Electrode manufacturing system with excellent electrode slurry coating uniformity and electrode manufacturing method using the same

Abstract

The present invention relates to an electrode manufacturing system and an electrode manufacturing method using the same. According to the present invention, as the electrode current collector undergoes the first coating and drying process of the electrode slurry passes through the heat pipe guide roller, the electrode slurry can be uniformly coated for the second time.

Description

Technical Field

[0001] This application claims priority to Korean Patent Application No. 10-2020-0138481 filed on October 23, 2020, and Korean Patent Application No. 10-2020-0142411 filed on October 29, 2020, and the contents of these Korean patent applications are incorporated herein by reference as a part of this specification.

[0002] The present invention relates to an electrode manufacturing system having excellent electrode slurry coating uniformity and an electrode manufacturing method using the same. Background Art

[0003] With the development of technology and the increasing demand for mobile devices, the demand for secondary batteries is also rapidly increasing. Among them, lithium secondary batteries are widely used as energy sources for various electronic products and various mobile devices due to their high energy density, high operating voltage, and excellent storage and life characteristics.

[0004] As the application fields of secondary batteries expand, the demand for higher-capacity secondary batteries is rapidly increasing. As a method to increase the capacity of secondary batteries, technologies to increase the loading amount of the electrode mixture layer are being studied. After the electrode slurry is coated on the current collector, the electrode for the secondary battery is prepared by drying and rolling. However, in order to increase the loading amount of the electrode mixture layer, a large amount of electrode slurry needs to be coated on the current collector. In order to increase the coating amount of the electrode slurry, a higher level of coating uniformity is required.

[0005] Figure 1 Shown is a conventional process for manufacturing electrodes. Figure 1 The diagram shows the process of discharging the electrode slurry through the electrode slurry tank mold to the electrode current collector located on the coating roller. Figure 1 In the embodiment, the electrode slurry tank mold 20 discharges the electrode slurry onto the electrode current collector 10, and the electrode current collector 10 passes through the coating roller 30 rotating in one direction (R). The electrode current collector 10 is transferred in the machine direction (MD) while passing through the coating roller 30 rotating in one direction (R). The electrode slurry tank mold 20 discharges the electrode slurry onto the electrode current collector 10 through the electrode slurry discharge unit 21 and dries the electrode slurry to form an electrode mixture layer 11, in which the electrode slurry having a specific width D is coated on the electrode current collector 10.

[0006] In order to maintain a constant thickness of the electrode mixture layer 11, the interval between the electrode slurry discharge unit 21 and the coating roller 10 should be controlled to be constant. In the past, for electrode slurry coating systems, attempts have been made to change the position or outer diameter of the coating roller 30 in consideration of the temperature of the external air. However, these attempts only considered the process of coating the electrode slurry on one surface of the electrode current collector 10.

[0007] Therefore, a technology for efficiently coating the electrode slurry on both surfaces of the electrode current collector is needed. Summary of the Invention

[0008] Technical issues

[0009] The present invention solves at least some of the above problems. For example, one aspect of the present invention provides an electrode manufacturing system capable of achieving coating uniformity when coating an electrode slurry on both surfaces of an electrode current collector and an electrode manufacturing method using the same.

[0010] Technical Solution

[0011] The present invention provides an electrode manufacturing method. In one example, the electrode manufacturing system according to the present invention includes: a first coating unit for discharging electrode slurry onto a first surface, the first surface being a surface opposite to the surface of the electrode collector contacting the first coating roller when the electrode collector passes through the first coating roller; a primary drying furnace for drying the electrode collector with the electrode slurry coated on the first surface; n heat pipe guide rollers for reducing temperature deviation in the width direction of the electrode collector passing through the primary drying furnace by heating the electrode collector; a second coating unit for discharging electrode slurry onto a second surface, the second surface being a surface opposite to the surface of the electrode collector contacting the second coating roller when the electrode collector passes through the second coating roller; and a secondary drying furnace for drying the electrode collector with the electrode slurry coated on the second surface, wherein n is an integer between 1 and 20.

[0012] In a specific example, the heat pipe guide roller is located between the outlet of the primary drying furnace and the inlet of the second coating unit on the moving path of the electrode current collector.

[0013] In a more specific example, 2 to 4 heat pipe guide rollers are located between the outlet of the primary drying furnace and the inlet of the second coating unit on the moving path of the electrode current collector.

[0014] In yet another example, in the second coating unit, a separation distance between the electrode slurry discharge portion and the surface of the second coating roller satisfies the following condition 1:

[0015] [Condition 1]

[0016] |Gap side -Gap center |<5μm

[0017] Here, Gap siderepresents a separation distance between the electrode slurry discharge portion and the surface of the second coating roller at a side portion in the transverse direction (TD) of the second coating roller,

[0018] Gap center It represents the separation distance between the electrode slurry discharge portion and the surface of the second coating roller at the center portion in the transverse direction (TD) of the second coating roller.

[0019] In a specific example, the second coating roller includes a flow path for passing a constant temperature medium.

[0020] In one example, the electrode manufacturing system according to the present invention further includes: an unwinding unit formed at the front end of the first coating unit and supplying the electrode current collector to the first coating unit; and a rewinding unit formed at the rear end of the secondary drying furnace and winding the electrode substrate coated with the electrode slurry and dried.

[0021] In a specific example, the system further includes a conveying line for continuously transferring the electrode current collector from the point in time when the electrode current collector is supplied by the unwinding unit until the electrode current collector is wound in the rewinding unit.

[0022] In one example, the system further includes a reversing roller located between the primary drying furnace and the second coating unit and reversing positions of the first surface and the second surface of the electrode current collector.

[0023] In yet another example, the system further includes a temperature sensor for detecting a surface temperature of the electrode current collector passing through the heat pipe guide roller.

[0024] In addition, the present invention provides an electrode manufacturing method using the above-mentioned system. In one example, the electrode manufacturing method according to the present invention includes: while the electrode collector is supported by a first coating roller, coating the first surface of the electrode collector with an electrode slurry for a first time; as the electrode collector with the electrode slurry coated on the first surface passes through a drying furnace, primary drying of the electrode collector is performed; as the electrode collector after the primary drying is passed through n heat pipe guide rollers, reducing the temperature deviation of the electrode collector; while the electrode collector is supported by a second coating roller, coating the second surface of the electrode collector with an electrode slurry for a second time; and as the electrode collector with the electrode slurry coated on the second surface passes through a drying furnace, secondary drying of the electrode collector is performed, wherein n is an integer between 1 and 20.

[0025] In one example, in the method, after the temperature deviation decreases, the temperature of the electrode current collector satisfies the following condition 2:

[0026] [Condition 2]

[0027] |T side -T center |<2(℃)

[0028] Here, T side represents the average temperature at the points corresponding to 10% and 90% in the width direction of the electrode current collector, T center represents the temperature at the center point in the width direction of the electrode current collector.

[0029] In one example, in the electrode manufacturing method according to the present invention, the first coating to the secondary drying are performed continuously.

[0030] In yet another example, the method further includes: inverting the first surface and the second surface of the electrode current collector after primary drying.

[0031] In one example, during the second coating of the electrode slurry, the temperature deviation between the center and side portions of the second coating roller in the transverse direction (TD) is equal to or less than 2° C. This can be performed by including a flow path through which a constant temperature medium passes in the second coating roller.

[0032] In one specific example, the electrode to be manufactured is an electrode for a pouch-type secondary battery.

[0033] Beneficial effects

[0034] According to the electrode manufacturing system and method of the present invention, even if a temperature change occurs during the drying process after the electrode slurry is first coated on one surface of the electrode collector, the electrode slurry can be uniformly coated by controlling the interval between the electrode collector and the discharge port of the electrode slurry tank mold when the electrode slurry is coated for the second time. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The diagram shows a process of discharging electrode slurry through an electrode slurry tank die onto an electrode current collector located on a coating roller in a conventional manner.

[0036] Figure 2 is a schematic diagram illustrating an electrode manufacturing system according to an embodiment of the present invention.

[0037] Figure 3 The results obtained by using a thermal imaging camera to photograph the surface temperature of the electrode current collector passing through the heat pipe guide roller are shown.

[0038] Figure 4 is a schematic diagram of an electrode manufacturing system according to another embodiment of the present invention.

[0039] Figure 5 The graph shows the results obtained by photographing the surface temperature change of the electrode current collector when it passes through three heat pipe guide rollers.

[0040] Figure 6 FIG. 1 is a schematic diagram illustrating the formation position of a heat pipe guide roller in an electrode manufacturing system according to an embodiment of the present invention.

[0041] Figure 7 This is the result obtained by photographing the surface temperature of the second coating roller.

[0042] Figure 8 The separation distance between the discharge unit of the electrode slurry tank mold and the second coating roller whose surface is unevenly heated due to incompletely cooled electrode current collector is shown.

[0043] Figure 9 is a schematic diagram illustrating a second coating roller according to one embodiment of the present invention.

[0044] Figure 10 is a schematic diagram illustrating a cross-sectional structure of a second coating roller according to one embodiment of the present invention.

[0045] Figure 11 : is a graph showing the results of measuring the loading amount of the electrode slurry discharged from the second electrode slurry tank mold based on the difference in deformation amount between the side portion and the center portion of the second coating roller. DETAILED DESCRIPTION

[0046] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. The terms and words used in this specification and claims should not be construed as limited to common or dictionary terms, and the inventor may appropriately define the concepts of the terms to best describe the invention. The terms and words should be interpreted as having meanings and concepts consistent with the technical ideas of the present invention.

[0047] The present invention provides an electrode manufacturing system. In one example, the electrode manufacturing system according to the present invention includes: a first coating unit for discharging electrode slurry onto a first surface, the first surface being the surface opposite to the surface of the electrode collector contacting the first coating roller when the electrode collector passes through the first coating roller; a primary drying furnace for drying the electrode collector coated with the electrode slurry on the first surface; n heat pipe guide rollers for heating the electrode collector to reduce temperature deviation in the width direction of the electrode collector after passing through the primary drying furnace; a second coating unit for discharging electrode slurry onto a second surface, the second surface being the surface opposite to the surface of the electrode collector contacting the second coating roller when the electrode collector passes through the second coating roller; and a secondary drying furnace for drying the electrode collector coated with the electrode slurry on the second surface, where n is an integer between 1 and 20.

[0048] The number of the heat pipe guide rollers is in the range of 1 to 15, 1 to 10, 1 to 5, 2 to 4, or 2 to 3. The temperature in the width direction of the electrode collector passing through the primary drying furnace can be uniformly adjusted, and the interval between the electrode collector and the discharge port of the electrode slurry tank mold can be controlled when the electrode slurry is coated for the second time.

[0049] In one specific example, the heat pipe guide roller is located between the exit of the primary drying furnace and the entrance of the second coating unit along the path of the electrode current collector. In the present invention, the electrode current collector, having passed through the primary drying furnace, passes through the heat pipe guide roller before reaching the second coating unit. For example, the heat pipe guide roller can be located at the exit of the primary drying furnace, at the midpoint mentioned above, and / or at a point before reaching the second coating unit, etc.

[0050] In one specific example, 2 to 4 heat pipe guide rollers are located between the outlet of the primary drying furnace and the inlet of the second coating unit on the moving path of the electrode current collector. In the present invention, one or more heat pipe guide rollers can be formed. When one heat pipe guide roller is formed, the temperature deviation in the width direction of the electrode current collector can be controlled to be equal to or less than 2°C. In addition, when two or more heat pipe guide rollers are formed, the temperature deviation in the width direction of the electrode current collector can be controlled to be equal to or less than 1°C. However, through experiments, it was found that when 5 or more heat pipe guide rollers are used, the efficiency decreases accordingly.

[0051] In one example, in the second coating unit, the separation distance between the electrode slurry discharge portion and the surface of the second coating roller satisfies the following condition 1:

[0052] [Condition 1]

[0053] |Gap side -Gap center |<5μm

[0054] Here, Gap side represents the separation distance between the electrode slurry discharge portion and the surface of the second coating roller on the side in the transverse direction (TD) of the second coating roller,

[0055] Gap center It represents the separation distance between the electrode slurry discharge portion and the surface of the second coating roller at the center portion in the transverse direction (TD) of the second coating roller.

[0056] In the present invention, the "center" of a roll refers to the center point of the roll in the width direction or transverse direction (TD). Furthermore, the "side" of a roll refers to the points corresponding to 10% and 90% of the roll's length in the width direction or transverse direction (TD). For example, the separation distance or temperature of the "side" of a roll refers to the average of the values ​​measured at the points corresponding to 10% and 90% of the roll's length in the width direction or transverse direction (TD).

[0057] When manufacturing electrodes, a process is applied to form an electrode mixture layer on each of the two surfaces of the electrode current collector. The electrode substrate, having undergone the first coating process and the primary drying process, undergoes a second coating process. When the second coating process is applied to the electrode current collector, which has not yet fully cooled after the primary drying process, heat is transferred to the coating roller. The coating roller is heated by the transferred heat, exhibiting different volume expansions in different areas.

[0058] In the present invention, by pre-controlling the temperature of the electrode current collector in the width direction before performing the second coating process, the separation distance between the electrode slurry discharge portion in the second coating unit and the surface of the second coating roller can be kept constant. The value of the above condition 1 can be less than 5μm, specifically, in the range of 0.01 to 5μm, 0.1 to 5μm, 1 to 5μm, 1.5 to 4.5μm, 2 to 4μm, or 1 to 3μm. In the present invention, when condition 1 satisfies 0μm, it means that the diameter of each area of ​​the second coating roller is the same. Considering the measurement limit, the value of 0.01μm is undoubtedly correct.

[0059] In one example, the second coating roller includes a flow path for a constant-temperature medium. In the present invention, by forming a flow path for the constant-temperature medium in the second coating roller, it is possible to achieve uniform temperature across all regions of the second coating roller while controlling the temperature within a specific range. This differs from techniques that heat or cool specific regions of the coating roller to cause deformation in that region.

[0060] In the present invention, "constant temperature medium" refers to a medium that is controlled to maintain a temperature within a specific range, and can be a gaseous or liquid medium. Specifically, the constant temperature medium is water or oil in a constant temperature state, or air or an inert gas whose temperature is controlled within a specific range. For example, the constant temperature medium can be constant temperature water.

[0061] The electrode current collector that has passed through the above-mentioned primary drying furnace has not yet completely cooled. For example, the temperature of the electrode current collector may be 300°C or higher. If the electrode current collector passes through the second coating roller while in contact with the second coating roller, the surface temperature of the second coating roller is also heated to a similar temperature range. The second coating roller heated to a high temperature shows an uneven temperature distribution in each region and shows different volume expansion rates in the center and the side. According to the present invention, by forming a flow path for the constant temperature medium to pass through in the second coating roller, it is possible to eliminate the temperature unevenness of the roller itself and maintain a temperature that minimizes the difference in volume expansion rate between the regions.

[0062] For example, assuming that the coating roller is made of aluminum or an aluminum alloy and has an outer diameter thickness of 1T, the difference in deformation between the center and side portions when the roller temperature is within the range of 26 to 27°C is greater than the difference in deformation when the roller temperature is within the range of 32 to 33°C. Therefore, the present invention not only reduces the temperature of the coating roller but also controls the temperature of the coating roller to reduce the difference in deformation between the various regions of the coating roller.

[0063] In one embodiment, the second coating roller includes: a roller rotating surface; a rotating shaft that provides driving force to the roller rotating surface; a temperature controller including a heater that heats incoming cooling water; and a constant temperature water flow path through which constant temperature water supplied from the temperature controller flows while supporting the electrode current collector. For example, the constant temperature water flow path is evenly distributed across the inner surface of the roller rotating surface. Thus, in the present invention, the outer diameter temperature of the second coating roller can be controlled to remain constant.

[0064] In a specific example, the constant temperature water flow path has a water jacket shape, wherein the inner surface of the second coating roller is evenly heated. The water jacket-shaped constant temperature water flow path can be tightly attached to the inner surface of the second coating roller. The surface temperature of the second coating roller can be controlled within the range of 31 to 33°C by the constant temperature water.

[0065] In one example, the electrode manufacturing system according to the present invention further includes: an unwinding unit, which is formed at the front end of the first coating unit and supplies the electrode current collector to the first coating unit; and a rewinding unit, which is formed at the rear end of the secondary drying furnace and winds the electrode substrate coated with the electrode slurry and dried. The electrode current collector in the form of a metal foil is supplied in a state of being wound in the unwinding unit. The supplied electrode current collector passes through the first coating unit that discharges the electrode slurry on the first surface of the electrode collector, the primary drying furnace, the second coating unit that discharges the electrode slurry on the second surface of the electrode collector, and the secondary drying furnace in sequence, and is then wound on the rewinding unit. After the electrode slurry is coated on both surfaces of the electrode collector and dried, the electrode collector passes through a slitting unit and a punching unit, etc.

[0066] In one specific example, the electrode manufacturing system according to the present invention further includes a conveyor line for continuously transferring the electrode current collector from the time the electrode current collector is supplied from the unwinding unit until the electrode current collector is wound in the rewinding unit. According to the electrode manufacturing system of the present invention, electrodes are manufactured through a continuous process, which can improve process efficiency and product uniformity. The conveyor line continuously supplies and transfers the electrode current collector, which passes through the first coating unit, the primary drying furnace, the second coating unit, and the secondary drying furnace in sequence.

[0067] In one example, the system further includes a reversing roller between the primary drying furnace and the second coating unit, which reverses the position of the first surface and the second surface of the electrode collector. For example, the electrode collector passing through the first coating unit and the primary drying furnace arrives at the second coating unit after passing through a process in which the positions of the upper and lower surfaces are reversed by the reversing roller. In this case, the electrode collector moves along the machine direction (MD), and the upper and lower positions are reversed in the transverse direction (TD). In another example, in the electrode manufacturing system according to the present invention, the first coating unit and the primary drying furnace are located at the lower end, and the second coating unit is located at the upper end. In this way, the moving direction of the electrode collector passing through the primary drying furnace changes from the first direction to the second direction, thereby passing through the second coating unit.

[0068] In one embodiment, the electrode manufacturing system according to the present invention includes a temperature sensor for detecting the surface temperature of each area of ​​the second coating roller. The temperature sensor can measure the average temperature of the second coating roller. However, the second coating roller can also be divided into multiple areas in the transverse direction (TD) and the temperature can be measured in each divided area. By dividing the second coating roller into 3 to 10 areas in the transverse direction (TD) and measuring the temperature of each area, the distance separated from the slurry discharge unit of the second coating unit can be predicted and calculated in each area.

[0069] The present invention also provides an electrode manufacturing method using the above-mentioned system. In one example, the electrode manufacturing method according to the present invention includes: while the electrode collector is supported by a first coating roller, coating the first surface of the electrode collector with electrode slurry for a first time; as the electrode collector with the electrode slurry coated on the first surface passes through a drying furnace, primary drying of the electrode collector is performed; as the electrode collector after the primary drying is passed through n heat pipe guide rollers, reducing the temperature deviation of the electrode collector; while the electrode collector is supported by a second coating roller, coating the second surface of the electrode collector with electrode slurry for a second time; as the electrode collector with the electrode slurry coated on the second surface passes through the drying furnace, secondary drying of the electrode collector is performed, wherein n is an integer between 1 and 20.

[0070] In one embodiment, in this method, after the temperature deviation decreases, the temperature of the electrode current collector satisfies the following condition 2:

[0071] [Condition 2]

[0072] |T side -T center |<2(℃)

[0073] Here, T side represents the average temperature at the points corresponding to 10% and 90% in the width direction of the electrode current collector, T center Indicates the temperature at the center point in the width direction of the electrode current collector.

[0074] Specifically, in condition 2, the deviation between the temperature of the center portion and the temperature of the side portion of the electrode current collector can be less than 2°C, specifically, it can be in the range of 0.01 to 2°C, 0.1 to 2°C, 0.2 to 2°C, 1.2 to 2°C, 0.2 to 0.9°C, or 0.3 to 0.7°C. The present invention minimizes the temperature deviation of each region in the width direction of the electrode current collector, specifically controlling the temperature deviation within a specific range. Thus, the discharge amount of the electrode slurry discharged to the electrode current collector is controlled in the second coating process.

[0075] In one example, in the electrode manufacturing method according to the present invention, the first coating to the secondary drying are performed continuously. This can be performed by a conveyor line that continuously transfers the electrode current collector, and can improve process efficiency and product uniformity.

[0076] In another example, the method may further include inverting the first and second surfaces of the electrode current collector after primary drying. The inversion operation may be performed by a reversing roller, etc., and after the electrode current collector with the electrode slurry applied to the first surface is primary dried, the electrode slurry is applied to the second surface of the electrode current collector.

[0077] In particular, in the second coating roller, the temperature deviation between the center and the side in the transverse direction (TD) of the second coating roller is equal to or less than 2°C. Specifically, in the second coating roller, the temperature deviation between the center and the side may be less than 2°C, or in the range of 0.01 to 2°C, or 0.5 to 1.5°C. The present invention minimizes the temperature deviation of each area based on the surface temperature of the second coating roller and specifically controls the temperature deviation within a specific range. Thus, the discharge amount of the electrode slurry discharged to the electrode current collector passing through the second coating roller is controlled.

[0078] In one embodiment, the second coating roller circulates a constant temperature medium through a flow path formed in the roller. The constant temperature medium is water or oil in a constant temperature state, or air or an inert gas whose temperature is controlled within a specific range. For example, the constant temperature medium can be constant temperature water.

[0079] In a specific example, the temperatures of the center and side portions of the second coating roller in the transverse direction (TD) may be in the range of 30 to 33° C., respectively. Specifically, the temperatures of the center and side portions of the second coating roller may be in the range of 31 to 33° C., respectively. In the present invention, it was found that the deformation amounts at the two points can be adjusted to be the same or at the same level.

[0080] In one specific example, the electrode to be manufactured is an electrode for a pouch-type secondary battery. Furthermore, electrode slurry is a general term for a slurry-like composition containing electrode active materials. A positive electrode or negative electrode refers to an electrode for a secondary battery, specifically a lithium secondary battery.

[0081] In one example, the electrode refers to a positive electrode and / or a negative electrode of a lithium secondary battery.

[0082] The positive electrode has a structure of a two-layer positive electrode active material layer stacked on a positive electrode current collector. In one example, the positive electrode active material layer includes a positive electrode active material, a conductive material, and a binder polymer, and if necessary, may further include a positive electrode additive commonly used in the art.

[0083] The positive electrode active material may be a lithium-containing oxide and may be the same or different. A lithium-containing transition metal oxide may be used as the lithium-containing oxide.

[0084] For example, the lithium-containing transition metal oxide may be selected from the group consisting of Li x CoO2(0.5<x<1.3), Li x NiO2(0.5<x<1.3), Li x MnO2(0.5<x<1.3), Li x Mn2O4(0.5 <x<1.3)、Li x (Ni a Co b Mn c )O2(0.5 <x<1.3,0<a<1,0<b<1,0<c<1,a+b+c=1)、Li x Ni 1-y Co y O2(0.5 <x<1.3,0<y<1)、Li x Co 1-y Mn y O2(0.5 <x<1.3,0<y<1)、Li x Ni 1-y Mn y O2(0.5 <x<1.3,0≤y<1)、Li x (Ni a Co b Mn c )O4(0.5 <x<1.3,0<a<2,0<b<2,0<c<2,a+b+c=2)、Li x Mn 2-z Ni z O4(0.5 <x<1.3,0<z<2)、Li x Mn 2-z Co zO4 (0.5 < x < 1.3, 0 < z < 2), Li x Any one or a mixture of two or more selected from the group consisting of CoPO4 (0.5 < x < 1.3) and Li x Any one or a mixture of two or more selected from the group consisting of FePO4 (0.5 < x < 1.3), and the lithium-containing transition metal oxide may be coated with a metal or a metal oxide, such as aluminum (Al). In addition, in addition to the lithium-containing transition metal oxide, at least one selected from the group consisting of sulfides, selenides, and halides may be used.

[0085] The positive electrode active material layer may contain 94.0 to 98.5% by weight of the positive electrode active material. When the content of the positive electrode active material satisfies the above range, it is advantageous in terms of manufacturing a high-capacity battery and providing sufficient positive electrode conductivity or adhesion between electrode materials.

[0086] The current collector for the positive electrode is a metal with high conductivity, and any metal that can be easily attached to the positive electrode active material slurry and does not react within the voltage range of the electrochemical device can be used. Specifically, non-limiting examples of the current collector for the positive electrode include aluminum, nickel, or foils made by combining them.

[0087] The positive electrode active material layer further includes a conductive material. Based on the total weight of the mixture including the positive electrode active material, the conductive material is usually added in an amount of 1 to 30% by weight. There is no particular limitation on such a conductive material as long as it has conductivity without causing chemical changes in the secondary battery. For example, one or more selected from the group consisting of graphite, such as natural graphite or artificial graphite; carbon black, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal carbon black; conductive fibers, such as carbon fibers or metal fibers; metal powders, such as carbon fluoride, aluminum, or nickel powders; conductive whiskers, such as zinc oxide or potassium titanate; conductive metal oxides, such as titanium oxide; and polyphenylene derivatives can be used as the conductive material.

[0088] The negative electrode has a structure in which a negative electrode active material layer with a two-layer structure is stacked on a negative electrode current collector. In one example, the negative electrode active material layer includes a negative electrode active material, a conductive material, and an adhesive polymer, and if necessary, may further include negative electrode additives commonly used in the art.

[0089] The negative electrode active material may include a carbon material, lithium metal, silicon, or tin. When using a carbon material as the negative electrode active material, both low-crystalline carbon and high-crystalline carbon can be used. Typical examples of low-crystalline carbon include soft carbon and hard carbon. Typical examples of high-crystalline carbon include one or more selected from the group consisting of natural graphite, condensated graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesophase carbon microspheres, mesophase pitch, and high-temperature calcined carbon (such as petroleum or coal tar pitch-derived coke).

[0090] Non-limiting examples of the current collector for the negative electrode include copper, gold, nickel, or foil made of a copper alloy or a combination thereof. In addition, the current collector may be used by stacking substrates made of the above materials.

[0091] In addition, the negative electrode may include a conductive material and a binder commonly used in the art.

[0092] [Detailed description of preferred embodiments]

[0093] The present invention will be described in more detail below with reference to the accompanying drawings and other figures. Since the present invention allows for various variations and numerous embodiments, specific embodiments will be shown in the drawings and described in detail in the text. However, this is not intended to limit the invention to the specific forms disclosed, and it should be understood that it encompasses all variations, equivalents, and alternatives within the spirit and scope of the invention.

[0094] (First embodiment)

[0095] Figure 2 Schematic diagram illustrating an electrode manufacturing system according to an embodiment of the present invention. Figure 2 , the electrode collector 110 is supplied from the uncoiler 151. The supplied electrode collector 110 passes through the first coating roller 131. When the electrode collector 110 passes through the first coating roller 131, the electrode slurry is discharged from the electrode slurry tank mold 121, thereby forming a first electrode mixture layer 111 on the first surface of the electrode collector 110. After the electrode collector 110 passes through the primary drying furnace 141, the first surface and the second surface of the electrode collector 110 are reversed by a reversing roller (not shown). The electrode collector 110 passes through the second coating roller 100, at which time, the electrode slurry is discharged from the second electrode slurry tank mold 122, thereby forming the second electrode mixture layer 112. After that, the electrode collector 110 passes through the secondary drying furnace 142 and is then wound on the rewinder 152.

[0096] exist Figure 2 In the process, the electrode current collector 110 that has passed through the primary drying furnace 141 passes through the second coating roller 100 in an incompletely cooled state. At this time, the surface of the second coating roller 100 is unevenly heated by the incompletely cooled electrode current collector 110. The unevenly heated regions of the second coating roller 100 cause different volume expansions, and the distances separated from the discharge unit of the electrode slurry tank mold 122 become uneven depending on the temperature.

[0097] In the present invention, the electrode current collector 110 passing through the primary drying furnace 141 passes through a heat pipe guide roller. The heat pipe guide roller 101 has a heating coil or a constant temperature water flow path inside. Thus, the heat pipe guide roller 101 controls the electrode current collector 110 to have a constant temperature across its width.

[0098] Figure 3The results obtained by photographing the surface temperature of the electrode current collector 110 passing through the heat pipe guide roller 101 using a thermal imaging camera are shown. Figure 3 , the temperature of the electrode current collector 100 that has been heated is not uniform in the width direction (transverse direction (TD)) when passing through the primary drying furnace 141. It can be seen that as the electrode current collector 110 passes through the heat pipe guide roller 101, the temperature non-uniformity problem is significantly solved.

[0099] Thus, according to the present invention, by arranging the heat pipe guide roller 101 at the outlet side of the primary drying furnace 141 , the temperature non-uniformity in the width direction of the electrode current collector 101 can be effectively solved.

[0100] (Second embodiment)

[0101] Figure 4 FIG2 is a schematic diagram illustrating an electrode manufacturing system according to another embodiment of the present invention. Figure 4 The electrode current collector 110 supplied from the uncoiler 151 passes through a first coating unit comprising a first coating roller 131 and an electrode slurry tank mold 121, a primary drying furnace 141, a second coating unit comprising a second electrode slurry tank mold 122, and a secondary drying furnace 142 before being wound onto the rewinder 152. Three heat pipe guide rollers 101, 102, and 103 are located between the primary drying furnace 141 and the second coating unit along the travel path of the electrode current collector 110. Heat pipe guide rollers 101, 102, and 103 are located at the exit, midpoint, and just before reaching the second coating unit of the primary drying furnace 141, respectively.

[0102] also, Figure 5 This diagram shows the results of using a thermal imaging camera to capture the surface temperature of the electrode current collector 110 as it passes through the three heat pipe guide rollers 101, 102, and 103. The temperature of the electrode current collector 110 heated by passing through the primary drying furnace 141 is non-uniform in the width direction (transverse direction (TD)). However, this temperature non-uniformity rapidly decreases as the electrode current collector 110 sequentially passes through the three heat pipe guide rollers 101, 102, and 103.

[0103] (Third embodiment)

[0104] In the present invention, the temperature deviation in the width direction of the electrode current collector according to the position of the heat pipe guide roller is measured. Specifically, in the electrode manufacturing system, one heat pipe guide roller is installed at one position, and Figure 6The points shown in (1) to (5) represent various positions. The surface temperature of the heat pipe guide roller is controlled at 30°C. The results are shown in Table 1. In Table 1, the side temperature is the average value of the temperature measured at the points corresponding to 10% and 90% in the width direction of the electrode collector, and the center temperature is the temperature of the center of the electrode collector based on the length in the width direction. In Examples 1 to 3, the temperature of the electrode collector is measured at a point (position (5)) before the electrode collector reaches the second coating unit.

[0105] [Table 1]

[0106]

[0107] Referring to Table 1, when using a single heat pipe guide roller, the temperature deviation between the side and center portions of the electrode current collector can be controlled to be equal to or less than 2°C. The temperature deviation may vary depending on the application position of the heat pipe guide roller, but it can be seen that the effect of reducing the temperature deviation is greater as the heat pipe guide roller is closer to the exit of the primary drying furnace.

[0108] For reference, in the comparative example, in the case where the heat pipe guide roller was not applied, the temperature deviation between the side and center portions of the electrode current collector before reaching the second coating unit (position (5)) was 2.8°C.

[0109] (Fourth embodiment)

[0110] In the present invention, the temperature deviation in the width direction of the electrode current collector according to the position of the heat pipe guide roller is measured. Specifically, in the electrode manufacturing system, 2 to 5 heat pipe guide rollers are installed, and Figure 6 The points shown in (1) to (5) represent various positions. The surface temperature of the heat pipe guide roller was controlled at 30°C. The results are shown in Table 2. In Table 2, the side temperature is the average of the temperatures measured at the points corresponding to 10% and 90% in the width direction of the electrode collector, and the center temperature is the temperature of the center of the electrode collector based on the length in the width direction. The temperature of the electrode collector was measured at a point (position (5)) before the electrode collector reached the second coating unit.

[0111] [Table 2]

[0112]

[0113] Referring to Table 2, as the number of heat pipe guide rollers increases, the temperature deviation across the width of the electrode current collector significantly decreases. Specifically, when two or more heat pipe guide rollers are used, the temperature deviation across the width of the electrode current collector is controlled to be equal to or less than 1°C. However, when five or more heat pipe guide rollers are used, the efficiency decreases.

[0114] (Fifth embodiment)

[0115] Figure 7 , which shows the results obtained by photographing the surface temperature of the second coating roller 100 using a thermal imaging camera. Figure 7 The surface of the second coating roller 100 was unevenly heated by the electrode current collector 110, which had not yet fully cooled. Specifically, it was unevenly heated by the electrode current collector, one surface of which had the electrode slurry applied to it. Specifically, the temperature of the center of the second coating roller 100 was approximately 299.24°C, and the temperatures of the two side portions were approximately 299.15°C. Similarly, the volume of the second coating roller 100, heated to a high temperature, rapidly expanded, and the distance separating it from the discharge unit of the electrode slurry tank mold may become uneven depending on the temperature.

[0116] Figure 8 Schematic illustration of the separation distance between the discharge unit of the electrode slurry tank mold and the second coating roller whose surface is unevenly heated due to incomplete cooling of the electrode current collector (omitted). Figure 8 The second coating roller 100 includes a roller surface that rotates around a roller rotation axis. The second coating roller exhibits different expansion rates in different regions according to changes in surface temperature. Figure 8 As shown, the diameter of the center portion of the second coating roller 100 becomes larger than the diameter of the side portion of the second coating roller 100. The uneven expansion of the second coating roller 100 results in an uneven separation distance between the second coating roller 100 and the discharge unit of the electrode slurry tank mold 122.

[0117] In this regard, according to the present invention, by forming a flow path for the constant temperature medium to flow through the second coating roller 100, it is possible to maintain a uniform temperature throughout the entire area of ​​the second coating roller 100. Thus, the separation distance between the second coating roller 100 and the discharge unit of the electrode slurry tank mold 122 can be kept constant.

[0118] (Sixth embodiment)

[0119] Figure 9 Schematic diagram showing a second coating roller according to one embodiment of the present invention. Figure 9 The second coating roller 200 is fixed to the drive motor 210 and rotates, and has a structure in which a flow path for constant temperature water is formed. The temperature of the constant temperature water is kept constant at approximately 32°C by a temperature controller 220 including a heater 221. The constant temperature water heated in the temperature controller 220 flows into the second coating roller 220 through the constant temperature water inflow path 201. The inflowing constant temperature water circulates inside the second coating roller 200 and is then discharged through the constant temperature water outflow path 202. In addition, the temperature controller 220 heats the cooling water flowing in through the cooling water inflow path 231, and the used cooling water is discharged through the cooling water outflow path 232.

[0120] (Seventh embodiment)

[0121] Figure 10 Schematic diagram showing the cross-sectional structure of a second coating roller according to one embodiment of the present invention. Second coating roller 300 includes a roller surface 310 that rotates about a roller rotation axis 320 and has a water jacket 301 tightly attached to the inner surface of roller surface 310. Constant temperature water flows through the interior of water jacket 301 and maintains a constant temperature on roller surface 310.

[0122] (Eighth embodiment)

[0123] The volume expansion level of each area of ​​the second coating roller according to temperature was calculated. Specifically, a constant temperature water jacket was formed inside the second coating roller, and the surface temperature of the second coating roller was measured according to the temperature of the constant temperature water. In addition, the displacement caused by the volume expansion of each point of the second coating roller according to temperature was measured. The results are shown in Table 3. A roller with a length of 1200 mm in the transverse direction (TD) was used as the second coating roller, and the center of the second coating roller represented the midpoint of the second coating roller in the transverse direction (TD). In addition, the side of the second coating roller represented the average value of two points 480 mm from the midpoint in the transverse direction (TD) of the second coating roller.

[0124] [Table 3]

[0125]

[0126] Referring to Table 3, when the temperature of the side and center of the second coating roller was 26°C, the difference in deformation between the two points was 2 μm. In addition, when the temperature of the side and center of the second coating roller was 34°C, the difference in deformation between the two points was 2 μm.

[0127] In this regard, if the temperatures of the side and center portions of the second coating roller are controlled within a range of 30 to 33°C, particularly within a range of 31 to 33°C, the difference in deformation amount between the two points is controlled to be equal to or less than 1 μm. In particular, when the temperature of the side portion of the second coating roller is 32°C and the temperature of the center portion of the second coating roller is 33°C, the deformation amounts at the two points are the same.

[0128] This shows that the amount of deformation at each point does not decrease even when the temperature of the second coating roller is maintained at room temperature or when the temperature of the second coating roller is controlled to a high temperature.

[0129] In addition, in the present invention, the amount of electrode slurry discharged from the electrode slurry tank mold is measured based on the difference in deformation between the side and center of the second coating roller. Specifically, the amount of electrode slurry loaded onto the electrode current collector on the second coating roller is measured in the transverse direction (TD). The measurement results are shown in FIG. Figure 11 .

[0130] refer to Figure 11The amount of electrode slurry loaded varies in the width direction on both sides of the center (position 0 mm) of the transverse direction (TD) of the second coating roller. Specifically, when the difference in deformation between the side and center of the second coating roller is 0 or 2 μm, the difference in loading between the side and center of the second coating roller exceeds 5 mg / 25 cm. 2 In this regard, when the difference in deformation amount between the side portion and the center portion of the second coating roller is 4 μm, the difference in loading amount between the side portion and the center portion is about 7 mg / 25 cm 2 In addition, when the difference in deformation between the side and center portions of the second coating roller was 8, 12, or 16 μm, the difference in loading between the side and center portions was approximately 15 mg / 25 cm 2 or higher.

[0131] In the present invention, the temperature of the side and center portions of the second coating roller is controlled within the range of 31 to 33°C, and the temperature difference between the two points is equal to or less than 2°C. As a result, the difference in the amount of electrode slurry loaded in the width direction can be controlled to be equal to or less than 5 mg / 25 cm. 2 .

[0132] The present invention has been described in more detail above with reference to the accompanying drawings and examples. Therefore, the embodiments described in this specification and the configurations depicted in the accompanying drawings are merely preferred embodiments of the present invention and do not represent the entire technical concept of the present invention. It should be understood that various equivalents and variations may be substituted for these embodiments at the time of filing this application.

[0133] [Explanation of Reference Numerals]

[0134] 10, 110: electrode current collector

[0135] 11: Electrode mixture layer

[0136] 20: Electrode slurry tank mold

[0137] 21: Electrode slurry discharge unit

[0138] 30: coating roller

[0139] 100, 200, 300: Second coating roller

[0140] 101, 102, 103: Heat pipe guide rollers

[0141] 111: First electrode mixture layer

[0142] 112: Second electrode mixture layer

[0143] 121: First electrode slurry tank mold

[0144] 122: Second electrode slurry tank mold

[0145] 131: First coating roller

[0146] 141: Primary drying furnace

[0147] 142: Secondary drying furnace

[0148] 151: Uncoiler

[0149] 152: Rewinding Machine

[0150] 201: Constant temperature water inflow path

[0151] 202: Constant temperature water outflow path

[0152] 210: Drive motor

[0153] 220: Temperature controller

[0154] 221: Heater

[0155] 231: Cooling water inflow path

[0156] 232: Cooling water outflow path

[0157] 301: Water Jacket

[0158] 310: Roller surface

[0159] 320: Roller rotation axis

[0160] (1), (2), (3), (4), (5): Positions of heat pipe guide rollers

Claims

1. An electrode manufacturing system comprising: a first coating unit for discharging the electrode slurry onto a first surface, the first surface being a surface opposite to a surface of the electrode current collector in contact with the first coating roller when the electrode current collector passes through the first coating roller; a primary drying furnace, for drying the electrode current collector with the electrode slurry coated on the first surface; n heat pipe guide rollers, for reducing a temperature deviation in a width direction of the electrode current collector passing through the primary drying furnace by heating the electrode current collector, wherein n is an integer between 1 and 20; a second coating unit for discharging the electrode slurry onto a second surface, the second surface being a surface opposite to a surface of the electrode current collector in contact with the second coating roller when the electrode current collector passes through the second coating roller; and a secondary drying furnace for drying the electrode current collector with the electrode slurry coated on the second surface; Wherein, the second coating roller includes a flow path for a constant temperature medium to pass through, Wherein, in the second coating unit, the separation distance between the electrode slurry discharge portion and the surface of the second coating roller satisfies the following condition 1: [Condition 1] |Gap side -Gap center |<5μm Among them, Gap side represents a separation distance between the electrode slurry discharge portion and the surface of the second coating roller at a side portion in the transverse direction (TD) of the second coating roller, Among them, Gap center It represents the separation distance between the electrode slurry discharge portion and the surface of the second coating roller at the center portion in the transverse direction (TD) of the second coating roller. 2 . The system according to claim 1 , wherein the heat pipe guide roller is located between an outlet of the primary drying furnace and an inlet of the second coating unit on a moving path of the electrode current collector. 3 . The system according to claim 1 , wherein 2 to 4 heat pipe guide rollers are located between the outlet of the primary drying furnace and the inlet of the second coating unit on the moving path of the electrode current collector.

4. The system according to claim 1, further comprising: an unwinding unit formed at a front end of the first coating unit and supplying the electrode current collector to the first coating unit; and A rewinding unit is formed at the rear end of the secondary drying furnace and winds up the electrode substrate coated with the electrode slurry and dried. 5 . The system according to claim 4 , further comprising a conveying line for continuously transferring the electrode current collector from a point in time when the electrode current collector is supplied by the unwinding unit until the electrode current collector is wound in the rewinding unit. 6 . The system according to claim 1 , further comprising a reversing roller located between the primary drying furnace and the second coating unit and reversing positions of the first and second surfaces of the electrode current collector. 7 . The system according to claim 1 , further comprising a temperature sensor for detecting a surface temperature of the electrode current collector passing through the heat pipe guide roller.

8. A method for manufacturing an electrode, comprising: In a state where the electrode current collector is supported by the first coating roller, coating the electrode slurry on the first surface of the electrode current collector for the first time; As the electrode current collector with the electrode slurry coated on the first surface passes through a drying furnace, the electrode current collector is preliminarily dried; As the primary drying of the electrode current collector is completed, the electrode current collector passes through n heat pipe guide rollers to reduce the temperature deviation of the electrode current collector, wherein n is an integer between 1 and 20; coating the electrode slurry on the second surface of the electrode collector for a second time while the electrode collector is supported by the second coating roller; and As the electrode current collector with the electrode slurry coated on the second surface passes through a drying furnace, the electrode current collector is subjected to secondary drying. During the second coating of the electrode slurry, a constant temperature medium passes through a flow path included in the second coating roller. When the electrode slurry is coated for the second time, the separation distance between the electrode slurry discharge portion and the surface of the second coating roller satisfies the following condition 1: [Condition 1] |Gap side -Gap center |<5μm Among them, Gap side represents a separation distance between the electrode slurry discharge portion and the surface of the second coating roller at a side portion in the transverse direction (TD) of the second coating roller, Among them, Gap center It represents the separation distance between the electrode slurry discharge portion and the surface of the second coating roller at the center portion in the transverse direction (TD) of the second coating roller.

9. The method according to claim 8, wherein after the temperature deviation decreases, the temperature of the electrode current collector satisfies the following condition 2: [Condition 2] |T side -T center |<2(℃) Where T side represents the average value of the temperature at the points corresponding to 10% and 90% in the width direction of the electrode current collector, Where T center represents the temperature at the center point in the width direction of the electrode current collector.

10. The method according to claim 8, wherein the first coating to the secondary drying are performed continuously. 11 . The method according to claim 8 , further comprising inverting the first surface and the second surface of the electrode current collector after primary drying is completed. 12 . The method of claim 8 , wherein during the second coating of the electrode slurry, a temperature deviation between a center portion and a side portion of the second coating roller in a transverse direction (TD) is equal to or less than 2° C. 13 . The method according to claim 8 , wherein the electrode to be manufactured is an electrode for a pouch-type secondary battery.

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