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 single particle. 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 a total metal content other than lithium of 100 mol% based on the total metal content other than lithium of 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 - 0014282, filed with the Korean Intellectual Property Office on January 30, 2024, the entire content of which is 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 have used rechargeable lithium batteries with high energy density and 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 - size, 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 the remaining cobalt reserves are not large, 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 a single particle; 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 50 mol%, and the second positive electrode active material is in the form of a single particle.

[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 due to the high powder compaction density, high energy density and long cycle life characteristics can be achieved. 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] In this document, terms are used only to describe embodiments and 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 exclude the possibility of 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 are used to label 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 from 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 method or by transmission electron microscope images or scanning electron microscope images. Alternatively, it can be measured by using dynamic light scattering method, 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

[0029] ,

[0028] , , , 50 , 50 , ,

[0030] ) 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 a single particle. The positive electrode active material further includes: a second positive electrode active material including a lithium-rich manganese composite oxide, 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 50 mol%, and the second positive electrode active material is in the form of a single particle.

[0033] The positive electrode active material does not include expensive cobalt or contains only a very small amount of cobalt and low-cost manganese. Therefore, the cost is reduced, and large-scale production can be increased. Additionally, 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 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 that can be included is about 30 wt% to about 95 wt%, for example, about 35 wt% to about 90 wt% or about 40 wt% to about 90 wt%. The amount of the second positive electrode active material that can be included is about 5 wt% to about 70 wt%, for example, about 10 wt% to about 65 wt% or about 10 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 has a reduced cobalt content. Among the alternatives, due to the small amount of lithium available in the structure, 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 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 a 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 a single particle. The single particle may have a spherical shape, an ellipsoidal shape, a plate shape, an irregular shape, or a combination thereof.

[0039] The average particle size (D 50 ) of the first positive electrode active material may be from about 0.5 μm to about 8 μm, for example, from about 1 μm to about 7 μm or from about 1 μm to about 5 μm. As used herein, unless otherwise limited, the average particle size (D 50 ) means the diameter of the particle having a cumulative volume of 50% by volume in the particle size distribution obtained by randomly measuring the sizes (diameter or major axis length) of about 20 particles in the scanning electron microscope image of the positive electrode active material.

[0040] In the layered lithium nickel manganese-based composite oxide, based on the total metal content other than lithium of 100 mol%, the nickel content may be greater than or equal to about 50 mol%, for example, about 50 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 satisfies the above range, high capacity can be achieved even when the cobalt content is reduced, and the structural stability can be increased.

[0041] Based on the total metal content other than lithium in the layered lithium nickel manganese composite oxide at 100 mol%, the manganese content can be, for example, 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 satisfies 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 advantageously maintains a stable layered structure even when the cobalt element is excluded from the structure. Based on the total metal content other than lithium in the layered lithium nickel manganese composite oxide at 100 mol%, 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 mo1% 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 satisfies the above range, a stable layered structure can be maintained even when cobalt is excluded, the problem of structural collapse due to charging and discharging 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 the particles including the layered lithium nickel manganese composite oxide can 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, that is, the aluminum is uniformly distributed in the layered lithium nickel manganese composite oxide. This can 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 oxide, thereby synthesizing the layered lithium nickel manganese composite oxide (for example, lithium nickel manganese aluminum composite oxide) using a nickel manganese aluminum composite hydroxide as the precursor. 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 simultaneously.

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

[0045] [Chemical Formula 1]

[0046] Lia1 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, in which case 0.6 ≤ x1 ≤ 0.8, 0.1 ≤ y1 ≤ 0.39, 0.01 ≤ z1 ≤ 0.03, and 0 ≤ w1 ≤ 0.29 may be satisfied, or, for example, 0.6 ≤ x1 ≤ 0.8, 0.1 ≤ y1 ≤ 0.39, 0.01 < z1 ≤ 0.03, and 0 ≤ w1 ≤ 0.29 may be satisfied.

[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 from about 0 mol% to about 0.01 mol%.

[0051] Coating

[0052] The first positive electrode active material may include: a core particle including a layered lithium nickel manganese composite oxide, and a coating located on the surface of the core particle and including Al, B, Mg, Ti, V, W, Y, Zr, or a combination thereof. As an example, the coating of the first positive electrode active material may include Al, Y, or a combination of Al and Y. In the first positive electrode active material, based on the total metal content other than lithium of 100 mol%, the Al content may be about 0.1 mol% to about 3.0 mol%, and in the first positive electrode active material, based on the total metal content other than lithium of 100 mol%, the Y content may be about 0.01 mol% to about 0.5 mol%. This may be the optimal coating composition 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 liable to suffer chemical erosion from components in the electrolyte. Accordingly, 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 the layered lithium nickel manganese composite oxide may have significantly different residual lithium contents and different characteristics on the surfaces of particles from oxides with different compositions (such as lithium nickel cobalt manganese composite oxides, lithium nickel cobalt aluminum composite oxides, lithium cobalt oxides, etc.), it may be impossible to form a satisfactory uniform film-like coating 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 the core particles for coating, and (iii) removing the solvent and then drying and heat-treating the residue. This method is a molten salt wet coating method and is a pre-addition method in which salts of coating raw materials are first dissolved and then active material particles (i.e., core particles) are added 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-added wet methods, in the coating method according to the present disclosure, the content of the coating element 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% excluding lithium on the surface, the content of the coating element 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 partial 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 the side reaction with the electrolyte, and reducing the gas generation amount. Therefore, the 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 can 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 the side reaction with the electrolyte can be suppressed. The thickness of the coating can be measured by, for example, 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, and 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 a 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 in a single 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 measurement data and 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 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 the decrease 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 varies, 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 about 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 can, for example, include layered aluminum compounds such as aluminum oxide, lithium aluminum oxide (e.g., LiAlO2), or a combination thereof.

[0062] Second positive electrode active material

[0063] The second positive electrode active material includes a lithium-manganese-rich composite oxide, in which the molar ratio of lithium to the total metal content other than lithium is about 1.1 to about 3 and the manganese content based on 100 mol% of the total metal content other than lithium is greater than or equal to about 50 mol%, and the second positive electrode active material is in the form of a single particle. In this context, the single particle can 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 oxidation-reduction 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 other than lithium can 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 other than lithium, the content of manganese can be greater than or equal to about 50 mol%, for example, about 50 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-manganese-rich composite oxide of the second positive electrode active material can 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 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.

[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 can be in the form of single particles, and the average particle size (D 50) may be smaller than the average particle size 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 as the a lattice constant. For example, the positive electrode active material may have an a lattice constant greater than or equal to about In addition, 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, problems 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, for example, 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 using 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 then put 3 g of the material into a mold (about 1.298 cm 2in the area), and the die rod is slowly inserted into the die body. After placing the die in a hydraulic press and then pressing it with a pressure of about 4 tons (metric tons) for about 30 seconds, its height is measured to obtain the powder compaction 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, where 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 ~ about 40 mg / cm 2 , for example, about 10 mg / cm 2 ~ about 30 about mg / cm 2 or about 10 mg / cm 2 ~ 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 beneficial, 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 rechargeable lithium battery with high capacity and high energy density.

[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 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)acrylate esterified styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, and nylon, but are not limited thereto.

[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 chemical changes. Examples of the conductive material can 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 can include Al foil, etc., but is not limited thereto.

[0087] Rechargeable lithium battery

[0088] Some embodiments provide a rechargeable lithium battery, which includes the aforementioned positive electrode, negative electrode, and electrolyte. As an example, the rechargeable lithium battery can 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). As Figure 1 shown, the rechargeable lithium battery 100 can include a sealing member 60 that seals the housing 50. Additionally, in Figure 2 , the rechargeable lithium battery 100 can include a positive electrode lead tab 11, a positive electrode terminal 12, a negative electrode lead tab 21, and a negative electrode terminal 22. As Figure 3 and Figure 4 shown, the rechargeable lithium battery 100 includes electrode tabs 70 that serve as a circuit path for guiding the current formed in the electrode assembly 40 to the outside, i.e., a positive electrode tab 71 and a negative electrode tab 72.

[0090] A rechargeable lithium battery according to some embodiments can be recharged at a high voltage or is 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 material, wherein in order to utilize the reversible positive electrode capacity of the second positive electrode active material, an initial charge must be performed at an upper limit voltage (i.e., initial charge upper limit voltage) greater than or equal to about 4.60 V, for example, about 4.65 V. Although subsequent charging is performed at a voltage lower than the initial upper limit voltage (i.e., subsequent charge upper limit voltage), the rechargeable lithium battery according to some embodiments designed to be driven in a 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 charging voltage can 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] The material that reversibly intercalates / deintercalates lithium ions may include, for example, crystalline carbon, amorphous carbon, or a combination thereof as a carbon-based negative electrode active material. The crystalline carbon can be natural graphite or artificial graphite that is irregular, flaky, sheet-like, spherical, or fibrous. The amorphous carbon can be soft carbon, hard carbon, mesophase pitch carbonization product, calcined coke, etc.

[0097] 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.

[0098] The material capable of doping / dedoping lithium can be a Si-based negative electrode active material or a Sn-based negative electrode active material. The Si-based negative electrode active material may include silicon, a silicon-carbon composite, SiO x(0 < x ≤ 2), Si-Q alloy (where Q is an element selected from 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 material can be Sn, SnO x (0 < x ≤ 2) (e.g., SnO2), Sn alloy, or combinations thereof.

[0099] The silicon-carbon composite can be a composite of silicon and amorphous carbon. The average particle size (D 50 ) of the silicon-carbon composite particles can be, for example, about 0.5 μm to about 20 μm. According to some embodiments, the silicon-carbon composite can be in the form of silicon particles and amorphous carbon coated on the surface of the silicon particles. For example, the silicon-carbon composite can include secondary particles (cores) in which silicon primary particles are aggregated and an amorphous carbon coating (shell) on the surface of the secondary particles. Amorphous carbon can also be present between the silicon primary particles. For example, the silicon primary particles can be coated with amorphous carbon. The secondary particles can be dispersed in the amorphous carbon matrix.

[0100] The silicon-carbon composite can further include crystalline carbon. For example, the silicon-carbon composite can include: a core including crystalline carbon and silicon particles and an amorphous carbon coating on the surface of the core. The amorphous carbon can 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 as silicon alone, in the form of a silicon alloy, or in an oxidized form of silicon. The oxidized form of silicon can be SiO xIt is represented by (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] Si-based negative electrode active material or Sn-based negative electrode active material can be mixed with carbon-based negative electrode active material. When mixing and using Si-based negative electrode active material or Sn-based negative electrode active material with 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 carbon-based negative electrode active material, lithium metal, lithium metal alloy, transition metal oxide, tin-based negative electrode active material, and 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, polyethylene oxide, polyvinylpyrrolidone, epichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene-propylene-diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, or a combination thereof.

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

[0109] The dry binder can be a polymer material capable of becoming fibers and can be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0110] Conductive material

[0111] 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 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); or mixtures thereof.

[0112] Based on 100 wt% of the negative electrode active material layer, the content of the negative electrode active material can 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 can be about 0.5 wt% to about 5 wt%. For example, the negative electrode active material layer can 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 can 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 can be in the form of a foil, sheet, or foam. The thickness of the negative electrode current collector can 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 a rechargeable lithium battery can be an electrolyte solution that can 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 can include carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, aprotic solvents, or combinations thereof.

[0118] 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, ethylene glycol dimethyl ether, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. Additionally, ketone solvents may include cyclohexanone, etc. Alcohol solvents may include ethanol, isopropanol, etc. 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 solvents 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 at a volume ratio of about 1:1 to about 1:9.

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

[0122] The electrolyte solution can 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 both 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, polyether imides, polyamide imides, polybenzimidazoles, polyether sulfones, 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 from about 1 nm to about 2000 nm, for example, from about 100 nm to about 1000 nm or from about 100 nm to about 700 nm.

[0133] The organic material and the inorganic material may be mixed in one coating or may exist in the form of a stack of a coating including the organic material and a coating including the inorganic material.

[0134] The thickness of the coating may be from about 0.5 μm to about 20 μm, for example, from about 1 μm to about 10 μm or from about 1 μm to about 5 μm.

[0135] 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.

[0136] Example 1

[0137] 1. Preparation of positive electrode active material

[0138] (1) Preparation of first positive electrode active material

[0139] Ni 0.75 Mn 0.25 (OH)2, LiOH, and Al2O3 are mixed so that the molar ratio of (Ni + Mn):Li:Al is 1:1:0.02, and then, it is first heat-treated at 845 °C for 8 hours in an oxygen atmosphere to prepare a layered lithium nickel manganese composite oxide in the form of single particles having a composition of LiNi 0.75 Mn 0.23 Al 0.02 O2 and having an average particle size (D 50 ) of about 3 μm.

[0140] Aluminum sulfate and yttrium nitrate were added to a distilled water solvent and mixed, and then layered lithium nickel manganese composite oxide was added and mixed for about 45 minutes. Here, based on the total metal content excluding lithium in 100 mol% of the final small particles, the aluminum content of aluminum sulfate was designed to be 0.4 mol%, and the yttrium content of yttrium nitrate was designed and mixed to be 0.05 mol%. The solvent was removed from the mixed solution, dried at 190 °C, and then heat-treated at 825 °C for 8 hours in an oxygen atmosphere to prepare a first positive electrode active material.

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

[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 at 950 °C for 24 hours in an oxygen atmosphere to prepare a second positive electrode active material in the form of single particles with an average particle size (D 50 ) of about 2 μm, including a lithium-rich manganese composite oxide (Li 1.5 Ni 0.25 Mn 0.75 O2).

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

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

[0146] 90 wt% of the first positive electrode active material and 10 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 cell

[0148] 98.5 wt% of the prepared final positive electrode active material, 1.0 wt% of polyvinylidene fluoride binder, and 0.5 wt% of 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 manufacture a positive electrode.

[0149] 97.5 wt% of graphite negative electrode active material, 1.5 wt% of carboxymethyl cellulose, and 1 wt% of styrene butadiene rubber were mixed in an aqueous solvent to prepare a negative electrode active material layer slurry. The negative electrode active material layer slurry was coated on a copper foil current collector, and then dried and pressed to manufacture a negative electrode.

[0150] An electrolyte solution using a polytetrafluoroethylene diaphragm and prepared by dissolving 1M LiPF6 in a mixed solvent of ethylene carbonate and dimethyl carbonate with a volume ratio of 3:7 is used to manufacture a rechargeable lithium battery cell.

[0151] Example 2

[0152] The positive electrode active material and the rechargeable lithium battery cell are manufactured 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.

[0153] Example 3

[0154] The positive electrode active material and the rechargeable lithium battery cell are manufactured 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.

[0155] Example 4

[0156] The positive electrode active material and the rechargeable lithium battery cell are manufactured 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 are mixed to obtain the final positive electrode active material.

[0157] Example 5

[0158] The positive electrode active material and the rechargeable lithium battery cell are manufactured in substantially the same manner as in Example 1, except that 50 wt% of the first positive electrode active material and 50 wt% of the second positive electrode active material are mixed to obtain the final positive electrode active material.

[0159] Example 6

[0160] The positive electrode active material and the rechargeable lithium battery cell are manufactured in substantially the same manner as in Example 1, except that 40 wt% of the first positive electrode active material and 60 wt% of the second positive electrode active material are mixed to obtain the final positive electrode active material.

[0161] Comparative Example 1

[0162] 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 is used alone as the final positive electrode active material.

[0163] Comparative Example 2

[0164] The positive electrode active material and the rechargeable lithium battery cell were manufactured in substantially the same manner as in Example 1, except that the second positive electrode active material was used alone as the final positive electrode active material.

[0165] The manufacturing methods of Examples 1 to 6 and Comparative Examples 1 and 2 are shown in Table 1.

[0166] (Table 1)

[0167]

[0168] Evaluation Example 1: Mixed density of positive electrode active material layer

[0169] The mixing density according to the pressing strength of each of the positive electrode active material layers manufactured in Examples 1 to 6 and Comparative Examples 1 and 2 was measured, and the results are shown in Table 2.

[0170] (Table 2)

[0171] Mixed density (g / cc) Example 1 3.07 Example 2 3.06 Example 3 3.05 Example 4 3.03 Example 5 3.01 Example 6 3.00 Comparative Example 1 3.08 Comparative Example 2 2.95

[0172] As shown in Table 2, the mixing density of the positive electrode active material layers manufactured according to Examples 1 to 6 is higher than that of the positive electrode active material layer of Comparative Example 2. In the case of Comparative Example 1, the mixing density is higher than that of Examples 1 to 6. However, as can be seen in Evaluation Example 2 described below, the 4.45V capacity of Comparative Example 1 is very low. Therefore, overall, the rechargeable lithium battery cells manufactured in Examples 1 to 6 are further improved compared to the rechargeable lithium battery cells manufactured in Comparative Examples 1 and 2.

[0173] Evaluation Example 2: Evaluation of battery cell performance )

[0174] The rechargeable lithium battery cells of Examples 1 to 6 and Comparative Examples 1 and 2 were initially charged at 4.65V, and then charged at 4.45V by reducing the voltage. More specifically, the rechargeable lithium battery cells of Examples 1 to 6 and Comparative Examples 1 and 2 were charged at a constant current of 0.2C to 4.65V at 25°C, then held at this voltage until the current became 0.05C, and then discharged at a constant current of 0.2C to 2.5V, thereby performing the first charge and discharge. Subsequently, the battery cells were charged at a constant current of 0.2C to 4.45V at 25°C, then held at this voltage until the current became 0.05C, and then discharged at a constant current of 0.2C to 2.5V, thereby performing the second charge and discharge. In Table 3, the second discharge capacity is provided as the "4.45V capacity".

[0175] Subsequently, at 45°C, the battery cell was repeatedly charged and discharged at 1.0C within a voltage range of 3.0V to 4.45V for at least 50 times to calculate the ratio of the 50th cycle discharge capacity to the second discharge capacity, which is provided as "4.45V cycle life" in Table 3.

[0176] Then, at 25°C, the battery cell was charged and discharged at a rate of 0.2C / 0.2C within a voltage range of 3.0V to 4.45V to calculate the energy density. The energy density was obtained 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).

[0177] (Table 3)

[0178]

[0179] As shown in Table 3, in the cases of Examples 1 to 6, the capacity and cycle life characteristics were improved compared to Comparative Example 1, and the utilization rate of the positive electrode was improved due to the high energy density. In the case of Comparative Example 2, the energy density was higher than that of Examples 1 to 6. However, as seen in Evaluation Example 1 above and Evaluation Example 3 below, the mixed density was low and the gas generation amount was large. Therefore, overall, the rechargeable lithium battery cells manufactured in Examples 1 to 6 were improved compared to the rechargeable lithium battery cells manufactured in Comparative Examples 1 and 2.

[0180] Evaluation Example 3: Evaluation of gas generation amount after storage at 80°C

[0181] The rechargeable lithium battery cells manufactured in Examples 1 to 6 and Comparative Examples 1 and 2 were manufactured as 4.4V level 30mAh battery cells, placed at 80°C for 30 days, and the gas generation amount (cc / g) on the 30th day was measured using residual gas analysis (RGA) and shown in Table 4.

[0182] (Table 4)

[0183] Gas generation amount (cc / g, 80°C, 30th day) Example 1 12.5 Example 2 12.7 Example 3 12.8 Example 4 13.5 Example 5 14.0 Example 6 13.9 Comparative Example 1 12.1 Comparative Example 2 14.2

[0184] Referring to Table 4, in the cases of Examples 1 to 6 (using a positive electrode active material including a first positive electrode active material in the form of single particles and a second positive electrode active material in the form of single particles), the gas generation amount during high-temperature storage was reduced compared to Comparative Example 2.

[0185] 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 included within the spirit and scope of the appended claims.

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 single particles; And A second positive electrode active material, comprising a lithium-manganese-rich composite oxide, wherein the molar ratio of lithium to the total metal content other than lithium in the lithium-manganese-rich composite oxide is 1.1 to 3, and based on the total metal content other than lithium of 100 mol% of the lithium-manganese-rich composite oxide, the manganese content is greater than or equal to 50 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 the 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 included is 30 wt% to 95 wt%, and the 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 the total metal content other than lithium of 100 mol% of the layered lithium nickel manganese composite oxide, the nickel content of the layered lithium nickel manganese composite oxide is 60 mol% to 80 mol%, and the manganese content is greater than or equal to 10 mol%.

4. The positive electrode active material according to claim 1, wherein based on the total metal content other than lithium of 100 mol% of 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 the total metal content other than lithium of 100 mol% of the layered lithium nickel manganese composite oxide, the 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 0.5 μm to 8 μm.

9. The positive electrode active material according to claim 1, wherein the first positive electrode active material comprises a core particle in the form of single particles and a coating on the surface of the core particle, and the coating comprises Al, Y, or a combination of Al and Y.

10. The positive electrode active material according to claim 1, wherein the lithium-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 the total metal content other than lithium of 100 mol% of the lithium-manganese-rich composite oxide, the 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 0.1 μm to 5 μm.

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

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

15. The positive electrode according to claim 14, wherein the mixing 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 lower 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 comprises 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.

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