Title of the invention: electrode drying method for suppressing binder floating and electrode drying system using same technical field [One] This application was filed on 2020.10.12. Claims the benefit of priority based on Korean Patent Application No. 10-2020-0130848, and all contents disclosed in the Korean patent application are incorporated as a part of this specification. [2] The present invention relates to an electrode drying method for suppressing floating of a binder by performing a constant-rate drying step in a state in which a traveling angle is formed, and an electrode drying system to which the same is applied. background [3] With the increase in technology development and demand for mobile devices, the demand for secondary batteries is also rapidly increasing. Among them, a lithium secondary battery is widely used as an energy source for various electronic products as well as various mobile devices because of its high energy density and operating voltage and excellent preservation and lifespan characteristics. [4] In addition, secondary batteries are attracting attention as an energy source for electric vehicles or hybrid electric vehicles, which have been proposed as a solution to air pollution such as gasoline vehicles and diesel vehicles using fossil fuels. In order to be applied as an energy source for electric vehicles, high-power batteries are required. [5] A secondary battery, particularly a pouch-type secondary battery, includes an electrode assembly having a structure in which a separator is interposed between a positive electrode and a negative electrode, and the positive electrode and the negative electrode. The positive electrode and the negative electrode have a structure in which a mixture layer is applied on a current collector. Specifically, the electrode slurry is applied on the current collector, and then the electrode is manufactured through a drying process. [6] 1 shows an electrode drying process according to the prior art. The electrode drying method shown in FIG. 1 illustrates a process in which the negative electrode substrate coated with the negative electrode slurry is dried while horizontally moving. Referring to FIG. 1, (a) is the state immediately after the negative electrode slurry is applied on the copper foil, which is the negative electrode current collector, (b) is the constant rate drying step, (c) is the state of the electrode after the decreasing rate drying step. will be. In (a), the negative electrode slurry includes a carbon (C) component as an active material, carbon black (CB) as a conductive material, binder components (SBR, CMC), and water (H 2 O) as a solvent. (a) Referring to the graph below, each component is dispersed in a uniform concentration according to the height of the mixture layer. (b) is a state in which the height of the mixture layer is lowered to 2/3 level as the solvent (H2O) inside is evaporated during the constant rate drying step. At the same time, the concentrations of the active material (C), the conductive material (CB), and the binder (SBR, CMC) components are arranged in a state of increasing upward. Furthermore, (c) shows that during the reduction rate drying step, the active material (C) component with high specific gravity is concentrated downward and the conductive material (CB) and binder (SBR, CMC) components with relatively low specific gravity are concentrated on the surface side. can [7] This is a phenomenon in which the binder component having a relatively low specific gravity is lifted toward the surface in the process of drying the electrode. The lifting phenomenon of the binder causes a decrease in bonding strength between the current collector and the mixture layer, and the binder concentrated near the surface reduces electrical conductivity and inhibits the movement of lithium ions. [8] [9] Therefore, there is a need for a technology capable of effectively suppressing the lifting of the binder component generated during the drying process without impairing the process efficiency. DETAILED DESCRIPTION OF THE INVENTION technical challenge [10] The present invention was devised to solve the above problems, and an object of the present invention is to provide an electrode drying method and system for effectively suppressing a lifting phenomenon of a binder component in a drying process for an electrode. means of solving the problem [11] The present invention provides a method for drying an electrode. In one example, the electrode drying method according to the present invention includes a constant-rate drying step in which the electrode substrate coated with the electrode slurry is dried while driving in a state forming an inclination angle with respect to a horizontal plane; and a falling-rate drying step in which the electrode substrate is dried while traveling horizontally. [12] In one example, in the constant constant drying step, the running angle of the electrode substrate with respect to the horizontal plane is in the range of 10 degrees to 350 degrees. [13] In one specific example, the constant-rule drying step includes n sections (n ​​is an integer greater than or equal to 2), and the driving angle of the p-th section and the driving angle of the q-th section satisfy the following condition 1. [14] [Condition 1] [15] |θp - θq| > 10(°) [16] In condition 1, [17] θp represents the driving angle of the pth section, [18] θq represents the driving angle (θq) of the qth section, [19] p and q are each different arbitrary integers between 1 and n. [20] In another example, the constant drying step includes a section in which the driving angle is increased, a section in which the driving angle is maintained, and a section in which the driving angle is decreased, based on the driving angle of the electrode substrate with respect to the horizontal plane. [21] In one example, in the constant-rate drying step and the reduced-rate drying step, each independently drying the electrode substrate is performed in any one or two or more ways of hot air drying, heating coil drying, induction heating drying and light irradiation drying. . [22] In another example, the average drying temperature (T1) of the constant rate drying step is lower than the average drying temperature (T2) of the decreasing rate drying step. [23] In one example, the electrode drying method according to the present invention includes a predrying step of heating the electrode substrate before the constant rate drying step. [24] In one example, the electrode drying method according to the present invention further comprises an electrode slurry coating step of forming an electrode substrate coated with a slurry containing an active material, a binder polymer and a solvent on at least one surface of the electrode current collector, the electrode slurry The coating step, the constant rate drying step, and the reducing rate drying step are performed continuously or sequentially. [25] In one example, the electrode is an electrode for a pouch-type secondary battery. In one specific example, the electrode is a cathode. [26] [27] In addition, the present invention provides an electrode drying system to which the electrode drying method described above is applied. In one example, the electrode drying system according to the present invention includes: a conveyor line traveling in a state in which an electrode substrate having a structure in which an electrode slurry is applied to at least one surface of an electrode current collector is mounted; and a heating unit positioned on the moving path of the conveyor line to heat the electrode sheet. The conveyor line, at a point passing through the heating unit, a constant rate drying section running with an inclination with respect to a horizontal plane; and a reduced rate drying section running horizontally. [28] In another example, the electrode drying system includes an angle adjusting unit for controlling the traveling angle of the conveyor line. Effects of the Invention [29] The electrode drying method and system according to the present invention can suppress the lifting phenomenon of the binder component during the drying process for the electrode and improve the adhesion between the electrode mixture layer and the electrode current collector. Brief description of the drawing [30] 1 shows the content and movement of components in an electrode slurry applied on a current collector while performing a conventional electrode drying method. [31] 2 is a schematic diagram illustrating a process according to an electrode drying method according to an embodiment of the present invention. [32] 3 is a schematic diagram illustrating a process according to an electrode drying method according to another embodiment of the present invention. [33] 4 is a schematic diagram illustrating changes in the shape and components of the electrode slurry during the constant-modulus drying step according to an embodiment of the present invention. Best mode for carrying out the invention [34] Hereinafter, the present invention will be described in detail. Prior to this, the terms or words used in the present specification and claims are not to be construed as being limited to their ordinary or dictionary meanings, and the inventor must properly understand the concept of the term in order to best describe his invention. It should be interpreted as meaning and concept consistent with the technical idea of ​​the present invention based on the principle that it can be defined in [35] [36] The present invention provides an electrode drying method for effectively suppressing a lifting phenomenon of a binder component during a drying process. In one embodiment, the electrode drying method according to the present invention includes a constant-rate drying step in which the electrode substrate coated with the electrode slurry is dried while driving in a state in which an inclination angle is formed with respect to a horizontal plane; and a falling-rate drying step in which the electrode substrate is dried while traveling horizontally. [37] As described above, the binder component having a relatively low specific gravity is lifted toward the surface. The lifting phenomenon of the binder causes a decrease in bonding strength between the current collector and the mixture layer, and the binder concentrated near the surface reduces electrical conductivity and inhibits the movement of lithium ions. [38] In the present invention, in the constant-modulus drying step, by imparting an inclination angle to the electrode substrate, lifting of the binder is suppressed. Specifically, in the constant rate drying step, the solvent component remains in the mixture layer, which may cause the flow of the components inside the layer. In the constant-modulus drying step, when an inclination angle is given to the electrode substrate, a phenomenon in which the movement path of the binder component toward the surface becomes longer occurs. Through this, it is possible to suppress a phenomenon in which the binder component is concentrated near the surface of the mixture layer during the drying process. [39] In one embodiment, in the constant constant drying step, the traveling angle with respect to the horizontal plane of the electrode substrate is in the range of 10 degrees to 350 degrees. When the traveling angle with respect to the electrode substrate increases, the path through which the binder component moves toward the surface becomes longer, so it is advantageous to suppress the phenomenon that the binder component flows toward the surface. However, if the traveling angle becomes too large, the electrode slurry may be separated from the current collector before drying to a certain level or the shape may be broken. Specifically, in the constant constant drying step, the traveling angle with respect to the horizontal plane of the electrode substrate is in the range of 10 degrees to 70 degrees, 30 degrees to 60 degrees, and as another example, 100 to 160 degrees and 130 to 150 degrees. In some cases, the electrode substrate may undergo a section in which it is rotated or twisted so that the top and bottom are reversed during the constant-modulus drying step. Through this, it is possible to induce the binder component that has moved toward the surface of the mixture layer to move back toward the current collector. [40] In one embodiment, the constant rate drying step includes n sections (n ​​is an integer greater than or equal to 2). For example, among the n sections, the driving angle of the p-th section and the driving angle of the q-th section satisfy condition 1 below. [41] [Condition 1] [42] |θp - θq| > 10(°) [43] In condition 1, [44] θp represents the driving angle of the pth section, [45] θq represents the driving angle (θq) of the qth section, [46] p and q are each different arbitrary integers between 1 and n. [47] Condition 1 above means that, during the constant-modulus drying step, the electrode substrate passes through two or more sections having different traveling angles. For example, it is possible to pass through a section having a relatively low driving angle (range of 10 to 30 degrees) and then passing a section having a high driving angle (range of 30 to 80 degrees). [48] In a specific embodiment, the constant drying step includes a section in which the driving angle is increased, a section in which the driving angle is maintained, and a section in which the driving angle is decreased, based on the driving angle of the electrode substrate with respect to the horizontal plane. For example, it is also possible to sequentially pass through a low driving angle section, a high driving angle section, and a low driving angle section. As another example, it is also conceivable that the low driving angle section and the high driving angle section are repeated 2 to 5 times. [49] In the present invention, the means for drying the electrode substrate is not particularly limited, and hot air drying, induction heating drying, UV irradiation drying, etc. may be applied. The hot air drying may be performed by supplying heated air, and the heating coil drying is a method of directly heating an electrode substrate through heating by a coil. Induction heating drying is to indirectly heat the electrode substrate through the induction heating method. In addition, a method of heating by irradiating light such as infrared rays or ultraviolet rays may be applied. In one embodiment, in the constant-rate drying step and the reduced-rate drying step, each independently drying the electrode substrate is performed in any one or two or more ways of hot air drying, heating coil drying, induction heating drying and light irradiation drying. do. [50] In one embodiment, the average drying temperature (T1) of the constant rate drying step may be set to be lower than the average drying temperature (T2) of the decreasing rate drying step. In the constant rate drying step, the solvent component remains in the mixture layer, and when rapid heating to a high temperature is performed, bubbles or cracks may occur. In the present invention, for example, the constant rate drying step is performed in the range of 50 to 200 degrees, and the decreasing rate drying step is performed in the range of 150 to 500 degrees, but the temperature of the constant rate drying step is controlled to be lower than the temperature of the decreasing rate drying step can do. [51] In another embodiment, the electrode drying method according to the present invention includes a predrying step of heating the electrode substrate before the constant rate drying step. This prevents the interface from spreading or surface cracks from occurring due to the difference in the coefficient of thermal expansion between the mixture layer and the current collector while the electrode substrate is rapidly heated. For example, the pre-drying step may be performed at a low temperature of 100 degrees or less or an induction heating method. By applying the induction heating method, it is possible to effectively relieve the stress of the current collector while maintaining the process efficiency. For example, the pre-drying step can be performed in the range of 50 to 100 degrees. [52] In another embodiment, the electrode drying method according to the present invention further comprises an electrode slurry coating step of forming an electrode substrate coated with a slurry containing an active material, a binder polymer and a solvent on at least one surface of the electrode current collector, , the electrode slurry coating step, the constant rate drying step and the decreasing rate drying step are performed continuously or sequentially. After the electrode slurry is applied on the current collector, the electrode substrate may be continuously dried. Through this, process efficiency can be improved, and the quality uniformity of the electrode can be improved. For example, through a conveyor line, the electrode current collector moves continuously, and after applying the electrode slurry on the current collector, a drying process including a constant rate drying step and a decreasing rate drying step is performed. [53] The electrode drying method of the present invention can be applied when manufacturing an electrode for a secondary battery. In one example, the secondary battery is a lithium secondary battery. The shape of the secondary battery is not particularly limited, and has a pouch-type or cylindrical structure, for example, the secondary battery is a cylindrical battery. In addition, the electrode is a positive electrode or a negative electrode of a secondary battery, for example, a negative electrode for a secondary battery. [54] The secondary battery may include an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode; a non-aqueous electrolyte for impregnating the electrode assembly; and a battery case containing the electrode assembly and the electrolyte. [55] In the present invention, the secondary battery includes an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode; an electrolyte for impregnating the electrode assembly; and a battery case containing the electrode assembly and the non-aqueous electrolyte. The non-aqueous electrolyte is, for example, an electrolyte containing a lithium salt. [56] The positive electrode has a structure in which positive electrode active material layers are laminated on both surfaces of 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. [57] The positive active material may be a lithium-containing oxide, and may be the same or different. As the lithium-containing oxide, a lithium-containing transition metal oxide may be used. [58] For example, the lithium-containing transition metal oxide is Li x CoO 2 (0.5 10(°) In condition 1, θp represents the driving angle of the p-th section, θq represents the driving angle θq of the q-th section, and p and q are different arbitrary integers between 1 and n, respectively. . [Claim 4] According to claim 1, wherein the constant drying step, based on the traveling angle of the electrode substrate with respect to the horizontal plane, the electrode drying method comprising a section in which the traveling angle is increased, a section in which the traveling angle is maintained, and a section in which the traveling angle is decreased. [Claim 5] The method of claim 1, wherein in the constant rate drying step and the reduced rate drying step, each independently drying the electrode substrate is any one or two or more of hot air drying, heating coil drying, induction heating drying and light irradiation drying. Electrode drying method, characterized in that. [Claim 6] The method according to claim 1, wherein the average drying temperature (T1) of the constant rate drying step is lower than the average drying temperature (T2) of the decreasing rate drying step. [Claim 7] The electrode drying method according to claim 1, further comprising a predrying step of heating the electrode substrate before the constant rate drying step. [Claim 8] The method of claim 1, further comprising an electrode slurry coating step of forming an electrode substrate in which a slurry containing an active material, a binder polymer, and a solvent is applied on at least one surface of the electrode current collector, the electrode slurry coating step, the constant rate drying step, and the lapse rate An electrode drying method in which drying steps are performed sequentially or sequentially. [Claim 9] The method of claim 1, wherein the electrode is a negative electrode. [Claim 10] Conveyor line running in the state of mounting the electrode substrate having a structure in which the electrode slurry is applied to at least one surface of the electrode current collector; And located on the moving path of the conveyor line, including a heating unit for heating the electrode sheet, the conveyor line, at a point passing through the heating unit, a constant-ratio drying section running with an inclination to the horizontal plane; And an electrode drying system comprising a drying section at a rate that runs horizontally. [Claim 11] The electrode drying system according to claim 10, further comprising an angle adjusting unit for controlling a traveling angle of the conveyor line.