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

Abstract

Disclosed are a negative electrode plate for a rechargeable lithium battery and a rechargeable lithium battery including the same. The negative electrode plate for a rechargeable lithium battery 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 in which primary particles are assembled, and a coating layer surrounding the secondary particles and including amorphous carbon, and has an orientation degree of 90 or less and a d002 of 3.356 Å to 3.360 Å; the second negative electrode active material includes artificial graphite; and the third negative electrode active material includes a core including silicon nanoparticles and amorphous carbon, and an amorphous carbon coating layer surrounding the core and including amorphous carbon.

Description

[0001] This application claims priority and benefit to Korean Patent Application No. 10-2024-0175701, filed on November 29, 2024, with the Korean Intellectual Property Office, and Korean Patent Application No. 10-2024-0175705, filed on November 29, 2024, the entire disclosure of which is incorporated herein by reference. Technical Field

[0002] An aspect of the present invention 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 lithium batteries with high energy density and high capacity is increasing rapidly. Therefore, research and development to improve the performance of rechargeable lithium batteries are 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 one aspect of the present invention, a negative electrode plate for a rechargeable lithium battery is provided, which exhibits high energy density and boost charging performance.

[0006] According to another aspect of the embodiments of the present invention, a negative electrode plate for a rechargeable lithium battery is provided, which exhibits reduced expansion of silicon-based active materials, reduced fast charging time, extended cycle life, 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. The first negative electrode active material comprises natural graphite and a coating, the natural graphite comprising secondary particles in which primary particles are assembled, the coating surrounding the secondary particles and comprising amorphous carbon, and the first negative electrode active material having an orientation degree of 90 or less and a d002 in the range of 3.356 Å to 3.360 Å; the second negative electrode active material comprises artificial graphite; and the third negative electrode active material comprises a core and an amorphous carbon coating, the core comprising silicon nanoparticles and amorphous carbon, the amorphous carbon coating surrounding the core and comprising amorphous carbon.

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

[0010] The negative electrode plate for a rechargeable lithium battery according to one or more embodiments of the present invention can provide boost charging performance, thereby achieving excellent rechargeable lithium battery performance.

[0011] The negative electrode plate for a rechargeable lithium battery according to one or more embodiments of the present invention can provide reduced expansion of silicon-based active materials, reduced fast charging time, extended cycle life and high energy density, thereby achieving excellent rechargeable lithium battery performance. Attached Figure Description

[0012] 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 schematic diagram of the first negative electrode active material according to an embodiment; Figure 2 This is a schematic diagram of the third negative electrode active material according to an embodiment; Figure 3 This is a schematic diagram showing the interparticle distance in the active material of the third negative electrode; and Figures 4 to 7 This is a schematic diagram illustrating a rechargeable lithium battery according to some embodiments. Detailed Implementation

[0013] 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.

[0014] 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.

[0015] Unless otherwise stated herein, the singular may include multiple terms. Furthermore, unless otherwise stated, “A or B” may mean “including A”, “including B”, or “including both A and B”.

[0016] In this specification, “combination of them” can refer to mixtures, laminates, complexes, copolymers, alloys, blends and / or reaction products of the components.

[0017] Unless otherwise defined herein, particle size can refer to the average particle diameter. Alternatively, particle size refers to the average particle size (or average particle diameter) (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 by 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% volume 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.

[0018] When the particles are spherical, the size can refer to the diameter.

[0019] The negative electrode plate for a rechargeable lithium battery according to one or more embodiments can provide (e.g., simultaneously provide) extended cycle life, high energy density, boost charging performance, and improved expansion characteristics.

[0020] A negative electrode plate for a rechargeable lithium battery according to one or more embodiments includes a negative electrode active material, wherein the negative electrode active material comprises a mixture of a first negative electrode active material, a second negative electrode active material, and a third negative electrode active material. In one or more embodiments, the first negative electrode active material comprises natural graphite, which includes secondary particles in which primary particles are assembled or arranged and a coating surrounding the secondary particles and comprising amorphous carbon, and has an orientation degree of 90 or less and a d002 in the range of 3.356 Å to 3.360 Å; the second negative electrode active material comprises artificial graphite; and the third negative electrode active material comprises a core comprising silicon nanoparticles and amorphous carbon, and an amorphous carbon coating surrounding the core and comprising amorphous carbon.

[0021] The negative electrode plate for rechargeable lithium batteries may include this mixture as the negative electrode active material, thereby providing high capacity retention, high energy density, boost charging performance and improved lifespan.

[0022] In the embodiments, the content of the mixture may be 95 wt% or more of the total negative electrode active material of the negative electrode plate, for example, 95 wt% to 100 wt%, 99 wt% to 100 wt% or 100 wt%.

[0023] In the embodiments, the content of the negative electrode active material (e.g., a mixture) can be from 90 wt% to 99.5 wt% of the negative electrode plate, for example, from 95 wt% to 99.5 wt% or from 90 wt% to 99 wt%. Within the above range, capacity improvement can be achieved.

[0024] If the mixture does not contain the first negative electrode active material, the low electrode plate density makes it difficult to achieve a battery with high energy density, and the boost charging performance may deteriorate.

[0025] If the mixture does not contain a second negative electrode active material, it may not exhibit an extended cycle life effect under high temperature conditions.

[0026] If the mixture does not contain a third negative electrode active material, the increase in capacity per unit volume may be reduced.

[0027] In the embodiments, the content of the first negative electrode active material in the mixture can be from 20 wt% to 75 wt%, for example, 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%. The content of the active material of the second negative electrode can be 54wt%, 55wt%, 56wt%, 57wt%, 58wt%, 59wt%, 60wt%, 61wt%, 62wt%, 63wt%, 64wt%, 65wt%, 66wt%, 67wt%, 68wt%, 69wt%, 70wt%, 71wt%, 72wt%, 73wt%, 74wt%, or 75wt%, and in one embodiment, it can be 20wt% to 65wt% or 20wt% to 60wt%, and the content of the active material of the second negative electrode can be 20wt% to 75wt%, for example, 20wt%, 21wt%, 22wt%, 23wt%, 24wt%, 25wt%, 26wt%. %, 27wt%, 28wt%, 29wt%, 30wt%, 31wt%, 32wt%, 33wt%, 34wt%, 35wt%, 36wt %, 37wt%, 38wt%, 39wt%, 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%, The content of the active material of the third negative electrode can be 67wt%, 68wt%, 69wt%, 70wt%, 71wt%, 72wt%, 73wt%, 74wt%, or 75wt%, and in one embodiment, it can be 20wt% to 65wt% or 20wt% to 60wt%, and the content of the active material of the third negative electrode can be 1wt% to 20wt%, for example, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt%, or 20wt%, and in one embodiment,The concentration can be 1wt% to 15wt%, 1wt% to 10wt%, or 5wt% to 7wt%. Within these ranges, boost charging performance can be provided, and the effect of improving fast charging cycle life can be further enhanced.

[0028] In an embodiment, the content of the third negative electrode active material in the mixture can be from 1 wt% to 15 wt%, for example, 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%. 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%, for example, 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%. In one embodiment, it can be from 86 wt% to 99 wt%. The weight ratio of the first negative electrode active material to the second negative electrode active material relative to 100 parts by weight of the total amount of the first and second negative electrode active materials can be in the range of 10:90 to 90:10, for example, 25:75 to 75:25 or 50:50. Within the aforementioned range, boost charging performance and improved fast charging cycle life can be achieved.

[0029] In this embodiment, the density of the negative electrode plate can be from 1.3 g / cc to 1.7 g / cc, for example, from 1.3 g / cc to 1.68 g / cc. Within this range, high energy density and improved boost charging performance can be achieved.

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

[0031] (1) Active material of the first negative electrode The first negative electrode active material comprises natural graphite and a coating, wherein the natural graphite contains secondary particles in which primary particles are assembled or arranged, and the coating surrounds the secondary particles and contains amorphous carbon. The first negative electrode active material has an orientation degree of 90 or less and a d002 of 3.356 Å to 3.360 Å.

[0032] As used herein, “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 Cu Kα rays.

[0033] As used herein, “d002” can refer to the interplanar spacing of the (002) plane of the first negative electrode active material, as measured by X-ray diffraction analysis using Cu Kα rays.

[0034] Natural graphite is generally advantageous as a negative electrode active material in batteries, but its high resistivity can lead to poor charging characteristics. Furthermore, due to its numerous internal pores, side reactions can adversely affect extended cycle life and expansion rate.

[0035] The first negative electrode active material is prepared by significantly reducing the average particle size of the secondary particles of natural graphite to a fine particle form in order to provide low resistance and offset the efficiency reduction caused by the increase in the specific surface area of ​​the secondary particles. The first negative electrode active material is calcined at the following temperature to reduce the specific surface area and provide (e.g., simultaneously provide) high efficiency.

[0036] In this regard, the first negative electrode active material comprises natural graphite, amorphous carbon, and a coating, and satisfies the aforementioned orientation degree and d002. Therefore, the first negative electrode active material improves the battery capacity and significantly increases the charge rate (C-rate), thereby enhancing the boost 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, suppressed side reactions with the electrolyte, and improved lifespan.

[0037] As the orientation degree decreases, the edge faces of natural graphite become oriented in random directions, thereby increasing the random orientation of the negative electrode active material. This facilitates the insertion and extraction of lithium ions into and from the natural graphite secondary particles, thus improving the capacity characteristics of the rechargeable lithium battery. In embodiments, for example, the orientation degree can be 80 or less, such as 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 one embodiment, it can be 10 to 80, 20 to 80, 30 to 80, 40 to 80, or 50 to 80. The orientation degree can be obtained by adjusting the average particle size (D50) of the secondary particles and the long axis length of the primary particles. In the first negative electrode active material, the average particle size (D50) of the secondary particles can be significantly reduced to lower the high resistivity of natural graphite.

[0038] In an embodiment, as described below, the average particle size (D50) of the secondary particles in the first negative electrode active material is significantly smaller than the long axis length of the primary particles. In an embodiment, the secondary particles can be prepared by wrinkling the primary particles. In an embodiment, the first negative electrode active material can include amorphous carbon and can be prepared by heat treatment at a temperature of 2500°C or higher as described below, thereby achieving a high degree of graphitization. A high degree of graphitization can help improve the capacity of the negative electrode active material and prevent or substantially prevent the efficiency reduction caused by the decrease in the average particle size of the secondary particles and the increase in the specific surface area. In an embodiment, the d002 of the first negative electrode active material is 3.356 Å to 3.360 Å. Within the above range, the decrease in battery efficiency caused by the increase in the specific surface area of ​​the first negative electrode active material, which includes secondary particles with a relatively small average particle size (D50), can be offset, and high capacity can be provided. 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 an Hg cumulative pore volume of 0.01 mL / g to 0.06 mL / g, for example, 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 one embodiment, it can have an Hg cumulative pore volume of 0.02 mL / g to 0.06 mL / g or 0.03 mL / g to 0.06 mL / g. Within the above range, significantly higher negative electrode active material efficiency can be achieved due to the small pores (i.e., voids) in the first negative electrode active material and the appropriate amount of amorphous carbon therein. Furthermore, the internal surface area of ​​the first negative electrode active material that reacts with the electrolyte is not excessively large, and it maintains sufficient density to allow for good electrolyte impregnation, thereby ensuring an appropriate lifetime without excessive side reactions. Hg cumulative pore volume can be a characteristic of negative electrode active materials prepared by the preparation method described below, in order to reduce specific surface area while including small particles of natural graphite.

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

[0041] In an embodiment, B may be the perimeter of the actual shape of the first negative electrode active material.

[0042] The sphericity of the active material of the first negative electrode can be a value obtained when a three-dimensional particle is projected onto a two-dimensional plane. For example, sphericity can be the ratio of the outline of a real particle to the outline of a circle with the same area as the real particle.

[0043] In Equation 1, area A represents the area of ​​a circle with a perimeter that is the same as the actual perimeter B of the particle, which has been obtained using a pressure-controlled scanning electron microscope (CP-SEM) through an SEM image of the electrode profile and calculated from the profile image using the Image J program. In this embodiment, the actual perimeter can refer not only to the perimeter when the particle has a perfectly spherical shape, but also to the length obtained along the perimeter even when the particle is not perfectly spherical and has non-uniform regions.

[0044] In the embodiments, the sphericity of the first negative electrode active material can be 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 one embodiment, it can be 0.90 to 1.0, 0.90 to 0.98, or 0.90 to 0.95. When the sphericity falls within the above range, the expansion rate during charge and discharge can be effectively suppressed.

[0045] In this embodiment, 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 internal pores of the first negative electrode active material and side reactions with the electrolyte can be reduced, thereby improving its lifetime characteristics. For example, the aggregate density can be 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 one embodiment, it can be from 1.70 g / cc to 1.80 g / cc.

[0046] In the embodiments, the first negative electrode active material can have a tap density of 0.75 g / cc to 1.20 g / cc, for example, 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 g / cc. c. Tap densities of 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 one embodiment, tap densities may be from 0.75 g / cc to 1.0 g / cc or from 0.95 g / cc to 1.20 g / cc. Within the aforementioned range, the internal pores of the first negative electrode active material and side reactions with the electrolyte can be reduced, and lifetime characteristics can be improved. Tap density can be achieved by using a conversion factor of 0.2907 cm⁻¹. 3 The average value was calculated by performing three processes with a pressure of 108 N on a GeoPyc 1360 micromeritics bottle with a chamber diameter of 19.1 mm and a chamber diameter of 19.1 mm.

[0047] In an embodiment, the first negative electrode active material may have a 10m 2 Specific surface area per g or less, for example, 1 m² 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 / g, and in one embodiment, it can have 1m². 2 / g to 10m 2 The specific surface area is measured in g. Within the above range, the internal pores of the first negative electrode active material and side reactions with the electrolyte can be reduced, and lifetime characteristics can be improved. Specific surface area can be the BET specific surface area. The BET specific surface area can be measured using a Macsorb HM Model-1208 (MOUNTECH).

[0048] In embodiments, the internal porosity of the first negative electrode active material can be 2% or less, for example, 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 one embodiment, it can be 1.8% or less, 1.5% or less, 1.0% to 1.5%, or 1.0% to 1.3%. Within the above ranges, 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 a Barrett-Joyner-Halenda (BJH) analytical instrument.

[0049] The composition of the active material of the first negative electrode will be described in further detail here.

[0050] The first negative electrode active material includes: natural graphite, comprising secondary particles in which primary particles are assembled; and a coating surrounding the secondary particles and comprising amorphous carbon.

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

[0052] In embodiments, the primary particles may have a major axis length of 10 μm to 200 μm, for example, 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. The major axis lengths are 125μm, 130μm, 135μm, 140μm, 145μm, 150μm, 155μm, 160μm, 165μm, 170μm, 175μm, 180μm, 185μm, 190μm, 195μm, or 200μm, and in one embodiment, they can have major axis lengths of 10μm to 100μm, 30μm to 60μm, or 20μm to 50μm. Within the above ranges, secondary particles can be easily assembled, and the proportions described below can be easily achieved.

[0053] Here, "major axis length" refers to the length of the longest axis between the facing edges when the primary particles are formed into a plate shape.

[0054] In the embodiments, the primary particles may be formed in plate or sheet shape, but the invention is not limited thereto.

[0055] In the embodiments, the average particle size (D50) of the secondary particles can be 30 μm or less. Within the above range, the secondary particles can easily achieve the proportions described below. For example, the average particle size (D50) of the secondary particles can be 5 μm or greater and 10 μm or less, such as 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm, and in one embodiment, it can be 6 μm or greater and less than 8 μm. Within the above range, the secondary particles can easily achieve the aforementioned orientation and sphericity.

[0056] The secondary particles can be spherical, but the invention is not limited thereto.

[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 less than or equal to 10. Within this range, the resistance of the first negative electrode active material does not increase, and the boost charging performance does not decrease. 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 one embodiment, it can be 3 to 6, 4 to 6, or 5 to 6. Within the above range, the secondary particles can easily achieve the aforementioned orientation and sphericity.

[0058] Amorphous carbon can be incorporated into a coating surrounding the surface of the secondary particles. Amorphous carbon can reduce the internal porosity of the first negative electrode active material and suppress side reactions between the first negative electrode active material and the electrolyte, thereby improving rate performance.

[0059] In the embodiments, the thickness of the coating containing amorphous carbon can be from 5 nm to 50 nm, for example, 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 one embodiment, it can be from 10 nm to 50 nm or from 20 nm to 50 nm. Within the above range, side reactions with the electrolyte can be suppressed, and rate performance 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 primary particles.

[0062] In this embodiment, natural graphite and amorphous carbon may 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) relative to 100 parts by weight of the total amount of natural graphite and amorphous carbon in the first negative electrode active material. Within the above range, side reactions with the electrolyte can be suppressed, and rate performance can be improved.

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

[0064] (1) Primary particles with the aforementioned long axis length are obtained by grinding natural graphite raw material with an average particle size (D50) of 120 μm or greater. In an embodiment, the natural graphite raw material can be ground by applying an air jet milling method. Air jet milling may include grinding at 5 kg / cm² at room temperature. 2 Up to 20kg / cm 2 Grinding natural graphite raw materials under certain conditions.

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

[0066] Assembly is the process used to achieve a sphericity of 0.85 or greater, and can be achieved using a high-intensity mixer equipped with a high-speed rotating rotor and stator. During sphericification, the average particle size (D50) of the secondary particles can be adjusted by changing the pressure, shear rate, etc.

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

[0068] There are no particular limitations on amorphous carbon precursors, as long as they are materials that form carbides. For example, precursors may include one or more of phenolic resins, furan resins, epoxy resins, polyacrylonitrile resins, polyamide resins, polyimide resins, polyamide-imide resins, synthetic bitumen, petroleum bitumen, coal tar, and coal tar.

[0069] During mixing, natural graphite and amorphous carbon in the final product (i.e., the first negative electrode active material) can be added in the weight ratio described above.

[0070] (4) The first negative electrode active material is obtained by calcining and heat treatment of the mixture obtained by mixing.

[0071] In embodiments, heat treatment can be performed at 2500°C or higher, for example, between 2500°C and 3500°C, or for example, between 2500°C and 3000°C. Within the above range, the first negative electrode active material comprising secondary particles satisfying the above proportions can readily achieve the above-mentioned orientation, d002, and sphericity.

[0072] The heat treatment can be maintained for 1 to 5 hours, for example, 1 to 4 hours, 1 to 3 hours, or 2 to 3 hours.

[0073] Figure 1 This is a schematic 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 in which a plurality of primary particles 1 are assembled or arranged; amorphous carbon 5, present on the surface of the primary particles; and a coating 7, surrounding the secondary particles 3 and comprising the amorphous carbon 5. (See reference...) Figure 1 Since the secondary particles 3 are assembled by shaping the primary particles 1 into a curved shape, natural graphite has a smaller size and a denser internal structure, which allows for the minimization or reduction of internal pores, reduces side reactions with the electrolyte, and improves cycle life.

[0075] (2) Active material of the second negative electrode In the embodiments, the average particle size (D50) of the artificial graphite can be from 10 μm to 20 μm, for example, from 13 μm to 18 μm or from 15 μm to 20 μm. Within the above range, since the specific surface area does not increase significantly, the side reactions with the electrolyte do not increase, and the boost charging performance does not decrease.

[0076] In the embodiments, the artificial graphite may have a maximum particle size of 30 μm to 40 μm.

[0077] In an embodiment, the artificial graphite may have a lower agglomerate density than the agglomerate density of the first negative electrode active material, for example, the artificial graphite may have a agglomerate density of 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, the artificial graphite may have a tap density of 0.5 g / cc to 1.0 g / cc or 0.5 g / cc to 0.9 g / cc.

[0079] In this embodiment, the specific surface area of ​​the artificial graphite can be 10 m². 2 / g or less, for example, 1m 2 / g to 10m 2 / g. Specific surface area can be BET specific surface area.

[0080] In this embodiment, the orientation degree of the artificial graphite may be 90 or greater, for example, 90 to 100 or greater than 90 and less than or equal to 100. The orientation degree can be measured by the method described above.

[0081] Artificial graphite can have, but is not limited to, spherical shapes.

[0082] Artificial graphite may include one or more of single particles, primary particles, secondary particles in which primary particles are assembled, and tertiary particles in which secondary particles are assembled.

[0083] In one embodiment, the secondary particles, which are assembled with primary particles, may further include a coating containing amorphous carbon on their surface.

[0084] (3) Active material of the third negative electrode The third negative electrode active material includes: a core comprising silicon nanoparticles and amorphous carbon; and an amorphous carbon coating surrounding the core and comprising amorphous carbon.

[0085] In an embodiment, the third negative electrode active material may be a binary negative electrode active material comprising silicon and amorphous carbon.

[0086] In an embodiment, the interparticle distance between silicon nanoparticles contained in the core of the third negative electrode active material can be 100 nm or less, 90 nm or less, 80 nm or less, 70 nm or less, 65 nm or less, 60 nm or less, 55 nm or less, 50 nm or less, 45 nm or less, 40 nm or less, or 35 nm or less. When the interparticle distance between silicon nanoparticles falls within the above range, the size of the pores and the total pore volume contained in the core can be reduced. When the interparticle distance between silicon nanoparticles falls within the above range, the pore volume in the third negative electrode active material can be reduced, and electrolyte permeation into the core during battery operation can be prevented or substantially prevented by reducing the interparticle distance between silicon nanoparticles. As a result, side reactions between the electrolyte and the third negative electrode active material can be suppressed, thereby improving battery life.

[0087] Here, the interparticle distance between silicon nanoparticles refers to the center-to-center distance between silicon nanoparticles. (See reference...) Figure 3 Each silicon nanoparticle 2 has a minor axis length a and a major axis length b, and the interparticle distance d is the center-to-center distance between silicon nanoparticles 2.

[0088] The interparticle distance between silicon nanoparticles can mean that the number of silicon nanoparticles having an interparticle distance within the above range is 50% to 100% of the total number of silicon nanoparticles included in the core, for example, 60% to 100%, 70% to 100% or 80% to 100%.

[0089] In the embodiments, the average particle size (D50) of the silicon nanoparticles can be from 50 nm to 150 nm, for example, 50 nm or larger, 60 nm or larger, 70 nm or larger, or 80 nm or larger and 150 nm or smaller, 140 nm or smaller, 130 nm or smaller, or 115 nm or smaller. When the average particle size (D50) of the silicon nanoparticles falls within the above range, side reactions with the electrolyte can be suppressed and the expansion of the silicon nanoparticles can be reduced, thereby improving initial efficiency and lifetime characteristics.

[0090] In the embodiments, the silicon nanoparticles may have a full width at half maximum (FWHM) at an X-ray diffraction angle (2θ) using Cu Kα rays on the (111) plane in the range of 0.3° to 7°. Therefore, lifetime characteristics can be improved.

[0091] The full width at half maximum (FWHM) of the X-ray diffraction angle (2θ) of the (111) plane of silicon nanoparticles using Cu Kα rays can be adjusted by changing the size of the silicon particles or by changing the process for preparing the silicon nanoparticles.

[0092] In the embodiments, the aspect ratio of the silicon nanoparticles can be from 2 to 8, for example, from 2 to 6; the minor axis length 'a' of the silicon nanoparticles can be from 20 nm to 50 nm; and the major axis length 'b' can be from 50 nm to 300 nm. When the aspect ratio, major axis length 'b', and minor axis length 'a' of the silicon nanoparticles fall within the above ranges, the side reactions between the third negative electrode active material and the electrolyte can be suppressed, and the expansion of the silicon nanoparticles can be reduced, thereby improving the initial efficiency and lifetime characteristics.

[0093] In the embodiments, the content of silicon nanoparticles relative to the total weight of the third negative electrode active material can be 20wt% to 80wt%, 30wt% to 70wt%, 30wt% to 60wt%, or 30wt% to 50wt%. When the content of silicon nanoparticles falls within the above range, the battery capacity can be improved.

[0094] The amorphous carbon contained in the core can be soft carbon, hard carbon, mesophase pitch carbide, calcined coke, or a combination thereof.

[0095] When the core contains amorphous carbon, the pore volume of the third negative electrode active material can be reduced, thereby suppressing side reactions with the electrolyte. Furthermore, if the silicon nanoparticles in the third negative electrode active material expand, this buffers them to suppress battery expansion. Additionally, since amorphous carbon acts as a binder, breakage of the third negative electrode active material is mitigated, thus maintaining its shape well.

[0096] In this embodiment, the coating comprises amorphous carbon and can have a thickness of 1 nm to 900 nm, for example, 5 nm to 800 nm. This reduces the specific surface area of ​​the third negative electrode active material and prevents or substantially prevents electrolyte inflow into the third negative electrode active material. Consequently, side reactions with the electrolyte can be minimized or reduced, and battery life characteristics can be improved.

[0097] The amorphous carbon contained in the coating can be soft carbon, hard carbon, mesophase pitch carbide, calcined coke or a combination thereof, and can be the same as or different from the amorphous carbon contained in the core.

[0098] In the embodiments, the content of amorphous carbon relative to the total weight of the third negative electrode active material can be from 20 wt% to 80 wt%, for example, from 20 wt% to 70 wt%, from 20 wt% to 60 wt%, from 20 wt% to 50 wt%, or from 20 wt% to 40 wt%. When the content of amorphous carbon falls within the above range, the side reactions between the third negative electrode active material and the electrolyte can be suppressed.

[0099] The average particle size (D50) of the third negative electrode active material according to the embodiment can be from 2 μm to 15 μm, for example, from 3 μm to 13 μm or from 5 μm to 10 μm. When the average particle size of the third negative electrode active material falls within the above range, lithium ions can easily diffuse into the third negative electrode active material, and the battery resistance and charge / discharge rate characteristics can be improved. Furthermore, by suppressing excessive increase in the specific surface area of ​​the third negative electrode active material, side reactions with the electrolyte can be reduced.

[0100] The average particle size (D50) of the third negative electrode active material can be appropriately adjusted by regulating the crushing and grinding conditions during the preparation of the third negative electrode active material.

[0101] In this embodiment, the third negative electrode active material may have a content of 3.0 × 10⁻⁶. -2 cm 3 / g or less, for example, 2.5 × 10 -2 cm 3 / g or less, 2.3×10 -2 cm 3 / g or less, 2.0×10 -2 cm 3 / g or less, 1.9×10 -2 cm 3 / g or less, 1.8×10 -2 cm 3 / g or less, 1.7×10 -2 cm 3 / g or less, 1.6×10 -2 cm 3 / g or less, 1.5×10 -2 cm 3 / g or less, 1.4×10 -2 cm 3 / g or less, 1.3×10 -2 cm 3 / g or less, 1.2×10 -2 cm 3 / g or less, 1.1×10 -2 cm 3 / g or less, 1.0×10 -2 cm 3 / g or less, 0.9×10 -2 cm 3 / g or less, 0.8×10 -2 cm 3 / g or less, 0.7×10 - 2 cm 3 / g or less, 0.6×10-2 cm 3 / g or less or 0.5×10 -2 cm 3 The total pore volume of pores with a size of 200 nm or smaller is within the range of / g or smaller. Within the above range, side reactions between the electrolyte and silicon nanoparticles can be suppressed, thereby improving initial efficiency and lifetime characteristics.

[0102] The total pore volume of pores with a size of 200 nm or smaller can be quantitatively measured using the Barrett-Joyner-Halenda (BJH) analytical instrument.

[0103] In this embodiment, the pore size of the third negative electrode active material can be 200 nm or smaller, for example, 170 nm or smaller, 150 nm or smaller, 130 nm or smaller, 100 nm or smaller, or 50 nm or smaller. When the pore size is controlled within the above range, side reactions between the electrolyte and silicon nanoparticles can be reduced, and a battery with improved initial efficiency and lifetime characteristics can be obtained.

[0104] In this embodiment, the BET specific surface area of ​​the third negative electrode active material can be 10 m². 2 / g or less. When the BET specific surface area falls within the above range, the battery efficiency characteristics can be improved by suppressing side reactions with the electrolyte.

[0105] In the embodiments, in the third negative electrode active material, the weight ratio of silicon nanoparticles to amorphous carbon relative to the total amount of silicon nanoparticles and amorphous carbon can be 80:20 to 20:80, for example, 70:30 to 30:70, 70:30 to 40:60, or 70:30 to 50:50. When the content of silicon nanoparticles and amorphous carbon falls within the above range, the volume of internal pores can be reduced, and amorphous carbon can diffuse uniformly (substantially uniformly) in and on the surface of the third negative electrode active material. As a result, side reactions with the electrolyte can be suppressed, and the performance of the third negative electrode active material can be improved.

[0106] A method for preparing the third negative electrode active material according to an embodiment will be described.

[0107] The method for preparing the active material of the third negative electrode includes the following steps: preparing a mixture by mixing and dispersing silicon nanoparticles and amorphous carbon; preparing a molded body by pressing after spraying and drying the mixture; and heat-treating the molded body.

[0108] The mixture was prepared by mixing and dispersing silicon nanoparticles and amorphous carbon. The silicon nanoparticles and amorphous carbon are as described above.

[0109] The prepared mixture is sprayed and dried before being pressed to form a molded body.

[0110] Drying can be carried out using a spray dryer at temperatures ranging from 50°C to 150°C.

[0111] In this embodiment, pressing can be performed at a pressure of 50 MPa to 150 MPa, for example, 75 MPa to 150 MPa or 75 MPa to 125 MPa. When the molded body is pressed within the above pressure range, the distance between the silicon nanoparticles can be appropriately maintained, and the pore volume formed in the third negative electrode active material can be controlled, thereby suppressing side reactions between the electrolyte and the silicon nanoparticles and improving initial efficiency and lifetime characteristics.

[0112] The active material for the third negative electrode is prepared by heat treatment of the resulting molded body.

[0113] In this embodiment, the heat treatment can be performed at 700°C to 1100°C, for example, 800°C to 1050°C or 900°C to 1000°C. When heat treatment is performed within the above temperature range, the amorphous carbon is carbonized, thereby improving the strength of the third negative electrode active material. Furthermore, the conductivity of the third negative electrode active material can be improved, thereby improving the initial efficiency of the battery.

[0114] Heat treatment can be carried out in a furnace with a nitrogen (N2) atmosphere.

[0115] In an embodiment, the third negative electrode active material may have a sphericity of 0.7 or greater and 1.0 or less. Sphericity refers to the ratio (Lb / La) of the minor axis length (Lb) to the major axis length (La) when the third negative electrode active material has a circular or elliptical shape.

[0116] In the embodiments, the third negative electrode active material may have an elliptical or circular cross-section. Therefore, a sphericity of 1.0 means that the negative electrode active material is actually perfectly spherical, and those skilled in the art will understand that the maximum value of sphericity is 1.0 and cannot exceed 1.0.

[0117] In this embodiment, the sphericity of the third negative electrode active material is 0.7 or greater, and the surface area of ​​the third negative electrode active material can be reduced, which reduces the contact area between the third negative electrode active material and the electrolyte or lithium. Therefore, side reactions with the electrolyte can be reduced, reactions with lithium can be reduced, and volume expansion can be reduced through the uniform expansion of the third negative electrode active material.

[0118] When the BET specific surface area of ​​the active material of the third negative electrode is 10m² 2 / g, for example, 0.5m 2 / g to 10m 2At a BET specific surface area of ​​10 m² / g, the effect caused by the reduction in surface area can be more effectively demonstrated. 2 / g or less, and according to one embodiment, 0.5m 2 / g to 10m 2 At a concentration of / g, contact with the electrolyte can be reduced to suppress side reactions, thereby helping to improve performance and increase initial efficiency.

[0119] In other words, because the third negative electrode active material according to the embodiment has a sphericity of 0.7 or greater and a sphericity of 10 μm... 2 With a BET specific surface area of ​​ / g or less, the third negative electrode active material can be an active material with reduced side reactions with the electrolyte and reduced reactions with lithium.

[0120] In the third negative electrode active material, silicon nanoparticles are primary particles, wherein these primary particles (i.e., at least one primary particle) that assemble into secondary particles can be included in the silicon-carbon composite. Therefore, the silicon-carbon composite can include secondary particles in which Si nanoparticles are assembled.

[0121] In the embodiments, the silicon nanoparticles may be formed in the form of thin sheets, plates, or spheres, but the invention is not limited thereto. Furthermore, at least one primary particle may be assembled into a spherical secondary particle.

[0122] In embodiments, amorphous carbon may be configured to cover the surface of the secondary particles. That is, the third negative electrode active material according to embodiments may include a core comprising silicon nanoparticles, and, according to an example, may include a core of secondary particles in which at least one primary particle, as a silicon nanoparticle, is assembled or arranged, and amorphous carbon surrounding the core. In embodiments, the core refers to a region located within the active material. Since the core is surrounded by amorphous carbon, the core refers to a region not exposed to the outside. Therefore, the core can be considered as a region located within the amorphous carbon surrounding it.

[0123] Furthermore, amorphous carbon can fill the spaces between primary particles to cover their surfaces. Similarly, the amorphous carbon filling the spaces between primary particles can reduce the pore volume of the third negative electrode active material, thereby suppressing side reactions with the electrolyte, and if the primary particles, which are silicon nanoparticles, expand, the amorphous carbon can fill the spaces between them. Moreover, since the amorphous carbon filling the spaces between primary particles acts as a binder, it prevents or substantially prevents the breakage of the third negative electrode active material particles, thereby improving conductivity.

[0124] Amorphous carbon can be soft carbon, hard carbon, mesophase pitch carbides, calcined coke, or a combination thereof.

[0125] Silicon nanoparticles can be sheet-like or plate-like. In other words, silicon nanoparticles can be plate-like with a long axis and a short axis. In embodiments, the long axis / short axis ratio (e.g., width / thickness) of the silicon particles can be in the range of 5 to 20. When the long axis / short axis ratio of the silicon particles falls within the above range, the expansion of the Si nanoparticles can be reduced, thereby improving the initial efficiency and lifetime characteristics of the battery containing the active material.

[0126] In the embodiments, the particle size of the silicon nanoparticles can be from 10 nm to 200 nm. The particle size can be the average particle size. Here, the average particle size can refer to the particle size (D50) measured by cumulative pore volume. Unless otherwise defined in the specification, the particle size (D50) refers to the diameter of particles whose cumulative pore volume is 50% of the particle size distribution. When the size of the Si nanoparticles falls within the above range, side reactions between the third negative electrode active material and the electrolyte can be suppressed, and the expansion of the Si nanoparticles can be reduced, thereby improving the initial efficiency and lifespan characteristics of the battery.

[0127] In the embodiments, when the silicon nanoparticles are secondary particles in which at least one primary particle is assembled, the particle size of the secondary particles can be from 2 μm to 15 μm or from 5 μm to 10 μm. In the embodiments, the particle size of the primary particles can be from 10 nm to 200 nm. When the average particle size of the third negative electrode active material falls within the above range, lithium ions can easily diffuse into the third negative electrode active material, and the resistance and rate performance can be improved.

[0128] In the embodiments, the full width at half maximum (FWHM) of the diffraction peaks on the (111) plane of the silicon particles, as measured by X-ray diffraction using Cu Kα rays, can be between 0.3° and 7°. When the FWHM of the Si particles falls within the above range, the battery life characteristics can be improved.

[0129] X-ray diffraction measurements were performed using Cu Kα rays as the target rays. The measurement conditions included 2θ = 40° to 50°, a scan rate of 0.04 to 0.06 (° / s), and a step size of 0.01 to 0.03 (° / step).

[0130] In the embodiments, the mixing ratio of silicon nanoparticles to amorphous carbon can be 8:2 to 2:8 or 7:3 to 5:5 (by weight). In the embodiments, the silicon nanoparticles are assembled into secondary particles present in the third negative electrode active material. As a result, the mixing ratio of silicon nanoparticles to amorphous carbon can also be considered as the mixing ratio of secondary particles to amorphous carbon. When the mixing ratio of silicon nanoparticles to amorphous carbon falls within the above range, it can achieve the advantage of excellent capacity, especially the advantage of higher capacity compared with crystalline carbon negative electrode active materials.

[0131] Furthermore, amorphous carbon can exist as a coating on the surface of secondary particles, and in addition to the form of a coating, amorphous carbon can also fill between primary particles. In embodiments, regardless of whether amorphous carbon is filled between primary particles, exists as a coating, or exists in any other form, the total content of amorphous carbon contained in the third negative electrode active material can be from 20 wt% to 80 wt% relative to 100 wt% of the total amount of the third negative electrode active material.

[0132] In the embodiments, when amorphous carbon is present as a coating on or around the surface of the secondary particles, the amorphous carbon can exist on the surface of the secondary particles with a thickness of 1 nm to 1000 nm, for example, 30 nm to 200 nm. When the thickness of the amorphous carbon layer falls within the above range, the conductivity of the third negative electrode active material can be further improved, and the contact with the electrolyte can be reduced, thereby effectively suppressing the increase in resistance caused by the generation of by-reaction products.

[0133] In this embodiment, the particle size of the third negative electrode active material can be 40 μm or smaller, or 2 μm to 15 μm. When the particle size of the third negative electrode active material falls within the above range, lithium ions can easily diffuse into the third negative electrode active material, which can improve the battery's resistance and rate performance.

[0134] The third negative electrode active material according to the embodiment can be prepared by the following process.

[0135] First, silicon particles are prepared. These silicon particles can be nanoparticles with a particle size of 10 nm to 200 nm. These silicon nanoparticles can be obtained by performing conventional processes for preparing nanoparticles, such as grinding processes. For example, the FWHM (111) of the diffraction peaks on the (111) plane of the silicon nanoparticles, as measured by X-ray diffraction using CuKα rays, can be 0.3° to 7°.

[0136] A silicon particle solution is prepared by dispersing silicon particles in a solvent. As a solvent, any suitable alcohol that does not oxidize the silicon particles and is readily volatile can be used; for example, isopropanol, ethanol, methanol, butanol, or combinations thereof can be used. In the examples, the concentration of the silicon particle dispersion is from 10 wt% to 30 wt%.

[0137] The prepared silicon particle solution is spray-dried. Following the above process, nanoscale silicon particles (primary particles) are assembled to prepare micron-sized spherical Si secondary particles. The secondary particles may include internal pores, i.e., gaps between the primary particles. According to the spray drying process, the sphericity of the negative electrode active material can be adjusted by regulating the nozzle type and atmosphere. Specifically, a two-fluid nozzle can be used as the nozzle to form fine particles by mixing a two-phase fluid consisting of liquid and gas. When using a two-fluid nozzle, fine spherical particles can be formed, and due to the small particle size, no additional grinding process is required, thus allowing the spherical shape to be maintained. When using a disc-shaped nozzle that sprays while rotating, large particles are formed, and due to the large particle size, an additional grinding process is required, and the particles are formed in various forms such as spherical, elliptical, or annular shapes. Therefore, this type of nozzle is not suitable for embodiments of the present invention.

[0138] Furthermore, spray drying is suitable when carried out in an N2 atmosphere (e.g., while N2 is flowing (or blown) at a flow rate of 40 L / min to 50 L / min or 30 L / min to 40 L / min). When the flow rate of N2 during the spray drying process falls within the above range, particles in the form of spherical shapes with appropriate sizes can be formed. When the N2 flow rate is less than 30 L / min, the sprayed products may aggregate, which is undesirable due to the increased particle size. When the flow rate is greater than 50 L / min, there may be problems with the resulting particle size being too small and producing a large amount of fine powder.

[0139] Spray drying can be performed at temperatures between 120°C and 170°C. When spray drying is performed within this temperature range, the temperature is sufficiently higher than the boiling point of the solvent, which is suitable because the micron-sized spherical Si particles are thoroughly dried through rapid evaporation.

[0140] The micron-sized Si secondary particles, in spherical form, from the assembled Si primary nanoparticles, are mixed with an amorphous carbon precursor. In the embodiments, the mixing ratio of the secondary particles to the amorphous carbon precursor can be 80:20 to 20:80 or 60:40 to 50:50 (by weight).

[0141] The amorphous carbon precursor can be polyimide resin, furan resin, phenolic resin, polyvinyl alcohol resin, poly(meth)acrylic acid resin, polyurethane resin, cellulose resin, epoxy resin, polystyrene resin, petroleum pitch, coal tar pitch, raw coke, mesophase pitch, coal-based oil, heavy petroleum oil, coke, or a combination thereof.

[0142] The obtained mixture is subjected to compression molding. The compression molding process can be performed under pressure (e.g., 20 MPa to 150 MPa) that allows the micron-sized Si secondary particles to maintain a spherical shape. In embodiments, the compression molding process can be performed for 1 to 5 minutes. According to the compression molding process, the micron-sized spherical Si secondary particles and the amorphous carbon precursor can adhere firmly to each other, and the amorphous carbon precursor can be easily inserted between the primary particles. Therefore, the amorphous carbon precursor can be easily inserted into the pores formed in the secondary particles, and the amorphous carbon can be present in an appropriate amount (with an appropriate thickness) between the primary particles in the final negative electrode active material, thus forming a coating of appropriate thickness on the surface of the secondary particles. Without the compression molding process, the adhesion between the micron-sized spherical secondary particles and the amorphous carbon precursor is weak. Furthermore, since the amorphous carbon precursor does not easily insert between the primary particles and is mostly located on the surface of the secondary particles, it is undesirable for the amorphous carbon to exist on the surface of the secondary particles with an excessively large thickness in the final negative electrode active material.

[0143] A negative electrode active material for rechargeable lithium batteries is prepared by heat-treating the obtained compression-molded product. In embodiments, the heat treatment process can be performed at 400°C to 1200°C or 700°C to 1000°C. When the heat treatment process is performed within the above temperature range, the shape of the negative electrode active material can remain spherical, and the conductivity of the negative electrode active material can be improved and the initial efficiency of the battery can be improved as the amorphous carbon is carbonized. In embodiments, the heat treatment process can be performed under an N2 atmosphere. According to the heat treatment process, the amorphous carbon precursor is converted into amorphous carbon integrated into the negative electrode active material.

[0144] Figure 2 This is a schematic diagram of the third negative electrode active material according to an embodiment.

[0145] Reference Figure 2 The third negative electrode active material includes: a core 4 containing amorphous carbon and silicon nanoparticles 2; and a coating 6 surrounding the core 4, wherein the core includes pores 8.

[0146] In the embodiments, in addition to the first negative electrode active material, the second negative electrode active material and the third negative electrode active material described above, the negative electrode plate may also include a fourth negative electrode active material that is different from the first negative electrode active material, the second negative electrode active material and the third negative electrode active material described above.

[0147] The fourth negative electrode active material may include materials capable of reversibly inserting / deintercalating lithium ions, lithium metal, lithium-metal alloys, materials capable of doping and dedoping lithium, or transition metal oxides.

[0148] Materials capable of reversibly embedding / desorbing lithium ions can be carbon-based negative electrode active materials. For example, crystalline carbon, amorphous carbon, or a combination thereof. Examples of crystalline carbon can be graphite, such as natural graphite or artificial graphite in irregular shapes, plate-like, flaky, spherical, or fibrous forms, and examples of amorphous carbon can be soft carbon, hard carbon, mesophase pitch carbide, or calcined coke.

[0149] In embodiments, the alloy of lithium and a metal can 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.

[0150] As materials capable of doping and dedoping lithium, Si-based negative electrode active materials or Sn-based negative electrode active materials can be used. Si-based negative electrode active materials can be silicon, silicon-carbon composites, SiO x (0 < x ≤ 2), Si-Q alloys (where Q is selected from alkali metals, alkaline earth metals, group 13 elements, group 14 elements (excluding Si), group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof), or combinations thereof. Sn-based negative electrode active materials can be Sn, SnO2, Sn-based alloys, or combinations thereof.

[0151] The silicon-carbon composite can be a composite of silicon and amorphous carbon. According to embodiments, the silicon-carbon composite can include silicon particles coated with amorphous carbon on their surfaces. For example, the silicon-carbon composite can include secondary particles (cores) in which silicon primary particles are aggregated and an amorphous carbon coating (shells) located on the surfaces of the secondary particles. Amorphous carbon can also be located between the silicon primary particles such that the silicon primary particles can be coated with amorphous carbon. The secondary particles can be dispersed in an amorphous carbon matrix.

[0152] The silicon-carbon composite can also include crystalline carbon. For example, the silicon-carbon composite can include a core containing crystalline carbon and silicon particles and an amorphous carbon coating located on the surface of the core.

[0153] Si-based negative electrode active materials or Sn-based negative electrode active materials can be used in combination with carbon-based negative electrode active materials.

[0154] Binder The negative electrode plate for a rechargeable lithium battery can also include a binder.

[0155] In embodiments, the content of the binder can be 0.5 wt% to 5 wt% of the negative electrode plate.

[0156] The binder can cause the particles of the negative electrode active material to adhere well to each other and cause the negative electrode active material to adhere well to the current collector. As the binder, a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof can be used.

[0157] Non-aqueous adhesives may be polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyimide, or combinations thereof.

[0158] Waterborne adhesives may be selected from styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluorinated elastomers, polyethylene oxide, polyvinylpyrrolidone, polyepoxygenated alcohol, 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.

[0159] If an aqueous binder is used as the negative electrode binder, it may further include a cellulose compound capable of imparting viscosity. As a cellulose compound, one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, or their alkali metal salts may be used in combination. In the embodiments, Na, K, or Li may be used as the alkali metal.

[0160] Dry binders can be fibrous polymeric materials, such as polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or combinations thereof.

[0161] conductive materials The negative electrode plate used in rechargeable lithium batteries may also include conductive materials.

[0162] In the embodiments, the content of conductive material can be greater than 0 wt% of the negative electrode plate and 5 wt% or less of the negative electrode plate.

[0163] Conductive materials impart conductivity to electrodes, and any suitable electrically conductive material that does not cause chemical changes can be used in the constructed battery. Some 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, or carbon nanotubes; metallic materials, in the form of metal powders or metal fibers, containing copper, nickel, aluminum, or silver; conductive polymers, such as polyphenylene derivatives; or mixtures thereof.

[0164] The negative electrode current collector can be stacked on at least one of the negative electrode plates.

[0165] The negative electrode current collector can be selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrate coated with conductive metal, and combinations thereof.

[0166] The negative electrode plate for a rechargeable lithium battery according to an embodiment 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.

[0167] By incorporating a mixture as the negative electrode active material and carbon nanotubes as the conductive material, negative electrode plates for rechargeable lithium batteries can provide high capacity retention, high energy density, boost charging performance, and improved fast charging cycle life.

[0168] The negative electrode plate can include carbon nanotubes as a conductive material, thereby reducing fast charging time, extending cycle life, and reducing the expansion of silicon-based active materials, thus increasing energy density.

[0169] When carbon nanotubes are included as the conductive material, the negative electrode plate may include a mixture of negative electrode active materials, thereby enhancing the effect of reducing fast charging time and extending cycle life.

[0170] Carbon nanotubes, as conductive materials, possess a one-dimensional structure and form a conductive network. This network maintains the connection between the active materials of the negative electrode during battery charging and discharging, thus inhibiting battery degradation. Furthermore, carbon nanotubes can reduce fast charging time, extend cycle life, and minimize the expansion of the active materials of the negative electrode, thereby increasing the battery's energy density.

[0171] In the embodiments, carbon nanotubes may have an average diameter of 0.5 nm to 5 nm (e.g., 0.5 nm to 3 nm or 1 nm to 5 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 the above ranges, reduced fast charging time, extended cycle life, and reduced swelling effects can be provided. Here, "average diameter" refers to the average diameter of the carbon nanotube, "diameter of carbon nanotube" refers to the diameter of a carbon nanotube with a circular cross-section, and when the cross-section of the carbon nanotube is, for example, irregular in shape rather than circular, it also refers to the maximum length of the cross-section.

[0172] In the embodiments, carbon nanotubes can have a diameter of 30,000 m. 2 / g to 100,000m 2 Specific surface area (SSA) per g, for example, 50,000 m² 2 / g to 100,000m 2 The specific surface area (SSA) is / g. Within the above range, a negative electrode with high conductivity can be manufactured by reducing the powder resistance of the slurry for the negative electrode, which includes a mixture of negative electrode active materials.

[0173] Specific surface area (SSA) is used as a criterion for determining whether a negative electrode slurry prepared using a conductive material dispersion can provide low powder resistance, said conductive material dispersion being prepared using carbon nanotubes having a specific surface area as described below. While SSA measurement can be straightforward for carbon nanotubes, measuring the SSA of the dispersed carbon nanotubes within a conductive material dispersion is challenging.

[0174] The SSA of carbon nanotube dispersions can be calculated using the Malvern particle size analyzer.

[0175] 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 are single-walled carbon nanotubes.

[0176] In the embodiments, carbon nanotubes can have a diameter of 240 μm. 2 / g to 280m 2 / g BET specific surface area. Within the above range, the conductivity of slurries containing negative electrode active materials can be easily improved.

[0177] In the embodiments, the carbon nanotube content can be 95 wt% or more of the conductive material, for example, 95 wt% to 100 wt%.

[0178] In an embodiment, the content of conductive material (e.g., carbon nanotubes) can be from 0.01 parts by weight to 5 parts by weight, for example, from 0.01 parts by weight to 0.2 parts by weight or from 0.03 parts by weight to 0.05 parts by weight, relative to 100 parts by weight of the mixture of negative electrode active materials. Within the above range, reduced fast charging time, extended cycle life, and reduced expansion effects can be achieved.

[0179] In one embodiment, the conductive material may be included in the negative electrode plate at a concentration of 0.01 wt% to 5 wt% (e.g., 0.01 wt% to 0.2 wt%). Within this range, an increase in energy density and an improvement in boost charging characteristics can be achieved, as well as an extension of cycle life and a reduction in expansion. In another embodiment, the conductive material (e.g., carbon nanotubes) may be included in the negative electrode plate at a concentration of 0.03 wt% to 0.05 wt%. Since the content of the negative electrode active material does not decrease within this range, the battery capacity does not decrease.

[0180] In another embodiment, a rechargeable lithium battery is provided, including a negative electrode plate for a rechargeable lithium battery.

[0181] A rechargeable lithium battery may include a negative electrode plate and a positive electrode for use in a rechargeable lithium battery. The negative electrode plate may be substantially the same as described above.

[0182] 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.

[0183] Positive electrode active material The positive electrode active material may include compounds capable of intercalating and deintercalating lithium (lithium intercalation compounds). In embodiments, at least one of lithium in a composite oxide of a metal selected from cobalt, manganese, nickel, and combinations thereof may be used.

[0184] The composite oxide can be a lithium transition metal composite oxide. Some 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.

[0185] As an example, the following compounds, 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 O 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 O 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 O 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 aNiG 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); and Li a FePO4 (0.90≤a≤1.8).

[0186] 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.

[0187] In embodiments, 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 composite oxide, the high-nickel positive electrode active material has 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.

[0188] 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.

[0189] 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.

[0190] Conductive materials can impart electrical conductivity (e.g., electroconductivity) 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.

[0191] In the embodiments, A1 can be used as a current collector, but this disclosure is not limited thereto.

[0192] Rechargeable lithium batteries may also include an electrolyte.

[0193] electrolyte Electrolytes used in rechargeable lithium batteries may include non-aqueous organic solvents and lithium salts.

[0194] Non-aqueous organic solvents can be used as a medium for transporting ions that participate in the electrochemical reactions of a battery.

[0195] Non-aqueous organic solvents can be carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, aprotic solvents, or combinations thereof.

[0196] 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.

[0197] 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.

[0198] 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.

[0199] Non-aqueous organic solvents can be used alone or in combination of two or more.

[0200] 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.

[0201] 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. 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).

[0202] Rechargeable lithium batteries may also include a separator.

[0203] diaphragm Depending on the type of rechargeable lithium battery, a separator may be present between the positive and negative electrodes. The separator may include 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 / polyethylene / polypropylene three-layer separators, etc.)).

[0204] The membrane may include a porous substrate and a coating comprising organic, inorganic, or combinations thereof on one or both or opposite surfaces of the porous substrate.

[0205] The porous substrate can be a polymer membrane 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).

[0206] Organic materials may include polymers such as polyvinylidene fluoride or (meth)acrylic acid polymers.

[0207] 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.

[0208] Organic and inorganic materials can be mixed in a coating, or coatings containing organic materials and coatings containing inorganic materials can be stacked.

[0209] Rechargeable lithium batteries Based on their shape, rechargeable lithium batteries can be classified into cylindrical batteries, prismatic batteries, pouch batteries, or coin-shaped batteries, etc.

[0210] Figures 4 to 7 This is a schematic diagram illustrating a rechargeable lithium battery according to some embodiments. Figure 4 A cylindrical battery is shown; Figure 5 A prismatic battery is shown; Figure 6 and Figure 7 A pouch-type battery is shown. (See reference) Figures 4 to 7 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 4 As shown, the rechargeable lithium battery 100 may include a sealing member 60 of the sealed housing 50. (As illustrated...) Figure 5 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 6 and Figure 7As 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.

[0211] 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.

[0212] Electronic devices or electric vehicles may include the rechargeable lithium battery.

[0213] Examples and comparative examples of the present invention will be described herein. However, the following examples are provided as illustrations, and the present invention is not limited thereto.

[0214] 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 ground into primary particles with a plate-like shape and a long axis length of 30 μm using an air jet milling method. The primary particles were then assembled into secondary particles using a spherical device; the secondary particles were spherical and had an average particle size (D50) of 7 μm. Pitch carbon was added to the secondary particles, mixed, and heat-treated in a furnace at 3000 °C for 2 hours to prepare the first negative electrode active material. The addition of pitch carbon resulted in a natural graphite:amorphous carbon weight ratio of 90:10 in the first negative electrode active material.

[0215] (2) Active material of the second negative electrode Artificial graphite (spherical, average particle size (D50): 15μm, aggregate density: 1.5g / cc, tap density: 0.9g / cc, specific surface area BET: 1.5m²) was used. 2 / g, orientation degree: 100) as the active material for the second negative electrode. Artificial graphite is a secondary particle in which primary particles are assembled.

[0216] (3) Preparation of the active material of the third negative electrode A dispersion was prepared by mixing silicon nanoparticles (aspect ratio: 5, average particle size: approximately 100 nm) and petroleum asphalt (amorphous carbon) in isopropanol solvent at a weight ratio of 70:30 and dispersing the mixture using a homogenizer. The resulting dispersion was spray-dried at 120 °C using a spray dryer. The spray-dried product (precursor) was pressed using a powder press at 50 MPa and heat-treated in a furnace at 1000 °C under a N2 atmosphere to obtain a reaction product comprising a core containing amorphous carbon and silicon nanoparticles, and a coating containing amorphous carbon formed on the surface of the core. The resulting reaction product was ground and classified through a 325-mesh sieve to prepare the third negative electrode active material (C-1).

[0217] The resulting third negative electrode active material has an interparticle distance of 65 nm between silicon particles, an average particle size (D50) of 8.3 μm, and a particle size of 2.95 × 10⁻⁶. -2 cm 3 / g is the total pore volume of pores with a size of 200nm or smaller.

[0218] The interparticle distance of silicon nanoparticles was obtained by analyzing the cross-section of silicon nanoparticles via TEM and measuring the intercenter distance of silicon nanoparticles.

[0219] The pore volume is measured using the following steps: Silicon nanoparticles are placed in a porosimetry instrument (product name: ASAP series, manufacturer: Micromeritics Instruments), heated to 623K at 10K / min, pretreated for 2 to 10 hours (vacuum at 100mmHg or less), and then subjected to a relative pressure (P / P) adjusted to 0.01 or less in liquid nitrogen. o Measurements were performed at a relative pressure of 0.01 to 0.995. Specifically, measurements were taken by nitrogen adsorption at 32 points with relative pressures from 0.01 to 0.14, followed by nitrogen desorption at 24 points with relative pressures up to 0.14. Here, BET calculations can typically be performed down to the relative pressure (P / P). o The point with a value of 0.1.

[0220] (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.

[0221] A negative electrode active material slurry was prepared by mixing a mixture of 97.5 wt% of negative electrode active material, 1.5 wt% of styrene-butadiene rubber as a binder, and 1.0 wt% of carboxymethyl cellulose as an additive in distilled water.

[0222] A negative electrode plate is manufactured by coating a copper current collector with a negative electrode active material slurry, and then drying and rolling the slurry-coated current collector.

[0223] A half-cell is constructed using a negative electrode plate, a lithium metal counter electrode, and an electrolyte. The electrolyte is a mixed solvent (volume ratio 3:7) in which 1 M LiPF6 is dissolved in ethylene carbonate and dimethyl carbonate.

[0224] Example 2 Except for modifying the spheroidization conditions in Example 1, the first negative electrode active material was prepared in the same manner as in Example 1. The prepared first negative electrode active material was used to fabricate the negative electrode plate and half-cell in the same manner as in Example 1.

[0225] Example 3 Except for modifying the spheroidization conditions in Example 1, the first negative electrode active material was prepared in the same manner as in Example 1. The prepared first negative electrode active material was used to fabricate the negative electrode plate and half-cell in the same manner as in Example 1.

[0226] Example 4 and Example 5 Except for modifying the weight ratios of the components in Example 1 as shown in Table 1 below, the negative electrode plate and half cell are manufactured in the same manner as in Example 1.

[0227] Comparison Example 1 The first negative electrode active material is prepared in the same manner as in Example 1, except that pitch carbon is not added in the preparation of the first negative electrode active material in Example 1. The prepared first negative electrode active material is used to manufacture the negative electrode plate and half-cell in the same manner as in Example 1.

[0228] Comparison Example 2 Natural graphite raw material with an average particle size (D50) of 120 μm or larger was pulverized into primary particles with an elongation length of 120 μm using an air jet milling method. The primary particles were then assembled into secondary particles with an average particle size of 20 μm using a spheroidizing device. The first negative electrode active material was prepared by adding pitch carbon to the secondary particles, mixing them, and then heat-treating the resulting mixture in a furnace at 1200 °C for 2 hours. The addition of pitch carbon resulted in a natural graphite:amorphous carbon weight ratio of 90:10 in the first negative electrode active material.

[0229] The prepared first negative electrode active material is used to manufacture the negative electrode plate and half cell in the same manner as in Example 1.

[0230] Comparison Example 3 Flake-shaped natural graphite raw material with an average particle size (D50) of 80 μm was pulverized into primary particles with an elongation length of 7 μm using an air jet milling method. 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 first negative electrode active material was prepared by adding pitch carbon to the secondary particles, mixing them, and then heat-treating the resulting mixture in a furnace at 1200 °C for 2 hours. The addition of pitch carbon resulted in a natural graphite:amorphous carbon weight ratio of 90:10 in the first negative electrode active material.

[0231] The prepared first negative electrode active material is used to manufacture the negative electrode plate and half cell in the same manner as in Example 1.

[0232] 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 used in Example 1.

[0233] (Experimental Example 1): Evaluation of the active material of the first negative electrode Particle density (unit: g / cc): Aggregate density was measured using a Carver 4350.L (CARVER) aggregometer. The powder density was measured after 1.0 g of each of the first negative electrode active materials from the example and comparative examples were added to the mold, while the mold was held under a pressure of 2.0 tons for 30 seconds.

[0234] Orientation degree: Orientation was measured using an XRD analyzer X'PertPro (PANalytical). The ratio of the diffraction peak intensity I(002) of the (002) plane to the diffraction peak intensity I(110) of the (110) plane was measured for each first negative electrode active material of the example and comparative examples by using X-ray diffraction analysis of Cu Kα rays.

[0235] d002 (unit: Å): d002 was measured using an XRD analyzer X'PertPro (PANalytical). The interplanar spacing of the (002) plane of each first negative electrode active material in the example and comparative examples was measured by X-ray diffraction analysis of Cu Kα rays.

[0236] Sphericity: Sphericity was measured using a Morphologi 4 (Malvern) sphericity analyzer. For each first negative electrode active material in the example and comparative examples, values ​​A and B in Equation 1 were obtained, and then sphericity was calculated according to Equation 1.

[0237] Hg cumulative pore volume (unit: mL / g): The cumulative Hg pore volume of each first negative electrode active material in the example and comparative examples was measured using an AutoPore V (Micromertics) Hg intrusion porosimetry method. The first negative electrode active material was placed in a dedicated sample cup, surrounded by mercury, and pressures ranging from 0.2 psi to 60,000 psi were applied to allow the mercury to penetrate into the first negative electrode active material. The mercury porosity was then measured by monitoring changes in the mercury volume in the capillary rod reservoir. Pore sizes ranging from 0.01 μm to 100 μm can be measured using the above method. Generally, pores with a size of 0.01 μm or larger and 5 μm or smaller are considered pores in the first negative electrode active material.

[0238] (Experimental Example 2) Evaluation of Battery Characteristics The charge and discharge capacities were measured by charging and discharging the manufactured half-cells at 0.1C. The measured discharge capacities are shown in Table 1 below, and the coulombic efficiency (discharge capacity / charge capacity × 100%) was measured.

[0239] The manufactured half-cell was subjected to one cycle of 0.2C constant current (CC) / constant voltage (CV) charging and 0.2C discharging, one cycle of 0.5C CC charging and 0.2C discharging, one cycle of 1C CC charging and 0.2C discharging, and one cycle of 2C CC charging and 0.2C discharging, and then the charging characteristics were calculated. Here, the charging conditions were a 10mV cutoff in the CC phase and a 15-hour cutoff in the CV phase, and the discharging condition was a 1.5V cutoff. The charging characteristics were measured at each C rate. The charging characteristics were expressed by calculating the ratio of the 2C CC charging capacity to the 0.2C CC charging capacity.

[0240] Energy density (unit: Wh / L): (Battery discharge capacity (Ah) × Average battery voltage (V)) / Battery volume (L) Energy density is a value obtained by dividing the product of the discharge capacity obtained by discharging the battery cell at a C-rate of 0.1C to 1C within the operating voltage range of the battery cell by the average voltage of the corresponding battery, and then dividing the battery volume.

[0241] Fast charging time (in seconds): Fast charging time refers to the time required to charge a battery from 8% SOC (State of Charge) to 80% SOC using constant current charging. Fast charging time is evaluated by identifying charging modes that do not reach the upper limit voltage of 4.2V during charging.

[0242] Fast charging cycle life (unit: cycles): A cycle is defined as charging from 8% SOC to 80% SOC and discharging at a constant current of 0.33C to a voltage of 2.8V, based on a defined fast charge time, and evaluating the large battery by cycling until 80% SOH (State of Health).

[0243] Table 1

[0244]

[0245] *Weight ratio: First negative electrode active material : Second negative electrode active material : Third negative electrode active material.

[0246] Boost charging performance should be evaluated by considering both fast charging time and fast charging cycle life.

[0247] As shown in Table 1, the negative electrode active materials for rechargeable lithium batteries in each example can provide high energy density and adequate boost charging performance due to short fast charging time and long fast charging cycle life.

[0248] However, as shown in Table 1, it can be confirmed that since the negative electrode active material of each comparative example does not meet the composition of the present invention, the fast charging time increases and the fast charging cycle life decreases, resulting in a significant reduction in boost charging performance.

[0249] 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 into primary particles with an elongation length of 30 μm using an air jet milling method. The primary particles were then assembled into spherical secondary particles with an average particle size (D50) of 7 μm using a spheroidizing device. The first negative electrode active material was prepared by adding pitch carbon to the secondary particles, mixing them, and then heat-treating the resulting mixture in a furnace at 3000 °C for 2 hours. The addition of pitch carbon resulted in a natural graphite:amorphous carbon weight ratio of 90:10 in the first negative electrode active material.

[0250] (2) Active material of the second negative electrode Artificial graphite (spherical, average particle size (D50): 15 μm, agglomerate density: 1.5 g / cc, tap density: 0.9 g / cc, specific surface area BET: 1.5 m²) was used as the active material for the second negative electrode. 2 / g, orientation degree: 100). Artificial graphite consists of secondary particles in which primary particles are assembled.

[0251] (3) Preparation of the active material of the third negative electrode A dispersion was prepared by mixing silicon nanoparticles (aspect ratio: 5, average particle size: approximately 100 nm) and petroleum asphalt (amorphous carbon) in isopropanol solvent at a weight ratio of 70:30 and dispersing the mixture using a homogenizer. The resulting dispersion was spray-dried at 120 °C using a spray dryer. The spray-dried product (precursor) was pressed using a powder press at 50 MPa and heat-treated in a furnace at 1000 °C under a N2 atmosphere to obtain a reaction product comprising a core containing amorphous carbon and silicon nanoparticles, and a coating containing amorphous carbon formed on the surface of the core. The resulting reaction product was ground and classified through a 325-mesh sieve to prepare the third negative electrode active material (C-1).

[0252] The resulting third negative electrode active material has an interparticle distance of 65 nm between silicon nanoparticles, an average particle size (D50) of 8.3 μm, and a particle size of 2.95 × 10⁻⁶.-2 cm 3 / g is the total pore volume of pores with a size of 200nm or smaller.

[0253] The interparticle distance of silicon nanoparticles was obtained by analyzing the cross-section of silicon nanoparticles via TEM and measuring the intercenter distance of silicon nanoparticles.

[0254] The pore volume was measured using the following steps: Silicon nanoparticles were placed in a porosimetry apparatus (product name: ASAP series, manufacturer: Micromeritics Instruments), heated to 623 K at 10 K / min, pretreated for 2 to 10 hours (under vacuum of 100 mmHg or less), and then subjected to a relative pressure (P / P) adjusted to 0.01 or less in liquid nitrogen. o Measurements were performed at a relative pressure of 0.01 to 0.995. Specifically, measurements were taken by nitrogen adsorption at 32 points with relative pressures from 0.01 to 0.14, followed by nitrogen desorption at 24 points with relative pressures up to 0.14. Here, BET calculations can typically be performed down to the relative pressure (P / P). o The point with a value of 0.1.

[0255] (4) Based on a mixture of 100 parts by weight of negative electrode active material, a mixture of negative electrode active material is prepared by mixing 47 parts by weight of first negative electrode active material, 47 parts by weight of second negative electrode active material and 6 parts by weight of third negative electrode active material.

[0256] A negative electrode active material slurry was prepared by mixing 97.5 wt% of a mixture of negative electrode active materials, 0.04 wt% of single-walled carbon nanotubes (SWCNTs) as conductive materials, and 2.46 wt% of styrene-butadiene rubber as a binder in distilled water.

[0257] The negative electrode plate is manufactured by coating a copper current collector with a negative electrode active material slurry, drying it, and then rolling the resulting current collector.

[0258] A half-cell is constructed using a negative electrode plate, a lithium metal counter electrode, and an electrolyte. The electrolyte is a mixed solvent (volume ratio 3:7) in which 1 M LiPF6 is dissolved in ethylene carbonate and dimethyl carbonate.

[0259] Example 7 Except for modifying the spheroidization conditions in Example 6, the first negative electrode active material was prepared in the same manner as in Example 6. The prepared first negative electrode active material was used to fabricate the negative electrode plate and half-cell in the same manner as in Example 6.

[0260] Example 8 Except for modifying the spheroidization conditions in Example 6, the first negative electrode active material was prepared in the same manner as in Example 6. The prepared first negative electrode active material was used to fabricate the negative electrode plate and half-cell in the same manner as in Example 6.

[0261] Examples 9 and 10 Except for modifying the weight ratios of the components in Example 6 as shown in Table 2 below, the negative electrode plate and half cell are manufactured in the same manner as in Example 6.

[0262] Example 11 The negative electrode plate and half cell are fabricated in the same manner as in Example 6, except that Denka black (carbon black, D-2) is used instead of carbon nanotubes as the conductive material.

[0263] (Experimental Example 3): Evaluation of the active material of the first negative electrode Aggregate density (g / cc), orientation, d002 (Å), Hg cumulative pore volume (mL / g), and sphericity were evaluated in the same manner as in Experimental Example 1.

[0264] (Experimental Example 4) Evaluation of Battery Characteristics Capacity (unit: mAh / g) and Charging C rate (unit: %) The manufactured half-cells were charged and discharged at 0.1C to measure the charge and discharge capacities. The measured discharge capacities are shown in Table 2 below, and the coulombic efficiency (discharge capacity / charge capacity × 100%) was measured.

[0265] The manufactured half-cell was subjected to one cycle of 0.2C constant current (CC) / constant voltage (CV) charging and 0.2C discharging, one cycle of 0.5C CC charging and 0.2C discharging, one cycle of 1C CC charging and 0.2C discharging, and one cycle of 2C CC charging and 0.2C discharging, and then the charging characteristics were calculated. Here, the charging conditions were a 10mV cutoff in the CC phase and a 15-hour cutoff in the CV phase, and the discharging condition was a 1.5V cutoff. The charging characteristics were measured at each C rate. The charging characteristics were expressed by calculating the ratio of the 2C CC charging capacity to the 0.2C CC charging capacity.

[0266] Fast charging time (in seconds): Fast charging time refers to the time required to charge a battery from 8% SOC to 80% SOC using constant current charging, and is evaluated by identifying charging modes that do not reach the upper limit voltage of 4.2V during charging.

[0267] Fast charging cycle life (unit: cycles): A cycle is defined as charging from 8% SOC to 80% SOC and discharging at a constant current of 0.33C to a voltage of 2.8V, based on a defined fast charge time, and the large battery is evaluated by cycling until 80% SOC.

[0268] Expansion rate (unit: %) The expansion rate was measured using a thickness monitoring system (TMS).

[0269] Each battery manufactured according to the example and comparative examples was evaluated by charge-discharge (0.5C / 0.5C) at 45°C under conditions including a charging voltage of 4.35V and a discharging voltage of 2.8V, while the battery thickness was continuously monitored in real time during charge-discharge cycles. The expansion rate was evaluated by comparing the thickness at 50 cycles with the thickness at one cycle.

[0270] Expansion rate = (Battery thickness after 50 cycles - Battery thickness after 1 cycle) / Battery thickness after 1 cycle × 100% Table 2

[0271] *In Table 2, C-1: Silicon-carbon composite D-1: SWCNT D-2: Denka Black Weight ratio: first negative electrode active material : second negative electrode active material : third negative electrode active material.

[0272] As shown in Table 2, the example negative electrode plate for rechargeable lithium batteries provides the effects of reducing the expansion of silicon-based active materials, reducing fast charging time, extending cycle life and increasing energy density, thus exhibiting excellent rechargeable lithium battery performance.

[0273] Although some examples of the invention have been described above, the invention is not limited thereto, and various modifications can be made within the scope of the claims, detailed description, and drawings. It will be understood that such modifications fall within the scope of the invention.

Claims

1. A negative electrode plate, the negative electrode plate comprising: 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. The first negative electrode active material comprises natural graphite and a coating. The natural graphite includes secondary particles in which primary particles are arranged. The coating surrounds the secondary particles and comprises amorphous carbon. The first negative electrode active material has an orientation degree of 90 or less and a d002 in the range of 3.356 Å to 3.360 Å. The second negative electrode active material includes artificial graphite. The third negative electrode active material includes a core and an amorphous carbon coating. The core comprises silicon nanoparticles and amorphous carbon. The amorphous carbon coating surrounds the core and contains amorphous carbon. 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 an Hg cumulative 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 major axis length of the primary particles is in the range 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, Amorphous carbon is also present on the surface of the primary particles.

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, Amorphous carbon includes one or more mixtures selected from soft carbon, hard carbon, mesophase pitch carbides and calcined coke.

12. The negative electrode plate according to claim 1, wherein, The active material of the first negative electrode comprises natural graphite and amorphous carbon in a weight ratio of 90:10 to 75:25, relative to the total amount of 100 parts by weight of natural graphite and amorphous carbon.

13. The negative electrode plate according to claim 1, wherein, The interparticle distance between the silicon nanoparticles contained in the core of the third negative electrode active material is 100 nm or less.

14. The negative electrode plate according to claim 1, wherein, The average particle size D50 of the silicon nanoparticles is 50 nm to 150 nm.

15. The negative electrode plate according to claim 1, wherein, The active material of the third negative electrode has a density of 3.0 × 10⁻⁶. - 2 cm 3 / g or smaller is the total pore volume of pores with a size of 200nm or smaller.

16. The negative electrode plate according to claim 1, wherein, The active material of the third negative electrode comprises silicon nanoparticles and amorphous carbon in a weight ratio of 80:20 to 20:80, relative to the total amount of 100 parts by weight of silicon nanoparticles and amorphous carbon.

17. 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 15 wt% of the third negative electrode active material.

18. The negative electrode plate according to claim 1, wherein, The negative electrode plate also includes a conductive material, which includes carbon nanotubes.

19. The negative electrode plate according to claim 18, wherein, The carbon nanotubes are included in the negative electrode plate at a concentration of 0.01 wt% to 5 wt%.

20. A rechargeable lithium battery, said rechargeable lithium battery comprising: The negative electrode plate according to any one of claims 1 to 19; and Positive electrode.

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