Positive electrode and rechargeable lithium battery

Abstract

Disclosed are a positive electrode for a rechargeable lithium battery and a rechargeable lithium battery. The positive electrode includes a current collector, a first positive electrode active material layer on the current collector, and a second positive electrode active material layer on the first positive electrode active material layer. The first positive electrode active material layer includes: a first positive electrode active material including a lithium transition metal composite oxide as secondary particles formed by agglomeration of a plurality of primary particles; and a second positive electrode active material including a lithium transition metal composite oxide as a single particle. The second positive electrode active material layer includes: a third positive electrode active material including a lithium transition metal composite oxide as secondary particles formed by agglomeration of a plurality of primary particles; and a fourth positive electrode active material including a lithium transition metal composite oxide as secondary particles.

Description

Technical Field

[0001] A positive electrode for a rechargeable lithium battery and a rechargeable lithium battery are disclosed. Background Technology

[0002] Portable devices such as cellular phones, laptops, and smartphones, as well as electric vehicles, typically use rechargeable lithium batteries with high energy density and portability as their power source. There is significant interest in high-energy-density rechargeable lithium batteries as a power source or energy storage source for applications such as hybrid or electric vehicles.

[0003] With the increasing demand for high-performance rechargeable lithium batteries, there is a growing need for designs that can exhibit high energy density, high capacity and long lifespan, as well as high output or fast charging characteristics. Summary of the Invention

[0004] Disclosed examples include positive electrodes for rechargeable lithium batteries and rechargeable lithium batteries themselves, which have high energy density and desired or improved output characteristics and fast charging characteristics.

[0005] In some exemplary embodiments, the positive electrode for a rechargeable lithium battery includes a current collector, a first positive electrode active material layer on the current collector, and a second positive electrode active material layer on the first positive electrode active material layer. The first positive electrode active material layer includes: a first positive electrode active material comprising a lithium transition metal composite oxide in the form of secondary particles formed by the aggregation of multiple primary particles; and a second positive electrode active material comprising a lithium transition metal composite oxide in the form of single particles and having an average particle size (D) smaller than the average particle size of the first positive electrode active material. 50 The second positive electrode active material layer includes: a third positive electrode active material comprising a lithium transition metal composite oxide and having the form of secondary particles formed by the aggregation of multiple primary particles; and a fourth positive electrode active material comprising a lithium transition metal composite oxide, having the form of secondary particles formed by the aggregation of multiple primary particles, and having a smaller average particle size (D) than the third positive electrode active material. 50 Small average particle size (D) 50 ).

[0006] Some example embodiments include a rechargeable lithium battery that includes the positive electrode, negative electrode, and electrolyte.

[0007] The positive electrode according to some example embodiments can exhibit high energy density and high capacity, while also having high output characteristics and fast charging characteristics. Attached Figure Description

[0008] Figures 1 to 4 This is a schematic diagram illustrating a rechargeable lithium battery according to some example embodiments. Detailed Implementation

[0009] Hereinafter, exemplary embodiments will be described in detail so that those skilled in the art can readily implement them. However, this disclosure may be implemented in many different forms and is not to be construed as limited to the exemplary embodiments set forth herein.

[0010] The terminology used herein describes exemplary embodiments only and is not intended to limit this disclosure. Unless the context clearly indicates otherwise, singular expressions include plural expressions.

[0011] As used herein, “combinations of” refers to mixtures, laminates, complexes, copolymers, alloys, blends, reaction products, etc. of the components.

[0012] It should be understood here that terms such as “comprising,” “including,” or “having” are intended to specify the presence of the features, quantities, steps, elements, or combinations thereof embodied, but do not preclude the possibility of the presence or addition of one or more other features, quantities, steps, elements, or combinations thereof.

[0013] In the accompanying drawings, the thickness of layers, films, panels, regions, etc., is exaggerated for clarity, and the same reference numerals denote the same elements throughout the specification. It will be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" another element, the element may be directly on said other element, or an intervening element may be present. Conversely, when an element is referred to as being "directly on" another element, no intervening element is present.

[0014] In addition, the term "layer" here includes not only shapes that form across the entire surface when viewed from a plan view, but also shapes that form on a portion of the surface.

[0015] The average particle size can be measured using methods well known to those skilled in the art (e.g., by a particle size analyzer, or by transmission electron microscopy or scanning electron microscopy images). Alternatively, the average particle size value can be obtained by measuring using dynamic light scattering, performing data analysis, counting the number of particles in each particle size range, and thereby calculating the average particle size. Unless otherwise defined, the average particle size can refer to the diameter (D) of particles having a cumulative volume of 50% of the particle size distribution. 50 As used herein, unless otherwise defined, mean particle size refers to the diameter of 50% by volume of particles in a particle size distribution obtained by randomly measuring the size (diameter or major axis length) of approximately 20 particles in a scanning electron microscope image.50 ).

[0016] Here, "or" is not interpreted as having an exclusive meaning. For example, "A or B" is interpreted as including A, B, A+B, etc.

[0017] The term "metal" is interpreted as encompassing common metals, transition metals, and metalloids (semi-metals).

[0018] When the terms “about” or “substantially” are used in conjunction with numerical values ​​in this specification, they mean that the relevant numerical value includes a tolerance of ±10% around the stated value. When a range is specified, the range includes all values ​​within that range, such as increments of 0.1%.

[0019] positive electrode According to some example embodiments, the positive electrode includes a current collector, a first positive electrode active material layer on the current collector, and a second positive electrode active material layer on the first positive electrode active material layer. The first positive electrode active material layer includes a first positive electrode active material and a second positive electrode active material. The first positive electrode active material includes a lithium transition metal composite oxide and has the form of secondary particles formed by the aggregation of multiple primary particles. The second positive electrode active material includes a lithium transition metal composite oxide, is in the form of single particles, and has a particle size (D) larger than the average particle size of the first positive electrode active material. 50 Small average particle size (D) 50 The second positive electrode active material layer includes a third positive electrode active material and a fourth positive electrode active material. The third positive electrode active material includes a lithium transition metal composite oxide and is in the form of secondary particles formed by the aggregation of multiple primary particles. The fourth positive electrode active material includes a lithium transition metal composite oxide and is in the form of secondary particles formed by the aggregation of multiple primary particles, and has a larger average particle size (D) than the third positive electrode active material. 50 Small average particle size (D) 50 ).

[0020] According to some example embodiments, the positive electrode can have a bilayer or multilayer structure, and can be designed to simultaneously or concurrently improve or increase energy density and output characteristics. The first positive electrode active material layer on the current collector can be configured to improve or increase energy density, and the second positive electrode active material layer on the first positive electrode active material layer can be configured to improve or increase output characteristics and fast charging characteristics.

[0021] The second positive electrode active material layer may be or include a region in contact with the negative electrode, separated by a separator or solid electrolyte layer. By coating this region with a mixed positive electrode active material having desired or improved output characteristics of a third and fourth positive electrode active material, the overall output characteristics of the battery can be improved or enhanced. According to some example embodiments, the positive electrode can have desired or improved output characteristics compared to a positive electrode with only a first positive electrode active material layer, and can have a higher energy density compared to a positive electrode with only a second positive electrode active material layer. Furthermore, the positive electrode according to some exemplary embodiments can achieve higher output characteristics and energy density than a positive electrode comprising a current collector, a second positive electrode active material layer, and a first positive electrode active material layer stacked in that order.

[0022] First positive electrode active material layer The first positive electrode active material can be large particles in the form of secondary particles, while the second positive electrode active material can be small particles in the form of single particles. A very high capacity and energy density can be achieved by using a mixed positive electrode active material comprising both the first and second positive electrode active materials. When such a first positive electrode active material layer is disposed on the surface of the current collector in a multilayer positive electrode structure, the energy density can be improved or increased.

[0023] The average particle size (D) of the active material of the first positive electrode 50 The particle size can be from about 10 μm to about 25 μm, for example, from about 10 μm to about 20 μm, from about 11 μm to about 18 μm, or from about 12 μm to about 16 μm. The average particle size (D) of the active material of the second positive electrode... 50 The particle size can be from about 1 μm to about 8 μm, for example, from about 1 μm to about 6 μm, or from about 2 μm to about 4 μm. When the first positive electrode active material and the second positive electrode active material each exhibit any of the above particle size ranges, the energy density can be improved or increased, and high capacity and long lifetime characteristics can be achieved. Here, the average particle size (D) 50 The particle size distribution can be obtained by selecting about 20 random particles from the scanning electron microscope image of the positive electrode active material, measuring their particle size (diameter or major axis length), and taking the size of the particles whose cumulative volume is 50% from the particle size distribution as the average particle size.

[0024] The shape of the first positive electrode active material is not particularly limited, but it can be, for example, spherical or elliptical. The second positive electrode active material can have various shapes, such as polyhedron, sphere, ellipse, plate, rod, or irregular shape.

[0025] In the first positive electrode active material layer, based on the total amount of the first positive electrode active material and the second positive electrode active material, the content of the first positive electrode active material can be about 60 wt% to about 95 wt%, for example, about 60 wt% to about 90 wt%, about 70 wt% to about 80 wt%, or about 65 wt% to about 75 wt%, and the content of the second positive electrode active material can be about 5 wt% to about 40 wt%, for example, about 10 wt% to about 40 wt%, about 20 wt% to about 30 wt%, or about 25 wt% to about 35 wt%. When the first positive electrode active material and the second positive electrode active material are mixed in any of the above ratios, the energy density can be improved or increased, which is advantageous for achieving high capacity and long life characteristics.

[0026] The lithium transition metal composite oxide of the first positive electrode active material and the lithium transition metal composite oxide of the second positive electrode active material can each independently be or include at least one of a lithium nickel-based composite oxide, a lithium cobalt-based composite oxide, a lithium manganese-based composite oxide, a lithium iron phosphate-based compound, a lithium iron manganese phosphate-based compound, and combinations thereof. For example, both the lithium transition metal composite oxide of the first positive electrode active material and the lithium transition metal composite oxide of the second positive electrode active material can be or include a lithium nickel-based composite oxide, in which case, high capacity can be achieved while exhibiting high energy density and output characteristics.

[0027] The lithium transition metal composite oxide of the first positive electrode active material and the lithium transition metal composite oxide of the second positive electrode active material can be the same as or different from each other, and can each independently be represented by Chemical Formula 1.

[0028] Chemical Formula 1: Li a1 Ni x1 M 1 y1 O 2-b1 X b1 In Chemical Formula 1, 0.9 ≤ a1 ≤ 1.8, 0.3 ≤ x1 < 1, 0 < y1 ≤ 0.7, 0.9 ≤ x1 + y1 ≤ 1.1 and 0 ≤ b1 ≤ 0.1, M 1 is or includes one or more of Al, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is or includes one or more of F, P, and S.

[0029] In Chemical Formula 1, 0.3 ≤ x1 ≤ 0.99, 0.01 ≤ y1 ≤ 0.7; or 0.4 ≤ x1 ≤ 0.99, 0.01 ≤ y1 ≤ 0.6; or 0.5 ≤ x1 ≤ 0.99, 0.01 ≤ y1 ≤ 0.5; or 0.6 ≤ x1 ≤ 0.99, 0.01 ≤ y1 ≤ 0.4; or 0.7 ≤ x1 ≤ 0.99, 0.01 ≤ y1 ≤ 0.3; or 0.8 ≤ x1 ≤ 0.99, 0.01 ≤ y1 ≤ 0.2; or 0.9 ≤ x1 ≤ 0.99, 0.01 ≤ y1 ≤ 0.1; or 0.91 ≤ x1 ≤ 0.99, 0.01 ≤ y1 ≤ 0.09.

[0030] For example, the first positive electrode active material and the second positive electrode active material may be or include a high-nickel type positive electrode active material. In the high-nickel type positive electrode active material, based on 100 mol% of the metals other than lithium in the lithium transition metal composite oxide, the nickel content may be greater than or equal to about 80 mol%, greater than or equal to about 85 mol%, greater than or equal to about 90 mol%, greater than or equal to about 91 mol%, or greater than or equal to about 94 mol% and less than or equal to about 99 mol%. In this case, high energy density and output characteristics can be exhibited while high capacity is also exhibited.

[0031] The lithium transition metal composite oxide of the first positive electrode active material and the lithium transition metal composite oxide of the second positive electrode active material may each independently be or include a lithium nickel cobalt composite oxide represented by Chemical Formula 2.

[0032] Chemical Formula 2: Li a2 Ni x2 Co y2 M 2 z2 O 2-b2 X b2 In Chemical Formula 2, 0.9 ≤ a2 ≤ 1.8, 0.3 ≤ x2 < 1, 0 < y2 ≤ 0.7, 0 ≤ z2 ≤ 0.7, 0.9 ≤ x2 + y2 + z2 ≤ 1.1, and 0 ≤ b2 ≤ 0.1, M 2 is or includes one or more of Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is or includes one or more of F, P, and S.

[0033] In Chemical Formula 2, for example, 0.7 ≤ x2 < 1, 0 < y2 ≤ 0.3, 0 ≤ z2 ≤ 0.3; or 0.8 ≤ x2 < 1, 0 < y2 ≤ 0.2, 0 ≤ z2 ≤ 0.2; or 0.9 ≤ x2 < 1, 0 < y2 ≤ 0.1, 0 ≤ z2 ≤ 0.1.

[0034] The lithium transition metal composite oxide of the first positive electrode active material and the lithium transition metal composite oxide of the second positive electrode active material can both be independently or include at least one of the lithium nickel cobalt manganese composite oxide, lithium nickel cobalt aluminum composite oxide and lithium nickel cobalt aluminum manganese composite oxide represented by chemical formula 3.

[0035] Chemical formula 3: Li a3 Ni x3 Co y3 M 3 z3 M 4 w3 O 2-b3 X b3 In chemical formula 3, 0.9 ≤ a³ ≤ 1.8, 0.3 ≤ x³ ≤ 0.98, 0.01 ≤ y³ ≤ 0.69, 0.01 ≤ z³ ≤ 0.69, 0 ≤ w³ ≤ 0.69, 0.9 ≤ x³ + y³ + z³ + w³ ≤ 1.1 and 0 ≤ b³ ≤ 0.1, M 3 M is or includes one or more of Al, Mn and combinations thereof. 4 X is or includes one or more of B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is or includes one or more of F, P, and S.

[0036] The first positive electrode active material includes secondary particles in which two or more primary particles are aggregated, and at least a portion of the primary particles may have a radially aligned structure. When at least a portion of the primary particles are radially aligned within the secondary particles, the secondary particles may have multiple lithium diffusion paths between grain boundaries on the surface side, and many crystal faces capable of lithium migration are exposed to the outside, thereby improving lithium diffusion and ensuring high initial efficiency and capacity. Furthermore, when the primary particles are radially aligned, the pores exposed on the surface face towards the center of the secondary particles, thereby promoting lithium diffusion. Due to the radially aligned primary particles, uniform contraction and expansion are possible during lithium insertion / extraction and / or insertion, and pores exist in the (001) direction, which is the direction of particle expansion, during lithium insertion / extraction, thus forming a buffer. Additionally, due to the radial alignment of the primary particles, the probability of cracking during the contraction and expansion of the active material can be reduced, and the internal pores further mitigate volume changes to reduce cracking between primary particles during charging and discharging, resulting in improved lifetime characteristics and reduced resistance increase in the rechargeable lithium battery.

[0037] The secondary particles of the first positive electrode active material may include an internal portion and an external portion. The internal portion includes an irregular porous structure, and the external portion includes radially arranged structures surrounding the internal region. An irregular porous structure means that the structure has primary particles and pores, but the pore size, shape, and position may not always be regular. Unlike the primary particles in the external portion, the primary particles in the internal portion can be arranged randomly. A radially arranged structure refers to at least some of the primary particles being arranged radially.

[0038] The secondary particles have a porous structure in their internal portion, which reduces the distance lithium ions need to diffuse into the interior. Externally, the primary particles are radially positioned, facilitating lithium ion insertion into the surface. Furthermore, the small size of the primary particles makes it easier to ensure lithium migration paths between grains. Additionally, the small size of the primary particles and the porosity between them mitigate volume changes during charging and discharging, thus minimizing stress caused by these volume changes. These positive electrode active materials can reduce the resistance of rechargeable lithium batteries and improve capacity and lifespan characteristics.

[0039] The second positive electrode active material is in the form of single particles. These single particles can exist independently without grain boundaries, consist of a single particle, and can be or include single particles, monolithic structures, integral structures, or non-agglomerated particles in which the particles do not aggregate but exist as an independent phase in morphology. They can also be represented as single particles (integral particles, single crystals), for example, as single crystals. According to some example embodiments, the first positive electrode active material layer can exhibit improved lifetime characteristics while achieving high capacity and high energy density by including the second positive electrode active material in the form of single particles.

[0040] However, the second positive electrode active material in single-particle form has a longer internal lithium migration path than the positive electrode active material in polycrystalline form, and therefore the lithium migration rate may be relatively low, resulting in relatively low output characteristics. Therefore, in some example embodiments, a multilayer positive electrode design with both high energy density and high output characteristics includes a second positive electrode active material layer on top of a first positive electrode active material layer, which has the desired or improved output characteristics.

[0041] Meanwhile, the loading level of the first positive electrode active material layer can be approximately 10 mg / cm³. 2 Approximately 40 mg / cm 2 For example, approximately 10 mg / cm³ 2 Approximately 30 mg / cm 2 or about 10mg / cm 2 Approximately 20 mg / cm 2Additionally, the density of the first positive electrode active material layer in the pressed final positive electrode can be from about 3.0 g / cc to about 3.7 g / cc, for example, from about 3.3 g / cc to about 3.6 g / cc or from about 3.4 g / cc to about 3.58 g / cc.

[0042] Second positive electrode active material layer The third positive electrode active material can be expressed as large particles in the form of secondary particles, and the fourth positive electrode active material can be expressed as small particles in the form of secondary particles. The second positive electrode active material layer can achieve very high output characteristics and fast charging characteristics through a mixed positive electrode active material including the third and fourth positive electrode active materials. In a multi-layered positive electrode structure, by providing this second positive electrode active material layer, which is in contact with the negative electrode through a separator or similar material, on the outermost surface, output characteristics can be improved or enhanced, while simultaneously or concurrently improving or enhancing capacity and energy density.

[0043] The average particle size (D) of the active material of the third positive electrode 50 The particle size can be from about 10 μm to about 25 μm, for example, from about 10 μm to about 20 μm, from about 11 μm to about 18 μm, or from about 12 μm to about 16 μm. The average particle size (D) of the fourth positive electrode active material... 50 The particle size can be from about 2 μm to about 9 μm, for example, from about 2 μm to about 8 μm, or from about 3 μm to about 6 μm. When the third and fourth positive electrode active materials each exhibit the above particle size ranges, the output characteristics can be improved while simultaneously improving or increasing the energy density. Here, the average particle size (D...) 50 The particle size distribution can be obtained by selecting about 20 random particles from the scanning electron microscope image of the positive electrode active material, measuring their particle size (diameter or major axis length), and taking the size of the particles whose cumulative volume is 50% from the particle size distribution as the average particle size.

[0044] Both the third and fourth positive electrode active materials are in the form of secondary particles, and their shapes are not particularly limited, but can be, for example, spherical, elliptical, etc.

[0045] In the second positive electrode active material layer, based on the total amount of the third positive electrode active material and the fourth positive electrode active material, the content of the third positive electrode active material can be about 60 wt% to about 95 wt%, for example, about 60 wt% to about 90 wt%, about 70 wt% to about 80 wt%, or about 75 wt% to about 85 wt%, and the content of the fourth positive electrode active material can be about 5 wt% to about 40 wt%, for example, about 10 wt% to about 40 wt%, about 20 wt% to about 30 wt%, or about 15 wt% to about 25 wt%. When the third positive electrode active material and the fourth positive electrode active material are mixed in any of the above ratios, the energy density can be improved or increased while improving the output characteristics.

[0046] The lithium transition metal composite oxide of the third positive electrode active material and the lithium transition metal composite oxide of the fourth positive electrode active material can each independently be or include at least one of lithium nickel-based composite oxides, lithium cobalt-based composite oxides, lithium manganese-based composite oxides, lithium iron phosphate-based compounds, lithium iron manganese phosphate-based compounds, and combinations thereof. For example, both the lithium transition metal composite oxide of the third positive electrode active material and the lithium transition metal composite oxide of the fourth positive electrode active material can be or include lithium nickel-based composite oxides. In this case, high capacity can be achieved while exhibiting high energy density and output characteristics.

[0047] The lithium transition metal composite oxide of the third positive electrode active material and the lithium transition metal composite oxide of the fourth positive electrode active material can be the same as or different from each other, and each can independently be represented by Chemical Formula 1.

[0048] Chemical Formula 1: Li a1 Ni x1 M 1 y1 O 2-b1 X b1 In Chemical Formula 1, 0.9 ≤ a1 ≤ 1.8, 0.3 ≤ x1 < 1, 0 < y1 ≤ 0.7, 0.9 ≤ x1 + y1 ≤ ., and 0 ≤ b1 ≤ 0.1, M 1 is or includes one or more of Al, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is or includes one or more of F, P, and S.

[0049] In Chemical Formula 1, 0.3 ≤ x1 ≤ 0.99, 0.01 ≤ y1 ≤ 0.7; or 0.4 ≤ x1 ≤ 0.99, 0.01 ≤ y1 ≤ 0.6; or 0.5 ≤ x1 ≤ 0.99, 0.01 ≤ y1 ≤ 0.5; or 0.6 ≤ x1 ≤ 0.99, 0.01 ≤ y1 ≤ 0.4; or 0.7 ≤ x1 ≤ 0.99, 0.01 ≤ y1 ≤ 0.3; or 0.8 ≤ x1 ≤ 0.99, 0.01 ≤ y1 ≤ 0.2; or 0.9 ≤ x1 ≤ 0.99, 0.01 ≤ y1 ≤ 0.1; or 0.91 ≤ x1 ≤ 0.99, 0.01 ≤ y1 ≤ 0.09.

[0050] For example, the third positive electrode active material and the fourth positive electrode active material may be or include a high-nickel type positive electrode active material. In the high-nickel type positive electrode active material, based on 100 mol% of the metals other than lithium in the lithium transition metal composite oxide, the nickel content may be greater than or equal to about 80 mol%, greater than or equal to about 85 mol%, greater than or equal to about 90 mol%, greater than or equal to about 91 mol%, or greater than or equal to about 94 mol% and less than or equal to about 99 mol%. In this case, high energy density and output characteristics can be exhibited while achieving high capacity.

[0051] The lithium transition metal composite oxide of the third positive electrode active material and the lithium transition metal composite oxide of the fourth positive electrode active material may each independently be or include a lithium nickel cobalt composite oxide represented by Chemical Formula 2.

[0052] Chemical Formula 2: Li a2 Ni x2 Co y2 M 2 z2 O 2-b2 Xb2 In Chemical Formula 2, 0.9 ≤ a2 ≤ 1.8, 0.3 ≤ x2 < 1, 0 < y2 ≤ 0.7, 0 ≤ z2 ≤ 0.7, 0.9 ≤ x2 + y2 + z2 ≤ 1.1, and 0 ≤ b2 ≤ 0.1, M 2 is or includes one or more of Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is or includes one or more of F, P, and S.

[0053] In Chemical Formula 2, for example, 0.7 ≤ x2 < 1, 0 < y2 ≤ 0.3, 0 ≤ z2 ≤ 0.3; or 0.8 ≤ x2 < 1, 0 < y2 ≤ 0.2, 0 ≤ z2 ≤ 0.2; or 0.9 ≤ x2 < 1, 0 < y2 ≤ 0.1, 0 ≤ z2 ≤ 0.1.

[0054] Both the lithium transition metal composite oxide of the third positive electrode active material and the lithium transition metal composite oxide of the fourth positive electrode active material can be independently or include at least one of the lithium nickel cobalt manganese composite oxide, lithium nickel cobalt aluminum composite oxide, and lithium nickel cobalt aluminum manganese composite oxide represented by chemical formula 3.

[0055] Chemical formula 3: Li a3 Ni x3 Co y3 M 3 z3 M 4 w3 O 2-b3 X b3 In chemical formula 3, 0.9 ≤ a³ ≤ 1.8, 0.3 ≤ x³ ≤ 0.98, 0.01 ≤ y³ ≤ 0.69, 0.01 ≤ z³ ≤ 0.69, 0 ≤ w³ ≤ 0.69, 0.9 ≤ x³ + y³ + z³ + w³ ≤ 1.1 and 0 ≤ b³ ≤ 0.1, M 3 It is or includes one or more of Al, Mn and combinations thereof, M 4 X is or includes one or more of B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is or includes one or more of F, P, and S.

[0056] The third positive electrode active material may include secondary particles in which two or more primary particles are aggregated, and at least a portion of the primary particles may have a radially aligned structure. The description of the secondary particles with a radially aligned structure is the same as that of the secondary particles of the first positive electrode active material, and therefore a detailed description is omitted.

[0057] The loading level of the second positive electrode active material layer can be approximately 10 mg / cm³. 2 Up to approximately 40 mg / cm 2 For example, approximately 10 mg / cm³ 2 Approximately 30 mg / cm 2 or about 10mg / cm 2 Approximately 20 mg / cm 2 Additionally, the density of the second positive electrode active material layer in the rolled final positive electrode can be from about 3.0 g / cc to about 3.7 g / cc, for example, from about 3.3 g / cc to about 3.6 g / cc, or from about 3.4 g / cc to about 3.58 g / cc.

[0058] The thickness of the first positive electrode active material layer and the thickness of the second positive electrode active material layer can be the same or different, and based on the SEM image of the cross-section of the positive electrode, they can both be about 20 μm to about 200 μm, for example, about 30 μm to about 150 μm, or about 40 μm to about 100 μm.

[0059] The ratio of the thickness of the first positive electrode active material layer to the thickness of the second positive electrode active material layer can be configured to be from about 10:90 to about 90:10, for example, from about 20:80 to about 80:20, from about 30:70 to about 70:30, from about 40:60 to about 60:40, or it can be designed to be from 10:90 to 40:60, or it can be designed to be from about 60:40 to about 90:10.

[0060] In addition to the aforementioned positive electrode active material, the first positive electrode active material layer and the second positive electrode active material layer may further include a binder and / or a conductive material.

[0061] adhesive The binder improves the adhesion properties between the positive electrode active material particles and between the positive electrode active material particles and the current collector. Examples of binders may include, but are not limited to, at least one of the following: polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylate resin, polyester resin, and nylon.

[0062] conductive materials Conductive materials may be included to provide electrode conductivity, and any conductive material may be conductive unless it causes a chemical change in the battery. Examples of conductive materials may include at least one of the following: carbon-based materials, such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, carbon nanotubes, etc.; metallic materials, including metal powders or metal fibers of at least one of copper, nickel, aluminum, silver, etc.; conductive polymers, such as polyphenylene derivatives; or mixtures thereof.

[0063] Based on a 100wt% positive electrode active material layer, the contents of binder and conductive material can each be from about 0.5wt% to about 5wt% or from about 1wt% to about 3wt%.

[0064] Rechargeable lithium batteries Some example embodiments include a rechargeable lithium battery comprising the aforementioned positive electrode, negative electrode, and electrolyte. This rechargeable lithium battery may be or includes a lithium-ion battery using a liquid electrolyte, or it may be or includes an all-solid-state rechargeable battery or a semi-solid-state rechargeable battery using a solid electrolyte. Hereinafter, for convenience, the structure of the lithium-ion battery is described in detail.

[0065] Rechargeable lithium batteries can be classified according to their shape, such as cylindrical, prismatic, pouch-shaped, and coin-shaped. Figures 1 to 4 This is a schematic diagram illustrating a rechargeable lithium battery according to some example embodiments, wherein, Figure 1 It is a cylindrical battery. Figure 2 It is a prismatic battery, and Figure 3 and Figure 4 It is a pouch battery. (See reference) Figures 1 to 4 The rechargeable lithium battery 100 includes an electrode assembly 40 and a housing 50 therein, wherein the electrode assembly 40 has a separator 30 disposed between a positive electrode 10 and a negative electrode 20. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte (not shown). The rechargeable lithium battery 100 may include a sealing member 60 for sealing the housing 50, such as... Figure 1 As shown. In Figure 2 In this context, the rechargeable lithium battery 100 may include a positive electrode lead connector 11, a positive electrode terminal 12, a negative electrode lead connector 21, and a negative electrode terminal 22. For example... Figure 3 and Figure 4 As shown, the rechargeable lithium battery 100 includes Figure 4 The electrode terminals 70 shown and forming an electrical path for guiding the current formed in the electrode assembly 40 to the outside of the rechargeable lithium battery 100 (i.e., Figure 3 (The positive electrode terminal 71 and the negative electrode terminal 72 shown in the diagram).

[0066] negative electrode The negative electrode for a rechargeable lithium battery includes a current collector and a negative electrode active material layer on the current collector. The negative electrode active material layer includes a negative electrode active material and may further include a binder and / or a conductive material.

[0067] For example, the negative electrode active material layer may include about 90 wt% to about 99 wt% of negative electrode active material, about 0.5 wt% to about 5 wt% of binder, and about 0 wt% to about 5 wt% of conductive material.

[0068] Negative electrode active material 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 / de-doping lithium, or a transition metal oxide.

[0069] 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, for example, natural graphite or artificial graphite that is irregular, flaky, lamellar, spherical, or fibrous. The amorphous carbon may be or include at least one of soft carbon, hard carbon, mesophase pitch carbonized product, calcined coke, etc.

[0070] The lithium metal alloy includes an alloy of lithium and a metal, and the metal includes at least one of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn.

[0071] The material capable of doping / de-doping lithium may be or include 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 including at least one of an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element (excluding Si), a Group 15 element, a Group 16 element, a transition metal, a rare earth element, and a combination thereof), or a combination thereof. The Sn-based negative electrode active material may be or include at least one of Sn, SnO2, a Sn-based alloy, and a combination thereof.

[0072] The silicon-carbon composite may be or include a composite of silicon and amorphous carbon. According to some exemplary embodiments, the silicon-carbon composite may be in the form of silicon particles and amorphous carbon coated on the surface of the silicon particles. For example, the silicon-carbon composite may include secondary particles (cores) in which silicon primary particles are assembled and an amorphous carbon coating layer (shells) 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.

[0073] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include a core and an amorphous carbon coating layer on the surface of the core, and the core includes crystalline carbon and silicon particles.

[0074] 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.

[0075] The binder is configured to adhere the negative electrode active material particles to each other and also adhere the negative electrode active material to the current collector. The binder may be or include a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0076] Non-aqueous adhesives may include at least one of polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyimide, and combinations thereof.

[0077] Waterborne adhesives may include at least one of styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepoxychloropropane, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0078] When the aqueous binder is used as the negative electrode binder, it may further include a cellulose-based compound capable of imparting viscosity. As a cellulose-based compound, one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and their alkali metal salts may be mixed. The alkali metal may be or include at least one of Na, K, and Li.

[0079] The dry binder may be or include a polymeric material capable of being turned into fibers, and may be or include at least one of, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, and combinations thereof.

[0080] The conductive material is included to provide electrode conductivity, and any conductive material may be conductive unless it causes a chemical change. Examples of conductive materials include: carbon-based materials, such as at least one of 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 of at least one of copper, nickel, aluminum, silver, etc.; conductive polymers, such as polyphenylene derivatives; or mixtures thereof.

[0081] The negative electrode current collector may be or include at least one of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrate coated with conductive metal, and combinations thereof.

[0082] electrolyte Electrolytes used in rechargeable lithium batteries may include non-aqueous organic solvents and lithium salts.

[0083] Non-aqueous organic solvents constitute the medium for transporting ions that participate in the electrochemical reactions of the battery.

[0084] Non-aqueous organic solvents may be or include at least one of carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, aprotic solvents, and combinations thereof.

[0085] Carbonate solvents may include at least one of 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), and butyl carbonate (BC).

[0086] Ester solvents may include at least one of the following: methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanoic acid lactone, mevalonate lactone, caprolactone, etc.

[0087] Ether solvents may include at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. Additionally, ketone solvents may include cyclohexanone, etc. Alcohol solvents may include ethanol, isopropanol, etc., and aprotic solvents may include at least one of the following: nitriles, such as R-CN (wherein R is a C2 to C20 straight-chain, branched, or cyclic hydrocarbon group, and may include double bonds, aromatic rings, or ether groups), etc.; amides, such as dimethylformamide; dioxolane, such as 1,3-dioxolane, 1,4-dioxolane, etc.; sulfolane, etc.

[0088] Non-aqueous organic solvents can be used alone or in combination of two or more solvents.

[0089] When using carbonate solvents, cyclic carbonates and chain carbonates can be mixed, and the cyclic carbonates and chain carbonates can be mixed in a volume ratio of about 1:1 to about 1:9.

[0090] Lithium salts dissolved in organic solvents can supply lithium ions in batteries, enabling basic operation of rechargeable lithium batteries and improving lithium ion transport between the positive and negative electrodes. Examples of lithium salts include 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+1At least one of the following: (SO2) (where x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalate)phosphate (LiDFBOP), and lithium bis(oxalate)borate (LiBOB).

[0091] diaphragm Depending on the type of rechargeable lithium battery, a separator may be present between the positive and negative electrodes. The separator may include at least one of polyethylene, polypropylene, polyvinylidene fluoride, multilayer films of two or more layers thereof, and hybrid multilayer films (such as polyethylene / polypropylene double-layer separators, polyethylene / polypropylene / polyethylene triple-layer separators, polypropylene / polypropylene / polypropylene triple-layer separators, etc.).

[0092] The membrane may include a porous substrate and a coating layer on one or both surfaces of the porous substrate, comprising organic materials, inorganic materials or combinations thereof.

[0093] The porous substrate may be or include a polymer membrane, which is formed from or includes any one of the following polymers or copolymers or mixtures thereof, including polyolefins (such as at least one of polyethylene and polypropylene), polyesters (such as polyethylene terephthalate and polybutylene terephthalate), polyacetal, polyamide, polyimide, polycarbonate, polyetherketone, polyaryletherketone, polyetheretherketone, polyetheretherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene ether, cyclic olefin copolymers, polyphenylene sulfide, polyethylene naphthalate, glass fiber, and TEFLON (polytetrafluoroethylene).

[0094] Organic materials may include polymers such as polyvinylidene fluoride or (meth)acrylic acid polymers.

[0095] Inorganic materials may include inorganic particles, including at least one of Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof, but are not limited thereto.

[0096] Organic and inorganic materials can be mixed in a coating layer, or a coating layer containing organic materials and a coating layer containing inorganic materials can be stacked together.

[0097] The rechargeable lithium battery according to some example embodiments can be used in automobiles, mobile phones and / or various types of electrical devices, but this disclosure is not limited thereto.

[0098] Examples and comparative examples of this disclosure are described below. However, the following examples are merely examples of this disclosure, and this disclosure is not limited to these examples.

[0099] Example 1 1. Preparation of the active material for the first positive electrode The first nickel-based complex hydroxide (Ni) was synthesized as a precursor for the first positive electrode active material via a co-precipitation method described below. 0.945 Co 0.04 Al 0.015 (OH)2). Nickel sulfate (NiSO4·6H2O), cobalt sulfate (CoSO4·7H2O), and sodium aluminum sulfate (NaAl(SO4)2·12H2O) were mixed in a molar ratio of 94.5:4:1.5 and dissolved in distilled water as a solvent to prepare a mixed solution of metal raw materials. In addition, ammonia water (NH4OH) was prepared as a complexing agent and sodium hydroxide (NaOH) as a precipitating agent to form a complexing compound.

[0100] Step 1: 2.5kW / m 3 The concentration of NH4OH was 0.40 M, the pH was 10.5 to 11.5, and the reaction time was 6 hours. First, 0.40M ammonia solution is added to the reactor. (At 2.5 kW / m³) 3 Under controlled stirring power and a reaction temperature of 50°C, a mixed solution of metal raw materials and a complexing agent (NH4OH) were added at rates of 85 mL / min and 10 mL / min, respectively, to initiate the reaction. To maintain the pH, the reaction was carried out for 6 hours, with NaOH added concurrently. As a result, the obtained core particles were confirmed to have an average particle size (D0.05) of approximately 6.5 μm to 7.5 μm. 50 After that, proceed to the second step as follows.

[0101] Step 2: 2.0kW / m 3 The concentration of NH4OH was 0.45 M, the pH was 10.5 to 11.5, and the reaction time was 18 hours. By varying the addition rates to 85 mL / min and 12 mL / min, a mixed solution of metal raw materials and a complexing agent were added while maintaining the reaction temperature at 50°C. The complexing agent was adjusted to a concentration of 0.45 M. To maintain the pH, the reaction was carried out for 18 hours, during which NaOH was added. Here, the stirring power in this second step was reduced to 2.0 kW / m³. 3 The stirring power was lower than that of the first step. The reaction confirmed that the product particles, including the core and intermediate layer, had an average particle size (D) of 13.5 μm to 14 μm. 50 After that, proceed to the third step as follows.

[0102] Step 3: 1.5kW / m 3 The concentration of NH4OH was 0.45 M, the pH was 10.5 to 11.5, and the reaction time was 14 hours. While maintaining a reaction temperature of 50°C, the mixed solution of metal raw materials and the complexing agent were added at a rate substantially the same as in the second step, and the concentration of the complexing agent was substantially the same as in the second step. To maintain the pH, the reaction proceeded for 14 hours while adding NaOH. Here, the stirring power was reduced to 1.5 kW / m³. 3 Its stirring power is lower than that in the second step. The obtained material is washed and dried in hot air at about 150°C for 24 hours to obtain the first nickel-based composite hydroxide (Ni 0.945 Co 0.04 Al 0.015 (OH)2).

[0103] A first nickel-based composite hydroxide with a molar ratio of Li / (Ni+Co+Al)=0.96 and LiOH were placed in a calcination furnace, and then heat-treated for 7 hours at 700°C under an oxygen atmosphere for 8 hours to obtain the first positive electrode active material. The first positive electrode active material was confirmed to contain a first lithium-nickel composite oxide (Li... 0.96 Ni 0.945 Co 0.04 Al 0.015 O2) and average particle size (D 50 The particles are secondary particles of approximately 13.8 μm.

[0104] 2. Preparation of the active material for the second positive electrode The precursor for the second positive electrode active material synthesized by co-precipitation method: the second nickel-based complex hydroxide (Ni 0.94 Co 0.04 Al 0.01 Mn 0.01 (OH)2). Nickel sulfate (NiSO4·6H2O), cobalt sulfate (CoSO4·7H2O), sodium aluminum sulfate (NaAl(SO4)2·12H2O), and manganese sulfate (MnSO4·H2O) were dissolved in distilled water as a solvent in a molar ratio of 94:4:1:1 to prepare a mixed solution. The subsequent synthesis of the second nickel-based complex hydroxide was carried out in essentially the same manner as the preparation of the first nickel-based complex hydroxide.

[0105] The prepared second nickel-based composite hydroxide and lithium hydroxide were mixed in a 1:1 molar ratio, followed by heat treatment at 850°C under an oxygen atmosphere. The heat-treated product was then pulverized using an airflow impact crusher to obtain an average particle size (D) of approximately 3 μm. 50The second lithium-nickel composite oxide (LiNi) in single-particle form 0.94 Co 0.04 Al 0.1 Mn 0.01 O2).

[0106] 3. Fabrication of the first positive electrode active material layer The first positive electrode active material and the second positive electrode active material are mixed at a weight ratio of 7:3 to prepare the positive electrode active material.

[0107] A first positive electrode active material slurry was prepared by mixing 97.7 wt% of a mixed positive electrode active material, 1.2 wt% of polyvinylidene fluoride binder, and 1.1 wt% of carbon nanotube conductive material. This first positive electrode active material slurry was then coated onto an aluminum foil current collector, followed by drying and pressing to form the first positive electrode active material layer. The loading level of the first positive electrode active material layer was 10 mg / cm³. 2 The density of the first positive electrode active material layer is approximately 3.5 g / cc.

[0108] 4. Preparation of the precursor of the active material for the third positive electrode The precursor for the third positive electrode active material, synthesized via co-precipitation as described below, is a third nickel-based complex hydroxide (Ni...). 0.945 Co 0.04 Al 0.015 (OH)2). Nickel sulfate (NiSO4·6H2O), cobalt sulfate (CoSO4·7H2O), and sodium aluminum sulfate (NaAl(SO4)2·12H2O) were dissolved in distilled water as a solvent in a molar ratio of 94.5:4:1.5 to prepare a mixed solution of metal raw materials. Additionally, ammonia water (NH4OH) and sodium hydroxide (NaOH) were prepared as a precipitant to form a complex compound.

[0109] Step 1: 2.5kW / m 3 The concentration of NH4OH was 0.40 M, the pH was 10.5 to 11.5, and the reaction time was 6 hours. First, 0.40M ammonia solution is added to the reactor. (At 2.5 kW / m³) 3 Under controlled stirring power and a reaction temperature of 50°C, a mixed solution of metal raw materials and a complexing agent (NH4OH) were added at rates of 85 mL / min and 10 mL / min, respectively. To maintain pH, hydroxide (NaOH) was added simultaneously, and the reaction was allowed to proceed for 6 hours. As a result, the obtained core particles were confirmed to have an average particle size (D0) of approximately 6.5 μm to 7.5 μm. 50 After that, proceed to the second step as follows.

[0110] Step 2: 2.0kW / m3 The concentration of NH4OH was 0.45 M, the pH was 10.5 to 11.5, and the reaction time was 18 hours. While maintaining a reaction temperature of 50°C, the mixed metal raw material solution and complexing agent were added at varying rates of 85 mL / min and 12 mL / min, with the complexing agent concentration adjusted to 0.45 M. To maintain the pH, NaOH was added, and the reaction was allowed to proceed for 18 hours. Here, the stirring power was reduced to 2.0 kW / m. 3 The reaction was carried out at a lower stirring power than the first step. This reaction confirmed that the product particles, including the core and intermediate layer, had an average particle size (D0.05) of 13.5 μm to 14 μm. 50 After that, proceed to the third step as follows.

[0111] Step 3: 1.5kW / m 3 The concentration of NH4OH was 0.45 M, the pH was 10.5 to 11.5, and the reaction time was 14 hours. While maintaining a reaction temperature of 50°C, the addition rates of the metal raw material mixture and the complexing agent, as well as the concentration of the complexing agent, were set to be essentially the same as in the second step. To maintain the pH, the reaction was carried out for 14 hours, with NaOH added during the process. Here, the stirring power was reduced to 1.5 kW / m³. 3 The stirring power is lower than that of the second step. The obtained material is washed and dried in hot air at about 150°C for 24 hours to obtain the third nickel-based composite hydroxide (Ni 0.945 Co 0.04 Al 0.015 (OH)2).

[0112] 5. Preparation of the precursor for the fourth positive electrode active material The precursor for the fourth positive electrode active material, prepared by the co-precipitation method described later, is the fourth nickel-based complex hydroxide (Ni...). 0.94 Co 0.04 Mn 0.02 (OH)2). Nickel sulfate (NiSO4·6H2O), cobalt sulfate (CoSO4·7H2O), and manganese sulfate (MnSO4·H2O) were dissolved in distilled water as a solvent in a molar ratio of 94:4:2 to prepare a mixed solution of the metal raw materials. Ammonia water (NH4OH) and sodium hydroxide (NaOH) as a precipitant were prepared to form a complex compound.

[0113] First, 0.25M ammonia solution is added to the reactor. (3.0 kW / m³) 3The reaction was initiated simultaneously with the addition of a mixed metal raw material solution and a complexing agent at stirring power of 142 mL / min and a reaction temperature of 50 °C, respectively. To maintain the pH, the reaction was carried out for 30 hours while NaOH was added. As a result of the reaction, the average particle size (D) of the obtained particles was... 50 The reaction was complete when the particle size reached approximately 4 μm. The resulting material was washed and dried in hot air at approximately 150 °C for 24 hours to produce the fourth nickel-based composite hydroxide (Ni... 0.94 Co 0.04 Mn 0.02 (OH)2).

[0114] 6. Preparation of the active materials for the third and fourth positive electrodes 80wt% of the third nickel-based complex hydroxide (Ni 0.945 Co 0.04 Al 0.015 (OH)2) and 20wt% of the fourth nickel complex hydroxide (Ni 0.94 Co 0.04 Mn 0.02 (OH)2) was mixed, and LiOH was added to make the molar ratio of total metals other than Li to Li 1:1. Subsequently, the mixture was heat-treated by raising the temperature to 700°C for 8 hours in an oxygen atmosphere and holding the temperature for 7 hours to prepare the mixed positive electrode active material.

[0115] As confirmed by scanning electron microscopy (SEM) analysis, the active material of the third positive electrode exists as secondary particles with an internal portion having an irregular porous structure and an external portion having a radially arranged structure. The average particle size (D) of the secondary particles is... 50 The particle size was approximately 14 μm. The fourth positive electrode active material was confirmed to be in the form of secondary particles containing aggregates of multiple primary particles, wherein the secondary particles had an average particle size of approximately 4 μm (D). 50 ).

[0116] 7. Fabrication of the second positive electrode active material layer A second positive electrode active material slurry was prepared by mixing 97.7 wt% of the mixed positive electrode active material prepared in step six, 1.2 wt% of polyvinylidene fluoride binder, and 1.1 wt% of carbon nanotube conductive material. This second positive electrode active material slurry was then coated onto the first positive electrode active material layer and dried to form the second positive electrode active material layer, followed by pressing. The loading level of the second positive electrode active material layer was 10 mg / cm³. 2 The density of the pressed second positive electrode active material layer is approximately 3.38 g / cc.

[0117] SEM analysis of the pressed positive electrode showed that the first positive electrode active material layer had a thickness of approximately 47.5 μm, and the second positive electrode active material layer had a thickness of approximately 47.5 μm.

[0118] 8. Manufacturing of rechargeable lithium battery cells (semi-cells) A polytetrafluoroethylene (PTFE) separator is placed between the manufactured positive electrode and the lithium counter electrode, and then inserted into the battery casing. An electrolyte prepared by dissolving 1 M LiPF6 in a mixed solvent by mixing ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a volume ratio of 2:4:4, and adding 1.5 wt% ethylene carbonate to the mixture is injected into the casing, thereby manufacturing a rechargeable lithium battery using conventional methods.

[0119] Comparison Example 1 The positive electrode and the rechargeable lithium battery cell are manufactured in essentially the same manner as in Example 1, except that a first positive electrode active material layer with a thickness of about 95 μm is formed separately without forming a second positive electrode active material layer.

[0120] Comparison Example 2 The positive electrode and the rechargeable lithium battery cell are manufactured in essentially the same manner as in Example 1, except that a second positive electrode active material layer with a thickness of about 95 μm is formed separately instead of a first positive electrode active material layer.

[0121] Evaluation Example: Evaluation of Cell Performance Initial charge and discharge were performed at 25°C by charging the semi-monomers according to Example 1 and Comparative Examples 1 to 2 at a constant current of 0.2C to an upper limit voltage of 4.25V and discharging them at 0.2C to a discharge cutoff voltage of 3.0V, thereby measuring the initial discharge capacity, as shown in Table 1. Furthermore, the density of the positive electrode active material layer was multiplied by the initial discharge capacity to obtain the capacity per unit volume, as shown in Table 1.

[0122] After the initial charge and discharge, a second charge and discharge cycle is performed at 0.5C / 0.5C within a voltage range of 3.0V to 4.25V, followed by a third charge and discharge cycle at 1C / 1C, a fourth charge and discharge cycle at 2C / 2C, and a fifth charge and discharge cycle at 3C / 3C. The ratio of the discharge capacity of the fifth cycle to the initial discharge capacity is calculated and presented as the output characteristic.

[0123] Table 1

[0124] Referring to Table 1, Example 1 shows significantly improved output characteristics compared to Comparative Example 1, and significantly improved unit volume capacity compared to Comparative Example 2, which confirms that unit volume capacity and output characteristics are improved simultaneously or concurrently.

[0125] While this disclosure has been described in conjunction with exemplary embodiments now considered practical, it will be understood that this disclosure is not limited to the disclosed exemplary embodiments. Rather, it is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

[0126] Description of reference numerals in the attached figures: 100: Rechargeable lithium battery 10: Positive electrode 11: Positive electrode lead connector 12: Positive electrode terminal 20: Negative electrode 21: Negative electrode lead connector 22: Negative electrode terminal 30: Diaphragm 40: Electrode assembly 50: Casing 60: Sealing component 70: Electrode connector 71: Positive electrode connector 72: Negative electrode connector.

Claims

1. A positive electrode for a rechargeable lithium battery, the positive electrode comprising: current collector; A first positive electrode active material layer is disposed on the current collector; as well as The second positive electrode active material layer is located on top of the first positive electrode active material layer. The first positive electrode active material layer comprises: a first positive electrode active material, comprising a lithium transition metal composite oxide, and in the form of secondary particles formed by the aggregation of multiple primary particles; and a second positive electrode active material, comprising a lithium transition metal composite oxide in the form of single particles, and having a particle size D greater than that of the first positive electrode active material. 50 Small average particle size D 50 ,and The second positive electrode active material layer includes: a third positive electrode active material comprising a lithium transition metal composite oxide in the form of secondary particles formed by the aggregation of multiple primary particles; and a fourth positive electrode active material comprising a lithium transition metal composite oxide in the form of secondary particles formed by the aggregation of multiple primary particles, and having a larger average particle size D than the third positive electrode active material. 50 Small average particle size D 50 .

2. The positive electrode according to claim 1, wherein: The average particle size D of the first positive electrode active material 50 The range is from 10μm to 25μm, and The average particle size D of the second positive electrode active material 50 The range is from 1μm to 8μm.

3. The positive electrode according to claim 1, wherein, In the first positive electrode active material layer, based on the total amount of the first positive electrode active material and the second positive electrode active material, the content of the first positive electrode active material is 60wt% to 95wt%, and the content of the second positive electrode active material is 5wt% to 40wt%.

4. The positive electrode according to claim 1, wherein, Both the lithium transition metal composite oxide of the first positive electrode active material and the lithium transition metal composite oxide of the second positive electrode active material independently include lithium nickel composite oxides.

5. The positive electrode according to claim 1, wherein, Both the lithium transition metal composite oxide of the first positive electrode active material and the lithium transition metal composite oxide of the second positive electrode active material are independently represented by chemical formula 1: Chemical Formula 1 Li a1 Ni x1 M 1 y1 O 2-b1 X b1 Among them, in Chemical Formula 1, 0.9 ≤ a1 ≤ 1.8, 0.3 ≤ x1 < 1, 0 < y1 ≤ 0.7, 0.9 ≤ x1 + y1 ≤ 1.1 and 0 ≤ b1 ≤ 0.1, M 1 includes one or more of Al, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn and Zr, and X includes one or more of F, P and S.

6. The positive electrode according to claim 1, wherein, The first positive electrode active material layer has a density of 3.0 g / cc to 3.7 g / cc.

7. The positive electrode according to claim 1, wherein: The average particle size D of the third positive electrode active material 50 The range is from 10μm to 25μm, and The average particle size D of the fourth positive electrode active material 50 The range is from 2μm to 9μm.

8. The positive electrode according to claim 1, wherein, In the second positive electrode active material layer, based on the total amount of the third positive electrode active material and the fourth positive electrode active material, the content of the third positive electrode active material is 60wt% to 95wt%, and the content of the fourth positive electrode active material is 5wt% to 40wt%.

9. The positive electrode according to claim 1, wherein, The lithium transition metal composite oxide of the third positive electrode active material and the lithium transition metal composite oxide of the fourth positive electrode active material both independently include lithium-nickel composite oxides.

10. The positive electrode according to claim 1, wherein, The lithium transition metal composite oxide of the third positive electrode active material and the lithium transition metal composite oxide of the fourth positive electrode active material are both independently represented by chemical formula 1: Chemical Formula 1 Li a1 Ni x1 M 1 y1 O 2-b1 X b1 Among them, in Chemical Formula 1, 0.9 ≤ a1 ≤ 1.8, 0.3 ≤ x1 < 1, 0 < y1 ≤ 0.7, 0.9 ≤ x1 + y1 ≤ 1.1 and 0 ≤ b1 ≤ 0.1, M 1 includes one or more of Al, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X includes one or more of F, P, and S.

11. The positive electrode according to claim 1, wherein, The second positive electrode active material layer has a density of 3.0 g / cc to 3.7 g / cc.

12. The positive electrode according to claim 1, wherein: The first positive electrode active material layer has a thickness of 20 μm to 200 μm, and The second positive electrode active material layer has a thickness of 20 μm to 200 μm.

13. The positive electrode according to claim 1, wherein, The ratio of the thickness of the first positive electrode active material layer to the thickness of the second positive electrode active material layer is in the range of 10:90 to 90:

10.

14. A rechargeable lithium battery, said rechargeable lithium battery comprising: The positive electrode according to claim 1; negative electrode; as well as Electrolytes.

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