Device for manufacturing negative electrode for secondary batteries

Abstract

The present invention relates to an apparatus for manufacturing a negative electrode for a secondary battery and a method for manufacturing a negative electrode using the same. The negative electrode manufacturing apparatus includes an upper block, a middle block, and a lower block, and a double slot die including a first slot and a second slot for discharging a negative electrode slurry through the gaps between the upper block and the middle block and between the middle block and the lower block, and among the upper lip, the middle lip, and the lower lip located at the tip of each block, the upper lip and the lower lip apply a magnetic field of the same polarity, and the middle lip applies a magnetic field of the opposite polarity to the upper lip. As a result, the carbon-based negative electrode active material in the discharged negative electrode slurry can be applied so that the crystal plane is oriented nearly perpendicular to the surface of the negative electrode current collector. Therefore, the manufactured negative electrode has an advantage that not only the carbon-based negative electrode active material has an excellent degree of orientation, but also that it is easy to apply to a mass production process.

Description

[Technical Field]

[0001] The present invention relates to an apparatus for manufacturing a negative electrode for use in a secondary battery and a method for manufacturing a negative electrode for a secondary battery using the same.

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0173289, dated December 13, 2022, and all contents disclosed in the documents of this Korean patent application are incorporated herein by reference. [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 a secondary battery is a chargeable and dischargeable power generating element having a laminated structure of a positive electrode / separator / negative electrode. Generally, 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 of the secondary battery, lithium ions released from the positive electrode are absorbed into the carbon-based negative electrode active material of the negative electrode. During discharge, the lithium ions contained in the carbon-based negative electrode active material are absorbed into the lithium metal oxide of the positive electrode, allowing for repeated charging and discharging.

[0005] Examples of the negative electrode active material used in the negative electrode include graphite materials such as natural graphite and artificial graphite. Such graphite has a layered structure, in which carbon atoms form a network structure and many planar layers are stacked. During charging, lithium ions penetrate 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, since the electrical resistivity of graphite in the plane direction of the layers is lower than that in the stacking direction of the layers, a detour electron conduction path is formed along the plane direction of the layers.

[0006] In this regard, a technique for magnetically orienting graphite contained in a negative electrode has been proposed to improve the charging performance of lithium secondary batteries using graphite. Specifically, during the formation of the negative electrode, the (0,0,2) crystal plane of the graphite is oriented in a magnetic field so that it is nearly parallel to the negative electrode current collector, and then fixed in place. In this case, the edge plane of the graphite faces the positive electrode active layer, which facilitates the insertion and desorption of lithium ions and shortens the electron conduction path, improving the electronic conductivity of the negative electrode and thereby improving the charging performance of the battery.

[0007] This graphite orientation can be induced by applying a magnetic field to an undried negative electrode slurry containing graphite coated on a negative electrode current collector. However, considering the production speed during actual mass production of negative electrodes, it is difficult to ensure a sufficient magnetic field application time to induce graphite alignment in the negative electrode slurry. Furthermore, if the strength of the magnetic field applied to the negative electrode slurry coated on the electrode sheet is increased to solve this problem, the graphite is attracted to the magnetic field at the end of the magnetic field, which disrupts the orientation of the graphite aligned perpendicular to the metal sheet, resulting in a limited degree of graphite orientation in the final negative electrode active layer.

[0008] Therefore, there is a need for a negative electrode manufacturing technology that can realize a high degree of graphite orientation and that can be applied to mass production of negative electrodes for secondary batteries. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Korean Patent Publication No. 10-2018-0048131 Summary of the Invention [Problem to be solved by the invention]

[0010] An object of the present invention is to provide a negative electrode manufacturing technique that can realize a high degree of crystalline orientation of a carbon-based negative electrode active material such as graphite contained in a negative electrode active layer and that can be applied to mass production of negative electrodes for secondary batteries. [Means for solving the problem]

[0011] To solve the above problem, In one embodiment, the present invention comprises: An apparatus for producing an electrode sheet coated with a negative electrode slurry containing a carbon-based negative electrode active material, a double slot die including an upper block, an intermediate block, and a lower block, a first slot provided in the gap between the upper block and the intermediate block and for discharging a first negative electrode slurry, and a second slot provided in the gap between the intermediate block and the lower block and for discharging a second negative electrode slurry; a coating roll that faces the first slot and the second slot of the double slot die and transports the electrode sheet coated with the negative electrode slurry discharged from each slot, The upper block, intermediate block, and lower block each have an upper lip, intermediate lip, and lower lip that form a discharge outlet at their tip, and the upper lip and lower lip exhibit magnetism with the same polarity, while the intermediate lip exhibits magnetism with a polarity opposite to that of the upper lip.

[0012] In this case, the upper lip, middle lip, and lower lip may have a structure including at least one of a permanent magnet and an electromagnet, and thus may apply a magnetic field having a strength of 500 G to 3,000 G when discharging the negative electrode slurry.

[0013] Also, the double slot die may satisfy the following formula 1:

[0014] [Formula 1] 10≦G / M≦50

[0015] (In Equation 1, G represents the strength of the magnetic field (unit: G) applied at the upper lip, middle lip, and lower lip; M represents the speed at which the electrode sheet is moved by the coating roll (unit: m / min)

[0016] The negative electrode manufacturing apparatus may further include a drying unit that dries the negative electrode slurry applied to the electrode sheet.

[0017] The drying unit may be disposed at a position where the negative electrode slurry discharged from the double slot die can reach within 20 seconds from the time when the negative electrode slurry is applied to the electrode sheet.

[0018] In one embodiment, the present invention further comprises: The method includes applying the negative electrode slurry to which the magnetic field is applied onto an electrode sheet using the above-described negative electrode manufacturing apparatus according to the present invention, The present invention provides a method for producing a negative electrode for a secondary battery, wherein the negative electrode slurry contains a carbon-based negative electrode active material.

[0019] In this case, the average thickness of the negative electrode slurry applied to the electrode sheet may be greater than the distance between the slots of a double slot die provided in an apparatus for manufacturing a negative electrode and a coating roll, and the average thickness of the negative electrode slurry applied to the electrode sheet may be 100 μm or more.

[0020] The step of applying the negative electrode slurry to the electrode sheet may be performed at a speed of 5 m / min to 100 m / min.

[0021] The negative electrode slurry may have a viscosity of 2,000 cps to 15,000 cps at 25°C.

[0022] The method may further include, after the step of applying the negative electrode slurry to the electrode sheet, drying the applied negative electrode slurry to form a negative electrode active layer.

[0023] Here, the negative electrode active layer may have an alignment degree of the carbon-based negative electrode active material relative to the surface of the electrode sheet represented by the following formula 2 of 0.9 or less:

[0024] [Formula 2] OI=I 004 / I 110

[0025] In Equation 2, I 004 represents the area of ​​the peak representing the (0,0,4) crystal plane when measuring the negative electrode active layer by X-ray diffraction spectroscopy (XRD), I 110 represents 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). [Effects of the Invention]

[0026] The apparatus for manufacturing a negative electrode for a secondary battery according to the present invention can apply a carbon-based negative electrode active material in the discharged negative electrode slurry so that the crystal plane of the carbon-based negative electrode active material is oriented nearly perpendicular to the surface of the negative electrode current collector, thereby providing the advantages of a manufactured negative electrode having excellent orientation of the carbon-based negative electrode active material and being easily applicable to mass production processes. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a cross-sectional view schematically showing an apparatus for manufacturing a negative electrode for a secondary battery according to the present invention. [Figure 2] 1 is a perspective view showing the structure of a double die coater provided in an apparatus for manufacturing a negative electrode for a secondary battery according to the present invention. [Figure 3] 3 is a conceptual diagram illustrating the principle of magnetically aligning a carbon-based negative electrode active material of a negative electrode slurry and applying it to an electrode sheet using a dual die coater according to the present invention. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0028] Because the present invention is susceptible to various modifications and can have various embodiments, specific embodiments are described in detail in the detailed description.

[0029] However, this is not intended to limit the invention to any particular embodiment, but rather to be understood as including all modifications, equivalents, or alternatives falling within the spirit and scope of the invention.

[0030] In the present invention, terms such as "comprise" and "have" are intended to specify the presence of features, numbers, steps, operations, components, parts or combinations thereof described in the specification, and may be understood as not precluding the presence or additional possibility of one or more other features, numbers, steps, operations, components, parts or combinations thereof.

[0031] 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.

[0032] Furthermore, in the present invention, "comprising as a main component" may mean containing 50 wt% or more (or 50 vol% or more), 60 wt% or more (or 60 vol% or more), 70 wt% or more (or 70 vol% or more), 80 wt% or more (or 80 vol% or more), 90 wt% or more (or 90 vol% or more), or 95 wt% or more (or 95 vol% or more) of the defined component relative to the total weight (or volume). For example, "comprising graphite as a main component as a negative electrode active material" may mean containing 50 wt% or more, 60 wt% or more, 70 wt% or more, 80 wt% or more, 90 wt% or more, or 95 wt% or more of graphite relative to the total weight of the negative electrode active material. In some cases, it may mean that the entire negative electrode active material is composed of graphite, with graphite accounting for 100 wt%.

[0033] In the present invention, the term "lip portion" refers to a region including the upper lip of the upper block, the middle lip of the middle block, and the lower lip of the lower block. The lip portion may include the space formed between the lips, i.e., the region where each lip is disposed in the first slot and the second slot.

[0034] Similarly, in the present invention, the term "main body" refers to a region including the upper body of the upper block, the middle body of the middle block, and the lower body of the lower block. The main body may include spaces formed between the bodies, i.e., regions where the bodies are arranged in the first slot and the second slot.

[0035] The present invention will now be described in more detail.

[0036] <Secondary battery negative electrode manufacturing equipment>

[0037] In one embodiment, the present invention comprises: An apparatus for producing an electrode sheet coated with a negative electrode slurry containing a carbon-based negative electrode active material, a double slot die including an upper block, an intermediate block, and a lower block, a first slot provided in the gap between the upper block and the intermediate block and for discharging a first negative electrode slurry, and a second slot provided in the gap between the intermediate block and the lower block and for discharging a second negative electrode slurry; a coating roll that faces the first slot and the second slot of the double slot die and transports the electrode sheet coated with the negative electrode slurry discharged from each slot, The upper block, intermediate block, and lower block each have an upper lip, intermediate lip, and lower lip that form a discharge outlet at their tip, and the upper lip and lower lip exhibit magnetism with the same polarity, while the intermediate lip exhibits magnetism with a polarity opposite to that of the upper lip.

[0038] The secondary battery negative electrode manufacturing apparatus according to the present invention is an apparatus that is applied when manufacturing a negative electrode to be used in a secondary battery, and has a configuration in which a negative electrode slurry containing a carbon-based negative electrode active material is applied onto a negative electrode current collector to manufacture an electrode sheet.

[0039] Specifically, Fig. 1 is a cross-sectional view showing the structure of an apparatus for manufacturing a secondary battery anode according to the present invention. Referring to Fig. 1, the apparatus for manufacturing anode (10) comprises a double slot die (100) and a coating roll (200). The coating roll (200) rotates to move an electrode sheet (300) and apply anode slurry to the surface of the electrode sheet (300).

[0040] The double slot die 100 includes a first slot 151 and a second slot 152, and can apply two types of negative electrode slurries, which may be the same or different, onto the negative electrode current collector in a dual manner. As shown in FIG. 2 , the first slot 151 can be formed between the upper die 110 and the middle die 120, and the second slot 152 can be formed between the middle die 120 and the lower die 130, respectively.

[0041] For example, the double slot die 100 may have a first spacer 141 and a second spacer 142 sequentially interposed between the upper die 110, the middle die 120, and the lower die 130, respectively, to form gaps therebetween, thereby forming passages, i.e., slots 151 and 152, through which the anode slurry can flow. In this case, the vertical height of the slot may be determined by the thickness (Y-axis direction) of the first spacer 141 and / or the second spacer 142 that form the gap between the dies. The thickness of the first spacer 141 and / or the second spacer 142 may be controlled depending on the application and capacity of the secondary battery.

[0042] Here, the thickness of each spacer 141 and 142 may independently be 50 μm to 2,000 μm, specifically 50 μm to 1,500 μm, 500 μm to 1,200 μm, 800 μm to 1,200 μm, 80 μm to 200 μm, 200 μm to 500 μm, or 400 μm to 700 μm.

[0043] In addition, the first spacer 141 and / or the second spacer 142 may be cut open in one region to form openings 141a and 142a, and may be interposed in the remaining edge regions of the opposing surfaces of the upper die 110, the intermediate die 120, and the lower die 130, excluding one side. As a result, discharge ports through which the negative electrode slurry can be discharged to the outside, i.e., the first slot 151 and the second slot 152, are formed only between the leading ends of the upper die 110, the intermediate die 120, and the lower die 130. In this case, the leading ends of the upper die 110, the intermediate die 120, and the lower die 130 include an upper lip 111, a middle lip 121, and a lower lip 131, and the slots 151 and 152 can be said to be locations formed by separating the lips 111, 121, and 131.

[0044] In addition, the first spacer 141 and the second spacer 142 also function as gaskets to prevent the negative electrode slurry from leaking from the gaps between the dies 110, 120, and 130, except for the areas where the first slot 151 and the second slot 152 are formed, so they are preferably made of a material with sealing properties.

[0045] Meanwhile, the upper die 110, the middle die 120, and the lower die 130 may include an upper lip 111, a middle lip 121, and a lower lip 131 located at each end, as well as an upper body 112, a middle body 122, and a lower body 132 extending from each lip and closely contacting a first spacer 141 and / or a second spacer 142 to form a passage through which the anode slurry can fluidly move.

[0046] Additionally, the upper lip 111, the middle lip 121, and the lower lip 131 exhibit magnetism. Specifically, the upper lip 111 and the lower lip 131 exhibit magnetism having the same polarity, and the middle lip 121 exhibits magnetism having the opposite polarity to that of the upper lip 111. As a result, a magnetic field can be formed in the first slot 151 and the second slot 152 formed by the lips 111, 121, and 131 in a direction perpendicular to the direction in which the negative electrode slurry is discharged.

[0047] As shown in FIG. 3, the path along which the negative electrode slurry is dispensed and applied can be divided into a section A where the carbon-based negative electrode active material CM (e.g., graphite) is not oriented and a section B where it is oriented. The carbon-based negative electrode active material CM of the negative electrode slurry is not affected by magnetism in the non-oriented section A, which includes the space between the main bodies 112, 122, and 132 of each die (i.e., section I: main body), and thus moves with a high degree of freedom. However, the orientation section B includes the space between the upper lip 111, the middle lip 121, and the lower lip 131, which exhibit the same polarity of magnetism (i.e., section II: lip). In the lip section, the middle lip 121, which exhibits the opposite polarity of magnetism to the upper lip 111, is interposed between the upper lip 111 and the lower lip 131, which exhibit the same polarity of magnetism. This allows for attractive forces to act between the lips 111, 121, and 131, forming a magnetic field direction MD that is perpendicular to the direction in which the negative electrode slurry is dispensed. Therefore, before the negative electrode slurry is discharged onto the negative electrode current collector, the carbon-based negative electrode active material CM, i.e., graphite, contained in the negative electrode slurry may be oriented so that its (0,0,2) crystal plane is approximately perpendicular to the negative electrode current collector. The oriented graphite is converted to a crystal orientation perpendicular to the surface of the electrode sheet 300 (or negative electrode current collector) along the fluid motion direction FD of the negative electrode slurry itself during discharge of the negative electrode slurry. Because the graphite is coated onto the negative electrode current collector with its crystal plane converted to be perpendicular to the surface of the electrode sheet (i.e., corresponding to the coating region III), it can have a high degree of orientation without the application of a separate magnetic field after coating the negative electrode slurry.

[0048] The upper lip 111, the middle lip 121, and the lower lip 131 may include electromagnets and / or permanent magnets to exhibit magnetism. The electromagnets may include both DC and AC electromagnets. The permanent magnets may include both ferromagnetic and soft magnetic magnets, such as NdFeB magnets, SmCo magnets, ferrite magnets, alnico magnets, FeCrCo magnets, and bond magnets (Nd-Fe-B, Sm-Fe-N, Sm-Co, and ferrite magnets).

[0049] Furthermore, because the negative electrode manufacturing apparatus applies a magnetic field before the negative electrode slurry is applied to the electrode sheet, the applied magnetic field can be weaker than when the magnetic field is applied after the negative electrode slurry is applied to the electrode sheet. The applied magnetic field strength can be within a predetermined range. In other words, the upper lip 111, the middle lip 121, and the lower lip 131 can apply a magnetic field that satisfies a predetermined strength range when discharging the negative electrode slurry. Specifically, the upper lip 111, the middle lip 121, and the lower lip 131 can be applied with the same magnetic field. In this case, the strength of the applied magnetic field may be 500G to 3,000G (Gauss), more specifically 500G to 2,500G, 500G to 2,000G, 500G to 1,500G, 1,000G to 2,000G, 2,000G to 2,500G, 2,000G to 3,000G, 500G to 1,500G, or 500G to 900G.

[0050] By adjusting the strength of the magnetic field applied to upper lip 111, middle lip 121, and lower lip 131 within the above range, the present invention can achieve uniform crystalline orientation of the carbon-based negative electrode active material before the negative electrode slurry is discharged through first slot 151 and second slot 152. Furthermore, the present invention can adjust the crystalline orientation of the carbon-based negative electrode active material to be nearly perpendicular to the surface of the electrode sheet, depending on the fluid momentum and / or direction of the discharged negative electrode slurry. Furthermore, the present invention can prevent difficulties in discharging the negative electrode slurry due to a narrow separation distance between the lips, which may occur when the strength of the magnetic field applied to upper lip 111, middle lip 121, and lower lip 131 exceeds the above range.

[0051] Furthermore, the double slot die 100 orients the crystal plane of the carbon-based negative electrode active material nearly horizontal to the surface of the electrode sheet 300 (or negative electrode current collector) before discharging the negative electrode slurry, and then, during discharging the negative electrode slurry, the crystal plane of the carbon-based negative electrode active material can be converted to nearly perpendicular to the surface of the electrode sheet 300 (or negative electrode current collector) depending on the fluid momentum and / or direction of the slurry. The ratio of the strength of the magnetic field applied to each lip to the coating speed of the negative electrode slurry, i.e., the speed at which the electrode sheet is moved by the coating roll 200, can be controlled to satisfy a predetermined range. Specifically, the double slot die 100 can satisfy the following equation 1:

[0052] [Formula 1] 10≦G / M≦50

[0053] In Equation 1, G represents the strength of the magnetic field (unit: G) applied at the upper lip, middle lip, and lower lip; M represents the speed (unit: m / min) at which the electrode sheet is moved by the coating roll.

[0054] The orientation of the carbon-based negative electrode active material contained in the negative electrode slurry can be affected by the strength of the applied magnetic field, the distance from the magnet to which the magnetic field is applied, the fluid momentum and / or direction of the negative electrode slurry containing the carbon-based negative electrode active material, etc. Therefore, in the present invention, the ratio (G / M) of the strength of the magnetic field (G) applied to each lip to the speed (M) of the electrode sheet moving by the coating roll can be 10 to 50 to satisfy Equation 1, so that the crystal plane of the carbon-based negative electrode active material in the negative electrode slurry applied to the electrode sheet can be oriented nearly perpendicular to the surface of the electrode sheet 300. More specifically, the double slot die 100 may satisfy Equation 1 at 10 to 50 (i.e., 10≦G / M≦50), 10 to 40 (i.e., 10≦G / M≦40), 10 to 30 (i.e., 10≦G / M≦30), 10 to 20 (i.e., 10≦G / M≦20), 15 to 30 (i.e., 15≦G / M≦30), 25 to 50 (i.e., 25≦G / M≦50), 35 to 49 (i.e., 35≦G / M≦49), or 20 to 40 (i.e., 20≦G / M≦40).

[0055] Meanwhile, the first slot 151 and the second slot 152 formed by the lips 111, 121, and 131 may be positioned so that the negative electrode slurry is discharged perpendicular to the surface of the negative electrode current collector. To this end, the double slot die 100 may be disposed perpendicular to the surface of the electrode sheet 300. Preferably, the double slot die 100 may be disposed such that a rotatable coating roll 200, as shown in FIG. 1, faces the first slot 151 and the second slot 152 of the double slot die 100. In this way, the double slot die 100 may apply the negative electrode slurry to the surface of the electrode sheet 300 (or the negative electrode current collector) that moves with the rotation of the coating roll 200.

[0056] Furthermore, the negative electrode manufacturing apparatus 10 according to the present invention may further include a drying unit (not shown) that dries the negative electrode slurry applied to the electrode sheet 300. The drying unit may be disposed at a position where it can reach a drying time within 20 seconds, specifically 0.01 to 20 seconds, 0.01 to 15 seconds, 0.01 to 10 seconds, or 0.01 to 5 seconds, from the time when the negative electrode slurry discharged from the double slot die 100 is applied to the electrode sheet.

[0057] The drying unit functions to remove the solvent contained in the negative electrode slurry to form a negative electrode active layer and also to fix the oriented carbon-based negative electrode active material within the negative electrode slurry. To this end, the drying unit may be disposed at a position where the negative electrode slurry can be dried before the crystalline orientation of the carbon-based negative electrode active material coated on the surface of the electrode sheet 300 is reduced.

[0058] The drying unit is also formed to include a wall (not shown) that blocks off the periphery except for an entrance / exit through which the electrode sheet 300 coated with the negative electrode slurry is introduced and removed, and a dryer (not shown) for drying the electrode sheet on the wall on the side through which the electrode sheet 300 coated with the negative electrode slurry is removed.

[0059] When the electrode sheet 300 coated with the negative electrode slurry enters the drying unit through an inlet, energy such as light, heat, or the like supplied from the opposite wall is transferred to the electrode sheet 300. 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.

[0060] The dryer can apply energy such as light, wavelength, or heat and can be any dryer commonly used in the art, without any particular limitation. For example, the dryer may be an ultraviolet dryer, a near-infrared dryer, a far-infrared dryer, a hot air dryer, a vacuum oven, or the like, which may be used alone or in combination.

[0061] The negative electrode manufacturing apparatus according to the present invention, having the above-described configuration, realizes a crystalline orientation of the carbon-based negative electrode active material nearly horizontal to the surface of the negative electrode current collector before the negative electrode slurry is dispensed onto the negative electrode sheet, and then, during the dispensing of the negative electrode slurry, the crystalline orientation of the carbon-based negative electrode active material in the slurry can be adjusted to nearly perpendicular to the surface of the negative electrode current collector depending on the fluid momentum and / or direction of the negative electrode slurry. Therefore, negative electrodes manufactured using the above-described negative electrode manufacturing apparatus have excellent crystalline orientation of the carbon-based negative electrode active material relative to the negative electrode current collector. Furthermore, since a separate process for orienting the carbon-based negative electrode active material is not required after applying the negative electrode slurry, there are advantages in that additional equipment for negative electrode manufacturing is not required and that it is easily applicable to mass production processes.

[0062] <Method of manufacturing negative electrode for secondary battery>

[0063] In one embodiment, the present invention further comprises: The method includes applying a negative electrode slurry to an electrode sheet while applying a magnetic field thereto using the negative electrode manufacturing apparatus according to the present invention; The negative electrode slurry provides a method for producing a negative electrode for a secondary battery containing a carbon-based negative electrode active material.

[0064] A method for manufacturing a negative electrode for a secondary battery according to the present invention is a method for manufacturing a negative electrode using the above-described negative electrode manufacturing apparatus according to the present invention, and includes a step of applying a negative electrode slurry to an electrode sheet while applying a magnetic field. That is, the manufacturing method is characterized in that the application of a magnetic field to a negative electrode slurry containing a carbon-based negative electrode active material and the application of the negative electrode slurry to an electrode sheet (i.e., a negative electrode current collector) are performed simultaneously. As a result, the manufacturing method does not require separate crystal orientation of the carbon-based negative electrode active material after application of the negative electrode slurry, and therefore has the advantages of being economical due to its simple process and easy application to mass production due to its excellent processability.

[0065] The negative electrode slurry may contain a carbon-based negative electrode active material that has been magnetically oriented by the negative electrode manufacturing apparatus according to the present invention, as described above. The magnetic orientation may be achieved by forming a magnetic field parallel to the surface of the electrode sheet.

[0066] In addition, the above manufacturing method can control the distance between the slot die slot, i.e., the lip portion including the upper lip, middle lip, and lower lip, provided in the negative electrode manufacturing apparatus and the coating roll according to the average thickness of the negative electrode slurry to be applied so that the crystal orientation of the carbon-based negative electrode active material is nearly perpendicular to the electrode sheet (or negative electrode current collector).

[0067] The orientation of the oriented crystal plane of the oriented carbon-based negative electrode active material may change depending on the fluid motion direction of the negative electrode slurry when the negative electrode slurry is discharged. Therefore, to allow the orientation of the crystal plane of the oriented carbon-based negative electrode active material to change to nearly 90° when the negative electrode slurry is discharged, the average thickness of the negative electrode slurry may be adjusted to be greater than the distance between the lip of a slot die and a coating roll in a negative electrode manufacturing apparatus. For example, the average thickness of the negative electrode slurry applied to the electrode sheet may be adjusted to 1.01 to 2.00 times, 1.01 to 1.80 times, 1.01 to 1.50 times, 1.1 to 1.5 times, or 1.2 to 1.9 times the distance between the lip of a slot die and a coating roll in a negative electrode manufacturing apparatus. In addition, the average thickness of the negative electrode slurry applied to the electrode sheet may be 100 μm or more. Specifically, the average thickness of the negative electrode slurry applied to the electrode sheet can be 100 μm or more and 300 μm or less, 110 μm or more and 190 μm or less, 200 μm or more and 300 μm or less, 150 μm or more and 230 μm or less, 100 μm or more and 250 μm or less, or 100 μm or more and 200 μm or less.

[0068] Furthermore, the fluid momentum of the negative electrode slurry during discharging can affect the alignment of the carbon-based negative electrode active material. Therefore, the viscosity of the negative electrode slurry can be adjusted to a predetermined range so that the crystalline orientation of the carbon-based negative electrode active material, which is pre-oriented before discharging, can be easily controlled during the slurry application process. Specifically, the negative electrode slurry can have a viscosity of 2,000 cps to 15,000 cps at 25°C, more specifically, 2,000 cps to 14,000 cps, 2,000 cps to 12,000 cps, 2,000 cps to 10,000 cps, 5,000 cps to 15,000 cps, 10,000 cps to 15,000 cps, 9,000 cps to 13,000 cps, 11,000 cps to 14,000 cps, 250 cps to 3000 cps, 300 cps to 4000 cps, 300 cps to 5000 cps, 300 cps to 5000 cps, 300 cps to 6000 cps, 300 cps to 6000 cps, 300 cps to 7000 cps, 300 cps to 8000 cps, 300 cps to 8000 cps, 300 cps to 9000 cps, 300 cps to 4000 cps, 300 cps to 5000 cps, 300 cps to 6000 cps, 300 cps to 8000 cps, 30 The average speed may be 0 cps or more and 6800 cps or less, 2500 cps or more and 6700 cps or less, 3000 cps or more and 6000 cps or less, 3500 cps or more and 6000 cps or less, 3600 cps or more and 5700 cps or less, 4000 cps or more and 6000 cps or less, 5000 cps or more and 6000 cps or less, 4000 cps or more and 5000 cps or less, 3500 cps or more and 4800 cps or less, 5400 cps or more and 6900 cps or less, or 3500 cps or more and 4900 cps or less.

[0069] Furthermore, the step of applying the negative electrode slurry to the electrode sheet with the magnetic force applied thereto may be performed on the electrode sheet being transported at a predetermined speed, which may be the same as the speed at which the negative electrode slurry is applied to the electrode sheet.

[0070] For example, the step of applying the negative electrode slurry to the electrode sheet may be performed at a speed of 5 m / min to 100 m / min, specifically 40 m / min to 100 m / min, 50 m / min to 100 m / min, 60 m / min to 90 m / min, 40 m / min to 80 m / min, or 40 m / min to 60 m / min.

[0071] By performing the negative electrode slurry application step within the above speed range, the present invention can favorably increase the fluid momentum of the negative electrode slurry when it is discharged. As a result, the present invention can convert the crystalline orientation of the carbon-based negative electrode active material, which was horizontal with respect to the electrode sheet (or negative electrode current collector) before application, to a nearly vertical orientation after application. Furthermore, by performing the negative electrode slurry application step within the above speed range, the present invention can prevent the negative electrode slurry from being unevenly applied to the surface of the electrode sheet due to an excessively slow application speed. Furthermore, the present invention can prevent a decrease in process efficiency and productivity and prevent a reduction in the degree of orientation due to the disruption of the crystalline alignment of the carbon-based negative electrode active material present in the negative electrode slurry caused by an excessively fast application speed.

[0072] In addition, the method for manufacturing a negative electrode for a secondary battery according to the present invention may further include, after the step of applying the negative electrode slurry to the electrode sheet while the magnetic field is applied, a step of drying the applied negative electrode slurry to form a negative electrode active layer.

[0073] The step of forming the negative electrode active layer refers to a process of fixing the carbon-based negative electrode active material contained in the negative electrode slurry onto the electrode sheet by drying the negative electrode slurry. This step may be applied without any particular limitation as long as it can fix the carbon-based negative electrode active material contained in the negative electrode slurry coated on the electrode sheet while minimizing changes in the degree of orientation of the carbon-based negative electrode active material with respect to the surface of the electrode sheet.

[0074] Specifically, the drying may be performed by applying energy such as light, wavelength, or heat, and may be performed by using an ultraviolet dryer, a near-infrared dryer, a far-infrared dryer, a hot air dryer, a vacuum oven, or the like, either alone or in combination.

[0075] Meanwhile, the carbon-based negative electrode active material contained in the negative electrode slurry may include those commonly used as carbon-based negative electrode active materials for lithium secondary batteries. Specifically, the carbon-based negative electrode active material refers to a material primarily composed of carbon atoms, and may include graphite. The graphite may include at least one of natural graphite and artificial graphite, and preferably includes natural graphite or a mixture of natural graphite and artificial graphite.

[0076] 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.). In particular, graphite granules assembled using multiple pieces of highly crystalline natural graphite are preferred. Furthermore, one graphite granule may be formed by the aggregation of 2 to 100, preferably 3 to 20, flake graphite particles.

[0077] Such a carbon-based negative electrode active material, specifically graphite, may have a spherical particle shape. The sphericity of the graphite particles may be 0.75 or greater, e.g., 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. A sphericity of 1 indicates that the particle shape is spherical. The sphericity may be measured using a particle shape analyzer. By achieving a nearly spherical shape for the carbon-based negative electrode active material, the present invention has the advantages of improving the electrical conductivity of the negative electrode active layer, thereby improving battery capacity, and increasing the specific surface area of ​​the negative electrode active material, thereby improving adhesion between the negative electrode active layer and the current collector.

[0078] The carbon-based negative electrode active material has an average particle size (D 50), specifically, an average particle size (D 50 ) can be shown.

[0079] The average particle size of spherical natural graphite is preferably as small as possible to maximize the degree of disorder in the direction of expansion of each particle, thereby preventing particle expansion during charging with lithium ions. However, if the particle size of natural graphite is less than 5.0 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 can occur, resulting in a decrease in inter-particle adhesion and adhesion between the particles and the current collector due to repeated charge and discharge, which can significantly reduce cycle performance.

[0080] In addition, the negative electrode slurry may further include a conductive material, a binder, a thickener, etc., in addition to the carbon-based negative electrode active material, and these may be those commonly used in the art.

[0081] 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.

[0082] For example, the negative electrode active layer may contain carbon black, carbon nanotubes, carbon fibers, etc., alone or in combination, as a conductive material.

[0083] The content of the conductive material may be 0.1 to 10 parts by weight, specifically 0.1 to 8 parts by weight, 0.1 to 5 parts by weight, 0.1 to 3 parts by weight, 2 to 6 parts by weight, or 0.5 to 2 parts by weight, based on 100 parts by weight of the total negative electrode active layer. By controlling the content of the conductive material within the above range, the present invention can prevent a decrease in charge capacity due to an increase in negative electrode resistance caused by a low content of conductive material, and can prevent problems such as a decrease in charge capacity due to a decrease in the content of negative electrode active material caused by an excessive amount of conductive material, or a decrease in fast charge characteristics due to an increase in the loading amount of the negative electrode active layer.

[0084] The binder is a component that aids in bonding between the negative electrode active material and the conductive material, etc., and bonding to the negative electrode current collector. It may be suitably used within a range that does not degrade 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.

[0085] 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 slurry. By controlling the content of the binder contained in the negative electrode slurry within the above range, the present invention can prevent a decrease in the adhesive strength of the negative electrode active layer due to a low content of binder or a decrease in the electrical properties of the electrode due to an excessive amount of binder.

[0086] The method for manufacturing a secondary battery negative electrode sheet according to the present invention has the above-described configuration, and thus has the advantage of being able to uniformly align the carbon-based negative electrode active material of the negative electrode slurry applied to the negative electrode current collector with a high degree of orientation.

[0087] <Secondary battery negative electrode>

[0088] Furthermore, in one embodiment, the present invention provides The negative electrode for a secondary battery manufactured by the above-described manufacturing method is provided.

[0089] The negative electrode for a lithium secondary battery according to the present invention includes a negative electrode active layer, which includes a carbon-based negative electrode active material as a main component, on at least one surface of a negative electrode current collector. The negative electrode active layer is a layer that realizes the electrical activity of the negative electrode. The negative electrode active layer is fabricated by coating both surfaces of the electrode current collector with an electrode slurry including a carbon-based negative electrode active material that realizes an electrochemical redox reaction during charge and discharge of the battery, followed by drying and rolling the coating.

[0090] Here, the negative electrode active layer is formed by applying a negative electrode slurry to an electrode sheet in a magnetic field using the above-mentioned negative electrode manufacturing apparatus, followed by drying. The negative electrode active layer exhibits a high degree of crystalline orientation of the carbon-based negative electrode active material, which is the main component, relative to the surface of the electrode sheet, thereby providing high energy density and charge / discharge performance.

[0091] Specifically, in the negative electrode according to the present invention, the carbon-based negative electrode active material contained in the negative electrode active layer may be aligned at a predetermined angle relative to the electrode sheet (or negative electrode current collector). This alignment of the carbon-based negative electrode active material may reduce the degree of disorder in the negative electrode active layer, thereby reducing electrode resistance and providing a path for lithium ion migration. The crystalline orientation of the carbon-based negative electrode active material (e.g., graphite) may be determined by crystal plane analysis of the carbon-based negative electrode active material contained in the negative electrode active layer.

[0092] For example, in the negative electrode active layer, the carbon-based negative electrode active material may be aligned in a certain direction relative to the negative electrode current collector, and when the negative electrode active layer is measured by X-ray diffraction spectroscopy (XRD), the average alignment degree of the carbon-based negative electrode active material, represented by the following Formula 2, may be 0.9 or less:

[0093] [Formula 2] OI=I 004 / I 110

[0094] In Equation 2, I 004 represents the area of ​​the peak representing the (0,0,4) crystal plane when measuring the negative electrode active layer by X-ray diffraction spectroscopy (XRD), I 110 represents 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).

[0095] Equation 2 above can be an index showing the degree to which the crystalline structure of the spherical carbon-based negative electrode active material is aligned in a certain direction, specifically, relative to the surface of the negative electrode current collector, during X-ray diffraction measurement. More specifically, the negative electrode active layer exhibits peaks of 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 the carbon-based negative electrode active material, graphite, during X-ray diffraction measurement, and these represent the (0,0,2) plane, (1,0,0) plane, (1,0,1)R plane, (1,0,1)H plane, (0,0,4) plane, and (1,1,0) plane. In addition, the peak appearing at 2θ=43.4±0.2° is thought to be an overlap of the peaks corresponding to the (1,0,1)R plane of the carbon-based negative electrode active material and the (1,1,1) plane of the current collector, for example, copper (Cu).

[0096] The degree of alignment (OI) of the carbon-based negative electrode active material can be measured by the area ratio of the peak at 2θ=77.5±0.2°, which indicates the (1,1,0) plane, to the peak at 2θ=54.7±0.2°, which indicates the (0,0,4) plane, specifically, the area ratio obtained by integrating the intensities of the above peaks. Here, the peak at 2θ=54.7±0.2° is a peak indicating the (0,0,4) plane, which is one of the crystal planes of graphite and is tilted relative to the negative electrode current collector. Therefore, the closer the OI value is to 0, the closer the tilt relative to the surface of the negative electrode current collector is to 90°, and the larger the OI value is, the closer the tilt relative to the surface of the negative electrode current collector is to 0° or 180°. In view of this, in the negative electrode active layer according to the present invention, the carbon-based negative electrode active material is aligned nearly perpendicular to the negative electrode current collector, for example, at an angle of 60° or more, 70° or more, 70° to 90°, 80° to 90°, 65° to 85°, or 70° to 85° with respect to the negative electrode current collector. Therefore, the degree of alignment (OI) of the carbon-based negative electrode active material may be lower than when the carbon-based negative electrode active material is not magnetically aligned.

[0097] In the negative electrode according to the present invention, the degree of alignment (OI) according to Equation 2 when measured by X-ray diffraction on the surface of the negative electrode active layer may be 0.9 or less, specifically 0.8 or less, 0.7 or less, 0.6 or less, 0.1 to 0.9, 0.2 to 0.8, 0.3 to 0.7, 0.2 to 0.6, or 0.4 to 0.6.

[0098] Meanwhile, the average thickness of the negative electrode active layer may be 50 μm to 300 μm, specifically 50 μm to 250 μm, 100 μm to 250 μm, or 100 μm to 200 μm. By adjusting the average thickness of the negative electrode active layer within the above range, the present invention can not only increase the energy density of the electrode but also uniformly control the degree of disorder of the carbon-based negative electrode active material contained in the negative electrode active layer.

[0099] 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. For example, the negative electrode current collector may include copper, stainless steel, nickel, titanium, calcined carbon, etc. In the case of copper or stainless steel, it may also include those that have been surface-treated with carbon, nickel, titanium, silver, etc. In addition, the average thickness of the negative electrode current collector may be preferably 1 μm to 500 μm, taking into account the conductivity and total thickness of the negative electrode to be manufactured.

[0100] The present invention will be described in more detail below with reference to examples and experimental examples.

[0101] 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.

[0102] Examples 1 to 5 and Comparative Examples 1 and 2. Production of sheets for secondary battery negative electrodes

[0103] First, natural graphite and artificial graphite were prepared as carbon-based active materials (average particle size: 4±1 μm, sphericity: 0.94±0.2), and a first negative electrode slurry and a second negative electrode slurry were produced using the prepared carbon-based active materials.

[0104] Specifically, the first negative electrode slurry was prepared by mixing natural graphite and artificial graphite in a weight ratio of 2:8 to prepare a graphite mixture as the negative electrode active material, carbon black as the conductive material, and carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) as binders. 95 parts by weight of the graphite mixture, 1 part by weight of carbon black, 1.5 parts by weight of CMC, and 2.5 parts by weight of SBR were mixed with water to a solids content of 50% to prepare the first negative electrode slurry.

[0105] The second negative electrode slurry was prepared using the same method as the first negative electrode slurry, but using only artificial graphite as the carbon-based active material. The viscosity of the first and second negative electrode slurries was adjusted to 4700±200 cps at 25°C.

[0106] Separately, a negative electrode manufacturing apparatus was prepared, including a double slot die having first and second slots into which a negative electrode slurry could be discharged at the tip of an upper block, a first spacer, a middle block, a second spacer, and a lower block, and a coating roll positioned facing the slots of the slot die. In this case, the negative electrode manufacturing apparatus had: i) the type of magnetic polarity imparted to the upper lip of the upper block, the middle lip of the middle block, and the lower lip of the lower block; ii) the magnetic field strength applied to the lip portion including the upper lip, middle lip, and lower lip; and iii) the ratio (G / M) of the magnetic field strength (G) applied to the lip portion to the moving speed (M) of the copper sheet (i.e., electrode sheet) adjusted as shown in Table 1 below.

[0107] The prepared anode slurry was placed in the prepared anode manufacturing equipment and applied to the surface of a copper sheet (thickness: 8 μm) transported at a speed (M) of 50 m / min. Next, hot air was continuously blown onto the applied anode slurry to dry it, forming an anode active layer.

[0108] [Table 1]

[0109] Experimental example

[0110] The orientation exhibited by the carbon-based negative electrode active material of the negative electrode for secondary battery manufactured using the negative electrode manufacturing apparatus according to the present invention was evaluated.

[0111] Specifically, X-ray diffraction spectroscopy (XRD) was performed on three arbitrary points of the negative electrode active layer of each of the negative electrodes manufactured in Examples 1 to 5 and Comparative Examples 1 and 2. The measurement conditions for X-ray diffraction (XRD) were as follows:

[0112] - Target: Cu (Kα-ray) graphite monochromator - Slit: Divergence slit = 1 degree, Receiving slit = 0.1 mm, Scattering slit = 1 degree - Measurement area: (1,1,0) plane: 76.5 degrees < 2θ < 78.5 degrees / (0,0,4) plane: 53.5 degrees < 2θ < 56.0 degrees

[0113] The degree of alignment (OI) of each carbon-based negative electrode active material was calculated from the spectrum measured under the above conditions, and the average degree of alignment (OI) was calculated from the calculated degrees of alignment (OI) of the carbon-based negative electrode active material at three points. The results are shown in Table 2.

[0114] [Formula 2] OI=I 004 / I 110

[0115] In Equation 2, I 004 represents the area of ​​the peak representing the (0,0,4) crystal plane when measuring the negative electrode active layer by X-ray diffraction spectroscopy (XRD), I 110 represents 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).

[0116] [Table 2]

[0117] As shown in Table 2 above, it can be seen that the negative electrode manufactured using the negative electrode manufacturing apparatus according to the present invention has a high degree of orientation of the carbon-based negative electrode active material contained in the negative electrode active layer.

[0118] This means that when a magnetic field of the same polarity is applied to the upper and lower lips of the double slot die and a magnetic field of the opposite polarity is applied to the middle lip during discharge of the negative electrode slurry, an attractive force acts between the lips, orienting the crystal plane of the carbon-based negative electrode active material nearly horizontally to the surface of the electrode sheet (or negative electrode current collector). When a negative electrode slurry containing such a carbon-based negative electrode active material is discharged onto the electrode sheet at a predetermined speed, the crystal orientation of the carbon-based negative electrode active material changes to nearly perpendicular to the surface of the electrode sheet (or negative electrode current collector) depending on the fluid momentum and direction of the negative electrode slurry.

[0119] From these results, the anode manufacturing apparatus according to the present invention can apply the carbon-based anode active material in the discharged anode slurry so that it is oriented at a predetermined angle relative to the surface of the anode current collector. This not only results in an excellent degree of orientation of the carbon-based anode active material in the manufactured anode, but also has the advantage of being easily applicable to mass production processes.

[0120] 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.

[0121] 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 can be defined by the claims. [Explanation of symbols]

[0122] 10: Apparatus for manufacturing a negative electrode for a secondary battery according to the present invention 100: Double die coater 110: Upper die 111: Upper lip 112: Upper body 120: Intermediate die 121: Middle lip 122: Intermediate body 130: Lower die 131: Lower lip 132: Lower body 130: Spacer 141 and 142: first spacer and second spacer 141a and 142a: Openings 151 and 152: 1st and 2nd slots 200: Coating roll 300: Electrode sheet A: Unoriented section B: Orientation section I: Main body II: Lip III: Coating area MD: Magnetic field direction CM: Carbon-based negative electrode active material

Claims

1. An apparatus for manufacturing an electrode sheet coated with a negative electrode slurry containing a carbon-based negative electrode active material, a double slot die including an upper block, an intermediate block, and a lower block, a first slot provided in the gap between the upper block and the intermediate block and for discharging a first negative electrode slurry, and a second slot provided in the gap between the intermediate block and the lower block and for discharging a second negative electrode slurry; a coating roll that faces the first slot and the second slot of the double slot die and transports an electrode sheet coated with the negative electrode slurry discharged from each slot, the upper block, the intermediate block, and the lower block each have an upper lip, an intermediate lip, and a lower lip that form an outlet at their tip, and the upper lip and the lower lip exhibit magnetism having the same polarity, and the intermediate lip exhibits magnetism having a polarity opposite to that of the upper lip.

2. 2. The apparatus for manufacturing a negative electrode for a secondary battery according to claim 1, wherein the upper lip, the middle lip, and the lower lip apply a magnetic field having a strength of 500 G to 3,000 G when discharging the negative electrode slurry.

3. 2. The apparatus for manufacturing a negative electrode for a secondary battery according to claim 1, wherein the double slot die satisfies the following formula 1: [Formula 1] 10≦G / M≦50 In Formula 1, G represents the strength of the magnetic field (unit: G) applied at the upper lip, middle lip, and lower lip; M represents the speed (unit: m / min) at which the electrode sheet is moved by the coating roll.

4. The apparatus for manufacturing a negative electrode for a secondary battery according to claim 1 , wherein the upper lip, the middle lip, and the lower lip have a structure including at least one of a permanent magnet and an electromagnet.

5. The negative electrode manufacturing apparatus further includes a drying unit that dries the negative electrode slurry applied to the electrode sheet, 2. The apparatus for manufacturing a negative electrode for a secondary battery according to claim 1, wherein the drying unit is disposed at a position where the drying unit reaches within 20 seconds from the time when the negative electrode slurry discharged from the double slot die is applied to the electrode sheet.

6. The method includes applying a negative electrode slurry to which a magnetic field is applied onto the electrode sheet using the negative electrode manufacturing apparatus according to any one of claims 1 to 5, The negative electrode slurry contains a carbon-based negative electrode active material.

7. 7. The method of claim 6, wherein an average thickness of the negative electrode slurry applied to the electrode sheet is greater than a distance between the slots of the double slot die and the coating roll provided in the negative electrode manufacturing apparatus.

8. The method for manufacturing a negative electrode for a secondary battery according to claim 6 , wherein the average thickness of the negative electrode slurry applied to the electrode sheet is 100 μm or more.

9. 7. The method for manufacturing a negative electrode for a secondary battery according to claim 6, wherein the step of applying the negative electrode slurry to the electrode sheet is performed at a speed of 5 m / min to 100 m / min.

10. 7. The method for producing a negative electrode for a secondary battery according to claim 6, wherein the negative electrode slurry has a viscosity of 2,000 cps to 15,000 cps at 25°C.

11. 7. The method of claim 6, further comprising the step of drying the coated negative electrode slurry to form a negative electrode active layer after the step of coating the negative electrode slurry on the electrode sheet.

12. 12. The method for manufacturing a negative electrode for a secondary battery according to claim 11, wherein the negative electrode active layer has an alignment degree of the carbon-based negative electrode active material with respect to the surface of the electrode sheet, represented by the following formula 2, of 0.9 or less: [Formula 2] O.I=I ００４ / I １１０ In Equation 2, I ００４ represents the area of ​​the peak representing the (0,0,4) crystal plane when the negative electrode active layer is subjected to X-ray diffraction spectroscopy (XRD), I １１０ represents the area of ​​the peak indicating the (1,1,0) crystal plane when the negative electrode active layer is subjected to X-ray diffraction spectroscopy (XRD).

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