Electrode drying system and electrode drying method

Abstract

The present application provides an electrode drying system and method that determine the position of a first drying zone to which an electrode to be dried, which is in a constant rate zone state, moves based on the electrode surface temperature, and can automatically adjust the number of first drying zones and perform heat compensation for drying zones surrounding the first drying zone to match the desired adhesive strength and drying rate of the electrode to be dried.

Description

[Technical Field]

[0001] The present invention relates to an electrode drying system and an electrode drying method.

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0146755, filed October 30, 2023, and all contents disclosed in the documents of this Korean patent application are incorporated herein by reference. [Background technology]

[0003] With the technological development and increasing demand for mobile devices, there has been a surge in demand for rechargeable, compact, and high-capacity secondary batteries. Among secondary batteries, lithium secondary batteries, which have high energy density and voltage, have been commercialized and are widely used.

[0004] A lithium secondary battery is constructed by impregnating an electrolyte containing lithium salt in an electrode assembly, which consists of a positive electrode and a negative electrode, each of which has an active material coated on a current collector and a porous separator between them. The electrode is manufactured by coating a current collector with a slurry, in which the active material, binder, and conductive material are dispersed in a solvent, followed by drying and pressing.

[0005] Generally, the adhesive strength between the current collector and the slurry is determined during the drying process, and the adhesive strength is a key quality factor for preventing heat wrinkles of the electrode.

[0006] The drying step is carried out by passing the electrode to be dried sequentially through a plurality of drying zones arranged along one direction.

[0007] To increase the adhesive strength, it is necessary to design a long constant-rate period in which the surface temperature of the electrode is maintained constant, and minimize migration of the binder during the drying process.

[0008] Specifically, among the multiple drying zones, the drying zone in which the surface temperature of the electrode is maintained constant is identified as the constant rate zone, and the drying temperature of that drying zone is lowered to design the constant rate zone to be longer.

[0009] Currently, the only way to determine the drying area that falls within the constant rate section is for the user to visually check whether the electrode surface changes from glossy to matte during drying. However, this method has the drawbacks of being cumbersome as the user must visually check every time, and of lowering accuracy as the result value varies from user to user. Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention aims to provide an electrode drying system and method that, unlike conventional drying methods that visually determine the constant rate zone, determines the position of the first drying zone to which the electrode to be dried, which is in a constant rate zone state, moves based on the electrode surface temperature, and can automatically adjust the number of first drying zones and compensate for the heat quantity in drying zones surrounding the first drying zone according to the desired adhesive strength and drying rate of the electrode to be dried. [Means for solving the problem]

[0011] In order to solve the above problem, according to one embodiment of the present invention, there is provided an electrode drying system including: a plurality of drying zones arranged along one direction, each including a drying space in which electrodes to be dried are dried and a heat supply unit configured to provide a predetermined amount of heat to the drying space; a moving unit that moves the electrodes to be dried so that they pass through the plurality of drying zones sequentially to be dried; a plurality of temperature sensors that are provided in each of the plurality of drying zones and measure the surface temperature of the electrodes to be dried in each drying zone; a determining unit that determines, based on the surface temperatures of the electrodes to be dried measured by the plurality of temperature sensors, a plurality of first drying zones among the plurality of drying zones to which the electrodes to be dried move in a constant modulus state (T state) in which the change in surface temperature is maintained below a predetermined value; and a first adjusting unit that is configured to adjust the amount of heat supplied from the heat supply unit in each first drying zone to increase or decrease the number of first drying zones determined by the determining unit.

[0012] Furthermore, the determination unit can determine, as the first dry area, at least one dry area located behind a second dry area in which the electrode surface temperature is the highest, among the plurality of dry areas.

[0013] The difference (T2-T1) between the electrode surface temperature (T2) in the second drying area and the electrode surface temperature (T1) in the first drying area may be 5°C or less.

[0014] In addition, the first adjustment unit can adjust the heat supply amount of each first drying area to a first heat supply amount (A) that is lower than a preset heat supply amount in order to increase the number of first drying areas determined by the determination unit.

[0015] The electrode drying system may also include a second adjustment unit that adjusts the heat supply amount of at least one or more third drying zones located in front of the first drying zone and the heat supply amount of at least one or more fourth drying zones located behind the first drying zone to be higher than a predetermined heat supply amount, based on the first heat supply amount (A).

[0016] In addition, the second adjusting unit can adjust the heat supply amount of the third drying area to a second heat supply amount (B) that is 25% to 50% higher than the first heat supply amount than the preset heat supply amount, and can adjust the heat supply amount of the fourth drying area to a third heat supply amount (C) that is 25% to 50% higher than the first heat supply amount (A) than the preset heat supply amount.

[0017] In addition, the second adjustment unit can adjust the heat supply amount of the third drying zone and the heat supply amount of the fourth drying zone to be higher than the predetermined heat supply amount, based on the difference between the drying rate (D1) of the electrode to be dried that has passed through multiple drying zones sequentially and completed drying and a predetermined target drying rate (D0).

[0018] In addition, the second adjustment unit can adjust the heat supply amount of the third drying area and the heat supply amount of the fourth drying area to be higher than the preset heat supply amount until the difference between the dryness rate (D1) of the electrode to be dried and the preset target dryness rate (D0) is adjusted to be within the allowable error range.

[0019] The electrode to be dried may be a current collector and a negative electrode including a negative electrode slurry layer provided on the current collector.

[0020] According to another embodiment of the present application, there is provided an electrode drying method using the electrode drying system, comprising: a determination step of determining, among a plurality of drying areas, a plurality of first drying areas in which the electrode to be dried moves to a constant rate state (T state) in which the change in surface temperature is maintained below a predetermined value; and a first adjustment step of adjusting the amount of heat supplied from the heat supply unit in each first drying area in order to increase or decrease the number of first drying areas determined in the determination step.

[0021] In addition, in the method, the determination step can determine that at least one or more drying areas among the multiple drying areas (100) that are located behind the second drying area in which the electrode surface temperature is highest is the first drying area.

[0022] In the method, the difference (T2-T1) between the electrode surface temperature (T2) in the second drying zone and the electrode surface temperature (T1) in the first drying zone may be 5°C or less.

[0023] In addition, in the above method, the first adjustment step can adjust the heat supply amount of each first drying area to a first heat supply amount (A) lower than a predetermined heat supply amount in order to increase the number of first drying areas determined in the determination step.

[0024] The method may further include a second adjustment step of adjusting the heat supply amount of at least one or more third drying zones located in front of the first drying zone and the heat supply amount (C) of at least one or more fourth drying zones located behind the first drying zone to be higher than the predetermined heat supply amount, based on the first heat supply amount (A). [Effects of the Invention]

[0025] The electrode drying system of the present application determines the position of the first drying zone to which the electrode to be dried, which is in a constant rate zone state, moves based on the electrode surface temperature, and automatically adjusts the number of first drying zones and performs heat compensation for drying zones surrounding the first drying zone according to the desired adhesive strength and drying rate of the electrode to be dried, thereby offering the advantages of excellent electrode drying quality, efficiency of the drying process, and productivity of the drying process. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 is a block diagram of an electrode drying system according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0027] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An electrode drying system according to an embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

[0028] Furthermore, regardless of the drawing symbols, identical or corresponding components will be given the same or similar reference numbers, and duplicate descriptions thereof will be omitted, and the size and shape of each component shown in the drawings may be exaggerated or reduced for the sake of convenience.

[0029] FIG. 1 is a block diagram of an electrode drying system (1) according to an embodiment of the present invention.

[0030] Referring to FIG. 1, the electrode drying system (1) includes a plurality of drying sections (100), a moving section (200), a plurality of temperature sensors (300), a determining section (400), and a first adjusting section (500).

[0031] The plurality of drying zones (100) are arranged along one direction and each include a drying space (110) in which the electrode (10) to be dried is dried, and a heat supply unit (120) provided to provide a predetermined amount of heat to the drying space (110). The one direction may be the moving direction of the moving unit (200).

[0032] In this specification, "one direction" refers to the travel direction (M) or the path of movement of the moving part (200) in which the target electrode (10) passes through multiple dry zones (100).

[0033] The plurality of drying zones (100) may include chambers (or drying rooms) configured to pass through the electrodes to be dried and providing a drying space (110). The chambers may further include an air intake fan that generates an air intake from the outside, an exhaust fan that generates an exhaust flow from inside the chamber, and a circulation fan that generates a circulation flow inside the chamber. The chambers may be arranged at predetermined intervals along one direction on the moving path (M) of the moving unit (200).

[0034] The number of the drying zones (100) may be, for example, 10 or more, 20 or more, 30 or more, and preferably 10.

[0035] The moving unit (200) moves the electrode (10) to be dried so that it passes through a plurality of drying zones (100) sequentially and is dried. The moving unit (200) can move the electrode (10) to be dried in one direction (M). The moving unit (200) can intermittently stop moving so that the electrode to be dried stays in the plurality of drying zones (100) for a certain period of time, or the electrode to be dried can move through the drying zones at a slow speed. As an example, the moving unit (200) can be configured in a roll-to-roll manner, including a plurality of transfer rolls, in which the plurality of transfer rolls continuously transfer the electrode (10) to be dried.

[0036] The electrode to be dried (10) may be a current collector (or electrode sheet) coated with a slurry in which an active material, a binder, and a conductive material are dispersed in a solvent, and the application may be performed by coating or rolling. If the electrode to be dried is a positive electrode, the electrode may be a positive electrode current collector (positive electrode sheet) coated with or rolled with a positive electrode slurry, and if the electrode to be dried is a negative electrode, the electrode may be a negative electrode current collector (negative electrode sheet) coated with or rolled with a negative electrode slurry. The positive electrode and negative electrode slurries may each be active material, a binder, and a conductive material dispersed in a solvent.

[0037] The drying rate of the electrode to be dried (10) may increase as it passes through multiple drying zones. For example, if the electrode to be dried exhibits a drying rate of 1% or less when moving through the first drying zone, it may exhibit a drying rate of 1% or more when moving through the second drying zone located after the first drying zone.

[0038] The plurality of temperature sensors 300 are installed in the plurality of drying zones 100, respectively, and can measure the surface temperature of the electrodes 10 to be dried in each drying zone. The plurality of temperature sensors 300 can measure the surface temperature of the electrodes 10 moving through the drying zones in real time. For example, the temperature sensors may be infrared thermometers, but are not limited thereto, and various known devices capable of measuring the surface temperature of electrodes may be used.

[0039] The determination unit (400) determines a plurality of first drying zones (101) among the plurality of drying zones (100) in which the drying target electrode (10) moves to a constant rate state (T state) where the change in surface temperature is maintained below a predetermined value, based on the surface temperatures of the drying target electrode (10) measured by the plurality of temperature sensors (300). For example, the drying target electrode in the constant rate state may be a drying zone in which the temperature change is 0.1°C or less, 0.5°C or less, or 1°C or less.

[0040] In the past, it was necessary to visually inspect the constant rate state of the electrode to be dried each time, but the present invention can improve the accuracy of determining the constant rate section by determining the drying area through which the electrode to be dried in a constant rate state moves based on the surface temperature of the electrode.

[0041] Specifically, the electrode drying process may be comprised of a preheating section (a section in which the temperature increases while the moisture content decreases slightly), a constant rate section (a section in which the moisture content decreases significantly while the temperature remains constant), and a falling rate section (a section in which the moisture content decreases slightly while the temperature increases).

[0042] In the section where the water content decreases significantly, the binder migrates to the surface of the electrode coating layer (slurry layer), causing binder migration in the constant rate section.

[0043] In this case, as the constant rate drying time increases, the binder migration speed decreases, and as the constant rate drying speed increases, the binder migration speed increases. In other words, if the preheating period in electrode drying is shortened, the constant rate drying time increases relatively, which may result in a decrease in binder migration.

[0044] The number of first drying zones (101) determined by the determining unit (400) may be at least two, three, or four or more. The length of the constant rate interval can be determined depending on the number of first drying zones (101). For example, if the number of first drying zones (101) increases, the constant rate interval may become longer, and if the number of first drying zones (101) decreases, the constant rate interval may become shorter.

[0045] The electrode (10) to be dried passing through the multiple drying zones in sequence may reach a preheating zone, a constant rate zone, and a falling rate zone in sequence. For example, the first drying zone (101) may be preceded by at least one drying zone equivalent to the preheating zone, and the first drying zone (101) may be followed by at least one drying zone equivalent to the falling rate zone.

[0046] The first adjusting unit (500) adjusts the amount of heat supplied from the heat supply unit (120) in each first drying zone (101) to increase or decrease the number of first drying zones (101) determined by the determining unit (400). The first adjusting unit (500) can adjust the adhesive strength of the electrodes to be dried by increasing or decreasing the number of first drying zones (101). For example, as the number of first drying zones (101) increases, the constant rate interval becomes longer and the adhesive strength of the electrodes to be dried is adjusted to be higher, and as the number of first drying zones (101) decreases, the constant rate interval becomes shorter and the adhesive strength of the electrodes to be dried is adjusted to be lower.

[0047] In the present invention, the adhesive strength of the electrode to be dried means the adhesive strength between the current collector in the electrode to be dried and the slurry.

[0048] Unlike the conventional manual method of visually determining the surface temperature of the electrode to be dried, the electrode drying system of the present invention automatically determines the first drying zone (101) based on the surface temperature of the electrode to be dried and adjusts the number of first drying zones (101) using an algorithm.

[0049] In one example, the determination unit (400) can determine that at least one drying area located behind a second drying area (102) having the highest electrode surface temperature among the multiple drying areas (100) is the first drying area (101).

[0050] In the present invention, the "front" and "rear" of the first drying zone (101) may represent relative positions based on the entrance (S) of the electrode to be dried. For example, when comparing the positions of two drying zones, the drying zone closer to the entrance (S) of the electrode to be dried can be represented as being relatively "front" (also referred to as the "upstream" side), and the drying zone farther from the entrance (S) of the electrode to be dried can be represented as being relatively "rear" (also referred to as the "downstream" side).

[0051] In one embodiment, the difference (T2-T1) between the electrode surface temperature (T2) of the second drying zone (102) and the electrode surface temperature (T1) of the first drying zone (101) may be 5°C or less. For example, the determination unit (400) may determine a drying zone having a difference of 5°C or less from the electrode surface temperature of the second drying zone (102) as the first drying zone (101). If there are 10 drying zones, the second drying zone (102) may be the third or fourth drying zone.

[0052] More specifically, when the electrode surface temperature of the second drying area (102) is 59°C, the determination unit (400) can determine that the drying area located behind (downstream of) the second drying area (102) and having an electrode surface temperature of 54°C or higher is the first drying area (101).

[0053] The electrode surface temperature (T2) of the second drying zone (102) refers to the electrode surface temperature of the electrode to be dried while it is staying or moving within the second drying zone (102), and can be measured by a sensor (300) installed in the second drying zone (102). Similarly, the electrode surface temperature (T1) of the first drying zone refers to the electrode surface temperature of the electrode to be dried while it is staying or moving within the first drying zone (101), and can be measured by a temperature sensor (300) installed in the first drying zone (101). For convenience, in the present invention, the temperature sensors installed in different drying zones will be denoted by the same reference numeral "300."

[0054] The first adjusting unit (500) can adjust the heat supply amount of each first drying zone (101) to a first heat supply amount (A) lower than the preset heat supply amount in order to increase the number of first drying zones (101) determined by the determining unit (400). Conversely, the first adjusting unit (500) can adjust the heat supply amount of each first drying zone (101) to a first heat supply amount (A) higher than the preset heat supply amount in order to decrease the number of first drying zones (101) determined by the determining unit (400). The first adjusting unit (500) can adjust the heat supply amount of each first drying zone (101) higher or lower than the preset heat supply amount to provide a drying target electrode having a desired adhesive strength.

[0055] On the other hand, when the heat supply amount of the first drying area (101) is adjusted to a first heat supply amount (A) lower than the preset heat supply amount, the electrode to be dried can exhibit a lower drying rate than when the heat supply amount is the preset amount.

[0056] In other words, the higher the adhesive strength of the electrode to be dried, the lower the drying rate may become. This lowered drying rate can be improved by heat compensation, which increases the amount of heat supplied to the drying areas around the first drying area (101).

[0057] The electrode drying system according to the present application may include a second adjusting unit (600) that adjusts the heat supply amount of at least one third drying zone (103) located in front of (upstream of) the first drying zone (101) and the heat supply amount of at least one fourth drying zone (104) located behind the first drying zone (101) to be higher than a preset heat supply amount, based on the first heat supply amount (A). The second adjusting unit (600) can adjust the heat supply amount of at least one third drying zone (103) located in front of the first drying zone (101) and the heat supply amount of at least one fourth drying zone (104) located behind the first drying zone (101) to be higher than a preset heat supply amount, in order to compensate for the first heat supply amount (A).

[0058] The electrodes to be dried in the third drying zone (103) may be in a preheating zone, and the electrodes to be dried in the fourth drying zone (104) may be in a decreasing rate zone. The length of the preheating zone may be determined depending on the number of third drying zones (103), and the length of the decreasing rate zone may be determined depending on the number of fourth drying zones (104). For example, the length of the preheating zone may increase as the number of third drying zones (103) increases, and the length of the decreasing rate zone may increase as the number of fourth drying zones (104) increases. In addition, the second drying zone (102) is located in front of the first drying zone (101), and therefore may be included in the third drying zone (103).

[0059] In one embodiment, the second adjusting unit (600) adjusts the heat supply amount of the third drying area (103) to a second heat supply amount (B) that is 25% to 50% higher than the first heat supply amount (A) than the preset heat supply amount, and adjusts the heat supply amount of the fourth drying area (104) to a third heat supply amount (C) that is 25% to 50% higher than the first heat supply amount (A) than the preset heat supply amount.

[0060] For example, if the first heat supply amount (A) is lower than the preset heat supply amount by "x", the second heat supply amount (B) and the third heat supply amount (C) can be adjusted to be 0.25 to 0.5x higher than the preset heat supply amount, respectively.

[0061] The second heat supply amount (B) of the third drying zone (103) and the third heat supply amount (C) of the fourth drying zone (104) may be higher than the preset heat supply amount by 25%, 30%, 35%, 40%, 45% or 50% of the first heat supply amount (A).

[0062] The heat supplying unit (120) may include an infrared heater (121) for supplying radiant heat to the drying space (110) and a hot air blower (122) for supplying convection heat to the drying space (110).

[0063] The infrared heater 121 may be a mid-infrared heater 121 or a near-infrared heater 121. Here, the mid-infrared heater 121 is a heater that radiates mid-infrared rays with a wavelength of about 2 to 5 μm, and the near-infrared heater 121 is a heater that radiates near-infrared rays with a wavelength of about 0.7 to 1.5 μm.

[0064] The first adjusting unit (500) can increase the number of first drying zones (101) by reducing the amount of heat supplied by the radiant heat of the infrared heaters (121) and the convective heat of the hot air blowers (122), and can provide heat compensation by increasing the amount of heat supplied by the radiant heat of the infrared heaters (121) and the convective heat of the hot air blowers (122) of other drying zones located before and after the first drying zone (101).

[0065] In the present invention, the amount of heat supply may include the amount of radiant heat supplied by the infrared heater 121 and the amount of convective heat supplied by the hot air blower 122. The amount of radiant heat supplied is determined by the temperature (°C) of the infrared heater 121, and the amount of convective heat supplied by the hot air blower is determined by the fan speed (rpm).

[0066] For example, the first adjusting unit (500) can adjust the temperature of the infrared heater (121) lower than a preset temperature and the fan speed (rpm) of the hot air blower (122) lower than a preset speed, thereby reducing the amount of heat supplied to the first drying zone (101). Also, the second adjusting unit (600) can adjust the temperature of the infrared heater (121) higher than a preset temperature and the fan speed (rpm) of the hot air blower (122) higher than a preset speed, thereby increasing the amount of heat supplied to the third drying zone (103) and the fourth drying zone (104).

[0067] More specifically, the first adjusting unit (500) reduces the temperature of the infrared heater (121) in the first drying zone (101) by 4°C below the preset temperature and reduces the fan speed of the hot air blower (122) by 100 rpm below the preset speed, and the second adjusting unit (600) increases the temperature of the infrared heater (121) in the third and fourth drying zones (103, 104) by 1 to 2°C above the preset temperature and increases the fan speed of the hot air blower (122) in the third and fourth drying zones (103, 104) by 25 to 50 rpm above the preset speed, thereby compensating for the reduced heat supply in the first drying zone (101).

[0068] In one example, the first adjusting unit (500) can adjust the number of first drying zones based on a preset target adhesive strength of the electrode to be dried.

[0069] If the adhesive strength of the electrode to be dried that has passed through multiple drying zones in sequence and completed drying is equal to or less than the target adhesive strength, the first adjusting unit (500) can adjust the heat supply amount in the first drying zone (101) to a first heat supply amount (A) that is lower than a preset heat supply amount, thereby increasing the number of first drying zones (101).

[0070] In another example, the second adjustment unit (600) can adjust the heat supply amount (B) of the third drying zone (103) and the heat supply amount (C) of the fourth drying zone (104) to be higher than the preset heat supply amount, based on the difference between the drying rate (D1) of the electrode to be dried that has passed through multiple drying zones sequentially and completed drying and a preset target drying rate (D0).

[0071] For example, the second adjusting unit (600) can adjust the heat supply amount (B) of the third drying zone (103) and the heat supply amount (C) of the fourth drying zone (104) higher than the preset heat supply amount until the difference between the dryness rate (D1) of the electrode to be dried and the preset target dryness rate (D0) is adjusted to within the allowable error range. The second adjusting unit (600) can repeatedly adjust the heat supply amount (B) of the third drying zone (103) and the heat supply amount (C) of the fourth drying zone (104) higher than the preset heat supply amount by 25 to 50% of the first heat supply amount (A) until the difference between the dryness rate (D1) of the electrode to be dried and the preset target dryness rate (D0) is adjusted to within the allowable error range.

[0072] For example, the second adjusting unit 600 may adjust the drying rate D1 of the electrode to be dried within an allowable error range of a preset target drying rate D0 by repeatedly increasing the temperature of the infrared heater 121 and the fan speed of the hot air blower 122 in the third drying zone 103 and the fourth drying zone 104. The allowable error range may be within a range of ±1%.

[0073] The target drying rate means a drying rate at which over-drying, under-drying, and heat wrinkles are prevented, and the electrode drying system according to the present invention can improve product quality by ensuring a desired adhesive strength through the first adjusting unit (500) and adjusting the electrode drying rate to the target drying rate through heat compensation in the third drying zone (103) and the fourth drying zone (104) through the second adjusting unit (600).

[0074] In one embodiment, the electrode to be dried may be a negative electrode including a current collector and a negative electrode slurry layer provided on the current collector. The negative electrode may be a coated negative electrode coated with a negative electrode slurry layer, or may be a rolled negative electrode obtained by rolling the coated negative electrode.

[0075] The negative electrode slurry may include a negative electrode active material, a binder, a conductive material, and a dispersion medium.

[0076] Examples of the negative electrode active material include carbon-based active materials, silicon-based active materials, etc. Specifically, artificial graphite, natural graphite, hard carbon, soft carbon, graphitized carbon fiber, graphitized mesocarbon microbead, petroleum coke, resin molded body, carbon fiber, pyrolytic carbon, Si, SiO x Silicon oxide represented by (0 < x ≦ 2), lithium titanate (LTO), lithium metal, or two or more of these may be included, but are not limited thereto.

[0077] The binder may be made of various types of binder polymers such as polyvinylidene fluoride - hexafluoropropylene copolymer (PVDF - co - HEP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, styrene - butadiene rubber (SBR), fluorine rubber, and various copolymers.

[0078] The dispersion medium may independently use N - methylpyrrolidone, acetone, water, etc.

[0079] The conductive material is not particularly limited as long as it does not cause a chemical change in the battery and has conductivity. For example, carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber and metal fiber; metal powders such as fluorocarbon, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives may be used.

[0080] In the negative electrode in which the constant rate section is designed by the drying system according to the present invention, the binder is not distributed excessively on the surface of the slurry layer but is located inside the active material layer, and the electrode contact between the current collector and the slurry layer is stable, improving the resistance characteristics and increasing the minimum adhesive strength between the current collector and the slurry layer.

[0081] The present application also relates to an electrode drying method, which utilizes the electrode drying system, and therefore, the following description will be omitted if it overlaps with the above description.

[0082] The drying method includes a determination step of determining, among the plurality of drying zones (100), a plurality of first drying zones (101) in which the electrode to be dried moves to a constant rate state (T state) in which the change in surface temperature is maintained below a predetermined value, and a first adjustment step of adjusting the amount of heat supplied from the heat supply unit in each first drying zone (101) in order to increase or decrease the number of first drying zones (101) determined in the determination step.

[0083] For example, the determination step can determine that at least one drying area among the multiple drying areas (100) located behind the second drying area (102) having the highest electrode surface temperature is the first drying area (101).

[0084] Specifically, the difference (T2-T1) between the electrode surface temperature (T2) in the second drying zone (102) and the electrode surface temperature (T1) in the first drying zone (101) may be 5°C or less.

[0085] In one example, the first adjustment step can adjust the heat supply amount of each first drying zone to a first heat supply amount (A) lower than a predetermined heat supply amount in order to increase the number of first drying zones determined in the determination step.

[0086] The drying method may also include a second adjusting step of adjusting, based on the first heat supply amount (A), a heat supply amount (B) of at least one or more third drying areas (103) located in front of the first drying area (101) and a heat supply amount (C) of at least one or more fourth drying areas (104) located behind the first drying area (101) to be higher than a predetermined heat supply amount.

[0087] The second adjusting step may be a heat quantity compensating step of compensating for the reduced amount of heat supply due to the first adjusting step.

[0088] In addition, the second adjustment step can adjust the heat supply amount (B) of the third drying zone (103) and the heat supply amount (C) of the fourth drying zone (104) to be higher than the preset heat supply amount, based on the difference between the drying rate (D1) of the electrode to be dried that has passed through the plurality of drying zones (100) sequentially and completed drying and a preset target drying rate (D0).

[0089] The preferred embodiments of the present invention described above have been disclosed for illustrative purposes, and those skilled in the art having ordinary skill in the art will be able to make various modifications, changes, and additions within the spirit and scope of the present invention, and such modifications, changes, and additions should be considered to fall within the scope of the following claims. [Industrial Applicability]

[0090] The electrode drying system according to one embodiment of the present invention has the advantages of excellent electrode drying quality, efficiency of the drying process, and productivity of the drying process.

Claims

1. a plurality of drying zones arranged along one direction, each including a drying space in which the electrodes to be dried are dried and a heat supply unit provided to provide a predetermined amount of heat to the drying space; a moving unit that moves the electrode to be dried so that the electrode passes through the plurality of drying zones in sequence and is dried; a plurality of temperature sensors provided in the plurality of drying zones, respectively, for measuring the surface temperatures of the electrodes to be dried in the respective drying zones; a determination unit that determines, based on the surface temperatures of the electrodes to be dried measured by the temperature sensors, a plurality of first drying zones among the plurality of drying zones through which the electrodes to be dried move in a constant rate state where a change in the surface temperature is maintained at or below a predetermined value; a first adjustment unit that adjusts the amount of heat supplied from the heat supply unit in each first drying zone in order to increase or decrease the number of first drying zones determined by the determination unit.

2. The electrode drying system according to claim 1 , wherein the determination unit determines, as the first drying area, at least one drying area among the plurality of drying areas that is located behind a second drying area having the highest electrode surface temperature.

3. 3. The electrode drying system of claim 2, wherein the difference (T2-T1) between the electrode surface temperature (T2) in the second drying area and the electrode surface temperature (T1) in the first drying area is 5° C. or less.

4. 2. The electrode drying system according to claim 1, wherein the first adjustment unit adjusts the heat supply amount of each first drying zone to a first heat supply amount that is lower than a preset heat supply amount in order to increase the number of first drying zones determined by the determination unit.

5. 5. The electrode drying system according to claim 4, further comprising a second adjusting unit that adjusts the heat supply amounts of at least one or more third drying zones located in front of the first drying zone and at least one or more fourth drying zones located behind the first drying zone to be higher than preset heat supply amounts, based on the first heat supply amount.

6. 6. The electrode drying system of claim 5, wherein the second adjusting unit adjusts the heat supply amount of the third drying zone to a second heat supply amount that is higher than a preset heat supply amount by 25% to 50% of the first heat supply amount, and adjusts the heat supply amount of the fourth drying zone to a third heat supply amount that is higher than the preset heat supply amount by 25% to 50% of the first heat supply amount.

7. 6. The electrode drying system according to claim 5, wherein the second adjustment unit adjusts the heat supply amount of the third drying zone and the heat supply amount of the fourth drying zone to be higher than the predetermined heat supply amount, based on a difference between a drying rate of the electrode to be dried that has passed through the plurality of drying zones sequentially and completed drying and a predetermined target drying rate.

8. 8. The electrode drying system according to claim 7, wherein the second adjustment unit adjusts the heat supply amounts of the third drying zone and the fourth drying zone to be higher than the preset heat supply amounts until a difference between the dryness rate of the electrode to be dried and a preset target dryness rate is adjusted to fall within an allowable range.

9. The electrode drying system according to claim 1 , wherein the electrode to be dried is a negative electrode including a current collector and a negative electrode slurry layer provided on the current collector.

10. An electrode drying method using the electrode drying system according to claim 1, a determining step of determining, among the plurality of drying zones, a plurality of first drying zones through which the electrode to be dried moves in a constant rate state in which the change in surface temperature is maintained at or below a predetermined value; a first adjustment step of adjusting the amount of heat supplied from the heat supply unit in each first drying zone in order to increase or decrease the number of first drying zones determined in the determination step.

11. The electrode drying method according to claim 10 , wherein the determining step determines, as the first drying area, at least one drying area among the plurality of drying areas that is located behind a second drying area having the highest electrode surface temperature.

12. 12. The electrode drying method according to claim 11, wherein the difference (T2-T1) between the electrode surface temperature (T2) in the second drying zone and the electrode surface temperature (T1) in the first drying zone is 5°C or less.

13. 11. The electrode drying method according to claim 10, wherein the first adjusting step adjusts the heat supply amount of each first drying zone to a first heat supply amount that is lower than a preset heat supply amount in order to increase the number of first drying zones determined in the determining step.

14. 14. The electrode drying method according to claim 13, further comprising a second adjusting step of adjusting, based on the first heat supply amount, the heat supply amounts of at least one or more third drying zones located in front of the first drying zone and at least one or more fourth drying zones located behind the first drying zone to be higher than predetermined heat supply amounts, respectively.

Images