Positive electrode active material, positive electrode, and rechargeable lithium battery

Abstract

The present application provides a positive electrode active material, a positive electrode including the positive electrode active material, and a rechargeable lithium battery including the positive electrode. The positive electrode active material includes a first positive electrode active material including a layered lithium nickel manganese-based composite oxide and in the form of secondary particles including a plurality of primary particles and having an average particle diameter (D50) of about 10 [mu] m to about 25 [mu] m, and a second positive electrode active material including a plurality of secondary particles having an average particle diameter (D50) of about 10 [mu] m to about 25 [mu] m. And the second positive electrode active material includes a layered lithium nickel cobalt-based composite oxide and is in the form of a single particle, and the average particle diameter (D50) of the single particle is about 0.5 [mu] m to about 8 [mu] m.

Description

Technical Field

[0001] Embodiments of the present disclosure described herein relate to a positive electrode active material, a positive electrode including the positive electrode active material, and a rechargeable lithium battery including the positive electrode. Background Art

[0002] Portable information devices (such as cellular phones, laptop computers, smart phones, etc.) and / or electric vehicles utilize rechargeable lithium batteries as a driving power source due to their relatively high energy density and portability. Recently, research has been actively conducted to use rechargeable lithium batteries with high energy density as a driving power source for hybrid or electric vehicles, as well as an energy storage power source for an energy storage system or a power wall.

[0003] Various positive electrode active materials for rechargeable lithium batteries have been studied. For example, lithium nickel-based oxides, lithium nickel manganese cobalt composite oxides, lithium nickel cobalt aluminum composite oxides, and lithium cobalt-based oxides have been used as positive electrode active materials. However, as the demand for large-sized, high-capacity, or high-energy density rechargeable lithium batteries increases, the supply of the rare metal cobalt used in these active materials is expected to be severely restricted. Therefore, due to its high cost and limited reserves, there is a need or desire to develop positive electrode active materials that exclude cobalt or significantly reduce its content. Summary of the Invention

[0004] One or more aspects of the embodiments relate to a positive electrode active material having a high energy density, excellent or appropriate cycle life characteristics under high voltage operating conditions, and excellent or appropriate high temperature storage characteristics. That is, the positive electrode active material has a high volumetric capacity and energy density, excellent or appropriate initial charge / discharge efficiency, cycle life characteristics under high voltage conditions, and excellent or appropriate high temperature storage characteristics.

[0005] Additional aspects will be set forth in part in the description that follows and in part will be obvious from the description, or may be learned by practice of the embodiments presented in the present disclosure.

[0006] In one or more embodiments, the positive electrode active material includes a first positive electrode active material and a second positive electrode active material. The first positive electrode active material includes a layered lithium nickel manganese composite oxide and includes (e.g., each) secondary particles (e.g., in the form of secondary particles) formed by aggregating a plurality of primary particles, and the average particle diameter (D 50 ) of the secondary particles is about 10 μm to about 25 μm. The second positive electrode active material includes a layered lithium nickel cobalt composite oxide and includes single particles (e.g., each being an integral particle) (e.g., in the form of single particles), and the average particle diameter (D 50 ) of the single particles is about 0.5 μm to about 8 μm.

[0007] In one or more embodiments, the positive electrode includes a positive electrode current collector and a positive electrode active material layer on the positive electrode current collector, wherein the positive electrode active material layer includes the aforementioned positive electrode active material.

[0008] In one or more embodiments, the rechargeable lithium battery includes a positive electrode, a negative electrode, and an electrolyte. Brief Description of the Drawings

[0009] Figures 1 to 4 Schematic diagrams each showing a rechargeable lithium battery according to one or more embodiments.

[0010] Reference Numerals

[0011] 100: Rechargeable lithium battery 10: Positive electrode

[0012] 11: Positive electrode lead tab 12: Positive electrode terminal

[0013] 20: Negative electrode 21: Negative electrode lead tab

[0014] 22: Negative electrode terminal 30: Separator

[0015] 40: Electrode assembly 50: Housing

[0016] 60: Sealing member 70: Electrode tab

[0017] 71: Positive electrode tab 72: Negative electrode tab Detailed Description of the Embodiments

[0018] Hereinafter, one or more embodiments will be described in more detail so that those of ordinary skill in the art can more easily implement them. However, the present disclosure may be embodied in many different forms and is not to be construed as limited to the one or more embodiments set forth herein.

[0019] As used herein, 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" as used herein, when before / after a list of elements, modify the entire list of elements and not individual elements of the list. For example, "at least one of a, b, and c", "selected from at least one of a, b, and 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.

[0020] The terms used in this specification are for the purpose of describing particular embodiments only and are not intended to limit the scope of the present disclosure. Unless the context clearly dictates otherwise, singular forms include plural forms.

[0021] As used herein, "a combination thereof" refers to a mixture, laminate, composite, copolymer, alloy, blend, reaction product, etc. of the respective components.

[0022] In this specification, it should be understood that terms such as "comprising," "including," or "having" are intended to indicate the presence of specified features, quantities, steps (e.g., actions or tasks), elements, and / or combinations thereof (e.g., any suitable ones), but do not preclude the presence or addition of one or more other features, quantities, steps (e.g., actions or tasks), elements, and / or combinations thereof (e.g., any suitable ones).

[0023] In the drawings, for clarity, the dimensions (e.g., thickness) of layers, films, panels, regions, etc. are enlarged, and the same reference numerals throughout the drawings denote the same elements, and repeated descriptions thereof may not be provided in the specification. It will be understood that if (e.g., when) an element (such as a layer, film, region, or substrate) is referred to as being "on" another element (such as a layer, film, region, or substrate), it may be directly on the other element (such as a layer, film, region, or substrate), or intervening elements may also be present. In contrast, if (e.g., when) an element (such as a layer, film, region, or substrate) is referred to as being "directly on" another element (such as a layer, film, region, or substrate), no intervening elements are present.

[0024] In addition, a "layer" in this specification includes not only a shape formed on the entire surface when (e.g., when) viewed from a plan view, but also a shape formed on a partial surface.

[0025] In the present disclosure, when the particles are spherical, "diameter" indicates the particle size or average particle size, and when the particles are non-spherical, "diameter" indicates the major axis length or average major axis length. The average particle size can be measured by methods suitable for those skilled in the art, for example, by a particle size analyzer or by transmission electron microscope images or scanning electron microscope images. In one or more embodiments, the average particle size value can be obtained by measuring using the dynamic light scattering method, performing data analysis, counting the number of particles in each particle size range, and calculating accordingly. Unless otherwise defined, the average particle size (D 50 ) may refer to the diameter of the particles with a cumulative volume of 50% by volume in the particle size distribution. As used herein, if (e.g., when) no other definition is provided, the average particle size (D 50) refers to the diameter of the particles with a cumulative volume of 50% by volume in the particle size distribution obtained by randomly measuring the sizes (diameter or major axis length) of about 20 particles in a scanning electron microscope image.

[0026] In this text, "or" is not interpreted in an exclusive sense. For example, "A or B" is interpreted to include A, B, A + B, etc.

[0027] "Metal" is interpreted to include the concepts of ordinary metals, transition metals, and metalloids (semi-metals).

[0028] Positive electrode active material

[0029] In one or more embodiments, the positive electrode active material includes a first positive electrode active material and a second positive electrode active material. The first positive electrode active material includes a layered lithium nickel manganese composite oxide and includes secondary particles (e.g., in the form of secondary particles) formed by aggregating a plurality of primary particles, and the average particle size (D 50 ) is about 10 μm to about 25 μm. The second positive electrode active material includes a layered lithium nickel cobalt composite oxide and includes single particles (e.g., in the form of single particles), and the average particle size (D 50 ) is about 0.5 μm to about 8 μm.

[0030] The positive electrode active material can have or achieve high-density characteristics, so it can have a high capacity per unit volume and a high energy density, and exhibit excellent or appropriate characteristics at high voltages. Because this positive electrode active material has a low cost and satisfies high-capacity, high-voltage, and high-density characteristics, the rechargeable lithium battery using this positive electrode active material can be installed in an electric vehicle or a hybrid vehicle, and long-distance driving of the electric vehicle or hybrid vehicle can be ensured.

[0031] Based on the total of about 100 wt% of the first positive electrode active material and the second positive electrode active material, the content of the first positive electrode active material can be about 60 wt% to about 95 wt%, for example, about 70 wt% to about 90 wt%, and the content of the second positive electrode active material can be about 5 wt% to about 40 wt%, for example, about 10 wt% to about 30 wt%. If the first positive electrode active material and the second positive electrode active material are mixed within these ratios, the energy density can be maximized or increased, and the cycle life characteristics and high-temperature storage characteristics at high voltages can be improved.

[0032] First positive electrode active material

[0033] Due to the rising price of the rare metal cobalt, it is necessary to develop a positive electrode active material that excludes cobalt (e.g., does not include cobalt) or reduces its content (e.g., amount). For example, positive electrode active materials having an olivine crystal structure (such as lithium iron phosphate (LFP), lithium manganese phosphate (LMP), lithium manganese iron phosphate (LMFP), etc.) or a spinel crystal structure (such as lithium manganese oxide (LMO), etc.) have limitations in achieving high capacity due to the small amount of lithium available in the structure. Layered lithium nickel manganese-based positive electrode active materials have excellent or appropriate capacity and efficiency characteristics due to the high amount of lithium available in the structure, making them suitable as materials for high-capacity batteries. However, due to the removal of cobalt, which plays a key role in the layered structure, the structural stability is reduced, the resistance increases, and it becomes more difficult to ensure long cycle life characteristics. In addition, layered lithium nickel manganese-based positive electrode active materials that exclude cobalt (e.g., do not include cobalt) may have a problem of accelerated side reactions with the electrolyte under high voltage and high temperature conditions, which can lead to increased gas generation and deterioration of the cycle life characteristics.

[0034] Accordingly, in one or more embodiments, a method for improving the capacity and cycle life characteristics of a first positive electrode active material at high voltage may include appropriately or suitably adjusting the ratio of nickel and manganese in the layered lithium nickel manganese-based composite oxide, introducing other elements (such as aluminum) in addition to nickel and manganese, or introducing a substantially uniform coating by applying a suitable or appropriate coating method.

[0035] The first positive electrode active material includes a layered lithium nickel manganese-based composite oxide and includes (e.g., each) secondary particles (e.g., in the form of secondary particles) made by aggregating a plurality of primary particles, and the average particle size (D 50 ) of the secondary particles is about 10 μm to about 25 μm. The first positive electrode active material can be expressed as large particles.

[0036] The average particle size (D 50 ) of the secondary particles can 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. Herein, the average particle size (D 50 ) refers to the diameter of the particle with a cumulative volume of 50% by volume in the particle size distribution obtained by randomly measuring the sizes (diameter or major axis length) of about 20 particles in the scanning electron microscope image of the positive electrode active material.

[0037] The shape of the secondary particles may be, for example, spherical shape, ellipsoidal shape, polygonal shape, irregular shape, and / or a combination thereof (e.g., any suitable combination). In the present text, the polygonal shape refers to a three-dimensional figure having a plurality of angles, such as a polygonal prism and a polygonal pyramid. The shape of the primary particles constituting the secondary particles may be, for example, spherical shape, ellipsoidal shape, polygonal shape, plate shape (e.g., in the form of a plate), needle shape, irregular shape, and / or a combination thereof (e.g., any suitable combination).

[0038] In the layered lithium nickel manganese composite oxide, based on 100 mol% of the total metals other than lithium (e.g., total metals), the nickel content (e.g., amount) may be greater than or equal to about 60 mol%, for example, may be about 60 mol% to about 80 mol%, about 65 mol% to about 80 mol%, about 70 mol% to about 80 mol%, about 60 mol% to about 79 mol%, about 60 mol% to about 78 mol%, or about 60 mol% to about 75 mol%. If the nickel content (e.g., amount) satisfies the above range, even if the cobalt content (e.g., amount) decreases, high capacity can be achieved and the structural stability can be increased.

[0039] Based on 100 mol% of the total metals other than lithium (e.g., excluding lithium) in the layered lithium nickel manganese composite oxide (e.g., total metals), the manganese content (e.g., amount) may be greater than or equal to about 10 mol%, for example, greater than or equal to about 15 mol%, for example, may be about 15 mol% to about 40 mol%, about 15 mol% to about 35 mol%, about 15 mol% to about 30 mol%, or about 20 mol% to about 30 mol%. If the manganese content (e.g., amount) satisfies the above range, the positive electrode active material can improve the structural stability while achieving or having high capacity.

[0040] The layered lithium nickel manganese composite oxide may be a lithium nickel manganese aluminum composite oxide further including aluminum in addition to nickel and manganese. If the layered lithium nickel manganese composite oxide contains aluminum, even if the cobalt element is excluded (for example, not included) in the structure, it is beneficial to maintain a stable layered structure. The aluminum content (for example, amount) based on the total metal other than lithium in the layered lithium nickel manganese aluminum composite oxide may be greater than or equal to 0 mol% and less than or equal to about 3 mol%, greater than or equal to about 0.1 mol%, greater than or equal to about 0.5 mol% or greater than or equal to about 1 mol%. For example, it may be about 1 mol% to about 3 mol%, about 1 mol% to about 2.5 mol%, about 1 mol% to about 2 mol% or about 1.5 mol% to about 2.5 mol%. If the aluminum content (for example, amount) satisfies the above range, even if cobalt is excluded (for example, not included), a stable layered structure can be maintained, the problem of structure collapse caused by charging and discharging can be suppressed or reduced, and the long cycle life characteristics of the positive electrode active material can be achieved.

[0041] According to one or more embodiments, the concentration of aluminum within the particles including the layered lithium nickel manganese composite oxide may be substantially uniform. For example, it means that there is no obvious aluminum concentration gradient from the center to the surface within the particles. In other words, the aluminum concentration inside the particles is neither higher nor lower than that outside, resulting in a substantially uniform distribution of aluminum throughout the particles. This may be a structure obtained by using an aluminum raw material during the precursor generation process and not doping aluminum additionally during the synthesis process of the layered lithium nickel manganese composite oxide, so that a nickel manganese aluminum hydroxide is used as a precursor to synthesize the composite oxide. The particles may include secondary particles in which a plurality of primary particles are aggregated (for example, may be in the form of secondary particles), and the aluminum content (for example, amount) within the primary particles may be the same or similar regardless of the position of the primary particles. For example, if primary particles are selected at random positions in the cross-section of the secondary particles and the aluminum content (for example, amount) is measured inside rather than at the interface of the primary particles, regardless of the position of the primary particles, for example, whether the primary particles are close to the center or the surface of the secondary particles, the aluminum content (for example, amount) may be the same / similar / substantially uniform. In this structure, even if cobalt is absent or present in a small amount (for example, a very small amount), a stable layered structure can be maintained, and no aluminum by-products or aluminum aggregates are generated, thereby simultaneously improving the capacity, efficiency and cycle life characteristics of the positive electrode active material.

[0042] The layered lithium nickel manganese composite oxide may be represented by Chemical Formula 1.

[0043] Chemical Formula 1

[0044] Li a1 Ni x1 Mn y1 Al z1M 1 w1 O 2-b1 X b1

[0045] In Chemical Formula 1, 0.9 ≤ a1 ≤ 1.8, 0.6 ≤ x1 ≤ 0.8, 0.1 ≤ y1 ≤ 0.4, 0 ≤ z1 ≤ 0.03, 0 ≤ w1 ≤ 0.3, 0.9 ≤ x1 + y1 + z1 + w1 ≤ 1.1, and 0 ≤ b1 ≤ 0.1, M 1 is one or more elements selected from B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, and Zr, and X is one or more elements selected from F, P, and S.

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

[0047] In Chemical Formula 1, for example, 0.6 ≤ x1 ≤ 0.79, 0.6 ≤ x1 ≤ 0.78, 0.6 ≤ x1 ≤ 0.75, 0.65 ≤ x1 ≤ 0.8, or 0.7 ≤ x1 ≤ 0.79; 0.1 ≤ y1 ≤ 0.35, 0.1 ≤ y1 ≤ 0.30, 0.1 ≤ y1 ≤ 0.29, 0.15 ≤ y1 ≤ 0.39, or 0.2 ≤ y1 ≤ 0.3; 0.01 ≤ z1 ≤ 0.025, 0.01 < z1 ≤ 0.02, or 0.01 < z1 ≤ 0.019; 0 ≤ w1 ≤ 0.28, 0 ≤ w1 ≤ 0.27, 0 ≤ w1 ≤ 0.26, 0 ≤ w1 ≤ 0.25, 0 ≤ w1 ≤ 0.24, 0 ≤ w1 ≤ 0.23, 0 ≤ w1 ≤ 0.22, 0 ≤ w1 ≤ 0.21, 0 ≤ w1 ≤ 0.2, 0 ≤ w1 ≤ 0.15, 0 ≤ w1 ≤ 0.1, or 0 ≤ w1 ≤ 0.09.

[0048] For example, the layered lithium nickel manganese composite oxide may not include (e.g., may exclude any) cobalt or may include a small amount (e.g., substantially a very small amount) of cobalt, and based on 100 mol% of the total metal excluding (e.g., not including) lithium (e.g., total metal), the cobalt content (e.g., amount) may be from about 0 mol% to about 0.01 mol%.

[0049] Coating

[0050] The first positive electrode active material may include a core particle and a coating. The core particle includes a layered lithium nickel manganese composite oxide. The coating is located on the surface of the core particle and includes Al, B, Mg, Ti, V, W, Y, Zn, Zr, and / or a combination thereof (e.g., any suitable combination).

[0051] If (e.g., when) the battery operates under high voltage or high temperature conditions, the layered lithium nickel manganese composite oxide is vulnerable to chemical erosion by components in the electrolyte, and thus may undergo many side reactions with the electrolyte, resulting in an increased amount of gas generation, thereby deteriorating the battery cycle life and safety. However, these problems can be solved by introducing a coating according to one or more embodiments therein.

[0052] For example, the coating may be an Al coating including Al, and may optionally further include elements such as B, Mg, Ti, V, W, Y, Zn, and Zr. When the Al coating is introduced, the high voltage performance of the first positive electrode active material can be further improved.

[0053] Because the layered lithium nickel manganese composite oxide and oxides with different compositions (e.g., lithium nickel cobalt manganese composite oxide, lithium nickel cobalt aluminum composite oxide, lithium cobalt oxide, etc.) may have significantly different residual lithium contents on the particle surface and have different one or more suitable properties, it is impossible to form a satisfactory coating in the form of a substantially uniform film in a similar coating method. Accordingly, one or more embodiments may introduce a substantially uniform coating into the first positive electrode active material by the following method: (i) adding coating raw materials to an aqueous solvent and mixing them to prepare a coating solution in which the salts are completely dissolved in the salt solution wet coating method; (ii) adding the core particles to the coating solution and mixing them to continue the coating; and (iii) removing the solvent, followed by drying and heat treatment. This method is the salt solution wet coating method and is also a pre-adding method in which the salts and coating raw materials are completely dissolved and then the active material particles (i.e., the core particles) are added. By this method, a substantially uniform and thin coating can be successfully formed on the surface of the layered lithium nickel manganese composite oxide.

[0054] According to the coating method, compared with general dry methods or wet methods after addition, the content (e.g., amount) of coating elements on the surface of the active material particles can be further increased. For example, if (e.g., when) measured by EP-EDS analysis, based on the total metals other than lithium on the surface of about 100 at%, the content (e.g., amount) of coating elements on the surface of the first positive electrode active material can be about 5 at% to about 35 at%, for example, about 5 at% to about 30 at%, about 5 at% to about 25 at%, about 5 at% to about 20 at% or about 10 at% to about 20 at%. Within these content (e.g., amount) ranges, the coating can effectively improve the high-voltage characteristics without increasing the resistance of the first positive electrode active material.

[0055] The coating can include (e.g., can be in the form of) a film continuously surrounding the surface of the core particles, for example, or can include (e.g., can be in the form of) a shell surrounding the entire surface of the core particles. This is different from the structure in which only a part of the surface of the core particles is locally coated. According to one or more embodiments, the coating can be formed to completely cover the surface of the core particles and can be formed to be very thin and substantially uniform in thickness, so that the positive electrode active material does not increase resistance or reduce capacity, improves structural stability, effectively suppresses or reduces side reactions with the electrolyte, reduces the amount of gas generated under high-voltage and high-temperature conditions, and realizes long cycle life characteristics.

[0056] According to this method, the thickness of the coating of the first positive electrode active material can be about 5 nm to about 200 nm, for example about 5 nm to about 150 nm, about 5 nm to about 100 nm, about 5 nm to about 80 nm, about 5 nm to about 50 nm or about 10 nm to about 50 nm. If the coating satisfies these thickness ranges, the structural stability of the positive electrode active material can be improved without increasing resistance or reducing capacity due to the coating, and side reactions with the electrolyte can be effectively suppressed or reduced. The thickness of the coating can be measured by, for example, SEM, TEM, TOF-SIMS, XPS or EDS analysis, for example, can be measured by EDS line profile analysis of the cross-section of the positive electrode active material.

[0057] The coating according to one or more embodiments is characterized by a thin and substantially uniform thickness, at the level of several nanometers to several hundred nanometers. For example, the deviation of the coating thickness in one positive electrode active material particle can be less than or equal to about 20%, less than or equal to about 18%, or less than or equal to about 15%. In this context, the deviation of the coating thickness refers to the deviation of the coating thickness within one positive electrode active material particle. For example, the deviation of the coating thickness can be calculated as follows: measure the thickness of about 10 points in the electron microscope image of the cross-section of a single positive electrode active material particle to calculate the arithmetic mean, and then divide the absolute value of the difference between one measurement data and the arithmetic mean by the arithmetic mean and multiply by 100%. The fact that the deviation or standard deviation of the coating thickness satisfies the above range means that a coating with a substantially uniform thickness is formed in the form of a good or appropriate film on the surface of the positive electrode active material particle. Accordingly, the structural stability of the positive electrode active material is improved, the side reaction with the electrolyte can be effectively suppressed or reduced, and the increase in resistance or the decrease in capacity caused by the coating can be minimized or reduced.

[0058] For example, if an Al coating is introduced, based on the total metal excluding (e.g., not including) lithium in about 100 mol% of the total first positive electrode active material, the Al content (e.g., amount) of the coating can be about 0.1 mol% to about 3.0 mol%, for example, about 0.1 mol% to about 2.0 mol%, about 0.5 mol% to about 1.5 mol%, or about 0.7 mol% to about 1.3 mol%.

[0059] If an Al coating is introduced, the coating can include, for example, layered aluminum compounds, such as aluminum oxide, lithium aluminum oxide (e.g., LiAlO2), and / or a combination thereof (e.g., any suitable combination).

[0060] Based on the total metal (i.e., total metal) excluding lithium in the total first positive electrode active material at about 100 mol%, the respective contents (e.g., amounts) of the coating elements (i.e., coating components) can vary depending on the type (species) of the coating element, but can be from about 0.01 mol% to about 5 mol%, for example, from about 0.05 mol% to about 3 mol% or from about 0.1 mol% to about 2 mol%. For example, in one embodiment, in the first positive electrode active material, based on 100 mol% of the total metal excluding lithium, the content of the coating element of the coating is from about 0.1 mol% to about 2 mol%. In other words, as a further example, based on 100 mol% of the total metal excluding lithium, the content of the coating component in the first positive electrode active material is generally in the range of about 0.01 mol% to about 5 mol%, specifically exemplified by from about 0.05 mol% to about 3 mol% or from about 0.1 mol% to about 2 mol%. For example, the first positive electrode active material may include a first coating containing aluminum on the surface of the core particles and a second coating containing zirconium on the first coating.

[0061] Second positive electrode active material

[0062] The second positive electrode active material includes a layered lithium nickel cobalt composite oxide, includes single particles (e.g., in the form of single particles), and has an average particle diameter (D 50 ) of about 0.5 μm to about 8 μm. The second positive electrode active material can be expressed as small particles.

[0063] In this context, single particles can exist alone, have no grain boundaries within the particle, include one particle (e.g., consist of one particle), and can be a monolithic structure, an integral structure, or non-aggregated particles, where the particles do not aggregate with each other but exist as independent phases morphologically and can be represented as integral particles or single crystals, for example, as single crystals.

[0064] The average particle diameter (D 50 ) of the single particles can 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. The shape of the single particles can be, for example, spherical, ellipsoidal, polygonal, irregular shape, and / or a combination thereof (e.g., any suitable combination).

[0065] In the layered lithium nickel cobalt composite oxide of the second positive electrode active material, the nickel content (e.g., amount) based on 100 mol% of the total metal (e.g., total metal) excluding (e.g., not including) lithium can be, for example, about 50 mol% to about 70 mol%, for example, about 55 mol% to about 70 mol% or about 55 mol% to about 65 mol%. For example, the second positive electrode active material can be a medium-nickel positive electrode active material containing about 50 mol% to about 70 mol% of nickel. When the nickel in the second positive electrode active material satisfies the above content (e.g., amount) range, excellent or appropriate cycle life characteristics can be achieved under high voltage driving conditions where the upper limit charging voltage is greater than or equal to about 4.45V. The medium-nickel second positive electrode active material can be described as a material for high voltage charging greater than or equal to about 4.45V.

[0066] The nickel content (e.g., amount) based on 100 mol% of the total metal (e.g., total metal) excluding (e.g., not including) lithium in the layered lithium nickel cobalt composite oxide of the second positive electrode active material can be, for example, about 10 mol% to about 30 mol% or about 15 mol% to about 20 mol% less than the nickel content (e.g., amount) based on 100 mol% of the total metal (e.g., total metal) excluding (e.g., not including) lithium in the layered lithium nickel manganese composite oxide of the first positive electrode active material.

[0067] The layered lithium nickel cobalt composite oxide can be represented by Chemical Formula 2, and can be represented by Chemical Formula 3 as a specific example.

[0068] Chemical Formula 2

[0069] Li a2 Ni x2 Co y2 M 2 z2 O 2-b2 X b2

[0070] In Chemical Formula 2, 0.9 ≤ a2 ≤ 1.2, 0.5 ≤ x2 ≤ 0.7, 0.1 ≤ y2 ≤ 0.5, 0 ≤ z2 ≤ 0.4, 0.9 ≤ x2 + y2 + z2 ≤ 1.1, and 0 ≤ b2 ≤ 0.1, M 2 is one or more elements selected from Al, B, Ba, Ca, Ce, 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.

[0071] Chemical Formula 3

[0072] Li a3 Ni x3 Co y3M 3 z3 M 4 w3 O 2-b3 X b3

[0073] In Chemical Formula 3, 0.9 ≤ a3 ≤ 1.2, 0.5 ≤ x3 ≤ 0.7, 0.1 ≤ y3 ≤ 0.4, 0.1 ≤ z3 ≤ 0.3, 0 ≤ w3 ≤ 0.1, 0.9 ≤ x3 + y3 + z3 + w3 ≤ 1.1, and 0 ≤ b3 ≤ 0.1, M 3 is one or more elements selected from Al and Mn, M 4 is 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 is one or more elements selected from F, P, and S.

[0074] As an example, the second positive electrode active material may include core particles containing a layered lithium nickel cobalt composite oxide and a coating on the surface of the core particles. The coating may include, for example, Al, B, Co, Mg, Si, Ti, V, W, Zn, Zr, and / or a combination thereof (e.g., any suitable combination). Based on the total metal (e.g., total metal) excluding lithium in the second positive electrode active material by 100 wt%, 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%.

[0075] Positive electrode

[0076] In one or more embodiments, a positive electrode for a rechargeable lithium battery including the aforementioned positive electrode active material is provided. For example, the positive electrode includes 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 may include the aforementioned positive electrode active material and may further optionally include a binder, a conductive material, and / or a combination thereof (e.g., any suitable combination).

[0077] According to one or more embodiments, the loading level of the positive electrode active material layer may be about 10 mg / cm 2 to about 40 mg / cm 2 , for example about 10 mg / cm 2 to about 30 mg / cm 2 or about 10 mg / cm 2 to about 20 mg / cm 2In addition, the density of the positive electrode active material layer in the finally pressed positive electrode can be from about 3.3 g / cc to about 3.7 g / cc, such as from about 3.3 g / cc to about 3.6 g / cc or from about 3.4 g / cc to about 3.58 g / cc. When applying the positive electrode active material according to one or more embodiments, implementing such a loading level and positive electrode density is advantageous, and a positive electrode that meets the loading level and positive electrode density within the above range is suitable for achieving a high-capacity, high-energy density rechargeable lithium battery. The density of the positive electrode active material layer refers to the ratio of the weight to the volume of the pressed positive electrode active material layer. The density of the positive electrode active material layer can be measured as follows: measuring the cross-sectional area, thickness, and weight of the positive electrode active material layer excluding the positive electrode current collector, calculating the volume by multiplying the cross-sectional area and the thickness, and dividing the weight by the volume.

[0078] Binder

[0079] 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, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, and nylon.

[0080] Conductive material

[0081] A conductive material (e.g., an electronic conductor) is included to provide electrode conductivity, and any conductive material can be used as the conductive material unless it causes a chemical change. Examples of the conductive material may include carbon-based materials (such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, carbon nanotube, etc.); metal-based materials including metal powders or metal fibers such as copper, nickel, aluminum, silver, etc.; conductive polymers (such as polyphenylene derivatives); and / or a mixture thereof (e.g., any suitable one).

[0082] Based on 100 wt% of the positive electrode active material layer, the respective contents (e.g., amounts) of the binder and the conductive material can be from about 0.5 wt% to about 5 wt%.

[0083] The positive electrode current collector may include Al foil, but the present disclosure is not limited thereto.

[0084] Rechargeable lithium battery

[0085] One or more embodiments provide a rechargeable lithium battery, which includes the aforementioned positive electrode, negative electrode, and electrolyte. As an example, the rechargeable lithium battery may include a positive electrode, a negative electrode, a separator between the positive electrode and the negative electrode, and an electrolyte solution (i.e., the electrolyte).

[0086] The rechargeable lithium battery can be classified into a cylindrical shape, a prismatic shape, a pouch shape, a coin shape, etc. according to its shape. Figures 1 to 4 Schematic diagrams each showing a rechargeable lithium battery according to one or more embodiments, where Figure 1 is a cylindrical battery, Figure 2 is a prismatic battery, and Figure 3 and Figure 4 are pouch-shaped batteries. Referring to Figures 1 to 4 , the rechargeable lithium battery 100 includes an electrode assembly 40 (which has a separator 30 inserted between a positive electrode 10 and a negative electrode 20) and a housing 50 (in which the electrode assembly 40 is accommodated). The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte solution. As shown in Figure 1 , the rechargeable lithium battery 100 may include a sealing member 60 that seals the housing 50. Additionally, in Figure 2 , 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. As shown in Figure 3 and Figure 4 , the rechargeable lithium battery 100 includes electrode tabs 70, for example, a positive electrode tab 71 and a negative electrode tab 72 that serve as a circuit path for guiding the current formed in the electrode assembly 40 to the outside.

[0087] The rechargeable lithium battery according to one or more embodiments can be rechargeable at a high voltage or can be suitable for driving at a high voltage. For example, the charging limit voltage of the rechargeable lithium battery can be greater than or equal to about 4.45 V, and can be about 4.45 V to about 4.7 V, about 4.45 V to about 4.6 V, or about 4.45 V to about 4.55 V, etc. By applying the positive electrode active material according to one or more embodiments, even when (e.g., when) charging at a high voltage, the rechargeable lithium battery can significantly reduce the gas generation amount and can achieve high capacity and long cycle life characteristics.

[0088] Negative electrode

[0089] The negative electrode may include a negative electrode current collector and a negative electrode active material layer on the negative electrode current collector, and the negative electrode active material layer may further include a negative electrode active material, a binder, a conductive material, and / or a combination thereof (e.g., any suitable combination).

[0090] Negative electrode active material

[0091] The negative electrode active material may include a material that reversibly intercalates / deintercalates lithium ions, lithium metal, a lithium metal alloy, a material capable of doping / dedoping lithium, or a transition metal oxide.

[0092] 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 natural graphite or artificial graphite that is amorphous or in the form of flakes, sheets, spheres, or fibers (e.g., in the form of fibers). The amorphous carbon may be soft carbon, hard carbon, mesophase pitch carbonization product, calcined coke, etc.

[0093] The lithium metal alloy includes an alloy of lithium and a metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn.

[0094] 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), a Si-Q alloy (where Q is an element selected from alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements (excluding Si), Group 15 elements, Group 16 elements, transition metals, rare earth elements, and / or a combination thereof (e.g., any suitable combination), such as Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, and / or a combination thereof (e.g., any suitable combination)) and / or a combination thereof (e.g., any suitable combination). The Sn-based negative electrode active material may be Sn, SnO x (0 < x ≤ 2) (e.g., SnO2), a Sn alloy, and / or a combination thereof (e.g., any suitable combination).

[0095] The silicon-carbon composite may be a composite of silicon and amorphous carbon. The average particle size (D 50 ) may be, for example, about 0.5 μm to about 20 μm. According to one or more embodiments, the silicon-carbon composite may include (e.g., may be in the following form) silicon particles and amorphous carbon coated on the surface of the silicon particles. For example, it may include secondary particles (cores) in which silicon primary particles are aggregated and an amorphous carbon coating (shell) on the surface of the secondary particles. Amorphous carbon may also be present between the silicon primary particles. For example, the silicon primary particles may be coated with amorphous carbon. The secondary particles may be dispersed in an amorphous carbon matrix.

[0096] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include a core containing crystalline carbon and silicon particles and an amorphous carbon coating on the surface of the core. The crystalline carbon may be artificial graphite, natural graphite, and / or a combination thereof (e.g., any suitable combination). The amorphous carbon may include soft carbon or hard carbon, mesophase pitch carbonized products, and calcined coke.

[0097] When the silicon-carbon composite includes silicon and amorphous carbon, based on 100 wt% of the silicon-carbon composite, the silicon content (e.g., amount) may be about 10 wt% to about 50 wt%, and the content (e.g., amount) of the amorphous carbon may be about 50 wt% to about 90 wt%. Additionally, if (e.g., when) the silicon-carbon composite includes silicon, amorphous carbon, and crystalline carbon, then based on 100 wt% of the silicon-carbon composite, the silicon content (e.g., amount) may be about 10 wt% to about 50 wt%, the content (e.g., amount) of the crystalline carbon may be about 10 wt% to about 70 wt%, and the content (e.g., amount) of the amorphous carbon may be about 20 wt% to about 40 wt%.

[0098] Additionally, the thickness of the amorphous carbon coating may be about 5 nm to about 100 nm. The average particle diameter (D 50 ) of the silicon particles (primary particles) may be about 10 nm to about 1 μm or about 10 nm to about 200 nm. The silicon particles may exist in the form of elemental silicon, a silicon alloy, or an oxidized form of silicon. The oxidized form of silicon may be represented by SiO x (0 < x ≤ 2). For example, the atomic content (e.g., amount) ratio of Si:O indicating the degree of oxidation may be about 99:1 to about 33:67. As used herein, if (e.g., when) no other definition is provided, the average particle diameter (D 50 ) indicates the diameter of the particles in which the cumulative volume in the particle size distribution is about 50 vol%.

[0099] The Si-based negative electrode active material or the Sn-based negative electrode active material may be mixed with the carbon-based negative electrode active material. When the Si-based negative electrode active material or the Sn-based negative electrode active material is mixed and used with the carbon-based negative electrode active material, the mixing ratio may be a weight ratio of about 1:99 to about 90:10.

[0100] Binder

[0101] The binder is used to bond the negative electrode active material particles well to each other and is also used to bond the negative electrode active material to the negative electrode current collector. The binder may be a non-aqueous binder, an aqueous binder, a dry binder, and / or a combination thereof (e.g., any suitable combination).

[0102] The non-aqueous binder may include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, and / or a combination thereof (e.g., any suitable combination).

[0103] 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 a combination thereof (e.g., any suitable combination).

[0104] When the aqueous binder is used as a binder in the negative electrode active material layer, a cellulose compound capable of imparting viscosity may be further included. As the cellulose compound, one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and alkali metal salts thereof may be mixed and used. The alkali metal may be Na, K, or Li.

[0105] The dry binder may be a polymer material capable of becoming fibers, and may be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, and / or a combination thereof (e.g., any suitable combination).

[0106] Conductive material

[0107] A conductive material (e.g., an electronic conductor) is included to provide electrode conductivity, and any conductive material may be used as the conductive material unless it causes a chemical change. Examples of the conductive material include carbonaceous materials (such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, carbon nanotube, etc.); metallic materials including metal powders or metal fibers such as copper, nickel, aluminum, silver, etc.; conductive polymers (such as polyphenylene derivatives); and / or a mixture thereof (e.g., any suitable mixture).

[0108] Based on 100 wt% of the negative electrode active material layer, the content (e.g., amount) of the negative electrode active material may be about 95 wt% to about 99.5 wt%, and based on 100 wt% of the negative electrode active material layer, the content (e.g., amount) of the binder may be about 0.5 wt% to about 5 wt%. For example, based on 100 wt% of the negative electrode active material layer, the negative electrode active material layer may include about 90 wt% to about 99 wt% of the negative electrode active material, about 0.5 wt% to about 5 wt% of the binder, and about 0.5 wt% to about 5 wt% of the conductive material.

[0109] Negative electrode current collector

[0110] 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, a sheet, or a 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.

[0111] Electrolyte

[0112] For example, the electrolyte for a rechargeable lithium battery may be an electrolyte that may include a non-aqueous organic solvent and a lithium salt.

[0113] The non-aqueous organic solvent serves as a medium for transporting ions participating in the electrochemical reaction of the battery. The non-aqueous organic solvent may include carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, aprotic solvents, and / or a combination thereof (e.g., any suitable combination).

[0114] 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 cyclic hydrocarbon 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); sulfolane, etc.

[0115] The non-aqueous organic solvent may be used alone or as a mixture of two or more types, and if two or more types are used as a mixture, the mixing ratio may be appropriately adjusted according to the desired or appropriate battery performance, which is suitable for those skilled in the art.

[0116] When using carbonate solvents, cyclic carbonates and chain carbonates may be mixed and used, and the cyclic carbonate and the chain carbonate may be mixed at a volume ratio of about 1:1 to about 1:9.

[0117] The non-aqueous organic solvent may further include an aromatic hydrocarbon organic solvent. For example, a carbonate solvent and an aromatic hydrocarbon organic solvent may be mixed and used at a volume ratio of about 1:1 to about 30:1.

[0118] The electrolyte may further include vinylene carbonate, vinylene carbonate or ethylene carbonate compounds to improve the battery cycle life.

[0119] Examples of the ethylene carbonate compounds may include fluoroethylene carbonate, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate and cyanoethylene carbonate.

[0120] The lithium salt dissolved in the non-aqueous organic solvent supplies lithium ions in the battery, ensuring the basic operation of the rechargeable lithium battery and improving the transport of lithium ions between the positive electrode and the negative electrode. 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+1 SO2) (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).

[0121] The concentration of the lithium salt may be in the range of about 0.1 M to about 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte has appropriate or proper ionic conductivity and viscosity, and thus excellent or proper performance can be achieved, and lithium ions can move effectively.

[0122] Separator

[0123] Depending on the type (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 or a multilayer film of two or more of its layers, such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, a polypropylene / polyethylene / polypropylene three-layer separator, etc.

[0124] The separator may include a porous substrate and a coating on one or both surfaces (e.g., opposite surfaces) of the porous substrate, and the coating includes an organic material, an inorganic material and / or a combination thereof (e.g., any suitable combination).

[0125] The porous substrate may be a polymer film formed from any one polymer selected from polyolefins (such as polyethylene and polypropylene), polyesters (such as polyethylene terephthalate and polybutylene terephthalate), polyacetals, polyamides, polyimides, polycarbonates, polyether ketones, polyaryl ether ketones, polyetherimides, polyamideimides, polybenzimidazoles, polyethersulfones, polyphenylene ethers, cycloolefin copolymers, polyphenylene sulfides, polyethylene naphthalate, glass fibers, and polytetrafluoroethylene (e.g., Teflon), or a copolymer or mixture of two or more of them.

[0126] 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).

[0127] The organic material may include a (meth)acrylic copolymer, which includes a first structural unit derived from (meth)acrylamide, and a second structural unit including at least one of a structural unit derived from (meth)acrylic acid or (meth)acrylate and a structural unit derived from (meth)acrylamidosulfonic acid or its salt.

[0128] The inorganic material may include inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, and boehmite, but the present disclosure is not limited thereto. The average particle size (D 50 ) may be about 1 nm to about 2000 nm, e.g., about 100 nm to about 1000 nm or about 100 nm to about 700 nm.

[0129] The organic material and the inorganic material may be mixed in one coating, or coatings including the organic material and coatings including the inorganic material may be stacked.

[0130] 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.

[0131] Embodiments and comparative examples of the present disclosure are 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 embodiments.

[0132] Example 1

[0133] 1. Preparation of the positive electrode active material

[0134] (1) Preparation of the first positive electrode active material

[0135] Ni 0.75 Mn0.23 Al 0.02 (OH)₂ and LiOH are mixed to have a molar ratio of Li / (Ni + Mn + Al) = 1.05, and then, an initial heat treatment is carried out at 845 °C for 8 hours in an oxygen atmosphere to prepare a first lithium nickel manganese composite oxide, which has secondary particles with an average particle size (D 50 ) of about 14 μm in the form of Li 1.05 Ni 0.75 Mn 0.23 Al 0.02 O₂ composition.

[0136] A coating solution is prepared by adding aluminum sulfate to a distilled water solvent and then stirring the mixture at about 350 rpm for about 5 minutes. It is confirmed that the salt is completely dissolved in the colorless and transparent coating solution. While continuously stirring the coating solution, 500 g of the first lithium nickel manganese composite oxide is added thereto for 1.5 minutes, and then, it is stirred for about 45 minutes. Herein, based on the total metal other than lithium in 100 mol% of the first positive electrode active material, the aluminum content (e.g., amount) of aluminum sulfate is designed to be 1.0 mol%. After removing the solvent from the mixed solution by using a suction pump and a pressure filter, vacuum drying is carried out at 190 °C.

[0137] After adding zirconia to the dried product, a second heat treatment is carried out at 825 °C for 8 hours in an oxygen atmosphere to prepare the first positive electrode active material. Based on the total metal other than lithium in 100 mol% of the final first positive electrode active material, the zirconium content (e.g., amount) of zirconia is designed to be 0.2 mol%.

[0138] (2) Preparation of the second positive electrode active material

[0139] Ni 0.6 Co 0.1 Mn 0.3 (OH)₂ and LiOH are mixed to have a molar ratio of Li / (Ni + Co + Mn) = 1.05, and a first heat treatment is carried out at 930 °C for 8 hours in an oxygen atmosphere. The obtained mixture is pulverized by a jet mill to prepare a lithium nickel cobalt composite oxide (Li 50 ) in the form of single particles with an average particle size (D 1.05 Ni 0.6 Co 0.1 Mn 0.3 O₂) of about 3.5 μm.

[0140] (3) Preparation of the mixed positive electrode active material

[0141] The first positive electrode active material and the second positive electrode active material are mixed at a weight ratio of 90:10 to prepare the final positive electrode active material.

[0142] In summary, the preparation of the positive electrode active material involves three main steps (e.g., actions or tasks): First, a lithium nickel manganese composite oxide is manufactured by mixing Ni 0.75 Mn 0.23 Al 0.02 (OH)2 and LiOH, heat treatment, coating with aluminum sulfate, and adding zirconia; Second, a lithium nickel cobalt composite oxide is prepared by mixing Ni 0.6 Co 0.1 Mn 0.3 (OH)2 and LiOH, heat treatment, and pulverization; Finally, the two obtained materials are mixed at a weight ratio of 90:10 to form the final positive electrode active material.

[0143] 2. Manufacture of a rechargeable lithium battery cell

[0144] 96 wt% of the positive electrode active material, 2 wt% of the polyvinylidene fluoride binder, and 2 wt% of the carbon nanotube conductive material are mixed to prepare a positive electrode active material layer slurry, and the positive electrode active material layer slurry is coated on an aluminum foil current collector, and then dried and pressed to manufacture a positive electrode.

[0145] A polytetrafluoroethylene separator is arranged between the positive electrode and the lithium metal counter electrode to manufacture an electrode assembly, and after inserting the electrode assembly into the battery case, an electrolyte solution 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.

[0146] Example 2

[0147] The positive electrode active material and the rechargeable lithium battery cell are manufactured in substantially the same manner as in Example 1, except that the first positive electrode active material and the second positive electrode active material are mixed at a weight ratio of 80:20 to prepare the final positive electrode active material.

[0148] Example 3

[0149] The positive electrode active material and the rechargeable lithium battery cell are manufactured in substantially the same manner as in Example 1, except that the first positive electrode active material and the second positive electrode active material are mixed at a weight ratio of 70:30 to prepare the final positive electrode active material.

[0150] Example 4

[0151] The positive electrode active material and the rechargeable lithium battery cell were fabricated in substantially the same manner as in Example 1, except that the first positive electrode active material and the second positive electrode active material were mixed at a weight ratio of 60:40 to prepare the final positive electrode active material.

[0152] Comparative Example 1

[0153] The positive electrode active material and the rechargeable lithium battery cell were fabricated in substantially the same manner as in Example 1, except that only the first positive electrode active material was used as the positive electrode active material.

[0154] Comparative Example 2

[0155] The positive electrode active material and the rechargeable lithium battery cell were fabricated in substantially the same manner as in Example 1, except that only the second positive electrode active material was used as the positive electrode active material.

[0156] The powder compact density (pellet density) of each of the positive electrode active materials of Examples 1 to 4 and Comparative Examples 1 and 2 was measured, which is shown as PD in Table 1. 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 into a hydraulic press, and pressing it for 30 seconds under a pressure of 3 tons to measure the height, the powder compact density was obtained.

[0157] Evaluation Example 1: Evaluation of Initial Charge and Discharge Capacity, Efficiency, and Cycle Life Characteristics

[0158] The rechargeable lithium battery cells of Examples 1 to 4 and Comparative Examples 1 and 2 were 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 1, the initial charge capacity and the initial discharge capacity are provided, and the ratio of the latter to the former is shown as the initial charge and discharge efficiency (i.e., efficiency). In addition, the initial discharge capacity was multiplied by the powder compact density and then expressed as the capacity per unit volume in Table 1.

[0159] Subsequently, at 45°C, within the voltage range of 3.0V to 4.45V, the rechargeable lithium battery cells were charged and discharged at 1.0C for 50 cycles. In Table 1, the ratio of the 50th discharge capacity to the initial discharge capacity is shown as the cycle life.

[0160] Evaluation Example 2: Evaluation of High-Temperature Storage Characteristics

[0161] The rechargeable lithium battery cell initially charged to 4.45 V in Evaluation Example 1 was stored at 90 °C for 24 hours, and then the gas generation amount was measured, and the results are shown in Table 1.

[0162] Table 1

[0163]

[0164]

[0165] Referring to Table 1, the positive electrode active materials of Examples 1 to 4 all exhibited a powder tap density of 3.29 g / cc or higher, and the rechargeable lithium battery cells of Examples 1 to 4 exhibited improved volumetric capacity per unit compared to the rechargeable lithium battery cells of the comparative examples, and also maintained excellent or appropriate cycle life characteristics. In addition, the rechargeable lithium battery cells of the examples exhibited a low gas generation amount in the high-temperature storage evaluation.

[0166] Compared with the examples, Comparative Example 1 using only the first positive electrode active material exhibited a high initial discharge capacity per unit weight. However, due to the decrease in the powder tap density of the positive electrode active material, the volumetric capacity per unit decreased, which was confirmed to be disadvantageous in terms of energy density.

[0167] Compared with the examples, Comparative Example 1 exhibited slightly deteriorated cycle life characteristics and a much higher gas generation amount when stored at a high temperature (for example, when).

[0168] Compared with the examples, Comparative Example 2 using only the second positive electrode active material exhibited a high initial discharge capacity per unit weight, but due to the significant decrease in the powder tap density of the positive electrode active material, the volumetric capacity per unit deteriorated significantly, which was disadvantageous in terms of energy density.

[0169] Comparative Example 3 using a high-nickel-based positive electrode active material in the form of single particles as the second positive electrode active material exhibited a sharp decline in cycle life in the high-voltage region. It was confirmed that it was difficult for the high-nickel-based positive electrode active material to be driven in the high-voltage region where the upper limit charging voltage was increased to 4.45 V. The positive electrode active material according to one or more embodiments can be said to be a material improved or optimized for high-voltage driving conditions where the upper limit charging voltage is 4.45 V or higher.

[0170] Those of ordinary skill in the art will recognize that, in view of the overall content of the present disclosure, each appropriate feature of the various embodiments of the present disclosure can be partially or fully combined with each other, and can be interlocked and operated technically in various appropriate ways, and each embodiment can be implemented independently of each other or in combination with each other in any appropriate way, unless otherwise stated or implied.

[0171] In the context of the present application, and unless otherwise defined, the terms "use", "using", and "used" may be regarded as synonymous with the terms "utilize", "utilizing", and "utilized", respectively.

[0172] Furthermore, when describing embodiments of the inventive concept, the use of "may" refers to "one or more embodiments of the inventive concept". Also, the term "exemplary" is intended to indicate an example or illustration.

[0173] As used herein, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0174] The battery manufacturing apparatus, battery management system (BMS) apparatus, and / or any other related apparatus or components according to embodiments of the present invention 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 respective components of the apparatus may be formed on one integrated circuit (IC) chip or on separate IC chips. Additionally, the respective 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. Furthermore, the respective 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 (such as, for example, random access memory (RAM)) in a computing device. The computer program instructions may also be stored in other non-transitory computer-readable media (such as, for example, CD-ROM, flash drive, etc.). Also, those skilled in the art should recognize that, without departing from the scope of the present disclosure, the functions of various computing devices 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.

[0175] Although the present invention has been described in connection with presently considered practical exemplary 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.

Claims

1. A positive electrode active material, comprising: A first positive electrode active material, comprising a layered lithium nickel manganese composite oxide and being in the form of secondary particles, each of the secondary particles comprising a plurality of primary particles, and the average particle size of the secondary particles being 10 μm to 25 μm, and A second positive electrode active material, comprising a layered lithium nickel cobalt composite oxide and being in the form of single particles, and the average particle size of the single particles being 0.5 μm to 8 μm.

2. The positive electrode active material according to claim 1, wherein Based on a total of 100 wt% of the first positive electrode active material and the second positive electrode active material, the amount of the first positive electrode active material is 60 wt% to 95 wt%, and the amount of the second positive electrode active material is 5 wt% to 40 wt%.

3. The positive electrode active material according to claim 1, wherein Based on 100 mol% of the total metals other than lithium in the layered lithium nickel manganese composite oxide, the layered lithium nickel manganese composite oxide of the first positive electrode active material has a nickel content of 60 mol% to 80 mol% and a manganese content of 10 mol% or more.

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

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

6. The positive electrode active material according to claim 1, wherein Based on 100 mol% of the total metals other than lithium in the layered lithium nickel manganese composite oxide, the cobalt content in the layered lithium nickel manganese composite oxide of the first positive electrode active material is 0 mol% to 0.01 mol%.

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

8. The positive electrode active material according to claim 1, wherein The first positive electrode active material comprises core particles, the core particles comprising a layered lithium nickel manganese composite oxide, and A coating on the surface of the core particles, the coating comprising Al, B, Mg, Ti, V, W, Y, Zn, Zr or a combination thereof.

9. The positive electrode active material according to claim 8, wherein The coating comprises Al and is in the form of a shell continuously surrounding the surface of the core particles.

10. The positive electrode active material according to claim 8, wherein The coating has a thickness of 5 nm to 200 nm.

11. The positive electrode active material according to claim 8, wherein In the first positive electrode active material, based on 100 mol% of the total metals other than lithium, the content of the coating elements of the coating is 0.01 mol% to 5 mol%.

12. The positive electrode active material according to claim 1, wherein, Based on the total metals other than lithium in 100 mol% of the layered lithium nickel cobalt composite oxide, the nickel content in the layered lithium nickel cobalt composite oxide of the second positive electrode active material is 50 mol% to 70 mol%.

13. The positive electrode active material according to claim 12, wherein the second positive electrode active material is used for high voltage charging at a voltage greater than or equal to 4.45V.

14. The positive electrode active material according to claim 1, wherein the nickel content of the second positive electrode active material based on the total metals other than lithium in 100 mol% of the layered lithium nickel cobalt composite oxide is less than the nickel content of the first positive electrode active material based on the total metals other than lithium in 100 mol% of the layered lithium nickel manganese composite oxide.

15. The positive electrode active material according to claim 1, wherein the layered lithium nickel cobalt composite oxide of the second positive electrode active material is represented by Chemical Formula 2: Chemical Formula 2 Li a2 Ni x2 Co y2 M 2 z2 O 2-b2 X b2 Among them, in Chemical Formula 2, 0.9 ≤ a2 ≤ 1.2, 0.5 ≤ x2 ≤ 0.7, 0.1 ≤ y2 ≤ 0.5, 0 ≤ z2 ≤ 0.4, 0.9 ≤ x2 + y2 + z2 ≤ 1.1, and 0 ≤ b2 ≤ 0.1, M 2 is one or more elements selected from Al, B, Ba, Ca, Ce, 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.

16. A positive electrode, comprising: a positive electrode current collector; and a positive electrode active material layer on the positive electrode current collector, wherein the positive electrode active material layer comprises the positive electrode active material according to any one of claims 1 to 15.

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

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

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

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

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