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

Abstract

The present invention relates to a magnetic alignment device for a negative electrode and a method for manufacturing a negative electrode using the same. The magnetic alignment device applies a magnetic field to the negative electrode slurry by introducing magnet parts respectively to the upper and lower parts of a negative electrode current collector on which a negative electrode slurry is applied, and applies a stronger magnetic field to a second region of the magnet part located downstream along the transport direction of the negative electrode current collector than a first region of the magnet part located upstream, and disposes a drying part adjacent to the end of the second region to which the stronger magnetic field is applied, thereby advantageously producing a negative electrode in which the degree of alignment of the carbon-based negative electrode active material contained in the negative electrode slurry is significantly high.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0131352, dated October 13, 2022, and all contents disclosed in the documents of this Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a magnetic alignment device capable of aligning carbon-based negative electrode active materials contained in a negative electrode active layer at a high level during the manufacture of a negative electrode, and a method of manufacturing a negative electrode using the same. [Background technology]

[0003] BACKGROUND ART In recent years, secondary batteries have been widely used not only in small devices such as portable electronic devices but also in medium to large devices such as battery packs for hybrid cars and electric cars or power storage devices.

[0004] Such secondary batteries are chargeable and dischargeable power generating elements having a laminated structure of a positive electrode / separator / negative electrode. In general, the positive electrode contains a lithium metal oxide as a 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, the lithium ions contained in the carbon-based negative electrode active material are absorbed into the lithium metal oxide of the positive electrode, thereby allowing for repeated charging and discharging.

[0005] Examples of anode active materials used in the anode include graphite materials such as natural graphite. Such graphite has a layered structure, in which carbon atoms form a network structure, and many planar layers are stacked. During charging, lithium ions penetrate from the edge surfaces (surfaces where layers overlap) of such graphite layers and diffuse between the layers. During discharging, lithium ions can be desorbed and released from the edge surfaces of the layers. Furthermore, since the electrical resistivity of graphite in the plane direction of the layers is lower than that in the stacking direction of the layers, a detour electron conduction path is formed along the plane direction of the layers.

[0006] In relation to this, a technique for magnetically orienting graphite contained in a negative electrode has been proposed to improve the charging performance of the negative electrode in conventional graphite-based lithium secondary batteries. Specifically, the (002) crystal plane of the graphite is oriented in a magnetic field during the formation of the negative electrode, and then fixed in place. In this case, the edge face of the graphite layer faces the positive electrode active layer, which facilitates the insertion and desorption of lithium ions and shortens the electron conduction path, thereby improving the electronic conductivity of the negative electrode. This can improve the charging performance of the battery.

[0007] To this end, a method for aligning graphite by applying a magnetic field to a negative electrode slurry containing graphite as a carbon-based negative electrode active material using a magnetic device has been used during negative electrode manufacturing. However, this method requires permanent magnets to be placed above and below the thin metal plate coated with the negative electrode slurry, making it difficult to maintain a constant magnetic force. Furthermore, this method not only has low workability, but also has limitations in that the graphite in the final negative electrode active layer is poorly aligned because an attractive force caused by the magnetic force occurs at the end of the permanent magnet, i.e., the end of the magnetic field, causing the graphite aligned perpendicular to the thin metal plate to break down. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Korean Patent Publication No. 10-2018-0048131 [Patent Document 2] Korean Patent Publication No. 10-2022-0060017 Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to provide a magnetic alignment device for manufacturing a negative electrode in which a carbon-based negative electrode active material contained in a negative electrode active layer has excellent vertical alignment characteristics relative to a negative electrode current collector, and a method for manufacturing a negative electrode using the same. [Means for solving the problem]

[0010] In order to solve the above-mentioned problems, in one embodiment, the present invention provides: A magnetic alignment device for manufacturing a negative electrode for aligning a carbon-based negative electrode active material, a first magnet unit and a second magnet unit, which are respectively positioned above and below a negative electrode current collector coated with a negative electrode slurry containing a carbon-based negative electrode active material in a transport direction, and which apply a magnetic force; a drying unit that dries the negative electrode slurry to which magnetic force is applied by the first magnet unit and the second magnet unit, The first magnet unit and the second magnet unit are each divided into a first region located upstream and a second region located downstream based on the transfer direction of the negative electrode current collector, The magnetic alignment device is characterized in that a magnetic field having a stronger magnetic force strength than that of the first region is applied to the second region.

[0011] In this case, the drying section may be disposed adjacent to the second region ends of the first magnet section and the second magnet section.

[0012] Furthermore, the first magnet portion and the second magnet portion each include a plurality of unit magnets arranged in the transport direction (x-axis direction) and width direction (y-axis direction) of the negative electrode current collector, respectively, and of the plurality of unit magnets, the unit magnets arranged in the second region of the first magnet portion and the second magnet portion may be arranged in a Halbach array.

[0013] The first and second magnet parts may have a length of 0.5 m to 10 m in the direction of transport of the negative electrode current collector, and the length of the second region may be shorter than the length of the first region. Specifically, the second region may occupy 5% to 50% of the total length of the first and second magnet parts.

[0014] The first magnet portion and the second magnet portion may be spaced apart from each other by a distance of 10 mm to 50 mm, and the first magnet portion and the second magnet portion may include magnets having opposite poles.

[0015] Furthermore, in one embodiment, the present invention provides 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; and drying the negative electrode slurry in which the carbon-based negative electrode active material is aligned to form a negative electrode active layer.

[0016] Here, the carbon-based negative electrode active material may include at least one of natural graphite and artificial graphite.

[0017] In addition, the negative electrode active layer may have a degree of alignment (OI) of 0.1 to 5.0, as represented by the following formula 1, due to the self-alignment of the carbon-based negative electrode active material contained therein.

[0018] [Formula 1] OI=I 004 / I 110

[0019] In Equation 1, I 004 represents the area of the peak representing the (004) crystal plane when the negative electrode active layer is measured by X-ray diffraction spectroscopy (XRD), I 110 represents the area of the peak indicating the (110) crystal plane when the negative electrode active layer is measured by X-ray diffraction spectroscopy (XRD). [Effects of the Invention]

[0020] The magnetic alignment apparatus according to the present invention has an advantage that it can manufacture a negative electrode in which the carbon-based negative electrode active material contained in the negative electrode slurry has a significantly high degree of alignment. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a structural diagram illustrating a magnetic alignment device for a negative electrode according to the present invention; [Figure 2] 10 is a perspective view showing the arrangement of unit magnets included in the first magnet portion and the second magnet portion. FIG. [Figure 3] 10A and 10B are images showing the alignment of the ab-axis crystal planes of graphite depending on whether or not a magnetic field is applied to the negative electrode slurry during the formation of the negative electrode active layer. (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. DETAILED DESCRIPTION OF THE INVENTION

[0022] Because the present invention is susceptible to various modifications and can have various embodiments, specific embodiments are described in detail in the detailed description.

[0023] However, this is not intended to limit the invention to any particular embodiment, but rather to be understood as including all modifications, equivalents, or alternatives falling within the spirit and scope of the invention.

[0024] In the present invention, terms such as "comprise" and "have" are intended to specify the presence of features, numbers, steps, operations, components, parts or combinations thereof described in the specification, and may be understood as not precluding the presence or possibility of addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof.

[0025] Furthermore, in the present invention, when a layer, film, region, plate, or other portion is described as being "on" another portion, this includes not only the case where it is "directly on" the other portion, but also the case where there is another portion therebetween. Conversely, when a layer, film, region, plate, or other portion is described as being "under" the other portion, this includes not only the case where it is "directly under" the other portion, but also the case where there is another portion therebetween. Furthermore, in this application, being "located on" can include not only the case where it is located at the top, but also the case where it is located at the bottom.

[0026] Furthermore, in the present invention, "comprising as a main component" may mean containing 50 wt% or more (or 50 vol% or more), 60 wt% or more (or 60 vol% or more), 70 wt% or more (or 70 vol% or more), 80 wt% or more (or 80 vol% or more), 90 wt% or more (or 90 vol% or more), or 95 wt% or more (or 95 vol% or more) of the defined component relative to the total weight (or total volume). For example, "comprising graphite as a main component as a negative electrode active material" may mean containing 50 wt% or more, 60 wt% or more, 70 wt% or more, 80 wt% or more, 90 wt% or more, or 95 wt% or more of graphite relative to the total weight of the negative electrode active material. In some cases, it may mean that the entire negative electrode active material is made up of graphite, with the graphite accounting for 100 wt%.

[0027] Furthermore, 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 a specific crystal plane (e.g., the ab-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 aligned at a predetermined inclination with respect to the surface of the negative electrode current collector, as shown in (b) of Figure 3. This may differ from (a) of Figure 3, in which the particles of the carbon-based negative electrode active material themselves are aligned in a predetermined direction only within the negative electrode active layer, but have no directionality relative to the negative electrode current collector.

[0028] Furthermore, "high orientation of the carbon-based negative electrode active material" may mean that a specific crystal plane (e.g., the ab-axis crystal plane of graphite) exhibiting a two-dimensional planar structure of the carbon-based negative electrode active material contained in the negative electrode active layer frequently has a predetermined inclination with respect to the surface of the negative electrode current collector. In some cases, it may also mean that the crystal plane of the carbon-based negative electrode active material contained in the negative electrode active layer is aligned at a high angle (e.g., an angle close to perpendicular, greater than 45°, specifically 60° or greater) with respect to the surface of the negative electrode current collector.

[0029] In addition, the term "high degree of alignment of the carbon-based negative electrode active material" refers to the "degree of alignment (S 60 / 0and / or OI) has a large value, and it may mean that a specific crystal plane (e.g., the ab-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 aligned at a low angle (e.g., less than 45°) with respect to the surface of the negative electrode current collector. Conversely, "the carbon-based negative electrode active material has a low degree of alignment" means that the "degree of alignment (S 60 / 0 and / or OI)" has a small value, which may mean that the crystal plane of the carbon-based negative electrode active material contained in the negative electrode active layer is aligned at a high angle (e.g., an angle close to perpendicular, 45° or more, specifically 60° or more) relative to the surface of the negative electrode current collector.

[0030] In addition, in this specification, the term "crystal plane of a carbon-based negative electrode active material" refers to a plane where atoms of the carbon-based negative electrode active material form the outer shape of a crystal, and in the present invention, may refer to a crystal plane including a flat surface of the carbon-based negative electrode active material or a crystal plane including the a-axis / ab-axis of the carbon-based negative electrode active material crystal.

[0031] Furthermore, in this specification, "average particle size (D 50 )" refers to the particle size at which the cumulative value in the particle size distribution of particles is 50%, and is also called the median diameter.

[0032] The present invention will now be described in more detail.

[0033] <Magnetic alignment device for negative electrodes> In one embodiment, the present invention comprises: A magnetic alignment device for manufacturing a negative electrode for aligning a carbon-based negative electrode active material, a first magnet unit and a second magnet unit, which are respectively positioned above and below a negative electrode current collector coated with a negative electrode slurry containing a carbon-based negative electrode active material in a transport direction, and which apply a magnetic force; a drying unit that dries the negative electrode slurry to which magnetic force is applied by the first magnet unit and the second magnet unit, The first magnet unit and the second magnet unit are each divided into a first region located upstream and a second region located downstream based on the transfer direction of the negative electrode current collector, The magnetic alignment device is characterized in that a magnetic field having a stronger magnetic force strength than that of the first region is applied to the second region.

[0034] The magnetic alignment device for a negative electrode according to the present invention is an apparatus used in manufacturing a negative electrode for a secondary battery, and can align the carbon-based negative electrode active material contained in the negative electrode slurry in a direction perpendicular to the negative electrode current collector by applying a magnetic field to the surface of the negative electrode current collector on which a negative electrode slurry containing a carbon-based negative electrode active material is applied, i.e., the surface of the negative electrode slurry. 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, and the negative electrode manufactured in this manner can exhibit improved charge / discharge performance by increasing lithium ion mobility and reducing resistance during battery charge / discharge.

[0035] Here, "aligned perpendicular to the negative electrode current collector" means that the crystal planes of the carbon-based negative electrode active material are aligned. Specifically, "aligned perpendicular to the negative electrode current collector" can mean that the crystal planes of the carbon-based negative electrode active material constituting the spherical particles, specifically, the crystal planes of the graphite crystals that indicate the planar direction of the graphite having a two-dimensional structure, are aligned 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° relative to the negative electrode current collector, preferably 70 to 110° or 80 to 100°.

[0036] To this end, as shown in FIG. 1, the magnetic alignment device 10 according to the present invention includes a first magnet unit 110a and a second magnet unit 110b, which are respectively positioned above and below a negative electrode current collector coated with a negative electrode slurry containing a carbon-based negative electrode active material in a transport direction thereof to apply magnetic force, and a drying unit 120 which dries the negative electrode slurry to which magnetic force has been applied by the first magnet unit 110a and the second magnet unit 110b.

[0037] In the magnetic alignment device, the first magnet unit 110a and the second magnet unit 110b are respectively disposed on the upper and lower sides of the electrode sheet being transported, i.e., the negative electrode current collector on which the negative electrode slurry is applied, and serve to apply a magnetic field to the surface of the negative electrode slurry S. In the present invention, the first magnet unit 110a and the second magnet unit 110b are disposed on the upper and lower sides of the negative electrode current collector so that, when a magnetic field is applied to the negative electrode slurry S being coated on the current collector and transported, the magnetic field is uniformly applied to the exposed surface of the negative electrode slurry S (i.e., the upper surface) and the surface in contact with the current collector (i.e., the lower surface). This increases the alignment of the carbon-based negative electrode active material, specifically, the inclination of the carbon-based negative electrode active material relative to the negative electrode current collector, compared to when magnet units are disposed only on the upper surface of the negative electrode current collector (inclination of the carbon-based negative electrode active material: approximately 60 to 65°), thereby achieving vertical alignment of the carbon-based negative electrode active material.

[0038] In this case, the first magnet portion 110a and the second magnet portion 110b may include magnets 111a and 111b, and support portions 112a and 112b for fixing the magnets, in order to apply a magnetic field to the surface of the negative electrode slurry S, respectively.

[0039] 2, if the direction in which the negative electrode current collector C coated with the negative electrode slurry S is transported is defined as the x-axis direction and the width direction of the transported negative electrode current collector is defined as the y-axis direction, the first magnet portion 110a and the second magnet portion 110b may include a plurality of unit magnets in the x-axis direction and the y-axis direction, respectively. The unit magnets may form magnet rows including m (where m is an integer of 2 or more) and n (where n is an integer of 2 or more) unit magnets in the x-axis direction and the y-axis direction, respectively, and thus one magnet portion may include m × n unit magnets.

[0040] The first magnet portion 110a and the second magnet portion 110b may be divided into first regions 1111a and 1111b located upstream in the direction of transport of the negative electrode current collector, i.e., the x-axis direction, and second regions 1112a and 1112b located downstream. Here, the second regions 1112a and 1112b may have a stronger magnetic force (or magnetic field) strength than the first regions 1111a and 1111b, and may apply a magnetic field thereto.

[0041] This difference in magnetic force strength can be realized using a method commonly used in the art, but preferably, the unit magnets arranged in the first regions 1111a and 1111b are arranged so that the north or south pole (i.e., a single pole) of the magnet is exposed on the surface of the magnet to apply a uniform magnetic field, and the unit magnets arranged in the second regions 1112a and 1112b are arranged in a Halbach array. Here, the Halbach array refers to an arrangement method that improves electric field strength by controlling the arrangement of the unit magnets. The Halbach array can realize a magnetic force that is 1.5 times stronger than when the unit magnets are arranged with the same pole. By disposing a plurality of unit magnets having a Halbach array in the second regions 1112a and 1112b of the first and second magnet units, a strong magnetic field is applied to the second regions 1112a and 1112b located downstream of the direction of transfer of the negative electrode slurry, and then a relatively weaker magnetic field is applied to the first regions 1111a and 1111b located upstream compared to the second regions 1112a and 1112b. This allows the carbon-based negative electrode active material to be aligned nearly perpendicular to the negative electrode current collector, thereby further improving the electrical performance of the negative electrode. By including a plurality of unit magnets having a Halbach array in the entire region, a decrease in the transfer efficiency of the negative electrode current collector can be prevented.

[0042] In this case, the first regions 1111a and 1111b and the second regions 1112a and 1112b may have a certain ratio of the magnetic force applied to the surfaces of the first magnet portion 110a and the second magnet portion 110b and / or the magnetic force applied to the space between the first magnet portion 110a and the second magnet portion 110b.

[0043] As one example, the second regions 1112a and 1112b may apply a magnetic force of 10,000 G or more, 11,000 G or more, 10,000 to 15,000 G, 10,000 to 12,000 G, or 11,000 to 12,000 G to the surfaces of the first magnet portion 110a and the second magnet portion 110b, and the ratio of the magnetic force of the second regions 1112a and 1112b to the magnetic force of the first regions 1111a and 1111b may be 1.4 or more, 1.5 or more, 1.6 or more, 1.4 to 5.0, 1.4 to 3.0, 1.4 to 2.5, or 1.5 to 2.0.

[0044] As another example, the second regions 1112a and 1112b may apply a magnetic force of 8,000 G or more, 9,000 G or more, 10,000 G or more, 8,000 to 12,000 G, or 8,500 to 11,000 G to the space between the first magnet section 110a and the second magnet section 110b, and the ratio of the magnetic force of the second regions 1112a and 1112b to the magnetic force of the first regions 1111a and 1111b may be 1.4 or more, 1.5 or more, 1.6 or more, 1.4 to 2.5, 1.4 to 2.2, 1.5 to 1.8, or 1.6 to 2.0.

[0045] The ratio of the sizes of the first regions 1111a and 1111b to the second regions 1112a and 1112b may be adjusted to a constant value. Specifically, the length of the second regions 1112a and 1112b in the direction of movement of the negative electrode current collector may be shorter than that of the first regions 1111a and 1111b. Specifically, the second regions 1112a and 1112b may occupy 5 to 50% of the total length of the first magnet portion 110a and the second magnet portion 110b, more specifically 5 to 40%, 10 to 30%, or 10 to 20%, with the remaining portion being occupied by the first regions 1111a and 1111b. For example, the upstream first regions 1111a and 1111b may occupy 85% of the total length of the first magnet unit 110a and the second magnet unit 110b, and the downstream second regions 1112a and 1112b may occupy 15%. A strong magnetic field applied by the magnet unit may significantly align the carbon-based negative electrode active material in the negative electrode slurry nearly perpendicular to the negative electrode current collector. However, an excessively strong magnetic field may hinder the transfer of the negative electrode current collector, reducing the efficiency of negative electrode manufacturing. A slow transfer speed may increase the time the negative electrode current collector is exposed to high-temperature negative electrode slurry. If the negative electrode current collector coated with the negative electrode slurry is exposed to high temperatures for a long period of time, a stress deviation may occur between the coated portion of the negative electrode current collector coated with the negative electrode slurry and the uncoated portion of the negative electrode current collector not coated with the negative electrode slurry. Stress deviation between the coated and uncoated regions can cause wrinkles and / or breaks at the boundaries between them, reducing the structural reliability of the electrode. However, the present invention prevents this problem by adjusting the proportions of the second regions 1112a and 1112b, to which a strong magnetic field is applied, of the first and second magnet units 110a and 110b to less than 50% of the total length of the magnet units. At the same time, the present invention can effectively achieve high alignment of the carbon-based negative electrode active material without significantly increasing the overall size of the magnet units or the magnitude of the applied magnetic force.

[0046] Meanwhile, the unit magnets 111a and 111b may include electromagnets and / or permanent magnets. The electromagnets may include both DC and AC electromagnets. The permanent magnets may include both ferromagnetic and soft magnetic magnets, such as NdFeB magnets, SmCo magnets, ferrite magnets, alnico magnets, FeCrCo magnets, and bond magnets (Nd-Fe-B, Sm-Fe-N, Sm-Co, and ferrite magnets).

[0047] In addition, the first magnet unit 110a and the second magnet unit 110b may be positioned facing each other along the direction of transfer of the negative electrode slurry S and may be arranged to have opposite poles. For example, the north pole of the first magnet 111a of the first magnet unit 110a may face the south pole of the second magnet 111b of the second magnet unit 110b, or the south pole of the first magnet 111a of the first magnet unit 110a may face the north pole of the second magnet 111b of the second magnet unit 110b. When an electrode sheet passes through a space where the north pole and south pole face each other, vertical alignment of the carbon-based negative electrode active material with respect to the negative electrode current collector C may be more effectively achieved between the first magnet unit 110a and the second magnet unit 110b.

[0048] The distance between the first magnet part 110a and the second magnet part 110b may be 10 mm to 50 mm, specifically 10 mm to 40 mm, 20 mm to 50 mm, or 15 mm to 45 mm. By adjusting the distance between the first magnet part 110a and the second magnet part 110b within the above range, the present invention can more efficiently align the carbon-based negative electrode active material contained in the negative electrode slurry S.

[0049] Furthermore, the first magnet portion 110a and the second magnet portion 110b may have a length of 0.5 m to 10 m in the direction of movement of the negative electrode current collector (i.e., the x-axis direction), and the lengths of the first magnet portion 110a and the second magnet portion 110b may be suitably adjusted depending on the movement speed of the negative electrode current collector coated with the negative electrode slurry and / or the time for which magnetic force is applied to the negative electrode slurry during negative electrode manufacturing. For example, when the movement speed of the negative electrode current collector coated with the negative electrode slurry is 3±0.2 m / min, the lengths of the first magnet portion 110a and the second magnet portion 110b may be 3±0.5 m, and when the movement speed is 6±0.2 m / min, the lengths of the first magnet portion 110a and the second magnet portion 110b may be 6±0.5 m. In the present invention, by adjusting the overall length of the first magnet part 110a and the second magnet part 110b as described above, the carbon-based negative electrode active material contained in the negative electrode slurry can be aligned nearly vertically.

[0050] In addition, the magnetic alignment device 10 may be coupled to a transfer unit 20 to transfer the negative electrode current collector coated with negative electrode slurry containing a carbon-based negative electrode active material in one direction, specifically, in the process direction. To this end, the transfer unit 20 may be any method commonly used in the industry to transfer an electrode sheet C coated with electrode slurry S during electrode manufacturing, without any particular limitations. For example, the transfer unit 20 may be a roll-to-roll method or a conveyor belt transfer method to which a magnetic field can be applied.

[0051] Furthermore, in the magnetic alignment device 10, the drying unit 120 serves to dry the negative electrode slurry S in which the carbon-based negative electrode active material has been aligned by the first magnet unit 110a and the second magnet unit 110b, thereby fixing the aligned carbon-based negative electrode active material.

[0052] The drying section 120 is formed to include a wall (not shown) that blocks the periphery except for an entrance / exit through which the electrode sheet C coated with the slurry S is introduced and conveyed, and a dryer (not shown) for drying the electrode sheet on the wall on the side from which the electrode sheet C coated with the electrode slurry S is drawn out.

[0053] When the electrode sheet C coated with the electrode slurry S enters through the inlet of the drying unit 120, energy such as light, wavelength, and heat supplied from the wall on the opposite side is transferred to the electrode sheet C. Therefore, the wall is preferably made of a heat insulating material to prevent internal energy from being transferred to the outside and causing heat loss.

[0054] In addition, the drying unit 120 may be disposed adjacent to the ends of the second regions 1112a and 1112b of each magnet unit to prevent the carbon-based negative electrode active material aligned by the first magnet unit 110a and the second magnet unit 110b from tilting toward the negative electrode current collector C and losing its vertical alignment. Here, "the ends of the second regions are disposed adjacent to the drying unit" may mean that the ends of the second regions 1112a and 1112b are disposed adjacent to or separated by a predetermined distance from the entrance and exit of the drying unit 120, which introduces and delivers the electrode sheet C coated with the negative electrode slurry S. This arrangement allows the negative electrode slurry S away from the ends of the second regions to be directly introduced into the drying unit 120 and continuously dried without being affected by the magnetic field of the second regions 1112a and 1112b, which have a strong magnetic force. As a result, the carbon-based negative electrode active material in the dried negative electrode slurry (i.e., negative electrode active layer) can maintain and achieve a perpendicular or nearly perpendicular alignment with respect to the negative electrode current collector.

[0055] Here, the ends of the second regions 1112a and 1112b and the drying unit 120 (specifically, the inlet and outlet of the drying unit) are disposed adjacent to each other when observed from their sides, as shown in FIG. 2, and the separation distance may be close to 0 mm. In some cases, the separation distance between the ends of the second regions 1112a and 1112b and the drying unit 120 may be 10 mm or less, 8 mm or less, 5 mm or less, 3 mm or less, 0.5 to 5 mm, 5 to 10 mm, or 1 to 3 mm. By adjusting the separation distance between the ends of the second regions and the drying unit as described above, the present invention can prevent damage to the alignment of the carbon-based negative electrode active material aligned perpendicular or nearly perpendicular to the negative electrode current collector due to excessive separation distance. Furthermore, when the magnet units 110a and 110b are installed in the drying unit 120, it can prevent a decrease in economy that would occur due to the purchase of expensive heat-resistant magnets.

[0056] Furthermore, the drying unit 120 may be configured to perform a two-stage drying process to maintain the alignment of the carbon-based negative electrode active material contained in the negative electrode active layer, although the drying method is not limited thereto. Specifically, the drying unit 120 may include a first dryer that dries the negative electrode slurry using light and a second dryer that dries the negative electrode slurry using heat, and the first dryer and the second dryer may operate continuously to dry the negative electrode slurry.

[0057] The first dryer is a device for pre-drying the negative electrode slurry and may irradiate the surface of the negative electrode slurry with light or wavelengths, as described above. Drying negative electrode slurry is typically performed by applying high-temperature hot air, but this method can lengthen the drying time of the negative electrode slurry and disrupt the alignment of the carbon-based negative electrode active material in the negative electrode slurry. Furthermore, increasing the hot air temperature to address this issue increases the tendency for the slurry surface to dry, resulting in migration of the binder along with the volatilized solvent to the slurry surface and reduced adhesion strength between the active material layer and the negative electrode current collector. The present invention may be configured to pre-dry the electrode slurry by irradiating energy in the form of light or wavelengths using a first dryer, thereby enabling the negative electrode slurry to be dried while maintaining high alignment of the carbon-based negative electrode active material without these issues. The first dryer may include, for example, an ultraviolet dryer, a near-infrared dryer, or a far-infrared dryer. Specifically, it may include a far-infrared dryer that emits energy with a wavelength of 1 μm or more, more specifically, 5 μm or more, 10 μm or more, or 20 μm or more, to achieve a uniform drying rate for the electrode slurry. Unlike near-infrared dryers and infrared dryers commonly used in the industry, the far-infrared dryer emits light or has a long wavelength, making it more energy efficient. Furthermore, it has the advantage of being able to apply energy uniformly 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 period of time.

[0058] At this time, the first dryer was 50 kW / m 2 ~1,000kW / m 2 and specifically 50 kW / m 2 ~500kW / m 2 , 50kW / m 2 ~250kW / m 2 , or 50kW / m 2 ~200kW / m 2 By controlling the power density of the first dryer within the above range, the present invention can prevent uneven drying of the active material layer caused by an excessive power density.

[0059] The second dryer may apply heat to the negative electrode slurry pre-dried by light or wavelength to uniformly and completely dry it. The second dryer may include any dryer commonly used in the art, without any particular limitation. Specifically, the second dryer may include a hot air dryer, a vacuum oven, or the like, used alone or in combination.

[0060] The magnetic alignment device according to the present invention has the above-described configuration, and thus can reduce the attractive force of the carbon-based negative electrode active material due to the magnetic force generated at the end of the magnet portion, thereby significantly increasing the degree of alignment of the carbon-based negative electrode active material contained in the negative electrode slurry, thereby advantageously enabling the manufacture of a negative electrode with excellent electrical performance.

[0061] <Method of manufacturing the negative electrode> In one embodiment, the present invention further comprises: 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; and drying the negative electrode slurry in which the carbon-based negative electrode active material is aligned to form a negative electrode active layer.

[0062] 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 according to the present invention described above, thereby aligning the carbon-based negative electrode active material in the negative electrode slurry perpendicular or nearly perpendicular to the surface of the negative electrode current collector (or to the direction of transport of the electrode sheet).

[0063] In the method for preparing the negative electrode, the steps of applying the negative electrode slurry to the negative electrode current collector and drying the negative electrode slurry may be performed in a manner commonly used in the art.

[0064] In addition, the step of aligning the carbon-based negative electrode active material contained in the negative electrode slurry may involve sequentially applying magnetic fields with different magnetic forces to the negative electrode slurry coated on the surface of the negative electrode current collector using a magnetic alignment device according to the present invention.

[0065] The magnetic alignment device has a first magnet unit and a second magnet unit respectively disposed above and below the negative electrode current collector along the direction of movement of the negative electrode current collector (i.e., the x-axis direction). The first magnet unit and the second magnet unit can be divided into first regions 1111a and 1111b located upstream in the direction of movement of the negative electrode current collector, i.e., the x-axis direction, and second regions 1112a and 1112b located downstream. The second regions 1112a and 1112b can apply a magnetic field with a stronger magnetic force than the first regions 1111a and 1111b.

[0066] In this case, the first regions 1111a and 1111b and the second regions 1112a and 1112b may have a certain ratio of the magnetic force applied to the surfaces of the first magnet portion and the second magnet portion and / or the magnetic force applied to the space between the first magnet portion and the second magnet portion.

[0067] As one example, the second regions 1112a and 1112b may apply a magnetic force of 10,000 G or more, 11,000 G or more, 10,000 to 15,000 G, 10,000 to 12,000 G, or 11,000 to 12,000 G to the surfaces of the first magnet portion 110a and the second magnet portion 110b, and the ratio of the magnetic force of the second regions 1112a and 1112b to the magnetic force of the first regions 1111a and 1111b may be 1.4 or more, 1.5 or more, 1.6 or more, 1.4 to 5.0, 1.4 to 3.0, 1.4 to 2.5, or 1.5 to 2.0.

[0068] As another example, the second regions 1112a and 1112b may apply a magnetic force of 8,000 G or more, 9,000 G or more, 10,000 G or more, 8,000 to 12,000 G, or 8,500 to 11,000 G to the space between the first magnet section 110a and the second magnet section 110b, and the ratio of the magnetic force of the second regions 1112a and 1112b to the magnetic force of the first regions 1111a and 1111b may be 1.4 or more, 1.5 or more, 1.6 or more, 1.4 to 2.5, 1.4 to 2.2, 1.5 to 1.8, or 1.6 to 2.0.

[0069] The present invention aligns the carbon-based negative electrode active material contained in the negative electrode slurry using the magnetic alignment device having the above-described configuration, thereby aligning and maintaining the carbon-based negative electrode active material more nearly perpendicular to the negative electrode current collector.

[0070] The 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.

[0071] Meanwhile, the carbon-based negative electrode active material contained in the negative electrode slurry may include a carbon-based negative electrode active material commonly used in lithium secondary batteries. Specifically, the carbon-based negative electrode active material refers to a material primarily composed of carbon atoms, and may include graphite. The graphite may include at least one of natural graphite and artificial graphite, and preferably includes natural graphite or a mixture of natural graphite and artificial graphite.

[0072] In addition, the negative electrode slurry may further include a conductive material, a binder, a thickener, etc., in addition to the carbon-based negative electrode active material, and these may be materials commonly used in the art.

[0073] <Anode for lithium secondary batteries> Furthermore, in one embodiment, the present invention provides The negative electrode for a lithium secondary battery is manufactured using the magnetic alignment apparatus according to the present invention.

[0074] The negative electrode for a lithium secondary battery according to the present invention includes a negative electrode active layer including a carbon-based negative electrode active material on at least one surface of a negative electrode current collector. The negative electrode active layer is a layer that realizes the electrical activity of the negative electrode and is fabricated by coating both surfaces of the electrode current collector with an electrode slurry including a negative electrode active material that realizes an electrochemical redox reaction during charge and discharge of the battery, followed by drying and rolling. The negative electrode active layer includes a carbon-based negative electrode active material as the negative electrode active material to realize electrical activity through a reversible redox reaction during charge and discharge of the battery. Specifically, the carbon-based negative electrode active material refers to a material primarily composed of carbon atoms, and may include graphite. The graphite may include at least one of natural graphite and artificial graphite, and preferably includes natural graphite or a mixture of natural graphite and artificial graphite. For example, the carbon-based negative electrode active material may contain natural graphite or artificial graphite alone, or may contain a mixture of natural graphite and artificial graphite. In this case, the mixture ratio of natural graphite to artificial graphite may be 5-40:60-95 or 10-30:70-90 by weight. By containing natural graphite and artificial graphite in the above-mentioned mixture ratio, the carbon-based negative electrode active material may achieve high orientation of the carbon-based negative electrode active material on the surface of the negative electrode current collector while strengthening the adhesion between the negative electrode current collector and the negative electrode active layer.

[0075] The carbon-based negative electrode active material is preferably a spherical graphite granule formed by the aggregation of multiple flake graphite particles. Examples of flake graphite include natural graphite, artificial graphite, mesophase calcined carbon (bulk mesophase) made from tar or pitch, and graphitized cokes (raw coke, green coke, pitch coke, needle coke, petroleum coke, etc.). A graphite granule assembled from multiple pieces of highly crystalline natural graphite is particularly preferred. Furthermore, one graphite granule may be formed by the aggregation of 2 to 100, preferably 3 to 20, flake graphite particles.

[0076] Such a carbon-based negative electrode active material, specifically, graphite, may have a spherical particle shape. In this case, the sphericity of the graphite particles may be 0.75 or greater, 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" refers to the ratio of the shortest diameter (minor axis) to the longest diameter (major axis) among any diameters passing through the center of a particle, and a sphericity of 1 indicates that the particle shape is spherical. The sphericity may be measured using a particle shape analyzer. By achieving a nearly spherical shape for the carbon-based negative electrode active material, the present invention has the advantages of improving the electrical conductivity of the negative electrode active layer, thereby improving the capacity of the battery, and increasing the specific surface area of the negative electrode active material, thereby improving the adhesion between the negative electrode active layer and the current collector.

[0077] The carbon-based negative electrode active material has an average particle size (D 50 ), specifically, an average particle size (D 50 ) can be shown.

[0078] The average particle size of spherical natural graphite is preferably as small as possible to maximize the degree of disorder in the direction of expansion of each particle, thereby preventing particle expansion due to charging with lithium ions. However, if the particle size of natural graphite is less than 0.5 μm, the number of particles per unit volume increases, requiring a large amount of binder, which can result in low sphericity and sphericity yield. On the other hand, if the maximum particle size exceeds 10 μm, excessive expansion occurs, and repeated charge / discharge cycles can reduce the adhesion between particles and between the particles and the current collector, resulting in a significant decrease in cycle performance.

[0079] In a negative electrode active layer including such a carbon-based negative electrode active material, the alignment of the carbon-based negative electrode active material in a direction perpendicular to the negative electrode current collector can be achieved by the magnetic alignment device according to the present invention. The present invention can further reduce electrode resistance by aligning the crystal planes of the carbon-based negative electrode active material contained in the negative electrode active layer in a specific direction, thereby further improving the charging performance of the negative electrode active layer.

[0080] 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.

[0081] For example, in the negative electrode active layer, the carbon-based negative electrode active material is aligned perpendicularly to the negative electrode current collector, and when the negative electrode active layer is measured by X-ray diffraction spectroscopy (XRD), the degree of alignment (OI) of the carbon-based negative electrode active material, represented by the following Equation 1, may satisfy a range of 0.1 to 5.0.

[0082] [Formula 1] OI=I 004 / I 110

[0083] In Equation 1, I 004 represents the area of the peak representing the (004) crystal plane when the negative electrode active layer is measured by X-ray diffraction spectroscopy (XRD), I 110 represents the area of the peak indicating the (110) crystal plane when the negative electrode active layer is measured by X-ray diffraction spectroscopy (XRD).

[0084] The crystal plane orientation of the carbon-based negative electrode active material can be determined by crystal plane analysis of the carbon-based negative electrode active material, such as X-ray diffraction spectroscopy. The degree of alignment (OI) of the carbon-based negative electrode active material, expressed by Equation 1, can be an index of the direction in which the crystalline structure of the carbon-based negative electrode active material is aligned during X-ray diffraction measurement, specifically, the degree to which the ab-axis crystal plane, which represents the two-dimensional planar structure of the carbon-based negative electrode active material, is aligned relative to the surface of the negative electrode current collector. For example, if the negative electrode active layer contains graphite as the carbon-based negative electrode active material, the X-ray diffraction spectroscopy analysis of the negative electrode active layer will reveal peaks at 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°, which are the peaks for graphite. This refers to the (002), (100), (101)R, (101)H, (004), and (110) crystal planes of the graphite contained in the negative electrode active layer. In general, graphite has graphene layers positioned on the a-axis and b-axis planes, and these graphene layers are stacked along the c-axis, resulting in a hexagonal or rhombohedral crystal structure. The crystal plane peaks represent the plane characteristics of such a crystal structure. The peak appearing at 2θ = 43.4 ± 0.2° may be due to the overlap of the (101)R plane of the carbon-based material and the (111) plane of the current collector, e.g., Cu.

[0085] The present invention can measure the degree of alignment (OI) of graphite by measuring the area ratio of the peak at 2θ = 77.5 ± 0.2° representing the (110) plane to the peak at 2θ = 54.7 ± 0.2° representing the (004) plane, specifically, the area ratio obtained by integrating the intensities of these peaks. X-ray diffraction was measured using CuK α radiation as the target beam, and to improve peak intensity resolution, the target beam was extracted using a monochromator. Measurement conditions were 2θ = 10° to 90°, a scan speed (° / s) of 0.044 to 0.089, and a step size of 0.026° / step. Furthermore, the (004) plane appearing at 2θ = 54.7 ± 0.2° indicates the thickness direction characteristic (c-axis direction characteristic) of the layered structure in which two-dimensional planar structures of graphite layers are stacked, and the (110) plane appearing at 2θ = 77.5 ± 0.2° indicates the planar characteristic (ab-axis direction characteristic) of the stacked graphite layers. Therefore, the smaller the (004) plane peak, which indicates the thickness direction characteristic of the graphite layer planes, and the larger the (110) plane peak, which indicates the planar characteristic of the graphite layer planes, 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 degree of alignment (OI) value is to 0, the closer the angle or tilt of the graphite layer surface with respect to the negative electrode current collector surface is to 90°, and the larger the value is, the closer the tilt with respect to the negative electrode current collector surface is to 0° or 180°.

[0086] In this respect, in the negative electrode active layer according to the present invention, the carbon-based negative electrode active material is aligned perpendicular to the negative electrode current collector, and therefore the degree of alignment (OI) of graphite may be lower than when the carbon-based negative electrode active material is not aligned perpendicularly. Specifically, the degree of alignment of the carbon-based negative electrode active material contained in the negative electrode active layer may be 0.1 to 5.0, 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, 1.0 to 3.5, 1.0 to 4.5, 1.0 to 5.0 ... The degree of alignment of the carbon-based negative electrode active material contained in the negative electrode active layer may be within the above range, for example, 0.5 to 3.0, 0.9 to 2.9, 0.1 to 2.4, 0.1 to 2.1, 0.1 to 1.9, 2.0 to 5.0, 2.0 to 4.0, 2.1 to 3.9, 2.5 to 3.9, 3.1 to 4.5, 0.1 to 0.6, 0.15 to 0.6, 0.15 to 0.5, 0.2 to 0.5, 0.2 to 0.4, 0.25 to 0.45, or 0.3 to 0.5. When the degree of alignment of the carbon-based negative electrode active material contained in the negative electrode active layer satisfies the above range, lithium ion mobility can be improved, thereby further improving the safety of the battery.

[0087] In addition, the negative electrode active layer may be induced to uniformly align the carbon-based negative electrode active material vertically relative to the negative electrode current collector, and the alignment deviation of the carbon-based negative electrode active material measured arbitrarily per unit area may be small.

[0088] For example, when X-ray diffraction (XRD) is measured at any three points within a unit area (10 cm × 10 cm) of the negative electrode active layer, the deviation in the degree of alignment of the carbon-based negative electrode active material represented by Formula 1 may be less than 5% based on the average value, specifically, 4% or less, 3% or less, 2% or less, or 1% or less.

[0089] Meanwhile, the negative electrode active layer according to the present invention may further include, in addition to the negative electrode active material, a conductive material, a binder, and other additives, as needed.

[0090] The conductive material may include, but is not limited to, one or more of carbon black, acetylene black, ketjen black, carbon nanotubes, carbon fibers, and the like.

[0091] For example, the negative electrode active layer may contain carbon black, carbon nanotubes, carbon fibers, etc., alone or in combination, as a conductive material.

[0092] The content of the conductive material may be 0.1 to 10 parts by weight, specifically 0.1 to 8 parts by weight, 0.1 to 5 parts by weight, 0.1 to 3 parts by weight, 2 to 6 parts by weight, or 0.5 to 2 parts by weight, based on 100 parts by weight of the total negative electrode active layer. By controlling the content of the conductive material within the above range, the present invention can prevent a decrease in charge capacity due to an increase in the resistance of the negative electrode caused by a low content of conductive material. Furthermore, it can prevent problems such as a decrease in charge capacity due to a decrease in the content of the negative electrode active material caused by an excessive amount of conductive material, or a decrease in fast charge characteristics due to an increase in the loading amount of the negative electrode active layer.

[0093] The binder is a component that aids in bonding the active material and conductive material, etc., and in bonding to the current collector, and can be suitably used within a range that does not degrade the electrical properties of the electrode. Specifically, the binder can include one or more of vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, and fluororubber.

[0094] The content of the binder may be 0.1 to 10 parts by weight, 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, based on 100 parts by weight of the total negative electrode active layer. By controlling the content of the binder contained in the negative electrode active layer within the above range, the present invention can prevent a decrease in adhesive strength of the active layer due to a low content of binder or a decrease in electrical properties of the electrode due to an excessive amount of binder.

[0095] The negative electrode current collector is not particularly limited as long as it has high conductivity and does not induce chemical changes in the battery, and may be made of, for example, copper, stainless steel, nickel, titanium, calcined carbon, etc. In the case of copper or stainless steel, it may also be surface-treated with carbon, nickel, titanium, silver, etc. The average thickness of the negative electrode current collector is preferably 1 to 500 μm, taking into account the conductivity and total thickness of the negative electrode to be manufactured.

[0096] The present invention will be described in more detail below with reference to examples and experimental examples.

[0097] However, the following examples and experimental examples are merely illustrative of the present invention, and the content of the present invention is not limited to the following examples and experimental examples.

[0098] <Examples and Comparative Examples: Production of Negative Electrode for Lithium Secondary Battery> Using the magnetic alignment apparatus of the present invention having the structure shown in FIG. 1, a negative electrode for a lithium secondary battery in which a carbon-based negative electrode active material is aligned perpendicular to the negative electrode current collector was manufactured.

[0099] Specifically, natural graphite was prepared as the negative electrode active material, and 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. The negative electrode slurry was then cast onto a copper sheet being transported roll-to-roll (transport speed: 5 m / min) using a die coater. The negative electrode slurry was cast to an average thickness of 165 μm along the transport direction of the copper sheet.

[0100] Then, a magnetic field was applied to the negative electrode slurry by moving the copper sheet so that the applied negative electrode slurry passed between the first and second magnet units of the magnetic alignment device, where the separation distance between the first and second magnet units was adjusted to 20 mm (half the separation distance: 10 mm).

[0101] In addition, the first magnet part and the second magnet part were divided into a first region located upstream and a second region located downstream based on the direction of movement of the negative electrode current collector, and (1) the arrangement of the unit magnets contained in each of the first and second regions, (2) the magnetic field strength on the surface of the magnet contained in each region, and (3) the ratio (L1:L2) of the length of the first region (L1) to the length of the second region (L2) in the direction of movement of the negative electrode current collector were adjusted as shown in Table 1 below.

[0102] In addition, in order to dry the negative electrode slurry to which the magnetic field was applied, the copper sheet to which the magnetic field was applied was moved to a drying section, and the negative electrode slurry was dried to manufacture a negative electrode for a lithium secondary battery. (4) The distance between the end of the second region and the drying section was adjusted as shown in Table 1.

[0103] [Table 1]

[0104] <Experimental example> The following experiment was carried out to evaluate the degree of alignment of the carbon-based negative electrode active material as the performance of the magnetic alignment device according to the present invention.

[0105] Specifically, X-ray diffraction spectroscopy (XRD) was performed on the negative electrode active layers of the negative electrodes prepared in Examples 1 to 3 and Comparative Example 1 to measure the spectra. The measurement conditions for the X-ray diffraction (XRD) were as follows:

[0106] - Target: Cu (Kα-ray) graphite monochromator - Slit: Divergence slit = 1 degree, Receiving slit = 0.1 mm, Scattering slit = 1 degree - Measurement area: (1,1,0) plane: 76.5 degrees < 2θ < 78.5 degrees / (0,0,4) plane: 53.5 degrees < 2θ < 56.0 degrees

[0107] From the spectra measured under the above conditions, the average degree of alignment (OI) of each carbon-based negative electrode active material according to Formula 1 was calculated. The results are shown in Table 2.

[0108] [Formula 1] OI=I 004 / I 110

[0109] In Equation 1, I 004 represents the area of the peak representing the (004) crystal plane when the negative electrode active layer is measured by X-ray diffraction spectroscopy (XRD), I 110 represents the area of the peak indicating the (110) crystal plane when the negative electrode active layer is measured by X-ray diffraction spectroscopy (XRD).

[0110] [Table 2]

[0111] As shown in Table 2 above, the magnetic alignment apparatus according to the present invention can produce a negative electrode for a lithium secondary battery with a high degree of alignment of the carbon-based negative electrode active material and excellent surface characteristics. Specifically, the negative electrode of the example manufactured using the magnetic alignment apparatus according to the present invention has a high degree of alignment of the carbon-based negative electrode active material (I 004 / I 110 ) was found to be significantly low at 0.4 or less.

[0112] This means that the magnetic alignment device according to the present invention is equipped with a magnet unit that applies a strong magnetic force in a second region located downstream along the transport direction of the negative electrode current collector, and at the same time, is equipped with a drying unit adjacent to the end of the magnet unit, thereby enabling a high degree of alignment of the carbon-based negative electrode active material contained in the negative electrode slurry.

[0113] These results demonstrate that the magnetic alignment device according to the present invention has the advantage of being able to produce a negative electrode in which the carbon-based negative electrode active material contained in the negative electrode slurry is aligned nearly perpendicular to the negative electrode current collector.

[0114] Although the present invention has been described above with reference to preferred embodiments, it will be understood that a person skilled in the art or having ordinary knowledge in the art can make various modifications and changes to the present invention without departing from the spirit and technical scope of the present invention as set forth in the claims below.

[0115] Therefore, the technical scope of the present invention is not limited to the content described in the Summary of the Invention of the specification, but is defined by the claims. [Explanation of symbols]

[0116] 10: Magnetic alignment device 20:Transfer section 30: Coating section 110a: 1st magnet part 110b: Second magnet part 111a, 111b: a plurality of unit magnets 112a, 112b: Support part 1111a, 1111b: 1st area 1112a, 1112b: 2nd area 120:Drying section S: Negative electrode slurry C: Negative electrode current collector or electrode sheet

Claims

1. A magnetic alignment device for manufacturing a negative electrode for aligning a carbon-based negative electrode active material, a first magnet unit and a second magnet unit, which are respectively positioned above and below the negative electrode current collector coated with the negative electrode slurry containing the carbon-based negative electrode active material in a transport direction, and which apply a magnetic force; a drying unit that dries the negative electrode slurry to which magnetic force is applied by the first magnet unit and the second magnet unit, The first magnet unit and the second magnet unit are each divided into a first region located upstream and a second region located downstream based on a transfer direction of the negative electrode current collector, A magnetic alignment device, wherein a magnetic field having a stronger magnetic force strength than that of the first region is applied to the second region.

2. The magnetic alignment device of claim 1 , wherein the drying section is disposed adjacent to second region ends of the first magnet section and the second magnet section.

3. the first magnet portion and the second magnet portion each include a plurality of unit magnets arranged in a transfer direction (x-axis direction) and a width direction (y-axis direction) of the negative electrode current collector, respectively; 2. The magnetic alignment device according to claim 1, wherein the unit magnets arranged in the second region of the first magnet portion and the second region of the second magnet portion among the plurality of unit magnets are arranged in a Halbach array.

4. The magnetic alignment device according to claim 1 , wherein the length of the second region of the first magnet portion and the second magnet portion in the transfer direction of the negative electrode current collector is shorter than the length of the first region.

5. The magnetic alignment device of claim 4, wherein the second region of the first magnet portion and the second region of the second magnet portion each occupy a length of 5% to 50% of the total length of the first magnet portion and the second magnet portion.

6. 2. The magnetic alignment device according to claim 1, wherein the first magnet portion and the second magnet portion have a length of 0.5 m to 10 m in a direction in which the negative electrode current collector is transferred.

7. The magnetic alignment device 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 magnetic alignment device of claim 1 , wherein the first magnet portion and the second magnet portion include magnets having opposite polarities.

9. 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 of claim 1; and drying the negative electrode slurry in which the carbon-based negative electrode active material is aligned to form a negative electrode active layer.

10. The method of claim 9 , wherein the carbon-based negative electrode active material includes at least one of natural graphite and artificial graphite.

11. The degree of alignment (O.I) of the carbon-based negative electrode active material in the negative electrode active layer, represented by the following formula 1, is 0.1 to 5.0, [Formula 1] O.I=I ００４ / I １１０ In Formula 1, I ００４ represents the area of the peak representing the (004) crystal plane when the negative electrode active layer is measured by X-ray diffraction spectroscopy (XRD), I １１０ The method for producing a negative electrode according to claim 9 or 10, wherein σ represents the area of a peak indicating a (110) crystal plane when the negative electrode active layer is subjected to X-ray diffraction spectroscopy (XRD).

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