples of ethylene carbonate compounds may include fluoroethylene carbonate, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate or cyanoethylene carbonate.

[0170] The lithium salt dissolved in the non-aqueous organic solvent supplies lithium ions in the rechargeable lithium 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. Non-limiting examples of the lithium salt may include at least one selected from LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide; LiFSI), LiC4F9SO3, LiN(C x F 2x+1 SO2)(C y F 2y+ 1SO2)(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).

[0171] The concentration of the lithium salt may be in the range of about 0.1M to about 2.0M. If (for example, when) the concentration of the lithium salt is within the above range, the electrolyte has a suitable or appropriate ionic conductivity and viscosity, so excellent or appropriate performance can be achieved, and lithium ions can move effectively.

[0172] Separator

[0173] According to the type or kind of the rechargeable lithium battery, the 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, a polytetrafluoroethylene separator or a multi-layer film of two or more layers thereof (such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, a polypropylene / polyethylene / polypropylene three-layer separator, etc.).

[0174] The separator may include a porous substrate and a coating on one or both surfaces (e.g., two opposite surfaces) of the porous substrate, the coating including an organic material, an inorganic material, and / or a combination thereof (e.g., any suitable combination).

[0175] The porous substrate may be a polymer film formed from any one polymer selected from the following or a copolymer or mixture of two or more thereof: polyolefins (such as polyethylene and / or polypropylene), polyesters (such as polyethylene terephthalate and / or polybutylene terephthalate), polyacetals, polyamides, polyimides, polycarbonates, polyether ketones, polyaryl ether ketones, polyetherimides, polyamideimides, polybenzimidazoles, polyethersulfones, polyphenylene ethers, cycloolefin copolymers, polyphenylene sulfides, polyethylene naphthalate, glass fiber, and polytetrafluoroethylene (e.g., Teflon).

[0176] The porous substrate may have a thickness of about 1 μm to about 40 μm, e.g., 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.

[0177] The organic material may include a (meth)acrylic copolymer, the (meth)acrylic copolymer including: a first structural unit derived from (meth)acrylamide, and a second structural unit including at least one of a structural unit derived from (meth)acrylic acid or (meth)acrylate and / or a structural unit derived from (meth)acrylamidosulfonic acid or a salt thereof.

[0178] The inorganic material may include inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and / or a combination thereof (e.g., any suitable combination), but embodiments of the present disclosure are not limited thereto. The average particle size (D 50 ) of the inorganic particles may be about 1 nm to about 2000 nm, e.g., about 100 nm to about 1000 nm or about 100 nm to about 700 nm.

[0179] The organic material and the inorganic material may be mixed in one coating or may exist in a form in which a coating including the organic material and a coating including the inorganic material are stackable.

[0180] The thickness of the coating may be about 0.5 μm to about 20 μm, e.g., about 1 μm to about 10 μm or about 1 μm to about 5 μm.

[0181] Examples and comparative examples of the present disclosure will be described in more detail herein. However, the following examples are only examples of the present disclosure, and the present disclosure is not limited to the following examples.

[0182] Example 1

[0183] 1. Preparation of the positive electrode active material

[0184] Nickel-based composite hydroxide (Ni 50 Co 0.55 Mn 0.24 (OH)2) with an average particle size (D 0.21 ) of about 19 μm as a large particle precursor is mixed with Li2CO3 to have a molar ratio of Li / (Ni + Co + Mn) (shown as "initial Li / (Ni + Co + Mn)" in Table 2) = 1.09. Then, the first heat treatment is carried out at 900 °C for 8 hours in an oxygen atmosphere. Subsequently, after pulverization and filtration, the product of the first heat treatment is mixed with nickel-based composite hydroxide (Ni 50 Co 0.55 Mn 0.24 (OH)2) with an average particle size (D 0.21 ) of about 2.7 μm as a small particle precursor so that the weight ratio between the large particle precursor and the small particle precursor is 80:20, and Li2CO3 is further added thereto so that the molar ratio of Li to the total metal of the small particle precursor is Li / (Ni + Co + Mn) = 0.8. Then, the second heat treatment is carried out at 850 °C for 8 hours in an oxygen atmosphere. Subsequently, the product of the second heat treatment is pulverized and filtered to obtain the final positive electrode active material.

[0185] Figure 5 is the SEM image showing the final positive electrode active material of Example 1. In Figure 5 , large particles (first positive electrode active material) in the form of secondary particles formed by aggregating a plurality of primary particles and small particles (second positive electrode active material, third positive electrode active material) in the form of secondary particles formed by aggregating a plurality of primary particles but having a smaller particle size than that of the large particles are observed. When measured by the SEM image, the average particle size (D 50 ) of the large particles is about 19 μm and the average particle size (D 50 ) of the small particles is about 3 μm.

[0186] Figure 6 is the SEM image showing the cross-section of the final positive electrode active material of Example 1 cut by using a focused ion beam (FIB). In Figure 6In it, large particles above and five small particles below are shown. Each small particle is respectively designated as A1, A2, A3, A4, and A5. The cross-section of each small particle is measured by SEM-EDS quantitative analysis to measure the respective contents (e.g., amounts) of Ni, Co, and Mn, and the results are shown in Table 1. SEM-EDS analysis is performed using a Philips FEI Titan 80-300 at an acceleration voltage of 15 kV.

[0187] Table 1 (unit: mol%)

[0188] Small particle precursor A1 A2 A3 A4 A5 Ni 55.0 55.0 57.8 57.1 57.5 57.2 Co 24.0 23.9 22.7 23.6 23.2 23.4 Mn 21.0 21.1 19.5 19.3 19.3 19.4

[0189] Reference Figure 6 And referring to Table 1, it is confirmed that the primary particles forming the secondary particles of small particle A1 do not have a needle-like structure and have Ni, Co, and Mn contents that are substantially the same as those of the small particle precursor. Small particle A1 corresponds to the second positive electrode active material. In contrast, each of the other small particles A2 - A5 shows that the corresponding secondary particles include needle-like primary particles, but the Ni content (e.g., amount) has increased by about 2 mol% to about 3 mol% compared to the small particle precursor. Additionally, the content (e.g., amount) of each of Co and Mn is slightly lower than the content (e.g., amount) of each of Co and Mn in the small particle precursor. These A2 - A5 correspond to the third positive electrode active material.

[0190] Without being bound by any particular theory, it should be understood that a part of the injected / added small particle precursor contacts and reacts with the lithium-rich large particles to receive lithium and nickel from the large particles, resulting in the synthesis of primary particles having a needle-like shape and an increased nickel content (e.g., amount). Similarly, it should be understood that since the other part of the injected / added small particle precursor maintains the nickel content (e.g., amount) unchanged, the primary particles do not become needle-like but their shape remains unchanged.

[0191] 2. Manufacture of rechargeable lithium battery cells

[0192] 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 the 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 the positive electrode.

[0193] An electrode assembly is manufactured by inserting a polytetrafluoroethylene separator between the positive electrode and the lithium metal counter electrode, the electrode assembly is inserted into a battery case, and then an electrolyte (the electrolyte is prepared by dissolving 1 M LiPF6 in a mixed solvent of ethylene carbonate and dimethyl carbonate with a volume ratio of 3:7) is injected therein to manufacture a rechargeable lithium battery cell (half cell) by a conventional method.

[0194] Comparative Example 1

[0195] Apply a conventional method of synchronously (e.g., simultaneously) heat-treating large particle precursors, small particle precursors, and Li2CO3. For example, the positive electrode active material and the rechargeable lithium battery cell according to Comparative Example 1 are manufactured in substantially the same manner as in Example 1, except that the large particle precursors and the small particle precursors are mixed at a weight ratio of 70:30, Li2CO3 is added thereto so that the molar ratio of Li to the total metal of the large particle precursors and the small particle precursors is Li / (Ni + Co + Mn) = 1.03, and only the first heat treatment is carried out at 900 °C for 8 hours to obtain the final positive electrode active material.

[0196] Example 2

[0197] The positive electrode active material and the rechargeable lithium battery cell are manufactured in substantially the same manner as in Example 1, except that when the large particle precursors and Li2CO3 are mixed in Example 1, aluminum oxide is further added thereto in an amount of 0.14 parts by weight based on the total metal other than lithium in 100 parts by weight of the large particle precursors for Al doping. In addition, when the small particle precursors and Li2CO3 are added, aluminum oxide is further added thereto in an amount of 0.1 parts by weight based on the total metal other than lithium in 100 parts by weight of the product of the first heat treatment and the small particle precursors for Al coating by carrying out the second heat treatment.

[0198] Comparative Example 2

[0199] The positive electrode active material and the rechargeable lithium battery cell are manufactured in substantially the same manner as in Comparative Example 1, except that when the large particle precursors, the small particle precursors, and Li2CO3 are mixed, aluminum oxide is further added thereto in an amount of 0.14 parts by weight based on the total metal other than lithium in 100 parts by weight of the large particle precursors and the small particle precursors for Al doping. In addition, after the first heat treatment, pulverization and filtration are carried out, and aluminum oxide is further added thereto in an amount of 0.1 parts by weight based on the total metal other than lithium in 100 parts by weight of the product of the first heat treatment and the small particle precursors for Al coating by carrying out the second heat treatment at 850 °C for 8 hours.

[0200] Comparative Example 3

[0201] The positive electrode active material and the rechargeable lithium battery cell are manufactured in substantially the same manner as in Example 2, except that when the large particle precursors and Li2CO3 are mixed, the molar ratio of Li / (Ni + Co + Mn) becomes 1.03.

[0202] Table 2 simply shows the manufacturing process designs of the positive electrode active materials of Example 1, Example 2, and Comparative Examples 1 to 3. In addition, the pellet densities of the final positive electrode active materials of Example 1, Example 2, and Comparative Examples 1 to 3 were each measured, and the results are shown in Table 2. By placing 3 g of each positive electrode active material into a mold (area: 1.298 cm 2 ), slowly inserting a die bar into the mold body, placing the mold set in a hydraulic press, and pressing at 3 tons (metric tons) for 30 seconds to measure the height, the pellet density (shown as "PD" in Table 2) was measured.

[0203] Evaluation Example 1: Evaluation of Initial Charge / Discharge Capacity, Efficiency, and Cycle Life Characteristics

[0204] The rechargeable lithium battery cells of Example 1, Example 2, and Comparative Examples 1 to 3 were each charged at a constant current of 0.2C to 4.45V at 25°C and then charged at a constant voltage to 0.05C, and then discharged at 0.2C to 3.0V for initial charge and discharge. In Table 2, the initial charge capacity and the initial discharge capacity are provided, and the ratio of the initial discharge capacity to the initial charge capacity as the initial charge / discharge efficiency is also shown in Table 2 as efficiency.

[0205] Subsequently, each battery cell was repeatedly charged and discharged 50 times at 1.0C in the voltage range of 3.0V to 4.45V at 45°C. In Table 2, the ratio of the 50th discharge capacity to the initial discharge capacity was calculated and provided as the cycle life.

[0206] Table 2

[0207]

[0208] Referring to Table 2, compared with Comparative Example 1, Example 1 showed an increased initial discharge capacity, a greatly increased initial charge / discharge efficiency, and improved cycle life characteristics. Similarly, compared with Comparative Examples 2 and 3, Example 2 showed an increased initial discharge capacity, a greatly increased initial charge / discharge efficiency, and improved cycle life characteristics.

[0209] Comparative Example 3 reduced the Li content (e.g., amount) introduced during the first heat treatment such that the molar ratio of Li to the total metal other than Li in the large particle precursor was 1.03, showing that the lithium-rich large particles were not fully formed and small particles (such as the third positive electrode active material) could not be formed, which confirmed that the increase in the initial discharge capacity was not much, and thus the initial charge / discharge efficiency was hardly improved.

[0210] As used herein, terms such as "substantially", "about" and similar terms are used as approximate terms and not as terms of degree, and are intended to account for the inherent deviations of measured or calculated values that would be recognized by a person of ordinary skill in the art. As used herein, "about" or "approximate" also includes the recited value and means within an acceptable deviation range of the specific value as determined by a person of ordinary skill in the art considering the measurement in question and the errors associated with the measurement of a particular quantity (i.e., the 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.

[0211] In the context of the present disclosure, and unless otherwise defined, the terms "use", "using" and "used" may be regarded as synonymous with the terms "utilize", "utilizing" and "utilized", respectively.

[0212] Any numerical range set forth herein is intended to include all sub-ranges of the same numerical precision that fall within the set forth range. For example, the range "1.0 to 10.0" is intended to include all sub-ranges between the recited minimum value 1.0 and the recited maximum value 10.0 (and including 1.0 and 10.0), i.e., 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 set forth herein is intended to include all lower numerical limits that fall therein, and any minimum numerical limit set forth in this specification is intended to include all higher numerical limits that fall 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 set forth herein.

[0213] The apparatus for preparing the positive electrode active material, the battery management system (BMS) apparatus, and / or any other relevant apparatus or component according to the embodiments of the present disclosure described herein may be implemented using any suitable hardware, firmware (e.g., application specific integrated circuit), software, or a combination of software, firmware, and hardware. For example, the various components of the apparatus may be formed on one integrated circuit (IC) chip or on separate IC chips. Additionally, the various components of the apparatus may be implemented on a flexible printed circuit film, tape carrier package (TCP), or printed circuit board (PCB), or formed on a substrate. Further, the various components of the apparatus may 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 may be implemented using standard memory devices in a computing device, such as, for example, random access memory (RAM). The computer program instructions may also be stored in other non-transitory computer-readable media, such as, for example, a CD-ROM or a flash drive, etc. Moreover, those skilled in the art should recognize that, without departing from the scope of the present disclosure, the functions of various computing devices may be combined or integrated into a single computing device, or the functions of a dedicated computing device may be distributed over one or more other computing devices.

[0214] Those skilled in the art will recognize that, given the overall content of the present disclosure, each appropriate feature of the various embodiments of the present disclosure may be partially or fully combined or combined with each other, and may be linked and operated technically in various appropriate ways, and unless otherwise stated or implied, each embodiment may be implemented independently of each other or in combination with each other in any appropriate way.

[0215] Although the present disclosure has been described in connection with what are presently considered to be example embodiments, it is to be understood that the present disclosure is not limited to the disclosed embodiments. On the contrary, the present disclosure 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: The first positive electrode active material includes a first lithium nickel-based composite oxide and is in the form of secondary particles including a plurality of primary particles, wherein the average particle diameter D of the secondary particles 50 is 10 μm to 25 μm; The second positive electrode active material, including a second lithium nickel-based composite oxide and in the form of secondary particles including a plurality of primary particles, wherein the average particle size D of the secondary particles 50 is 0.5 μm to 8 μm; and The third positive electrode active material, which includes a third lithium nickel-based composite oxide and is in the form of secondary particles including a plurality of primary particles, wherein the average particle diameter D 50 is 0.5 μm to 8 μm, wherein the primary particles of the secondary particles constituting the third positive electrode active material are needle-shaped, and wherein the nickel content of the third lithium nickel composite oxide based on the total metal other than lithium in 100 mol% of the third lithium nickel composite oxide is higher than the nickel content of the second lithium nickel composite oxide based on the total metal other than lithium in 100 mol% of the second lithium nickel composite oxide.

2. The positive electrode active material according to claim 1, wherein the nickel content of the third lithium nickel composite oxide based on the total metal other than lithium in 100 mol% of the third lithium nickel composite oxide is 1 mol% to 5 mol% higher than the nickel content of the second lithium nickel composite oxide based on the total metal other than lithium in 100 mol% of the second lithium nickel composite oxide.

3. The positive electrode active material according to claim 1, wherein the second lithium nickel composite oxide and the third lithium nickel composite oxide further comprise a metal M other than lithium and nickel, and the content of the metal M in the third lithium nickel composite oxide based on the total metal other than lithium in 100 mol% of the third lithium nickel composite oxide is 1 mol% to 5 mol% lower than the content of the metal M in the second lithium nickel composite oxide based on the total metal other than lithium in 100 mol% of the second lithium nickel composite oxide.

4. The positive electrode active material according to claim 1, wherein the secondary particles of the third positive electrode active material have a spherical shape, an ellipsoidal shape, a polygonal shape, an irregular shape, or a combination thereof, but do not have a needle shape.

5. The positive electrode active material according to claim 1, wherein the primary particles constituting the secondary particles in the second positive electrode active material have a spherical shape, an ellipsoidal shape, a polygonal shape, a plate shape, an irregular shape, or a combination thereof, but do not have a needle shape.

6. The positive electrode active material according to claim 1, wherein the nickel content of the first lithium nickel composite oxide based on the total metal other than lithium in 100 mol% of the first lithium nickel composite oxide, the nickel content of the second lithium nickel composite oxide based on the total metal other than lithium in 100 mol% of the second lithium nickel composite oxide, and the nickel content of the third lithium nickel composite oxide based on the total metal other than lithium in 100 mol% of the third lithium nickel composite oxide are each independently 50 mol% to 99 mol%.

7. The positive electrode active material according to claim 6, wherein The nickel content of the first lithium nickel-based composite oxide based on the total metal other than lithium in the first lithium nickel-based composite oxide of 100 mol%, the nickel content of the second lithium nickel-based composite oxide based on the total metal other than lithium in the second lithium nickel-based composite oxide of 100 mol%, and the nickel content of the third lithium nickel-based composite oxide based on the total metal other than lithium in the third lithium nickel-based composite oxide of 100 mol% are each independently 50 mol% to 70 mol%.

8. The positive electrode active material according to claim 1, wherein the first lithium nickel-based composite oxide is represented by Chemical Formula 1, the second lithium nickel-based composite oxide is represented by Chemical Formula 3, and the third lithium nickel-based composite oxide is represented by Chemical Formula 5: Chemical Formula 1 Li a1 Ni x1 M 1 y1 O 2-b1 X b1 In Chemical Formula 1, 0.9 ≤ a1 ≤ 1.2, 0.5 ≤ x1 < 1, 0 < y1 ≤ 0.5, 0.9 ≤ x1 + y1 ≤ 1.1, and 0 ≤ b1 ≤ 0.1, M 1 is one or more elements selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more elements selected from F, P, and S, Chemical Formula 3 Li a3 Ni x3 M 4 y3 O 2-b3 X b3 In Chemical Formula 3, 0.9 ≤ a3 ≤ 1.2, 0.5 ≤ x3 < 1, 0 < y3 ≤ 0.5, 0.9 ≤ x3 + y3 ≤ 1.1, and 0 ≤ b3 ≤ 0.1, M 4 is one or more elements selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more elements selected from F, P, and S, Chemical Formula 5 Li a5 Ni x5 M 7 y5 O 2-b5 X b5 In Chemical Formula 5, 0.9 ≤ a5 ≤ 1.2, 0.5 ≤ x5 < 1, 0 < y5 ≤ 0.5, 0.9 ≤ x5 + y5 ≤ 1.1, and 0 ≤ b5 ≤ 0.1, M 7 is one or more elements selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more elements selected from F, P, and S.

9. The positive electrode active material according to claim 1, wherein based on the total weight of 100 wt% of the first positive electrode active material, the second positive electrode active material, and the third positive electrode active material, the amount of the first positive electrode active material is 60 wt% to 85 wt%, and the total amount of the second positive electrode active material and the third positive electrode active material is 15 wt% to 40 wt%.

10. The positive electrode active material according to claim 1, wherein based on the total weight of 100 wt% of the second positive electrode active material and the third positive electrode active material, the amount of the second positive electrode active material is 10 wt% to 90 wt%, and the amount of the third positive electrode active material is 10 wt% to 90 wt%.

11. A method for preparing a positive electrode active material, comprising: Mix a first nickel hydroxide with an average particle diameter D 50 in the range of 10 μm to 25 μm and a first lithium raw material such that the molar ratio of lithium in the first lithium raw material to the total metal of the first nickel hydroxide is greater than or equal to 1.09, and perform a first heat treatment to obtain a first heat treatment product, and Mix the first heat treatment product and a second nickel hydroxide with an average particle size D 50 of 0.5 μm to 8 μm and a second lithium raw material, and perform a second heat treatment.

12. The method according to claim 11, wherein the molar ratio of lithium in the first lithium raw material to the total metal of the first nickel-based hydroxide is 1.09 to 1.

2.

13. The method according to claim 11, wherein the molar ratio of lithium in the second lithium raw material to the total metal of the second nickel-based hydroxide is less than 1.

14. The method according to claim 11, wherein the first heat treatment is carried out in a temperature range of 750 °C to 1000 °C, and the second heat treatment is carried out in a temperature range of 700 °C to 900 °C.

15. The method according to claim 11, wherein the mixing ratio of the first nickel-based hydroxide to the second nickel-based hydroxide is 60:40 to 85:15 by weight.

16. The method according to claim 11, wherein when mixing the first heat treatment product, the second nickel-based hydroxide, and the second lithium raw material, a coating raw material is added thereto and the second heat treatment is carried out.

17. The method according to claim 16, wherein the coating raw material is an aluminum raw material, and the aluminum raw material is mixed such that based on 100 parts by weight of the total metal other than lithium in the first heat treatment product and the second nickel-based hydroxide, the aluminum content of the first heat treatment product and the second nickel-based hydroxide is 0.1 part by weight to 2 parts by weight.

18. The method according to claim 11, wherein the method further includes a pulverization process after the first heat treatment and / or the second heat treatment.

19. A positive electrode comprising the positive electrode active material according to any one of claims 1 to 10 or the positive electrode active material prepared by the method according to any one of claims 11 to 18.

20. A rechargeable lithium battery comprising the positive electrode according to claim 19, a negative electrode, and an electrolyte.

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