Anode, manufacturing method therefor, and electrochemical device comprising same

Abstract

Disclosed are an anode, a manufacturing method therefor, and an electrochemical device comprising same, the anode comprising: a current collector; and an anode active material layer positioned on at least one surface of the current collector and including assembled particles and a second binder which fixes and binds the assembled particles, wherein the assembled particles include an anode active material, a conductive material, and a first binder, and the first binder binds and fixes the anode active material and the conductive material.

Description

Cathode, method for manufacturing same, and electrochemical device including same

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

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

[0003] The rapid increase in fossil fuel use has led to a growing demand for alternative and clean energy sources. As part of this, the most actively researched area is the field of electrochemical power generation and storage. Secondary batteries are a prime example of electrochemical devices that utilize electrochemical energy, and their applications are expanding. Lithium secondary batteries, a representative type of secondary battery, are not only used as an energy source for mobile devices, but are also increasingly being used as a power source for electric and hybrid electric vehicles, replacing gasoline and diesel vehicles, which are major sources of air pollution. Their applications are also expanding to include auxiliary power sources through grid integration.

[0004] A lithium secondary battery is composed of an electrode assembly having a porous separator interposed between a positive electrode and a negative electrode, each of which has an active material applied to an electrode current collector, and an electrolyte containing a lithium salt is impregnated therein. The electrode is manufactured by applying a slurry in which an active material, a binder, and a conductive agent are dispersed in a solvent to a current collector, and then drying and pressing the slurry.

[0005] Furthermore, the fundamental performance characteristics of lithium secondary batteries—capacity, output, and lifespan—are significantly influenced by the anode material. To maximize battery performance, the anode active material must possess electrochemical reaction potentials approaching those of lithium metal, exhibit high reversibility in its reaction with lithium ions, and exhibit rapid lithium ion diffusion within the active material.

[0006] Carbon-based materials, which have been mainly used as a material for constituting the negative electrode of lithium secondary batteries, have a theoretical capacity limit of 372 m Ah / g, which acts as an obstacle in the process of increasing energy density. Silicon-based materials are being considered as an alternative to solve this problem. Silicon has a theoretical capacity of 4010 m Ah / g, which is more than 10 times higher than that of general carbon-based materials. However, while the charge / discharge efficiency of carbon-based materials is around 92%, silicon-based materials have a low charge / discharge efficiency of around 80%. In addition, the volume change rate during charge / discharge is high at over 300%, which causes the conductive path to be broken during continuous charge / discharge processes, preventing them from functioning as active materials.

[0007] To improve the problem of silicon-based materials having lower conductivity than carbon-based materials and the problem of reduced electrical contact between particles due to large electrode expansion when using silicon-based materials, linear conductive materials such as carbon nanotubes (CNTs) have been additionally used. However, there are still limitations in improving the problem of electrode deterioration due to the non-uniform distribution of silicon-based materials and linear conductive materials.

[0008] The problem to be solved by the present invention is to provide a cathode having improved conductivity through improved electrical contact, a method for manufacturing the cathode, and an electrochemical device including the cathode.

[0009] In order to solve the problem of the present invention, according to one aspect of the present invention, a cathode of the following embodiment is provided.

[0010] According to the first implementation example,

[0011] The entire house; and

[0012] A negative electrode active material layer positioned on at least one surface of the above-mentioned collector, comprising assembled particles and a second binder, wherein the second binder fixes and connects the assembled particles;

[0013] The above-mentioned assembly particle is a negative electrode characterized in that it includes a negative electrode active material, a conductive material, and a first binder, and the first binder connects and fixes the negative electrode active material and the conductive material.

[0014] According to the second embodiment, in the first embodiment,

[0015] The above negative electrode active material may be a silicon-based active material alone or a mixture of a silicon-based active material and a carbon-based active material.

[0016] According to the third embodiment, in the second embodiment,

[0017] The above silicon-based active material is silicon (Si), silicon oxide (SiOx (0 <x≤2), 탄화규소(SiC), 또는 이들 중 2 이상을 포함할 수 있다.

[0018] According to the fourth embodiment, in the second embodiment or the third embodiment,

[0019] The above carbon-based active material may include natural graphite, artificial graphite, graphene, or two or more thereof.

[0020] According to the fifth embodiment, in any one of the first to fourth embodiments,

[0021] The above conductive material may include a linear conductive material, a point-shaped conductive material, or two or more thereof.

[0022] According to the sixth embodiment, in the fifth embodiment,

[0023] The linear conductive material may include carbon nanotubes, carbon nanofibers, graphene, or two or more thereof.

[0024] According to the seventh embodiment, in the fifth embodiment or the sixth embodiment,

[0025] The above dot-shaped conductive material may include carbon black, Denka black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, or two or more thereof.

[0026] According to the eighth embodiment, in any one of the first to seventh embodiments,

[0027] The above first binder may include a diene polymer, an acrylate polymer, a styrene polymer, a polyacrylonitrile polymer, a vinyl polymer, a polyoxide polymer, a polyacrylamide, or two or more thereof.

[0028] According to the ninth embodiment, in any one of the first to eighth embodiments,

[0029] The second binder may include a diene polymer, an acrylate polymer, a styrene polymer, or two or more thereof.

[0030] According to the tenth embodiment, in any one of the first to ninth embodiments,

[0031] Among 100 parts by weight of the above-mentioned assembled particles, the content of the negative electrode active material may be 80 to 99 parts by weight, the content of the conductive material may be 0.001 to 0.5 parts by weight, and the content of the first binder may be 0.1 to 2 parts by weight.

[0032] According to the eleventh embodiment, in any one of the first to tenth embodiments,

[0033] The average particle diameter (D50) of the above-mentioned assembled particles may be 10 to 20 μm.

[0034] According to the 12th embodiment, in any one of the 1st to 11th embodiments,

[0035] The above negative active material is a mixture of a silicon-based active material and a carbon-based active material, and the content of the silicon-based active material may be 5 to 25 parts by weight based on 100 parts by weight of the carbon-based active material.

[0036] According to the 13th embodiment, in any one of the first to twelfth embodiments,

[0037] The above negative electrode active material layer may further include an additional carbon-based active material, an additional conductive material, or both.

[0038] According to the 14th embodiment, in any one of the first to 13th embodiments,

[0039] The negative electrode active material layer may include 100 parts by weight of the assembled 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.

[0040] According to the 15th implementation example,

[0041] A step of manufacturing granulated particles by 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;

[0042] A step of preparing a cathode slurry by mixing the above-mentioned assembled particles with a second binder and a second aqueous dispersion medium; and

[0043] A method for manufacturing a negative electrode according to any one of the first to fourteenth embodiments is provided, including a step of applying the negative electrode slurry on at least one surface of a current collector, drying, and rolling to form a negative electrode active material layer.

[0044] According to the 16th embodiment, in the 15th embodiment,

[0045] The above negative electrode active material may be a silicon-based active material alone or a mixture of a silicon-based active material and a carbon-based active material.

[0046] According to the 17th embodiment, in the 15th embodiment or the 16th embodiment,

[0047] The above negative electrode slurry may further include an additional carbon-based active material, an additional conductive material, or both.

[0048] According to the 18th embodiment, in any one of the 15th to 17th embodiments,

[0049] The above spray drying method includes a step of drying by spraying the slurry into hot air, and the temperature of the hot air introduced may be 130°C to 210°C.

[0050] According to the 19th implementation example,

[0051] An electrochemical device is provided comprising a cathode according to any one of the first to fourteenth embodiments.

[0052] According to the 20th embodiment, in the 19th embodiment,

[0053] The above electrochemical device may be a secondary battery.

[0054] According to one embodiment of the present invention, an anode can be provided that ensures uniform dispersion of the binder and the conductive material within the anode active material layer by utilizing granulated particles comprising a negative electrode active material, a conductive material, and a binder. In particular, when a silicon-based active material is used as the negative electrode active material, or when a silicon-based active material and a carbon-based active material are used together, the silicon-based active material is not locally aggregated but is evenly dispersed within the negative electrode active material layer, and especially when used together with a carbon-based active material, the carbon-based active material and the silicon-based active material can be evenly dispersed, thereby minimizing the volume expansion problem caused by the silicon-based active material while sufficiently demonstrating the high capacity of the silicon-based active material. As a result, the cell performance of an electrochemical device such as a secondary battery employing such a negative electrode can be significantly improved. In addition, in the case of assembled particles, since the surface of the particles may be rougher than that of existing graphite particles due to the assembled state of fine particles, assembled particles with increased sphericity in terms of particle shape can prevent problems such as electrode surface sinking or uneven loading by part during electrode coating, and can also have a uniform dispersion effect of the binder, which can be advantageous in improving the quality of the electrode and the processability during electrode coating.

[0055] The following drawings attached to this specification illustrate preferred embodiments of the present invention, and serve to further understand the technical idea of ​​the present invention together with the contents of the invention described above, and therefore the present invention should not be interpreted as being limited to matters described in such drawings.

[0056] Figure 1 is a schematic diagram schematically showing the surface and center portions of the assembled particles included in an electrode according to one embodiment of the present invention.

[0057] Figure 2 is a schematic diagram of a negative electrode active material layer manufactured using a conventional method.

[0058] Figure 3 is a schematic diagram of a negative electrode active material layer according to one embodiment of the present invention.

[0059] Hereinafter, the present invention will be described in more detail to help understand the present invention.

[0060] Terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0061] The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0062] Additionally, throughout this specification, when it is said that a part “includes” a component, this does not mean that other components are excluded, but rather that other components may be included, unless otherwise specifically stated.

[0063] In addition, the terms "about", "substantially", etc. used throughout this specification are used in the sense of numerical values ​​or near numerical values ​​when manufacturing and material tolerances inherent to the meanings stated are presented, and are used to prevent unscrupulous infringers from unfairly exploiting disclosures that mention exact or absolute values ​​to aid understanding of this specification.

[0064] Throughout this specification, the description of “A and / or B” means “A or B or both.”

[0065] The “glass transition temperature (Tg)” used herein is measured by a conventional method known in the art, and may be measured by, for example, differential scanning calorimetry (DSC).

[0066] In this specification, the term "porosity" means the ratio of the volume occupied by pores to the total volume in a certain structure, and its unit is vol%, and can be used interchangeably with terms such as porosity, porosity, etc. In the present invention, the measurement of the porosity is not particularly limited, and according to an embodiment of the present invention, for example, it can be measured according to the BET (Brunauer-Emmett-Teller) measurement method using nitrogen gas or the mercury penetration method (Hg porosimeter) and ASTM D-2873. Alternatively, the true density of the membrane can be calculated from the density (apparent density) of the membrane and the composition ratio of materials included in the membrane and the density of each component, and the porosity of the membrane can be calculated from the difference between the apparent density and the true density (net density).

[0067] As used herein, the "average particle diameter (D50)" refers to the particle diameter at the 50% point of the cumulative distribution of particle numbers according to particle diameter, and the particle diameter may be measured using a laser diffraction method. Specifically, the powder to be measured is dispersed in a dispersion medium, and then introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac S3500), and the difference in diffraction patterns according to particle size is measured when the particles pass through the laser beam, thereby calculating the particle size distribution. By calculating the particle diameter at the point where the cumulative distribution of particle numbers according to particle diameter in the measuring device becomes 50%, the D50 particle diameter can be measured.

[0068] The "thickness" of each layer included in the electrode in this specification may refer to a value measured by a known method for measuring thickness. The method for measuring thickness is not limited thereto, but may be, for example, a value measured using a thickness gauge (Mitutoyo, VL-50S-B).

[0069] As used herein, "specific surface area" may refer to a value measured by a known method for measuring specific surface area. The method for measuring specific surface area is not limited thereto, but may be, for example, a value measured by a fluidized or fixed method.

[0070]

[0071] According to one aspect of the present invention,

[0072] The entire house; and

[0073] A negative electrode active material layer positioned on at least one surface of the above-mentioned collector, comprising assembled particles and a second binder, wherein the second binder fixes and connects the assembled particles;

[0074] A negative electrode can be provided, characterized in that the above-mentioned assembled particles include a negative electrode active material, a conductive material, and a first binder, and the first binder connects and fixes the negative electrode active material and the conductive material.

[0075]

[0076] <Assembled particles>

[0077] The above assembled particles are described in detail below.

[0078] In the present invention, the assembled particles may have the form of composite particles including a negative electrode active material, a conductive material, and a first binder, and further including optional components added as needed.

[0079] In one embodiment of the present invention, the assembled particles may be secondary particles formed by bonding and assembling two or more negative electrode active material particles by the first binder. The assembled particles included in the negative electrode according to one embodiment of the present invention may be referred to as powder, granules, etc.

[0080]

[0081] FIG. 1 is a schematic diagram illustrating the surface and center portions of the assembled particles included in the negative electrode of one embodiment of the present invention. Referring to this, in one embodiment of the present invention, the assembled particles may have a greater amount of the first binder included in the surface portion (102) of the assembled particles than the amount of the first binder included in the center portion (101) of the assembled particles. The amount of the binder may refer to weight or volume.

[0082] Together with or independently of this, the assembled particles have a content (wt%) (B) of the first binder included in the center (101) of the assembled particles relative to 100 wt% of the total weight of the assembled particles. c / G t ) compared to the content (wt%) of the first binder included in the surface portion (102) of the assembled particles (B s / G t ) may be higher. Here, the above B c is the weight of the binder included in the center, Bs is the weight of the binder included in the surface, and G t refers to the total weight of the assembled particles.

[0083] Together with or independently of this, the assembled particles have a content (vol%) (B) of the first binder included in the center (101) of the assembled particles relative to 100 vol% of the total volume of the assembled particles. c / G t ) compared to the content (vol%) of the first binder included in the surface portion (102) of the assembled particles (B s / G t ) may be higher. Here, Bc is the volume of binder included in the center, Bs is the volume of binder included in the surface, and G t refers to the total volume of the assembled particles.

[0084] Here, the surface portion may refer to an area near the surface of the granulated particle up to a predetermined depth in the direction of the center of the granulated particle from the surface of the granulated particle. The center portion refers to a portion other than the surface portion. In one embodiment of the present invention, the surface portion may refer to a surface area specifically, from the surface of the granulated particle toward the inside, specifically, up to 30% of the radius in the direction of the center of the granulated particle. In one embodiment of the present invention, the surface portion may refer to a surface area up to 30% of the radius from the surface of the granulated particle, a surface area up to 20% of the radius, a surface area up to 15% of the radius, a surface area up to 10% of the radius, or a surface area up to 5% of the radius. Preferably, the surface portion may refer to a surface area up to 20% of the radius from the surface of the granulated particle.

[0085] Meanwhile, in one embodiment of the present invention, the surface portion may refer to an area from the center of the assembled particle to the surface of the assembled particle after 70% of the radius toward the outside of the assembled particle. In one embodiment of the present invention, the surface portion may refer to an area from, for example, after 80%, after 85%, after 90%, or after 95% of the radius to the surface of the assembled particle.

[0086] In one embodiment of the present invention, the center of the granulated particle may mean a point that is half the longest diameter of the granulated particle. In the present invention, the radius may mean 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 invention, the surface portion and the center portion may be distinguished based on points that are the same distance from each surface of the granulated particle along each radius, specifically, points that are up to 30% of the radius from the surface, up to 20% of the radius, up to 10% of the radius, up to 5% of the radius, or up to 1% of the radius.

[0087] In one embodiment of the present invention, the content of the first binder in a region from the center of the particle to the surface of the particle at a radius of 90% relative to the total weight of the particle in the region may be 50 wt% or more, 60 wt% or more, 70 wt% or more, 80 wt% or more, or 90 wt% or more.

[0088] In another embodiment of the present invention, the content of the first binder in a region from the center of the particle to the surface of the particle at 95% of the particle radius may 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 particle in the region.

[0089] In another embodiment of the present invention, the content of the first binder in a region from the center of the particle to the surface of the particle at a radius of 99% relative to 100 wt% of the total weight of the particle may be 50 wt% or more, 60 wt% or more, 70 wt% or more, 80 wt% or more, or 90 wt% or more.

[0090] In one embodiment of the present invention, the content of the first binder in a region from the center of the particle to the surface of the particle at a radius of 90% relative to the total volume of the particle in the region may be 50 vol% or more, 60 vol% or more, 70 vol% or more, 80 vol% or more, or 90 vol% or more.

[0091] In another embodiment of the present invention, the content of the first binder in a region from the center of the assembled particle to the surface of the assembled particle at a radius of 95% of the particle, relative to 100 vol% of the total volume of the assembled particle in that region, may be 50 vol% or more, 60 vol% or more, 70 vol% or more, 80 vol% or more, or 90 vol% or more.

[0092] In another embodiment of the present invention, the content of the first binder in a region from the center of the particle to the surface of the particle at a radius of 99% relative to the total volume of the particle in the region may be 50 vol% or more, 60 vol% or more, 70 vol% or more, 80 vol% or more, or 90 vol% or more.

[0093] In one embodiment of the present invention, the content of the first binder in a surface area of ​​the assembled particles up to 10% of the radius from the surface of the assembled particles may 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 assembled particles in that area.

[0094] In another embodiment of the present invention, the content of the first binder in a surface area of ​​the assembled particles up to 5% of the radius from the surface of the assembled particles may 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 assembled particles in that area.

[0095] In another embodiment of the present invention, the content of the first binder in a region from the surface of the particle to the surface of the particle after 1% of the radius may 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 particle in that region.

[0096] In one embodiment of the present invention, the content of the first binder in a surface area of ​​the assembled particles up to 10% of the radius from the surface of the assembled particles may 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 weight of the assembled particles in that area.

[0097] In another embodiment of the present invention, the content of the first binder in a surface area of ​​the granulated particles up to 5% of the radius from the surface of the granulated particles may be 50 vol% or more, 60 vol% or more, 70 vol% or more, 80 wt% or more, or 90 vol% or more, based on 100 vol% of the total weight of the granulated particles in that area.

[0098] In another embodiment of the present invention, the content of the first binder in a region from the surface of the particle to the surface of the particle after 1% of the radius of the particle may 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 weight of the particle in that region.

[0099] According to one embodiment of the present invention, a surface region having a high binder content is confirmed from the surface to a predetermined depth toward the center of the particle, and a portion other than the surface region, that is, a center region (core region) surrounded by the surface region, may have a lower binder distribution than the surface region.

[0100] To describe the above-described assembled particle in more detail, the assembled particle may have a central portion including a plurality of negative electrode active materials; and a surface portion including a first binder that is positioned on all or part of the outer side of the central portion and binds the negative electrode active materials. That is, in the central portion of the assembled particle, the plurality of negative electrode active materials form an aggregate while making surface contact, line contact, point contact, or two or more of these contacts, and in the surface portion of the assembled particle, the first binder is positioned on all or part of the outer side of the aggregate, thereby fixing and binding the plurality of negative electrode active materials in the central portion of the assembled particle to each other.

[0101] According to one embodiment of the present invention, a small amount of the first binder may also be included in the central portion, which may serve to connect and secure the plurality of negative electrode active materials in the central portion. However, as previously described, it is preferable that the content of the first binder be higher in the surface portion than in the central portion.

[0102] Meanwhile, in one embodiment of the present invention, the granulated particles may have an aspect ratio of 0.5 to 1.0, preferably 0.75 to 1.0. The aspect ratio may refer to the ratio of the major axis length to the minor axis length of the granulated particles. In another embodiment of the present invention, the average aspect ratio of the granulated particles may have a value of 0.5 to 1.0, preferably 0.75 to 1.0, and in this case, the average aspect ratio may refer to the ratio of the average major axis length to the average minor axis length of the granulated particles. At this time, the average minor axis length may refer to the average value of the length in the axial direction having the shortest length of the granulated particles, and the average major axis length may 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 satisfies this range, it is advantageous in terms of having sufficient fluidity suitable for the process.

[0103] The above negative electrode active material may be a silicon-based active material alone or a mixture of a silicon-based active material and a carbon-based active material.

[0104] The above silicon-based active material is silicon (Si), silicon oxide (SiOx (0 <x≤2), 탄화규소(SiC), 또는 이들 중 2 이상을 포함할 수 있다.

[0105] The above carbon-based active material may include natural graphite, artificial graphite, graphene, or two or more thereof. In this case, the natural graphite and artificial graphite may be in the form of a sphere, plate, or needle.

[0106] The conductive material may include a linear conductive material, a dot-shaped conductive material, or two or more thereof. That is, the conductive material may include one or more types of linear conductive material, one or more types of dot-shaped conductive material, or two or more types of linear conductive material and dot-shaped conductive material, respectively.

[0107] In the above dot-shaped conductive material, “dot-shaped” may mean having a spherical particle shape and an average diameter (D50) in the range of 10 to 500 nm, specifically 15 to 100 nm.

[0108] In addition, the dot-shaped conductive material may be applied if it is a spherical particle-shaped conductive material having the above-mentioned average diameter. Specific examples of the dot-shaped conductive material may independently include carbon black, Denka black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, etc., or two or more thereof.

[0109] In the linear conductive material, “linear” means a particle shape such as a needle, for example, having an aspect ratio (ratio of length to diameter) of 10 to 1,000, specifically 20 to 500. For example, according to one embodiment of the present invention, the linear conductive material may have an average diameter of 10 to 500 nm, specifically 20 to 300 nm. In addition, the linear conductive material used in one embodiment of the present invention may have an average length of 3 to 50 μm, specifically 5 to 30 μm, more specifically 5 to 20 μm, more specifically 10 to 20 μm, more specifically 13 to 17 μm.

[0110] Here, the average diameter is the arithmetic mean of the diameters of the vertical plane in the longitudinal direction of the linear conductive material, and can be obtained, for example, from an SEM image taken with a field emission scanning electron microscope at a magnification of 2,000 to 50,000 times. In addition, the average length is the arithmetic mean of the lengths of the linear conductive material, and can be obtained in the same manner as the average diameter.

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

[0112] The single-walled carbon nanotubes described above are formed by connecting hexagons of six carbon atoms to form a single tube-shaped carbon nanotube with only one wall (graphite plane). These single-walled carbon nanotubes exhibit excellent electrical properties due to their one-dimensional structure, and exhibit a variety of electrical properties depending on their hexagonal honeycomb-shaped molecular asymmetry (chirality) structure and diameter.

[0113] A double-walled carbon nanotube is a carbon nanotube having two walls, and a multi-walled carbon nanotube is a carbon nanotube having multiple walls.

[0114] The average diameter of the single-walled carbon nanotubes may be 0.5 nm to 15 nm. According to one embodiment of the present invention, the average diameter of the single-walled carbon nanotubes may be 1 to 10 nm, or 1 to 5 nm, or 1 to 2 nm. When the average diameter of the single-walled carbon nanotubes satisfies this range, the electrical conductivity of the cathode can be maintained even if the single-walled carbon nanotubes are included in a very small amount. The BET specific surface area of ​​the single-walled carbon nanotubes is 500 m 2 / g to 1,500 m 2 / g, or 900 m2 / g to 1,200 m 2 / g. When the above range is satisfied, a conductive dispersion having a desirable solid content can be derived. The BET specific surface area can be measured through a nitrogen adsorption 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 to 100 ㎛, or 5 to 50 ㎛. The aspect ratio can be confirmed by obtaining the average aspect ratio of 15 single-walled carbon nanotubes with a large aspect ratio and 15 single-walled carbon nanotubes with a small aspect ratio when observing the single-walled carbon nanotube powder through an SEM.

[0115] Single-walled carbon nanotubes have a larger aspect ratio than multi-walled carbon nanotubes or double-walled carbon nanotubes, making them longer and larger in volume, allowing them to be used in small quantities to build electrical networks.

[0116] The above linear conductive material surrounds the silicon-based active material, so that the structure of the negative electrode active material layer including the silicon-based active material can be maintained during charge and discharge, and the silicon-based active material can continuously maintain contact even with a large volume change, so that electron supply can be smoothly provided even during long-term cycling, contributing to a long lifespan, and since the electron movement distance can be increased, the negative electrode active materials located above and below the negative electrode active material layer can all participate in the charge and discharge reaction, so that high-rate charge and discharge performance can be improved.

[0117] In addition, the conductive material and the additional conductive material optionally included in the above-described assembled particles, as described later, can contact the negative electrode active material over a large area, thereby improving the high-rate characteristics.

[0118] According to one embodiment of the present invention, when the conductive material uses an assembled particle including both a linear conductive material and a dot-shaped conductive material, the linear conductive material and the dot-shaped conductive material are uniformly distributed within the negative electrode active material layer, so that the advantageous effects of the linear conductive material and the dot-shaped conductive material can be exhibited simultaneously, and in particular, compared to a negative electrode using a conventional linear conductive material, an electrical network can be sufficiently constructed within the negative electrode active material layer even with a smaller content, so that excellent conductivity and expansion suppression performance of the silicon-based active material can be realized.

[0119] In one embodiment of the present invention, the content of the conductive material may be 0.001 to 0.5 parts by weight, or (0.05) to 0.1 parts by weight, based on 100 parts by weight of the negative electrode active material.

[0120]

[0121] According to one embodiment of the present invention, the first binder may include a diene polymer, an acrylate polymer, a styrene polymer, a polyacrylonitrile polymer, a vinyl polymer, a polyoxide polymer, a polyacrylamide, or two or more thereof.

[0122] Examples of the diene polymer include polymers containing monomer units derived from conjugated dienes such as butadiene and isoprene, and hydrogenated products thereof. The proportion of monomer units derived from conjugated dienes in the diene polymer may usually be 40 wt% or more, preferably 50 wt% or more, and more preferably 60 wt% or more. Specifically, examples thereof include conjugated diene homopolymers such as polybutadiene or polyisoprene; aromatic vinyl-conjugated diene copolymers such as styrene-butadiene copolymers (SBR), which may be carboxyl-modified; cyanated vinyl-conjugated diene copolymers such as acrylonitrile-butadiene copolymers (NBR); hydrogenated SBR, hydrogenated NBR, and the like.

[0123] Examples of the above acrylate polymer may include a polymer containing monomer units derived from acrylic acid ester and / or methacrylic acid ester. The proportion of monomer units derived from acrylic acid ester and / or methacrylic acid ester in the acrylate polymer may usually be 40% by weight or more, preferably 50% by weight or more, and more preferably 60% by weight or more. Specific examples of acrylate polymers include cross-linked acrylate polymers such as 2-ethylhexyl acrylate-methacrylic acid-acrylonitrile-ethylene glycol dimethacrylate copolymer, 2-ethylhexyl acrylate-methacrylic acid-methacrylonitrile-diethylene glycol dimethacrylate copolymer, 2-ethylhexyl acrylate-styrene-methacrylic acid-ethylene glycol dimethacrylate copolymer, butyl acrylate-acrylonitrile-diethylene glycol dimethacrylate copolymer, and butyl acrylate-acrylic acid-trimethylolpropane trimethacrylate copolymer; Examples thereof include copolymers of ethylene and (meth)acrylic acid esters, such as ethylene-methyl acrylate copolymers, ethylene-methyl methacrylate copolymers, ethylene-ethyl acrylate copolymers, and ethylene-ethyl methacrylate copolymers; graft polymers obtained by grafting a radically polymerizable monomer onto the above copolymers of ethylene and (meth)acrylic acid esters; and the like. Meanwhile, examples of the radically polymerizable monomer used in the graft polymers include methyl methacrylate, acrylonitrile, and methacrylic acid. In addition, copolymers of ethylene and (meth)acrylic acid, such as ethylene-acrylic acid copolymers and ethylene-methacrylic acid copolymers, can be used as dispersion-type binders.

[0124] The above styrene polymer is a polymer having a repeating unit derived from a styrene monomer, and may include a styrene homopolymer (polystyrene), a styrene copolymer, etc. Examples of the above styrene copolymers include styrene-butadiene copolymer (SBR), styrene-ethylene-butadiene copolymer, styrene-butadiene-propylene copolymer, styrene-butadiene-acrylate copolymer (SBR-acrylate) (e.g., styrene-n-butyl acrylate-itaconic acid-methyl methacrylate-acrylonitrile copolymer, styrene-n-butyl acrylate-itaconic acid-methyl methacrylate-acrylonitrile copolymer, etc.), styrene-isoprene 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 There may be block copolymers, such as copolymers.

[0125] The above polyacrylonitrile-based polymer may include polyacrylonitrile, acrylamide-acrylonitrile-acrylic acid terpolymer, etc.

[0126] Examples of the above vinyl polymers include polyvinyl alcohol, polyvinyl propylene, and polyvinyl acetate.

[0127] The above polyoxide polymer may include polyethylene oxide, polypropylene oxide, etc.

[0128] In one embodiment of the present invention, the content of the first binder may be 0.5 to 20 parts by weight, or 2 to 10 parts by weight, based on 100 parts by weight of the negative electrode active material.

[0129]

[0130] In one embodiment of the present invention, the content of the negative active material may be 80 to 99 parts by weight, or 82 to 98 parts by weight, of 100 parts by weight of the assembled particles, the content of the conductive material may be 0.001 to 0.5 parts by weight, or 0.05 to 0.1 parts by weight, and the content of the first binder may be 0.5 to 20 parts by weight, or 2 to 10 parts by weight.

[0131] When the contents of the negative active material, conductive material, and first binder in the above-mentioned assembled particles satisfy this range, it may be more advantageous in terms of (uniformity of the assembled particle shape and particle size distribution).

[0132] In addition, the average particle diameter (D50) of the above-mentioned assembled particles may be 10 to 20 μm, or 13 to 18 μm. When the negative electrode active material is a silicon-based active material, the average particle diameter (D50) of the silicon-based active material may 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 diameter (D50) of the carbon-based active material may be 8 to 18 μm, or 10 to 16 μm.

[0133] When the range of the average particle diameter of the above-mentioned assembled particles and the negative electrode active material satisfies the above, it may be more advantageous in terms of uniformity of the assembled particle shape and particle size distribution.

[0134] In one embodiment of the present invention, the negative electrode active material is a mixture of a silicon-based active material and a carbon-based active material, and the content of the silicon-based active material may 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 content ratio of the silicon-based active material and the carbon-based active material satisfies this, it may be more advantageous in terms of inter-particle dispersion within the assembled particles.

[0135]

[0136] <Cathode active material layer>

[0137] The negative electrode of the present invention comprises a current collector and a negative electrode active material layer positioned on at least one surface of the current collector, and the negative electrode active material layer comprises assembled particles including a negative electrode active material, a conductive material, and a first binder; and a second binder.

[0138]

[0139] In one embodiment of the present invention, the negative electrode active material layer may have a porosity of 20 vol% to 40 vol%, and when the porosity is within this range, electrolyte impregnation property, shape stability, and ionic conductivity may be further improved.

[0140] Meanwhile, according to one embodiment of the present invention, the thickness of the negative electrode active material layer may be, for example, 30 µm to 300 µm, but is not limited thereto.

[0141] According to another embodiment of the present invention, the negative electrode active material layer may be composed of a single layer including one unit active material layer.

[0142] According to one embodiment of the present invention, the negative electrode active material layer may have a multilayer structure in which two or more unit active material layers are laminated. In this case, the electrode materials included in each unit active material layer, for example, the negative electrode active material and binder, may be the same or different for each layer, but are not limited thereto.

[0143]

[0144] In one embodiment of the present invention, the second binder may include a diene polymer, an acrylate polymer, a styrene polymer, or two or more thereof.

[0145] Examples of the diene polymer include polymers containing monomer units derived from conjugated dienes such as butadiene and isoprene, and hydrogenated products thereof. The proportion of monomer units derived from conjugated dienes in the diene polymer may usually be 40 wt% or more, preferably 50 wt% or more, and more preferably 60 wt% or more. Specifically, examples thereof include conjugated diene homopolymers such as polybutadiene or polyisoprene; aromatic vinyl-conjugated diene copolymers such as styrene-butadiene copolymers (SBR), which may be carboxyl-modified; cyanated vinyl-conjugated diene copolymers such as acrylonitrile-butadiene copolymers (NBR); hydrogenated SBR, hydrogenated NBR, and the like.

[0146] Examples of the above acrylate polymer may include a polymer containing monomer units derived from acrylic acid ester and / or methacrylic acid ester. The proportion of monomer units derived from acrylic acid ester and / or methacrylic acid ester in the acrylate polymer may usually be 40% by weight or more, preferably 50% by weight or more, and more preferably 60% by weight or more. Specific examples of acrylate polymers include cross-linked acrylate polymers such as 2-ethylhexyl acrylate-methacrylic acid-acrylonitrile-ethylene glycol dimethacrylate copolymer, 2-ethylhexyl acrylate-methacrylic acid-methacrylonitrile-diethylene glycol dimethacrylate copolymer, 2-ethylhexyl acrylate-styrene-methacrylic acid-ethylene glycol dimethacrylate copolymer, butyl acrylate-acrylonitrile-diethylene glycol dimethacrylate copolymer, and butyl acrylate-acrylic acid-trimethylolpropane trimethacrylate copolymer; Examples thereof include copolymers of ethylene and (meth)acrylic acid esters, such as ethylene-methyl acrylate copolymers, ethylene-methyl methacrylate copolymers, ethylene-ethyl acrylate copolymers, and ethylene-ethyl methacrylate copolymers; graft polymers obtained by grafting a radically polymerizable monomer onto the above copolymers of ethylene and (meth)acrylic acid esters; and the like. Meanwhile, examples of the radically polymerizable monomer used in the graft polymers include methyl methacrylate, acrylonitrile, and methacrylic acid. In addition, copolymers of ethylene and (meth)acrylic acid, such as ethylene-acrylic acid copolymers and ethylene-methacrylic acid copolymers, can be used as dispersion-type binders.

[0147] The above styrene polymer is a polymer having a repeating unit derived from a styrene monomer, and may include a styrene homopolymer (polystyrene), a styrene copolymer, etc. Examples of the above styrene copolymers may 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, and styrene-ethylene-propylene-styrene block copolymer.

[0148] Among these, diene polymers and cross-linked acrylate polymers are preferred, and cross-linked acrylate polymers are particularly preferred, from the viewpoint that granules having excellent adhesion to a current collector and surface smoothness can be obtained, and electrodes for electrochemical devices having high electrostatic capacity and low internal resistance can be manufactured.

[0149] In the negative electrode active material layer, the content of the second binder may be 0.5 to 4 parts by weight, or 1 to 2 parts by weight, based on 100 parts by weight of the assembled particles.

[0150] In one embodiment of the present invention, the negative electrode active material layer may further include an additional carbon-based active material, an additional conductive material, or both. That is, in addition to the assembled particles and the second binder, the negative electrode active material layer may further include an additional carbon-based active material, or may further include an additional conductive material, or may further include both an additional carbon-based active material and an additional conductive material.

[0151] In one embodiment of the present invention, the negative electrode active material layer may include 100 parts by weight of the granulated particles, 80 to 99 parts by weight, or 85 to 95 parts by weight, of the additional carbon-based active material, 0.01 to 2 parts by weight, or 0.05 to 0.5 parts by weight, of the additional conductive material, and 1 to 4 parts by weight, or 1.5 to 2.5 parts by weight, of the second binder.

[0152] When the contents of the assembled particles, additional carbon-based active material, additional conductive material, and second binder in the above-described negative electrode active material layer satisfy this range, excellent electrode quality can be secured, which can be more advantageous in terms of cell performance.

[0153] Meanwhile, in some cases, a filler, which is a component that suppresses expansion of the negative electrode active material layer, may be additionally added to the negative electrode active material layer. The filler is not particularly limited as long as it is a fibrous material that does not cause a chemical change in the battery, and for example, an olefin polymer such as polyethylene or polypropylene; a fibrous material such as glass fiber or carbon fiber is used.

[0154] Fig. 2 is a schematic diagram of a negative electrode active material layer manufactured from 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) in a conventional manner. Referring to Fig. 2, it can be seen that the conductive material is unevenly dispersed within the negative electrode active material layer and clumps together in a specific area (part A), or a plurality of silicon-based active materials (10) are aggregated between carbon-based active materials (20), resulting in significantly reduced dispersibility (part B).

[0155] On the other hand, Fig. 3 is a schematic diagram of a negative electrode active material layer according to one embodiment of the present invention. Referring to Fig. 3, granulated particles (50) including a negative electrode active material, a conductive material, and a first binder are separately manufactured, and by applying these granulated particles together with a second binder, an anode can be provided in which uniform dispersion of the silicon-based active material and the conductive material is secured within the negative electrode active material layer (see part C). Specifically, when a silicon-based active material is included as the negative electrode active material during the manufacture of the granulated particles, a linear conductive material is used as the conductive material, and a carbon-based active material (20) is used as an additional negative electrode active material together with these granulated particles (50), it can be seen that, unlike the conventional negative electrode of Fig. 2, the silicon-based active material within the granulated particles does not aggregate between the carbon-based active materials (20), and the dispersibility is greatly improved.

[0156] The current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, copper, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. can be used. The current collector can also form fine unevenness on its surface to increase the adhesive strength of the negative electrode active material, and various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric are possible.

[0157] In one embodiment of the present invention, a primer layer may be formed entirely or partially on the collector.

[0158] The above primer layer includes a binder for the primer layer and a conductive material for the primer layer, and the sum of the contents of the binder and the conductive material in the primer layer may be 90 wt% or more.

[0159] An electrode according to one embodiment of the present invention includes a negative electrode active material layer including assembled particles, wherein the primer layer includes a binder and a conductive material, and the sum of the contents of the binder and the conductive material is 90 wt% or more, thereby ensuring stability of the primer layer over time, and thus exhibiting excellent physical properties such as adhesive strength and lifespan characteristics, but the present invention is not limited thereto.

[0160] According to one embodiment of the present invention, the primer layer includes a binder for the primer layer and a conductive material for the primer layer, and may further include a dispersant.

[0161] According to one embodiment of the present invention, the primer layer may include a binder for the primer layer and a conductive material for the primer layer, but may substantially not include a dispersant.

[0162] According to one embodiment of the present invention, the binder for the primer layer may be used without particular limitation as long as it is a known binder used in a primer layer.

[0163] According to another embodiment of the present invention, the binder for the primer layer may preferably use a polymer capable of ensuring stability of the primer layer over time. Specifically, the binder for the primer layer may have a glass transition temperature (Tg) of 45°C or less.

[0164] According to another embodiment of the present invention, the binder for the primer layer is, 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-hexafluoropropylene fluoride-co-hexafluoropropylene), polyvinylidene fluoride-co-trichloroethylene, polymethylmethacrylate, polyethylhexylacrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene, polypropylene, polyethylene-co-vinyl acetate, polyethylene oxide, polypropylene oxide, polyarylate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, or two or more thereof.Specifically, the binder may include styrene butadiene rubber (SBR), nitrile butadiene rubber (NBR), polymethylmethacrylate, polyethylhexylacrylate, polybutylacrylate, or two or more thereof.

[0165] According to another embodiment of the present invention, the binder for the primer layer may be a mixture of one or two or more types selected from the above-described types while having the above-described glass transition temperature value.

[0166] According to another embodiment of the present invention, the binder for the primer layer may be styrene butadiene rubber (SBR) having a glass transition temperature (Tg) of -40°C to 45°C, nitrile butadiene rubber (NBR) having a glass transition temperature (Tg) of -40°C to 45°C, or a mixture thereof.

[0167] According to one embodiment of the present invention, the conductive material for the primer layer has a specific surface area of ​​30 m 2 / g to 1,400 m 2 / g and may have a spherical shape. At this time, the size of the primary particle of the conductive material having a spherical shape may be, for example, 10 nm to 100 nm, specifically 15 nm to 70 nm, but is not limited thereto.

[0168] According to another embodiment of the present invention, the conductive material for the primer layer has a specific surface area of ​​10 m 2 / g to 400 m 2 / g may have a tubular shape. At this time, the conductive material having a tubular shape may have a cross-sectional diameter in a direction orthogonal to the longitudinal direction of 0.1 to 3 nm, specifically 0.3 to 1.5 nm, but is not limited thereto.

[0169] The conductive material for the primer layer is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and for example, graphite such as natural graphite or artificial graphite; carbon black-based carbon compounds such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black; conductive fibers such as carbon fibers or metal fibers; metal particles such as fluorocarbon, aluminum, and nickel particles; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives may be used. However, specifically, in order to uniformly mix the conductive material and improve conductivity, the conductive material may include activated carbon, graphite, carbon black, carbon nanotubes, or a mixture of two or more thereof, and more specifically, the conductive material may include activated carbon.

[0170] According to one embodiment of the present invention, the primer layer includes the above-described composition and may have a thickness of 300 nm to 1.5 ㎛, specifically 700 nm to 1.3 ㎛, but is not limited thereto.

[0171]

[0172] <Method for manufacturing cathode>

[0173] According to one aspect of the present invention, there is provided a step of manufacturing granulated particles by 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;

[0174] A step of preparing a cathode slurry by mixing the above-mentioned assembled particles with a second binder and a second aqueous dispersion medium; and

[0175] A method for manufacturing a negative electrode according to one embodiment of the present invention is provided, including a step of applying the negative electrode slurry on at least one surface of a current collector, drying, and rolling to form a negative electrode active material layer.

[0176]

[0177] First, a composition including a negative active material, a conductive agent, a first binder, and a first aqueous dispersion medium is dried by spray drying to produce granulated particles.

[0178] A negative electrode active material, a conductive material, a first binder, and optionally, an additive are dispersed or dissolved in a dispersion medium (which may be a solvent for the first binder), thereby obtaining a composition in which the negative electrode active material, the conductive material, the first binder, and / or other additives are dispersed or dissolved.

[0179] As a dispersion medium used to obtain the above composition, water is most preferably used, but an organic solvent may also be used. Examples of the organic solvent include alkyl alcohols such as methyl alcohol, ethyl alcohol, and propyl alcohol; alkyl ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran, dioxane, and diglyme; amides such as diethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone (hereinafter also referred to as NMP), and dimethylimidazolidinone; sulfur-based solvents such as dimethyl sulfoxide and sulfolane; and the like, but alcohols are preferred. When an organic solvent having a boiling point lower than water is used in combination, the drying speed during fluid granulation can be accelerated. In addition, since the dispersibility or solubility of the negative electrode binder can be changed, the viscosity and fluidity of the slurry can be adjusted depending on the amount or type of the dispersion medium, thereby improving production efficiency.

[0180] The amount of the dispersion medium used when preparing the above composition may be an amount such that the solid content concentration of the composition is usually in the range of 0.1 to 20 wt%, or 0.5 to 10 wt%, or 1 to 5 wt%.

[0181] The method or order of dispersing or dissolving the negative electrode active material, conductive material, first binder, etc. in the dispersion medium is not particularly limited, and examples thereof include a method of adding the negative electrode active material, conductive material, and first binder to the dispersion medium and mixing them, a method of first dissolving or dispersing the first binder in the dispersion medium, and then finally adding the negative electrode active material and conductive material and mixing them, etc. As a mixing means, a mixing device such as a ball mill, a sand mill, a bead mill, a pigment disperser, a stone mill, an ultrasonic disperser, a homogenizer, and a planetary mixer may be mentioned. The mixing may be performed, for example, at a temperature ranging from room temperature to 80°C for 10 minutes to several hours.

[0182] Next, the composition is spray-dried. Spray drying is a method of drying by spraying a slurry into hot air. The spraying method of the device used in spray drying includes a rotating disc method and a nozzle pressurization method. The rotating disc method is a method in which the composition is introduced almost at the center of a high-speed rotating disc, and the composition is placed outside the disc by the centrifugal force of the disc, and then dried in the form of a mist. The rotation speed of the disc depends on the size of the disc, but is usually 5,000 rpm to 35,000 rpm, preferably 15,000 rpm to 30,000 rpm. On the other hand, the nozzle pressurization method is a method in which the composition is passed through a thin nozzle while simultaneously spraying a high-pressure fluid such as air or another liquid to spray it in the form of a mist, thereby drying.

[0183] In one embodiment of the present invention, the temperature of the hot air (the temperature of the hot air being introduced) can be controlled to be 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, based on the reactor inlet temperature (at the time of introduction), in terms of forming a granulated particle structure having a high content of the first binder on the surface. When the temperature of the hot air supplied satisfies this range, the negative active material, the conductive agent, and the first binder are uniformly dispersed within the assembled particles, and as a result, each component is dispersed within the assembled particles manufactured under these hot air temperature conditions, so that the capacity can be uniformly developed during cell manufacturing. Specifically, when the temperature of the hot air supplied is higher than this range, drying proceeds quickly, and during rapid drying, the drying of the solvent (water) in the sprayed droplets is faster than the alignment of the particles within the droplets, and only the small silicon particles move quickly in the solvent drying direction, so that the silicon particles in the assembled particles are not uniformly dispersed and may aggregate, or in severe cases, only the silicon particles may aggregate to form separate assembled particles. In this way, an electrode manufactured using the assembled particles obtained by not uniformly dispersing the silicon particles and agglomerating them, or by only agglomerating the silicon particles, may exhibit non-uniform capacity. Conversely, if the hot air temperature is excessively low, the droplets may not be sufficiently dried during the time they are in contact with the hot air and may stick to the inner wall of the chamber and dry. In this case, due to uneven drying, the particles may be formed in which the negative electrode active material, conductive material, and first binder are unevenly distributed within the particles, and the collection rate may also be low. In addition, if the temperature of the hot air satisfies this range, the droplets are uniformly sprayed, and the shape of the resulting particles becomes uniform, so that the performance of the electrode can be improved.

[0184]

[0185] In the spray drying method, the method of inhaling hot air is not particularly limited, and examples thereof include a method in which the hot air and the spray direction are parallel to each other in the horizontal direction, a method in which the hot air is sprayed from the top of the drying tower and then descends together with the hot air, a method in which the sprayed droplets come into countercurrent contact with the hot air, and a method in which the sprayed droplets initially come into parallel with the hot air and then fall by gravity to come into countercurrent contact. Meanwhile, in one embodiment of the present invention, the outlet temperature of the reactor during the spray drying (the temperature of the hot air discharged from the reactor) can be controlled to be 90°C to 130°C.

[0186] If the outlet temperature and / or the difference between the inlet and outlet temperatures, △T, is low, drying may not be performed properly, resulting in the formation of particles with a large amount of residual solvent, which may prevent uniformly shaped spherical particles from being formed and may result in the formation of aggregated particles that are agglomerated or irregularly shaped. On the other hand, if the inlet temperature is too high and △T is large, overdrying may result in poor assembly, resulting in particles with a significantly small D50 and a low aspect ratio. Therefore, in order to achieve a high aspect ratio, minimize binder agglomeration, and control the particle size to an appropriate level, it is necessary to control the inlet temperature and outlet temperature within an appropriate range.

[0187] Additionally, the result obtained by optionally spray drying, i.e., the surface of the assembled particles, can be heat-treated to harden them. At this time, the heat treatment temperature can usually be 80°C to 300°C.

[0188]

[0189] Thereafter, the above-mentioned assembled particles are mixed with a second binder and a second aqueous dispersion medium to prepare a negative electrode slurry.

[0190] At this time, the second aqueous dispersion medium used may refer to the first aqueous dispersion medium described above, and the slurry manufacturing process may refer to the composition manufacturing process for manufacturing the above-described granulated particles.

[0191]

[0192] Next, the negative electrode slurry is applied to at least one surface of the current collector, dried, and rolled to form a negative electrode active material layer.

[0193] The slurry prepared by the above-described method is applied onto a current collector. At this time, a primer layer including a conductive material for a primer layer and a binder for a primer layer may be provided on at least one side of the current collector, as described above.

[0194] In one embodiment of the present invention, the method of coating the slurry on at least one surface of the collector may use a general method commonly used in the art, such as spray coating, dip coating, gravure coating, die coating, etc.

[0195] In one embodiment of the present invention, the drying may be performed using a conventional drying method used in electrode manufacturing. For example, the drying may be performed at a temperature of 30°C to 200°C or 40°C to 80°C. Additionally, the drying may be performed using air for 2 to 20 minutes or 2 to 10 minutes.

[0196] The above-mentioned rolling step is typically a press process using rolls. In a roll press process, two cylindrical rolls are aligned vertically and parallel with a narrow gap between them, rotated in opposite directions, and electrodes are interlocked between them to apply pressure. The rolls can also be subjected to temperature control, such as heating or cooling.

[0197] As described above, the negative electrode active material may be a silicon-based active material alone, or a mixture of a silicon-based active material and a carbon-based active material. In addition, the negative electrode slurry may further include an additional carbon-based active material, an additional conductive material, or both.

[0198]

[0199] Additionally, according to one aspect of the present invention, an electrochemical device comprising a cathode according to one embodiment of the present invention is provided.

[0200] The electrochemical device includes all devices that undergo an electrochemical reaction, and specific examples thereof include capacitors such as all types of primary batteries, secondary batteries, fuel cells, solar cells, or supercapacitor devices. In the present invention, the electrochemical device may preferably be a secondary battery, and more preferably, a lithium-ion secondary battery.

[0201] In addition, according to one embodiment of the present invention, an energy storage device including the secondary battery as a unit battery can be provided.

[0202] The above secondary battery may be configured such that an electrode assembly including a negative electrode, a positive electrode, and a separator according to one embodiment of the present invention is housed in a battery case (cylindrical case, square case, pouch, etc.) together with a lithium-containing non-aqueous electrolyte.

[0203] The above positive electrode may have a positive electrode active material layer including a positive electrode active material, a binder, and optionally a conductive material, etc. on at least one surface of the current collector.

[0204] The above cathode active material is not limited to a lithium transition metal oxide or a lithium metal iron phosphate, as long as it is in the form of a metal oxide, and 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; chemical formula Li 1+x Mn 2-x Lithium manganese oxides such as O4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, Cu2V2O7; chemical formula LiNi 1-x M xNi-site type lithium nickel oxide represented by O2 (where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga and x = 0.01 to 0.3); chemical formula LiMn 2-x M x Lithium manganese complex oxides represented by O2 (wherein, M = Co, Ni, Fe, Cr, Zn or Ta, and x = 0.01 to 0.1) or Li2Mn3MO8 (wherein, M = Fe, Co, Ni, Cu or Zn); Li where some of the Li in the chemical formula is replaced by aluminum ions. 1+x (Ni a Co b Mn c Al d ) 1-x O2(x = 0 ~ 0.03, a = 0.3 ~ 0.95, b = 0.01 ~ 0.35, c = 0.01 ~ 0.5, d = 0.001 ~ 0.03, a+b+c+d=1); lithium metal phosphate LiM P O4 (wherein M = Fe, CO, Ni, or Mn), disulfide compounds; Fe2(MoO4)3, etc., but are not limited to these.

[0205] In one embodiment of the present invention, the binder included in the positive electrode is not particularly limited as long as it is used as a binder material for an electrochemical device, but may include, for example, a diene polymer, an acrylate polymer, a fluorine polymer, a styrene polymer, or two or more thereof.

[0206] Examples of the diene polymer include polymers containing monomer units derived from conjugated dienes such as butadiene and isoprene, and hydrogenated products thereof. The proportion of monomer units derived from conjugated dienes during the diene polymerization may usually be 40 wt% or more, preferably 50 wt% or more, and more preferably 60 wt% or more.

[0207] Specifically, examples thereof include conjugated diene homopolymers such as polybutadiene or polyisoprene; aromatic vinyl-conjugated diene copolymers such as styrene-butadiene copolymer (SBR), which may also be carboxyl-modified; cyanated vinyl-conjugated diene copolymers such as acrylonitrile-butadiene copolymer (NBR); hydrogenated SBR, hydrogenated NBR, and the like.

[0208] The above styrene polymer is a polymer having a repeating unit derived from a styrene monomer, and may include a styrene homopolymer (polystyrene), a styrene copolymer, etc. Examples of the above styrene copolymers may 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, and styrene-ethylene-propylene-styrene block copolymer.

[0209] Examples of the above acrylate polymer may include a polymer containing monomer units derived from acrylic acid ester and / or methacrylic acid ester. The proportion of monomer units derived from acrylic acid ester and / or methacrylic acid ester in the acrylate polymer may usually be 40 wt% or more, preferably 50 wt% or more, and more preferably 60 wt% or more. Specific examples of acrylate polymers include crosslinked acrylate polymers such as 2-ethylhexyl acrylate-methacrylic acid-acrylonitrile-ethylene glycol dimethacrylate copolymer, 2-ethylhexyl acrylate-methacrylic acid-methacrylonitrile-diethylene glycol dimethacrylate copolymer, 2-ethylhexyl acrylate-styrene-methacrylic acid-ethylene glycol dimethacrylate copolymer, butyl acrylate-acrylonitrile-diethylene glycol dimethacrylate copolymer, and butyl acrylate-acrylic acid-trimethylolpropane trimethacrylate copolymer; Examples thereof include copolymers of ethylene and (meth)acrylic acid esters, such as ethylene-methyl acrylate copolymers, ethylene-methyl methacrylate copolymers, ethylene-ethyl acrylate copolymers, and ethylene-ethyl methacrylate copolymers; graft polymers obtained by grafting a radically polymerizable monomer onto the above copolymers of ethylene and (meth)acrylic acid esters; and the like. Meanwhile, examples of the radically polymerizable monomer used in the graft polymers include methyl methacrylate, acrylonitrile, and methacrylic acid. In addition, copolymers of ethylene and (meth)acrylic acid, such as ethylene-acrylic acid copolymers and ethylene-methacrylic acid copolymers, can be used as dispersion-type binders.

[0210] The above fluorine-based polymer may include polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), and polyvinylidene fluoride copolymers such as PVDF-HFP, and specifically, may include polytetrafluoroethylene (PTFE), and more specifically, may be polytetrafluoroethylene (PTFE).

[0211] The above separator may be a conventional porous polymer film used as a conventional separator, for example, a porous polymer film made of a polyolefin polymer such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, which may be used alone or in a laminated manner. In addition, an insulating thin film having high ion permeability and mechanical strength may be used. The separator may include a safety reinforced separator (SRS) in which a ceramic material is thinly coated on the surface of the separator. In addition, a conventional porous non-woven fabric, for example, a non-woven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. may be used, but is not limited thereto.

[0212] The above electrolyte solution includes a lithium salt as an electrolyte and an organic solvent for dissolving the same.

[0213] The above lithium salt can be used without limitation as long as it is one commonly used in electrolytes for secondary batteries, and for example, the anion of the above lithium salt is 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 - One type selected from the group consisting of can be used.

[0214] As the organic solvent included in the above electrolyte, any commonly used one can be used without limitation, and representative examples thereof include at least one selected from the group consisting of propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, methylpropyl carbonate, dipropyl carbonate, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, vinylene carbonate, sulfolane, gamma-butyrolactone, propylene sulfite, and tetrahydrofuran.

[0215] In particular, among the above carbonate-based organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, are high-viscosity organic solvents with high dielectric constants and thus can be preferably used because they easily dissociate lithium salts in the electrolyte. In addition, when a low-viscosity, low-dielectric constant linear carbonate such as dimethyl carbonate and diethyl carbonate is mixed and used in an appropriate ratio with these cyclic carbonates, an electrolyte having high electrical conductivity can be produced, so that the electrolyte can be used even more preferably.

[0216] Optionally, the electrolyte stored according to the present invention may further include additives such as an overcharge prevention agent included in a conventional electrolyte.

[0217] According to one embodiment of the present invention, a lithium secondary battery is formed by placing a separator between a positive electrode and a negative electrode to form an electrode assembly, placing the electrode assembly in, for example, a pouch, a cylindrical battery case, or a square battery case, and then injecting an electrolyte to complete the secondary battery. Alternatively, the electrode assembly may be laminated, then impregnated with an electrolyte, and the resulting product may be placed in a battery case and sealed to complete the lithium secondary battery.

[0218] At this time, since the specific structure of the secondary battery and energy storage device is known in the prior art, a description thereof is omitted in this specification.

[0219]

[0220] Hereinafter, the present invention will be described in detail with examples to specifically illustrate it. However, the examples according to the present invention may be modified in various ways, and the scope of the present invention should not be construed as being limited to the examples described below. These examples are provided to more fully explain the present invention to those of average skill in the art.

[0221]

[0222] Example

[0223] [Example 1]

[0224] 1. Cathode

[0225] (1) Preparation of assembled particles

[0226] Si (average particle size (D50): 3㎛) as a silicon-based active material, spherical natural graphite (average particle size (D50): 18㎛) 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 and a suspension was prepared through a homogenizer.

[0227] The manufactured composition was introduced into a spray dryer with hot air under a pressure range of -40 mmH2O and dried. At this time, the conditions of the spray dryer were controlled as follows: inlet temperature 160°C, outlet temperature 90°C, and rotation speed 18,000 rpm.

[0228] The above-described assembled particles had a central portion including a plurality of silicon-based active materials, carbon-based active materials, and conductive materials, and a surface portion including a first binder located outside the central portion and binding the plurality of silicon-based active materials, carbon-based active materials, and conductive materials. The obtained assembled particles had an average particle diameter (D50) of 15 μm and an aspect ratio of 1.1.

[0229]

[0230] (2) Preparation of the entire collector with primer layer

[0231] Carbon black (specific surface area: 30 m) as a conductive material for the primer layer 2 / g, particle size: (70 nm)), 30 parts by weight, styrene-butadiene rubber (SBR) (T) as a binder for the primer layer g : -15℃, 69 parts by weight, 1 part by weight of carboxymethyl cellulose (CMC) as a dispersant and water as a dispersion medium were mixed to prepare a slurry for a primer layer. At this time, the content ratio of the conductive agent, binder, and dispersant in the slurry for the primer layer was the same as the content ratio of the conductive agent, binder, and dispersant in the primer layer formed thereafter. The solid content ratio of the slurry for the primer layer was 7 wt%.

[0232] The prepared slurry for the primer layer was applied to one surface of a copper current collector (thickness: 10 μm) and dried at 130°C to form a primer layer on the entire surface of the copper current collector.

[0233]

[0234] (3) Manufacturing of cathode

[0235] The above-obtained granulated particles, natural graphite (average particle diameter (D50): 16 μm) as a carbon-based active material, single-walled carbon nanotubes as an additional conductive material, and SBR (styrene butadiene rubber) and CMC (carbonyl methylene cellulose) as second binders were mixed with water as a dispersion medium in a weight ratio of (10:86:3:1) to prepare a slurry having a viscosity of approximately (3000) cPs through a homogenizer. At this time, the solid content in the slurry was (50) wt%.

[0236]

[0237] The above-mentioned manufactured slurry is applied to both sides of the prepared primer layer equipped current collector by (doctor blade) method, dried using (hot air drying) device under (110) temperature and (10 minutes) time conditions, and rolled by roll pressing method, so that (10) mg / 25 cm of weight per unit area is applied to both sides of the current collector. 2 A negative electrode having a negative electrode active material layer having a loading amount was manufactured.

[0238]

[0239] (4) Manufacturing of secondary batteries

[0240] An electrode assembly was manufactured using a porous polyethylene film (thickness: 10 μm) as a separator between the previously manufactured negative electrode and lithium metal. After the electrode assembly was embedded in a coin-type battery case, a liquid electrolyte containing 10 wt% FEC (fluoroethylene carbonate) mixed in a solvent containing ethylene carbonate, dimethylene carbonate, and diethyl carbonate in a volume ratio of 1:2:1, and 1 M LiPF6 dissolved therein was used to manufacture a coin cell secondary battery by injecting, sealing, and chemically forming the solution.

[0241]

[0242] [Example 2]

[0243] Granulated particles were manufactured in the same manner as in Example 1, except that the composition was manufactured by mixing Si (average particle diameter (D50): 3 μm) as a silicon-based active material, spherical natural graphite (average particle diameter (D50): 18 μm) as a carbon-based active material, polyacrylamide as a first binder, and water as a dispersion medium in a weight ratio of 10:100:0.5:100 using a homogenizer. The obtained granulated particles had an average particle diameter (D50) of 15 μm and an aspect ratio of 1.1.

[0244]

[0245] A negative electrode and a secondary battery including the same were manufactured using the same method as Example 1, except that the assembled particles manufactured in this way were used.

[0246]

[0247] [Example 3]

[0248] The granulated particles were manufactured in the same manner as in Example 1, except that the composition was manufactured by mixing Si (average particle diameter (D50): 3 μm) as a silicon-based active material, spherical natural graphite (average particle diameter (D50): 18 μm) as a carbon-based active material, polyacrylamide as a first binder, and water as a dispersion medium in a weight ratio of 15:100:0.5:100 using a homogenizer. The obtained granulated particles had an average particle diameter (D50) of 15 μm and an aspect ratio of 1.1.

[0249]

[0250] A negative electrode and a secondary battery including the same were manufactured using the same method as Example 1, except that the assembled particles manufactured in this way were used.

[0251]

[0252] [Example 4]

[0253] Granulated particles were manufactured in the same manner as in Example 1, except that the composition was manufactured by mixing Si (average particle diameter (D50): 3 μm) as a silicon-based active material, spherical natural graphite (average particle diameter (D50): 18 μm) as a carbon-based active material, polyacrylamide as a first binder, and water as a dispersion medium in a weight ratio of 20:100:0.5:100 using a homogenizer. The obtained granulated particles had an average particle diameter (D50) of 15 μm and an aspect ratio of 1.1.

[0254]

[0255] A negative electrode and a secondary battery including the same were manufactured using the same method as Example 1, except that the assembled particles manufactured in this way were used.

[0256]

[0257] [Comparative Example 1]

[0258] As a silicon-based active material, Si (average particle diameter (D50): 3 μm), as a carbon-based active material, spherical natural graphite (average particle diameter (D50): 18 μm), single-walled carbon nanotubes, SBR (styrene butadiene rubber), and CMC (carbonyl methylene cellulose) were mixed with water as a dispersion medium in a weight ratio of 5:90.9:0.1:3:1 and a slurry with a viscosity of approximately 5000 cPs was prepared through a homogenizer. At this time, the solid content in the slurry was 50 wt%.

[0259] The above-mentioned manufactured slurry is applied to both sides of the prepared primer layer equipped current collector by (doctor blade) method, dried using (hot air drying) device under (110) temperature and (10 minutes) time conditions, and rolled by roll pressing method, so that 10mg / 25cm of weight per unit area is applied to both sides of the current collector. 2 A negative electrode having a negative electrode active material layer having a loading amount was manufactured.

[0260]

[0261] A secondary battery was manufactured using the same method as Example 1, except that the negative electrode manufactured in this way was used.

[0262]

[0263] [Comparative Example 2]

[0264] When manufacturing the assembled particles, Si (average particle diameter (D50): 3㎛) as a silicon-based active material, spherical natural graphite (average particle diameter (D50): 18㎛) 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 and then a composition was manufactured through a homogenizer.

[0265] The composition thus manufactured was introduced into a spray dryer with hot air under a pressure range of -40 mmH2O and dried. At this time, the conditions of the spray dryer were the same as in Example 1, except that the inlet temperature was controlled to 120°C, the outlet temperature to 60°C, and the rotation speed to 18,000 rpm, to manufacture granulated particles. The average particle diameter (D50) of the obtained granulated particles was 35 μm, and the aspect ratio was 2.1.

[0266]

[0267] A negative electrode and a secondary battery including the same were manufactured using the same method as Example 1, except that the assembled particles manufactured in this way were used.

[0268]

[0269] [Comparative Example 3]

[0270] When manufacturing the assembled particles, Si (average particle diameter (D50): 3㎛) as a silicon-based active material, spherical natural graphite (average particle diameter (D50): 18㎛) 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 and then a composition was manufactured through a homogenizer.

[0271] The composition thus manufactured was introduced into a spray dryer with hot air under a pressure range of -40 mmH2O and dried. At this time, the conditions of the spray dryer were the same as in Example 1, except that the inlet temperature was controlled to 220°C, the outlet temperature to 120°C, and the rotation speed to 18,000 rpm, to manufacture granulated particles. The average particle diameter (D50) of the obtained granulated particles was 7 μm, and the aspect ratio was 1.4.

[0272]

[0273] A negative electrode and a secondary battery including the same were manufactured using the same method as Example 1, except that the assembled particles manufactured in this way were used.

[0274]

[0275] [Evaluation Results]

[0276] Evaluation of first discharge capacity, initial efficiency, and capacity retention rate

[0277] The secondary batteries manufactured in Examples 1 to 4 and Comparative Examples 1 to 3 were subjected to an initial charge / discharge test using the following method, and then the life characteristics were evaluated.

[0278] For the first two cycles, charging was performed in CC / CV mode, charging was performed in CC mode at a current of 0.1C to 0.005V, and charging was terminated when the current was 0.05C at the end voltage of 0.005V. Discharging was performed in CC mode, and the end voltage of discharge was 1.5V and the current was maintained at 0.1C. For the subsequent cycles, charging was performed in CC / CV mode, charging was performed in CC mode at a current of 0.3C to 0.01V, and charging was terminated when the current was 0.01C at the end voltage of 0.01V. Discharging was performed in CC mode, and the current was maintained at 0.5C and the end voltage of discharge was 1.5V.

[0279] In Table 1 below, the initial efficiency (%) is obtained as a percentage of the initial discharge capacity to the initial charge capacity. In addition, the capacity retention rate is obtained as a percentage of the 50th discharge capacity to the 3rd discharge capacity.

[0280]

[0281] First discharge capacity (mAh / g) Initial efficiency (%) Capacity retention rate (%, 50th / 3rd discharge capacity) Example 150790.479 Example 25119288 Example 35109186 Example 45139082 Comparative example 14908870 Comparative example 24659071 Comparative example 35808664

[0282] Referring to Table 1 above, it can be seen that the secondary batteries employing the negative electrodes manufactured according to Examples 1 to 4 exhibit superior life characteristics than the secondary batteries of Comparative Examples 1 to 3.

Claims

1. The entire house; and A negative electrode active material layer positioned on at least one surface of the above-mentioned collector, comprising assembled particles and a second binder, wherein the second binder fixes and connects the assembled particles; A negative electrode characterized in that the above-mentioned assembled particles include a negative electrode active material, a conductive material, and a first binder, and the first binder connects and fixes the negative electrode active material and the conductive material.

2. In paragraph 1, A negative electrode characterized in that the negative electrode active material is a silicon-based active material alone or a mixture of a silicon-based active material and a carbon-based active material.

3. In paragraph 2, The above silicon-based active material is silicon (Si), silicon oxide (SiOx (0 <x≤2), 탄화규소(SiC), 실리콘계 합금(MxSiy, M:Ni,Ti,Fe,Zr,Nb) 또는 이들 중 2 이상을 포함하는 것을 특징으로 하는 음극.

4. In paragraph 2, A negative electrode characterized in that the carbon-based active material comprises natural graphite, artificial graphite, graphene, or two or more thereof.

5. In paragraph 1, A cathode characterized in that the conductive material comprises a linear conductive material, a dot-shaped conductive material, or two or more thereof.

6. In paragraph 5, A cathode characterized in that the linear conductive material comprises carbon nanotubes, carbon nanofibers, graphene, or two or more thereof.

7. In paragraph 5, A cathode characterized in that the dot-shaped conductive material comprises carbon black, Denka black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, or two or more thereof.

8. In paragraph 1, A negative electrode characterized in that the first binder comprises a diene polymer, an acrylate polymer, a styrene polymer, a polyacrylonitrile polymer, a vinyl polymer, a polyoxide polymer, a polyacrylamide, or two or more thereof.

9. In paragraph 1, A negative electrode characterized in that the second binder comprises a diene polymer, an acrylate polymer, a styrene polymer, or two or more thereof.

10. In paragraph 1, A negative electrode characterized in that the content of the negative electrode active material is 80 to 99 parts by weight among 100 parts by weight of the above-mentioned assembled particles, the content of the conductive material is 0.001 to 0.5 parts by weight, and the content of the first binder is 0.1 to 2 parts by weight.

11. In paragraph 1, A cathode characterized in that the average particle diameter (D50) of the above-mentioned assembled particles is 10 to 20㎛.

12. In paragraph 2, An anode characterized in that the negative electrode active material is a mixture of a silicon-based active material and a carbon-based active material, and the content of the silicon-based active material is 5 to 25 parts by weight based on 100 parts by weight of the carbon-based active material.

13. In paragraph 1, A negative electrode characterized in that the negative electrode active material layer further includes an additional carbon-based active material, an additional conductive material, or both.

14. In paragraph 13, A negative electrode characterized in that the negative electrode active material layer comprises 100 parts by weight of the assembled 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 step of manufacturing granulated particles by drying a composition including a negative electrode active material, a conductive agent, a first binder, and a first aqueous dispersion medium by a spray drying method; A step of preparing a cathode slurry by mixing the above-mentioned assembled particles with a second binder and a second aqueous dispersion medium; and A method for manufacturing the negative electrode of claim 1, comprising the step of applying the negative electrode slurry on at least one surface of a current collector, drying, and rolling to form a negative electrode active material layer.

16. In paragraph 15, A method for manufacturing a negative electrode, characterized in that the negative electrode active material is a silicon-based active material alone or a mixture of a silicon-based active material and a carbon-based active material.

17. In paragraph 15, A method for manufacturing a negative electrode, characterized in that the negative electrode slurry further includes an additional carbon-based active material, an additional conductive material, or both.

18. In paragraph 15, A method for manufacturing a cathode, characterized in that the spray drying method includes a step of spraying and drying the slurry in hot air, and the temperature of the hot air introduced is 130°C to 210°C.

19. An electrochemical device comprising a cathode according to any one of claims 1 to 14.

20. In paragraph 19, An electrochemical device characterized in that the electrochemical device is a secondary battery.

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