Electrode drying system and electrode drying method

Abstract

The present technology relates to a system for drying an electrode, and the system includes: an oven that applies hot air and radiant heat to an electrode sheet; and a controller that receives information about a drying standby time and controls the amount of heat supplied to the oven. Here, the controller controls to supply reduced heat to the oven during an initial drying time after the electrode sheet is supplied after the drying standby time.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2020-0162423, filed on November 27, 2020, and Korean Patent Application No. 10-2021-0162711, filed on November 23, 2021, the contents of which are incorporated herein by reference as part of this specification.

[0002] The present invention relates to an electrode drying system and an electrode drying method, and more particularly, to an electrode drying system and an electrode drying method for suppressing over-drying during initial drying of an electrode sheet supplied to an oven after a drying standby time when the electrode sheet is not supplied to the oven. Background Art

[0003] Recently, secondary batteries capable of charging and discharging have been widely used as an energy source for wireless mobile devices. In addition, secondary batteries have attracted attention as an energy source for electric vehicles, hybrid electric vehicles, etc., which are proposed as solutions to air pollution of existing gasoline vehicles and diesel vehicles using fossil fuels. Therefore, due to the advantages of secondary batteries, various applications using secondary batteries are currently very diverse, and it is expected that secondary batteries will be applied to many fields and products in the future.

[0004] According to the composition of electrodes and electrolytes, such secondary batteries can be classified into lithium-ion batteries, lithium-ion polymer batteries, lithium polymer batteries, etc., among which the use of lithium-ion polymer batteries, which are less likely to leak electrolytes and are easy to manufacture, is increasing. Generally, according to the shape of the battery case, secondary batteries are classified into cylindrical batteries and prismatic batteries in which the electrode assembly is built into a cylindrical or square metal can, and pouch-type batteries in which the electrode assembly is built into a pouch-shaped case of an aluminum laminate. The electrode assembly built into the battery case is composed of a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, and is a power generation element capable of charging and discharging. The electrode assembly is classified into a jelly roll type wound in the case where a separator is interposed between a long strip-shaped positive electrode and negative electrode coated with active materials; and a stacked type in which a plurality of positive electrodes and negative electrodes of a predetermined size are sequentially stacked while interposing a separator therebetween.

[0005] By applying a positive electrode paste containing a positive electrode active material and a negative electrode paste containing a negative electrode active material to a positive electrode current collector and a negative electrode current collector, respectively, to form a positive electrode active material layer and a negative electrode active material layer, and then drying and rolling them, a positive electrode and a negative electrode are formed.

[0006] At this time, the drying conditions of the electrodes affect the quality and physical properties of the electrodes. In particular, during the drying process, the adhesion force and coupling level on the electrode surface can be significantly changed according to the control of the drying deviation in the width direction of the electrode and the time point when drying is completed.

[0007] In addition, the electrode sheet coated with the electrode paste undergoes a drying process while moving through the drying section as a continuous process. However, there may be a time interval between the electrode paste coating process and the drying process, and during the drying standby period when the electrode sheet is not supplied to the drying section in the oven, excess heat accumulates inside the oven. When the electrode sheet is supplied to the oven in such a state where excess heat has accumulated, due to excessive heat accumulation in the oven, cracks or wrinkles may occur in the electrode during the initial drying section.

[0008] In particular, due to excessive drying in the initial drying section, cracks occur in the electrode, generating electrode powder, and the electrode powder is dispersed along the convection of the hot air in the oven, thus contaminating the surrounding electrodes and reducing the electrode quality. Therefore, it is very important to prevent excessive drying in the initial drying section of the electrode.

[0009] Therefore, an electrode drying technique is needed to prevent excessive drying during the initial drying section. Summary of the Invention

[0010] Technical Problem

[0011] It is believed that the present invention solves at least some of the above problems. For example, one aspect of the present invention provides an electrode drying system and an electrode drying method for preventing electrode cracks by suppressing excessive drying that may occur during initial drying, which is caused by excess heat accumulated in the oven from the electrode sheet supplied to the oven after the drying standby time in the electrode drying process including the drying standby time.

[0012] Technical Solution

[0013] The system for drying an electrode for solving the above problems according to the present invention includes: an oven that applies hot air and radiant heat to the electrode sheet; and a controller that receives information about the drying standby time when the supply of the electrode sheet to the oven is stopped, and determines and controls the heat supplied to the oven according to the length of the drying standby time, wherein the controller controls to supply less heat to the oven during the initial drying time after the supply of the electrode sheet after the drying standby time than the general supply heat (Q t ).

[0014] In an electrode drying system according to an embodiment of the present invention, the controller controls to supply the general supply heat (Q t ) to the oven after the initial drying time has passed.

[0015] In an electrode drying system according to an embodiment of the present invention, the initial drying time (T) is chronologically divided into n (n≥2) time periods, and at T 1 , T 2 , T 3 ... T n each heat supplied to the oven is defined as Q 1 , Q 2 , Q 3 ... Q n , and the controller controls the heat supplied to the oven to satisfy the following relationship:

[0016] Q 1 < Q 2 < Q 3 <... < Q n ≤ Q t

[0017] In an electrode drying system according to an embodiment of the present invention, as the drying standby time increases, the controller controls to reduce the ratio (Q 1 ) of the heat (Q 1 ) supplied to the initial time period (T t ) to the general supply heat (Q 1 / Q t ).

[0018] In an electrode drying system according to an embodiment of the present invention, the oven includes at least one hot air nozzle that applies convective heat by supplying hot air to the electrode sheet and at least one heater that applies radiant heat to the electrode sheet.

[0019] In an electrode drying system according to an embodiment of the present invention, the controller controls the heat supplied to the oven in such a way as to increase or decrease at least one of the conditions including the temperature of the hot air ejected from the hot air nozzle, the speed of the hot air, and the output of the heater.

[0020] In an electrode drying system according to an embodiment of the present invention, the controller uniformly controls the heat supplied to the entire oven.

[0021] An electrode drying system according to an embodiment of the present invention further includes an electrode sheet sensor that senses that the electrode sheet is not supplied to the oven and transmits information about the drying standby time to the controller.

[0022] The electrode drying system according to an embodiment of the present invention further includes a measurement unit that collects information on the drying amount of the electrode sheet and transmits the collected information to the controller. Here, the controller determines the drying level of the electrode sheet based on the information on the drying amount received from the measurement unit and changes the heat supplied to the oven in real time.

[0023] In the electrode drying system according to an embodiment of the present invention, the measurement unit collects information on at least one of the solid content and the surface temperature of the electrode sheet before and after passing through the oven.

[0024] In the electrode drying system according to an embodiment of the present invention, the measurement unit includes at least one of a web gauge and a temperature measuring instrument.

[0025] The method for drying an electrode sheet according to the present invention includes: (a) a process of collecting information on the drying standby time, which is the time interval during which the supply of the electrode sheet to the oven for drying the electrode sheet is stopped; (b) a process of determining the heat condition to be supplied to the oven when the electrode sheet is supplied to the oven after the drying standby time; and (c) a process of supplying the electrode sheet to the oven after the drying standby time and drying the electrode sheet under the heat condition determined in process (b). Here, process (b) includes determining a heat condition in which less heat than the general supply heat (Q t ) is supplied to the oven during the initial drying time.

[0026] In the method for drying an electrode sheet according to an embodiment of the present invention, process (b) includes determining a heat condition in which the general supply heat (Q t ) is supplied to the oven after the initial drying time has passed.

[0027] In the method for drying an electrode sheet according to an embodiment of the present invention, in process (b), the initial drying time (T) is chronologically divided into n (n≥2) time periods. When at T 1 , T 2 , T 3 ... T n the respective heats supplied to the oven are defined as Q 1 , Q 2 , Q 3 ... Q n it is determined that the heat supplied to the oven satisfies the following relationship:

[0028] Q 1 < Q 2 < Q3 <...<Q n ≤Q t

[0029] In the method for drying an electrode sheet according to an embodiment of the present invention, in the step (b), the heat condition is determined such that as the drying standby time increases, the heat (Q 1 ) supplied to the initial time period (T 1 ) and the ratio (Q t ) of the generally supplied heat (Q 1 / Q t ) decrease.

[0030] Advantageous Effects

[0031] According to the present invention, in the case where there is a drying standby time when the electrode sheet is not supplied to the oven, since the control reduces the heat supplied to the electrode sheet supplied to the oven after the drying standby time, over-drying during the initial drying time is suppressed, and accordingly, cracks generated on the electrode sheet are prevented, thereby suppressing contamination inside the oven.

[0032] When the electrode drying system and the electrode drying method of the present invention are applied, the electrode manufacturing cost can be reduced by reducing the heat consumption in the electrode drying standby state. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a schematic diagram showing the structure of an electrode drying system according to an embodiment of the present invention.

[0034] Figure 2 is a schematic diagram showing the structure of an oven according to an embodiment of the present invention.

[0035] Figure 3 is a schematic diagram showing the structure of an electrode drying system according to another embodiment of the present invention.

[0036] Figure 4 is a flowchart showing the sequence of an automatic electrode drying control method according to the present invention.

[0037] Figure 5 is a photograph obtained by photographing an electrode sheet dried according to an embodiment of the present invention using a thermal imaging camera.

[0038] Figure 6 is a photograph obtained by photographing an electrode sheet dried according to a comparative example using a thermal imaging camera.

[0039] Figure 7 is a graph showing the results of the solid content measured over time of the dried electrode sheets according to the examples and the comparative examples. Detailed implementation manners

[0040] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. Terms and words used in this specification and claims should not be construed as limited to ordinary terms or dictionary terms, and the inventor can appropriately define the concept of the terms to best describe his invention. The terms and words should be construed as having meanings and concepts consistent with the technical concept of the present invention.

[0041] In this application, it should be understood that terms such as "including" or "having" are intended to indicate the presence of the described features, quantities, steps, operations, components, parts, or combinations thereof in this application, and they do not pre-exclude the possibility of the presence or addition of one or more other features or quantities, steps, operations, components, parts, or combinations thereof. In addition, when a part of, for example, a layer, film, region, plate, etc. is referred to as being "on" another part, this includes not only the case where this part is "directly" on the other part, but also the case where other parts are inserted between this part and the other part. On the other hand, when a part of, for example, a layer, film, region, plate, etc. is referred to as being "under" another part, this includes not only the case where this part is "directly" under the other part, but also the case where other parts are inserted between this part and the other part. In addition, being to be disposed "on" in this application may include the cases of being disposed on the bottom as well as on the top.

[0042] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

[0043] Figure 1 is a schematic diagram showing the structure of an electrode drying system according to an embodiment of the present invention.

[0044] Referring to Figure 1 , a system 100 for drying an electrode according to the present invention includes: an oven 110 that is divisible into a plurality of drying zones 111, 112, and 113 along the x-axis as the electrode transfer direction, and the oven applies hot air and radiant heat to the electrode sheet 10; and a controller 130 that receives information on a drying standby time when the supply of the electrode sheet to the oven 110 is stopped, and determines and controls the heat supplied to the oven 110 according to the length of the drying standby time.

[0045] In the present invention, the drying standby time refers to the time interval during which the electrode sheet is not supplied to the oven due to various process-related reasons. The drying standby time may specifically be in the range of 30 seconds to 30 minutes, 30 seconds to 20 minutes, or 1 minute to 15 minutes.

[0046] Heat accumulates in the oven when the supply of the electrode sheet to the oven is stopped, and when the electrode sheet is supplied to the oven in a state where excessive heat has been accumulated, the electrode is over-dried due to the accumulated excessive heat, resulting in cracks in the electrode. Therefore, when there is a drying standby time, control is required to temporarily reduce the heat supplied to the oven.

[0047] Thus, the electrode drying system of the present invention is used to suppress cracks generated in the electrode due to accumulated excessive heat, and the controller 130 of the present invention controls to supply less heat to the oven during the initial drying time after the supply of the electrode sheet after the drying standby time than the general supply heat (Q t ). Here, the general supply heat (Q t ) refers to the heat generally supplied into the oven in the absence of a drying standby time.

[0048] In addition, in the present invention, the initial drying time may refer to a predetermined time interval after the supply of the electrode sheet to the oven, and may specifically refer to a time interval of 60 minutes after the supply of the electrode sheet to the oven, a time interval of 30 minutes after the supply of the electrode sheet to the oven, a time interval of 20 minutes after the supply of the electrode sheet to the oven, a time interval of 10 minutes after the supply of the electrode sheet to the oven, or a time interval of 5 minutes after the supply of the electrode sheet to the oven. When the supplied heat is less than the general supply heat (Q t ), the length of the initial drying time may vary according to the length of the drying standby time, and when the drying standby time is relatively long, excessive heat accumulates in the oven, so the initial drying time may become longer. On the other hand, when the drying standby time is relatively short, relatively less excessive heat accumulates in the oven, so the initial drying time may become shorter.

[0049] In addition, in the present invention, the x-axis refers to the direction of electrode transfer, the y-axis refers to the direction perpendicular to the transfer direction of the electrode on the electrode surface, as the width direction of the electrode. The z-axis corresponds to the direction of jetting hot air or radiant heat in the oven, as the direction perpendicular to the electrode surface.

[0050] In a specific example, the initial drying time (T) is divided into n (n is equal to or greater than 2) time periods in chronological order. When at T 1 , T 2 , T 3 ... T n the respective heats supplied to the oven are defined as Q 1 , Q2 , Q 3 ... Q n When, the controller controls the heat supplied to the oven to satisfy the following relationship:

[0051] Q 1 < Q 2 < Q 3 <... < Q n ≤ Q t

[0052] That is, the controller of the present invention controls to supply less heat to the oven during the initial drying time than the general supply heat (Q t ), gradually increases the supply heat, and supplies the general supply heat (Q t ) to the oven after the initial drying time has passed.

[0053] In the drying system of the present invention, when there is no drying standby time, the generally set heat (Q t ) is supplied to the oven, but when there is a drying standby time, the controller in the drying system of the present invention controls to supply less heat to the oven during the initial drying time than the general supply heat (Q t ).

[0054] Specifically, for example, the initial drying time (T) can be divided into 4 time periods, and each time period is sequentially divided into T 1 , T 2 , T 3 and T 4 . In addition, assuming that the supply heats corresponding to the time periods T 1 , T 2 , T 3 and T 4 are Q 1 , Q 2 , Q 3 and Q 4 , then the supply heat corresponding to the initial time period T 1 is set to have a value less than the general oven supply heat Q t , and the controller controls driving conditions such as the temperature of hot air, the speed of hot air, and the output of the heater so that the reduced heat Q 1 can be supplied to the oven during the initial time period T 1 .

[0055] In addition, in the time period T 1 after the initial time period T 2 , the heat Q 2 is set to be supplied to the oven. Q2 is set to be greater than Q 1 and is set to be less than Q t (i.e., the general supply heat quantity) (Q t >...>Q 2 >Q 1 ). And the supply heat quantity Q 2 corresponding to T 3 and T 4 as the time period after T 3 and Q 4 is set in the same way as Q 2 (Q t >Q 4 >Q 3 >Q 2 >Q 1 ). Similarly, in the case of the existence of a drying standby time, by supplying reduced heat during the initial drying time and gradually increasing the supplied heat over time, over-drying can be suppressed.

[0056] In one embodiment of the present invention, as the drying standby time increases, the controller controls to reduce the ratio of the heat quantity (Q 1 ) supplied to the initial time period (T 1 ) to the general supply heat quantity (Q t ). 1 / Q t )

[0057] For example, in the case where the drying standby time is 4 minutes and in the case where the drying standby time is 2 minutes, the heat quantity Q 1 supplied during the initial time period T 1 is set to be different. The set value of Q 1 varies according to the length of the drying standby time.

[0058] In the above example, if Q 1 / Q t is 75% when the drying standby time is 4 minutes, then Q 1 / Q t can be 85% when the drying standby time is 2 minutes. Since the excess heat accumulated in the oven increases as the drying standby time increases, Q 1 / Q t is set to be smaller to attenuate it. The value of Q 1 / Q t can vary according to the length of the drying standby time, specifically in the range of 50 - 90%, 55 - 85%, 60 - 75%, or 60 - 70%.

[0059] When the controller supplies reduced heat to the oven during the control of the initial drying time, it uniformly controls the heat supplied to the entire oven. In the case where there is a drying standby time when the electrode sheet is not supplied to the oven, excess heat accumulates in the entire area of the oven. Therefore, in order to reduce the excess heat, it is preferable to uniformly perform the above control on the entire oven.

[0060] Hereinafter, the configuration of the electrode drying system according to the present invention will be described in detail.

[0061] Referring to Figure 1 , the electrode drying system 100 according to the present invention includes an oven 110. The oven 110 has a chamber shape, provides a space in which the electrode sheet 10 to be dried can move in the oven 110, and prevents the heat used for drying from escaping.

[0062] In addition, the electrode sheet 10 may have a structure in which an electrode active material layer 12 is formed by coating a slurry for electrode formation including an electrode active material on a current collector sheet 11. The electrode slurry may be applied to at least one surface of the current collector.

[0063] In this case, the current collector may be a positive current collector or a negative current collector, and the electrode active material may be a positive electrode active material or a negative electrode active material. In addition, in addition to the electrode active material, the electrode slurry may further include a conductive material and a binder.

[0064] In the present invention, the positive current collector generally has a thickness of 3 to 500 μm. The positive current collector is not particularly limited as long as it has high conductivity and does not cause chemical changes in the battery. Examples of the positive current collector include stainless steel; aluminum; nickel; titanium; sintered carbon; or aluminum or stainless steel whose surface is treated with carbon, nickel, titanium, silver or the like. The current collector may have fine irregularities on its surface to increase the adhesion of the positive electrode active material, and may be in various forms, such as a film, sheet, foil, net, porous body, foam, and non-woven fabric.

[0065] The sheet for the negative current collector generally has a thickness of 3 to 500 μm. The negative current collector is not particularly limited as long as it has conductivity and does not cause chemical changes in the battery, and examples thereof include copper; stainless steel; aluminum; nickel; titanium; sintered carbon; copper or stainless steel whose surface is treated with carbon, nickel, titanium, silver or the like; aluminum cadmium alloy; or the like. In addition, similar to the positive current collector, fine irregularities may be formed on the surface to enhance the adhesion of the negative electrode active material, and it may be used in various forms, such as a film, sheet, foil, net, porous body, foam, and non-woven fabric.

[0066] In the present invention, the positive electrode active material is a material capable of causing an electrochemical reaction, which is a lithium transition metal oxide and contains two or more transition metals. Examples thereof include: layered compounds such as lithium cobalt oxide (LiCoO 2 ) and lithium nickel oxide (LiNiO 2 ) substituted by one or more transition metals; lithium manganese oxide substituted by one or more transition metals; lithium nickel oxide represented by the molecular formula LiNi 1-y M y O 2 (where M = Co, Mn, Al, Cu, Fe, Mg, B, Cr, Zn or Ga and contains at least one of the above elements, 0.01 ≤ y ≤ 0.7); lithium nickel oxide represented by the molecular formula Li 1+z Ni b Mn c Co 1-(b+c+d) M d O (2-e) A e , such as Li 1+z Ni 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 , Li 1+z Ni 0.4 Mn 0.4 Co 0.2 O 2 etc. (where -0.5 ≤ z ≤ 0.5, 0.1 ≤ b ≤ 0.8, 0.1 ≤ c ≤ 0.8, 0 ≤ d ≤ 0.2, 0 ≤ e ≤ 0.2, b + c + d < 1, M = Al, Mg, Cr, Ti, Si or Y, and A = F, P or Cl); olivine-based lithium metal phosphate represented by the molecular formula Li 1+x M 1-y M' y PO 4-z X z (where M = transition metal, preferably Fe, Mn, Co or Ni, M' = Al, Mg or Ti, X = F, S or N, and -0.5 ≤ x ≤ 0.5, 0 ≤ y ≤ 0.5, 0 ≤ z ≤ 0.1).

[0067] Examples of the negative electrode active material include: carbon such as non-graphitized carbon and graphitized carbon; metal composite oxides such as Li x Fe 2 O 3 (0 ≤ x ≤ 1), Li x WO 2 (0 ≤ x ≤ 1), Sn x Me 1-x Me’ y Oz (Me: Mn, Fe, Pb, Ge; Me’: Al, B, P, Si, Group 1, 2 and 3 elements in the periodic table, halogens; 0 < x ≤ 1; 1 ≤ y ≤ 3; 1 ≤ z ≤ 8); lithium alloy; silicon alloy; tin alloy; metal oxides such as SnO, SnO 2 , PbO, PbO 2 , Pb 2 O 3 , Pb 3 O 4 , Sb 2 O 3 , Sb 2 O 4 , Sb 2 O 5 , GeO, GeO 2 , Bi 2 O 3 , Bi 2 O 4 and Bi 2 O 5 ; conductive polymers such as polyacetylene; and Li - Co - Ni - based materials.

[0068] The conductive material is usually added in an amount of 1 to 30% by weight based on the total weight of the mixture including the positive electrode active material. There is no particular limitation on such a conductive material as long as it has conductivity and does not cause chemical changes in the battery. Examples thereof include: graphite such as natural graphite and artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black; conductive fibers such as carbon fibers and metal fibers; metal powders such as carbon fluoride powder, aluminum powder, 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; and the like.

[0069] As a component for binding between the auxiliary active material and the conductive material and for binding with the current collector, the binder is added in an amount of 1 to 30% by weight based on the total weight of the mixture including the positive electrode active material. Examples of such a binder include: polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene - propylene - diene terpolymer (EPDM), sulfonated EPDM, styrene - butadiene rubber, fluororubber, various copolymers, and the like.

[0070] Meanwhile, this electrode paste can be prepared by dissolving an electrode active material, a conductive material, and a binder in a solvent. The type of the solvent is not particularly limited as long as it can disperse the electrode active material, and a water solvent or a non-aqueous solvent can be used. For example, the solvent can be a solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and one of them can be used alone or a mixture of two or more of them can be used. The amount of the solvent can be used in consideration of the coating thickness, yield, and processability of the paste so that the paste can be adjusted to have an appropriate viscosity, and there is no particular limitation.

[0071] Referring to Figure 1 , the oven 110 can be divided into a plurality of drying zones 111, 112, and 113, and each drying zone includes a hot air nozzle 114 that applies convective heat by supplying hot air to the electrode sheet 10 and a heater 115 that applies radiant heat to the electrode sheet 10. Referring to Figure 1 , the hot air nozzle 114 and the heater 115 can be arranged at regular intervals along the conveying direction (MD direction, x direction) of the electrode sheet 10, and hot air or radiant heat is applied in a direction perpendicular to the electrode sheet 10. In Figure 1 , it is shown that the hot air nozzle 114 and the infrared heater 115 are located on the upper part of the electrode sheet 10, that is, on the lower surface of the top plate of the oven 110, but when the electrode active material layer is formed on both surfaces of the current collector, the hot air nozzle 114 and the heater 115 can be located on the upper and lower parts of the electrode sheet 10, respectively. In addition, Figure 1 it is shown that a case including both a hot air nozzle and a heater as a drying device, but only one of the hot air nozzle and the heater can be included as a drying device.

[0072] On the other hand, the hot air nozzle 114 includes a main body unit and a spraying unit. The main body unit constitutes the main body of the hot air nozzle and fixes the hot air nozzle 114 to the top of the oven. In addition, the main body unit is empty inside and transfers the hot air transferred from a hot air supply source (not shown) to the spraying unit. On the other hand, the spraying unit is provided on the lower surface of the main body unit. The spraying unit communicates with the main body unit, and a spraying hole part for spraying hot air is formed on the lower surface of the spraying unit. The spraying hole part can have a structure in which a plurality of holes are arranged at regular intervals

[0073] In addition, in a specific example of the present invention, the heater 115 can be an infrared heater, and the infrared heater can include an infrared lamp that irradiates infrared rays to the electrode and a bracket that supports the infrared lamp. The shape of the infrared lamp is not particularly limited. For example, rod-shaped lamps can be arranged side by side along the conveying direction of the electrode while extending in the width direction of the electrode.

[0074] The hot air nozzles 114 and the heaters 115 may be alternately arranged in the moving direction of the electrode sheet 10 so as to uniformly supply hot air and infrared rays to the surface of the electrode sheet 10. However, the type of the arrangement is not particularly limited, and the arrangement of the hot air nozzles 114 and the infrared heaters 115 may be appropriately changed by those skilled in the art according to the drying conditions.

[0075] The drying system of the present invention can control the heat supplied to the oven in such a way as to increase or decrease at least one of the conditions including the temperature of the hot air ejected from the hot air nozzle, the velocity of the hot air, and the output of the heater.

[0076] In addition, the oven 110 may include at least one transfer roller 116 for transferring the electrode. A plurality of transfer rollers 116 may be arranged at regular intervals along the transfer direction of the electrode sheet 10. The transfer rollers 116 support the electrode sheet 10 during the drying process and transfer the electrode sheet 10 to the outside of the oven 110. In addition, the drying amount of the electrode sheet can also be controlled by adjusting the rotation speed of the transfer roller.

[0077] The electrode drying system 100 according to the present invention may further include an electrode sheet sensor 120 which senses that the electrode sheet 10 is not supplied to the oven 110 and transmits information about the drying standby time to the controller 130. The electrode sheet sensor 120 may be installed at a portion near the entrance of the oven for supplying the electrode sheet. The type of the sensor 120 is not limited as long as it can sense whether the electrode sheet is supplied. Therefore, the sensor may use a scheme for sensing weight or an imaging camera scheme.

[0078] The controller 130 of the present invention is connected to a first drive controller 117, a second drive controller 118, and a third drive controller 119 respectively installed in the first drying zone 111, the second drying zone 112, and the third drying zone 113. Accordingly, the controller 130 may command to reduce the heat supplied thereto. If the sensor 120 senses that the electrode sheet is not supplied to the oven, the sensor 120 transmits information about the drying standby time to the controller 130. The controller 130 receives the information about the drying standby time, determines the conditions of the heat to be supplied to the oven 110, and transmits the determined heat conditions to the drive controllers 117, 118, and 119 when the electrode sheet 10 is supplied to the oven 110. In this way, the drying controllers 117, 118, and 119 of the oven control the hot air nozzles 114 and the heaters 115 to reduce the supplied heat.

[0079] Figure 2is a schematic view showing the structure of an oven according to an embodiment of the present invention. Referring to Figure 2 , the electrode drying system 100 according to the present invention may further include a mesh frame 150 for controlling the radiant heat emitted from the heater 115. The mesh frame 150 is disposed between the heater 115 and the electrode active material layer 12, and can adjust the surface area of the electrode 10 exposed to the radiant heat. The transmission of the radiant heat emitted from the heater 115 can be blocked or reduced by the mesh frame 150. As needed, the electrode drying system according to the present invention can control the heat supplied to the electrode 10 by adjusting the area of the radiant heat exposed to the electrode 10 via the mesh frame 150.

[0080] As described above, the oven 110 of the electrode drying system 100 according to the present invention can be divided into a plurality of drying zones 111, 112, and 113. In this case, at least one mesh frame 150 is disposed between the electrode active material layer 12 and the heater 115 included in each drying section. That is, the mesh frame 150 can be disposed in each of all the heaters 115 included in the oven 110.

[0081] At this time, the size and number of the mesh frames 150 can be set differently according to the drying process. Here, the length of the mesh frame 150 in the electrode transfer direction (x-axis direction) can be set to be equal to or greater than the length of the heater 115 in the electrode transfer direction (x-axis direction) to effectively block infrared rays and prevent drying deviation in the electrode transfer direction. In addition, it is preferable to arrange a plurality of mesh frames having a small width direction length so that the electrode 10 can finely adjust the area exposed to the radiant heat of the heater 115.

[0082] In the present invention, the mesh frame 150 can be a plate-like member made of a material that does not transmit infrared rays. Specifically, the mesh frame 150 can be made of any material that is not damaged in the high-temperature environment in the oven and does not transmit radiant heat. In addition, the mesh frame 150 can be made of a material that does not transmit radiant heat, or a metal or polymer material (which may or may not transmit infrared rays) can be coated with a material that does not transmit radiant heat to form the main body of the mesh frame 150. Examples of the material that does not transmit radiant heat include vitreous insulating materials, inorganic materials such as metal oxides, carbon-based materials, etc., but the present invention is not limited to these examples.

[0083] The shape of the mesh frame 150 can be variously modified according to the drying conditions. The mesh frame 150 may not form holes on the surface to block the radiant heat. Or, the mesh frame 150 may form holes in the direction in which the radiant heat is radiated so as to only partially block the radiant heat.

[0084] Figure 5 is a photograph obtained by photographing an electrode sheet dried according to an embodiment of the present invention using a thermal imaging camera,Figure 6 is a photograph obtained by photographing an electrode sheet dried by a conventional electrode drying system using a thermal imaging camera. Referring to these drawings, in the electrode sheet manufactured by supplying less heat than the generally supplied heat in the initial drying section according to an embodiment of the present invention, compared with Figure 6 , the temperature of the electrode surface is lower in the initial region (see the inside of the frame formed by the dotted line). Therefore, it is expected that the electrode drying system of the present invention can reduce the generation of cracks by equalizing the drying amount of the initially manufactured electrodes.

[0085] Figure 3 is a schematic diagram showing the structure of an electrode drying system according to another embodiment of the present invention. Referring to Figure 3 , the electrode drying system 200 of the present invention includes: an oven 210 that provides a space for the movement and drying of the electrode sheet 10 and includes a drying device for applying hot air and / or radiant heat to the electrode sheet 10; a controller 230 that receives information on the drying standby time when the supply of the electrode sheet to the oven is stopped and determines and controls the heat supplied to the oven according to the length of the drying standby time; an electrode sheet sensor 220 that senses that the electrode sheet 10 is not supplied to the oven 210 and transmits the information on the drying standby time to the controller 230; a measurement unit 240 that collects information on the drying amount of the electrode sheet 10 that has passed through the oven 210 and transmits the collected information to the controller 230. Here, the controller 230 determines the drying level of the electrode sheet 10 based on the information on the drying amount received from the measurement unit 240 (240a and 240b) and controls the drying intensity of the oven 210 according to the determined drying level.

[0086] According to the electrode drying system, in the case where the electrode sheet is supplied to the oven after having a drying standby time, less heat is supplied during the initial drying time to prevent initial over-drying, and in the drying process after the initial drying time has passed, the drying amount of the electrode is adjusted according to the drying level of the electrode, so that the drying level of the electrode becomes uniform. That is, the measurement unit 240 (240a and 240b) can collect information on the drying amount of the electrode sheet in real time, and the controller 230 can determine the drying level of the electrode sheet based on the collected information on the drying amount, so as to periodically adjust the drying amount of the electrode sheet according to the drying level of the electrode sheet, and accordingly can control the drying level of the electrode to become uniform.

[0087] The information on the drying amount includes information on at least one of the solid content and the surface temperature of the electrode sheet. The electrode drying system of the present invention determines the drying level of the electrode sheet based on the information on the solid content and / or temperature collected by the measuring unit. The measuring unit may include at least one of a web-gauge for measuring the loading amount of the electrode sheet and a thermometer to collect information on the solid content and the surface temperature of the electrode sheet.

[0088] Referring to Figure 3 , the measuring units 240a and 240b include a web-gauge for measuring the loading amount of the electrode sheet, and the measuring units 240a and 240b can be respectively installed at the inlet and the outlet of the oven 210, and measure the loading amount before drying the electrode sheet and the loading amount after drying the electrode sheet. The measuring unit may further include a calculation unit to derive the solid content, and the calculation unit may derive the solid content of the electrode active material layer 12 from the measured loading amount using a pre-input calculation formula. The solid content can be derived from the loading amount using a formula known in the relevant art.

[0089] When the drying level of the electrode sheet is excessive (over-dried), the solid content becomes greater than the reference value, and when the drying level of the electrode sheet is insufficient, the solid content becomes less than the reference value. Therefore, the solid content can be an indicator for identifying the drying level of the electrode sheet.

[0090] The controller 230 can determine the drying level of the electrode based on the information on the drying amount received from the measuring units 240a and 240b, and control the drying intensity of the oven 210 according to the determined drying level, so as to adjust the drying amount of the electrode sheet in real time.

[0091] In order for the controller 230 to adjust the drying amount of the electrode sheet in real time, the measuring units 240a and 240b are set to periodically collect information on the drying amount of the electrode sheet at fixed time intervals, and whenever the information on the drying amount is received from the measuring units 240a and 240b, the controller 230 determines the drying level of the electrode sheet and periodically controls the drying intensity of the oven.

[0092] Hereinafter, the process of controlling the drying amount by the controller 230 will be described in detail. The controller 230 can receive information about the load amount and / or drying amount before / after drying the electrode sheet, such as the temperature of the electrode surface, from the measurement units 240a and 240b, and receive the input of a reference value for determining whether the drying level of the electrode sheet is excessive or insufficient. In addition, the controller 230 determines whether the drying level of the electrode sheet is excessive, insufficient, or appropriate by comparing the information about the drying amount with the reference value, and determines the method of controlling the drying intensity by quantitatively identifying the degree of excessive or insufficient drying by comparing the information about the drying amount with the reference value. When determining the drying level and drying amount of the electrode sheet, the controller 230 can control at least one of the moving speed of the transfer roller, the heater, and the hot air nozzle, thereby adjusting the drying amount of the electrode sheet.

[0093] The control of the drying intensity by the controller is performed periodically at fixed time intervals. In a specific example, the controller can repeatedly control the drying intensity of the oven at a cycle of 5 to 20 minutes, preferably 6 to 15 minutes, but the present invention is not limited to these examples.

[0094] Furthermore, the measurement unit is set to periodically collect information about the drying amount of the electrode sheet at fixed time intervals according to the control of the drying intensity by the controller. In a specific example, the measurement unit collects information about the drying amount 1 to 5 minutes before the time point when the controller is expected to control the drying intensity. That is, the measurement unit does not collect information about the drying amount of the electrode sheet in a timely manner after controlling the drying intensity of the oven, but collects information about the drying amount of the electrode sheet after a predetermined time from the start of the controller's control of the drying intensity. This is because according to the change in the drying intensity of the oven, it takes a certain amount of time for the effect of drying amount adjustment to appear.

[0095] The measurement unit sets the average value or median value of the information about the drying amount collected within the predetermined time as the representative value of the information about the drying amount, and transmits this value to the controller.

[0096] In addition, the measurement unit may include a thermometer capable of measuring the surface temperature of the electrode sheet. By measuring the temperature in the oven, the heat supplied to the oven can be controlled more precisely.

[0097] In addition, the present invention provides an electrode drying method.

[0098] Figure 4 is a flowchart showing the steps of the electrode drying method according to the present invention.

[0099] Refer to Figure 4, the method for drying an electrode sheet according to the present invention includes: (a) a step of collecting information on the drying standby time, which is the time interval during which the supply of the electrode sheet to an oven for drying the electrode sheet is stopped; (b) a step of determining the conditions of the heat to be supplied to the oven when the electrode sheet is supplied to the oven after the drying standby time; and (c) a step of supplying the electrode sheet to the oven after the drying standby time and drying the electrode sheet under the heat conditions determined in step (b). Here, step (b) includes determining a heat condition in which less heat than the normal supply heat (Q t ) is supplied to the oven during the initial drying time.

[0100] Step (b) is a step of setting the heat condition for the initial drying time according to the length of the drying standby time when there is a drying standby time. When setting the heat condition, the initial drying time T is divided into n time periods in chronological order (n≥2, n is an integer), and the heat (Q 1 ) supplied in the initial time period (T 1 ) is less than the normal supply heat (Q t ), and the heat (Q 2 ...T n ) supplied in the subsequent time periods (T 2 ...Q n ) can be set to satisfy the following relationship.

[0101] Q 1 <Q 2 <Q 3 <...<Q n ≤Q t

[0102] That is, step (b) includes determining a heat condition in which the normal supply heat (Q t ) is supplied to the oven after the initial drying time has passed.

[0103] In addition, the heat condition is set such that as the drying standby time increases, the ratio (Q 1 / Q 1 ) of the heat (Q t ) supplied to the initial time period (T 1 ) to the normal supply heat (Q t ) decreases.

[0104] Specifically, the process (b) includes a process of setting different initial drying times according to the length of the drying standby time, as shown in Table 1 below. Table 1 below shows the conditions of the heat supplied to the oven according to the drying standby time (1 minute, 1 minute 30 seconds, 2 minutes 30 seconds). In Table 1, the length of the electrode sheet is the moving length of the electrode sheet supplied to the oven with the drying standby time, and it can be understood as the time elapsed after the electrode sheet is supplied to the oven. The length of the small electrode sheet represents the initial stage of the drying time, and the length of the large electrode sheet represents the later stage of the drying time. In addition, the values shown in the drying standby time column of Table 1 represent the percentage of the heat supplied at the corresponding electrode sheet length assuming that the general supplied heat Q t is 100 (Q n / Q t × 100).

[0105] [Table 1]

[0106]

[0107] Referring to Table 1, when the drying standby time is 1 minute, the heat supplied to the oven during the initial drying time (the length of the electrode sheet is between 1 and 100) is set to 85% of the general supplied heat. During the next drying period (the length of the electrode sheet is between 100 and 200), the heat supplied to the oven in the process is set to 90% of the general supplied heat. During the next drying period (the length of the electrode sheet is between 200 and 300), the heat supplied to the oven is set to 95% of the general supplied heat, and during the next drying period (the length of the electrode sheet is equal to or greater than 300), the heat supplied to the oven is set to the general supplied heat. Similarly, according to the method for manufacturing an electrode of the present invention, when the electrode sheet is supplied to the oven with the drying standby time, less heat than the general supplied heat is supplied during the initial drying time, and after the electrode sheet is started to be supplied to the oven, the heat gradually increases with time, and the general supplied heat is supplied to the oven after the initial time has passed.

[0108] At this time, the heat set for each period and the increase in heat are not limited, and can be appropriately selected by those of ordinary skill in the art considering various variables affecting the process (such as the material properties of the electrode paste, the solid content of the electrode paste, the season, etc.).

[0109] Furthermore, referring to Table 1, compared with the case where the drying standby time is 1 minute, when the drying standby time is 2 minutes 30 seconds, a further reduced amount of heat is set to be provided during the initial drying period (the length of the electrode sheet: 1 to 100).

[0110] Figure 7Shows the solid content of the electrode sheet manufactured by applying the drying system and method according to the present invention over time. Figure 7 Examples 1 and 2 are the results of measuring the solid content over time of the electrode sheet dried under the heat conditions set according to the standby time as shown in Table 1 with drying standby times of 2 minutes and 30 seconds and 1 minute, respectively. Refer to Figure 7 , in the electrode drying system according to the present invention, reduced heat is supplied during the initial drying time, and thus, over-drying does not occur during the initial stage. Therefore, even after a period of time, the solid content remains at a low level and the deviation is small.

[0111] In addition, Figure 7 Comparative Example 1 of Figure 7 shows the solid content of the electrode sheet dried by applying the heat conditions set in Example 2 with a drying standby time of 4 minutes and 30 seconds, and Figure 7 Comparative Example 2 of

[0112] shows the solid content of the electrode sheet dried by generally supplying heat also during the initial drying period, which is different from the present invention. Refer to

[0113] [Description of Reference Numerals]

[0114] 100, 200: Electrode drying system

[0115] 10: Electrode sheet

[0116] 11: Current collector

[0117] 12: Electrode active material layer

[0118] 110, 210: Oven

[0119] 111, 211: First drying zone

[0120] 112, 212: Second drying zone

[0121] 113, 213: Third drying zone

[0122] 114, 214: Hot air nozzles

[0123] 115, 215: Infrared heaters

[0124] 116, 216: Conveyor rollers

[0125] 117, 217: First drive controller

[0126] 118, 218: Second drive controller

[0127] 119, 219: Third drive controller

[0128] 120, 220: Electrode sheet sensor

[0129] 130, 230: Controller

[0130] 240a, 240b: Measuring unit

[0131] 150: Screen frame

Claims

1. A system for drying an electrode, the system comprises: an oven that applies hot air and radiant heat to an electrode sheet; and a controller that receives information related to a drying standby time for stopping the supply of the electrode sheet to the oven and determines and controls the heat supplied to the oven based on the length of the drying standby time, wherein the controller controls to supply less heat than a general supply heat amount (Qt) to the oven during an initial drying time after supplying the electrode sheet after the drying standby time, wherein the general supply heat amount refers to the heat generally supplied into the oven in the absence of a drying standby time.

2. The system according to claim 1, wherein the controller is configured to control the supply of the general supply heat (Q t ) to the oven after the initial drying time has elapsed.

3. The system according to claim 1, wherein the initial drying time (T) is divided into n time periods in chronological order, and at T 1 , T 2 , T 3 ... T n each amount of heat supplied to the oven is defined as Q 1 , Q 2 , Q 3 ... Q n , and the controller controls the heat supplied to the oven to satisfy the following relationship: Q 1 <Q 2 <Q 3 <...<Q n ≤Q t and wherein n is equal to or greater than 2.

4. The system according to claim 3, wherein as the drying standby time increases, the controller controls to reduce the ratio (Q 1 / Q 1 ) of the heat (Q t ) supplied to the initial time period (T 1 ) to the general supply heat (Q t ).

5. The system according to claim 1, wherein the oven includes at least one hot air nozzle that applies convective heat by supplying hot air to the electrode sheet and at least one heater that applies radiant heat to the electrode sheet.

6. The system according to claim 5, wherein the controller controls the heat supplied to the oven in a manner of increasing or decreasing at least one of conditions including the temperature of the hot air ejected from the hot air nozzle, the velocity of the hot air, and the output of the heater.

7. The system according to claim 1, wherein the controller uniformly controls the heat supplied to the oven throughout the oven.

8. The system according to claim 1, further comprising an electrode sheet sensor that senses that the electrode sheet is not supplied to the oven and transmits information about the drying standby time to the controller.

9. The system according to claim 1, further comprising a measurement unit that collects information about the drying amount of the electrode sheet and transmits the collected information to the controller, wherein the controller determines the drying level of the electrode sheet based on the information about the drying amount received from the measurement unit and changes the heat supplied to the oven in real time.

10. The system according to claim 9, wherein the measurement unit collects information about at least one of the solid content and the surface temperature of the electrode sheet before and after passing through the oven.

11. The system according to claim 10, wherein the measurement unit includes at least one of a web gauge and a temperature measuring instrument.

12. A method for drying an electrode sheet, the method comprises: (a) a process of collecting information about a drying standby time, which is a time interval for stopping the supply of the electrode sheet to an oven for drying the electrode sheet; (b) a process of determining heat conditions to be supplied to the oven when supplying the electrode sheet to the oven after the drying standby time; and (c) a process of supplying the electrode sheet to the oven after the drying standby time and drying the electrode sheet under the heat conditions determined in process (b), wherein step (b) includes determining a heat condition for supplying less heat to the oven during the initial drying time than the generally supplied heat (Q t ), wherein the general supply heat amount refers to the heat generally supplied into the oven in the absence of a drying standby time.

13. The method according to claim 12, wherein the step (b) includes determining the heat condition for supplying the general supply heat (Q t ) to the oven after the initial drying time has elapsed.

14. The method according to claim 13, wherein in the step (b), the initial drying time (T) is divided into n time periods in chronological order, and at T 1 , T 2 , T 3 ... T n each amount of heat supplied to the oven is defined as Q 1 , Q 2 , Q 3 ... Q n , it is determined that the heat supplied to the oven satisfies the following relationship: Q 1 <Q 2 <Q 3 <...<Q n ≤Q t and wherein n is equal to or greater than 2.

15. The method according to claim 14, wherein in the step (b), the conditions for heat are determined such that as the drying standby time increases, the ratio (Q 1 / Q 1 ) of the heat (Q t ) supplied to the initial time period (T 1 ) to the general supply heat (Q t ) decreases.

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