Positive electrode active material, and rechargeable lithium battery and all-solid-state rechargeable battery including same

Abstract

The invention relates to a positive electrode active material, and a rechargeable lithium battery and an all-solid-state rechargeable battery including the same. The positive electrode active material includes: a first positive electrode active material including a first lithium-manganese-rich composite oxide in which a molar ratio of lithium to total metals other than lithium is 1.06-1.2, and a manganese content based on 100 mol% of the total metals other than lithium in the first lithium-manganese-rich composite oxide is 30 mol% or more; and a second positive electrode active material including a second lithium-manganese-rich composite oxide in which the molar ratio of lithium to the total metal other than lithium is greater than 1.2 and less than or equal to 2, the manganese content based on 100 mol% of the total metal content other than lithium in the second lithium-manganese-rich composite oxide is greater than or equal to 30 mol%, and the second positive electrode active material includes a second lithium-manganese-rich composite oxide in which the molar ratio of lithium to the total metal other than lithium is greater than 1.2 and less than or equal to 2. And an average particle diameter of the second positive electrode active material is smaller than an average particle diameter of the first positive electrode active material.

Description

Technical Field

[0001] A positive electrode active material, a rechargeable lithium battery including the positive electrode active material, and a all-solid-state rechargeable battery are disclosed. Background Art

[0002] 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 to carry as a driving power source. Also, research has been conducted on using rechargeable lithium batteries with high energy density as a driving power source or a power storage source for hybrid vehicles or electric vehicles.

[0003] Various positive electrode active materials have been studied to realize rechargeable lithium batteries for different uses. Among them, lithium nickel-based oxides, lithium nickel manganese cobalt-based composite oxides, lithium nickel cobalt aluminum-based composite oxides, and lithium cobalt-based oxides are most commonly used as positive electrode active materials. However, although the demand for large-sized rechargeable lithium batteries with high capacity or high energy density has recently increased, the supply of positive electrode active materials containing rare metal cobalt is expected to be severely short. And because cobalt is expensive and the remaining reserves are not much, it is necessary to develop positive electrode active materials that exclude cobalt or reduce its content. Summary of the Invention

[0004] Some embodiments provide a lithium-rich manganese positive electrode active material having a high capacity and improved packing density, ensuring high capacity per unit volume and long cycle life characteristics. A rechargeable lithium battery can be provided with the lithium-rich manganese positive electrode active material.

[0005] In some embodiments, the positive electrode active material includes: a first positive electrode active material including a first lithium-rich manganese composite oxide, wherein (i) the molar ratio of lithium to the total metal other than lithium in the first lithium-rich manganese composite oxide is about 1.06 to about 1.2, and (ii) the manganese content of the first lithium-rich manganese composite oxide based on 100 mol% of the total metal content other than lithium in the first lithium-rich manganese composite oxide is greater than or equal to about 30 mol%; and a second positive electrode active material including a second lithium-rich manganese composite oxide, (i) wherein the molar ratio of lithium to the total metal other than lithium in the second lithium-rich manganese composite oxide is greater than about 1.2 and less than or equal to about 2, (ii) wherein the manganese content of the second lithium-rich manganese composite oxide based on 100 mol% of the total metal content other than lithium in the second lithium-rich manganese composite oxide is greater than or equal to about 30 mol%, and (iii) the average particle size (D 50 ) of the second positive electrode active material is smaller than the average particle size (D 50 ) of the first positive electrode active material.

[0006] In some embodiments, a rechargeable lithium battery is provided, which includes a positive electrode including a positive electrode active material, a negative electrode, and an electrolyte.

[0007] The positive electrode active material according to some embodiments maximizes the capacity while minimizing the production cost. The positive electrode active material also minimizes the disadvantage of the low density of the lithium-rich manganese positive electrode active material while maintaining the advantage of high capacity, thereby providing high capacity and high density, and achieving high capacity per unit volume and excellent high-temperature cycle life characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figures 1 to 4 A schematic diagram showing a rechargeable lithium battery according to some embodiments.

[0009] Figure 5 A graph showing the capacity retention rate according to the number of cycles for evaluating the cycle life characteristics of a battery cell including the mixed positive electrode active material of Example 1, a battery cell including only the first positive electrode active material of Example 1, and a battery cell including only the second positive electrode active material of Example 1.

[0010] <DESCRIPTION OF REFERENCE NUMERALS>

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

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

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

[0014] 22: Negative electrode terminal 30: Separator

[0015] 40: Electrode assembly 50: Housing

[0016] 60: Sealing member 70: Electrode tab

[0017] 71: Positive electrode tab 72: Negative electrode tab DETAILED DESCRIPTION

[0018] 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 implemented in many different forms and is not limited to the example embodiments set forth herein.

[0019] Terms are used herein only to describe embodiments and do not necessarily limit the present disclosure. Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0020] 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.

[0021] As used herein, terms such as "comprises", "includes", or "have" are intended to indicate the presence of a specific feature, quantity, step, element, or a combination thereof, but they do not preclude the possibility of the presence or addition of one or more other features, quantities, steps, elements, or a combination thereof.

[0022] In the drawings, for clarity, the thickness of layers, films, panels, regions, etc. is 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 there may also be intervening elements. 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), there are no intervening elements.

[0023] In addition, "layer" as used 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.

[0024] The average particle size can be measured by methods well known to those skilled in the art, for example, by a particle size analyzer, by a transmission electron microscope image, or by a scanning electron microscope image. Optionally, the average particle size value can be obtained by: using the dynamic light scattering method, performing data analysis, counting the number of particles in each particle size range, and calculating therefrom. Unless otherwise defined, the average particle size (D 50 ) means the diameter of the particle at which the cumulative volume in the particle size distribution is 50% by volume. As used herein, when no other limitation is provided, the average particle size (D 50 ) means the diameter of the particle at which the cumulative volume in the particle size distribution is 50% by volume, obtained by randomly measuring the sizes (diameter or major axis length) of about 20 particles in a scanning electron microscope image.

[0025] As used herein, "or" is not construed in an exclusive sense. For example, "A or B" is construed to include A, B, A + B, etc.

[0026] "Metal" is construed to include the concepts of common metals, transition metals, and metalloids (semi-metals).

[0027] Positive electrode active material

[0028] In some embodiments, the positive electrode active material includes: a first positive electrode active material including a first lithium-rich manganese composite oxide, wherein the molar ratio of lithium to the total metal other than lithium in the first lithium-rich manganese composite oxide is about 1.06 to about 1.2 and the manganese content of the first lithium-rich manganese composite oxide based on 100 mol% of the total metal other than lithium in the first lithium-rich manganese composite oxide is greater than or equal to about 30 mol%; and a second positive electrode active material including a second lithium-rich manganese composite oxide, wherein the molar ratio of lithium to the total metal other than lithium in the second lithium-rich manganese composite oxide is greater than about 1.2 and less than or equal to about 2 and the manganese content of the second lithium-rich manganese composite oxide based on 100 mol% of the total metal other than lithium in the second lithium-rich manganese composite oxide is greater than or equal to about 30 mol%, and the average particle size (D 50 ) of the second positive electrode active material is less than the average particle size (D 50 ) of the first positive electrode active material.

[0029] The positive electrode active material according to some embodiments is a lithium-rich manganese (LMR) positive electrode active material (hereinafter, may be simply referred to as "LMR material"), and may also be represented as including a lithium-rich manganese composite oxide. The LMR material is a layered positive electrode active material including an excessive amount of lithium and including manganese in a relatively high relative content, and has a high capacity due to the new principle of oxygen oxidation-reduction (O-redox) and the capacity through conventional transition metal oxidation-reduction. The LMR material also has a high proportion of low-cost manganese, and thus is an ultra-low-cost next-generation positive electrode active material. The LMR material can be defined as a composite oxide having a layered structure, which specifically has a molar ratio of lithium to the total metal other than lithium greater than about 1 and less than or equal to about 2, and a manganese content greater than or equal to about 30 mol% based on about 100 mol% of the total metal other than lithium. The LMR material excessively includes lithium, and thus has different characteristics from conventional layered positive electrode active materials and a different composition applicable to the new mechanism of O-redox.

[0030] Because the LMR material has a higher proportion of lithium and manganese than conventional layered positive electrode active materials, as the proportion of LiCoO with a high theoretical volume density (packing density, about 4.9 g / cc) 2 and the proportion of LiNiO with a high theoretical volume density (about 4.6 g / cc) 2 decrease, while the proportion of LiMnO with a low theoretical volume density (about 4.04 g / cc) 2 and the proportion of Li 2 MnO 3As the proportion increases, although showing a high capacity (mAh / g), the LMR material has a lower volume density than the conventional layered positive electrode active material, which results in a decrease in the total energy density (Wh / L).

[0031] Some embodiments of the present disclosure relate to new positive electrode active materials that can prevent the low volume density of LMR materials while also maintaining a high capacity. The positive electrode active materials according to some embodiments can not only be low-cost, economical, and mass-producible, but also have a high capacity according to the oxidation-reduction of oxygen, and also exhibit an increased volume density. Therefore, they have an improved capacity per unit volume. Accordingly, a rechargeable lithium battery applying the positive electrode active material can be installed in an electric vehicle or a hybrid vehicle to achieve long-distance driving. According to some embodiments, compared with the positive electrode active material composed of a single type, the positive electrode active material in which the first positive electrode active material and the second positive electrode active material are mixed can exhibit an improved volume density while maintaining a high capacity, thereby maximizing the advantages of the LMR material.

[0032] Based on a total of 100 wt% of the first positive electrode active material and the second positive electrode active material, the amount of the first positive electrode active material included can be greater than about 50 wt% and less than about 100 wt%. For example, it can be about 60 wt% to about 95 wt%, about 70 wt% to about 95 wt%, or about 80 wt% to about 90 wt%. Also based on 100 wt% of the first positive electrode active material and the second positive electrode active material, the amount of the second positive electrode active material included can be greater than about 0 wt% and less than about 50 wt%. For example, it can be about 5 wt% to about 40 wt%, about 5 wt% to about 30 wt%, or about 10 wt% to about 20 wt%. When mixed in these proportions, the energy density can be maximized while having a high capacity, and the cycle life characteristics can be improved.

[0033] The first positive electrode active material can be in the form of particles having an average particle size (D 50 ) larger than the average particle size (D 50 ) of the second positive electrode active material. The average particle size (D 50 ) of the first positive electrode active material can be greater than or equal to about 5 μm. For example, it can be greater than or equal to about 5 μm and less than or equal to about 20 μm, about 6 μm to about 15 μm, or about 7 μm to about 12 μm. The first positive electrode active material can be in the form of secondary particles made by aggregating a plurality of primary particles.

[0034] The second positive electrode active material can be in the form of particles having an average particle size (D 50 ) smaller than the average particle size (D 50 ) of the first positive electrode active material, and the second positive electrode active material can be represented as small particles. The average particle size (D50 ) may be less than or equal to about 7 μm. For example, it may be greater than or equal to about 1 μm and less than or equal to about 7 μm, greater than or equal to about 1 μm and less than about 7 μm, greater than or equal to about 1 μm and less than or equal to about 6.5 μm, be about 2 μm to about 6.5 μm, or about 3 μm to about 6 μm. The second positive electrode active material may be in the form of secondary particles made by aggregating a plurality of primary particles, may be single particles, or may be a mixture thereof. When the second positive electrode active material is in the form of single particles, the cycle life characteristics and cycle stability can be improved.

[0035] The single particles can exist alone, without grain boundaries within the particles, consist of one particle, and can be referred to as single particles, monolithic structures, integral structures, or non-aggregated particles, where the particles do not aggregate with each other but exist as independent phases morphologically. Further, the particles can be represented as single particles, integral particles, or single crystals. For example, they can be represented as single crystals. The single particles can exist alone, or the single particles can aggregate together. For example, 2 to 10 single particles can aggregate and contact each other.

[0036] Since the first positive electrode active material is an LMR material and corresponds to large particles, in some embodiments, the amounts of Mn and Li that reduce the volume density in the first positive electrode active material are minimized to improve the volume density of the entire positive electrode active material, and O-redox is less used to improve the cycle life characteristics and stability of the positive electrode active material.

[0037] The second positive electrode active material is also an LMR material and corresponds to small particles. And despite the low volume density of the second electrode active material, the second positive electrode active material can play a role in increasing the total capacity and improving the cycle life characteristics, and it can minimize the pores by being located in the voids of the large particles, thereby maintaining the density. In some embodiments, the proportion of Mn in the second positive electrode active material can be increased to reduce the material cost.

[0038] The first lithium-rich manganese composite oxide of the first positive electrode active material may have a molar ratio of lithium in the first lithium-rich manganese composite oxide to the total metal other than lithium in the first lithium-rich manganese composite oxide in the range of greater than or equal to about 1.06 and less than or equal to about 1.2 (e.g., greater than about 1.06 and less than or equal to about 1.2, greater than or equal to about 1.1 to less than or equal to about 1.2, greater than about 1.1 and less than or equal to about 1.2, or greater than or equal to about 1.1 and less than or equal to about 1.15). The second lithium-rich manganese composite oxide of the second positive electrode active material may have a molar ratio of lithium in the second lithium-rich manganese composite oxide to the total metal other than lithium in the second lithium-rich manganese composite oxide in the range of greater than about 1.2 to less than or equal to about 2 (e.g., greater than about 1.2 to less than or equal to about 1.8, greater than about 1.2 to less than or equal to about 1.5, greater than or equal to 1.25 to less than or equal to about 1.5, or greater than or equal to about 1.3 and less than or equal to about 1.45). In the large particles of the first positive electrode active material (hereinafter, may be simply referred to as "the first positive electrode active material" or "large particles"), lithium is applied thereto in excess of the metal, but at the minimum content to minimize the deterioration of the volume density of the active material. Also, the O-redox ratio is reduced to suppress gas generation and metal dissolution and to improve the average voltage drop (voltage decay). In the small particles of the second positive electrode active material (hereinafter, may be simply referred to as "the second positive electrode active material" or "small particles"), the lithium content may be further increased according to the application of O-redox to maintain a high capacity. In other words, the first positive electrode active material and the second positive electrode active material are designed to have the above-mentioned molar ratio of lithium to the total metal other than lithium to increase the discharge capacity (mAh / g) and the volume density (g / cc) simultaneously, and thus, improve the capacity per unit volume (mAh / cc), thereby increasing the energy density (Wh / L), and further improving the cycle life characteristics.

[0039] In an embodiment of the present disclosure, based on the total metal content of about 100 mol% excluding lithium in the first lithium-rich manganese composite oxide, the first lithium-rich manganese composite oxide of the first positive electrode active material may have a nickel content of about 45 mol% or higher, and based on the total metal content of about 100 mol% excluding lithium in the second lithium-rich manganese composite oxide, the second lithium-rich manganese composite oxide of the second positive electrode active material may have a nickel content of less than about 45 mol%. In other words, the first positive electrode active material may be a medium-nickel LMR material with a medium nickel content, and the second positive electrode active material may be a low-nickel LMR material with a relatively low nickel content. By increasing the Ni content while decreasing the Mn content, the deterioration of the volume density caused by the large particles of the first positive electrode active material can be minimized. By using less O-redox, gas generation and metal dissolution can be suppressed, and the average voltage drop problem can be solved. By decreasing the Ni content and increasing the Mn content, the cost of the small particles of the second positive electrode active material is reduced while maintaining the advantages of LMR with high capacity.

[0040] Based on the total of 100 mol% of nickel and manganese in the first lithium-rich manganese composite oxide, the first lithium-rich manganese composite oxide of the first positive electrode active material may have a nickel content greater than or equal to about 45 mol% (e.g., 45 mol% to 70 mol%) and a manganese content less than or equal to about 55 mol% (e.g., 30 mol% to 55 mol%). Specifically, a nickel content of about 45 mol% to about 65 mol% and a manganese content of about 35 mol% to about 55 mol%, or a nickel content of about 50 mol% to about 60 mol% and a manganese content of about 40 mol% to about 50 mol% may be used.

[0041] Based on the total of 100 mol% of nickel and manganese in the second lithium-rich manganese composite oxide, the second lithium-rich manganese composite oxide of the second positive electrode active material may have a nickel content of about 10 mol% to less than about 45 mol% and a manganese content greater than about 55 mol% to about 90 mol%. Specifically, a nickel content of about 20 mol% to less than about 45 mol% and a manganese content greater than about 55 mol% to about 80%, or a nickel content of about 25 mol% to about 40 mol% and a manganese content of about 60 mol% to about 75% may be used.

[0042] The first positive electrode active material and the second positive electrode active material are designed to have the Ni ratio and Mn ratio as described above to simultaneously increase the initial discharge capacity (mAh / g) and the volume density (g / cc), and thus improve the capacity per unit volume (mAh / cc), thereby enhancing the cycle life characteristics.

[0043] In the entire mixture of the first positive electrode active material and the second positive electrode active material, the molar ratio of lithium to the total metal other than lithium may be about 1.1 to about 1.3, for example, about 1.1 to about 1.2. Additionally, based on the total 100 mol% of nickel and manganese in the above entire mixture, the nickel content may be about 35 mol% to about 65 mol% or about 40 mol% to about 55 mol%, and the manganese content may be about 35 mol% to about 65 mol% or about 45 mol% to about 60 mol%.

[0044] The first lithium-rich manganese composite oxide of the first positive electrode active material may include, for example, at least one of the metal oxides represented by Chemical Formula 1 and Chemical Formula 2.

[0045] [Chemical Formula 1]

[0046] Li 1+x1 (Ni y1 Mn z1 M 1 1-y1-z1 ) 1-x1 O 2-b1 X 1 b1

[0047] In Chemical Formula 1, 0.03 ≤ x1 ≤ 0.09, 0.45 ≤ y1 ≤ 0.7, 0.3 ≤ z1 ≤ 0.55, and 0 ≤ b1 ≤ 0.1, M 1 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 1 is one or more elements selected from F, P, and S.

[0048] [Chemical Formula 2]

[0049] (1 - x2)(LiNi y2 Mn z2 M 2 1-y2-z2 O 2-b2 X 2 b2 ) + x2(Li 2 (Mn t1 M 2 1-t1 )O 3-b3 X 2 b3 )

[0050] In Chemical Formula 2, 0.06 ≤ x2 ≤ 0.2, 0.5 ≤ y2 ≤ 1.0, 0 ≤ z2 ≤ 0.5, 0 ≤ b2 ≤ 0.1, 0.9 ≤ t1 ≤ 1, and 0 ≤ b3 ≤ 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 2 is one or more elements selected from F, P, and S.

[0051] Chemical formula 1 represents a solid solution phase and chemical formula 2 represents a composite phase. The first lithium-rich manganese composite oxide can be, for example, a combination of the solid solution phase represented by chemical formula 1 and the composite phase represented by chemical formula 2 at room temperature. In this case, it includes both the solid solution phase and the composite phase, and can be, for example, a material in which the composite phase and the solid solution phase are mixed, or a material in which the composite phase and the solid solution phase coexist. The oxygen in the structure of the first lithium-rich manganese composite oxide is relatively stable, so there are fewer structural changes caused by oxygen defects during the charging and discharging processes, and the problem of voltage drop caused by oxygen generation and structural deterioration is effectively solved.

[0052] The second lithium-rich manganese composite oxide of the second positive electrode active material can be represented by at least one of chemical formula 3 and chemical formula 4. Chemical formula 3 represents a solid solution phase and chemical formula 4 represents a composite phase. As an example, the second lithium-rich manganese composite oxide can be represented by chemical formula 4.

[0053] [Chemical formula 3]

[0054] Li 1+x3 (Ni y3 Mn z3 M 3 1-y3-z3 ) 1-x3 O 2-b4 X 3 b4

[0055] In chemical formula 3, 0.09 < x3 ≤ 0.33, 0.1 ≤ y3 < 0.45, 0.55 < z3 ≤ 0.9, and 0 ≤ b4 ≤ 0.1, M 3 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 3 is one or more elements selected from F, P, and S.

[0056] [Chemical formula 4]

[0057] (1 - x4)(LiNi y4 Mn z4 M 4 1-y4-z4 O 2-b5 X 4 b5 ) + x4(Li 2 (Mnt2 M 4 1-t2 )O 3-b6 X 4 b6 )]

[0058] In Chemical Formula 4, 0.2 < x4 ≤ 1, 0.5 ≤ y4 ≤ 1.0, 0 ≤ z4 ≤ 0.5, 0 ≤ b5 ≤ 0.1, 0.9 ≤ t2 ≤ 1 and 0 ≤ b6 ≤ 0.1, M 4 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 4 is one or more elements selected from F, P, and S.

[0059] In each of the first lithium-rich manganese composite oxide and the second lithium-rich manganese composite oxide, the cobalt content based on the total metal content excluding lithium of 100 mol% may be about 0 mol% to about 1 mol%, about 0 mol% to about 0.1 mol%, or about 0 mol% to about 0.01 mol%.

[0060] The difference between the average particle diameter (D 50 ) of the first positive electrode active material and the average particle diameter (D 50 ) of the second positive electrode active material may be less than or equal to about 6 μm. In conventional layered positive electrode active materials (such as lithium nickel composite oxides, lithium cobalt oxides, etc.), many attempts have been made to increase the energy density by mixing large particles and small particles. However, in these attempts, whether the difference in the average particle diameter is large or small has no significant effect on the resistance or other performance parameters. However, in the LMR materials according to some embodiments, if the difference in the average particle diameter between the large particles and the small particles is too large (for example, greater than about 6 μm), the capacity may deteriorate, or at least no increase in capacity occurs due to the mixing of the large particles and the small particles. It should be understood that as the resistance difference between the large particles and the small particles increases, ions flow in the direction of lower resistance. Accordingly, in some embodiments, the large particles and the small particles are designed to have an average particle diameter difference of less than or equal to about 6 μm to maximize the capacity and also improve the bulk density.

[0061] The value obtained by subtracting the average particle diameter (D 50 ) of the second positive electrode active material from the average particle diameter (D 50 ) of the first positive electrode active material may be, for example, about 1 μm to about 6 μm, about 2 μm to about 5 μm, or about 2.5 μm to about 4.5 μm. By adjusting the difference in the average particle diameter between the large particles and the small particles within these ranges, high capacity can be achieved, and the energy density can be improved by providing an increased bulk density.

[0062] The positive electrode active material according to some embodiments can achieve a high pellet density. For example, the pellet density of the positive electrode active material can be greater than or equal to about 2.9 g / cc, for example, about 2.9 g / cc to about 3.7 g / cc, about 2.9 g / cc to about 3.6 g / cc, or about 2.9 g / cc to about 3.5 g / cc. A rechargeable lithium battery using such a positive electrode active material can have a high energy density. The pellet density can be measured by the following method. Weigh the positive electrode active material, put 3 g of the positive electrode active material into a mold with an area of about 1.298 cm 2 and slowly insert the die rod into the mold body. After placing the mold set in a hydraulic press and pressing it with a pressure of about 3.3 tons (metric tons) for about 30 seconds, measure its height to obtain the pellet density.

[0063] Determined by X-ray diffraction analysis (XRD), the first positive electrode active material as large particles can have a lattice constant a greater than or equal to about greater than or equal to about or about to about For example, the lattice constant a of the first positive electrode active material can be greater than or equal to about In addition, the ratio of the lattice constant c of the first positive electrode active material to the lattice constant a of the first positive electrode active material can be less than or equal to about 4.968, less than or equal to about 4.960, and can be about 4.955 to about 4.965. When the first positive electrode active material with the lattice constant a and the ratio of the lattice constant c to the lattice constant a within these ranges is applied, the energy density can be effectively improved by maintaining the packing density of the LMR material.

[0064] The first positive electrode active material and the second positive electrode active material can each have a surface residual lithium content of less than or equal to about 0.3 wt%, 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% based on their total weight. This can be distinguished from high-nickel positive electrode active materials with a nickel content exceeding about 70 mol%.

[0065] Positive electrode

[0066] 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 can further include other types of positive electrode active material. Additionally, the positive electrode active material layer can optionally further include a binder, a conductive material, or a combination thereof.

[0067] According to some embodiments, the loading level of the positive electrode active material layer can be about 10 mg / cm 2 to about 40 mg / cm 2 , for example, about 10 mg / cm 2 to about 30 mg / cm 2 or about 10 mg / cm 2 to about 20 mg / cm 2 . The density of the positive electrode active material layer in the finally pressed positive electrode can be about 2.6 g / cc to about 3.7 g / cc, for example, about 2.6 g / cc to about 3.6 g / cc or about 2.8 g / cc to about 3.58 g / cc. When applying the positive electrode active material according to some embodiments, using such a loading level and density of the positive electrode active material layer is advantageous, and a positive electrode that satisfies the loading level and density of the positive electrode active material layer within the above ranges can provide a rechargeable lithium battery with high capacity and high energy density.

[0068] The positive electrode according to some embodiments may be capable of achieving a high capacity (mAh / g) and, at the same time, achieving a high packing density (g / cc). Accordingly, the volumetric capacity of the positive electrode can be greater than or equal to about 550 mAh / cc, for example, greater than or equal to about 560 mAh / cc, greater than or equal to about 570 mAh / cc, greater than or equal to about 580 mAh / cc, from about 550 to about 650 mAh / cc or from about 580 to about 630 mAh / cc.

[0069] Binder

[0070] The binder improves the binding characteristics between the positive electrode active material particles and the binding characteristics between the positive electrode active material particles and the positive electrode current collector. Examples of the binder can include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylate esterified styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, and nylon. However, the present disclosure is not limited to such examples.

[0071] Conductive material

[0072] It includes a conductive material to provide electrode conductivity. Any conductive material can be used as the conductive material as long as it does not cause chemical changes. 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.

[0073] Based on 100 wt% of the positive electrode active material layer, the respective contents of the binder and the conductive material can be about 0.5 wt% to about 5 wt%.

[0074] The positive electrode current collector can include Al foil, etc., but is not limited thereto.

[0075] Rechargeable lithium battery

[0076] Some embodiments provide a rechargeable lithium battery including the aforementioned positive electrode, negative electrode, and electrolyte. The aforementioned positive electrode active material can be applied not only to lithium ion batteries but also to all-solid-state rechargeable batteries. 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. The all-solid-state rechargeable battery can include a positive electrode, a negative electrode, and a solid electrolyte layer between the positive electrode and the negative electrode. For convenience, the configuration of a lithium ion battery using an electrolyte will be described in detail below.

[0077] The rechargeable lithium battery can be classified into a cylindrical battery, a prismatic battery, a pouch battery, a coin-shaped battery, etc. according to its shape. Figures 1 to 4 For showing a schematic diagram of a rechargeable lithium battery according to some embodiments, wherein Figure 1 is a cylindrical battery, Figure 2 is a prismatic battery, and Figure 3 and Figure 4 are pouch batteries. Referring to Figures 1 to 4 , the rechargeable lithium battery 100 includes an electrode assembly 40 (with a separator 30 inserted between the positive electrode 10 and the negative electrode 20) and a housing 50 that houses the electrode assembly 40. The positive electrode 10, the negative electrode 20, and the separator 30 can be impregnated with an electrolyte (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 4As shown, the rechargeable lithium battery 100 includes electrode tabs 70 that serve as a circuit path for leading the current formed in the electrode assembly 40 to the outside of the battery, that is, a positive electrode tab 71 and a negative electrode tab 72.

[0078] The rechargeable lithium battery according to some embodiments can be charged or driven at a high voltage, and thus exhibits improved characteristics under high voltage conditions.

[0079] In order to utilize the reversible positive electrode capacity of the positive electrode active material of the lithium-rich manganese material, the initial charge can be carried out at about 4.60 V or higher (for example, about 4.65 V) (i.e., the initial charge voltage). Then, subsequent charging can be carried out in a voltage range lower than the initial charge voltage. Since the rechargeable lithium battery according to some embodiments is designed to be driven in a high voltage region, subsequent charging can be carried out in a voltage range of about 4.3 V or higher. For example, after the second cycle, the charging voltage can be about 4.3 V or higher, such as about 4.3 V to about 4.6 V, about 4.3 V to about 4.55 V, or about 4.4 V to about 4.50 V. Although the rechargeable lithium battery applying the positive electrode active material according to some embodiments can be charged at a high voltage, it can have high capacity and long cycle life characteristics.

[0080] Generally speaking, there is a problem that as O-redox is more manifested, after O-redox activation, the average discharge voltage (hereinafter, may also be simply referred to as "average voltage") decreases. However, in the positive electrode active material according to some embodiments, the proportion of O-redox is appropriately controlled to increase the average discharge voltage. For example, the rechargeable lithium battery according to some embodiments can have an average discharge voltage greater than or equal to about 3.8 V (for example, greater than or equal to about 3.83 V or greater than or equal to about 3.84 V) (relative to Li / Li + ). Herein, the average discharge voltage means the average discharge voltage measured by manufacturing a half-cell monomer using the positive electrode applying the positive electrode active material according to some embodiments in the second cycle. The half-cell monomer can be first charged and discharged at a voltage of about 4.60 V or higher, and then recharged and discharged at a voltage lower than 4.60 V. The average discharge voltage can be calculated, for example, by dividing the integral of the area under the curve in the voltage-capacity graph by the discharge capacity.

[0081] Negative electrode

[0082] The negative electrode may include a negative electrode current collector and a negative electrode active material layer on the negative electrode current collector, and the negative electrode active material layer may further include a negative electrode active material, a binder, a conductive material, or a combination thereof.

[0083] Negative electrode active material

[0084] 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.

[0085] The material that reversibly intercalates / deintercalates lithium ions may include, for example, crystalline carbon, amorphous carbon, or a combination thereof as a carbon-based negative electrode active material. The crystalline carbon may be amorphous, flakes, sheets, spherical, or fibrous natural graphite or artificial graphite. The amorphous carbon may be soft carbon, hard carbon, mesophase pitch carbonized product, calcined coke, etc.

[0086] 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.

[0087] The material capable of doping / dedoping lithium may be a Si-based negative electrode active material or a Sn-based negative electrode active material. The Si-based negative electrode active material may include silicon, a silicon-carbon composite, SiO x (0 < x ≤ 2), a Si-Q alloy (where Q is an element selected from alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements (excluding Si), Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof). For example, Q may be 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). The Sn-based negative electrode active material may be Sn, SnO x (0 < x ≤ 2) (for example, SnO 2 ), a Sn alloy, or a combination thereof.

[0088] 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. 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 an amorphous carbon matrix.

[0089] The silicon-carbon composite may further include crystalline carbon. 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 crystalline carbon may be artificial graphite, natural graphite, or a combination thereof. The amorphous carbon may include soft carbon or hard carbon, mesophase pitch carbonization products, and calcined coke.

[0090] When the silicon-carbon composite includes silicon and amorphous carbon, based on 100 wt% of the silicon-carbon composite, the content of silicon may be about 10 wt% to about 50 wt%, and the content of amorphous carbon may 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 may be about 10 wt% to about 50 wt%, the content of crystalline carbon may be about 10 wt% to about 70 wt%, and the content of amorphous carbon may be about 20 wt% to about 40 wt%.

[0091] The thickness of the amorphous carbon coating may be about 5 nm to about 100 nm. The average particle size (D 50 ) of the silicon particles (primary particles) may be about 10 nm to about 1 μm or about 10 nm to about 200 nm. The silicon particles may exist in the form of elemental silicon, a silicon alloy, or an oxidized form of silicon. The oxidized form of silicon may be represented by SiO x (0 < x ≤ 2). At this time, the atomic content ratio of Si:O indicating the degree of oxidation may be about 99:1 to about 33:67.

[0092] The Si-based negative electrode active material or the Sn-based negative electrode active material may be mixed with the carbon-based negative electrode active material. When the Si-based negative electrode active material or the Sn-based negative electrode active material is mixed with the carbon-based negative electrode active material, the mixing ratio of the Sn-based negative electrode active material to the carbon-based negative electrode active material may be a weight ratio of about 1:99 to about 90:10.

[0093] Binder

[0094] The binder is used to bond the negative electrode active material particles to each other and also bond the negative electrode active material to the negative electrode current collector. The binder may be a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0095] The non-aqueous binder may include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

[0096] The aqueous binder may include styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, epichlorohydrin polymer, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, or a combination thereof.

[0097] When the aqueous binder is used as a binder in the negative electrode active material layer, it may include a cellulose compound capable of imparting viscosity. 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.

[0098] 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.

[0099] Conductive material

[0100] A conductive material is included to provide electrode conductivity, and any conductive material may be used as long as the conductive material does not cause 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 such as copper, nickel, aluminum, silver, etc.; conductive polymers (such as polyphenylene derivatives); or mixtures thereof.

[0101] 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.

[0102] Current collector

[0103] 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.

[0104] Electrolyte

[0105] The electrolyte for a rechargeable lithium battery may include a non-aqueous organic solvent and a lithium salt.

[0106] 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.

[0107] 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, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. The ketone solvents may include cyclohexanone, etc. The alcohol solvents may include ethanol, isopropanol, etc., and the aprotic solvents may include nitriles such as R-CN (where R is a C2-C20 straight-chain, branched-chain, or cycloalkyl group and may include double bonds, aromatic rings, or ether groups, etc.); amides (such as dimethylformamide); dioxolanes (such as 1,3-dioxolane, 1,4-dioxolane, etc.); sulfolane, etc.

[0108] The non-aqueous organic solvents may be used alone or as a mixture of two or more of their types. When used as a mixture of two or more of their types, the mixing ratio can be adjusted according to the desired battery performance, which is well known to those skilled in the art.

[0109] When using carbonate solvents, cyclic carbonates and chain carbonates can be mixed and used. The cyclic carbonate and the chain carbonate can be mixed in a volume ratio of about 1:1 to about 1:9.

[0110] The non-aqueous organic solvent may include aromatic hydrocarbon organic solvents. For example, the carbonate solvent and the aromatic hydrocarbon organic solvent can be mixed and used in a volume ratio of about 1:1 to about 30:1.

[0111] The electrolyte may further include vinylene carbonate, vinylene carbonate or ethylene carbonate compounds to improve the battery cycle life. Examples of ethylene carbonate compounds may include fluoroethylene carbonate, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate and cyanoethylene carbonate.

[0112] The lithium salt dissolved in the non-aqueous organic solvent supplies lithium ions in the battery, ensuring the basic operation of the rechargeable lithium battery and improving the transport of lithium ions between the positive and negative electrodes. Examples of lithium salts include those selected from LiPF 6 , LiBF 4 , LiSbF 6 , LiAsF 6 , LiClO 4 , LiAlO 2 , LiAlCl 4 , LiPO 2 F 2 , LiCl, LiI, LiN(SO 3 C 2 F 5 ), 2 , Li(FSO 2 ), 2 N (lithium bis(fluorosulfonyl)imide; LiFSI), LiC 4 F 9 SO 3 , LiN(C x F 2x+1 SO 2 )(C y F 2y+1 SO 2 )(where x and y are each integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluoro bis(oxalate) phosphate (LiDFBOP) and lithium bis(oxalate) borate (LiBOB), and at least one of them.

[0113] The concentration of the lithium salt may be in the range of about 0.1 M to about 2.0 M. When the concentration of the lithium salt is within this range, the electrolyte has appropriate ionic conductivity and viscosity. Therefore, excellent performance can be achieved and lithium ions can move effectively.

[0114] Separator

[0115] 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, a polytetrafluoroethylene 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.).

[0116] 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.

[0117] The porous substrate may be a polymer film formed of any one polymer selected from the following or a copolymer or mixture of two or more thereof: polyolefins (such as polyethylene and polypropylene), polyesters (such as polyethylene terephthalate and polybutylene terephthalate), polyacetals, polyamides, polyimides, polycarbonates, polyether ketones, polyarylether ketones, polyetherimides, polyamideimides, polybenzimidazoles, polyethersulfones, polyphenylene ethers, cycloolefin copolymers, polyphenylene sulfides, polyethylene naphthalate, glass fibers, and polytetrafluoroethylene

[0118] 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).

[0119] The organic material may include a (meth)acrylamide copolymer, which includes a first structural unit derived from (meth)acrylamide, and a second structural unit including at least one of a structural unit derived from (meth)acrylic acid or (meth)acrylate and a structural unit derived from (meth)acrylamidosulfonic acid or its salt.

[0120] The inorganic material may include those selected from Al 2 O 3 、SiO 2 、TiO 2 、SnO 2 、CeO 2 、MgO、NiO、CaO、GaO、ZnO、ZrO 2 、Y 2 O 3 、SrTiO 3 、BaTiO 3 、Mg(OH) 2 、boehmite, and inorganic particles of their combinations, but the present disclosure is 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.

[0121] Organic materials and inorganic materials can be mixed in a single coating, or a coating comprising an organic material and a coating comprising an inorganic material can be stacked.

[0122] The thickness of the coating can be from about 0.5 μm to about 20 μm, for example, from about 1 μm to about 10 μm or from about 1 μm to about 5 μm.

[0123] Examples and comparative examples of the present disclosure are described below. However, the following examples are merely illustrative of the present disclosure, and the present disclosure is not limited to the following examples.

[0124] Example 1

[0125] 1. Preparation of positive electrode active material

[0126] (1) Preparation of large particles of the first positive electrode active material

[0127] Ni 0.5 Mn 0.5 (OH) 2 and LiOH are mixed to have a molar ratio of Li / (Ni + Mn) of about 1.12, and then heat-treated at 1000 °C for 24 hours in an oxygen atmosphere to prepare a first positive electrode active material comprising a lithium-rich manganese composite oxide (Li 50 )(Ni 1.06 Ni 0.5 Mn 0.5 ) 0.94 O 2 ) in the form of secondary particles with an average particle size (D

[0128] (2) Preparation of small particles of the second positive electrode active material

[0129] Ni 0.35 Mn 0.65 CO 3 and LiOH are mixed to have a molar ratio of Li / (Ni + Mn) of about 1.35, and then heat-treated at 900 °C for 24 hours to prepare a second positive electrode active material comprising a lithium-rich manganese composite oxide (Li 50 )(Ni 1.15 Ni 0.35 Mn 0.65 ) 0.85 O 2 ) in the form of secondary particles with an average particle size (D

[0130] (3) Preparation of the mixed positive electrode active material

[0131] Based on the total weight of the mixed positive electrode active material, 80 wt% of the first large-sized positive electrode active material particles and 20 wt% of the second small-sized positive electrode active material particles are mixed to prepare a mixed positive electrode active material having a final composition of Li / (Ni + Mn) = 1.17 and Ni:Mn = 47:53.

[0132] 2. Manufacture of a rechargeable lithium battery single cell (half cell single cell)

[0133] Based on the total weight of the positive electrode active material layer slurry, 92 wt% of the prepared positive electrode active material, 4 wt% of polyvinylidene fluoride binder, and 4 wt% of carbon nanotube conductive material are mixed to prepare a positive electrode active material layer slurry. The slurry is coated on an aluminum foil current collector, and then dried and pressed to fabricate a positive electrode. The loading level of the positive electrode active material layer is 10 mg / cm 2 And the density of the positive electrode active material layer in the finally roll-pressed positive electrode is about 3.5 g / cc.

[0134] The positive electrode is used together with a lithium counter electrode as the negative electrode, a polytetrafluoroethylene separator, and an electrolyte, which is prepared as follows: Dissolve 1 M LiPF 6 in a mixed solvent of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate in a volume ratio of 2:4:4, and then add 1.5 wt% of vinylene carbonate thereto. Then, a rechargeable lithium battery cell is prepared from these components according to a conventional method.

[0135] Example 2

[0136] A rechargeable lithium battery cell is prepared in substantially the same manner as in Example 1, except that a first positive electrode active material having a composition of Li 1.06 (Ni 0.5 Mn 0.5 ) 0.94 O 2 composition and an average particle size (D 50 ) of about 10 μm and a second positive electrode active material having a composition of Li 1.15 (Ni 0.35 Mn 0.65 ) 0.85 O 2 composition and an average particle size (D 50 ) of about 6.5 μm are mixed at a weight ratio of 8:2 to prepare a positive electrode active material.

[0137] Comparative Example 1

[0138] A rechargeable lithium battery cell is prepared in substantially the same manner as in Example 1, except that only a positive electrode active material having a composition of Li / (Ni + Mn) = 1.17 and Ni:Mn = 47:53 and an average particle size (D50 ) is a positive electrode active material with a particle size of about 6.11 μm.

[0139] Comparative Example 2

[0140] A rechargeable lithium battery cell was prepared in substantially the same manner as in Example 1, except that a first positive electrode active material having Li 1.15 (Ni 0.35 Mn 0.65 ) 0.85 O 2 composition and an average particle size (D 50 ) of about 6.5 μm and a second positive electrode active material having Li 1.15 (Ni 0.35 Mn 0.65 ) 0.85 O 2 composition and an average particle size (D 50 ) of about 3.3 μm were mixed at a weight ratio of 8:2 to prepare a positive electrode active material.

[0141] Comparative Example 3

[0142] A rechargeable lithium battery cell was prepared in substantially the same manner as in Example 1, except that a first positive electrode active material having Li 1.06 (Ni 0.66 Mn 0.34 ) 0.94 O 2 composition and an average particle size (D 50 ) of about 10 μm and a second positive electrode active material having Li 1.06 Ni 0.75 Mn 0.25 O 2 composition and an average particle size (D 50 ) of about 3.5 μm were mixed at a weight ratio of 7:3 to prepare a positive electrode active material having a final composition of Li / (Ni + Mn) = 1.1 and Ni:Mn = 69:31.

[0143] Comparative Example 4

[0144] A rechargeable lithium battery cell was prepared in substantially the same manner as in Example 1, except that a first positive electrode active material having Li 1.03 Ni 0.75 Mn 0.25 O 2 composition and an average particle size (D 50 ) of about 9 μm and a second positive electrode active material having Li 1.06 Ni 0.75 Mn 0.25 O2 The second positive electrode active material having a composition and an average particle diameter (D 50 ) of about 3.5 μm is mixed at a weight ratio of 8:2 to prepare a positive electrode active material.

[0145] Evaluation Example 1: Evaluation of initial charge / discharge capacity, initial charge / discharge efficiency, average voltage, pellet density, and unit volume capacity

[0146] The battery cell using a material rich in lithium and manganese is initially charged at 4.65 V and then charged at 4.45 V.

[0147] The rechargeable lithium battery cells of Examples 1 to 2 and Comparative Examples 1 to 4 are charged at a constant current of 0.1 C at 4.65 V. Subsequently, they are maintained at this voltage until the current reaches 0.05 C. Then, they are discharged at a constant current of 0.1 C at 2.5 V to perform the first charge and discharge cycle. Subsequently, at 25 °C, the battery is charged at a constant current of 0.2 C at 4.45 V, then maintained at this voltage until the current reaches 0.05 C, and discharged at a constant current of 0.2 C at 2.5 V to perform the second charge and discharge cycle. For the second charge and discharge cycle, the initial charge capacity, the initial discharge capacity, and the ratio of the initial discharge capacity to the initial charge capacity are shown as efficiency in Tables 1 and 2.

[0148] In all evaluation examples, the battery cells using the mixed positive electrode active material, the battery cells using only the first positive electrode active material, the battery cells using only the second positive electrode active material, and the comparative examples are evaluated equally. The results are shown in Tables 1 and 2.

[0149] In addition, the average voltage (V with respect to Li / Li + ) at the initial discharge (discharge in the second cycle) of each of the examples and comparative examples was evaluated, and the results are shown in Tables 1 and 2. In Tables 1 and 2, Me = Ni + Mn. The average voltage is obtained by integrating the area under the discharge voltage curve (voltage-capacity graph) after the initial charge and discharge of the battery cell and then dividing this integral by the discharge capacity.

[0150] After pressing at a pressure of 3.3 tons for 30 seconds, the pellet density of each of the positive electrode active materials of the examples and comparative examples was measured. In addition, the unit volume capacity was determined as the product of the initial discharge capacity and the pellet density.

[0151]

[0152]

[0153] Referring to Table 1, Example 1, which mixes large particles and small particles, exhibits a high initial discharge capacity, which is similar to the calculated predicted value of 80% of the initial discharge capacity of large particles and 20% of the initial discharge capacity of small particles. Compared with the respective densities of large particles and small particles, Example 1 also exhibits an increased density, thus significantly increasing the capacity per unit volume.

[0154] Example 2, in which large particles and small particles are mixed, also exhibits a high initial discharge capacity, which is similar to the calculated predicted value of 80% of the initial discharge capacity of large particles and 20% of the initial discharge capacity of small particles. Compared with the respective densities of large particles and small particles, Example 2 also exhibits an increased density, thus significantly increasing the capacity per unit volume.

[0155] Comparative Example 1, which has the same final composition as Examples 1 and 2 but only uses the positive electrode active material with a particle size of 6.11 μm, exhibits an initial discharge capacity lower than or similar to that of Examples 1 and 2, confirming that this is very disadvantageous in terms of the capacity per unit volume.

[0156] In Table 2, Comparative Example 2, in which large particles and small particles are lithium-rich manganese-based and have the same composition, does not exhibit an increase in density.

[0157] Comparative Example 3, in which lithium nickel manganese composite oxide is used as small particles instead of lithium-rich manganese composite oxide, does not exhibit an increase in the initial discharge capacity and does not exhibit an increase in density.

[0158] Comparative Example 4, in which large particles and small particles are not lithium-rich manganese-based but lithium nickel manganese composite oxide is applied, exhibits a reduced initial discharge capacity.

[0159] Evaluation Example 2: Evaluation of high temperature cycle life characteristics

[0160] For the battery cells of Example 1 that apply the mixed positive electrode active material, the battery cells that only apply the first positive electrode active material of Example 1, and the battery cells that only apply the second positive electrode active material of Example 1, after the first charge and discharge and the second charge and discharge in Evaluation Example 1, at 45 °C, each battery cell is repeatedly charged and discharged 70 times or more at a voltage range of 2.5 V to 4.45 V at 1.0 C to measure the capacity retention rate according to the number of cycles, that is, the ratio of the discharge capacity per cycle to the initial discharge capacity (i.e., the discharge capacity of the second cycle). The results are as Figure 5 shown.

[0161] Refer to Figure 5, compared with the case of only applying the first positive electrode active material of Example 1, the battery cell of Example 1 exhibits significantly improved cycle life characteristics. In addition, compared with the case of only applying the small particles of the second electrode active material of Example 1, the battery cell of Example 1 includes 20 wt% of small particles but still exhibits almost the same high cycle life characteristics.

[0162] Although the present disclosure has been described in connection with exemplary embodiments currently regarded as practical, it should be understood that the present disclosure is not limited to the disclosed embodiments. On the contrary, the present disclosure 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 first lithium-rich manganese composite oxide, wherein (i) a molar ratio of lithium in the first lithium-rich manganese composite oxide to total metals other than lithium in the first lithium-rich manganese composite oxide is 1.06 to 1.2, and (ii) a manganese content of the first lithium-rich manganese composite oxide based on 100 mol % of the total metal content other than lithium in the first lithium-rich manganese composite oxide is greater than or equal to 30 mol %; and A second positive electrode active material, comprising a second lithium-rich manganese composite oxide, (i) wherein the molar ratio of lithium in the second lithium-rich manganese composite oxide to the total metal content other than lithium in the second lithium-rich manganese composite oxide is greater than 1.2 and less than or equal to 2, (ii) wherein the manganese content of the second lithium-rich manganese composite oxide based on 100 mol % of the total metal content other than lithium in the second lithium-rich manganese composite oxide is greater than or equal to 30 mol %, and (iii) the average particle size D of the second positive electrode active material is less than 0.1 mol %. 50 smaller than the average particle size D of the first positive electrode active material 50 .

2. The positive electrode active material according to claim 1, wherein Based on 100 wt % in total of the first positive electrode active material and the second positive electrode active material, (i) the first positive electrode active material is included in an amount greater than 50 wt % and less than 100 wt %, and (ii) the second positive electrode active material is included in an amount greater than 0 wt % and less than 50 wt %.

3. The positive electrode active material according to claim 1, wherein Based on 100 wt % of the total of the first positive electrode active material and the second positive electrode active material, (i) the first positive electrode active material is included in an amount of 60 wt % to 95 wt %, and (ii) the second positive electrode active material is included in an amount of 5 wt % to 40 wt %.

4. The positive electrode active material according to claim 1, wherein the average particle size D of the first positive electrode active material is 50 Greater than or equal to 5 μm and less than or equal to 20 μm, and The average particle size of the second positive electrode active material is D 50 Greater than or equal to 1 μm and less than or equal to 7 μm.

5. The positive electrode active material of claim 1, wherein the first lithium-rich manganese composite oxide of the first positive electrode active material has a molar ratio of lithium in the first lithium-rich manganese composite oxide to the total metals other than lithium in the first lithium-rich manganese composite oxide greater than 1.1 and less than or equal to 1.2, and The second lithium-rich manganese composite oxide of the second positive electrode active material has a molar ratio of lithium in the second lithium-rich manganese composite oxide to total metals other than lithium in the second lithium-rich manganese composite oxide greater than 1.2 and less than or equal to 1.

5.

6. The positive electrode active material according to claim 1, wherein The first lithium-rich manganese composite oxide of the first positive electrode active material has a nickel content greater than or equal to 45 mol % based on 100 mol % of the total metal content excluding lithium in the first lithium-rich manganese composite oxide, and The second lithium-rich manganese composite oxide of the second positive electrode active material has a nickel content of less than 45 mol % based on 100 mol % of the total metal content excluding lithium in the second lithium-rich manganese composite oxide.

7. The positive electrode active material according to claim 1, wherein The first lithium-manganese-rich composite oxide of the first positive electrode active material has a nickel content of 45 mol% to 70 mol% and a manganese content of 30 mol% to 55 mol% based on 100 mol% in total of nickel and manganese in the first lithium-manganese-rich composite oxide, and The second lithium-manganese-rich composite oxide of the second positive electrode active material has a nickel content of 10 mol% to less than 45 mol% and a manganese content of greater than 55 mol% to 90 mol%, based on a total of 100 mol% of nickel and manganese in the second lithium-manganese-rich composite oxide.

8. The positive electrode active material according to claim 1, wherein Based on the entire mixture of the first positive electrode active material and the second positive electrode active material, (i) the molar ratio of lithium to total metals other than lithium in the entire mixture is 1.1 to 1.3, and (ii) based on 100 mol% in total of nickel and manganese in the entire mixture, the nickel content is 35 mol% to 65 mol% and the manganese content is 35 mol% to 65 mol%.

9. The positive electrode active material of claim 1, wherein the first lithium-manganese-rich composite oxide of the first positive electrode active material comprises at least one of the metal oxides represented by Chemical Formula 1 and Chemical Formula 2: Chemical formula 1 Li 1+x1 (Ni y1 Mr z1 M 1 1-y1-z1 ) 1-x1 O 2-b1 X 1 b1 in, In Chemical Formula 1, 0.03≤x1≤0.09, 0.45≤y1≤0.7, 0.3≤z1≤0.55, and 0≤b1≤0.1, M 1 is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y and Zr, and X 1 is one or more elements selected from F, P and S, Chemical formula 2 (1-x2)(LiNi y2 Mn z2 M 2 1-y2-z2 O 2-b2 X 2 b2 )+x2(Li2(Mn t1 M 2 1-t1 )O 3-b3 X 2 b3 )] Wherein, in Chemical Formula 2, 0.06≤x2≤0.2, 0.5≤y2≤1.0, 0≤z2≤0.5, 0≤b2≤0.1, 0.9≤t1≤1 and 0≤b3≤0.1, M 2 is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y and Zr, and X 2 is one or more elements selected from F, P and S.

10. The positive electrode active material of claim 1, wherein the second lithium-rich manganese composite oxide of the second positive electrode active material is represented by at least one of Chemical Formula 3 and Chemical Formula 4: Chemical formula 3: Li 1+x3 (Ni y3 Mr z3 M 3 1-y3-z3 ) 1-x3 O 2-b4 X 3 b4 in, In Chemical Formula 3, 0.09 < x3 ≤ 0.33, 0.1 ≤ y3 < 0.45, 0.55 < z3 ≤ 0.9, and 0 ≤ b4 ≤ 0.1, M 3 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 3 is one or more elements selected from F, P, and S, Chemical formula 4: (1-x4)(LiNi y4 Mn z4 M 4 1-y4-z4 O 2-b5 X 4 b5 )+x4(Li2(Mn t2 M 4 1-t2 )O 3-b6 X 4 b6 )] Among them, in Chemical Formula 4, 0.2 < x4 ≤ 1, 0.5 ≤ y4 ≤ 1.0, 0 ≤ z4 ≤ 0.5, 0 ≤ b5 ≤ 0.1, 0.9 ≤ t2 ≤ 1, and 0 ≤ b6 ≤ 0.1, M 4 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 4 is one or more elements selected from F, P, and S.

11. The positive electrode active material according to claim 1, wherein In each of the first lithium-rich manganese composite oxide and the second lithium-rich manganese composite oxide, a cobalt content based on 100 mol % of a total metal content excluding lithium is 0 mol % to 1 mol %.

12. The positive electrode active material according to claim 1, wherein the first positive electrode active material is in the form of secondary particles made by aggregating a plurality of primary particles, and The second positive electrode active material is in the form of secondary particles, single particles or a combination thereof.

13. The positive electrode active material according to claim 1, wherein the average particle size D of the first positive electrode active material is 50 Subtract the average particle size D of the second positive electrode active material 50 The values ​​obtained were less than or equal to 6 μm.

14. The positive electrode active material according to claim 11, wherein the average particle size D of the first positive electrode active material is 50 minus the average particle size D of the second positive electrode active material 50 The values ​​obtained were 2 μm to 5 μm.

15. The positive electrode active material of claim 1, wherein the positive electrode active material has a pellet density greater than or equal to 2.9 g / cc.

16. A rechargeable lithium battery comprising: A positive electrode comprising the positive electrode active material according to any one of claims 1 to 15; negative electrode, and Electrolyte.

17. The rechargeable lithium battery of claim 16, wherein the positive electrode has a capacity per unit volume greater than or equal to 550 mAh / cc.

18. The rechargeable lithium battery of claim 16, wherein the rechargeable lithium battery has a voltage greater than or equal to 3.8 V vs. Li / Li + The average discharge voltage.

19. An all-solid-state rechargeable battery comprising: A positive electrode comprising the positive electrode active material according to any one of claims 1 to 15; Negative electrode; and A solid electrolyte layer is between the positive electrode and the negative electrode.

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