Magnetic alignment device for negative electrodes and method for manufacturing negative electrodes using the same

Abstract

The present invention relates to a magnetic alignment device used in manufacturing a negative electrode and a method for manufacturing a negative electrode using the same. The magnetic alignment device measures the alignment degree of a negative electrode active layer dried in a state in which a carbon-based negative electrode active material is aligned in real time, and can easily control the strength of a magnetic field by individually adjusting the separation distance of unit magnets constituting a magnet array of a magnet part according to the alignment degree of the carbon-based negative electrode active material thus measured, which is advantageous in that the alignment degree and uniformity of the crystal plane of the carbon-based negative electrode active material are high.

Description

[Technical Field]

[0001] This application claims priority under Korean Patent Application No. 10-2022-0116176 dated September 15, 2022, and all content disclosed in the said Korean Patent Application is incorporated herein as part of this specification.

[0002] The present invention relates to a magnetic alignment device capable of uniformly aligning negative electrode active material in the negative electrode active layer during negative electrode manufacturing, and to a method for manufacturing a negative electrode using the same. [Background technology]

[0003] In recent years, secondary batteries have been widely applied not only to small devices such as portable electronic devices, but also to medium- and large-scale devices such as battery packs for hybrid and electric vehicles, or power storage devices.

[0004] Such a secondary battery is a power generation element capable of charging and discharging, consisting of a stacked structure of a positive electrode / separating membrane / negative electrode. Generally, the positive electrode contains lithium metal oxide as the positive electrode active material, and the negative electrode contains a carbon-based negative electrode active material such as graphite. During charging, lithium ions released from the positive electrode are absorbed into the carbon-based negative electrode active material of the negative electrode, and during discharging, lithium ions contained in the carbon-based negative electrode active material are absorbed into the lithium metal oxide of the positive electrode, resulting in a configuration in which charging and discharging are repeated.

[0005] In this case, graphite materials such as natural graphite can be used as the negative electrode active material. Such graphite has a layered structure in which carbon atoms form a network structure, and is formed by stacking many planar layers. During charging, lithium ions enter from the edge surfaces (surfaces where the layers overlap) of such graphite layers and diffuse between the layers. During discharge, lithium ions can be released from the edge surfaces of the layers. In addition, because the electrical resistivity of graphite in the plane direction of the layers is lower than in the direction of stacking the layers, a conduction path for electrons that bypasses the plane direction of the layers is formed.

[0006] In this regard, a technique has been proposed for conventional lithium secondary batteries using graphite to improve the charging performance of the negative electrode by orienting the graphite contained in the negative electrode using a magnetic field. Specifically, the negative electrode is formed by orienting the (002) crystal plane of the graphite in a magnetic field so that it is almost perpendicular to the negative electrode current collector, and then fixing it in place. In this case, the edge surface of the graphite layer faces the positive electrode active layer, so that lithium ions are inserted and removed smoothly, and at the same time the electron conduction path is shortened, which can improve the electron conductivity of the negative electrode, thereby improving the charging performance of the battery.

[0007] However, while it is possible to induce graphite orientation by applying a magnetic field to an undried anode slurry, the conditions for the applied magnetic field can vary depending on various variables such as the loading amount and thickness of the graphite-containing anode slurry. However, there is a limitation in that it is difficult to reflect such variables in real time during actual anode manufacturing, which makes it difficult to uniformly realize graphite orientation in the anode active layer.

[0008] Furthermore, a single negative electrode manufacturing device will produce a variety of negative electrode models with different specifications, but it is not easy to control the magnetic field application means, i.e., permanent magnets, provided in the manufacturing device according to the specifications of the negative electrodes being manufactured.

[0009] Therefore, there is a need for a technology that allows for easy control of the magnetic field application means according to the specifications of the manufactured anode, such as the thickness of the anode active layer, and / or the manufacturing conditions of the anode, such as the loading amount of the anode slurry, and that can manufacture an anode active layer in which carbon-based anode active materials such as graphite, aligned with a high degree of alignment, are uniformly distributed. [Overview of the Initiative] [Problems that the invention aims to solve]

[0010] The object of the present invention is to provide an alignment device that can uniformly align carbon-based anode active material within the anode active layer by easily adjusting the strength of the magnetic field applied to the anode slurry during anode manufacturing, and a method for manufacturing an anode using the same. [Means for solving the problem]

[0011] To solve the above-mentioned problems, in one embodiment, the present invention, A magnetic alignment device for a negative electrode, which applies a magnetic force to a negative electrode sheet coated with a negative electrode slurry containing a carbon-based negative electrode active material on a negative electrode current collector, thereby orienting the carbon-based negative electrode active material, A first magnet section and a second magnet section are positioned at the top and bottom of the electrode sheet while it is in motion, An alignment measurement unit is positioned downstream of the first and second magnet sections, with reference to the direction of travel of the electrode sheet, and measures the degree of alignment of the carbon-based negative electrode active material relative to the negative electrode current collector. The system includes a control unit that adjusts the separation distance between the first magnet unit and the second magnet unit according to the degree of alignment of the carbon-based negative electrode active material measured by the alignment measurement unit, The first and second magnet sections described above each include a plurality of unit magnets arranged in the width direction of the negative electrode slurry, and the unit magnets individually perform vertical vertical movement relative to the moving electrode sheet to adjust the separation distance between them and opposing unit magnets around the electrode sheet, thereby providing a magnetic alignment device for the negative electrode.

[0012] In this case, the alignment measurement unit may include two or more non-contact measuring instruments along the width direction of the electrode sheet in motion, and the non-contact measuring instruments may include one or more of the following: spectrophotometer, colorimeter, photometer, infrared spectrometer (FT-IR), nuclear magnetic resonance spectrometer (NMR), X-ray diffraction spectrometer (XRD), near-end X-ray fluorescence spectrometer (NEXAFS), and X-ray photoelectron spectrometer (XPS).

[0013] Furthermore, the control unit can calculate an alignment deviation from the alignment of two or more carbon-based negative electrode active materials measured along the width direction of the electrode sheet while it is in motion, and adjust the separation distance between the unit magnet of the first magnet section and the unit magnet of the second magnet section located at that point according to the calculated alignment deviation.

[0014] For this purpose, the control unit may include a database in which the distance adjustment value between the first magnet part and the second magnet part according to the alignment degree deviation of the carbon-based negative electrode active material is stored.

[0015] In addition, each of the first magnet part and the second magnet part includes a plurality of unit magnets arranged in the width direction of the negative electrode slurry, and the unit magnets can move up and down in a direction perpendicular to the electrode sheet during running individually, and the separation distance from the unit magnet facing the electrode sheet as the center can be adjusted.

[0016] In addition, each unit magnet provided in the first magnet part and the second magnet part may include a support part fixed individually to each unit magnet, and a distance adjustment means connected to the support part and guiding the up and down movement of the support part in a direction perpendicular to the electrode sheet during running.

[0017] In addition, the first magnet part and the second magnet part may include magnets having opposite poles to each other, and their separation distance can be adjusted to 10 mm to 50 mm.

[0018] In addition, the magnetic alignment device may further include a drying part for drying the negative electrode slurry in which the carbon-based negative electrode active material is aligned, between the first magnet part, the second magnet part, and the alignment degree measurement part.

[0019] In addition, in one embodiment of the present invention, applying a negative electrode slurry containing a carbon-based negative electrode active material onto a negative electrode current collector; aligning the carbon-based negative electrode active material contained in the negative electrode slurry using the magnetic alignment device according to the present invention described above; drying the negative electrode slurry in which the carbon-based negative electrode active material is aligned to form a negative electrode active layer; measuring the alignment degree of the carbon-based negative electrode active material contained in the formed negative electrode active layer, and adjusting the distance between the first magnet part and the second magnet part provided in the magnetic alignment device, and providing a method for manufacturing a negative electrode including these steps.

[0020] In this case, the spacing between the first magnet section and the second magnet section can be adjusted so that, when measuring the degree of alignment for any three points included in any region (10 cm horizontally and 10 cm vertically) on the negative electrode active layer, the average color coordinate deviation (ΔL*, Δa*, Δb*) between each point satisfies two or more of the following conditions: ΔL* < 2.0, Δa* < 0.5, and Δb* < 0.5.

[0021] Furthermore, the manufactured negative electrode active layer may have an alignment degree of 0.1 to 5.0 for the carbon-based negative electrode active material represented by the following formula 1.

[0022] [Formula 1] OI=I 004 / I 110

[0023] In Equation 1, I 004 This indicates the area of ​​the peak representing the (004) crystal plane when measured by X-ray diffraction spectroscopy (XRD) for the negative electrode active layer. I 110 This indicates the area of ​​the peak representing the (110) crystal plane when measured by X-ray diffraction spectroscopy (XRD) for the negative electrode active layer.

[0024] Furthermore, in one embodiment of the present invention, Negative electrode current collector and The negative electrode current collector is provided on at least one surface and includes a negative electrode active layer containing a carbon-based negative electrode active material, The above negative electrode active layer satisfies the condition that when measuring the color coordinates of any three points included in a unit region, the average color coordinate deviation between each point is ΔL* < 2.0, Δa* < 0.5, and Δb* < 0.5 for at least two of these conditions. The present invention provides a negative electrode for lithium secondary batteries manufactured by the negative electrode manufacturing method described above.

[0025] In this case, the anode active layer may have an alignment degree of 0.1 to 5.0 of the carbon-based anode active material represented by the following formula 1.

[0026] [Formula 1] OI=I 004 / I 110

[0027] In Equation 1, I 004 This indicates the area of ​​the peak representing the (0,0,4) crystal plane when measured by X-ray diffraction spectroscopy (XRD) for the negative electrode active layer. I 110 This shows the area of ​​the peak indicating the (1,1,0) crystal plane when measured by X-ray diffraction (XRD) spectroscopy for the negative electrode active layer. [Effects of the Invention]

[0028] The magnetic alignment device according to the present invention can measure the degree of alignment of a negative electrode active layer dried with carbon-based negative electrode active material in an aligned state in real time. By individually adjusting the separation distance of the unit magnets constituting the magnet row of the magnet section according to the measured degree of alignment of the carbon-based negative electrode active material, the strength of the magnetic field applied to the negative electrode slurry can be easily controlled. This has the advantage of providing a high degree of alignment and uniformity of the carbon-based negative electrode active material. [Brief explanation of the drawing]

[0029] [Figure 1] This is a structural diagram showing the schematic configuration of the magnetic alignment device according to the present invention. [Figure 2] This image shows the alignment of the ab-axis crystal planes of graphite when a magnetic field is applied to the negative electrode slurry during negative electrode active layer formation. (a) shows the case where no magnetic field is applied and the graphite crystal planes are not aligned, and (b) shows the case where a magnetic field is applied and the graphite crystal planes are aligned. [Modes for carrying out the invention]

[0030] Since the present invention can be modified in various ways and may have a variety of embodiments, specific embodiments will be described in detail in the detailed description.

[0031] However, this is not intended to limit the present invention to any particular embodiment, but rather to include all modifications, equivalents, or substitutions that fall within the spirit and technical scope of the present invention.

[0032] In the present invention, terms such as "includes" and "have" are intended to specify the presence of features, numbers, stages, operations, components, parts, or combinations thereof as described in the specification, without prejudice to the presence or possibility of adding one or more other features, numbers, stages, operations, components, parts, or combinations thereof.

[0033] Furthermore, in this invention, when a part such as a layer, film, region, or plate is described as being "on top" of another part, this includes not only the case where it is "directly on top" of the other part, but also the case where another part is located in between. Conversely, when a part such as a layer, film, region, or plate is described as being "below" another part, this includes not only the case where it is "directly below" the other part, but also the case where another part is located in between. Also, in this application, being "on top" may include being located not only at the top but also at the bottom.

[0034] Furthermore, in the present invention, "contains as a main component" may mean that the defined component is contained in an amount of 50% by weight or more (or 50% by volume or more), 60% by weight or more (or 60% by volume or more), 70% by weight or more (or 70% by volume or more), 80% by weight or more (or 80% by volume or more), 90% by weight or more (or 90% by volume or more), or 95% by weight or more (or 95% by volume or more) of the total weight (or total volume) of the defined component. For example, "contains graphite as a main component as the negative electrode active material" may mean that graphite is contained in an amount of 50% by weight or more, 60% by weight or more, 70% by weight or more, 80% by weight or more, 90% by weight or more, or 95% by weight or more of the total weight of the negative electrode active material, and in some cases it may also mean that the entire negative electrode active material consists of graphite and contains 100% by weight of graphite.

[0035] In addition, in this specification, "the carbon-based negative electrode active material is oriented" or "the carbon-based negative electrode active material is aligned" may mean that, as shown in (b) of FIG. 2, a specific crystal plane (for example, the a-b axis crystal plane of graphite) showing the two-dimensional planar structure of the carbon-based negative electrode active material constituting the negative electrode active material particles is arranged with a predetermined inclination with respect to the surface of the negative electrode current collector. This may be different from the case where, as shown in (a) of FIG. 2, the particles of the carbon-based negative electrode active material are aligned in a predetermined direction only inside the negative electrode active layer but have no directionality with respect to the negative electrode current collector.

[0036] In addition, "the orientation of the carbon-based negative electrode active material is high" may mean that the frequency of a specific crystal plane (for example, the a-b axis crystal plane of graphite) showing the two-dimensional planar structure of the carbon-based negative electrode active material contained in the negative electrode active layer having a predetermined inclination with respect to the surface of the negative electrode current collector is high. Also, in some cases, it may mean that the crystal plane of the carbon-based negative electrode active material contained in the negative electrode active layer is arranged at a high angle (for example, an angle close to perpendicular, more than 45°, specifically 60° or more) with respect to the surface of the negative electrode current collector.

[0037] In addition, "the degree of alignment of the carbon-based negative electrode active material is high" means that the "degree of alignment (O.I)" mentioned in this specification has a large value, and a specific crystal plane (for example, the a-b axis crystal plane of graphite) showing the two-dimensional planar structure of the carbon-based negative electrode active material contained in the negative electrode active layer is arranged at a low angle (for example, less than 45°) with respect to the surface of the negative electrode current collector. Conversely, "the degree of alignment of the carbon-based negative electrode active material is low" means that the "degree of alignment (O.I)" has a small value, and the above crystal plane of the carbon-based negative electrode active material contained in the negative electrode active layer is arranged at a high angle (for example, an angle close to perpendicular, 45° or more, specifically 60° or more) with respect to the surface of the negative electrode current collector.

[0038] Furthermore, in this specification, "average particle diameter (D 50 )" means the particle diameter at which the integrated value in the particle size distribution of the particles becomes 50%, and this is also referred to as the median diameter.

[0039] The present invention will be described in more detail below.

[0040] <Negative electrode magnetic alignment device> In one embodiment, the present invention is described as follows: A magnetic alignment device for a negative electrode, which applies a magnetic force to a negative electrode sheet coated with a negative electrode slurry containing a carbon-based negative electrode active material on a negative electrode current collector, thereby orienting the carbon-based negative electrode active material, A first magnet section and a second magnet section are positioned at the top and bottom of the electrode sheet while it is in motion, An alignment measurement unit is positioned downstream of the first and second magnet sections, with reference to the direction of travel of the electrode sheet, and measures the degree of alignment of the carbon-based negative electrode active material relative to the negative electrode current collector. The system includes a control unit that adjusts the separation distance between the first magnet unit and the second magnet unit according to the degree of alignment of the carbon-based negative electrode active material measured by the alignment measurement unit, The first and second magnet sections each include a plurality of unit magnets arranged in the width direction of the negative electrode slurry, and the unit magnets individually perform vertical movement relative to the moving electrode sheet to adjust the separation distance between them and opposing unit magnets around the electrode sheet, providing a magnetic alignment device for the negative electrode.

[0041] The magnetic alignment device for a negative electrode according to the present invention refers to a device applied during the manufacturing of a negative electrode used in a secondary battery. The magnetic alignment device can align the carbon-based negative electrode active material contained in the negative electrode slurry perpendicular to the negative electrode current collector by applying a magnetic field to the surface of the negative electrode current collector coated with a negative electrode slurry containing a carbon-based negative electrode active material. Here, the magnetic alignment device measures the degree of alignment of the carbon-based negative electrode active material contained in the dried negative electrode active layer after the negative electrode slurry containing the aligned carbon-based negative electrode active material has been dried. By reflecting the measured degree of alignment in the separation distance of the magnets placed above and below the electrode sheet during movement, the strength of the magnetic field applied to the negative electrode slurry can be controlled in real time. As a result, the magnetic alignment device can realize uniform alignment of the carbon-based negative electrode active material contained in the negative electrode slurry. Furthermore, a negative electrode manufactured in this way can exhibit the effect of increased lithium ion mobility during battery charging and discharging, reduced resistance, and improved charging and discharging performance.

[0042] Here, alignment perpendicular to the negative electrode current collector means that the crystal planes of the carbon-based negative electrode active material are aligned. Specifically, "the carbon-based negative electrode active material is aligned perpendicular to the negative electrode current collector" may mean that the crystal planes of the carbon-based negative electrode active material constituting the spherical particles, specifically the crystal planes of graphite that show the planar direction of graphite having a two-dimensional structure, are aligned and arranged perpendicular to the surface of the negative electrode current collector. In this case, the planar direction of the graphite may have an average inclination of 60 to 120° with respect to the negative electrode current collector, preferably an average inclination of 70 to 110° or 80 to 100°.

[0043] To this end, the magnetic alignment device 10 according to the present invention has a configuration that includes a first magnet section 110a and a second magnet section 110b, respectively, which are arranged above and below the electrode sheet in motion, i.e., the negative electrode current collector C to which the negative electrode slurry S is applied, as shown in Figure 1; an alignment degree measuring section 120, which is arranged downstream of the first magnet section 110a and / or the second magnet section 110b with reference to the direction of motion of the electrode sheet, and measures the degree of alignment of the carbon-based negative electrode active material with respect to the negative electrode current collector; and a control unit 130, which adjusts the separation distance between the first magnet section 110a and the second magnet section 110b according to the degree of alignment of the carbon-based negative electrode active material measured by the alignment degree measuring section.

[0044] In the magnetic alignment device 10 described above, the first magnet section 110a and the second magnet section 110b are positioned above and below the electrode sheet while it is in motion, respectively, and play a role in applying a magnetic field to the surface of the negative electrode slurry S.

[0045] Here, the first magnet section 110a and the second magnet section 110b each include a plurality of unit magnets along the width direction of the negative electrode slurry in order to apply a magnetic field to the surface of the negative electrode slurry S, and may include means for adjusting the distance between them, i.e., the separation distance, by having the plurality of unit magnets move up and down at the upper and lower parts of the negative electrode slurry, respectively. Specifically, the first magnet section 110a and the second magnet section 110b each include a first magnet row 112a and a second magnet row 112b in which a plurality of unit magnets are arranged along the width direction of the moving negative electrode slurry, a support section (not shown) provided on the magnet row 112a and 112b and individually fixed to each unit magnet, and distance adjustment means 111a and 111b connected to the support section and inducing the up and down movement of the support section (or the up and down movement of the unit magnets) in a direction perpendicular to the electrode sheet while it is moving.

[0046] At this time, the distance adjustment means 111a and 111b receive a spacing adjustment value from the control unit 130 and can operate to adjust the separation distance between the first magnet unit 110a and the second magnet unit 110b in accordance with the transmitted spacing adjustment value.

[0047] The first magnet section 110a and the second magnet section 110b, having this configuration, allow for easy control of the magnetic field strength applied to the negative electrode slurry S by adjusting their separation distance. Specifically, the closer the separation distance between the first magnet section 110a and the second magnet section 110b, the stronger the magnetic field strength applied to the negative electrode slurry S; and the wider the separation distance, the weaker the magnetic field strength applied to the negative electrode slurry S.

[0048] Furthermore, the first magnet portion 110a and the second magnet portion 110b may be positioned along the width direction of the electrode sheet on which the negative electrode slurry S is placed so as to face each other, and may be arranged so as to have opposite poles. For example, the north pole of the first magnet row 112a of the first magnet portion 110a may face the south pole of the second magnet row 112b of the second magnet portion 110b, or the south pole of the first magnet row 112a of the first magnet portion 110a may face the north pole of the second magnet row 112b of the second magnet portion 110b. When the electrode sheet passes through the space between the north and south poles facing each other in this way, the vertical alignment of the carbon-based negative electrode active material with respect to the negative electrode current collector C can be more effectively achieved between the first magnet portion 110a and the second magnet portion 110b.

[0049] Furthermore, the first magnet section 110a is positioned on top of the moving electrode sheet, and a Halbach arrangement may be applied to the first magnet row 112a in order to apply a high magnetic field to the carbon-based negative electrode active material of the negative electrode slurry S. Here, the Halbach arrangement is a permanent magnet arrangement that can provide a magnet with a high magnetic field strength by gradually changing the magnetization direction of the magnets. When magnets having a Halbach arrangement are applied as the first magnet row 112a of the first magnet section 110a, there is an advantage that the strength of the magnetic field applied to the negative electrode slurry S can be adjusted without significantly changing the separation distance between the first magnet section 110a and the second magnet section 110b.

[0050] Here, the separation distance between the first magnet section 110a and the second magnet section 110b can be 10 mm to 50 mm, specifically 10 mm to 40 mm, 20 mm to 50 mm, or 15 mm to 45 mm, and the separation distance between the first magnet section 110a and the second magnet section 110b can be the same as the separation distance between the first magnet array 112a and the second magnet array 112b. The present invention makes it possible to more efficiently align the carbon-based negative electrode active material contained in the negative electrode slurry S by adjusting the separation distance between the first magnet section 110a and the second magnet section 110b to the above range.

[0051] Furthermore, in the magnetic alignment device 10 described above, the alignment degree measuring unit 120 is located downstream of the first magnet section 110a and / or the second magnet section 110b with reference to the direction of travel of the electrode sheet, and plays the role of measuring the degree of alignment of the carbon-based negative electrode active material oriented by the first magnet section 110a and the second magnet section 110b in real time.

[0052] In this case, the alignment measurement unit 120 can be applied without particular limitation as long as it is a means / method commonly used in the industry to measure the alignment of carbon-based anode active materials, but preferably it may include a non-contact measuring instrument that can prevent damage and / or changes in the state of the anode active layer. Specifically, the alignment measurement unit may include a non-contact measuring instrument that measures the degree to which the crystal planes of the carbon-based anode active material are oriented, or that measures physical properties that appear differently depending on the degree of alignment of the carbon-based anode active material. For example, the non-contact measuring instrument may include one or more of the following: spectrophotometer, colorimeter, photometer, infrared spectrometer (FT-IR), nuclear magnetic resonance spectrometer (NMR), X-ray diffraction spectrometer (XRD), near-end X-ray fluorescence spectrometer (NEXAFS), and X-ray photoelectron spectrometer (XPS).

[0053] As one example, the alignment measurement unit described above may include non-contact measuring instruments such as a spectrophotometer or colorimeter that can perform rapid alignment measurement, taking into account the speed at which alignment is measured.

[0054] The above-mentioned colorimeter is a device that includes a light source and an image sensor. When the negative electrode active layer is photographed, the color information of the surface of the negative electrode active layer is converted into color coordinate values ​​and detected, making measurement easy and offering the advantage of being easily applicable to continuous processes. Here, the above color coordinate values ​​can be expressed using methods such as SCI (Specular Component Included) or SCE (Specular Component Excluded), standard light source D65 (color temperature: 6500K), or CIE 1976. As one example, when the degree of alignment of the carbon-based negative electrode active material according to the present invention is expressed using the CIE 1976 method (L*, a*, b*), the following conditions can be met: 30 ≤ L* ≤ 40, a* ≥ 0.3, b* ≥ 0.4.

[0055] Furthermore, the alignment measurement unit 120 can measure the alignment of the carbon-based anode active material more precisely by arranging two or more non-contact measuring instruments along the width direction of the electrode sheet while it is moving, thereby enabling real-time measurement of the alignment of the carbon-based anode active material. In this case, it becomes possible to measure the alignment of the carbon-based anode active material in the width direction of the electrode sheet, which can further improve the reliability of the manufactured anode.

[0056] Furthermore, the alignment measurement unit 120 may include two or more non-contact measuring instruments along the direction of travel of the electrode sheet. Specifically, the alignment measurement unit 120 may have a first measuring instrument 121 and a second measuring instrument 122 arranged in succession along the direction of travel of the electrode sheet. In this case, the error rate of the alignment of the carbon-based negative electrode active material, which is measured in real time, can be reduced.

[0057] In the magnetic alignment device 10 described above, the control unit 130 can play a role in controlling the separation distance between the first magnet unit 110a and the second magnet unit 110b. For this purpose, the magnetic alignment device 10 receives the degree of alignment of the carbon-based negative electrode active material measured by the degree of alignment measuring units 120, which are arranged at two or more points along the width direction of the electrode sheet, and can calculate the deviation between them. That is, the control unit 130 can calculate the degree of alignment deviation from the degree of alignment of two or more carbon-based negative electrode active materials measured along the width direction of the electrode sheet while it is in motion.

[0058] Furthermore, the control unit 130 transmits the spacing adjustment value between the unit magnet of the first magnet unit 110a and the unit magnet of the second magnet unit 110b, corresponding to the alignment deviation calculated in this manner, to the unit magnet of the first magnet unit 110a and the unit point of the second magnet unit 110b at that location, respectively, and can adjust the separation distance between the first magnet unit 110a and the second magnet unit 110b to match the transmitted spacing adjustment value.

[0059] To carry out this series of processes, the control unit 130 may include a database (not shown) in which spacing adjustment values ​​between the first magnet section 110a and the second magnet section 110b are stored for each deviation in the degree of alignment of two or more carbon-based negative electrode active materials.

[0060] Here, the above-mentioned spacing adjustment value refers to a value indicating the degree to which the current spacing between the first magnet section 110a and the second magnet section 110b is adjusted in order to reduce the alignment deviation. For example, if the alignment at the first point measured by the alignment measurement unit including a spectrophotometer is L*=35.0 and a*=0.54, and the alignment at the second point is L*=37.0 and a*=0.75, the spacing between the first magnet section 110a and the second magnet section 110b can be narrowed by 1 to 5 mm in order to reduce the alignment deviation ΔL*=2.0 and Δa*=0.21.

[0061] Such spacing adjustment values ​​can be obtained and stored by using an existing pre-measurement device to secure data on the change in the degree of alignment of the carbon-based negative electrode active material due to the change in the separation distance between the first magnet section 110a and the second magnet section 110b.

[0062] Furthermore, the degree of alignment of the carbon-based anode active material can change depending on the density (or concentration) of the carbon-based anode active material contained in the anode slurry S, and therefore the density (or concentration) of the carbon-based anode active material contained in the anode slurry S can affect the strength of the magnetic field.

[0063] Therefore, the database may further include information on the spacing adjustment values ​​between the first magnet section 110a and the second magnet section 110b for each deviation in alignment measured at two or more locations, as well as information on the density (or concentration) of the carbon-based anode active material in the anode slurry to correct the alignment deviation of the carbon-based anode active material. Furthermore, the spacing adjustment values ​​mentioned above may be values ​​that reflect the data on the density (or concentration) of the carbon-based anode active material in the anode slurry stored in the database.

[0064] Furthermore, the magnetic alignment device 10 may further include a drying unit 140 positioned between the first magnet section 110a and the second magnet section 110b and the alignment degree measuring unit 120, for drying the negative electrode slurry S in which the carbon-based negative electrode active material has been aligned by the first magnet section 110a and the second magnet section 110b.

[0065] The drying section 140 is formed by a wall (not shown) that blocks the surrounding area except for the inlet and outlet through which the electrode sheet coated with slurry S is drawn in and discharged, and a dryer (not shown) for drying the electrode sheet located on the wall side from which the electrode sheet coated with electrode slurry is drawn out.

[0066] When the electrode sheet coated with electrode slurry enters the drying section 140 through the inlet, energy such as light, wavelength, and heat supplied from the opposite wall is transferred. Therefore, it is preferable that the wall be made of an insulating material so as to prevent internal energy from being transferred to the outside and causing heat loss.

[0067] Furthermore, although the method of the above-mentioned dryer is not limited, it may have a configuration that performs a two-stage drying process in order to maintain the alignment of the carbon-based anode active material contained in the anode active layer. Specifically, the above-mentioned dryer may include a first dryer that dries the anode slurry using light and a second dryer that dries the anode slurry using heat, and the first and second dryers can operate continuously to dry the anode slurry.

[0068] The first dryer described above is a device for pre-drying the negative electrode slurry and, as stated above, can irradiate the surface of the negative electrode slurry with light or wavelength. Generally, when drying a negative electrode slurry, it can be done by applying hot air at a high temperature. However, in this case, the drying time of the negative electrode slurry is long, which can disrupt the alignment of the carbon-based negative electrode active material in the negative electrode slurry. Furthermore, when the temperature of the hot air is increased to solve this problem, the tendency for drying to occur on the slurry surface increases, leading to a phenomenon where the binder concentrates on the slurry surface due to the volatilizing solvent (migration), which reduces the adhesion strength between the active material layer and the negative electrode current collector. The present invention may have a configuration that pre-dries the electrode slurry by irradiating energy in the form of light or wavelength using the first dryer, so as to be able to dry the negative electrode slurry while maintaining a high degree of alignment of the carbon-based negative electrode active material without such problems. Such first dryers may include, for example, ultraviolet dryers, near-infrared dryers, and far-infrared dryers, and more specifically, far-infrared dryers that emit energy with wavelengths of 1 μm or more, more specifically 5 μm or more, 10 μm or more, or 20 μm or more, in order to realize a uniform drying rate of the electrode slurry. Unlike near-infrared dryers and infrared dryers that are commonly used in this industry, the above far-infrared dryers have longer light or wavelengths and are more energy efficient. Furthermore, the above far-infrared dryers have the advantage that they can uniformly apply energy not only to the surface but also to the interior of the negative electrode slurry, thereby increasing the adhesion between the negative electrode slurry and the negative electrode current collector in a short time.

[0069] At this time, the first dryer has a capacity of 50 kW / m 2 ~1,000kW / m 2 It can release energy at a power density of 50 kW / m³ 2 ~500kW / m 2 , 50kW / m 2 ~250kW / m 2 , or 50kW / m 2 , and 200kW / m 2Energy can be released at this power density. By controlling the power density of the first dryer within the above range, the present invention can prevent non-uniform drying of the active material layer from being induced by excessive power density.

[0070] Furthermore, a second dryer may apply heat to uniformly and completely dry the anode slurry that has been pre-dried by light or wavelength. Such a second dryer may include, without particular limitation, any that is commonly used in the industry, but specifically may include a hot air dryer, a vacuum oven, etc., either alone or in combination.

[0071] The magnetic alignment device according to the present invention, having the above-described configuration, can reflect the state of the negative electrode slurry in real time and uniformly guide the alignment of the internal carbon-based negative electrode active material. As a result, the manufactured negative electrode can exhibit the effect of increased lithium ion mobility during battery charging and discharging, reduced resistance, and improved charge / discharge performance.

[0072] <Method for manufacturing a negative electrode> Furthermore, in one embodiment of the present invention, The steps include: applying a negative electrode slurry containing a carbon-based negative electrode active material onto the negative electrode current collector; Using the magnetic alignment apparatus according to the present invention described above, the steps include aligning the carbon-based negative electrode active material contained in the negative electrode slurry, The process involves drying a negative electrode slurry in which carbon-based negative electrode active materials are aligned to form a negative electrode active layer, The present invention provides a method for manufacturing a negative electrode, which includes the steps of measuring the degree of alignment of the carbon-based negative electrode active material contained in the formed negative electrode active layer and adjusting the distance between a first magnet section and a second magnet section provided in a magnetic alignment device.

[0073] The method for manufacturing a negative electrode according to the present invention involves applying a negative electrode slurry containing a carbon-based negative electrode active material onto a negative electrode current collector, and applying a magnetic field to the surface of the applied negative electrode slurry using the magnetic alignment device of the present invention described above, thereby aligning the carbon-based negative electrode active material in the negative electrode slurry so that it is perpendicular to the surface of the negative electrode current collector (or to the direction of travel of the electrode sheet). Furthermore, by continuously drying the negative electrode slurry thereafter, the above manufacturing method can form a negative electrode active layer in which the perpendicular alignment of the carbon-based negative electrode active material is maintained.

[0074] In this case, the method for manufacturing the negative electrode can measure the degree of alignment of the carbon-based negative electrode active material contained in the dried negative electrode active layer in real time by using the magnetic alignment device described above, and adjust the distance between the first magnet part and the second magnet part, which are located at the top and bottom of the electrode sheet, respectively, according to the measured degree of alignment. Specifically, the manufacturing method can measure the degree of alignment of the carbon-based negative electrode active material at two or more points along the width direction of the negative electrode active layer in real time, and if deviations occur, adjust the distance between the first magnet part and the second magnet part provided in the magnetic alignment device to reduce those deviations.

[0075] The negative electrode active layer manufactured in this manner has a uniform distribution of carbon-based negative electrode active material aligned perpendicularly to the negative electrode current collector, and the deviation during alignment measurement may be remarkably low. For example, when measuring the alignment of carbon-based negative electrode active material using a spectrophotometer, the average color coordinate deviation (ΔL*, Δa*, Δb*) representing the alignment deviation for any three points within any region (10 cm horizontally and 10 cm vertically) on the negative electrode active layer may satisfy two or more of the conditions ΔL* < 2.0, Δa* < 0.5, and Δb* < 0.5, and more specifically, two or more of the conditions ΔL* < 1.0, Δa* < 0.3, and Δb* < 0.3. If the above conditions are not met, the distance between the first magnet part and the second magnet part, i.e., the separation distance, can be adjusted. By including such a configuration, the present invention can maintain a uniform alignment of the carbon-based negative electrode active material contained in the negative electrode active layer, thereby further improving the reliability of the negative electrode.

[0076] In the above-described negative electrode manufacturing method, the steps of applying the negative electrode slurry to the negative electrode current collector and drying the negative electrode slurry can be carried out in a manner commonly applied in this industry.

[0077] Furthermore, in the step of aligning the carbon-based anode active material contained in the anode slurry using a magnetic alignment device, the magnetic field application conditions can be adjusted to improve the alignment efficiency of the carbon-based anode active material. Specifically, the degree of alignment of the carbon-based anode active material can be adjusted by the strength of the magnetic field, the application time, etc.

[0078] For example, the above magnetic field may be applied with a magnetic field strength of 0.5 to 2.0 T, and more specifically, with magnetic field strengths of 0.9 to 1.5 T, 1.0 to 1.4 T, or 1.0 to 1.2 T.

[0079] Furthermore, the above magnetic field may be applied for a period of 0.1 to 20 seconds, more specifically for a period of 0.5 to 15 seconds, 0.5 to 12 seconds, 1 to 10 seconds, or 2 to 8 seconds.

[0080] <Negative electrode for lithium secondary batteries> In one embodiment, the present invention provides a negative electrode manufactured using the magnetic alignment apparatus according to the present invention described above.

[0081] The negative electrode manufactured according to the present invention includes a carbon-based negative electrode active material and includes a negative electrode active layer on at least one surface of the negative electrode current collector, and the negative electrode active layer may have a structure in which the carbon-based negative electrode active material is uniformly dispersed and aligned perpendicular to the negative electrode current collector. As one example, when measuring the degree of alignment at any three points contained within any region (10 cm horizontally and 10 cm vertically) on the negative electrode active layer, the deviation of the average color coordinates between each point (ΔL*, Δa*, Δb*) representing the degree of alignment may satisfy two or more of the following conditions: ΔL* < 2.0, Δa* < 0.5, and Δb* < 0.5.

[0082] The negative electrode for a lithium secondary battery according to the present invention includes a negative electrode active layer containing a carbon-based negative electrode active material on both sides of the negative electrode current collector. The negative electrode active layer is a layer that embodies the electrical activity of the negative electrode and is manufactured by applying an electrode slurry containing a negative electrode active material that embodies an electrochemical oxidation-reduction reaction during battery charging and discharging to both sides of the electrode current collector, and then drying and rolling it. The negative electrode active layer contains a carbon-based negative electrode active material as the negative electrode active material in order to embody electrical activity through a reversible oxidation-reduction reaction during battery charging and discharging. Specifically, the carbon-based negative electrode active material means a material mainly composed of carbon atoms, and such a carbon-based negative electrode active material may include graphite. The graphite may include one or more of natural graphite and artificial graphite, but preferably it may include natural graphite or a mixture of natural graphite and artificial graphite. For example, the carbon-based anode active material may contain natural graphite or artificial graphite alone, or in some cases, a mixture of natural and artificial graphite. In this case, the mixing ratio of natural and artificial graphite may be 5-40:60-95 or 10-30:70-90 by weight. By containing natural and artificial graphite in the above-mentioned mixing ratio, the carbon-based anode active material can achieve a strong adhesion between the anode current collector and the anode active layer while exhibiting high orientation of the carbon-based anode active material to the surface of the anode current collector.

[0083] The carbon-based anode active material described above is preferably a spherical graphite granule formed by the aggregation of multiple flake-shaped graphite particles. Examples of flake-shaped graphite include natural graphite, artificial graphite, mesophase-calcined carbon (bulk mesophase) made from tar and pitch, and graphitized cokes (such as green coke, green coke, pitch coke, needle coke, and petroleum coke). In particular, a material assembled using multiple highly crystalline natural graphite particles is preferred. Furthermore, a single graphite granule can be formed by the aggregation of 2 to 100, preferably 3 to 20, flake-shaped graphite particles.

[0084] Such carbon-based negative electrode active materials, specifically graphite, can have a spherical particle morphology. In this case, the sphericity of the graphite particles can be 0.75 or higher, for example, 0.75 to 1.0, 0.75 to 0.95, 0.8 to 0.95, or 0.90 to 0.99. Here, "sphericity" can mean the ratio of the shortest diameter (minor axis) to the longest diameter (major axis) among any diameters passing through the center of the particle. A sphericity of 1 means that the particle morphology is spherical. The above sphericity can be measured using a particle shape analyzer. The present invention has the advantage that by realizing the shape of the carbon-based negative electrode active material to be close to spherical, the electrical conductivity of the negative electrode active layer can be increased, thereby improving the capacity of the battery, and the specific surface area of ​​the negative electrode active material can be increased, thereby improving the adhesion between the negative electrode active layer and the current collector.

[0085] Furthermore, the above carbon-based negative electrode active material has an average particle size (D) of 0.5 μm to 10 μm. 50 ) can be shown, specifically an average particle size (D) of 2μm~7μm, 0.5μm~5μm, or 1μm~3μm. 50 ) can be shown.

[0086] The average particle size of spherical natural graphite can be made smaller to maximize the degree of disorder in the expansion direction for each particle, which can prevent particle expansion due to lithium ion charging. However, when the particle size of natural graphite is less than 0.5 μm, a large amount of binder is required due to the increase in the number of particles per unit volume, which can lead to a low degree of spheroidization and spheroidization yield. On the other hand, when the maximum particle size exceeds 10 μm, expansion becomes severe, and repeated charging and discharging can reduce inter-particle binding and binding between particles and current collectors, which can significantly reduce cycle characteristics.

[0087] In a negative electrode active layer containing such a carbon-based negative electrode active material, the degree of alignment of the carbon-based negative electrode active material can be controlled to be constant. The present invention can lower the electrode resistance by aligning the crystal planes of the carbon-based negative electrode active material contained in the negative electrode active layer in a certain direction, thereby improving the charging performance of the negative electrode active layer.

[0088] Here, the degree of alignment (i.e., orientation) of the carbon-based negative electrode active material (e.g., graphite) can be determined by crystal plane analysis of the graphite.

[0089] As one example, the above-mentioned negative electrode active layer has carbon-based negative electrode active material aligned perpendicularly to the negative electrode current collector, and when measuring the degree of alignment (CIE color coordinates: L*, a*, b*) of the negative electrode active layer using a spectrophotometer, it can satisfy 30≦L*≦40, 0.3≦a*≦0.8, 0.4≦b*≦0.9, and can satisfy 33≦L*≦37, 0.55≦a*≦0.65, 0.65≦b*≦0.75. Here, the values ​​of L* and a* may be smaller as the degree of alignment of the carbon-based negative electrode active material contained in the negative electrode active layer increases, and the value of b* may be larger as the degree of alignment of the carbon-based negative electrode active material contained in the negative electrode active layer increases.

[0090] Here, "color coordinates" refer to the coordinates in the CIE color space, which are color values ​​defined by the CIE (International Commission on Illumination). Any position in the CIE color space can be represented by three coordinate values: L*, a*, and b*. Here, the L* value represents brightness; L*=0 represents black, and L*=100 represents white. The a* value represents whether the color with that color coordinate is biased towards pure red (pure magenta) or pure green, and the b* value represents whether the color with that color coordinate is biased towards pure yellow (pure yellow) or pure blue. Specifically, the above a* value has a range of -a to +a, the maximum value of a* (a*max) represents pure red (pure magenta), and the minimum value of a* (a*min) represents pure green (pure green). For example, a negative a* value indicates a color biased towards pure green, while a positive a* value indicates a color biased towards pure red. Comparing a*=80 and a*=50, a*=80 means that a*=80 is closer to pure red than a*=50. Also, the above b* value has a range of -b to +b. The maximum value of b* (b*max) represents pure yellow, and the minimum value of b* (b*min) represents pure blue. For example, a negative b* value indicates a color biased towards pure yellow, while a positive b* value indicates a color biased towards pure blue. Comparing b*=80 and b*=20, b*=80 means that b*=80 is closer to pure yellow than b*=20.

[0091] As another example, in the above-mentioned negative electrode active layer, the carbon-based negative electrode active material is aligned perpendicularly to the negative electrode current collector, and the degree of alignment (OI) of the carbon-based negative electrode active material, expressed in the following formula 1, can satisfy 0.1 to 5.0 when X-ray diffraction spectroscopy (XRD) is performed on the negative electrode active layer.

[0092] [Formula 1] OI=I 004 / I 110

[0093] In Equation 1, I 004 This indicates the area of ​​the peak representing the (004) crystal plane when measured by X-ray diffraction spectroscopy (XRD) for the negative electrode active layer. I 110 This indicates the area of ​​the peak representing the (110) crystal plane when measured by X-ray diffraction spectroscopy (XRD) for the negative electrode active layer.

[0094] The crystal plane orientation of the carbon-based anode active material can be determined by crystal plane analysis of the carbon-based anode active material, such as X-ray diffraction spectroscopy. The degree of alignment (OI) of the carbon-based anode active material, expressed by Equation 1 above, can serve as an indicator of the direction in which the crystal structure of the carbon-based anode active material is aligned during X-ray diffraction measurement. Specifically, it indicates the degree to which the ab-axis crystal plane, which shows the two-dimensional planar structure of the carbon-based anode active material, is aligned with respect to the surface of the anode current collector. For example, when the anode active layer contains graphite as the carbon-based anode active material, the peaks for graphite during X-ray diffraction spectroscopy of the anode active layer are 2θ = 26.5±0.2°, 42.4±0.2°, 43.4±0.2°, 44.6±0.2°, 54.7±0.2°, and 77.5±0.2°. This shows the (002), (100), (101)R, (101)H, (004), and (110) crystal planes of the graphite contained in the negative electrode active layer. Generally, in the case of graphite, graphene layers are placed on the a-axis and b-axis planes, and such graphene layers are stacked along the c-axis, resulting in a hexagonal or rhombohedral crystal structure. Here, the crystal plane peaks mentioned above are peaks that show the plane characteristics of such a crystal structure. Furthermore, the peak appearing at 2θ = 43.4 ± 0.2° can be considered to be an overlap of the peak corresponding to the (101)R plane of a carbon-based material and the (111) plane of a current collector, such as Cu.

[0095] This invention allows for the measurement of graphite alignment (OI) by the area ratio of the peak at 2θ = 77.5 ± 0.2° representing the (110) plane and the peak at 2θ = 54.7 ± 0.2° representing the (004) plane, specifically, the area ratio obtained by integrating the intensities of the above peaks. Furthermore, X-ray diffraction was measured using the CuKα line as the target line, and to improve the peak intensity resolution, the target line was extracted using a monochromator. At this time, the measurement conditions were 2θ = 10° to 90°, scan speed (° / s) of 0.044 to 0.089, and step size of 0.026° / step. Furthermore, the (004) plane appearing at 2θ = 54.7 ± 0.2° indicates the thickness-direction characteristics (c-axis direction characteristics) of a layered structure in which two-dimensional planar structures of graphite layers are stacked, while the (110) plane appearing at 2θ = 77.5 ± 0.2° indicates the planar characteristics (ab-axis direction characteristics) of the stacked graphite layers. Therefore, the smaller the (004) plane peak, which indicates the thickness-direction characteristics of the graphite layer plane, and the larger the (110) plane peak, which indicates the planar characteristics of the graphite layer, the higher the angle at which the graphite planes are aligned with respect to the negative electrode current collector surface. In other words, the closer the alignment degree (OI) is to 0, the closer the angle or inclination of the graphite layer surface with respect to the negative electrode current collector surface is to 90°, and the larger the value, the closer the inclination with respect to the negative electrode current collector surface is to 0° or 180°. In this respect, the negative electrode active layer according to the present invention may have a lower degree of graphite alignment (OI) compared to the case where no magnetic field is applied, because the carbon-based negative electrode active material is aligned perpendicularly to the negative electrode current collector.Specifically, the degree of alignment of the carbon-based anode active material contained in the anode active layer can be 0.1 to 5.0, and more specifically, 0.1 to 4.5, 0.1 to 4.0, 0.1 to 3.5, 0.1 to 3.0, 0.1 to 2.5, 0.1 to 2.0, 0.1 to 1.0, 0.5 to 2.9, 1.0 to 4.5, 1.1 to 4.1, 1.5 to 4.0, 1.1 to 3.5, 1 Possible ranges include 0.5-3.0, 0.9-2.9, 0.1-2.4, 0.1-2.1, 0.1-1.9, 2.0-5.0, 2.0-4.0, 2.1-3.9, 2.5-3.9, 3.1-4.5, 0.1-0.6, 0.15-0.6, 0.15-0.5, 0.2-0.5, 0.2-0.4, 0.25-0.45, or 0.3-0.5.

[0096] Furthermore, the above-mentioned negative electrode active layer may uniformly induce vertical alignment of the carbon-based negative electrode active material relative to the negative electrode current collector, resulting in a low deviation in the degree of alignment of the carbon-based negative electrode active material when measured arbitrarily per unit area.

[0097] As one example, the above-mentioned negative electrode active layer can satisfy two or more of the following conditions when measuring the degree of alignment of any three points contained within any region (10 cm horizontally and 10 cm vertically) on the negative electrode active layer: the average color coordinate deviation (ΔL*, Δa*, Δb*) between each point is ΔL* < 2.0, Δa* < 0.5, and Δb* < 0.5. Specifically, it can satisfy two or more of the following conditions: ΔL* < 1.0, Δa* < 0.3, and Δb* < 0.3.

[0098] As another example, in the above-mentioned negative electrode active layer, when X-ray diffraction spectroscopy (XRD) measurements are taken at any three points within a unit area (10 cm × 10 cm) of the negative electrode active layer, the alignment deviation of the carbon-based negative electrode active material represented by Equation 1 may be less than 5% based on the average value, and specifically may be 4% or less, 3% or less, 2% or less, or 1% or less.

[0099] On the other hand, the negative electrode active layer according to the present invention may optionally further contain a conductive material, a binder, other additives, etc., along with the negative electrode active material.

[0100] The above conductive material may contain, but is not limited to, one or more of the following: carbon black, acetylene black, Ketjen black, carbon nanotubes, carbon fibers, etc.

[0101] As one example, the above-mentioned negative electrode active layer may contain carbon nanotubes or carbon fibers alone or in combination as conductive materials.

[0102] In this case, the content of the conductive material may be 0.1 to 10 parts by weight per 100 parts by weight of the entire negative electrode active layer, specifically 0.1 to 8 parts by weight, 0.1 to 5 parts by weight, 0.1 to 3 parts by weight, or 2 to 6 parts by weight. By controlling the content of the conductive material within the above range, the present invention can prevent an increase in the resistance of the negative electrode and a decrease in charging capacity due to a low content of conductive material. Furthermore, by controlling the content of the conductive material within the above range, the present invention can prevent problems such as a decrease in the content of the negative electrode active material and a decrease in charging capacity due to an excessive amount of conductive material, or a decrease in rapid charging characteristics due to an increase in the loading amount of the negative electrode active layer.

[0103] Furthermore, the above-mentioned binder is a component that assists in the bonding of the active material to conductive materials and to the current collector, and can be suitably applied within a range that does not degrade the electrical properties of the electrode. Specifically, it may contain one or more of the following: vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, and fluororubber.

[0104] The binder content may be 0.1 to 10 parts by weight per 100 parts by weight of the entire negative electrode active layer, specifically 0.1 to 8 parts by weight, 0.1 to 5 parts by weight, 0.1 to 3 parts by weight, or 2 to 6 parts by weight. By controlling the binder content in the negative electrode active layer within the above range, the present invention can prevent a decrease in the adhesive strength of the active layer due to a low binder content or a decrease in the electrical properties of the electrode due to an excessive amount of binder.

[0105] Furthermore, the negative electrode current collector is not particularly limited as long as it has high conductivity without inducing chemical changes in the battery. For example, copper, stainless steel, nickel, titanium, and calcined carbon can be used, and in the case of copper or stainless steel, those with surface treatments such as carbon, nickel, titanium, or silver can also be used. The average thickness of the negative electrode current collector can be suitably applied in the range of 1 to 500 μm, taking into consideration the conductivity and total thickness of the manufactured negative electrode.

[0106] The present invention will be described in more detail below with reference to examples and experimental examples.

[0107] However, the following examples and experimental examples are illustrative of the present invention, and the content of the present invention is not limited to the following examples and experimental examples.

[0108] <Examples 1-2 and Comparative Example: Manufacturing of a negative electrode for lithium secondary batteries> A negative electrode for a lithium secondary battery was manufactured using the magnetic alignment device of the present invention having the structure shown in Figure 1, and the number of non-contact measuring instruments provided in the alignment degree measurement section was adjusted as shown in Table 1.

[0109] Specifically, natural graphite was first prepared as the negative electrode active material. 97 parts by weight of the negative electrode active material and 3 parts by weight of styrene-butadiene rubber (SBR) were mixed with water to form a negative electrode slurry. This slurry was then cast onto a copper sheet being transported roll-to-roll (transport speed: 3 m / min) using a die coater. The negative electrode slurry was cast so that it had a three-line stripe pattern along the direction of travel of the copper sheet. The average thickness of the negative electrode slurry for the first and third lines was adjusted to 100 μm, and the average thickness of the negative electrode slurry for the second line, located in the center, was adjusted to 200 μm.

[0110] Subsequently, a magnetic field was applied to the negative electrode slurry by moving a copper plate so that the coated negative electrode slurry passed between the first magnet section and the second magnet section. Here, the distance adjustment means was adjusted to individually adjust the separation distance between the unit magnets in the first magnet row (containing 5 to 20 unit magnets) and the second magnet row (containing 5 to 20 unit magnets), respectively, according to the spacing reference value transmitted from the control unit. Here, the separation distance between the first magnet row and the second magnet row was adjusted to 20 to 40 mm according to the spacing reference value transmitted from the control unit, and the strength of the applied magnetic field was 1.0 T.

[0111] Furthermore, in order to dry the negative electrode slurry to which a magnetic field has been applied, a copper sheet to which a magnetic field has been applied was moved to the drying section, and the negative electrode slurry was dried to manufacture a negative electrode for a lithium secondary battery. However, immediately after drying the negative electrode slurry, the degree of alignment of the carbon-based negative electrode active material in the dried negative electrode slurry, i.e., the negative electrode active layer, was measured, and the measured degree of alignment was transmitted to the control unit, which then transmitted a reference value for the spacing between the unit magnets of the first magnet unit and the second magnet unit according to the degree of alignment it received.

[0112] Here, the alignment of the carbon-based anode active material was measured using spectrophotometers or X-ray diffraction spectrometers (XRD) installed at three points along the width direction of the electrode sheet as alignment measurement units, as shown in Table 1. The alignment measured at each point in the alignment measurement units was transmitted to the control unit. The control unit calculated the alignment deviation from the alignment of each starting point received. Subsequently, the control unit compared the spacing adjustment value between the first magnet unit 110a and the second magnet unit 110b with the calculated alignment deviation for each deviation between the alignments of the carbon-based anode active material stored in the database, and transmitted the corresponding spacing adjustment value to the unit magnet of the first magnet unit 110a and the unit point of the second magnet unit 110b at that point, respectively. The first magnet unit 110a and the second magnet unit 110b continuously performed the anode manufacturing process while adjusting the separation distance of the unit magnets at that point to match the received spacing adjustment value.

[0113] [Table 1]

[0114] Here, when a spectrophotometer was used as the alignment measurement unit, the alignment of the carbon-based anode active material was obtained as CIE color coordinates (L*, a*, b*), and when an X-ray diffraction spectrometer (XRD) was used as the alignment measurement unit, the alignment of the carbon-based anode active material was obtained using the following formula 1. The measurement conditions for the above X-ray diffraction (XRD) are as follows.

[0115] - Target: Cu(Kα-ray) graphite monochromator - Slit: Divergent slit = 1 degree, Receiving slit = 0.1 mm, Scattering slit = 1 degree

[0116] [Formula 1] OI=I 004 / I 110

[0117] In Equation 1, I 004 This indicates the area of ​​the peak representing the (0,0,4) crystal plane when measured by X-ray diffraction spectroscopy (XRD) for the negative electrode active layer. I110 This shows the area of ​​the peak indicating the (1,1,0) crystal plane when measured by X-ray diffraction (XRD) spectroscopy for the negative electrode active layer.

[0118] <Experimental Example: Evaluation of Alignment Uniformity of Carbon-Based Anode Active Materials> To evaluate the alignment uniformity of the carbon-based negative electrode active material as a performance indicator for the magnetic alignment device according to the present invention, the following experiment was conducted.

[0119] Specifically, in the negative electrode active layer of each negative electrode manufactured in the examples and comparative examples, three points were arbitrarily set in the direction of travel and width of the negative electrode during manufacturing, and these points were designated as points A to F. At this time, each point was set to have a size of 10 cm in width and 10 cm in height.

[0120] The degree of alignment of the carbon-based anode active material at each set point was measured using a spectrophotometer and an X-ray diffraction spectrometer. From the measured degree of alignment, i) the average degree of alignment (i.e., the average value of the degree of alignment at each point) and ii) the deviation from the above average degree of alignment were calculated for the carbon-based anode active material contained at each point.

[0121] At this time, the measurement conditions for the spectrophotometer and X-ray diffraction spectrometer were adjusted to be the same as in Example 1, and the results are shown in Table 2 below.

[0122] [Table 2]

[0123] As shown in Table 2 above, it was found that the negative electrode manufactured using the magnetic alignment device according to the present invention exhibited a high degree of alignment of the carbon-based negative electrode active material contained in the negative electrode active layer. Furthermore, it was confirmed that the negative electrode active layer of the manufactured negative electrode showed a low deviation between the degree of alignment at any three points and their average value. This means that the magnetic alignment device according to the present invention uniformly aligns the carbon-based negative electrode active material on the negative electrode current collector with a high degree of alignment.

[0124] These results show that the magnetic alignment device according to the present invention can align the carbon-based negative electrode active material with a high degree of alignment and uniformity relative to the negative electrode current collector by measuring the degree of alignment of the carbon-based negative electrode active material in real time and individually reflecting it in the unit magnets included in the first magnet row of the first magnet section and the second magnet row of the second magnet section.

[0125] While preferred embodiments of the present invention have been described above with reference to those skilled in the art or those with ordinary knowledge in the art, it will be understood that the present invention can be modified and altered in various ways without departing from the spirit and technical scope of the invention as described in the claims below.

[0126] Therefore, the technical scope of the present invention is not limited to what is described in the summary of the invention in the specification, but is defined by the claims. [Explanation of Symbols]

[0127] 10: Magnetic alignment device 20:Transfer section 30: Coating section (die coater) 110a: 1st magnet part 111a: First distance adjustment means 112a: 1st magnet row 110b: Second magnet part 111b: Second distance adjustment means 112b: Second magnet row 120: Alignment degree measurement unit 121: 1st spectrophotometer 122:Second spectrophotometer 130: Control Unit 140:Drying section C: Negative electrode current collector S: Negative electrode slurry

Claims

1. A magnetic alignment device for a negative electrode, which applies a magnetic force to a negative electrode sheet coated with a negative electrode slurry containing a carbon-based negative electrode active material on a negative electrode current collector, thereby orienting the carbon-based negative electrode active material, A first magnet section and a second magnet section are positioned at the top and bottom of the electrode sheet while it is in motion, An alignment measurement unit is positioned downstream of the first and second magnet sections with reference to the direction of travel of the electrode sheet, and measures the degree of alignment of the carbon-based negative electrode active material with respect to the negative electrode current collector. The set includes a control unit that adjusts the separation distance between the first magnet unit and the second magnet unit according to the degree of alignment of the carbon-based negative electrode active material measured by the alignment measurement unit, The first magnet section and the second magnet section each include a plurality of unit magnets arranged in the width direction of the negative electrode slurry, and each unit magnet individually moves up and down in a direction perpendicular to the moving electrode sheet to adjust the separation distance from the unit magnet opposite to the electrode sheet around the electrode sheet, in a magnetic alignment device for the negative electrode.

2. The magnetic alignment device for a negative electrode according to claim 1, wherein the alignment degree measuring unit includes two or more non-contact measuring instruments along the width direction of the electrode sheet while it is in motion.

3. The magnetic alignment device for a negative electrode according to claim 2, wherein the non-contact measuring instrument includes one or more of the following: a spectrophotometer, a colorimeter, a photometer, an infrared spectrometer, a nuclear magnetic resonance spectrometer, an X-ray diffraction spectrometer, a near-end X-ray fluorescence spectrometer, and an X-ray photoelectron spectrometer.

4. The control unit calculates an alignment deviation from the alignment of two or more carbon-based negative electrode active materials measured along the width direction of the electrode sheet while it is in motion, and adjusts the separation distance between the unit magnet of the first magnet section and the unit magnet of the second magnet section, which are placed at the measurement point, according to the calculated alignment deviation, as described in claim 1.

5. The magnetic alignment device for a negative electrode according to claim 1, wherein the control unit includes a database storing spacing adjustment values ​​between the unit magnet of the first magnetic unit and the unit magnet of the second magnetic unit, corresponding to the alignment deviation of the carbon-based negative electrode active material.

6. Each unit magnet provided in the first magnet section and the second magnet section is Each unit magnet and its individually fixed support part, The magnetic alignment device for a negative electrode according to claim 1, further comprising: a distance adjusting means connected to the support portion for guiding the vertical movement of the support portion in a direction perpendicular to the electrode sheet while it is in motion.

7. The magnetic alignment device for a negative electrode according to claim 1, wherein the separation distance between the first magnet portion and the second magnet portion is 10 mm to 50 mm.

8. The negative electrode magnetic alignment device according to claim 1, wherein the first magnet portion and the second magnet portion include magnets having opposite poles to each other.

9. The magnetic alignment apparatus for a negative electrode according to claim 1, further comprising a drying section between the first magnet section and the second magnet section and the alignment degree measuring section for drying the negative electrode slurry in which the carbon-based negative electrode active material is aligned.

10. The steps include: applying a negative electrode slurry containing a carbon-based negative electrode active material onto the negative electrode current collector; A step of aligning the carbon-based negative electrode active material contained in the negative electrode slurry using the negative electrode magnetic alignment device described in claim 1, The steps include: drying the anode slurry in which the carbon-based anode active material is aligned to form an anode active layer; A method for manufacturing a negative electrode, comprising the steps of: measuring the degree of alignment of carbon-based negative electrode active material contained at two or more points along the width direction of the formed negative electrode active layer; and adjusting the distance between the first magnet portion and the second magnet portion provided in the magnetic alignment device in accordance with the deviation of the measured degree of alignment.

11. The method for manufacturing a negative electrode according to claim 10, wherein the distance between the first magnet portion and the second magnet portion is adjusted so that, when measuring the degree of alignment for any three points included in any region (10 cm horizontally and 10 cm vertically) present on the negative electrode active layer, the average color coordinate deviation (ΔL*, Δa*, Δb*) between each point satisfies two or more of the following conditions: ΔL* < 2.0, Δa* < 0.5, and Δb* < 0.

5.

12. In the aforementioned anode active layer, the degree of alignment (O.I) of the carbon-based anode active material represented by the following formula 1 is 0.1 to 5.

0. [Formula 1] O. I=I004 / I110 In Equation 1, I004 represents the area of ​​the peak indicating the (004) crystal plane when X-ray diffraction spectroscopy is performed on the negative electrode active layer. The method for manufacturing a negative electrode according to claim 10, wherein I110 represents the area of ​​the peak indicating the (110) crystal plane when X-ray diffraction spectroscopic measurement is performed on the negative electrode active layer.

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