Composite particles comprising electrode material and electrode for electrochemical device comprising the same

Abstract

The present disclosure relates to an electrode and an electrochemical device including the electrode. The electrode includes a current collector and an electrode active material layer formed on the current collector, wherein the electrode active material layer includes particles, and the particles have a binder content ratio in a surface portion that is higher than the binder content ratio in a core portion.

Description

Technical Field

[0001] This application claims priority to Korean Patent Application No. 10-2022-0013754 filed in Korea on January 28, 2022, and Korean Patent Application No. 10-2022-0031703 filed in Korea on March 14, 2022. The present disclosure relates to a composite particle for a dry electrode and an electrode for an electrochemical device including the composite particle. Background Art

[0002] Due to the rapid increase in the use of fossil fuels, the demand for the use of alternative energy and clean energy is increasing. As part of the attempt to meet this demand, the most actively studied field is the field of power generation and energy storage using electrochemistry. At present, a typical example of an electrochemical device using electrochemical energy includes a secondary battery, and its application has gradually expanded. Recently, a lithium secondary battery, which is a representative of such a secondary battery, has been used not only as an energy source for mobile instruments, but also as a power source for electric vehicles and hybrid electric vehicles, which can replace vehicles that use fossil fuels and are considered to be one of the main causes of air pollution, such as gasoline vehicles and diesel vehicles. In addition, by forming a grid, the application of such a lithium secondary battery has even been extended to a supplementary power source for electricity.

[0003] This secondary battery is manufactured by an electrode forming step, an electrode assembly forming step and a formation step. Typically, in the electrode forming step, a process including an electrode slurry preparation step, a step of coating the electrode slurry on an electrode current collector, and a drying step is used. In addition, after the drying step, post-steps such as a pressing step, a slitting step, a winding step, or similar steps are performed. Among these steps, the electrode slurry preparation step is a step of mixing the components for forming an electrode active material layer that are configured to actually perform an electrochemical reaction in the electrode. In particular, the electrode active material as the basic element of the electrode is mixed with a binder for bonding between powder particles and adhering to the current collector, a solvent for imparting viscosity and dispersing the powder, or the like to prepare a slurry with fluidity.

[0004] In electrodes using a slurry coating process for forming an electrode active material layer according to prior art, the binder material in the electrode is not evenly distributed across the thickness of the electrode. Instead, a larger amount of the binder material is concentrated on the surface of the electrode active material layer. Consequently, there is a problem of insufficiently ensuring the bonding force between the electrode active material layer and the current collector. This phenomenon is caused by the binder material migrating toward the surface layer as the slurry solvent evaporates during slurry drying.

[0005] Under these circumstances, there is an increasing demand for developing electrodes for electrochemical devices in which a binder material is uniformly distributed. Summary of the Invention

[0006] Technical issues

[0007] The present disclosure is designed to solve the problems of the prior art, and thus the present disclosure is directed to providing an electrode comprising an electrode active material layer in which a binder is uniformly distributed in the thickness direction thereof. The present disclosure is also directed to providing a granular particle comprising an electrode material exhibiting a specific binder distribution, and a dry electrode obtained by using the granular particle. It will be readily understood that the objects and advantages of the present disclosure can be achieved by the means set forth in the appended claims and combinations thereof.

[0008] Technical Solution

[0009] According to a first embodiment of the present disclosure, there is provided a particle for use in an electrode for an electrochemical device, the particle comprising an electrode active material and an electrode binder, wherein the electrode active materials are bonded to each other by the electrode binder, and based on 100 wt % of the total weight of the electrode active material and the electrode binder, the content of the electrode binder in the surface portion of the particle is higher than the content of the electrode binder in the core portion of the particle, the surface portion of the particle is an area from the surface of the particle toward the center of the particle to 30% of the radius, and the core portion of the particle is an area outside the surface portion of the particle.

[0010] According to a second embodiment of the present disclosure, there is provided a particle as defined in the first embodiment, wherein the surface portion of the particle is an area to 20% of the radius from the surface of the particle toward the center of the particle.

[0011] According to a third embodiment of the present disclosure, there is provided a particle as defined in the first or second embodiment, wherein the surface portion of the particle is an area to 10% of the radius from the surface of the particle toward the center of the particle.

[0012] According to a fourth embodiment of the present disclosure, there is provided a particle as defined in any one of the first to third embodiments, which has an aspect ratio of 0.5 to 1.0.

[0013] According to a fifth embodiment of the present disclosure, there is provided a particle as defined in any one of the first to fourth embodiments, which has an aspect ratio of 0.75 to 1.0.

[0014] According to a sixth embodiment of the present disclosure, there is provided a particle as defined in any one of the first to fifth embodiments, the particle size (D50 ) is 0.1μm to 1000μm.

[0015] According to a seventh embodiment of the present disclosure, there is provided the particle as defined in any one of the first to sixth embodiments, which includes two or more types of electrode active materials.

[0016] According to an eighth embodiment of the present disclosure, an electrode for an electrochemical device is provided, comprising: a current collector; and an electrode active material layer disposed on the current collector, wherein the electrode active material layer comprises an electrode active material and an electrode binder, and particles as defined in any one of the first to seventh embodiments are introduced into the electrode active material layer and integrated therein in a layered structure.

[0017] According to a ninth embodiment of the present disclosure, there is provided the electrode for an electrochemical device as defined in the eighth embodiment, wherein the electrode active material layer has a multilayer structure including two or more unit active material layers stacked therein.

[0018] According to a tenth embodiment of the present disclosure, an electrode for an electrochemical device as defined in the eighth or ninth embodiment is provided, wherein when the electrode active material layer is divided into an upper part and a lower part based on a point corresponding to 50% of the thickness of the electrode active material layer from the current collector, the electrode active material layer shows a difference of 10 weight % or less between the content (weight %) of the electrode binder based on 100 weight % of the upper part and the content (weight %) of the electrode binder based on 100 weight %.

[0019] According to an eleventh embodiment of the present disclosure, an electrode for an electrochemical device as defined in any one of the eighth to tenth embodiments is provided, wherein the electrode active material layer shows a difference of 10 weight % or less between the content (weight %) of the electrode binder in a region from the surface layer portion of the electrode active material layer toward the current collector to 15% of the thickness of the electrode active material layer and the content (weight %) of the electrode binder in a region from the surface portion of the electrode active material layer toward the current collector to 15% of the thickness of the electrode active material layer.

[0020] According to a twelfth embodiment of the present disclosure, there is provided an electrode for an electrochemical device as defined in any one of the eighth to eleventh embodiments, wherein the current collector includes a primer layer disposed on at least one surface thereof, and the primer layer at least partially or entirely covers the surface of the current collector and includes a second conductive material and a second binder.

[0021] According to a thirteenth embodiment of the present disclosure, there is provided an electrochemical device including: a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, wherein the negative electrode is the electrode as defined in any one of the eighth to twelfth embodiments.

[0022] Beneficial effects

[0023] The particles according to the present disclosure have a higher binder content in the surface portion, so when a flattening process such as calendering is performed after the particles are applied to the current collector to form an electrode active material layer, the particles are reduced from the electrode active material layer. Therefore, the contamination of the device (such as a calendering roller) used in the flattening process is reduced. In addition, when an electrode is manufactured by using the particles, the resulting electrode shows a uniform distribution of the binder in the thickness direction of the electrode active material layer. As a result, excellent adhesion between the electrode active material layer and the current collector can be provided, and the shape stability of the electrode active material layer can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings illustrate preferred embodiments of the present disclosure and, together with the foregoing disclosure, are used to provide a further understanding of the technical features of the present disclosure. Therefore, the present disclosure is not to be construed as being limited to the drawings.

[0025] Figure 1 is a scanning electron microscope (SEM) image of particles according to an embodiment of the present disclosure.

[0026] Figure 2 A cross section of an electrode obtained by the method according to Example 1 is shown.

[0027] Figure 3 is a graph showing the distribution of the binder in the electrode obtained by the method according to Example 1 in the thickness direction of the electrode active material layer.

[0028] Figure 4 A cross section of an electrode obtained by the method according to Comparative Example 4 is shown.

[0029] Figure 5 is a graph showing the distribution of the binder in the electrode obtained by the method according to Comparative Example 4 in the thickness direction of the electrode active material layer.

[0030] Figure 6 is a schematic diagram illustrating an electrode according to an embodiment of the present disclosure.

[0031] Figure 7 Schematic diagram showing the calculation of the QBR value of the electrode layer.

[0032] Figure 8A cross-sectional image of particles prepared according to Example 1 is shown.

[0033] Figure 9 A cross-sectional image of particles prepared according to Example 2 is shown.

[0034] Figure 10 A cross-sectional image of particles prepared according to Example 3 is shown.

[0035] Figure 11 A cross-sectional image of particles prepared according to Comparative Example 1 is shown.

[0036] Figure 12 A cross-sectional image of particles prepared according to Comparative Example 2 is shown.

[0037] Figure 13a and Figure 13b Graph showing the content of the binder resin from the core to the surface portion of the particles obtained according to Examples 1 and 2 and Comparative Examples 1 and 2.

[0038] Figure 14 The electrode loading distribution of the negative electrode according to Example 1 is shown.

[0039] Figure 15 The electrode loading distribution of the negative electrode according to Comparative Example 1 is shown.

[0040] Figure 16 is a photographic image showing particles immobilized in cured epoxy resin.

[0041] Figure 17 is a schematic diagram illustrating the separation of a surface portion of a particle from its core portion according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0042] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Before the description, it should be understood that the terms used in the specification and the appended claims should not be interpreted as being limited to the common meanings and dictionary meanings, but should be interpreted based on the meanings and concepts of the technical aspects of the present disclosure on the basis of the principle that the inventor is allowed to appropriately define the terms for the best interpretation.

[0043] Throughout the specification, the expression "a component comprises an element" does not exclude the existence of any additional elements, but means that the component may further include other elements.

[0044] As used herein, the terms "approximately," "substantially," and the like are used to indicate a meaning adjacent to the stated numerical value when presenting acceptable manufacturing and material errors specific to the stated meaning, and are used to prevent unscrupulous infringers from improperly using the disclosure content including exact numerical values ​​or absolute numerical values ​​provided to aid understanding of the present disclosure content.

[0045] As used herein, the expression "A and / or B" means "A, B, or both."

[0046] The specific terms used in this disclosure are for convenience and are not limiting. It will be apparent to those skilled in the art that terms indicating directions such as "top," "bottom," "left," "right," "front," "back," "inside," and "outside" may be used to describe relative positions or directions between constituent elements, rather than absolute positions, or may indicate positions or directions referenced in the accompanying drawings. In addition to the terms themselves, these terms include words including them, their derivatives, and words of similar meaning.

[0047] As used herein, the term "glass transition temperature (Tg)" is measured by conventional methods known to those skilled in the art, and can be measured, for example, by differential scanning calorimetry (DSC).

[0048] As used herein, the term "porosity" refers to the volume occupied by pores based on the total volume of the structure, expressed in percentage (%), and can be used interchangeably with terms such as void ratio, porosity, etc. According to the present disclosure, the method for determining porosity is not particularly limited. According to an embodiment of the present disclosure, porosity can be measured by a BET (Brunauer-Emmett-Teller) method using nitrogen or a mercury porosimeter (Hg porosimeter) in accordance with ASTM D-2873. In addition, the net density of the separator can be calculated from the density (apparent density) of the separator and the composition ratio of the components contained in the separator and the density of each component, and the porosity of the separator can be calculated from the difference between the apparent density and the net density.

[0049] As used herein, the term "average particle size (D 50)" refers to the particle size at 50% in the cumulative distribution of the number of particles as a function of particle size. The particle size can be determined by using a laser diffraction method. Specifically, the powder to be analyzed is dispersed in a dispersion medium and introduced into a commercially available laser diffraction particle size analyzer (e.g., Microtrac S3500) to measure the difference in diffraction patterns depending on the particle size when the particles pass through the laser beam, and then the particle size distribution can be calculated. Then, D 50 It can be determined by calculating the particle size at 50% of the cumulative distribution of particle numbers depending on particle size in the analyzer system.

[0050] Herein, the "thickness" of each layer contained in the electrode may be a value measured by any known method of measuring thickness. For example, the thickness may be determined using a thickness gauge (commercially available from Mitutoyo, VL-50S-B), but is not limited thereto.

[0051] As used herein, the term "specific surface area" may be a value determined by any known method for determining specific surface area. For example, the specific surface area may be determined by a fluidized method or a fixed method, but is not limited thereto.

[0052] The present disclosure relates to a particle for an electrode, and an electrode for an electrochemical device formed by integrating the particle into a layered structure by pressurization. According to the present disclosure, the electrochemical device includes any device that performs an electrochemical reaction, and specific examples thereof include all types of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors such as supercapacitor devices. Preferably, the electrochemical device can be a secondary battery, more preferably a lithium ion secondary battery.

[0053] <Particles>

[0054] Hereinafter, the particles for electrodes according to the present disclosure will be described in detail. According to the present disclosure, the particles may be provided in the form of composite particles comprising an electrode active material and an electrode binder, as well as optional ingredients added as needed. According to an embodiment of the present disclosure, the particles may be secondary particles formed by binding two or more electrode active material particles to each other through an electrode binder and granulating. According to the present disclosure, the electrode active material may refer to a collection of particles, wherein the diameter of each particle of the electrode active material may be 0.05 μm to 2 μm. According to an embodiment of the present disclosure, the electrode active material may be present in an amount of 80 wt % or more, or 90 wt % or more, based on the total weight of the particles, and the electrode binder may be present in an amount of 20 wt % or less, or 10 wt % or less, based on the total weight of the particles. According to an embodiment of the present disclosure, the particles may further comprise an electrode conductive material as an optional ingredient, if desired. The electrode conductive material may be present in an amount of 0.1 wt % to 20 wt %, preferably 0.1 wt % to 10 wt %, based on 100 wt % of the particles. For example, the conductive material may be present in the particles in an amount of about 0.1 wt % to 5 wt %.

[0055] According to an embodiment of the present disclosure, the content of the electrode active material in the particles may be 85% to 98% by weight. Within the above-defined range, the content of the electrode binder may be 0.5% to 10% by weight, and the content of the electrode conductive material may be 0.5% to 5% by weight. According to another embodiment of the present disclosure, the content of the electrode active material may be 90% to 98% by weight, the content of the electrode binder may be 0.5% to 5% by weight, and the content of the electrode conductive material may be 0.5% to 5% by weight.

[0056] Figure 17 Schematic diagram showing the surface portion and the core portion of the particle according to the present disclosure. Figure 17 In the particle according to the present disclosure, the amount of the electrode binder contained in the surface portion 102 of the particle is higher than the amount of the electrode binder contained in the core portion 101 of the particle. Herein, the amount of the binder may refer to its weight or volume.

[0057] In combination with this, or independently of this, in the particle, the content (wt%) of the electrode binder contained in the surface portion 102 of the particle based on 100 wt% of the total weight of the particle (B s / G t ) is higher than the content (wt%) of the electrode binder contained in the core portion 101 of the particle based on 100 wt% of the total weight of the particle (B c / G t ). In this paper, Bc Refers to the weight of the binder contained in the core part, B s Refers to the weight of the adhesive contained in the surface part, G t Refers to the total weight of the particles.

[0058] In conjunction with this, or independently of this, in the particle, the content (volume %) of the electrode binder contained in the surface portion 102 of the particle based on 100 volume % of the total volume of the particle (B s / G t ) is higher than the content (volume %) of the electrode binder contained in the core portion 101 of the particle based on 100 volume % of the total volume of the particle (B c / G t ). In this paper, B c Refers to the volume of the binder contained in the core part, B s Refers to the volume of the adhesive contained in the surface part, G t Refers to the total volume of the particles.

[0059] As used herein, the surface portion may refer to an area close to the surface of a particle and extending from the surface of the particle to a predetermined depth in a direction toward the center of the particle. The core portion refers to the portion other than the surface portion. In particular, according to an embodiment of the present disclosure, the surface portion may refer to a surface area that is 30%, 20%, 15%, 10%, or 5% of the radius from the surface of the particle to the center of the particle. Preferably, the surface portion may refer to a surface area that is 20% of the radius from the surface of the particle to the center of the particle.

[0060] Meanwhile, according to an embodiment of the present disclosure, the surface portion may refer to an area between the surface of the particle and 70% or more of the radius from the center of the particle toward the outside of the particle. For example, according to an embodiment of the present disclosure, the surface portion may refer to an area between the surface of the particle and 80% or more, 85% or more, 90% or more, or 95% or more of the radius.

[0061] According to an embodiment of the present disclosure, the center of a particle may refer to a point corresponding to 1 / 2 of the maximum diameter of the particle. According to the present disclosure, a radius may refer to the distance from the center of the particle to each point on the surface of the particle. According to an embodiment of the present disclosure, the surface portion and the core portion may be distinguished from each other based on the point having the same distance from each surface of the particle along each radius, in particular, a point at 30%, 20%, 10%, 5% or 1% of the corresponding radius from the surface.

[0062] According to an embodiment of the present disclosure, in a region between the particle surface and 90% or more of a radius from the center of the particle, the content of the electrode binder may be 50 wt % or more, 60 wt % or more, 70 wt % or more, 80 wt % or more, or 90 wt % or more, based on 100 wt % of the total weight of the particle in the corresponding region.

[0063] According to another embodiment of the present disclosure, in a region between the particle surface and 95% or more of the radius from the center of the particle, the content of the electrode binder may be 50 wt % or more, 60 wt % or more, 70 wt % or more, 80 wt % or more, or 90 wt % or more, based on 100 wt % of the total weight of the particle in the corresponding region.

[0064] According to another embodiment of the present disclosure, in a region between the particle surface and 99% or more of a radius from the center of the particle, the content of the electrode binder may be 50 wt % or more, 60 wt % or more, 70 wt % or more, 80 wt % or more, or 90 wt % or more, based on 100 wt % of the total weight of the particle in the corresponding region.

[0065] According to an embodiment of the present disclosure, in a region between the particle surface and 90% or more of a radius from the center of the particle, the content of the electrode binder may be 50% by volume or more, 60% by volume or more, 70% by volume or more, 80% by volume or more, or 90% by volume or more based on 100% by volume of the total volume of the particle in the corresponding region.

[0066] According to another embodiment of the present disclosure, in a region between the particle surface and 95% or more of a radius from the center of the particle, the content of the electrode binder may be 50% by volume or more, 60% by volume or more, 70% by volume or more, 80% by volume or more, or 90% by volume or more based on 100% by volume of the total volume of the particle in the corresponding region.

[0067] According to another embodiment of the present disclosure, in a region between the particle surface and 99% or more of a radius from the center of the particle, the content of the electrode binder may be 50 volume % or more, 60 volume % or more, 70 volume % or more, 80 volume % or more, or 90 volume % or more based on 100 volume % of the total volume of the particle in the corresponding region.

[0068] According to an embodiment of the present disclosure, in the particle surface region between the surface of the particle and 10% of the radius from the surface of the particle, the content of the electrode binder may be 50 wt % or more, 60 wt % or more, 70 wt % or more, 80 wt % or more, or 90 wt % or more, based on 100 wt % of the total weight of the particle in the corresponding region.

[0069] According to another embodiment of the present disclosure, in the particle surface region between the surface of the particle and 5% of the radius from the surface of the particle, the content of the electrode binder may be 50 wt % or more, 60 wt % or more, 70 wt % or more, 80 wt % or more, or 90 wt % or more, based on 100 wt % of the total weight of the particle in the corresponding region.

[0070] According to another embodiment of the present disclosure, in the particle surface region between the surface of the particle and 1% of the radius from the surface of the particle, the content of the electrode binder may be 50 wt % or more, 60 wt % or more, 70 wt % or more, 80 wt % or more, or 90 wt % or more, based on 100 wt % of the total weight of the particle in the corresponding region.

[0071] According to an embodiment of the present disclosure, in the particle surface region between the surface of the particle and 10% of the radius from the surface of the particle, the content of the electrode binder may be 50 volume % or more, 60 volume % or more, 70 volume % or more, 80 volume % or more, or 90 volume % or more based on 100 volume % of the total volume of the particle in the corresponding region.

[0072] According to another embodiment of the present disclosure, in the particle surface region between the surface of the particle and 5% of the radius from the surface of the particle, the content of the electrode binder may be 50 volume % or more, 60 volume % or more, 70 volume % or more, 80 volume % or more, or 90 volume % or more based on 100 volume % of the total volume of the particle in the corresponding region.

[0073] According to another embodiment of the present disclosure, in the particle surface region between the surface of the particle and 1% of the radius from the surface of the particle, the content of the electrode binder may be 50 volume % or more, 60 volume % or more, 70 volume % or more, 80 volume % or more, or 90 volume % or more based on 100 volume % of the total volume of the particle in the corresponding region.

[0074] Figure 1 is a schematic diagram showing a scanning electron microscope (SEM) image of particles according to an embodiment of the present disclosure. Figure 1, it is determined that the surface area from the surface of the particle to a predetermined depth toward the center of the particle has a high content of binder, and the part outside the surface area, that is, the core part (central part) surrounded by the surface part, shows a lower binder distribution compared with the surface part.

[0075] The particles will be described in more detail. The particles may include: a core portion, the core portion containing a plurality of electrode active material particles; and a surface portion, the surface portion being disposed wholly or partially outside the core portion and containing an electrode binder, the electrode active material particles being bound to each other by the electrode binder. In other words, in the core portion of the particle, a plurality of electrode active material particles form an aggregate while they are in contact with each other through surface contact, linear contact, point contact, or two or more contact modes thereof. In addition, in the surface portion of the particle, the electrode binder can fix and bind the electrode active material particles of the core portion of the particle to each other, while being partially or wholly disposed outside the aggregate.

[0076] According to an embodiment of the present disclosure, the core portion may further include a small amount of electrode binder, so that the electrode binder can be used to interconnect and fix the electrode active material particles in the core portion. However, as described above, it is preferred that the content of the electrode binder in the surface portion is higher than the content of the electrode binder in the core portion.

[0077] Meanwhile, according to an embodiment of the present disclosure, the aspect ratio of the particles can be 0.5 to 1.0, preferably 0.75 to 1.0. The aspect ratio can refer to the ratio of the major axis length of the particles based on the minor axis length. According to another embodiment of the present disclosure, the average aspect ratio of the particles can be 0.5 to 1.0, preferably 0.75 to 1.0. In this case, the average aspect ratio can refer to the ratio of the average minor axis length of the particles based on the average major axis length. In this article, the average minor axis length refers to the average value of the length in the direction of the axis with the shortest length in the particles, and the average major axis length refers to the average value of the length in the direction of the axis with the maximum length in the particles. When the aspect ratio of the particles meets the above-defined range, the advantage is that the particles have sufficient fluidity suitable for the process.

[0078] Meanwhile, according to an embodiment of the present disclosure, the average particle size of the particles may be 0.1 μm to 1000 μm based on the longest diameter of the particles. According to another embodiment of the present disclosure, the average particle size (D 50 ) can be in the range of 0.1 μm to 1000 μm.

[0079] <Dry Electrode>

[0080] In another aspect of the present disclosure, an electrode for an electrochemical device is provided, comprising: a current collector; and an electrode active material layer disposed on the current collector. The electrode active material layer comprises an electrode active material and an electrode binder, and is formed by pressurizing particles having the aforementioned characteristics into a layered structure. The electrode active material layer and the current collector are described in more detail below.

[0081] <Electrode Active Material Layer>

[0082] The electrode active material layer includes an electrode active material and an electrode binder. According to the present disclosure, the electrode active material layer can be formed by integrating the particles into a layered structure under pressure. When the particles are introduced into the electrode, these particles cannot maintain their initial state in terms of the aspect ratio of the particle size range due to the calendering step described below. The electrode active material layer can include particles in an amount of 80% by weight or more, 90% by weight or more, 95% by weight or more, or 99% by weight or more based on 100% by weight of the electrode active material layer. At the same time, according to an embodiment of the present disclosure, the electrode active material layer can further include electrode active materials, electrode binders, electrode conductive materials, or the like that exist in a free state without being granulated and incorporated into the particles. In a modification, the electrode active material layer can further include particles that do not fall within the scope of the aspect ratio and / or particle size defined above.

[0083] The electrode active material layer has pores derived from the interstitial volume as the space between the particles and exhibits porosity resulting from this structure. According to an embodiment of the present disclosure, the porosity of the electrode active material layer is preferably 20% to 40% by volume in consideration of wettability with an electrolyte, shape stability, ionic conductivity, or the like.

[0084] Meanwhile, according to an embodiment of the present disclosure, the thickness of the electrode active material layer may be 30 μm to 300 μm, but is not limited thereto.

[0085] According to another embodiment of the present disclosure, the electrode active material layer may include a single layer including one unit active material layer.

[0086] According to another embodiment of the present disclosure, the electrode active material layer may have a multilayer structure including two or more unit active material layers stacked therein. In this article, the electrode materials contained in each unit active material layer, such as the electrode active material and the electrode binder, may be the same or different, but the scope of the present disclosure is not limited thereto. In addition, if necessary, each layer may include an electrode conductive material, and the electrode conductive material of each layer may be the same or different.

[0087] <Electrode Active Material Layer>

[0088] In addition, according to an embodiment of the present disclosure, when the electrode active material layer is divided into an upper part and a lower part based on a point corresponding to 50% of the thickness of the electrode active material layer from the current collector, the electrode active material layer may show a difference of 10 wt % or less between the content (wt %) of the binder in the upper part based on 100 wt % and the content (wt %) of the binder in the lower part based on 100 wt %. In addition, the electrode active material layer may show a difference of 10 wt % or less between the content (wt %) of the binder in the region from the current collector toward the electrode surface layer portion to 15% of the thickness of the electrode active material layer and the content (wt %) of the binder in the region from the surface portion of the electrode active material layer toward the current collector to 15% of the thickness of the electrode active material layer.

[0089] This distribution of the binder may be due to the fact that the electrode active material layer according to the present disclosure is formed by compression of particles. As described below, the method for manufacturing an electrode according to the present disclosure is characterized in that particles containing an electrode material are prepared, the particles are distributed on a current collector or the like, and then pressurized so that the particles can be integrated into a layered structure. In the case where the method for manufacturing an electrode includes slurry preparation, during the drying of the slurry, the binder migrates due to the evaporation of the solvent, so that the binder is concentratedly distributed on the surface portion of the electrode. However, according to the present disclosure, the method for compressing and integrating particles is applied in a dry state without using any solvent, so that binder migration does not occur. Therefore, the binder shows a uniform distribution in the thickness direction.

[0090] <Electrode Materials>

[0091] According to an embodiment of the present disclosure, the electrode active material layer may include an electrode active material and an electrode binder, and may further include an electrode conductive material if necessary. For example, the mixing ratio of the electrode active material, the electrode conductive material, and the electrode binder in the electrode active material layer may be 80-99 parts by weight: 0.5-10 parts by weight: 0.5-10 parts by weight (electrode active material: electrode conductive material: electrode binder), particularly 90-99 parts by weight: 0.5-5 parts by weight: 0.5-10 parts by weight.

[0092] The electrode can be either positive or negative.

[0093] When the electrode is a positive electrode, the electrode active material, i.e., the positive electrode active material is not particularly limited as long as it includes a lithium transition metal oxide, a lithium metal iron phosphorus oxide, or a metal oxide. Specific examples of the positive electrode active material include at least one selected from the following: layered compounds such as lithium cobalt oxide (LiCoO2) and lithium nickel oxide (LiNiO2), or those substituted with one or more transition metals; lithium manganese oxides such as those represented by the chemical formula Li 1+x Mn 2-x O4 (wherein x is 0-0.33), LiMnO3, LiMn2O3 and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5 or Cu2V2O7; compounds represented by the formula LiNi 1-x M x Ni-site lithium nickel oxide represented by O2 (wherein M is Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x is 0.01-0.3); 2-x M x Lithium manganese composite oxide represented by Li2Mn3MO8 (wherein M is Co, Ni, Fe, Cr, Zn or Ta, and x is 0.01-0.1); Li2Mn3MO8 (wherein M is Fe, Co, Ni, Cu or Zn); wherein Li is partially replaced by aluminum ions; 1+x (Ni a Co b Mn c Al d ) 1-x O2 (x is 0-0.03, a is 0.3-0.95, b is 0.01-0.35, c is 0.01-0.5, d is 0.001-0.03, a+b+c+d=1); lithium metal phosphorus oxide LiMPO4 (wherein M is Fe, Co, Ni or Mn); disulfide compound; Fe2(MoO4)3; or the like. However, the scope of the present disclosure is not limited thereto.

[0094] According to another embodiment of the present disclosure, when the electrode is used as a negative electrode, the electrode active material may be a negative electrode active material. Specific examples of negative electrode active materials include: carbon, such as non-graphitizable carbon or graphite-based carbon; metal composite oxides, such as Li x Fe2O3(0≤x≤1), Li x WO2(0≤x≤1), and Sn x Me 1-x Me' y O z(Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, an element of Group 1, 2 or 3 in the periodic table, a halogen; 0 < x ≤ 1; 1 ≤ y ≤ 3; 1 ≤ z ≤ 8); lithium metal; lithium alloy; silicon-based alloy; tin-based alloy; silicon oxides such as SiO, SiO / C and SiO2; 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 type materials; or the like. However, the scope of the present disclosure is not limited thereto.

[0095] Meanwhile, according to an embodiment of the present disclosure, the particles may include two or more different electrode active materials in one particle. The electrode active material is not particularly limited as long as it is any one selected from the examples listed above. For example, the particles may include artificial graphite and natural graphite as the electrode active material, and the artificial graphite and natural graphite may be mixed in a predetermined ratio.

[0096] The electrode conductive material is not particularly limited as long as it has conductivity and does not cause any chemical change in the corresponding battery. Specific examples of the electrode conductive material include: graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black or thermal black; conductive fibers such as carbon fibers or metal fibers; carbon fluoride; metal powders such as aluminum powder or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium dioxide; conductive polymers such as polyphenylene derivatives; or the like. In particular, the electrode conductive material may include at least one selected from the group consisting of activated carbon, graphite, carbon black and carbon nanotubes, and more particularly includes activated carbon in order to improve the uniform mixing and conductivity of the electrode conductive material. Meanwhile, according to an embodiment of the present disclosure, the particles may include two or more different conductive materials in one particle. For example, the particles may include carbon black and carbon nanotubes mixed in a predetermined ratio.

[0097] According to the present disclosure, the electrode binder is not particularly limited as long as it is used as a binder material for an electrochemical device. For example, the electrode binder may include a diene polymer, an acrylate polymer, a fluorinated polymer, a styrene polymer, or two or more of them.

[0098] Specific examples of diene polymers include polymers containing monomer units derived from conjugated dienes, such as butadiene or isoprene, and hydrogenated products thereof. The proportion of monomer units derived from conjugated dienes in the diene polymer may generally be 40% by weight or greater, preferably 50% by weight or greater, and more preferably 60% by weight or greater.

[0099] In particular, the diene polymer may include: a conjugated diene homopolymer, such as polybutadiene or polyisoprene; an aromatic vinyl-conjugated diene copolymer, such as styrene-butadiene copolymer (SBR), optionally modified with a carboxyl group; a vinyl cyanide-conjugated diene copolymer, such as acrylonitrile-butadiene copolymer (NBR); hydrogenated SBR, hydrogenated NBR, or the like.

[0100] Styrenic polymers are polymers having repeating units derived from styrene monomers and may include styrene homopolymers (polystyrene), styrene copolymers, or the like. Specific examples of styrene copolymers include styrene-ethylene-butadiene copolymers, styrene-butadiene-propylene copolymers, styrene-isoprene copolymers, styrene-acrylic acid-n-butylitaconic acid-methyl methacrylate-acrylonitrile copolymers, block copolymers such as styrene-butadiene block copolymers, styrene-butadiene-styrene block copolymers, styrene-ethylene-butadiene-styrene block copolymers, styrene-isoprene block copolymers, or styrene-ethylene-propylene-styrene block copolymers, or the like.

[0101] Specific examples of the acrylic polymer include polymers containing monomer units derived from acrylate and / or methacrylate. The proportion of monomer units derived from acrylate and / or methacrylate in the acrylic polymer may generally be 40% by weight or greater, preferably 50% by weight or greater, and more preferably 60% by weight or greater. Specific examples of acrylic polymers include cross-linked acrylic 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, butyl acrylate-acrylic acid-trimethylolpropane trimethacrylate, or the like; copolymers of ethylene and (meth)acrylic acid esters such as ethylene-methyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-ethyl methacrylate copolymer, or the like; graft polymers containing copolymers of ethylene and (meth)acrylic acid esters grafted with a radically polymerizable monomer; or the like. Specific examples of radically polymerizable monomers used in the graft polymer include methyl methacrylate, acrylonitrile, methacrylic acid, or the like. Furthermore, a copolymer of ethylene and (meth)acrylic acid, such as an ethylene-acrylic acid copolymer, an ethylene-methacrylic acid copolymer, or the like, may be used as the dispersion-type adhesive.

[0102] The fluorinated polymer may include a polyvinylidene copolymer, such as polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), or PVDF-HFP, particularly polytetrafluoroethylene (PTFE), and more particularly, the fluorinated polymer may be polytetrafluoroethylene (PTFE).

[0103] Meanwhile, according to an embodiment of the present disclosure, the particles may include two or more different binder components in one particle. For example, the particles may include styrene-butadiene rubber (SBR) mixed with an acrylic polymer in a predetermined ratio as a binder component.

[0104] According to an embodiment of the present disclosure, when the electrode is a positive electrode, the positive electrode binder may include a fluorinated copolymer. According to a specific embodiment, the positive electrode may include PTFE in the fluorinated copolymer, and more preferably, the PTFE may be included in an amount of 60% by weight or more based on the total binder weight. At the same time, the positive electrode binder may further include a fluorinated copolymer other than PTFE, a styrene copolymer, a polyolefin copolymer, PEO (polyethylene oxide), an acrylate copolymer, or the like.

[0105] Meanwhile, according to an embodiment of the present disclosure, when the electrode is a negative electrode, the negative electrode binder may include at least one of a diene polymer and a styrene polymer in an amount of 60% by weight or more based on the total binder weight. According to a specific embodiment, the negative electrode may include a styrene-butadiene block copolymer in an amount of 60% by weight or more based on the total binder weight. Meanwhile, the negative electrode binder may further include a fluorinated copolymer, a polyolefin copolymer, PEO (polyethylene oxide), an acrylate copolymer, or the like.

[0106] Meanwhile, according to an embodiment of the present disclosure, when the electrode binder includes an electrode binder having a double bond, and for example, when the electrode is a negative electrode, the first QBR (Quantified Binder Ratio) of the negative active material layer may be 2.0 or less.

[0107] The first QBR is defined by the following mathematical formula:

[0108] First QBR=ABs / ABf

[0109] Wherein ABs represents the average value of the double bond content in the surface region of the negative electrode active material from the outermost surface of the negative electrode active material layer to 15% or less of the total thickness of the negative electrode active material layer, and ABf represents the average value of the double bond content in the bottom region of the negative electrode active material from the interface of the negative electrode active material layer facing the current collector to 15% or less of the total thickness of the negative electrode active material layer.

[0110] Figure 6 Schematic diagram showing an electrode according to an embodiment of the present disclosure. Figure 6 , the electrode 10 includes: an electrode current collector 12; and an electrode active material layer 11, which is provided on the electrode current collector 12 and contains an electrode active material and a fluorinated electrode binder.

[0111] Based on the total thickness d of the electrode active material layer 11, the electrode active material layer 11 has an electrode active material layer surface area 11s from the outermost surface of the electrode active material layer to 15% or less of the total thickness of the electrode active material layer, and an electrode active material layer bottom area 11f from the interface of the electrode active material layer facing the current collector to 15% or less of the total thickness of the electrode active material layer.

[0112] In the above mathematical formula of the first QBR, ABs represents the average double bond content of the binder in the negative electrode active material layer surface region 11s, and ABf represents the average double bond content of the binder in the negative electrode active material layer bottom region 11f.

[0113] Herein, the first QBR may be calculated by the following method.

[0114] First, the electrode for which the first QBR is to be determined is selected, and a cross section of the negative electrode is obtained by argon ion milling. Next, an energy dispersive X-ray spectroscopy (EDS) detector of a scanning electron microscope (SEM) instrument is used to perform EDS mapping of the components in the negative electrode active material layer of the electrode portion.

[0115] Next, a line profile was extracted from the EDS dot plot results along the thickness direction of the negative electrode active material layer. The average value of the double bond content of the binder in the electrode layer surface region, Bs, and the average value of the double bond content of the binder in the electrode layer bottom region, Bf, were extracted from the line profile results. The first QBR was then calculated using the following mathematical formula:

[0116] First QBR=ABs / ABf

[0117] In this article, the surface area of ​​the electrode active material layer is the area from the outermost surface of the electrode active material to up to 15% of the total thickness d of the electrode active material layer along the thickness direction of the electrode active material layer, and the bottom area of ​​the electrode active material layer is the area from the interface of the electrode active material layer facing the current collector to up to 15% of the total thickness d of the electrode active material layer.

[0118] Figure 7 : is a schematic diagram showing the calculation of the first QBR value of the electrode active material layer. Figure 7, the X-axis represents the thickness of the electrode active material layer, that is, the distance from the surface to the current collector, and the Y-axis represents the intensity of the fluorine component. Line A represents the intensity of the double bond component of the binder extracted by the EDS dot diagram of the double bond component in the electrode active material layer of the electrode cross section, and line B represents a trend line showing the trend of line A, and is drawn by the LOWESS smoothing method, that is, by smoothing in the Locally-Weighted Scatterplot Smoother mode. Figure 7 In , Bs represents the strength of the binder in the surface portion of the electrode, and Bf represents the strength of the binder in the bottom portion of the electrode (the portion facing the current collector).

[0119] The first QBR value is a value indicating the uniformity of distribution of the electrode binder in the thickness direction of the electrode active material layer by the ratio of the electrode binder content in the surface region of the electrode active material layer to the electrode binder content in the bottom region of the electrode active material layer. In this context, the electrode binder content can be inferred from the double bond components contained in the electrode binder.

[0120] The first QBR value may be 2.0 or less, or 0.6 to 2.0, 0.9 to 2.0, 0.6 to 1.4, 0.9 to 1.4, or 0.9 to 1.1.

[0121] When the first QBR satisfies the above-defined range, the binder may not migrate to the electrode surface, and the content of the electrode binder contained in the surface region of the electrode active material layer may be no greater than the content of the electrode binder contained in the bottom region of the electrode active material layer. Furthermore, the binder is uniformly distributed in the thickness direction of the electrode active material layer, thereby improving the adhesion between the current collector and the electrode active material layer, and advantageously increasing the conductivity and charge / discharge rate on the surface of the electrode active material layer.

[0122] Meanwhile, according to an embodiment of the present disclosure, the negative electrode may include a negative electrode binder having a double bond as a binder component, such as a styrene-butadiene copolymer, wherein the first QBR value may be 2.0 or less.

[0123] According to an embodiment of the present disclosure, when the electrode binder includes a fluorinated binder as a binder component, and for example, when the electrode is a positive electrode, the positive electrode active material layer may have a second QBR (Quantified Binder Ratio), wherein the second QBR is defined by the following mathematical formula:

[0124] Second QBR=CBs / CBf

[0125] Wherein CBs represents the average value of the fluorine content in the surface region of the electrode layer from the outermost surface of the electrode active material layer to 15% or less of the total thickness of the electrode active material layer, and CBf represents the average value of the fluorine content in the bottom region of the electrode active material layer from the interface of the electrode active material layer facing the current collector to 15% or less of the total thickness of the electrode active material layer.

[0126] The second QBR value may be 1.1 or less. According to an embodiment of the present disclosure, the second QBR value may be 0.95 or greater, 0.97 or greater, 1.03 or less, 1.05 or less, or 0.95 to 1.05.

[0127] When the second QBR satisfies the above-defined range, the fluorinated electrode binder may not migrate to the electrode surface, and the content of the fluorinated electrode binder contained in the surface region of the electrode active material layer may be no greater than the content of the fluorinated electrode binder contained in the bottom region of the electrode active material layer. In addition, the binder is uniformly distributed in the thickness direction of the electrode active material layer, thereby improving the adhesion between the current collector and the electrode active material layer, and advantageously improving the conductivity and charge / discharge rate on the surface of the electrode active material layer.

[0128] Meanwhile, according to an embodiment of the present disclosure, the positive electrode may include a fluorinated binder as a binder component, wherein the second QBR value may be 1.1 or less.

[0129] Meanwhile, according to the present disclosure, the electrode binder may include a diene polymer and a cross-linked acrylate polymer so as to obtain an active material layer having excellent binding properties to a current collector or excellent surface smoothness and manufacture an electrode for an electrochemical device having high electrostatic capacitance and low internal resistance.

[0130] Although the shape of the electrode binder is not particularly limited, the electrode binder preferably has a granular shape because the granular electrode binder exhibits high binding properties and can suppress degradation of the resulting electrode due to degradation of electrostatic capacity or repeated charge / discharge cycles. For example, granular electrode binders include binders containing dispersible binder particles dispersed in water (such as in the case of latex) or powdered binders obtained by drying a dispersion. Such granular binders can be preferably used in the negative electrode.

[0131] A filler may also be added to the electrode active material layer as a component to suppress swelling of the electrode active material layer. The filler is not particularly limited, as long as it is a fibrous material and does not cause any chemical changes in the corresponding battery. Specific examples of fillers include: olefin polymers such as polyethylene or polypropylene; fibrous materials such as glass fiber or carbon fiber; and the like.

[0132] The current collector is not particularly limited as long as it has high conductivity and does not cause any chemical changes in the corresponding battery. Specific examples of the current collector include stainless steel, aluminum, nickel, titanium, calcined carbon, copper, or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like. In addition, fine surface irregularities may be formed on the surface of the current collector to enhance the bonding strength with the electrode active material. The current collector may be used in various shapes including films, sheets, foils, meshes, porous bodies, foams, non-woven fabrics, or the like.

[0133] Meanwhile, according to an embodiment of the present disclosure, the conductive primer layer may be entirely or partially coated on the current collector.

[0134] The primer layer may include a binder for the primer layer (hereinafter also referred to as a second binder) and a conductive material for the primer layer (hereinafter also referred to as a second conductive material), and the sum of the content of the second binder and the content of the second conductive material may be 90 weight % or more in the primer layer.

[0135] The electrode according to an embodiment of the present disclosure includes an electrode active material layer containing the particles, and may further include a primer layer containing a second binder and a second conductive material, wherein the sum of the content of the second binder and the content of the second conductive material is 90% by weight or more. In this way, the stability of the primer layer can be ensured and excellent physical properties such as adhesion and life characteristics can be provided. However, the scope of the present disclosure is not limited thereto.

[0136] According to an embodiment of the present disclosure, the primer layer includes a second binder and a second conductive material, and may further include a dispersant.

[0137] According to another embodiment of the present disclosure, the primer layer includes a second binder and a second conductive material, and may substantially exclude a dispersant.

[0138] According to still another embodiment of the present disclosure, the second binder is not particularly limited as long as it is a known binder for the primer layer.

[0139] According to yet another embodiment of the present disclosure, preferably, the second binder may include a polymer capable of ensuring the stability of the primer layer over time. In particular, the second binder may have a glass transition temperature (Tg) of 45° C. or lower.

[0140] According to another embodiment of the present disclosure, specific examples of the second binder include styrene-butadiene rubber (SBR), butadiene rubber (BR), nitrile rubber (NBR), styrene-butadiene-styrene block copolymer (SBS), styrene-ethylene-butadiene block copolymer (SEB), styrene-(styrene-butadiene)-styrene block copolymer, natural rubber (NR), isoprene rubber (IR), ethylene-propylene-diene terpolymer (EPDM), poly(ethylene-co-propylene-co-5-methylene-2-norbornene), polytetrafluoroethylene (PTFE), polyvinylidene fluoride, polyvinyl chloride, polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene (PTFE), polyvinyl chloride, polyvinylidene fluoride-co-hexafluoropropylene, and polyvinylidene fluoride-co-trichloroethylene. The second adhesive may include styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), polymethylmethacrylate, polyethylhexylacrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene, polypropylene, polyethylene-co-vinyl acetate, polyethylene oxide, polypropylene oxide, polyarylate, cyanoethylpullulan, cyanoethylpolyvinylalchol, or two or more thereof. More specifically, the second adhesive may include styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), polymethylmethacrylate, polyethylhexylacrylate, polybutylacrylate, or two or more thereof.

[0141] According to another embodiment of the present disclosure, the second adhesive may be any one selected from the above-listed examples and having a glass transition temperature within the above-defined range, or a mixture of two or more thereof.

[0142] According to yet another embodiment of the present disclosure, the second adhesive may include styrene-butadiene rubber (SBR) having a glass transition temperature (Tg) of -40 to 45°C, nitrile-butadiene rubber (NBR) having a glass transition temperature of -40 to 45°C, or a mixture thereof.

[0143] According to an embodiment of the present disclosure, the specific surface area of ​​the second conductive material may be 30 m 2 / g to 1,400m 2 / g and may be spherical. Herein, the primary particles of the conductive material having a spherical shape may have a particle size of 10 nm to 100 nm, specifically 15 nm to 70 nm, but is not limited thereto.

[0144] According to another embodiment of the present disclosure, the specific surface area of ​​the second conductive material may be 10 m 2 / g to 400m 2 Herein, the diameter of the cross section of the conductive material having the tube shape in a direction perpendicular to the longitudinal direction may be 0.1 nm to 3 nm, specifically 0.3 nm to 1.5 nm.

[0145] The second conductive material is not particularly limited, as long as it has conductivity without causing any chemical changes in the corresponding battery. Specific examples of conductive materials include: graphite, such as natural graphite or artificial graphite; carbon black-based carbonaceous compounds, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; conductive fibers, such as carbon fibers or metal fibers; carbon fluoride; metal powders, such as aluminum powder or nickel powder; conductive whiskers, such as zinc oxide or potassium titanate; conductive metal oxides, such as titanium dioxide; conductive polymers, such as polyphenylene derivatives; or the like. In particular, the second conductive material may include activated carbon, graphite, carbon black, carbon nanotubes, or a mixture of two or more thereof, more particularly activated carbon, in order to achieve uniform mixing of the conductive materials and improve conductivity.

[0146] According to an embodiment of the present disclosure, the undercoat layer includes the above-mentioned composition, and the thickness thereof may be 300 nm to 1.5 μm, for example 700 nm to 1.3 μm, but is not limited thereto.

[0147] <Method for preparing granules>

[0148] According to an embodiment of the present disclosure, particles contained in the active material layer may be prepared by a method including: mixing an electrode active material with an electrode binder to prepare a slurry; and spray-drying the slurry.

[0149] First, an electrode active material and an electrode binder, and optionally another conductive material or additive, are dispersed or dissolved in a dispersion medium (a solvent for a negative electrode binder) to obtain a slurry comprising the electrode active material and the electrode binder and optionally having an electrode conductive material and / or other additives dispersed or dissolved therein.

[0150] The dispersion medium for obtaining the slurry may most suitably be water, but an organic solvent may also be used. Specific examples of organic solvents include: alkyl alcohols such as methanol, ethanol or propanol; alkyl ketones such as acetone or methyl ethyl ketone; ethers such as tetrahydrofuran, dioxane or diethylene glycol; amides such as diethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone (hereinafter also referred to as NMP), or dimethylimidazolidinone; sulfur solvents such as dimethyl sulfoxide or sulfane; or the like. However, the organic solvent is preferably an alcohol. When an organic solvent having a lower boiling point than water is used in combination, the drying rate during fluidized granulation can be increased. In addition, since the dispersibility or solubility of the negative electrode binder can be changed, the viscosity or fluidity of the slurry can be controlled according to the amount or type of the dispersion medium, thereby improving production efficiency.

[0151] The amount of the dispersion medium used in preparing the slurry may generally be such an amount that the solid content of the slurry may be 1 to 50 wt %, 5 to 50 wt %, or 10 to 30 wt %.

[0152] The method or order of dispersing or dissolving the electrode active material, electrode binder, or the like is not particularly limited. For example, such methods may include: a method of adding the electrode active material and the electrode binder to a dispersion medium and mixing them; a method of dissolving or dispersing the electrode binder in the dispersion medium and finally adding the electrode active material and mixing them; or a similar method. When the slurry includes a conductive material and / or an additive, these ingredients can be introduced during the introduction of the electrode active material. Specific examples of mixing means may include systems for mixing, such as a ball mill, a sand mill, a bead mill, a pigment dispersion system, a stone mill, an ultrasonic dispersion system, a homogenizer, a planetary mixer, or the like. For example, mixing can be performed at a temperature ranging from room temperature to 80°C for 10 minutes to several hours.

[0153] Next, the slurry is spray-dried. The spray-drying method includes spraying and drying the slurry in hot air. The spray process used in the system for spray drying includes a turntable process, a nozzle pressurization process, or a similar process. The turntable process includes introducing the slurry into the center of a high-speed rotating disc, causing the slurry to be located outside the disc by the centrifugal force of the disc, and then drying the slurry into a mist phase. The rotational speed of the disc depends on the size of the disc, but can generally be 5,000rpm to 35000rpm, preferably 15,000rpm to 30,000rpm. At the same time, the nozzle pressurization process includes spraying a high-pressure fluid, such as air or another type of liquid, in combination, while allowing the slurry to pass through a thin nozzle so that the slurry is sprayed and dried into a mist phase.

[0154] According to an embodiment of the present disclosure, the hot air temperature can be controlled to 80°C to 250°C based on the reactor inlet temperature (at the time of introduction) in order to form a granular structure with a high content of electrode binder on the surface. According to an embodiment of the present disclosure, taking into account the gradient of the binder content and the aspect ratio, the hot air temperature can be preferably controlled to 175°C to 220°C, more preferably 180°C to 220°C. In the spray drying method, the method for hot air intake is not particularly limited. For example, the hot air intake method may include: a method of using hot air flowing in a horizontal direction parallel to the injection direction; a method of spraying the slurry near the top of the drying tower and allowing the sprayed slurry to fall together with the hot air; a method of allowing the sprayed droplets to contact the hot air in a countercurrent mode; a method of allowing the sprayed droplets to first flow parallel to the initial hot air and then fall by gravity so that they can contact the hot air in a countercurrent mode; or a similar method. Meanwhile, according to an embodiment of the present disclosure, in the spray drying process, the outlet temperature of the reactor (the temperature of the hot air discharged from the reactor) may be controlled to 90°C to 130°C.

[0155] When the outlet temperature is low or the difference ΔT between the inlet temperature and the outlet temperature is low, it is not possible to fully dry the particles, thereby forming particles containing a large amount of residual solvent, failing to form spherical particles having a uniform shape, and the particles may agglomerate or may form an amorphous state. Meanwhile, when the inlet temperature is too high and ΔT is large, excessive drying occurs, granulation cannot be achieved, and D 50 Therefore, in order to achieve a high aspect ratio, in order to suppress the agglomeration of the 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.

[0156] Furthermore, the product obtained from the spray drying, ie, the particles, may be subjected to a heat treatment as appropriate to solidify the surface thereof, wherein the heat treatment temperature may generally be 80°C to 300°C.

[0157] <Method for producing electrodes>

[0158] According to an embodiment of the present disclosure, a method for manufacturing an electrode includes the steps of: applying a plurality of particles to a current collector; and pressurizing the applied particles to form an electrode active material layer.

[0159] The particles prepared by the above method are applied to a current collector. Herein, as described above, the primer layer including the second conductive material and the second binder may be entirely or partially disposed on at least one surface of the current collector.

[0160] According to an embodiment of the present disclosure, the particles prepared as described above can be supplied to a roller-type press-forming system by a supply device such as a screw feeder to form an active material layer, wherein the current collector can be provided to the roller of the press-forming system while the particles are supplied so that the active material layer can be directly laminated on the current collector. In one variation, the particles can be applied to the current collector and adjusted to a uniform thickness by using a scraper or the like, and then formed by a press system to form an electrode active material layer.

[0161] In the above-mentioned method, the temperature during roll press molding is generally 0°C to 200°C, and is preferably higher than the melting point or glass transition temperature of the electrode binder, and more preferably, at least 20°C higher than the melting point or glass transition temperature of the electrode binder. The molding rate in roll press molding can generally be 0.1m / min to 20m / min, or 1m / min to 10m / min. In addition, the pressing linear pressure between the rollers can be 0.2kN / cm to 30kN / cm, or 0.5kN / cm to 10kN / cm.

[0162] In order to eliminate the thickness deviation of the formed electrode and increase the density of the electrode active material layer so that the electrode can have a high capacity, further pressurization can be performed if necessary. The post-pressing method is usually carried out through a roller pressing process. In the roller pressing process, two cylindrical rollers are allowed to stand vertically parallel to each other with a small gap and rotate in opposite directions to pressurize the electrode inserted between the rollers. The rollers can control the temperature and, for example, can be heated or cooled.

[0163] According to another embodiment of the present disclosure, a secondary battery including an electrode assembly and an energy storage system including the secondary battery as a unit cell are provided, wherein the electrode assembly includes a positive electrode, a negative electrode, and a separator, wherein the electrode assembly is housed in a battery case (e.g., a cylindrical case, a prismatic case, a pouch, or the like) together with a lithium-containing non-aqueous electrolyte. In this article, at least one of the positive electrode and the negative electrode may be an electrode disclosed herein.

[0164] The specific example of separator can include the porous polymer film conventionally used as separator, such as the porous polymer film made of the polyolefin polymer including ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer or ethylene / methacrylate copolymer, or their laminate. In addition, an insulating film with high ion permeability and mechanical strength can be used. The separator can include a safety reinforced separator (SRS), the surface of which is coated with a thin layer of ceramic material. In addition, conventional porous nonwoven fabrics can be used, such as the nonwoven fabrics made of high melting point glass fiber, polyethylene terephthalate fiber or the like. However, the scope of the present disclosure is not limited thereto.

[0165] The electrolyte includes a lithium salt as an electrolyte salt and an organic solvent for dissolving the lithium salt.

[0166] Any lithium salt conventionally used for electrolytes of secondary batteries may be used without particular limitation. For example, the anion of the lithium salt may be any one selected from the group consisting of: - 、Cl - Br - , 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 - .

[0167] The organic solvent contained in the electrolyte may be any conventionally used organic solvent without particular limitation. Typical examples of the organic solvent 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, sulfane, γ-butyrolactone, propylene sulfite, and tetrahydrofuran.

[0168] In particular, among carbonate organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, are organic solvents with high viscosity and high dielectric constant and are therefore preferably used because they can easily dissociate the lithium salts in the electrolyte. More preferably, when such cyclic carbonates are mixed with linear carbonates with low viscosity and low dielectric constant, such as dimethyl carbonate or diethyl carbonate, an electrolyte with higher conductivity can be prepared.

[0169] The electrolyte used according to the present disclosure may further include additives contained in conventional electrolytes, such as an overcharge preventing agent, or the like, as appropriate.

[0170] The lithium secondary battery according to an embodiment of the present disclosure can be obtained by inserting a separator between the positive electrode and the negative electrode to form an electrode assembly, introducing the electrode assembly into a bag, a cylindrical battery case, or a prismatic battery case, and then injecting an electrolyte therein to complete the secondary battery. In one variation, the lithium secondary battery can be obtained by stacking the electrode assemblies, impregnating the stack with an electrolyte, and introducing the resulting product into a battery case, followed by sealing.

[0171] Herein, since structures of a secondary battery and an energy storage system are well known to those skilled in the art, description thereof will be omitted in this disclosure.

[0172] The following examples will be described more fully so that the present disclosure can be easily understood. However, the following examples can be embodied in a variety of different forms and should not be construed as being limited to the exemplary embodiments set forth herein. On the contrary, these exemplary embodiments are provided so that the present disclosure will be thorough and complete, and will fully convey the scope of the present disclosure to those skilled in the art.

[0173] Example

[0174] [Example 1]

[0175] 1. Negative electrode

[0176] (1) Preparation of a current collector with a primer layer

[0177] First, 30 parts by weight of carbon black (specific surface area: 30 m2 / g, particle size (70nm)), 69 parts by weight of styrene-butadiene rubber (SBR) (Tg: -15°C) as a second binder, and 1 part by weight of carboxymethyl cellulose (CMC) as a dispersant were mixed in water as a dispersion medium to prepare a slurry for an undercoat layer. The weight ratio of the conductive material, binder, and dispersant in the slurry was the same as that of the conductive material, binder, and dispersant in the undercoat layer to be formed later. The slurry for the undercoat layer had a solid content of 7% by weight.

[0178] The prepared slurry for an undercoat layer was applied to one surface of a copper current collector (thickness: 10 μm) and dried at 130° C. to form an undercoat layer on the entire surface of the copper current collector.

[0179] (2) Preparation of particles for negative electrode active material layer

[0180] First, 1.91 parts by weight of natural graphite with a sphericity of 0.95 as a negative electrode active material and 76.5 parts by weight of artificial graphite with an average sphericity of 0.9, carbon black (Super C65) as a negative electrode conductive material, carboxymethyl cellulose (daicel 2200, aqueous solution, solid content 1.5% by weight) as a negative electrode dispersant, and modified styrene-butadiene copolymer (trade name: AX-B119) as a negative electrode binder were mixed in water as a dispersion medium at a weight ratio of 95.6:1.0:1.1:2.3 by a homogenizer to prepare a slurry with a viscosity of about 1000 cPs. Here, the slurry has a solid content of 30% by weight. In the weight ratio, the carboxymethyl cellulose is calculated based on the solid content.

[0181] The resulting slurry is introduced into a spray dryer together with hot air and dried under a pressure condition of -40 mm H2O. Here, the spray dryer is controlled to an inlet temperature of 180°C, an outlet temperature of 90°C, and a rotation speed of 18,000 rpm. The resulting particles are passed through an industrial sieve to remove coarse powder having a size of 150 μm or larger, and fine powder having a size of less than 40 μm is separated therefrom. The separated fine powder is mixed with the particles from which only the coarse powder is removed to prepare particles for a negative electrode, which contain a larger amount of fine powder than the initial particles. The particles have a core portion comprising a plurality of negative electrode active material particles and a negative electrode conductive material, and a surface portion arranged outside the core portion and comprising a negative electrode binder, through which the negative electrode active material is bonded to the negative electrode conductive material. The average particle size (D 50 ) is 66.5 μm and the aspect ratio is 0.96. Figure 8This is a cross-sectional image of a particle prepared according to Example 1, processed by the EPMA (electron probe micro analyze) method described below. The closed curve shown in the image is a curve drawn by connecting points with the same distance from the surface.

[0182] (3) Manufacturing of negative electrode

[0183] The particles prepared as described above were uniformly applied to one surface of the current collector having the primer layer to a thickness of 1 / 25 cm by using a thickness control rod. 2 Then, using a sheeting machine, a roll-to-roll hot press molding system, pressing was performed at a pressure of 0.7 tons / cm and a temperature of 60° C. at a rate of 2 m / min to form a negative electrode active material layer, thereby providing a negative electrode.

[0184] [Example 2]

[0185] The particles were obtained in the same manner as in Example 1, except that the spray dryer was controlled to have an inlet temperature of 180°C and an outlet temperature of 130°C. The average particle size (D 50 ) is 61.4 μm and the aspect ratio is 0.99. Figure 9 Shown is an image of a cross section of particles prepared from Example 2, as processed by the EPMA method described below. The closed curve shown in the image is a curve drawn by connecting points having the same distance from the surface.

[0186] [Example 3]

[0187] The particles were obtained in the same manner as in Example 1, except that the spray dryer was controlled to have an inlet temperature of 200° C. and an outlet temperature of 110° C. The average particle size (D 50 ) is 35.8 μm and the aspect ratio is 0.77.

[0188] Figure 10 Shown is an image of a cross section of particles prepared from Example 3, as processed by the EPMA method described below. The closed curve shown in the image is a curve drawn by connecting points having the same distance from the surface.

[0189] [Comparative Example 1]

[0190] The particles were obtained in the same manner as in Example 1, except that the spray dryer was controlled to have an inlet temperature of 170° C. and an outlet temperature of 70° C. The average particle size (D 50) was 42.8 μm, and the aspect ratio was 0.75. Furthermore, a negative electrode was obtained in the same manner as in Example 1, except that the particles prepared in Comparative Example 1 were used instead of the particles prepared in Example 1. In Comparative Example 1, the particles were slightly overdried and had an aspect ratio of 0.75 or less, and uniform spherical particles could not be formed, with large deviations between the particles. Figure 11 Shown is a cross-sectional image of particles prepared from Comparative Example 1, as processed by the EPMA method described below. Figure 11 , it can be seen that the binder resin (light color) is distributed over the entire cross section of the particle. The closed curve shown in the image is a curve drawn by connecting points that have the same distance from the surface.

[0191] [Comparative Example 2]

[0192] The particles were obtained in the same manner as in Example 1, except that the spray dryer was controlled to have an inlet temperature of 170°C and an outlet temperature of 140°C. The average particle size (D 50 ) was 78.0 μm, and the aspect ratio was 0.37. In Comparative Example 2, due to the small difference between the inlet temperature and the outlet temperature, the solvent was not sufficiently removed, thereby forming particles having a large amount of residual solvent, and thus uniform spherical particles could not be formed, and the particles had a high moisture content and showed agglomeration.

[0193] Figure 12 Shown is a cross-sectional image of particles prepared from Comparative Example 2, as processed by the EPMA method described below. Figure 12 , it can be seen that the binder resin (light color) is distributed over the entire cross section of the particle. The closed curve shown in the image is a curve drawn by connecting points that have the same distance from the surface.

[0194] [Comparative Example 3]

[0195] Granules were obtained in the same manner as in Example 1, except that the spray dryer was controlled to an inlet temperature of 230°C and an outlet temperature of 90°C. In Comparative Example 3, excessive drying occurred due to a large difference between the inlet and outlet temperatures, resulting in granulation failure. Therefore, it was not possible to produce granules.

[0196] [Comparative Example 4]

[0197] First, 19.1 parts by weight of natural graphite with a sphericity of 0.95 and 76.5 parts by weight of artificial graphite with an average sphericity of 0.9 as negative electrode active materials, 1 part by weight of carbon black (Super C65) as a negative electrode conductive material, 2.3 parts by weight of styrene-butadiene rubber (SBR) as a negative electrode binder, 1.1 parts by weight of carboxymethyl cellulose (CMC) as a binder which also serves as a thickener, and water as a dispersion medium are mixed to prepare a slurry with a solid content of 47% by weight.

[0198] The slurry was coated on one surface of a copper foil (Cu) having a thickness of 10 μm as a negative electrode current collector, and the top active material layer and the bottom active material layer formed as mentioned above were pressed by a roll pressing process using a dryer equipped with a hot air blower and an IR heater. In this way, a slurry having a dry basis loading per unit area of ​​400 mg / 25 cm was obtained. 2 The negative electrode has a negative electrode active material layer.

[0199] Determination of binder distribution in granules

[0200] The distribution of the binder in the particles was measured by using an electron probe microanalyzer (EPMA) (JXA-8350F, -15 kV, 20 nm level dot diagram conditions) to analyze the radial distribution of the cross section of the particles. First, the binder in the particles obtained according to each of Examples 1 to 3 and Comparative Examples 1 and 2 was dyed using OsO4. The binder was dyed by introducing the particles into a glass material using OsO4 crystals or an aqueous solution and reacting by evaporating the reagent. Next, the particles were mixed with an epoxy resin and fixed and cured in a silicon mold to obtain a granule matrix (granulematrix) (see Figure 16). Then, a cross-sectional sample was prepared from the particle matrix by using an ion milling device (Hitachi IM5000, accelerating voltage: 6kV). The cross section was made under the conditions of an accelerating voltage of 6kV and a discharge current of 400μA, and the milling time was appropriately controlled so that the mask could not be completely etched. The prepared cross-sectional sample was fixed in the EPMA system, the particle was placed in the center of the display, and the cross-sectional scan was performed by the level point mode. After the scan was completed, an image was generated in the form of a mass map taking into account the atomic number effect, absorption effect, and fluorescence excitation effect. Then, from the obtained mass map, the elements of 0 to 4 wt% were set to 0~255 5 contrast, and the Os map was extracted. The Os map was combined into a single layer with the conventional backscattered electron image obtained from the EPMA analysis using photoshop, and then a closed curve was drawn in units of 30 pixels from the boundary of the obtained particle to analyze the Os content arranged in each closed curve. The Os content was corrected by introducing the surface area of ​​the closed curve at the corresponding position, so that the relative content of one position could be compared with the relative content of another position. Figure 13a The distribution (content) of the binder resin in each portion along the radius of the particle according to each of Examples and Comparative Examples is shown. Figure 13b The cumulative distribution of the binder resin along the radius of each particle according to each of the Examples and Comparative Examples is shown. Referring to the results, it can be seen that the binder content in the surface portion, which is within 70% or more of the radius of the particle surface, is higher than that in the core portion of the particles according to each of Examples 1 to 3. In contrast, in the case of the particles obtained from Comparative Examples 1 and 2, the binder content is higher in the core portion than in the surface portion.

[0201] Determination of binder distribution in negative electrode active material layer

[0202] The negative electrode obtained according to each of Example 1 and Comparative Example 4 was subjected to a sufficient chemical reaction (deposition) for 3 hours or more by introducing the negative electrode into a glass material having OsO4 crystals or an aqueous solution and evaporating the reagent. Then, a cross section of the negative electrode according to each of the examples and comparative examples was manufactured from the negative electrode reacted with Os by using Ar ion milling.

[0203] Then, EDS mapping of constituent elements in the negative electrode active material layer of the cross section in the thickness direction of the negative electrode according to each of Example 1 and Comparative Example 4 was performed using an EDS detector of an SEM instrument.

[0204] Figure 2 The EDS mapping results of the electrode according to Example 1 are shown. Figure 4 The EDS mapping results of the electrode according to Comparative Example 4 are shown. Referring to these results, it can be seen from the electrode according to Example 1 that a larger amount of binder resin is distributed in the surface portion of the particles compared to the core portion of the particles. In addition, the electrode according to Example 1 is obtained by compressing the particles, and it can be seen that the binder is uniformly distributed in the thickness direction of the electrode. In contrast, it can be seen from the electrode according to Comparative Example 4 that the surface layer portion of the electrode has a higher binder content ratio. Unlike the manufacturing method of the electrode according to Example 1, the electrode according to Comparative Example 4 is obtained by a process of electrode slurry coating and drying, and this binder distribution is caused by binder migration caused by solvent evaporation.

[0205] at the same time, Figure 3 and Figure 5 Each is a graph drawn in the following manner: extracting a line profile from the EDS point diagram results along the thickness direction of the negative electrode active material layer, and then extracting the average value of the Os content of the binder bound to Os in the surface area of ​​the negative electrode active material layer (from the surface toward the current collector to 15%) and the average value of the Os content of the binder bound to Os in the bottom area of ​​the electrode layer (from the current collector toward the surface layer part to 15%) from the line profile results. Figure 3 and Figure 5 Results are shown separately for the electrode according to Example 1 and the electrode according to Comparative Example 4. Referring to these results, the electrode according to Example 1 showed smaller deviation in binder distribution in the electrode thickness direction than the electrode according to Comparative Example 4.

[0206] Determination of electrode loading distribution

[0207] The surface of the negative electrode according to each of Example 1 and Comparative Example 1 (negative electrode active material layer surface, 100 mm×150 mm size) was determined based on the electrode loading. The surface of each negative electrode was scanned by using an inductance analyzer (TSS20, Lasertec). Then, the induced current was allowed to flow from the negative electrode at predetermined intervals to determine information on the negative electrode active material itself formed on the current collector. An image illustrating uniformity was obtained based on the uniformity (component distribution, thickness, porosity, etc.) of the negative electrode active material layer. It can be seen that the negative electrode according to Example 1 shows a uniform negative electrode active material loading over the entire negative electrode surface, while the negative electrode according to Comparative Example 1 shows a difference in loading between the left and right sides of the negative electrode. Figure 14 The electrode loading distribution of the negative electrode according to Example 1 is shown, and it can be seen that the negative electrode shows a uniform distribution over the entire surface thereof. Figure 15The electrode loading distribution of the negative electrode according to Comparative Example 1 is shown, and it can be seen that the negative electrode shows deviation by region.

Claims

1. A particle for an electrode, comprising an electrode active material and an electrode binder, wherein the electrode active materials are bound to each other by the electrode binder, The content of the electrode binder in the surface portion of the particle is higher than the content of the electrode binder in the core portion of the particle, based on 100 wt % of the total weight of the electrode active material and the electrode binder, The surface portion of the particle is a region extending from the surface of the particle toward the center of the particle to 30% of the radius, and the core portion of the particle is a region other than the surface portion of the particle. 2 . The particle for an electrode according to claim 1 , wherein the surface portion of the particle is a region ranging from a surface of the particle to 20% of a radius toward a center of the particle. 3 . The particle for an electrode according to claim 1 , wherein the surface portion of the particle is a region ranging from a surface of the particle to 10% of a radius toward a center of the particle. The particle for an electrode according to claim 1 , having an aspect ratio of 0.5 to 1.

0. The particle for an electrode according to claim 1 , having an aspect ratio of 0.75 to 1.

0.

6. The particle for electrode according to claim 1, wherein the particle size D 50 0.1μm to 1000μm. The particle for an electrode according to claim 1 , comprising two or more types of electrode active materials.

8. An electrode for an electrochemical device, comprising: Current collector; and an electrode active material layer provided on the current collector, The electrode active material layer comprises an electrode active material and an electrode binder, and the particles according to claim 1 are introduced into the electrode active material layer and integrated therein in a layered structure. 9 . The electrode for an electrochemical device according to claim 8 , wherein the electrode active material layer has a multilayer structure including two or more unit active material layers stacked therein.

10. An electrode for an electrochemical device according to claim 8, wherein when the electrode active material layer is divided into an upper part and a lower part based on a point corresponding to 50% of the thickness of the electrode active material layer from the current collector, the electrode active material layer shows a difference of 10 weight % or less between the content of the electrode binder expressed in weight % based on 100 weight % of the upper part and the content of the electrode binder expressed in weight % based on 100 weight % of the lower part.

11. An electrode for an electrochemical device according to claim 8, wherein the electrode active material layer shows a difference between the content of the electrode binder expressed in weight % in a region from the current collector toward the electrode surface layer portion to 15% of the thickness of the electrode active material layer and the content of the electrode binder expressed in weight % in a region from the electrode active material layer surface portion toward the current collector to 15% of the thickness of the electrode active material layer of 10 weight % or less.

12. The electrode for an electrochemical device according to claim 8, wherein the current collector includes a primer layer provided on at least one surface thereof, and the primer layer at least partially or entirely covers the surface of the current collector and includes a second conductive material and a second binder.

13. An electrochemical device comprising: A positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, wherein the negative electrode is the electrode according to claim 8.

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