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

Abstract

The invention relates to a positive electrode active material, a positive electrode, and a rechargeable lithium battery. The positive electrode active material includes a first positive electrode active material including a layered lithium nickel manganese-based composite oxide, the first positive electrode active material being in the form of a secondary particle in which a plurality of primary particles are aggregated. The positive electrode active material further includes: a second positive electrode active material including a lithium-manganese-rich composite oxide, in which a molar ratio of lithium to a total metal content other than lithium of the lithium-manganese-rich composite oxide is about 1.1 to about 3, and a molar ratio of lithium to total metal content other than lithium is about 1 to about 3 based on 100 mol% of the lithium-manganese-rich composite oxide; the manganese content is greater than or equal to about 60 mol%, and the second positive electrode active material is in the form of a single particle. The positive electrode active material according to some embodiments maximizes initial charge and discharge capacities while minimizing production costs, securing a long cycle life, and improving high voltage characteristics and high temperature storage characteristics.

Description

[0001] Cross - reference to related applications

[0002] This application claims the priority and benefit of Korean Patent Application No. 10 - 2024 - 0014283, filed with the Korean Intellectual Property Office on January 30, 2024, the entire contents of which are incorporated herein by reference. Technical field

[0003] This application discloses a positive electrode active material, a positive electrode including the same, and a rechargeable lithium battery. Background art

[0004] Portable information devices (such as cellular phones, laptop computers, smart phones, etc.) and electric vehicles use rechargeable lithium batteries with high energy density and easy portability as a driving power source. Recently, further research has been actively conducted to use rechargeable lithium batteries with high energy density as a driving power source for hybrid vehicles or electric vehicles, or as a power storage power source.

[0005] Various positive electrode active materials have been studied to realize rechargeable lithium batteries for these applications. Lithium nickel - based oxides, lithium nickel manganese cobalt composite oxides, lithium nickel cobalt aluminum composite oxides, and lithium cobalt oxides are mainly used as positive electrode active materials. However, although the demand for large - sized, high - capacity, or high - energy - density rechargeable lithium batteries has recently increased, the supply of positive electrode active materials containing rare - metal cobalt is expected to be in short supply in the future. Therefore, since cobalt is expensive and there are not many remaining cobalt reserves, it is necessary to develop positive electrode active materials that do not contain cobalt or reduce the amount of cobalt used. Summary of the invention

[0006] Some embodiments provide a positive electrode active material that can achieve high density, high capacity (i.e., initial charge and discharge capacity), long cycle life, and high energy density, as well as a positive electrode and a rechargeable lithium battery using the positive electrode active material.

[0007] In some embodiments, the positive electrode active material includes: a first positive electrode active material including a layered lithium nickel manganese composite oxide, the first positive electrode active material being in the form of secondary particles in which a plurality of primary particles are aggregated; and a second positive electrode active material including a lithium - rich manganese composite oxide, wherein the molar ratio of lithium to the total metal content other than lithium in the lithium - rich manganese composite oxide is about 1.1 to about 3, and based on the total metal content other than lithium of 100 mol% of the lithium - rich manganese composite oxide, the manganese content is greater than or equal to about 60 mol%, and the second positive electrode active material is in the form of single particles.

[0008] In some 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 a positive electrode active material.

[0009] In some embodiments, a rechargeable lithium battery including a positive electrode, a negative electrode, and an electrolyte is provided.

[0010] The positive electrode active material according to some embodiments maximizes the capacity while minimizing the production cost, ensures a long cycle life, and improves the high-voltage characteristics and high-temperature storage characteristics. The rechargeable lithium battery using the positive electrode active material can exhibit high initial charge and discharge capacities and initial charge and discharge efficiencies (hereinafter also referred to as efficiencies) even under high-voltage operating conditions, and can achieve high energy density and long cycle life characteristics due to the high powder compaction density. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figures 1 to 4 FIG. is a schematic diagram showing a rechargeable lithium battery according to some embodiments.

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

[0013] Figure 7 and Figure 8 is an SEM image of the second positive electrode active material prepared in Example 1.

[0014] <DESCRIPTION OF REFERENCE NUMERALS>

[0015] 100: Rechargeable lithium battery 10: Positive electrode

[0016] 11: Positive electrode lead tab 12: Positive electrode terminal

[0017] 20: Negative electrode 21: Negative electrode lead tab

[0018] 22: Negative electrode terminal 30: Separator

[0019] 40: Electrode assembly 50: Housing

[0020] 60: Sealing member 70: Electrode tab

[0021] 71: Positive electrode tab 72: Negative electrode tab DETAILED DESCRIPTION

[0022] Hereinafter, specific embodiments will be described in detail so that those of ordinary skill in the art can easily implement them. However, the present disclosure can be embodied in many different forms and is not to be construed as limited to the exemplary embodiments set forth herein.

[0023] The terms used herein to describe embodiments are not intended to limit the present disclosure. Unless the context clearly indicates otherwise, singular expressions include plural expressions.

[0024] As used herein, "a combination thereof" means a mixture of components, a laminate, a composite, a copolymer, an alloy, a blend, a reaction product, etc.

[0025] In this document, it should be understood that terms such as "comprising," "including," or "having" are intended to indicate the presence of specific features, quantities, steps, elements, or combinations thereof, but these terms do not preclude the presence or addition of one or more other features, quantities, steps, elements, or combinations thereof.

[0026] In the drawings, for clarity, the dimensions (e.g., thickness) of layers, films, panels, regions, etc. are enlarged, and throughout the specification, the same reference numerals denote the same elements. It will be understood that 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. In contrast, 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.

[0027] In addition, a "layer" herein includes not only a shape formed on the entire surface when viewed in a plan view, but also a shape formed on a partial surface.

[0028] The average particle diameter can be measured by methods well known to those skilled in the art, for example, by a particle size analyzer using laser diffraction or by transmission electron microscope images or scanning electron microscope images. Optionally, it can be measured by using dynamic light scattering methods, performing data analysis, counting the number of particles in each particle size range, and thereby calculating to obtain the average particle diameter value. Unless otherwise defined, the average particle diameter (D 50 ) can mean the diameter of the particles with a cumulative volume of 50% by volume in the particle size distribution. As used herein, when no other limitation is provided, the average particle diameter (D 50 ) means 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.

[0029] In this document, "or" is not interpreted in an exclusive sense. For example, "A or B" is interpreted to include A, B, A + B, etc.

[0030] "Metal" is interpreted to include the concepts of common metals, transition metals, and metalloids (semi-metals).

[0031] Positive electrode active material

[0032] In some embodiments, the positive electrode active material includes: a first positive electrode active material including a layered lithium nickel manganese composite oxide, and the first positive electrode active material is in the form of secondary particles in which a plurality of primary particles are aggregated. The positive electrode active material further includes: a second positive electrode active material including a lithium-manganese-rich composite oxide, where the molar ratio of lithium to the total metal content excluding lithium is about 1.1 to about 3, and the manganese content based on 100 mol% of the total metal content excluding lithium is greater than or equal to about 60 mol%, and the second positive electrode active material is in the form of single particles.

[0033] The positive electrode active material does not include expensive cobalt or contains only a very small amount of cobalt and manganese with low cost. Therefore, the cost is reduced, large-scale production can be increased, and in addition, excellent characteristics (such as high energy density characteristics at high voltages) are achieved, and the capacity is further increased. The positive electrode active material has the advantages of achieving high capacity, high powder compaction density, and maximizing the energy density of the battery. This positive electrode active material is inexpensive and also satisfies high capacity, high voltage, and high energy density characteristics. If a rechargeable lithium battery using the positive electrode active material is installed in an electric vehicle or a hybrid vehicle, long-distance driving can be achieved.

[0034] Based on the total of the first positive electrode active material and the second positive electrode active material being 100 wt%, the amount of the first positive electrode active material included can be about 30 wt% to about 95 wt%, for example, about 35 wt% to about 90 wt% or about 40 wt% to about 80 wt%. The amount of the second positive electrode active material included can be about 5 wt% to about 70 wt%, for example, about 10 wt% to about 65 wt% or about 20 wt% to about 60 wt%. When mixed in the above ratios, high capacity can be achieved while maximizing the energy density.

[0035] First positive electrode active material

[0036] Recently, with the sharp rise in the price of the rare metal cobalt, there is a need to develop a positive electrode active material that does not contain cobalt or reduces the cobalt content. Among the alternatives, due to the small amount of lithium available in the structure, positive electrode active materials with 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 large amount of lithium available in the structure, layered lithium nickel manganese-based positive electrode active materials have excellent capacity and efficiency characteristics, making them suitable as materials for high-capacity batteries. However, with the removal of cobalt, which plays a key role in the layered structure, the structural stability decreases, the resistance increases, and it is difficult to ensure long cycle life characteristics. In addition, the layered lithium nickel manganese-based positive electrode active material excluding cobalt may have the problem of accelerating the side reaction with the electrolyte under high voltage and high temperature conditions, resulting in an increase in gas generation and deterioration of the cycle life characteristics.

[0037] Accordingly, in some embodiments, the ratio of nickel and manganese in the layered lithium nickel manganese-based composite oxide is appropriately adjusted, other elements (such as aluminum) are introduced in addition to nickel and manganese, or a uniform coating is introduced by applying an appropriate coating method, thereby providing a method for improving the capacity and cycle life characteristics of the positive electrode active material at high voltage.

[0038] In some embodiments, the first positive electrode active material includes a layered lithium nickel manganese-based composite oxide, and the first positive electrode active material is in the form of secondary particles in which a plurality of primary particles are aggregated. Herein, the shape of the secondary particles can be spherical, ellipsoidal, polyhedral, or irregular. When the first positive electrode active material is applied in the form of secondary particles, the density of the final positive electrode active material increases, and the capacity, charge-discharge efficiency, rate characteristics, and output characteristics are improved.

[0039] The average particle size (D 50 ) of the first positive electrode active material can be about 10 μm to about 25 μm, for example, about 11 μm to about 20 μm or about 12 μm to about 18 μm. As used herein, when not otherwise limited, the average particle size (D 50 ) means 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 the scanning electron microscope image of the positive electrode active material.

[0040] In the layered lithium nickel manganese composite oxide, based on the total metal content other than lithium of 100 mol%, the nickel content can be greater than or equal to about 60 mol%, for example, about 60 mol% to about 80 mol%, about 65 mol% to about 80 mol%, about 70 mol% to about 80 mol%, about 60 mol% to about 79 mol%, about 60 mol% to about 78 mol% or about 60 mol% to about 75 mol%. If the nickel content meets the above range, high capacity can be achieved even if the cobalt content is reduced, and the structural stability can be increased.

[0041] Based on the total metal content other than lithium of 100 mol% in the layered lithium nickel manganese composite oxide, the manganese content can, for example, be greater than or equal to about 10 mol%, greater than or equal to about 15 mol%, for example, 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 meets the above range, the positive electrode active material can improve the structural stability while achieving high capacity.

[0042] The layered lithium nickel manganese composite oxide can be a lithium nickel manganese aluminum composite oxide further including aluminum in addition to nickel and manganese. If the lithium nickel manganese aluminum composite oxide contains aluminum, it is advantageously possible to maintain a stable layered structure even if the cobalt element is excluded from the structure. Based on the total metal content other than lithium of 100 mol% of the layered lithium nickel manganese composite oxide, the aluminum content can be greater than or equal to about 0 mol%, greater than or equal to about 0.1 mol%, greater than or equal to about 0.5 mol% or greater than or equal to about 1 mol%, for example, greater than or equal to 0 mol% and less than or equal to 3 mol%, about 1 mol% to about 3 mol%, about 1 mol% to about 2.5 mol%, about 1 mol% to about 2 mol% or about 1.5 mol% to about 2.5 mol%. If the aluminum content meets the above range, a stable layered structure can be maintained even if cobalt is excluded, the problem of structural collapse due to charge and discharge can be suppressed, and the long cycle life characteristics of the positive electrode active material can be achieved.

[0043] According to some embodiments, the concentration of aluminum in particles including layered lithium nickel manganese composite oxides may be uniform. "Uniform" means that in the particles, there is no concentration gradient of aluminum from the center to the surface, or the aluminum concentration outside the particles is neither higher nor lower than the aluminum concentration inside, and the aluminum in the particles is uniformly distributed, i.e., the aluminum is uniformly distributed in the layered lithium nickel manganese composite oxides. This may be a structure obtained by using an aluminum raw material during the production of the precursor and not doping aluminum additionally during the synthesis of the layered lithium nickel manganese composite oxides, thus synthesizing the layered lithium nickel manganese composite oxides (e.g., lithium nickel manganese aluminum composite oxides) by using nickel manganese aluminum composite hydroxide as the precursor. The particles may be in the form of secondary particles in which a plurality of primary particles are aggregated, and regardless of the position of the primary particles, the aluminum content inside the primary particles may be the same or similar. That is, if primary particles are selected at random positions in the cross-section of the secondary particles and the aluminum content inside the primary particles rather than at their interfaces is measured, regardless of the position of the primary particles, i.e., whether the primary particles are close to the center or the surface of the secondary particles, the aluminum content may be the same / similar / uniform. In this structure, even without cobalt or with a very small amount of cobalt present, a stable layered structure can be maintained, and no aluminum by-products or aluminum aggregates are generated, thereby improving the capacity, efficiency, and cycle life characteristics of the positive electrode active material.

[0044] The layered lithium nickel manganese composite oxides may be specifically represented by Chemical Formula 1.

[0045] [Chemical Formula 1]

[0046] Li a1 Ni x1 Mn y1 Al z1 M 1 w1 O 2-b1 X b1

[0047] 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.

[0048] Moreover, in Chemical Formula 1, 0.9 ≤ a1 ≤ 1.5 or 0.9 ≤ a1 ≤ 1.2. Additionally, Chemical Formula 1 may include aluminum, where the case where 0.6 ≤ x1 ≤ 0.8, 0.1 ≤ y1 ≤ 0.39, 0.01 ≤ z1 ≤ 0.03, and 0 ≤ w1 ≤ 0.29 may be satisfied, or, for example, the case where 0.6 ≤ x1 ≤ 0.8, 0.1 ≤ y1 ≤ 0.39, 0.01 < z1 ≤ 0.03, and 0 ≤ w1 ≤ 0.29 may be satisfied.

[0049] In Chemical Formula 1, for example, 0.6 ≤ x1 ≤ 0.79, 0.6 ≤ x1 ≤ 0.78, 0.6 ≤ x1 ≤ 0.75, 0.65 ≤ x1 ≤ 0.8 or 0.7 ≤ x1 ≤ 0.79; 0.1 ≤ y1 ≤ 0.35, 0.1 ≤ y1 ≤ 0.30, 0.1 ≤ y1 ≤ 0.29, 0.15 ≤ y1 ≤ 0.39 or 0.2 ≤ y1 ≤ 0.3; 0.01 ≤ z1 ≤ 0.025, 0.01 < z1 ≤ 0.02 or 0.01 < z1 ≤ 0.019; and 0 ≤ w1 ≤ 0.28, 0 ≤ w1 ≤ 0.27, 0 ≤ w1 ≤ 0.26, 0 ≤ w1 ≤ 0.25, 0 ≤ w1 ≤ 0.24, 0 ≤ w1 ≤ 0.23, 0 ≤ w1 ≤ 0.22, 0 ≤ w1 ≤ 0.21, 0 ≤ w1 ≤ 0.2, 0 ≤ w1 ≤ 0.15, 0 ≤ w1 ≤ 0.1 or 0 ≤ w1 ≤ 0.09.

[0050] The layered lithium nickel manganese composite oxide may not include cobalt or may include a small amount of cobalt such that, based on the total metal content excluding lithium of 100 mol%, the cobalt content may be about 0 mol% to about 0.01 mol%.

[0051] Coating

[0052] The first positive electrode active material may include: core particles including a layered lithium nickel manganese composite oxide; and a coating located on the surface of the core particles and including Al, B, Mg, Ti, V, W, Y, Zr, or a combination thereof. As an example, the core particles of the first positive electrode active material may include Al, Zr, or a combination thereof, and the coating of the first positive electrode active material may include Al. This may be the optimal coating component in the first positive electrode active material and may further improve the capacity characteristics and cycle life characteristics at high voltages.

[0053] When the battery is operated under high voltage or high temperature conditions, the layered lithium nickel manganese composite oxide is prone to chemical erosion from the components in the electrolyte. Therefore, side reactions with the electrolyte may occur, resulting in an increase in the amount of gas generation and thus deteriorating the battery cycle life and safety. However, these problems can be solved by introducing a coating according to an embodiment of the present disclosure.

[0054] Since layered lithium nickel manganese composite oxides and oxides with different compositions (such as lithium nickel cobalt manganese composite oxides, lithium nickel cobalt aluminum composite oxides, lithium cobalt oxides, etc.) may have significantly different residual lithium contents on the particle surfaces and different properties, it may not be possible to form a satisfactory and uniform coating in the form of a film by conventional coating methods. However, in some embodiments, a uniform coating can be introduced onto the first positive electrode active material by the following method: (i) First, adding salts of coating raw materials to an aqueous solvent and then mixing them to prepare a coating solution in which the salts of coating raw materials are completely dissolved by a molten salt method, (ii) mixing the coating solution with core particles for coating, and (iii) removing the solvent, then drying and heat-treating the residue. This method is a molten salt wet coating method and a pre-addition method of first dissolving salts of coating raw materials and then adding active material particles (i.e., core particles) thereto. By this method, a coating can be successfully formed as a uniform thin film on the surface of the layered lithium nickel manganese composite oxide.

[0055] Compared with conventional dry methods or post-addition wet methods, in the coating method according to the present disclosure, the content of coating elements on the surface of the first positive electrode active material can be further increased. For example, when measured using EP-EDS analysis, based on the total metal content of about 100 at% on the surface excluding lithium, the content 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 ranges, the coating can effectively improve the high-voltage characteristics without increasing the resistance of the positive electrode active material.

[0056] The coating can be in the form of a film continuously surrounding the surface of the core particles, for example, in the form of a shell surrounding the entire surface of the core particles. This is different from the coating structure in which a part of the surface of the core particles is coated. According to some embodiments, the coating can be formed to completely cover the surface of the core particles and have a very thin and uniform thickness, improving the structural stability of the positive electrode active material without increasing the resistance or deteriorating the capacity, effectively suppressing side reactions with the electrolyte, and reducing the gas generation amount. Therefore, long cycle life characteristics under high voltage and high temperature conditions can be achieved.

[0057] According to this method, the coating of the first positive electrode active material may have a thickness of 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 meets these thickness ranges, the structural stability of the positive electrode active material can be improved without increasing the resistance or reducing the capacity due to the coating, and side reactions with the electrolyte can be suppressed. The thickness of the coating can be measured by scanning electron microscopy (SEM), transmission electron microscopy (TEM), time-of-flight secondary ion mass spectrometry (TOF-SIMS), X-ray photoelectron spectroscopy (XPS), or energy-dispersive X-ray spectrometer (EDS) analysis. For example, the thickness of the coating can also be measured by EDS line profile analysis of the cross-section of the positive electrode active material.

[0058] According to some embodiments, the thickness of the coating can be thin and uniform, 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%. Herein, the deviation of the coating thickness refers to the deviation of the coating thickness in one positive electrode active material particle. For example, the deviation of the coating thickness can be calculated as follows: measure the thickness at about 10 points in the electron microscope image of the cross-section of a single positive electrode active material particle to calculate the arithmetic mean, then divide the arithmetic mean by the absolute value of the difference between a measured data and the arithmetic mean, and multiply by 100%. The fact that the deviation or standard deviation of the coating thickness meets the above range means that a coating with a uniform thickness is formed as a film on the surface of the core particle of the positive electrode active material. Accordingly, the structural stability of the positive electrode active material is improved, side reactions with the electrolyte can be effectively suppressed, and the increase in resistance or reduction in capacity caused by the coating can be minimized.

[0059] Based on the total metal content other than lithium in 100 mol% of the first positive electrode active material, depending on the type of coating element, the content of the coating element changes, but can be about 0.01 mol% to about 5 mol%, for example, about 0.05 mol% to about 3 mol% or about 0.1 mol% to about 2 mol%.

[0060] If an Al coating is introduced, based on the total metal content other than lithium in 100 mol% of the first positive electrode active material, the Al content 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%.

[0061] The Al coating may, for example, include a layered aluminum compound such as aluminum oxide, lithium aluminum oxide (a specific example thereof being LiAlO₂), or a combination thereof.

[0062] Second positive electrode active material

[0063] The second positive electrode active material includes a lithium-rich manganese composite oxide (LMR), and the second positive electrode active material is in the form of single particles, wherein the molar ratio of lithium to the total metal content excluding lithium is about 1.1 to about 3, and the manganese content based on 100 mol% of the total metal content excluding lithium is greater than or equal to about 60 mol%. Herein, the single particles may have a spherical shape, an ellipsoidal shape, a plate shape, an irregular shape, or a combination thereof.

[0064] As an LMR material which is a layered positive electrode active material including excessive lithium and a relatively high amount of manganese, high capacity is achieved by applying a new principle of oxygen redox and traditional capacity is achieved by the redox of transition metals. Due to the high proportion of low-cost manganese, the LMR material can be a super-low-cost and next-generation positive electrode active material.

[0065] In the second positive electrode active material, the molar ratio of lithium to the total metal content excluding lithium may be about 1.1 to about 3, for example, about 1.2 to about 2.5, about 1.3 to about 2.3, or about 1.5 to about 2.1. Additionally, in the second positive electrode active material, based on 100 mol% of the total metal content excluding lithium, the manganese content may be greater than or equal to about 60 mol%, for example, about 60 mol% to about 90 mol%, about 60 mol% to about 80 mol%, about 60 mol% to about 75 mol%, about 60 mol% to about 70 mol%, or about 62 mol% to about 68 mol%.

[0066] The lithium-rich manganese composite oxide of the second positive electrode active material may be represented, for example, by Chemical Formula 2.

[0067] [Chemical Formula 2]

[0068] Li 1+x2 (Ni y2 Mn z2 M 2 1-y2-z2 ) 1-x2 O 2-b2 X b2

[0069] In Chemical Formula 2, 0.04 ≤ x₂ ≤ 0.5, 0.1 ≤ y₂ ≤ 0.5, 0.5 ≤ z₂ ≤ 0.9, 0.9 ≤ y₂ + z₂ ≤ 1.1, and 0 ≤ b₂ ≤ 0.1, M 2is one or more elements selected from Al, 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.

[0070] Moreover, in Chemical Formula 2, 0.05 ≤ x2 ≤ 0.4 or 0.06 ≤ x2 ≤ 0.3, 0.2 ≤ y2 ≤ 0.4, and 0.6 ≤ z2 ≤ 0.8 or 0.3 ≤ y2 ≤ 0.4 and 0.6 ≤ z2 ≤ 0.7.

[0071] The second positive electrode active material may be in the form of single particles, and the average particle diameter (D 50 ) of the second positive electrode active material may be smaller than the average particle diameter of the first positive electrode active material and may be, for example, about 0.1 μm to about 5 μm, about 0.5 μm to about 4 μm, or about 1 μm to about 3 μm.

[0072] In the lithium-manganese-rich composite oxide of the second positive electrode active material, based on the total metal content excluding lithium of 100 mol%, the cobalt content may be about 0 mol% to about 0.01 mol%.

[0073] The second positive electrode active material may have a surface residual lithium content of less than or equal to about 0.3 wt%, for example, less than or equal to about 0.2 wt%, less than or equal to about 0.1 wt%, or about 0.001 wt% to about 0.1 wt%. This may be different from high-nickel materials having a nickel content exceeding about 70 mol%.

[0074] In X-ray diffraction analysis (XRD), the second positive electrode active material may have about or greater, for example, about or greater, about or greater, or about to about a lattice constant. For example, the positive electrode active material may have an a lattice constant greater than or equal to about . Additionally, the ratio of the c lattice constant to the a lattice constant may be less than or equal to about 4.968, for example, less than or equal to about 4.965, less than or equal to about 4.960, or about 4.955 to about 4.965. If the a lattice constant of the positive electrode active material and the ratio of the c lattice constant to the a lattice constant respectively satisfy this range, the problem of voltage drop during charging and discharging caused by the second positive electrode active material can be effectively prevented, the energy density can be increased, and the capacity characteristics and cycle life characteristics in the high-voltage region can be improved.

[0075] Powder tap density

[0076] The positive electrode active material according to some embodiments may have a high powder tap density. For example, the powder tap density of the positive electrode active material layer may be about 3.0 g / cc to about 3.7 g / cc, such as about 3.0 g / cc to about 3.5 g / cc, about 3.0 g / cc to about 3.3 g / cc, or about 3.0 g / cc to about 3.2 g / cc. A rechargeable lithium battery applying such a positive electrode active material can achieve a high energy density.

[0077] The powder tap density can be measured by the following method. Weigh the positive electrode active material, and put 3 g of the material into a mold (with an area of about 1.298 cm 2 . Then, slowly insert a die rod into the mold body. After placing the mold in a hydraulic press and pressing it with a pressure of about 4 tons (metric tons) for about 30 seconds, measure its height to obtain the powder tap density.

[0078] Positive electrode

[0079] In some embodiments, the positive electrode includes a positive electrode current collector and a positive electrode active material layer on the positive electrode current collector, wherein the positive electrode active material layer includes the aforementioned positive electrode active material. In addition to the aforementioned positive electrode active material, the positive electrode active material layer may further include other types of positive electrode active materials. Additionally, the positive electrode active material layer may optionally include a binder, a conductive material, or a combination thereof.

[0080] According to some embodiments, the loading level of the positive electrode active material layer may be about 10 mg / cm 2 to about 40 mg / cm 2 , such as about 10 mg / cm 2 to about 30 mg / cm 2 or about 10 mg / cm 2 to about 20 mg / cm 2 . Additionally, the density (mixing density) of the positive electrode active material layer in the finally pressed positive electrode may be about 3.0 g / cc to about 3.7 g / cc, such as about 3.0 g / cc to about 3.5 g / cc, about 3.0 g / cc to about 3.3 g / cc, or about 3.0 g / cc to about 3.2 g / cc. When applying the positive electrode active material according to some embodiments, such a loading level and mixing density of the positive electrode active material layer are facilitated, and such a loading level and mixing density of the positive electrode active material layer satisfy the positive electrode within the above range suitable for implementing a high-capacity, high-energy density rechargeable lithium battery.

[0081] Binder

[0082] The binder improves the binding characteristics of the positive electrode active material particles to each other and the binding characteristics of the positive electrode active material particles to the positive electrode current collector. Examples of binders that can be used in embodiments include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resins, (meth)acrylic resins, polyester resins, and nylon.

[0083] Conductive material

[0084] It includes a conductive material to provide electrode conductivity, and any conductive material can be used as the conductive material unless it causes a chemical change. Examples of conductive materials 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); or mixtures thereof.

[0085] Based on 100 wt% of the positive electrode active material layer, the content of each of the binder and the conductive material can be about 0.5 wt% to about 5 wt%.

[0086] The positive electrode current collector may include, but is not limited to, Al foil, etc.

[0087] Rechargeable lithium battery

[0088] Some embodiments provide a rechargeable lithium battery that 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).

[0089] Depending on the shape, the rechargeable lithium battery can be classified into a cylindrical battery, a prismatic battery, a pouch battery, a coin-shaped battery, etc. Figures 1 to 4 For a schematic diagram showing a rechargeable lithium battery according to some embodiments, wherein Figure 1 a cylindrical battery is shown, Figure 2 a prismatic battery is shown, and Figure 3 and Figure 4 a pouch battery is shown. Referring to Figures 1 to 4 , the rechargeable lithium battery 100 includes an electrode assembly 40 and a housing 50 that houses the electrode assembly 40. The electrode assembly 40 has a separator 30 inserted between the positive electrode 10 and the negative electrode 20. The positive electrode 10, the negative electrode 20, and the separator 30 can be impregnated with an electrolyte solution (not shown). AsFigure 1 As shown, 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 Figure 3 and Figure 4 shown, the rechargeable lithium battery 100 includes electrode tabs 70 that serve as a circuit path for guiding the current formed in the electrode assembly 40 to the outside, that is, a positive electrode tab 71 and a negative electrode tab 72.

[0090] The rechargeable lithium battery according to some embodiments may be rechargeable at a high voltage or suitable for driving at a high voltage, and exhibits improved characteristics under high voltage conditions.

[0091] The rechargeable lithium battery includes a second positive electrode active material rich in lithium manganese. In order to utilize the reversible positive electrode capacity of the second positive electrode active material, the initial charge must be performed at an upper limit voltage greater than or equal to about 4.60 V, for example, about 4.65 V (i.e., the initial charge upper limit voltage). Although the subsequent charge is performed at a voltage lower than the initial upper limit voltage (i.e., the subsequent charge upper limit voltage), the rechargeable lithium battery according to some embodiments designed to be driven in the high voltage region can be charged within a voltage range greater than or equal to about 4.45 V. For example, after the second cycle, the charge voltage may be greater than or equal to about 4.45 V, such as about 4.45 V to about 4.6 V, about 4.45 V to about 4.55 V, or about 4.45 V to about 4.50 V. By applying the positive electrode active material according to some embodiments, even when charging at a high voltage, the rechargeable lithium battery can significantly reduce the amount of gas generated and can achieve high capacity and long cycle life characteristics.

[0092] Negative electrode

[0093] The negative electrode may include a negative electrode current collector and a negative electrode active material layer on the negative electrode current collector and including a negative electrode active material, and the negative electrode active material layer may further include a binder, a conductive material, or a combination thereof.

[0094] Negative electrode active material

[0095] 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.

[0096] Materials capable of reversibly embedding / desorbing lithium ions may include, for example, crystalline carbon, amorphous carbon, or a combination thereof as carbonaceous negative electrode active materials. The crystalline carbon may be natural graphite or artificial graphite that is irregular, flaky, sheet-like, spherical, or fibrous. The amorphous carbon may be soft carbon, hard carbon, mesophase pitch carbonization products, calcined coke, etc.

[0097] Lithium metal alloys include alloys of lithium with metals selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn.

[0098] Materials capable of doping / dedoping lithium may be Si-based negative electrode active materials or Sn-based negative electrode active materials. The Si-based negative electrode active materials may include silicon, silicon-carbon composites, SiO x (0 < x ≤ 2), Si-Q alloys (where Q is an element selected from the following: alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements (excluding Si), Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof, for example, Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof) or combinations thereof. The Sn-based negative electrode active materials may be Sn, SnO x (0 < x ≤ 2) (for example, SnO2), Sn alloys, or combinations thereof.

[0099] The silicon-carbon composite may be a composite of silicon and amorphous carbon. The average particle size (D 50 ) of the silicon-carbon composite particles may be, for example, about 0.5 μm to about 20 μm. According to some embodiments, the silicon-carbon composite may be in the form of silicon particles and amorphous carbon coated on the surface of the silicon particles. For example, the silicon-carbon composite 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 the amorphous carbon matrix.

[0100] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include: a core including crystalline carbon and silicon particles and an amorphous carbon coating on the surface of the core. The amorphous carbon may include soft carbon, hard carbon, mesophase pitch carbonization products, and / or calcined coke.

[0101] When the silicon-carbon composite includes silicon and amorphous carbon, based on 100 wt% of the silicon-carbon composite, the content of silicon can be about 10 wt% to about 50 wt%, and the content of amorphous carbon can be about 50 wt% to about 90 wt%. Additionally, when the silicon-carbon composite includes silicon, amorphous carbon, and crystalline carbon, based on 100 wt% of the silicon-carbon composite, the content of silicon can be about 10 wt% to about 50 wt%, the content of crystalline carbon can be about 10 wt% to about 70 wt%, and the content of amorphous carbon can be about 20 wt% to about 40 wt%.

[0102] Additionally, the thickness of the amorphous carbon coating can be about 5 nm to about 100 nm. The average particle size (D 50 ) of the silicon particles (primary particles) can be about 10 nm to about 1 μm or about 10 nm to about 200 nm. The silicon particles can exist alone as silicon, in the form of a silicon alloy, or in an oxidized form of silicon. The oxidized form of silicon can be represented by SiO x (0 < x ≤ 2). The atomic content ratio of Si:O indicating the degree of oxidation can be about 99:1 to about 33:67.

[0103] 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. 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 can be a weight ratio of about 1:99 to about 90:10. The negative electrode includes at least one of a carbon-based negative electrode active material, lithium metal, a lithium metal alloy, a transition metal oxide, a tin-based negative electrode active material, and a silicon-based negative electrode active material.

[0104] Binder

[0105] The binder is used to bond the negative electrode active material particles to each other and is also used to bond the negative electrode active material to the negative electrode current collector. The binder can be a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0106] 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, or a combination thereof.

[0107] The aqueous binder can include styrene-butadiene rubber, (meth)acrylate esterified styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, poly(ethylene oxide), polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, or a combination thereof.

[0108] When an aqueous binder is used as a binder in the negative electrode active material layer, a cellulose compound capable of imparting viscosity may be further included. As the cellulose compound, one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and its alkali metal salts may be mixed and used. The alkali metal may be Na, K, or Li.

[0109] 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, or a combination thereof.

[0110] Conductive material

[0111] A conductive material is included to provide electrode conductivity, and any conductive material may be used as the conductive material unless it causes a chemical change. Examples of the conductive material include: 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 of copper, nickel, aluminum, silver, etc.; conductive polymers (such as polyphenylene derivatives); or mixtures thereof.

[0112] Based on 100 wt% of the negative electrode active material layer, the content 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 of the binder may be about 0.5 wt% to about 5 wt%. For example, the negative electrode active material layer may include about 90 wt% to about 99 wt% of the negative electrode active material, about 0.5 wt% to about 5 wt% of the binder, and about 0.5 wt% to about 5 wt% of the conductive material.

[0113] Current collector

[0114] 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.

[0115] Electrolyte

[0116] The electrolyte for the rechargeable lithium battery may be an electrolyte solution that may include a non - aqueous organic solvent and a lithium salt.

[0117] 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, or combinations thereof.

[0118] The carbonate solvents may include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc. The ester solvents may include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, caprolactone, etc. The ether solvents may include dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, ethylene glycol dimethyl ether, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. Additionally, the ketone solvents may include cyclohexanone, etc. The alcohol solvents may include ethanol, isopropanol, etc. The aprotic solvents may include nitriles (such as, R-CN, where R is a C2-C20 straight-chain hydrocarbon group, branched-chain hydrocarbon group, 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.

[0119] The non-aqueous organic solvent can be used alone or as a mixture of two or more types, and when using a mixture of two or more types, the mixing ratio can be appropriately adjusted according to the desired battery performance, which is widely known to those skilled in the art.

[0120] When using carbonate solvents, cyclic carbonates and chain carbonates can be mixed and used, and the cyclic carbonate and the chain carbonate can be mixed in a volume ratio of about 1:1 to about 1:9.

[0121] The non-aqueous organic solvent may further include aromatic hydrocarbon organic solvents. For example, the carbonate solvent and the aromatic hydrocarbon organic solvent can be mixed in a volume ratio of about 1:1 to about 30:1 and used.

[0122] The electrolyte solution may further include vinylene ethylene carbonate, vinylene carbonate, or ethylene carbonate compounds to improve the battery cycle life.

[0123] 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.

[0124] Lithium salts dissolved in non-aqueous organic solvents supply lithium ions in a battery, ensuring the basic operation of rechargeable lithium batteries and improving the transport of lithium ions between the positive electrode and the negative electrode. Examples of lithium salts 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).

[0125] The concentration of the lithium salt can be in the range of about 0.1 M to about 2.0 M. When the concentration of the lithium salt is within this range, the electrolyte solution has appropriate ionic conductivity and viscosity. Therefore, excellent performance can be achieved and lithium ions can move effectively.

[0126] Separator

[0127] Depending on the type of rechargeable lithium battery, a separator may be present between the positive electrode and the negative electrode. The separator may include a polyethylene separator, a polypropylene separator, a polyvinylidene fluoride separator, or a multilayer film of two or more 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.).

[0128] The separator may include a porous substrate and a coating on one or two surfaces of the porous substrate, and the coating includes an organic material, an inorganic material, or a combination thereof.

[0129] 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.

[0130] The porous substrate may have a thickness of about 1 μm to about 40 μm, for example, about 1 μm to about 30 μm, about 1 μm to about 20 μm, about 5 μm to about 15 μm, or about 10 μm to about 15 μm.

[0131] The organic material may include a (meth)acrylic copolymer, which includes a first structural unit and a second structural unit. The first structural unit is derived from (meth)acrylamide, and the second structural unit includes 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.

[0132] The inorganic material may include inorganic particles selected from the following: Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof, but not limited thereto. The average particle size (D 50 ) of the inorganic particles may be about 1 nm to about 2000 nm, for example, about 100 nm to about 1000 nm or about 100 nm to about 700 nm.

[0133] The organic material and the inorganic material may be mixed in a single coating or may exist in the form of a stack of a coating including the organic material and a coating including the inorganic material. The thickness of the coating may be about 0.5 μm to about 20 μm, for example, about 1 μm to about 10 μm or about 1 μm to about 5 μm.

[0134] Embodiments and comparative examples of the present disclosure are described below. However, the following embodiments are only embodiments of the present disclosure, and the present disclosure is not limited to the following embodiments.

[0135] Example 1

[0136] 1. Preparation of positive electrode active material

[0137] (1) Preparation of first positive electrode active material

[0138] Ni 0.75 Mn 0.23 Al 0.02 (OH)2 and LiOH are mixed at a molar ratio of 1:1.05 and then initially heat-treated in an oxygen atmosphere at 845 °C for 8 hours to prepare a layered lithium nickel manganese composite oxide in the form of secondary particles having a composition of Li 1.05 Ni 0.75 Mn 0.23 Al 0.02 O2 and an average particle size (D 50 ) of about 14 μm.

[0139] Aluminum sulfate was added to a distilled water solvent, and then stirred at about 350 rpm for about 5 minutes to prepare a coating solution. It was confirmed that the salt was completely dissolved in the coating solution, which became colorless and transparent. Subsequently, 500 g of layered lithium nickel manganese composite oxide was added to the coating solution over 1.5 minutes while continuously stirring the coating solution, and then further stirred for about 45 minutes. Herein, based on the total metal content other than lithium of 100 mol% in the final large particles, the aluminum content in the aluminum sulfate was designed to be 1.0 mol%. After completion of stirring, it was confirmed that the supernatant had a pH of 5.5. After removing the solvent from the mixed solution using a suction pump and a filter press, a coated product was obtained by vacuum drying at 190 °C.

[0140] The coated product was secondarily heat-treated in an oxygen atmosphere at 825 °C for 8 hours to prepare a first positive electrode active material.

[0141] Figure 5 and Figure 6 The SEM image of the first positive electrode active material is shown.

[0142] (2) Preparation of second positive electrode active material

[0143] Ni 0.25 Mn 0.75 (OH)2 and LiOH were mixed to have an Li / (Ni + Mn) molar ratio of about 1.5, and then heat-treated in an oxygen atmosphere at 950 °C for 24 hours to prepare a second positive electrode active material in the form of single particles having an average particle diameter (D 50 ) of about 2 μm and including a lithium-rich manganese composite oxide (Li 1.5 Ni 0.25 Mn 0.75 O2).

[0144] Figure 7 and Figure 8 The SEM image showing the second positive electrode active material is shown.

[0145] (3) Preparation of final positive electrode active material

[0146] 95 wt% of the first positive electrode active material and 5 wt% of the second positive electrode active material were mixed to prepare a final positive electrode active material.

[0147] 2. Manufacture of rechargeable lithium battery single cell

[0148] 98.5 wt% of the prepared final positive electrode active material, 1.0 wt% of a polyvinylidene fluoride binder, and 0.5 wt% of a carbon nanotube conductive material were mixed to prepare a positive electrode active material layer slurry, and the slurry was coated on an aluminum foil current collector and then dried and pressed to fabricate a positive electrode.

[0149] Mix 97.5 wt% of graphite negative electrode active material, 1.5 wt% of carboxymethyl cellulose, and 1 wt% of styrene-butadiene rubber in an aqueous solvent to prepare a negative electrode active material layer slurry. Coat the negative electrode active material layer slurry on a copper foil current collector, and then dry and press it to fabricate a negative electrode.

[0150] Use a polytetrafluoroethylene separator, and 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 used to fabricate a rechargeable lithium battery cell.

[0151] Example 2

[0152] Fabricate the positive electrode active material and the rechargeable lithium battery cell in substantially the same manner as in Example 1, except that 90 wt% of the first positive electrode active material and 10 wt% of the second positive electrode active material are mixed to obtain the final positive electrode active material.

[0153] Example 3

[0154] Fabricate the positive electrode active material and the rechargeable lithium battery cell in substantially the same manner as in Example 1, except that 85 wt% of the first positive electrode active material and 15 wt% of the second positive electrode active material are mixed to obtain the final positive electrode active material.

[0155] Example 4

[0156] Fabricate the positive electrode active material and the rechargeable lithium battery cell in substantially the same manner as in Example 1, except that 80 wt% of the first positive electrode active material and 20 wt% of the second positive electrode active material are mixed to obtain the final positive electrode active material.

[0157] Example 5

[0158] Fabricate the positive electrode active material and the rechargeable lithium battery cell in substantially the same manner as in Example 1, except that 75 wt% of the first positive electrode active material and 25 wt% of the second positive electrode active material are mixed to obtain the final positive electrode active material.

[0159] Example 6

[0160] Fabricate the positive electrode active material and the rechargeable lithium battery cell in substantially the same manner as in Example 1, except that 70 wt% of the first positive electrode active material and 30 wt% of the second positive electrode active material are mixed to obtain the final positive electrode active material.

[0161] Example 7

[0162] The positive electrode active material and the rechargeable lithium battery cell were fabricated in substantially the same manner as in Example 1, except that 65 wt% of the first positive electrode active material and 35 wt% of the second positive electrode active material were mixed to obtain the final positive electrode active material.

[0163] Example 8

[0164] The positive electrode active material and the rechargeable lithium battery cell were fabricated in substantially the same manner as in Example 1, except that 60 wt% of the first positive electrode active material and 40 wt% of the second positive electrode active material were mixed to obtain the final positive electrode active material.

[0165] Example 9

[0166] The positive electrode active material and the rechargeable lithium battery cell were fabricated in substantially the same manner as in Example 1, except that 55 wt% of the first positive electrode active material and 45 wt% of the second positive electrode active material were mixed to obtain the final positive electrode active material.

[0167] Comparative Example 1

[0168] 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 alone was used as the final positive electrode active material.

[0169] Comparative Example 2

[0170] 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 second positive electrode active material alone was used as the final positive electrode active material.

[0171] The manufacturing methods of Examples 1 to 9, Comparative Example 1 and Comparative Example 2 are each shown in Table 1.

[0172] (Table 1)

[0173]

[0174] Evaluation Example 1: Mixed density of positive electrode active material layer

[0175] The mixing density according to the pressing strength of each of the positive electrode active material layers prepared in Examples 1 to 9, Comparative Example 1 and Comparative Example 2 was measured, and the results are shown in Table 2.

[0176] (Table 2)

[0177] Mixed density (g / cc) Example 1 3.15 Example 2 3.19 Example 3 3.23 Example 4 3.30 Example 5 3.37 Example 6 3.45 Example 7 3.41 Example 8 3.31 Example 9 3.26 Comparative Example 1 3.10 Comparative Example 2 2.95

[0178] As shown in Table 2, the positive electrode active material layers of Examples 1 to 9 exhibit a higher mixing density than those of the comparative examples.

[0179] Evaluation Example 2: Evaluation of single cell performance

[0180] The rechargeable lithium battery cells of Examples 1 to 9 and Comparative Examples 1 and 2 were initially charged at 4.65 V and then charged at 4.45 V by reducing the voltage. More specifically, the rechargeable lithium battery cells of Examples 1 to 9 and Comparative Examples 1 and 2 were charged at a constant current of 0.2 C to 4.65 V at 25°C, then held at that voltage until the current became 0.05 C, and then discharged at a constant current of 0.2 C to 2.5 V to perform the first charge and discharge. Subsequently, the battery cells were charged at a constant current of 0.2 C to 4.45 V at 25°C, then held at that voltage until the current became 0.05 C, and then discharged at a constant current of 0.2 C to 2.5 V to perform the second charge and discharge. In Table 3, the second discharge capacity is provided as the "4.45 V capacity".

[0181] Subsequently, at 45°C, the battery cells were repeatedly charged and discharged at 1.0 C within a voltage range of 3.0 V to 4.45 V at least 50 times to calculate the ratio of the 50th cycle discharge capacity to the second discharge capacity, which is provided as the "4.45 V cycle life" in Table 3.

[0182] Then, at 25°C, the battery cells were charged and discharged at a rate of 0.2 C / 0.2 C within a voltage range of 3.0 V to 4.45 V to calculate the energy density. The energy density was obtained by using the following calculation equation: {driving voltage (V) × capacity (Ah) / battery cell weight (kg)}, where the capacity was calculated by multiplying the positive electrode weight (g) by the discharge capacity (mAh / g).

[0183] (Table 3)

[0184]

[0185] As shown in Table 3, compared with Comparative Examples 1 and 2, Examples 1 to 9 exhibit the same or improved cycle life characteristics and high energy density, which confirms the improved use of the positive electrode. However, compared with Examples 1 to 9, Comparative Example 2 exhibits a high energy density. However, as in Evaluation Example 1 above, Comparative Example 2 has the disadvantage of a very low mixing density. Accordingly, compared with the rechargeable lithium battery cells of Comparative Examples 1 and 2, the rechargeable lithium battery cells of Examples 1 to 9 have been greatly improved overall.

[0186] Although the present disclosure has been described in connection with exemplary embodiments presently regarded as practical, it is to be understood that the invention is not limited to the disclosed embodiments. On the contrary, the invention is intended to cover various modifications and equivalent arrangements.

Claims

1. A positive electrode active material, comprising: A first positive electrode active material, comprising a layered lithium nickel manganese composite oxide, wherein the first positive electrode active material is in the form of secondary particles in which a plurality of primary particles are aggregated; and A second positive electrode active material, comprising a lithium and manganese-rich composite oxide, wherein a molar ratio of lithium to a total metal content other than lithium in the lithium and manganese-rich composite oxide is 1.1 to 3, and based on 100 mol% of the total metal content other than lithium in the lithium and manganese-rich composite oxide, a manganese content is greater than or equal to 60 mol%, and the second positive electrode active material is in the form of single particles.

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, an amount of the first positive electrode active material included is 30 wt% to 95 wt%, and an amount of the second positive electrode active material included is 5 wt% to 70 wt%.

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

4. The positive electrode active material according to claim 1, wherein based on 100 mol% of the total metal content other than lithium in the layered lithium nickel manganese composite oxide, the layered lithium nickel manganese composite oxide further comprises aluminum in an amount greater than or equal to 0 mo1% and less than or equal to 3 mol%.

5. The positive electrode active material according to claim 4, wherein the aluminum is uniformly distributed in the layered lithium nickel manganese composite oxide.

6. The positive electrode active material according to claim 1, wherein based on 100 mol% of the total metal content other than lithium in the layered lithium nickel manganese composite oxide, a cobalt content in the layered lithium nickel manganese composite oxide 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 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 , 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 average particle diameter D of the first positive electrode active material 50 is from 10 μm to 25 μm.

9. The positive electrode active material according to claim 1, wherein the first positive electrode active material comprises a core particle and a coating on a surface of the core particle, the core particle is in the form of secondary particles in which a plurality of primary particles are aggregated, and the coating comprises Al. The positive electrode active material according to claim 1, wherein the lithium and manganese-rich composite oxide of the second positive electrode active material is represented by Chemical Formula 2: Chemical Formula 2 Li 1+x2 (Ni y2 Mn z2 M 2 1-y2-z2 ) 1-x2 O 2-b2 X b2 , Among them, In Chemical Formula 2, 0.04 ≤ x2 ≤ 0.5, 0.1 ≤ y2 ≤ 0.5, 0.5 ≤ z2 ≤ 0.9, 0.9 ≤ y2 + z2 ≤ 1.1, and 0 ≤ b2 ≤ 0.1, M 2 is one or more elements selected from Al, 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.

11. The positive electrode active material according to claim 1, wherein based on 100 mol% of the total metal content other than lithium in the lithium and manganese-rich composite oxide, a cobalt content is 0 mol% to 0.01 mol%.

12. The positive electrode active material according to claim 1, wherein the average particle diameter D of the second positive electrode active material 50 is from 0.1 μm to 5 μm.

13. The positive electrode active material according to claim 1, wherein the average particle size D of the second positive electrode active material 50 is smaller than the average particle size D of the first positive electrode active material 50 .

14. A positive electrode, comprising: A positive electrode current collector, and The positive electrode active material layer on the positive electrode current collector includes the positive electrode active material according to any one of claims 1 to 13.

15. The positive electrode according to claim 14, wherein the mixed density of the positive electrode active material layer is 3.0 g / cc to 3.7 g / cc.

16. A rechargeable lithium battery, comprising: the positive electrode according to claim 14 or 15, a negative electrode, and an electrolyte.

17. The rechargeable lithium battery according to claim 16, wherein the initial charging upper limit voltage is greater than or equal to 4.60 V, and wherein the subsequent charging upper limit voltage is less than the initial charging upper limit voltage, and the subsequent charging upper limit voltage is greater than or equal to 4.45 V.

18. The rechargeable lithium battery according to claim 16, wherein the negative electrode includes at least one of a carbon-based negative electrode active material, a lithium metal, a lithium metal alloy, a transition metal oxide, a tin-based negative electrode active material, and a silicon-based negative electrode active material.

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