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 the benefit of priority based on Korean Patent Application No. 10-2022-0116176 dated September 15, 2022, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

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

[0003] 2. Description of the Related 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-sized devices such as battery packs for hybrid and electric vehicles and power storage devices.

[0004] Such secondary batteries are power generating elements capable of being charged and discharged and have 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 repeated charging and discharging.

[0005] In this case, examples of the negative electrode active material used in the negative electrode include graphite materials such as natural graphite. Such graphite has a layered structure, in which carbon atoms form a network structure, and many layers that spread out in a planar shape are stacked. During charging, lithium ions penetrate from the edge faces (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 faces of the layers. In addition, 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 detouring electron conduction path is formed along the plane direction of the layers.

[0006] In this regard, a technique has been proposed for magnetically orienting the graphite contained in the negative electrode in order to improve the charging performance of the negative electrode in lithium secondary batteries using graphite. Specifically, the (002) crystal plane of the graphite is oriented in a magnetic field during the formation of the negative electrode so that it is almost perpendicular to the negative electrode current collector, and then fixed. In this case, the edge face of the graphite layer faces the positive electrode active layer, so that the insertion and desorption of lithium ions is smoothly performed, and at the same time, the electron conduction path is shortened, improving the electronic conductivity of the negative electrode, thereby improving the charging performance of the battery.

[0007] However, although a magnetic field may be applied to undried negative electrode slurry to induce the orientation of graphite, the conditions of the applied magnetic field may vary depending on various variables such as the loading amount and thickness of the negative electrode slurry containing graphite. However, since it is difficult to reflect such variables in real time during the manufacture of an actual negative electrode, there is a problem in that it is difficult to uniformly realize the orientation of graphite in the negative electrode active layer.

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

[0009] Therefore, there is a demand for a technology that can easily control a magnetic field application means according to the specifications of the negative electrode to be manufactured, such as the thickness of the negative electrode active layer, and / or the negative electrode manufacturing conditions, such as the loading amount of the negative electrode slurry, and can manufacture a negative electrode active layer in which a carbon-based negative electrode active material, such as graphite, aligned with a high degree of alignment is uniformly distributed. Summary of the Invention [Problem to be solved by the invention]

[0010] An object of the present invention is to provide an alignment device capable of uniformly aligning a carbon-based negative electrode active material in a negative electrode active layer by easily adjusting the strength of a magnetic field applied to a negative electrode slurry during the manufacture of a negative electrode, and a method for manufacturing a negative electrode using the same. [Means for solving the problem]

[0011] In order to solve the above-mentioned problems, in one embodiment, the present invention comprises: A magnetic alignment device for a negative electrode, which applies a magnetic force to a negative electrode sheet in which a negative electrode slurry containing a carbon-based negative electrode active material is applied onto a negative electrode current collector, thereby orienting the carbon-based negative electrode active material, a first magnet portion and a second magnet portion respectively disposed above and below the traveling electrode sheet; an alignment degree measuring unit that is disposed downstream of the first magnet unit and the second magnet unit with respect to the running direction of the electrode sheet and that measures the alignment degree of the carbon-based negative electrode active material with respect to the negative electrode current collector; and a control unit that adjusts a distance between the first magnet unit and the second magnet unit according to the alignment degree of the carbon-based negative electrode active material measured by the alignment degree 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 the unit magnets individually move up and down in a vertical direction relative to the running electrode sheet to adjust the distance between the unit magnets facing each other around the electrode sheet, thereby providing a negative electrode magnetic alignment device.

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

[0013] In addition, the control unit may calculate an alignment deviation from the alignment of two or more carbon-based negative electrode active materials measured along the width direction of the traveling electrode sheet, and adjust a separation distance between a unit magnet of the first magnet unit and a unit magnet of the second magnet unit arranged at a corresponding point according to the calculated alignment deviation.

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

[0015] In addition, 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 the unit magnets can individually perform vertical lifting motion relative to the running electrode sheet to adjust the distance between the unit magnets facing each other around the electrode sheet.

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

[0017] Furthermore, the first magnet portion and the second magnet portion may include magnets having opposite poles, and the distance between them may be adjusted to be in the range of 10 mm to 50 mm.

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

[0019] In one embodiment, the present invention further comprises: applying a negative electrode slurry including 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; drying the negative electrode slurry in which the carbon-based negative electrode active material is aligned to form a negative electrode active layer; and 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 the first magnet unit and the second magnet unit provided in the magnetic alignment device.

[0020] In this case, the distance between the first magnet part and the second magnet part can be adjusted so that, when measuring the alignment degree at any three points included in any area (10 cm wide and 10 cm long) 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] In addition, the prepared negative electrode active layer may have an alignment degree of the carbon-based negative electrode active material represented by the following formula 1 of 0.1 to 5.0.

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

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

[0024] Further, in one embodiment, the present invention provides A negative electrode current collector; a negative electrode active layer provided on at least one surface of the negative electrode current collector and including a carbon-based negative electrode active material; The negative electrode active layer satisfies two or more of the following conditions when the average color coordinate deviation between each point is measured for any three points included in a unit area: ΔL*<2.0, Δa*<0.5, and Δb*<0.5; There is provided a negative electrode for a lithium secondary battery, which is manufactured by the method for manufacturing a negative electrode according to the present invention.

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

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

[0027] In formula 1, I 004 indicates the area of ​​the peak representing the (0,0,4) crystal plane in the X-ray diffraction spectroscopy (XRD) measurement of the negative electrode active layer, I 110 indicates the area of ​​the peak indicating the (1,1,0) crystal plane when the negative electrode active layer is measured by X-ray diffraction spectroscopy (XRD). Effect of the Invention

[0028] The magnetic alignment device according to the present invention can measure in real time the degree of alignment of the negative electrode active layer dried in a state in which the carbon-based negative electrode active material is aligned, and can easily control the strength of the magnetic field applied to the negative electrode slurry by individually adjusting the separation distance of the unit magnets constituting the magnet array of the magnet unit in accordance with the measured degree of alignment of the carbon-based negative electrode active material, thereby providing the advantage of high degree of alignment and uniformity of the carbon-based negative electrode active material. [Brief description of the drawings]

[0029] [Figure 1] 1 is a structural diagram showing a schematic configuration of a magnetic alignment device according to the present invention; [Diagram 2] 13 is an image showing the alignment of the ab-axis crystal planes of graphite depending on whether or not a magnetic field is applied to a negative electrode slurry during the formation of a negative electrode active layer, where (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 PREFERRED EMBODIMENTS

[0030] Since the present invention can be modified in various ways and can have various embodiments, specific embodiments are described in detail in the detailed description.

[0031] However, this is not intended to limit the invention to any particular embodiment, but is understood to include all modifications, equivalents, or alternatives falling within the spirit and scope of the invention.

[0032] In the present invention, the terms "comprise" and "have" are intended to specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but are understood as not precluding the presence or additional possibility of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0033] In addition, 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 in between. 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 in between. In addition, in the present application, being "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.

[0034] In the present invention, "containing as a main component" may mean containing 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 defined component relative to the total weight (or total volume). For example, "containing graphite as a main component as a negative electrode active material" may mean containing 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 graphite relative to the total weight of the negative electrode active material, and in some cases, it may mean that the entire negative electrode active material is made 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 a specific crystal plane (e.g., the ab-axis crystal plane of graphite) showing a two-dimensional planar structure of the carbon-based negative electrode active material constituting the negative electrode active material particles is arranged to have a predetermined inclination based on the surface of the negative electrode current collector, as shown in (b) of Figure 2. This may be different from the case where the particles of the carbon-based negative electrode active material themselves 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, as shown in (a) of Figure 2.

[0036] In addition, "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) showing a two-dimensional planar structure of the carbon-based negative electrode active material contained in the negative electrode active layer has a high frequency of having a certain inclination with respect to the surface of the negative electrode current collector. 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 aligned at a high angle (e.g., an angle close to vertical, more than 45°, specifically 60° or more) with respect to the surface of the negative electrode current collector.

[0037] In addition, "high degree of alignment of carbon-based negative electrode active material" may mean that the "degree of alignment (OI)" referred to in this specification is large, and a specific crystal plane (e.g., the ab-axis crystal plane of graphite) showing a 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, "low degree of alignment of carbon-based negative electrode active material" may mean that the "degree of alignment (OI)" is small, and 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 vertical, 45° or more, specifically 60° or more) with respect to the surface of the negative electrode current collector.

[0038] Furthermore, in this specification, the term "average particle size (D 50 ) refers to the particle size at which the cumulative value in the particle size distribution of the particles is 50%, and is also called the median diameter.

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

[0040] <Negative electrode magnetic alignment device> In one embodiment, the present invention comprises: A magnetic alignment device for a negative electrode, which applies a magnetic force to a negative electrode sheet in which a negative electrode slurry containing a carbon-based negative electrode active material is applied onto a negative electrode current collector, thereby orienting the carbon-based negative electrode active material, a first magnet portion and a second magnet portion respectively disposed above and below the traveling electrode sheet; an alignment degree measuring unit that is disposed downstream of the first magnet unit and the second magnet unit with respect to the running direction of the electrode sheet and that measures the alignment degree of the carbon-based negative electrode active material with respect to the negative electrode current collector; and a control unit that adjusts a distance between the first magnet unit and the second magnet unit according to the alignment degree of the carbon-based negative electrode active material measured by the alignment degree measurement unit, The first magnet unit and the second magnet unit each include a plurality of unit magnets arranged in the width direction of the negative electrode slurry, and the unit magnets individually move up and down in a vertical direction relative to the running electrode sheet to adjust the distance between the unit magnets facing each other around the electrode sheet.

[0041] The magnetic alignment device for a negative electrode according to the present invention means a device applied when manufacturing a negative electrode for use in a secondary battery. The magnetic alignment device can align the carbon-based negative 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 the negative electrode slurry containing the carbon-based negative active material is applied, i.e., the surface of the negative electrode slurry. Here, the magnetic alignment device measures the degree of alignment of the carbon-based negative active material contained in the negative electrode active layer formed by drying the negative electrode slurry containing the aligned carbon-based negative active material. The measured degree of alignment can be reflected in the separation distance between the magnet units disposed on the upper and lower parts of the running electrode sheet, thereby controlling the strength of the magnetic field applied to the negative electrode slurry in real time. As a result, the magnetic alignment device can realize uniform alignment of the carbon-based negative active material contained in the negative electrode slurry. In addition, the negative electrode manufactured in this manner can exhibit an effect of increasing the mobility of lithium ions during charging and discharging of the battery and reducing resistance, thereby improving charge and discharge performance.

[0042] Here, being aligned in a direction perpendicular to the negative electrode current collector means that the crystal plane of the carbon-based negative electrode active material is aligned. Specifically, "the carbon-based negative electrode active material is aligned perpendicular to the negative electrode current collector" may mean that the crystal plane of the carbon-based negative electrode active material constituting the spherical particles, specifically, the crystal plane showing the plane direction of the graphite having a two-dimensional structure among the crystal planes of graphite, is aligned perpendicular to the surface of the negative electrode current collector. At this time, the plane direction of the graphite may have an average inclination of 60 to 120° with respect to the negative electrode current collector, and preferably has 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 includes a first magnet unit 110a and a second magnet unit 110b, which are respectively disposed above and below a traveling electrode sheet, i.e., a negative electrode current collector C on which a negative electrode slurry S is applied, as shown in FIG. 1, an alignment degree measuring unit 120, which is disposed downstream of the first magnet unit 110a and / or the second magnet unit 110b based on the traveling direction of the electrode sheet, and measures the alignment degree of the carbon-based negative electrode active material with respect to the negative electrode current collector, and a control unit 130, which adjusts the distance between the first magnet unit 110a and the second magnet unit 110b in accordance with the alignment degree of the carbon-based negative electrode active material measured by the alignment degree measuring unit.

[0044] In the magnetic alignment device 10, the first magnet section 110a and the second magnet section 110b are respectively disposed above and below the traveling electrode sheet, and serve to apply a magnetic field to the surface of the negative electrode slurry S.

[0045] Here, the first magnet unit 110a and the second magnet unit 110b each include a plurality of unit magnets along the width direction of the negative electrode slurry S in order to apply a magnetic field to the surface of the negative electrode slurry S, and may include a means for adjusting the interval between them, i.e., the separation distance, by performing up-and-down movements of the plurality of unit magnets at the top and bottom of the negative electrode slurry, respectively. Specifically, the first magnet unit 110a and the second magnet unit 110b each may 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 running negative electrode slurry, a support unit (not shown) individually fixed to each unit magnet provided in the magnet rows 112a and 112b, and distance adjustment units 111a and 111b connected to the support unit and for inducing the up-and-down movement of the support unit (or the up-and-down movement of the unit magnets) in a direction perpendicular to the running electrode sheet.

[0046] At this time, the distance adjustment means 111a and 111b may operate to receive a distance adjustment value from the control unit 130 and adjust the separation distance between the first magnet unit 110a and the second magnet unit 110b according to the received distance adjustment value.

[0047] The first magnet unit 110a and the second magnet unit 110b have such a configuration, and thus by adjusting the distance between them, the strength of the magnetic field applied to the negative electrode slurry S can be easily controlled. That is, the strength of the magnetic field applied to the negative electrode slurry S can be increased as the distance between the first magnet unit 110a and the second magnet unit 110b becomes narrower, and the strength of the magnetic field applied to the negative electrode slurry S can be decreased as the distance between them becomes wider.

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

[0049] In addition, the first magnet unit 110a is disposed above the traveling electrode sheet, and a Halbach array may be applied to the first magnet row 112a in order to apply a strong magnetic field to the carbon-based negative electrode active material of the negative electrode slurry S. Here, the Halbach array is a permanent magnet arrangement, and a magnet with a high magnetic field strength may be provided by gradually changing the magnetization direction of the magnet. When a magnet having a Halbach array is applied to the first magnet row 112a of the first magnet unit 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 unit 110a and the second magnet unit 110b.

[0050] Here, the distance between the first magnet portion 110a and the second magnet portion 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, and the distance between the first magnet portion 110a and the second magnet portion 110b may be the same as the distance between the first magnet array 112a and the second magnet array 112b. By adjusting the distance between the first magnet portion 110a and the second magnet portion 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.

[0051] In addition, in the magnetic alignment device 10, the alignment degree measuring unit 120 is located downstream of the first magnet unit 110a and / or the second magnet unit 110b based on the running direction of the electrode sheet, and serves to measure the alignment degree of the carbon-based negative electrode active material oriented by the first magnet unit 110a and the second magnet unit 110b in real time.

[0052] At this time, the alignment degree measuring unit 120 may be applied without any particular limitation as long as it is a means / method commonly used in the art for measuring the alignment degree of a carbon-based negative active material, and may preferably include a non-contact measuring device capable of preventing damage and / or change in state of the negative active layer. Specifically, the alignment degree measuring unit may include a non-contact measuring device for measuring the degree to which a crystal plane of the carbon-based negative active material is oriented, or for measuring a physical property that appears differently depending on the degree of alignment of the carbon-based negative active material. For example, the non-contact measuring device may include one or more of a spectrophotometer, a colorimeter, a photometer, an infrared spectrometer (FT-IR), a nuclear magnetic resonance spectrometer (NMR), an X-ray diffraction spectrometer (XRD), a near-edge X-ray fluorescence spectrometer (NEXAFS), and an X-ray photoelectron spectrometer (XPS).

[0053] As an example, the alignment degree measuring unit may include a non-contact measuring device such as a spectrophotometer or a colorimeter capable of quickly measuring the alignment degree, taking into consideration the speed of measuring the alignment degree.

[0054] The color difference meter is a device including a light source and an image sensor, and when an image of the negative active layer is taken, color information of the surface of the negative active layer is converted into color coordinate values ​​and detected, which is advantageous in that it is easy to measure and can be easily applied to a continuous process, etc. Here, the color coordinate values ​​may be expressed in a method such as SCI (Specular Component Included) or SCE (Specular Component Excluded), standard light source D65 (color temperature: 6500K), CIE 1976, etc. As an example, the degree of alignment of the carbon-based negative active material according to the present invention may satisfy 30≦L*≦40, a*≧0.3, b*≧0.4 when expressed in the CIE 1976 method (L*, a*, b*).

[0055] In addition, the alignment degree measuring unit 120 may measure the alignment degree of the carbon-based negative electrode active material in real time by disposing two or more non-contact type measuring devices along the width direction of the running electrode sheet in order to measure the alignment degree of the carbon-based negative electrode active material more precisely. In this case, since it is possible to measure the alignment degree of the carbon-based negative electrode active material in the width direction of the electrode sheet, the reliability of the manufactured negative electrode may be further improved.

[0056] In addition, the alignment measuring unit 120 may include two or more non-contact measuring devices along the running direction of the electrode sheet. Specifically, the alignment measuring unit 120 may include a first measuring device 121 and a second measuring device 122 that are continuously arranged along the running direction of the electrode sheet. In this case, it is possible to reduce an error rate for the alignment degree of the carbon-based negative electrode active material measured in real time.

[0057] In the magnetic alignment device 10, the control unit 130 may control the distance between the first magnet unit 110a and the second magnet unit 110b. To this end, the magnetic alignment device 10 may receive the alignment degrees of the carbon-based negative active material measured by the alignment degree measuring units 120 disposed at two or more points along the width direction of the electrode sheet, and calculate the deviation therebetween. That is, the control unit 130 may calculate the alignment deviation from the alignment degrees of two or more carbon-based negative active materials measured along the width direction of the electrode sheet during running.

[0058] In addition, the control unit 130 may transmit a spacing adjustment value between the unit magnets of the first magnet unit 110a and the unit magnets of the second magnet unit 110b according to the alignment deviation calculated in this manner to the unit magnets of the first magnet unit 110a and the unit points of the second magnet unit 110b at the corresponding points, respectively, and adjust the separation distance between the first magnet unit 110a and the second magnet unit 110b so that it matches the transmitted spacing adjustment value.

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

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

[0061] The above-mentioned gap adjustment value can be obtained and stored by obtaining data regarding the amount of change in the alignment degree of the carbon-based negative electrode active material due to the change in the distance between the first magnet part 110a and the second magnet part 110b using a pre-installed measurement device.

[0062] In addition, since the degree of alignment of the carbon-based negative electrode active material may change depending on the density (or concentration) of the carbon-based negative electrode active material contained in the negative electrode slurry S, the density (or concentration) of the carbon-based negative electrode active material contained in the negative electrode slurry S may affect the strength of the magnetic field.

[0063] Therefore, the database may further include information on the density (or concentration) of the carbon-based negative electrode active material in the negative electrode slurry for correcting the alignment deviation of the carbon-based negative electrode active material along with information on the gap adjustment value between the first magnet unit 110a and the second magnet unit 110b for each alignment deviation measured at two or more points. Also, the gap adjustment value may be a value reflecting data on the density (or concentration) of the carbon-based negative electrode active material in the negative electrode slurry stored in the database.

[0064] In addition, the magnetic alignment device 10 may further include a drying unit 140 that is disposed between the first magnet unit 110a and the second magnet unit 110b and the alignment degree measuring unit 120 and dries the negative electrode slurry S in which the carbon-based negative electrode active material is aligned by the first magnet unit 110a and the second magnet unit 110b.

[0065] The drying section 140 includes a wall (not shown) that blocks the periphery except for an entrance / exit through which the electrode sheet coated with the slurry S is introduced and conveyed out, and a dryer (not shown) for drying the electrode sheet on the wall on the side from which the electrode sheet coated with the electrode slurry is drawn out.

[0066] When the electrode sheet coated with the electrode slurry enters through the inlet of the drying unit 140, energy such as light, heat, and the like supplied from the wall on the opposite side is transferred to the electrode sheet. 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.

[0067] In addition, the dryer may have a configuration that performs 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 type of the dryer is not limited thereto. Specifically, the dryer 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 be operated continuously to dry the negative electrode slurry.

[0068] The first dryer is a device for pre-drying the negative electrode slurry, and may irradiate light or wavelengths onto the surface of the negative electrode slurry as described above. In general, the negative electrode slurry may be dried by applying hot air at a high temperature. However, in this case, the drying time of the negative electrode slurry becomes long, and the alignment of the carbon-based negative electrode active material in the negative electrode slurry may be disturbed. In addition, if the temperature of the hot air is increased to solve this problem, the tendency of drying at the surface of the slurry increases, and a phenomenon (migration) occurs in which the binder is concentrated on the surface of the slurry due to the volatilized solvent, and the adhesion strength between the active material layer and the negative electrode current collector decreases. The present invention may have a configuration in which the electrode slurry is pre-dried by irradiating energy in the form of light or wavelengths using the first dryer so that the negative electrode slurry can be dried while maintaining a high degree of alignment of the carbon-based negative electrode active material without such problems. The first dryer may include, for example, an ultraviolet dryer, a near infrared dryer, a far infrared dryer, etc., and may specifically 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 in order to realize a uniform drying speed of the electrode slurry. The far infrared dryer has a long light or wavelength and is highly energy efficient, unlike near infrared dryers and infrared rays commonly used in the industry. Furthermore, the far infrared dryer has the advantage that it can apply energy uniformly not only to the surface of the negative electrode slurry but also to the inside, thereby increasing the adhesive strength between the negative electrode slurry and the negative electrode current collector in a short time.

[0069] At this time, the first dryer is 50 kW / m 2 ~1,000kW / m 2 The power density of the device is 50 kW / m. 2 ~500kW / m 2 , 50kW / m 2 ~250kW / m 2 , or 50 kW / m 2 , and 200 kW / m 2In the present invention, by controlling the power density of the first dryer within the above range, it is possible to prevent uneven drying of the active material layer caused by an excessive power density.

[0070] In addition, 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, and may include, for example, a hot air dryer, a vacuum oven, etc., used alone or in combination.

[0071] Since the magnetic alignment device according to the present invention has the above-mentioned configuration, it can reflect the state of the negative electrode slurry in real time and uniformly induce the alignment of the internal carbon-based negative electrode active material. Therefore, the manufactured negative electrode can exhibit the effect of increasing the mobility of lithium ions and reducing the resistance during charging and discharging of the battery, thereby improving the charge and discharge performance.

[0072] <Method of manufacturing the negative electrode> In one embodiment, the present invention further comprises: applying a negative electrode slurry including 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; drying the negative electrode slurry in which the carbon-based negative electrode active material is aligned to form a negative electrode active layer; and 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 the first magnet unit and the second magnet unit provided in the magnetic alignment device.

[0073] The method for manufacturing a negative electrode according to the present invention can align the carbon-based negative active material in the negative electrode slurry so as to be perpendicular to the surface of the negative electrode current collector (or the running direction of the electrode sheet) by applying a magnetic field to the surface of the applied negative electrode slurry using the magnetic alignment device of the present invention. In addition, the manufacturing method can form a negative electrode active layer in which the vertical alignment of the carbon-based negative active material is maintained by subsequently continuously drying the negative electrode slurry.

[0074] In this case, the manufacturing method of the negative electrode may 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 above-mentioned magnetic alignment device, and may adjust the distance between the first magnet unit and the second magnet unit respectively disposed on the upper and lower parts of the electrode sheet according to the measured degree of alignment. Specifically, the manufacturing method may 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 a deviation occurs, adjust the distance between the first magnet unit and the second magnet unit provided in the magnetic alignment device to reduce the deviation.

[0075] In the negative electrode active layer thus manufactured, the carbon-based negative electrode active material aligned perpendicular to the negative electrode current collector is uniformly distributed, and the deviation during the measurement of the alignment degree may be significantly low. For example, when the alignment degree of the carbon-based negative electrode active material is measured using a spectrophotometer, the average color coordinate deviation (ΔL*, Δa*, Δb*) representing the alignment degree deviation at any three points included in any area (10 cm wide and 10 cm long) on ​​the negative electrode active layer may satisfy two or more of the following conditions: ΔL*<2.0, Δa*<0.5, and Δb*<0.5, and more specifically, may satisfy two or more of the following conditions: ΔL*<1.0, Δa*<0.3, and Δb*<0.3. If the above conditions are not satisfied, the interval between the first magnet part and the second magnet part, i.e., the separation distance, may be adjusted. By including such a configuration, the present invention may maintain the alignment degree of the carbon-based negative electrode active material contained in the negative electrode active layer uniformly, thereby further improving the reliability of the negative electrode.

[0076] 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.

[0077] In addition, in the step of aligning the carbon-based negative active material contained in the negative electrode slurry using a magnetic alignment device, the magnetic field application conditions may be controlled to improve the alignment efficiency of the carbon-based negative active material. Specifically, the degree of alignment of the carbon-based negative active material may be controlled by the strength, application time, etc. of the magnetic field.

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

[0079] Moreover, the magnetic field may be applied for 0.1 to 20 seconds, and more specifically, for 0.5 to 15 seconds, 0.5 to 12 seconds, 1 to 10 seconds, or 2 to 8 seconds.

[0080] <Negative electrodes 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 active material and a negative active layer on at least one surface of a negative current collector, and the negative active layer may have a structure in which the carbon-based negative active material is uniformly dispersed and aligned perpendicularly to the negative current collector. As one example, when the alignment degree is measured at any three points included in an arbitrary area (10 cm wide and 10 cm long) on ​​the negative active layer, the deviation of the average color coordinates (ΔL*, Δa*, Δb*) between each point, which indicates the alignment degree, 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 including a carbon-based negative electrode active material on both sides 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 manufactured by applying an electrode slurry including a negative electrode active material that realizes an electrochemical oxidation-reduction reaction during charging and discharging of the battery to both sides of the electrode current collector, and then drying and rolling the same. The negative electrode active layer includes a carbon-based negative electrode active material as a negative electrode active material to realize electrical activity through a reversible oxidation-reduction reaction during charging and discharging of the battery. 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 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 some cases. In this case, the mixture ratio of natural graphite to artificial graphite may be 5-40:60-95, or 10-30:70-90, based on weight. By containing natural graphite and artificial graphite in the above-mentioned mixture ratio, the carbon-based negative electrode active material may realize 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.

[0083] The carbon-based negative electrode active material is preferably a spherical graphite granule formed by the aggregation of a plurality of flake graphite. Examples of flake graphite include natural graphite, artificial graphite, mesophase calcined carbon (bulk mesophase) made from tar and pitch, graphitized cokes (raw coke, green coke, pitch coke, needle coke, petroleum coke, etc.), etc. In particular, a graphite granule assembled from a plurality of highly crystalline natural graphites is preferable. In addition, one graphite granule may be formed by the aggregation of 2 to 100 flake graphite particles, preferably 3 to 20 flake graphite particles.

[0084] Such a carbon-based negative electrode active material, specifically, graphite, may have a spherical particle shape, and the sphericity of the graphite particles may be 0.75 or more, for example, 0.75 to 1.0, 0.75 to 0.95, 0.8 to 0.95, or 0.90 to 0.99. Here, the "sphericity" may 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, and when the sphericity is 1, it means that the particle shape is spherical. The sphericity may be measured using a particle shape analyzer. The present invention has the advantages of realizing a shape of the carbon-based negative electrode active material close to a sphere, thereby realizing high 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 adhesive force between the negative electrode active layer and the current collector.

[0085] In addition, the carbon-based negative electrode active material has an average particle size (D 50 ), specifically, the average particle size (D 50 ) can be shown.

[0086] 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 so as to prevent the expansion of the particles due to charging of lithium ions. 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, and the sphericity and sphericity yield may be reduced. On the other hand, when the maximum particle size exceeds 10 μm, the expansion becomes intense, and the adhesion between particles and between the particles and the current collector decreases due to repeated charging and discharging, and the cycle characteristics may be significantly reduced.

[0087] In the negative electrode active layer including such a carbon-based negative electrode active material, the degree of alignment of the carbon-based negative electrode active material can be controlled to a constant level. The present invention can reduce electrode resistance by aligning the crystal plane of the carbon-based negative electrode active material contained in the negative electrode active layer in a constant 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 graphite.

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

[0090] Here, the term "color coordinates" refers to coordinates in the CIE color space, which are color values ​​defined by the CIE (Commossion International de l'Eclairage), and any position in the CIE color space can be expressed by three coordinate values: L*, a*, and b*. Here, the L* value represents brightness, and L*=0 represents black, and L*=100 represents white. The a* value represents whether the color having the color coordinates is biased toward pure magenta or pure green, and the b* value represents whether the color having the color coordinates is biased toward pure yellow or pure blue. Specifically, the a* value ranges from -a to +a, and the maximum value of a* (a*max) represents pure magenta, and the minimum value of a* (a*min) represents pure green. For example, if the a* value is negative, it means that the color is biased toward pure green, and if it is positive, it means that the color is biased toward pure red. When comparing a*=80 and a*=50, it means that a*=80 is closer to pure red than a*=50. In addition, the above b* value ranges from -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, if the b* value is negative, it means that the color is biased toward pure yellow, and if it is positive, it means that the color is biased toward pure blue. When comparing b*=80 and b*=20, it means that b*=80 is closer to pure yellow than b*=20.

[0091] In another example, the negative electrode active layer may have a carbon-based negative electrode active material aligned perpendicular to the negative electrode current collector, and the degree of alignment (OI) of the carbon-based negative electrode active material, represented by the following Equation 1, may be 0.1 to 5.0 when the negative electrode active layer is measured by X-ray diffraction spectroscopy (XRD).

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

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

[0094] The crystal plane orientation of the carbon-based negative electrode active material can be determined by a 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 represented by the above formula 1 can be an index indicating the direction in which the crystal 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 indicating the two-dimensional planar structure of the carbon-based negative electrode active material is aligned with respect to the surface of the negative electrode current collector. For example, when the negative electrode active layer contains graphite as the carbon-based negative electrode active material, the negative electrode active layer exhibits 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 peaks for graphite during X-ray diffraction spectroscopy analysis. This refers to the (002) plane, (100) plane, (101)R plane, (101)H plane, (004) plane, and (110) plane of the crystal planes of graphite contained in the negative electrode active layer. In general, 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 to have a hexagonal or rhombohedral crystal structure. Here, the above crystal plane peak is a peak that indicates the plane characteristics of such a crystal structure. In addition, the peak that appears at 2θ=43.4±0.2° may be considered to be an overlap of the peaks corresponding to the (101)R plane of the carbon-based material and the (111) plane of the current collector, for example, Cu.

[0095] In the present invention, the degree of alignment (OI) of graphite can be measured 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. In addition, the X-ray diffraction was measured using CuKα radiation as a target line, and the target line was extracted and measured using a monochromator device to improve the peak intensity resolution. At this time, the measurement conditions were 2θ=10°-90°, a scan speed (° / s) of 0.044-0.089, and a step size of 0.026° / step. In addition, 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 the two-dimensional planar structure of the graphite layers is laminated, and the (110) plane appearing at 2θ=77.5±0.2° indicates the planar characteristic (ab-axis direction characteristic) of the laminated graphite layers. Therefore, the smaller the (004) plane peak indicating the thickness direction characteristic of the graphite layer plane, and the larger the (110) plane peak indicating the planar characteristic of the graphite layer, the higher the angle at which the graphite plane is aligned with respect to the negative electrode current collector surface. In other words, the closer the OI value is to 0, the closer the angle or inclination of the graphite layer surface to the negative electrode current collector surface is to 90°, and the larger the OI value is, the closer the inclination to the negative electrode current collector surface is to 0° or 180°. In this aspect, in the negative electrode active layer according to the present invention, since the carbon-based negative electrode active material is aligned perpendicular to the negative electrode current collector, the degree of alignment (OI) of graphite may be lower than when a magnetic field is not applied.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 4 ... It can be 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.

[0096] Furthermore, in the negative electrode active layer, vertical alignment of the carbon-based negative electrode active material with respect to the negative electrode current collector may be uniformly induced, and the alignment deviation of the carbon-based negative electrode active material measured arbitrarily per unit area may be low.

[0097] As one example, when the degree of alignment of the negative electrode active layer is measured for any three points included in any area (10 cm wide and 10 cm long) on ​​the negative electrode active layer, the average color coordinate deviation (ΔL*, Δa*, Δb*) between each point may satisfy two or more of the following conditions: ΔL*<2.0, Δa*<0.5, and Δb*<0.5, and more specifically, may satisfy two or more of the following conditions: ΔL*<1.0, Δa*<0.3, and Δb*<0.3.

[0098] In another example, in the negative electrode active layer, when X-ray diffraction spectroscopy (XRD) is measured at any three points present in a unit area (10 cm x 10 cm) of the negative electrode active layer, the alignment deviation 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.

[0099] Meanwhile, the negative electrode active layer according to the present invention may further selectively contain a conductive material, a binder, other additives, and the like, in addition to the negative electrode active material, as necessary.

[0100] 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.

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

[0102] At this time, 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, 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 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 the conductive material. In addition, 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 due to an excessive amount of the conductive material, resulting in a decrease in charge capacity, or a decrease in rapid charge characteristics due to an increase in the loading amount of the negative electrode active layer.

[0103] In addition, the binder is a component that aids in bonding between the active material and the conductive material and the current collector, and may be suitably used within a range that does not deteriorate the electrical properties of the electrode. Specifically, the binder may include any 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.

[0104] 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 the binder, or a decrease in electrical properties of the electrode due to an excessive amount of the binder.

[0105] The negative electrode current collector is not particularly limited as long as it has high conductivity without inducing chemical changes in the battery, and may be, for example, copper, stainless steel, nickel, titanium, calcined carbon, etc., and in the case of copper or stainless steel, it may be surface-treated with carbon, nickel, titanium, silver, etc. The average thickness of the negative electrode current collector may be suitably 1 to 500 μm, taking into consideration the conductivity and total thickness of the negative electrode to be manufactured.

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

[0107] 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.

[0108] <Examples 1 to 2 and Comparative Example: Production of negative electrode for lithium secondary battery> A negative electrode was manufactured using the magnetic alignment apparatus of the present invention having the structure shown in FIG. 1, and the number of non-contact measuring devices installed in the alignment degree measuring unit was adjusted as shown in Table 1 to manufacture a negative electrode for a lithium secondary battery.

[0109] Specifically, natural graphite was first 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, which was then cast using a die coater onto a copper sheet being transferred roll-to-roll (transfer speed: 3 m / min). At this time, the negative electrode slurry was cast so as to have a three-line stripe pattern along the running direction of the copper sheet, and 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] Thereafter, 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 magnet unit and the second magnet unit. Here, the first magnet unit and the second magnet unit individually adjusted the separation distance of the unit magnets provided in the first magnet row (including 5 to 20 unit magnets) and the second magnet row (including 5 to 20 unit magnets) according to the interval reference value transmitted from the control unit by adjusting the distance adjustment means. Here, the separation distance between the first magnet row and the second magnet row was adjusted to 20 to 40 mm according to the interval reference value transmitted from the control unit, and the strength of the applied magnetic field was 1.0 T.

[0111] 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 unit, 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 alignment degree of the dried negative electrode slurry, i.e., the carbon-based negative electrode active material in the negative electrode active layer, was measured, and the measured alignment degree was transmitted to a control unit, and the control unit transmitted a reference value for the interval between the unit magnets of the first magnet unit and the second magnet unit according to the alignment degree received.

[0112] Here, the alignment degree of the carbon-based negative active material was measured using a spectrophotometer or an X-ray diffraction spectrometer (XRD) installed at three points along the width direction of the electrode sheet as an alignment degree measuring unit as shown in Table 1. The alignment degree at each point measured by the alignment degree measuring unit was transmitted to a control unit. The control unit calculated the alignment degree deviation from the received alignment degree at each starting point. Thereafter, the control unit compared the calculated alignment degree deviation with the interval adjustment value between the first magnet unit 110a and the second magnet unit 110b according to the deviation between the alignment degrees of the carbon-based negative active material stored in the database, and transmitted the corresponding interval adjustment value to the unit magnet of the first magnet unit 110a at the corresponding point and the unit point of the second magnet unit 110b, respectively. The first magnet unit 110a and the second magnet unit 110b continuously performed the negative electrode manufacturing process while adjusting the separation distance of the unit magnets at the corresponding points to match the received interval adjustment value.

[0113] [Table 1]

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

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

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

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

[0118] <Experimental Example: Evaluation of Alignment Uniformity of Carbon-Based Negative Electrode Active Material> The following experiment was carried out to evaluate the uniformity of alignment of the carbon-based negative electrode active material as the performance of the magnetic alignment device according to the present invention.

[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 each of the running direction and width direction of the negative electrode during manufacture, to set points A to F. At this time, each point was set to have a size of 10 cm in width and 10 cm in length.

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

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

[0122] [Table 2]

[0123] As shown in Table 2, the negative electrode manufactured using the magnetic alignment device according to the present invention had a high degree of alignment of the carbon-based negative active material contained in the negative active layer. In addition, it was confirmed that the negative active layer of the manufactured negative electrode had a low deviation between the alignment degree at any three points and their average value. This means that the magnetic alignment device according to the present invention aligns the carbon-based negative active material uniformly on the negative 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 high alignment and uniformity relative to the negative electrode current collector by measuring the alignment degree of the carbon-based negative electrode active material in real time and individually reflecting the result to the unit magnets included in the first magnet row of the first magnet unit and the second magnet row of the second magnet unit.

[0125] 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 may make various modifications and changes to the present invention without departing from the spirit and technical scope of the present invention as described in the claims below.

[0126] Therefore, the technical scope of the present invention is not limited to the contents described in the Summary of the Invention of 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 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 in which a negative electrode slurry containing a carbon-based negative electrode active material is applied onto a negative electrode current collector, thereby orienting the carbon-based negative electrode active material, a first magnet portion and a second magnet portion respectively disposed above and below the traveling electrode sheet; an alignment degree measuring unit that is disposed downstream of the first magnet unit and the second magnet unit with respect to a running direction of the electrode sheet and that measures an alignment degree of the carbon-based negative electrode active material with respect to a negative electrode current collector; a control unit that adjusts a distance between the first magnet unit and the second magnet unit according to the alignment degree of the carbon-based negative electrode active material measured by the alignment degree 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 vertical direction relative to the running electrode sheet to adjust the separation distance between the unit magnet facing the electrode sheet and the electrode sheet.

2. The negative electrode magnetic alignment device according to claim 1 , wherein the alignment measuring unit includes two or more non-contact measuring devices arranged along a width direction of the traveling electrode sheet.

3. The negative electrode magnetic alignment device of claim 2, wherein the non-contact measuring instrument includes one or more of 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. 2. The negative electrode magnetic alignment device of claim 1, wherein 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 the electrode sheet is moving, and adjusts a separation distance between the unit magnets of the first magnet unit and the unit magnets of the second magnet unit arranged at a measurement point in accordance with the calculated alignment deviation.

5. 2 . The negative electrode magnetic alignment device of claim 1 , wherein the control unit includes a database storing a gap adjustment value between the unit magnets of the first magnet unit and the unit magnets of the second magnet unit according to an 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 a support portion which is fixed individually to each unit magnet; 2. The negative electrode magnetic alignment device according to claim 1, further comprising: a distance adjustment means connected to the support and configured to induce an elevation movement of the support in a direction perpendicular to the electrode sheet during movement.

7. 2. The negative electrode 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 negative pole magnetic alignment device of claim 1 , wherein the first magnet portion and the second magnet portion include magnets having opposite poles.

9. 2. The magnetic alignment device of claim 1, further comprising a drying unit between the first magnet unit, the second magnet unit and the alignment degree measuring unit, the drying unit drying the negative electrode slurry in which the carbon-based negative electrode active material is aligned.

10. applying a negative electrode slurry including 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 by using the negative electrode magnetic alignment device according to claim 1; drying the negative electrode slurry in which the carbon-based negative electrode active material is aligned to form a negative electrode active layer; measuring an alignment degree of the carbon-based negative electrode active material contained in two or more points along a width direction of the formed negative electrode active layer, and adjusting a gap between the first magnet unit and the second magnet unit provided in the magnetic alignment device based on a deviation of the measured alignment degree.

11. 11. The method of claim 10, wherein the distance between the first magnet part and the second magnet part is adjusted such that, when measuring the alignment of three arbitrary points included in an arbitrary region (10 cm wide and 10 cm long) on ​​the negative electrode active layer, the average color coordinate deviation (ΔL*, Δa*, Δb*) between the points satisfies two or more of the following conditions: ΔL*<2.0, Δa*<0.5, and Δb*<0.

5.

12. In the negative electrode active layer, the degree of alignment (O.I) of the carbon-based negative electrode active material 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 in X-ray diffraction spectroscopy measurement of the negative electrode active layer, I １１０ The method for producing a negative electrode according to claim 10 , wherein R represents the area of ​​a peak indicating a (110) crystal plane in X-ray diffraction spectroscopy of the negative electrode active layer.

13. A negative electrode current collector; a negative electrode active layer provided on at least one surface of the negative electrode current collector and including a carbon-based negative electrode active material; the negative electrode active layer satisfies two or more of the following conditions when the average color coordinate deviation between any three points included in a unit area is measured: ΔL*<2.0, Δa*<0.5, and Δb*<0.5; A negative electrode for a lithium secondary battery, produced by the method for producing a negative electrode according to claim 10.

14. In the negative electrode active layer, the degree of alignment (O.I) of the carbon-based negative electrode active material 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 in X-ray diffraction spectroscopy measurement of the negative electrode active layer, I １１０ The negative electrode for a lithium secondary battery according to claim 13, wherein m represents the area of ​​a peak indicating a (110) crystal plane in X-ray diffraction spectroscopy of the negative electrode active layer.

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