Negative electrode manufacturing apparatus for secondary battery

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 apparatus for manufacturing a negative electrode includes an upper block, a middle block, and a lower block, 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 a coating roll, and the upper lip, the middle lip, and the lower lip located at the tip of each block are configured to apply a magnetic field of the same polarity. As a result, the carbon-based negative electrode active material in the discharged negative electrode slurry can be applied in a state in which 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 orientation degree of the carbon-based negative electrode active material is excellent, but also it is easy to apply to a mass production process.

Description

[Technical field]

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

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0173300 dated December 13, 2022, and all contents disclosed in the documents of said Korean patent application are incorporated herein by reference. [Background technology]

[0003] 2. Description of the Related Art In recent years, secondary batteries have been widely used not only in small devices such as portable electronic devices, but also in medium- to large-sized devices such as battery packs for hybrid and electric vehicles and power storage devices.

[0004] Such a secondary battery is a power generating element capable of being charged and discharged, which has a laminated structure of a positive electrode / a separator / a 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. When the secondary battery is charged, lithium ions released from the positive electrode are absorbed into the carbon-based negative electrode active material of the negative electrode, and when the secondary battery is discharged, the lithium ions contained in the carbon-based negative electrode active material are absorbed into the lithium metal oxide of the positive electrode, thereby repeating 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 a large number of layers that spread out in a planar shape are stacked. During charging, lithium ions penetrate from the edge surface (surface where the layers overlap) of such graphite layers and diffuse between the layers, and during discharging, lithium ions can be desorbed and released from the edge surface of the layers. In addition, since the electrical resistivity of graphite in the plane direction of the layers is lower than that in the stacking direction of the layers, a detouring electron conduction path is formed along the plane direction of the layers.

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

[0007] Such graphite orientation can be induced by applying a magnetic field to the negative electrode slurry containing graphite coated on the negative electrode current collector and not drying the negative electrode slurry. However, when considering the production speed during mass production of actual negative electrodes, there is a problem that it is difficult to secure a sufficient magnetic field application time to induce graphite alignment in the negative electrode slurry. In addition, when the strength of the magnetic field applied to the negative electrode slurry coated on the electrode sheet is increased to solve this problem, a phenomenon occurs in which the graphite is pulled by the magnetic field at the end of the magnetic field, and the orientation of the graphite aligned perpendicular to the metal sheet is destroyed, resulting in a limitation that the orientation of the graphite in the negative electrode active layer finally manufactured is low.

[0008] Therefore, there is a need for a negative electrode manufacturing technique that can realize a high degree of graphite orientation and is applicable 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 method for manufacturing a negative electrode, which can realize a high degree of crystal orientation of a carbon-based negative electrode active material such as graphite contained in a negative electrode active layer and can be applied to mass production of negative electrodes for secondary batteries. [Means for solving the problem]

[0011] In order to solve the above problems, the present invention provides, in one embodiment, An apparatus for producing an electrode sheet coated with a negative electrode slurry containing a carbon-based negative electrode active material, comprising: a double slot die including an upper block, a middle block, and a lower block, a first slot provided through a space between the upper block and the middle block and for discharging a first negative electrode slurry, and a second slot provided through a space between the middle 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 on which the negative electrode slurry discharged from each slot is applied, The upper block, intermediate block and lower block are provided with an upper lip, intermediate lip and lower lip forming an outlet at each tip, and the upper lip, intermediate lip and lower lip exhibit magnetic properties of the same polarity.

[0012] At this time, the upper lip and the lower lip may have a structure including at least one of a permanent magnet and an electromagnet, and thus a magnetic field having a strength of 500 G to 3,000 G may be applied when the negative electrode slurry is discharged.

[0013] In addition, the above-mentioned double slot die may satisfy the following formula 1:

[0014] [Formula 1] 50≦G / M≦250

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

[0016] In addition, the negative electrode manufacturing apparatus may further include a drying unit that dries the negative electrode slurry applied to the electrode sheet, and the drying unit may be disposed at a position where the drying unit can reach within 20 seconds from the time when the negative electrode slurry discharged from the slot die is applied to the electrode sheet.

[0017] In one embodiment, the present invention provides a method for producing a composition comprising: The method includes applying the negative electrode slurry to which a magnetic field is applied onto an electrode sheet using the above-described negative electrode manufacturing apparatus according to the present invention, The negative electrode slurry contains a carbon-based negative electrode active material.

[0018] In this case, the average thickness of the negative electrode slurry applied to the electrode sheet may be greater than a distance between a slot of a slot die provided in a negative electrode manufacturing apparatus and a coating roll, and the average thickness of the negative electrode slurry applied to the electrode sheet may be 100 μm or more.

[0019] The step of applying the negative electrode slurry to the electrode sheet may be performed at a speed of 5 to 100 m / min.

[0020] In addition, 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.

[0021] Here, the negative electrode active layer may have an alignment index (OI) of 0.9 or less of the carbon-based negative electrode active material with respect to the surface of the electrode sheet, which is represented by the following Formula 2:

[0022] [Formula 2] OI=I 004 / I 110

[0023] In formula 2, I 004represents the area of ​​the peak showing the (004) crystal plane in the X-ray diffraction spectroscopy (XRD) measurement of the negative electrode active layer, I 110 represents the area of ​​the peak indicating the (110) crystal plane when the negative electrode active layer is measured by X-ray diffraction spectroscopy (XRD). Effect of the Invention

[0024] 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 a discharged negative electrode slurry in a state where the carbon-based negative electrode active material is oriented nearly perpendicular to the surface of a negative electrode current collector, thereby providing an advantage that the carbon-based negative electrode active material in the manufactured negative electrode has an excellent degree of orientation and is easily applicable to a mass production process. [Brief description of the drawings]

[0025] [Figure 1] 1 is a cross-sectional view showing a schematic configuration of an apparatus for manufacturing a negative electrode for a secondary battery according to the present invention. [Diagram 2] FIG. 2 is a perspective view showing a structure of a double die coater provided in the apparatus for manufacturing a negative electrode for a secondary battery according to the present invention. [Diagram 3] 4 is a conceptual diagram illustrating the principle of applying a carbon-based negative electrode active material of a negative electrode slurry to an electrode sheet in a magnetically aligned state by a dual die coater according to the present invention. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Since the present invention can be modified in various ways and can have various embodiments, specific embodiments are described in detail in the detailed description.

[0027] However, this is not intended to limit the invention to any particular embodiment, but it should be understood to include all modifications, equivalents, or alternatives falling within the spirit and scope of the invention.

[0028] 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.

[0029] In addition, in the present invention, when a layer, film, region, plate, or other portion is described as being "on" another portion, this includes not only the case where it is "directly on" the other portion, but also the case where there is another portion in between. Conversely, when a layer, film, region, plate, or other portion is described as being "under" the other portion, this includes not only the case where it is "directly under" the other portion, but also the case where there is another portion in between. In addition, in the present application, being "on" can include not only the case where it is located at the top, but also the case where it is located at the bottom.

[0030] In the present invention, "containing as a main component" may mean containing 50% by weight or more (or 50% by volume or more), 60% by weight or more (or 60% by volume or more), 70% by weight or more (or 70% by volume or more), 80% by weight or more (or 80% by volume or more), 90% by weight or more (or 90% by volume or more), or 95% by weight or more (or 95% by volume or more) of the defined component relative to the total weight (or total volume). For example, "containing graphite as a main component as a negative electrode active material" may mean containing 50% by weight or more, 60% by weight or more, 70% by weight or more, 80% by weight or more, 90% by weight or more, or 95% by weight or more of graphite relative to the total weight of the negative electrode active material, and in some cases, it may mean that the entire negative electrode active material is made of graphite and contains 100% by weight of graphite.

[0031] 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 a space formed between the lips, i.e., a region where the lips are disposed in the first slot and the second slot.

[0032] 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 a space formed between the bodies, i.e., a region where the bodies are disposed in the first slot and the second slot.

[0033] The present invention will now be described in more detail.

[0034] <Negative electrode manufacturing equipment for secondary batteries>

[0035] 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, comprising: a double slot die including an upper block, a middle block, and a lower block, a first slot provided through a space between the upper block and the middle block and for discharging a first negative electrode slurry, and a second slot provided through a space between the middle 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 on which the negative electrode slurry discharged from each slot is applied, The upper block, intermediate block and lower block are provided with an upper lip, intermediate lip and lower lip forming an outlet at each tip, and the upper lip, intermediate lip and lower lip exhibit magnetic properties of the same polarity.

[0036] The secondary battery negative electrode manufacturing apparatus according to the present invention is an apparatus applied when manufacturing a negative electrode for use 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.

[0037] Specifically, FIG. 1 is a cross-sectional view showing a schematic structure of an apparatus for manufacturing a negative electrode for a secondary battery according to the present invention. The negative electrode manufacturing apparatus 10 is composed of a double slot die 100 and a coating roll 200, and has a structure in which an electrode sheet 300 is moved by the rotation of the coating roll 200 while a negative electrode slurry is applied to the surface.

[0038] The double slot die 100 includes a first slot 151 and a second slot 152, and can double-coat two types of negative electrode slurries, which may be the same or different, onto the negative electrode current collector. As shown in FIG 2, the first slot 151 can be formed between the upper die 110 and the middle die 120 facing each other, and the second slot 152 can be formed between the middle die 120 and the lower die 130 facing each other.

[0039] For example, in the double slot die 100, a first spacer 141 and a second spacer 142 are sequentially interposed between the upper die 110, the middle die 120, and the lower die 130, respectively, to provide gaps therebetween, thereby forming passages, i.e., slots 151 and 152, through which the negative electrode slurry can move. In this case, the vertical height of the slots can be determined by the thickness (Y-axis direction) of the first spacer 141 and / or the second spacer 142 that realizes the gaps between the dies, and the thickness of the first spacer 141 and / or the second spacer 142 can be controlled depending on the application and capacity of the secondary battery. Specifically, 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.

[0040] In addition, the first spacer 141 and / or the second spacer 142 may be interposed in the remaining portion of the edge region of each of the opposing surfaces of the upper die 110, the intermediate die 120, and the lower die 130 except for one side. As a result, the 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. Here, the leading ends of the upper die 110, the intermediate die 120, and the lower die 130 include the upper lip 111, the intermediate lip 121, and the lower lip 131, and it can be said that the slots 151 and 152 through which the negative electrode slurry is discharged are portions formed by separating the lips 111, 121, and 131 from each other.

[0041] 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 each of the dies 110, 120, and 130, except for the areas where the first slot 151 and the second slot 152 are formed, so it is preferable that they are made of a material having sealing properties.

[0042] Meanwhile, the upper die 110, the intermediate die 120 and the lower die 130 may include an upper lip 111, an intermediate lip 121 and a lower lip 131 located at each end, as well as an upper body 112, an intermediate 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 negative electrode slurry can fluidly move.

[0043] In addition, the upper lip 111, the middle lip 121, and the lower lip 131 exhibit magnetism. Specifically, the upper lip 111, the middle lip 121, and the lower lip 131 may exhibit magnetism having the same polarity, and thus a magnetic field may be formed in the first slot 151 and the second slot 152 formed by the lips 111, 121, and 131 in the same direction as the direction in which the negative electrode slurry is discharged.

[0044] As shown in FIG. 3, when the path along which the negative electrode slurry is discharged and applied is 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 including the space between the main bodies 112, 122, and 132 of each die (i.e., I: main body section), and therefore moves with a high degree of freedom. However, the oriented section B includes the space between the upper lip 111, the middle lip 121, and the lower lip 131 that exhibit magnetism of the same polarity (i.e., II: lip section), and in the lip section, a repulsive force acts and a magnetic field direction MD may be formed in the same direction as the direction along which the negative electrode slurry is discharged. As a result, the carbon-based negative electrode active material CM, i.e., graphite, contained in the negative electrode slurry before the negative electrode slurry is applied to the negative electrode current collector may be oriented so that the (002) crystal plane is approximately perpendicular to the negative electrode current collector. The oriented graphite is applied to the negative electrode current collector while maintaining the oriented state (i.e., corresponds to III: coating region), so that the graphite can have a high degree of orientation without the application of a separate magnetic field after application of the negative electrode slurry.

[0045] In this case, 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 electromagnets and AC electromagnets. In addition, the permanent magnets may include both ferromagnetic magnets and soft magnetic magnets, including NdFeB magnets, SmCo magnets, ferrite magnets, alnico magnets, FeCrCo magnets, bond magnets (Nd-Fe-B, Sm-Fe-N, Sm-Co, ferrite magnets), etc.

[0046] In addition, since the negative electrode manufacturing apparatus applies a magnetic field before the negative electrode slurry is applied to the electrode sheet, a magnetic field with a weaker strength can be applied compared to the case where the magnetic field is applied after the negative electrode slurry is applied to the electrode sheet. The magnetic field strength at this time can satisfy a predetermined range. In other words, a magnetic field that satisfies a predetermined strength range can be applied to the upper lip 111, the intermediate lip 121, and the lower lip 131 when the negative electrode slurry is discharged. Specifically, the same magnetic field can be applied to the upper lip 111, the intermediate lip 121, and the lower lip 131. 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.

[0047] The negative electrode manufacturing apparatus of the present invention may uniformly realize the crystal orientation of the carbon-based negative electrode active material before the negative electrode slurry is discharged through the first slot 151 and the second slot 152 by adjusting the strength of the magnetic field applied to the upper lip 111, the middle lip 121, and the lower lip 131 within the above range. In addition, the negative electrode manufacturing apparatus may maintain the orientation so that the uniformly crystal-oriented carbon-based negative electrode active material is applied onto the negative electrode current collector without changing the degree of orientation after being discharged. In addition, the present invention may prevent the strength of the magnetic field applied to the upper lip 111, the middle lip 121, and the lower lip 131 from exceeding the above range, narrowing the distance between the lips, and making it difficult to discharge the negative electrode slurry.

[0048] In addition, the double slot die 100 may orient the crystal plane of the carbon-based negative electrode active material nearly perpendicular to the surface of the electrode sheet 300 (or negative electrode current collector) before discharging the negative electrode slurry. In addition, the double slot die 100 may control the ratio between the strength of the magnetic field applied to each lip and the coating speed of the negative electrode slurry, in other words, the speed at which the electrode sheet is moved by the coating roll 200, to satisfy a predetermined range so that the carbon-based negative electrode active material, whose crystal plane is oriented before discharging, is coated on the electrode sheet 300 (or negative electrode current collector) while maintaining the orientation state. More specifically, the double slot die 100 may satisfy the following formula 1:

[0049] [Formula 1] 50≦G / M≦250

[0050] In formula 1, G represents the strength of the magnetic field applied at the top lip, middle lip, and bottom lip (unit: G); M represents the speed at which the electrode sheet is moved by the coating roll (unit: m / min).

[0051] The orientation of the carbon-based negative active material contained in the negative electrode slurry may be affected by the strength of the applied magnetic field, the distance of the magnet to which the magnetic field is applied, the fluid momentum and / or the direction of movement of the negative electrode slurry containing the carbon-based negative active material, etc. Therefore, in the present invention, the ratio (G / M) of the strength of the magnetic field (G) applied to each lip and the speed (M) of the electrode sheet moving by the coating roll may be 50 to 250 to satisfy Equation 1, so that the crystal plane of the carbon-based negative active material of the negative electrode slurry applied to the electrode sheet may be oriented nearly perpendicular to the surface of the electrode sheet 300. More specifically, the double slot die 100 may satisfy Equation 1 at 50-100 (i.e., 50≦G / M≦100), 50-150 (i.e., 50≦G / M≦150), 100-200 (i.e., 100≦G / M≦200), 150-250 (i.e., 150≦G / M≦250), 50-90 (i.e., 50≦G / M≦90), 180-240 (i.e., 180≦G / M≦240), 150-250 (i.e., 150≦G / M≦250), or 50-130 (i.e., 50≦G / M≦130).

[0052] The first slot 151 and the second slot 152 may be positioned such 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, in the negative electrode manufacturing apparatus of the present invention, as shown in FIG. 1, a rotatably installed coating roll 200 is disposed to face the first slot 151 and the second slot 152 of the double slot die 100, and the negative electrode slurry may be applied to the surface of the electrode sheet 300 (or the negative electrode current collector) as the electrode sheet 300 (or the negative electrode current collector) moves due to the rotation of the coating roll 200.

[0053] Furthermore, the negative electrode manufacturing apparatus 10 according to the present invention may further include a drying section (not shown) that dries the negative electrode slurry applied to the electrode sheet 300, and the drying section may be disposed at a position where it can reach a dry state within 20 seconds, specifically, 0.01 seconds to 20 seconds, 0.01 seconds to 15 seconds, 0.01 seconds to 10 seconds, or 0.01 seconds to 5 seconds, from the time when the negative electrode slurry discharged from the slot die 100 is applied to the electrode sheet.

[0054] 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 in 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 crystal orientation of the carbon-based negative electrode active material applied to the surface of the electrode sheet 300 is reduced.

[0055] In addition, the drying section includes a wall (not shown) that blocks 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 from which the electrode sheet 300 coated with the negative electrode slurry is removed.

[0056] When the electrode sheet 300 coated with the negative electrode slurry enters through an inlet of the drying unit, energy such as light, heat, and the like supplied from the opposite wall is transferred thereto. 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.

[0057] The dryer can apply energy such as light, wavelength, heat, etc., and may be any dryer commonly used in the art without any particular limitations. For example, the dryer may be an ultraviolet dryer, a near-infrared dryer, a far-infrared dryer, a hot air dryer, a vacuum oven, etc., which may be used alone or in combination.

[0058] The negative electrode manufacturing apparatus according to the present invention has the above-mentioned configuration, and thus induces crystal orientation of the carbon-based negative electrode active material before the negative electrode slurry is discharged onto the negative electrode sheet, and the carbon-based negative electrode active material can be applied in a state in which it is oriented nearly perpendicular to the surface of the negative electrode current collector. As a result, the carbon-based negative electrode active material of the negative electrode manufactured has excellent orientation. In addition, since the negative electrode manufacturing apparatus does not require a separate orientation process for orienting the carbon-based negative electrode active material after the application of the negative electrode slurry, it has the advantage that additional facilities for manufacturing the negative electrode are not required and it is easily applicable to mass production processes.

[0059] <Method of manufacturing negative electrode for secondary battery>

[0060] In one embodiment, the present invention provides a method for producing a composition comprising: The method includes applying a negative electrode slurry to which a magnetic field is applied, to an electrode sheet 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, which contains a carbon-based negative electrode active material.

[0061] The 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 of the present invention, and includes a step of applying a negative electrode slurry to which a magnetic field is applied onto an electrode sheet. 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 onto an electrode sheet (i.e., a negative electrode current collector) are performed simultaneously. As a result, the manufacturing method has the advantage that it is economical since the process is simple and easy to apply to mass production since it does not require separate crystal orientation of the carbon-based negative electrode active material after application of the negative electrode slurry.

[0062] Here, the negative electrode slurry may contain a carbon-based negative electrode active material that is magnetically oriented by the negative electrode manufacturing apparatus according to the present invention as described above. Also, the magnetic orientation may be performed by forming a magnetic field perpendicular to the surface of the electrode sheet before the negative electrode slurry is discharged onto the electrode sheet.

[0063] In addition, the manufacturing method may control a distance between a slot of a slot die provided in an anode manufacturing apparatus, i.e., a lip portion including an upper lip, a middle lip, and a lower lip, and a coating roll according to an average thickness of the anode slurry to be applied to the electrode sheet while maintaining the crystal orientation of the carbon-based anode active material. Even if the carbon-based anode active material is oriented before discharging such that a specific crystal plane has a predetermined angle with respect to the surface of the electrode sheet, the angle or degree of orientation may change due to fluid movement according to the angle at which the anode slurry is applied to the surface of the electrode sheet when it is discharged.

[0064] Therefore, in the present invention, in order to minimize the fluid momentum according to the angle at which the negative electrode slurry is applied during application of the negative electrode slurry, the average thickness of the negative electrode slurry applied to the electrode sheet may be adjusted to be greater than the distance between the lip of the slot die and the coating roll of the 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 the slot die and the coating roll of the negative electrode manufacturing apparatus.

[0065] In addition, the step of applying the negative electrode slurry to the electrode sheet to which the magnetic field has been applied may be performed on the electrode sheet transported at a predetermined speed. The transport speed may be the same as the speed at which the negative electrode slurry is applied to the electrode sheet. For example, the step of applying the negative electrode slurry to the electrode sheet may be performed at a speed of 5 to 100 m / min, specifically, 5 to 35 m / min, 10 to 35 m / min, 20 to 35 m / min, 10 to 30 m / min, 5 to 20 m / min, 5 to 25 m / min, or 15 to 25 m / min.

[0066] By performing the step of applying the negative electrode slurry within the above speed range, the present invention can prevent the negative electrode slurry from being unevenly applied on the surface of the electrode sheet due to an extremely slow application speed, and can prevent a decrease in process efficiency and productivity, and can prevent a decrease in the degree of orientation due to a loss of crystal alignment of the carbon-based negative electrode active material present in the negative electrode slurry due to an excessively fast application speed.

[0067] 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, a step of drying the applied negative electrode slurry to form a negative electrode active layer.

[0068] 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 of the negative electrode slurry applied to the electrode sheet while minimizing loss of the degree of orientation of the carbon-based negative electrode active material with respect to the surface of the electrode sheet.

[0069] Specifically, the drying may be performed by applying energy such as light, wavelength, heat, etc., and may be performed by using an ultraviolet dryer, a near-infrared dryer, a far-infrared dryer, a hot air dryer, a vacuum oven, etc., alone or in combination.

[0070] Meanwhile, the carbon-based negative electrode active material contained in the negative electrode slurry may include a carbon-based negative electrode active material commonly used in lithium secondary batteries. Specifically, the carbon-based negative electrode active material refers to a material mainly composed of carbon atoms. Such a carbon-based negative electrode active material may include graphite. The graphite may include at least one of natural graphite and artificial graphite, and preferably includes natural graphite or a mixture of natural graphite and artificial graphite.

[0071] The carbon-based negative electrode active material is preferably a spherical graphite granule formed by the aggregation of a plurality of flake graphite. Examples of flake graphite include natural graphite, artificial graphite, mesophase calcined carbon (bulk mesophase) made from tar and pitch, graphitized cokes (raw coke, green coke, pitch coke, needle coke, petroleum coke, etc.), etc., and in particular, a graphite granule assembled from a plurality of highly crystalline natural graphite is preferable. In addition, one graphite granule may be formed by the aggregation of 2 to 100 flake graphite particles, preferably 3 to 20 flake graphite particles.

[0072] Such a carbon-based negative electrode active material, specifically graphite, may have a spherical particle shape, and in this case, the sphericity of the graphite particles may be 0.75 or more, for example, 0.75 to 1.0, 0.75 to 0.95, 0.8 to 0.95, or 0.90 to 0.99.

[0073] Here, the "sphericity" may refer 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 when the sphericity is 1, it means that the particle shape is spherical. The sphericity may be measured using a particle shape analyzer. The present invention realizes a shape of the carbon-based negative electrode active material close to a sphere, thereby realizing high electrical conductivity of the negative electrode active layer, thereby improving the capacity of the battery. In addition, the present invention has an advantage that the specific surface area of ​​the negative electrode active material can be increased, thereby improving the adhesive force between the negative electrode active layer and the current collector.

[0074] In addition, the carbon-based negative electrode active material has an average particle size (D 50 ), specifically, the average particle size (D 50 ) can be shown.

[0075] The average particle size of the spherical natural graphite is preferably as small as possible to maximize the degree of disorder in the direction of expansion of each particle so as to prevent the expansion of the particles due to charging with lithium ions. However, if the particle size of the natural graphite is less than 5.0 μm, a large amount of binder is required due to the increase in the number of particles per unit volume, and the sphericity and sphericity yield may be reduced. On the other hand, if the maximum particle size exceeds 10 μm, the expansion becomes so intense that repeated charging and discharging reduces the adhesion between particles and between the particles and the current collector, and the cycle characteristics may be significantly reduced.

[0076] In addition, the negative electrode slurry may further include a conductive material, a binder, a thickener, and the like, in addition to the carbon-based negative electrode active material, and these may be applied to those commonly used in the art.

[0077] 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.

[0078] For example, the negative electrode active layer may contain carbon black, carbon nanotubes, carbon fibers, etc., alone or in combination, as a conductive material.

[0079] At this time, the content of the conductive material may be 0.1 to 10 parts by weight, specifically 0.1 to 8 parts by weight, 0.1 to 5 parts by weight, 0.1 to 3 parts by weight, 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 the negative electrode resistance from increasing due to a low content of conductive material, resulting in a decrease in charge capacity. In addition, it can prevent problems such as a decrease in the content of the negative electrode active material due to an excessive amount of conductive material, resulting in a decrease in charge capacity, or a decrease in rapid charge characteristics due to an increase in the loading amount of the negative electrode active layer.

[0080] In addition, the binder is a component that aids in bonding between the negative electrode active material and the conductive material and the like and bonding to the negative electrode current collector, and may be suitably applied within a range that does not deteriorate the electrical properties of the electrode. Specifically, the binder may include any one or more of vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, and fluororubber.

[0081] 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 adhesive strength of the negative electrode active layer due to a low content of the binder, or a decrease in electrical properties of the electrode due to an excessive amount of the binder.

[0082] The method for producing a secondary battery negative electrode sheet according to the present invention has the above-mentioned configuration, and thus has the advantage that the carbon-based negative electrode active material of the negative electrode slurry applied onto the negative electrode current collector can be uniformly aligned with a high degree of orientation.

[0083] <Secondary battery negative electrode>

[0084] Furthermore, in one embodiment, the present invention provides a secondary battery negative electrode produced by the above-mentioned production method.

[0085] 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 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 manufactured 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 oxidation-reduction reaction during charging and discharging of the battery, and then drying and rolling the coating.

[0086] Here, the negative electrode active layer is formed by applying a negative electrode slurry to which a magnetic field is applied using the above-mentioned negative electrode manufacturing apparatus, and then drying the negative electrode slurry on an electrode sheet. The carbon-based negative electrode active material, which is the main component, exhibits a high crystal orientation with respect to the surface of the electrode sheet, thereby providing high energy density and charge / discharge performance.

[0087] Specifically, in the negative electrode according to the present invention, the carbon-based negative active material contained in the negative active layer may be aligned at a predetermined angle with respect to the electrode sheet (or negative current collector). Such alignment of the carbon-based negative active material may reduce the degree of disorder in the negative active layer, thereby reducing the electrode resistance and providing a path for lithium ions to move. In this case, the crystal orientation of the carbon-based negative active material (e.g., graphite) may be determined by crystal plane analysis of the carbon-based negative active material contained in the negative active layer.

[0088] As one example, the negative electrode active layer may have a carbon-based negative electrode active material aligned in a certain direction with respect to the negative electrode current collector, and may have an average degree of alignment (OI) of 0.9 or less of the carbon-based negative electrode active material, as represented by the following Formula 2, when the negative electrode active layer is measured by X-ray diffraction spectroscopy (XRD):

[0089] [Formula 2] OI=I 004 / I 110

[0090] In formula 2, I 004 represents the area of ​​the peak showing the (004) crystal plane in the X-ray diffraction spectroscopy (XRD) measurement of the negative electrode active layer, I 110 represents the area of ​​the peak indicating the (110) crystal plane when the negative electrode active layer is measured by X-ray diffraction spectroscopy (XRD).

[0091] The formula 2 above can be an index showing the degree to which the crystal structure of the spherical carbon-based negative electrode active material is aligned in a certain direction, specifically, with respect to the surface of the negative electrode current collector, when measured by X-ray diffraction. More specifically, the negative electrode active layer shows 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° for the carbon-based negative electrode active material graphite when measured by X-ray diffraction, which indicate the (002) plane, (100) plane, (101)R plane, (101)H plane, (004) plane, and (110) plane. In addition, the peak appearing at 2θ=43.4±0.2° may be due to an overlap of the peaks corresponding to the (101)R plane of the carbon-based negative electrode active material and the (111) plane of the current collector, for example, copper (Cu).

[0092] Among these, 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° representing the (110) plane and the peak at 2θ=54.7±0.2° representing the (004) plane, specifically, the area ratio obtained by integrating the intensities of the above peaks. Here, the peak at 2θ=54.7±0.2° is a peak representing the (004) plane, which is one of the crystal planes of graphite and has an inclination with respect to the negative electrode current collector, so that the closer the value of the degree of alignment (OI) is to 0, the closer the inclination with respect to the surface of the negative electrode current collector is to 90°, and the larger the value is, the closer the inclination with respect 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° to the negative electrode current collector, so that 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.

[0093] 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.

[0094] 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.

[0095] The negative electrode current collector is not particularly limited as long as it has high conductivity without inducing chemical changes in the battery. For example, copper, stainless steel, nickel, titanium, calcined carbon, etc. can be used as the negative electrode current collector, and in the case of copper or stainless steel, it can also be surface-treated with carbon, nickel, titanium, silver, etc. The average thickness of the negative electrode current collector can be suitably applied to be 1 to 500 μm, taking into consideration the conductivity and total thickness of the negative electrode to be manufactured.

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

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

[0098] Examples 1 to 5 and Comparative Examples 1 to 2. Production of secondary battery negative electrode sheet

[0099] 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.

[0100] 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 a negative electrode active material, carbon black as a 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 carboxymethyl cellulose (CMC), and 2.5 parts by weight of styrene-butadiene rubber (SBR) were mixed with water to a solid content of 50% to prepare the first negative electrode slurry.

[0101] The second negative electrode slurry was prepared in the same manner 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 6300±200 cps at 25° C.

[0102] Separately, a negative electrode manufacturing apparatus was prepared, which included a double slot die having a first slot and a second slot in which an upper block, a first spacer, a middle block, a second spacer, and a lower block were sequentially stacked and a coating roll arranged to face the slot of the slot die. In this case, in the negative electrode manufacturing apparatus, i) the type of magnetic polarity given 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 part including the upper lip, the middle lip, and the lower lip, and iii) the ratio (G / M) of the magnetic field strength (G) applied to the lip part and the moving speed (M) of the copper thin sheet (i.e., the electrode sheet) were adjusted as shown in Table 1 below.

[0103] The negative electrode slurry prepared earlier was put into the prepared negative electrode manufacturing equipment, and the negative electrode slurry was applied to the surface of a copper sheet (thickness: 8 μm) that was being transported at a speed (M) of 50 m / min. Next, hot air was continuously blown onto the applied negative electrode slurry to dry it, forming a negative electrode active layer.

[0104] [Table 1]

[0105] Experimental Example

[0106] The orientation exhibited by the carbon-based negative electrode active material of the secondary battery negative electrode produced using the negative electrode production apparatus according to the present invention was evaluated.

[0107] Specifically, X-ray diffraction spectroscopy (XRD) was performed on three arbitrary points of the negative electrode active layer of each of the negative electrodes produced in Examples 1 to 5 and Comparative Examples 1 and 2. The measurement conditions for X-ray diffraction (XRD) were as follows:

[0108] - Target: Cu (Kα-ray) graphite monochromator - Slit: Divergence slit = 1 degree, receiving slit = 0.1 mm, scattering slit = 1 degree - Measurement area: (110) plane: 76.5 degrees < 2θ < 78.5 degrees / (004) plane: 53.5 degrees < 2θ < 56.0 degrees

[0109] From the spectrum measured under the above conditions, the degree of alignment (OI) of each carbon-based negative electrode active material according to formula 2 was calculated, and the average degree of alignment (OI) of the carbon-based negative electrode active material at the three calculated points was obtained. The results are shown in Table 2.

[0110] [Formula 2] OI=I 004 / I 110

[0111] In formula 2, I 004 represents the area of ​​the peak showing the (004) crystal plane in the X-ray diffraction spectroscopy (XRD) measurement of the negative electrode active layer, I 110 represents the area of ​​the peak indicating the (110) crystal plane when the negative electrode active layer is measured by X-ray diffraction spectroscopy (XRD).

[0112] [Table 2]

[0113] As shown in Table 2, 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.

[0114] This means that when the negative electrode slurry is applied to the electrode sheet (or negative electrode current collector) at a predetermined speed after the tips of the upper block, middle block and lower block constituting the double slot die, i.e., each lip portion, are given magnetism of the same polarity when the negative electrode slurry is discharged, the crystal plane of the carbon-based negative electrode active material is oriented nearly perpendicular to the electrode sheet before the negative electrode slurry is discharged, and the carbon-based negative electrode active material is applied to the electrode sheet and maintained in this induced orientation state to form a negative electrode active layer.

[0115] From these results, the negative electrode manufacturing apparatus according to the present invention can apply the carbon-based negative electrode active material in the discharged negative electrode slurry in a state in which the carbon-based negative electrode active material is oriented at a predetermined angle relative to the surface of the negative electrode current collector, and therefore has the advantage that not only is the orientation of the carbon-based negative electrode active material of the manufactured negative electrode excellent, but it is also easily applicable to mass production processes.

[0116] Although the present invention has been described above with reference to preferred embodiments, it will be understood that a person skilled in the art or having ordinary knowledge in the art may make various modifications and changes to the present invention without departing from the spirit and technical scope of the present invention as described in the claims below.

[0117] Therefore, the technical scope of the present invention is not limited to the contents described in the Summary of the Invention of the specification, but can be defined by the claims. [Explanation of symbols]

[0118] 10: Apparatus for manufacturing anodes for secondary batteries according to the present invention 100: Double slot die 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 141: First spacer 142: Second spacer 151: 1st slot 152: 2nd slot 200: Coating roll 300: Electrode sheet A: Unoriented section B: Orientation section I: Main body II: Lip section III: Coating area MD: Magnetic field direction CM: Carbon-based negative electrode active material

Claims

1. An apparatus for manufacturing a secondary battery anode, which manufactures an electrode sheet coated with anode slurry containing a carbon-based anode active material, comprising: a double slot die including an upper block, a middle block, and a lower block, a first slot disposed between the upper block and the middle block and for discharging a first negative electrode slurry, and a second slot disposed between the middle 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 on which the negative electrode slurry is applied, the negative electrode slurry being 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 respective tips, and the upper lip, the intermediate lip and the lower lip each exhibit magnetic properties of the same polarity.

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 the negative electrode slurry is discharged.

3. The double slot die satisfies the following formula 1: [Formula 1] 50≦G / M≦250 In Formula 1, G represents the strength of the magnetic field applied at the top lip, the middle lip, and the bottom lip (unit: G); 2. The apparatus for manufacturing a negative electrode for a secondary battery according to claim 1, wherein M represents a 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 apparatus for manufacturing a negative electrode for a secondary battery further includes a drying unit for drying 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 a point in time when the negative electrode slurry discharged from the double slot die is applied to the electrode sheet.

6. The method includes applying the negative electrode slurry to which a magnetic field is applied onto an electrode sheet by using the apparatus for manufacturing a negative electrode for a secondary battery according to claim 1, The negative electrode slurry contains a carbon-based negative electrode active material.

7. The manufacturing method of the 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 greater than the separation distance between the slot of the double slot die provided in the negative electrode manufacturing apparatus for the secondary battery and the coating roll.

8. The manufacturing method of the 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. The manufacturing method of the 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 to 100 m / min.

10. The manufacturing method of the negative electrode for a secondary battery according to claim 6, further comprising a step of drying the applied negative electrode slurry to form a negative electrode active layer after the step of applying the negative electrode slurry to the electrode sheet.

11. In the negative electrode active layer, the alignment degree (O.I) of the carbon-based negative electrode active material with respect to the surface of the electrode sheet represented by the following formula 2 is 0.9 or less, [Formula 2] O.I=I ００４ / I １１０ In formula 2, I ００４ represents the area of ​​the peak indicating the (004) crystal plane when the negative electrode active layer is measured by X-ray diffraction spectroscopy (XRD), I １１０ The method for producing a negative electrode for a secondary battery according to claim 10, wherein m represents the area of ​​a peak indicating a (110) crystal plane in X-ray diffraction spectroscopy (XRD) measurement of the negative electrode active layer.

Images