Lithium-ion secondary battery comprising electrode manufactured by dry manufacturing method

Abstract

A dry electrode according to the present invention exhibits uniform distribution of a binder resin and / or an electrode active material in the thickness direction of an electrode active material layer, and thus exhibits excellent adhesion between the electrode active material layer and a current collector and improves the shape stability of the electrode active material layer. In addition, in the electrode active material layer of the dry electrode, the electrode active material does not have uniform alignment but has irregular alignment. A secondary battery, according to the present invention, comprising the dry electrode has an ohmic resistance that decreases according to a change in the state of charge (SOC), so as to have low heat generation if a high current such as high-speed charging is applied, and thus exhibits high battery driving safety and is advantageous with respect to thermal management of a battery.

Description

Lithium-ion secondary battery comprising an electrode manufactured by a dry manufacturing method

[0001] The present invention relates to a secondary battery including a dry electrode manufactured by a dry method.

[0002] This application claims priority to Korean Application No. 10-2023-0101870, filed August 3, 2023, the entire disclosure of which is incorporated herein by reference.

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

[0004] These lithium-ion secondary batteries are manufactured through an electrode manufacturing process, an electrode assembly manufacturing process, and a chemical reaction process. Typically, the electrode manufacturing process involves manufacturing an electrode slurry, coating it on an electrode current collector, and drying it. Furthermore, subsequent processes such as a rolling process, a slitting process, and a winding process follow after drying. Among these, the electrode slurry manufacturing process is a process of mixing ingredients for forming an electrode active material layer where an actual electrochemical reaction occurs in the electrode. Specifically, the electrode slurry is a process of mixing essential elements of the electrode, such as electrode active materials, other additives such as conductive materials and fillers, binders for inter-powder bonding and adhesion to the current collector, and solvents for viscosity and powder dispersion, to manufacture a slurry having fluidity.

[0005] In this way, in electrodes where the slurry coating method is applied to form the electrode active material layer, there is a problem in that the binder material within the electrode is not evenly distributed in the direction of the electrode thickness, but rather a larger amount is concentrated on the surface of the electrode active material layer, so that the bonding force between the electrode active material layer and the current collector is not sufficiently secured. This phenomenon is caused by migration of the binder material to the surface layer as the solvent evaporates during slurry drying.

[0006] To solve these problems, drying devices that can control the evaporation rate of the solvent while ensuring that the inside and outside of the electrode active material layer are dried uniformly are being considered. However, these drying devices are very expensive and require considerable cost and time to operate, which is disadvantageous in terms of manufacturing process. In addition, when the slurry is dried, the electrode active material settles to the bottom, resulting in a phenomenon in which the electrode active material particles are densely packed. This creates an electrode structure that is disadvantageous for high-speed charging, especially in the case of the negative electrode.

[0007] Accordingly, research on manufacturing dry electrodes that do not use solvents has been actively conducted recently. The dry electrode can be manufactured by dispersing composite particles (electrode granules) containing an active material and a binder resin on a current collector and compressing the dispersed electrode granules. The electrode granules can be manufactured by a spray drying method and can be obtained by uniformly dispersing electrode components (electrode active material, conductive material, binder, etc.) in a spray solution and atomizing it. Alternatively, the electrode active material and binder resin can be shear-mixed under dry conditions without a solvent, and then a composite powder in which the electrode active material and binder resin are complexed is dispersed and compressed on a current collector. When shear-mixing under the dry conditions is performed, the binder resin is finely divided and fiberized by the applied shear force, and the fiberized electrode active material and binder resin can form a composite material.

[0008]

[0009] The problem to be solved by the present invention is to provide a dry electrode in which the distribution of the binder, the distribution of the electrode active material, or both are uniform in the thickness direction of the electrode active material layer, and a secondary battery including the same. In addition, the present invention aims to provide a secondary battery including a dry electrode in which at least one of the positive electrode and the negative electrode is manufactured by a dry manufacturing method, and in which the ohmic resistance (ohm resistance, Ω) changes according to the state of charge (SOC) section.

[0010] In addition, it will be readily apparent that the objects and advantages of the present invention can be realized by the means or methods described in the claims and combinations thereof.

[0011]

[0012] The present invention relates to a lithium ion secondary battery including a dry electrode.

[0013] The above dry electrode is manufactured by a dry manufacturing method,

[0014] An electrode active material layer comprising an electrode active material and an electrode binder,

[0015] The electrode active material layer includes granules according to the spray drying result of a composition including an electrode active material and an electrode binder, or includes a composite material in which an electrode active material and a fiberized electrode binder are complexed, or includes both of the above.

[0016] The above lithium ion secondary battery has an ohmic resistance that changes according to changes in the charging SOC (State of Charge).

[0017] A second aspect of the present invention is that, in the aforementioned aspect, the change in the ohmic resistance is such that the ohmic resistance decreases as the charging SOC (State of Charge) increases.

[0018] A third aspect of the present invention is that in any one of the aforementioned aspects, the lithium ion secondary battery has a greater initial ohm resistance change rate (change amount) in the SOC section than in the subsequent section.

[0019] A fourth aspect of the present invention is that in any one of the aforementioned aspects, the ohm resistance change rate (change amount) is greater in the section before SOC 50% than in the section after SOC 50%.

[0020] A fifth aspect of the present invention is that in any one of the aforementioned aspects, the electrode active material includes a negative electrode active material, and the dry electrode is a negative electrode.

[0021] A sixth aspect of the present invention is any one of the aforementioned aspects, wherein the dry electrode comprises: a current collector; and an electrode active material layer positioned on the current collector; wherein the electrode active material layer is an accumulation of the granules, and the content of the electrode binder in the surface portion of the granules is greater than the content of the electrode binder in the center portion based on 100 wt% of the total weight of the electrode active material and the electrode binder, and the surface portion is an area from the surface of the electrode granules to 20% of the radius in the direction of the center of the electrode granules, and the center portion is a portion other than the surface portion.

[0022] The seventh aspect of the present invention is that in any one of the aforementioned aspects, the surface portion is an area extending from the surface of the electrode granule to 10% of the radius in the direction of the center of the electrode granule.

[0023] An eighth aspect of the present invention is any one of the aforementioned aspects, wherein the electrode granule has an aspect ratio of 0.75 to 1.0.

[0024] The ninth aspect of the present invention is any one of the aforementioned aspects, wherein the electrode granules have a particle size (D 50 ) is 0.1 to 1,000㎛.

[0025] The tenth aspect of the present invention is that in any one of the aforementioned aspects, the electrode active material includes two or more types of electrode active materials.

[0026] An eleventh aspect of the present invention is any one of the aforementioned aspects, wherein the lithium ion secondary battery has an average value of ohm resistance values ​​in the SOC 0% to SOC 20% range, and an ohm resistance value in the SOC 80% range or later is higher than the average value.

[0027] The twelfth aspect of the present invention is that in any one of the aforementioned aspects, the lithium ion secondary battery has lower ohmic resistance in a section after SOC 10% than in a section below SOC 10%.

[0028] The 13th aspect of the present invention is that in any one of the aforementioned aspects, the lithium ion secondary battery has a difference between the ohm resistance value at the SOC 80% point and the ohm resistance value at the SOC 5% point that is 1% or more compared to the difference between the minimum and maximum values ​​of the ohm resistance throughout the entire SOC measurement period.

[0029] The fourteenth aspect of the present invention is that in any one of the aforementioned aspects, when a graph of the change rate (change amount) of resistance over the entire SOC measurement period is checked, at least one arbitrary tangent line can have a negative slope.

[0030] Each of the above embodiments may be implemented independently or in combination of more than one of them.

[0031]

[0032] The dry electrode according to the present invention exhibits a uniform distribution of the binder resin and / or the electrode active material in the thickness direction of the electrode active material layer, thereby providing excellent adhesion between the electrode active material layer and the current collector and improving the morphological stability of the electrode active material layer. In addition, the dry electrode has an irregular orientation rather than a uniform orientation of the electrode active material within the electrode active material layer. The secondary battery according to the present invention including the dry electrode has a decrease in ohmic resistance according to a change in the charging SOC (State of Charge), and thus, when a high current such as a fast charge is applied, heat generation is low, resulting in high battery operation safety and being advantageous in terms of battery heat management.

[0033]

[0034] The following drawings attached to this specification illustrate preferred embodiments of the present invention, and serve to further understand the technical idea of ​​the present invention together with the contents of the invention described above, and therefore the present invention should not be interpreted as being limited to matters described in such drawings.

[0035] Figure 1 shows an SEM image of the granule particles for electrodes confirmed in this example.

[0036] Figure 2 shows a cross-section of an electrode manufactured by a manufacturing method according to Example 1 of the present invention.

[0037] Figure 3 is a graph showing the distribution of binder content along the thickness direction of the electrode active material layer in an electrode manufactured by a manufacturing method according to Example 1 of the present invention.

[0038] Figure 4 shows a cross-section of an electrode manufactured by a manufacturing method according to Comparative Example 4 of the present invention.

[0039] Figure 5 is a graph showing the distribution of binder content along the thickness direction of the electrode active material layer in an electrode manufactured by a manufacturing method according to Comparative Example 4 of the present invention.

[0040] Figure 6 is a schematic diagram of an electrode according to one embodiment of the present invention.

[0041] Figure 7 is a schematic diagram for calculating the QBR value of an electrode layer.

[0042] Figure 8 shows a cross-sectional image of the granule particles for electrodes manufactured in Example 1.

[0043] Figure 9 shows a cross-sectional image of the granule particles for electrodes manufactured in Example 2.

[0044] Figure 10 shows a cross-sectional image of the granule particles for electrodes manufactured in Example 3.

[0045] Figure 11 shows a cross-sectional image of the granule particles for electrodes manufactured in Comparative Example 1.

[0046] Figure 12 shows a cross-sectional image of granule particles for electrodes manufactured in Comparative Example 2.

[0047] Figures 13 and 14 are graphs showing the content of binder resin from the center to the surface of the electrode granule particles obtained in Examples 1 and 2 and Comparative Examples 1 and 2.

[0048] Figure 15 is a photographic image showing granules for electrodes fixed in a cured epoxy resin.

[0049] Figure 16 is a schematic diagram schematically showing the surface and center portions of the granule particles for electrodes of the present invention.

[0050] Figure 17 shows the measured ohm resistance (ohm resistance, Ω) for each SOC section in a battery according to each embodiment of the present invention.

[0051] Figure 18 shows the change rate of ohmic resistance (ohm resistance, Ω) measured by SOC section in a battery according to an embodiment and a comparative example of the present invention.

[0052] Figure 19 shows the ct resistance and ohm resistance by SOC in a battery according to each embodiment of the present invention.

[0053]

[0054] The present invention will be described in detail below. However, the present invention is not limited to the following description, and each component may be modified or selectively combined as needed. Therefore, it should be understood that all modifications, equivalents, and alternatives included within the spirit and technical scope of the present invention are included.

[0055] Throughout this specification, when it is said that a part "includes" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0056] In addition, the terms "about", "substantially", etc. used throughout this specification are used in the sense of numerical values ​​or near numerical values ​​when manufacturing and material tolerances inherent to the meanings stated are presented, and are used to prevent unscrupulous infringers from unfairly exploiting disclosures that mention exact or absolute values ​​to aid understanding of this specification.

[0057]

[0058] Throughout this specification, the description of “A and / or B” means “A or B or both.”

[0059] Certain terminology used in this specification is for convenience and not limitation. Terms such as "upper," "lower," "left," "right," "front," "rear," "inner," and "outer" are not absolute positions, but are used to describe relative positions or directions between components, or may indicate positions or directions in drawings to which reference is made. These terms include, in addition to themselves, words containing them, derivatives thereof, and words of similar meaning.

[0060] The “glass transition temperature (Tg)” used herein is measured by a conventional method known in the art, and may be measured by, for example, differential scanning calorimetry (DSC).

[0061] In this specification, the term "porosity" means the ratio of the volume occupied by pores to the total volume in a certain structure, and its unit is vol%, and can be used interchangeably with terms such as porosity, porosity, etc. In the present invention, the measurement of the porosity is not particularly limited, and according to an embodiment of the present invention, for example, it can be measured according to the BET (Brunauer-Emmett-Teller) measurement method using nitrogen gas or the mercury penetration method (Hg porosimeter) and ASTM D-2873. Alternatively, the true density can be calculated from the density (apparent density) of the measurement object and the composition ratio of materials included in the measurement object and the density of each component, and the porosity can be calculated from the difference between the apparent density and the true density (net density).

[0062] As used herein, the "average particle diameter (D50)" refers to the particle diameter at the 50% point of the cumulative distribution of particle numbers according to particle diameter. The measurement of particle diameters such as the D50 can be performed using a laser diffraction method. Specifically, after the powder to be measured is dispersed in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac S3500), and when the particles pass through the laser beam, the difference in the diffraction pattern according to particle size is measured to calculate the particle size distribution. By calculating the particle diameter at the point where it becomes 50% of the cumulative distribution of particle numbers according to particle diameter in the measuring device, the D50 particle diameter can be measured.

[0063] The "thickness" of each layer included in the electrode in this specification may refer to a value measured by a known method for measuring thickness. The method for measuring thickness is not limited thereto, but may be, for example, a value measured using a thickness gauge (Mitutoyo, VL-50S-B).

[0064] As used herein, "specific surface area" may refer to a value measured by a known method for measuring specific surface area. The method for measuring specific surface area is not limited thereto, but may be, for example, a value measured by a fluidized or fixed method.

[0065]

[0066] The present invention relates to a secondary battery comprising a dry electrode manufactured by a dry manufacturing method. The secondary battery may be a lithium ion secondary battery.

[0067] The above dry electrode may include an electrode active material layer including an electrode active material and an electrode binder. In addition, the electrode may further include a current collector, and the electrode active material layer may be disposed on one or both sides of the current collector.

[0068] In one embodiment of the present invention, the dry electrode includes an electrode active material layer, and the electrode active material layer may be formed by accumulating electrode granules by applying pressure. Alternatively, the electrode active material layer may be formed by compressing electrode powder in which an electrode active material and a fiberized electrode binder are combined into a film shape. Alternatively, the electrode active material layer may be formed by mixing the granules and the electrode powder and accumulating them by applying pressure.

[0069] In the present invention, the term 'dry electrode' means a result manufactured by integrating the electrode granule(s) and / or the electrode powder into a layered structure by pressing, i.e., including an electrode active material layer. Specifically, the granules and / or electrode powder may be dispersed on the surface of a current collector to a predetermined thickness and then compressed together with the current collector to manufacture an electrode, or the material itself may be integrated into a layered structure having a predetermined thickness by pressing (or formed into a film) and then laminated with the current collector. Here, the process of dispersing and pressing the granules and / or electrode powder is performed dry without adding a solvent, and is differentiated from the prior art in that no solvent is used in the electrode active material layer manufacturing step, compared to the prior art in which a method of applying and drying a slurry mixed with a solvent is applied.

[0070]

[0071] According to one embodiment of the present invention, a lithium ion secondary battery may be manufactured by forming an electrode assembly by placing an insulating film between a positive electrode and a negative electrode, placing the electrode assembly in, for example, a pouch, a cylindrical battery case, or a square battery case, and then injecting an electrolyte. Alternatively, the lithium ion secondary battery may be manufactured by stacking the electrode assemblies, then impregnating them with an electrolyte, and placing the resulting product in a battery case and sealing it. The insulating film may be a separator, a solid electrolyte film, or both.

[0072]

[0073] In one embodiment of the present invention, the secondary battery according to the present invention can have an ohmic resistance that changes according to a change in the state of charge (SOC).

[0074] In the present invention, the secondary battery is not limited to the charge / discharge rate, and the ohmic resistance change described below can be confirmed within the above range. For example, the secondary battery can be charged / discharged at a rate between 0.001 C and 10 C, or between 0.001 C and 5 C.

[0075] In one embodiment of the present invention, the secondary battery including at least one dry electrode among the negative electrode and the positive electrode may exhibit a tendency for the ohmic resistance to decrease as the SOC increases. Fig. 17 shows the ohm resistance measured at each SOC section using the lithium ion secondary battery according to the present invention. In addition, referring to Fig. 18, the lithium ion secondary battery according to the present invention may exhibit a negative (-) tendency in the ohm resistance change rate of the battery as the SOC increases during charging. In the present invention, the ohm resistance change rate may be greater in a section before SOC 50% than in a section after SOC 50%. That is, the ohm resistance change rate may exhibit a pattern of decreasing more rapidly in the section from the first measured SOC point to SOC 20%, or SOC 30%, or SOC 50% than in the section from SOC 20% to the last measured SOC point, or from SOC 30% to the last measured SOC point, or from SOC 50% to the last measured SOC point.

[0076] In the present specification, the first measured SOC point may be any one of SOC 0% to SOC 10%. For example, it may be any one of 1%, 2%, 3% 4%, 5%, 6%, 7%, 8%, 9%, or 10%. Alternatively, the first measured SOC point may be a point at which ohmic resistance can be separated. Meanwhile, the last measured SOC point may be any one of SOC 70% or SOC 75% or SOC 80% or SOC 90%. For example, it may be 75%, 80%, 85%, or 90%.

[0077] Ohmic resistance, one of the resistance components of electrochemical devices such as batteries, has the property of impeding the flow of current, and its magnitude tends to change depending on the magnitude of the applied current. In the case of dry electrodes, since there is no process that induces particle orientation, such as drying of wet slurry, the tendency for the electrode active materials to be oriented in a certain direction in the electrode active material layer is low. Therefore, the directionality of the volume change of the electrode active material particles during charge and discharge of the battery is non-uniform, and gaps may occur between the electrode active material particles. In a battery containing a dry electrode, the change in ohmic resistance during charging may be due to this non-uniform aspect of the directionality of the volume change of the electrode active material particles. (Despite the change in ohmic resistance) In addition, when the electrode is manufactured by the dry method, the overall resistance, including ohmic resistance, tends to decrease because many of the electrode active material particles have exposed basal planes, and the kinetics of the electrode also tends to become faster. In one embodiment of the present invention, the dry electrode may be a negative electrode, and the negative electrode may include a negative electrode active material that exhibits a volume expansion phenomenon during charge and discharge, such as a carbon negative electrode active material, a silicon-based negative electrode active material, or a tin-based negative electrode active material.

[0078]

[0079] Referring to Fig. 18, the electrode manufactured by the wet method of Comparative Example 3 does not show such a significant decrease in ohmic resistance. This is because, when manufacturing an electrode by wet slurry drying, the electrode active material may settle to the bottom of the slurry during slurry drying and become densely integrated, and the particle arrangement may exhibit a parallel arrangement, thereby increasing orientation. In particular, carbon materials such as graphite have a strong tendency to integrate in a way that increases orientation. Accordingly, the volume change of the electrode active material during charge / discharge of the battery may exhibit a specific directionality, but this volume change is accompanied by little change in the spacing between the electrode active material particles. It is thought that the wet electrode exhibits little or no change in ohmic resistance because the rate of separation between the electrode active materials due to volume changes during charge / discharge is low. In addition, the wet electrode has the characteristic of extremely little exposure of the basal surface during the drying process.

[0080] In one embodiment of the present invention, the secondary battery may have an average value of the ohm resistance value in the section from the first measured SOC point to SOC 20% higher than the average value of the ohm resistance value in the section after SOC 80%. In the present specification, the subsequent section means the section up to the last measured SOC point. For example, the first measured point may be SOC 0%, and the section after SOC 80% may be the section up to SOC 100%, but is not limited thereto. Meanwhile, the average value of the resistance value means an average value calculated by measuring the ohm resistance value at a predetermined interval, for example, an SOC 1% interval, and adding up the ohm resistance values ​​of each SOC in the corresponding section.

[0081] In one embodiment of the present invention, the secondary battery may have a value of ohm resistance at any point in a section prior to 10% SOC, higher than a value of ohm resistance at any point in a section after 10% SOC, or after 20% SOC, or after 30% SOC, or after 40% SOC, or after 50% SOC, or after 60% SOC, or after 70% SOC, or after 80% SOC.

[0082] In one embodiment of the present invention, the secondary battery may have a value of ohm resistance at any point in a section before SOC 20%, or after SOC 30%, or after SOC 40%, or after SOC 50%, or after SOC 60%, or after SOC 70%, or after SOC 80%, higher than a value of ohm resistance at any point in a section after SOC 20%, or after SOC 30%, or after SOC 40%, or after SOC 50%, or after SOC 60%, or after SOC 70%, or after SOC 80%.

[0083] In one embodiment of the present invention, the secondary battery may have a value of ohm resistance at any point in a section before SOC 30%, higher than a value of ohm resistance at any point in a section after SOC 30%, or after SOC 40%, or after SOC 50%, or after SOC 60%, or after SOC 70%, or after SOC 80%.

[0084] In one embodiment of the present invention, the secondary battery may have a lower ohmic resistance in a section after 10% SOC than in a section before 10% SOC. In one embodiment of the present invention, the secondary battery may have a lower ohmic resistance in a section after 20% SOC than in a section before 20% SOC. In one embodiment of the present invention, the secondary battery may have a lower ohmic resistance in a section after 30% SOC than in a section before 30% SOC.

[0085] In one embodiment of the present invention, the secondary battery may exhibit a difference between the ohm resistance value at the SOC 80% point and the ohm resistance value at the SOC 5% point or the first point where the ohm resistance can be separated, which is 1% or more, 3% or more, 5% or more, 10% or more, 20% or more, or 30% or more compared to the difference between the minimum value and the maximum value of the ohm resistance throughout the SOC measurement period.

[0086] In one embodiment of the present invention, the secondary battery may exhibit a difference between the ohm resistance value at the SOC 50% point and the ohm resistance value at the SOC 5% point or the first point where the ohm resistance can be separated, which is 1% or more, 3% or more, 5% or more, 10% or more, 20% or more, or 30% or more compared to the difference between the minimum value and the maximum value of the ohm resistance throughout the SOC measurement period.

[0087] In one embodiment of the present invention, the secondary battery may exhibit a difference between the ohm resistance value at the SOC 30% point and the ohm resistance value at the SOC 5% point or the first point where the ohm resistance can be separated, which is 1% or more, 3% or more, 5% or more, 10% or more, 20% or more, or 30% or more compared to the difference between the minimum value and the maximum value of the ohm resistance throughout the SOC measurement period.

[0088] In one embodiment of the present invention, when the change rate (change amount) of the resistance component, particularly the ohm resistance, of the lithium ion secondary battery is checked for the entire SOC measurement period, any one or more tangent lines may have a (-) slope. In one embodiment of the present invention, the secondary battery may have a greater initial ohm resistance change rate (change amount) in the SOC section than in the subsequent section. Preferably, the ohm resistance change rate (decrease amount) may refer to an ohm resistance decrease rate (decrease amount), and the initial ohm resistance decrease rate (decrease amount) may be greater than in the subsequent section. In one specific embodiment, the battery may have a greater ohm resistance decrease rate (decrease amount) in the first measured SOC point (e.g., SOC 0%) to SOC 20% section than in the section after SOC 20%. Alternatively, the battery may have a greater ohm resistance reduction rate in the range from the first measured SOC point (e.g., SOC 0%) to SOC 30% than in the range after SOC 30%. Alternatively, the battery may have a greater ohm resistance reduction rate in the range from the first measured SOC point (e.g., SOC 0%) to SOC 40% than in the range after SOC 40%. Alternatively, the battery may have a greater ohm resistance reduction rate in the range from the first measured SOC point (e.g., SOC 0%) to SOC 50% than in the range after SOC 50%.

[0089]

[0090] Meanwhile, in the present invention, the ohmic resistance change rate can be calculated based on the following equation 1.

[0091]

[0092] (Formula 1) Ohmic Resistance change = (R soc / R i )x 100

[0093]

[0094] In the above formula 1, Ri is the ohmic resistance at the lowest SOC that can separate the ohmic resistance and charge transfer resistance from the Nyquist plot, and R soc represents the ohmic resistance at each SOC.

[0095] As described above, since the orientation of the electrode active material particles included in the electrode active material layer of the dry electrode is non-uniform, both the electrode using the binder fiberization method and the granular method have the above-described ohmic resistance change. In particular, the above-described ohmic resistance change is significantly more pronounced in the case of the granular method, as confirmed in the examples described below, and is further significantly more pronounced in the granular method electrode where the binder resin is concentrated on the surface.

[0096] Meanwhile, according to Joule's Law, power is proportional to the product of the square of the current and the resistance, so as the current and resistance increase during battery operation, the amount of heat generated increases. In the case of a secondary battery to which the dry electrode of the present invention is applied, the ohmic resistance is lowered in the range where rapid charging is mainly applied, such as SOC 15% to 85% or SOC 20% to 80%, which is advantageous in terms of battery heat management and safety improvement.

[0097] In the present invention, the resistance value according to SOC can be confirmed through an in situ EIS measurement method. This is done by connecting two channels to one jig, charging is performed on one channel, and EIS is measured on the other channel at regular intervals or at regular SOC intervals, so that EIS can be measured simultaneously with charging. The EIS measurement interval can be measured at 1% SOC intervals. In one embodiment, multiple charge / discharge cycles are performed, and the average value of the EIS results measured at each SOC can be used as a representative value. Here, the EIS measurement method for an electrochemical device commonly applied in the present technical field can be applied. Meanwhile, the charge / discharge and EIS measurement of the battery can be performed at room temperature. The ratio of the ohm resistance and the CT resistance can be calculated from the Nyquist plot obtained at this time. Figure 19 shows the values ​​and ratios of ohm resistance and CT resistance according to SOC measured through the batteries of Examples 1, 2, and 4. Referring to this, it was confirmed that the ohm resistance of the secondary battery according to the present invention decreased as the SOC increased. In addition, it was confirmed that the CT resistance also decreased along with this. However, it was confirmed that the battery including the wet electrode according to Comparative Example 3 had a slightly decreased ct resistance, but the degree of change in ohm resistance according to the change in SOC was significantly lower than that of the present invention.

[0098]

[0099] Meanwhile, in the present invention, the SOC is expressed as a percentage (%) by dividing the currently usable battery capacity by the total capacity to indicate the remaining capacity of the battery. The SOC can be calculated using the current integration method. The current integration method can calculate the SOC by integrating the input and output current of the battery and adding or subtracting it from the initial capacity. Here, the current can be measured through a current sensor installed in the charge / discharge path of the battery.

[0100]

[0101] Next, each component of the lithium ion secondary battery according to the present invention will be described in detail.

[0102]

[0103] <Granules for electrodes>

[0104] In the present invention, the electrode granule may have a form of composite particles including an electrode active material, an electrode binder, and optional components added as needed. In one embodiment of the present invention, the electrode granule may be a secondary particle formed by bonding and assembling two or more electrode active material particles by the electrode binder. In the present invention, the electrode active material may mean a collection of particles, wherein each particle of the electrode active material may have a diameter of 0.05 μm to 2 μm. In one embodiment of the present invention, the electrode active material may be 80 wt% or more or 90 wt% or more of the total weight of the electrode granule, and the electrode binder may be included in an amount of 20 wt% or less or 10 wt% or less. In one embodiment of the present invention, the electrode granule may further include an electrode conductive material as an optional component as needed. The above electrode conductive material may be included in an amount of 0.1 wt% to 20 wt%, preferably 0.1 wt% to 10 wt%, relative to 100 wt% of the electrode granules. For example, the conductive material may be included in an amount of about 0.1 wt% to 5 wt% of the electrode granules.

[0105] According to one embodiment of the present invention, the content of the electrode active material in the electrode granules may be 85 wt% to 98 wt%. Within the above range, the content of the electrode binder may be 0.5 wt% to 10 wt%, and the content of the electrode conductive material may be 0.5 wt% to 5 wt%. According to another embodiment, the content of the electrode active material may be 90 wt% to 98 wt%, the content of the electrode binder may be 0.5 wt% to 5 wt%, and the content of the electrode conductive material may be 0.5 wt% to 5 wt%.

[0106]

[0107] Fig. 16 is a schematic diagram showing the surface and center portions of the electrode granule of the present invention. Referring to this, in the present invention, the electrode granule may have a greater amount of electrode binder included in the surface portion (102) of the electrode granule than in the center portion (101) of the electrode granule. Alternatively, the electrode granule may exhibit a tendency for the content of the binder resin to increase from the center portion toward the surface portion. The amount of the binder may refer to weight or volume.

[0108]

[0109] Together with or independently of this, the electrode granule for the electrode has a content (wt%) (B) of electrode binder included in the center (101) of the electrode granule relative to 100 wt% of the total weight of the electrode granule c / G t ) compared to the electrode granule, the content (wt%) of the electrode binder included in the surface portion (102) of the electrode granule (B s / G t ) may be higher. Here, Bc is the weight of the binder included in the center, Bs is the weight of the binder included in the surface, and G t refers to the total weight of granule particles for electrodes.

[0110] Together with or independently of this, the electrode granules have a content (vol%) (B) of electrode binder contained in the center (101) of the electrode granules relative to 100 vol% of the total volume of the electrode granules. c / G t ) compared to the electrode granule, the content (vol%) of the electrode binder included in the surface portion (102) of the electrode granule (B s / G t ) may be higher. Here, Bc is the volume of binder included in the center, Bs is the volume of binder included in the surface, and G t refers to the total volume of granule particles for electrodes.

[0111] Here, the surface portion may refer to an area near the surface of the electrode granule from the surface of the electrode granule to a predetermined depth toward the center of the electrode granule. The center portion refers to a portion other than the surface portion. In one embodiment of the present invention, the surface portion may refer to a surface area from the surface of the electrode granule toward the inside, specifically, up to 30% of the radius toward the center of the electrode granule. In one embodiment of the present invention, the surface portion may refer to a surface area from the surface of the electrode granule to 30% of the radius, up to 20% of the radius, up to 15% of the radius, up to 10% of the radius, or up to 5% of the radius. Preferably, the surface portion may refer to a surface area from the surface of the electrode granule to 20% of the radius.

[0112] Meanwhile, in one embodiment of the present invention, the surface portion may mean an area from the center of the electrode granule to the surface of the electrode granule after 70% of the radius toward the outside of the electrode granule. In one embodiment of the present invention, the surface portion may mean an area from the center of the electrode granule to the surface of the electrode granule after 80%, 85%, 90%, or 95% of the radius, for example.

[0113] In one embodiment of the present invention, the center of the electrode granule may mean a point at half the longest diameter of the electrode granule. In the present invention, the radius may mean a distance from the center of the electrode granule to each point on the surface of the electrode granule. In one embodiment of the present invention, the surface portion and the center portion may be distinguished based on points that are the same distance from each surface of the electrode granule along each radius, specifically, points that are up to 30% of the radius from the surface, up to 20% of the radius, up to 10% of the radius, up to 5% of the radius, or up to 1% of the radius.

[0114] In one embodiment of the present invention, the content of the electrode binder relative to 100 wt% of the total weight of the electrode granules in a region from the center of the electrode granule particle to the surface of the electrode granule after 90% of the radius may be 50 wt% or more, 60 wt% or more, 70 wt% or more, 80 wt% or more, or 90 wt% or more.

[0115] In another embodiment of the present invention, the content of the electrode binder relative to 100 wt% of the total weight of the electrode granules in a region from the center of the electrode granule to the surface of the electrode granule at 95% of the particle radius may be 50 wt% or more, 60 wt% or more, 70 wt% or more, 80 wt% or more, or 90 wt% or more.

[0116] In another embodiment of the present invention, in a region from the center of the electrode granule particle to the surface of the electrode granule after 99% of the radius, the content of the electrode binder relative to 100 wt% of the total weight of the electrode granule in the region may be 50 wt% or more, 60 wt% or more, 70 wt% or more, 80 wt% or more, or 90 wt% or more.

[0117] In one embodiment of the present invention, the content of the electrode binder relative to 100 vol% of the total volume of the electrode granules in a region from the center of the electrode granule particle to the surface of the electrode granule after 90% of the radius may be 50 vol% or more, 60 vol% or more, 70 vol% or more, 80 vol% or more, or 90 vol% or more.

[0118] In another embodiment of the present invention, the content of the electrode binder in a region from the center of the electrode granule to the surface of the electrode granule at 95% of the particle radius may be 50 vol% or more, 60 vol% or more, 70 vol% or more, 80 vol% or more, or 90 vol% or more, based on 100 vol% of the total volume of the electrode granule in that region.

[0119] In another embodiment of the present invention, the content of the electrode binder in a region from the center of the electrode granule particle to the surface of the electrode granule after 99% of the radius may be 50 vol% or more, 60 vol% or more, 70 vol% or more, 80 vol% or more, or 90 vol% or more, based on 100 vol% of the total volume of the electrode granule in the region.

[0120] In one embodiment of the present invention, the content of the electrode binder in a surface area of ​​the electrode granules from the surface of the electrode granule particles to 10% of the radius may be 50 wt% or more, 60 wt% or more, 70 wt% or more, 80 wt% or more, or 90 wt% or more, based on 100 wt% of the total weight of the electrode granules in that area.

[0121] In another embodiment of the present invention, the content of the electrode binder in a region of the electrode granule surface from the surface of the electrode granule particle to a radius of 5 may be 50 wt% or more, 60 wt% or more, 70 wt% or more, 80 wt% or more, or 90 wt% or more, based on 100 wt% of the total weight of the electrode granule in that region.

[0122] In another embodiment of the present invention, the content of the electrode binder in a region from the surface of the electrode granule particle to the surface of the electrode granule after 1% of the radius may be 50 wt% or more, 60 wt% or more, 70 wt% or more, 80 wt% or more, or 90 wt% or more, based on 100 wt% of the total weight of the electrode granule in that region.

[0123]

[0124] In one embodiment of the present invention, the content of the electrode binder in a surface area of ​​the electrode granules from the surface of the electrode granule particles to 10% of the radius may be 50 vol% or more, 60 vol% or more, 70 vol% or more, 80 vol% or more, or 90 vol% or more, based on 100 vol% of the total weight of the electrode granules in that area.

[0125] In another embodiment of the present invention, the content of the electrode binder in the electrode granule surface area from the electrode granule particle surface to 5 of the radius may be 50 vol% or more, 60 vol% or more, 70 vol% or more, 80 wt% or more, or 90 vol% or more, based on 100 vol% of the total weight of the electrode granule in the area.

[0126] In another embodiment of the present invention, the content of the electrode binder relative to 100 vol% of the total weight of the electrode granules in a region from the surface of the electrode granule particle to the surface of the electrode granule after 1% of the radius may be 50 vol% or more, 60 vol% or more, 70 vol% or more, 80 vol% or more, or 90 vol% or more.

[0127] Figure 1 schematically illustrates an SEM image of granule particles for electrodes according to an embodiment of the present invention. Referring to this, a surface region with a high binder content is confirmed from the surface to the center of the particle to a predetermined depth, and a portion other than the surface region, that is, a central region (core region) surrounded by the surface region, has a lower binder distribution than the surface region.

[0128] To describe the above electrode granule in more detail, the electrode granule may have a central portion including a plurality of electrode active materials; and a surface portion including an electrode binder that is positioned on all or part of the outer side of the central portion and binds the electrode active materials. That is, in the central portion of the electrode granule, the plurality of electrode active materials form an aggregate while making surface contact, line contact, point contact, or two or more of these contacts, and in the surface portion of the electrode granule, the electrode binder is positioned on all or part of the outer side of the aggregate, thereby fixing and binding the plurality of electrode active materials in the central portion of the electrode granule to each other.

[0129]

[0130] According to one embodiment of the present invention, a small amount of electrode binder may be further included in the central portion, which may serve to connect and fix a plurality of electrode active materials in the central portion. However, as described above, it is preferable that the content ratio of the electrode binder is higher in the surface portion than in the central portion. In one embodiment of the present invention,

[0131] Meanwhile, in one embodiment of the present invention, the electrode granules may preferably have an aspect ratio of more than 0.75 and 1.0. The aspect ratio may refer to the ratio of the major axis length to the minor axis length of the electrode granules. In another embodiment of the present invention, the average aspect ratio of the electrode granules may have a value of 0.5 to 1.0, preferably 0.75 to 1.0, and in this case, the average aspect ratio may refer to the ratio of the average minor axis length to the average major axis length of the electrode granule particles. At this time, the average minor axis length may refer to the average value of the length in the axial direction having the shortest length of the electrode granules, and the average major axis length may refer to the average value of the length in the axial direction having the longest length of the electrode granules. When the aspect ratio of the electrode granules satisfies this range, it is advantageous in terms of having sufficient fluidity suitable for the process.

[0132] Meanwhile, in one embodiment of the present invention, the particle size of the electrode granules may range from 0.1 to 1,000 μm based on the longest particle diameter. In another embodiment of the present invention, the average particle size (D50) of the electrode granules may range from 0.1 to 1,000 μm.

[0133]

[0134] Electrode powder and its manufacturing method

[0135] In the present invention, the electrode powder includes an electrode active material and an electrode binder, and may include optional components such as a conductive material added as needed. The electrode powder may include a finely fiberized electrode binder as described below, and may have a shape in which electrode materials such as electrode active material particles are bound by the fine fibers of the electrode binder.

[0136] In a specific embodiment, the electrode powder may be obtained by a manufacturing method comprising: (a) a step of manufacturing a powder blend including an electrode active material, a conductive material, and a binder resin; (b) a step of kneading the powder blend to manufacture a mixture lump; and (c) a step of pulverizing the mixture lump to obtain a mixed powder for an electrode.

[0137]

[0138] First, an electrode active material and an electrode binder are mixed to obtain a uniform dry powder blend (a). The powder blend may further include any desired materials, such as a conductive material. The mixing is not particularly limited as long as dry mixing is performed, and may be performed, for example, by introducing the electrode materials into a device such as a mixer or blender. In one embodiment of the present invention, the mixing is preferably performed so that the crystallinity of the binder resin in the obtained dry powder blend is 50% or less, and process conditions may be controlled to ensure such crystallinity. For example, the mixing time may be performed for 1 second to 20 minutes. The temperature of the mixture may be controlled in the range of 20°C to 70°C. Additionally, the mixing can be performed in a mixer under process conditions of 500 rpm to 20,000 rpm, 5,000 rpm to 20,000 rpm, or 1000 rpm to 15,000 rpm, or 10,000 rpm to 15,000 rpm.

[0139]

[0140] Next, the powder blend obtained above is subjected to a kneading step to fiberize the electrode binder (b). Through this kneading process, the binder resin is fiberized, thereby combining or linking the electrode active material and conductive powders, thereby forming a lump-shaped blend. The fiberization refers to a process of dividing a polymer into small particles, and for example, a mechanical shear force is applied to generate a large number of fine fibers (fibrils).

[0141] The above kneading is not limited to a specific method. In a specific embodiment of the present invention, the kneading may be performed using a kneader, for example. For example, the kneader may be a twin-screw extruder, a single-screw extruder, a batch kneader, a continuous kneader, or the like.

[0142] In one embodiment of the present invention, the kneading may be controlled at a speed of 10 rpm to 100 rpm. For example, the kneading may be controlled at a speed of 20 rpm or more or 70 rpm or less within the above range. Meanwhile, in one embodiment of the present invention, the kneading step may be controlled at a shear rate in the range of 5 / sec to 1,000 / sec. In a specific embodiment of the present invention, the kneading may be performed for 1 minute to 30 minutes, and the shear rate may be controlled in the range of 10 / sec to 500 / sec. Meanwhile, the kneading may be performed at a temperature in the range of 70°C to 200°C, specifically, 90°C to 150°C. The temperature may be the temperature inside the kneader or the temperature of the kneading object. Alternatively, the temperatures of both may be controlled within the above range.

[0143] If the process is performed at a low temperature outside the above range, the fiberization and lump formation by kneading of the binder do not occur well during the kneading process, so that film formation does not occur easily during calendaring. In addition, if the process is performed at too high a temperature, the fiberization of the binder occurs rapidly and the fibers that have already been formed may be cut by excessive shear force thereafter, which is not preferable. As described above, since the kneading process applies a relatively low shear force at a high temperature, there is no concern about the fine differentiation / damage of the electrode active material or the cutting of the binder fiber, and an electrode powder including a finely fiberized binder resin can be obtained. In addition, the fiberized binder resin has high uniformity in the thickness and / or length of the fiber.

[0144] Meanwhile, the binder resin may undergo fiberization in step (a), but the fibers formed in step (a) are thick and difficult to be refined to a degree that can achieve the tensile strength and tensile elongation required for a dry electrode. In the present invention, the fine fiberization of the binder resin is preferably performed primarily through step (b).

[0145] Non-limiting examples of binder resins suitable for the fiberization process may include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyolefin, or a mixture of two or more thereof, specifically, polytetrafluoroethylene (PTFE), and even more specifically, polytetrafluoroethylene (PTFE). Specifically, the polytetrafluoroethylene (PTFE) may be included in an amount of 30 wt% or more based on the total binder resin weight. Meanwhile, in this case, the binder resin may additionally include polyethylene oxide (PEO) and / or polyvinylidene fluoride-cohexafluoropropylene (PVdF-HFP), in addition to the aforementioned components.

[0146]

[0147] Next, the lumpy blend produced through the above kneading step is ground again to obtain a mixed powder for electrodes. At this time, the grinding is not particularly limited, but can be performed using a known grinding device such as a blender or grinder. In one embodiment of the present invention, considering the aspect of film formation, the particle size of the obtained electrode mixture powder may preferably be in the range of 30 μm to 180 μm.

[0148] Meanwhile, in the present invention, the crystallinity (c) of the binder resin contained in the electrode mixed powder may be 20% or less. This crystallinity can be controlled by adjusting at least one of process conditions, kneading time, kneading temperature, rotation speed (rpm), and shear speed.

[0149]

[0150] Dry electrode

[0151] A dry electrode according to one aspect of the present invention is an electrode for an electrochemical device, comprising: a current collector; and an electrode active material layer positioned on the current collector. The electrode active material layer contains an electrode active material and an electrode binder, and may be formed by accumulating electrode granules having the above-described structural characteristics, electrode powder, or both into a layered structure by pressurization.

[0152] Below, the electrode active material layer and current collector are described in more detail.

[0153]

[0154] <Electrode active material layer>

[0155] The electrode active material layer contains an electrode active material and an electrode binder. In the present invention, the electrode active material layer may have a form in which the electrode granules or electrode powder or both are pressurized and integrated into a layered structure. When the electrode granules are introduced into the electrode, the aspect ratio or particle size range may not be maintained in the initial state due to the calendaring process described below. The electrode active material layer may contain 80 wt% or more, 90 wt% or more, 95 wt% or more, or 99 wt% or more of the electrode granules relative to 100 wt% of the electrode active material layer. Meanwhile, in one embodiment, the electrode active material layer may further contain an electrode active material, an electrode binder, an electrode conductive agent, etc. that are not granulated and are present in a free state without being included in the electrode granules. Alternatively, the electrode active material layer may further contain electrode granule particles having an aspect ratio and / or particle size range that do not fall within the above-described range.

[0156]

[0157] In one embodiment of the present invention, the electrode active material layer preferably has a porosity of 20 vol% to 40 vol%, considering aspects such as electrolyte impregnation property, shape stability, and ionic conductivity. In one embodiment of the present invention, the electrode active material layer into which the electrode granules are introduced may have pores provided by interstitial volume, which is a space between the electrode granules, and may exhibit porous characteristics derived from this structure.

[0158]

[0159] Meanwhile, according to one embodiment of the present invention, the thickness of the electrode active material layer may be, for example, 30 μm to 300 μm, but is not limited thereto.

[0160] According to another embodiment of the present invention, the electrode active material layer may be composed of a single layer including one unit active material layer.

[0161]

[0162] According to another embodiment of the present invention, the electrode active material layer may have a multilayer structure in which two or more unit active material layers are laminated. At this time, the electrode materials included in each unit active material layer, for example, the electrode active material and the electrode binder, may be the same or different for each layer, but are not limited thereto. In addition, if necessary, each layer may include an electrode conductive material, and at this time, the electrode conductive materials of each layer may also be the same or different.

[0163]

[0164] In addition, in one embodiment of the present invention, the electrode active material layer has a uniform distribution of the binder based on the thickness direction. In a specific embodiment, the electrode active material layer may have a difference of 10 wt% or less in the binder content (wt%) in the upper 100 wt% and in the binder content (wt%) in the lower 100 wt% at the upper and lower points based on a point that is 50% from the current collector in the thickness of the electrode active material layer. In addition, based on the thickness of the electrode active material layer, the difference of the binder content in a region of up to 15% in the thickness direction from the current collector toward the electrode surface and a region of up to 15% in the direction from the surface of the electrode active material layer toward the current collector may have a value of 10 wt% or less.

[0165]

[0166] This distribution of the binder may be due to the fact that the electrode active material layer according to the present invention is manufactured by pressing the electrode granules and / or electrode powder. As described below, the electrode manufacturing method of the present invention is characterized in that after manufacturing electrode granule particles or electrode powder containing an electrode material, they are dispersed and pressed to a predetermined thickness on a current collector or release paper and accumulated. In the case of an electrode manufacturing method involving slurry manufacturing, migration of the binder is induced by evaporation of the solvent during slurry drying, so that the binder is intensively distributed on the surface of the electrode. However, in the present invention, a method of pressing and accumulating dry electrode granule particles and / or electrode powder without using a solvent is applied, so that the binder migration phenomenon does not occur. Accordingly, the binder is uniformly distributed in the thickness direction in each unit layer.

[0167]

[0168] Electrode material

[0169] According to one embodiment of the present invention, 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 to 99 parts by weight: 0.5 to 10 parts by weight: 0.5 to 10 parts by weight of electrode active material: electrode conductive material: electrode binder, and specifically, 90 to 99 parts by weight: 0.5 to 5 parts by weight: 0.5 to 10 parts by weight.

[0170]

[0171] The above electrode may be an anode or a cathode.

[0172] In the case where the above electrode is a positive electrode, the positive electrode active material, which is an electrode active material, is not limited to a lithium transition metal oxide or a lithium metal iron phosphate, if it is in the form of a metal oxide, and for example, a layered compound such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; chemical formula Li 1+x Mn 2-x Lithium manganese oxides such as O4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, Cu2V2O7; chemical formula LiNi 1-x M x Ni-site type lithium nickel oxide represented by O2 (where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga and x = 0.01 to 0.3); chemical formula LiMn 2-x M xLithium manganese complex oxides represented by O2 (wherein, M = Co, Ni, Fe, Cr, Zn or Ta, and x = 0.01 to 0.1) or Li2Mn3MO8 (wherein, M = Fe, Co, Ni, Cu or Zn); Li where some of the Li in the chemical formula is replaced by aluminum ions. 1+x (Ni a Co b Mn c Al d ) 1-x O2(x = 0 ~ 0.03, a = 0.3 ~ 0.95, b = 0.01 ~ 0.35, c = 0.01 ~ 0.5, d = 0.001 ~ 0.03, a+b+c+d=1); lithium metal phosphate LiM P O4 (wherein M = Fe, CO, Ni, or Mn), disulfide compounds; Fe2(MoO4)3, etc., but are not limited to these.

[0173]

[0174] When the above electrode is a cathode, the cathode active material is, for example, a graphite-based carbon material such as non-graphitizable carbon, natural graphite or artificial graphite; Li x Fe2O3(0≤x≤1), Li x WO2(0≤x≤1), Sn x Me 1-x Me' y O z (Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, elements of group 1, 2, and 3 of the periodic table, halogens; 0 <x≤1; 1≤y≤3; 1≤z≤8) 등의 금속 복합 산화물; 리튬 금속; 리튬 합금; 규소; 규소계 합금; 주석; 주석계 합금; SiO x(0 <X≤2), SiO, SiO / C, SiO2등의 규소계 재료; SnO, SnO2, 등의 주석계 재료; PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, 및 Bi2O5등의 금속 산화물; 폴리아세틸렌 등의 도전성 고분자; Li-Co-Ni 계 재료 등을 사용할 수 있으나, 이들만으로 한정되는 것은 아니다. 한편, 전술한 옴저항 변화 패턴을 발휘하기 위해서 상기 전극활물질은 충방전에 따른 부피 팽창율이 높은 흑연계 탄소 재료, 규소, 규소계 합금, 규소계 재료, 주석, 주석계 합금, 주석계 재료 중 하나 이상을 포함할 수 있다.

[0175] Meanwhile, in one embodiment of the present invention, the electrode active material may include two or more different electrode active material materials. Specifically, the electrode granule particles may include two or more different electrode active material materials within one particle. The electrode active material materials are not particularly limited as long as they are the components described above. For example, the electrode granules may include artificial graphite and natural graphite as electrode active materials, and the artificial graphite and natural graphite may be mixed in a predetermined ratio.

[0176]

[0177] The electrode conductive material is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and for example, graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black; conductive fiber such as carbon fiber or metal fiber; metal powder such as fluorocarbon, aluminum, nickel powder; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxide such as titanium oxide; conductive materials such as polyphenylene derivatives, etc. may be used. Specifically, in order to uniformly mix the electrode conductive material and improve conductivity, 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 specifically, may include activated carbon. Meanwhile, in one embodiment of the present invention, the electrode granule particle may include two or more different conductive materials in one particle. For example, the above electrode granules may contain a mixture of carbon black and carbon nanotubes as conductive materials in a predetermined ratio.

[0178]

[0179] In the present invention, the electrode binder is not particularly limited as long as it is used as a binder material for an electrochemical device, but may include, for example, a diene polymer, an acrylate polymer, an olefin polymer, a fluorine polymer, a styrene polymer, or two or more thereof.

[0180] Examples of the diene polymer include polymers containing monomer units derived from conjugated dienes such as butadiene and isoprene, and hydrogenated products thereof. The proportion of monomer units derived from conjugated dienes during the diene polymerization may usually be 40 wt% or more, preferably 50 wt% or more, and more preferably 60 wt% or more.

[0181] Specifically, examples thereof include conjugated diene homopolymers such as polybutadiene or polyisoprene; aromatic vinyl-conjugated diene copolymers such as styrene-butadiene copolymer (SBR), which may also be carboxyl-modified; cyanated vinyl-conjugated diene copolymers such as acrylonitrile-butadiene copolymer (NBR); hydrogenated SBR, hydrogenated NBR, and the like.

[0182] The above styrene polymer is a polymer having a repeating unit derived from a styrene monomer, and may include a styrene homopolymer (polystyrene), a styrene copolymer, etc. Examples of the above styrene copolymers may include block copolymers such as styrene-ethylene-butadiene copolymer, styrene-butadiene-propylene copolymer, styrene-isoprene copolymer, styrene-n-butyl acrylate-itaconic acid-methyl methacrylate-acrylonitrile copolymer, styrene-n-butyl acrylate-itaconic acid-methyl methacrylate-acrylonitrile copolymer, styrene-butadiene block copolymer, styrene-butadiene-styrene block copolymer, styrene-ethylene-butylene-styrene block copolymer, styrene-isoprene block copolymer, and styrene-ethylene-propylene-styrene block copolymer.

[0183] Examples of the above acrylate polymer may include a polymer containing monomer units derived from acrylic acid ester and / or methacrylic acid ester. The proportion of monomer units derived from acrylic acid ester and / or methacrylic acid ester in the acrylate polymer may usually be 40 wt% or more, preferably 50 wt% or more, and more preferably 60 wt% or more. Specific examples of acrylate polymers include crosslinked acrylate polymers such as 2-ethylhexyl acrylate-methacrylic acid-acrylonitrile-ethylene glycol dimethacrylate copolymer, 2-ethylhexyl acrylate-methacrylic acid-methacrylonitrile-diethylene glycol dimethacrylate copolymer, 2-ethylhexyl acrylate-styrene-methacrylic acid-ethylene glycol dimethacrylate copolymer, butyl acrylate-acrylonitrile-diethylene glycol dimethacrylate copolymer, and butyl acrylate-acrylic acid-trimethylolpropane trimethacrylate copolymer; Examples thereof include copolymers of ethylene and (meth)acrylic acid esters, such as ethylene-methyl acrylate copolymers, ethylene-methyl methacrylate copolymers, ethylene-ethyl acrylate copolymers, and ethylene-ethyl methacrylate copolymers; graft polymers obtained by grafting a radically polymerizable monomer onto the above copolymers of ethylene and (meth)acrylic acid esters; and the like. Meanwhile, examples of the radically polymerizable monomer used in the graft polymers include methyl methacrylate, acrylonitrile, and methacrylic acid. In addition, copolymers of ethylene and (meth)acrylic acid, such as ethylene-acrylic acid copolymers and ethylene-methacrylic acid copolymers, can be used as dispersion-type binders.

[0184] The above olefin polymer may include at least one of polyethylene, polypropylene, and polybutylene. In one embodiment of the present invention, the electrode powder including a fiberizing binder may include the polyethylene polymer.

[0185]

[0186] The fluorine-based polymer may include polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), and a polyvinylidene fluoride copolymer such as PVDF-HFP, and specifically, may include polytetrafluoroethylene (PTFE), and more specifically, may be polytetrafluoroethylene (PTFE). In one embodiment of the present invention, the electrode powder including a fiberizing binder may include polytetrafluoroethylene.

[0187]

[0188] Meanwhile, in one embodiment of the present invention, the binder resin may contain two or more different materials. Specifically, the electrode granule particles may contain two or more different binder materials within a single particle. For example, the electrode granule may contain a binder material of styrene-butadiene rubber (SBR) and an acrylate polymer mixed in a predetermined ratio.

[0189]

[0190] In one embodiment of the present invention, when the electrode is a fiber electrode powder type electrode, the electrode binder may include a fluorinated copolymer. In a specific embodiment, the electrode may include PTFE among the fluorinated copolymers, and more preferably, PTFE may be included in an amount of 60 wt% or more based on the total binder weight. Meanwhile, it goes without saying that the electrode binder may further include a fluorinated copolymer, a styrene copolymer, a polyolefin copolymer, PEO (polyethylene oxide), an acrylate copolymer, etc. other than PTFE.

[0191]

[0192] Meanwhile, in one embodiment of the present invention, when the electrode is formed by accumulating granules, the electrode binder may include at least one of a diene polymer and a styrene polymer, and may contain at least 60 wt% of these based on the total binder weight. In a specific embodiment, the electrode binder may contain at least 60 wt% of a styrene-butadiene block copolymer based on the total binder weight. Meanwhile, the electrode binder may, of course, further contain a fluorine-based copolymer, a polyolefin-based copolymer, PEO (polyethylene oxide), an acrylate-based copolymer, etc.

[0193]

[0194] Meanwhile, according to one embodiment of the present invention, when the electrode binder includes an electrode binder having a double bond, for example, when the electrode is a negative electrode, the negative electrode active material layer may have a first QBR (Quantified Binder Ratio) of 2.0 or less.

[0195]

[0196] The above first QBR is defined by the following mathematical formula.

[0197]

[0198] (Formula 2) 1st QBR = ABs / ABf

[0199]

[0200] In the above mathematical formula, ABs represents the average value of the double bond content in the negative electrode active material layer surface region from the outermost surface of the negative electrode active material layer to within 15% of the total thickness of the negative electrode active material layer, and ABf represents the average value of the double bond content in the negative electrode active material layer bottom region from the negative electrode active material layer interface facing the current collector to within 15% of the total thickness of the negative electrode active material layer.

[0201]

[0202] Fig. 6 is a schematic diagram of an electrode according to one embodiment of the present invention. Referring to Fig. 6, the electrode (10) includes an electrode current collector (12); and an electrode active material layer (11) positioned on the electrode current collector (12) and including an electrode active material and a fluorine-containing electrode binder.

[0203] The above 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 within 15% of the total thickness (d) of the electrode active material layer, and an electrode active material layer bottom area (11f) from the electrode active material layer interface facing the electrode current collector to within 15% of the total thickness (d) of the electrode active material layer, based on the total thickness (d).

[0204]

[0205] In the above mathematical expression 1 QBR, ABs means the average value of the content of double bonds of the binder in the surface area (11s) of the electrode active material layer, and ABf means the average value of the content of double bonds of the binder in the bottom area (11f) of the electrode active material layer.

[0206]

[0207] At this time, the first QBR can be calculated using the following method.

[0208]

[0209] First, an electrode for which the first QBR is to be confirmed is selected, and a cross-section of the selected negative electrode is manufactured using argon ion milling. Then, the components within the negative electrode active material layer of the manufactured electrode cross-section are mapped using an energy dispersive X-ray spectroscopy (EDS) detector of a scanning electron microscope (SEM).

[0210] From the EDS mapping results, a line profile is extracted in the direction of the thickness of the negative electrode active material layer, and among the extracted line profile results, the average value (Bs) of the double bond content of the binder in the surface area of ​​the electrode layer and the average value (Bf) of the double bond content of the binder in the bottom area of ​​the electrode layer are extracted, and the first QBR value is calculated using the following equation.

[0211]

[0212] 1st QBR = ABs / ABf

[0213]

[0214] At this time, the surface area of ​​the electrode active material layer is an area from the outermost surface in the thickness direction of the electrode active material layer to within 15% of the total thickness of the electrode active material layer, and the bottom area of ​​the electrode active material layer is an area from the interface of the electrode active material layer facing the current collector to within 15% of the total thickness of the electrode active material layer.

[0215]

[0216] The above first QBR value is a numerical value that represents the uniformity of the electrode binder distribution in the thickness direction within the electrode active material layer through the ratio of the content of the electrode binder contained in the surface region to the content of the electrode binder contained in the bottom region of the electrode active material layer. At this time, the content of the electrode binder can be inferred through the double bond component contained in the electrode binder used.

[0217] The first QBR value may be 2.0 or less, or 0.6 to 2.0, or 0.9 to 2.0, or 0.6 to 1.4, or 0.6 to 1.4, or 0.9 to 1.4, or 0.9 to 1.1.

[0218] When the above first QBR satisfies this range, the binder migrates to the electrode surface, so that the content of the electrode binder contained in the surface area is not large compared to the content of the electrode binder contained in the bottom area of ​​the electrode active material layer, and the distribution of the binder in the thickness direction of the electrode active material layer is uniform, and as a result, the adhesive force between the current collector and the electrode active material layer is improved, and the conductivity on the surface of the electrode active material layer and the charge / discharge rate accordingly can also be increased, which is advantageous.

[0219] Meanwhile, in one embodiment of the present invention, the electrode may include an electrode binder having a double bond as a binder material, for example, a styrene-butadiene copolymer, and in this case, the second QBR value may be 2.0 or less.

[0220]

[0221] According to one embodiment of the present invention, when the electrode includes a fluorine-based binder as a binder material, the electrode active material layer has a second QBR (Quantified Binder Ratio) of 1.1 or less, and the second QBR can be defined by the following mathematical formula:

[0222]

[0223] (Formula 3) 2nd QBR = CBs / CBf

[0224]

[0225] In the above mathematical formula, CBs represents the average value of the fluorine content of the electrode binder in the electrode layer surface area from the outermost surface of the electrode active material layer to within 15% of the total thickness of the electrode layer, and CBf represents the average value of the fluorine content of the electrode binder in the electrode active material layer bottom area from the electrode active material layer interface facing the electrode current collector to within 15% of the total thickness of the electrode active material layer.

[0226] The second QBR value is 1.1 or less, and according to one embodiment of the present invention, the first QBR value may be 0.95 or more, 0.97 or more, 1.03 or less, 1.05 or less, and may also be 0.95 to 1.05.

[0227] When the above second QBR value satisfies the range of 1.1 or less, the fluorine-containing electrode binder migrates to the electrode surface, so that the content of the fluorine-containing electrode binder contained in the surface region is not large compared to the content of the fluorine-containing electrode binder contained in the bottom region of the electrode active material layer, and the distribution of the binder in the thickness direction of the electrode active material layer is uniform, and as a result, the adhesive force between the current collector and the electrode active material layer is improved, and the conductivity on the surface of the electrode active material layer and the charge / discharge speed accordingly can also be increased, which is advantageous.

[0228] Meanwhile, in one embodiment of the present invention, the electrode may include a fluorine-based binder resin, and in this case, the second QBR value may be 1.1 or less.

[0229]

[0230] Fig. 7 is a schematic diagram for calculating the first or second QBR value of the electrode active material layer. Referring to Fig. 7, the X-axis represents the thickness of the electrode active material layer, i.e., the distance from the surface toward the current collector, and the Y-axis represents the intensity of the measured binder component, the intensity of the fluorine component, or the intensity of the double bond. Line A represents the intensity of the double bond component of the binder having the double bond extracted by EDS mapping the binder component in the electrode active material layer of the electrode cross-section, and line B is a trend line showing the tendency of line A, which is a line smoothed using the LOWESS smoothing method, i.e., the locally-weighted scatterplot smoother method. In Fig. 7, Bs represents the binder intensity of the electrode surface portion, and Bf represents the binder intensity of the lower part of the electrode (the current collector-facing portion).

[0231]

[0232] Meanwhile, in the present invention, the electrode binder may include a diene polymer and a cross-linked acrylate polymer from the viewpoint of being able to obtain an active material layer having excellent bonding properties with a current collector and surface smoothness, and also being able to manufacture an electrode for an electrochemical device having high electrostatic capacity and low internal resistance.

[0233]

[0234] The above electrode binder has no particular limitations on its shape, but is preferably particulate, as it has good binding properties and can suppress deterioration due to reduction in the electrostatic capacity of the formed electrode or deterioration caused by repeated charge and discharge. Examples of the particulate electrode binder include, for example, a binder in a state in which dispersed binder particles are dispersed in water, such as latex, or a powder obtained by drying such a dispersion. Such a particulate binder can preferably be included in the negative electrode.

[0235] Meanwhile, in some cases, the electrode active material layer may additionally contain a filler that suppresses expansion of the electrode active material layer. The filler is not particularly limited as long as it is a fibrous material that does not cause chemical changes in the battery, and examples thereof include olefin polymers such as polyethylene and polypropylene; and fibrous materials such as glass fiber and carbon fiber.

[0236]

[0237] The current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, copper, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. can be used. The current collector can also form fine unevenness on its surface to increase the adhesiveness of the electrode active material, and various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric are possible.

[0238]

[0239] Meanwhile, in one embodiment of the present invention, the entire collector may be coated with a conductive primer, either entirely or partially.

[0240] The primer layer includes a binder for the primer layer (hereinafter, the second binder) and a conductive material for the primer layer (hereinafter, the second conductive material), and the sum of the contents of the second binder and the second conductive material in the primer layer may be 90 wt% or more.

[0241] An electrode according to one embodiment of the present invention includes an electrode active material layer including electrode granules, wherein the primer layer includes a second binder and a second conductive agent, and the sum of the contents of the second binder and the second conductive agent is 90 wt% or more, thereby ensuring stability of the primer layer over time, and thus exhibiting excellent physical properties such as adhesive strength and lifespan characteristics, but the present invention is not limited thereto.

[0242] According to one embodiment of the present invention, the primer layer includes a second binder and a second conductive material, and may further include a dispersant.

[0243] According to another embodiment of the present invention, the primer layer may include a second binder and a second conductive agent, but may substantially not include a dispersant.

[0244] According to one embodiment of the present invention, the second binder may be used without particular limitation as long as it is a known binder used in a primer layer.

[0245] According to another embodiment of the present invention, it may be preferable for the second binder to use a polymer capable of ensuring stability of the primer layer over time. Specifically, the second binder may have a glass transition temperature (Tg) of 45°C or less.

[0246] According to another embodiment of the present invention, the second binder is, for example, styrene butadiene rubber (SBR), butadiene rubber (BR), nitrile butadiene rubber (NBR), styrene butadiene styrene block polymer (SBS), styrene ethylene butadiene block polymer (SEB), styrene-(styrene butadiene)-styrene block polymer, natural rubber (NR), isoprene rubber (IR), ethylene-propylene-diene terpolymer (EPDM), poly(ethylene-co-propylene-co-5-methylene-2-norbornene) polytetrafluoroethylene (PTFE), polyvinylidene fluoride, polyvinyl chloride, polyvinylidene fluoride-hexafluoropropylene fluoride-co-hexafluoropropylene), polyvinylidene fluoride-co-trichloroethylene, polymethylmethacrylate, polyethylhexylacrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene, polypropylene, polyethylene-co-vinyl acetate, polyethylene oxide, polypropylene oxide, polyarylate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, or two or more thereof.Specifically, the binder may include styrene butadiene rubber (SBR), nitrile butadiene rubber (NBR), polymethylmethacrylate, polyethylhexylacrylate, polybutylacrylate, or two or more thereof.

[0247] According to another embodiment of the present invention, the second binder may be a mixture of one or two or more types selected from the above-described types while having the above-described glass transition temperature value.

[0248] According to another embodiment of the present invention, the second binder may be styrene butadiene rubber (SBR) having a glass transition temperature (Tg) of -40°C to 45°C, nitrile butadiene rubber (NBR) having a glass transition temperature (Tg) of -40°C to 45°C, or a mixture thereof.

[0249] According to one embodiment of the present invention, the second conductive material has a specific surface area of ​​30 m 2 / g to 1,400 m 2 / g and may have a spherical shape. At this time, the size of the primary particle of the conductive material having a spherical shape may be, for example, 10 nm to 100 nm, specifically 15 nm to 70 nm, but is not limited thereto.

[0250] According to another embodiment of the present invention, the second conductive material has a specific surface area of ​​10 m 2 / g to 400 m 2 / g may have a tubular shape. At this time, the conductive material having a tubular shape may have a cross-sectional diameter in a direction orthogonal to the longitudinal direction of 0.1 to 3 nm, specifically 0.3 to 1.5 nm, but is not limited thereto.

[0251] The second conductive material is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and for example, graphite such as natural graphite or artificial graphite; carbon black-based carbon compounds such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black; conductive fibers such as carbon fibers or metal fibers; metal powders such as fluorocarbon, aluminum, and nickel powders; conductive whiskeys such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives may be used. However, specifically, in order to uniformly mix the conductive material and improve conductivity, the conductive material may include activated carbon, graphite, carbon black, carbon nanotubes, or a mixture of two or more thereof, and more specifically, the conductive material may include activated carbon.

[0252] According to one embodiment of the present invention, the primer layer includes the above-described composition and may have a thickness of 300 nm to 1.5 ㎛, specifically 700 nm to 1.3 ㎛, but is not limited thereto.

[0253]

[0254] <Method for manufacturing granules for electrodes>

[0255] According to one embodiment of the present invention, the electrode granules can be manufactured by a method including a step of preparing a slurry by mixing an electrode active material and an electrode binder with a dispersion medium; and a step of spray drying the slurry.

[0256] First, the electrode active material and electrode binder, and optionally an additional conductive material or additive, are dispersed or dissolved in a dispersion medium (a solvent for the negative electrode binder), thereby obtaining a slurry in which the electrode active material and electrode binder, together with the electrode conductive material and / or other additives, are dispersed or dissolved.

[0257] As the dispersion medium used to obtain the above slurry, water is most preferably used, but an organic solvent may also be used. Examples of the organic solvent include alkyl alcohols such as methyl alcohol, ethyl alcohol, and propyl alcohol; alkyl ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran, dioxane, and diglyme; amides such as diethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone (hereinafter also referred to as NMP), and dimethylimidazolidinone; sulfur-based solvents such as dimethyl sulfoxide and sulfolane; and the like, but alcohols are preferred. When an organic solvent having a boiling point lower than water is used in combination, the drying speed during fluid granulation can be accelerated. In addition, since the dispersibility or solubility of the negative electrode binder can be changed, the viscosity and fluidity of the slurry can be adjusted depending on the amount or type of the dispersion medium, thereby improving production efficiency.

[0258] The amount of the dispersion medium used when preparing the above slurry may be an amount such that the solid concentration of the slurry is usually in the range of 1 to 50 wt%, or 5 to 50 wt%, or 10 to 30 wt%.

[0259] The method or order of dispersing or dissolving the electrode active material and electrode binder, etc. in the dispersion medium is not particularly limited, and examples thereof include a method of adding the electrode active material and electrode binder to the dispersion medium and mixing them, a method of dissolving or dispersing the electrode binder in the dispersion medium, and then finally adding the electrode active material and mixing them, etc. When the slurry contains a conductive material and / or additives, these components may be added when the electrode active material is added. Examples of the mixing means include mixing devices such as a ball mill, a sand mill, a bead mill, a pigment disperser, a stone mill, an ultrasonic disperser, a homogenizer, and a planetary mixer. The mixing may be performed, for example, at a temperature ranging from room temperature to 80°C for 10 minutes to several hours.

[0260] Next, the slurry is spray-dried. Spray drying is a method of drying by spraying the slurry into hot air. The spraying method of the device used in spray drying includes a rotating disc method and a nozzle pressurization method. The rotating disc method is a method in which the slurry is introduced almost to the center of a high-speed rotating disc, and the slurry is placed outside the disc by the centrifugal force of the disc, and then dried in the form of a mist. The rotation speed of the disc depends on the size of the disc, but is usually 5,000 rpm to 35,000 rpm, preferably 15,000 rpm to 30,000 rpm. On the other hand, the nozzle pressurization method is a method in which the slurry is passed through a thin nozzle while simultaneously spraying a high-pressure fluid such as air or another liquid to spray it in the form of a mist, thereby drying.

[0261] In one embodiment of the present invention, the temperature of the hot air can be controlled to 80°C to 250°C based on the reactor inlet temperature (at the time of injection) in terms of forming an electrode granule structure having a high electrode binder content on the surface. In the present invention, considering the binder content gradient and aspect ratio, it can be preferably controlled to 175°C to 220°C, more preferably 180°C to 220°C. In the spray drying method, the method of sucking the hot air is not particularly limited, and examples thereof include a method in which the hot air and the spray direction are parallel to each other horizontally, a method in which the hot air is sprayed from the top of the drying tower and then descends together with the hot air, a method in which the sprayed droplets come into countercurrent contact with the hot air, and a method in which the sprayed droplets initially come into parallel with the hot air and then fall by gravity to come into countercurrent contact. Meanwhile, in one embodiment of the present invention, the outlet temperature of the reactor during the spray drying (the temperature of the hot air discharged from the reactor) can be controlled to 90°C to 130°C.

[0262] If the outlet temperature and / or the difference between the inlet and outlet temperatures, ΔT, is low, drying may not be performed properly, resulting in the formation of particles with a large amount of residual solvent, which may prevent uniformly shaped spherical particles from being formed and may result in the formation of electrode granules that are agglomerated or irregularly shaped. On the other hand, if the inlet temperature is too high and ΔT is large, overdrying may result in particles that are not assembled and have a very small D50 and a low aspect ratio. Therefore, in order to achieve a high aspect ratio, minimize binder agglomeration, and control the particle size at an appropriate level, it is necessary to control the inlet and outlet temperatures within an appropriate range.

[0263]

[0264] Additionally, the surface of the resulting product obtained by optional spray drying, i.e., granules for electrodes, can be heat-treated to harden it. At this time, the heat treatment temperature can usually be from 80°C to 300°C.

[0265]

[0266] <Method for manufacturing electrodes>

[0267] According to one embodiment of the present invention, the method for manufacturing the electrode may include a step of dispersing an electrode material including a plurality of electrode granules or electrode powders or both described above on a current collector; and a step of pressing the dispersed electrode material to form an electrode active material layer.

[0268] Any one of the electrode materials manufactured by the above-described method is dispersed on a current collector. At this time, a primer layer including a second conductive material and a second binder as described above may be provided on at least one entire or partial surface of the current collector.

[0269] According to one embodiment of the present invention, prepared electrode granules can be supplied to a roll-type pressure molding device using a supply device such as a screw feeder to form an active material layer, and at this time, the current collector can be sent to the roll of the pressure molding device at the same time as the supply of the electrode granules, thereby directly laminating the active material layer on the current collector. Alternatively, the electrode granules can be dispersed on the current collector, the thickness can be adjusted evenly using a blade or the like, and then formed using a pressure device to form an electrode active material layer.

[0270] In these methods, the temperature during roll pressure forming is usually 0°C to 200°C, preferably higher than the melting point or glass transition temperature of the electrode binder, and more preferably 20°C or higher than the melting point or glass transition temperature. The forming speed during roll pressure forming may usually be 0.1 to 20 m / min, or 1 to 10 m / min. In addition, the press line pressure between the rolls may usually be 0.2 to 30 kN / cm, or 0.5 to 10 kN / cm.

[0271] To eliminate the gap in thickness of the molded electrode and increase the density of the electrode active material layer to achieve higher capacity, additional pressurization may be performed as needed. A common post-pressurization method is a roll press process. In the roll press process, two cylindrical rolls are aligned vertically and parallel with a narrow gap between them, each rotating in opposite directions. The electrode is then interlocked and pressed between them. The rolls can also be used for temperature control, such as heating or cooling.

[0272] Alternatively, a dry electrode can be manufactured by calendering and pressing a manufactured electrode material to manufacture a dry electrode film, and then laminating the dry electrode film and the current collector.

[0273] This calendering is a process of processing the electrode material into a film form, and can be pressed into a film form to have an average thickness of, for example, 50 μm to 300 μm. In one embodiment of the present invention, the calendering can be performed using a calender device including a roll press section in which two rollers are arranged to face each other. The calender device can include at least one roll press section. For example, a plurality of roll press sections are arranged continuously so that pressing of the electrode mixture powder can be performed in multiple stages. Meanwhile, one or more rollers in the calendering device can be independently controlled in temperature from 50°C to 200°C. In addition or independently of this, the rotational speed ratio of the two rollers in the one or more roll press sections can be controlled at a ratio of 1:1 to 1:3. When the calendering step is performed as described above, a dry electrode film that functions as an electrode mixture can be manufactured. This dry electrode film is also called a free-standing film or a self-supporting film. Such a dry electrode film may have sufficient mechanical strength to be used in the manufacturing process of an energy storage device without any external support elements such as a current collector, a support web, or other structures. Alternatively, it may be combined with a support such as a current collector and used in the manufacture of a battery. Meanwhile, in one embodiment of the present invention, the obtained dry electrode film has a crystallinity (d) of the binder resin in the dry electrode film of 10% or less. If the crystallinity of the obtained dry electrode film exceeds 10%, the crystallinity can be controlled by adjusting the gap between the two rollers of the roll press unit or by controlling the speed ratio. For example, the degree of fiberization of the binder can be increased by reducing the gap and / or increasing the speed ratio.

[0274]

[0275] According to another embodiment of the present invention, a secondary battery is provided, in which an electrode assembly including the positive electrode, the negative electrode, and the insulating film is housed in a battery case (cylindrical case, square case, pouch, etc.), and an energy storage device including the same as a unit battery. At this time, at least one of the positive electrode and the negative electrode may be the electrode described above. For example, the negative electrode may be a dry electrode. Meanwhile, the battery may further include a lithium-containing non-aqueous electrolyte.

[0276]

[0277] When a separator is included in the above electrode assembly, the separator may be a conventional porous polymer film used as a conventional separator, for example, a porous polymer film made of a polyolefin polymer such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, which may be used alone or in a laminated manner. In addition, an insulating thin film having high ion permeability and mechanical strength may be used. The separator may include a safety reinforced separator (SRS) in which a ceramic material is thinly coated on the surface of the separator. In addition, a conventional porous non-woven fabric, for example, a non-woven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. may be used, but is not limited thereto.

[0278] Alternatively, if the insulating film is a solid electrolyte film, the solid electrolyte film may include a solid electrolyte material, and the solid electrolyte material may include one or more of an oxide-based solid electrolyte, a sulfide-based solid electrolyte, and a polymer-based solid electrolyte. In addition, if the lithium ion secondary battery is an all-solid-state battery, the dry electrode of the present invention may further include the above-described solid electrolyte material.

[0279] The above electrolyte solution includes a lithium salt as an electrolyte and an organic solvent for dissolving the same.

[0280] The above lithium salt can be used without limitation as long as it is one commonly used in electrolytes for secondary batteries, and for example, the anion of the above lithium salt is F - , Cl - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - One type selected from the group consisting of can be used.

[0281] As the organic solvent included in the above electrolyte, any commonly used one can be used without limitation, and representative examples thereof include at least one selected from the group consisting of propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, methylpropyl carbonate, dipropyl carbonate, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, vinylene carbonate, sulfolane, gamma-butyrolactone, propylene sulfite, and tetrahydrofuran.

[0282] In particular, among the above carbonate-based organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, are high-viscosity organic solvents with high dielectric constants and thus can be preferably used because they easily dissociate lithium salts in the electrolyte. In addition, when a low-viscosity, low-dielectric constant linear carbonate such as dimethyl carbonate and diethyl carbonate is mixed and used in an appropriate ratio with these cyclic carbonates, an electrolyte having high electrical conductivity can be produced, so that the electrolyte can be used even more preferably.

[0283] Optionally, the electrolyte stored according to the present invention may further include additives such as an overcharge prevention agent included in a conventional electrolyte.

[0284] According to one embodiment of the present invention, a lithium ion secondary battery is formed by placing a separator between a positive electrode and a negative electrode to form an electrode assembly, placing the electrode assembly in, for example, a pouch, a cylindrical battery case, or a square battery case, and then injecting an electrolyte to complete the secondary battery. Alternatively, the electrode assembly may be laminated, then impregnated with an electrolyte, and the resulting product may be placed in a battery case and sealed to complete the lithium ion secondary battery.

[0285]

[0286] Meanwhile, since the specific structure of the lithium ion secondary battery and energy storage device in the present invention is known in the prior art, a description thereof is omitted in this specification.

[0287]

[0288] In the present invention, the above-described embodiments may each be implemented independently. Alternatively, two or more of the above-described embodiments may be implemented in combination.

[0289] Hereinafter, the present invention will be described in detail with examples to specifically illustrate it. However, the examples according to the present invention may be modified in various ways, and the scope of the present invention should not be construed as being limited to the examples described below. These examples are provided to more fully explain the present invention to those of average skill in the art.

[0290]

[0291] [Example 1]

[0292] 1. Cathode

[0293] (1) Preparation of the entire collector with primer layer

[0294] As a second challenge material, carbon black (specific surface area: 30 m 2 / g, particle size: (70 nm)), 30 parts by weight, styrene-butadiene rubber (SBR) (T) as a second binder g : -15℃) 69 parts by weight of a conductive agent, 1 part by weight of carboxymethyl cellulose (CMC) as a dispersant, and water as a dispersing medium were mixed to prepare a slurry for a primer layer. At this time, the content ratio of the conductive agent, binder, and dispersant in the slurry was the same as the content ratio of the conductive agent, binder, and dispersant in the primer layer formed thereafter. The solid content ratio of the slurry for the primer layer was 7 wt%.

[0295] The prepared slurry for the primer layer was applied to one surface of a copper current collector (thickness: 10 μm) and dried at 130°C to form a primer layer on the entire surface of the copper current collector.

[0296]

[0297] (2) Preparation of granules for electrodes for the negative electrode active material layer

[0298] 1.91 parts by weight of natural graphite with a sphericity of 0.95 as a negative active material, 76.5 parts by weight of artificial graphite with an average sphericity of 0.9, carbon black (SuperC65) as a negative conductive material, carboxymethyl cellulose (daicel2200, aqueous solution, solid content 1.5 wt%) as a negative dispersant, and modified styrene butadiene copolymer (Grade Name: AX-B119) as a negative binder were mixed with water as a dispersion medium in a weight ratio of 95.6:1.0:1.1:2.3, and a slurry having a viscosity of about 1000 cPs was prepared through a homogenizer. At this time, the solid content in the slurry was 30 wt%. In the above weight ratio, carboxymethyl cellulose is calculated on a solid content basis.

[0299] The manufactured slurry was introduced into a spray dryer together with hot air under a pressure range of -40 mmH2O and dried. At this time, the conditions of the spray dryer were controlled as an inlet temperature of 180°C, an outlet temperature of 90°C, and a rotation speed of 18,000 rpm. The obtained electrode granules were sieved using an industrial sieve to remove coarse particles larger than 150 μm, and fine particles smaller than 40 μm were separated again. The separated fine particles were mixed with the electrode granules from which only the coarse particles were removed, to finally prepare anode granules containing a larger amount of fine particles than the conventional electrode granules. The electrode granules had a central portion including a plurality of cathode active materials and cathode conductive materials, and a surface portion including a cathode binder located on the outside of the central portion to bind the cathode active materials and cathode conductive materials. The average particle diameter (D50) of the obtained electrode granules was 66.5 μm, and the aspect ratio was 0.96. Fig. 8 shows a cross-sectional image of the electrode granule particles manufactured in Example 1, which was processed using the EPMA (electron probe micro analyze) method described below. The closed curves shown in the image connect points having the same distance from the surface.

[0300]

[0301] (3) Manufacturing of cathode

[0302] Using a thickness adjustment bar on one side of the collector having the above primer layer, the collector is 25 cm 2 The previously prepared electrode granules were evenly applied in an amount of 400 mg per unit, and a sheeting machine, a roll-to-roll hot rolling forming device, was used to form a negative electrode active material layer by applying pressure of 0.7 tons per cm at a temperature of 60°C and a speed of 2 m per minute, thereby manufacturing a negative electrode.

[0303]

[0304] [Example 2]

[0305] Granules for electrodes were manufactured in the same manner as in Example 1, except that the inlet temperature of the spray dryer was controlled at 180°C and the outlet temperature was controlled at 130°C. The average particle diameter (D50) of the obtained granules for electrodes was 61.4 μm, and the aspect ratio was 0.99. Fig. 9 shows a cross-sectional image of the granule particles for electrodes manufactured in Example 2, processed by the EPMA method described below. The closed curves shown in the image connect points having the same distance from the surface.

[0306]

[0307] [Example 3]

[0308] Granules for electrodes were manufactured in the same manner as in Example 1, except that the inlet temperature of the spray dryer was controlled at 200°C and the outlet temperature was controlled at 110°C. The average particle diameter (D50) of the obtained granules for electrodes was 35.8 μm, and the aspect ratio was 0.77.

[0309]

[0310] Figure 10 shows a cross-sectional image of the granule particles for electrodes manufactured in Example 3, processed using the EPMA method described below. The closed curves shown in the image connect points having the same distance from the surface to the center of the granule particles for electrodes.

[0311]

[0312] [Example 4]

[0313] 96 g of natural graphite, 1 g of carbon black as a conductive material, and 3 g of polytetrafluoroethylene (PTFE) as a binder were placed in a blender and mixed at 10,000 rpm for 1 minute to prepare a mixture. The temperature of the kneader was stabilized at 80°C, and the mixture was placed in the kneader and operated at 25 rpm for 5 minutes under a cover pressure of 1.1 atm to obtain a mixture lump. The mixture lump was placed in a blender and ground at 10,000 rpm for 30 seconds to obtain a mixed powder for electrodes. The obtained mixed powder for electrodes was classified into particles of 150 μm to 1000 μm using a multi-stage classifier. Thereafter, the classified powder for electrodes was placed in a lab calender (roll diameter: 200 mm, roll temperature: 100°C, roll speed ratio: 1.5) and subjected to several calendering processes to produce an electrode film.

[0314]

[0315] The two electrode films were positioned on both sides of the current collector coated with the primer layer, and laminated using a compression roll maintained at 100°C to manufacture a negative electrode. At this time, the rolling ratio of the electrode film in the lamination step was 39%. The rolling ratio of the electrode film was calculated as the ratio of the thickness of the electrode film after the lamination step to the thickness of the electrode film before the lamination step.

[0316]

[0317] [Comparative Example 1]

[0318] Electrode granules were manufactured in the same manner as in Example 1, except that the inlet temperature of the spray dryer was controlled at 170°C and the outlet temperature was controlled at 70°C. The average particle diameter (D50) of the obtained electrode granules was 42.8 μm, and the aspect ratio was 0.75. In addition, a negative electrode was manufactured in the same manner as in Example 1, except that the electrode granules manufactured in Comparative Example 1 were used instead of the electrode granules manufactured in Example 1. In Comparative Example 1, the electrode granules were somewhat overdried, showing an aspect ratio of less than 0.75, and uniform spherical particles were not formed, and there was a large variation between particles. Fig. 11 shows a cross-sectional image of the electrode granule particles manufactured in Comparative Example 1 processed by the EPMA method described below. Referring to this, it was confirmed that the binder resin (light color) was distributed over the entire cross-section of the electrode granules. The closed curves shown in the image connect points having the same distance from the surface.

[0319] [Comparative Example 2]

[0320] Granules for electrodes were manufactured in the same manner as in Example 1, except that the inlet temperature of the spray dryer was controlled at 170°C and the outlet temperature was 140°C. The average particle diameter (D50) of the obtained granules for electrodes was 78.0 μm, and the aspect ratio was 0.37. In Comparative Example 2, the difference between the inlet and outlet temperatures was small, so the solvent was not sufficiently removed, resulting in the formation of particles with a large amount of residual solvent, and thus, spherical particles of a uniform shape were not formed, the moisture content was high, and there was agglomeration between the particles.

[0321] Figure 12 shows a cross-sectional image of the electrode granule particles manufactured in Comparative Example 2, processed using the EPMA method described below. Referring to this, it can be confirmed that the binder resin (light color) is distributed across the entire cross-section of the electrode granule. The closed curves shown in the image connect points that are the same distance from the surface.

[0322]

[0323] [Comparative Example 3]

[0324] A slurry having a solid content of 47 wt% was prepared by mixing 19.1 parts by weight of natural graphite with an average sphericity of 0.95 as a negative active material, 76.5 parts by weight of artificial graphite with an average sphericity of 0.9, 1 part by weight of carbon black (Super-C 65) as a negative conductive material, 2.3 parts by weight of styrene butadiene rubber (SBR) as a negative binder, 1.1 parts by weight of carboxymethyl cellulose (CMC) as a binder and thickener, and water as a dispersion medium.

[0325] The slurry is coated on one side of a copper (Cu) thin film, which is a negative electrode current collector with a thickness of 10 ㎛, and the upper and lower active material layers thus formed are simultaneously rolled by a roll pressing method using a drying device equipped with a hot air blower and an IR heater, so that the weight after drying per unit area is 400 mg / 25 cm 2 A negative electrode having a negative electrode active material layer having a loading amount was manufactured.

[0326]

[0327] [Confirmation of binder distribution in the negative electrode active material layer]

[0328] The cathodes manufactured in Examples 1, 4, and Comparative Example 3 were placed together in a glass vial using OsO4 crystals or an aqueous solution, and the reagent was evaporated to allow sufficient chemical reaction (deposition) for 3 hours or more. Thereafter, the cathodes reacted with Os were milled using argon ion milling to produce cross-sections of the cathodes of Examples and Comparative Examples.

[0329] Using the EDS detector of the SEM equipment, EDS mapping was performed on the components within the negative electrode active material layer of the negative electrode thickness direction cross-sections of Examples 1, 4, and Comparative Example 3.

[0330] Fig. 2 shows the EDS mapping results of the electrode of Example 1, and Fig. 4 shows the EDS mapping results of the electrode of Comparative Example 3. Referring to these, it can be confirmed that the binder resin was distributed on the surface of the electrode granules rather than in the center of the electrode granules in the electrode of Example 1. In addition, the electrode of Example 1 was manufactured by compressing the electrode granules, and it can be confirmed that the binder was evenly distributed in the direction of the electrode thickness. On the other hand, it was confirmed that the electrode of Comparative Example 3 had a high binder content ratio in the electrode surface. Unlike the electrode manufacturing method of Example 1, the electrode of Comparative Example 3 was manufactured by electrode slurry coating and drying, and such binder distribution was due to binder migration due to solvent evaporation.

[0331] Meanwhile, FIGS. 3 and 5 are graphs showing the average value of the Os content of the binder bonded to Os in the surface area of ​​the negative electrode active material layer (the area from the surface to 15% in the direction of the current collector) and the average value of the Os content of the binder bonded to Os in the bottom area of ​​the electrode layer (the area from the current collector to 15% in the direction of the surface) among the extracted line profile results, obtained by extracting a line profile from the EDS mapping results in the direction of the thickness of the negative electrode active material layer. FIG. 3 is for the electrode of Example 1, and FIG. 5 is for the electrode of Comparative Example 3. Referring to these, it was confirmed that the deviation of the binder distribution based on the electrode thickness direction in the electrode according to Example 1 was less than that in the electrode of Comparative Example 3.

[0332] Meanwhile, the electrode of Example 4 contained a fluorine-based binder, and as described above, EDS mapping was performed and a QBR calculation was performed, and a QBR value of 1.1 or less was confirmed.

[0333]

[0334] [Measurement of ohmic resistance and its rate of change (amount of change) according to changes in charging SOC (State of Charge)]

[0335] Lithium-ion secondary batteries were manufactured using the electrodes of Example 1, Example 2, Example 4, and Comparative Example 3, and the ohmic resistance and its change rate (change amount) according to the state of charge (SOC) of each battery were determined.

[0336]

[0337] LiNi as a cathode active material 0.8 Co 0.1 Mn 0.1 O2, carbon black as a conductive agent, and polyvinylidene fluoride (PVdF) as a binder were added to N-methylpyrrolidone (NMP) as a solvent at a weight ratio of 96:2:2 to prepare a positive electrode active material slurry. The positive electrode active material slurry was coated on a sheet-shaped aluminum current collector and dried to obtain a final positive electrode loading of 4.0 mAh / cm. 2 The polarity was prepared to make this happen.

[0338] _

[0339] A separator was interposed between the positive electrode manufactured above and the negative electrode manufactured in Examples 1, 2, 4 and Comparative Example 3, and an electrode assembly was manufactured by pressing at 70°C and a pressure of 6.5 MPa for 20 seconds. After the electrode assembly was formed into a coin cell, a non-aqueous electrolyte solution prepared by dissolving LiPF6 in an organic solvent (Eethylene carbonate: Diethyl carbonate = 1:1 (v:v)) to a concentration of 1 M was injected to manufacture a lithium secondary battery.

[0340] Next, the resistance value according to SOC was measured for each battery. First, the obtained battery was charged from 2.5 V to 4.2 V in CC-CV mode at 0.33 C-rate (0.05 C cut off), and after a 10-minute rest period, it was discharged from 4.2 V to 2.5 V in CC mode at 0.33 C-rate. This was repeated three times. The charge and discharge were performed at 25°C. After discharging the battery and a 30-minute rest period, the resistance value was confirmed using in situ EIS (Electrochemical impedance spectroscopy) measurement. Each battery was connected to two channels, and charging was performed on one channel, while measuring EIS at regular intervals on the other channel, thereby measuring EIS during charging. The measurement was performed at room temperature (25°C) at a 0.33 C-rate, from SOC 0% to SOC 100% in SOC 1% units. The above SOC is based on the battery capacity confirmed through the above battery charging and discharging.

[0341] EIS was performed using Solaton's 1470E cell test system and Frequency response analyzer 1255B, and the resistance was measured through electrochemical impedance spectroscopy analysis under the conditions of a scan range of 100,000 Hz to 10,000 Hz and an amplitude of 10 mV at 25°C. From the Nyquist plot obtained at this time, the values ​​and change rates (amount of change) of ohm resistance and CT resistance at each SOC were calculated, respectively. The ratio of the ohm resistance to the CT resistance was measured for changes in units of 1% of SOC. The ohm resistance change rate was calculated based on the following Equation 1.

[0342]

[0343] (Formula 1) Ohmic Resistance change = (R soc / R i)x 100

[0344]

[0345] In the above formula 1, R i is the ohmic resistance at the lowest SOC that can separate the ohmic resistance and charge transfer resistance from the Nyquist plot, and R soc represents the ohmic resistance at each SOC.

[0346] Fig. 19 shows the ratio of ohm resistance and CT resistance according to SOC measured through the batteries of Examples 1, 2, and 4. Meanwhile, SOC is expressed as a percentage (%) by dividing the currently usable battery capacity by the total capacity to indicate the remaining capacity of the battery. Referring to Fig. 19, it was confirmed that the batteries of Examples 1, 2, and 4 had a tendency for the ohm resistance to decrease as the SOC increased.

[0347] Meanwhile, Fig. 17 shows the ohm resistance measured for each SOC section for the batteries of Examples 1, 2, and 4. In addition, Fig. 18 shows the decrease rate of the ohm resistance for each SOC section for Examples 1, 2, 4, and Comparative Example 3. The lithium ion secondary battery according to the present invention may exhibit a tendency for the ohm resistance of the battery to decrease as the SOC increases during charging. In addition, it was confirmed that the lithium ion secondary battery according to the present invention has a negative (-) tendency in the ohm resistance change rate of the battery as the SOC increases during charging. Referring to the drawings, it was confirmed that the ohm resistance change rate of the batteries of Examples 1, 2, and 4 was greater in the initial section, the sections before SOC 20%, SOC 30%, SOC 40%, and SOC 50%, respectively, than in the sections after SOC 20%, SOC 30%, SOC 40%, and SOC 50%. On the other hand, it was confirmed that the resistance change rate according to SOC of the battery of Comparative Example 3 (consisting only of wet electrodes) was smaller than that of the embodiment.

[0348] As described above, the secondary battery according to the present invention can improve process convenience by omitting the slurry drying process during electrode manufacturing, and since the binder resin and the electrode active material are uniformly distributed in the thickness direction in the electrode active material layer, sufficient bonding force between the electrode active material layer and the current collector can be secured. In addition, as the charging SOC increases, the rate of decrease in ohmic resistance increases, which is advantageous for heat management during rapid charging of the battery.

[0349]

[0350] [Checking the distribution of binder in electrode granules]

[0351] Using EPMA (JXA-8350F, -15 kV, 20 nA stage mapping conditions), the radial profile of the electrode granule cross-section was analyzed to confirm the binder distribution within the electrode granule. First, the electrode granules obtained in each of Examples 1 and 2 were dyed with OsO4 to determine the binder within each granule. The dyeing was performed by placing the electrode granules in a glass vial with OsO4 crystals or an aqueous solution, and then evaporating the reagent to react. Afterwards, the granules were mixed with epoxy resin, fixed in a silicone mold, and cured to obtain an electrode granule matrix (see Fig. 15). Next, a cross-sectional sample was prepared using the electrode granule matrix using an ion milling device (Hitachi IM5000, accelerating voltage: 6 kV). The cross-sectional fabrication conditions were an accelerating voltage of 6 kV and an emission current of 400 μA, and the milling time was appropriately adjusted so that the mask was not completely destroyed. The fabricated cross-sectional sample was fixed to the EPMA device, the electrode granule was positioned at the center of the display, and a cross-sectional scan was performed using the stage mapping method. Upon completion of the scan, an image was created in the form of a mass map considering the atomic number effect, absorption effect, and fluorescence excitation effect. From the obtained mass map, 0 to 4 wt% of elements were designated with 0 to 255 5 contrast, and an Os map was extracted. The conventional backscatter electron image and the Os map obtained during the EPMA analysis were merged into one layer using Photoshop, and then a closed curve was drawn in 30-pixel units from the boundary of the electrode granule obtained here, and the Os content located at each closed curve was analyzed. The Os content was supplemented by introducing the surface area of ​​the closed curve at the corresponding location so that the relative amount at each location could be compared. Figure 13 shows the distribution (content) of the binder resin at each part along the radius of the electrode granule of each example and comparative example.Figure 14 shows the cumulative distribution of binder resin along the radius of the electrode granules of each example and comparative example. Referring to this, it can be confirmed that the electrode granules of examples 1, 2, and 4 have a higher binder content in the surface portion up to the electrode granule surface after 70% of the radius, especially after 80%, than in the center portion. On the other hand, the electrode granules obtained in comparative examples 1 and 2 were confirmed to have a higher binder content in the center portion than in the surface portion.

Claims

1. A lithium ion secondary battery including a dry electrode manufactured by a dry manufacturing method, The above dry electrode includes an electrode active material layer including an electrode active material and an electrode binder, The electrode active material layer includes granules according to the spray drying result of a composition including an electrode active material and an electrode binder, or includes a composite material in which an electrode active material and a fiberized electrode binder are combined, or includes both of the above. The above lithium ion secondary battery is a lithium ion secondary battery in which the ohmic resistance changes according to the change in the charging SOC (State of Charge).

2. In paragraph 1, A lithium ion secondary battery in which the above ohmic resistance changes as the state of charge (SOC) increases.

3. In paragraph 1, A lithium-ion secondary battery in which the above ohm resistance change rate is greater in the section before 50% SOC than in the section after 50% SOC.

4. In paragraph 1, A lithium ion secondary battery wherein the above electrode active material includes a negative electrode active material, and the dry electrode is a negative electrode.

5. In paragraph 1, The above dry electrode includes a current collector; and an electrode active material layer positioned on the current collector; wherein the electrode active material layer is an aggregate of the above granules; A lithium ion secondary battery, wherein the content of electrode binder in the surface portion of the granule is greater than the content of electrode binder in the center portion of the granule based on 100 wt% of the total weight of the electrode active material and the electrode binder, the surface portion is an area from the surface of the electrode granule to 20% of the radius in the direction of the center of the electrode granule, and the center is a portion other than the surface portion.

6. In paragraph 5, A lithium ion secondary battery, wherein the surface portion is an area extending from the surface of the electrode granule to 10% of the radius toward the center of the electrode granule.

7. In paragraph 5, A lithium ion secondary battery, wherein the electrode granules for the above electrode have an aspect ratio of 0.75 to 1.

0.

8. In paragraph 5, The above electrode granules have a particle size (D 50 ) is 0.1 to 1,000㎛.

9. In paragraph 1, A lithium ion secondary battery wherein the electrode active material layer includes two or more electrode active material materials.

10. In paragraph 1, The above lithium ion secondary battery is a lithium ion secondary battery in which the average value of the ohm resistance value in the SOC 0% to SOC 20% range is higher than the average value of the ohm resistance value in the SOC 80% range and thereafter.

11. In paragraph 1, The above lithium ion secondary battery is a lithium ion secondary battery having lower ohmic resistance in the section after SOC 10% compared to the section below SOC 10%.

12. In paragraph 1, The above lithium ion secondary battery is a lithium ion secondary battery in which the difference between the ohm resistance value at the SOC 80% point and the ohm resistance value at the SOC 5% point is 1% or more compared to the difference between the minimum and maximum values ​​of the ohm resistance throughout the entire SOC measurement period.

13. In paragraph 1, The above lithium ion secondary battery is a lithium ion secondary battery in which, when checking the resistance change rate graph for the entire SOC measurement period, at least one tangent line has a negative (-) slope.

14. In paragraph 1, The above lithium ion secondary battery is a lithium ion secondary battery in which the initial ohm resistance change rate in the SOC section is greater than that in the subsequent section.

Images