Dry negative electrode plate for rechargeable lithium battery and rechargeable lithium battery comprising the same

Abstract

Disclosed are a dry negative electrode plate for a rechargeable lithium battery and a rechargeable lithium battery including the same. The dry negative electrode plate for a rechargeable lithium battery includes a negative electrode active material and a binder, and 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 including natural graphite including secondary particles arranged of primary particles, and a coating including amorphous carbon and surrounding the secondary particles, the first negative electrode active material having an orientation degree of 90 or less and a d002 of 3.356 Å to 3.360 Å, the second negative electrode active material including artificial graphite, and the binder including polytetrafluoroethylene, polyvinylidene fluoride, polyolefin, or a mixture thereof.

Description

[0001] This application claims priority and benefit to Korean Patent Application No. 10-2024-0175703, filed on November 29, 2024, Korean Patent Application No. 10-2024-0175702, and Korean Patent Application No. 10-2024-0175709, all filed on November 29, 2024, with the entire disclosure of all such Korean patent applications incorporated herein by reference. Technical Field

[0002] An aspect of the present invention relates to a dry negative electrode plate for a rechargeable lithium battery and a rechargeable lithium battery including the dry 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. The positive and negative electrodes contain active materials that can insert and extract lithium ions, and generate electrical energy through oxidation and reduction reactions when lithium ions are inserted into the negative electrode / extracted from the positive electrode or vice versa. Summary of the Invention

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

[0006] According to another aspect of the present invention, a rechargeable lithium battery including a dry negative electrode plate is provided.

[0007] According to one or more embodiments of the present invention, a dry negative electrode plate for a rechargeable lithium battery comprises a negative electrode active material and a binder, 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, the first negative electrode active material comprising: natural graphite, comprising secondary particles arranged in a primary particle arrangement; and a coating surrounding the secondary particles and comprising amorphous carbon, the first negative electrode active material having an orientation degree of 90 or less and a d002 of 3.356 Å to 3.360 Å, the second negative electrode active material comprising graphite, the third negative electrode active material comprising: natural graphite, secondary particles arranged in a primary particle arrangement, and a binder comprising: a primary negative electrode active material, a secondary negative electrode active material ... The negative electrode active material includes one or more of the following: negative electrode active material (i), comprising a core containing silicon nanoparticles and amorphous carbon, and an amorphous carbon coating surrounding the core and comprising amorphous carbon; negative electrode active material (ii), comprising a composite of silicon and crystalline carbon, and an amorphous carbon coating on the surface of the composite comprising amorphous carbon; and negative electrode active material (iii), comprising silicon nanoparticles and an amorphous carbon coating on the surface of the silicon nanoparticles having a sphericity of 0.9 to 1.0, and the binder comprising polytetrafluoroethylene, polyvinylidene fluoride, polyolefin, or mixtures thereof.

[0008] According to one or more embodiments of the present invention, a rechargeable lithium battery includes the aforementioned dry negative electrode plate for a rechargeable lithium battery; and a positive electrode. Attached Figure Description

[0009] The above and other aspects, objects, features, and advantages of the invention will become more apparent to those skilled in the art from the further detailed description of some embodiments of the invention with reference to the accompanying drawings, in which: Figure 1 This is a conceptual diagram of the first negative electrode active material according to an embodiment; Figure 2 This is a conceptual diagram of the negative electrode active material (i) of the third negative electrode active material according to the embodiment; Figure 3 This is a conceptual diagram of the interparticle distance in the negative electrode active material (i) of the third negative electrode active material; Figure 4 This is a conceptual diagram of the negative electrode active material (ii) of the third negative electrode active material according to the embodiment; and Figures 5 to 8 This is a schematic view of a rechargeable lithium battery according to some embodiments. Detailed Implementation

[0010] Some embodiments of the present invention will be described in further detail herein. However, the embodiments are presented by way of example, and the invention is not limited thereto, and is to be defined by the scope of the claims.

[0011] 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 one or more components are present in between.

[0012] Unless otherwise stated herein, the singular may also include the plural. Furthermore, unless otherwise stated, “A or B” may mean “including A,” “including B,” or “including both A and B.”

[0013] In this specification, “combination of them” may mean mixtures of components, laminates, complexes, copolymers, alloys, blends and reaction products.

[0014] Unless otherwise defined herein, particle size can refer to the average particle diameter. Furthermore, particle size refers to the average particle size (or average particle diameter) D50, which is 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, such as using a particle size analyzer, transmission electron microscopy, or scanning electron microscopy. Alternatively, the average particle size can be measured using a measuring device utilizing 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 from this count. Optionally, the average particle size can be measured using laser diffraction methods. When measuring average particle size using laser diffraction methods, more specifically, the average particle size D50 can be calculated based on a 50% volume percentage particle size distribution after the target particles are dispersed in a dispersion medium, the particles are introduced into a commercially available laser diffraction particle size measurement device (such as the MT 3000 from Microtrac), and the particles are irradiated with ultrasound at an output of 60W at approximately 28kHz.

[0015] When the particles are spherical, size can refer to diameter.

[0016] A dry negative electrode plate for a rechargeable lithium battery according to one or more embodiments can provide high energy density, boost charging efficiency, and long lifespan.

[0017] A dry negative electrode plate for a rechargeable lithium battery according to one or more embodiments includes a negative electrode active material and a binder, 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; the first negative electrode active material includes natural graphite and a coating; the natural graphite includes secondary particles assembled or arranged from primary particles; the coating includes amorphous carbon surrounding the secondary particles; 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; and the second negative electrode active material includes graphite. The third negative electrode active material includes one or more of the following: negative electrode active material (i), comprising a core containing silicon nanoparticles and amorphous carbon, and an amorphous carbon coating comprising amorphous carbon; negative electrode active material (ii), comprising a composite of silicon and crystalline carbon, and an amorphous carbon coating on the surface of the composite comprising amorphous carbon; and negative electrode active material (iii), comprising silicon nanoparticles and an amorphous carbon coating on the surface of the silicon nanoparticles having a sphericity of 0.9 to 1.0, and the binder comprising polytetrafluoroethylene, polyvinylidene fluoride, polyolefin, or mixtures thereof.

[0018] Dry negative electrode plates for rechargeable lithium batteries incorporate a mixture as the negative electrode active material, thus providing high capacity retention, as well as high energy density, boost charging performance, and improved lifespan.

[0019] In the present invention, the total negative electrode active material based on the dry negative electrode plate may include the mixture in an amount of 95% by weight or more (e.g., 95% by weight to 100% by weight, 99% by weight to 100% by weight or 100% by weight).

[0020] In the embodiments, the negative electrode active material (e.g., a mixture) may be included in the dry negative electrode plate in an amount of 90% to 99% by weight. Within the above range, a capacity improvement effect can be achieved.

[0021] If the first negative electrode active material is absent in the mixture, the low plate density makes it difficult to achieve a battery with high energy density and may reduce the boost charging effect.

[0022] If the mixture does not contain a second negative electrode active material, the long lifespan effect may be reduced under high temperature conditions.

[0023] If the mixture does not contain a third negative electrode active material, the increase in capacity per unit volume may be reduced.

[0024] In the embodiments, the first negative electrode active material, the second negative electrode active material, and the third negative electrode active material in the mixture may be included in amounts of 20 wt% to 75 wt%, 20 wt% to 75 wt%, and 1 wt% to 20 wt%, respectively. Within the above ranges, boost charging effect and boost charging life can be easily provided.

[0025] In the embodiments, the first negative electrode active material can be in the following proportions: 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%. The first negative electrode active material may be included in the mixture in amounts of 57wt%, 58wt%, 59wt%, 60wt%, 61wt%, 62wt%, 63wt%, 64wt%, 65wt%, 66wt%, 67wt%, 68wt%, 69wt%, 70wt%, 71wt%, 72wt%, 73wt%, 74wt%, or 75wt%, and in embodiments, the first negative electrode active material may be included in the mixture in amounts of 20wt% to 65wt% or 20wt% to 60wt%, and may be included in amounts of 20wt%, 21wt%, 22wt%, 23wt%, 24wt%, 25wt%, 26wt%, 27wt%, 28wt%, 29wt%, or 29wt%. t%, 30wt%, 31wt%, 32wt%, 33wt%, 34wt%, 35wt%, 36wt%, 37wt%, 38wt%, 39 wt%, 40wt%, 41wt%, 42wt%, 43wt%, 44wt%, 45wt%, 46wt%, 47wt%, 48wt%, 49 wt%, 50wt%, 51wt%, 52wt%, 53wt%, 54wt%, 55wt%, 56wt%, 57wt%, 58wt%, 59 wt%, 60wt%, 61wt%, 62wt%, 63wt%, 64wt%, 65wt%, 66wt%, 67wt%, 68wt%, 69 The second negative electrode active material may be included in amounts of wt%, 70wt%, 71wt%, 72wt%, 73wt%, 74wt%, or 75wt%, and in embodiments, the second negative electrode active material may be included in amounts of 20wt% to 65wt% or 20wt% to 60wt%, and the third negative electrode active material may be included in amounts of 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt%, or 20wt%, and in embodiments,The third negative electrode active material can be included in amounts of 1% to 15% by weight, 1% to 10% by weight, or 5% to 7% by weight. Within these ranges, the boost charging effect and boost charging life can be further improved.

[0026] In the embodiments, the content of the third negative electrode active material in the mixture is in the range of 1% to 15% by weight (e.g., 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, or 15 wt%), and the sum of the contents of the first negative electrode active material and the second negative electrode active material is in the range of 85% to 99% by weight (e.g., 85 wt%, 86 wt%, 87 wt%, 88 wt%, 89 wt%, 90 wt%, 91 wt%, 92 wt%, 93 wt%, 94 wt%, 95 wt%, 96 wt%, 97 wt%, 98 wt%, or 99 wt%). In the embodiments, the sum of the contents of the first negative electrode active material and the second negative electrode active material is 86 wt% to 99 wt% or 90 wt% to 99 wt%. In this case, based on a total of 100 parts by weight of the first negative electrode active material and the second negative electrode active material, the weight ratio of the first negative electrode active material to the second negative electrode active material can be in the range of 10:90 to 90:10 (e.g., 25:75 to 75:25, 40:60 to 60:40, or 50:50). Within the above range, a boost charging effect can be achieved, and a boost charging life improvement effect can be realized.

[0027] In an embodiment, a third negative electrode active material may be included with a specific capacity of 500 mAh / g or less.

[0028] In an embodiment, the dry negative electrode plate can have a density of 1.3 g / cc to 1.7 g / cc (e.g., 1.3 g / cc to 1.68 g / cc). Within this range, high energy density and easy boost charging can be achieved.

[0029] Each component of the negative electrode active material will be described in further detail here.

[0030] (1) Active material of the first negative electrode The first negative electrode active material comprises: natural graphite, including secondary particles assembled or arranged from primary particles; and a coating surrounding the secondary particles and comprising amorphous carbon, wherein 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.

[0031] In this specification, the term "orientation degree" may 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.

[0032] In this specification, the term "d002" may refer to the interplanar spacing of the (002) plane of the first negative electrode active material, as measured by X-ray diffraction analysis using Cu Kα rays.

[0033] Natural graphite is generally advantageous as a negative electrode active material for batteries, but it may exhibit poor charging characteristics due to its high resistivity. Furthermore, the numerous internal pores in natural graphite can adversely affect long cycle life and expansion rate due to side reactions.

[0034] The first negative electrode active material can be manufactured by significantly reducing the average particle size of the secondary particles of natural graphite to a small particle form to provide low resistance, and by calcining the secondary particles at a temperature to offset the efficiency reduction caused by the increase in the specific surface area of ​​the secondary particles, thus reducing the specific surface area and providing high efficiency at the same time.

[0035] 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 can improve battery capacity and significantly increase the charge rate (C-rate), thereby enhancing the boost charging performance of rechargeable lithium batteries. Although the first negative electrode active material comprises natural graphite, it can significantly reduce resistance and provide high energy density, suppression of side reactions with the electrolyte, and improved battery life.

[0036] The lower the orientation degree, the more randomly oriented the edge planes of natural graphite are, leading to an increase in the random orientation of the first negative electrode active material. This promotes lithium-ion insertion into and extraction from the secondary particles of natural graphite, thereby improving the capacity characteristics of the rechargeable lithium battery. In embodiments, for example, the orientation degree can be 80 or less (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48). The orientation degree can be 10 to 80, 20 to 80, 30 to 80, 40 to 80, or 50 to 80, and in the embodiments, the orientation degree can be 10 to 80, 20 to 80, 30 to 80, 40 to 80, or 50 to 80. The above-mentioned orientation degree can be achieved by controlling 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 is significantly reduced to improve the high resistivity of natural graphite.

[0037] 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 manufactured by wrinkling the primary particles. In an embodiment, the first negative electrode active material comprises amorphous carbon, and as described below, the first negative electrode active material can have a high degree of graphitization when manufactured by heat treatment at 2500°C or higher. A high degree of graphitization can help improve the capacity of the first negative electrode active material and can prevent or substantially prevent efficiency reduction due to the decrease in the average particle size of the secondary particles and the increase in specific surface area. In an embodiment, the d002 of the first negative electrode active material is 3.356 Å to 3.360 Å. Within this range, the decrease in battery efficiency due to the increase in 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, thereby providing high capacity. For example, d002 could 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, 3.3579 Å. Å, 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.

[0038] According to embodiments, the first negative electrode active material can have a cumulative Hg pore volume of 0.01 mL / g to 0.06 mL / g (e.g., 0.01 mL / g, 0.02 mL / g, 0.03 mL / g, 0.04 mL / g, 0.05 mL / g, or 0.06 mL / g), and in embodiments, the first negative electrode active material can have a cumulative Hg 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, a significantly higher efficiency of the first negative electrode active material can be achieved due to the small pores (i.e., empty spaces) inside the first negative electrode active material and the appropriate amount of amorphous carbon inside the first negative electrode active material. Furthermore, the internal area of ​​the first negative electrode active material reacting with the electrolyte is not excessively large, and a density level that allows for good electrolyte impregnation can be maintained, thereby maintaining an appropriate lifetime without excessive side reactions. Although the first negative electrode active material comprises small particles of natural graphite, the Hg cumulative pore volume can be a characteristic of the first negative electrode active material manufactured by the manufacturing method described below, in order to reduce the specific surface area.

[0039] According to an embodiment, the first negative electrode active material can have a sphericity S of 0.85 or greater, according to the following Equation 1: Equation 1 Sphericity S = 4π × A / B 2 , Where A represents the area of ​​the first negative electrode active material, and B represents the perimeter of the shape of the first negative electrode active material.

[0040] In an embodiment, B may be the actual perimeter of the shape of the first negative electrode active material.

[0041] The sphericity of the first negative electrode active material can be a value obtained by projecting three-dimensional particles onto a two-dimensional plane. For example, sphericity can be the ratio of the boundary of the actual particle shape to the boundary of a circle with the same area.

[0042] In Equation 1 above, area A represents the area of ​​the circle, whose circumference is the same as the actual circumference B of the particle, which has been calculated from the cross-sectional image obtained using a pressure-controlled scanning electron microscope (CP-SEM) and the ImageJ program. In this embodiment, the actual circumference can refer not only to the circumference when the particle has a perfectly spherical shape, but also to the length obtained along the circumference even if the particle is not perfectly spherical and has non-uniform regions.

[0043] In embodiments, the first negative electrode active material may have a sphericity of 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 embodiments, the first negative electrode active material may have a sphericity of 0.90 to 1.0, 0.90 to 0.98, or 0.90 to 0.95. When the sphericity falls within the above range, the expansion rate during charging and discharging can be suppressed more effectively.

[0044] In this embodiment, the first negative electrode active material can have a particle density of 1.60 g / cc to 1.80 g / cc. Within this range, the internal porosity of the first negative electrode active material and side reactions with the electrolyte can be reduced, thereby improving lifetime characteristics. For example, the particle density can be in the range of 1.70 g / cc to 1.80 g / cc. 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 the embodiments, the aggregate density can be from 1.70 g / cc to 1.80 g / cc.

[0045] In the embodiments, the first negative electrode active material may have a concentration of 0.75 g / cc to 1.20 g / cc (e.g., 0.75 g / cc, 0.76 g / cc, 0.77 g / cc, 0.78 g / cc, 0.79 g / cc, 0.80 g / cc, 0.81 g / cc, 0.82 g / cc, 0.83 g / cc, 0.84 g / cc, 0.85 g / cc, 0.86 g / cc, 0.87 g / cc, 0.88 g / cc, 0.89 g / cc, 0.90 g / cc, 0.91 g / cc, 0.92 g / cc, 0.93 g / cc, 0.94 g / cc, 0.95 g / cc, 0.96 g / cc, 0.97 g / cc, 0.98 g / cc, 0.99 g / cc). The tap density is 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. In the embodiments, the first negative electrode active material may have a tap density of 0.75 g / cc to 1.0 g / cc or 0.95 g / cc to 1.20 g / cc. Within the aforementioned range, the internal porosity of the first negative electrode active material and its side reactions with the electrolyte can be reduced, thereby improving lifetime characteristics. Tap density can be achieved by using a material with a density of 0.2907 cm⁻¹. 3 The GeoPyc 1360 micrometer bottle (Micromeritics) with a chamber diameter of 19.1 mm and a conversion factor of / mm was used to calculate the average value by performing three processes of applying a pressure of 108 N.

[0046] In an embodiment, the first negative electrode active material may have a 10m 2 / g or less (e.g., 1m) 2 / g, 1.5m 2 / g、2m 2 / g, 2.5m 2 / g、3m 2 / g, 3.5m 2 / g、4m 2 / g, 4.5m 2 / g、5m 2 / g, 5.5m 2 / g、6m 2 / g, 6.5m 2 / g、7m 2 / g, 7.5m2 / g、8m 2 / g, 8.5m 2 / g、9m 2 / g, 9.5m 2 / g or 10m 2 The specific surface area is 1 m² / g, and in the embodiments, the first negative electrode active material can have a specific surface area of ​​1 m² / g. 2 / g to 10m 2 The specific surface area is measured in g. Within this range, the internal porosity of the first negative electrode active material and its side reactions with the electrolyte can be reduced, thereby improving lifetime characteristics. Specific surface area can be the BET specific surface area. The BET specific surface area can be measured using a MOUNTECH Macsorb HM Model-1208.

[0047] In embodiments, the internal porosity of the first negative electrode active material can be 2% or less (e.g., 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, or 2%), and in embodiments, the internal porosity of the first negative electrode active material 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 within the porosity can be quantitatively measured using a Barrett-Joyner-Halenda (BJH) analytical apparatus.

[0048] The composition of the active material of the first negative electrode will be described in further detail here.

[0049] The first negative electrode active material includes: natural graphite, including secondary particles assembled from primary particles; and a coating surrounding the secondary particles and including amorphous carbon.

[0050] Natural graphite can be in flake or flake-like form (e.g., needle-like, scaly, or plate-like) natural graphite.

[0051] In embodiments, the primary particles can have a size from 10 μm to 200 μm (e.g., 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, 105 μm, 110 μm, 115 μm, 120 μm, 125 μm). The primary particles may have a major axis length of 10 μm to 100 μm, 30 μm to 60 μm, or 20 μm (or 200 μm). Within these ranges, assembly into secondary particles can be facilitated, and the ratios described below can be readily achieved.

[0052] Here, "major axis length" refers to the length of the longest axis between opposite sides when the primary particle is plate-shaped.

[0053] In this embodiment, the primary particles may be plate-shaped, but the invention is not limited thereto.

[0054] In embodiments, the secondary particles may have an average particle size D50 of 30 μm or less. Within the above range, the ratios described below can be readily achieved. For example, the secondary particles may have an average particle size D50 of 5 μm or more and 10 μm or less (e.g., 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm), and in embodiments, the secondary particles may have an average particle size D50 of 6 μm or more and 8 μm or less. Within the above range, the aforementioned orientation and sphericity can be readily achieved.

[0055] The secondary particles can be spherical, but the invention is not limited thereto.

[0056] In an embodiment, 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 can remain unchanged and the boost charging performance can remain unchanged. For example, the ratio can be 2.1, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, or 10, and in an embodiment, the ratio can be 3 to 6, 4 to 6, or 5 to 6. Within the above range, the aforementioned orientation and sphericity can be easily achieved.

[0057] Amorphous carbon is contained in 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 the charge / discharge rate characteristics.

[0058] In the embodiments, the coating comprising amorphous carbon may have a thickness of 5 nm to 50 nm (e.g., 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, 20 nm, 21 nm, 22 nm, 23 nm, 24 nm, 25 nm, 26 nm, 27 nm, 28 nm, 29 nm, 30 nm, 31 nm, 32 nm, 33 nm, 34 nm, 35 nm, 36 nm, 37 nm, 38 nm, 39 nm, 40 nm, 41 nm, 42 nm, 43 nm, 44 nm, 45 nm, 46 nm, 47 nm, 48 nm, 49 nm, or 50 nm), and in the embodiments, the coating comprising amorphous carbon may have a thickness of 10 nm to 50 nm or 20 nm to 50 nm. Within the above range, side reactions with the electrolyte can be suppressed, and the charge / discharge rate characteristics can be improved.

[0059] Amorphous carbon can be one or more mixtures selected from soft carbon, hard carbon, mesophase pitch carbides and calcined coke.

[0060] Amorphous carbon can also exist on the surface of primary particles.

[0061] In an embodiment, the natural graphite and amorphous carbon in a total of 100 parts by weight of the first negative electrode active material can be included in a weight ratio of 90:10 to 75:25 (e.g., 90:10 to 80:20, 90:10 to 85:15, or 90:10 to 88:12). Within the above range, side reactions with the electrolyte can be effectively suppressed, and the charge / discharge rate characteristics can be improved.

[0062] Here, a method for preparing the active material of the first negative electrode will be described.

[0063] (1) Primary particles with the aforementioned long axis length are obtained by grinding natural graphite raw materials having an average particle size D50 of 120 μm or greater. In an embodiment, the natural graphite raw materials 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.

[0064] (2) Use a spheroidizing device to assemble primary particles into secondary particles.

[0065] Assembly is a process designed to achieve a sphericity of 0.85 or higher, and can be performed using a high-intensity mixer equipped with a high-speed rotating rotor and stator. In the sphericification process, the average particle size D50 of the secondary particles can be controlled by varying pressure, shear rate, etc.

[0066] (3) The obtained secondary particles are mixed with the amorphous carbon precursor.

[0067] There are no particular limitations on amorphous carbon precursors, as long as they are materials that form carbides. For example, amorphous carbon 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.

[0068] In the mixing process, natural graphite and amorphous carbon can be added to the final product (i.e., the first negative electrode active material) so that natural graphite and amorphous carbon can exist in the above weight ratio.

[0069] (4) The first negative electrode active material is obtained by calcining and heat treatment of the mixture obtained by mixing.

[0070] In an embodiment, the heat treatment may be performed at 2500°C or higher (e.g., 2500°C to 3500°C, or 2500°C to 3000°C). Within the above range, the first negative electrode active material comprising secondary particles satisfying the above ratios can be heat-treated to readily obtain the above-mentioned orientation degree, d002, and sphericity.

[0071] The heat treatment can be maintained for 1 to 5 hours (e.g., 1 to 4 hours, 1 to 3 hours, or 2 to 3 hours).

[0072] Figure 1 This is a conceptual diagram of the first negative electrode active material according to an embodiment.

[0073] Reference Figure 1 The first negative electrode active material includes: natural graphite, secondary particles 3 comprising multiple primary particles 1 assembled or arranged; amorphous carbon 5 present on the surface of the primary particles 1; and a coating 7 surrounding the secondary particles 3 and including 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 minimization or reduction of internal porosity, reduces side reactions with the electrolyte, and improves cycle life.

[0074] (2) Active material of the second negative electrode The second negative electrode active material can be graphite. In embodiments, the second negative electrode active material can be at least one of natural graphite and artificial graphite. For example, the second negative electrode active material can be natural graphite.

[0075] In the embodiments, the artificial graphite may have an average particle size D50 of 10 μm to 20 μm (e.g., 13 μm to 18 μm or 15 μm to 20 μm). Within the above range, the specific surface area may not increase significantly, thereby suppressing the increase of side reactions with the electrolyte and preventing or substantially preventing the degradation of boost charging performance.

[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, 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 lower tap density than the tap density of the first negative electrode active material, for example, it 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 artificial graphite can have a thickness of 10m. 2 / g or less (e.g., 1m) 2 / g to 10m 2 The specific surface area is ( / g). Specific surface area can be the BET specific surface area.

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

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

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

[0083] In an embodiment, the secondary particles assembled from the primary particles in the artificial graphite may further include a coating comprising amorphous carbon on their surface.

[0084] (3) Active material of the third negative electrode In an embodiment, the third negative electrode active material is a silicon-based negative electrode active material and includes one or more of the following: negative electrode active material (i) comprising a core containing silicon nanoparticles and amorphous carbon, and an amorphous carbon coating surrounding the core and comprising amorphous carbon; negative electrode active material (ii) comprising a composite of silicon and crystalline carbon, and an amorphous carbon coating formed or located on the surface of the composite and comprising amorphous carbon; and negative electrode active material (iii) comprising silicon nanoparticles and an amorphous carbon coating formed or located on the surface of the silicon nanoparticles and having a sphericity of 0.9 to 1.0.

[0085] Negative electrode active material (i) The negative electrode active material (i) includes: a core comprising silicon nanoparticles and amorphous carbon; and an amorphous carbon coating surrounding the core and comprising amorphous carbon.

[0086] In the embodiments, the negative electrode active material (i) may be a binary negative electrode active material including silicon and amorphous carbon.

[0087] In the embodiments, in the negative electrode active material (i), the interparticle distance between the silicon nanoparticles included in the core 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 the silicon nanoparticles falls within the above range, the size of the pores included in the core and the total pore volume can be reduced. When the interparticle distance between the silicon nanoparticles is within the above range, the volume of pores present in the negative electrode active material (i) can be reduced, and the interparticle distance between the silicon nanoparticles can be narrowed, thereby preventing or substantially preventing electrolyte from penetrating into the core during battery operation. As a result, side reactions between the electrolyte and the negative electrode active material (i) can be suppressed, thereby improving battery life.

[0088] Here, the interparticle distance between silicon nanoparticles refers to the distance between the centers of the silicon nanoparticles. (See reference...) Figure 3 The silicon nanoparticles 2 have a short axis length a and a long axis length b, and the interparticle distance d is the distance between the centers of the silicon nanoparticles 2.

[0089] The number of silicon nanoparticles having interparticle distances within the above range is 50% to 100% of the total number of silicon nanoparticles included in the core (e.g., 60% to 100%, 70% to 100%, or 80% to 100%).

[0090] In the embodiments, the silicon nanoparticles may have an average particle size D50 of 50 nm to 150 nm (e.g., 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.

[0091] In the embodiments, the silicon nanoparticles can have a full width at half maximum (FWHM) of 0.3° to 7° at an X-ray diffraction angle (2θ) on the (111) plane using Cu Kα rays. Therefore, lifetime characteristics can be improved.

[0092] The free wave height (FWHM) of silicon nanoparticles at the X-ray diffraction angle (2θ) on the (111) plane using Cu Kα rays can be controlled by adjusting the size of the silicon nanoparticles or changing the manufacturing process of the silicon nanoparticles.

[0093] In the embodiments, the silicon nanoparticles may have an aspect ratio of 2 to 8 (e.g., 2 to 6), and the silicon nanoparticles may have a minor axis length a of 20 nm to 50 nm and a major axis length b of 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, side reactions between the negative electrode active material (i) and the electrolyte can be suppressed, and the expansion of the silicon nanoparticles can be reduced, thereby improving initial efficiency and lifetime characteristics.

[0094] In the embodiments, silicon nanoparticles may be included in amounts ranging from 20% to 80% by weight, 30% to 70% by weight, 30% to 60% by weight, or 30% to 50% by weight, based on the total weight of the negative electrode active material (i). When the content of silicon nanoparticles is within the above range, the battery capacity can be improved.

[0095] The amorphous carbon contained in the core can be soft carbon, hard carbon, mesophase pitch carbide, calcined coke, or a combination thereof.

[0096] Including amorphous carbon in the core can reduce the pore volume of the negative electrode active material (i), thereby suppressing side reactions with the electrolyte. Furthermore, it can buffer the expansion of silicon nanoparticles within the negative electrode active material (i), thus suppressing battery swelling. Additionally, amorphous carbon acts as a binder, mitigating the breakage of the negative electrode active material (i) and maintaining its shape well.

[0097] In this embodiment, the coating may comprise amorphous carbon and may have a thickness of 1 nm to 900 nm (e.g., 5 nm to 800 nm). This can reduce the specific surface area of ​​the negative electrode active material (i) and prevent the introduction of electrolyte into the negative electrode active material (i). As a result, side reactions with the electrolyte can be minimized or reduced, and the battery life characteristics can be improved.

[0098] The amorphous carbon included 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.

[0099] In the embodiments, based on the total weight of the negative electrode active material (i), amorphous carbon may be included in an amount of 20% to 80% by weight (e.g., 20% to 70% by weight, 20% to 60% by weight, 20% to 50% by weight, or 20% to 40% by weight). When the content of amorphous carbon is within the above range, side reactions between the negative electrode active material (i) and the electrolyte can be suppressed.

[0100] The negative electrode active material (i) according to the embodiment can have an average particle size D50 of 2 μm to 15 μm (e.g., 3 μm to 13 μm or 5 μm to 10 μm). When the average particle size of the negative electrode active material (i) is within the above range, lithium ions can easily diffuse into the negative electrode active material (i), thereby improving battery resistance and C-rate characteristics. Furthermore, side reactions with the electrolyte can be reduced by suppressing excessive increases in the specific surface area of ​​the negative electrode active material (i).

[0101] The average particle size D50 of the negative electrode active material (i) can be appropriately adjusted by controlling the decomposition and grinding conditions during the manufacturing of the negative electrode active material (i).

[0102] In the embodiments, in the negative electrode active material (i), pores with a size of 200 nm or smaller can have a size of 3.0 × 10⁻⁶. -2 cm 3 / g or less (e.g., 2.5 × 10⁶ g) -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 is approximately 1 g or less. Within this range, side reactions between the electrolyte and the negative electrode active material (i) can be suppressed, thereby improving initial efficiency and lifetime characteristics.

[0103] 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 apparatus.

[0104] In the embodiments, the negative electrode active material (i) may have a pore size of 200 nm or smaller (e.g., 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 the negative electrode active material (i) can be reduced, and a battery with improved initial efficiency and lifespan characteristics can be obtained.

[0105] In the embodiment, the negative electrode active material (i) may have a 10m 2 A BET specific surface area of ​​ / g or less. When the BET specific surface area is within the above range, side reactions with the electrolyte can be suppressed, thereby improving the efficiency characteristics of the battery.

[0106] In the embodiments, the negative electrode active material (i) may include silicon nanoparticles and amorphous carbon in a weight ratio of 80:20 to 20:80 (e.g., 70:30 to 30:70, 70:30 to 40:60, or 70:30 to 50:50) based on a total of 100 parts by weight. When the content of silicon nanoparticles and amorphous carbon is within the above range, the internal pore volume can be reduced, and the amorphous carbon can be uniformly (substantially uniformly) dispersed in the interior and surface of the negative electrode active material (i). As a result, side reactions with the electrolyte can be suppressed, and the performance of the negative electrode active material (i) can be improved.

[0107] A method for preparing the negative electrode active material (i) according to the embodiments will be described.

[0108] The method for preparing the negative electrode active material (i) includes: mixing and dispersing silicon nanoparticles and amorphous carbon to prepare a mixture; spraying, drying and compressing the mixture to manufacture a molded body; and heat-treating the molded body.

[0109] Silicon nanoparticles and amorphous carbon were mixed and dispersed to prepare a mixture. The silicon nanoparticles and amorphous carbon were as described above.

[0110] The prepared mixture is sprayed, dried, and compressed to create a molded body.

[0111] Drying can be performed using a spray dryer at temperatures ranging from 50°C to 150°C.

[0112] In an embodiment, compression can be performed at a pressure of 50 MPa to 150 MPa (e.g., 75 MPa to 150 MPa or 75 MPa to 125 MPa). When the molded body is compressed within the aforementioned pressure range, the spacing between silicon nanoparticles can be appropriately maintained, and the volume of pores formed within the negative electrode active material (i) can be controlled, thereby suppressing side reactions between the electrolyte and the negative electrode active material (i) and improving initial efficiency and lifetime characteristics.

[0113] The molded body is heat-treated to prepare the negative electrode active material (i).

[0114] In this embodiment, the heat treatment can be performed at a temperature of 700°C to 1100°C (e.g., 800°C to 1050°C or 900°C to 1000°C). When heat treatment is performed within the above temperature range, the strength of the negative electrode active material (i) can be enhanced due to the carbonization of the amorphous carbon. Furthermore, the conductivity of the negative electrode active material (i) can be improved, and the initial efficiency of the battery can be improved.

[0115] Heat treatment can be performed in a furnace under a nitrogen (N2) atmosphere.

[0116] In an embodiment, the negative electrode active material (i) may have a sphericity of 0.7 or greater, and in another embodiment, the negative electrode active material (i) 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 negative electrode active material (i) is circular or elliptical.

[0117] In one specific embodiment, the negative electrode active material (i) may have an elliptical or circular cross-section. Therefore, a sphericity of 1.0 means that the negative electrode active material (i) is substantially a perfect spherical shape. Thus, those skilled in the art will understand that the maximum value of sphericity is 1.0 and cannot exceed 1.0.

[0118] When the sphericity of the negative electrode active material (i) is 0.7 or greater, the surface area of ​​the negative electrode active material (i) can be reduced. Therefore, since the area of ​​the negative electrode active material (i) in contact with the electrolyte or the area of ​​the negative electrode active material (i) reacting with lithium is reduced, side reactions with the electrolyte and reactions with lithium can be reduced. Furthermore, volume expansion can be reduced through the uniform expansion of the negative electrode active material (i) in the negative electrode.

[0119] When the BET specific surface area of ​​the negative electrode active material (i) is 10m² 2 / g or less (e.g., from 0.5m) 2 / g to 10m 2 When the BET specific surface area of ​​the negative electrode active material (i) is 10 m² / g, this effect of reducing the specific surface area can be more effective. 2 / g or less, or, according to the embodiments, the BET specific surface area of ​​the negative electrode active material (i) is 0.5m². 2 / g to 10m 2 At / g, the following advantages can be achieved: performance can be improved by reducing contact with the electrolyte to suppress side reactions, and initial efficiency can be enhanced.

[0120] That is, because the negative electrode active material (i) 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 negative electrode active material (i) can be an active material with reduced side reactions with the electrolyte and also with reduced reactions with lithium.

[0121] In the negative electrode active material (i), silicon nanoparticles are primary particles, and these primary particles can be included in the silicon-carbon composite as secondary particles assembled from at least one primary particle. Therefore, the silicon-carbon composite can include secondary particles assembled from Si nanoparticles.

[0122] In the embodiments, the silicon nanoparticles may be in the form of sheets or sheet-like structures, spheres, etc., but the present invention is not limited thereto. Furthermore, secondary particles assembled from at least one primary particle may have a spherical shape.

[0123] In embodiments, amorphous carbon may be configured to cover the surface of the secondary particles. That is, the negative electrode active material (i) according to an embodiment may include a core comprising silicon nanoparticles, and according to an example, may include secondary particles (core) assembled as at least one primary particle of silicon nanoparticles and amorphous carbon surrounding the core. In embodiments, the core refers to a region located within the negative electrode active material (i). That is, the core refers to a region that is not exposed to the outside because the core is surrounded by amorphous carbon. Therefore, the core may be referred to as a region located within the amorphous carbon surrounding the core.

[0124] Furthermore, amorphous carbon can be filled between the primary particles. When amorphous carbon is filled between the primary particles, it can be seen that the amorphous carbon is configured to cover the surface of the primary particles. In this way, when amorphous carbon is filled between the primary particles, the pore volume of the negative electrode active material (i) can be reduced, thereby suppressing side reactions with the electrolyte. In addition, when the primary particles, which are silicon nanoparticles, expand, the amorphous carbon can buffer this expansion. Furthermore, since the amorphous carbon filled between the primary particles can act as a binder, it can prevent or substantially prevent the particles of the negative electrode active material (i) from breaking down and improve conductivity.

[0125] Amorphous carbon can be soft carbon, hard carbon, mesophase pitch carbides, calcined coke, or a combination thereof.

[0126] Silicon nanoparticles can be sheet-like or sheet-like. That is, silicon nanoparticles can be sheet-like with a long axis and a short axis. In embodiments, the long axis / short axis ratio (e.g., width / thickness ratio) of the silicon nanoparticles can be in the range of 5 to 20. When the long axis / short axis ratio of the silicon nanoparticles 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 including the negative electrode active material (i).

[0127] In the embodiments, the silicon nanoparticles may have a particle size of 10 nm to 200 nm. The particle size may be the average particle size. In this case, the average particle size may refer to the particle size D50 measured by cumulative volume. Unless otherwise defined in this specification, particle size D50 refers to the average particle size D50 of particles having a cumulative volume of 50% in the particle size distribution. When the size of the Si nanoparticles falls within the above range, side reactions between the negative electrode active material (i) and the electrolyte are suppressed, and the expansion of the Si nanoparticles is reduced, thereby improving the initial efficiency and lifespan characteristics of the battery.

[0128] In an embodiment, when at least one primary particle is assembled into a secondary particle, the secondary particle may have a particle size of 2 μm to 15 μm, and in another embodiment, the secondary particle may have a particle size of 5 μm to 10 μm. In another embodiment, the primary particle may have a particle size of 10 nm to 200 nm. When the average particle size of the negative electrode active material (i) is within the above range, lithium ions can easily diffuse into the negative electrode active material (i), and the resistance and C-rate characteristics can be improved.

[0129] In the embodiments, the full width at half maximum (FWHM) (111) of the diffraction peak on the (111) plane of the silicon nanoparticles, as measured by X-ray diffraction using Cu Kα rays, can be from 0.3 degrees (°) to 7 degrees (°). When the FWHM (111) of the Si nanoparticles falls within the above range, the battery life characteristics can be improved.

[0130] X-ray diffraction measurements were performed using Cu Kα rays as the target rays. In this case, measurements were performed under the following conditions: 2θ = 40° to 50°, scan rate (° / s) of 0.04 to 0.06, and step size (° / step) of 0.01 to 0.03.

[0131] In the embodiments, the mixing ratio of silicon nanoparticles and amorphous carbon can be from 8:2 to 2:8 by weight, and in some embodiments, it can be from 7:3 to 5:5 by weight. In these embodiments, since the silicon nanoparticles exist in the negative electrode active material (i) as secondary particles assembled from primary particles, the mixing ratio of silicon nanoparticles and amorphous carbon can be considered as the mixing ratio of secondary particles and amorphous carbon. When the mixing ratio of silicon nanoparticles and amorphous carbon falls within the above range, better capacity (especially higher capacity compared to crystalline carbon negative electrode active materials) can be achieved.

[0132] In embodiments, amorphous carbon may be present as a coating on the surface of the secondary particles, and may also be filled between the secondary particles in addition to this coating form. In embodiments, regardless of whether the amorphous carbon is filled between the primary particles, present as a coating, or present in any other form, the total content of amorphous carbon included in the negative electrode active material (i) may be from 20% to 80% by weight, based on a total of 100% by weight of the negative electrode active material (i).

[0133] In the embodiments, when amorphous carbon is present as a coating applied to and surrounding 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 (e.g., 30 nm to 200 nm). When the thickness of the amorphous carbon coating falls within the above range, the conductivity of the negative electrode active material (i) can be further improved, and contact with the electrolyte can be reduced, thereby effectively suppressing the increase in resistance due to the generation of by-reaction products.

[0134] In the embodiments, the negative electrode active material (i) may have a particle size of 40 μm or smaller (e.g., a particle size of 2 μm to 15 μm). When the particle size of the negative electrode active material (i) falls within the above range, lithium ions can easily diffuse into the negative electrode active material (i) and can improve battery resistance and C-rate characteristics.

[0135] The negative electrode active material (i) according to the embodiment can be manufactured by the following process.

[0136] First, silicon particles are prepared. These silicon particles can be nanoparticles, and in the embodiments, they can be nanoparticles with a particle size of 10 nm to 200 nm. These nano-sized silicon particles can be obtained by performing conventional processes for producing nanoparticles, such as grinding processes. In the embodiments, the full width at half maximum (FWHM) (111) of the diffraction peaks on the (111) plane of the silicon nanoparticles, as measured by X-ray diffraction using Cu Kα rays, can be 0.3 degrees (°) to 7 degrees (°).

[0137] Silicon particles are dispersed in a solvent to prepare a silicon particle solution. An alcohol that is readily volatile and does not oxidize the silicon particles can be used as the solvent. For example, isopropanol, ethanol, methanol, butanol, or combinations thereof can be used as the solvent. In the examples, the concentration of the silicon particle dispersion is from 10% to 30% by weight.

[0138] The prepared silicon particle solution is spray-dried. Through this process, nanoscale silicon particles (primary particles) are assembled to fabricate micron-sized spherical Si secondary particles. The secondary particles may include internal pores (i.e., gaps between primary particles). This spray-drying process can control the sphericity of the fabricated negative electrode active material (i) by controlling the type of nozzle and the atmosphere used. Specifically, it is desirable to use a two-fluid nozzle capable of forming fine particles by mixing two fluids (liquid and gas). When using a two-fluid nozzle, fine spherical particles can be formed. Because the formed particles have a small size, no additional grinding process is required, allowing the spherical shape to be maintained. When a disc-shaped nozzle that sprays while rotating is used as the nozzle, large particles are formed, and an additional grinding process is required due to the large particle size. Furthermore, it is not desirable to form particles with various shapes such as spherical, elliptical, and annular shapes.

[0139] In this embodiment, the spray drying process is performed in an N2 atmosphere (e.g., by blowing N2 in at a flow rate of 40 L / min to 50 L / min or 30 L / min to 40 L / min). When the N2 flow rate in the spray drying process falls within the above range, spherical particles of appropriate size can be formed. When the N2 flow rate is less than 30 L / min, undesirable agglomeration of the sprayed product may occur due to the increased particle size. On the other hand, when the N2 flow rate is greater than 50 L / min, there may be a problem of the manufactured particles being too small and generating a large amount of fine powder.

[0140] In this embodiment, the spray drying process can be performed at 120°C to 170°C. When the spray drying process is performed within the above temperature range, the temperature is sufficiently higher than the boiling point of the solvent, so the micron-sized spherical Si secondary particles can be expected to be sufficiently dried through rapid evaporation.

[0141] The obtained Si primary nanoparticles are assembled into micron-sized Si secondary particles with a spherical shape, which are then mixed with an amorphous carbon precursor. In the embodiments, the mixing ratio of the secondary particles and the amorphous carbon precursor can be from 80:20 to 20:80 by weight, or from 60:40 to 50:50 by weight.

[0142] The amorphous carbon precursor may 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 pitch, raw coke, mesophase pitch, kerosene, heavy petroleum oil, coke, or a combination thereof.

[0143] The resulting mixture is compressed and molded. This compression molding process can be performed under pressure (e.g., at 20 MPa to 150 MPa) that maintains the spherical shape of the micron-sized Si secondary particles. Furthermore, the compression molding process can be performed for 1 to 5 minutes. When the compression molding process is performed, the micron-sized spherical Si secondary particles and the amorphous carbon precursor can adhere firmly to each other, and the amorphous carbon precursor can easily insert between the primary particles. Therefore, since the amorphous carbon precursor can easily insert into the pores formed inside the secondary particles, amorphous carbon can exist in the final negative electrode active material (i) between the primary particles in an appropriate amount (appropriate thickness). As a result, amorphous carbon can form a coating of appropriate thickness on the surface of the secondary particles. If the compression molding process is not performed, the micron-sized spherical Si secondary particles and the amorphous carbon precursor cannot adhere firmly to each other, and the amorphous carbon precursor cannot easily insert between the primary particles but is mostly located on the surface of the secondary particles. As a result, the amorphous carbon in the final negative electrode active material (i) undesirably exists on the surface of the secondary particles in an excessively thick thickness.

[0144] The resulting compression-molded product is heat-treated to manufacture the negative electrode active material (i). In an embodiment, 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 (i) can be maintained as a spherical shape. Furthermore, since the amorphous carbon is carbonized, the conductivity of the negative electrode active material (i) can be improved, and the initial efficiency of the battery can be improved. In addition, the heat treatment process can be performed under an N2 atmosphere. When the amorphous carbon precursor is converted into amorphous carbon through this heat treatment process, the amorphous carbon precursor is included as amorphous carbon in the negative electrode active material (i).

[0145] Figure 2 This is a conceptual diagram of the negative electrode active material (i) of the third negative electrode active material according to the embodiment.

[0146] Reference Figure 2 The negative electrode active material (i) comprises: a core 4, comprising amorphous carbon and silicon nanoparticles 2; and a coating 6 surrounding the core 4. In this case, pores 8 are included within the core 4.

[0147] Negative electrode active material (ii) The negative electrode active material (ii) includes a composite of silicon and crystalline carbon and an amorphous carbon coating formed on the surface of the composite and including amorphous carbon.

[0148] In the embodiments, the negative electrode active material (ii) may be a ternary negative electrode active material including silicon, crystalline carbon, and amorphous carbon.

[0149] In an embodiment, the negative electrode active material (ii) may include a composite of silicon and crystalline carbon (core) and an amorphous carbon coating formed on the surface of the core. In an embodiment, the crystalline carbon may be present in the core. In an embodiment, the amorphous carbon may be in contact with each of the silicon and crystalline carbon in the core.

[0150] In the embodiments, the negative electrode active material (ii) may have an aspect ratio of 1 to 2.5 (e.g., 1 to 2). Within the above range, the negative electrode active material (ii) can expand in a more uniform direction, and the expansion of the negative electrode active material (ii) in the negative electrode can be effectively reduced. The aspect ratio can be measured by photographs taken using a controlled pressure scanning electron microscope (CP-SEM). The aspect ratio refers to the ratio of the maximum major axis length to the maximum minor axis length of the negative electrode active material (ii).

[0151] In the embodiments, the silicon and crystalline carbon composite can have an aspect ratio of 1 to 2.5 (e.g., 1 to 2). Within this range, the negative electrode active material (ii) can swell in a more uniform direction, and the expansion of the negative electrode active material (ii) in the negative electrode can be effectively reduced. The aspect ratio can be measured by photographs taken using CP-SEM. The aspect ratio refers to the ratio of the maximum major axis length to the maximum minor axis length of the composite.

[0152] In some embodiments, the composite of silicon and crystalline carbon may include pores.

[0153] In embodiments, the pores can be tubular or plate-like, and can form a network within the core. In the silicon and crystalline carbon composite, the porosity can be suitably controlled. In embodiments, for example, the porosity (total pore volume) can be from 2% to 50% by volume.

[0154] In an embodiment, the negative electrode active material (ii) may include crystalline carbon (core) having pores formed therein, amorphous carbon (shell) formed on the surface of the core, silicon particles dispersed in the pores, and amorphous carbon present in the pores.

[0155] In an embodiment, based on a total of 100 parts by weight of silicon and crystalline carbon, the weight ratio of silicon to crystalline carbon in the silicon and crystalline carbon composite can be in the range of 10:90 to 90:10. Within this range, better capacity can be provided (especially higher capacity compared to negative electrode active materials made of crystalline carbon). In an embodiment, for example, the weight ratio can be from 50:50 to 80:20, and higher capacity can be exhibited within the above range.

[0156] In the embodiments, the silicon may be spherical and have an average particle size D50 of 10 nm to 150 nm (e.g., 40 nm to 120 nm). Within the above range, the cycle life characteristics of the battery can be improved.

[0157] Silicon can be silicon (Si) particles.

[0158] In the embodiments, the crystalline carbon can have a major axis length of 5 μm to 20 μm (e.g., 5 μm to 10 μm) and an aspect ratio of 4 to 10 (e.g., 4 to 8). Within these ranges, the cycle life characteristics of the battery can be improved, and swelling does not occur because the dry negative electrode plate does not undergo excessive volume expansion during the charging and discharging of the rechargeable lithium battery. The aspect ratio can be measured by CP-SEM. The aspect ratio is the ratio of the maximum major axis length to the maximum minor axis length.

[0159] Crystalline carbon can be natural graphite, artificial graphite, or a combination thereof.

[0160] In an embodiment, the crystalline carbon may be in the form of a rod with an elliptical cross-section.

[0161] Amorphous carbon coatings can be formed on the surface of the composite to improve its conductivity, thereby further improving its performance. They can also reduce the direct contact between silicon and the electrolyte, thus effectively suppressing the increase in resistance caused by the generation of by-reaction products.

[0162] In the embodiments, the amorphous carbon coating may have a thickness of 5 nm to 1000 nm (e.g., 5 nm to 30 nm). Within the above range, the thickness level of the amorphous carbon coating can be such that there is no electron transfer resistance problem.

[0163] The amorphous carbon in the amorphous carbon coating and the amorphous carbon present in the core can be petroleum pitch, coal pitch, or a combination thereof.

[0164] In the embodiments, the content of the amorphous carbon coating in the negative electrode active material (ii) can be from 10% to 60% by weight of the negative electrode active material (ii). Within the above range, the performance improvement effect of the battery can be achieved.

[0165] In an embodiment, the negative electrode active material (ii) may comprise 20% to 70% by weight of silicon, 3% to 50% by weight of crystalline carbon, and 20% to 50% by weight of amorphous carbon. Within the above range, the expansion of the negative electrode active material (ii) due to charging and discharging can be effectively suppressed, and cycle life and output characteristics can be improved.

[0166] Figure 4 This is a conceptual diagram of the negative electrode active material (ii) of the third negative electrode active material according to the embodiment.

[0167] Reference Figure 4The negative electrode active material (ii) includes silicon particles 11, crystalline carbon 13, and amorphous carbon 15. Amorphous carbon 15 is present between silicon particles 11 and crystalline carbon 13, and amorphous carbon 15 may also be present as a coating surrounding silicon particles 11 and crystalline carbon 13.

[0168] Here, a method for preparing the negative electrode active material (ii) will be described.

[0169] The negative electrode active material (ii) can be prepared by mixing silicon particles, artificial graphite, and amorphous carbon in a solvent to prepare a mixture, followed by spray drying and heat treatment of the mixture. The solvent can be isopropanol, ethanol, methanol, or combinations thereof. In embodiments, spray drying can be performed at 90°C to 120°C, and heat treatment can be performed at 900°C to 1000°C in a nitrogen atmosphere, argon atmosphere, hydrogen atmosphere, or combinations thereof.

[0170] Negative electrode active material (iii) The negative electrode active material (iii) includes silicon nanoparticles and an amorphous carbon coating disposed on the surface of the silicon nanoparticles.

[0171] In this embodiment, because the negative electrode active material (iii) has a spherical shape, it can be well dispersed throughout the dry negative electrode plate, thereby reducing the expansion rate of the dry negative electrode plate during charging and discharging. Furthermore, when the negative electrode active material (iii) is mixed with crystalline carbon (i.e., the second negative electrode active material), the spherical shape of the negative electrode active material (iii) allows for better insertion between the crystalline carbon molecules, thus resulting in better dispersion throughout the negative electrode.

[0172] In the embodiment, according to Equation 1 above, the negative electrode active material (iii) has a sphericity S of 0.9 to 1.0. Within this range, the expansion rate of the dry negative electrode plate during charging and discharging can be easily reduced.

[0173] The negative electrode active material (iii) according to the embodiment may have a sphericity of 0.92 to 0.98 or 0.92 to 0.95. When the sphericity of the negative electrode active material (iii) falls within the above range, the expansion rate of the dry negative electrode plate can be suppressed more effectively during charging and discharging.

[0174] The negative electrode active material (iii) may include pores, and the pores may include mesopores. Here, mesopores may refer to pores having a pore size of 2 nm to 50 nm. When the negative electrode active material (iii) includes mesopores, the effect of the dry negative electrode plate can be significant.

[0175] When the first negative electrode active material is mixed with the second negative electrode active material, the negative electrode active material (iii) having the above-mentioned sphericity and mesopority can easily provide long life, high energy density and boost charging effect at the same time.

[0176] In an embodiment, the negative electrode active material (iii) may further include macropores as pores having a pore size greater than 50 nm. Since pores with a pore size greater than 50 nm are classified as macropores, there is no need to limit the maximum value of macropores, but the pore size can be as high as 500 nm. It is desirable to include such macropores in an amount of 1 volume% or less based on the total pore volume. In this case, macropores may be present in an amount of at least 0 volume%, that is, macropores may not actually exist within the negative electrode active material (iii).

[0177] In an embodiment, the negative electrode active material (iii) may further include micropores as pores having a pore size greater than 0 nm and less than 2 nm. The micropores included in the negative electrode active material (iii) may correspond to the volume (%) of the total pore volume excluding mesopores, or if the pores also include macropores, they may correspond to the volume excluding both mesopores and macropores.

[0178] Here, the term "aperture" refers to the diameter of the pore when the pore has a circular cross-section, or the length of the longest axis on the cross-section if the pore cross-section is not circular.

[0179] In an embodiment, the negative electrode active material (iii) may have a mesopore volume ratio of 30% or more but less than 70% to the total pore volume of the negative electrode active material (iii) ((mesopore volume / total pore volume) × 100%). Within the above range, long lifetime, high energy density, and boost charging performance can be further improved. For example, the ratio may be from 30% to 68%.

[0180] The total pore volume can be the total volume of pores including mesopores and formed in the negative electrode active material (iii), regardless of pore size. In an embodiment, the total pore volume can be 0.001 cm³. 3 / g to 0.01cm 3 Within the range of / g, or within 0.005cm 3 / g to 0.05cm 3 Within the range of / g.

[0181] Both total pore volume and mesopore volume can be quantitatively measured using a Barrett-Joyner-Halenda (BJH) analytical apparatus.

[0182] According to Equation 2 below, the negative electrode active material (iii) can have a value ranging from 1.1 to 1.6: Equation 2 Span = (D90 - D10) / D50 Wherein, D10 represents the particle size of the negative electrode active material (iii) particles having a cumulative volume of 10% in the particle size distribution, D50 represents the particle size of the negative electrode active material (iii) particles having a cumulative volume of 50% in the particle size distribution, and D90 represents the particle size of the negative electrode active material (iii) particles having a cumulative volume of 90% in the particle size distribution.

[0183] The methods for measuring D10, D50, and D90 are as described above.

[0184] In the embodiments, the span value can be 1.1 to 1.55, or it can be 1.1 to 1.5.

[0185] When the range of the negative electrode active material (iii) falls within the above range, it means that the negative electrode active material (iii) essentially does not contain fine particles. That is, since the negative electrode active material (iii) contains almost no irregularly shaped fine particles with a size of 1 μm or smaller, the negative electrode active material (iii) can exhibit a low specific surface area, thereby reducing side reactions with the electrolyte and improving lifetime.

[0186] In this embodiment, the negative electrode active material (iii) can have a low specific surface area. In this case, the specific surface area can be as low as 0.5 m². 2 / g to 2m 2 / g, 0.8m 2 / g to 2m 2 / g or 0.8m 2 / g to 1.5m 2 Within the range of / g. Specific surface area is lower than that with approximately 3m². 2 The specific surface area of ​​conventional silicon-carbon composite negative electrode active materials is expressed as / g.

[0187] Silicon nanoparticles can have a particle size of 10 nm to 1000 nm, and according to embodiments, can have a particle size of 10 nm to 200 nm, or 20 nm to 150 nm. When the particle size of silicon nanoparticles falls within the above range, excessive volume expansion that occurs during charging and discharging can be suppressed, and the interruption of conductive paths due to particle fragmentation during charging and discharging can be prevented or substantially prevented.

[0188] Silicon nanoparticles can be assembled to form silicon secondary particles. According to embodiments, the silicon secondary particles can have an average particle size D50 of 1 μm to 15 μm. For example, the average particle size D50 of the silicon secondary particles can be in the range of 1 μm to 10 μm or 6 μm to 8 μm.

[0189] In amorphous carbon coatings, the amorphous carbon can be soft carbon or hard carbon, mesophase pitch carbides, calcined coke, or a combination thereof.

[0190] In the embodiments, the amorphous carbon coating may have a thickness of 1 nm to 2 μm, 1 nm to 500 nm, 10 nm to 300 nm, or 20 nm to 200 nm. When the thickness of the amorphous carbon coating falls within the above range, silicon volume expansion during charging and discharging can be effectively suppressed.

[0191] In the embodiments, in the negative electrode active material (iii), based on a total of 100 wt% of the negative electrode active material (iii), the content of silicon nanoparticles can be in the range of 55 wt% to 64 wt%, or in the range of 58 wt% to 62 wt%. In the embodiments, based on a total of 100 wt% of the negative electrode active material (iii), the content of the amorphous carbon coating can be in the range of 36 wt% to 45 wt%, or in the range of 38 wt% to 42 wt%. Within the above ranges, the capacity of the dry negative electrode plate can be improved, and particle stability can be enhanced.

[0192] The negative electrode active material (iii) may also include a polymer layer disposed on the amorphous carbon coating.

[0193] The polymer layer may include a copolymer of polyvinyl alcohol and polyacrylic acid. The copolymer may be a cross-linked copolymer in which polyvinyl alcohol and polyacrylic acid are cross-linked. When the negative electrode active material (iii) also includes a polymer layer, the volume expansion of the negative electrode active material (iii) during charging and discharging can be more effectively suppressed.

[0194] Since the polymer layer comprises polyvinyl alcohol and polyacrylic acid, the polymer layer can prevent or substantially prevent the electrolyte from penetrating into the negative electrode active material (iii) during charging and discharging (especially into the empty spaces (such as pores) of the negative electrode active material (iii), thereby more effectively suppressing the side reactions between the negative electrode active material (iii) and the electrolyte.

[0195] Polyvinyl alcohol and polyacrylic acid are water-based polymers and environmentally friendly polymers.

[0196] In the embodiments, the polymer layer comprises a copolymer of polyvinyl alcohol and polyacrylic acid, for example, a crosslinked polymer or crosslinked copolymer of polyvinyl alcohol and polyacrylic acid. That is, the polymer of the polymer layer can be a crosslinked polymer of polyvinyl alcohol and polyacrylic acid. When polyvinyl alcohol and polyacrylic acid are crosslinked and included in the polymer layer as a crosslinked polymer, the polymer layer can remain undissolved in the solvents (especially water) used in the manufacture of the negative electrode active material (iii) layer.

[0197] In the embodiments, in the negative electrode active material (iii), when both silicon nanoparticles and amorphous carbon coating are referred to as a silicon-carbon composite, the content of the polymer layer, based on 100 parts by weight of the silicon-carbon composite, can be in the range of 0.01 parts by weight to 3 parts by weight, or in the range of 1.2 parts by weight to 2.1 parts by weight. When the content of the polymer layer falls within the above range, the effect produced by the formation of the polymer layer can be further enhanced.

[0198] In the embodiments, the mixing ratio of polyvinyl alcohol and polyacrylic acid in the polymer layer can be a weight ratio of 3:97 to 40:60, 6:94 to 40:60, or 6:94 to 20:80. When the mixing ratio of polyvinyl alcohol and polyacrylic acid falls within the above ranges, that is, when the content of polyacrylic acid is higher than the content of polyvinyl alcohol, the cycle life characteristics can be further improved.

[0199] In the embodiments, it is also desirable to control the ratio of functional groups contained in polyvinyl alcohol and polyacrylic acid included in the polymer layer. In the embodiments, the molar ratio of OH groups contained in polyvinyl alcohol to COOH groups contained in polyacrylic acid can be from 5:95 to 50:50, and in some embodiments, it can be from 10:90 to 30:70. When the molar ratio of functional groups meets the above range, the effect of polymer layer formation can be further improved, and the cycle life characteristics can be further improved.

[0200] The negative electrode active material (iii) can be prepared by the following process.

[0201] Micron-sized silicon particles are ground to produce nano-sized primary silicon particles. The grinding process can be performed using conventional processes such as ball milling. Dispersants can be used in the grinding process. Dispersants can be stearic acid, boron nitride (BN), MgS, polyvinylpyrrolidone (PVP), or combinations thereof. The amount of dispersant used is sufficient as long as it enables the grinding process of silicon particles. Therefore, there is no need to limit the amount of dispersant.

[0202] In the embodiments, the silicon primary particles may have a particle size of 1 nm to 1000 nm, 10 nm to 200 nm, or 20 nm to 150 nm.

[0203] The resulting mixture is dried. This drying process can be performed using a spray drying process. By using a spray drying process, a dried product with particles having a more uniform particle size and spherical shape can be formed, and secondary particles assembled from primary particles can also be formed. When the dried product has particles with a uniform particle size and spherical shape, the subsequently formed amorphous carbon layer can be formed more uniformly on the entire surface of the secondary particles.

[0204] The dried product is mixed with an amorphous carbon precursor.

[0205] Petroleum coke, coal coke, petroleum pitch, coal pitch, raw coke, or combinations thereof can be used as precursors for amorphous carbon.

[0206] The resulting mixture is subjected to compression molding.

[0207] The resulting product can undergo further compression molding. This compression molding process reduces the porosity within the negative electrode active material (iii), thereby effectively suppressing side reactions.

[0208] The compression molding process can be performed at pressure levels that can maintain the spherical shape of the resulting product (especially the negative electrode active material (iii) as the final product), and can be performed at pressures, for example, greater than 0 MPa and 30 MPa or less, greater than 0 MPa and 20 MPa or less, or 5 MPa to 20 MPa.

[0209] Compression molding can be performed using cold isostatic pressing (CIP). When compression molding is performed within the pressure range described above, porosity can be appropriately reduced while maintaining a spherical shape without producing fine particles.

[0210] Next, the resulting compression-molded product is carbonized. The carbonization process can be performed at 600°C to 1000°C. Dispersants can be removed during this carbonization process. Furthermore, the carbonization process can be performed in an N2 atmosphere, a helium atmosphere, or a combination thereof. Through this carbonization process, the amorphous carbon precursor is converted into amorphous carbon, thus forming an amorphous carbon coating around the surface of the compression-molded product.

[0211] When the carbonization process is performed within the aforementioned temperature range, the problem of excessive growth of Si particles can be suppressed, the formation of SiC can be inhibited, and the electrical conductivity of amorphous carbon can be improved. Furthermore, when some of the amorphous carbon can be inserted into the pores formed between the primary particles and disposed on the surface of the primary particles, amorphous carbon can be included to surround the surface of the primary particles. When the atmosphere of the carbonization process meets the above conditions, amorphous carbon can be effectively formed while suppressing silicon oxidation and SiC formation, thereby reducing the resistance of the negative electrode active material (iii).

[0212] Instead of mixing the dried product with the amorphous carbon precursor, a vapor-phase coating process using an amorphous carbon precursor gas can be performed on the dried product. In this case, an amorphous carbon coating can be formed on the surface of the dried product without performing a separate carbonization process. Therefore, a compression molding process can be performed after the vapor-phase coating process. The conditions for the compression molding process are as described above.

[0213] When the negative electrode active material (iii) layer according to the embodiment further includes a polymer layer, a process can be further performed to mix the manufactured negative electrode active material (iii) (referred to as silicon-carbon composite) and the polymer solution, dry the resulting mixture, and then heat-treat the mixture.

[0214] Polymer solutions can be prepared by mixing polyvinyl alcohol and polyacrylic acid in a solvent. In this case, the solvent can be water, ethanol, or a combination thereof.

[0215] At this point, the mixing ratio of the silicon-carbon composite and the polymer solution can be appropriately adjusted so that the above-mentioned polymer content and the mixing ratio of polyvinyl alcohol and polyacrylic acid can be achieved in the manufactured negative electrode active material (iii).

[0216] According to the heat treatment process, a condensation reaction occurs between the OH groups of polyvinyl alcohol and the COOH groups of polyacrylic acid. As a result, polyvinyl alcohol and polyacrylic acid can be crosslinked to form a crosslinked polymer.

[0217] In this embodiment, the heat treatment process can be performed at 150°C to 200°C. When the heat treatment process is performed within the above temperature range, condensation reaction (i.e., crosslinking reaction) can easily occur, thereby promoting the formation of crosslinked polymers.

[0218] The heat-treated product then undergoes a grading process. This grading process can be performed using sieves to make the span values ​​of the negative electrode active material (iii) (defined by Equation 2 above) 1.1 to 1.6. For example, the grading process can be performed to obtain negative electrode active material (iii) with a particle size that makes the span values ​​of D10, D50, and D90 obtained by the negative electrode active material (iii) 1.1 to 1.6.

[0219] 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 dry negative electrode plate may also include a negative electrode active material (a fourth negative electrode active material) that is different from the first to the third negative electrode active materials described above.

[0220] The fourth negative electrode active material may further include materials capable of reversibly inserting / deintercalating lithium ions, lithium metal, lithium and metal alloys, materials capable of doping and dedoping lithium, or transition metal oxides.

[0221] Materials capable of reversibly inserting / deintercalating lithium ions can include carbon-based negative electrode active materials, such as crystalline carbon, amorphous carbon, or combinations thereof. Examples of crystalline carbon include graphite (such as amorphous, plate-like, sheet-like, or quasi-sheet-like, spherical, or fibrous natural or synthetic graphite), and examples of amorphous carbon include soft or hard carbon, mesophase pitch carbides, calcined coke, etc.

[0222] As an alloy of lithium and a metal, 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 can be used.

[0223] As a material capable of doping / dedoping lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material can be used. The Si-based negative electrode active material can be silicon, a silicon-carbon composite, SiO x (0 < x ≤ 2), a Si-Q alloy (where Q is 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 a combination thereof. The Sn-based negative electrode active material can be Sn, SnO2, a Sn-based alloy, or a combination thereof.

[0224] The silicon-carbon composite can be a composite of silicon and amorphous carbon. According to an embodiment, the silicon-carbon composite can be in the form of silicon particles whose surfaces are coated with amorphous carbon. For example, the silicon-carbon composite can include secondary particles (cores) assembled from silicon primary particles and an amorphous carbon coating (shell) provided on the surface of the secondary particles. The amorphous carbon can be provided between the silicon primary particles, for example, such that the silicon primary particles can be coated with amorphous carbon. The secondary particles can be dispersed in an amorphous carbon matrix.

[0225] 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 provided on the surface of the core.

[0226] The Si-based negative electrode active material or the Sn-based negative electrode active material can be used in combination with a carbon-based negative electrode active material.

[0227] Binder The dry negative electrode plate for a rechargeable lithium battery can include a first binder.

[0228] There is no particular limitation on including the first binder as long as it is fibrillatable in the manufacture of the following dry electrode film. Fibrillation can refer to the process of dividing a polymer into fine particles. For example, fibrillation can be performed using mechanical shear force or the like. The fibrillated polymer fibers have their surfaces loosened to produce a large number of fine fibers, and the produced fine fibers entangle the negative electrode active material and / or the following conductive material to manufacture the dry electrode film.

[0229] In embodiments, the first adhesive may include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyolefins, or mixtures thereof. In embodiments, the first adhesive may include polytetrafluoroethylene, and in embodiments, it may be polytetrafluoroethylene. In embodiments, based on the total weight of the first adhesive, it may include one or more of polytetrafluoroethylene and polyvinylidene fluoride (PVDF) in an amount of 60% by weight or more (e.g., 90% by weight to 100% by weight, or 100% by weight).

[0230] In an embodiment, the first binder may be included in the dry electrode membrane in a fibrous state.

[0231] In an embodiment, the dry electrode film may include 80% to 99.5% (e.g., 90% to 99.5% by weight) of a negative electrode active material and 0.5% to 20% (e.g., 0.5% to 10% by weight) of a first binder. Within the above range, the manufacture of the dry electrode film can be facilitated, and the fibrous binder can improve the bond strength between the materials constituting the electrode.

[0232] Dry electrode films may also include conductive materials.

[0233] There are no particular limitations on the conductive material, as long as it is conductive and does not cause chemical changes in the battery. For example, graphite (such as natural graphite, artificial graphite, etc.), carbon black compounds (such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, etc.), conductive fibers (such as carbon fibers, metal fibers, etc.), metal powders (such as fluorocarbon compounds, aluminum, nickel powder, etc.), conductive whiskers (such as zinc oxide, potassium titanate, etc.), conductive metal oxides (such as titanium oxide), and conductive materials (such as polyphenylene derivatives, etc.) can be used as conductive materials. In embodiments, to uniformly mix the conductive material and improve its conductivity, the conductive material may include one or more selected from the group consisting of activated carbon, graphite, carbon black, and carbon nanotubes. In embodiments, the conductive material may include activated carbon.

[0234] In an embodiment, the dry electrode film may include 80% to 99% by weight (e.g., 90% to 99.5% by weight) of a negative electrode active material, 0.5% to 20% by weight (e.g., 0.5% to 10% by weight) of a first binder, and 0.5% to 20% by weight (e.g., 0.5% to 10% by weight) of a conductive material. Within the above range, the manufacture of the dry electrode film can be facilitated, and the effect of imparting electrical conductivity can be achieved.

[0235] The negative electrode active material layer also includes a second binder, and the second binder may include a non-fibrous binder. For example, the non-fibrous binder may include one or more selected from polyethylene oxide, polyvinylidene fluoride, and polyvinylidene fluoride-co-hexafluoropropylene.

[0236] Dry electrode films can be manufactured through the following steps: (a) Preparing a powder mixture comprising a negative electrode active material and a binder containing a first binder; (b) Kneading the powder mixture to prepare a mixed material; (c) Grinding the mixture to obtain electrode powder; and (d) The electrode powder is rolled to obtain a film.

[0237] First, the negative electrode active material and a binder including a first binder are mixed to prepare a powder mixture. Mixing is performed such that the negative electrode active material and the binder are uniformly (substantially uniformly) distributed in the mixture. In this case, since the mixture is mixed in powder form, there are no limitations, as long as simple mixing of the above components is permitted. In an embodiment, the mixture is used to manufacture a dry electrode film, and the mixture does not contain a solvent. Mixing can be performed by dry mixing and can be performed, for example, by introducing the material into a device such as a stirrer. The mixture may further include a conductive material.

[0238] In this embodiment, there is no particular limitation on the mixing time, but mixing can be performed from 1 second to 10 minutes. Similarly, there is no particular limitation on the mixing speed, but it can be appropriately controlled within the range of approximately 3000 rpm to 30000 rpm. As an example, the mixture can be prepared by mixing at 5000 rpm to 20000 rpm for 30 seconds to 2 minutes (e.g., mixing at 10000 rpm to 15000 rpm for 30 seconds to 5 minutes) in a mixer to ensure high homogeneity and control the crystallinity of the binder resin.

[0239] Next, a kneading process for fiberizing the binder is performed on the mixture obtained above. Kneading is a process in which the negative electrode active material and / or conductive material are bonded or connected while the binder is fiberized to form a mixture material with a solid content of 100% by weight.

[0240] In an embodiment, the kneading in step (b) can be controlled at a speed of 10 rpm to 100 rpm. For example, the kneading can be controlled at a speed of 40 rpm to 70 rpm. The kneading can be performed for 1 minute to 30 minutes. For example, the kneading can be performed for 3 minutes to 7 minutes at a speed of 40 rpm to 70 rpm. Simultaneously, the kneading can be controlled at a shear rate in the range of 10 / s to 500 / s. In an embodiment of the present invention, the kneading can be performed for 1 minute to 30 minutes, and the shear rate can be controlled in the range of 30 / s to 100 / s.

[0241] Furthermore, the kneading step can be performed under conditions of high temperature and pressure above atmospheric pressure. In one embodiment, kneading of the mixture can be performed at a temperature range of 70°C to 200°C, and in another embodiment, kneading of the mixture can be performed at a temperature range of 90°C to 150°C.

[0242] Furthermore, kneading can be performed at pressures above atmospheric pressure (particularly at pressures between 1 atm and 3 atm), and in the embodiments, at pressures between 1.1 atm and 3 atm. If kneading is performed at very high pressures exceeding the aforementioned range, excessive shear force and pressure may lead to undesirable fiber breakage or excessive increase in the density of the mixture. That is, according to embodiments of the invention, a low-shear mixing process is performed under conditions of high temperature and pressure above atmospheric pressure, rather than a high-shear mixing process, and the intended effects of the invention can be achieved.

[0243] Then, the mixture prepared by the kneading step is refmilled to obtain electrode powder.

[0244] The mixture prepared by kneading can be directly crushed. However, in this case, the mixture can be pressed under high pressure and high temperature, causing it to form a thin film. As a result, there is a problem that the film density becomes too high or a uniform film cannot be obtained. Therefore, according to an embodiment of the invention, the prepared mixture undergoes a grinding step.

[0245] Grinding can be performed using known grinding devices (such as stirrers or grinders), but the invention is not limited thereto. In embodiments of the invention, the grinding speed can be controlled within the range of 3000 rpm to 30000 rpm. In embodiments, the grinding time can be suitably controlled within the range of 1 second to 10 minutes. However, the grinding speed and time are not particularly limited to the above ranges. As an example, grinding can be performed at a speed of 5000 rpm to 20000 rpm for 30 seconds to 10 minutes, or at a speed of 10000 rpm to 18000 rpm for 30 seconds to 5 minutes. When sufficient grinding is performed within the above ranges, film formation can be promoted and the generation of fine particles can be reduced.

[0246] Electrode powder is heated and pressed to form a film. In an embodiment, the electrode powder obtained by performing the grinding steps described above is subjected to a rolling process.

[0247] Electrode powder is processed into a sheet-like film by hot pressing via a rolling process. The rolling process can be performed using a pair of opposing rolling rollers. In embodiments of the invention, the rolling process can be performed by passing the electrode powder through multiple rolling rollers.

[0248] Electrode powder can be pretreated before the rolling process.

[0249] The pretreatment process can be performed by applying heat to the electrode powder, maintaining its temperature at 80°C or higher (in this embodiment, 100°C or higher) for a certain (e.g., predetermined) time period. The pretreatment process can be performed for one minute or longer, and the pretreatment time can be appropriately adjusted according to the amount of powder. For example, the temperature of the electrode powder can be maintained at 80°C or higher for one minute or longer, or at 100°C or higher for one minute or longer. In this embodiment, the heating temperature of the electrode powder is controlled below the melting point of the binder resin to prevent or substantially prevent deterioration of the electrode components (e.g., binder resin) included in the electrode powder. For example, the heating temperature can be controlled below 320°C. The pretreatment process can be performed using conventional heating devices such as convection ovens or infrared heating devices. In this case, it is desirable that the electrode powder does not stagnate during stirring and heating.

[0250] In examples of the present invention, the dry electrode film may have a thickness of 100 μm to 200 μm, but is not particularly limited thereto. For example, the dry electrode film may have a thickness of 100 μm to 150 μm.

[0251] The negative electrode may also include a current collector.

[0252] There are no particular limitations on the current collector, as long as it provides high conductivity without causing chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, copper, copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, or polymer substrates coated with conductive metals such as carbon, nickel, titanium, and silver can be used as current collectors. Current collectors can also have fine irregularities formed on their surface to increase the adhesion of the negative electrode active material, and can be in various forms (such as films, sheets, foils, meshes, porous bodies, foams, nonwoven fabrics, etc.).

[0253] In embodiments of the present invention, the current collector may have a thickness of 10 μm to 50 μm, but the present invention is not particularly limited thereto. For example, the current collector may have a thickness of 10 μm to 20 μm.

[0254] Another embodiment provides a rechargeable lithium battery including a dry negative electrode plate for a rechargeable lithium battery.

[0255] A rechargeable lithium battery may include a dry negative electrode plate and a positive electrode for use in a rechargeable lithium battery. The dry negative electrode plate may be substantially the same as described above.

[0256] positive electrode The positive electrode for a rechargeable lithium-ion 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 a conductive material. For example, the positive electrode may also include additives that can be used as a sacrificial positive electrode.

[0257] Positive electrode active material The positive electrode active material may include compounds capable of intercalating and deintercalating lithium (lithium-intercalating compounds). In embodiments, at least one of lithium and a composite oxide of a metal selected from cobalt, manganese, nickel, and combinations thereof may be used.

[0258] The composite oxide can be a lithium transition metal composite oxide. Examples of composite oxides may include lithium nickel oxides, lithium cobalt oxides, lithium manganese oxides, lithium iron phosphate compounds, cobalt-free lithium nickel manganese oxides, or combinations thereof.

[0259] 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, and 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, and 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, and 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, and 0<α<2); Lia 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, and 0≤e≤0.1); Li a NiG b O2 (0.90≤a≤1.8, and 0.001≤b≤0.1); Li a CoG b O2 (0.90≤a≤1.8, and 0.001≤b≤0.1); Li a Mn 1-b G b O2 (0.90≤a≤1.8, and 0.001≤b≤0.1); Li a Mn2G b O4 (0.90≤a≤1.8, and 0.001≤b≤0.1); Li a Mn 1-g G g PO4 (0.90≤a≤1.8, and 0≤g≤0.5); Li (3-f) Fe2(PO4)3 (0≤f≤2); or Li a FePO4 (0.90≤a≤1.8).

[0260] 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; L 1 It is Mn, Al, or a combination thereof.

[0261] The positive electrode active material can be, for example, a high-nickel positive electrode active material, based on 100 mol% of metals other than lithium in a lithium transition metal complex oxide. 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.

[0262] 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.

[0263] 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 including 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.

[0264] 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 batteries. 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.

[0265] In the embodiments, A1 can be used as a current collector, but this disclosure is not limited thereto.

[0266] Rechargeable lithium batteries may also include an electrolyte.

[0267] electrolyte Electrolytes used in rechargeable lithium batteries may include non-aqueous organic solvents and lithium salts.

[0268] Non-aqueous organic solvents can be used as media for transporting ions that participate in the electrochemical reactions of a battery.

[0269] Non-aqueous organic solvents can be carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, aprotic solvents, or combinations thereof.

[0270] 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.

[0271] 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.

[0272] 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., and aprotic solvents may include: nitriles, such as R-CN (wherein R is a C2 to C20 straight-chain, branched, or cyclic hydrocarbon group, and may include double bonds, aromatic rings, or ether bonds, etc.); amides, such as dimethylformamide; dioxolane, such as 1,3-dioxolane, 1,4-dioxolane, etc.; sulfolane, etc.

[0273] Non-aqueous organic solvents can be used alone or in combination of two or more.

[0274] In the embodiments, when using carbonate solvents, 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.

[0275] Lithium salts dissolved in organic solvents supply lithium ions in batteries, enabling basic operation of rechargeable lithium batteries and improving lithium ion transport between the positive and negative electrodes. Examples of lithium salts include 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).

[0276] Rechargeable lithium batteries may also include a separator.

[0277] diaphragm Depending on the type of rechargeable lithium battery, a separator may be present between the positive and negative electrodes. The separator may include multilayer membranes of polyethylene, polypropylene, polyvinylidene fluoride, or two or more layers thereof, and may include mixed multilayer membranes such as polyethylene / polypropylene bilayer membranes, polyethylene / polypropylene / polyethylene trilayer membranes, polypropylene / polypropylene / polypropylene trilayer membranes, etc.

[0278] The membrane may include a porous substrate and a coating on one or both (or opposite) surfaces of the porous substrate, comprising organic materials, inorganic materials, or combinations thereof.

[0279] The porous substrate can be a polymer film formed from any one of polyolefins (such as polyethylene and polypropylene), polyesters (such as polyethylene terephthalate and polybutylene terephthalate), polyacetal, polyamide, polyimide, polycarbonate, polyetherketone, polyaryletherketone, polyetherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene ether, cyclic olefin copolymers, polyphenylene sulfide, polyethylene naphthalate, glass fiber and polytetrafluoroethylene (e.g., TEFLON) or copolymers or mixtures of two or more of them.

[0280] Organic materials may include polymers such as polyvinylidene fluoride or (meth)acrylic acid polymers.

[0281] 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.

[0282] Organic and inorganic materials can be mixed in a coating, or coatings containing organic materials and coatings containing inorganic materials can be stacked.

[0283] Rechargeable lithium batteries Rechargeable lithium batteries can be classified according to their shape, such as cylindrical, prismatic, pouch, or coin-shaped batteries.

[0284] Figures 5 to 8 This is a schematic diagram illustrating a rechargeable lithium battery according to some embodiments. Figure 5 A cylindrical battery is shown; Figure 6 A prismatic battery is shown; and Figure 7 and Figure 8 A pouch-type battery is shown. (See reference) Figures 5 to 8The 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 5 As shown, the rechargeable lithium battery 100 may include a sealing member 60 of the sealed housing 50. (As illustrated...) Figure 6 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 7 and Figure 8 As shown, the rechargeable lithium battery 100 may include electrode terminals 70, which serve as electrical paths for inducing 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.

[0285] 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 electrical devices.

[0286] Electronic devices or electric vehicles may include rechargeable lithium batteries.

[0287] Examples and comparative examples of the present invention will be described herein. However, it will be understood that the following examples are provided as examples of the present invention and are not intended to limit the present invention.

[0288] 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 spherical secondary particles with an average particle size D50 of 7 μm using a spheroidizing device. Pitch carbon was added to the secondary particles, mixed, and then heat-treated in a sintering 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.

[0289] (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, BET specific surface area: 1.5m²) was used. 2 / g, and orientation degree: 100) as the active material for the second negative electrode. Artificial graphite is a secondary particle assembled from primary particles.

[0290] (3) Preparation of negative electrode active material (i) in the third negative electrode active material Silicon nanoparticles (aspect ratio: 5, and average particle size: approximately 100 nm) and petroleum asphalt (amorphous carbon) were mixed in isopropanol solvent at a weight ratio of 70:30 and dispersed using a homogenizer to prepare a dispersion. The prepared dispersion was sprayed at 120 °C using a spray dryer. The resulting spray-dried product (precursor) was pressurized to 50 MPa using a powder press and then heat-treated in a furnace at 1000 °C under N2 atmosphere to produce a reaction product comprising a core containing amorphous carbon and silicon nanoparticles, and a coating of amorphous carbon formed on the surface of the core. The resulting reaction product was ground and classified using a 325-mesh sieve to prepare a third negative electrode active material (i.e., negative electrode active material (i)) (C-1).

[0291] The prepared third negative electrode active material has the following characteristics: a total pore volume of 2.95 × 10⁻⁶ pores with a size of 200 nm or smaller. -2 cm 3 / g; the interparticle distance between silicon nanoparticles is 65nm; the average particle size D50 is 8.3μm. The interparticle distance between silicon nanoparticles was determined by analyzing the cross-section of the silicon nanoparticles using TEM and calculating the distance between the centers of the silicon nanoparticles. Pore volume was determined by placing silicon nanoparticles into a porosity measuring device (device name: ASAP series, manufacturer: Micromeritics Instrument Corp), heating the silicon nanoparticles to 623K at 10K / min, and pretreating the silicon nanoparticles for 2 to 10 hours (vacuum pressure: 100mmHg or less), and then applying a relative pressure (P / P o The pore volume is measured in liquid nitrogen with a relative pressure controlled to 0.01 or less. Specifically, it is measured by nitrogen adsorption at 32 points with a relative pressure of 0.01 to 0.995, followed by nitrogen desorption at 24 points with a relative pressure of 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.

[0292] (4) Mix 47% by weight of the first negative electrode active material, 47% by weight of the second negative electrode active material and 6% by weight of the third negative electrode active material to prepare a mixture of negative electrode active materials.

[0293] 98.5% by weight of the prepared negative electrode active material mixture and 1.5% by weight of polytetrafluoroethylene (PTFE) (D-1) as a binder were placed in a solvent-free mixer and mixed at 10,000 rpm for 1 minute to obtain a mixture. The obtained mixture was then placed in a kneader and kneaded at 110°C and 60 rpm for 5 minutes to obtain a mixture material. Subsequently, the mixture material was placed in a mixer and ground at 10,000 rpm for 40 seconds to obtain electrode powder. Then, the electrode powder was repeatedly pressed using a rolling roller (roller diameter: 200 mm, roller temperature: 80°C) to obtain a negative electrode active material layer (thickness: 150 μm).

[0294] The negative electrode active material is laminated onto a copper current collector and rolled to manufacture a dry negative electrode plate.

[0295] A half-cell is constructed using a dry negative electrode plate, a lithium metal counter electrode, and an electrolyte. The electrolyte is a mixed solvent (volume ratio 3:7) of ethylene carbonate and dimethyl carbonate in which 1 M of LiPF6 is dissolved.

[0296] Example 2 Except for changing 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 manufacture a dry negative electrode plate and a half-cell in the same manner as in Example 1.

[0297] Example 3 Except for changing 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 manufacture a dry negative electrode plate and a half-cell in the same manner as in Example 1.

[0298] Examples 4 to 6 Except for changing the weight ratio of each component in Example 1 as shown in Table 1 below, the dry negative electrode plate and half cell are manufactured in the same manner as in Example 1.

[0299] Comparison Example 1 The first negative electrode active material was prepared in the same manner as in Example 1, except that pitch carbon was not added when preparing the first negative electrode active material in Example 1. A dry negative electrode plate and a half-cell were then manufactured using the prepared first negative electrode active material in the same manner as in Example 1.

[0300] Comparison Example 2 Flake-shaped natural graphite raw material with an average particle size D50 of 120 μm or greater was ground into fine primary particles with a long axis 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. Pitch carbon was added to the secondary particles, mixed, and then heat-treated in a sintering furnace at 1200 °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.

[0301] The prepared first negative electrode active material was used to manufacture the dry negative electrode plate and half cell in the same manner as in Example 1.

[0302] Comparison Example 3 Flake-shaped natural graphite raw material with an average particle size D50 of 80 μm was ground into primary particles with a long axis 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. Pitch carbon was added to the secondary particles, mixed, and then heat-treated in a sintering furnace at 1200 °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.

[0303] The prepared first negative electrode active material was used to manufacture the dry negative electrode plate and half cell in the same manner as in Example 1.

[0304] Compare Example 4 Except that silicon oxide (C-2) is used instead of the third negative electrode active material in Example 1, the dry negative electrode plate and half cell are manufactured in the same manner as in Example 1.

[0305] Compare Example 5 The dry negative electrode plate and half cell are manufactured in the same manner as in Example 1, except that 1.5% by weight of styrene-butadiene rubber (D-2) is used instead of polytetrafluoroethylene (PTFE) as a binder in Example 1.

[0306] (Experimental Example 1): Evaluation of the active material of the first negative electrode Particle density (unit: g / cc) The agglomerate density was measured using a CARVER 4350.L agglomerate density meter. The agglomerate density was measured as the density of the powder by placing 1.0 g of the first negative electrode active material from each of the example and comparative examples into a mold and holding the first negative electrode active material under a pressure of 2.0 tons for 30 seconds.

[0307] Orientation degree: Orientation was measured using a PANalytical's X'Pert Pro as an XRD analysis apparatus. For each of the first negative electrode active materials in the example and comparative examples, 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, was calculated.

[0308] d002 (unit: Å) d002 was measured using a PANalytical's X'Pert Pro as an XRD analysis apparatus. For each of the first negative electrode active materials in the example and comparative examples, the interplanar spacing of the (002) plane was measured using Cu Kα X-ray diffraction analysis.

[0309] Sphericity: Sphericity was measured using a Malvern Morphologi 4 as a sphericity analyzer. For each of the first negative electrode active materials in the example and comparative examples, the values ​​of A and B in Equation 1 were calculated, and then the sphericity was calculated according to Equation 1.

[0310] Mercury cumulative pore volume (unit: mL / g) For each of the first negative electrode active materials in the example and comparative examples, the cumulative pore volume of mercury was measured using a Mercury intrusion porosimetry (Micromeritics, AutoPoreV). The first negative electrode active material was placed in a dedicated sample cup and surrounded by mercury, and a pressure ranging from 0.2 psi to 60,000 psi was applied to force the mercury into the negative first electrode active material. The mercury porosity was then measured by measuring the volume change of the mercury as it decreased in the capillary rod reservoir. Pore sizes that can be measured in this way range from 0.01 μm to 100 μm. In the first negative electrode active material, pores with a pore size of 0.01 μm to 5 μm are typically defined as pores in the first negative electrode active material.

[0311] (Experimental Example 2) Evaluation of Battery Characteristics The manufactured half-cells were charged and discharged at 0.1C to measure their charge and discharge capacities. The measured discharge capacities are shown in Table 1 below. Additionally, the coulombic efficiency (discharge capacity / charge capacity × 100%) was measured.

[0312] The manufactured half-cell was subjected to one cycle of constant current (CC) / constant voltage (CV) charging and discharging at 0.2C, one cycle of CC charging and discharging at 0.5C, one cycle of CC charging and discharging at 0.2C, and one cycle of CC charging and discharging at 1C, and then the charging characteristics were calculated. The charging conditions were: 10mV cutoff for the CC phase; 15 hours cutoff for the CV phase; and a 1.5V cutoff for the discharging phase. Charging characteristics were measured at each C rate. The charging characteristics were expressed as the ratio of the 2C CC charging capacity to the 0.2C CC charging capacity.

[0313] Energy density (unit: Wh / L): (Battery discharge capacity (Ah) × Average battery voltage (V)) / Battery volume (L) Energy density is a value obtained by multiplying the discharge capacity calculated by discharging the battery at a C-rate of 0.1C to 1C within its operating voltage range by the average voltage of the corresponding single cell, and then dividing the volume of the single cell.

[0314] Boost charging time (in seconds): Boost charging time refers to the time taken to charge 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.

[0315] Boost charging life (unit: cycles): Once the boost charging time is determined, the large battery is evaluated for one cycle: charging from 8% SOC to 80% SOC and discharging at a discharge voltage of 2.8V and a constant current of 0.33C until SOH reaches 80%.

[0316] Table 1

[0317] *Weight ratio: First negative electrode active material : Second negative electrode active material : Third negative electrode active material.

[0318] The effectiveness of boost charging is evaluated by combining boost charging time and boost charging life.

[0319] As shown in Table 1 above, the example negative electrode active material for rechargeable lithium batteries provides high energy density and has a short boost charging time and a long boost charging lifetime, thereby providing full boost charging performance.

[0320] However, as shown in Table 1 above, the negative electrode active material of the comparative example does not meet the composition of the present invention, and it can be seen that because these negative electrode active materials have a long boost charging time and a short boost charging lifetime, the boost charging effect is significantly lower than that of the example.

[0321] Example 7 (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 spherical secondary particles with an average particle size D50 of 7 μm using a spheroidizing device. Pitch carbon was added to the secondary particles, mixed, and then heat-treated in a sintering 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.

[0322] (2) Artificial graphite (spherical, average particle size D50: 15μm, agglomerate density: 1.5g / cc, tap density: 0.9g / cc, BET specific surface area: 1.5m²) was used. 2 / g, and orientation degree: 100) as the active material for the second negative electrode. Artificial graphite is a secondary particle assembled from primary particles.

[0323] (3) Artificial graphite with an average particle size D50 of 3 μm to 5 μm and an aspect ratio of 4 to 10, silicon nanoparticles with an average particle size D50 of 100 nm, and petroleum asphalt as amorphous carbon were mixed in a weight ratio of 20:40:40 and dispersed in isopropanol solvent, and then dispersed using a homogenizer to prepare a dispersion. The dispersion was spray-dried at 120 °C using a spray dryer. The resulting spray-dried product was heat-treated in a furnace at 1000 °C under a nitrogen atmosphere to form a silicon-carbon composite (core) of artificial graphite and silicon particles and an amorphous carbon coating formed on the surface of the core. The resulting product was ground and graded through a 400-mesh sieve to prepare a third negative electrode active material (i.e., negative electrode active material (ii)) (C-1), which has a silicon-carbon composite (core) of artificial graphite and silicon particles and an amorphous carbon coating formed on the surface of the core.

[0324] The third negative electrode active material comprises a composite of silicon and artificial graphite (core) and amorphous carbon (shell) formed on the surface of the core. The silicon particle to artificial graphite weight ratio in the third negative electrode active material is 50:50, the amorphous carbon coating thickness is 30 nm, and the aspect ratio of the third negative electrode active material is 1 to 2.5. The third negative electrode active material contains 40% by weight artificial graphite, 40% by weight silicon particles, and 20% by weight amorphous carbon.

[0325] (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.

[0326] 98.5% by weight of the prepared negative electrode active material mixture and 1.5% by weight of polytetrafluoroethylene (PTFE) as a binder were placed in a solvent-free mixer and mixed at 10,000 rpm for 1 minute to obtain a mixture. The obtained mixture was then placed in a kneader and kneaded at 110°C and 60 rpm for 5 minutes to obtain a mixture material. Subsequently, the mixture material was placed in a mixer and ground at 10,000 rpm for 40 seconds to obtain electrode powder. Then, the electrode powder was repeatedly pressed using a rolling roller (roller diameter: 200 mm, roller temperature: 80°C) to obtain a negative electrode active material layer (thickness: 150 μm).

[0327] The negative electrode active material is laminated onto a copper current collector and rolled to manufacture a dry negative electrode plate.

[0328] A half-cell is constructed using a dry negative electrode plate, a lithium metal counter electrode, and an electrolyte. The electrolyte is a mixed solvent (volume ratio 3:7) of ethylene carbonate and dimethyl carbonate in which 1 M of LiPF6 is dissolved.

[0329] Example 8 Except for changing the spheroidization conditions in Example 7, the first negative electrode active material was prepared in the same manner as in Example 7. The prepared first negative electrode active material was used to manufacture a dry negative electrode plate and a half-cell in the same manner as in Example 7.

[0330] Example 9 Except for changing the spheroidization conditions in Example 7, the first negative electrode active material was prepared in the same manner as in Example 7. The prepared first negative electrode active material was used to manufacture a dry negative electrode plate and a half-cell in the same manner as in Example 7.

[0331] Example 10 and Example 11 Except for changing the weight ratio of each component as shown in Table 2 below, the dry negative electrode plate and half cell are manufactured in the same manner as in Example 7.

[0332] Comparison Example 6 The first negative electrode active material is prepared in the same manner as in Example 7, except that pitch carbon is not added when preparing the first negative electrode active material in Example 7. A dry negative electrode plate and a half-cell are then manufactured using the prepared first negative electrode active material in the same manner as in Example 7.

[0333] Compare Example 7 Flake-shaped natural graphite raw material with an average particle size D50 of 120 μm or greater was ground into fine primary particles with a long axis 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. Pitch carbon was added to the secondary particles, mixed, and then heat-treated in a sintering furnace at 1200 °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.

[0334] The prepared first negative electrode active material is used to manufacture the dry negative electrode plate and half cell in the same manner as in Example 7.

[0335] Compare Example 8 Except that silicon oxide (C-2) is used instead of the third negative electrode active material in Example 7, the dry negative electrode plate and half cell are manufactured in the same manner as in Example 7.

[0336] (Experimental Example 3): Evaluation of the active material of the first negative electrode Aggregate density (g / cc); orientation; d002 (Å); sphericity; and mercury cumulative pore volume (mL / g) were measured in the same manner as in Experimental Example 1.

[0337] (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. In addition, the coulombic efficiency (discharge capacity / charge capacity × 100%) was measured.

[0338] The manufactured half-cell was subjected to one cycle of constant current (CC) / constant voltage (CV) charging and discharging at 0.2C, one cycle of CC charging and discharging at 0.5C, one cycle of CC charging and discharging at 0.2C, and one cycle of CC charging and discharging at 1C, and then the charging characteristics were calculated. Here, the charging conditions were: 10mV cutoff for the CC phase; 15 hours cutoff for the CV phase; and a 1.5V cutoff for the discharging phase. Charging characteristics were measured at each C rate. The charging characteristics were expressed as the ratio of the 2C CC charging capacity to the 0.2C CC charging capacity.

[0339] DC internal resistance (DC-IR, unit: Ω) Half-cells manufactured according to the example and comparative examples underwent a single charge / discharge cycle under the following conditions: charging at 0.2C with constant current / constant voltage (CC / CV) and a cutoff condition of 10mV and 0.01C; resting for 10 minutes; discharging at 0.2C with constant current (CC) and a cutoff condition of 1.5V; and resting for 10 minutes. Subsequently, the voltage drop (V) was measured when a 3C current was allowed to flow for 1 second at SOC50 (the state where the battery is charged to 50% of its capacity when its total charge capacity is 100%; meaning the battery is discharged to 50% when considered as a discharge state). The resistance value was calculated from the measured voltage and the applied current (3C), and the result was expressed as DC internal resistance (DC-IR).

[0340] Rion (unit: Ω): A symmetrical cell was fabricated using a dry negative electrode plate to measure the EIS, from which the Rion could be calculated using the Nyquist plot.

[0341] Energy density (unit: Wh / L): (Battery discharge capacity (Ah) × Average battery voltage (V)) / Battery volume (L) Energy density is a value obtained by multiplying the discharge capacity calculated by discharging the battery at a C-rate of 0.1C to 1C within its operating voltage range by the average voltage of the corresponding single cell, and then dividing the volume of the single cell.

[0342] Boost charging time (in seconds): Boost charging time refers to the time taken to charge 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.

[0343] Boost charging life (unit: cycles): Once the boost charging time is determined, the large battery is evaluated for one cycle: charging from 8% SOC to 80% SOC and discharging at a discharge voltage of 2.8V and a constant current of 0.33C until SOH reaches 80%.

[0344] Table 2

[0345] *In Table 2, C-1: Third negative electrode active material (i.e., negative electrode active material (ii)) C-2: Silicon oxide D-1: PTFE Weight ratio: Based on 100 parts by weight of negative electrode active material, the ratio of first negative electrode active material to second negative electrode active material to third negative electrode active material.

[0346] As shown in Table 2 above, the dry negative electrode plate can provide boost charging effect because it has a short boost charging time and a long boost charging life. Furthermore, the dry negative electrode plate can increase the reliability of battery performance because it exhibits a long life and high energy density.

[0347] However, as shown in Table 2 above, the dry negative electrode plates of Comparative Examples 6 and 7, which do not include the first negative electrode active material of the present invention, have either a long boost charging time or a short boost charging lifetime, and therefore cannot provide a boost charging effect. Furthermore, the dry negative electrode plate of Comparative Example 8, which does not include the third negative electrode active material of the present invention, has a low energy density.

[0348] Example 12 (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 spherical secondary particles with an average particle size D50 of 7 μm using a spheroidizing device. Pitch carbon was added to the secondary particles, mixed, and then heat-treated in a sintering 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.

[0349] (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, BET specific surface area: 1.5m²) was used. 2 / g, and orientation degree: 100) as the active material for the second negative electrode. Artificial graphite is a secondary particle assembled from primary particles.

[0350] (3) Preparation of the negative electrode active material (iii) of the third negative electrode active material Silicon particles with an average particle size of 8 μm were ball-milled to produce primary particles with an average particle size D50 of 100 nm. The primary particles were mixed with stearic acid at a weight ratio of 20:80, and the resulting mixture was spray-dried to prepare secondary particles with an average particle size D50 of 7 μm and including pores.

[0351] The prepared secondary particles and petroleum asphalt were mixed at a weight ratio of 60:40, and the resulting mixture was subjected to compression molding at a pressure of 10 MPa using cold isostatic pressing. Subsequently, the resulting compression-molded product was carbonized at a temperature of 1000°C under a nitrogen atmosphere.

[0352] Next, the carbonized products were subjected to a classification process using a sieve to achieve a span value of 1.1 in Equation 2 above, thereby preparing the third negative electrode active material (i.e., negative electrode active material (iii)) (C-1). The third negative electrode active material (i.e., negative electrode active material (iii)) (C-1) is a silicon-carbon composite, which comprises secondary particles with an average particle size D50 of 7 μm assembled from primary silicon particles coated with 30 nm thick soft carbon and having an average particle size D50 of 100 nm, and a soft carbon coating coated with the secondary particles. At this time, based on the total weight of the third negative electrode active material, the content of silicon nanoparticles is 60% by weight, and the content of soft carbon is 40% by weight. In addition, the D10, D50, and D90 of the third negative electrode active material were measured using a particle analyzer (trade name: LS 13 320, manufacturer: Beckman Coulter), and the span value of Equation 2 above was calculated.

[0353] Furthermore, the sphericity was calculated from the cross-sectional images measured by CP-SEM using the ImageJ program, and a sphericity of 0.98 was obtained. Additionally, the total pore volume and mesopore volume of the fabricated third negative electrode active material were measured using a Barrett-Joyner-Halenda (BJH) analytical apparatus.

[0354] The BJH measurement is performed using a BJH (model name: ASAP 2020, manufacturer: Micromeritics) analytical apparatus by measuring the adsorption / desorption of the third negative electrode active material adsorbed on the sample according to the pressure change while using nitrogen gas at a temperature of -198°C to change the pressure from 0 mHg to 950 mmHg.

[0355] The prepared third negative electrode active material has a sphericity of 0.98, a mesopore volume / total pore volume ratio of 68%, and a micropore size of 0.8 μm. 2 Specific surface area per g, 0.007 cm² 3 The total pore volume of BJH is / g, the D10 is 4.7μm, the D50 is 8.2μm, and the D90 is 13.7μm.

[0356] (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.

[0357] 98.5% by weight of the prepared negative electrode active material mixture and 1.5% by weight of polytetrafluoroethylene (PTFE) (D-1) as a binder were placed in a solvent-free mixer and mixed at 10,000 rpm for 1 minute to obtain a mixture. The obtained mixture was then placed in a kneader and kneaded at 110°C and 60 rpm for 5 minutes to obtain a mixture material. Subsequently, the mixture material was placed in a mixer and ground at 10,000 rpm for 40 seconds to obtain electrode powder. Then, the electrode powder was repeatedly pressed using a rolling roller (roller diameter: 200 mm, roller temperature: 80°C) to obtain a negative electrode active material layer (thickness: 150 μm).

[0358] The negative electrode active material is laminated onto a copper current collector and rolled to manufacture a dry negative electrode plate.

[0359] A half-cell is constructed using a dry negative electrode plate, a lithium metal counter electrode, and an electrolyte. The electrolyte is a mixed solvent (volume ratio 3:7) of ethylene carbonate and dimethyl carbonate in which 1 M of LiPF6 is dissolved.

[0360] Example 13 Except for changing the spheroidization conditions in Example 12, the first negative electrode active material was prepared in the same manner as in Example 12. The prepared first negative electrode active material was used to manufacture a dry negative electrode plate and a half-cell in the same manner as in Example 12.

[0361] Examples 14 and 15 Except for changing the weight ratio of the components in Example 12 as shown in Table 3 below, the dry negative electrode plate and half cell are manufactured in the same manner as in Example 12.

[0362] Compare Example 9 Flake-shaped natural graphite raw material with an average particle size D50 of 120 μm or greater was ground into fine primary particles with a long axis 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. Pitch carbon was added to the secondary particles, mixed, and then heat-treated in a sintering furnace at 1200 °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.

[0363] The prepared first negative electrode active material was used to manufacture the dry negative electrode plate and half cell in the same manner as in Example 12.

[0364] Compare Example 10 Flake-shaped natural graphite raw material with an average particle size D50 of 80 μm was ground into primary particles with a long axis 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. Pitch carbon was added to the secondary particles, mixed, and then heat-treated in a sintering furnace at 1200 °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.

[0365] The prepared first negative electrode active material was used to manufacture the dry negative electrode plate and half cell in the same manner as in Example 12.

[0366] Compare Example 11 Except that silicon oxide (C-2) is used instead of the third negative electrode active material in Example 12, the dry negative electrode plate and half cell are manufactured in the same manner as in Example 12.

[0367] (Experimental Example 5): Evaluation of the active material of the first negative electrode Aggregate density (g / cc); orientation; d002 (Å); sphericity; and mercury cumulative pore volume (mL / g) were measured in the same manner as in Experimental Example 1.

[0368] (Experimental Example 6) 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 3 below. In addition, the coulombic efficiency (discharge capacity / charge capacity × 100%) was measured.

[0369] The manufactured half-cell was subjected to one cycle of constant current (CC) / constant voltage (CV) charging and discharging at 0.2C, one cycle of CC charging and discharging at 0.5C, one cycle of CC charging and discharging at 0.2C, and one cycle of CC charging and discharging at 1C, and then the charging characteristics were calculated. Here, the charging conditions were: 10mV cutoff for the CC phase; 15 hours cutoff for the CV phase; and a 1.5V cutoff for the discharging phase. Charging characteristics were measured at each C rate. The charging characteristics were expressed as the ratio of the 2C CC charging capacity to the 0.2C CC charging capacity.

[0370] Energy density (unit: Wh / L): (Battery discharge capacity (Ah) × Average battery voltage (V)) / Battery volume (L) Energy density is a value obtained by multiplying the discharge capacity calculated by discharging the battery at a C-rate of 0.1C to 1C within its operating voltage range by the average voltage of the corresponding single cell, and then dividing the volume of the single cell.

[0371] Efficiency (unit: %) Efficiency is calculated using the same method as for capacity and charge rate characteristics. Efficiency is calculated as: First cycle discharge capacity / First cycle charge capacity × 100% (Mars discharge / Mars charge × 100%).

[0372] Boost charging time (in seconds): Boost charging time refers to the time taken to charge 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.

[0373] Boost charging life (unit: cycles): Once the boost charging time is determined, the large battery is evaluated for one cycle: charging from 8% SOC to 80% SOC and discharging at a discharge voltage of 2.8V and a constant current of 0.33C until SOH reaches 80%.

[0374] Expansion rate (unit: %) Expansion rate was measured using the Thickness Monitoring System (TMS) method.

[0375] With a charging voltage of 4.35V and a discharging voltage of 2.8V, the thickness of batteries manufactured according to the example and comparative examples was evaluated in real time during charging / discharging (0.5C / 0.5C) at 45°C to evaluate the increase in thickness after 50 cycles compared to the thickness after 1 cycle.

[0376] Expansion rate = (Battery thickness after 50 cycles - Battery thickness after 1 cycle) / Battery thickness after 1 cycle × 100% Table 3

[0377] *In Table 3, C-1: Silicon-carbon composite C-2: Silicon oxide Weight ratio: Based on 100 parts by weight of negative electrode active material, the ratio of first negative electrode active material to second negative electrode active material to third negative electrode active material.

[0378] As shown in Table 3 above, it can be seen that the example dry negative electrode plate for rechargeable lithium batteries has high energy density, high charge rate (C-rate), high efficiency, short boost charging time, long boost charging lifetime, and low expansion rate. Therefore, the example dry negative electrode plate provides (e.g., simultaneously) high energy density, long lifetime, boost charging performance, and improved expansion characteristics.

[0379] On the other hand, the dry negative electrode plates of Comparative Examples 9 and 10, which do not include the first negative electrode active material of the present invention, have short boost charging lifetime, low energy density, and low charge rate (C-rate). Comparative Example 11, which does not include the third negative electrode active material of the present invention, has low energy density and high expansion rate.

[0380] The dry negative electrode plate for rechargeable lithium batteries described in the example can provide high energy density, boost charging efficiency, long lifespan, and improved expansion characteristics, thus exhibiting excellent rechargeable lithium battery performance.

[0381] Although some embodiments of the invention have been described above, the invention is not limited thereto. Therefore, it will be understood that various changes and modifications can be made within the scope of the claims, the detailed description of the invention, and the accompanying drawings, and such changes and modifications also fall within the scope of the invention.

Claims

1. A dry negative electrode plate for a rechargeable lithium battery, the dry negative electrode plate comprising a negative electrode active material and a binder, in, 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. The first negative electrode active material comprises: natural graphite, including secondary particles arranged in a primary particle configuration; and a coating surrounding the secondary particles and comprising amorphous carbon, wherein the first negative electrode active material has an orientation degree of 90 degrees or less, and the first negative electrode active material has a d002 of 3.356 Å to 3.360 Å. The second negative electrode active material includes graphite. The third negative electrode active material includes one or more of the following: The negative electrode active material (i) includes a core comprising silicon nanoparticles and amorphous carbon, and an amorphous carbon coating surrounding the core and comprising amorphous carbon. The negative electrode active material (ii) comprises a composite of silicon and crystalline carbon and an amorphous carbon coating comprising amorphous carbon on the surface of the composite; and The negative electrode active material (iii) comprises silicon nanoparticles and an amorphous carbon coating on the surface of the silicon nanoparticles having a sphericity of 0.9 to 1.

0. The adhesive includes polytetrafluoroethylene, polyvinylidene fluoride, polyolefins, or mixtures thereof.

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

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

5. The dry 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 dry negative electrode plate according to claim 1, wherein, The primary particles have a plate-like shape, and the secondary particles have a spherical shape.

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

8. The dry negative electrode plate according to claim 1, wherein, The secondary particles have an average particle size D50 of 30 μm or less.

9. The dry negative electrode plate according to claim 1, wherein, The primary particles have additional amorphous carbon on their surface.

10. The dry negative electrode plate according to claim 1, wherein, Amorphous carbon is one or more of soft carbon, hard carbon, mesophase pitch carbides, and calcined coke.

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

12. The dry negative electrode plate according to claim 1, wherein, The second negative electrode active material comprises artificial graphite, which has an average particle size D50 of 10 μm to 20 μm, a bulk density of 1.1 g / cc to 1.6 g / cc, and a particle size of 10 m... 2 / g or smaller specific surface area and 90 or greater degree of orientation.

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

14. The dry negative electrode plate according to claim 1, wherein, The average particle size D50 of the silicon nanoparticles in the negative electrode active material (i) is in the range of 50 nm to 150 nm.

15. The dry negative electrode plate according to claim 1, wherein, The negative electrode active material (i) has a pore size of 3.0 × 10⁻⁶ for pores with a size of 200 nm or smaller. -2 cm 3 / g or less of total pore volume.

16. The dry negative electrode plate according to claim 1, wherein, Based on a total of 100 parts by weight of silicon nanoparticles and amorphous carbon in the negative electrode active material (i), the silicon nanoparticles and amorphous carbon are included in a weight ratio of 80:20 to 20:

80.

17. The dry negative electrode plate according to claim 1, wherein, The negative electrode active material (ii) has an aspect ratio of 1 to 2.

5.

18. The dry negative electrode plate according to claim 1, wherein, The negative electrode active material (ii) comprises silicon, crystalline carbon, and amorphous carbon in amounts of 20% to 70% by weight, 3% to 50% by weight, and 20% to 50% by weight, respectively.

19. The dry negative electrode plate according to claim 1, wherein, The negative electrode active material (iii) includes pores, and the pores include mesopores.

20. The dry negative electrode plate according to claim 1, wherein, The negative electrode active material (iii) has a ratio of 30% or more and less than 70% of the mesopore volume to the total pore volume of the negative electrode active material (iii).

21. The dry negative electrode plate according to claim 1, wherein, According to the following Equation 2, the negative electrode active material (iii) has a range of values ​​from 1.1 to 1.6: Equation 2 Span = (D90 - D10) / D50 in, D10 indicates that the particle size of the negative electrode active material (iii) has a cumulative volume of 10% in the particle size distribution. D50 indicates that the particle size of the negative electrode active material (iii) has a cumulative volume of 50% in the particle size distribution. D90 indicates that the negative electrode active material (iii) has a cumulative volume of 90% in the particle size distribution.

22. The dry negative electrode plate according to claim 1, wherein, Based on a total of 100% by weight of the negative electrode active material (iii), silicon nanoparticles and amorphous carbon coatings are present in amounts of 55% to 64% by weight and 36% to 45% by weight, respectively.

23. The dry negative electrode plate according to claim 1, wherein, The negative electrode active material (iii) also includes a polymer layer on the amorphous carbon coating.

24. The dry negative electrode plate according to claim 23, wherein, The polymer layer comprises polyvinyl alcohol and polyacrylic acid.

25. The dry negative electrode plate according to claim 1, wherein, The mixture comprises the first negative electrode active material, the second negative electrode active material, and the third negative electrode active material in amounts of 20% to 75% by weight, 20% to 75% by weight, and 1% to 15% by weight, respectively.

26. A rechargeable lithium battery, said rechargeable lithium battery include ： A dry negative electrode plate for a rechargeable lithium battery according to any one of claims 1 to 25; and Positive electrode.

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