Anode, and electrochemical device comprising same

Abstract

Presented are an anode for an electrochemical device and an electrochemical device comprising same, the anode comprising: a current collector; and an anode active material layer located on the current collector, wherein: the anode active material layer includes powder including a silicon-based active material, a linear conductive material, and a binder for powder; the degree of dispersion of the powder in the anode active material layer is 1 x 10-2 to 10 x 10-2; the standard deviation of the degree of dispersion of the powder is 1 x 10-3 to 3 x 10-3; and the volume expansion rate of the anode active material layer is 3 to 30%.

Description

Cathode and electrochemical device including same

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

[0002] This application claims priority to Korean Application No. 10-2024-0088547 and Korean Application No. 10-2024-0088548, filed July 4, 2024, 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 structured such that an electrolyte containing a lithium salt is impregnated into an electrode assembly with 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. The electrode is manufactured by applying a slurry in which an active material, a powder binder, and a conductive material 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] Conventional anodes that are a mixture of silicon-based materials and carbon-based materials (e.g., graphite-based materials) have attempted to improve the swelling phenomenon caused by the expansion of the silicon-based materials during charging by using a powder binder with a large modulus or increasing the amount of the powder binder. In addition, since silicon-based materials have lower conductivity than graphite-based materials, conductive materials such as carbon nanotubes (CNTs) have been additionally used to improve this. However, considering the capacity and material cost, there is a practical limit to the content of the powder binder and conductive material. Therefore, there was a problem that the powder binder with a large modulus and the conductive material such as CNT were not uniformly distributed throughout the silicon-based and graphite-based materials within the electrode, which did not sufficiently suppress the expansion of the silicon-based material and improve the conductivity.

[0008] The problem solved by the present invention is to provide a cathode having greatly reduced volume expansion characteristics and improved powder dispersion, 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 powder of the following embodiment is provided.

[0010] According to the first embodiment of the present invention,

[0011] The entire house; and

[0012] A negative electrode active material layer positioned on the above-mentioned collector;

[0013] The above negative active material layer comprises a powder including a silicon-based active material, a linear conductive material, and a powder binder,

[0014] The dispersion degree of the powder within the negative electrode active material layer is 1 x 10 -2 10 x 10 -2 , and the standard deviation of the dispersion of the above powder is 1 x 10 -3 4 x 10 -3 And,

[0015] An anode for an electrochemical device is provided, wherein the volume expansion rate of the anode active material layer is 3 to 35%.

[0016] According to the second embodiment of the present invention, in the first embodiment,

[0017] The dispersion degree of the powder within the negative electrode active material layer is 1 x 10 -2 5 x 10 -2 , and the standard deviation of the dispersion of the above powder is 1 x 10 -3 3.5 x 10 -3 It could be.

[0018] According to a third embodiment of the present invention, in the first embodiment or the second embodiment,

[0019] The volume expansion rate of the above negative electrode active material layer may be 3 to 33%.

[0020] According to the fourth embodiment of the present invention, in any one of the first to third embodiments,

[0021] The above negative electrode active material layer may include a powder, a carbon-based active material, and a binder for the negative electrode layer.

[0022] According to the fifth embodiment of the present invention, in the fourth embodiment,

[0023] Based on 100 parts by weight of the negative electrode active material layer, the negative electrode active material layer may include 1 to 10 parts by weight of powder, 70 to 99 parts by weight of carbon-based active material, and 0.1 to 10 parts by weight of binder for the negative electrode layer.

[0024] According to the sixth embodiment of the present invention, in any one of the first to fifth embodiments,

[0025] The above negative electrode active material layer may include a powder, a carbon-based active material, a binder for the negative electrode layer, and a conductive material for the negative electrode layer.

[0026] According to the seventh embodiment of the present invention, in the sixth embodiment,

[0027] Based on 100 parts by weight of the negative electrode active material layer, the negative electrode active material layer may include 1 to 10 parts by weight of powder, 70 to 99 parts by weight of carbon-based active material, 0.01 to 5 parts by weight of a conductive material for the negative electrode layer, and 0.1 to 10 parts by weight of a binder for the negative electrode layer.

[0028] According to the eighth embodiment of the present invention, in any one of the first to seventh embodiments,

[0029] The above silicon-based active material is silicon (Si), silicon oxide (SiOx (0 <x≤2), Si / C 복합체 또는 이들 중 2 이상을 포함할 수 있다.

[0030] According to the ninth embodiment of the present invention, in any one of the first to eighth embodiments,

[0031] The linear conductive material may include a single-walled carbon nanotube (SWCNT), a multi-walled carbon nanotube (MWCNT), a carbon nanofiber, or two or more thereof.

[0032] According to the tenth embodiment of the present invention, in any one of the first to ninth embodiments,

[0033] The above binder may include at least one of a linear binder and a point-shaped binder.

[0034] According to the eleventh embodiment of the present invention, in the tenth embodiment,

[0035] The above binder may include a linear binder and a dot-shaped binder.

[0036] According to the 12th embodiment of the present invention, in the 10th embodiment or the 11th embodiment,

[0037] The linear binder may include an acrylate polymer, and the dot-shaped binder may include a diene polymer, a styrene polymer, or two or more thereof.

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

[0039] The above powder may have a central portion including a silicon-based active material and a linear conductive material; and a surface portion including a powder binder that is located on all or part of the outer side of the central portion and binds the silicon-based active material and the linear conductive material.

[0040] According to the 14th embodiment of the present invention, in the 13th embodiment,

[0041] The content (wt%) of the powder binder relative to the total weight of 100 wt% of the above silicon-based active material, linear conductive material, and powder binder is greater in the surface portion than in the center portion of the powder,

[0042] The above surface portion is an area near the powder surface from the powder surface to a predetermined depth in the direction of the powder center, and the center may be a part other than the surface portion.

[0043] According to the fifteenth embodiment of the present invention, in any one of the first to fourteenth embodiments,

[0044] Based on 100 parts by weight of the powder, the powder may include 80 to 98 parts by weight of a silicon-based active material, 0.2 to 10 parts by weight of a linear conductive material, and 0.5 to 10 parts by weight of a powder binder.

[0045] According to the 16th embodiment of the present invention, in any one of the 1st to 15th embodiments,

[0046] The above powder may further include a carbon-based active material.

[0047] According to the 17th embodiment of the present invention, in any one of the 1st to 16th embodiments,

[0048] The above powder may further contain a dispersant.

[0049] According to the 18th embodiment of the present invention, in the 17th embodiment,

[0050] The above dispersant may include carboxymethylcellulose (CMC).

[0051] According to the 19th embodiment of the present invention,

[0052] A method for manufacturing an anode for an electrochemical device according to any one of the first to eighteenth embodiments is provided, the method including a step of forming a cathode active material layer using a powder including a silicon-based active material, a linear conductive material, and a powder binder.

[0053] According to the 20th embodiment of the present invention, in the 19th embodiment,

[0054] The method for manufacturing the above cathode may include a wet process, a dry process, or a process applying both.

[0055] According to the 21st embodiment of the present invention, in the 20th embodiment,

[0056] The above wet process may include a step of preparing a negative electrode slurry by mixing the powder and the binder for the negative electrode layer, or the powder, the binder for the negative electrode layer, and the conductive material for the negative electrode layer together in a dispersion medium; and a step of applying and drying the negative electrode slurry on at least one surface of a current collector to form a negative electrode active material layer.

[0057] According to the 22nd embodiment of the present invention, in the 20th embodiment or the 21st embodiment,

[0058] The above dry process comprises a step of dry mixing the powder and a fiberizable binder, or the powder, a fiberizable binder, and a conductive material for a cathode layer to produce a mixture;

[0059] A step of kneading the above-mentioned mixture to prepare a mixture lump, and pulverizing the mixture lump to obtain a mixed powder for an electrode;

[0060] A step of forming an electrode film by injecting the above electrode-use mixed powder between a plurality of rolls and performing a calendaring process; and

[0061] It may include a step of laminating the above electrode film on a metal current collector.

[0062] According to the 23rd embodiment of the present invention, in any one of the 20th to 22nd embodiments,

[0063] The above dry process may include a step of directly applying and rolling the powder alone, or the powder and the binder for the negative electrode layer together, or the powder, the binder for the negative electrode layer, and the conductive material for the negative electrode layer together, onto the current collector.

[0064] According to the 24th embodiment of the present invention, in any one of the 19th to 23rd embodiments,

[0065] The above negative electrode active material layer may further include a carbon-based active material.

[0066] According to the 25th embodiment of the present invention,

[0067] An electrochemical device is provided comprising a cathode for an electrochemical device according to any one of the first to eighteenth embodiments.

[0068] According to the 26th embodiment of the present invention, in the 25th embodiment,

[0069] The above electrochemical device may be a secondary battery.

[0070] According to one embodiment of the present invention, a negative electrode has a dispersion degree of powder including a silicon-based active material, a linear conductive material, and a powder binder within a negative electrode active material layer that satisfies a predetermined range, so that the powders are evenly distributed without agglomeration in one part of the negative electrode active material layer, and the standard deviation of the dispersion degree also has a low value, and further, compared to a conventional negative electrode using a silicon-based active material, deterioration due to shrinkage and expansion of the silicon-based active material is prevented, so that the negative electrode has a very low volume expansion rate, thereby significantly improving the conductivity within the negative electrode active material layer and the electrochemical performance such as the life characteristics of a secondary battery.

[0071] The negative electrode according to one embodiment of the present invention can be applied to both wet electrodes and dry electrodes, thereby significantly improving the performance of a secondary battery employing such electrodes.

[0072] 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.

[0073] Figures 1 to 3 are SEM photographs of powder included in the cathode according to Example 1.

[0074] Figure 4 is an SEM photograph of the powder included in the cathode according to Example 2.

[0075] Figures 5a to 5c are SEM photographs of powders included in the cathodes according to Comparative Examples 1-1, 2-1, and 3-1, respectively.

[0076] Figure 6 is a photograph of a powder manufacturing device according to one embodiment of the present invention.

[0077] Figure 7 is a schematic diagram of a powder (C) according to one embodiment of the present invention, a spherical powder (A) of the prior art, and a crushed powder (B) obtained by further increasing the shear force during electrode manufacturing using the spherical powder.

[0078] Figure 8 is an image for evaluating the degree of dispersion of powder in the negative electrode active material layer of the electrode of Example 2 (T2-3), Comparative Example 1-1 (T1-1), Comparative Example 2-2 (T2-2), and Comparative Example 4 (Ref.).

[0079] Hereinafter, the present invention will be described in more detail to help understand the present invention.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] Throughout this specification, the description of “A and / or B” means “A or B or both.”

[0085] 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).

[0086] 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).

[0087] The "thickness" of each layer included in the electrode in this specification may represent 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) or a value measured on an image obtained by observing a cross-section using an XRM (X-ray microscope) (e.g., ZEISS Xradia Versa620).

[0088] 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.

[0089] According to one aspect of the present invention, there is provided a current collector comprising: a negative electrode active material layer positioned on the current collector; wherein the negative electrode active material layer comprises a powder including a silicon-based active material, a linear conductive material, and a powder binder;

[0090] The dispersion degree of the powder within the negative electrode active material layer is 1 x 10 -2 10 x 10 -2 , and the standard deviation of the dispersion of the above powder is 1 x 10 -3 4 x 10 -3 And,

[0091] An anode for an electrochemical device is provided, wherein the volume expansion rate of the anode active material layer is 3 to 35%.

[0092] The dispersion of powder within the above negative electrode active material layer is 1 x 10 -2 10 x 10 -2 According to one embodiment of the present invention, the dispersion degree of the powder in the negative electrode active material layer is 1 x 10 -2 5 x 10 -2 , or 1 x 10 -2 4.4 x 10 -2 , or 4.4 x 10 -2 10 x 10 -2 , or 2 x 10 -2 5 x 10 -2 , or 2 x 10 -2 4.4 x 10 -2 , or 4.4 x 10 -2 5 x 10 -2 It could be.

[0093] The above dispersion degree is a numerical value indicating the degree of uniformity with which the powder containing the silicon-based active material is distributed within the negative electrode active material layer. As the dispersion degree value approaches 0 or 0, it means that the powder containing the silicon-based active material is evenly mixed within the negative electrode active material layer. As the dispersion degree value approaches 1, it means that the powder containing the silicon-based active material is aggregated and clumped together in one part within the negative electrode active material layer.

[0094] The dispersion of powder in the above negative electrode active material layer is 1 x 10 -2 10 x 10 -2When the range is satisfied, the powder is uniformly distributed throughout the negative electrode active material layer, which can significantly improve electrochemical performance, such as preventing deterioration due to shrinkage and expansion of the silicon-based active material, improving conductivity within the negative electrode active material layer, and improving the life characteristics of the secondary battery.

[0095] The standard deviation of the powder dispersion within the above negative electrode active material layer is 1 x 10 -3 4 x 10 -3 According to one embodiment of the present invention, the standard deviation of the dispersion of powder in the negative electrode active material layer is 1 x 10 -3 3.5 x 10 -3 , or 1.5 x 10 -3 3.5 x 10 -3 , or 1 x 10 -3 2.85 x 10 -3 , or 2.85 x 10 -3 4 x 10 -3 , or 1.5 x 10 -3 2.85 x 10 -3 , or 2.85 x 10 -3 3.5 x 10 -3 It could be.

[0096] When the standard deviation of the dispersion degree of the powder within the above-mentioned negative electrode active material layer satisfies this range, the deviation between the dispersion degrees of the powder is small, so that the negative electrode can be manufactured with reproducibility and high quality uniformity of the negative electrode can be secured.

[0097] At this time, the dispersion degree of the powder and its standard deviation within the negative electrode active material layer can be obtained by the following method.

[0098] First, the negative electrode, which is the target for evaluating the degree of powder dispersion within the negative electrode active material layer, is selected, and the cross-section of the negative electrode active material layer is measured using a scanning electron microscope (SEM) (e.g., manufacturer: JEOL, equipment name: JSM-7200) to obtain an image, and the image measured using the SEM can be analyzed pixel by pixel using an image analysis program.

[0099] By utilizing the contrast between the Si of the silicon-based active material and the carbon-based active material (e.g., graphite) in the cathode active material layer, it is possible to distinguish whether the material filling the image pixel is a carbon-based active material or a silicon-based active material.

[0100] For example, the image pixels of the analysis area within the negative electrode active material layer are divided into 20 X 20 (width X height) sections, the area ratio of the area of ​​interest (the area where the powder containing the silicon-based active material is present) in each section is calculated, and the sample distribution of these 400 area ratios can be defined as the dispersion value.

[0101] At this time, the sample variance can be calculated using the equation 1 below for each value of the 400 area ratios, and this can be provided as a dispersion value.

[0102] [Formula 1]

[0103] s²= Σ(y - y')² / (n-1)

[0104] In the above formula, s² represents the sample variance, or dispersion, and represents the variance value obtained from the sample. It is denoted as s² to distinguish it from the population variance (σ²).

[0105] Σ(y - y')² is the sum of squared deviations, and is more specifically as follows.

[0106] y: each observation

[0107] y': sample mean (y-bar)

[0108] (y - y'): The difference (deviation) between each observation and the sample mean

[0109] (y - y')²: squared deviation

[0110] Σ: Sum of squared deviations for all observations

[0111] n - 1 represents the degrees of freedom, specifically:

[0112] n: sample size (number of observations)

[0113] The reason for dividing by n-1 instead of n is due to Bessel's correction.

[0114] The reason why the sum of squared deviations in the above equation 1 is divided by 'n-1' is because when calculating the variance using the sample mean, the sample mean itself is a value calculated from the sample data, so one constraint is created. That is, when n-1 of the n deviations are determined, the sum of the deviations is always 0, so the last one is automatically determined, and therefore the actual degrees of freedom become n-1, and through this, an unbiased estimator of the population variance can be obtained. Through the above formula, the degree of spread of the sample data can be accurately measured.

[0115] In the example of calculating the dispersion described above, it is exemplified that the image pixels of the analysis area within the negative electrode active material layer can be divided into sections of 20 X 20 (width X height). However, in order to analyze the dispersion more precisely, the dispersion can be calculated by setting various sections, such as 900 sections of 30 X 30 or 2500 sections of 50 X 50.

[0116] In one embodiment of the present invention, a cross-section of a negative electrode active material layer, which is a target for evaluating the degree of dispersion of powder in the negative electrode active material layer, is measured using SEM to obtain four SEM images of different areas, and from each image, a portion where powder including a silicon-based active material does not exist is determined as 400 areas with a total number of positions of 20 X 20, and the degree of dispersion is calculated, and the standard deviation of the degree of dispersion for the four calculated images can be calculated.

[0117] According to one embodiment of the present invention, the SEM image may have a magnification of 100 to 500 times, or 200 to 400 times, and a length and width of 500 to 2000 mm and 700 to 1500 mm, or 900 to 1300 mm and 1000 to 1200 mm, respectively.

[0118] The volume expansion ratio of the negative electrode active material layer is 3 to 35%. According to one embodiment of the present invention, the volume expansion ratio of the negative electrode active material layer may be 3 to 33%, or 5 to 31%, or 14.1 to 30.6%, or 3 to 14.1%, or 14.1 to 35%, 3 to 16.6%, or 16.6% to 35%, or 3 to 30.6%.

[0119] When the volume expansion rate of the negative electrode active material layer satisfies this range, the linear conductive material and powder binder included together with the silicon-based active material in the powder connect and fix the silicon-based active material, thereby controlling the volume expansion rate to a value lower than the inherent expansion rate of the silicon-based active material. Therefore, the conductive network formed by the linear conductive material in the negative electrode active material layer is stably maintained, thereby improving the resistance characteristics and enhancing the life stability of the electrochemical device employing the same.

[0120] The volume expansion rate of the above negative electrode active material layer can be calculated by measuring the thickness of the negative electrode active material layer using an X-ray microscope and using the following equation.

[0121] The volume expansion rate of the above negative electrode active material layer can be defined by the following equation 2.

[0122] [Formula 2]

[0123] Volume expansion rate (%) = (electrode thickness after 100 charges - initial electrode thickness) / initial electrode thickness X 100

[0124]

[0125] The above negative electrode active material layer may include a powder, a carbon-based active material, and a binder for the negative electrode layer.

[0126] Based on 100 parts by weight of the negative electrode active material layer, the negative electrode active material layer may include 1 to 10 parts by weight, or 2 to 8 parts by weight, or 1 to 5 parts by weight, or 5 to 10 parts by weight of powder, 70 to 99 parts by weight, or 80 to 98 parts by weight, or 70 to 92 parts by weight, or 92 to 99 parts by weight of the carbon-based active material, and 0.1 to 10 parts by weight, or 0.8 to 5 parts by weight, or 0.1 to 2 parts by weight, or 2 to 10 parts by weight, or 2 to 5 parts by weight of a binder for the negative electrode layer.

[0127] The above negative electrode active material layer may include a powder, a carbon-based active material, a binder for the negative electrode layer, and a conductive material for the negative electrode layer.

[0128] Based on 100 parts by weight of the negative electrode active material layer, the negative electrode active material layer may include 1 to 10 parts by weight of powder, or 2 to 8 parts by weight, or 1 to 5 parts by weight, or 5 to 10 parts by weight, 70 to 99 parts by weight of the carbon-based active material, or 80 to 98 parts by weight, or 70 to 92 parts by weight, or 92 to 99 parts by weight, 0.01 to 5 parts by weight of a conductive material for the negative electrode layer, or 0.1 to 2 parts by weight, or 0.01 to 1 part by weight, or 1 to 5 parts by weight, or 1 to 2 parts by weight, and 0.1 to 10 parts by weight of a binder for the negative electrode layer, or 0.8 to 5 parts by weight, or 0.1 to 2 parts by weight, or 2 to 10 parts by weight, or 2 to 5 parts by weight.

[0129] The above powder comprises a silicon-based active material, a linear conductive material, and a powder binder. The powder binder can serve to connect and fix the silicon-based active material and the linear conductive material.

[0130] In the present invention, the powder may be referred to as a granule, powder, granule, or coarse particle.

[0131] In the present invention, the powder may have the form of a composite particle including a silicon-based active material, a linear conductive material, and a binder for the powder, and further including optional components (such as additional conductive agents) added as needed.

[0132] In one embodiment of the present invention, the silicon-based active material may include one or more silicon-based active material particles.

[0133] The above powder may be a secondary particle in which one or more silicon-based active material particles are connected and fixed by a powder binder.

[0134] An anode active material including a silicon-based active material, which has excellent capacity but has limited application due to large volume change, is manufactured in advance as a powder of a predetermined shape according to one embodiment of the present invention, and the silicon-based active material is connected and fixed by a linear conductive material and a powder binder uniformly dispersed within the powder, so that even if there is a change in the volume of the silicon-based active material within the anode active material layer later, a conductive network within the anode active material layer can be stably formed by the linear conductive material that is uniformly dispersed and connected by line contact, and as a result, the electrical properties, such as the life characteristics, of an electrochemical device such as a secondary battery employing such a cathode can be significantly improved.

[0135] According to one embodiment of the present invention, the product of the circularity and solidity of the powder may be 0.7 to 0.9, or 0.7 to 0.88, or 0.7 to 0.87, or 0.7 to 0.86. In this case, the circularity and solidity may be defined by the following equations 3 and 4, respectively.

[0136] [Formula 3]

[0137] Sphericity = 4π(pi) * (actual area of ​​the powder) / (perimeter of the powder) 2

[0138] [Formula 4]

[0139] Fidelity = (Actual area of ​​the powder) / Convex hull area of ​​the powder

[0140] Here, the convex outer surface area of ​​the powder is the entire area covered by the convex hull of the powder, which means the area of ​​the simplest convex polygon created by connecting the outermost points of the powder.

[0141] The sphericity of the above powder may be 0.96 or less, or 0.60 to 0.96, or 0.70 to 0.90.

[0142] The sphericity of the above powder can be defined by the following equation.

[0143] Sphericity of powder = 4π(pi) X (area of ​​measured powder) / (perimeter of measured powder) 2

[0144] The sphericity of the above powder has a numerical value between 0 and 1, and the closer it is to 1, the more perfect the spherical shape is.

[0145] The sphericity of the above powder can be measured according to a standard test method.

[0146] For example, using a particle size analyzer (e.g., Malvern Morphology 4), 10,000 powders can be optically imaged and the sphericity of the obtained powders can be calculated by taking a numerical average.

[0147] The above fidelity is a numerical value that evaluates whether the outer shape of the powder is uneven or densely packed. The above fidelity is calculated by the above-mentioned formula 2, i.e., “Fidelity = (actual area of ​​powder) / convex outer area of ​​powder (Convex Hull Area)”. Therefore, when the fidelity is 1, the powder has a perfect convex shape, i.e., a shape without grooves or defects on the surface. As the fidelity decreases below 1, it means that the surface of the powder is uneven or has a structure with a void in the center.

[0148] The above fidelity can be calculated by optically obtaining images of 10,000 powders using a particle size analyzer (e.g., Malvern Morphology 4), obtaining the actual area (a) of each powder and the convex outer area (b) of the powders from the obtained images, and calculating the ratio (a / b) of these.

[0149] In a case where the product of the circularity and solidity of the powder according to one embodiment of the present invention satisfies the above range, the powder is not a perfect sphere but has a certain degree of unevenness on the outer surface, thereby increasing the specific surface area and being advantageous in terms of electrochemical performance.

[0150] In one embodiment of the present invention, the average particle diameter (D50) of the powder may be 10 to 25 μm, or 14 to 20 μm.

[0151] Additionally, the particle size (D10) of the powder may be 5 to 10 μm, and the particle size (D90) of the powder may be 25 to 35 μm.

[0152] 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, after dispersing the powder to be measured in a dispersion medium, the particle size distribution can be calculated using a commercially available particle size analyzer (e.g., Malvern Morphology 4). By calculating the particle diameter at the 50% point of the cumulative distribution of particle numbers according to particle diameter in the measuring device, the D50 particle diameter can be measured. In the same manner, by calculating the particle diameters at the 10% and 90% points of the cumulative distribution of particle numbers according to particle diameter in the measuring device, the D10 particle diameter and the D90 particle diameter can be measured, respectively.

[0153] According to one embodiment of the invention, the angle of repose of the powder may be 35 to 80 degrees (°), or 40 to 70 degrees (°). When the angle of repose of the powder satisfies this range, the flowability of the powder is excellent, so that the process can be stably and continuously performed during powder transport or slurry mixing and supply, thereby improving productivity, the mixing degree within the slurry is excellent, agglomeration and sedimentation of the powder within the slurry are prevented, and the thickness of the obtained electrode is uniform and the surface quality is improved, which may be advantageous.

[0154] The angle of repose of the above powder can be measured by the USP 1274 or ASTM D 6393-99 method.

[0155] The above silicon-based active material is silicon (Si), silicon oxide (SiOx (0 <x≤2), Si / C 복합체, 또는 이들 중 2 이상을 포함할 수 있다. 상기 규소계 활물질의 구체적인 예로는 Si, SiO, SiO / C, SiO2등이 있고, 여기에 한정되지는 않는다.

[0156] The above Si / C composite (silicon-carbon composite) comprises silicon particles (e.g., silicon (Si), silicon oxide (SiOx (0)) within a carbon-based support (carbon matrix). <x≤2) 등)가 물리적으로 분산되거나 화학적으로 결합된 구조를 포함할 수 있다. 상기 탄소 담지체는 비정질 탄소(카본블랙, 활성탄, 하드 카본 등), 흑연, 카본나노튜브, 카본나노파이버, 그래핀 등을 포함할 수 있고, 또는 이들 중 2 이상을 포함할 수 있다. 또한, 상기 탄소 담지체는 비정질 탄소, 흑연, 카본나노튜브, 카본나노파이버, 그래핀 등으로 이루어질 수 있고, 또는 이들 중 2 이상으로 이루어질 수 있다.

[0157] According to one embodiment of the present invention, the content of the silicon-based particles relative to 100 parts by weight of the carbon carrier may be 5 to 45 parts by weight, or 10 to 40 parts by weight, or 15 to 35 parts by weight, or 20 to 30 parts by weight, or 5 to 20 parts by weight, or 20 to 45 parts by weight. According to one embodiment of the present invention, the carbon carrier may include activated carbon, and the silicon-based particles may include pure Si particles. The powder may further include another type of negative electrode active material in addition to the silicon-based active material.

[0158] When the silicon-based particles compared to the carbon carrier satisfy this content range, the lithium storage capacity can be increased while maintaining sufficient electrical conductivity, and the carbon carrier can effectively buffer the volume expansion of silicon to suppress cracking and detachment of the electrode structure, thereby improving the mechanical stability of the electrode and the charge / discharge characteristics (life characteristics) of the secondary battery.

[0159] Examples of the above other types of negative electrode active materials include carbon-based active materials such as non-graphitizable carbon, graphitic carbon (natural graphite, artificial graphite); Li x Fe2O3(0≤x≤1), Li x WO2(0≤x≤1), Sn x Me 1-x Me' y O z(Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, elements of group 1, 2, and 3 of the periodic table, halogens; 0≤x≤1; 1≤y≤3; 1≤z≤8) and other metal composite oxides; lithium metal; lithium alloys; silicon-based alloys; tin-based alloys; metal oxides such as SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, and Bi2O5; conductive polymers such as polyacetylene; Li-Co-Ni-based materials, etc. According to one embodiment of the present invention, the powder may further include at least one carbon-based active material such as natural graphite or artificial graphite.

[0160] The linear conductive material may include a single-walled carbon nanotube (SWCNT), a multi-walled carbon nanotube (MWCNT), a carbon nanofiber, or two or more thereof.

[0161] The above carbon nanotubes include carbon allotropes and aggregates thereof, in which graphite sheets have a cylindrical shape with a nano-sized diameter and an sp2 bonding structure. The carbon nanotube aggregate refers to a secondary structure formed by arranging or agglomerating a plurality of carbon nanotubes. For example, the carbon nanotube aggregate may be a bundle-type carbon nanotube in which a plurality of carbon nanotubes are arranged or aligned in a bundle or rope shape in a certain direction, or an entangled-type carbon nanotube in which a plurality of carbon nanotubes are entangled in a sphere or potato shape without a certain direction.

[0162] At this time, the multi-walled carbon nanotube is a small hollow tube composed of coaxial cylindrical surface sleeves of several hexagonal lattices of carbon atoms, and the single-walled carbon nanotube may be composed of a single carbon cylindrical surface. The wall of this tubular structure is composed of a hexagonal lattice similar to a graphite sheet, and the intersections of the hexagonal lattices are where carbon atoms are located, and each carbon atom is adjacent to a surrounding carbon atom, and at the same time, both ends (end caps) of the tube can be closed with a polygonal structure composed of pentagonal carbon rings.

[0163] The above linear conductive materials, especially single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs), have a dielectric constant of 500 m. 2 / g or more, or 500m 2 / g to 5,000m 2 / g, or 800m 2 / g or more, or 800m 2 / g to 5,000m 2 / g, or 900 m 2 / g to 2000 m 2 / g of BET surface area. By using a linear conductive material having a BET surface area as described above, a conductive network is formed between silicon-based negative electrode active materials, thereby further improving the cycle characteristics of a secondary battery.

[0164] The linear conductive material may have a length of 0.5 μm to 100 μm. For example, the single-walled carbon nanotube may have an average length of 2 μm to 100 μm, and the multi-walled carbon nanotube may have an average length of 0.3 μm to 30 μm. Meanwhile, the linear conductive material may have a cross-sectional diameter of 1 nm to 100 nm.

[0165] According to one embodiment of the present invention, the content of the linear conductive agent may be 0.2 to 10 parts by weight, or 0.2 to 5 parts by weight, or 0.3 to 5 parts by weight, or 0.2 to 3 parts by weight, or 0.2 to 2 parts by weight, or 0.2 to 1.6 parts by weight, or 0.3 to 1.6 parts by weight, based on 100 parts by weight of the powder. When the content of the linear conductive agent satisfies this range, the linear conductive agent effectively forms a conductive network between silicon-based negative electrode active materials in the powder, and the cycle characteristics of a secondary battery applying such powder can be further improved.

[0166] When the linear conductive material is directly added in solid form during the above powder manufacturing, it may clump together and not be uniformly mixed with the silicon-based active material, binder, etc., and thus the desired effect of adding the linear conductive material may not be achieved. Therefore, the powder may be manufactured by adding the linear conductive material in the form of a dispersion liquid containing a dispersant and a dispersion medium in addition to the linear conductive material.

[0167] According to one embodiment of the present invention, the linear conductive material dispersion may include a linear conductive material, a polymer dispersant containing an amine, and a dispersion medium.

[0168] Or, according to one embodiment of the present invention, the linear conductive material dispersion may include a linear conductive material, a polymer dispersant containing an amine, a phenolic compound containing two or more aromatic rings, and a dispersion medium.

[0169] In the case where the linear conductive material is added in the form of a dispersion as described above, even though a linear conductive material having a large specific surface area is used, the initial viscosity of the dispersion is low due to the excellent dispersibility of the linear conductive material, such as carbon nanotubes, and the change in viscosity over time is suppressed. In addition, when applied to the production of a slurry for powder production, the linear conductive material is uniformly positioned between the active materials, so that the micro-spaces between the electrode active materials can be maintained consistently even during the drying of the slurry to produce powder. In addition, the linear conductive material is uniformly distributed without agglomeration, so that a sufficient conductive path can be formed even with a small amount of the linear conductive material. The average diameter of the linear conductive material can be measured by photographing the linear conductive material powder with a scanning electron microscope, and the average length of the linear conductive material can be measured by photographing the linear conductive material dispersion with a scanning electron microscope. In addition, the linear conductive material included in the negative electrode active material layer can also be measured using a scanning electron microscope. That is, when an electrode active material layer including a linear conductive agent is dissolved and dispersed in a solvent such as a dispersion medium (e.g., water) and then separated into a supernatant and a lower layer through centrifugation, the active material mainly settles in the lower layer, and the supernatant contains the linear conductive agent. Therefore, the supernatant can be used to measure the average diameter and average length of the linear conductive agent in the negative electrode active material layer by observing it with a scanning electron microscope (SEM).

[0170] The linear conductive agent may be included in an amount of 0.01 to 5 wt%, preferably 0.01 to 3 wt%, more preferably 0.1 to 2 wt%, and even more preferably 0.1 to 1 wt%, based on the total weight of the linear conductive agent dispersion. When the content of the linear conductive agent satisfies the above range, the effect of improving the viscosity of the dispersion and the effect of improving the cycle characteristics of the secondary battery are excellent.

[0171] The above dispersant is intended to enable the linear conductive material to be evenly dispersed without agglomeration within the linear conductive material dispersion. The linear conductive material dispersion may use a polymer dispersant containing an amine as a dispersant and a phenolic compound containing two or more aromatic rings together. When the two specific dispersants are used together, the change in viscosity over time of the linear conductive material dispersion can be significantly reduced.

[0172] In one embodiment of the present invention, the dispersant may be included in an amount of 10 to 2000 parts by weight, preferably 50 to 1000 parts by weight, and more preferably 70 to 500 parts by weight, relative to 100 parts by weight of the linear conductive material. When the content of the dispersant satisfies this range, the viscosity of the linear conductive material dispersion is maintained appropriately, and the problem of the dispersant acting as an impurity and thus deteriorating the physical properties of the secondary battery can be prevented.

[0173] The polymer dispersant containing the above amine may be, for example, at least one selected from the group consisting of polyvinylpyrrolidone, polyacrylic acid hydrazide, poly-N-vinyl-5-methoxazolidon, N-alkyl polyimine, N-acetyl polyimine, polyacrylamide, poly-L-lysine hydrobromide, benzyl-dodecyl-dimethylammonium chloride, and polyethylenimine.

[0174] As described above, when a specific polymer dispersant containing amine in the polymer structure is applied, a further enhanced viscosity improvement effect and an effect of suppressing viscosity changes over time can be achieved.

[0175] The phenolic compound containing two or more aromatic rings can reduce the viscosity of a linear conductive dispersion, particularly an aqueous linear conductive dispersion, compared to a conventional one, and significantly improve the increase in viscosity over time due to the bulky structure generated by the two or more aromatic rings and the influence of a hydroxyl group contained in the phenol group.

[0176] The above phenolic compound may include at least one structure selected from the group consisting of a phenol structure, a catechol structure, a galol structure, and a naphthol structure in at least one of the aromatic rings, and specifically, may include at least one structure selected from the group consisting of a catechol structure and a galol structure in at least one of the aromatic rings. The phenol structure is a structure in which one hydroxyl group is bonded to a benzene ring, the catechol structure is a structure in which two hydroxyl groups are bonded to a benzene ring, the galol structure is a structure in which three hydroxyl groups are bonded to a benzene ring, and the naphthol structure is a structure in which one hydroxyl group is bonded to naphthalene.

[0177] When the phenolic compound containing two or more of the above aromatic rings includes the above structure, the interaction between the aromatic ring and the linear conductive material in the linear conductive material dispersion and the interaction by hydrogen bonding between the -OH of the phenolic compound and the polymer dispersant are appropriately balanced, thereby exhibiting the effect of reducing the viscosity of the linear conductive material dispersion and suppressing the increase in viscosity due to changes over time.

[0178] Specific examples of the phenolic compound containing two or more of the above aromatic rings may include at least one selected from the group consisting of baicalin, luteolin, taxifolin, myricetin, quercetin, rutin, catechin, epigallocatechin gallate, butein, piceatenol, and tannic acid, and preferably tannic acid, quercetin, epigallocatechin gallate, or a combination thereof.

[0179] In one embodiment of the present invention, the aromatic ring included in the phenolic compound including two or more aromatic rings may be one aromatic ring that is not fused with another aromatic ring or a structure in which two aromatic rings are fused to each other, and a structure in which three or more aromatic rings are fused to each other may not be included.

[0180] That is, the scope of phenolic compounds containing two or more aromatic rings may exclude those containing a structure in which three or more aromatic rings are fused within the molecular structure.

[0181] When the phenolic compound containing two or more aromatic rings has a structure in which three or more aromatic rings are fused within its molecular structure, the structure in which three or more aromatic rings are fused may exert a strong bonding force that is stronger than an appropriate level with the linear conductive material in the linear conductive material dispersion, thereby inducing coagulation between the linear conductive materials, and thus may not be suitable for improving the dispersibility of the linear conductive material. In addition, since the balance between the interaction between the aromatic ring and the linear conductive material in the linear conductive material dispersion and the interaction through hydrogen bonding between the -OH of the phenolic compound and the polymer dispersant is broken, it may be difficult to exert an appropriate viscosity reduction effect of the linear conductive material dispersion and an effect of suppressing viscosity increase due to changes over time.

[0182] Meanwhile, the phenolic compound may be included in an amount of 1 to 100 parts by weight, or 5 to 100 parts by weight, or 10 to 100 parts by weight, based on 100 parts by weight of the polymeric dispersant containing the amine. When the content of the polymeric dispersant containing the amine and the phenolic compound satisfies the above range, the effect of reducing the viscosity of the dispersion and increasing the storage stability is more excellent.

[0183] The above dispersion medium (solvent) is a liquid medium for dispersing the linear conductive material, the polymer dispersant, and the phenolic compound containing two or more aromatic rings. When the linear conductive material is directly mixed with a negative electrode active material, etc. and used as a powder slurry, it is used to supply the linear conductive material dispersion liquid by pre-dispersing it to prevent agglomeration.

[0184] The above dispersion medium may be any liquid medium used in the technical field of the present invention, as long as it can dissolve or disperse the linear conductive material, polymer dispersant, and phenolic compound containing two or more aromatic rings to a certain level or higher. The dispersion medium may be an aqueous solvent, for example, water.

[0185] The linear conductive dispersion of the present invention as described above can be manufactured by a manufacturing method comprising: (1) a step of manufacturing a mixture by mixing a linear conductive material (e.g., carbon nanotubes, etc.), a polymer dispersant, a phenolic compound containing two or more aromatic rings, and a dispersion medium; and (2) a step of milling the mixture.

[0186] In step (1), a mixture is prepared by mixing a linear conductive material, a polymer dispersant, a phenolic compound containing two or more aromatic rings, and a dispersion medium.

[0187] The above mixture preparation step can be performed under temperature conditions in which the physical properties of the mixture, including viscosity, do not change due to evaporation of the dispersion medium. For example, it can be performed at a temperature of 50°C or lower, more specifically, from 5°C to 50°C.

[0188] In step (2), the above mixture is dispersed to prepare a linear conductive dispersion.

[0189] The above milling can be performed by a method such as a ball mill, a bead mill, a disc mill, a basket mill, a high pressure homogenizer, etc., and more specifically, it can be performed by a milling method using a disc mill or a high pressure homogenizer.

[0190] When milling using the above disk mill, the size of the beads can be appropriately determined depending on the type and amount of the linear conductive material and the type of the dispersant, and specifically, the diameter of the beads can be 0.1 mm to 5 mm, more specifically, 0.5 mm to 4 mm. In addition, the bead milling process can be performed at a speed of 2,000 rpm to 10,000 rpm, and more specifically, can be performed at a speed of 5,000 rpm to 9,000 rpm.

[0191] Milling by the high-pressure homogenizer is achieved by pressurizing the mixture with a plunger pump of the high-pressure homogenizer, for example, and pushing it through the gap of the homogenization valve, thereby generating forces such as cavitation, shear, impact, and explosion when passing through the gap.

[0192] The above milling process can be performed depending on the degree of dispersion of the linear conductive material dispersion, and can be performed specifically for 30 to 120 minutes, more specifically for 60 to 90 minutes.

[0193] In one embodiment of the present invention, the content of the powder binder may be 0.5 to 10 parts by weight, or 0.5 to 8 parts by weight, or 0.5 to 7 parts by weight, or 0.5 to 6 parts by weight, or 0.5 to 5 parts by weight, or 0.5 to 4 parts by weight, or 0.5 to 2 parts by weight, or 1 to 8 parts by weight, or 1 to 7 parts by weight, or 1 to 6 parts by weight, or 1 to 5 parts by weight, or 1 to 4 parts by weight, or 1 to 2 parts by weight, based on 100 parts by weight of the powder. When the content of the above powder binder satisfies this range, it plays a role in connecting and fixing the silicon-based active material and the linear conductive material within the powder, thereby minimizing the effect of volume expansion of the silicon-based active material, and when the powder is later applied to the negative electrode of a secondary battery, it does not cause the problem of increasing resistance by hindering the movement of lithium ions, thereby improving the cycle characteristics of the secondary battery.

[0194] In one embodiment of the present invention, the powder binder may include at least one of a linear binder and a dot-shaped binder.

[0195] The linear binder acts as a binding agent in a composition containing an active material, and may refer to a polymer compound having a structure in which the polymer chains are mainly arranged linearly without branches, or may have a limited branched or network structure by including some cross-linking agents or radically polymerizable monomers. Such linear binders are generally dissolved in a solvent, and the polymer exists in a uniform solution state without particle form. The linear binder dissolved in this way is evenly mixed with the active material and the conductive material in a slurry, and after electrode manufacturing, it can play a role in stably binding the active material and the conductive material to the current collector by forming a film or adhesive layer through interactions between the polymer chains during the drying and heat treatment processes.

[0196] The above dot-shaped binder may refer to a binder having the property of not completely dissolving in the solvent when dispersed in the solvent, maintaining a dot-shaped form while having a size of several hundred nanometers, thus having good dispersibility and being able to well surround the surface of the active material, and having low viscosity compared to the solid content, making it easy to control the binder content compared to the active material. By using such a dot-shaped binder together with a silicon-based active material and a linear conductive material in a powder, the surface of the active material can be sufficiently covered while maintaining the dispersibility of the linear conductive material.

[0197] The above-mentioned dot-shaped binder has no particular limitations on its shape, but is preferably in the form of particles, as it has good binding properties and can suppress deterioration due to reduction in the electrostatic capacity of the formed electrode or repeated charge / discharge cycles. Examples of the dot-shaped binder in the form of particles include those in which dispersed binder particles are dispersed in a solvent such as water, such as latex, or those in the form of powder obtained by drying such a dispersion.

[0198] Meanwhile, binders such as PTFE (Polytetrafluoroethylene) have a linear polymer chain structure, but are characterized by remaining in a solid powder state without dissolving in solvents. These binders are generally used in dry processes and are not processed into slurry form using solvents or dispersion media. PTFE binders exist in a fibrous or particle-like state within the electrode composition, and can play a role in fixing the active material and conductive material to the current collector through thermal compression or physical entanglement. Therefore, unlike typical slurry-based linear binders or dot-shaped binders, PTFE binders can be viewed as having a bonding mechanism based on structural entanglement and compressive force rather than solubility or dispersibility.

[0199] The above linear binder may include an acrylate polymer.

[0200] 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 cross-linked acrylate polymers such as acrylamide-acrylate copolymer, 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 radically polymerizable monomers used in the above graft polymers include methyl methacrylate, acrylonitrile, and methacrylic acid.

[0201] According to one embodiment of the present invention, the acrylate polymer may include an acrylamide-acrylate copolymer.

[0202] The above dot-shaped binder may include a diene polymer, a styrene polymer, or two or more thereof.

[0203] 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 (SBRs), which may be carboxyl-modified; cyanated vinyl-conjugated diene copolymers such as acrylonitrile-butadiene copolymers (NBRs); hydrogenated SBRs, hydrogenated NBRs, and the like.

[0204] 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.

[0205] In addition, in one embodiment of the present invention, the powder binder may include a linear binder and a dot-shaped binder. In one embodiment of the present invention, the binder may include an acrylate polymer (e.g., an acrylamide-acrylate copolymer, an acrylamide-acrylic acid-acrylonitrile copolymer, etc.) as a linear binder and a diene polymer or a styrene polymer (e.g., a styrene-butadiene copolymer (SBR), etc.) as a dot-shaped binder.

[0206] When the above powder binder includes both a linear binder and a dot-shaped binder, it provides a synergistic effect that comprehensively improves mechanical, electrical, and chemical stability in electrodes and secondary batteries, which can be advantageous in the design of secondary batteries that require high energy density, long life, and high reliability.

[0207] First, the linear binder has a long and continuous molecular structure, which increases the bonding strength between the active material and the current collector in the electrode, effectively dispersing the mechanical stress that may occur during electrode manufacturing and secondary battery operation, thereby preventing peeling or cracking of the electrode. The dot-shaped binder has a three-dimensional bonding structure, and in addition to improving local adhesive strength, it absorbs the stress caused by volume expansion during charge and discharge, thereby preventing physical damage to the electrode caused by repeated charge and discharge. Therefore, by using these linear binders and dot-shaped binders together, the mechanical stability of the electrode is improved, and the stability is maintained even during repeated charge and discharge cycles, which can result in extending the life of the battery.

[0208] In addition, the linear binder enables uniform dispersion of the active material within the electrode, thereby improving the conductivity and electrical contact of the electrode, and the point-like binder forms high-strength bonds at small contact points, thereby optimizing the contact between the active material and the electrolyte, thereby contributing to reducing the ion migration resistance. Therefore, the combination of the linear binder and the point-like binder can form a more efficient migration path of ions and electrons within the electrode, thereby improving the energy density and output characteristics.

[0209] According to one embodiment of the present invention, when the powder binder includes a linear binder and a dot-shaped binder, the weight ratio of the linear binder and the dot-shaped binder may be 70:30 to 30:70, or 60:40 to 40:60, or 70:50 to 50:70. When the weight ratio of the linear binder and the dot-shaped binder satisfies this range, the synergy effect resulting from the mixed use of the linear binder and the dot-shaped binder is further maximized, thereby improving the mechanical stability of the electrode and exhibiting the effect of improving the lifespan of the battery even in repeated charge / discharge cycles.

[0210] According to one embodiment of the present invention, the powder may comprise 80 to 98 parts by weight of a silicon-based active material, 0.5 to 10 parts by weight of a linear conductive material, and 0.5 to 10 parts by weight of a powder binder. Alternatively, the powder may comprise 85 to 95 parts by weight of a silicon-based active material, 0.5 to 5 parts by weight of a linear conductive material, and 0.5 to 8 parts by weight, or 0.5 to 7 parts by weight, or 0.5 to 6 parts by weight, or 0.5 to 5 parts by weight, or 0.5 to 4 parts by weight, or 1 to 8 parts by weight, or 1 to 7 parts by weight, or 1 to 6 parts by weight, or 1 to 5 parts by weight, or 1 to 4 parts by weight of a powder binder.

[0211] When the contents of the above silicon-based active material, linear conductive material, and powder binder satisfy this range, the cohesion between the active materials in the negative electrode increases, and the dispersibility of the linear conductive material and powder binder is significantly improved, so that the cell performance, such as the life characteristics of an electrochemical device equipped with such a negative electrode, can be greatly improved.

[0212] As described above, the powder may further include other types of negative electrode active materials in addition to the silicon-based active material.

[0213] Examples of the above other types of negative electrode active materials include carbon-based active materials such as non-graphitizable carbon, graphitic carbon (natural graphite, artificial graphite); Li x Fe2O3(0≤x≤1), Li x WO2(0≤x≤1), Sn x Me 1-x Me' y O z (Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, elements of group 1, 2, and 3 of the periodic table, halogens; 0≤x≤1; 1≤y≤3; 1≤z≤8) and other metal composite oxides; lithium metal; lithium alloys; silicon-based alloys; tin-based alloys; metal oxides such as SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, and Bi2O5; conductive polymers such as polyacetylene; Li-Co-Ni-based materials, etc. According to one embodiment of the present invention, the powder may further include at least one carbon-based active material such as natural graphite or artificial graphite.

[0214] According to one embodiment of the present invention, the powder may include 30 to 70 parts by weight of a silicon-based active material, 30 to 70 parts by weight of a negative electrode active material other than the silicon-based active material, 0.5 to 10 parts by weight of a linear conductive material, and 0.5 to 10 parts by weight of a binder.

[0215] Alternatively, the powder may include 35 to 70 parts by weight of a silicon-based active material, 35 to 70 parts by weight of a negative electrode active material other than the silicon-based active material, 0.5 to 5 parts by weight of a linear conductive material, and 0.5 to 5 parts by weight of a binder.

[0216] In one embodiment of the present invention, the silicon-based active material may be included in an amount of 75 wt% or more or 90 wt% or more of the total weight of the powder, and the binder for the powder may be included in an amount of 20 wt% or less or 10 wt% or less.

[0217] The conductive agent for the powder may be included in an amount of 0.1 wt% to 20 wt%, preferably 0.1 wt% to 10 wt%, based on 100 wt% of the powder. For example, the conductive agent in the powder may be included in an amount of about 0.1 wt% to 5 wt%.

[0218] According to one embodiment of the present invention, the content of the silicon-based active material in the powder may be 75 wt% to 98 wt%. Within the above range, the content of the powder binder may be 0.5 wt% to 10 wt%, and the content of the powder conductive material may be 0.5 wt% to 5 wt%. According to another embodiment, the content of the silicon-based active material may be 90 wt% to 98 wt%, the content of the powder binder may be 0.5 wt% to 5 wt%, and the content of the electrode conductive material may be 0.5 wt% to 5 wt%.

[0219] In one embodiment of the present invention, the powder may include a surface portion and a center portion, which is the remaining area excluding the surface portion. Specifically, the center portion of the powder may be defined as the intersection of the major axis (the longest length portion of the powder) and the minor axis (the shortest length portion of the powder) of the powder, the surface portion may be defined as the area connecting positions located a predetermined distance down from each position on the surface of the powder to the center of the powder, and the center portion may be defined as the remaining area excluding the surface portion.

[0220] Together with or independently of this, the powder has a content (wt%) of a powder binder contained in the center of the powder relative to 100 wt% of the total weight of the powder (B c / G t ) compared to the content (wt%) of the powder binder contained in the surface of the powder (B s / G t ) is more. Here, Bc is the weight of the powder binder included in the center, Bs is the weight of the powder binder included in the surface, and G t refers to the total weight of powder particles.

[0221] Together with or independently of this, the powder has a content (vol%) of a powder binder contained in the center of the powder relative to 100 vol% of the total volume of the powder (B c / G t ) compared to the content (vol%) of powder binder contained in the surface of the powder (B s / G t ) is more. Here, Bc is the volume of the powder binder included in the center, Bs is the volume of the powder binder included in the surface, and G t refers to the total volume of powder particles.

[0222] In one embodiment of the present invention, the surface portion may specifically mean a surface area from the surface of the powder toward the inside, specifically up to 30% of the distance (center distance) from each surface portion position to the center of the powder. In one embodiment of the present invention, the surface portion may mean a surface area up to 30% of the center distance from the surface of the powder, a surface area up to 20% of the center distance, a surface area up to 15% of the center distance, a surface area up to 10% of the center distance, or a surface area up to 5% of the center distance. Preferably, the surface portion may mean a surface area up to 20% of the center distance from the surface of the powder.

[0223] As described above, in the present invention, the center of the powder can be defined as the intersection of the major axis (the longest length portion of the powder) and the minor axis (the shortest length portion of the powder) of the powder.

[0224] Meanwhile, in one embodiment of the present invention, the surface portion may refer to an area from the center of the powder toward the outside of the powder to the powder surface after 70% of the center distance. In one embodiment of the present invention, the surface portion may refer to an area from the center of the powder to the powder surface after 80%, 85%, 90%, or 95% of the center distance, for example.

[0225] In one embodiment of the present invention, the center of the powder may refer to a point that is half the longest diameter of the powder. In the present invention, the center distance may refer to the distance from the center of the powder to each point on the surface of the powder. 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 powder along each center distance, specifically, points that are up to 30%, up to 20%, up to 10%, up to 5%, or up to 1% of the center distance from the surface.

[0226] In one embodiment of the present invention, the content of the powder binder in a region from the center of the powder particle to the surface of the powder at 90% of the center distance relative to 100 wt% of the total weight of the powder in that region may be 50 wt% or more, 60 wt% or more, 70 wt% or more, 80 wt% or more, or 90 wt% or more.

[0227] In another embodiment of the present invention, the content of the powder binder in a region from the center of the powder to the surface of the powder at a distance of 95% from the center 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, based on 100 wt% of the total weight of the powder in that region.

[0228] In another embodiment of the present invention, the content of the powder binder in a region from the center of the powder particle to the surface of the powder at a distance of 99% from the center of the powder particle 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 powder in that region.

[0229] In one embodiment of the present invention, the content of the powder binder in a region from the center of the powder particle to the surface of the powder at a distance of 90% from the center of the powder particle may be 50 vol% or more, 60 vol% or more, 70 vol% or more, 80 vol% or more, or 90 vol% or more, relative to 100 vol% of the total volume of the powder in that region.

[0230] In another embodiment of the present invention, the content of the powder binder in a region from the center of the powder to the surface of the powder at a distance of 95% from the center 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 volume of the powder in that region.

[0231] In another embodiment of the present invention, the content of the powder binder in a region from the center of the powder particle to the surface of the powder at a distance of 99% from the center of the powder 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 volume of the powder in that region.

[0232] In one embodiment of the present invention, the content of the powder binder in a powder surface area from the surface of the powder particle to 10% of the center distance relative to 100 wt% of the total weight of the powder in that area may be 50 wt% or more, 60 wt% or more, 70 wt% or more, 80 wt% or more, or 90 wt% or more.

[0233] In another embodiment of the present invention, the content of the powder binder in a powder surface area from the surface of the powder particle to a center distance of 5 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 powder in that area.

[0234] In another embodiment of the present invention, the content of the powder binder in a region from the surface of the powder particle to the surface of the powder after 1% of the center distance 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 powder in that region.

[0235] In one embodiment of the present invention, the content of the powder binder in a powder surface area from the surface of the powder particle to 10% of the center distance relative to 100 wt% of the total weight of the powder in that area may be 50 wt% or more, 60 wt% or more, 70 wt% or more, 80 wt% or more, or 90 wt% or more.

[0236] In another embodiment of the present invention, the content of the powder binder in a powder surface area from the surface of the powder particle to a center distance of 5 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 powder in that area.

[0237] In another embodiment of the present invention, the content of the powder binder in a region from the surface of the powder particle to the surface of the powder after 1% of the center distance 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 powder in that region.

[0238] According to one embodiment of the present invention, a surface region having a high content of powder binder 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 distribution of powder binder than the surface region.

[0239] To describe the powder in more detail, the powder may have a central portion including a plurality of silicon-based active materials; and a surface portion including a powder binder that is positioned on all or part of the outer side of the central portion and binds the silicon-based active materials. That is, in the central portion of the powder, the plurality of silicon-based 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 powder, the powder binder is positioned on all or part of the outer side of the aggregate, thereby fixing and binding the plurality of silicon-based active materials in the central portion of the powder to each other.

[0240] According to one embodiment of the present invention, a small amount of powder binder may be further included in the central portion, which may serve to connect and fix the plurality of silicon-based active materials in the central portion. However, as previously described, it is preferable that the content of powder binder be higher in the surface portion than in the central portion.

[0241] Meanwhile, in one embodiment of the present invention, the powder may have an aspect ratio of 0.5 to 0.94, or 0.7 to 0.93, or 0.75 to 0.91. The aspect ratio may refer to the ratio of the major axis length to the minor axis length of the powder. In another embodiment of the present invention, the average aspect ratio of the powders may have a value of 0.5 to 0.94, or 0.7 to 0.93, or 0.75 to 0.91, 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 powder 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 powder, 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 powder. When the aspect ratio or the average aspect ratio of the powder satisfies this range, it is advantageous in terms of having sufficient fluidity suitable for the process.

[0242] According to one embodiment of the present invention, the powder may further include a dispersant. The dispersant may include carboxymethylcellulose (CMC). The dispersant is further included in a composition comprising a silicon-based active material, a linear conductive material, a powder binder, and an aqueous dispersion medium in the step of manufacturing the powder described below, thereby enabling solid components such as the silicon-based active material, the linear conductive material, and the powder binder to be uniformly dispersed within the composition, thereby improving the stability of the composition and contributing to controlling the viscosity and flowability of the composition. The quality and performance of the powder manufactured through such a composition can be improved.

[0243]

[0244] 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.

[0245] 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.

[0246] 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.

[0247] 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 electrode active material and the powder binder, may be the same or different for each layer, but are not limited thereto.

[0248] The above carbon-based active material may include carbon such as graphite-based carbon, such as non-graphitizable carbon, natural black, or artificial graphite.

[0249] In one embodiment of the present invention, the binder for the cathode layer may be one or more of the powder binders described above. Specifically, the binder for the cathode layer may include a styrene butadiene copolymer (SBR, etc.).

[0250] In addition, the conductive material for the cathode layer may be a conventional conductive material used for electrodes, i.e., a conductive material in the form of a plate, dot, line, fiber, etc., and may include, for example, carbon black, Denka black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, etc., or two or more thereof, but is not limited thereto.

[0251] When the contents of the powder, carbon-based active material, conductive material for the negative electrode layer, and binder for the negative electrode layer in the above negative electrode active material layer satisfy this range, it may be more advantageous in terms of providing an appropriate energy density while at the same time providing sufficient life characteristics.

[0252] According to one embodiment of the present invention, the total weight of the linear conductive material in powder form and the binder for powder form may be greater than the total weight of the conductive material for the negative electrode layer and the binder for the negative electrode layer. Specifically, the total weight of the linear conductive material in powder form and the binder for powder form may be 1.1 to 10 times, or 1.5 to 5 times, greater than the total weight of the conductive material for the negative electrode layer and the binder for the negative electrode layer. In this case, when the total weight of the linear conductive material in powder form and the binder for powder form are greater than the total weight of the conductive material for the negative electrode layer and the binder for the negative electrode layer, it may be more advantageous in terms of positioning a sufficiently high modulus powder binder on the surface of the silicon-based active material.

[0253] 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.

[0254] 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 adhesiveness of the electrode active material, and various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric are possible.

[0255] In one embodiment of the present invention, a primer layer may be formed entirely or partially on the collector.

[0256] 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 powder binder and the conductive material in the primer layer may be 90 wt% or more.

[0257] An electrode according to one embodiment of the present invention includes a negative electrode active material layer including powder, wherein the primer layer includes a powder binder and a conductive material, and the sum of the powder binder and the conductive material is 90 wt% or more, thereby ensuring stability over time of the primer layer, and thus exhibiting excellent physical properties such as adhesive strength and lifespan characteristics, but the present invention is not limited thereto.

[0258] 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.

[0259] 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.

[0260] 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 powder binder used in the primer layer.

[0261] 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.

[0262] 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 powder binder may include styrene butadiene rubber (SBR), nitrile butadiene rubber (NBR), polymethylmethacrylate, polyethylhexylacrylate, polybutylacrylate, or two or more thereof.

[0263] 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.

[0264] 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.

[0265] 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.

[0266] 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.

[0267] 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 powders such as fluorocarbon, aluminum, and nickel powders; conductive whiskeys such as zinc oxide and 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.

[0268] 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.

[0269]

[0270] According to one aspect of the present invention, a method for manufacturing a negative electrode for an electrochemical device according to one embodiment of the present invention is provided, the method including the step of forming a negative electrode active material layer using a powder including a silicon-based active material, a linear conductive material, and a powder binder.

[0271] According to one embodiment of the present invention, the cathode including the powder may be an electrode obtained through various manufacturing processes such as a wet process or a dry process.

[0272] The above wet process may include a step of mixing the powder with a binder for the negative electrode layer and optionally a conductive material for the negative electrode layer in a dispersion medium, and then applying and drying the mixture on a current collector.

[0273] In addition, the dry process may include a step of dry mixing the powder and a fiberizable binder, or the powder, a fiberizable binder, and a conductive material for a negative electrode layer to prepare a mixture; a step of kneading the prepared mixture to prepare a mixture lump, and a step of pulverizing the mixture lump to obtain a mixed powder for an electrode; a step of feeding the mixed powder for an electrode between a plurality of rolls and performing a calendaring process to form a film for an electrode; and a step of laminating the film for an electrode onto a metal current collector.

[0274] In the step of manufacturing the mixture, in addition to the powder and the fiberizable binder, a conductive material for the negative electrode layer may be further included. At this time, the step of manufacturing the mixture may be carried out without any dispersion medium, or may be carried out by further including at least one of additives such as a very small amount of dispersion medium, a lubricant, a processing aid, etc. Here, the additives may be applied if they are components used in a typical electrode process. Here, "very small amount" means an amount used in the step of manufacturing the mixture but not substantially affecting the appearance, flowability, viscosity, etc. of the mixture, for example, a content of less than 0.1 wt% with respect to 100 wt% of the total mixture.

[0275]

[0276] At this time, the conditions during mixing can be in the range of 70℃ to 200℃ and under pressure higher than atmospheric pressure.

[0277] The above mixture can be prepared by mixing in a mixer at 5,000 rpm to 20,000 rpm for 30 seconds to 2 minutes, specifically at 10,000 rpm to 15,000 rpm for 30 seconds to 1 minute, to ensure uniformity.

[0278] The above-mentioned fiberizable binder is not particularly limited as long as it can be microfiberized by the step of manufacturing the mixed powder. A binder containing fluorine may be more preferable. The above-mentioned microfiberization refers to a process of dividing a polymer into small pieces and may be performed using, for example, a mechanical shear force. A specific example of such a fiberizable binder may include a fluorine-containing polymer, and specifically, may include polytetrafluoroethylene (PTFE) alone, or may further include at least one PVdF-based copolymer such as PVdF (polyvinylidene fluoride) or PVdF-HFP (polyvinylidene fluoride-co-hexafluoropropylene) in addition to PTFE.

[0279] The above mixing is not limited to a specific method. In a specific embodiment of the present invention, the mixing may be performed using a kneader, for example.

[0280] Specifically, the mixing can be controlled at a speed of 10 rpm to 100 rpm. For example, the mixing can be controlled at a speed of 20 rpm or more or 70 rpm or less within the above range. The mixing can be performed for 1 minute to 30 minutes. For example, the mixing can be performed at a speed of 40 rpm to 70 rpm within the above range for 3 minutes to 10 minutes. Meanwhile, the mixing can be controlled at a shear rate in the range of 10 / s to 500 / s. In one specific embodiment of the present invention, the mixing can be performed for 1 minute to 30 minutes, and the shear rate can be controlled in the range of 30 / s to 100 / s.

[0281] Additionally, this mixing step can be performed under conditions of high temperature and pressure higher than atmospheric pressure, and more specifically, under conditions of pressure higher than atmospheric pressure.

[0282] More specifically, the mixing can be performed at a temperature ranging from 70°C to 200°C, specifically, from 90°C to 150°C.

[0283] In addition, it can be performed under a pressure higher than atmospheric pressure, specifically under a pressure of 1 to 100 atm, and more specifically under a pressure of 10 to 80 atm. When the above pressure range is satisfied, the problem of excessive shear force and pressure being applied, which may cause the formed fibers to break or the density of the mixture mass to become too high can be prevented. That is, according to the present invention, when a low-shear mixing process is performed under conditions of high temperature and pressure higher than atmospheric pressure instead of high-shear mixing, the intended effect of the present invention can be achieved.

[0284] The above grinding step is not limited, but can be performed with a device such as a blender or grinder, and the grinding step can be specifically performed at a speed of 5,000 rpm to 20,000 rpm for 30 seconds to 10 minutes, specifically at a speed of 10,000 rpm to 18,000 rpm for 30 seconds to 2 minutes.

[0285] When the above grinding speed and time are satisfied, sufficient grinding can be achieved to form powder of a size suitable for filming, and the problem of excessive fine particles being generated in the mixture mass can be prevented. If necessary, a classification process can be performed to filter out powder exceeding a certain size or powder below a certain size.

[0286] The above calendaring can be performed, for example, by rolls that are present face to face, wherein the roll temperature can be from 50°C to 200°C, and the rotational speed ratio of the rolls can be controlled in the range of 1.0 to 2.0.

[0287] In addition, as a dry electrode using the above powder, there may be a dry electrode manufactured by directly applying the powder alone or additionally together with a binder for the negative electrode layer and / or a conductive material for the negative electrode layer onto a current collector and then going through a process such as rolling.

[0288]

[0289] According to one embodiment of the present invention, there is provided a step of manufacturing a powder by drying a composition including a silicon-based active material, a linear conductive material, a powder binder, and an aqueous dispersion medium by a spray drying method;

[0290] A step of preparing an electrode slurry by mixing the above powder with a carbon-based active material, a conductive material for a negative electrode layer, a binder for a negative electrode layer, and an aqueous dispersion medium (water) for a slurry; and

[0291] A method for manufacturing an electrode according to one embodiment of the present invention may be provided, including a step of applying the electrode slurry on at least one surface of a current collector and drying and rolling.

[0292]

[0293] First, a composition including a silicon-based active material, a linear conductive material, a powder binder, and an aqueous dispersion medium is dried by spray drying to produce a powder.

[0294] A silicon-based active material, a linear conductive material, a powder binder, and optionally, an additive are dispersed or dissolved in a dispersion medium (which may be a solvent for the powder binder), thereby obtaining a composition in which the silicon-based active material, the linear conductive material, the powder binder, and / or other additives are dispersed or dissolved.

[0295] 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 fluidized granulation can be accelerated. In addition, since the dispersibility or solubility of the binder for electrode powder 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.

[0296] 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 1 to 50 wt%, or 5 to 50 wt%, or 10 to 30 wt%.

[0297] The method or order of dispersing or dissolving the silicon-based active material, linear conductive material, powder binder, etc. in the dispersion medium is not particularly limited, and examples thereof include a method of adding the silicon-based active material, linear conductive material, and powder binder to the dispersion medium and mixing them, a method of first dissolving or dispersing the powder binder in the dispersion medium, and then finally adding the silicon-based active material and linear 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 can be mentioned. The mixing can be performed, for example, at a temperature ranging from room temperature to 80°C for 10 minutes to several hours.

[0298] 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.

[0299] In one embodiment of the present invention, the temperature of the hot air may be controlled to be 80°C to 250°C based on the reactor inlet temperature (at the time of injection) in terms of forming a powder structure with a high content of powder binder on the surface. In the present invention, considering the content gradient and aspect ratio of the powder binder, it may be preferably controlled to be 170°C to 250°C, more preferably 180°C to 200°C. In the spray drying method, the method of sucking the 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 horizontally, 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 and 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) may be controlled to be 90°C to 130°C.

[0300] 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 result in the formation of spherical particles of a uniform shape and the formation of powders 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 and the formation of particles with an extremely small D50 and a low aspect ratio. Therefore, in order to achieve a high aspect ratio, low agglomeration of the powder binder, and control the particle size at an appropriate level, it is necessary to control the inlet temperature and outlet temperature within an appropriate range.

[0301] Additionally, the result obtained by optionally spray drying, i.e., the surface of the powder, can be heat-treated to harden it. At this time, the heat treatment temperature can usually be 80°C to 300°C.

[0302]

[0303] Thereafter, the above powder is mixed with a carbon-based active material, a conductive material for the negative electrode layer, a binder for the negative electrode layer, and an aqueous dispersion medium for the slurry to prepare an electrode slurry.

[0304] At this time, the aqueous dispersion medium for the slurry used may refer to the aqueous dispersion medium described above, and the slurry manufacturing process may refer to the composition manufacturing process for powder manufacturing described above.

[0305] The viscosity of the electrode slurry may be 1,000 to 10,000 cPs, or 1,000 to 9,000 cPs.

[0306] Next, the electrode slurry is applied to at least one surface of the current collector, dried, and rolled to form a negative electrode active material layer.

[0307] 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 the negative electrode layer and a binder for the negative electrode layer may be provided on at least one side of the current collector, as described above.

[0308] 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, slot die coating, comma coating, etc.

[0309] 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 100°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.

[0310] 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.

[0311]

[0312] Additionally, according to one aspect of the present invention, an electrochemical device comprising an electrode according to one embodiment of the present invention is provided.

[0313] 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.

[0314] 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.

[0315] 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.

[0316] The above positive electrode may have a positive electrode active material layer including a positive electrode active material, a powder binder, and optionally a conductive material, etc., on at least one surface of the current collector.

[0317] 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 x Ni-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-xO2(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.

[0318] 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 powder for electrochemical devices, but may include, for example, a diene polymer, an acrylate polymer, a fluorine polymer, a styrene polymer, or two or more thereof.

[0319] 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.

[0320] 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 be carboxyl-modified; cyanated vinyl-conjugated diene copolymers such as acrylonitrile-butadiene copolymer (NBR); hydrogenated SBR, hydrogenated NBR, and the like.

[0321] 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.

[0322] 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 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.

[0323] 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).

[0324] 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.

[0325] The above electrolyte solution includes a lithium salt as an electrolyte and an organic solvent for dissolving the same.

[0326] 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.

[0327] 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.

[0328] 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.

[0329] Optionally, the electrolyte stored according to the present invention may further include additives such as an overcharge prevention agent included in a conventional electrolyte.

[0330] 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.

[0331] 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.

[0332]

[0333] 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.

[0334]

[0335] Example

[0336] [Example 1]

[0337] (1) Manufacturing of cathode

[0338] A composition having a viscosity of approximately 9000 cPs was prepared by mixing Si (Pure Si, FH6, average particle size (D50): 10 μm) as a silicon-based active material, single-walled carbon nanotubes (SWCNT) as a linear conductive material, graphite-based plate-shaped conductive material (SFG-6L), styrene-butadiene rubber (SBR A, styrene:butadiene molar ratio = 64:36) as a powder binder, and carboxymethyl cellulose (CMC, Daicell2200) as a dispersant with water as a dispersion medium in a weight ratio of 75:2:8:8:7 through a homogenizer. At this time, the solid content in the composition was 15 wt%.

[0339] 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 of 250°C, outlet temperature of 105°C, pressure of the two fluid nozzles of the spray dryer of 2.5 bar, and feed rate of the spray dryer of 10 cc / min. A photograph of the spray dryer used at this time is shown in Fig. 6.

[0340]

[0341] Half of the above dried results were prepared by removing particles larger than 150㎛ using an industrial sieve.

[0342] The powder has a central portion including a plurality of silicon-based active materials and linear conductive materials, and a surface portion including a powder binder located outside the central portion and binding the plurality of silicon-based active materials and linear conductive materials.

[0343]

[0344] The powder obtained above, as a carbon-based active material (a mixture of graphite-based active materials, artificial graphite and / or natural graphite, at a weight ratio of 1:1), carbon black (C65) as a conductive material for the negative electrode layer, and styrene butadiene rubber (SBR, styrene:butadiene molar ratio = 64:36) as a binder for the negative electrode layer were mixed with water as a dispersion medium at a weight ratio of 5:92:1:2 through a homogenizer at 3000 rpm to prepare a slurry having a viscosity of about 9000 cPs. At this time, the solid content in the slurry was 40 wt%.

[0345]

[0346] The above-mentioned manufactured slurry was applied to both sides of a copper collector (thickness: 10 um) using a slot die method, dried at 80°C for 0.5 hours using a conventional oven device, and rolled using a roll pressing method, so that a weight per unit area of ​​300 mg / 25 cm was applied to both sides of the collector. 2 A negative electrode having a negative electrode active material layer having a loading amount was manufactured.

[0347]

[0348] (2) Manufacturing of the anode

[0349] Li[Ni as a cathode active material 0.88 Co 0.07 Mn 0.04 ]Al 0.01 O2), a pre-dispersed solution of carbon black as a cathode conductive material and polyvinylidene fluoride (PVdF) as a binder for cathode powder were added to the dispersion medium NMP at a weight ratio of 96.5:1.5:2, and the mixture was stirred at 3500 rpm for 1 hour using a homogenizer to prepare a cathode active material slurry. The solid content of the carbon black pre-dispersed solution was 16%, and the final solid content of the slurry was prepared as 68%. The slurry was coated on both sides of an aluminum current collector having a thickness of 12 μm, and the coated slurry was dried using a drying device equipped with a hot air blower and an IR heater to form a cathode active material layer.

[0350] Afterwards, the above-mentioned positive electrode active material layer was rolled using a roll pressing method, and the weight after drying per unit area was 590 mg / 25 cm 2 A positive electrode having a positive electrode active material layer having a loading amount of was manufactured.

[0351]

[0352] (3) Manufacturing of secondary batteries

[0353] 1) Mono cell secondary battery

[0354] An electrode assembly was manufactured using a porous polyethylene film (thickness: 10 μm) as a separator between the previously manufactured positive and negative electrodes. After the electrode assembly was embedded in a battery case, a liquid electrolyte containing 1 M LiPF6 dissolved in a solvent containing ethylene carbonate, dimethylene carbonate, and diethyl carbonate in a volume ratio of 1:2:1 was used to manufacture a monocell secondary battery by injecting, sealing, and chemically forming the solution.

[0355]

[0356] 2) Half Coin Cell Secondary Battery

[0357] A half coin cell secondary battery was manufactured by incorporating lithium metal and the previously manufactured negative electrode into a coin cell case, and then using a liquid electrolyte containing 1M LiPF6 dissolved in a solvent containing ethylene carbonate, dimethylene carbonate, and diethyl carbonate mixed in a volume ratio of 1:2:1, and then pouring, sealing, and chemically forming the solution.

[0358]

[0359] [Example 2]

[0360] In powder manufacturing, the composition having a viscosity of about 9000 cPs was manufactured in the same manner as in Example 1, except that the composition was mixed with water as a dispersion medium in a weight ratio of 75:2:4:4:8:7 using a homogenizer, using Si (Pure Si, FH6, average particle size (D50): 10 μm) as a silicon-based active material, single-walled carbon nanotubes (SWCNT, SFG-6L) as a linear conductive material, graphite-based plate-shaped conductive material (SFG-6L), styrene-butadiene rubber (SBR A, styrene:butadiene molar ratio = 64:36) as a powder binder, polyacrylic acid copolymer (acrylamide / acrylonitrile / acrylic acid copolymer) as an acrylate polymer, and carboxymethyl cellulose (CMC, Daicell2200) as a dispersant.

[0361]

[0362] Using the obtained powder, a negative electrode and a secondary battery were manufactured using the same method as in Example 1.

[0363]

[0364] [Example 3]

[0365] In powder manufacturing, the composition having a viscosity of about 9000 cPs was manufactured in the same manner as in Example 1, except that the composition was mixed with water as a dispersion medium in a weight ratio of 75:2:8:8:7 using a homogenizer, using Si (Pure Si, FH6, average particle size (D50): 10 μm) as a silicon-based active material, single-walled carbon nanotubes (SWCNT, SFG-6L) as a linear conductive material, graphite-based plate-shaped conductive material (SFG-6L), styrene-butadiene rubber (SBR B, styrene:butadiene molar ratio = 42:58) as a powder binder, and carboxymethyl cellulose (CMC, Daicell2200) as a dispersant.

[0366]

[0367] Using the obtained powder, a negative electrode and a secondary battery were manufactured using the same method as in Example 1.

[0368]

[0369] [Comparative Example 1-1]

[0370] 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 such that the inlet temperature was 250°C, the outlet temperature was 105°C, the pressure of the two fluid nozzles of the spray dryer was 0.2 bar, and the feed rate of the spray dryer was 50 cc / min, and a powder was manufactured in the same manner as in Example 1.

[0371] A negative electrode and a secondary battery were manufactured in the same manner as in Example 1, except that the obtained powder was mixed at 1000 rpm using a homogenizer to prepare a slurry.

[0372]

[0373] [Comparative Example 1-2]

[0374] 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 such that the inlet temperature was 250°C, the outlet temperature was 105°C, the pressure of the two fluid nozzles of the spray dryer was 0.2 bar, and the feed rate of the spray dryer was 50 cc / min, and a powder was manufactured in the same manner as in Example 1.

[0375] Using the obtained powder, a negative electrode and a secondary battery were manufactured using the same method as in Example 1.

[0376]

[0377] [Comparative Example 2-1]

[0378] A powder was manufactured in the same manner as in Comparative Example 1-1, except that SBR A and a polyacrylic acid copolymer (acrylamide / acrylonitrile / acrylic acid copolymer) were used as a powder binder.

[0379] A negative electrode and a secondary battery were manufactured in the same manner as in Example 1, except that the obtained powder was mixed at 1000 rpm using a homogenizer to prepare a slurry.

[0380]

[0381] [Comparative Example 2-2]

[0382] 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 such that the inlet temperature was 250°C, the outlet temperature was 105°C, the pressure of the two fluid nozzles of the spray dryer was 0.2 bar, and the feed rate of the spray dryer was 50 cc / min, and a powder was manufactured in the same manner as in Comparative Example 2-1.

[0383] Using the obtained powder, a negative electrode and a secondary battery were manufactured using the same method as in Example 1.

[0384]

[0385] [Comparative Example 3-1]

[0386] 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 such that the inlet temperature was 250°C, the outlet temperature was 105°C, the pressure of the two fluid nozzles of the spray dryer was 0.2 bar, and the feed rate of the spray dryer was 50 cc / min, and a powder was manufactured in the same manner as in Example 3.

[0387] A negative electrode and a secondary battery were manufactured in the same manner as in Example 1, except that the obtained powder was mixed at 1000 rpm using a homogenizer to prepare a slurry.

[0388]

[0389] [Comparative Example 3-2]

[0390] 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 such that the inlet temperature was 250°C, the outlet temperature was 105°C, the pressure of the two fluid nozzles of the spray dryer was 0.2 bar, and the feed rate of the spray dryer was 50 cc / min, and a powder was manufactured in the same manner as in Comparative Example 3-1.

[0391] Using the obtained powder, a negative electrode and a secondary battery were manufactured using the same method as in Example 1.

[0392]

[0393] [Comparative Example 4]

[0394] (1) Manufacturing of cathode

[0395] Si (Pure Si, FH6, average particle size (D50): 10㎛) as a silicon-based active material, single-walled carbon nanotubes (SWCNT, SFG-6L) as a linear conductive material, carbon black (SuperC65) as a negative electrode layer conductive material, styrene-butadiene rubber (SBR A, styrene:butadiene molar ratio = 64:36) as a powder binder, and carboxymethyl cellulose (CMC, Daicell2200) as a dispersant were mixed with water as a dispersion medium at a weight ratio of 76.1:1.6:8.1:8.1:6.1 through a homogenizer at 3000 rpm to prepare a slurry having a viscosity of approximately 9000 cPs. At this time, the solid content in the composition was 40 wt%.

[0396]

[0397] The above-mentioned manufactured slurry was applied to both sides of a copper collector (thickness: 10 um) using a slot die method, dried at 80°C for 0.5 hours using a conventional oven device, and rolled using a roll pressing method, so that a weight per unit area of ​​300 mg / 25 cm was applied to both sides of the collector. 2 A negative electrode having a negative electrode active material layer having a loading amount was manufactured.

[0398]

[0399] FIG. 7 is a schematic diagram showing a powder according to an embodiment of the present invention (C, corresponding to the powder of Examples 1 to 3), a spherical powder of the prior art (A, corresponding to the powder of Comparative Examples 1-1, 2-1, 3-1), and a crushed powder (C, corresponding to Comparative Examples 1-2, 2-2, 3-2). Referring to FIG. 7, in the case of the spherical powder (A), the particle size of the powder is large, the degree of sphericity is close to a sphere, and the surface has a gentle shape, so that the fidelity also has a high value, and in the case of the crushed powder (B), when manufacturing an electrode using the spherical powder, the shear force is further increased, and in the process, the spherical powder is crushed by physical impact due to collision with each other, so that the particle size is relatively small compared to the spherical powder, and a sharp crushing surface is exposed, so that the degree of sphericity is also low. Meanwhile, the powder (C) according to one embodiment of the present invention is different from the spherical powder (A) in that the particle size is smaller and the degree of sphericity is smaller, and the crushed surface is exposed as a result of crushing, so that the binder (the binder distribution is indicated linearly in Fig. 7) is not uniformly distributed. Compared to the crushed type, it can be seen that the powder (C) still has a uniform binder distribution on the entire surface of the powder because there is no crushing phenomenon during the manufacturing process.

[0400]

[0401] [Evaluation Method]

[0402] Dispersity of powder and standard deviation of dispersion within the negative electrode active material layer

[0403] The method for measuring the dispersion degree and standard deviation of the dispersion degree of the powder in the negative electrode active material layer of the negative electrode of Example 2 and Comparative Examples 1-1, 2-2, and 4 was performed as follows.

[0404] The cross-section of the negative electrode active material layer of the target negative electrode was measured using a scanning electron microscope (SEM) (Manufacturer: JEOL, Equipment name: JSM-7200) to obtain an image, and the image (SEM image) measured by this SEM was analyzed on a pixel basis using the ImageJ program to measure the degree of dispersion of the powder containing the silicon-based active material within the negative electrode active material. At this time, the degree of dispersion was calculated for each of the four SEM images, and then the standard deviation was calculated from the degree of dispersion value of each image. The smaller the degree of dispersion value, the less the powder is clumped together in one part within the negative electrode active material layer, and the more evenly it is dispersed. In addition, the smaller the standard deviation of the degree of dispersion, the smaller the deviation of the degree of dispersion within the same negative electrode active material layer, and thus the more uniform the dispersion is evaluated.

[0405] Specifically, when measuring dispersion, the SEM image pixels of the analysis area within the negative electrode active material layer were divided into 20 X 20 (width X height) sections, and the area ratio of the area of ​​interest (area with powder containing silicon-based active material) in each section was calculated, and the sample distribution of these 400 area ratios was defined as the dispersion value.

[0406] At this time, the sample variance was calculated using Equation 1 below for each value of the 400 area ratios, and this was provided as a dispersion value.

[0407] [Formula 1]

[0408] s²= Σ(y - y')² / (n-1)

[0409] In the above formula, s² represents the sample variance, i.e., the degree of dispersion, and represents the variance value obtained from the sample. It is denoted as s² to distinguish it from the population variance (σ²).

[0410] Σ(y - y')² is the sum of squared deviations, and is more specifically as follows.

[0411] y: each observation

[0412] y': sample mean (y-bar)

[0413] (y - y'): The difference (deviation) between each observation and the sample mean

[0414] (y - y')²: squared deviation

[0415] Σ: Sum of squared deviations for all observations

[0416] n - 1 represents the degrees of freedom, specifically:

[0417] n: sample size (number of observations)

[0418] The standard deviation of the dispersion was obtained from the dispersions of four SEM images in the usual manner. That is, the arithmetic mean of the dispersions of the four SEM images was obtained, and the average of the results obtained by subtracting the mean from each dispersion was squared, and the square root of this was obtained as the standard deviation of the dispersions.

[0419] The results are shown in Table 1 and Fig. 8. For reference, the circles in Comparative Example 1-1 in Fig. 8 are illustrative indications of some of the locations where the powder is present, and the circles 1 to 4 in Comparative Example 4 are illustrative indications of dividing the SEM image into four areas for analysis.

[0420] Example 1: Comparison of standard deviations of variances (1-12.64x10) -2 8.30 X 10 -3 Comparative Example 2-23.73x10 -2 5.14 X 10 -3 Example 24.4x10 -2 2.85 X 10 -3

[0421] Volume expansion rate of the negative electrode active material layer

[0422] The volume expansion rate of the negative electrode active material layer of the negative electrodes of Examples 1 to 3 and Comparative Example 4 was calculated using Equation 2 below by measuring the thickness of the negative electrode active material layer using an XRM (X-ray microscope) (ZEISS Xradia Versa620). The results are shown in Table 2.

[0423] [Formula 2]

[0424] Volume expansion rate (%) = (electrode thickness after 100 charges - initial electrode thickness) / initial electrode thickness X 100

[0425] Comparative Example 4 Example 1 Example 2 Example 3 Initial electrode thickness 114118118118100 times charged state electrode thickness 160137.5134.5154 Volume expansion rate (%) 40.416.614.130.6

[0426]

[0427] Evaluation of the adhesion of the cathode

[0428] Double-sided tape was attached to a slide glass, and the negative electrodes manufactured in Examples 2 to 3 and Comparative Examples 1-1 and 2-2, which were punched out to a size of 20 mm X 100 mm, were placed on top of it, and adhered by rolling back and forth 10 times with a 2 kg roller, and then the force (adhesive force) at which the electrode was peeled off from the slide glass was measured using a UTM (TA) device at a speed of 10 mm / min. At this time, the measurement angle between the slide glass and the electrode was 90°. The measured adhesive force is shown in Table 3 below.

[0429] Adhesion (gf / cm) Example 254.42 Example 361.26 Comparative Example 1-129.6 Comparative Example 2-245.19

[0430]

[0431] Battery performance evaluation

[0432] The secondary batteries manufactured in Examples 2 to 3 and Comparative Examples 1-1, 1-2, 2-2, and 3-2, namely half-coin cell secondary batteries and mono-cell secondary batteries, were evaluated. After these secondary batteries underwent a sufficient activation (formation) process, the discharge capacity and capacity retention rate were evaluated using a battery charge / discharge tester (Battery Cycler). At this time, the measurements were made in a constant temperature chamber at 25°C to minimize the influence of temperature.

[0433] The half-coin cell secondary battery was discharged at a constant current (CC) discharge of 0.1 C. When the lower limit voltage (0.05 V) was reached, the battery was switched to CV mode and discharge was maintained until the current fell below 0.05 C. Afterwards, the battery was charged in CC mode at 0.1 C to the upper limit voltage (1.5 V), and the measurement was repeated for up to 3 cycles.

[0434] The first discharge efficiency of the battery was calculated as the ratio of the discharge capacity of the first cycle to the charge capacity of the first cycle, and the third cycle discharge efficiency of the battery was calculated as the ratio of the discharge capacity of the third cycle to the charge capacity of the third cycle. The results are shown in Table 4 below.

[0435] Referring to Table 4 below, it was found that the half coin cell secondary batteries of Examples 2 and 3 showed significantly increased charge and discharge capacities in the first and third cycles compared to Comparative Examples 1-1, 1-2, 2-2, and 3-2, and also showed excellent discharge efficiency in each cycle. This can be understood to be because the performance characteristics were improved because the powder used in the half coin cell secondary batteries of Examples 2 and 3 had a smaller sphericity and fidelity than the powder used in the Comparative Examples, thereby increasing the specific surface area of ​​the powder, thereby having relatively many reaction sites and enabling uniform dispersion within the electrode.

[0436] 0.1C cycleFirst cycle3rd cycleFirst charge capacity (mAh / g)First discharge capacity (mAh / g)First discharge efficiency (%)3rd charge capacity (mAh / g)3rd discharge capacity (mAh / g)3rd discharge efficiency (%)Comparative example 1-1569.1525.492.3516.5507.598.3Comparative example 1-2571.4528.392.5525.6519.398.8Comparative example 2-2549.3511.393.1502.3496.998.9Example 2581.1538.292.6528.6522.098.7Comparative example 3-2565.4527.893.4519.3513.899.0Example 3584.5543.893.0526.5519.398.6

[0437] The evaluation of the monocell secondary battery was conducted to confirm the average and standard deviation of capacity, developed capacity compared to design, and its standard deviation for the monocell, which is a secondary battery manufactured in Examples 1 to 3, by constant current (CC) charging: After charging at 0.33C, when the upper limit voltage (4.2V) was reached, the charging was switched to CV mode and maintained until the current became 0.05C or lower. Afterwards, the measurement was performed under the condition of discharging in CC mode at 0.33C to the lowest voltage (2.5V), and the results are shown in Table 5 below. At this time, the actual capacity was measured for three cells, and the average and standard deviation thereof were shown, and the developed capacity compared to design (%) was expressed as a percentage of the actual capacity compared to the design capacity based on 1C.

[0438] Discharge resistance (SOC50(30s)(Ω), SOC50(0.1s)(Ω)) is an index calculated using the voltage drop for a specific time in the state of the monocell, which is a secondary battery manufactured in Examples 1 to 3, and was calculated based on the voltage drop measured while discharging at a constant current for 30 seconds and 0.1 seconds, respectively, at a SOC (State of Charge) of 50%. Specifically, after the monocell was charged to SOC 50%, the set discharge current of 2.5 C-rate was applied, and the terminal voltage at 0.1 seconds and 30 seconds after the start of discharge was measured. At this time, the difference between the no-load voltage before the start and the voltage at each time point was divided by the current, and each discharge resistance was calculated according to the following formula:

[0439] SOC50(0.1s)(Ω) = (V0- V 0.1s ) / I

[0440] SOC50(30s)(Ω) = (V0- V 30s ) / I

[0441] Here, V0 is the no-load voltage (V) just before the start of discharge, V 0.1s is the voltage (V) at 0.1 seconds after the start of discharge, V 30s is the voltage (V) at 30 seconds after the start of discharge, and I is the discharge current (A).

[0442] Example 1 Example 2 Example 3 Actual capacity average (mAh) 77.53 77.23 77.63 Standard deviation 0.31 0.22 0.33 Designed capacity (%) 94.25 93.89 94.38 Discharge resistance SOC50 (30s) (Ω) 1.46 1.44 1.39 SOC50 (0.1s) (Ω) 0.59 0.57 0.55

[0443]

[0444] Observation of powder

[0445] The powders manufactured in Example 1, Example 2, Comparative Example 1-1, Comparative Example 2-1, and Comparative Example 3-1 were photographed using a scanning electron microscope (FE-SEM) (Hitachi S-4800 Scanning Electron Microscope) at a magnification of at least 300 times and at most 8,000 times, and the acceleration voltage was 5 kV to observe the detailed surface structure. The results are shown in Figs. 1 to 5. Specifically, Figs. 1 to 3 are SEM photographs of the powder manufactured in Example 1 observed at varying magnifications, Fig. 4 is an SEM photograph of the powder manufactured in Example 2, and Figs. 5a, 5b, and 5c are SEM photographs of the powders manufactured in Comparative Example 1-1, Comparative Example 2-1, and Comparative Example 3-1, respectively.

[0446]

[0447] Sphericity of powder

[0448] The sphericity of the powders manufactured in Example 2 and Comparative Example 1-1 was calculated by optically obtaining images of 10,000 particles of each powder using a particle size analyzer (Malvern Morphology 4), and calculating the sphericity of the obtained images of the powders by taking a numerical average using Equation 3 below. The results are shown in Table 6.

[0449] [Formula 3]

[0450] Sphericity of powder = 4π(pi) X (area of ​​measured powder) / (perimeter of measured powder) 2

[0451]

[0452] Fidelity of the powder

[0453] The fidelity of the powders manufactured in Example 2 and Comparative Example 1-1 was determined by optically obtaining images of 10,000 powders using a particle size analyzer (Malvern Morphology 4), and from the obtained images, the actual area (a) of each powder and the convex outer area (b) of the powders were obtained, and their ratio (a / b) was calculated using the following Equation 4. The results are shown in Table 6.

[0454] [Formula 4]

[0455] Fidelity = (Actual area of ​​the powder) / Convex hull area of ​​the powder

[0456] Here, the convex outer surface area of ​​the powder is the entire area covered by the convex hull of the powder, which means the area of ​​the simplest convex polygon created by connecting the outermost points of the powder.

[0457]

[0458] Average particle size of powder

[0459] The particle size distribution of the powders manufactured in Example 2 and Comparative Example 1-1 was calculated using a particle size analyzer (Malvern Morphology 4). The D50 particle size was measured by calculating the particle diameter at the point where the cumulative distribution of the number of particles according to the particle size in the measuring device was 50%. In the same manner, the particle diameters at the points where the cumulative distribution of the number of particles according to the particle size in the measuring device was 10% and 90% were calculated as the D10 and D90 particle sizes. The measurement results of these D50, D10, and D90 particle sizes are shown in Table 6.

[0460]

[0461] Angle of repose of powder

[0462] The angle of repose of the powder included in the cathode of Example 2 and Comparative Example 1-1 was measured according to the ASTM D 6393-99 method. The results are shown in Table 5.

[0463] Sphericity D50 Standard Fidelity Sphericity X Fidelity Average particle size (D50) Average particle size (D10) Average particle size (D90) Angle of repose (degrees (°)) Example 20.8970.9590.86014.257.56427.8350.1 Comparative example 1-10.9380.9850.92427.1311.5358.1932.5

Claims

1. The entire house; and A negative electrode active material layer positioned on the above-mentioned collector; The above negative active material layer comprises a powder including a silicon-based active material, a linear conductive material, and a powder binder, The dispersion degree of the powder within the negative electrode active material layer is 1 x 10 -2 10 x 10 -2 , and the standard deviation of the dispersion of the above powder is 1 x 10 -3 4 x 10 -3 And, A negative electrode for an electrochemical device having a volume expansion rate of the negative electrode active material layer of 3 to 35%.

2. In paragraph 1, The dispersion degree of the powder within the negative electrode active material layer is 1 x 10 -2 5 x 10 -2 , and the standard deviation of the dispersion of the above powder is 1 x 10 -3 3.5 x 10 -3 A cathode for an electrochemical device characterized by:

3. In paragraph 1, An anode for an electrochemical device, characterized in that the volume expansion rate of the anode active material layer is 3 to 33%.

4. In paragraph 1, An anode for an electrochemical device, characterized in that the anode active material layer comprises a powder, a carbon-based active material, and a binder for the anode layer.

5. In paragraph 4, An anode for an electrochemical device, characterized in that the anode active material layer comprises 1 to 10 parts by weight of powder, 70 to 99 parts by weight of carbon-based active material, and 0.1 to 10 parts by weight of a binder for the anode layer, based on 100 parts by weight of the anode active material layer.

6. In paragraph 1, An anode for an electrochemical device, characterized in that the anode active material layer includes a powder, a carbon-based active material, a binder for the anode layer, and a conductive material for the anode layer.

7. In paragraph 6, An anode for an electrochemical device, characterized in that the anode active material layer comprises 1 to 10 parts by weight of powder, 70 to 99 parts by weight of carbon-based active material, 0.01 to 5 parts by weight of a conductive material for the anode layer, and 0.1 to 10 parts by weight of a binder for the anode layer, based on 100 parts by weight of the anode active material layer.

8. In paragraph 1, The above silicon-based active material is silicon (Si), silicon oxide (SiOx (0 <x≤2), Si / C 복합체 또는 이들 중 2 이상을 포함하는 것을 특징으로 하는 전기화학소자용 음극.

9. In paragraph 1, An anode for an electrochemical device, characterized in that the linear conductive material comprises a single-walled carbon nanotube (SWCNT), a multi-walled carbon nanotube (MWCNT), a carbon nanofiber, or two or more thereof.

10. In paragraph 1, A cathode for an electrochemical device, characterized in that the binder comprises at least one of a linear binder and a dot-shaped binder.

11. In paragraph 10, A cathode for an electrochemical device, characterized in that the binder comprises a linear binder and a dot-shaped binder.

12. In paragraph 10, A cathode for an electrochemical device, characterized in that the linear binder comprises an acrylate polymer, and the dot-shaped binder comprises a diene polymer, a styrene polymer, or two or more thereof.

13. In paragraph 1, An anode for an electrochemical device, characterized in that the powder comprises a central portion including a silicon-based active material and a linear conductive material; and a surface portion including a powder binder that is located on all or part of the outer side of the central portion and binds the silicon-based active material and the linear conductive material.

14. In paragraph 13, The content (wt%) of the powder binder relative to the total weight of 100 wt% of the above silicon-based active material, linear conductive material, and powder binder is greater in the surface portion than in the center portion of the powder, An anode for an electrochemical device, characterized in that the surface portion is an area near the powder surface from the powder surface to a predetermined depth in the direction of the powder center, and the center portion is a portion other than the surface portion.

15. In paragraph 1, An anode for an electrochemical device, characterized in that the powder comprises 80 to 98 parts by weight of a silicon-based active material, 0.2 to 10 parts by weight of a linear conductive material, and 0.5 to 10 parts by weight of a powder binder, based on 100 parts by weight of the powder.

16. In paragraph 1, A cathode for an electrochemical device, characterized in that the powder further contains a carbon-based active material.

17. In paragraph 1, A cathode for an electrochemical device, characterized in that the powder further comprises a dispersant.

18. In paragraph 17, A cathode for an electrochemical device, characterized in that the dispersant comprises carboxymethyl cellulose (CMC).

19. A method for manufacturing a negative electrode for an electrochemical device according to claim 1, comprising a step of forming a negative electrode active material layer using a powder comprising a silicon-based active material, a linear conductive material, and a powder binder.

20. In paragraph 19, A method for manufacturing a cathode for an electrochemical device, characterized in that the method for manufacturing the cathode includes a process applying a wet process, a dry process, or both.

21. In paragraph 20, A method for manufacturing a negative electrode for an electrochemical device, characterized in that the wet process comprises a step of preparing a negative electrode slurry by mixing the powder and a binder for a negative electrode layer, or the powder, a binder for a negative electrode layer, and a conductive material for a negative electrode layer together in a dispersion medium; and a step of applying and drying the negative electrode slurry on at least one surface of a current collector to form a negative electrode active material layer.

22. In paragraph 20, The above dry process comprises a step of dry mixing the powder and a fiberizable binder, or the powder, a fiberizable binder, and a conductive material for a cathode layer to produce a mixture; A step of kneading the above-mentioned mixture to prepare a mixture lump, and pulverizing the mixture lump to obtain a mixed powder for an electrode; A step of forming an electrode film by injecting the above electrode-use mixed powder between a plurality of rolls and performing a calendaring process; and A method for manufacturing a negative electrode for an electrochemical device, characterized in that it comprises a step of laminating the above electrode film on a metal current collector.

23. In paragraph 20, A method for manufacturing a cathode for an electrochemical device, characterized in that the above dry process includes a step of directly applying and rolling powder alone, powder and a binder for a cathode layer together, or powder, a binder for a cathode layer, and a conductive material for a cathode layer together, onto a current collector.

24. In paragraph 19, A method for manufacturing a negative electrode for an electrochemical device, characterized in that the negative electrode active material layer further includes a carbon-based active material.

25. An electrochemical device comprising the cathode of any one of claims 1 to 18.

26. In paragraph 25, An electrochemical device characterized in that the electrochemical device is a secondary battery.

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