Negative electrode, method for manufacturing the same, and electrochemical device including the same

Abstract

Disclosed are a negative electrode, a method for manufacturing the same, and an electrochemical device comprising the same, the negative electrode comprising a current collector; and a negative electrode active material layer on at least one surface of the current collector and including granulated particles and a second binder, where the second binder holds and connects the granulated particles together, where the granulated particles include a negative electrode active material, a conductive material, and a first binder, wherein the first binder connects and holds the negative active material and the conductive material together.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a negative electrode, a method for manufacturing the same, and an electrochemical device including the same.

[0002] This application claims priority to Korean Patent Application No. 10-2023-0101869, filed on August 3, 2023, in Korea, the disclosure of which is incorporated herein by reference. BACKGROUND

[0003] As the use of fossil fuels is increasing, there is a growing demand for the use of alternative and clean energy, and in such circumstances, many studies are being conducted in the field of energy production and storage using electrochemistry. At present, a typical example of an electrochemical device using electrical energy and chemical energy is a secondary battery, and the range of applications of the secondary battery is gradually expanding. The most common secondary battery is a lithium secondary battery, and the lithium secondary battery is not only used as an energy source for mobile devices, but also used as a power source for electric vehicles and hybrid electric vehicles, which are considered to be one of the main causes of air pollution, as an alternative to vehicles using fossil fuels, such as gasoline vehicles and diesel vehicles, and they have a wide range of applications, including use as an auxiliary power source through a power grid.

[0004] The lithium secondary battery has a structure in which an electrode assembly including a positive electrode and a negative electrode each having an active material coating on an electrode current collector and a porous separator interposed between the positive electrode and the negative electrode is impregnated with an electrolyte containing a lithium salt, and an electrode is manufactured by coating a slurry in which an active material, a binder, and a conductive material are dispersed in a solvent on a current collector, drying, and roll-pressing.

[0005] In addition, the basic performance characteristics, capacity, output, and lifespan of the lithium secondary battery are greatly affected by the negative electrode material. In order to maximize the performance of the battery, the negative electrode active material needs to satisfy the requirements that the electrochemical reaction potential is close to lithium metal, the reversibility of the reaction with lithium ions is high, and the diffusion rate of lithium ions in the active material is high.

[0006] The theoretical capacity limit of a carbon-based material, which is mainly used to manufacture a negative electrode of a lithium secondary battery, is 372 mAh / g, which is a factor that hinders an increase in energy density. A silicon-based material is an emerging solution to this problem. The theoretical capacity of silicon is at the level of 4010 mAh / g, and the theoretical capacity of silicon is 10 times or more than that of a carbon-based material. However, the charge / discharge efficiency of a carbon-based material is at the level of 92%, while the charge / discharge efficiency of a silicon-based material is at the level of 80%, and the volume change is 300% or more during charge / discharge. When the conductive path is cut off during continuous charge / discharge, the silicon-based material does not work as an active material.

[0007] To address the problem that the electrical conductivity of silicon-based materials is lower than that of carbon-based materials and the problem that the electrical contact between particles is poor due to large electrode swelling when using silicon-based materials, wire-shaped conductive materials such as carbon nanotubes (CNTs) are additionally used, but addressing the problem of electrode degradation due to uneven dispersion of silicon-based materials and wire-shaped conductive materials remains challenging. SUMMARY

[0008] TECHNICAL PROBLEM

[0009] The present disclosure aims to provide a negative electrode having improved electrical conductivity through improved electrical contact, a method for manufacturing the same, and an electrochemical device including the same.

[0010] TECHNICAL SOLUTION

[0011] To address the above problems, according to one aspect of the present disclosure, a negative electrode of the following embodiments is provided.

[0012] According to a first embodiment,

[0013] A negative electrode is provided, including: a current collector; and

[0014] a negative electrode active material layer located on at least one surface of the current collector and including granulated particles and a second binder, wherein the second binder holds and connects the granulated particles together,

[0015] wherein the granulated particles include a negative electrode active material, a conductive material, and a first binder, wherein the first binder connects and holds the negative electrode active material and the conductive material together.

[0016] According to a second embodiment, in the first embodiment,

[0017] The negative electrode active material can include a single silicon-based active material, or a mixture of a silicon-based active material and a carbon-based active material.

[0018] According to a third embodiment, in the second embodiment,

[0019] The silicon-based active material can include silicon (Si), silicon oxide (SiOx (0 < x ≤ 2), silicon carbide (SiC), or two or more thereof.

[0020] According to a fourth embodiment, in the second or third embodiment,

[0021] The carbon-based active material can include natural graphite, artificial graphite, graphene, or two or more thereof.

[0022] According to a fifth embodiment, in any one of the first to fourth embodiments,

[0023] The conductive material can include linear conductive material, point conductive material, or two or more thereof.

[0024] According to a sixth embodiment, in the fifth embodiment,

[0025] The linear conductive material can include carbon nanotube, carbon nanofiber, graphene, or two or more thereof.

[0026] According to a seventh embodiment, in the fifth embodiment or the sixth embodiment,

[0027] The point conductive material can include carbon black, denka black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, or two or more thereof.

[0028] According to an eighth embodiment, in any one of the first embodiment to the seventh embodiment,

[0029] The first binder can include diene-based polymer, acrylate-based polymer, styrene-based polymer, polyacrylonitrile-based polymer, vinyl-based polymer, polyoxide-based polymer, polyacrylamide, or two or more thereof.

[0030] According to a ninth embodiment, in any one of the first embodiment to the eighth embodiment,

[0031] The second binder can include diene-based polymer, acrylate-based polymer, styrene-based polymer, or two or more thereof.

[0032] According to a tenth embodiment, in any one of the first embodiment to the ninth embodiment,

[0033] The amount of the negative active material can be 80 parts by weight to 99 parts by weight, the amount of the conductive material can be 0.001 parts by weight to 0.5 parts by weight, and the amount of the first binder can be 0.1 parts by weight to 2 parts by weight, based on 100 parts by weight of the granulated particle.

[0034] According to an eleventh embodiment, in any one of the first embodiment to the tenth embodiment,

[0035] The average particle size (D50) of the granulated particle can be 10 μm to 20 μm.

[0036] According to a twelfth embodiment, in any one of the first embodiment to the eleventh embodiment,

[0037] The negative active material can include a mixture of the silicon-based active material and the carbon-based active material, and the amount of the silicon-based active material is 5 parts by weight to 25 parts by weight based on 100 parts by weight of the carbon-based active material.

[0038] According to a thirteenth embodiment, in any one of the first to twelfth embodiments,

[0039] The negative active material layer can further include the additional carbon-based active material, the additional conductive material, or both.

[0040] According to a fourteenth embodiment, in any one of the first to thirteenth embodiments,

[0041] The negative active material layer can include 100 parts by weight of the granulated particle, 80 parts by weight to 99 parts by weight of the additional carbon-based active material, 0.01 parts by weight to 2 parts by weight of the additional conductive material, and 1 part by weight to 4 parts by weight of the second binder.

[0042] According to a fifteenth embodiment,

[0043] A method for manufacturing a negative electrode of any one of the first to fourteenth embodiments is provided, which includes the steps of: drying a composition including a negative active material, a conductive material, a first binder, and a first aqueous dispersion medium by a spray drying method to manufacture a granulated particle;

[0044] mixing the granulated particle with a second binder and a second aqueous dispersion medium to prepare a negative electrode slurry; and

[0045] coating the negative electrode slurry on at least one surface of a current collector, drying, and roll-pressing to form a negative active material layer.

[0046] According to a sixteenth embodiment, in the fifteenth embodiment,

[0047] The negative active material can include the silicon-based active material alone, or a mixture of the silicon-based active material and the carbon-based active material.

[0048] According to a seventeenth embodiment, in the fifteenth or sixteenth embodiment,

[0049] The negative electrode slurry can further include the additional carbon-based active material, the additional conductive material, or both.

[0050] According to an eighteenth embodiment, in any one of the fifteenth to seventeenth embodiments,

[0051] The spray drying method can include spraying and drying the slurry in hot air, and the temperature of the fed hot air can be in the range of 130°C to 210°C.

[0052] According to a nineteenth embodiment,

[0053] Provided is an electrochemical device including the negative electrode of any one of the first to fourteenth embodiments.

[0054] According to a twentieth embodiment, in the nineteenth embodiment,

[0055] The electrochemical device can be a secondary battery.

[0056] Advantages

[0057] According to one embodiment of the present disclosure, by using the granulated particles including the negative electrode active material, the conductive material, and the binder, a negative electrode in which the binder and the conductive material are uniformly dispersed in the negative electrode active material layer can be provided. In particular, when the silicon-based active material is used alone or in combination with the carbon-based active material as the negative electrode active material, the silicon-based active material is uniformly dispersed in the negative electrode active material layer without forming agglomerates in some areas, and in particular, when the silicon-based active material is used in combination with the carbon-based active material, the carbon-based active material and the silicon-based active material can be uniformly dispersed, thereby minimizing volume expansion caused by the silicon-based active material and securing high capacity of the silicon-based active material. Accordingly, it can be possible to significantly improve the battery performance of an electrochemical device such as a secondary battery using the negative electrode. Furthermore, since the granulated particles are particles formed by granulation of fine particles, they can have a rougher surface than graphite particles, and thus the granulated particles having high sphericity in terms of particle shape can prevent the electrode surface from being dented or uneven loading in the electrode coating, and the uniform dispersion effect of the binder can have a beneficial effect on the electrode quality and the electrode coating process efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0058] The accompanying drawings illustrate exemplary embodiments of the present disclosure and, together with the foregoing description, serve to provide a better understanding of the technical aspects of the present disclosure, and therefore, the present disclosure is not to be interpreted as being limited to the accompanying drawings.

[0059] Figure 1 FIG. 1 is a diagram schematically showing a surface portion and a center portion of a granulated particle included in an electrode according to one embodiment of the present disclosure.

[0060] Figure 2 FIG. 2 is a schematic diagram of a negative electrode active material layer formed by a conventional method.

[0061] Figure 3 FIG. 3 is a schematic diagram of a negative electrode active material layer according to one embodiment of the present disclosure. DETAILED DESCRIPTION

[0062] Hereinafter, the present disclosure will be described in greater detail to help the understanding of the present disclosure.

[0063] It should be understood that the terms or words used in the present specification and the appended claims should not be interpreted as being limited to the commonly used meanings and dictionary definitions, but should be interpreted based on the meanings and concepts corresponding to the technical aspects of the present disclosure on the basis of the principle that the inventor is allowed to define the terms appropriately for the best explanation of the present disclosure.

[0064] The terms used herein are used to describe the exemplary embodiments and are not intended to limit the present disclosure. As used herein, the singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0065] It should be further understood that the term "comprises" or "includes" when used in the specification, specifies the presence of stated elements, and does not preclude the presence or addition of one or more other elements, unless otherwise clearly indicated by context.

[0066] In addition, the terms "about" and "substantially" are used herein in the sense of being at or nearly at, given the manufacturing and material tolerances inherent in the circumstances, and to prevent unscrupulous infringers from unfairly exploiting the present disclosure in cases where precise or absolute numbers are stated to help understand the present disclosure.

[0067] In the present specification, 'A and / or B' as used herein means A or B or both.

[0068] The "glass transition temperature Tg" as used herein is measured by a method commonly used in the relevant field, and for example, can be measured by differential scanning calorimetry (DSC).

[0069] The "porosity" as used herein refers to the ratio of the pore volume in the structure with respect to its total volume, and is expressed in vol%, and can be used interchangeably with void fraction, porosity, etc. In the present disclosure, the measurement of porosity is not limited to a specific method, and according to one embodiment of the present disclosure, for example, the porosity can be measured by a Brunauer-Emmett-Teller (BET) measurement method using nitrogen, a Hg porosimeter, and ASTM D-2873. Alternatively, the net density of the partition can be calculated from the density (apparent density) of the partition, the composition ratio of the materials contained in the partition, and the density of each component, and the porosity of the partition can be calculated from the difference between the apparent density and the net density.

[0070] The "average particle size D50" as used herein refers to the particle size at 50% of the cumulative particle size distribution of the particles, and the particle size can be measured using a laser diffraction method. Specifically, the particle size distribution is calculated by dispersing the target powder in a dispersion medium, feeding it to a commercially available laser diffraction particle size measuring device (for example, Microtrac S3500), and measuring the difference in diffraction pattern according to the particle size when the particles pass through a laser beam. The particle size D50 can be measured by calculating the particle diameter at 50% of the cumulative particle size distribution of the particles in the measuring device.

[0071] The "thickness" of each layer included in the electrode as used herein can represent a value measured by a commonly used thickness measurement method. The thickness measurement method is not limited thereto, but the thickness can be, for example, a value measured using a thickness measuring device (Mitutoyo, VL-50S-B).

[0072] The "specific surface area" as used herein can represent a value measured by a known method for measuring the specific surface area. The method for measuring the specific surface area is not limited thereto, but the specific surface area can be, for example, a value measured by a flowable method or a fixed method.

[0073] According to one aspect of the present disclosure,

[0074] A negative electrode can be provided, which includes:

[0075] a negative electrode active material layer located on at least one surface of the current collector and containing granulated particles and a second binder, wherein the second binder holds and connects the granulated particles together,

[0076] wherein the granulated particles contain a negative electrode active material, a conductive material, and a first binder, and the first binder connects and holds the negative electrode active material and the conductive material together.

[0077] <Granulated particles>

[0078] Hereinafter, the granulated particles will be described in detail.

[0079] In the present disclosure, the granulated particles can have the form of composite particles containing a negative electrode active material, a conductive material, and a first binder, and, if necessary, any other component added.

[0080] In one embodiment of the present disclosure, the granulated particles can be secondary particles formed by granulating two or more negative electrode active material particles held together by the first binder. The granulated particles contained in the negative electrode according to one embodiment of the present disclosure can be referred to as powder, granules, or the like.

[0081] Figure 1A surface portion and a center portion of a granulated particle included in a negative electrode of one embodiment of the present disclosure are shown. Reference is made to FIG. 1. Figure 1 In one embodiment of the present disclosure, the amount of the first binder included in the surface portion 102 of the granulated particle can be greater than the amount of the first binder included in the center portion 101 of the granulated particle. The amount of the binder can refer to the weight or the volume.

[0082] Meanwhile or independently from this, the amount (wt%) of the first binder included in the surface portion 102 of the granulated particle (B s / G t ) can be greater than the amount (wt%) of the first binder included in the center portion 101 of the granulated particle (B c / G t ) based on the total weight 100 wt% of the granulated particle. Here, B c represents the weight of the binder included in the center portion, B s represents the weight of the binder included in the surface portion, and G t represents the total weight of the granulated particle.

[0083] Meanwhile or independently from this, the amount (vol%) of the first binder included in the surface portion 102 of the granulated particle (B s / G t ) can be greater than the amount (vol%) of the first binder included in the center portion 101 of the granulated particle (B c / G t ) based on the total volume 100 vol% of the granulated particle. Here, B c represents the volume of the binder included in the center portion, B s represents the volume of the binder included in the surface portion, and G t represents the total volume of the granulated particle.

[0084] Here, the surface portion can refer to a region near the surface of the granulated particle to a predetermined depth in a direction from the surface of the granulated particle toward the center of the granulated particle. The center portion refers to a region other than the surface portion. In one embodiment of the present disclosure, the surface portion can refer to a surface region up to 30% of the radius, particularly inward from the surface of the granulated particle, particularly toward the center of the granulated particle. In one embodiment of the present disclosure, the surface portion can refer to a surface region up to 30%, 20%, 15%, 10%, or 5% of the radius from the surface of the granulated particle. Preferably, the surface portion can refer to a surface region up to 20% of the radius from the surface of the granulated particle.

[0085] Meanwhile, in one embodiment of the present disclosure, the surface portion can refer to a region from the center of the granulated particle up to 70% or more of the radius in the outward direction of the granulated particle, up to the surface of the granulated particle. In one embodiment of the present disclosure, the surface portion can refer to a region, for example, from 80% or more, 85% or more, 90% or more, or 95% or more of the radius up to the surface of the granulated particle.

[0086] In one embodiment of the present disclosure, the center of the granulated particle can refer to a point of 1 / 2 of the longest diameter of the granulated particle. In the present disclosure, the radius can refer to a distance from the center of the granulated particle to each point on the surface of the granulated particle. In one embodiment of the present disclosure, the surface portion and the center portion can be divided based on points at the same distance from each surface of the granulated particle along each radius, specifically, points at 30%, 20%, 10%, 5%, or 1% of the radius from the surface.

[0087] In one embodiment of the present disclosure, in a region from 90% or more of the radius from the center of the granulated particle up to the surface of the granulated particle, the amount of the first binder can be 50% or more, 60% or more, 70% or more, 80% or more, or 90% or more by weight, based on the total weight 100% of the granulated particles in the corresponding region.

[0088] In another embodiment of the present disclosure, in a region from 95% or more of the radius from the center of the granulated particle up to the surface of the granulated particle, the amount of the first binder can be 50% or more, 60% or more, 70% or more, 80% or more, or 90% or more by weight, based on the total weight 100% of the granulated particles in the corresponding region.

[0089] In another embodiment of the present disclosure, in a region from 99% or more of the radius from the center of the granulated particle up to the surface of the granulated particle, the amount of the first binder can be 50% or more, 60% or more, 70% or more, 80% or more, or 90% or more by weight, based on the total weight 100% of the granulated particles in the corresponding region.

[0090] In one embodiment of the present disclosure, in a region from 90% or more of the radius from the center of the granulated particle up to the surface of the granulated particle, the amount of the first binder can be 50% or more, 60% or more, 70% or more, 80% or more, or 90% or more by volume, based on the total volume 100% of the granulated particles in the corresponding region.

[0091] In another embodiment of the present disclosure, in the region from the center of the granulated particle up to 95% or more of the radius of the granulated particle up to the surface of the granulated particle, the amount of the first binder can be 50 vol% or more, 60 vol% or more, 70 vol% or more, 80 vol% or more, or 90 vol% or more, based on 100 vol% of the total volume of the granulated particle in the corresponding region.

[0092] In another embodiment of the present disclosure, in the region from the center of the granulated particle up to 99% or more of the radius of the granulated particle up to the surface of the granulated particle, the amount of the first binder can be 50 vol% or more, 60 vol% or more, 70 vol% or more, 80 vol% or more, or 90 vol% or more, based on 100 vol% of the total volume of the granulated particle in the corresponding region.

[0093] In one embodiment of the present disclosure, in the region from the surface of the granulated particle up to 10% of the radius of the granulated particle, the amount of the first binder can be 50 wt% or more, 60 wt% or more, 70 wt% or more, 80 wt% or more, or 90 wt% or more, based on 100 wt% of the total weight of the granulated particle in the corresponding region.

[0094] In another embodiment of the present disclosure, in the region from the surface of the granulated particle up to 5% of the radius of the granulated particle, the amount of the first binder can be 50 wt% or more, 60 wt% or more, 70 wt% or more, 80 wt% or more, or 90 wt% or more, based on 100 wt% of the total weight of the granulated particle in the corresponding region.

[0095] In another embodiment of the present disclosure, in the region from the surface of the granulated particle up to 1% of the radius of the granulated particle, the amount of the first binder can be 50 wt% or more, 60 wt% or more, 70 wt% or more, 80 wt% or more, or 90 wt% or more, based on 100 wt% of the total weight of the granulated particle in the corresponding region.

[0096] In one embodiment of the present disclosure, in the region from the surface of the granulated particle up to 10% of the radius of the granulated particle, the amount of the first binder can be 50 vol% or more, 60 vol% or more, 70 vol% or more, 80 vol% or more, or 90 vol% or more, based on 100 vol% of the total volume of the granulated particle in the corresponding region.

[0097] In another embodiment of the present disclosure, the amount of the first binder can be 50% or more, 60% or more, 70% or more, 80% or more, or 90% or more by volume, based on 100% by volume of the total volume of the granulated particles in the region of the surface of the granulated particles up to 5% of the radius from the surface of the granulated particles.

[0098] In another embodiment of the present disclosure, the amount of the first binder can be 50% or more, 60% or more, 70% or more, 80% or more, or 90% or more by volume, based on 100% by volume of the total volume of the granulated particles in the region of the surface of the granulated particles up to 1% of the radius from the surface of the granulated particles.

[0099] According to one embodiment of the present disclosure, it is determined that the granulated particle has a surface portion region having a high binder content in a direction toward the center of the particle from the surface to a predetermined depth, and the binder distribution in a region other than the surface portion (i.e., a center portion (core portion) surrounded by the surface portion) can be lower than the surface portion.

[0100] The granulated particle is described in more detail, and the granulated particle can have a center portion including a plurality of negative electrode active materials; and a surface portion located outside all or a part of the center portion and including a first binder to bind the negative electrode active materials. That is, in the center portion of the granulated particle, the plurality of negative electrode active materials can form an agglomerate through surface contact, line contact, point contact, or two or more of these contacts, and in the surface portion of the granulated particle, the first binder can be located outside all or a part of the agglomerate and hold and bind the plurality of negative electrode active materials of the center portion of the granulated particle together.

[0101] According to one embodiment of the present disclosure, the center portion can further include a small amount of the first binder to connect and hold the plurality of negative electrode active materials of the center portion together. However, as described above, the ratio of the amount of the first binder in the surface portion is preferably higher than the ratio of the amount of the first binder of the center portion.

[0102] Meanwhile, in one embodiment of the present disclosure, the aspect ratio of the granulated particles can be 0.5 to 1.0, and preferably 0.75 to 1.0. The aspect ratio can refer to the ratio of the length of the long axis to the length of the short axis of the granulated particles. In another embodiment of the present disclosure, the value of the average aspect ratio of the granulated particles can be 0.5 to 1.0, preferably 0.75 to 1.0, and in this case, the average aspect ratio can refer to the ratio of the average length of the long axis to the average length of the short axis of the granulated particles. In this case, the average length of the short axis can refer to the average value of the length in the axial direction having the shortest length of the granulated particles, and the average length of the long axis can refer to the average value of the length in the axial direction having the longest length of the granulated particles. When the aspect ratio of the granulated particles is within the aforementioned range, this can have an advantageous effect on sufficient flowability suitable for the process.

[0103] The negative active material can include a single silicon-based active material, or a mixture of a silicon-based active material and a carbon-based active material.

[0104] The silicon-based active material can include silicon (Si), silicon oxide (SiOx (0 < x ≤ 2)), silicon carbide (SiC), or two or more thereof.

[0105] The carbon-based active material can include natural graphite, artificial graphite, graphene, or two or more thereof. In this case, the natural graphite and the artificial graphite can be spherical, plate-like, or needle-like.

[0106] The conductive material can include a linear conductive material, a point-like conductive material, or two or more thereof. That is, the conductive material can include at least one linear conductive material or at least one point-like conductive material, or both.

[0107] In the point-like conductive material, "point-like" can refer to a spherical particle shape having an average diameter D50 in the range of 10 nm to 500 nm, specifically 15 nm to 100 nm.

[0108] Further, the point-like conductive material can include any conductive material having a spherical particle shape of the above-described average diameter. Specific examples of the point-like conductive material can each independently include carbon black, denka black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, or two or more thereof.

[0109] In the linear conductive material, "linear" refers to a needle-like particle shape having an aspect ratio (ratio of length to diameter) in the range of, for example, 10 to 1,000, particularly 20 to 500. For example, according to one embodiment of the present disclosure, the linear conductive material can have an average diameter of 10 nm to 500 nm, particularly 20 nm to 300 nm. Further, the linear conductive material used in one embodiment of the present disclosure can have an average length of 3 µm to 50 µm, particularly 5 µm to 30 µm, more particularly 5 µm to 20 µm, more particularly 10 µm to 20 µm, more particularly 13 µm to 17 µm.

[0110] Here, the average diameter is the arithmetic average of the diameters of the linear conductive material in the vertical plane in the length direction, and can be calculated, for example, from a scanning electron microscope (SEM) image taken at a magnification of 2,000x to 50,000x by a field emission scanning electron microscope. Further, the average length is the arithmetic average of the lengths of the linear conductive material, and can be calculated by the same method as the average diameter.

[0111] The linear conductive material can include carbon nanotubes, carbon nanofibers, graphene, or two or more thereof. The carbon nanotubes can include, for example, single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes.

[0112] A single-walled carbon nanotube refers to a carbon nanotube formed of six carbon atoms connected in a hexagonal shape to form a tube in which the number of walls (graphene planes) is only one. The single-walled carbon nanotube has remarkable electrical properties due to the one-dimensional structure, and exhibits different electrical properties depending on the hexagonal honeycomb molecular asymmetric (chiral) structure and the diameter.

[0113] A double-walled carbon nanotube refers to a carbon nanotube in which the number of walls is two, and a multi-walled carbon nanotube refers to a carbon nanotube in which the number of walls is a plurality.

[0114] The average diameter of the single-walled carbon nanotube can be 0.5 nm to 15 nm. According to one embodiment of the present disclosure, the average diameter of the single-walled carbon nanotube can be 1 nm to 10 nm, or 1 nm to 5 nm, or 1 nm to 2 nm. When the average diameter of the single-walled carbon nanotube is in the foregoing range, the conductivity of the negative electrode can be maintained even with a small amount of single-walled carbon nanotubes. The single-walled carbon nanotube can have a BET specific surface area of 500 m 2 / g to 1,500 m 2 / g, or 900 m 2 / g to 1,200 m 2g. When the BET specific surface area is within the aforementioned range, an electrically conductive material dispersion having a preferable solid content can be produced. The BET specific surface area can be measured by the nitrogen absorption BET method. The aspect ratio of the single-walled carbon nanotube can be 50 to 20,000, or the length of the single-walled carbon nanotube can be 5 μm to 100 μm, or 5 μm to 50 μm. The aspect ratio can be calculated by averaging the aspect ratios of 15 single-walled carbon nanotubes having a high aspect ratio and 15 single-walled carbon nanotubes having a low aspect ratio when the single-walled carbon nanotube powder is observed by SEM.

[0115] The single-walled carbon nanotube is longer in length and larger in volume due to a higher aspect ratio than the multi-walled carbon nanotube or the double-walled carbon nanotube, and thus it can be more advantageous because an electric network can be formed even by using the single-walled carbon nanotube in a small amount.

[0116] The linear electrically conductive material can surround the silicon-based active material to maintain the structure of the negative active material layer containing the silicon-based active material during charging and discharging, and continuously maintain contact despite a large volume change of the silicon-based active material, thereby stably providing electrons during long-term cycling and contributing to a long lifespan, and can increase the movement distance of electrons so that the negative active material located in the upper and lower portions of the negative active material layer can participate in the charging and discharging reaction, thereby improving high-rate charging and discharging performance.

[0117] In addition, the other electrically conductive material, which is optionally contained in the granulation particles together with the electrically conductive material as described below, can contact the negative active material over a large area, thereby improving high-rate characteristics.

[0118] According to one embodiment of the present disclosure, when the granulation particles containing the electrically conductive material containing both the linear electrically conductive material and the point-like electrically conductive material are used, the linear electrically conductive material and the point-like electrically conductive material can be uniformly distributed in the negative active material layer, and the above-mentioned beneficial effects of the linear electrically conductive material and the point-like electrically conductive material can be simultaneously exerted, and in particular, by using in a smaller amount than a conventional negative electrode using the linear electrically conductive material, an electric network can be sufficiently formed in the negative active material layer, thereby achieving high electrical conductivity and expansion suppression performance of the silicon-based active material.

[0119] In one embodiment of the present disclosure, the amount of the electrically conductive material can be 0.001 parts by weight to 0.5 parts by weight, or 0.05 parts by weight to 0.1 parts by weight, based on 100 parts by weight of the negative active material.

[0120] According to one embodiment of the present disclosure, the first binder can include a diene-based polymer, an acrylate-based polymer, a styrene-based polymer, a polyacrylonitrile-based polymer, a vinyl-based polymer, a polyoxide-based polymer, polyacrylamide, or two or more thereof.

[0121] Examples of the diene-based polymer can include a polymer including a monomer unit derived from a conjugated diene such as butadiene or isoprene, and a hydrogenated product thereof. The ratio of the monomer unit derived from the conjugated diene in the diene-based polymer can generally be 40% by weight or more, preferably 50% by weight or more, and more preferably 60% by weight or more. Specifically, the diene-based polymer can include a conjugated diene homopolymer such as polybutadiene or polyisoprene; an aromatic vinyl-conjugated diene copolymer having a carboxyl modification such as a styrene-butadiene copolymer (SBR); a vinyl cyanide-conjugated diene copolymer such as an acrylonitrile-butadiene copolymer (NBR); a hydrogenated SBR, a hydrogenated NBR.

[0122] Examples of the acrylate-based polymer can include a polymer including a monomer unit derived from an acrylate and / or a methacrylate. The ratio of the monomer unit derived from the acrylate and / or the methacrylate in the acrylate-based polymer can generally be 40% by weight or more, preferably 50% by weight or more, and more preferably 60% by weight or more. Specific examples of the acrylate-based polymer can include a crosslinked acrylate-based polymer such as 2-ethylhexyl acrylate-methacrylic acid-acrylonitrile-ethylene glycol dimethacrylate copolymer, 2-ethylhexyl acrylate-methacrylic acid-methacrylonitrile-diglycol dimethacrylate copolymer, 2-ethylhexyl acrylate-styrene-methacrylic acid-ethylene glycol dimethacrylate copolymer, butyl acrylate-acrylonitrile-diglycol dimethacrylate copolymer, and butyl acrylate-acrylic acid-trihydroxymethylpropane trimethacrylate copolymer; a copolymer of ethylene and a (meth)acrylate such as ethylene-methyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-ethyl acrylate copolymer, and ethylene-ethyl methacrylate copolymer; a graft polymer having a radically polymerizable monomer grafted to a copolymer of ethylene and a (meth)acrylate. Meanwhile, the radically polymerizable monomer used for the graft polymer can include, for example, methyl methacrylate, acrylonitrile, methacrylic acid. In addition, a copolymer of ethylene and a (meth)acrylic acid such as ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer can be used as a dispersing binder.

[0123] Styrene-based polymers can include polymers having repeating units derived from styrene monomers, such as styrene homopolymers (polystyrene), styrene copolymers. Examples of styrene copolymers can include block copolymers, such as styrene-butadiene copolymers (SBR), styrene-ethylene-butadiene copolymers, styrene-butadiene-propylene copolymers, styrene-butadiene-acrylate copolymers (SBR-acrylate) (e.g., styrene-n-butyl acrylate-methyl methacrylate-acrylonitrile copolymers, styrene-n-butyl acrylate-itaconic acid-methyl methacrylate-acrylonitrile copolymers, etc.), styrene-isoprene copolymers, styrene-butadiene block copolymers, styrene-butadiene-styrene block copolymers, styrene-ethylene-butylene-styrene block copolymers, styrene-isoprene block copolymers, styrene-ethylene-propylene-styrene block copolymers.

[0124] Polyacrylonitrile-based polymers can include polyacrylonitrile, acrylamide-acrylonitrile-acrylic acid terpolymers.

[0125] Vinyl-based polymers can include polyvinyl alcohol, polyvinyl propylene, polyvinyl acetate.

[0126] Polyoxides-based polymers can include polyethylene oxide, polypropylene oxide.

[0127] In one embodiment of the present disclosure, the amount of the first binder can be 0.5 parts by weight to 20 parts by weight, or 2 parts by weight to 10 parts by weight, based on 100 parts by weight of the negative active material.

[0128] In one embodiment of the present disclosure, the amount of the negative active material can be 80 parts by weight to 99 parts by weight, or 82 parts by weight to 98 parts by weight, the amount of the conductive material can be 0.001 parts by weight to 0.5 parts by weight, or 0.05 parts by weight to 0.1 parts by weight, and the amount of the first binder can be 0.5 parts by weight to 20 parts by weight, or 2 parts by weight to 10 parts by weight, in 100 parts by weight of the granulated particles.

[0129] When the amounts of the negative active material, the conductive material, and the first binder in the granulated particles are within the aforementioned ranges, this can have a more beneficial effect on the granulated particle shape and particle size distribution uniformity.

[0130] Further, the average particle size D50 of the granulated particles can be 10 to 20 μm, or 13 to 18 μm. When the negative electrode active material includes a silicon-based active material, the average particle size D50 of the silicon-based active material can be 0.5 to 5 μm, or 1 to 3 μm. When the negative electrode active material further includes a carbon-based active material, the average particle size D50 of the carbon-based active material can be 8 to 18 μm, or 10 to 16 μm.

[0131] When the average particle sizes of the granulated particles and the negative electrode active material are in the aforementioned ranges, this can have a more beneficial effect on the granulated particle shape and particle size distribution uniformity.

[0132] In one embodiment of the present disclosure, the negative electrode active material can be a mixture of a silicon-based active material and a carbon-based active material, and the amount of the silicon-based active material can be 5 to 25 parts by weight, or 10 to 20 parts by weight, based on 100 parts by weight of the carbon-based active material. When the ratio of the amounts of the silicon-based active material and the carbon-based active material is in the aforementioned range, this can have a more beneficial effect on particle dispersion in the granulated particles.

[0133] <NEGATIVE ELECTRODE ACTIVE MATERIAL LAYER>

[0134] The negative electrode of the present disclosure includes a current collector and a negative electrode active material layer on at least one surface of the current collector, and the negative electrode active material layer includes granulated particles containing a negative electrode active material, a conductive material, and a first binder; and a second binder.

[0135] In one embodiment of the present disclosure, the porosity of the negative electrode active material layer can be 20 to 40 vol%, and when the porosity is in the aforementioned range, electrolyte wettability, shape stability, and ion conductivity can be further improved.

[0136] Meanwhile, according to one embodiment of the present disclosure, the thickness of the negative electrode active material layer can be, for example, 30 to 300 μm, but is not limited thereto.

[0137] According to another embodiment of the present disclosure, the negative electrode active material layer can be a single layer including one unit active material layer.

[0138] According to one embodiment of the present disclosure, the negative electrode active material layer can have a multi-layer structure including two or more unit active material layers stacked. In this case, the electrode materials, for example, the negative electrode active material and the binder, included in each unit active material layer can be the same or different for each layer, and are not limited thereto.

[0139] In one embodiment of the present disclosure, the second binder can include a diene-based polymer, an acrylate-based polymer, a styrene-based polymer, or two or more thereof.

[0140] Examples of the diene-based polymer can include a polymer including monomer units derived from a conjugated diene (e.g., butadiene or isoprene) and hydrogenated products thereof. The ratio of the monomer units derived from the conjugated diene in the diene-based polymer can generally be 40% by weight or more, preferably 50% by weight or more, and more preferably 60% by weight or more. Specifically, the diene-based polymer can include a conjugated diene homopolymer such as polybutadiene or polyisoprene; an aromatic vinyl-conjugated diene copolymer having a carboxyl modification such as a styrene-butadiene copolymer (SBR); a vinyl cyanide-conjugated diene copolymer such as an acrylonitrile-butadiene copolymer (NBR); hydrogenated SBR, hydrogenated NBR.

[0141] Examples of the acrylate-based polymer can include a polymer including monomer units derived from an acrylate and / or a methacrylate. The ratio of the monomer units derived from the acrylate and / or the methacrylate in the acrylate-based polymer can generally be 40% by weight or more, preferably 50% by weight or more, and more preferably 60% by weight or more. Specific examples of the acrylate-based polymer can include crosslinking-based acrylate polymers such as 2-ethylhexyl acrylate-methacrylic acid-acrylonitrile-ethylene glycol dimethacrylate copolymer, 2-ethylhexyl acrylate-methacrylic acid-methacrylonitrile-diglycol dimethacrylate copolymer, 2-ethylhexyl acrylate-styrene-methacrylic acid-ethylene glycol dimethacrylate copolymer, butyl acrylate-acrylonitrile-diglycol dimethacrylate copolymer, and butyl acrylate-acrylic acid-trihydroxymethyl propane trimethacrylate copolymer; copolymers of ethylene and (meth)acrylate such as ethylene-methyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-ethyl acrylate copolymer, and ethylene-ethyl methacrylate copolymer; graft polymers having a radically polymerizable monomer grafted to a copolymer of ethylene and (meth)acrylate. Meanwhile, the radically polymerizable monomer used for the graft polymer can include, for example, methyl methacrylate, acrylonitrile, methacrylic acid. In addition, copolymers of ethylene and (meth)acrylic acid such as ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer can be used as a dispersing binder.

[0142] The styrene-based polymer can include a polymer having a repeating unit derived from a styrene monomer, such as a styrene homopolymer (polystyrene), a styrene copolymer. Examples of the styrene copolymer can include block copolymers such as styrene-ethylene-butadiene copolymer, styrene-butadiene-propylene copolymer, styrene-isoprene copolymer, styrene-n-butyl acrylate-itaconic acid-methyl methacrylate-acrylonitrile copolymer, styrene-n-butyl acrylate-itaconic acid-methyl methacrylate-acrylonitrile copolymer, styrene-butadiene block copolymer, styrene-butadiene-styrene block copolymer, styrene-ethylene-butylene-styrene block copolymer, styrene-isoprene block copolymer, styrene-ethylene-propylene-styrene block copolymer.

[0143] Among them, the diene-based polymer and the cross-linking-based acrylate polymer are preferable, and the cross-linking-based acrylate polymer is particularly preferable, because a granular substance having good adhesion or good surface flatness to the current collector can be obtained, and an electrode for an electrochemical device having high electrostatic capacity and low internal resistance can be manufactured.

[0144] The amount of the second binder can be 0.5 parts by weight to 4 parts by weight, or 1 part by weight to 2 parts by weight, based on 100 parts by weight of the granulated particles in the negative electrode active material layer.

[0145] In one embodiment of the present disclosure, the negative electrode active material layer can further include an additional carbon-based active material, an additional conductive material, or both. That is, in addition to the granulated particles and the second binder, the negative electrode active material layer can further include an additional carbon-based active material or an additional conductive material, or both.

[0146] In one embodiment of the present disclosure, the negative electrode active material layer can include 100 parts by weight of the granulated particles; 80 parts by weight to 99 parts by weight or 85 parts by weight to 95 parts by weight of the additional carbon-based active material; 0.01 parts by weight to 2 parts by weight or 0.05 parts by weight to 0.5 parts by weight of the additional conductive material; and 1 parts by weight to 4 parts by weight or 1.5 parts by weight to 2.5 parts by weight of the second binder.

[0147] When the amounts of the granulated particles, the additional carbon-based active material, the additional conductive material, and the second binder in the negative electrode active material layer are within the aforementioned ranges, good electrode quality can be ensured, thereby improving battery performance.

[0148] Meanwhile, in some cases, the negative active material layer can further include a filler to suppress swelling of the negative active material layer, and the filler is not limited to a specific type and can include any fibrous material that does not cause any chemical change in the corresponding battery, and for example, can include an olefin-based polymer such as polyethylene, polypropylene; a fibrous material such as glass fiber, carbon fiber.

[0149] Figure 2 is a schematic view of a negative active material layer formed using a slurry obtained by mixing together a silicon-based active material 10, a carbon-based active material 20, and a conductive material (linear conductive material) 30 via a conventional method. Referring to Figure 2 , it is observed that the uneven dispersion of the conductive material in the negative active material layer and the agglomeration in a specific area (part A), or the agglomeration of the silicon-based active material 10 between the carbon-based active material 20, results in very poor dispersion (part B).

[0150] On the contrary, Figure 3 is a schematic view of a negative active material layer according to one embodiment of the disclosure. Referring to Figure 3 , by separately manufacturing a granulated particle 50 including a negative active material, a conductive material, and a first binder, and applying the granulated particle together with a second binder, a negative electrode in which the silicon-based active material and the conductive material are uniformly dispersed in the negative active material layer can be provided (see part C). Specifically, it can be seen that, when the silicon-based active material is included as the negative active material in the manufacture of the granulated particle, the linear conductive material is used as the conductive material, and the carbon-based active material 20 is used as an additional negative active material together with the granulated particle 50, the silicon-based active material in the granulated particle is not agglomerated between the carbon-based active material 20, and the dispersibility is significantly improved, as compared with Figure 2 the conventional negative electrode of

[0151] The current collector is not limited to a specific type and can include any material having high electrical conductivity and not causing any chemical change in the battery, for example, stainless steel, aluminum, nickel, titanium, sintered carbon, copper, or aluminum or stainless steel treated with carbon, nickel, titanium, or silver on the surface. In addition, the current collector can have a microtexture on the surface to increase the adhesion strength of the negative active material, and can be various types, for example, a film, a sheet, a foil, a mesh, a porous body, a foam, a nonwoven fabric, etc.

[0152] In one embodiment of the disclosure, the current collector can have a primer layer on all or a part of the current collector.

[0153] The primer layer can include a binder for the primer layer and a conductive material for the primer layer, and the sum of the amounts of the binder and the conductive material in the primer layer can be 90% by weight or more.

[0154] The electrode according to one embodiment of the present disclosure includes a negative electrode active material layer including granulated particles, and in this case, when the undercoat layer includes a binder and a conductive material such that the sum of the amounts of the binder and the conductive material is 90% by weight or more, it is possible to ensure the time-dependent stability of the undercoat layer, thereby achieving good properties such as adhesion strength and life characteristics, but the present disclosure is not limited thereto.

[0155] According to one embodiment of the present disclosure, the undercoat layer includes a binder for the undercoat layer and a conductive material for the undercoat layer, and can further include a dispersant.

[0156] According to one embodiment of the present disclosure, the undercoat layer includes a binder for the undercoat layer and a conductive material for the undercoat layer, but can substantially not include a dispersant.

[0157] According to one embodiment of the present disclosure, the binder for the undercoat layer can include any type of binder commonly used for the undercoat layer without limitation.

[0158] According to another embodiment of the present disclosure, the binder for the undercoat layer can preferably include a polymer that ensures the time-dependent stability of the undercoat layer. Specifically, the glass transition temperature Tg of the binder for the undercoat layer can be 45°C or less.

[0159] According to another embodiment of the present disclosure, the binder for the undercoat layer can include, for example, styrene butadiene rubber (SBR), butadiene rubber (BR), nitrile butadiene rubber (NBR), styrene butadiene styrene block polymer (SBS), styrene ethylene butadiene block polymer (SEB), styrene-(styrene butadiene)-styrene block polymer, natural rubber (NR), isoprene rubber (IR), ethylene-propylene-diene terpolymer (EPDM), poly(ethylene-co-propylene-co-5-methylene-2-norbornene), polytetrafluoroethylene (PTFE), polyvinylidene fluoride, polyvinyl chloride, polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethyl methacrylate, polyethylhexyl acrylate, polybutyl acrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, polyethylene, polypropylene, polyethylene-co-vinyl acetate, polyethylene oxide, polypropylene oxide, polyarylate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, or two or more thereof. Specifically, the binder can include styrene butadiene rubber (SBR), nitrile butadiene rubber (NBR), polymethyl methacrylate, polyethylhexyl acrylate, polybutyl acrylate, or two or more thereof.

[0160] According to another embodiment of the present disclosure, the binder for the undercoat layer can include butadiene styrene rubber (SBR) having a glass transition temperature Tg of -40℃ to 45℃, nitrile butadiene rubber (NBR) having a glass transition temperature Tg of -40℃ to 45℃, or a mixture thereof.

[0161] According to another embodiment of the present disclosure, the binder for the undercoat layer can include butadiene styrene rubber (SBR) having a glass transition temperature Tg of -40℃ to 45℃, nitrile butadiene rubber (NBR) having a glass transition temperature Tg of -40℃ to 45℃, or a mixture thereof.

[0162] According to one embodiment of the present disclosure, the conductive material for the undercoat layer has a specific surface area of 30 m 2 / g to 1,400 m 2 / g, and a spherical shape. In this case, the primary particle size of the conductive material having the spherical shape can be, for example, 10 nm to 100 nm, specifically 15 nm to 70 nm, but is not limited thereto.

[0163] According to another embodiment of the present disclosure, the conductive material for the undercoat layer can have a specific surface area of 10 m 2 / g to 400 m 2 / g, and a tubular shape. In this case, in the conductive material having the tubular shape, the diameter of the cross section in the direction perpendicular to the length direction can be 0.1 nm to 3 nm, and specifically 0.3 nm to 1.5 nm, but is not limited thereto.

[0164] The conductive material for the undercoat layer is not limited to a specific type, and can include any conductive material that does not cause any chemical change in the corresponding battery, and for example, can include graphite, such as natural graphite or artificial graphite; carbon compounds based on carbon black, such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black; conductive fibers, such as carbon fibers or metal fibers; fluorocarbon compounds; metal granulated particles, such as aluminum, nickel granulated particles; conductive whiskers, such as zinc oxide, potassium titanate; conductive metal oxides, such as titanium oxide; conductive materials, such as polyphenylene derivatives, but specifically, in order to uniformly mix the conductive material and improve the conductivity, the conductive material can include activated carbon, graphite, carbon black, carbon nanotubes, or a mixture thereof, and more specifically, activated carbon.

[0165] According to one embodiment of the present disclosure, the undercoat layer can include the above composition, and has a thickness of 300 nm to 1.5 μm, specifically 700 nm to 1.3 μm, but is not limited thereto.

[0166] <Method for manufacturing a negative electrode>

[0167] According to one aspect of the present disclosure, there is provided a method for manufacturing a negative electrode according to one embodiment of the present disclosure, including the steps of: drying a composition including a negative electrode active material, a conductive material, a first binder, and a first aqueous dispersion medium by a spray drying method to manufacture granulated particles;

[0168] mixing the granulated particles with a second binder and a second aqueous dispersion medium to prepare a negative electrode slurry; and

[0169] coating the negative electrode slurry on at least one surface of a current collector, drying and roll-pressing to form a negative electrode active material layer.

[0170] First, a composition including a negative electrode active material, a conductive material, a first binder, and a first aqueous dispersion medium is dried by a spray drying method to manufacture granulated particles.

[0171] The negative electrode active material, the conductive material, the first binder, and the optional additive are dispersed or dissolved in a dispersion medium (a solvent for the first binder) to obtain a composition in which the negative electrode active material, the conductive material, the first binder, and / or the additive are dispersed or dissolved.

[0172] The dispersion medium for obtaining the composition is most suitably water, but an organic solvent can be used. The organic solvent can include, for example, an alkyl alcohol such as methanol, ethanol, propanol; an alkyl ketone such as acetone, methyl ethyl ketone; an ether such as tetrahydrofuran, dioxane, di alkyl, diglyme; an amide such as diethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone (hereinafter referred to as NMP), dimethylimidazolidinone; a sulfur-based solvent such as dimethyl sulfoxide, sulfolane, but preferably an alcohol. When an organic solvent having a lower boiling point than water is used together, the drying speed in the fluidized bed granulation can be increased. In addition, since the dispersion or dissolution of the negative electrode binder can be changed, the viscosity or flowability of the slurry can be adjusted according to the amount or type of the dispersion medium, thereby improving the production efficiency.

[0173] The dispersion medium for preparing the composition can be included in an amount such that the solid concentration of the composition is generally in the range of 0.1 to 20% by weight, or 0.5 to 10% by weight, or 1 to 5% by weight.

[0174] The method or order of dispersing or dissolving the negative active material, the conductive material, and the first binder in the dispersion medium is not limited to a particular method or order, and can include, for example, a method of adding the negative active material, the conductive material, and the first binder to the dispersion medium and mixing them, a method of dissolving or dispersing the first binder in the dispersion medium and finally adding the negative active material and the conductive material and mixing them. The mixing device can include, for example, a ball mill, a sand mill, a bead mill, a pigment disperser, a stone mill, an ultrasonic disperser, a homogenizer, and a planetary mixer. The mixing can be performed, for example, in the range of room temperature to 80°C for 10 minutes to several hours.

[0175] Subsequently, the composition is subjected to spray drying. The spray drying method is a method of drying the slurry while spraying the slurry in hot air. The spray method of the apparatus used for the spray drying method includes a rotary disk method and a pressure nozzle method. The rotary disk method is a method of feeding the composition to the center of a disk rotating at almost high speed, pushing the composition to the periphery of the disk by the centrifugal force of the disk to generate a mist and dry it. The rotation rate of the disk depends on the size of the disk, but is generally 5,000 rpm to 35,000 rpm, and preferably 15,000 rpm to 30,000 rpm. Meanwhile, the pressure nozzle method is a method of spraying the composition with air or a liquid such as a high-pressure fluid through a fine nozzle to convert it into a mist and dry it.

[0176] In one embodiment of this disclosure, based on the reactor inlet temperature (input), the temperature of the hot air (the temperature of the fed hot air) can be controlled to 130°C to 210°C, 135°C to 200°C, or 130°C to 160°C, or 160°C to 210°C, or 160°C to 180°C, or 140°C to 190°C, or 140°C to 180°C, or 140°C to 160°C, or 160°C to 190°C, to form a granulated particle structure with a large amount of first binder on the surface. When the temperature of the fed hot air is within the aforementioned range, the negative electrode active material, the conductive material, and the first binder can be uniformly dispersed in the granulated particles, thereby achieving uniform dispersion of each component in the granulated particles manufactured under hot air temperature conditions and uniform capacity in battery manufacturing. Specifically, when the temperature of the fed hot air is higher than the aforementioned range, drying may proceed rapidly. During rapid drying, the solvent (water) in the sprayed droplets may dry faster than the particles in the droplets align, and only small silicon particles can move rapidly in the solvent drying direction. This results in uneven dispersion and agglomeration of silicon particles in the granulated particles, or, worse, agglomeration of silicon particles to form individual granulated particles. Uneven dispersion and agglomeration of silicon particles, or electrodes manufactured using granulated particles obtained from silicon particle agglomeration, may lead to uneven capacity. Conversely, when the hot air temperature is too low, the droplets may not dry sufficiently upon contact with the hot air, and may dry while adhering to the inner wall. In this case, due to uneven drying, granulated particles with uneven distribution of the negative electrode active material, conductive material, and first binder may form, resulting in low recovery rates. Furthermore, when the hot air temperature is within the aforementioned range, the shape of the granulated particles obtained by uniformly spraying droplets can be uniform, thereby improving electrode performance.

[0177] In spray drying, the hot air suction method is not limited to a specific method and may include, for example, a method in which hot air and spray droplets flow in parallel in the horizontal direction, a method of spraying from the top of the drying tower so that it falls together with the hot air, a method of countercurrent contact between the spray droplets and the hot air, and a method in which the spray droplets and hot air flow in parallel, fall by gravity, and contact each other countercurrently. Meanwhile, in one embodiment of this disclosure, in spray drying, the outlet temperature of the reactor (the temperature of the hot air released from the reactor) can be controlled between 90°C and 130°C.

[0178] When the outlet temperature and / or the temperature difference ΔT between the inlet and outlet is low, drying cannot proceed properly, potentially resulting in particles containing a large amount of residual solvent. This prevents the formation of uniformly shaped spherical particles, leading to agglomeration of granulated particles or amorphous granules. Conversely, when the inlet temperature is too high and ΔT is large, over-drying can cause granulation failure, potentially producing particles with very small particle size D50 and low aspect ratio. Therefore, to control the particle size at an appropriate level while maintaining a high aspect ratio and minimizing binder agglomeration, it is necessary to control the inlet and outlet temperatures within suitable ranges.

[0179] In addition, heating can be optionally performed to cure the surface of the product obtained by spray drying (i.e., granulated particles), and in this case, the heat treatment temperature can typically be from 80°C to 300°C.

[0180] Subsequently, the granulated particles can be mixed with a second binder and a second aqueous dispersion medium to prepare a negative electrode slurry.

[0181] In this case, the second aqueous dispersion medium used can be referenced to the first aqueous dispersion medium described above, and the slurry preparation process can be referenced to the composition preparation process for manufacturing granulated particles.

[0182] Subsequently, the negative electrode slurry is coated onto at least one surface of the current collector, dried, and rolled to form a negative electrode active material layer.

[0183] The slurry prepared by the above method is coated onto the current collector. In this case, the current collector may have an underlayer as described above on all or part of at least one surface, the underlayer comprising a conductive material for the underlayer and an adhesive for the underlayer.

[0184] In one embodiment of this disclosure, the method for coating a slurry onto at least one surface of a current collector may include any method commonly used in the relevant art, and may include, for example, spraying, dip coating, gravure coating, or die coating.

[0185] In one embodiment of this disclosure, drying can be performed using any drying method commonly used in the manufacture of electrodes. For example, drying can be carried out at 30°C to 200°C or 40°C to 80°C. Alternatively, drying can be performed in air for 2 to 20 minutes or 2 to 10 minutes.

[0186] The rolling process typically uses a pressing technique involving rolling rollers. During rolling, two cylindrical rollers are arranged parallel and vertically at a small interval. Electrodes are placed between the rollers, and pressing is achieved by rotating the rollers in opposite directions. The rollers can be heated or cooled to an adjustable temperature.

[0187] As described above, the negative active material can include a single silicon-based active material, or a mixture of a silicon-based active material and a carbon-based active material. In addition, the negative slurry can further contain an additional carbon-based active material or an additional conductive material, or both.

[0188] In addition, according to one aspect of the present disclosure, there is provided an electrochemical device including the negative electrode according to one embodiment of the present disclosure.

[0189] The electrochemical device can include any device in which an electrochemical reaction occurs, and specific examples can include any type of primary battery, secondary battery, fuel cell, solar cell, or capacitor such as a supercapacitor. In the present disclosure, preferably, the electrochemical device can be a secondary battery, and more preferably a lithium ion secondary battery.

[0190] In addition, according to one embodiment of the present disclosure, there can be provided an energy storage system including a secondary battery as a unit cell.

[0191] The secondary battery can include an electrode assembly including the negative electrode according to one embodiment of the present disclosure, a positive electrode, and a separator, and a battery case (cylindrical case, prismatic case, pouch, etc.) accommodating the electrode assembly together with a non-aqueous electrolyte containing lithium.

[0192] The positive electrode can have a positive active material layer containing a positive active material, a binder, and an optional conductive material on at least one surface of a current collector.

[0193] The positive active material can include any type of lithium transition metal oxide, lithium metal iron phosphate, or metal oxide without limitation, and can include, for example, a layered compound such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; a lithium manganese oxide represented by the formula LiMnO4 (x is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxide such as LiV3O8, LiV3O4, V2O5, Cu2V2O7; a lithium nickel oxide represented by the formula LiNi 1+x Mn 2-x O4 (x is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxide such as LiV3O8, LiV3O4, V2O5, Cu2V2O7; a lithium nickel oxide represented by the formula LiNi 1-x M x O2 (M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, x = 0.01 to 0.3); a lithium manganese composite oxide represented by the formula LiMn 2-x M x O2 (M = Co, Ni, Fe, Cr, Zn, or Ta, x = 0.01 to 0.1) or Li2Mn3MO8 (M = Fe, Co, Ni, Cu, or Zn); and an aluminum ion partially substituted Li in the formula1+x (Ni a Co b Mn c Al d ) 1-x O2(x = 0 to 0.03, a = 0.3 to 0.95, b = 0.01 to 0.35, c = 0.01 to 0.5, d = 0.001 to 0.03, a + b + c + d = 1); lithium metal phosphate LiM P O4(M = Fe, Co, Ni, or Mn); disulfide compounds; Fe2(MoO4)3, but are not limited thereto.

[0194] In one embodiment of the present disclosure, the binder included in the cathode can include any commonly used binder material for electrochemical devices without limitation, but can include, for example, a diene-based polymer, an acrylate-based polymer, a fluorine-based polymer, a styrene-based polymer, or two or more thereof.

[0195] Examples of the diene-based polymer can include a polymer including a conjugated diene (e.g., butadiene or isoprene) derived monomer unit and a hydrogenated product thereof. The ratio of the conjugated diene derived monomer unit in the diene-based polymer can generally be 40% by weight or more, preferably 50% by weight or more, and more preferably 60% by weight or more.

[0196] Specifically, the diene-based polymer can include a conjugated diene homopolymer such as polybutadiene or polyisoprene; an aromatic vinyl-conjugated diene copolymer with carboxyl modification such as a styrene-butadiene copolymer (SBR); a vinyl cyanide-conjugated diene copolymer such as an acrylonitrile-butadiene copolymer (NBR); a hydrogenated SBR, a hydrogenated NBR.

[0197] The styrene-based polymer can include a polymer having a styrene monomer derived repeating unit such as a styrene homopolymer (polystyrene), a styrene copolymer. Examples of the styrene copolymer can include a block copolymer such as a styrene-ethylene-butadiene copolymer, a styrene-butadiene-propylene copolymer, a styrene-isoprene copolymer, a styrene-n-butyl acrylate-itaconic acid-methyl methacrylate-acrylonitrile copolymer, a styrene-n-butyl acrylate-itaconic acid-methyl methacrylate-acrylonitrile copolymer, a styrene-butadiene block copolymer, a styrene-butadiene-styrene block copolymer, a styrene-ethylene-butylene-styrene block copolymer, a styrene-isoprene block copolymer, a styrene-ethylene-propylene-styrene block copolymer.

[0198] Examples of the acrylate-based polymer can include a polymer including monomer units derived from an acrylate and / or a methacrylate. The ratio of the monomer units derived from the acrylate and / or the methacrylate in the acrylate-based polymer can generally be 40% by weight or more, preferably 50% by weight or more, and more preferably 60% by weight or more. Specific examples of the acrylate-based polymer can include cross-linked acrylate-based polymers, such as 2-ethylhexyl acrylate-methacrylic acid-acrylonitrile-ethylene glycol dimethacrylate copolymer, 2-ethylhexyl acrylate-methacrylic acid-methacrylonitrile-diglycol dimethacrylate copolymer, 2-ethylhexyl acrylate-styrene-methacrylic acid-ethylene glycol dimethacrylate copolymer, butyl acrylate-acrylonitrile-diglycol dimethacrylate copolymer, and butyl acrylate-acrylic acid-trihydroxymethyl propane trimethacrylate copolymer; copolymers of ethylene and (meth)acrylate, such as ethylene-methyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-ethyl acrylate copolymer, and ethylene-ethyl methacrylate copolymer; and graft polymers having a radically polymerizable monomer grafted to a copolymer of ethylene and (meth)acrylate. Meanwhile, the radically polymerizable monomer used for the graft polymer can include, for example, methyl methacrylate, acrylonitrile, methacrylic acid. In addition, a copolymer of ethylene and (meth)acrylic acid, such as ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, can be used as a dispersing binder.

[0199] The fluorine-based polymer can include a polyvinylidene fluoride-based copolymer, such as polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), and PVDF-HFP, specifically, polytetrafluoroethylene (PTFE), and more specifically, polytetrafluoroethylene (PTFE).

[0200] The separator can include a porous polymer film generally used as a separator, such as a porous polymer film made of a polyolefin-based polymer, such as ethylene homopolymer, propylene homopolymer, ethylene / butylene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, used alone or stacked. In addition, an insulating film having high ion permeability and high mechanical strength can be used. The separator can include a safety reinforced separator (SRS) having a thin ceramic coating on the surface of the separator. In addition, a commonly used porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, but is not limited thereto.

[0201] The electrolyte solution includes a lithium salt as an electrolyte and an organic solvent for dissolving the electrolyte.

[0202] The lithium salt can include any lithium salt commonly used in electrolyte solutions for secondary batteries without limitation, and for example, the anion of the lithium salt can include at least one selected from the group consisting of F - , Cl - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - , and (CF3CF2SO2)2N - .

[0203] The organic solvent included in the electrolyte solution can include any commonly used organic solvent without limitation, and can generally include at least one selected from the group consisting of propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate, methylpropyl carbonate, dipropyl carbonate, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, vinylene carbonate, sulfolane, γ-butyrolactone, propylene sulfite, and tetrahydrofuran.

[0204] In particular, among these carbonate-based organic solvents, cyclic carbonates such as ethylene carbonate and propylene carbonate are high-viscosity organic solvents, and dissolve lithium salts well in electrolytes due to high dielectric constants. More preferably, when a mixture of cyclic carbonates at an optimal ratio with linear carbonates of low viscosity and low dielectric constant, such as dimethyl carbonate and diethyl carbonate, is used, an electrolyte solution having high electrical conductivity can be prepared.

[0205] Optionally, the electrolyte solution stored according to the present disclosure can further include an additive, such as an overcharge inhibitor included in a commonly used electrolyte solution.

[0206] A lithium secondary battery according to one embodiment of the present disclosure can be completed by placing a positive electrode and a negative electrode and a separator interposed between the positive electrode and the negative electrode to form an electrode assembly, placing the electrode assembly in, for example, a pouch, a cylindrical battery case, or a prismatic battery case, and injecting an electrolyte solution. Alternatively, the lithium secondary battery can be completed by stacking the electrode assembly, filling an electrolyte solution, placing the resulting product in a battery case, and sealing the battery case.

[0207] In this case, detailed structures of the secondary battery and the energy storage system are well known, and the description thereof is omitted.

[0208] Hereinafter, embodiments will be described in detail to particularly describe the present disclosure. However, the embodiments according to the present disclosure can be modified in many other forms, and the scope of the present disclosure should not be construed as being limited to the following embodiments. The embodiments of the present disclosure are provided to fully and completely inform those skilled in the art of the present disclosure.

[0209] Embodiments

[0210] [Example 1]

[0211] 1. Negative electrode

[0212] (1) Preparation of granulated particles

[0213] Si (average particle size D50: 3 μm) as a silicon-based active material, spherical natural graphite (average particle size D50: 18 μm) as a carbon-based active material, polyacrylamide as a first binder, and water as a dispersion medium were mixed in a weight ratio of 5:100:0.5:100 by a homogenizer to prepare a suspension.

[0214] The prepared composition was fed to a spray dryer together with hot air under a pressure range condition of -40 mmH2O to dry it. In this case, the conditions of the spray dryer were controlled to an inlet temperature of 160°C, an outlet temperature of 90°C, and a rotation rate of 18,000 rpm.

[0215] The granulated particles had a central portion including a plurality of silicon-based active materials, carbon-based active materials, and conductive materials, and a surface portion located outside the central portion and including a first binder that binds the plurality of silicon-based active materials, carbon-based active materials, and conductive materials. The average particle size D50 of the obtained granulated particles was 15 μm, and the aspect ratio was 1.1.

[0216] (2) Preparation of a current collector having a primer layer

[0217] 30 parts by weight of carbon black (specific surface area: 30 m 2 / g, particle size: 70 nm) as an electrically conductive material for the undercoat layer, 69 parts by weight of styrene-butadiene rubber (SBR) (Tg: -15°C) as a binder for the undercoat layer, and 1 part by weight of carboxymethyl cellulose (CMC) as a dispersant were mixed in water as a dispersion medium to prepare a slurry for the undercoat layer. In this case, the ratio of the amounts of the electrically conductive material, the binder, and the dispersant in the slurry for the undercoat layer was equal to the ratio of the amounts of the electrically conductive material, the binder, and the dispersant in the undercoat layer formed later. The percentage of solids in the slurry for the undercoat layer was 7% by weight.

[0218] The prepared slurry for the undercoat layer was coated on one surface of a copper current collector (thickness: 10 μm), and dried at 130°C to form an undercoat layer on the front surface of the copper current collector.

[0219] (3) Manufacture of the negative electrode

[0220] The obtained granulated particles, natural graphite (average particle size D50: 16 μm) as a carbon-based active material, single-walled carbon nanotubes as another electrically conductive material, styrene-butadiene rubber (SBR) as a second binder, and carboxymethyl cellulose (CMC) were mixed at a weight ratio of 10:86:3:1 with water as a dispersion medium by a homogenizer to prepare a slurry having a viscosity of about 3000 cPs level. In this case, the solid content in the slurry was 50% by weight.

[0221] The prepared slurry was coated on both surfaces of the current collector having the undercoat layer thus prepared by doctor blade coating, dried at 110°C for 10 minutes using a hot air dryer, and roll-pressed to manufacture a negative electrode having a negative electrode active material layer on both surfaces of the current collector, in which the load per unit area (weight basis) was 10 mg / 25 cm 2 .

[0222] (4) Manufacture of the secondary battery

[0223] An electrode assembly was manufactured using the negative electrode thus prepared and a lithium metal, and a porous polyethylene film (thickness: 10 μm) as a separator interposed therebetween. The electrode assembly was interposed in a coin-type battery case, a liquid electrolyte solution in which 1M LiPF6 was mixed in a solvent of ethylene carbonate, dimethyl carbonate, and diethyl carbonate at a volume ratio of 1:2:1 with 10% by weight of fluoroethylene carbonate (FEC) was then injected, and then sealed and aged to manufacture a coin unit secondary battery.

[0224] [Example 2]

[0225] A granulated particle was produced by the same method as in Example 1, except that Si (average particle size D50: 3 μm) as a silicon-based active material, spherical natural graphite (average particle size D50: 18 μm) as a carbon-based active material, polyacrylamide as a first binder, and water as a dispersion medium were mixed by a homogenizer in a weight ratio of 10:100:0.5:100 to prepare a composition. The average particle size D50 of the obtained granulated particle was 15 μm, and the aspect ratio was 1.1.

[0226] A negative electrode and a secondary battery including the same were produced by the same method as in Example 1, except that the granulated particle thus produced was used.

[0227] [Example 3]

[0228] A granulated particle was produced by the same method as in Example 1, except that Si (average particle size D50: 3 μm) as a silicon-based active material, spherical natural graphite (average particle size D50: 18 μm) as a carbon-based active material, polyacrylamide as a first binder, and water as a dispersion medium were mixed by a homogenizer in a weight ratio of 15:100:0.5:100 to prepare a composition. The average particle size D50 of the obtained granulated particle was 15 μm, and the aspect ratio was 1.1.

[0229] A negative electrode and a secondary battery including the same were produced by the same method as in Example 1, except that the granulated particle thus produced was used.

[0230] [Example 4]

[0231] A granulated particle was produced by the same method as in Example 1, except that Si (average particle size D50: 3 μm) as a silicon-based active material, spherical natural graphite (average particle size D50: 18 μm) as a carbon-based active material, polyacrylamide as a first binder, and water as a dispersion medium were mixed by a homogenizer in a weight ratio of 20:100:0.5:100 to prepare a composition. The average particle size D50 of the obtained granulated particle was 15 μm, and the aspect ratio was 1.1.

[0232] A negative electrode and a secondary battery including the same were produced by the same method as in Example 1, except that the granulated particle thus produced was used.

[0233] [Comparative Example 1]

[0234] Si (average particle size D50: 3 μm) as a silicon-based active material, spherical natural graphite (average particle size D50: 18 μm) as a carbon-based active material, single-walled carbon nanotube, butadiene styrene rubber (SBR), and carboxymethyl cellulose (CMC) were mixed with water as a dispersion medium in a weight ratio of 5:90.9:0.1:3:1 by a homogenizer to prepare a slurry having a viscosity of about 5000 cPs level. In this case, the solid content in the slurry was 50 wt%.

[0235] The prepared slurry was coated on both surfaces of the current collector having the undercoat layer thus prepared by a doctor blade coating, dried at 110°C for 10 minutes using a hot air dryer, and roll-pressed to manufacture a negative electrode having a negative active material layer on both surfaces of the current collector, in which the load per unit area (by weight) was 10 mg / 25cm 2 .

[0236] A negative electrode and a secondary battery including the same were manufactured by the same method as in Example 1, except that the granulated particles thus prepared were used.

[0237] [Comparative Example 2]

[0238] When the granulated particles were manufactured, Si (average particle size D50: 3 μm) as a silicon-based active material, spherical natural graphite (average particle size D50: 18 μm) as a carbon-based active material, polyacrylamide as a first binder, and water as a dispersion medium were mixed by a homogenizer in a weight ratio of 10:100:0.5:100 to prepare a composition.

[0239] The prepared composition was fed into a spray dryer with hot air under a pressure range condition of -40 mmH2O to dry it. In this case, the granulated particles were manufactured by the same method as in Example 1, except that the conditions of the spray dryer were controlled to an inlet temperature of 120°C, an outlet temperature of 60°C, and a rotation rate of 18,000 rpm. The average particle size D50 of the obtained granulated particles was 35 μm, and the aspect ratio was 2.1.

[0240] A negative electrode and a secondary battery including the same were manufactured by the same method as in Example 1, except that the granulated particles thus prepared were used.

[0241] [Comparative Example 3]

[0242] When the granulated particles were manufactured, Si (average particle size D50: 3 μm) as a silicon-based active material, spherical natural graphite (average particle size D50: 18 μm) as a carbon-based active material, polyacrylamide as a first binder, and water as a dispersion medium were mixed in a weight ratio of 10:100:0.5:100 by a homogenizer to prepare a composition.

[0243] The prepared composition was fed into a spray dryer together with hot air under a pressure range condition of -40 mmH2O to dry it. In this case, the granulated particles were manufactured by the same method as in Example 1, except that the conditions of the spray dryer were controlled to an inlet temperature of 220°C, an outlet temperature of 120°C, and a rotation rate of 18,000 rpm. The average particle size D50 of the obtained granulated particles was 7 μm, and the aspect ratio was 1.4.

[0244] The negative electrode and the secondary battery including the same were manufactured by the same method as in Example 1, except that the granulated particles thus prepared were used.

[0245] [Assessment Results]

[0246] Evaluation of first discharge capacity, initial efficiency and capacity retention

[0247] For each of the secondary batteries manufactured in Examples 1 to 4 and Comparative Examples 1 to 3, initial charge / discharge tests were performed by the following method, and the life characteristics were assessed.

[0248] In the first two cycles, charging was performed in a CC / CV mode, and after charging to 0.005 V with a 0.1C current in a CC mode, charging was ended when the current was 0.05C at the end-of-charge voltage (0.005 V). Discharging was performed in a CC mode, the end-of-discharge voltage was maintained at 1.5 V, and the current was maintained at 0.1C. In the subsequent cycles, charging was performed in a CC / CV mode, and after charging to 0.01 V with a 0.3C current in a CC mode, charging was ended when the current was 0.01C at the end-of-charge voltage (0.01 V). Discharging was performed in a CC mode, the current was maintained at 0.5C, and the end-of-discharge voltage was maintained at 1.5 V.

[0249] In Table 1 below, the initial efficiency (%) was obtained as a percentage of the initial discharge capacity to the initial charge capacity. In addition, the capacity retention rate was obtained as a percentage of the 50th discharge capacity to the 3rd discharge capacity.

[0250] [Table 1]

[0251]

[0252] Referring to Table 1 above, it was determined that the secondary battery using the negative electrode manufactured according to Examples 1 to 4 had better life characteristics than the secondary batteries of Comparative Examples 1 to 3.

Claims

1. A negative electrode comprising: a current collector; and a negative electrode active material layer located on at least one surface of the current collector and comprising granulated particles and a second binder, wherein the second binder holds and connects the granulated particles together, wherein the granulated particles comprise a negative electrode active material, a conductive material, and a first binder, wherein the first binder connects and holds the negative electrode active material and the conductive material together.

2. The negative electrode according to claim 1, wherein the negative electrode active material comprises a single silicon-based active material, or a mixture of the silicon-based active material and a carbon-based active material.

3. The negative electrode according to claim 2, wherein the silicon-based active material comprises silicon (Si); silicon oxide (SiOx(0 < x < 2); silicon carbide (SiC); a silicon-based alloy (M x Si y , M: Ni, Ti, Fe, Zr, Nb); or two or more thereof.

4. The negative electrode according to claim 2, wherein the carbon-based active material comprises natural graphite, artificial graphite, graphene, or two or more thereof.

5. The negative electrode according to claim 1, wherein the conductive material comprises a linear conductive material, a point-like conductive material, or two or more thereof.

6. The negative electrode according to claim 5, wherein the linear conductive material comprises carbon nanotubes, carbon nanofibers, graphene, or two or more thereof.

7. The negative electrode according to claim 5, wherein the point-like conductive material comprises carbon black, denka black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, or two or more thereof.

8. The negative electrode according to claim 1, wherein the first binder comprises a diene-based polymer, an acrylate-based polymer, a styrene-based polymer, a polyacrylonitrile-based polymer, a vinyl-based polymer, a polyoxide-based polymer, polyacrylamide, or two or more thereof.

9. The negative electrode according to claim 1, wherein the second binder comprises a diene-based polymer, an acrylate-based polymer, a styrene-based polymer, or two or more thereof.

10. The negative electrode according to claim 1, wherein the amount of the negative electrode active material is 80 parts by weight to 99 parts by weight, the amount of the conductive material is 0.001 parts by weight to 0.5 parts by weight, and the amount of the first binder is 0.1 parts by weight to 2 parts by weight, based on 100 parts by weight of the granulated particles.

11. The negative electrode according to claim 1, wherein the average particle size (D50) of the granulated particles is 10 μm to 20 μm.

12. The negative electrode according to claim 2, wherein the negative electrode active material comprises a mixture of the silicon-based active material and the carbon-based active material, and the amount of the silicon-based active material is 5 parts by weight to 25 parts by weight, based on 100 parts by weight of the carbon-based active material.

13. The negative electrode according to claim 1, wherein the negative electrode active material layer further comprises an additional carbon-based active material, an additional conductive material, or both.

14. The negative electrode according to claim 13, wherein the negative electrode active material layer comprises 100 parts by weight of the granulated particles, 80 to 99 parts by weight of the additional carbon-based active material, 0.01 to 2 parts by weight of the additional conductive material, and 1 to 4 parts by weight of the second binder.

15. A method for manufacturing the negative electrode according to claim 1, the method comprising the steps of: drying a composition comprising the negative electrode active material, the conductive material, the first binder, and a first aqueous dispersion medium by a spray drying method to manufacture the granulated particles; mixing the granulated particles with the second binder and a second aqueous dispersion medium to prepare a negative electrode slurry; and coating the negative electrode slurry on at least one surface of the current collector, drying, and roll-pressing to form the negative electrode active material layer.

16. The method for manufacturing a negative electrode according to claim 15, wherein the negative electrode active material comprises a single silicon-based active material, or a mixture of the silicon-based active material and a carbon-based active material.

17. The method for manufacturing a negative electrode according to claim 15, wherein the negative electrode slurry further comprises an additional carbon-based active material, an additional conductive material, or both.

18. The method for manufacturing a negative electrode according to claim 15, wherein the spray drying method comprises spraying and drying the slurry in hot air, and the temperature of the fed hot air is in the range of 130 to 210°C.

19. An electrochemical device comprising the negative electrode according to any one of claims 1 to 14.

20. The electrochemical device according to claim 19, wherein the electrochemical device is a secondary battery.

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