Negative electrode plate for rechargeable lithium battery and rechargeable lithium battery comprising the same

Abstract

The present invention relates to a negative electrode plate for a rechargeable lithium battery and a rechargeable lithium battery including the same, in which the negative electrode plate includes a negative electrode active material including a mixture of a first negative electrode active material, a second negative electrode active material, and a third negative electrode active material, the first negative electrode active material includes natural graphite including secondary particles assembled of primary particles, and an amorphous carbon coating layer containing amorphous carbon and surrounding the secondary particles, and has an orientation degree of 90 or less and a d002 value of 3.356 Å to 3.360 Å, the second negative electrode active material is artificial graphite, and the third negative electrode active material includes a composite of silicon and crystalline carbon, and an amorphous carbon coating layer containing amorphous carbon and formed on a surface of the composite.

Description

[0001] This application claims priority and benefit to Korean Patent Application No. 10-2024-0175700 and Korean Patent Application No. 10-2024-0175704, both filed on November 29, 2024, with the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference. Technical Field

[0002] An aspect of the embodiments of this disclosure relates to a negative electrode plate for a rechargeable lithium battery and a rechargeable lithium battery including the negative electrode plate. Background Technology

[0003] Recently, with the rapid proliferation of battery-powered electronic devices such as mobile phones, laptops, and electric vehicles, the demand for rechargeable batteries with high energy density and high capacity is increasing rapidly. Therefore, research and development to improve the performance of rechargeable lithium batteries is actively underway.

[0004] A rechargeable lithium battery is a battery that includes a positive electrode and a negative electrode containing active materials capable of inserting and deintercalating lithium ions, and generates electrical energy through redox reactions when lithium ions are deintercalated from the positive electrode and inserted into the negative electrode and deintercalated from the negative electrode and inserted into the positive electrode. Summary of the Invention

[0005] According to an embodiment of the present invention, a negative electrode plate for a rechargeable lithium battery is provided, exhibiting high energy density, boost charging, and long lifespan characteristics.

[0006] According to another aspect of the embodiments of the present invention, a negative electrode plate for a rechargeable lithium battery is provided, exhibiting reduced expansion of silicon-based active materials, shortened boost charging time, long lifespan, and high energy density.

[0007] According to another aspect of the present invention, a rechargeable lithium battery including the above-described negative electrode plate is provided.

[0008] According to one or more embodiments of the present invention, a negative electrode plate for a rechargeable lithium battery comprises: a negative electrode active material, including a mixture of a first negative electrode active material, a second negative electrode active material, and a third negative electrode active material, wherein the first negative electrode active material comprises: natural graphite, including secondary particles assembled from primary particles; and an amorphous carbon coating layer comprising amorphous carbon and surrounding the secondary particles, and the first negative electrode active material has an orientation degree of 90 or less and a d002 value of 3.356 Å to 3.360 Å, the second negative electrode active material is artificial graphite, and the third negative electrode active material comprises: a composite of silicon and crystalline carbon; and an amorphous carbon coating layer comprising amorphous carbon and formed on the surface of the composite.

[0009] According to one or more embodiments of the present invention, a rechargeable lithium battery includes the negative electrode plate and positive electrode described above for a rechargeable lithium battery. Attached Figure Description

[0010] The above and other aspects, objects, features, and advantages of the invention will become more apparent to those skilled in the art from the description of some embodiments of the invention with reference to the accompanying drawings, in which: Figure 1 This is a conceptual diagram of the first negative electrode active material according to an embodiment; Figure 2 This is a conceptual diagram of the third negative electrode active material according to an embodiment; Figures 3 to 6 This is a schematic diagram illustrating a rechargeable lithium battery according to an embodiment of the present invention; and Figure 7 The scanning electron microscope (SEM) evaluation results of the negative electrode plate according to the embodiment are shown. Detailed Implementation

[0011] Some embodiments of the invention will be described in more detail herein. However, these embodiments are presented by way of example, and the invention is not limited thereto; rather, it is defined by the scope of the claims.

[0012] Unless otherwise stated herein, when a component such as a layer, film, region, plate, etc. is referred to as being “on” another component, it includes not only the case where the component is “directly on” the other component, but also the case where there are one or more other components between them.

[0013] Unless otherwise stated herein, the singular may also include the plural. Furthermore, unless otherwise stated, “A or B” may mean “including A”, “including B”, or “including both A and B”.

[0014] In this specification, “combinations thereof” can refer to mixtures, laminates, composites, copolymers, alloys, blends and reaction products of the components.

[0015] Unless otherwise defined herein, particle size can refer to the average particle size. Alternatively, particle size refers to the average particle size (D50) as the diameter of particles that constitute 50% of the cumulative volume in a particle size distribution. The average particle size (D50) can be measured using methods known to those skilled in the art (e.g., using a particle size analyzer, transmission electron microscopy, or scanning electron microscopy). Alternatively, the average particle size can be measured using a measuring device that utilizes dynamic light scattering, and the average particle size (D50) value can be obtained by performing data analysis, counting the number of particles within each particle size range, and then calculating the D50 value. Optionally, the average particle size can be measured using laser diffraction. When measuring the average particle size using laser diffraction, more specifically, the average particle size (D50) can be calculated based on a 50% particle size distribution after dispersing the target particles in a dispersion medium, introducing the particles into a commercially available laser diffraction particle size measuring device (such as the MT 3000 from Microtrac), and irradiating the particles with ultrasound at an output of approximately 28 kHz at 60 W.

[0016] When the particles are spherical, the size can refer to the diameter.

[0017] The negative electrode plate for a rechargeable lithium battery according to the embodiment can provide low resistance, high energy density, and boost charging effect.

[0018] The negative electrode plate for a rechargeable lithium battery according to an embodiment includes: a negative electrode active material, comprising a mixture of a first negative electrode active material, a second negative electrode active material, and a third negative electrode active material, wherein the first negative electrode active material comprises: natural graphite, including secondary particles formed by the assembly of primary particles; and an amorphous carbon coating layer comprising amorphous carbon and surrounding the secondary particles, and having an orientation degree of 90 or less and a d002 value of 3.356 Å to 3.360 Å; the second negative electrode active material comprises or is composed of artificial graphite; the third negative electrode active material comprises: a composite of silicon and crystalline carbon; and an amorphous carbon coating layer comprising amorphous carbon and formed on the surface of the composite.

[0019] By including the above mixture as the negative electrode active material, the negative electrode plate for rechargeable lithium batteries can provide high capacity retention, high energy density, improved boost charging and fast charging life.

[0020] In embodiments, the mixture may be included in an amount of 95 wt% or greater (e.g., 95 wt% to 100 wt%, 99 wt% to 100 wt%, or 100 wt%) of the total negative electrode active material in the negative electrode plate. Within this range, the effect of the negative electrode plate can be easily achieved.

[0021] In the embodiments, the negative electrode active material (e.g., a mixture) may be included in an amount of 90 wt% to 99 wt% of the negative electrode plate. Within this range, capacity improvement can be achieved.

[0022] If the mixture does not include the first negative electrode active material, the electrode plate density may be reduced, making it difficult to achieve high energy density battery cells and weakening the boost charging effect.

[0023] If the mixture does not contain a second negative electrode active material, the long-life characteristics at high temperatures may deteriorate.

[0024] If the mixture does not include a third negative electrode active material, the increase in capacity per volume may be reduced.

[0025] In the embodiments, the mixture may be in the range of 20 wt% to 75 wt% (e.g., 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt%, 25 wt%, 26 wt%, 27 wt%, 28 wt%, 29 wt%, 30 wt%, 31 wt%, 32 wt%, 33 wt%, 34 wt%, 35 wt%, 36 wt%, 37 wt%, 38 wt%, 39 wt%, 40 wt%, 41 wt%, 42 wt%, 43 wt%, 44 wt%, 45 wt%, 46 wt%, 47 wt%, 48 wt%, 49 wt%, 50 wt%, 51 wt%, 52 wt%, 53 wt%, 54 wt%, 55 wt%, 56 wt%). The first negative electrode active material is included in amounts of 57wt%, 58wt%, 59wt%, 60wt%, 61wt%, 62wt%, 63wt%, 64wt%, 65wt%, 66wt%, 67wt%, 68wt%, 69wt%, 70wt%, 71wt%, 72wt%, 73wt%, 74wt%, or 75wt%), and in embodiments, the first negative electrode active material is included in amounts of 20wt% to 65wt%, or 20wt% to 60wt%, and the mixture may be in amounts of 20wt% to 75wt% (e.g., 20wt%, 21wt%, 22wt%, 23wt%, 24wt%, 25wt%, 26wt%, 27wt%, 28wt%). 29wt%, 30wt%, 31wt%, 32wt%, 33wt%, 34wt%, 35wt%, 36wt%, 37wt%, 38wt%, 39 wt%, 40wt%, 41wt%, 42wt%, 43wt%, 44wt%, 45wt%, 46wt%, 47wt%, 48wt%, 49wt %, 50wt%, 51wt%, 52wt%, 53wt%, 54wt%, 55wt%, 56wt%, 57wt%, 58wt%, 59wt%, 60wt%, 61wt%, 62wt%, 63wt%, 64wt%, 65wt%, 66wt%, 67wt%, 68wt%, 69wt%, 70w The mixture includes a second negative electrode active material in amounts of 71 wt%, 72 wt%, 73 wt%, 74 wt%, or 75 wt%, and in embodiments, it includes a second negative electrode active material in amounts of 20 wt% to 65 wt%, or 20 wt% to 60 wt%, and the mixture may include a third negative electrode active material in amounts of 1 wt% to 20 wt% (e.g., 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, or 20 wt%), and in embodiments,The mixture includes a third negative electrode active material in amounts of 1 wt% to 15 wt%, 1 wt% to 14 wt%, 1 wt% to 10 wt%, or 5 wt% to 7 wt%. Within this range, the mixture can readily achieve high energy density, exhibit boost charging performance, and improve lifetime under fast charging conditions.

[0026] In an embodiment, the total amount of the first negative electrode active material and the second negative electrode active material can be from 85 wt% to 99 wt% (e.g., 85 wt%, 86 wt%, 87 wt%, 88 wt%, 89 wt%, 90 wt%, 91 wt%, 92 wt%, 93 wt%, 94 wt%, 95 wt%, 96 wt%, 97 wt%, 98 wt%, or 99 wt%), and in an embodiment, the total amount of the first negative electrode active material and the second negative electrode active material can be from 86 wt% to 99 wt% or from 90 wt% to 99 wt%, and the third negative electrode active material can be included in an amount from 1 wt% to 15 wt% (e.g., 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, or 15 wt%), and in an embodiment, the third negative electrode active material can be included in an amount from 1 wt% to 14 wt% or from 1 wt% to 10 wt%. Within this range, boost charging and fast charging can improve lifespan.

[0027] In the embodiments, the third negative electrode active material may have a specific capacity of 500 mAh / g or less.

[0028] In this embodiment, based on a total of 100 parts by weight of the first negative electrode active material and the second negative electrode active material, the weight ratio of the first negative electrode active material to the second negative electrode active material can be from 10:90 to 90:10, for example, 25:75 to 75:25, 40:60 to 60:40, or 50:50. Within this range, the improvement effect on boost charging and fast charging lifespan can be further enhanced.

[0029] In this embodiment, the negative electrode plate can have a density of 1.3 g / cc to 1.7 g / cc (e.g., 1.3 g / cc to 1.68 g / cc). Within this range, high energy density and boost charging can be easily achieved.

[0030] Here, the components of the negative electrode active material will be described in more detail.

[0031] The first negative electrode active material comprises: natural graphite, including secondary particles formed by the assembly of primary particles; and an amorphous carbon coating layer comprising amorphous carbon and surrounding the secondary particles. In an embodiment, the orientation degree of the first negative electrode active material is 90 or less, and d002 is 3.356 Å to 3.360 Å.

[0032] In this specification, “orientation degree” can refer to the ratio of the diffraction peak intensity [I(002)] of the (002) plane to the diffraction peak intensity [I(110)] of the (110) plane, as measured by X-ray diffraction analysis using CuKα radiation, and is expressed as I(002) / I(110).

[0033] In this specification, "d002" may refer to the interplanar spacing of the (002) plane of the first negative electrode active material, as measured by X-ray diffraction analysis using CuKα radiation.

[0034] Natural graphite is generally advantageous as a negative electrode active material for batteries, but its high resistance may lead to poor charging characteristics, and its internal porosity may cause side reactions, thus negatively affecting long-term durability and expansion rate.

[0035] The first negative electrode active material addresses this issue by significantly reducing the average particle size of the secondary particles of natural graphite to make them fine particles, thereby effectively reducing resistivity. To offset the efficiency reduction caused by the increased specific surface area of ​​the secondary particles, the first negative electrode active material is calcined at the following temperature, thereby reducing the specific surface area while providing high efficiency.

[0036] In this embodiment, the first negative electrode active material comprises natural graphite and an amorphous carbon coating layer containing amorphous carbon, and satisfies the aforementioned orientation degree and d002. Therefore, the first negative electrode active material can enhance battery capacity and significantly improve charging C-rate characteristics, thereby enhancing the fast-charging performance of the rechargeable lithium battery. Although the first negative electrode active material comprises natural graphite, it can significantly reduce resistance and provide high energy density, suppress side reactions with the electrolyte, and improve battery life.

[0037] Lower orientation results in a more random arrangement of edge planes in natural graphite, which increases the disordered orientation of the first negative electrode active material. This facilitates lithium-ion insertion into / extraction from the secondary particles of natural graphite, thereby improving the capacity characteristics of rechargeable lithium batteries using them. In embodiments, for example, the orientation degree can be 80 or less (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48). The orientation degree can be 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, or 80), and in the embodiments, the orientation degree can be 10 to 80, 20 to 80, 30 to 80, 40 to 80, or 50 to 80. The orientation degree can be achieved by adjusting the average particle size (D50) of the secondary particles and the long axis length of the primary particles. The first negative electrode active material significantly reduces the average particle size (D50) of the secondary particles to address the high resistivity problem of natural graphite.

[0038] In an embodiment, as described below, the D50 of the secondary particles in the first negative electrode active material is substantially smaller than the long axis length of the primary particles. In an embodiment, the secondary particles are formed by crumpling the primary particles. In an embodiment, the first negative electrode active material comprises amorphous carbon and can be prepared by heat treatment at a temperature of 2500°C or higher to achieve a high degree of graphitization, as described below. This high degree of graphitization can enhance the capacity of the first negative electrode active material while mitigating the efficiency reduction due to the reduced average particle size (D50) of the secondary particles and the increased specific surface area. In an embodiment, the first negative electrode active material has a d002 value of 3.356 Å to 3.360 Å. Within this range, a first negative electrode active material comprising secondary particles with a relatively small average particle size (D50) can offset the battery efficiency reduction due to the increased specific surface area, thereby achieving high capacity. In embodiments, for example, d002 can be 3.356 Å, 3.3561 Å, 3.3562 Å, 3.3563 Å, 3.3564 Å, 3.3565 Å, 3.3566 Å, 3.3567 Å, ​​3.3568 Å, 3.3569 Å, 3.357 Å, 3.3571 Å, 3.3572 Å, 3.3573 Å, 3.3574 Å, 3.3575 Å, 3.3576 Å, 3.3577 Å, 3.3578 Å, 3.3 579Å, 3.358Å, 3.3581Å, 3.3582Å, 3.3583Å, 3.3584Å, 3.3585Å, 3.3586Å, 3.3587Å, 3.3588Å, 3.3589Å, 3.359Å, 3.3591Å, 3.3592Å, 3.3593Å, 3.3594Å, 3.3595Å, 3.3596Å, 3.3597Å, 3.3598Å, 3.3599Å, or 3.360Å.

[0039] According to embodiments, the first negative electrode active material can have a mercury (Hg) accumulation pore volume of 0.01 mL / g to 0.06 mL / g (e.g., 0.01 mL / g, 0.02 mL / g, 0.03 mL / g, 0.04 mL / g, 0.05 mL / g, or 0.06 mL / g), and in embodiments, the first negative electrode active material can have a mercury (Hg) accumulation pore volume of 0.02 mL / g to 0.06 mL / g, or 0.03 mL / g to 0.06 mL / g. Within this range, the first negative electrode active material has minimal internal porosity (i.e., empty space) and an appropriate amorphous carbon content, thereby resulting in excellent efficiency of the first negative electrode active material. Furthermore, the first negative electrode active material can maintain an optimal density to enable effective electrolyte impregnation while controlling the surface area reacting with the electrolyte to a level that is not excessive, thereby suppressing side reactions and ensuring sufficient lifetime. Hg cumulative pore volume can be a characteristic of negative electrode active materials, which include finely ground natural graphite and are prepared by the following preparation methods to minimize or reduce specific surface area.

[0040] In an embodiment, the first negative electrode active material may have a sphericity (S) of 0.85 or greater as defined in Equation 1 below: Equation 1 Sphericity (S) = 4π × A / B 2 , Where A is the area of ​​the first negative electrode active material and B is the perimeter of the shape of the first negative electrode active material.

[0041] In the embodiments, B may refer to the perimeter of the actual particle shape of the first negative electrode active material.

[0042] The sphericity of the active material of the first negative electrode can be determined by projecting the three-dimensional particle onto a two-dimensional plane. For example, sphericity can be defined as the ratio of the circumference of a circle with the same area as the projected particle to the actual circumference of the particle boundary.

[0043] In Equation 1, the area A is calculated by acquiring a cross-sectional SEM image of the electrode using controlled pressure scanning electron microscopy (CP-SEM) and then using that image to measure the actual perimeter B of the particle boundary using ImageJ software. Area A refers to the area of ​​a circle with a perimeter equal to B. In this embodiment, B may represent the total length measured along the particle boundary, regardless of whether the shape is a perfect sphere or a non-spherical shape with surface irregularities.

[0044] In an embodiment, the first negative electrode active material may have a sphericity of 0.85 to 1.0 (e.g., 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, or 1.0), and in another embodiment, the first negative electrode active material may have a sphericity of 0.90 to 1.0, 0.90 to 0.98, or 0.90 to 0.95. When the sphericity is within this range, expansion during charge / discharge cycles can be effectively suppressed.

[0045] In the embodiments, the first negative electrode active material may have a particle density of 1.60 g / cc to 1.80 g / cc. Within this range, the first negative electrode active material may exhibit reduced internal porosity and suppressed side reactions with the electrolyte, thereby improving lifetime characteristics. In the embodiments, for example, the particle density may be from 1.60 g / cc to 1.80 g / cc (e.g., 1.60 g / cc, 1.61 g / cc, 1.62 g / cc, 1.63 g / cc, 1.64 g / cc, 1.65 g / cc, 1.66 g / cc, 1.67 g / cc, 1.68 g / cc, 1.69 g / cc, 1.70 g / cc, 1.71 g / cc, 1.72 g / cc, 1.73 g / cc, 1.74 g / cc, 1.75 g / cc, 1.76 g / cc, 1.77 g / cc, 1.78 g / cc, 1.79 g / cc, or 1.80 g / cc), and in the embodiments, the particle density may be from 1.70 g / cc to 1.80 g / cc.

[0046] In the embodiments, the first negative electrode active material may have a concentration of 0.75 g / cc to 1.20 g / cc (e.g., 0.75 g / cc, 0.76 g / cc, 0.77 g / cc, 0.78 g / cc, 0.79 g / cc, 0.80 g / cc, 0.81 g / cc, 0.82 g / cc, 0.83 g / cc, 0.84 g / cc, 0.85 g / cc, 0.86 g / cc, 0.87 g / cc, 0.88 g / cc, 0.89 g / cc, 0.90 g / cc, 0.91 g / cc, 0.92 g / cc, 0.93 g / cc, 0.94 g / cc, 0.95 g / cc, 0.96 g / cc, 0.97 g / cc, 0.98 ...6 g / cc, 0.97 g / cc, 0.98 g / cc, 0.96 g / cc, 0.97 g / cc, 0.98 g / cc, 0.96 g / cc, 0.97 g / cc, 0.96 g / cc, 0.97 g / cc, 0.98 g / cc, 0.96 g / cc, 0.97 g / cc, 0.96 g / cc, 0.97 g / cc, 0.98 g / cc, 0.96 The tap density can be 0.99 g / cc, 1.00 g / cc, 1.01 g / cc, 1.02 g / cc, 1.03 g / cc, 1.04 g / cc, 1.05 g / cc, 1.06 g / cc, 1.07 g / cc, 1.08 g / cc, 1.09 g / cc, 1.10 g / cc, 1.11 g / cc, 1.12 g / cc, 1.13 g / cc, 1.14 g / cc, 1.15 g / cc, 1.16 g / cc, 1.17 g / cc, 1.18 g / cc, 1.19 g / cc, or 1.20 g / cc, and in the embodiments, it can have a tap density of 0.75 g / cc to 1.0 g / cc, or 0.95 g / cc to 1.20 g / cc. Within this range, the first negative electrode active material can exhibit reduced internal porosity and suppressed side reactions with the electrolyte, thereby improving lifetime characteristics. Tap density was measured using a GeoPyc 1360 specific gravity bottle from Micromeritics, equipped with a 19.1 mm diameter chamber and a specific gravity of 0.2907 cm⁻¹. 3 The conversion factor is / mm. The process involves applying a pressure of 108N three times and calculating the average of the results.

[0047] In an embodiment, the first negative electrode active material may have a 10m 2 / g or less (e.g., 1m) 2 / g, 1.5m 2 / g、2m 2 / g, 2.5m 2 / g、3m 2 / g, 3.5m 2 / g、4m 2 / g, 4.5m 2 / g、5m 2 / g, 5.5m 2 / g、6m 2 / g, 6.5m 2 / g、7m 2 / g, 7.5m2 / g、8m 2 / g, 8.5m 2 / g、9m 2 / g, 9.5m 2 / g or 10m 2 The specific surface area is 1 m² / g, and in the embodiments, the first negative electrode active material can have a specific surface area of ​​1 m² / g. 2 / g to 10m 2 The specific surface area is defined as / g. Within this range, the first negative electrode active material can exhibit reduced internal porosity and suppressed side reactions with the electrolyte, thereby improving lifetime characteristics. Specific surface area can be the BET specific surface area.

[0048] In embodiments, the first negative electrode active material may have an internal porosity of 2% or less (e.g., 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, or 2%), and in embodiments, the first negative electrode active material may have an internal porosity of 1.8% or less, 1.5% or less, 1.0% to 1.5%, or 1.0% to 1.3%. Within this range, side reactions between the first negative electrode active material and the electrolyte can be suppressed, thereby improving the lifespan of the rechargeable lithium battery. The total pore volume and mesopore volume can be quantitatively measured using Barrett-Joyner-Halenda (BJH) analysis.

[0049] Here, the composition of the active material of the first negative electrode is described in more detail.

[0050] The first negative electrode active material includes: natural graphite, including secondary particles assembled from primary particles; and a coating layer containing amorphous carbon and surrounding the secondary particles.

[0051] Natural graphite can be in the form of flakes or thin sheets (e.g., scaly sheets).

[0052] In the embodiments, the primary particles may have a size from 10 μm to 200 μm (e.g., 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, 105 μm, 110 μm, 115 μm, 120 μm, 125 μm). The primary particles have a major axis length of 10 μm to 100 μm, 30 μm to 60 μm, or 20 μm (m, 130 μm, 135 μm, 140 μm, 145 μm, 150 μm, 155 μm, 160 μm, 165 μm, 170 μm, 175 μm, 180 μm, 185 μm, 190 μm, 195 μm, or 200 μm), and in the embodiments, the primary particles may have a major axis length of 10 μm to 100 μm, 30 μm to 60 μm, or 20 μm to 50 μm. Within this range, assembly into secondary particles is easy, and the target ratios described below can be easily achieved.

[0053] When the primary particles are plate-shaped, "major axis length" refers to the length of the longest axis between two opposing surfaces.

[0054] In a specific example, the primary particles may be plate-shaped, but are not limited to this.

[0055] In embodiments, the secondary particles may have an average particle size (D50) of 30 μm or less. Within this range, the target ratios described below can be easily achieved. In embodiments, for example, the secondary particles may have an average particle size (D50) of 5 μm or greater and 10 μm or less (e.g., 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm), and in embodiments, the secondary particles may have an average particle size (D50) of 6 μm or greater and less than 8 μm. Within this range, the aforementioned orientation and sphericity can be easily achieved.

[0056] Secondary particles can be spherical, but are not limited to this.

[0057] In embodiments, the ratio of the major axis length of the primary particles to the average particle size (D50) of the secondary particles can be greater than 2 and 10 or less. Within this range, the resistance of the first negative electrode active material can remain unchanged, and the boost charging performance can remain unchanged. For example, the ratio can be 2.1, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, or 10, and in embodiments, the ratio can be 3 to 6 (e.g., 4 to 6 or 5 to 6). Within this range, the aforementioned orientation and sphericity can be easily achieved.

[0058] Amorphous carbon is contained in a coating layer surrounding the surface of the secondary particles. Amorphous carbon can reduce the porosity inside the first negative electrode active material and suppress side reactions between the first negative electrode active material and the electrolyte, thereby improving charge / discharge rate characteristics.

[0059] In the embodiments, the coating layer containing amorphous carbon may have a thickness of 5 nm to 50 nm (e.g., 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, 20 nm, 21 nm, 22 nm, 23 nm, 24 nm, 25 nm, 26 nm, 27 nm, 28 nm, 29 nm, 30 nm, 31 nm, 32 nm, 33 nm, 34 nm, 35 nm, 36 nm, 37 nm, 38 nm, 39 nm, 40 nm, 41 nm, 42 nm, 43 nm, 44 nm, 45 nm, 46 nm, 47 nm, 48 nm, 49 nm, or 50 nm), and in the embodiments, the coating layer containing amorphous carbon may have a thickness of 10 nm to 50 nm, or 20 nm to 50 nm. Within this range, side reactions with the electrolyte can be suppressed, and charge / discharge rate characteristics can be improved.

[0060] Amorphous carbon can be one or more of soft carbon, hard carbon, mesophase pitch carbides, and calcined coke.

[0061] Amorphous carbon can also exist on the surface of the primary particles.

[0062] In an embodiment, based on 100 parts by weight of the total amount of natural graphite and amorphous carbon in the first negative electrode active material, the natural graphite and amorphous carbon can be included in a weight ratio of 90:10 to 75:25 (e.g., 90:10 to 80:20, 90:10 to 85:15, or 90:10 to 88:12). Within this range, side reactions with the electrolyte can be effectively suppressed, and charge / discharge rate characteristics can be improved.

[0063] Here, a method for preparing the active material of the first negative electrode is described.

[0064] (1) Natural graphite raw material with an average particle size (D50) of 120 μm or larger is pulverized to obtain primary particles with the above-mentioned long axis length. In the embodiments, the natural graphite raw material can be pulverized using air jet milling. Air jet milling may include pulverizing at 5 kg / cm² at room temperature. 2 Up to 20kg / cm 2 Natural graphite raw materials are crushed under pressure.

[0065] (2) Use a spheroidizing device to assemble primary particles into secondary particles.

[0066] The assembly process aims to achieve a sphericity of 0.85 or greater and can be carried out using a high-intensity mixer equipped with a high-speed rotating rotor and stator. The average particle size (D50) of the secondary particles can be controlled by adjusting parameters such as pressure and shear rate during the spheroidization process.

[0067] (3) Mix the prepared secondary particles with the amorphous carbon precursor.

[0068] There are no particular restrictions on amorphous carbon precursors, as long as they form carbides. For example, amorphous carbon precursors may include one or more of the following: phenolic resin, furan resin, epoxy resin, polyacrylonitrile resin, polyamide resin, polyimide resin, polyamide-imide resin, pitch carbon, synthetic pitch, petroleum pitch, coal pitch, and tar.

[0069] During mixing, an amorphous carbon precursor can be added to achieve the above-mentioned weight ratio of natural graphite and amorphous carbon in the final product (i.e., the first negative electrode active material).

[0070] (4) The mixture obtained by mixing is calcined and heat-treated to obtain the first negative electrode active material.

[0071] In embodiments, the heat treatment can be performed at a temperature of 2500°C or higher (e.g., 2500°C to 3500°C, or 2500°C to 3000°C). Within this range, negative electrode active materials comprising secondary particles satisfying the above ratios can readily achieve the above-mentioned orientation, d002, and sphericity.

[0072] The heat treatment can be carried out for 1 to 5 hours (e.g., 1 to 4 hours, 1 to 3 hours, or 2 to 3 hours).

[0073] Figure 1 This is a conceptual diagram of the first negative electrode active material according to an embodiment.

[0074] Reference Figure 1 The first negative electrode active material includes: natural graphite, comprising secondary particles 3 formed by the assembly of primary particles 1; amorphous carbon 5, present on the surface of the primary particles 1; and an amorphous carbon coating layer 7, containing amorphous carbon 5 and surrounding the secondary particles 3. (Refer to...) Figure 1 The secondary particles 3 are formed by spheroidizing the bent primary particles 1 into an aggregated structure. This structure reduces the size of natural graphite while creating a dense internal structure that minimizes or reduces internal porosity, thereby suppressing side reactions with the electrolyte and enhancing cycle life.

[0075] (2) Active material of the second negative electrode In the embodiments, the artificial graphite may have an average particle size (D50) of 10 μm to 20 μm (e.g., 13 μm to 18 μm, or 15 μm to 20 μm). Within this range, the specific surface area may not be significantly increased, which minimizes or reduces side reactions with the electrolyte and maintains boost charging performance.

[0076] In the embodiments, the maximum particle size of the artificial graphite can be 30 μm to 40 μm.

[0077] In an embodiment, the artificial graphite may have a lower particle density than the particle density of the first negative electrode active material, for example, 1.1 g / cc to 1.6 g / cc, or 1.1 g / cc to 1.5 g / cc.

[0078] In an embodiment, the artificial graphite may have a tap density lower than that of the first negative electrode active material, for example, 0.5 g / cc to 1.0 g / cc, or 0.5 g / cc to 0.9 g / cc.

[0079] In this embodiment, the artificial graphite can have a thickness of 10m. 2 / g or less (e.g., 1m) 2 / g to 10m 2 The specific surface area is ( / g). Specific surface area can be the BET specific surface area.

[0080] In this embodiment, the artificial graphite may have an orientation degree of 90 or greater (e.g., 90 to 100, or greater than 90 and 100 or less). The orientation degree can be measured using the method described above.

[0081] The shape of the artificial graphite is not limited, but in some embodiments, the artificial graphite may be spherical.

[0082] Artificial graphite can be one or more of the following: single particles, primary particles, secondary particles formed by assembling primary particles, and tertiary particles formed by assembling secondary particles.

[0083] In an embodiment, the secondary particles formed by assembling the primary particles may additionally include a coating layer containing amorphous carbon on their surface.

[0084] (3) Active material of the third negative electrode The third negative electrode active material includes: a composite of silicon and crystalline carbon; and an amorphous carbon coating layer containing amorphous carbon and formed on the surface of the composite.

[0085] In the embodiments, the third negative electrode active material may be a three-component negative electrode active material consisting of silicon, crystalline carbon, and amorphous carbon.

[0086] In an embodiment, the third negative electrode active material may include: a composite core of silicon and crystalline carbon; and an amorphous carbon coating layer comprising amorphous carbon and formed on the surface of the core. In an embodiment, the amorphous carbon may also be present in the core. In an embodiment, the amorphous carbon may be in contact with each of the silicon and crystalline carbon in the core.

[0087] In embodiments, the third negative electrode active material can have an aspect ratio of 1 to 2.5 (e.g., 1 to 2). Within this range, the third negative electrode active material can undergo uniform (uniform or substantially uniform) directional expansion, which effectively suppresses expansion of the third negative electrode active material in the negative electrode. The aspect ratio can be measured by photographs taken using controlled pressure scanning electron microscopy (CP-SEM). The aspect ratio refers to the ratio of the maximum major axis length to the maximum minor axis length of the third negative electrode active material.

[0088] In the embodiments, the silicon and crystalline carbon composite can have an aspect ratio of 1 to 2.5 (e.g., 1 to 2). Within this range, the third negative electrode active material can undergo uniform (homogeneous or substantially uniform) directional expansion, which effectively suppresses the expansion of the third negative electrode active material in the negative electrode. The aspect ratio can be measured by photographs taken using CP-SEM. The aspect ratio refers to the ratio of the maximum major axis length to the maximum minor axis length of the composite.

[0089] In some embodiments, the silicon and crystalline carbon composite may contain pores.

[0090] In embodiments, the pores can be tubular or plate-like, and a network can be formed in the core. The porosity (total pore volume) in the silicon-crystalline carbon composite can be suitably adjusted, and the porosity can be, for example, from 2% to 50% by volume.

[0091] In an embodiment, the third negative electrode active material may include: a crystalline carbon core having internal pores; an amorphous carbon shell formed on the surface of the core; silicon particles dispersed in the pores; and amorphous carbon present in the pores.

[0092] In the embodiments, based on a total of 100 parts by weight of silicon and crystalline carbon, the weight ratio of silicon to crystalline carbon in the silicon-crystalline carbon composite can be from 10:90 to 90:10. Within this range, the composite can exhibit higher capacity, particularly compared to a third negative electrode active material composed of crystalline carbon. For example, the weight ratio can be from 50:50 to 90:10, or from 50:50 to 80:20, and higher capacity can be exhibited within this range.

[0093] In the embodiments, the silicon can have a spherical shape with an average particle size (D50) of 10 nm to 150 nm (e.g., 40 nm to 120 nm). Within this range, the cycle life of the battery can be improved.

[0094] Silicon can be silicon (Si) particles.

[0095] In embodiments, the crystalline carbon can have a major axis length of 5 μm to 20 μm (e.g., 5 μm to 10 μm) and an aspect ratio of 4 to 10 (e.g., 4 to 8). Within this range, the cycle life of the battery can be improved, and the negative electrode plate can exhibit minimal negative electrode expansion during charge / discharge cycles in a rechargeable lithium battery, thereby effectively suppressing excessive volume gain and preventing bulging. The aspect ratio can be measured by photographs taken using CP-SEM. The aspect ratio refers to the ratio of the maximum major axis length to the maximum minor axis length.

[0096] Crystalline carbon can include natural graphite, artificial graphite, or a combination thereof.

[0097] In the embodiments, the crystalline carbon may be rod-shaped with an elliptical cross-section.

[0098] The amorphous carbon coating formed on the surface of the composite enhances the conductivity of the composite, which further improves the performance and reduces the direct contact between silicon and the electrolyte, which can effectively suppress the increase in resistance caused by the formation of by-products.

[0099] In the embodiments, the amorphous carbon coating layer can have a thickness of 5 nm to 1000 nm (e.g., 5 nm to 30 nm). Within this range, the layer thickness can be sufficient to prevent or substantially prevent problems associated with electron transfer resistance.

[0100] The amorphous carbon in the amorphous carbon coating and core can be petroleum bitumen, coal bitumen, or a combination thereof.

[0101] In this embodiment, the amorphous carbon coating may be included in the third negative electrode active material in an amount of 10 wt% to 60 wt%. Within this range, improved battery performance can be achieved.

[0102] In an embodiment, the third negative electrode active material may comprise 20 wt% to 70 wt% silicon, 3 wt% to 50 wt% crystalline carbon, and 20 wt% to 50 wt% amorphous carbon. Within this range, the third negative electrode active material can effectively suppress expansion during charge / discharge cycles while improving cycle life and output characteristics.

[0103] Figure 2 This is a conceptual diagram of the third negative electrode active material according to an embodiment.

[0104] Reference Figure 2 The third negative electrode active material includes silicon particles 11, crystalline carbon 13, and amorphous carbon 15. Amorphous carbon 15 exists between silicon particles 11 and crystalline carbon 13, and may also exist in the coating layer surrounding silicon particles 11 and crystalline carbon 13.

[0105] Here, a method for preparing a third negative electrode active material is described.

[0106] The third negative electrode active material can be prepared by the following steps: mixing silicon particles, artificial graphite, and optionally amorphous carbon in a solvent to prepare a mixed solution; spray-drying the mixed solution; and heat-treating the dried mixed solution. The solvent can be isopropyl alcohol, ethanol, methanol, or a combination thereof. The spray-drying can be carried out at 90°C to 120°C, and the heat-treatment can be carried out at 900°C to 1000°C in a mixed atmosphere of nitrogen, argon, hydrogen, or a combination thereof.

[0107] In an embodiment, the negative electrode plate may further include a fourth negative electrode active material different from the above-mentioned first negative electrode active material, second negative electrode active material, and third negative electrode active material.

[0108] The fourth negative electrode active material may further include a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium and a metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

[0109] The material capable of reversibly intercalating / deintercalating lithium ions is a carbon-based negative electrode active material and may include, for example, crystalline carbon, amorphous carbon, or a combination thereof. Examples of crystalline carbon may include graphite, such as natural graphite or artificial graphite that is amorphous, plate-shaped (e.g., sheet-like), flaky, spherical, or fibrous, and examples of amorphous carbon may include soft carbon, hard carbon, mesophase pitch carbide, calcined coke, etc.

[0110] In an embodiment, the alloy of lithium and a metal may be 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.

[0111] A Si-based negative electrode active material or a Sn-based negative electrode active material can be used as a material capable of doping and dedoping lithium. The Si-based negative electrode active material can be silicon, a silicon-carbon composite, SiO x (0 < x ≤ 2), a Si-Q alloy (where Q is one selected from the group consisting of 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), or a combination thereof. The Sn-based negative electrode active material can be Sn, SnO2, a Sn-based alloy, or a combination thereof.

[0112] The silicon-carbon composite can be a composite of silicon and amorphous carbon. According to embodiments, the silicon-carbon composite can be in the form of silicon particles whose surfaces are coated with amorphous carbon. For example, the silicon-carbon composite can include secondary particles (cores) assembled with primary silicon particles and an amorphous carbon coating layer (shell) positioned on the surface of the secondary particles. Amorphous carbon can also be positioned between the primary silicon particles, and the primary silicon particles can, for example, be coated with amorphous carbon. The secondary particles can be dispersed in an amorphous carbon matrix.

[0113] Silicon-carbon composites may also include crystalline carbon. For example, a silicon-carbon composite may include a core comprising crystalline carbon and silicon particles, and an amorphous carbon coating layer present on the surface of the core.

[0114] Si-based or Sn-based negative electrode active materials can be used in combination with carbon-based negative electrode active materials.

[0115] adhesive The negative electrode plate used in rechargeable lithium batteries may also include an adhesive.

[0116] In an embodiment, the binder may be included in the negative electrode plate for a rechargeable lithium battery in an amount of 0.5 wt% to 5 wt%.

[0117] The binder can effectively adhere the negative electrode active material particles to each other and also effectively adhere the negative electrode active material to the current collector. The binder can include non-aqueous binders, aqueous binders, dry binders, or combinations thereof.

[0118] Non-aqueous adhesives may include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyimide, or combinations thereof.

[0119] Waterborne adhesives may be selected from 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.

[0120] If an aqueous binder is used as the negative electrode binder, it may further include a cellulose-based compound capable of imparting viscosity. The cellulose-based compound may include at least one of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, or an alkali metal salt thereof. In embodiments, the alkali metal may include Na, K, or Li.

[0121] Dry adhesives can be polymeric materials capable of taking the form of fibers. For example, dry adhesives can be polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or combinations thereof.

[0122] conductive materials The negative electrode plate used in rechargeable lithium batteries may also include conductive materials.

[0123] In an embodiment, conductive material may be included in the negative electrode plate for a rechargeable lithium battery in an amount greater than 0 wt% to 5 wt%.

[0124] Conductive materials can impart electrical conductivity (e.g., electroconductivity) to electrodes. Any suitable material that does not cause chemical changes in the battery (e.g., does not cause undesirable chemical changes in rechargeable lithium batteries) and conducts electrons can be used. Some non-limiting examples of conductive materials may include: carbon-based materials such as natural graphite, synthetic graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic materials in the form of metal powders or metal fibers, including copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0125] In embodiments, the negative electrode current collector may include copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, or a combination thereof.

[0126] The negative electrode current collector can be laminated on at least one surface of the negative electrode plate.

[0127] According to another embodiment, the negative electrode plate for a rechargeable lithium battery includes a negative electrode active material and a conductive material, wherein the negative electrode active material includes a mixture of a first negative electrode active material, a second negative electrode active material and a third negative electrode active material, and the conductive material includes carbon nanotubes.

[0128] The negative electrode plate for rechargeable lithium batteries can provide high capacity retention, high energy density, improved boost charging and fast charging life by including the above mixture as the negative electrode active material and carbon nanotubes as the conductive material.

[0129] By incorporating carbon nanotubes as conductive materials, the negative electrode plate can shorten the boost charging time, extend its lifespan, and reduce the expansion of silicon-based active materials, thereby increasing energy density.

[0130] In the embodiments, carbon nanotubes are included as conductive materials, and the negative electrode plate can be further enhanced by including a mixture of negative electrode active materials to reduce boost charging time and improve lifetime characteristics.

[0131] As conductive materials, one-dimensional conductive materials can form a conductive network that maintains connections between negative electrode active material particles during battery charging and discharging, thereby suppressing degradation. Additionally, carbon nanotubes offer benefits such as shortened boost charging time, longer lifespan, and reduced expansion of the third negative electrode active material, thereby increasing energy density.

[0132] In the embodiments, carbon nanotubes may have an average diameter of 0.5 nm to 3 nm (e.g., 1 nm to 3 nm), an average length of 5 μm or less (e.g., 1 μm to 2 μm), and a maximum length of 20 μm or less. Within these ranges, carbon nanotubes provide suitable dispersibility to impart conductivity and, compared to conventional multi-walled carbon nanotubes (MWCNTs) and carbon black, can form conductive networks between negative electrode active material particles and between the negative electrode active material and the substrate, even at low concentrations, thereby effectively suppressing degradation during battery cycling.

[0133] Here, "average diameter" refers to the average diameter of the carbon nanotube. If the cross-section of the carbon nanotube is circular, the diameter refers to the diameter of the circular carbon nanotube cross-section. If the cross-section is non-circular (e.g., irregular), the diameter refers to the length of the longest axis of the cross-section.

[0134] In this embodiment, specific surface area (SSA) is a criterion used to determine whether an electrode slurry prepared using a conductive material dispersion can provide low powder resistance, said conductive material dispersion being prepared using carbon nanotubes having the aforementioned specific surface area. While measuring the specific surface area of ​​the carbon nanotubes themselves may be easy, measuring the specific surface area of ​​the dispersed carbon nanotubes within a conductive material dispersion containing carbon nanotubes is not straightforward.

[0135] SSA can use the Malvern particle size analyzer to measure carbon nanotube dispersions.

[0136] Carbon nanotubes can be one or a mixture of single-walled carbon nanotubes and multi-walled carbon nanotubes. In an embodiment, for example, the carbon nanotubes can be single-walled carbon nanotubes.

[0137] In the embodiments, carbon nanotubes can have a diameter of 240 μm. 2 / g to 280m 2 The specific surface area is approximately 1 / g. Within this range, it is easy to enhance the conductivity of the slurry containing the negative electrode active material. In embodiments, carbon nanotubes may be included in an amount of 95 wt% or more (e.g., 95 wt% to 100 wt%) of the conductive material. The specific surface area may be the BET specific surface area.

[0138] In an embodiment, a mixture of 100 parts by weight of negative electrode active material may include conductive material, such as carbon nanotubes, in an amount of 0.01 parts by weight to 5 parts by weight (e.g., 0.01 parts by weight to 0.2 parts by weight). Within this range, the proportion of negative electrode active material can be maximized or increased (minimizing or reducing the decrease in negative electrode current density) to maintain the conductive network during the contraction and expansion of the negative electrode. However, the proportion of conductive material can vary depending on the type and content of silicon.

[0139] In an embodiment, based on a total negative electrode plate of 100 wt%, the content of conductive material can be from 0.01 wt% to 5 wt% (e.g., 0.01 wt% to 0.2 wt%). Within this range, increased energy density, improved boost charging characteristics, longer battery life, and reduced expansion can be achieved. In an embodiment, for example, carbon nanotubes as the conductive material can be included in the negative electrode plate in an amount of 0.03 wt% to 0.05 wt%. Within this range, the content of active material does not decrease, and therefore, the battery capacity does not decrease.

[0140] According to another embodiment, the rechargeable lithium battery includes a negative electrode plate for the rechargeable lithium battery.

[0141] A rechargeable lithium battery may include a negative electrode plate and a positive electrode for rechargeable lithium batteries. The negative electrode plate may be substantially the same as described above.

[0142] positive electrode The positive electrode for a rechargeable lithium battery may include a current collector and a layer of positive electrode active material on the current collector. The positive electrode active material layer may include positive electrode active material and may also include a binder and / or conductive material. For example, the positive electrode may also include additives that can be used as a sacrificial positive electrode.

[0143] Positive electrode active material The positive electrode active material may include compounds capable of intercalating and deintercalating lithium (lithium-intercalating compounds). In embodiments, at least one of lithium in a composite oxide selected from cobalt, manganese, nickel, and combinations thereof may be used.

[0144] The composite oxide can be a lithium transition metal composite oxide. Examples of composite oxides may include lithium nickel oxides, lithium cobalt oxides, lithium manganese oxides, lithium iron phosphate compounds, cobalt-free lithium nickel manganese oxides, or combinations thereof.

[0145] As an example, a compound represented by any of the following chemical formulas can be used: Li a A 1-b X b O 2-c D c(0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.05);Li a Mn 2-b X b The 4-c D c (0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.05);Li a Ni 1-b-c Co b X c The 2-α D α (0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.5,0<α<2);Li a Ni 1-b- c Mn b X c The 2-α D α (0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.5,0<α<2);Li a Ni b Co c L 1 d G e O2(0.90≤a≤1.8,0≤b≤0.9,0≤c≤0.5,0≤d≤0.5,0≤e≤0.1);Li a NiG b O2(0.90≤a≤1.8,0.001≤b≤0.1);Li a CoG b O2(0.90≤a≤1.8,0.001≤b≤0.1);Li a Mn 1-b G b O2(0.90≤a≤1.8,0.001≤b≤0.1);Li a Mn2G b O4(0.90≤a≤1.8,0.001≤b≤0.1);Li a Mn 1-g G g PO4(0.90≤a≤1.8,0≤g≤0.5);Li (3-f) Fe2(PO4)3(0≤f≤2); or Li a FePO4 (0.90≤a≤1.8).

[0146] In the above chemical formulas, A is Ni, Co, Mn, or a combination thereof; X is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, or a combination thereof; D is O, F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; and L 1 It is Mn, Al, or a combination thereof.

[0147] The positive electrode active material can be, for example, a high-nickel positive electrode active material, based on 100 mol% of metals other than lithium in a lithium transition metal complex oxide. High-nickel positive electrode active materials have a nickel content of 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%. High-nickel positive electrode active materials can achieve high capacity and can be applied to high-capacity, high-density rechargeable lithium batteries.

[0148] In an embodiment, based on a 100wt% positive electrode active material layer, the amount of positive electrode active material can be from about 90wt% to about 99.5wt%. In an embodiment, based on a 100wt% positive electrode active material layer, the amounts of binder and conductive material can be from about 0.5wt% to about 5wt%, respectively.

[0149] The binder enables the positive electrode active material particles to adhere well to each other and also enables the positive electrode active material to adhere well to the current collector. As a non-limiting example, examples of binders may include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylate resin, polyester resin, nylon, etc.

[0150] Conductive materials can impart conductivity (e.g., electrode conductivity) to electrodes. Any suitable material that does not cause chemical changes (e.g., does not cause undesirable chemical changes in rechargeable lithium batteries) and conducts electrons can be used in the battery. Examples of conductive materials can include: carbon-based materials such as natural graphite, synthetic graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic materials in the form of metal powders or fibers, including copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0151] In the embodiments, A1 can be used as a current collector, but this disclosure is not limited thereto.

[0152] Rechargeable lithium batteries may also include an electrolyte.

[0153] electrolyte Electrolytes used in rechargeable lithium batteries may include non-aqueous organic solvents and lithium salts.

[0154] Non-aqueous organic solvents can be used as a medium for transporting ions that participate in the electrochemical reactions of a battery.

[0155] Non-aqueous organic solvents can be carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, aprotic solvents, or combinations thereof.

[0156] Carbonate solvents may include any 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), butyl carbonate (BC), etc.

[0157] Ester solvents may include any one of methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanoic acid lactone, mevalonate lactone, valproic acid lactone, caprolactone, etc.

[0158] Ether solvents may include any 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. Aprotic solvents may include: nitriles, such as R-CN (where R is a C2 to C20 straight-chain, branched, or cyclic hydrocarbon group, and may include double bonds, aromatic rings, or ether bonds, etc.); amides, such as dimethylformamide; dioxolane, such as 1,3-dioxolane, 1,4-dioxolane, etc.; sulfolane, etc.

[0159] Non-aqueous organic solvents can be used alone or in combination of two or more.

[0160] In the embodiments, if a carbonate solvent is used, cyclic carbonates and chain carbonates can be mixed and used, and the cyclic carbonates and chain carbonates can be mixed in a volume ratio of about 1:1 to about 1:9.

[0161] Lithium salts dissolved in organic solvents supply lithium ions to the battery, allowing for basic operation of rechargeable lithium batteries and improving lithium ion transport between the positive and negative electrodes.

[0162] Examples of lithium salts include those selected from LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide, LiFSI), LiC4F9SO3, and LiN(C x F 2x+1 SO2)(C y F 2y+1 At 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).

[0163] Rechargeable lithium batteries may also include a separator.

[0164] diaphragm Depending on the type of rechargeable lithium battery, a separator may be present between the positive and negative electrodes. In embodiments, the separator may include any of polyethylene, polypropylene, polyvinylidene fluoride, or multilayer films of two or more layers thereof (e.g., hybrid multilayer films such as polyethylene / polypropylene two-layer separators, polyethylene / polypropylene / polyethylene three-layer separators, polypropylene / polypropylene / polypropylene three-layer separators, etc.)).

[0165] The membrane may include a porous substrate and a coating layer comprising organic material, inorganic material, or a combination thereof on one or two or opposite surfaces of the porous substrate.

[0166] Porous substrates can be polymer membranes formed from any polymer selected from the following, or copolymers or mixtures of two or more of them: polyolefins, such as polyethylene and polypropylene; polyesters, such as polyethylene terephthalate and polybutylene terephthalate; polyacetal; polyamide; polyimide; polycarbonate; polyetherketone; polyaryletherketone; polyetherimide; polyamideimide; polybenzimidazole; polyethersulfone; polyphenylene ether; cyclic olefin copolymers; polyphenylene sulfide; polyethylene naphthalate; glass fiber; and polytetrafluoroethylene (e.g., TEFLON). ® ).

[0167] Organic materials may include polymers such as polyvinylidene fluoride or (meth)acrylic acid polymers. Inorganic materials may include, but are not limited to, inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof.

[0168] Organic and inorganic materials can be mixed in a single coating layer, or coating layers comprising organic materials and coating layers comprising inorganic materials can be stacked.

[0169] Rechargeable lithium batteries Based on their shape, rechargeable lithium batteries can be classified into cylindrical batteries, prismatic batteries, pouch batteries, coin-shaped batteries, etc.

[0170] Figures 3 to 6 This is a schematic diagram illustrating a rechargeable lithium battery according to an embodiment. Figure 3 A cylindrical battery is shown; Figure 4 A prismatic battery is shown; Figure 5 and Figure 6 A pouch-type battery is shown. (See reference) Figures 3 to 6 The rechargeable lithium battery 100 may include an electrode assembly 40 and a housing 50 therein housing the electrode assembly 40. The electrode assembly 40 includes a separator 30 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). Figure 3 As shown, the rechargeable lithium battery 100 may include a sealing member 60 of the sealed housing 50. (As illustrated...) Figure 4 As shown, the rechargeable lithium battery 100 may include a positive lead terminal 14, a positive terminal 12, a negative lead terminal 21, and a negative terminal 22. Figure 5 and Figure 6 As shown, the rechargeable lithium battery 100 may include electrode terminals 70, which serve as electrical paths for guiding current formed in the electrode assembly 40 to the outside. The electrode terminals 70 may be, for example, a positive electrode terminal 71 and a negative electrode terminal 72.

[0171] As a non-limiting example, the rechargeable lithium battery according to the embodiments can be used in automobiles, mobile phones and / or various types of electronic devices.

[0172] Electronic devices or electric vehicles may contain rechargeable lithium batteries.

[0173] Examples and comparative examples of the present invention are described herein. However, the following examples are provided as illustrative embodiments of the present invention, and the present invention is not limited to these examples.

[0174] Example 1 (1) Preparation of the active material of the first negative electrode Flake-shaped natural graphite raw material with an average particle size (D50) of 120 μm was pulverized using air jet milling to obtain plate-shaped primary particles with a long axis length of 30 μm. The primary particles were then assembled into spherical secondary particles with an average particle size (D50) of 7 μm using a spheroidizing device. The secondary particles were mixed with pitch carbon and heat-treated in a calcining furnace at 3000 °C for 2 hours to prepare the first negative electrode active material. The amount of pitch carbon added was adjusted so that the weight ratio of natural graphite to amorphous carbon in the first negative electrode active material was 90:10.

[0175] (2) Active material of the second negative electrode Artificial graphite (spherical, average particle size D50: 15μm, particle density: 1.5g / cc, tap density: 0.9g / cc, BET specific surface area: 1.5m²) was used as the active material for the second negative electrode. 2 / g, orientation degree: 100). Artificial graphite consists of secondary particles formed by the assembly of primary particles.

[0176] (3) Preparation of the active material of the third negative electrode Artificial graphite with an average particle size (D50) of 3 μm to 5 μm and an aspect ratio of 4 to 10, silicon nanoparticles with a D50 of 100 nm, and petroleum-based pitch amorphous carbon were mixed in a weight ratio of 6:54:40 and dispersed in isopropanol solvent using a homogenizer to prepare a dispersion. The dispersion was spray-dried at 120 °C using a spray dryer. The spray-dried product was heat-treated in a nitrogen atmosphere furnace at 1000 °C to form a silicon-carbon composite core containing artificial graphite and silicon particles, and an amorphous carbon coating layer on the surface of the core. The resulting product was pulverized and sieved through a 400-mesh sieve to obtain a third negative electrode active material (C-1) comprising a silicon-carbon composite core containing artificial graphite and silicon particles, and an amorphous carbon coating layer formed on the surface of the core.

[0177] The third negative electrode active material comprises a silicon-artificial graphite composite core and an amorphous carbon shell formed on the surface of the core. The third negative electrode active material has a 5:5 weight ratio of silicon particles to artificial graphite, a 30 nm thick amorphous carbon coating layer, and an aspect ratio of 1 to 2.5. The third negative electrode active material comprises 54 wt% silicon particles, 6 wt% artificial graphite, and 40 wt% amorphous carbon.

[0178] (4) A mixture of negative electrode active materials is prepared by mixing 47 wt% of the first negative electrode active material, 47 wt% of the second negative electrode active material and 6 wt% of the third negative electrode active material.

[0179] A negative electrode active material slurry was prepared by mixing 97.5 wt% of the prepared negative electrode active material mixture, 1.5 wt% of styrene-butadiene rubber as a binder, and 1.0 wt% of carboxymethyl cellulose as an additive in distilled water.

[0180] The negative electrode active material slurry is coated onto the copper current collector, dried, and rolled to manufacture the negative electrode plate.

[0181] Figure 7 The SEM analysis results for the negative electrode plate are shown. (Refer to...) Figure 7 It can be seen that the negative electrode plate contains a third negative electrode active material A, a second negative electrode active material B, and a first negative electrode active material C.

[0182] A half-cell is constructed using a negative electrode plate, a lithium metal counter electrode, and an electrolyte. The electrolyte is a mixed solvent of ethylene carbonate and dimethyl carbonate (volume ratio 3:7) in which 1 M of LiPF6 is dissolved.

[0183] Example 2 Except for altering the spheroidization conditions, the first negative electrode active material was prepared in the same manner as in Example 1. Using the prepared first negative electrode active material, a negative electrode plate and a half-cell were fabricated in the same manner as in Example 1.

[0184] Example 3 Except for altering the spheroidization conditions, the first negative electrode active material was prepared in the same manner as in Example 1. Using the prepared first negative electrode active material, a negative electrode plate and a half-cell were fabricated in the same manner as in Example 1.

[0185] Example 4 and Example 5 Except for changing the weight ratio of each component as shown in Table 1 below, the negative electrode plate and half cell are manufactured in the same manner as in Example 1.

[0186] Comparison Example 1 The first negative electrode active material is prepared in the same manner as in Example 1, except that no pitch carbon is added during the preparation of the first negative electrode active material. Using the prepared first negative electrode active material, a negative electrode plate and a half-cell are manufactured in the same manner as in Example 1.

[0187] Comparison Example 2 Flake-shaped natural graphite raw material with an average particle size (D50) of 120 μm or larger was pulverized using air jet milling to obtain primary particles with a long axis length of 120 μm. The primary particles were then assembled into spherical secondary particles with an average particle size (D50) of 20 μm using a spheroidizing device. The secondary particles were mixed with pitch carbon and heat-treated in a calcining furnace at 1200 °C for 2 hours to prepare the first negative electrode active material. The amount of pitch carbon added was adjusted so that the weight ratio of natural graphite to amorphous carbon in the first negative electrode active material was 90:10.

[0188] Using the prepared first negative electrode active material, a negative electrode plate and a half cell are manufactured in the same manner as in Example 1.

[0189] Comparison Example 3 Flake-shaped natural graphite raw material with an average particle size (D50) of 80 μm was pulverized using air jet milling to obtain primary particles with a long axis length of 7 μm. The primary particles were then assembled into spherical secondary particles with an average particle size (D50) of 15.6 μm using a spheroidizing device. The secondary particles were mixed with pitch carbon and heat-treated in a calcining furnace at 1200 °C for 2 hours to prepare the first negative electrode active material. The amount of pitch carbon added was adjusted to achieve a weight ratio of natural graphite to amorphous carbon of 90:10 in the negative electrode active material.

[0190] Using the prepared first negative electrode active material, a negative electrode plate and a half cell are manufactured in the same manner as in Example 1.

[0191] Compare Example 4 The negative electrode plate and half cell are manufactured in the same manner as in Example 1, except that silicon oxide (C-2) is used instead of the third negative electrode active material.

[0192] (Experimental Example 1) Evaluation of the active material of the first negative electrode Particle density (unit: g / cc) Particle density was measured using a Carver 4350.L apparatus from Carver Corporation. To determine powder density, 1.0 g of each of the first negative electrode active material of the example and control examples were placed in a mold and compressed for 30 seconds under a pressure of 2.0 tons.

[0193] Orientation Orientation was measured using an X'Pert Pro XRD analyzer from Malvern Panalytical. For the first negative electrode active material of the example and comparative examples, the ratio I(002) / I(110) of the diffraction peak intensity of the (002) plane to that of the (110) plane was calculated by X-ray diffraction analysis using CuKα rays.

[0194] d002 (unit: Å) d002 was measured using an X'Pert Pro XRD analyzer from Malvern Panalytical. The interplanar spacing of the (002) plane was calculated by X-ray diffraction analysis using CuKα rays for the first negative electrode active material of the example and comparative examples.

[0195] Mercury accumulation pore volume (unit: mL / g) The cumulative pore volume of Hg was measured using an AutoPoreV Hg invasive porosimeter from Micromeritics. Measurements were performed on the first negative electrode active material for both the example and comparative examples using the AutoPoreV Hg invasive porosimeter from Micromeritics. Mercury was added to the first negative electrode active material, and a pressure of 0.1 psi was applied to force the mercury into the active material. The pressure was then increased to 60,000 psi, and the mercury porosity was measured by observing the volume change of the mercury. The measured pores ranged in size from 0.01 μm to 1 μm.

[0196] sphericity Sphericity was measured using a Morphologi 4 analyzer from Malvern Panalytical. For the first negative electrode active material of both the example and comparative examples, values ​​A and B in Equation 1 above were obtained, and sphericity was calculated according to Equation 1.

[0197] (Experimental Example 2) Evaluation of Battery Characteristics The manufactured half-cells were subjected to charge / discharge cycles at 0.1C to measure their charge and discharge capacities. The measured discharge capacities are shown in Table 1 below. Furthermore, the charge / discharge efficiency (discharge capacity / charge capacity × 100%) was calculated.

[0198] The manufactured half-cells were subjected to charge / discharge cycles as follows to evaluate their charging characteristics: one cycle of charging at 0.2C constant current (CC) and constant voltage (CV) and discharging at 0.2C; one cycle of charging at 0.5C CC and discharging at 0.2C; one cycle of charging at 1C CC and discharging at 0.2C; and one cycle of charging at 2C CC and discharging at 0.2C. The charge / discharge conditions were as follows: constant current (CC) charging with a cutoff voltage of 10mV, constant voltage (CV) charging with a cutoff time of 15 hours, and discharging with a cutoff voltage of 1.5V. Charging characteristics were measured at each C rate. The charging characteristic results were calculated and expressed as the ratio of the 2C CC charging capacity to the 0.2C CC charging capacity.

[0199] Energy density (unit: Wh / L) Energy density is evaluated by multiplying the cell capacity (Ah) by the average voltage (V) and then dividing by the cell volume.

[0200] Boost charging time (in minutes) Boost charging time refers to the time taken to charge a battery to 8% to 80% of its state of charge (SOC) under constant current charging conditions. This is evaluated by identifying charging modes that do not reach the maximum voltage of 4.2V during charging.

[0201] Fast charging life (unit: cycles) Once the boost charging time is determined, the battery is charged to 8% to 80% SOC (State of Charge), and then discharged at a constant current of 0.33C and a discharge voltage of 2.8V. This process is defined as one cycle, and fast-charge life is evaluated by the number of cycles until the battery reaches 80% SOH (State of Health).

[0202] Table 1

[0203] *Weight ratio: The proportion of the first negative electrode active material, the second negative electrode active material, and the third negative electrode active material in a total of 100 parts by weight of the three negative electrode active materials.

[0204] As shown in Table 1, the example negative electrode plates for rechargeable lithium batteries exhibit high energy density. To evaluate boost charging and long lifespan, both boost charging time and fast charging lifespan should be evaluated together. As shown in Table 1, the example negative electrode plates exhibit shorter boost charging time and longer fast charging lifespan, demonstrating their ability to effectively exhibit both boost charging and long lifespan effects.

[0205] However, as shown in Table 1, the negative electrode plate of the comparative example, which does not satisfy the composition of the negative electrode plate of the present invention, exhibits a longer boost charging time and a shorter fast charging life, resulting in a significantly weakened boost charging and long life effect compared to the example.

[0206] Example 6 (1) Preparation of the active material of the first negative electrode Flake-shaped natural graphite raw material with an average particle size (D50) of 120 μm was pulverized using air jet milling to obtain plate-shaped primary particles with a long axis length of 30 μm. These primary particles were then assembled into spherical secondary particles with an average particle size (D50) of 7 μm using a spheroidizing device. The secondary particles were mixed with pitch carbon and heat-treated in a calcining furnace at 3000 °C for 2 hours to prepare the first negative electrode active material. The amount of pitch carbon added was adjusted to achieve a weight ratio of natural graphite to amorphous carbon of 90:10 in the negative electrode active material.

[0207] (2) As the active material for the second negative electrode, artificial graphite (average particle size D50: 15 μm, particle density: 1.5 g / cc, tap density: 1.0 g / cc, BET specific surface area: 1.5 m²) was used. 2 / g, orientation degree: 100). Artificial graphite is formed from secondary particles through the assembly of primary particles.

[0208] (3) Artificial graphite with an average particle size (D50) of 3 μm to 5 μm and an aspect ratio of 4 to 10, silicon nanoparticles with a D50 of 100 nm, and petroleum-based pitch amorphous carbon were mixed in a weight ratio of 40:40:20, and the mixture was dispersed in isopropanol solvent using a homogenizer to prepare a dispersion. The dispersion was spray-dried at 120 °C using a spray dryer. The spray-dried product was heat-treated at 1000 °C in a nitrogen atmosphere furnace to form a silicon-carbon composite core containing artificial graphite and silicon particles, and an amorphous carbon coating layer on the surface of the core. The resulting product was pulverized and sieved through a 400-mesh sieve to obtain a third negative electrode active material (C-1) comprising a silicon-carbon composite core containing artificial graphite and silicon particles, and an amorphous carbon coating layer formed on the surface of the core.

[0209] The third negative electrode active material comprises a silicon-artificial graphite composite core and an amorphous carbon shell formed on the core surface. The third negative electrode active material has a silicon particle to artificial graphite weight ratio of 5:5, an amorphous carbon coating layer with a thickness of 30 nm, and an aspect ratio of 1 to 2.5. The third negative electrode active material comprises 40 wt% silicon particles, 40 wt% artificial graphite, and 20 wt% amorphous carbon.

[0210] (4) Based on 100 parts by weight of the negative electrode active material mixture, a negative electrode active material mixture is prepared by mixing 47 parts by weight of the first negative electrode active material, 47 parts by weight of the second negative electrode active material and 6 parts by weight of the third negative electrode active material.

[0211] A negative electrode active material slurry was prepared by mixing 96.96 wt% of the prepared negative electrode active material mixture, 0.04 wt% of single-walled carbon nanotubes (SWCNT, D-1) as a conductive material, 2.2 wt% of styrene-butadiene rubber as a binder, and 0.8 wt% of carboxymethyl cellulose (CMC) in distilled water.

[0212] The negative electrode active material slurry is coated onto the copper current collector, dried, and rolled to manufacture the negative electrode plate.

[0213] A half-cell is constructed using a negative electrode plate, a lithium metal counter electrode, and an electrolyte. The electrolyte is a mixed solvent of ethylene carbonate and dimethyl carbonate (volume ratio 3:7) in which 1 M of LiPF6 is dissolved.

[0214] Example 7 Except for altering the spheroidization conditions, the first negative electrode active material was prepared in the same manner as in Example 6. Using the prepared first negative electrode active material, a negative electrode plate and a half-cell were fabricated in the same manner as in Example 6.

[0215] Example 8 Except for altering the spheroidization conditions, the first negative electrode active material was prepared in the same manner as in Example 6. Using the prepared first negative electrode active material, a negative electrode plate and a half-cell were fabricated in the same manner as in Example 6.

[0216] Example 9 Except for modifying the weight ratio of each component of the negative electrode active material as shown in Table 2 below, the negative electrode plate and half cell are manufactured in the same manner as in Example 6.

[0217] (Experimental Example 3) Evaluation of the active material of the first negative electrode The active material of the first negative electrode was evaluated in the same manner as in Experimental Example 1.

[0218] (Experimental Example 4) Evaluation of Battery Characteristics Capacity (unit: mAh / g) and charge rate (unit: %) The manufactured half-cells were subjected to charge / discharge cycles at 0.1C to measure their charge / discharge capacity. The measured discharge capacity is shown in Table 2 below. Additionally, the charge / discharge efficiency (discharge capacity / charge capacity × 100%) was calculated.

[0219] The manufactured half-cells were subjected to charge / discharge cycles as follows to evaluate their charging characteristics: one cycle of charging at 0.2C constant current (CC) and constant voltage (CV) and discharging at 0.2C; one cycle of charging at 0.5C CC and discharging at 0.2C; one cycle of charging at 1C CC and discharging at 0.2C; and one cycle of charging at 2C CC and discharging at 0.2C. The charge / discharge conditions were as follows: constant current (CC) charging with a cutoff voltage of 10mV, constant voltage (CV) charging with a cutoff time of 15 hours, and discharging with a cutoff voltage of 1.5V. Charging characteristics were measured at each C rate. The charging characteristic results were calculated and expressed as the ratio of the 2C CC charging capacity to the 0.2C CC charging capacity.

[0220] DC internal resistance (DC-IR, unit: Ω) Half-cells manufactured according to the example and comparative examples were charged at 0.2C under constant current / constant voltage conditions at 25°C, 10mV, and a 0.01C cutoff condition, and then allowed to rest for 10 minutes. Subsequently, they were discharged at a constant current of 0.2C under a 1.5V cutoff condition and allowed to rest for 10 minutes. One cycle of charge and discharge was performed under these charge-discharge conditions. At SOC50 (the state of charge of the battery to 50% of its full capacity, which corresponds to 50% discharge in terms of the state of discharge), a current of 3C was applied for 1 second, and the resulting voltage drop (V) was measured. The resistance was calculated from the measured voltage drop and the applied current (3C), and the result was expressed as DC internal resistance (DC-IR).

[0221] Rion (unit: Ω) Symmetric monomers were fabricated using the prepared negative electrode plates, and then electrochemical impedance spectroscopy (EIS) was measured. Rion was calculated from the results using a Nyquist plot.

[0222] Boost charging time (in seconds) Boost charging time refers to the time taken to charge a battery to 8% to 80% of its state of charge (SOC) under constant current charging conditions. This is evaluated by identifying charging modes that do not reach the maximum voltage of 4.2V during charging.

[0223] Fast charging life (unit: cycles) Once the boost charging time is determined, the battery is charged to 8% to 80% of its SOC (State of Charge), and then discharged at a constant current of 0.33C and a discharge voltage of 2.8V. This process is defined as one cycle, and for pouch cells, fast-charge life is evaluated by the number of cycles until the battery reaches 80% of its State of Health (SOH).

[0224] Swelling rate (swelling, unit: %) The expansion rate was measured using a thickness monitoring system (TMS).

[0225] Batteries manufactured according to the example and comparative examples were subjected to charge / discharge cycle life tests at 45°C, with a charging voltage of 4.35V and a discharging voltage of 2.8V, at 0.5C / 0.5C cycles, while the battery thickness was monitored in real time. The thickness increase rate was calculated by comparing the fully discharged thickness after one cycle with the fully discharged thickness after 50 cycles.

[0226] Expansion rate (%) = (Battery thickness after 50 cycles - Battery thickness after 1 cycle) / Battery thickness after 1 cycle × 100 Table 2

[0227] *In Table 2, Weight ratio: first negative electrode active material : second negative electrode active material : third negative electrode active material.

[0228] As shown in Table 2, the example negative electrode plates for rechargeable lithium batteries exhibit reduced expansion of silicon-based active materials, short boost charging time, and long fast charging lifetime, demonstrating their effective boost charging performance. Furthermore, the example negative electrode plates possess low ion migration resistance (Rion), which is expected to promote smooth movement of lithium ions within the electrode plate, facilitating boost charging.

[0229] The negative electrode plate for a rechargeable lithium battery according to an embodiment of the present invention can exhibit excellent rechargeable lithium battery performance by providing high energy density, boost charging and long life characteristics.

[0230] The negative electrode plate for a rechargeable lithium battery according to an embodiment of the present invention comprises natural graphite with significantly reduced resistance, and can exhibit excellent rechargeable lithium battery performance by providing reduced expansion of silicon-based active materials, shortened boost charging time, long lifespan and high energy density.

[0231] Although some exemplary embodiments of the present invention have been described above, the present invention is not limited thereto, and it will be understood that various modifications can be made within the scope of the claims, detailed description and drawings of the present invention, and such modifications also fall within the scope of the present invention.

Claims

1. A negative electrode plate, the negative electrode plate comprising a negative electrode active material, the negative electrode active material comprising a mixture of a first negative electrode active material, a second negative electrode active material, and a third negative electrode active material. in, The first negative electrode active material comprises: natural graphite, including secondary particles arranged as primary particles; and an amorphous carbon coating layer comprising amorphous carbon and surrounding the secondary particles, wherein the first negative electrode active material has an orientation degree of 90 or less and a d002 value of 3.356 Å to 3.360 Å. The second negative electrode active material includes artificial graphite. The third negative electrode active material comprises: a composite of silicon and crystalline carbon; and an amorphous carbon coating layer containing amorphous carbon and formed on the surface of the composite. The negative electrode plate is used in rechargeable lithium batteries.

2. The negative electrode plate according to claim 1, wherein, The first negative electrode active material has a mercury accumulation pore volume of 0.01 mL g to 0.06 mL / g.

3. The negative electrode plate according to claim 1, wherein, The first negative electrode active material has a particle density of 1.60 g / cc to 1.80 g / cc.

4. The negative electrode plate according to claim 1, wherein, The first negative electrode active material has a sphericity of 0.85 or greater.

5. The negative electrode plate according to claim 1, wherein, The ratio of the major axis length of the primary particle to the average particle size D50 of the secondary particle is greater than 2 and less than or equal to 10.

6. The negative electrode plate according to claim 1, wherein, The primary particles are plate-shaped, and the secondary particles are spherical.

7. The negative electrode plate according to claim 1, wherein, The primary particles have a major axis length of 10 μm to 200 μm.

8. The negative electrode plate according to claim 1, wherein, The average particle size D50 of the secondary particles is 30 μm or smaller.

9. The negative electrode plate according to claim 1, wherein, The primary particles also include amorphous carbon on their surface.

10. The negative electrode plate according to claim 1, wherein, The natural graphite includes flake natural graphite.

11. The negative electrode plate according to claim 1, wherein, The amorphous carbon includes one or more of the following: soft carbon, hard carbon, mesophase pitch carbides, and calcined coke.

12. The negative electrode plate according to claim 9, wherein, Based on 100 parts by weight of the total amount of natural graphite and amorphous carbon in the first negative electrode active material, natural graphite and amorphous carbon are included in a weight ratio of 90:10 to 75:

25.

13. The negative electrode plate according to claim 1, wherein, The aspect ratio of the active material of the third negative electrode is 1 to 2.

5.

14. The negative electrode plate according to claim 1, wherein, The third negative electrode active material comprises 20 wt% to 70 wt% silicon, 3 wt% to 50 wt% crystalline carbon, and 20 wt% to 50 wt% amorphous carbon.

15. The negative electrode plate according to claim 1, wherein, The artificial graphite has a maximum particle size of 30 μm to 40 μm.

16. The negative electrode plate according to claim 1, wherein, The mixture comprises 20 wt% to 75 wt% of the first negative electrode active material, 20 wt% to 75 wt% of the second negative electrode active material, and 1 wt% to 20 wt% of the third negative electrode active material.

17. The negative electrode plate according to claim 1, wherein the negative electrode plate further comprises a conductive material. in, The conductive material includes carbon nanotubes.

18. The negative electrode plate according to claim 17, wherein, The carbon nanotubes are included in an amount of 0.01 wt% to 5 wt% based on the total weight of the negative electrode plate.

19. The negative electrode plate according to claim 17, wherein, The carbon nanotubes have an average diameter of 0.5 nm to 3 nm, an average length of 5 μm or less, and a length of 240 m. 2 / g to 280m 2 Specific surface area per g.

20. A rechargeable lithium battery, said rechargeable lithium battery comprising: For use in rechargeable lithium batteries, the negative electrode plate according to claim 1; as well as Positive electrode.

Images