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 used in manufacturing a negative electrode and a method for manufacturing a negative electrode using the same. The magnetic alignment device measures the loading amount of a negative electrode slurry applied to a negative electrode current collector in real time, and can easily control the strength of a magnetic field by adjusting the separation distance of a magnet part according to the measured loading amount of the negative electrode slurry, which is advantageous in that the degree of alignment of the crystal plane of a carbon-based negative electrode active material contained in a manufactured negative electrode active layer is uniformly high.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0116184, filed on September 15, 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 uniformly aligning a negative electrode active material in a negative electrode active layer 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, with carbon atoms forming a network structure and many planar layers stacked on top of each other. During charging, lithium ions penetrate through 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, because 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 response to this issue, a technique for magnetically orienting graphite contained in a negative electrode has been proposed to improve the charging performance of 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 plane of the graphite layer faces the positive electrode active layer, facilitating the insertion and desorption of lithium ions. At the same time, the electron conduction path is shortened, improving the electronic conductivity of the negative electrode and thereby improving the charging performance of the battery.

[0007] However, although graphite orientation can be induced by applying a magnetic field to undried negative electrode slurry, the conditions of the applied magnetic field may vary depending on various variables such as the loading amount and thickness of the graphite-containing negative electrode slurry. However, there is a limitation in that it is difficult to reflect these variables in real time during actual negative electrode manufacturing, making it difficult to achieve uniform graphite orientation.

[0008] Furthermore, a single negative electrode manufacturing device 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 device according to the specifications of the negative electrodes being manufactured.

[0009] Therefore, there is a need 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 loading amount and thickness of the negative electrode active layer, and / or negative electrode manufacturing conditions, such as the loading amount of the negative electrode slurry, and that can manufacture a negative electrode active layer in which the crystal planes of a carbon-based negative electrode active material, such as graphite, are uniformly aligned. [Prior art documents] [Patent documents]

[0010] [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]

[0011] An object of the present invention is to provide an alignment device capable of uniformly aligning the crystal planes of a carbon-based negative electrode active material contained in a negative electrode active layer by adjusting the strength of a magnetic field according to the loading amount of a negative electrode slurry containing a carbon-based negative electrode active material, and a method for manufacturing a negative electrode using the same. [Means for solving the problem]

[0012] In order to solve the above-mentioned problems, in one embodiment, the present invention provides: A magnetic alignment device for a negative electrode that 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; a loading amount measuring unit that is disposed upstream of the first magnet unit and the second magnet unit with respect to the running direction of the electrode sheet and that measures the loading amount of negative electrode slurry that is disposed on the electrode sheet; a control unit that adjusts a separation distance between the first magnet unit and the second magnet unit according to a loading amount of the negative electrode slurry measured by the loading amount 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 direction perpendicular to the running electrode sheet, thereby providing a negative electrode magnetic alignment device in which the separation distance between the unit magnets facing each other is adjustable around the electrode sheet.

[0013] In this case, the control unit may include a database in which a reference value of the gap between the first magnet unit and the second magnet unit according to the loading amount of the negative electrode slurry is stored, and may calculate the reference value of the gap corresponding to the loading amount of the negative electrode slurry measured by the loading amount measuring unit, thereby adjusting the separation distance between the first magnet unit and the second magnet unit.

[0014] Here, the distance between the first magnet part and the second magnet part may be 10 mm to 50 mm.

[0015] 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 guiding the up and down movement of the support part in a direction perpendicular to the running electrode sheet.

[0016] Additionally, the first and second magnet portions may include magnets having opposite poles.

[0017] The loading amount measuring unit may include at least one of a web gauge and an ultrasonic sensor.

[0018] Here, the ultrasonic sensor may include an ultrasonic generator that scans the surface of the negative electrode slurry with ultrasonic waves, an ultrasonic receiver that receives the returned ultrasonic waves after the ultrasonic waves generated by the ultrasonic generator scan the loaded electrode slurry, and a data transmitter that calculates the loading amount of the negative electrode slurry from data obtained by the scan and transmits the calculated amount to a control unit.

[0019] The magnetic alignment device may further include a drying unit that dries the negative electrode slurry in which the carbon-based negative electrode active material is aligned by the first magnet unit and the second magnet unit.

[0020] 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 a carbon-based negative electrode active material contained in a negative electrode slurry using a 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. The step of aligning the carbon-based negative electrode active material provides a method for manufacturing a negative electrode, in which the step is controlled by adjusting the distance between the negative electrode slurry and the magnet part of the magnetic alignment device according to the loading amount of the negative electrode slurry.

[0021] Here, the negative electrode slurry is 100 mg / 25 cm 2 ~500mg / 25cm 2 It can be applied at a loading of

[0022] In addition, the negative electrode active layer formed on the negative electrode current collector may have an alignment degree (OI) of the carbon-based negative electrode active material represented by the following formula 1 of 0.1 to 5.0.

[0023] [Formula 1] OI=I 004 / I 110

[0024] In Equation 1, I 004 represents the area of ​​the peak representing the (004) crystal plane in 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). [Effects of the Invention]

[0025] The magnetic alignment device according to the present invention can measure the loading amount of anode slurry applied to the anode current collector in real time, and can easily control the strength of the magnetic field by individually adjusting the separation distance between unit magnets constituting the magnet array of the magnet unit in accordance with the measured loading amount of anode slurry. This has the advantage that the degree of alignment of the crystal planes of the carbon-based anode active material contained in the manufactured anode active layer is uniformly high. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a structural diagram showing a schematic configuration of a magnetic alignment device according to the present invention; [Figure 2] 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

[0027] Because the present invention is susceptible to various modifications and can have various embodiments, specific embodiments are described in detail in the detailed description.

[0028] 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.

[0029] 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, and are understood as not precluding the presence or possible addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof.

[0030] 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.

[0031] Furthermore, in the present invention, "comprising as a main component" can mean that the defined component is contained in an amount of 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) based on the total weight (or total volume). For example, "comprising graphite as a main component as a negative electrode active material" can mean that graphite is contained in an amount of 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 based on the total weight of the negative electrode active material. In some cases, it can mean that the entire negative electrode active material is composed of graphite, with graphite accounting for 100 wt%.

[0032] 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 Figure 2(b). This may differ from the case where the carbon-based negative electrode active material particles 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, as shown in Figure 2(a).

[0033] 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.

[0034] Furthermore, "a carbon-based negative electrode active material with a high degree of alignment" may mean that the "degree of alignment (OI)" referred to herein is large, and 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 is aligned at a low angle (e.g., less than 45°) relative to the surface of the negative electrode current collector. Conversely, "a carbon-based negative electrode active material with a low degree of alignment" may mean that the "degree of alignment (OI)" is small, and 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 greater, specifically 60° or greater) relative to the surface of the negative electrode current collector.

[0035] 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.

[0036] The present invention will now be described in more detail.

[0037] <Negative electrode magnetic alignment device> In one embodiment, the present invention comprises: A magnetic alignment device for a negative electrode that 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; a loading amount measuring unit that is disposed upstream of the first magnet unit and the second magnet unit with respect to the running direction of the electrode sheet and that measures the loading amount of negative electrode slurry that is disposed on the electrode sheet; a control unit that adjusts a separation distance between the first magnet unit and the second magnet unit according to a loading amount of the negative electrode slurry measured by the loading amount 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 direction perpendicular to the running electrode sheet, thereby providing a negative electrode magnetic alignment device in which the separation distance between the unit magnets facing each other is adjustable around the electrode sheet.

[0038] The magnetic alignment device for a negative electrode according to the present invention is a device used in manufacturing a negative electrode for a secondary battery. It applies a magnetic field to the surface of a negative electrode current collector coated with a negative electrode slurry containing a carbon-based negative electrode active material, i.e., the surface of the negative electrode slurry, to align the carbon-based negative electrode active material contained in the negative electrode slurry in a direction perpendicular to the negative electrode current collector. The magnetic alignment device measures the conditions of the negative electrode slurry coated on the negative electrode current collector during magnetic field application, specifically, the loading amount of the negative electrode slurry, in real time, and controls the magnetic field strength of magnets disposed above and below the moving electrode sheet. As a result, the magnetic alignment device can achieve uniform alignment of the carbon-based negative electrode active material contained in the negative electrode slurry. The negative electrode manufactured in this manner can exhibit improved charge / discharge performance due to increased lithium ion mobility and reduced resistance during battery charge / discharge.

[0039] 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°.

[0040] To this end, the magnetic alignment device 10 according to the present invention includes a first magnet unit 120a and a second magnet unit 120b, which are respectively disposed above and below a traveling electrode sheet, i.e., a negative electrode current collector C coated with negative electrode slurry S, as shown in FIG. 1; a loading amount measuring unit 110, which is disposed upstream of the first magnet unit 120a and / or the second magnet unit 120b in terms of the traveling direction of the electrode sheet and measures the loading amount of negative electrode slurry S on the electrode sheet; and a control unit 130, which adjusts the separation distance between the first magnet unit 120a and the second magnet unit 120b according to the loading amount of negative electrode slurry measured by the loading amount measuring unit.

[0041] In the magnetic alignment device 10, the loading amount measuring unit 110 is located upstream of the first magnet unit 120a and / or the second magnet unit 120b in the running direction of the electrode sheet and serves to measure the loading amount of the negative electrode slurry S before the magnetic field applied by the magnet unit affects the negative electrode slurry. The loading amount measuring unit 110 may be any means / method commonly used in the art for measuring the loading amount of the negative electrode slurry S, and may include a non-contact measuring device that can prevent loss and / or change in state of the negative electrode slurry. For example, the loading amount measuring unit 110 may include one or more of a web gauge and an ultrasonic sensor. The ultrasonic sensor may include an ultrasonic receiver that generates ultrasonic waves, scans the loaded negative electrode slurry, and receives the returned ultrasonic waves; and a data transmitter that calculates the loading amount of the negative electrode slurry from data obtained by the scan and transmits the calculated amount to a control unit.

[0042] In addition, to more precisely measure the loading amount of the negative electrode slurry S, the loading amount measurement unit 110 may measure the loading amount of the negative electrode slurry S in real time by arranging two or more non-contact measuring devices in the width direction of the traveling negative electrode slurry S. The measured loading amount values ​​are transmitted to the control unit, and an average value thereof may be reflected as the loading amount of the negative electrode slurry. This has the advantage of more precisely measuring the loading amount of the negative electrode slurry applied using a die coater, etc.

[0043] The loading amount measuring unit 110 may include two or more non-contact measuring devices along the running direction of the electrode sheet. Specifically, the loading amount measuring unit 110 may include a first measuring device 111 and a second measuring device 112 that are successively arranged along the running direction of the electrode sheet. In this case, the error rate of the loading amount of negative electrode slurry measured in real time may be reduced.

[0044] In the magnetic alignment device 10, the control unit 130 may control the separation distance between the first magnet unit 120a and the second magnet unit 120b. To this end, the magnetic alignment device 10 receives the loading amount of the negative electrode slurry S measured by the loading amount measurement unit 110, compares the loading amount of the negative electrode slurry S with a reference interval value to recognize a reference interval value corresponding to the measured loading amount of the negative electrode slurry, and transmits the recognized reference interval value to the first magnet unit 120a and the second magnet unit 120b, respectively, to adjust the separation distance between the first magnet unit 120a and the second magnet unit 120b.

[0045] Here, the reference gap value refers to a value indicating the gap, i.e., the separation distance, between the first magnet unit 120a and the second magnet unit 120b according to the loading amount of negative electrode slurry S. This value may be stored in a database (not shown) provided in the control unit 130. The reference gap value may be a value obtained by obtaining data regarding the separation distance between the first magnet unit 120a and the second magnet unit 120b according to the loading amount of negative electrode slurry S using an existing conventional measuring device, selecting only data from the obtained data that most effectively realizes the alignment of the carbon-based negative electrode active material contained in the negative electrode slurry, and storing the selected data in the database.

[0046] In addition, even if the loading amount of the negative electrode slurry S is the same, the content of the carbon-based negative electrode active material may vary depending on the density (or concentration) of the carbon-based negative electrode active material contained in the negative electrode slurry. Furthermore, since the content of the carbon-based negative electrode active material affects the alignment of the crystal plane with respect to the negative electrode current collector C, the strength of the magnetic field may be adjusted depending on the content during alignment. Therefore, the database may further include information on the separation distance between the first magnet unit 120a and the second magnet unit 120b according to the loading amount of the negative electrode slurry S, as well as density (or concentration) information on the carbon-based negative electrode active material in the negative electrode slurry for each loading amount of the negative electrode slurry S to correct the loading amount of the negative electrode slurry S.

[0047] In addition, since the density (or concentration) of the carbon-based negative electrode active material may affect the magnetic field strength due to the compensation for the loading amount of the negative electrode slurry S, as described above, the interval reference value stored in the database may be a value reflecting data related to the density (or concentration) of the carbon-based negative electrode active material in the negative electrode slurry stored in the database.

[0048] Furthermore, in the magnetic alignment device 10, the first magnet part 120a and the second magnet part 120b are respectively arranged above and below the traveling electrode sheet, and serve to apply a magnetic field to the surface of the negative electrode slurry S.

[0049] Here, the first magnet unit 120a and the second magnet unit 120b may each include a plurality of unit magnets arranged along the width direction of the negative electrode slurry S to apply a magnetic field to the surface of the negative electrode slurry S. The plurality of unit magnets may each include a means for adjusting the spacing, i.e., the separation distance, by moving up and down above and below the negative electrode slurry. To this end, the first magnet unit 120a and the second magnet unit 120b may each include a first magnet array 122a and a second magnet array 122b in which a plurality of unit magnets are arranged along the width direction of the running negative electrode slurry, supports (not shown) individually fixed to each unit magnet included in the magnet arrays 122a and 122b, and distance adjustment means 121a and 121b connected to the supports and guiding the up and down movement of the support (or the up and down movement of the unit magnets) in a direction perpendicular to the running electrode sheet.

[0050] At this time, the distance adjusting means 121a and 121b may operate to receive a reference interval value from the control unit 130 and adjust the separation distance between the first magnet unit 120a and the second magnet unit 120b according to the received reference interval value.

[0051] The first magnet unit 120a and the second magnet unit 120b have such a configuration, and 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 120a and the second magnet unit 120b becomes smaller, and the strength of the magnetic field applied to the negative electrode slurry S can be decreased as the distance between them becomes larger.

[0052] Furthermore, the first magnet unit 120a and the second magnet unit 120b may be positioned in the width direction of the negative electrode slurry S to face each other and have opposite poles. For example, the first magnet unit 120a may be arranged so that the north pole of the first magnet row 122a faces the south pole of the second magnet row 122b of the second magnet unit 120b, or the south pole of the first magnet row 122a faces the north pole of the second magnet row 122b of the second magnet unit 120b. When an electrode sheet passes through a space where the north pole and the south pole face each other, the 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 120a and the second magnet unit 120b.

[0053] The first magnet unit 120a is disposed above the traveling electrode sheet, and a Halbach array may be applied to the first magnet array 122a to apply a strong magnetic field to the carbon-based negative electrode active material of the negative electrode slurry S. The Halbach array is a permanent magnet arrangement that can provide a magnet with a high magnetic field strength by gradually changing the magnetization direction of the magnet. The application of magnets with a Halbach array as the first magnet array 122a of the first magnet unit 120a has the advantage of being able to adjust the strength of the magnetic field applied to the negative electrode slurry S without significantly changing the separation distance between the first magnet unit 120a and the second magnet unit 120b.

[0054] Meanwhile, the separation distance between the first magnet portion 120a and the second magnet portion 120b may be 10 mm to 50 mm, specifically 10 mm to 40 mm, 20 mm to 50 mm, or 15 mm to 45 mm. Here, the separation distance between the first magnet portion 120a and the second magnet portion 120b may be the same as the separation distance between the first magnet array 122a and the second magnet array 122b. By adjusting the separation distance between the first magnet portion 120a and the second magnet portion 120b 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.

[0055] In addition, the magnetic alignment device 10 may further include a drying unit 140 that dries the negative electrode slurry S in which the carbon-based negative electrode active material is aligned by the first magnet unit 120a and the second magnet unit 120b.

[0056] The drying unit 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, 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.

[0057] When the electrode sheet coated with the electrode slurry enters through the inlet of the drying unit 140, energy such as light, wavelength, and heat 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.

[0058] Furthermore, the dryer 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 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 operate continuously to dry the negative electrode slurry.

[0059] 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. Generally, drying the negative electrode slurry is performed by applying high-temperature hot air. However, this method may result in a prolonged drying time for the negative electrode slurry, which may 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 a phenomenon known as migration, in which the binder evaporates and concentrates on the slurry surface, thereby reducing the adhesive 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 avoiding these issues and maintaining a high degree of alignment of the carbon-based negative electrode active material. The first dryer may include, for example, an ultraviolet dryer, a near-infrared dryer, or a far-infrared dryer. Specifically, the first dryer 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 of the electrode slurry. Unlike near-infrared dryers and infrared dryers commonly used in the industry, the far-infrared dryer emits light with a longer wavelength and is more energy efficient. Furthermore, the far-infrared dryer can apply energy uniformly not only to the surface but also to the interior of the negative electrode slurry, thereby advantageously increasing the adhesion between the negative electrode slurry and the negative electrode current collector in a short period of time.

[0060] At this time, the first dryer was 50 kW / m 2 ~1,000kW / m 2 It can emit energy at a power density of 50 kW / m 2 ~500kW / m 2 , 50kW / m 2 ~250kW / m 2 , or 50kW / m 2 , and 200 kW / m 2By 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.

[0061] 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.

[0062] The magnetic alignment device according to the present invention has the above-described configuration, and can reflect the state of the anode slurry in real time to uniformly induce alignment of the carbon-based anode active material therein. Therefore, the manufactured anode can exhibit an effect of increasing the mobility of lithium ions during charging and discharging of the battery, reducing resistance, and improving charge and discharge performance.

[0063] <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. The step of aligning the carbon-based negative electrode active material provides a method for manufacturing a negative electrode, in which the step is controlled by adjusting the distance between the negative electrode slurry and the magnet part of the magnetic alignment device according to the loading amount of the negative electrode slurry.

[0064] 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 then applying a magnetic field to the surface of the applied negative electrode slurry using the magnetic alignment device of the present invention described above, thereby aligning the carbon-based negative electrode active material in the negative electrode slurry so that it is perpendicular to the surface of the negative electrode current collector (or the running direction of the electrode sheet). Furthermore, the manufacturing method then involves continuously drying the negative electrode slurry, thereby forming a negative electrode active layer in which the perpendicular alignment of the carbon-based negative electrode active material is maintained.

[0065] The method for manufacturing the negative electrode can reflect the state of the negative electrode slurry, specifically the loading amount, in real time by using the magnetic alignment device described above, and can uniformly induce alignment of the carbon-based negative electrode active material therein. Therefore, the manufactured negative electrode can exhibit effects of increased lithium ion mobility and reduced resistance during battery charge and discharge, thereby improving charge and discharge performance.

[0066] Here, 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.

[0067] In addition, the negative electrode slurry may be applied to have a loading amount within a certain range, taking into consideration the alignment efficiency of the carbon-based negative electrode active material included in the negative electrode slurry and the drying efficiency of the negative electrode slurry.

[0068] As an example, the negative electrode slurry is 100 mg / 25 cm 2 ~500mg / 25cm 2 and specifically 150 mg / 25 cm 2 ~450mg / 25cm 2 , 150mg / 25cm 2 ~200mg / 25cm 2 , 200mg / 25cm 2 ~400mg / 25cm 2 , 200mg / 25cm 2 ~300mg / 25cm 2 , 250mg / 25cm 2~400mg / 25cm 2 , or 180 mg / 25 cm 2 ~420mg / 25cm 2 It can be applied at a loading of

[0069] In addition, in the step of aligning the carbon-based negative electrode active material contained in the negative electrode slurry using a magnetic alignment device, the magnetic field application conditions may be adjusted to enhance the alignment efficiency of the carbon-based negative electrode active material. Specifically, the degree of alignment of the carbon-based negative electrode active material may be adjusted by the strength and application time of the magnetic field.

[0070] For example, the magnetic field may be applied at a magnetic field strength of 0.5 to 2.0T, more specifically, at a magnetic field strength of 0.9 to 1.5T, 1.0 to 1.4T, or 1.0 to 1.2T.

[0071] The magnetic field may be applied for 0.1 to 20 seconds, more specifically for 0.5 to 15 seconds, 0.5 to 12 seconds, 1 to 10 seconds, or 2 to 8 seconds.

[0072] <Anode 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.

[0073] The negative electrode prepared according to the present invention includes a carbon-based negative electrode active material and a negative electrode active layer on at least one surface of a negative electrode current collector, and the negative electrode active layer may have an alignment index (OI) of the carbon-based negative electrode active material represented by the following Formula 1 of 0.1 to 5.0.

[0074] [Formula 1] OI=I 004 / I 110

[0075] In Equation 1, I 004 represents the area of ​​the peak representing the (004) crystal plane in X-ray diffraction spectroscopy (XRD) measurement of the negative electrode active layer, I 110indicates the area of ​​the peak indicating the (110) crystal plane when the negative electrode active layer is measured by X-ray diffraction spectroscopy (XRD).

[0076] 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 fabricated by coating both sides 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.

[0077] 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.

[0078] 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. The present invention advantageously achieves a nearly spherical shape for the carbon-based negative electrode active material, thereby improving the electrical conductivity of the negative electrode active layer and thereby improving the capacity of the battery. Furthermore, the present invention also provides an increased specific surface area of ​​the negative electrode active material, thereby improving the adhesion between the negative electrode active layer and the current collector.

[0079] The carbon-based negative electrode active material has an average particle size (D 50 ), specifically, an average particle size (D 50 ) can be shown.

[0080] The smaller the average particle size of spherical natural graphite, the more advantageous it is to maximize the degree of disorder in the direction of expansion of each particle, preventing particle expansion during lithium ion charging. 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, which can reduce the adhesion between particles and between the particles and the current collector during repeated charge and discharge, resulting in a significant decrease in cycle performance.

[0081] In a 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 consistent level. 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 consistent direction, thereby further improving the charging performance of the negative electrode active layer.

[0082] 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.

[0083] 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 0.1 to 5.0.

[0084] [Formula 1] OI=I 004 / I 110

[0085] In Equation 1, I 004 represents the area of ​​the peak representing the (004) crystal plane in 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).

[0086] 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.

[0087] 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 CuKα radiation as the target line, and to improve peak intensity resolution, the target line was extracted and measured 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°. 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 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 ... 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.

[0088] As another example, the negative electrode active layer may have a low degree of alignment of 1.0 or less according to the following equation 2 when measured by a near-edge X-ray fluorescence spectrometer (NEXAFS):

[0089] [Formula 2] S 60 / 0 =I60 B / A / I0 B / A

[0090] In the above formula 2, S 60 / 0 is the peak intensity ratio (I60) at an incident angle of 0° during near-edge X-ray fluorescence spectrometer (NEXAFS) measurement. B / A ) at an incident angle of 60° (I0 B / A ) value.

[0091] Near-edge X-ray absorption spectra, also known as near-edge NEXAFS (Near Edge X-ray Absorbance Fine Structure) spectra, are absorption spectra observed when electrons (K-shell inner-shell electrons) present in the occupied core levels (1s orbitals) of carbon atoms absorb the energy of irradiated X-rays and are excited to various unoccupied levels.

[0092] Here, the vacant level to which the electrons in the core level are excited is the sp2 π assigned to antibonding orbitals of a bond * sp that reflects the level and crystal disorder (edge ​​plane, non-orientation, etc.) 3 σ assigned to antibonding orbitals of a bond * There are vacant levels that belong to antibonding orbitals such as C—H bonds and C—O bonds. 2 In graphite, which has a crystalline structure in which hexagonal mesh structures are stacked by bonding, the plane of the hexagonal mesh surface (AB plane, described later) is the basal plane, and the plane where the edge of the hexagonal mesh appears is the edge plane. On the edge plane, carbon may have -C=O etc. at the end, so sp 3 The binding rate can be high.

[0093] Furthermore, unlike X-ray photoelectron spectroscopy (XPS), which measures the bond energy between atoms constituting a compound, near-edge NEXAFS spectra reflect the local structure near the carbon atom containing the excited core electrons, and can also reflect only the surface structure of the measured graphite particle. Therefore, the present invention makes it possible to measure the crystalline state (orientation) of a carbon-based negative electrode active material that forms spherical particles, i.e., graphite, by using near-edge NEXAFS spectra.

[0094] Meanwhile, the near-edge NEXAFS spectrum can be measured by a total electron quantity method, in which a sample is irradiated with synchrotron radiation at a fixed incident angle, and the energy of the irradiated synchrotron radiation is scanned from 280 eV to 320 eV, while measuring the sample current flowing into the sample to supplement the photoelectrons emitted from the sample. Specifically, in order to more quantitatively measure the degree of alignment of the carbon-based negative electrode active material contained in the negative electrode active layer, the present invention uses the degree of alignment (S 60 / 0 ) can be measured.

[0095] Generally, synchrotron radiation has a high linear polarization, so the incident direction of the synchrotron radiation is the sp 2 When parallel to the bond axis of the bond (-C=C-), the C1s level to π *The absorption peak intensity attributable to the transition to the level becomes larger, and conversely, the absorption peak intensity becomes smaller when the level is perpendicular. Therefore, highly oriented graphite (e.g., HOPG, single crystal graphite) has sp 2 Since the graphite crystals that form the bonds are highly aligned, the spectral shape changes significantly when the incident angle of the synchrotron radiation on the sample is changed. In contrast, low-oriented graphite (e.g., non-graphitic carbon deposition film) has sp 2 Because the carbon material that forms bonds has low orientation, the spectral shape hardly changes even when the angle of incidence of the synchrotron radiation on the sample is changed.

[0096] In addition, when the negative electrode active layer is measured with a near-edge NEXAFS spectrum (i.e., near-edge X-ray fluorescence spectrometer (NEXAFS)) at different incident angles to the surface of the negative electrode active layer, any first absorption peak intensity (I A ) to any second absorption peak intensity (I B ) percentage (I B / A ) may vary depending on the incident angle, which may indicate that the carbon-based negative electrode active material contained in the measured negative electrode active layer is regularly arranged (i.e., highly oriented). On the other hand, if the proportion I does not vary depending on the incident angle, it may indicate that the carbon-based negative electrode active material contained in the measured negative electrode active layer is irregularly arranged (i.e., poorly oriented).

[0097] Therefore, in order to measure the degree of alignment of the carbon-based negative electrode active material contained in the negative electrode active layer, the present invention measures the near-edge NEXAFS spectrum (i.e., near-edge X-ray fluorescence spectrometer (NEXAFS)) and incidents synchrotron radiation at different incident angles (0° and 60°) on the negative electrode active layer, and measures the C1s level to π * The intensity of the absorption peak (peak A = 287 ± 0.2 eV) attributed to the transition to the C1s level is related to the σ * The ratio of the intensity of the absorption peak (peak B = 293 ± 0.2 eV) attributable to the transition to the level (I B / A ) is calculated, the ratio of the intensity ratio between the incident angles (60° and 0°) (S 60 / 0 =I60 B / A / I0 B / A) can be calculated to quantitatively measure the degree of alignment of the carbon-based negative electrode active material.

[0098] That is, the degree of alignment of the carbon-based negative electrode active material contained in the negative electrode active layer is expressed as follows: i) As expressed by Equation 3, the degree of alignment of the carbon-based negative electrode active material contained in the negative electrode active layer is expressed as follows: * The intensity of the absorption peak (peak A = 287 ± 0.2 eV) attributed to the transition to the level (I60 A ) for the absorption peak (peak B = 293 ± 0.2 eV) intensity attributed to the transition from the C1s level to the σ level (I60 B ) percentage (I60 B / A ) is calculated, and ii) π is calculated from the C1s level measured at an incident angle of 0° as expressed in Eq. * The intensity of the absorption peak (peak A = 287 ± 0.2 eV) attributed to the transition to the level (I0 A ) from the C1s level to σ * The intensity of the absorption peak (peak B = 293 ± 0.2 eV) attributed to the transition to the level (I0 B ) percentage (I0 B / A ) and then iii) calculate the ratio of these (S 60 / 0 =I60 B / A / I0 B / A ) can be evaluated.

[0099] [Formula 3] I60 B / A =I60 B / I60 A

[0100] [Formula 4] I0 B / A =I0 B / I0 A

[0101] In Equation 3 and Equation 4, I60 A indicates the intensity of the strongest peak among the peaks present at 286±1.0 eV when the incident angle is 60°, I60 Bindicates the intensity of the strongest peak among the peaks present at 292.5±1.0 eV when the incident angle is 60°, I0 A indicates the intensity of the strongest peak among the peaks present at 286±1.0 eV when the incident angle is 0°, I0 B indicates the intensity of the strongest peak among the peaks present at 292.5±1.0 eV when the incident angle is 0°.

[0102] Here, the above S 60 / 0 The closer to 1, the lower the degree of alignment of the graphite crystals, and the closer to 0, the higher the degree of alignment of the graphite crystals. 60 / 0 ) may satisfy 1.0 or less, more specifically may satisfy 0.9 or less, 0.8 or less, 0.7 or less, 0.1 to 0.7, or 0.3 to 0.7.

[0103] 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 multiple carbon-based negative electrode active materials measured arbitrarily per unit area may be low.

[0104] For example, in the negative electrode active layer, 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 Equation 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.

[0105] In another example, the negative electrode active layer may have an alignment deviation of the carbon-based negative electrode active material represented by Equation 2 of less than 5% based on the average value when measured by a near-edge X-ray fluorescence spectrometer (NEXAFS) at any three points present in a unit area (10 cm × 10 cm) of the negative electrode active layer, specifically, 4% or less, 3% or less, 2% or less, or 1% or less.

[0106] 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.

[0107] 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.

[0108] For example, the negative electrode active layer may contain carbon nanotubes or carbon fibers as conductive materials, either alone or in combination.

[0109] 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 low content of conductive material from increasing the resistance of the negative electrode and reducing the charge capacity. Furthermore, by controlling the content of the conductive material within the above range, the present invention can prevent problems such as a decrease in the content of the negative electrode active material due to an excessive amount of conductive material, thereby reducing the charge capacity, or a decrease in fast charge characteristics due to an increase in the loading amount of the negative electrode active layer.

[0110] 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 selected from 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.

[0111] 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.

[0112] 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.

[0113] The present invention will be described in more detail below with reference to examples and experimental examples.

[0114] 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.

[0115] <Examples 1 and 2. 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 loading amount measuring unit was adjusted as shown in Table 1 to manufacture a negative electrode for a lithium secondary battery.

[0116] 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. The negative electrode slurry was then cast onto a copper sheet being transported roll-to-roll (transport speed: 3 m / min) using a die coater.

[0117] At this time, the average loading amount of the applied negative electrode slurry was 200 mg / 25 cm 2 The negative electrode slurry was cast onto the copper sheet for 20 seconds so that the average loading of the continuously applied negative electrode slurry was 400 mg / 25 cm 2 The negative electrode slurry was cast onto a copper thin plate for 20 seconds so that the negative electrode slurry was

[0118] Thereafter, a magnetic field was applied to the negative electrode slurry by moving the copper thin plate so that the applied negative electrode slurry passed through the loading amount measurement unit and between the first magnet unit and the second magnet unit.

[0119] The loading amount measuring unit included a web gauge as a non-contact measuring device, and the confocal measuring devices were included in the number shown in Table 1 below along the running direction of the copper sheet. The negative electrode slurry loading amount measured by the loading amount measuring unit was transmitted to the control unit, and the control unit recognized a gap reference value corresponding to the measured negative electrode slurry loading amount by comparing it with a gap reference value stored in a database, and transmitted the recognized gap reference value to the first magnet unit and the second magnet unit, respectively.

[0120] In addition, the first magnet unit and the second magnet unit were configured such that the separation distance between the unit magnets in the first magnet row (including 5 to 20 unit magnets) and the second magnet row (including 5 to 20 unit magnets) fixed to the support unit was individually adjusted by adjusting the distance adjustment means in accordance with the reference interval value transmitted from the control unit. Here, the separation distance between the first magnet row and the second magnet row was adjusted to 20 to 40 mm in accordance with the reference interval value transmitted from the control unit, and the strength of the applied magnetic field was 1.0 T.

[0121] [Table 1]

[0122] The copper sheet to which the magnetic field was applied was moved to a drying section to dry the negative electrode slurry, thereby producing a negative electrode for a lithium secondary battery.

[0123] <Comparative Example 1. Production of negative electrode for lithium secondary battery> A negative electrode for a lithium secondary battery was manufactured in the same manner as in Example 1, except that a magnetic alignment device not including a loading amount measurement unit and a control unit was used. At this time, the separation distance between the first magnet row (including 5 to 20 unit magnets) of the first magnet unit and the second magnet row (including 5 to 20 unit magnets) of the second magnet unit was adjusted to 30 mm.

[0124] <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 a performance of the magnetic alignment device according to the present invention.

[0125] Specifically, in each negative electrode manufactured in the examples and comparative examples, i) the average loading amount of the negative electrode slurry was 200 mg / 25 cm 2 The first unit area (10 cm × 10 cm) exists within the casting area, and ii) the average loading amount of the negative electrode slurry is 400 mg / 25 cm 2A second unit area (10 cm x 10 cm) was arbitrarily set within the casting area.

[0126] Thereafter, X-ray diffraction spectroscopy (XRD) and near-edge X-ray fluorescence spectroscopy (NEXAFS) were performed on three arbitrary points in each of the first and second unit regions to measure the spectra.

[0127] At this time, the measurement conditions for the near-edge X-ray fluorescence spectrometer (NEXAFS) and X-ray diffraction (XRD) are as follows.

[0128] (1) Near-end X-ray fluorescence spectrometer (NEXAFS) - Acceleration voltage: 1.0GeV~1.5GeV - Storage current: 80~350mA - Incident angle: 60° or 0°

[0129] (2) X-ray diffraction (XRD) - Target: Cu (Kα-ray) graphite monochromator - Slit: Divergence slit = 1 degree, Receiving slit = 0.1 mm, Scattering slit = 1 degree

[0130] From the spectra measured under the above conditions, i) the average alignment degree (i.e., the average value of the alignment degree at each point) and ii) the error rate between each point and the average alignment degree were calculated for each carbon-based negative electrode active material using Equation 1 and Equation 2. The results are shown in Table 2.

[0131] [Formula 1] OI=I 004 / I 110

[0132] In Equation 1, I 004 represents the area of ​​the peak representing the (004) crystal plane in 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).

[0133] [Formula 2] S 60 / 0 =I60 B / A / I0 B / A

[0134] In Equation 2, S 60 / 0 is the peak intensity ratio (I60) at an incident angle of 0° during near-edge X-ray fluorescence spectrometer (NEXAFS) measurement. B / A ) at an incident angle of 60° (I0 B / A ) value.

[0135] [Table 2]

[0136] As shown in Table 2 above, 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 electrode active material contained in the negative electrode active layer. Furthermore, it was confirmed that the error rate between the alignment degree at any three points and their average value was low, at 3% or less, for the negative electrode active layer of the manufactured negative electrode. This means that the magnetic alignment device according to the present invention uniformly aligns the carbon-based negative electrode active material on the negative electrode current collector with a high degree of alignment.

[0137] 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 loading amount of negative electrode slurry in real time and individually reflecting it 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.

[0138] 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.

[0139] 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]

[0140] 10: Magnetic alignment device 20:Transfer section 30: Coating section (die coater) 110: Loading amount measurement unit 111: First web gauge 112: Second web gauge 120a: First magnet section 121a: First distance adjustment means 122a: 1st magnet row 120b: Second magnet part 121b: Second distance adjustment means 122b: Second magnet row 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 that 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; a loading amount measuring unit that is disposed upstream of the first magnet unit and the second magnet unit with respect to the running direction of the electrode sheet and that measures a loading amount of negative electrode slurry disposed on the electrode sheet; a control unit that adjusts a separation distance between the first magnet unit and the second magnet unit according to the loading amount of the negative electrode slurry measured by the loading amount measurement unit, and increases a strength of a magnetic field applied to the negative electrode slurry as the separation distance becomes narrower, The first magnet unit and the second magnet unit each include a plurality of unit magnets arranged in a width direction of the negative electrode slurry, and each unit magnet moves up and down individually in a direction perpendicular to the traveling electrode sheet, and a separation distance between the unit magnet and the opposing unit magnet is adjusted around the electrode sheet; the control unit includes a database storing a reference value of a gap between the first magnet unit and the second magnet unit according to a loading amount of the negative electrode slurry; The distance reference value includes previously acquired data on the separation distance between the first magnet portion and the second magnet portion according to the loading amount of negative electrode slurry.

2. 2. The negative electrode magnetic alignment device of claim 1, wherein the control unit calculates a reference interval value corresponding to the loading amount of the negative electrode slurry measured by the loading amount measurement unit and adjusts a separation distance between the first magnet unit and the second magnet unit.

3. Each unit magnet provided in the first magnet portion and the second magnet portion is a support portion that is individually fixed to each unit magnet; 2. The negative electrode magnetic alignment device according to claim 1, further comprising: a distance adjusting means connected to the support portion and configured to induce vertical movement of the support portion in a direction perpendicular to the electrode sheet during movement.

4. 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.

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

6. The apparatus for magnetically aligning a negative electrode according to claim 1 , wherein the loading amount measuring unit includes at least one of a web gauge and an ultrasonic sensor.

7. The ultrasonic sensor an ultrasonic wave generating unit that scans the surface of the negative electrode slurry with ultrasonic waves; an ultrasonic wave receiving unit that receives ultrasonic waves returned from the ultrasonic wave generating unit after the ultrasonic waves have scanned the loaded negative electrode slurry; The negative electrode magnetic alignment device according to claim 6 , further comprising: a data transmission unit that calculates the loading amount of the negative electrode slurry from data obtained by scanning and transmits the calculated amount to the control unit.

8. The magnetic alignment device of claim 1 , further comprising a drying unit configured to dry the negative electrode slurry in which the carbon-based negative electrode active material is aligned by the first magnet unit and the second magnet unit.

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 negative electrode 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. the step of aligning the carbon-based negative electrode active material is controlled by adjusting a distance between the negative electrode slurry and a magnet part of the magnetic alignment device according to a loading amount of the negative electrode slurry.

10. The negative electrode slurry was 100 mg / 25 cm ２ ~500mg / 25cm ２ The method for producing a negative electrode according to claim 9 , wherein the coating is carried out at a loading amount of

11. 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 of the negative electrode active layer, I １１０ The method for producing a negative electrode according to claim 9 , wherein R 1 represents the area of ​​a peak indicating a (110) crystal plane when the negative electrode active layer is subjected to X-ray diffraction spectroscopy.

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